Note: Within nine months of the publication of the mention of the grant of the European patent in the European PatentBulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with theImplementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has beenpaid. (Art. 99(1) European Patent Convention).

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(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention of the grant of the patent: 30.08.2017 Bulletin 2017/35

(21) Application number: 08743811.5

(22) Date of filing: 12.03.2008

(51) Int Cl.:H05B 33/08 (2006.01)

(86) International application number: PCT/US2008/056737

(87) International publication number: WO 2008/112820 (18.09.2008 Gazette 2008/38)

(54) POWER CONTROL SYSTEM FOR CURRENT REGULATED LIGHT SOURCES

LEISTUNGSREGLERYSTEM FÜR STROMGESTEUERTE LICHTQUELLEN

SYSTÈME DE COMMANDE DE PUISSANCE POUR DES SOURCES DE LUMIÈRE RÉGULÉES EN COURANT

(84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MT NL NO PL PT RO SE SI SK TR

(30) Priority: 12.03.2007 US 894295 P

(43) Date of publication of application: 09.12.2009 Bulletin 2009/50

(73) Proprietor: Philips Lighting Holding B.V.5656 AE Eindhoven (NL)

(72) Inventor: MELANSON, John, L.Austin, TX 78703 (US)

(74) Representative: Verweij, Petronella Daniëlle et alPhilips Lighting B.V. Philips Lighting Intellectual Property High Tech Campus 455656 AE Eindhoven (NL)

(56) References cited: US-A- 5 315 214 US-A1- 2005 218 838US-A1- 2005 253 533

• BALOGH, LASZLO: "A DESIGN AND APPLICATION GUIDE FOR HIGH SPEED POWER MOSFET GATE DRIVE CIRCUITS" [Online] 2001, TEXAS INSTRUMENTS, INC , SEM-1400, UNITRODE POWER SUPPLY DESIGN SEMINAR, TOPIC II, TI LITERATURE NO. SLUP133 , XP002552367 Retrieved from the Internet: URL:http://focus.ti.com/lit/ml/slup169/slu p169.pdf> [retrieved on 2009-10-26] the whole document

• ZHENYU YU: "3.3V DSP for Digital Motor Control" [Online] June 1999 (1999-06), TEXAS INSTRUMENTS - APPLICATION REPORT SPRA550 , XP002552366 Retrieved from the Internet: URL:http://focus.ti.com/lit/an/spra550/spr a550.pdf> [retrieved on 2009-10-26] abstract page 3 pages 10-11

• INTERNATIONAL RECTIFIER: "Data Sheet No. PD60143-O, IR2127(S)/IR2128(S), Current Sensing Single Channel Driver" INTERNATIONAL RECTIFIER DATA SHEETS, [Online] 8 September 2004 (2004-09-08), pages 1-16, XP002552456 INTERNATIONAL RECTIFIER, EL SEGUNDO, CALIFORNIA, USA Retrieved from the Internet: URL:http://www.irf.com/product-info/datash eets/data/ir2127.pdf> [retrieved on 2009-10-27]

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• INTERNATIONAL RECTIFIER: "APPLICATION NOTE AN-978 RevD - HV Floating MOS-Gate Driver ICs" [Online] 23 March 2007 (2007-03-23), INTERNATIONAL RECTIFIER , EL SEGUNDO, CALIFORNIA , XP002552371 Retrieved from the Internet: URL:www.irf.com/technical-info/appnotes/an -978.pdf> [retrieved on 2009-10-26] the whole document

• Texas Instruments: "ADVANCED PFC/PWM COMBINATION CONTROLLERS", , 30 September 2005 (2005-09-30), XP055295194, Retrieved from the Internet: URL:http://www.ti.com/lit/ds/symlink/ucc28 514.pdf [retrieved on 2016-08-12]

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Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates in general to thefield of electronics and lighting, and more specifically toa system and method to controlling and/or providing pow-er to current regulated light sources, such as light emittingdiode light sources.

DESCRIPTION OF THE RELATED ART

[0002] The following patent application have been filedbefore and published after the priority date of the presentinvention and the present application makes referenceto them for explaining some embodiments.[0003] US 2009/0085625 will be referred to herein asMelanson III.[0004] US 2008/0272744 will be referred to herein asMelanson IV.[0005] US 2008/0272745 will be referred to herein asMelanson V.[0006] US 2008/0272755 will be referred to herein asMelanson VI.[0007] US 2008/0272747 will be referred to herein asMelanson VII.[0008] US 2008/0272746 will be referred to herein asMelanson VIII.[0009] The closest prior art to consider according toR42(1) EPC is US 2005/218838 A1 which concerns aLED lighting system comprising a LED load, PFC switch,a plurality of LED current control switches and a proces-sor controlling both PFC and LED switches.[0010] The document with title "ADVANCEDPFC/PWM COMBINATION CONTROLLERS",XP055295194, from Texas Instruments discloses com-bined PFC/PWM controllers.[0011] Commercially practical incandescent lightbulbs have been available for over 100 years. However,other light sources show promise as commercially viablealternatives to the incandescent light bulb. LEDs are be-coming particularly attractive as main stream light sourc-es in part because of energy savings through high effi-ciency light output, long life, and environmental incen-tives such as the reduction of mercury.[0012] LEDs are semiconductor devices and are driv-en by direct current. The brightness of the LED varies indirect proportion to the current flowing through the LED.Thus, increasing current supplied to an LED increasesthe brightness of the LED and decreasing current sup-plied to the LED dims the LED.[0013] Figure 1 depicts a switching light emitting diode(LED) driver system 100. The LED driver system 100includes a continuous current mode, buck-based powerconverter 102 to provide a constant mains voltageVmains to switching LED system 104. Voltage source

101 supplies an alternating current (AC) input mains volt-age Vmains to a full, diode bridge rectifier 103. The volt-age source 101 is, for example, a public utility, and theAC mains voltage Vmains is,for example, a 60 Hz/120 V mains voltage in the UnitedStates of America or a 50 Hz/230 V mains voltage inEurope. The rectifier 103 rectifies the input mains voltageVmains. The hold-up capacitor C1 holds an approximatelydirect current (DC) supply voltage VC1 across capacitorC1 relative to a reference voltage VR. Supply voltage VC1is also the output voltage of power converter 102 and theinput voltage for controller 106. Input filter capacitor C2provides a high pass filter for high frequency componentsof the output voltage of rectifier 103. A thermistor NTC1provides in-rush current protection for power converter102.[0014] The controller 106 is, for example, a SupertexHV9910B integrated circuit controller available from Su-pertex, Inc. of Sunnyvale, CA. The supply voltage VC1can vary from, for example, 8V to 450V. Controller 106incorporates an internal voltage regulator to operate di-rectly from the DC supply voltage VC. The controller 106provides a gate drive signal from the GATE output nodeto the n-channel metal oxide semiconductor field effecttransistor (MOSFET) Q1. Controller 106 modulates thegate drive signal and, thus, the conductivity of MOSFETQ1 to provide a constant current to switching LED system104. Controller 106 modifies the average resistance ofMOSFET Q1 by varying a duty cycle of a pulse widthmodulated gate drive signal VGATE. Resistor R1 and ca-pacitor C3 provide external connections for controller 106to the ground reference.[0015] Controller 106 generates and uses feedback tomaintain a constant current iLED. Controller 106 receivesa current feedback signal Vfb representing a feedbackvoltage Vfb sensed across sense resistor R2. The feed-back voltage Vfb is directly proportional to the LED currentiLED in LEDs 108. If the feedback voltage Vfb exceeds apredetermined reference corresponding to a desiredLED current, the controller 106 responds to the feedbackvoltage Vfb by decreasing the duty cycle of gate drivesignal GATE to increase the average resistance of MOS-FET Q1 over time. If the feedback voltage Vfb is less thana predetermined reference corresponding to the desiredLED current, the controller 106 responds to the feedbackvoltage Vfb by increasing the duty cycle of gate drive sig-nal VGATE to decrease the average resistance of MOS-FET Q1 over time.[0016] The switching LED system 104 includes a chainof one or more, serially connected LEDs 108. When theMOSFET Q1 is "on", i.e. conductive, diode D1 is reversedbias and, current iLED flows through the LEDs and charg-es inductor L1. When the MOSFET Q1 is "off", i.e. non-conductive, the voltage across inductor L1 changes po-larity, and diode D1 creates a current path for the LEDcurrent iLED. The inductor L1 is chosen so as to storeenough energy to maintain a constant current iLED whenMOSFET Q1 is "off".

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[0017] Figure 2 depicts a power control system 200,which includes a switching power converter 202. The rec-tifier 103 rectifies the input mains voltage Vmains and sup-plies a rectified, time-varying, primary supply voltage Vxto the switching power converter. The switching powerconverter 202 provides a power factor corrected, approx-imately constant voltage power to load 222.[0018] PFC and output voltage controller 214 controlsPFC switch 208 so as to provide power factor correctionand regulate the output voltage Vc of switching powerconverter 202. The goal of power factor correction tech-nology is to make the switching power converter 202 ap-pear resistive to the voltage source 101. Thus, the PFCand output voltage controller 214 attempts to control theinductor current iL so that the average inductor current iLis linearly and directly related to the primary supply volt-age Vx. The PFC and output voltage controller 214 sup-plies a pulse width modulated (PWM) control signal CS0to control the conductivity of switch 208. In at least oneembodiment, switch 208 is a field effect transistor (FET),and control signal CS0 is the gate voltage of switch 208.The values of the pulse width and duty cycle of controlsignal CSo depend on two feedback signals, namely, theprimary supply voltage Vx and the capacitor voltage/out-put voltage Vc. Output voltage Vc is also commonly re-ferred to as a "link voltage".[0019] To convert the input voltage Vx into a powerfactor corrected output voltage Vc, PFC and output volt-age controller 214 modulates the conductivity of PFCswitch 208. To regulate the amount of energy transferredand maintain a power factor close to one, PFC and outputvoltage controller 214 varies the period of control signalCS0 so that the input current iL tracks the changes ininput voltage Vx and holds the output voltage VC constant.Thus, as the input voltage Vx increases, PFC and outputvoltage controller 214 increases the period TT of controlsignal CS0, and as the input voltage Vx decreases, PFCand output voltage controller 214 decreases the periodof control signal CS0. At the same time, the pulse width(PW) of control signal CS0 is adjusted to maintain a con-stant duty cycle of control signal CS0, and, thus, hold theoutput voltage VC constant. The inductor current iL ramps’up’ when the switch 208 conducts, i.e. is "ON". The in-ductor current iL ramps down when switch 208 is non-conductive, i.e. is "OFF", and supplies inductor currentiL to recharge capacitor 206. The time period during whichinductor current iL ramps down is commonly referred toas the "inductor flyback time". Diode 211 prevents re-verse current flow into inductor 210. Inductor current iLis proportionate to the ’on-time’ of switch 208. In at leastone embodiment, the switching power converter 202 op-erates in discontinuous current mode, i.e. the inductorcurrent iL ramp up time plus the inductor flyback time isless than the period of the control signal CS0, which con-trols the conductivity of switch 208. Prodic, CompensatorDesign and Stability Assessment for Fast Voltage Loopsof Power Factor Correction Rectifiers, IEEE Transactionson Power Electronics, Vol. 22, No. 5, Sept. 2007, pp.

1719-1729 (referred to herein as "Prodic"), describes anexample of PFC and output voltage controller 214.[0020] In at least one embodiment, the PFC and outputvoltage controller 214 updates the control signal CS0 ata frequency much greater than the frequency of inputvoltage Vx. The frequency of input voltage Vx is generally50-60 Hz. The frequency 1/TT of control signal CS0 is,for example, between 20 kHz and 130 kHz. Frequenciesat or above 20 kHz avoid audio frequencies and frequen-cies at or below 130 kHz avoids significant switching in-efficiencies while still maintaining a good power factor of,for example between 0.9 and 1, and an approximatelyconstant output voltage VC.[0021] Capacitor 206 supplies stored energy to load212 when diode 211 is reverse biased. The capacitor 206is sufficiently large so as to maintain a substantially con-stant output voltage Vc, as established by a PFC andoutput voltage controller 214 (as discussed in more detailbelow). The output voltage Vc remains at a substantiallyconstant target value during constant load conditions.However, as load conditions change, the output voltageVc changes. The PFC and output voltage controller 214responds to the changes in voltage Vc by adjusting thecontrol signal CS0 to return the output voltage Vc to thetarget value. The PFC and output voltage controller 214includes a small capacitor 215 to filter any high frequencysignals from the primary supply voltage Vx.[0022] PFC and output voltage controller 214 controlsthe process of switching power converter 202 so that adesired amount of energy is transferred to capacitor 206.The desired amount of energy depends upon the voltageand current requirements of load 212. To determine theamount of energy demand of load 212, the PFC and out-put voltage controller 214 includes a compensator 228.Compensator 228 determines a difference between a ref-erence voltage VREF, which indicates a target voltage foroutput voltage Vc, and the actual output voltage Vcsensed from node 222 and received as feedback fromvoltage loop 218. The compensator 228 generally utilizestechnology, such as proportional integral (PI) type con-trol, to respond to differences in the output voltage Vcrelative to the reference voltage VREF- The PI controlprocesses the error so that the PFC and output voltagecontroller 214 smoothly adjusts the output voltage Vc toavoid causing rapid fluctuations in the output voltage Vcin response to small error signals. The compensator 228provides an output signal to the pulse width modulator(PWM) 230 to cause the PWM 230 to generate a controlsignal CSo that drives switch 208.[0023] An LED lighting system controller, such as con-troller 106, using a supply voltage that can vary from, forexample, 8V to 450V generally requires a more expen-sive integrated circuit relative to an integrated circuit de-signed to operate at a fraction of the maximum supplyvoltage. Using a conventional PFC controller with feed-back control, when the power demand of a load quicklydecreases, the output voltage Vc will momentarily in-crease while the PFC controller responds to output volt-

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age feedback by lowering the output voltage. Conven-tional switching power converters using compensatorsgenerally respond relatively slowly to large changes inload power demand. Additionally, conventional PFC con-trollers often include large and relatively expensive elec-trolytic capacitors to accommodate voltage spikes.

SUMMARY OF THE INVENTION

[0024] One embodiment of the present invention is de-fined by claim 1. A light emitting diode (LED) lighting sys-tem includes a power factor correction (PFC) and LEDdrive controller. The controller includes a digital signalprocessor, coupled to the LED feedback node and con-figured to: operate from a digital level supply voltage;generate a PFC control signal; and generate an LED cur-rent control signal. The controller further includes a firstbuffer, coupled to the processor, and configured to: op-erate from a medium level supply voltage. The mediumlevel supply voltage is greater than the digital level supplyvoltage. The controller is further configured to receivethe PFC control signal and convert the PFC control signalinto a PFC switch control signal to control conductivity ofa high voltage PFC switch. The controller further includesa second buffer, coupled to the processor, and config-ured to: operate from the medium level supply voltage;receive the LED current control signal; and convert theLED current control signal into an LED current controlswitch signal to control conductivity of a high voltage LEDcurrent control switch.[0025] Another embodiment of the present inventionis defined by claim 7. A method includes operating a dig-ital signal processor of a power factor correction (PFC)and output voltage controller from a digital level supplyvoltage and generating a PFC control signal; and gener-ating an LED current control signal. The method furtherincludes operating a first buffer, coupled to the processor,from a medium level supply voltage. The medium levelsupply voltage is greater than the digital level supply volt-age; receiving the PFC control signal. The method alsoincludes converting the PFC control signal into a PFCswitch control signal to control conductivity of a high volt-age PFC switch and operating a second buffer, coupledto the processor, from the medium level supply voltage.The method further includes receiving the LED currentcontrol signal and converting the LED current control sig-nal into an LED current control switch signal to controlconductivity of a high voltage LED current control switch.[0026] In a further example, a light emitting diode (LED)lighting system includes an LED lighting power system.During normal operation of the LED lighting system theLED lighting power system generates a first source volt-age relative to a common voltage. The first source voltageis a link voltage. The LED lighting power system includesa switching power supply having a power factor correc-tion (PFC) switch, wherein during normal operation ofthe LED lighting system, the PFC switch of the LED light-ing power system operates at a current node voltage less

than or equal to 0.1 times the first source voltage relativeto the common voltage reference. The LED lighting pow-er system also includes an LED current control switch,wherein during normal operation of the LED lighting sys-tem, the LED current control switch operates at a currentnode voltage less than or equal to 0.1 times the firstsource voltage relative to the common voltage reference.The LED lighting system further includes a PFC and out-put voltage controller coupled to conductivity controlnodes of the first and LED drive current switches. Duringnormal operation of the lighting control system, the con-troller operates from a second source voltage relative tothe common voltage and controls conductivity of the PFCswitch and the LED current control; and at least one LEDcoupled to the LED current control switch.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention may be better under-stood, and its numerous obj ects, features and advan-tages made apparent to those skilled in the art by refer-encing the accompanying drawings. The use of the samereference number throughout the several figures desig-nates a like or similar element.

Figure 1 (labeled prior art) depicts a switching lightemitting diode (LED) driver system

Figure 2 (labeled prior art) depicts a power controlsystem, which includes a switching power converter.

Figure 3 depicts a LED lighting system that includesa common reference node at a common referencevoltage.

Figure 4 depicts a LED lighting system.

Figures 5A, 5B, 5C, and 5D depict various switches.

Figure 5E depicts a driver circuit.

Figures 6A and 6B depict switching LED systems.

Figures 7-8 depict graphical relationships betweenvarious control signals, sense signals, and currentsof the LED lighting system of Figure 4.

Fig. 9 depicts a spread spectrum system.

Figure 10 depicts one embodiment of a feed forwardlighting power and control system.

Figure 11 depicts a switching LED system with mul-tiple current sense elements.

Figure 12 depicts a switching LED system with asingle current sense element.

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(45) Figure 13 depicts a graphical representation ofnon-overlapping control signals and current sensesignals.

Figure 14 depicts a graphical representation of over-lapping control signals and current sense signals.

Figure 15 depicts an embodiment of a controller ofthe lighting system of Figure 3.

DETAILED DESCRIPTION

[0028] A light emitting diode (LED) lighting system in-cludes a PFC and output voltage controller and a LEDlighting power system. The LED lighting power systemoperates from a primary supply voltage derived from aprimary power supply. The controller operates from anauxiliary power source supply, which provides an auxil-iary voltage less than a link voltage generated by the LEDlighting power system relative to a common referencevoltage at a common reference node. By utilizing a lowervoltage, in at least one embodiment, the controller canbe manufactured at a lower cost than a comparable con-troller supplied by the primary power supply utilized bythe LED lighting power system. Additionally, during nor-mal operation of the LED lighting system, a power factorcorrection (PFC) switch and an LED drive current switchof the LED lighting system, that respectively control pow-er factor correction and LED drive current, are coupledto the common reference node and have control node-to-common node, absolute voltage that allows the con-troller to control the conductivity of the switches. In atleast one embodiment, the PFC switch and the LED drivecurrent switch each have a control node-to-commonnode, absolute voltage within 15% of the link voltage rel-ative to the common reference voltage. Having a currentnode voltage within 15% of the absolute value of the linkvoltage relative to the common reference voltage allowsthe controller to effectively control the switches.[0029] In at least one embodiment, the controller 305is manufactured in a 12-20 Volt ("V") complimentary met-al oxide semiconductor (CMOS) integrated circuit proc-ess ("IC Process"), coupled to 200V -500V rated fieldeffect transistors (FETs) external to the integrated circuit(IC) controller. This embodiment is a particularly cost-effective combination of technologies. In a further refine-ment of the preferred embodiment, the IC Process alsoincludes 5V or lower transistors in the IC controller inaddition to the 12V - 20V transistors, allowing for densedigital designs. A digital controller, in .35 micron or finerprocess technology allows for a very small, cost effective,digital controller. A 12V - 20V process allows for the ap-propriate driving of the gates of external high-voltageFETs. In at least one embodiment, the IC controller iscontroller 305 (Figures 3 and 4). The foregoing voltagelimits typically indicate that the high voltage devices(which have approximately 12V of gate-source voltageto be fully turned on, and less than 1V to be fully turned

off) have sources at nearly the same voltage potential,in order that the same controller can drive both.[0030] An LED lighting system that includes dimmingcapability can be subject to rapid changes in power de-mand by a switching LED system load. The switchingLED system includes one or more light emitting diodes(LED(s)). For example, if the LED(s) are operating at fullintensity and a dimming level of 15% of full intensity isrequested, the power demand of the switching LED sys-tem is quickly and significantly reduced. In at least oneembodiment, the LED lighting system utilizes feedfor-ward control to allow the controller to concurrently modifypower demand by the LED lighting power system andpower demand of one or more switching LED systems.Thus, in at least one embodiment, the LED lighting sys-tem can quickly respond to the lower power demand byreducing power received from a power source, such asa mains source, and use a compensator, such as a pro-portional integral (PI) type control, to make relativelysmall corrections to maintain a desired LED lighting sys-tem output voltage.[0031] Additionally, in at least one embodiment, theLED lighting system includes multiple switching LED sys-tems, and each switching LED system includes at leastone LED. In at least one embodiment, the LED lightingsystem utilizes a common current sense device to pro-vide a common feedback signal to the controller repre-senting current in at least two of the switching LED sys-tems. In at least one embodiment, utilizing a commoncurrent sense device reduces a number of pins of thecontroller used for feedback and reduces a number ofcurrent sense devices.[0032] Figure 3 depicts a LED lighting system 300 thatincludes a common reference node 302 at a commonreference voltage Vcom, such as a ground reference dur-ing normal operation. The LED lighting system 300 op-erates from two supply voltages, Vx and VAUX, which areboth referenced to the common reference voltage. A thirdvoltage, VD (shown in Figure 15), can be generated in-ternal to the controller 305 and is preferably in the rangeof 1.5V - 5.0V, depending on the chosen CMOS technol-ogy. "Normal operation" refers to the operation of LEDlighting system 300 after power has been supplied to theLED lighting system 300 and any initial voltage or currenttransients have subsided. The LED lighting system 300generates a link voltage VC1. The PFC switch 308 andLED drive current control switch 310 have absolute, con-trol node-to-common node voltages within 15% of thedifference between the absolute link voltage VC1 minusthe common reference voltage Vcom, ie. VC1-Vcom. PFCand output voltage controller 305 (referred to as "control-ler 305") operates from an auxiliary supply voltage VAUX.The absolute value of auxiliary supply voltage VAUX isless than the absolute value of the link voltage VC1.[0033] Figures 5A, 5B, 5C, and 5D depict exemplaryembodiments of switch 530, which represents one em-bodiment of switches 308 and 310. Referring to Figure5A, the nodes of 532, 534, and 536 of generic switch 530

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represent respective control, common, and switchingnodes. Figures 5B, 5C, and 5D represent embodimentsof switch 530. Referring to Figure 5B, switch 540 is ann-channel MOSFET, and gate node 542, source node544, and drain node 546 respectively represent a controlnode, a common node, and a switching node. Referringto Figure 5C, switch 550 is a bipolar junction transistor(BJT), and base node 552, emitter node 554, and collec-tor 556 respectively represent a control node, a commonnode, and a switching node. Referring to Figure 5D,switch 560 is an insulated gate bipolar transistor (IGBT),and gate node 562, emitter node 564, and collector 566respectively represent a control node, a common node,and a switching node.[0034] Figure 5E depicts an exemplary driver circuit570, which represents one embodiment of drivers 307and 309. The source of p-channel FET 572 and the drainof n-channel FET 574 are connected together and pro-vide the output signal CSx where CSx represents controlsignals CS1 and CS2. The drain of p-channel FET 572 isconnected to the high side supply rail voltage, which isless than or equal to auxiliary voltage VAUX. The sourceof n-channel FET 574 is connected to the low side supplyrail voltage Vcom. FETs 572 and 574 share a gate node576 to receive the control signal CSx.[0035] Referring to Figure 3, diode rectifier 103 rectifiesthe input mains voltage Vmains and supplies a rectified,time-varying, primary supply voltage Vx to a switchingpower converter 303. In at least one embodiment, mainsvoltage Vmains is a mains voltage such as the mains volt-age Vmains in Figures 1 and 2. Referring to Figure 3, theauxiliary power supply 311 provides low voltage powerto the controller 305. Providing low voltage power to thecontroller 305 allows controller 305 to be manufacturedat a lower cost than higher voltage controllers. Addition-ally, during normal operation of the LED lighting system,a power factor correction (PFC) switch and an LED drivecurrent switch of the LED lighting system, that respec-tively control power factor correction and LED drive cur-rent, are coupled to the common reference node andhave control node-to-common node, absolute voltagethat allows the controller to control the conductivity of theswitches. During normal operation, the switching powerconverter 303 converts the primary supply voltage Vx intoan output, link voltage VC1. In at least one embodiment,by referencing controller 305 to the common referencenode and establishing the control node-to-common nodevoltages of switches 308 and 310 within 15% of the volt-age difference VC1-Vcom, controller 305 is able to controlthe conductivity of the switches 308 and 310 while oper-ating from the auxiliary voltage VAUX of auxiliary powersupply 311. In at least one embodiment, the voltages atcurrent nodes 312 and 313 are within +1V of the commonreference voltage Vcom. A current sense resistor may ormay not be required in the PFC switch 308, dependingon the control mode chosen for the controller 305. In thepreferred embodiment, controller 305 is a discontinuouscurrent mode controller and does not use a current sense

for controlling power factor correction.[0036] The auxiliary power supply 311 supplies powerto controller 305. The auxiliary power supply 311 pro-vides a supply voltage VAUX less than, such as approxi-mately from 1% to 15%, the absolute value of the linkvoltage VC1. For example, in at least one embodiment,the nominal RMS primary supply voltage Vx is 110V, andthe supply voltage VAUX is any value within the rangeof+1V to +15V, such as +1V, +3V, +5V, +12V, or +15V.Because controller 305 is powered by a relatively smallsupply voltage, controller 305 can be manufactured lessexpensively than a controller manufactured for highersupply voltages. The voltage VAUX is chosen commen-surate with the required drive voltage of the externalswitch. For an FET, this voltage is typically around 12V.For a bipolar transistor, current drive would often be used,and the voltage would be 1V - 2V.[0037] During normal operation, the switching powerconverter 303 converts the primary supply voltage Vx intoan output, link voltage VC1. In at least one embodiment,switching power converter 303 is a boost converter, i.e.link voltage VC1 > Vx. For a particular dimming level, theswitching power converter 303 provides an approximate-ly constant current iLED to LED light source 308. The cur-rent iLED varies with dimming levels but, in at least oneembodiment, is approximately constant for a particulardimming level. The switching power converter 303 in-cludes switch 308 to control the input current iin so thatthe average input current iin is linearly and directly relatedto the primary supply voltage Vx, thereby making theswitching power converter 303 appear resistive to volt-age source 301. By controlling the input current iin, switch308 also controls the value of link voltage VC1. Duringnormal operation of the LED lighting system 300, the linkvoltage VC1 has an approximately constant value overtime and, thus, approximates a DC voltage. In at leastone embodiment, the switching LED system 304 includesone or more individual LEDs or one or more parallel cou-pled strings of LED(s) as, for example, described in moredetail with reference to Figures 5A and 5B. The link volt-age VC1 is typically in the range of 200V - 500V, depend-ing on the AC mains voltage Vmains.[0038] Controller 305 generates PFC control signalCS1 to control the conductivity of switch 308. Controller305 includes a buffer 307 to provide the drive current forPFC control signal CS1. Controller 305 generates a digitalPFC control signal CS1D that is amplified by buffer 307to generate PFC switch control signal CS1. Buffer 307operates from a high side voltage supply rail of less thanor equal to auxiliary voltage VAUX and from a low sidevoltage supply rail of common voltage Vcom. Controller305 adjusts the pulse width of PFC control signal CS1 toincrease as the primary supply voltage Vx increases andto decrease as primary supply voltage Vx decreases toprovide power factor correction. Controller 305 maintainsa duty cycle of PFC control signal CS1 while adjustingthe pulse width of PFC control signal CS1 to maintain anapproximately constant link voltage VC1. Controller 305

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receives feedback signal Vx’ to detect the value of voltageVx. Controller 305 also receives feedback signal VC1’ todetect the value of voltage VC1. Controller 305 uses thevalue of detected feedback signals Vx’ and VC1’ to adjustPFC control signal CS1 so that switching power converter303 provides power factor correction and maintains anapproximately constant link voltage VC1.[0039] The controller 305 can be implemented to gen-erate the PFC control signal CS1 in any of a variety ofways, such as the exemplary ways described in Melan-son IV, Melanson V, and Melanson VII. The feedbacksignals Vx’ and VC1’ can be generated in any of a varietyof ways, such as the exemplary ways described in Me-lanson V, Melanson VI, and Melanson VIII.[0040] Controller 305 generates an LED current con-trol switch signal CS2 to modulate the conductivity of LEDdrive current control switch 310. Controller 305 generatesa digital LED current control signal CS2D that is amplifiedby buffer 309 to generate LED current control switch con-trol signal CS2. Controller 305 includes a buffer 309 toprovide the drive current for LED current control switchsignal CS2. Buffer 309 operates from a high side voltagesupply rail of less than or equal to auxiliary voltage VAUXand from a low side voltage supply rail of common voltageVcom. In at least one embodiment, LED current controlswitch signal CS2 is a duty cycle modulated gate drivesignal. The duty cycle modulated gate drive signal mod-ulating the conductivity of switch 310 controls the LEDcurrent iLED supplied by switching power converter 303.The current iLED serves as the drive current for switchingLED system 304. Adjusting the current iLED modifies theintensity of switching LED light system 304. The control-ler 305 modulates the conductivity of switch 310 so thatan average LED current iLED causes each LED in theswitching LED system 304 to illuminate at a desired in-tensity level. In a non-dimmed configuration of LED light-ing system 300, the desired intensity level is, for example,the full (100%) rated intensity of the LED(s) of the switch-ing LED system 304 or zero (0) intensity (off).[0041] As subsequently described in more detail, toregulate the LED drive current iLED, the controller 305receives a LED feedback signal LEDisense from a currentsense device 314. In at least one embodiment, the feed-back signal LEDisense is the current iLED or a scaled ver-sion of the current iLED. In another embodiment, the feed-back signal LEDisense is a voltage that is directly propor-tional to the current iLED. The controller 305 responds tothe feedback signal LEDisense by modifying the currentdelivered to the switching LED system 304 to maintain adesired LED current iLED and desired link voltage VC1.The current sense device 314 can be any device capableof sensing the LED current iLED. In at least one embod-iment, current sense device 314 is a resistor, and thefeedback signal LEDisense is a voltage sensed across theresistor. In at least one embodiment, the feedback signalLEDisense is sensed by a magnetic current sensor in theproximity of current flowing through an inductor (such asinductor 606 of Figure 6A or inductor 612 of Figure 6B)

in switching LED system 304. In at least one embodiment,current sense device 314 is a current mirror circuit. Cur-rent mirrors are generally not used in high voltage appli-cations. Controller 305 can generate LED current controlswitch signal CS2 in any of a variety of ways. MelansonIII describes an exemplary system and method for gen-erating LED current control switch signal CS2.[0042] In at least one embodiment, LED lighting sys-tem 300 can dim the LED(s) of switching LED system304, i.e. adjust the intensity of the LED(s) of switchingLED system 304, in response to a dimmer signal DV Thedimmer signal DV can be a digital dimming signal DV_digitalor an analog dimming signal DV_analog indicating a dim-ming level for switching LED system 304. Values of dim-mer signal Dv function as a target reference and are com-pared with LEDisense external to controller 305 or an in-tegral part of an integrated circuit version of controller305. In at least one embodiment, the controller 305 ad-justs LED current control switch signal CS2 to minimizea difference between the comparison between the dim-mer signal DV and the feedback signal LEDisense.[0043] In at least one embodiment, the dimmer signalDv represents a mapping of a conventional, duty cyclemodified dimmer signal to predetermined values differentthan the dimming level represented by the dimmer outputsignal value. In at least one embodiment, a conventionaldimmer 320 generates a dimming signal VDIM- The dim-ming signal VDIM is, for example, a duty cycle modified(i.e. phase-cut) analog signal whose duty cycle or phaseangle represents a dimming level. Mapping system 322includes a lighting output function that converts the dim-mer levels indicated by dimming signal VDIM to a digitaldimming signal DV_digital having values that map meas-ured light levels to perception based light levels. In atleast one embodiment, controller 305 uses the digitaldimming signal DV_digital directly to generate LED currentcontrol switch signal CS2. In at least one embodiment,digital-to-analog converter (DAC) 324 converts the digitaldimming signal DV_digital into a corresponding analogdimming signal DV_analog. The digital and analog versionsof dimming signal Dv are generically referred to here asdimming signal DV. Dimmer 320, mapping system 322,and DAC 324 are shown in "dashed lines" because dim-ming is optional for LED lighting system 300.[0044] Figure 4 depicts a LED lighting system 400,which represents one embodiment of LED lighting sys-tem 300. LED lighting system 400 includes switchingpower converter 402 to convert the rectified input voltageVx into an approximately DC link voltage Vci. Switchingpower converter 402 and controller 305 also provide pow-er factor correction. The switching power converter 402includes a switch 308 that turns ’on’ (conducts) and turns’off (nonconductive) in response to a PFC control signalCS1 generated by PFC and output voltage controller 305.When switch 308 is ’on’, inductor 408 energizes with thecurrent IL1 from the full-bridge diode rectifier 103. Whenswitch 308 is ’off, the inductor 408 drives current IL1through diode 412 to charge capacitor 408. The PFC

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control signal CS1 varies the duty cycle of switch 308 sothat the DC voltage link voltage VC1 on storage capacitor408 averages to a desired value of DC voltage Vci. In atleast one embodiment, steady state voltage VC1 has anaverage value in the range of 200 V to 400 V. In at leastone embodiment, current IL1 represents current iin of Fig-ure 3. PFC and output voltage controller 305 operatesas previously described to control the duty cycle of switch308 such that current IL1 is linearly proportional to theinput voltage Vx. Capacitor 432 provides filtering tosmooth inductor current IL1 so that the average inductorcurrent IL1 is sinusoid in phase with input signal Vx.[0045] Controller 305 generates LED current controlswitch signal CS2 based on the value of the comparator438 output signal Vcomp. In at least one embodiment,comparator output signal Vcomp is a voltage representinga logical "1" if the value of feedback signal LEDisense isgreater than an analog value of dimmer signal DV_analog.Otherwise, the value of comparator output signal Vcompis a logical "0". The dimmer signal DV is a target referencevalue, and controller 305 generates controls signal CS2to modify the current iLED to minimize differences be-tween feedback signal LEDisense and dimmer signalDV_analog. The dimmer signal DV_analog is scaled so thatwhen the difference between feedback signal LEDisenseand dimmer signal DV_analog is minimized, the intensityof the LED(s) of switching LED system 304 matches thedimming level indicated by dimmer signal DV_analog. Asthe dimming level indicated by dimmer signal DV_analogchanges, the value of comparator output signal Vcompalso changes so that controller 305 causes LED currentcontrol switch signal CS2 to track the changes in dimminglevel indicated by dimmer signal DV_analog. As previouslydescribed, in at least one embodiment, controller 305uses the comparator output signal Vcomp to generate LEDcurrent control switch signal CS2 as described in Melan-son III.[0046] Figures 6A and 6B depict exemplary embodi-ments of switching LED system 304. Switching LED sys-tem 600 includes one or more LED(s) 602. The LED(s)602 can be any type of LED including white, amber, othercolors, or any combination of LED colors. Additionally,the LED(s) 602 can be configured into any type of phys-ical arrangement, such as linearly, circular, spiral, or anyother physical arrangement. In at least one embodiment,each of LED(s) 602 is serially connected. Capacitor 604is connected in parallel with LED(s) 602 and providesfiltering to protect the LED(s) 602 from AC signals. In-ductor 606 smooths energy from LED current iLED tomaintain an approximately constant current iLED whenswitch 310 conducts. Diode 608 allows continuing currentflow when switch 310 opens.[0047] In switching LED system 610, inductor 612 isconnected in series with LED(s) 602 to provide energystorage and filtering. Inductor 612 smoothes energy fromLED current iLED to maintain an approximately constantcurrent iLED when switch 310 conducts. Diode 614 allowscontinuing current flow when switch 310 opens. Although

two specific embodiments of switching LED system 304have been described, switching LED system 304 can beany switching LED system.[0048] Figure 7 depicts a graphical relationship 700between the comparator voltage VCOMP, LED currentcontrol switch signal CS2, and current iLEDsense (Figure4). When LED current control switch signal CS2 is high,switch 310 conducts, and LED current iLED increases.When the comparator voltage VCOMP goes high, PFCand output voltage controller 305 keeps LED current con-trol switch signal CS2 high until the comparator voltageVCOMP goes low again. In this manner, the average cur-rent iLEDsense, and, thus, the average LED current iLED,is responsive to the dimmer signal Dv, and, thus, theintensity of the LED(s) in switching LED system are alsoresponsive to dimmer signal Dv.[0049] Figure 8 depicts a graphical relationship 800between LED current control switch signal CS2 and cur-rent iLED. The LED current iLED ramps up when LED cur-rent control switch signal CS2 is high (i.e. causes switch310 to conduct) and ramps down when LED current con-trol switch signal CS2 is low (i.e. causes switch 310 toturn ’off’). The average current iLED tracks the dimmersignal Dv. The intensity of switching LED system 304 isapproximately directly proportional to the driving LEDcurrent iLED.[0050] Fig. 9 depicts one embodiment of a spreadspectrum system 900. The spread spectrum system canbe included as part of controller 305 or can be constructedusing separate discrete components as a separate IC.Spread spectrum system 900 can also be implementedas code stored in a computer readable medium and ex-ecutable by controller 405. In general, spread spectrumsystem 900 receives an input signal TTarget and gener-ates an output signal TOUT. Output signal TOUT randomlyvaries from input signal TTarget within a predeterminedrange set by Δmax, and an average value of output signalTOUT equals input signal TTarget. Input signal TTarget is,for example, a pulse width of control signals CS1 and/orCS2. The value of Δmax is, for example, +/-10% of a nom-inal value of PFC control signal CS1. Multiple spreadspectrum system 900 can be used by controller 305 tospread the spectrum of multiple input signals such as thepulse widths of control signals CS1 and CS2.[0051] Spread spectrum system 900 includes a delta-sigma modulator 901. Delta-sigma modulator 901 in-cludes an adder 902 that adds the current value of inputsignal TTarget to a negative value of the previous valueof output signal TOUT to generate a difference signal TDiff.In at least one embodiment, spread spectrum system900 is initialized as startup with output signal TOUT = 0.The difference signal TDiff is processed by loop filter 904to generate a loop filter output signal U.[0052] The values of delta-sigma modulator output sig-nal TOUT are randomized around the values of input sig-nal TTarget. A random number generator 906 generatesrandom output values of random signal RN that are mul-tipled by Δmax to generate random signal RN’. During

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each cycle of spread spectrum system 900, adder 910adds the random signal RN’ to the loop filter output signalU, and quantizer 912 quantizes the sum of RN’ and U togenerate the quantization output signal TOUT. RandomNumber Generator 906 has predetermined value rangesset by a range limiting value Δmax. In at least one embod-iment, RN’ varies approximately 10%.[0053] Delta-sigma modulator 901 can be any delta-sigma modulator such as any first order or multi-orderdelta-sigma modulator described in, for example, Under-standing Delta-Sigma Data Converters by Schreier andTemes, IEEE Press, 2005, ISBN 0-471-46585-2 or asavailable from Cirrus Logic Inc. of Austin, TX, U.S.A. Thedelta-sigma modulator 901 provides noise-shaping andseeks to consistently generate values of delta-sigma out-put signal TOUT that minimize the difference between out-put signal TOUT and difference signal TDiff. Thus, delta-sigma modulator 901 helps ensure that the average out-put signal TOUT equals the average input signal TTarget.[0054] Figure 10 depicts one embodiment of a feedforward lighting power and control system 1000. Powerand control system 1000 preferably also includes a com-mon reference node for switches 308 and 310 (throughcurrent sense device 314) and controller 1002. Controller1002 represents one embodiment of controller 305. Con-troller 1002 is logically divided into two separate controlsystems, PFC control system 1004 to control power fac-tor correction and regulate the link voltage VC1 of switch-ing power converter 402, and switching LED system con-troller 1006 to control the LED current iLED and, thus,control the intensity (i.e. brightness) of switching LEDsystem 304.[0055] The power and control system 1000 utilizesfeed forward control so that PFC controller 1004 canmore rapidly respond to changing power demands ofSwitching LED system light source 304 due to dimming.When dimmer signal Dv indicates a change in the dim-ming level of light source 304, switching LED system con-troller 1006 responds to dimming signal Dv by decreasingthe pulse width of duty cycle modulated LED current con-trol switch signal CS2 to reduce the average values ofcurrent iLED. Decreasing current iLED reduces the powerdemand of light source 304.[0056] Feed forward control allows PFC system con-troller 1004 to anticipate power demand changes of lightsource 304 due to, for example, dimming. The PFC sys-tem controller 1004 is configured to provide a specificoutput voltage link voltage VC1 for a specific dimminglevel. In at least one embodiment, the controller 1004responds to comparison signal Vcomp, which indicates achange in requested dimming level and, thus, a changein power demand by light source 304 by proportionatelychanging the pulse width of LED current control switchsignal CS2. In at least one embodiment, the dimmer sig-nal Dv is provided directly to controller 1004 as shownby the dashed line 1008. However, providing dimmer sig-nal Dv to controller 1004 may require an extra pin forcontroller 1002, which generally adds cost to controller

1002. Using feed forward control, the controller 1002 canconcurrently modify power demand by the power factorcorrection control system 1004 and modify power sup-plied by the switching LED system controller 1006. Theterm "concurrently" includes short delays due to, for ex-ample, processing by controller 1006.[0057] In accordance with changes in a dimming levelindicated by the dimmer signal DV, in at least one em-bodiment, the PFC system controller 1004 includes a pro-portional integrator (PI) compensator 1010 that receivesa feedback signal link voltage VC1 representing the linkvoltage VC1 and generates an output signal using a PItransfer function, such as the PI transfer function andsystem of Melanson IV. However, because the dimmersignal DV anticipates power demand by light source 304,the PFC controller 1004 can concurrently respond to dim-ming level changes and, the PI compensator 1010, in atleast one embodiment, only makes power demand ad-justments of, for example, 10% of the total power deliv-ered by the power and control system 1000. Respondingmore rapidly to power demand changes in light source304 allows switching power converter 402 to utilize asmaller capacitor value, such as 4.7 mF for capacitor 408because increases of link voltage VC1 are reduced towithin the operating characteristics of ceramic, polypro-pylene, and other capacitors that have advantageousproperties relative to electrolytic capacitors such as bet-ter temperature characteristics because light source 304tends to generate higher temperatures better suited forceramic, polypropylene, and other higher temperaturecapacitors. In at least one embodiment, controller 1004generates PFC control signal CS1 in the same manneras controller 305 so that the changes in the dimming levelindicated by dimmer signal DV are commensurate withchanges to the power (VC1·iin) delivered by switchingpower converter 402 while maintaining an approximatelyconstant link voltage VC1.[0058] Figure 11 depicts a switching light source bank1100 having N+1 switching LED systems, where N is aninteger greater than or equal to 1. Switching LED systembank 1100 is a substitution for switching LED system304. In at least one embodiment, each light source 304.xis a light source such as switching LED system 304,where x denotes the xth light source and is, for example,an integer and a member of the set {0, ... , N}. Each ofthe N+1 light sources includes at least one LED and thenumber and color of each LED for each light source is amatter of design choice. Each light source 304.x is con-nected to a respective switch 1104.x, and each switch1104.x is an n-channel FET. In at least one embodiment,controller 305 independently controls each light source304.x by generating respective control signals CS2.0, ... ,CS2.N to control the conductivity of switches 1104.0, ...,1104N. The average values of the drive currentsiLED.0, ..., iLED.N control the respective intensity ofLED(s) of switching LED systems 304.0, ..., 304.N.Switching LED systems 304.0, ... , 304.N are connectedto respective current sense elements 314.0, ... , 314.N.

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[0059] The current sense elements 314.0, ... , 314.Ncan be different or identical. Each current sense element314.x provides a feedback signal LEDsense.x tocontroller 305. In at least one embodiment, controller 305generates each control signal CS2x in the same manneras the generation of LED current control switch signalCS2 (Fig. 4). The output signals of LEDisense.0, ...,LEDisense.N are fed back to controller 305 to allowcontroller 305 to adjust the switching frequency ofswitches 1104.0, ..., 1104.N and, thus, correlate LEDdrive currents iLED.0, ..., iLED.N with a desired intensityof the LED(s) of light sources 304.0, ..., 304.N. In at leastone embodiment, the desired intensity is a dimming levelindicated by dimmer signal DV. The type, number, andarrangement of LED(s) in switching LED systems304.0, ..., 304.N is a matter of design choice anddepends, for example, on the range of desired intensityand color temperatures of switching LED systems304.0, ..., 304.N.[0060] Figure 12 depicts a switching LED system bank1200, which represents a substitution for switching LEDsystem 304 (Figure 4). One current sense element 314provides a feedback signal LEDisense that represents theLED sense currents of all switching LED systems304.0, ..., 304.N to sense each of the LED sense currentsiLEDsense.0, ..., iLEDsense.N for respective switching LEDsystems 304.0, ..., 304.N. Each of the switches1204.0, ..., 1204.N have a common current node 1206.At the common current node 1206, all of the LED sensecurrents iLEDsense.0, ..., iLEDsense.N are combined, andthe feedback signal LEDisense from current sense device314 represents the combination of all of the LED sensecurrents iLEDsense.0, ..., iLEDsense.N. In at least oneembodiment, feedback signal iLEDsense = l/x-(iLEDsense.0+

iLEDsense.1 +, ..., + iLEDsense.N), where "x" is a scalingfactor of current sense device 314. Utilizing a commonsense element 314 reduces a number of pins for anintegrated circuit implementation of controller 1208,which reduces the cost of controller 1208. Controller1208 represents one embodiment of controller 305.[0061] Figure 13 depicts a graphical representation1300 of non-overlapping control signals and currentsense signals. The operation of LED source bank 1200and controller 1208 (Figure 12) are described in conduc-tion with the signals of Figure 13. Control signals CS2.0and CS2.N represent two exemplary control signals forcontrol signals CS2.0, ..., CS2.N. Control signals CS2.0and CS2.N are depicted with a duty cycle of 0.25, i.e.pulse width/period, and non-overlapping pulse widths.During each pulse of control signals CS2.O and CS2.N,respective currents iLEDsense.0 and iLEDsense.N flowthrough respective switches 1204.0 and 1204.N and arecombined into the single LEDisense feedback signal fromcurrent sense device 314.[0062] Referring to Figures 12 and 13, controller 1208includes an LED current detector 1210 that detects anddetermines the individual LED currents iLED in switchingLED systems 304.0, ..., 304.N from the LEDisense feed-

back signal. The location in time of each contribution ofcurrents iLEDsense.0 and iLEDsense.N in the feedback sig-nal LEDisense corresponds to the respective pulses ofcontrols signals CS2.0 and CS2.N.[0063] In at least one embodiment, in a dimmable con-figuration, dimmer signal Dv is used to indicate a dimminglevel for switching LED systems 304.0, ..., 304.N. Com-parator 438 compares the LEDisense feedback signal tothe dimmer signal Dv. Variations in the comparator outputsignal Vcomp occur at approximately the same time asthe contribution of currents iLEDsense.0 and iLEDsense.N tothe feedback signal LEDisense. Since controller 1208 gen-erates control signals CS2.0 and CS2.N, the times atwhich currents iLEDsense.0 and iLEDsense.N will vary thecomparator output signal Vcomp are also known by LEDcurrent detector 1210. By knowing which changes incomparator output signal Vcomp correspond to each par-ticular current of switching LED systems 304.0, ..., 304.N,controller 1208 can adjust each LED current controlswitch signal CS2.0 and CS2.N in response to the dimmersignal Dv to dim the LEDs of switching LED systems304.0 and 304.N to the dimming level indicated by dim-mer signal DV. In at least one embodiment, controller1208 generates each LED current control switch signalCS2.0, ..., CS2.N in any manner described in conjunctionwith controller 305.[0064] In at least one embodiment, the switching LEDsystems 304.0, ..., 304.N are not dimmed. In this embod-iment, LED current detector 1210 receives the feedbacksignal LEDisense directly. Since controller 1208 generatescontrol signals CS2.0 and CS2.N, the times at which cur-rents iLEDsense.0 and iLEDsense.N, LED current detector1210 detects the contribution of currents iLEDsense.0 andiLEDsense.N during any of the respective times duringwhich respective control signals CS2.0 and CS2.N arenon-overlapping.[0065] Figure 14 depicts a graphical representation1400 of overlapping control signals and current sensesignals for processing by controller 1208 to generatemultiple control signals for multiple light sources from asingle feedback signal LEDisense. The overlappingcontrol signals each have a duty cycle of 0.5. LED currentdetector 1210 detects the contributions of currentsiLEDsense.0 and iLEDsense.N in feedback signal LEDisenseor comparator output signal Vcomp at times when thecontrol signals CS2.0 and CS2.N are non-overlapping.For example, LED current detector 1210 detects thecontribution of iLEDsense.0 during times t1 to t2, t5 to t6, t9to t10, and so on. Likewise, LED current detector detectsthe contribution of iLEDsense.N during times t3 to t4, t7 tot8, and so on.[0066] Figure 15 depicts lighting system 1500, whichis one embodiment of lighting system 300. Lighting sys-tem 1500 includes PFC switch 1502, which is an n-chan-nel FET and represents one embodiment of switch 308.PFC switch 1502 operates between the primary supplyvoltage Vx and the common reference voltage Vcom. PFCswitch 1502 does not have to be connected directly to

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the primary supply voltage Vx. In at least one embodi-ment, PFC switch 1502 is coupled through other compo-nents (not shown) to a primary supply voltage node 1506conducting primary supply voltage Vx. Lighting system1500 also includes LED drive current control switch 1504,which is an n-channel FET and represents one embod-iment of switch 310. LED drive current control switch1504 is coupled through switching LED system 304 tolink voltage node 1508. LED drive current control switch1504 operates between the link voltage VC1 and the com-mon reference voltage Vcom. Voltages Vx and VC1 areboth switching power converter voltages and are collec-tively referred to as "high" supply voltages 1510 becausethey represent the highest voltages in the lighting system1500. Nodes 1506 and 1508 are referred to as high volt-age source nodes. PFC switch 1502 is, thus, referred toas a high voltage PFC switch, and LED current controlswitch 1504 is, thus, referred to as a high voltage LEDcurrent control switch. In at least one embodiment, theroot mean square (RMS) of high supply voltages 1510is greater than or equal to 100 V.[0067] The lighting system 1500 also includes PFC andoutput voltage controller 1512, which in at least one em-bodiment is identical to controller 305. PFC and outputvoltage controller 1512 operates from at least two differ-ent voltages, which are lower than the high voltages1510. Output buffers 307 and 309 operate between volt-ages VB and the common reference voltage. Voltage VBis less than or equal to auxiliary voltage VAUX and greaterthan or equal the digital voltage reference VD. The voltageVB is set to be sufficient to drive the gates of switches1502 and 1504 and, thus, control the conductivity ofswitches 1502 and 1504. Voltage VB is referred to as a"medium level" supply voltage. In at least one embodi-ment, the medium level supply voltage is in the range of8 V to 50 V.[0068] The lighting system 1500 also includes a digitalsignal processor (DSP) 1514 to generate PFC controlsignal CS1D and LED current control signal CS2D. TheDSP 1514 is coupled to an LED feedback node 1518.DSP 1514 operates between a digital supply voltage VDand the common reference voltage Vcom. The digital sup-ply voltage VD is sufficient to operate the digital compo-nents of DSP 1514 and is, for example, in the range of3 V to 8 V. A level shifter (LS) 1516 level shifts the digitalPFC control signal CS1D and digital LED current controlsignal CS2D from DSP 1514 to a level sufficient to controlthe conductivity of respective buffers 307 and 309. Thedigital supply voltage VD can be a stepped down versionof the auxiliary voltage VAUX generated internally by con-troller 1512.[0069] Thus, although the controller 1512 operatesfrom a digital voltage VD, and an auxiliary voltage VAUXand the switches operates from high voltages 1510, thelighting system 1500 has a common reference voltageVcom to allow all the components of lighting system 1500to work together. By operating from auxiliary voltageVAUX, the controller 1512 can be fabricated using lower

cost fabrication techniques than a controller operatingfrom the high voltages 1510.[0070] Thus, in at least one embodiment, a LED light-ing system controller operates from a supply voltageVAUX less than a link voltage VC1 generated by the LEDlighting power system relative to a common referencevoltage at a common reference node. By utilizing a lowervoltage, in at least one embodiment, the controller canbe manufactured at a lower cost than a comparable con-troller supplied by the primary power supply utilized bythe LED lighting power system. Additionally, during nor-mal operation of the LED lighting system, a power factorcorrection (PFC) switch and an LED drive current switchof the LED lighting system, that respectively control pow-er factor correction and LED drive current, are coupledto the common reference node and have control node-to-common node, absolute voltage that allows the con-troller to control the conductivity of the switches. In atleast one embodiment, the PFC switch and the LED drivecurrent switch each have a control node-to-commonnode, absolute voltage within 15% of an absolute valueof the link voltage relative to the common reference volt-age. In at least one embodiment, the LED lighting systemutilizes feed forward control to concurrently modify powerdemand by the LED lighting power system and powerdemand of one or more switching LED systems. In atleast one embodiment, the LED lighting system utilizesa common current sense device to provide a commonfeedback signal to the controller representing current inat least two of the switching LED systems.[0071] Although the present invention has been de-scribed in detail, it should be understood that variouschanges, substitutions and alterations can be made here-to without departing from the spirit and scope of the in-vention as defined by the appended claims.

Claims

1. A light emitting diode, LED, lighting system compris-ing:

at least one LED load (304, 304.0-304.N) includ-ing at least one LED (602); a LED feedback node(313) adapted to provide a LED current feed-back signal (LEDisense) representing at least onecurrent level in the at least one LED load and;a PFC switch (308, 1502);a LED current control switch (310, 1504) adapt-ed to control the current in the at least one LEDload;an integrated circuit power factor correction,PFC, and LED drive controller (305, 1512),characterised in that the controller comprises:

a digital signal processor (DSP), coupled tothe LED feedback node (313), and config-ured to:

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operate from a digital level supply volt-age;generate a PFC control signal (CS1D);andgenerate an LED current control signal(CS2D);

a first buffer (307), coupled to the digital sig-nal processor, and configured to:

operate from a medium level supplyvoltage (Vaux),

wherein the medium level supplyvoltage is greater than the digitallevel supply voltage;

receive the PFC control signal (CS1D);andconvert the PFC control signal (CS1D)into the PFC switch control signal (CS1)to control the conductivity of the PFCswitch; and

a second buffer (309), coupled to the digitalsignal processor, and configured to:

operate from the medium level supplyvoltage;receive the LED current control signal(CS2D); andconvert the LED current control signal(CS2D) into an LED current controlswitch signal (CS2) to control the con-ductivity of the LED current controlswitch.

2. The LED lighting system of claim 1 further compris-ing:

a common voltage reference node (Vcom);a first voltage source node adapted to conducta primary supply voltage (Vx);a second voltage source node adapted to con-duct a link voltage (VC1) of the LED lighting sys-tem;wherein the PFC switch (308, 1502) is coupledto the common voltage reference node (Vcom)and the first voltage source node; andwherein the LED current control switch (310,1504) is coupled to the common voltage refer-ence node (Vcom) and the second voltagesource node;wherein, during normal operation of the LEDlighting system, the PFC switch and an LED cur-rent control switch have respective control node-to-common node, absolute voltages that allowthe integrated circuit PFC and LED drive con-

troller to control the conductivity of the switchesand provide power factor correction and supplyan approximately constant current to the at leastone LED load for each dimming level indicatedby a dimmer signal (DV).

3. The LED lighting system of claim 2 wherein the con-trol node-to-common node, absolute voltages of thePFC switch (308, 1502) and the LED current controlswitch (310, 1504) are less than or equal to 0.15times a voltage at the second voltage source noderelative to a voltage at the common voltage referencenode (Vcom).

4. The LED lighting system of claim 2 wherein:

the PFC switch (308, 1502) and the LED currentcontrol switch (310, 1504) are members of thegroup consisting of: field effect transistors andinsulated gate bipolar transistors.

5. The LED lighting system of claim 2 or 3 further com-prising:

a current sense device (314) coupled to the LEDcurrent control switch (310, 1504) and the com-mon voltage reference node (Vcom), whereinduring normal operation of the LED lighting sys-tem a voltage across the current sense device(314) is less than or equal to 0.15 times a voltageat the second voltage source node relative tothe voltage at the common voltage referencenode (Vcom) and wherein the current sensing de-vice (314) is configured to provide the LED cur-rent signal for controlling the LED current controlswitch.

6. The LED lighting system of claim 5 further compris-ing:

a plurality of LED current control switches(1104.0-1104.N, 1204.0-1204.N) including theLED current control switch, wherein each LEDcurrent control switch is configured to controlcurrent to a respective one of a plurality of theat least one LED load (304, 304.0-304.N) andis coupled to the common voltage referencenode (Vcom), the second voltage source node,and the integrated circuit PFC and LED drivecontroller; andwherein the current sense device (314) is cou-pled to the LED current control switches, andwherein, during normal operation of the lightingsystem, the current sense device (314) is con-figured to sense the current in all of the LEDcurrent control switches and to provide the LEDcurrent signal (LEDisense) for use by the integrat-ed circuit PFC and LED drive controller to control

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current in all of the LED current control switches.

7. A method for controlling a PFC switch (308, 1502)and a LED current control switch (310, 1504) of alight emitting diode, LED, lighting system, whereinthe LED lighting system comprises at least one LEDload (304, 304.0-304.N) and a LED feedback node(313) adapted to provide a LED current feedbacksignal (LEDisense) representing at least one currentlevel in the at least one LED load, wherein the atleast one LED load includes at least one LED, char-acterized in that the method comprises: operatinga digital signal processor (DSP) of an integrated cir-cuit power factor correction, PFC, and LED drivecontroller (305, 1512) from a digital level supply volt-age by performing the steps of:

generating a PFC control signal (CS1D); andgenerating an LED current control signal(CS2D);

operating a first buffer (307), coupled to the digitalsignal processor from a medium level supply volt-age,wherein the medium level supply voltage isgreater than the digital level supply voltage, by per-forming the steps of:

receiving the PFC control signal (CS1D); andconverting the PFC control signal (CS1D) intothe PFC switch control signal (CS1) to controlthe conductivity of the PFC switch;

operating a second buffer (309), coupled to the dig-ital signal processor from the medium level supplyvoltage, by performing the steps of:

receiving the LED current control signal (CS2D);andconverting the LED current control signal (CS2D)into an LED current control switch signal (CS2)to control the conductivity of the LED currentcontrol switch.

8. The method of claim 7 wherein the integrated circuitPFC and LED driver controller (305, 1512) includesa voltage feedback node to receive an input voltagefeedback signal representing an input voltage levelprovided to the LED lighting system, further compris-ing:

generating the PFC control signal (CS1D) in re-sponse to the input voltage level represented bythe input voltage feedback signal; andgenerating the LED current control signal(CS2D) in response to the at least one currentlevel represented by the LED current feedbacksignal.

9. The method of claim 7 wherein the digital level supplyvoltage is in the range of 3 volts to 8 volts, the mediumlevel supply voltage is in the range of 8 volts to 50volts, and the PFC switch (308, 1502) is coupledbetween voltage nodes having a voltage differenceduring normal operation of the LED lighting systemof at least 100 volts, and the LED current controlswitch (310, 1504) is coupled between voltage nodeshaving a voltage difference during normal operationof the LED lighting system of at least 100 volts.

10. The method of claim 7 further comprising:

generating a link voltage (VC1) from a primarysupply-voltage (Vx);operating a switching power converter (303,402) of the LED lighting system from the primarysupply voltage (Vx) relative to a common voltagereference node (Vcom), wherein the switchingpower converter includes the PFC switch (308,1502);operating the PFC switch (308, 1502) at a con-trol node-to-common node, absolute voltage toallow the integrated circuit PFC and LED drivecontroller to control the PFC switch and providepower factor correction for the switching powerconverter;operating the LED current control switch (310,1504) at a control node-to-common node, abso-lute voltage to allow the integrated circuit PFCand LED drive controller to control the LED cur-rent control switch to supply an approximatelyconstant current to the at least one LED load foreach dimming level indicated by a dimmer sig-nal; andcontrolling the conductivity of the PFC switch(308, 1502) and the LED current control switch(310, 1504) with the integrated circuit PFC andLED drive controller (305, 1512).

11. The method of claim 10 wherein:

operating the PFC switch (308, 1502) of theswitching power converter at a control node-to-common node, absolute voltage to allow the in-tegrated circuit PFC and LED drive controller tocontrol the PFC switch and provide power factorcorrection for the switching power convertercomprises operating the PFC switch (308, 1502)at a control node-to-common node, absolutevoltage less than or equal to 0.15 times the firstsource voltage relative to the common voltagereference node (Vcom); andoperating the LED current control switch (310,1504) at a control node-to-common node, abso-lute voltage to allow the integrated circuit PFCand LED drive controller to control the LED cur-rent control switch to supply an approximately

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constant current to the at least one LED load foreach dimming level indicated by a dimmer signalcomprises operating the LED current controlswitch (310,1504) at a control node-to-commonnode, absolute voltage less than or equal to 0.15times the first source voltage relative to the com-mon voltage reference node (Vcom).

12. The method of claim 10 wherein the PFC and LEDcurrent control switches comprise field effect tran-sistors and controlling the conductivity of the PFCswitch (308, 1502) and LED current control switch(310, 1504) with the integrated circuit PFC and LEDdrive controller comprises providing respective dutycycle modified control signals to gates of the PFCswitch and LED current control switch.

13. The method of claim 10 further comprising:

receiving the primary supply voltage (Vx),wherein a root mean square (RMS) value of theprimary supply voltage (Vx) is greater than themedium level voltage;boosting the primary supply voltage (Vx) to thelink voltage (VC1), wherein boosting the primarysupply voltage (Vx) further comprises modulat-ing the conductivity of the PFC switch (308,1502) to generate a power factor corrected pri-mary supply voltage.

14. The method of claim 10 wherein controlling the con-ductivity of the LED current control switch (310,1504) further comprises:

receiving the LED current feedback signal(LEDisense) from the at least one LED load; andresponding to the LED current feedback signalto maintain a predetermined current to the atleast one LED load.

15. The method of claim 14 further comprising:

sensing a voltage across a resistor (314) repre-senting a current through the at least one LEDload (304), wherein the voltage sensed acrossthe resistor (314) is the LED current feedbacksignal (LEDisense).

16. The method of claim 10 further comprising:

operating additional LED current control switch-es at respective control node-to-common node,absolute voltages less than or equal to 0.15times the link voltage relative to the commonvoltage reference node (Vcom), wherein eachLED current control switch (310, 1504) is adapt-ed to control the current through a respectivechain of LEDs of the at least one LED load (304,

304.0-304.N) and wherein each chain of LEDsincludes at least one LED;receiving a LED current feedback signal repre-senting a respective current conducted by eachLED current control switch; andcontrolling the conductivity of each LED currentcontrol switch (310, 1504) with the integratedcircuit PFC and LED drive controller in responseto the respective LED current feedback signal.

17. The method of claim 16 wherein controlling the con-ductivity of each LED current control switch (310,1504) with the integrated circuit PFC and LED drivecontroller in response to the respective LED currentfeedback signal comprises:

determining during separate periods of time therespective currents conducted by each LED cur-rent control switch.

18. The method of claim 10 further comprising:

receiving a dimmer signal; andwherein controlling the conductivity of the PFCswitch (308, 1502) and the LED current controlswitch (310, 1504) further comprises:

concurrently controlling the conductivity ofthe PFC switch and the LED current controlswitch in accordance with changes in a dim-ming level indicated by the dimmer signal.

19. The method of claim 10 wherein the control node-to-common node, absolute voltage is less than orequal to approximately 15% of the link voltage (VC1)to the common voltage reference node (Vcom).

Patentansprüche

1. Leuchtdiode, LED, Beleuchtungssystem mit:

mindestens einer LED-Last (304, 304.0-304.N)mit mindestens einer LED (602);einen LED-Rückkopplungsknoten (313), der an-gepasst ist, um ein LED-Stromrückkopplungs-signal (LEDisense) zu Verfügung zu stellen diemindestens einen Strompegel in der mindes-tens einen LED-Last repräsentiert und;einen PFC-Schalter (308, 1502);einen LED-Stromsteuerschalter (310, 1504),der dazu ausgelegt ist den Strom in der mindes-tens einen LED-Last zu steuerneine integrierte Leistungsfaktorkorrektur, PFGund LED-Laufwerk eine integrierte Schaltungs-leistungsfaktorkorrektur, PFG und eine LED-Antriebssteuerung (305, 1512), dadurch ge-kennzeichnet, dass die Steuerung folgendes

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umfasst:

einen digitalen Signalprozessor (DSP), dermit dem LED-Rückkopplungsknoten (313)gekoppelt und konfiguriert ist um:

von einer digitalen Versorgungsspan-nung zu arbeiten;ein PFC-Steuersignal (CS1D) zu erzeu-gen; undein LED-Stromsteuersignal (CS2D) zuerzeugen;einen ersten Puffer (307), der mit demdigitalen Signalprozessor gekoppeltund konfiguriert ist um:

von einer mittleren Versorgungs-spannung (Vaux) zu arbeiten,wobei die mittlere Versorgungs-spannung größer als die digitalePegelversorgungsspannung istdas PFC-Steuersignals zu emp-fangen (CS1D); unddas PFC-Steuersignal (CS1D) indas PFC-Schalter-Steuersignal(CS1) umzuwandeln, um die Leit-fähigkeit des PFC-Schalters zusteuern; undeinen zweiten Puffer (309), der mitdem digitalen Signalprozessor ge-koppelt und konfiguriert ist um:

von der mittleren Versor-gungsspannung aus zu arbei-ten;das LED-Stromsteuersignal(CS2D) zu empfangen; unddas LED-Stromsteuersignal(CS2D) in ein LED-Stromregel-schaltersignal (CS2) umzu-wandeln, um die Leitfähigkeitdes LED-Stromregelschalterszu steuern.

2. LED-Beleuchtungssystem nach Anspruch 1, fernerumfassend:

einen gemeinsamen Spannungsreferenzkno-ten (Vcom);einen ersten Spannungsquellenknoten, der da-zu ausgelegt ist, eine primäre Versorgungs-spannung (Vx) zu leiten;einen zweiten Spannungsquellenknoten, derdazu ausgelegt ist, eine Verbindungsspannung(VC1) des LED-Beleuchtungssystems zu leiten;wobei der PFC-Schalter (308, 1502) mit demgemeinsamen Spannungsreferenzknoten(Vcom) und dem ersten Spannungsquellenkno-

ten gekoppelt ist; undwobei der LED-Stromsteuerschalter (310,1504) mit dem gemeinsamen Spannungsrefe-renzknoten (Vcom) und dem zweiten Span-nungsquellenknoten gekoppelt ist;wobei während des normalen Betriebs des LED-Beleuchtungssystems der PFC-Schalter undein LED-Stromsteuerschalter jeweils einenSteuerknoten -zu-gemeinsamen Knoten auf-weisen, wobei absolute Spannungen die inte-grierte Schaltung PFC- und LED-Antriebssteu-erung zur Steuerung der Leitfähigkeit der Schal-ter und eine Leistungsfaktorkorrektur zur Verfü-gung stellen und für jede, durch ein Dimmersi-gnal (Dv) angezeigte Dimmstufe, einen annä-hernd konstanten Strom an die mindestens eineLED-Last liefern.

3. LED-Beleuchtungssystem nach Anspruch 2, wobeider Steuerknoten-zu-gemeinsame Knoten, die Ab-solutspannungen des PFC-Schalters (308, 1502)und der LED-Stromsteuerschalter (310, 1504) klei-ner oder gleich dem 0,15-fachen einer Spannungder zweites Spannungsquellenknoten relativ zu ei-ner Spannung an der Gemeinsamer Spannungsre-ferenzknoten (Vcom) sind.

4. LED-Beleuchtungssystem nach Anspruch 2, wobei:

der PFC-Schalter (308, 1502) und der LED-Stromsteuerschalter (310, 1504) Mitglieder derGruppe sind, bestehend aus: Feldeffekttransis-toren und Bipolartransistoren mit isoliertemGate.

5. LED-Beleuchtungssystem nach Anspruch 2 oder 3,ferner umfassend:

eine Stromerfassungseinrichtung (314), die mitdem LED-Stromsteuerschalter (310, 1504) unddem gemeinsamen Spannungsreferenzknoten(Vcom) gekoppelt ist, wobei während des norma-len Betriebs des LED-Beleuchtungssystems ei-ne Spannung über der Stromerfassungseinrich-tung (314) kleiner oder gleich dem 0,15-facheneiner Spannung an dem zweiten Spannungs-quellenknoten relativ zu der Spannung am ge-meinsamen Spannungsreferenzknoten (Vcom)ist und wobei die Stromerfassungseinrichtung(314) konfiguriert ist, um das LED-StromRück-kopplungssignal zum Steuern des LED-Strom-steuerschalters bereitzustellen.

6. LED-Beleuchtungssystem nach Anspruch 5, fernerumfassend:

eine Mehrzahl von LED-Stromsteuerschaltern(1104.0-1104.N, 1204.0-1204.N), die den LED-

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Stromsteuerschalter enthalten, wobei jederLED-Stromsteuerschalter so konfiguriert ist,dass er einen Strom zu einem jeweiligen einerMehrzahl von mindestens einer LED-Last (304,304.0-304.N) steuert und mit dem gemeinsa-men Spannungsreferenzknoten (Vcom), demzweiten Spannungsquellenknoten und dem in-tegrierten Schaltkreis PFC und dem LED-An-triebsregler verbunden ist; undwobei die Stromerfassungseinrichtung (314) mitden LED-Stromsteuerschaltern gekoppelt istund wobei während des normalen Betriebs desBeleuchtungssystems die Stromerfassungsein-richtung (314) so konfiguriert ist, dass sie denStrom in allen LED-Stromsteuerschaltern zu er-fühlen und um das LED-Stromsignal (LEDisense)zur Verwendung durch die integrierte SchaltungPFC und LED-Antriebsregler zur Steuerung desStroms in allen LED-Stromregelschaltern be-reitzustellen.

7. Verfahren zum Steuern eines PFC-Schalters (308,1502) und eines LED-Stromsteuerschalters (310,1504) einer lichtemittierenden Diode, einer LED-Be-leuchtungsanlage wobei das LED-Beleuchtungs-system mindestens eine LED-Last (304,304.0-304.N) und einen LED-Rückkopplungsknoten(313) aufweist, der so ausgelegt ist, dass er ein LED-Stromrückkopplungssignal (LEDisense) bereitstellt,das mindestens einen Erfassungsstrompegel in demmindestens eine LED-Last repräsentiert, wobei diemindestens eine LED-Last mindestens eine LEDenthält, dadurch gekennzeichnet, dass das Ver-fahren umfasst:

betreiben eines digitalen Signalprozessors(DSP) einer integrierten Schaltungsleistungs-faktorkorrektur PFG und einer LED-Antriebs-steuerung (305, 1512) von einer digitalen Span-nungsversorgung indem die folgenden Schritteausführt werden:

erzeugen eines PFC-Steuersignals (CS1D);underzeugen eines LED-Stromsteuersignals(CS2D);betreiben eines ersten Puffers (307), der mitdem digitalen Signalprozessor von einerMittelpegel-Versorgungsspannung gekop-pelt ist, wobei die Mittelpegel-Versorgungs-spannung größer als die digitale Pegel-Ver-sorgungsspannung ist, indem die folgen-den Schritte durchgeführt werden:

empfangen des PFC-Steuersignals(CS1D); undUmwandlung des PFC - Steuersignals(CS1D) in das PFC - Schalter - Steuer-

signal (CS1) zur Steuerung der Leitfä-higkeit der PFC-Schalter;Betreiben eines zweiten Puffers (309),der mit dem digitalen Signalprozessorvon der Mittelpegel-Versorgungsspan-nung gekoppelt ist, durch Ausführender folgenden Schritte:

Empfangen des LED-Stromsteu-ersignals (CS2D); und Umwandelndes LED-Stromsteuersignals(CS2D) in ein LED-Stromsteuer-schaltersignal (CS2), um die Leit-fähigkeit des LED-Stromregel-schalters zu steuern.

8. Verfahren nach Anspruch 7, wobei der integrierteSchaltkreis PFC und der LED-Treiber-Controller(305, 1512) einen Spannungsrückkopplungsknotenenthalten, um ein Eingangsspannungs-Rückkopp-lungssignal zu empfangen, das einen Eingangs-spannungspegel darstellt, der an das LED-Beleuch-tungssystem geliefert wird, weiter umfassend:

Erzeugen des PFC-Steuersignals (CS1D) alsReaktion auf den Eingangsspannungspegel,der durch das Eingangsspannungs-Rückkopp-lungssignal repräsentiert wird; undErzeugen des LED-Stromsteuersignals (CS2D)in Reaktion auf den mindestens einen Strompe-gel, der durch das LED-Stromrückkopplungssi-gnal repräsentiert wird.

9. Verfahren nach Anspruch 7, wobei die Versorgungs-spannung des digitalen Pegels im Bereich von 3 Voltbis 8 Volt liegt, die Versorgungsspannung des Me-diumpegels im Bereich von 8 Volt bis 50 Volt liegtund der PFC-Schalter (308, 1502) zwischengeschal-tet ist die bei normalem Betrieb des LED-Beleuch-tungssystems von mindestens 100 Volt eine Span-nungsdifferenz aufweisen, und der LED-Stromregel-schalter (310, 1504) zwischen Spannungsknoten miteiner Spannungsdifferenz angekoppelt ist, die wäh-rend des normalen Betriebs des LED-Beleuchtungs-systems Mindestens 100volts beträgt.

10. Verfahren nach Anspruch 7, ferner umfassend:

Erzeugen einer Verbindungsspannung (VC1)aus einer primären Versorgungsspannung (Vx);Betreiben eines Schaltleistungswandlers (303,402) des LED-Beleuchtungssystems von derPrimärversorgungsspannung (Vx) relativ zu ei-nem gemeinsamen Spannungsreferenzknoten(Vcom), wobei der Schaltleistungswandler denPFC-Schalter (308, 1502) enthält;Betreiben des PFC-Schalters (308, 1502) an ei-nem Steuerknoten-zu-gemeinsamen Knoten,

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absolute Spannung, um dem integriertenSchaltkreis PFC und dem LED-Antriebsreglerzu ermöglichen, den PFC-Schalter zu steuernund eine Leistungsfaktorkorrektur für denSchaltleistungswandler vorzusehen;Betreiben des LED-Stromsteuerschalters (310,1504) an einem Steuerknoten-zu- gemeinsa-men Knoten, absolute Spannung, um dem inte-grierten Schaltkreis PFC und dem LED-An-triebsregler zu ermöglichen, den LED-Strom-steuerschalter zu steuern, um mindestens einenannähernd konstanten Strom zur LED-Last fürjeden Dimmwert zuzuführen, der durch ein Dim-mersignal angezeigt wird; undSteuern der Leitfähigkeit des PFC-Schalters(308, 1502) und des LED-Stromsteuerschalters(310, 1504) mit der integrierten PFC Schaltungund der LED-Antriebssteuerung (305, 1512).

11. Verfahren nach Anspruch 10, wobei:

Betreiben des PFC-Schalters (308, 1502) desSchaltleistungswandlers an einem Steuerkno-ten-zu-gemeinsamen Knoten, absolute Span-nung, um dem integrierten Schaltkreis PFC unddem LED-Antriebsregler die Steuerung desPFC-Schalters zu ermöglichen und eine Leis-tungsfaktorkorrektur für die Schaltleistung zuliefern Wandler umfasst das Betreiben des PFC-Schalters (308, 1502) an einem Steuerknoten-zu-gemeinsamen Knoten, eine absolute Span-nung, die kleiner oder gleich dem 0,15-fachender ersten Quellenspannung relativ zu dem ge-meinsamen Spannungsreferenzknoten (Vcom)ist; undBetreiben des LED-Stromsteuerschalters (310,1504) an einem Steuerknoten-zu- gemeinsa-men Knoten, absolute Spannung, um dem inte-grierten Schaltkreis PFC und dem LED-An-triebsregler zu ermöglichen, den LED-Strom-steuerschalter zu steuern, um dem mindestenseinen annähernd konstanten Strom zuzuführendie LED-Last für jeden Dimmpegel, der durchein Dimmersignal angezeigt wird, umfasst dasBetreiben des LED-Stromsteuerschalters (310,1504) an einem Steuerknoten-zu-gemeinsa-men Knoten, wobei die absolute Spannung klei-ner oder gleich dem 0,15-fachen der erstenQuellenspannung relativ zu dem gemeinsamenSpannungsreferenzknoten (Vcom) ist.

12. Verfahren nach Anspruch 10, wobei die PFC- undLED-Stromsteuerschalter Feldeffekttransistorenumfassen und die Leitfähigkeit des PFC-Schalters(308, 1502) und des LED-Stromsteuerschalters(310, 1504) steuern, wobei der integrierte Schalt-kreis PFC und der LED-Antriebsregler das Bereit-stellen des jeweiligen Tastverhältnisses umfassen,

das modifizierte Steuersignale zu Gates des PFC-Schalters und des LED-Stromregelschalters bereit-stellt.

13. Verfahren nach Anspruch 10, ferner umfassend:

Empfangen der Primärversorgungsspannung(Vx), wobei ein Wurzelmittelquadrat (RMS) derPrimärversorgungsspannung (Vx) größer alsdie Mittelpegelspannung ist;die Primärversorgungsspannung (Vx) zu ver-stärken um die Spannung (VC1) zu verbinden,wobei die Verstärkung der Primärversorgungs-spannung (Vx) ferner die Modulation der Leitfä-higkeit des PFC-Schalters (308, 1502) umfasst,um eine Leistungsfaktorkorrektur-Primärver-sorgungsspannung zu erzeugen.

14. Verfahren nach Anspruch 10, bei dem die Leitfähig-keit des LED-Stromsteuerschalters gesteuert wird(310, 1504) und ferner folgendes aufweist:

Empfangen des LED-Stromrückkopplungssig-nals (LEDisense) von der mindestens einen LED-Last; undReaktion auf das LED-Stromrückkopplungssig-nal, um einen vorbestimmten Strom auf der min-destens eine LED-Last aufrechtzuerhalten.

15. Verfahren nach Anspruch 14, ferner umfassend:

Erfassen einer Spannung über einenWiderstand (314), der einen Strom durch diemindestens eine LED-Last (304) darstellt, wobeidie über den Widerstand (314) erfassteSpannung das LED-Stromrückkopplungssignal(LEDisense) ist.

16. Verfahren nach Anspruch 10, ferner umfassend:

Betreiben von zusätzlichen LED-Stromregel-schalter an dem jeweiligen Steuerknoten-zu-ge-meinsamen Knoten, mit Absolutspannungenkleiner oder gleich dem 0,15-fachen der Verbin-dungsspannung relativ zu dem gemeinsamenSpannungsreferenzknoten (Vcom), wobei jederLED-Stromsteuerschalter (310, 1504) denStrom durch eine jeweilige Kette von LEDs dermindestens einen LED-Last (304, 304.0-304.N)steuert, und wobei jede Kette von LEDs mindes-tens eine LED enthält;Empfangen eines LED-Stromrückkopplungssi-gnals, das einen jeweiligen Strom darstellt, dervon jedem LED-Stromsteuerschalter geleitetwird; undSteuern der Leitfähigkeit jedes LED-Stromsteu-erschalters (310, 1504) mit der integriertenSchaltung PFC und der LED-Antriebssteuerung

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in Reaktion auf das jeweilige LED-Stromrück-kopplungssignal.

17. Verfahren nach Anspruch 16, wobei das Steuern derLeitfähigkeit jedes LED-Stromsteuerschalters (310,1504) mit der integrierten Schaltung PFC und derLED-Antriebssteuerung in Reaktion auf das jeweili-ge LED-Stromrückkopplungssignal folgendes um-fasst:

Bestimmen der jeweiligen Ströme während dergetrennten Zeiträume, die von jedem LED-Stromsteuerschalter durchgeführt werden.

18. Verfahren nach Anspruch 10, ferner umfassend:

Empfangen eines Dimmersignals; undwobei das Steuern der Leitfähigkeit des PFC-Schalters (308, 1502) und des LED-Stromsteu-erschalters (310, 1504) ferner folgendes um-fasst:

Gleichzeitiges Steuern der Leitfähigkeit desPFC-Schalters und des LED-Stromsteuer-schalters in Übereinstimmung mit Änderun-gen in einem Dimmpegel, der durch dasDimmersignal angezeigt wird.

19. Verfahren nach Anspruch 10, wobei der Steuerkno-ten-zu-gemeinsame Knoten, die absolute Spannungkleiner oder gleich etwa 15 % der Verbindungsspan-nung (VC1) zum gemeinsamen Spannungsreferenz-knoten (Vcom) ist.

Revendications

1. Système d’éclairage à diode électroluminescente,LED, comprenant :

au moins une charge à LED (304, 304.0-304.N)incluant au moins une LED (602) ;un noeud de rétroaction de LED (313) adaptépour fournir un signal de rétroaction de courantde LED (LEDisense) représentant au moins unniveau de courant dans l’au moins une chargeà LED ; etun commutateur à PFC (308, 1502) ;un commutateur de commande de courant deLED (310, 1504) adapté pour commander lecourant dans l’au moins une charge à LED ;une unité de commande d’excitation de LED età correction de facteur de puissance, PFC, àcircuit intégré (305, 1512), caractérisé en ceque l’unité de commande comprend :

un processeur de signal numérique (DSP),couplé au noeud de rétroaction de LED

(313), et configuré pour :

fonctionner à partir d’une tension d’ali-mentation de niveau numérique ;générer un signal de commande à PFC(CS1D) ; etgénérer un signal de commande decourant de LED (CS2D) ;un premier circuit tampon (307), coupléau processeur de signal numérique, etconfiguré pour :

fonctionner à partir d’une tensiond’alimentation de niveau moyen(Vaux),dans lequel la tension d’alimenta-tion de niveau moyen est supérieu-re à la tension d’alimentation de ni-veau numérique ;recevoir le signal de commande àPFC (CS1D) ; etconvertir le signal de commande àPFC (CS1D) en le signal de com-mande de commutateur à PFC(CS1) pour commander la conduc-tivité du commutateur à PFC ; etun second circuit tampon (309),couplé au processeur de signal nu-mérique, et configuré pour :

fonctionner à partir de la ten-sion d’alimentation de niveaumoyen ;recevoir le signal de comman-de de courant de LED (CS2D) ;etconvertir le signal de comman-de de courant de LED (CS2D)en un signal de commutateurde commande de courant deLED (CS2) pour commander laconductivité du commutateurde commande de courant deLED.

2. Système d’éclairage à LED selon la revendication1, comprenant en outre :

un noeud de référence de tension commune(Vcom) ;un premier noeud de source de tension adaptépour conduire une tension d’alimentation primai-re (Vx) ;un second noeud de source de tension adaptépour conduire une tension de liaison (VC1) dusystème d’éclairage à LED ;dans lequel le commutateur à PFC (308, 1502)est couplé au noeud de référence de tension

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commune (Vcom) et au premier noeud de sourcede tension ; etdans lequel le commutateur de commande decourant de LED (310, 1504) est couplé au noeudde référence de tension commune (Vcom) et ausecond noeud de source de tension ;dans lequel, durant le fonctionnement normaldu système d’éclairage à LED, le commutateurà PFC et un commutateur de commande de cou-rant de LED possèdent des tensions absoluesrespectives noeud de commande-à-noeudcommun qui permettent à l’unité de commanded’excitation de LED et à PFC à circuit intégré decommander la conductivité des commutateurset fournir une correction de facteur de puissanceet fournir un courant approximativement cons-tant à l’au moins une charge à LED pour chaqueniveau de gradation d’intensité lumineuse indi-qué par un signal de gradateur d’intensité lumi-neuse (DV).

3. Système d’éclairage à LED selon la revendication2, dans lequel les tensions absolues noeud de com-mande-à-noeud commun du commutateur à PFC(308, 1502) et du commutateur de commande decourant de LED (310, 1504) sont inférieures ou éga-les à 0,15 fois une tension au second noeud de sour-ce de tension par rapport à une tension au noeud deréférence de tension commune (Vcom).

4. Système d’éclairage à LED selon la revendication2, dans lequel :

le commutateur à PFC (308, 1502) et le com-mutateur de commande de courant de LED(310, 1504) sont des membres du groupe cons-titué de : transistors à effet de champ et transis-tors bipolaires à porte isolée.

5. Système d’éclairage à LED selon la revendication 2ou 3, comprenant en outre :

un dispositif de détection de courant (314) cou-plé au commutateur de commande de courantde LED (310, 1504) et au noeud de référencede tension commune (Vcom), dans lequel, durantle fonctionnement normal du système d’éclaira-ge à LED, une tension sur le dispositif de détec-tion de courant (314) est inférieure ou égale à0,15 fois une tension au second noeud de sour-ce de tension par rapport à la tension au noeudde référence de tension commune (Vcom) etdans lequel le dispositif de détection de courant(314) est configuré pour fournir le signal de cou-rant de LED pour commander le commutateurde commande de courant de LED.

6. Système d’éclairage à LED selon la revendication

5, comprenant en outre :

une pluralité de commutateurs de commandede courant de LED (1104.0-1104.N,1204.0-1204.N) incluant le commutateur decommande de courant de LED, dans lequel cha-que commutateur de commande de courant deLED est configuré pour commander le courantà l’une respective parmi une pluralité de l’aumoins une charge à LED (304, 304.0-304.N) etest couplé au noeud de référence de tensioncommune (Vcom), au second noeud de sourcede tension, et à l’unité de commande d’excitationde LED et à PFC à circuit intégré ; etdans lequel le dispositif de détection de courant(314) est couplé aux commutateurs de com-mande de courant de LED, et dans lequel, du-rant le fonctionnement normal du systèmed’éclairage, le dispositif de détection de courant(314) est configuré pour détecter le courant dansla totalité des commutateurs de commande decourant de LED et pour fournir le signal de cou-rant de LED (LEDisense) pour l’utilisation parl’unité de commande d’excitation de LED et àPFC à circuit intégré pour commander le courantdans la totalité des commutateurs de comman-de de courant de LED.

7. Procédé pour commander un commutateur à PFC(308, 1502) et un commutateur de commande decourant de LED (310, 1504) d’un système d’éclaira-ge à diode électroluminescente, dans lequel le sys-tème d’éclairage à LED comprend au moins unecharge à LED (304, 304.0-304.N) et un noeud derétroaction de LED (313) adapté pour fournir un si-gnal de rétroaction de courant de LED (LEDisense)représentant au moins un niveau de courant dansl’au moins une charge à LED, dans lequel l’au moinsune charge à LED inclut au moins une LED, carac-térisé en ce que le procédé comprend :

le fonctionnement d’un processeur de signal nu-mérique (DSP) d’une unité de commande d’ex-citation de LED et à correction de facteur depuissance, PFC, à circuit intégré (305, 1512) àpartir d’une tension d’alimentation de niveau nu-mérique en réalisant les étapes de :

la génération d’un signal de commande àPFC (CS1D) ; etla génération d’un signal de commande decourant de LED (CS2D) ;le fonctionnement d’un premier circuit tam-pon (307), couplé au processeur de signalnumérique à partir d’une tension d’alimen-tation de niveau moyen, dans lequel la ten-sion d’alimentation de niveau moyen est su-périeure à la tension d’alimentation de ni-

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veau numérique, en réalisant les étapesde :

la réception du signal de commande àPFC (CS1D) ; etla conversion du signal de commandeà PFC (CS1D) en le signal de comman-de de commutateur à PFC (CS1) pourcommander la conductivité du commu-tateur à PFC;le fonctionnement d’un second circuittampon (309), couplé au processeur designal numérique à partir de la tensiond’alimentation de niveau moyen, enréalisant les étapes de :

la réception du signal de comman-de de courant de LED (CS2D) ; etla conversion du signal de com-mande de courant de LED (CS2D)en un signal de commutateur decommande de courant de LED(CS2) pour commander la conduc-tivité du commutateur de comman-de de courant de LED.

8. Procédé selon la revendication 7, dans lequel l’unitéde commande d’excitation de LED et à PFC à circuitintégré (305, 1512) inclut un noeud de rétroactionde tension pour recevoir un signal de rétroaction detension d’entrée représentant un niveau de tensiond’entrée fourni au système d’éclairage à LED, com-prenant en outre :

la génération du signal de commande à PFC(CS1D) en réponse au niveau de tension d’en-trée représenté par le signal de rétroaction detension d’entrée ; etla génération du signal de commande de cou-rant de LED (CS2D) en réponse à l’au moins unniveau de courant représenté par le signal derétroaction de courant de LED.

9. Procédé selon la revendication 7, dans lequel la ten-sion d’alimentation de niveau numérique est dans laplage de 3 volts à 8 volts, la tension d’alimentationde niveau moyen est dans la plage de 8 volts à 50volts, et le commutateur à PFC (308, 1502) est cou-plé entre des noeuds de tension possédant une dif-férence de tension durant le fonctionnement normaldu système d’éclairage à LED d’au moins 100 volts,et le commutateur de commande de courant de LED(310, 1504) est couplé entre des noeuds de tensionpossédant une différence de tension durant le fonc-tionnement normal du système d’éclairage à LEDd’au moins 100 volts.

10. Procédé selon la revendication 7, comprenant en

outre :

la génération d’une tension de liaison (VC1) àpartir d’une tension d’alimentation primaire(Vx) ;le fonctionnement d’un convertisseur de puis-sance de commutation (303, 402) du systèmed’éclairage à LED à partir de la tension d’alimen-tation primaire (Vx) par rapport à un noeud deréférence de tension commune (Vcom), dans le-quel le convertisseur de puissance de commu-tation inclut le commutateur à PFC (308, 1502) ;le fonctionnement du commutateur à PFC (308,1502) à une tension absolue noeud de comman-de-à-noeud commun pour permettre à l’unité decommande d’excitation de LED et à PFC à cir-cuit intégré de commander le commutateur àPFC et fournir une correction de facteur de puis-sance pour le convertisseur de puissance decommutation ;le fonctionnement du commutateur de comman-de de courant de LED (310, 1504) à une tensionabsolue noeud de commande-à-noeud com-mun pour permettre à l’unité de commande d’ex-citation de LED et à PFC à circuit intégré decommander le commutateur de commande decourant de LED de fournir un courant approxi-mativement constant à l’au moins une charge àLED pour chaque niveau de gradation d’inten-sité lumineuse indiqué par un signal de grada-teur d’intensité lumineuse ; etla commande de la conductivité du commuta-teur à PFC (308, 1502) et du commutateur decommande de courant de LED (310, 1504) avecl’unité de commande d’excitation de LED et àPFC à circuit intégré (305, 1512).

11. Procédé selon la revendication 10, dans lequel :

le fonctionnement du commutateur à PFC (308,1502) du convertisseur de puissance de com-mutation à une tension absolue noeud de com-mande-à-noeud commun pour permettre à l’uni-té de commande d’excitation de LED et à PFCà circuit intégré de commander le commutateurà PFC et fournir une correction de facteur depuissance pour le convertisseur de puissancede commutation comprend le fonctionnementdu commutateur à PFC (308, 1502) à une ten-sion absolue noeud de commande-à-noeudcommun inférieure ou égale à 0,15 fois la pre-mière tension de source par rapport au noeudde référence de tension commune (Vcom) ; etle fonctionnement du commutateur de comman-de de courant de LED (310, 1504) à une tensionabsolue noeud de commande-à-noeud com-mun pour permettre à l’unité de commande d’ex-citation de LED et à PFC à circuit intégré de

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commander le commutateur de commande decourant de LED pour fournir un courant approxi-mativement constant à l’au moins une charge àLED pour chaque niveau de gradation d’inten-sité lumineuse indiqué par un signal de grada-teur d’intensité lumineuse comprend le fonction-nement du commutateur de commande de cou-rant de LED (310, 1504) à une tension absoluenoeud de commande-à-noeud commun infé-rieure ou égale à 0,15 fois la première tensionde source par rapport au noeud de référence detension commune (Vcom).

12. Procédé selon la revendication 10, dans lequel lescommutateurs à PFC et de commande de courantcomprennent des transistors à effet de champ et lacommande de la conductivité du commutateur àPFC (308, 1502) et du commutateur de commandede courant de LED (310, 1504) avec l’unité de com-mande d’excitation de LED et à PFC à circuit intégrécomprend la fourniture de signaux de commandemodifiés respectifs de cycle de service à des portesdu commutateur à PFC et du commutateur de com-mande de courant de LED.

13. Procédé selon la revendication 10, comprenant enoutre :

la réception de la tension d’alimentation primaire(Vx), dans lequel une valeur de moyenne qua-dratique (RMS) de la tension d’alimentation pri-maire (Vx) est supérieure à la tension de niveaumoyen ;l’augmentation de la tension d’alimentation pri-maire (Vx) à la tension de liaison (VC1), danslequel l’augmentation de la tension d’alimenta-tion primaire (Vx) comprend en outre la modu-lation de la conductivité du commutateur à PFC(308, 1502) pour générer une tension d’alimen-tation primaire à facteur de puissance corrigée.

14. Procédé selon la revendication 10, dans lequel lacommande de la conductivité du commutateur decommande de courant de LED (310, 1504) com-prend en outre :

la réception du signal de rétroaction de courantde LED (LEDisense) à partir de l’au moins unecharge à LED ; etla réponse au signal de rétroaction de courantde LED pour maintenir un courant prédéterminéà l’au moins une charge à LED.

15. Procédé selon la revendication 14, comprenant enoutre :

la détection d’une tension sur une résistance(314) représentant un courant à travers l’au

moins une charge à LED (304), dans lequel latension détectée sur la résistance (314) est lesignal de rétroaction de courant de LED(LEDisense).

16. Procédé selon la revendication 10, comprenant enoutre :

le fonctionnement de commutateurs de com-mande de courant de LED supplémentaires àdes tensions absolues respectives noeud decommande-à-noeud commun inférieures ouégales à 0,15 fois la tension de liaison par rap-port au noeud de référence de tension commune(Vcom), dans lequel chaque commutateur decommande de courant de LED (310, 1504) estadapté pour commander le courant à traversune chaîne respective de LEDs de l’au moinsune charge à LED (304, 304.0-304.N) et danslequel chaque chaîne de LEDs inclut au moinsune LED ;la réception d’un signal de rétroaction de courantde LED représentant un courant respectif con-duit par chaque commutateur de commande decourant de LED ; etla commande de la conductivité de chaque com-mutateur de commande de courant de LED(310, 1504) avec l’unité de commande d’excita-tion de LED et à PFC à circuit intégré en réponseau signal respectif de rétroaction de courant deLED.

17. Procédé selon la revendication 16, dans lequel lacommande de la conductivité de chaque commuta-teur de commande de courant de LED (310, 1504)avec l’unité de commande d’excitation de LED et àPFC à circuit intégré en réponse au signal respectifde rétroaction de courant de LED comprend :

la détermination, durant des périodes séparées,des courants respectifs conduits par chaquecommutateur de commande de courant de LED.

18. Procédé selon la revendication 10, comprenant enoutre :

la réception d’un signal de gradateur d’intensitélumineuse ; etdans lequel la commande de la conductivité ducommutateur à PFC (308, 1502) et du commu-tateur de commande de courant de LED (310,1504) comprend en outre :

la commande simultanée de la conductivitédu commutateur à PFC et du commutateurde commande de courant de LED confor-mément à des changements d’un niveau degradation d’intensité lumineuse indiqué par

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le signal de gradateur d’intensité lumineu-se.

19. Procédé selon la revendication 10, dans lequel latension absolue noeud de commande-à-noeud com-mun est inférieure ou égale à approximativement 15% de la tension de liaison (VC1) par rapport au noeudde référence de tension commune (Vcom).

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the reader’s convenience only. It does not form part of the Europeanpatent document. Even though great care has been taken in compiling the references, errors or omissions cannot beexcluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

• US 20090085625 A [0003]• US 20080272744 A [0004]• US 20080272745 A [0005]• US 20080272755 A [0006]

• US 20080272747 A [0007]• US 20080272746 A [0008]• US 2005218838 A1 [0009]

Non-patent literature cited in the description

• Compensator Design and Stability Assessment forFast Voltage Loops of Power Factor Correction Rec-tifiers. IEEE Transactions on Power Electronics, Sep-tember 2007, vol. 22 (5), 1719-1729 [0019]

• SCHREIER ; TEMES. Understanding Delta-SigmaData Converters. IEEE Press, 2005 [0053]

• Cirrus Logic Inc. [0053]