An Integrated High Efficiency Ultra-low Power DC/AC...
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An Integrated High Efficiency Ultra-low Power DC/AC Inverter for Liquid Crystal Driving in Electro-optic Diffractive Lenses Xiaomin Li and Dr. Alex Huang ECE, North Carolina State University Abstract Methods • An integrated high efficiency, ultra-low power liquid crystal driver for electro-optic diffractive lenses[1] is presented in this poster. The proposed LC driver provides an adjustable 3V to 15V RMS square wave output voltage to drive a liquid crystal in the electro-optic lens, which can be modeled as a 5nF capacitive load. This application is powered by a 3V lithium button cell or energy harvest devices. • Implemented in a 0.25μm 5V VGS, 12-45V VDS BCD technology, the proposed LC driver achieves peak power efficiency of 98%. The transaction time of LC driver output from high to low is 48us, which is 219 times faster than that when auto-sink scheme is disabled. • A reconfigurable hysteretic 2×/3×/4×/5× switched capacitor charge pump is developed for DC-DC conversion to enhance the power efficiency over a wide input-output voltage range. • An improved full bridge driving scheme is developed to reduce the DC/AC inversion power loss. • An auto-sink scheme is developed to speed up output transaction from high to low in different output modes. Objective • Maintain high power efficiency over the entire output voltage and load current range. • Compact system profile and low EMI noise. • Ultra-low power consumption control circuitry and fast response time. C1 C2 C3 V DC + - + - + - G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 C4 G11 G12 G13 + - + - 0 +V DC -V DC V IN Reconfigurable 2×/3×/4×/5× Charge Pump H-Bridge Inverter S1 S4 S2 S3 High Speed Level Shifters Low Speed Level Shifters C CP C LC G1 G2 G3 G13 S1 S2 S3 S4 2×3×4×5× Adaptive Control Fast Sink H-Bridge Control Flash ADC VREF Oscillator Frequency Divider Control Circuitry V OUT A V OUT B V OUT A -V OUT B G18 G18 Dead Time Control Figure1: Structure of the proposed LC driver 3X C1 C2 C3 + - + - + - G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 C4 G11 G12 G13 + - V DC V IN C1 C2 C3 + - + - + - G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 C4 G11 G12 G13 + - V DC V IN C CP C CP V IN 2X C1 C2 C3 + - + - + - G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 C4 G11 G12 G13 + - V DC C1 C2 C3 + - + - + - G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 C4 G11 G12 G13 + - V DC V IN C CP C CP φ A φ B 4X C1 C2 C3 + - + - + - G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 C4 G11 G12 G13 + - V IN V DC C1 C2 C3 + - + - + - G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 C4 G11 G12 G13 + - V DC C CP C CP φ A φ B V IN C1 C2 C3 + - + - + - G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 C4 G11 G12 G13 + - 5X C CP C1 C2 C3 + - + - + - G1 G2 G3 G4 G5 G6 G7 G8 G9 G10 C4 G11 G12 G13 + - V DC V DC V IN V IN C CP φ A φ B Figure 2: Operation of the proposed reconfigurable 2×/3×/4×/5× switched capacitor CP
Transcript of An Integrated High Efficiency Ultra-low Power DC/AC...
An Integrated High Efficiency Ultra-low Power DC/AC Inverter for Liquid Crystal Driving in Electro-optic Diffractive Lenses
Xiaomin Li and Dr. Alex HuangECE, North Carolina State University
Abstract Methods
• An integrated high efficiency, ultra-low powerliquid crystal driver for electro-optic diffractivelenses[1] is presented in this poster. Theproposed LC driver provides an adjustable 3Vto 15V RMS square wave output voltage todrive a liquid crystal in the electro-optic lens,which can be modeled as a 5nF capacitive load.This application is powered by a 3V lithiumbutton cell or energy harvest devices.• Implemented in a 0.25μm 5V VGS, 12-45VVDS BCD technology, the proposed LC driverachieves peak power efficiency of 98%. Thetransaction time of LC driver output from highto low is 48us, which is 219 times faster thanthat when auto-sink scheme is disabled.
• A reconfigurable hysteretic 2×/3×/4×/5× switchedcapacitor charge pump is developed for DC-DC conversionto enhance the power efficiency over a wide input-outputvoltage range.• An improved full bridge driving scheme is developed toreduce the DC/AC inversion power loss.• An auto-sink scheme is developed to speed up outputtransaction from high to low in different output modes.
Objective
• Maintain high power efficiency over the entireoutput voltage and load current range.• Compact system profile and low EMI noise.• Ultra-low power consumption control circuitryand fast response time.
C1 C2 C3 VDC
+- +- +-
G1 G2 G3 G4 G5
G6 G7 G8
G9 G10
C4
G11 G12
G13
+- +
-
0
+VDC
-VDC
VIN
Reconfigurable 2×/3×/4×/5× Charge Pump H-Bridge Inverter
S1 S4
S2 S3
High Speed Level Shifters Low Speed Level Shifters
CCPCLC
G1 G2 G3 G13 S1 S2 S3 S4
2×3×4×5×Adaptive Control
Fast
SinkH-Bridge Control
Flash
ADC
VREF
OscillatorFrequency
Divider
Control Circuitry
VOUTA
VOUTB
VOUTA-VOUTB
G18
G18
Dead Time
Control
Figure1: Structure of the proposed LC driver
3X
C1 C2 C3
+- +- +-
G1 G2 G3 G4 G5
G6 G7 G8
G9 G10
C4
G11 G12
G13
+-
VDC
VIN
C1 C2 C3
+-+-+-
G1 G2 G3 G4 G5
G6 G7 G8
G9 G10
C4
G11 G12
G13
+-
VDC
VIN
CCP
CCP
VIN
2X
C1 C2 C3
+- +- +-
G1 G2 G3 G4 G5
G6 G7 G8
G9 G10
C4
G11 G12
G13
+-
VDC
C1 C2 C3
+-+-+-
G1 G2 G3 G4 G5
G6 G7 G8
G9 G10
C4
G11 G12
G13
+-
VDC
VIN
CCP
CCP
φA
φB
4X
C1 C2 C3
+- +- +-
G1 G2 G3 G4 G5
G6 G7 G8
G9 G10
C4
G11 G12
G13
+-
VIN
VDC
C1 C2 C3
+-+-+-
G1 G2 G3 G4 G5
G6 G7 G8
G9 G10
C4
G11 G12
G13
+-
VDC
CCP
CCP
φA
φB
VIN
C1 C2 C3
+- +- +-
G1 G2 G3 G4 G5
G6 G7 G8
G9 G10
C4
G11 G12
G13
+-
5X
CCP
C1 C2 C3
+-+-+-
G1 G2 G3 G4 G5
G6 G7 G8
G9 G10
C4
G11 G12
G13
+-
VDC
VDC
VIN
VIN
CCP
φA
φB
Figure 2: Operation of the proposed reconfigurable
2×/3×/4×/5× switched capacitor CP
An Integrated High Efficiency Ultra-low Power DC/AC Inverter for Liquid Crystal Driving in Electro-optic Diffractive Lenses
Xiaomin Li and Dr. Alex HuangECE, North Carolina State University
Implementation Results
Conclusions
References
2X
/3X
/4X
/5X
SC
-CP
P
ower
Sta
ge
Inverter Power Stage
Leve
l Sh
ifte
rs
Flas
hA
DC
Com
p
Bia
sin
gOSC & ClkGen
Fast
-sin
k
1890μm
177
0μm
Figure 3: Chip microphotograph of the proposed LC driver
• Die area including all test pads is 3.3mm2. Allpowertrain transistors and the control circuitry areintegrated into this chip.•The package of the LC driver is a 5mm×5mm QFN.External components of the LC driver includes four100nF external flying capacitors and one 1μFoutput capacitor.
(a) (b)
(c) (d)
Figure 4: Measured output voltages of the proposed LC driver when (a) output step up 2x-
>3x->4x->5x; (b) measured output ripple; (c) output step down 5x->4x->3x->2x without fast-
sink; (d) output step down 5x->4x->3x->2x with fast-sink;
• Figure 4 shows the output ripple is 116mV. The falling time from ahigher output voltage to a lower output voltage is 10.5ms and 48μswithout and with fast-sink enable, respectively.•Figure 5 shows the measured power efficiency of the proposed LCdriver. The measured peak efficiency is 98%.
Figure 5: Measured power efficiencies
•However, on the boundary of differentVCRs, the switching frequency of CPincreased significantly thus efficiencydips can be observed.
•The verified silicon results show the LCdriver is suitable to be used in electro-optic lenses applications.
[1]Guoqiang Li et al., “High-efficiencyswitchable flat diffractive ophthalmiclens with three-layer electrode patternand two-layer via structures,” AppliedPhysics Letters, vol. 90, 111005, March2007.
