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![Page 1: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/1.jpg)
Class-D Audio Power Amplifier
Chun Wei Lin
![Page 2: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/2.jpg)
2015/2/11
MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
2
Outline
Introduction & background
Linear control v.s Switching control class-D audio amplifier
Modulator designs
Power stage designs
Low-pass (LC) filter designs
OC/OV/OT protections
Four switching power amplifier designs & results
Conclusions
![Page 3: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/3.jpg)
2015/2/11
MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Overview of Audio Systems
Technology trends
Compact and portable
High power efficiency
High fidelity (Hi-Fi)
Higher sampling frequency
Various digital media
Audio compression algorithms
![Page 4: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/4.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Objective of Audio Amplifier
Goal :
Reproducing input audio signals at sound-producing
output elements (i.e. loudspeakers, headphones)
with desired volume and power level.
Golden guidelines to designer
Efficient power delivery
Linear signal reproduction
![Page 5: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/5.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Class-A audio amplifier (High-end audio system - expensive)
Advantage: Low distortion(fully linear amplifier)
Disadvantage: Quiescent power dissipation,
poor efficiency, large heat-sink area
Class-A Audio Amplifier
refI
refILR
Iv
Ov1Ei
1Q
2Q
Li
CCV
CCV
2 3 4 t0
CQI
Ci
%254
1
4
2
CCLref
m
VRI
V
Duty Ratio=100%
![Page 6: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/6.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Class-B Audio Amplifier
Class-B audio amplifier
Advantage: No quiescent power dissipation,
up to 78.5% power efficiency!
Disadvantage: Crossover distortion
Iv Ov
LR
CCV
CCV
NQ
PQ Li
2 3 4 t0
Ci
%5.7844
CC
m
V
V
Duty Ratio=50%
B
E
B
![Page 7: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/7.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Class-AB Audio Amplifier
Class-AB audio amplifier
Advantage: up to 78.5% power efficiency and low distortion
2 3 4 t0
Ci
CQI
Iv
Ov
LR
refI
NQ
PQ Li
Ni
Pi
CCV
CCV
%5.7844
CC
m
V
V
50%<Duty Ratio<100%
![Page 8: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/8.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Switching Amp. v.s Linear Amp.
In today’s applications, the switching amplifier
is widely used because it features …
Theoretically 100% power efficiency
Less heat
Low cost
Hi-Fi (reach the industry standard of class AB )
Suitable for portable, fairy and quality device
![Page 9: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/9.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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+𝑉𝑆
Class-D (switching) audio amplifier
Advantage: high power efficiency (up to 90%), no heat sink
Disadvantage: large distortion originated from fast two-level
switching
Class-D Audio Amplifier
Gate
Drivers 𝑉𝑖𝑛
𝑉𝑠𝑤
𝑉𝑜𝑢𝑡
−𝑉𝑆
𝐿𝑜
𝐶𝑜 𝑅𝐿
Power Stage Modulator Low-Pass Filter
Modulator
![Page 10: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/10.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Power Efficiency v.s Output Power
0
20
40
60
80
100
0.0 0.2 0.4 0.6 0.8 1.0
Class-A ideal Class-B ideal Class-D simulated
Normalized output power (PL / PLMAX)
Po
wer
E
ffic
ien
cy (%
) Class-D audio amplifier features high power efficiency over a wide
range of power demand.
![Page 11: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/11.jpg)
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The switching operation of power amplifier brings undesired
distortion originated from I. the sudden request of two-level
control signal and II. the nonlinearities of power transistors.
Distortion Sources
Gate
Drivers
Low-pass
Filter 𝑉𝑜𝑢𝑡
𝑉𝑠𝑤
𝑅𝐿 𝐶𝑜
𝐿𝑜
+𝑉𝑠
−𝑉𝑠
tD,ON tD,OFF
RDS,ON
finite dV/dt
I
II
![Page 12: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/12.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Outline
Introduction & background
Linear control v.s Switching control class-D amplifier (CDA)
Modulator designs PWM, SDM, SMC
Power stage designs
Low-pass (LC) filter designs
OC/OV/OT protections
Four switching power amplifier designs & results
Conclusions
![Page 13: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/13.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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I. Pulse-Width Modulation (PWM) CDA 1/6
PWM
modulator
Low-pass
filter (LC) VIN VOUT
∆𝐼
Distortion
sources
𝑅𝐿
+
–
VIN
VC
VIN
VC
VPWM
VPWM
+𝑉𝑠
−𝑉𝑠
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I. Pulse-Width Modulation (PWM) CDA 2/6
PWM
modulator
Switching
power stage
Low-pass
filter (LC) VOUT
∆𝐼
𝑅𝐿
Verr VIN
+
Feedback compensation for minimizing the difference between
input and output signals.
– +
Loop
Filter
Feedback
compensation
![Page 15: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/15.jpg)
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I. Pulse-Width Modulation (PWM) CDA 3/6
M.A. Telechuk, A. Gribben, and C. Amadi, “True Filterless Class-D Audio Amplifier,” IEEE J. Solid-State
Circuits (JSSC), vol. 46, no. 12, pp. 2784 - 2793, Dec. 2011.
Feedback compensation, loop filter, Uniform PWM sampling
UPWM
modulator
+
–
+ –
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I. Pulse-Width Modulation (PWM) CDA 4/6
M.A. Telechuk, A. Gribben, and C. Amadi, “True Filterless Class-D Audio Amplifier,” IEEE J. Solid-State
Circuits (JSSC), vol. 46, no. 12, pp. 2784 - 2793, Dec. 2011.
I. Feedback, II. loop filter, III. Uniform PWM sampling
I II III
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I. Pulse-Width Modulation (PWM) CDA 5/6
M.A. Telechuk, A. Gribben, and C. Amadi, “True Filterless Class-D Audio Amplifier,” IEEE J. Solid-State
Circuits (JSSC), vol. 46, no. 12, pp. 2784 - 2793, Dec. 2011.
Two poles and one zero of loop filter
for higher audio band gain and better
distortion compensation.
147k 110k 221k
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I. Pulse-Width Modulation (PWM) CDA 6/6
Transfer function of loop filter:
Transfer function of amplifier:
Poles:
Zero:
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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II. Sigma Delta Modulation (SDM) CDA
SDM
modulator
Switching
power stage
Low-pass
filter (LC) Verr VOUT
+ VIN
+ -
Feedback
compensation
SDM applies feedback compensation inside modulator to
reduce the difference between input and output signals.
𝑅𝐿
![Page 20: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/20.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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II.A Delta Modulation (DM) 1/6
A digital audio processing system includes a delta modulator
(DM) which is first proposed in 1952.
A 1-bit quantizer and a integrator are used in the feedback
path to reduce the difference, e, between input signal Si
and output signal So.
integrator
e
quantizer
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Two disadvantages limit its application. First, output signal
So can not follow if input signal Si changes fast.
Secondly, the value of output signal So is unknown if the
value of input signal Si is DC voltage.
II.A Delta Modulation (DM) 2/6
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1-bit quantizer Integrator Delta modulator
II.A Delta Modulation (DM) 3/6
Si
So
SΔ
require pulse streams
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1-bit quantizer Integrator Delta modulator
II.A Delta Modulation (DM) 4/6
Si
So
SΔ
Si
SΔ
So
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Si & SΔ
e
So
II.A Delta Modulation (DM) 5/6
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Input signal Modulated signal after filtering
II.A Delta Modulation (DM) 6/6
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Sigma delta modulator (SDM) is proposed by moving the
output filter of the delta modulator in front of the subtraction.
Thus, the two integrator can be shared as shown below.
Those problems of delta modulator (DM) can be resolved
in sigma delta modulator because the input signal changes
slowly and smoothly by the integrator.
II.B Sigma Delta Modulation (SDM) 1/6
Si So
SΔ
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A general 1st-order sigma-delta modulator
A general n-th order sigma delta modulator
II.B Sigma Delta Modulation (SDM) 2/6
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1-bit quantizer Integrator First-order SDM
II.B Sigma Delta Modulation (SDM) 3/6
Si
So
SΔ
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1-bit quantizer Integrator First-order SDM
II.B Sigma Delta Modulation (SDM) 4/6
Si
So
SΔ
Si
So
SΔ
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Si
e
So
II.B Sigma Delta Modulation (SDM) 5/6
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Input signal Modulated signal after filtering
II.B Sigma Delta Modulation (SDM) 6/6
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II. Design of 7-th SDM CDA
E. Gaalaas, B.Y. Liu, N. Nishimura, R. Adams, and K. Sweetland, “Integrated Stereo ΔΣ Class D
Amplifier,” IEEE J. Solid-State Circuits (JSSC), vol. 40, no. 12, pp. 2288 - 2397, Dec. 2005.
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III. Sliding-Mode Controller (SMC) CDA 1/6
SMC
controller
Switching
power stage
Low-pass
filter (LC) Verr VOUT
+ VIN
+ -
Feedback
compensation
𝑅𝐿
SMC implements error function and switching function into
controller for reducing distortion without raising sampling
frequency.
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III. Sliding-Mode Controller (SMC) CDA 2/6
SMC controller
error function
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III. Sliding-Mode Controller (SMC) CDA 3/6
SMC controller
switching function
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III. Sliding-Mode Controller (SMC) CDA 4/6
2 adder
1 adder
simplify
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III. Sliding-Mode Controller (SMC) CDA 5/6
Feedback compensation
SMC
= 𝑬𝟏 + α𝒔𝑬𝟏 = 𝑬𝟏 + α𝑬𝟐
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III. Sliding-Mode Controller (SMC) CDA 6/6
M.A. Rojas-Gonzalez and E. Sanchez-Sinencio, “Low-Power High-Efficiency Class D Audio Power
Amplifiers,” IEEE J. Solid-State Circuits (JSSC), vol. 44, no.12, pp. 3272 - 3284, Dec. 2009.
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Outline
Introduction & background
Linear control v.s Switching control class-D amplifier (CDA)
Modulator designs
Power stage designs SE, BTL / finger, waffle layout
Low-pass (LC) filter designs
OC/OV/OT protections
Four switching power amplifier designs & results
Conclusions
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Single-End (SE) Power Stage
VOUT VPWM
+VS
-VS
SH
SL
VPWM
VOUT
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Bridge-Tied-Load (BTL) Power Stage
VOUT+ VPWM+
VOUT- VPWM-
+VS
-VS
+VS
-VS
SH
SL
SH
SL
VPWM+
VPWM-
VPWM+
VPWM- VPWM+ - VPWM-
VOUT+ - VOUT-
VPWM+ - VPWM-
VOUT+ - VOUT-
3 levels 2 levels
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Layouts of Power Stage
I. finger
II. waffle
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Designs of Power Stage
The operation of power stage is simply turning on/off
power transistors.
But the design of power stage affects the efficiency on
power delivery because it is in charge to delivery heavy
current into speaker.
How to design the aspect ratio of power inverter for
higher power efficiency is very important.
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Outline
Introduction & background
Linear control v.s PWM control Class-D amplifier (CDA)
Modulator designs
Power stage designs
Low-pass (LC) filter design Butterworth filter
OC/OV/OT protections
Four switching power amplifier designs & results
Conclusions
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LPF Design for CDAs 1/5
12
1)(
2 sssH
LCs
RCs
LC
sQ
ssV
sVsH
i
o
11
1
)(
)()(
22
002
2
0
Butterworth
Filter
𝐿
C R
Frequency (hz)
Frequency response curve
Gai
n (
dB
)
Bessel
Butterworth
Chebyshev
Elliptic
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RC
RC
2
12
1
LCs
RCs
LC
sQ
ssV
sVsH
i
o
11
1
)(
)()(
22
002
2
0
LPF Design of CDAs 2/5
12
1)(
2
sssH
LC
10
LCf
2
10
RCQ 0
Rf
Q
R
QC
QRC
00
0
2
1
RC
LLC
21
11
Qf
R
Q
R
CL
LC
00
2
0
2
02
11
LCff oc
2
12
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Fig. 2.5b LPF Design of CDAs 3/5
12
1)(
2
sssH
LCs
RCs
LC
sQ
ssV
sVsH
i
o
4
1
4
14
1
)(
)()(
22
002
2
0
Butterworth
Filter
𝐿
C R
𝐿 C
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LCs
RCs
LC
sQ
ssV
sVsH
i
o
4
1
4
14
1
)(
)()(
22
002
2
0
LPF Design of CDAs 4/5
12
1)(
2
sssH
LC4
10
LCf
42
10
RCQ 40
RC
RC
24
12
4
1
Rf
Q
R
QC
QRC
00
0
2444
1
RC
LLC
244
11
4
1
Qf
R
Q
R
CL
LC
00
2
0
2
024
1
4
1
LCff oc
22
12
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LPF Design of CDAs 5/5
Choice of inductance
DC resistance Efficiency
Maximum peak current prevent short-circuit
EMI Shielding inductance
Choice of capacitance
Effective series resistance Q=Xc/ESR Q varies with freq.
))(2(2
2
LINDDSON
L
in
out
RRRI
RI
P
P
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Outline
Introduction & background
Linear control v.s PWM control Class-D amplifier (CDA)
Modulator designs
Power stage designs
Low-pass (LC) filter design
OC/OV/OT protections Detections, protections
Four switching power amplifier designs & results
Conclusions
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Safe Operation Area (SOA)
IMAX
+ BVDS
-
M. Berkhout, “Integrated overcurrent protection system for class-D audio power amplifiers,” IEEE J.
Solid-State Circuits, vol. 40, no. 11, pp. 2237–2245, 2005.
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Over-Current (OC) Condition 1/3
B. Krabbenborg, “Protection of audio amplifiers based on temperature measurements in power
transistors,” Proc. IEEE Int. Solid-State Circuits Conf. (ISSCC), pp. 374–375, 2003.
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Over-Current (OC) Condition 2/3
B. Krabbenborg, “Protection of audio amplifiers based on temperature measurements in power
transistors,” Proc. IEEE Int. Solid-State Circuits Conf. (ISSCC), pp. 374–375, 2003.
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Over-Current (OC) Condition 3/3
B. Krabbenborg, “Protection of audio amplifiers based on temperature measurements in power
transistors,” Proc. IEEE Int. Solid-State Circuits Conf. (ISSCC), pp. 374–375, 2003.
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Series resistors & comparators
If or
Over-current (OC)
condition happens!
Over-Current (OC) Detection 1/3
VRH VREF > VRL
M. Berkhout, “Integrated overcurrent protection system for class-D audio power amplifiers,” IEEE J.
Solid-State Circuits, vol. 40, no. 11, pp. 2237–2245, 2005.
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Over-Current (OC) Detection 2/3
Parallel MOS & comparators
If
or
Over-current (OC)
condition happens!
VOUT
>
< VRH
VOUT VRL
M. Berkhout, “Integrated overcurrent protection system for class-D audio power amplifiers,” IEEE J.
Solid-State Circuits, vol. 40, no. 11, pp. 2237–2245, 2005.
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Over-Current (OC) Detection 3/3
VSL VRL >
Over-current
condition
happens!
Parallel sensing
M. Berkhout, “Integrated overcurrent protection system for class-D audio power amplifiers,” IEEE J.
Solid-State Circuits, vol. 40, no. 11, pp. 2237–2245, 2005.
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Over-Current (OC) Protection
Turning opposite power transistor when OC happens
Current limiting at 4Ω and 2Ω
M. Berkhout, “Integrated overcurrent protection system for class-D audio power amplifiers,” IEEE J.
Solid-State Circuits, vol. 40, no. 11, pp. 2237–2245, 2005.
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Over-Voltage (OV) Protections
𝑉𝑖𝑛
𝑉 𝑜𝑢𝑡
𝑉 𝑈𝐿1 𝑉 𝑈
𝐿2
𝑉𝑇𝐻1 𝑉𝑇𝐻2
Soft-clip Clip rate
= 0.7
Clip rate (hard-clipping)
= 0.9
Voltage-clipping
+ VDD
− VDD
C.-W. Lin and B.-S. Hsieh, An anti-clipping protection system for multilevel class-D amplifier, Proc.
IEEE Int. Conf. on Electr. Eng./Electron., Comput., Telecommun. and Inf. Technol., pp.129–133, 2011.
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Over-Temperature (OT) Detection 1/2
B. Krabbenborg, “Protection of audio amplifiers based on temperature measurements in power
transistors,” Proc. IEEE Int. Solid-State Circuits Conf. (ISSCC), pp. 374–375, 2003.
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Over-Temperature (OT) Detection 2/2
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Over-Temperature (OT) Detection & Protection
Tchip (°C)
VCTAT1
Vout (V)
VCTAT2
VZTC
25 125 100
CTAT
Bandgap
Zero TC
Bandgap
IZTC
ICTAT VCTAT1
VCTAT2
VZTC
VZTC
Thermal
Shutdown
(125°C)
Thermal
Protection
(100°C)
+
+
-
-
* CTAT: output current reduces with increasing temperature
* Zero TC: zero temperature coefficient
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Outline
Induction & background
Four switching power amplifier designs & results
High-fidelity multilevel filterless class-D audio amplifier
Multilevel amplifier with integrated protections
High-efficiency class-D amplifier power stages
Continuous-time LED dimming controller
Conclusions
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𝑉𝑝𝑤𝑚 (𝐼𝑝𝑤𝑚)
PWM Class-D Amplifier
𝑉𝑝𝑤𝑚 NPWM
modulator
Low-Pass Filter 𝑉𝑖𝑛 𝑉𝑜𝑢𝑡
𝑉𝑖𝑛
𝑉𝑐
𝑉𝑐
charging time ∆𝐼
∆𝑡↑
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Concept of proposed multilevel technique
PWM modulator
Multilevel
Signal
Generator
(MLSG)
1 0 0
0 0 0
1 0 0
0 1 0
Encoder
Multilevel
Converter
(MLC)
1 0 0
0 0 0
1 0 0
0 1 0
audio pulse width
control code
Bin
ary
nu
me
ric
audio
I II
III Chun-Wei Lin, Bing-Shiun Hsieh, “The multilevel technique for improving filterless class-D audio
amplifiers,” J. of Circuits Systems and Computers (JCSC), under-review 2012.
∆𝐼
∆𝑡
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I. Natural PWM Sampling
𝑉𝑖𝑛
𝑉𝑐
𝑉𝑝𝑤𝑚
𝑉1 𝑉2
𝑇𝑠
𝑡𝑛
𝑡𝑛1 𝑡𝑛2
𝑉𝑖𝑛_𝑎𝑣𝑔 =𝑉1 + 𝑉2
2=
1
2∙𝐴 ∙ 𝑡𝑛1 + 𝑡𝑛2
0.5𝑇𝑠 = 𝐴 ∙
𝑡𝑛𝑇𝑠
= 𝐴 ∙ 𝐷
= 𝑉𝑃𝑊𝑀(𝐷)
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II. Multilevel signal generator (MLSG) 1/3
Delay Cell
Adder
DFF
DFF
DFF
𝑽𝑷𝑾𝑴(𝒕)
𝑐𝑙𝑜𝑐𝑘
𝑽𝑴𝑳𝑺𝑮(𝒕)
𝑉𝑃𝑊𝑀 (𝑡 − 𝟏 · Δ𝑇)
𝑉𝑃𝑊𝑀(𝑡 − 𝟐 · Δ𝑇)
𝑉𝑃𝑊𝑀(𝑡 − 𝒌 · Δ𝑇)
= 𝑉𝑃𝑊𝑀 𝑡 − 𝑘 ∙𝑇𝑠
𝑀
𝑀
𝑘=1
![Page 68: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/68.jpg)
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II. Multilevel signal generator (MLSG) 2/3
𝑽𝑷𝑾𝑴 (𝒕 − 𝟏 · 𝚫𝑻)
𝑻𝑺 𝑻𝑺
𝒕𝒏
𝑨′
ΔT
ΔT
𝑽𝑷𝑾𝑴 (𝒕 − 𝟐 · 𝚫𝑻)
𝑽𝑷𝑾𝑴 (𝒕 − 𝒌 · 𝚫𝑻)
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II. Multilevel signal generator (MLSG) 3/3
𝑉𝑀𝐿𝑆𝐺 𝑡 = 𝑉𝑃𝑊𝑀 𝑡 − 𝑘 ∙𝑇𝑠
𝑀
𝑀
𝑘=1
𝑉𝑀𝐿𝑆𝐺 𝑡 𝑎𝑣𝑔 =1
𝑇𝑠 𝑉𝑀𝐿𝑆𝐺 𝑡
𝑇𝑠
0
𝑑𝑡 =1
𝑇𝑠 𝑉𝑃𝑊𝑀 𝑡 − 𝑘 ∙
𝑇𝑠
𝑀
𝑀
𝑘=1
𝑇𝑠
0
𝑑𝑡
=1
𝑇𝑠 𝐴′
𝑡𝑛
0
𝑀
𝑘=1
𝑑𝑡 = 𝐴′ ∙ 𝑀 ⋅𝑡𝑛
𝑇𝑠= 𝐴′ ∙ 𝑀 ⋅ 𝐷
MLSG output is:
Taking the average value within one period of carrier:
,where D is the duty ratio of PWM-modulated signal
The proposed MLSG is very simple and effective because it expresses
multilevel signal by all digital binary-weighted codes.
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III. Multilevel converter (MLC) 1/2
𝑉𝑝𝑤𝑚+ 𝑉𝑝𝑤𝑚−
V32 2 VVoV22 1 VVo
+𝑉2 +𝑉1 +𝑉2 +𝑉1
+𝑉2 +𝑉1 +𝑉2 +𝑉1
𝑆1
𝑆2
𝑆3
𝑆4
𝑆5
𝑆6
𝑆7
𝑆8
𝑆9
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III. Multilevel converter (MLC) 2/2
TDA
output
SA 1 1 1 1 1 0 0 0 0 0 0 0 0
SB 1 0 0 0 0 1 1 1 1 0 0 0 0
SC 0 1 1 0 0 1 1 0 0 1 1 0 0
SD 0 1 0 1 0 1 0 1 0 1 0 1 0
MLC output +3 +2.5 +2 +1.5 +1 +0.5 0 -0.5 -1 -1.5 -2 -2.5 -3
= VPWM+ – VPWM– a
a V1=1.0V, V2=1.5V.
Use 12 D flip-flops in MLSG for driving MLC
to output 13 voltage levels
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+
-
𝑉𝑖𝑛
𝑉𝑐 NPWM
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
12 DFFs
Encoder
𝑆𝐴 𝑆𝐵 𝑆𝐶 𝑆𝐷
𝑆1 𝑆2 𝑆3 𝑆4 𝑆5 𝑆6 𝑆7 𝑆8 𝑆9
MLSG
MLC
+ output -
Adder
+𝑉2 +𝑉1 +𝑉2 +𝑉1
+𝑉2 +𝑉1 +𝑉2 +𝑉1
![Page 73: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/73.jpg)
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Large capacitor (i.e. larger )
for linear integration
Triangular Waveform Generator - I
+
-
𝑉𝑖𝑛
𝑉𝑐
NPWM
+𝑉𝑆
−𝑉𝑆
𝐶𝑜
𝜏=RC
𝜏
![Page 74: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/74.jpg)
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Triangular Waveform Generator - II
Cascade connection (m1 & m2)
for larger on-resistance and larger
and enhancing the integration
𝜏
+𝑉𝑆
−𝑉𝑆
𝐶𝑜
𝜏=roC
𝑚1
𝑚2
+
-
𝑉𝑖𝑛
𝑉𝑐
NPWM
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Comparison of Output Waveform – I & II
Cascade connection can improve the
linearity of triangular generator!!
With output cascade Without output cascade
![Page 76: Class-D Audio Power Amplifier - MSIC D&T Laboratory140.125.35.23/course/Design_of_Audio_Band_Power_Amplifir/class_D... · 2015/2/11 MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin](https://reader031.fdocuments.in/reader031/viewer/2022022519/5b15a6667f8b9a382f8d4b36/html5/thumbnails/76.jpg)
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Output Waveform – II
Amplitude Variation due to
Process Variation!!
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Comparator (modulator) Design
MP1 MP2
MN3 MN4
MP5
R1
MN8
MP9MP10
MP11
CcVin- Vin+
Vout
1 2
3
4
5
35/1 35/1
30/1 30/1
40/240/2
6/1
30/1
M=12
40/1
M=6
3k
0.4pF
+
-
modulator
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Comparator Design
*********************************************************************************
* PROCESS : 0.35um MIXED MODE (2P4M,3.3V/5.0V) POLYCIDE *
*********************************************************************************
* Specifications :
* Open loop gain 98.0dB
* CMRR 117.5dB
* PSRR+- 115.0dB / 100.4dB
* PM 57.1deg
* Maximum output voltage swing 0.35V ~ 4.7V
* Power supply voltage +5.0V
* Unit gain frequency 81.3MHz (CL=2pf)
* Slew rate 103.0 V/us - 171.0V/us (CL=2pf)
* Settling time 50nsec
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DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
12 DFFs
𝑆𝐴 𝑆𝐵 𝑆𝐶 𝑆𝐷 MLSG
Adder
D
CLK
C_B C_D
C_D
C_B
C_DC_B
C_B
C_DC_D C_B
Q QBD
CLK Q
QB
D-FF
1
4
3 5
6
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DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
12 DFFs
𝑆𝐴 𝑆𝐵 𝑆𝐶 𝑆𝐷 MLSG
Adder
3bit
FA
2bit
FA
HA
HA
HA
HA
2bit
FA
(LSB)1A
(MSB)2A
1B
2B
1C
2C
1D
2D
(MSB)13S
12S
(LSB)11S
(MSB)23S
22S
(LSB)21S
(MSB)4S
(LSB)1S
2S
3S
1d
2d
3d
4d
5d
6d
7d
8d
Pad
Pad
Pad
Pad
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DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
12 DFFs
𝑆𝐴 𝑆𝐵 𝑆𝐶 𝑆𝐷 MLSG
Adder
1( )S LSB
HA
HA
HA 2A
2B
1A
1B
2S
3( )S MSB
2-bits FA
2 1 2
1 1 2
S d d
S d d
1-bit HA: 1( )S LSB
2S
1d
2d
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DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
DFF
𝑐𝑙𝑘
12 DFFs
𝑆𝐴 𝑆𝐵 𝑆𝐶 𝑆𝐷 MLSG
Adder
1( )S LSB
4 ( )S MSB
HA
HA
HA 2A
2B
1A
1B
2S
3-bits FA
HA HA 3A
3B
3S
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Encoder & MLC
Encoder
𝑆𝐴 𝑆𝐵 𝑆𝐶 𝑆𝐷
𝑆1 𝑆2 𝑆3 𝑆4 𝑆5 𝑆6 𝑆7 𝑆8 𝑆9
MLC
+ output -
+𝑉2 +𝑉1 +𝑉2 +𝑉1
+𝑉2 +𝑉1 +𝑉2 +𝑉1
1
2
3
4
5
6
7
8
9
A B B C A D
A B C D A B C D
B C D A B D
A B C D A B C D A B C D
A B C D B C D
A C
A B C B C D B C D
A B
A B C D A B C D
S S S S S S S
S S S S S S S S S
S S S S S S S
S S S S S S S S S S S S S
S S S S S S S S
S S S
S S S S S S S S S S
S S S
S S S S S S S S S S
A B CS S
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Chip photograph
III II
I
I. NPWM modulator
II. Multilevel Signal
Generator & Encoder
III. Multilevel Converter
TSMC 5V-0.35um
Area = 2.25mm2 with
40-pin DIP package
RL = 8Ω, Lo = 33uH
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Triangular Generator 1/3
Use guard-ring to block noise bypassing from substrate.
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Triangular Generator 2/3
The same current direction for current source matching.
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Triangular Generator 3/3
Power planning circles entire circuit.
VDD
Gnd
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Modulator (Two-stage amp.) 1/2
Common centroid matching of double poly capacitor.
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Modulator (Two-stage amp.) 2/2
Snake routing of poly resistor.
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Stick diagram for simplifying routing path of signals.
D-type Flip-Flop
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Well clock matching for minimizing timing delay.
Chains of D-type Flip-Flop 1/2
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72 DFFs within proposed MLSG.
Chains of D-type Flip-Flop 2/2
DFF
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4-bits Digital Adder
3bit
FA
2bit
FA
HA
HA
HA
HA
2bit
FA
(MSB)4S
(LSB)1S
2S
3S
1d
2d
3d
4d
5d
6d
7d
8d
Matching
sub-circuit
placement
and routing.
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Encoder
Encoder
𝑆𝐴 𝑆𝐵 𝑆𝐶 𝑆𝐷
𝑆1 𝑆2 𝑆3 𝑆4 𝑆5 𝑆6 𝑆7 𝑆8 𝑆9 Minimize layout into a square
for saving chip area.
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Share “Drain” or “Source” area between two transistor for
saving chip area.
Tapered Buffer
D D D D D S S S
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Whole Chip Plan
Power planning for well supplying entire chip
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Board Measurement
noise
source
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PCB Measurement
Supplies filter B
NC
co
nn
ecto
r for
hig
h fre
q. c
arrie
r, CL
Ks
BNC for output
BNC for input
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PCB Measurement
Less
noise
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Multilevel and PWM Signals
PWM signal
Multilevel signal
𝑚𝑢𝑙 𝑡 𝑎𝑣𝑔 = 𝐴′ ∙ 𝑀 ⋅ 𝐷
∝ 𝑉𝑃𝑊𝑀(𝑡)
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Multilevel and Filtering Signals
Multilevel signal
Recovered audio signal
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Spectrum of PWM amplifier without filter
0 2 4 6 8 10 12 14 16 18 20-120
-100
-80
-60
-40
-20
0
Frequency (kHz)
Mag
nit
ude
(dB
)
Freq. (kHz)
Mag
nit
ud
e(dB)
THD=50dB
≈0.316%
Vin = 1kHz, Vtri = 250kHz
RL = 8Ω, Lo = 33uH
SNR=70dB
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0 2 4 6 8 10 12 14 16 18 20-120
-100
-80
-60
-40
-20
0
Frequency (kHz)
Mag
nit
ude
(dB
)
Freq. (kHz)
Mag
nit
ud
e(dB)
Spectrum of PWM amplifier with filter
Vin = 1kHz, Vtri = 250kHz
RL = 8Ω, Co = 2.0uF, Lo = 127uH
THD=57dB
≈0.141%
SNR=72dB
BW = 10kHz, Q = 1
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0 2 4 6 8 10 12 14 16 18 20-120
-100
-80
-60
-40
-20
0
Frequency (kHz)
Mag
nit
ud
e (
dB
)
Freq. (kHz)
Mag
nit
ud
e(dB)
Spectrum of multilevel amplifier without filter
Vin = 1kHz, Vtri = 250kHz
RL = 8Ω, Lo = 33uH
THD=73dB
≈0.02%
SNR=85dB
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THD performance versus power delivery
0.01
0.1
1
10
1 50 100 150 200 250 300 350 400 450 500 550
Output power (mW)
TH
D (
%)
(100%) (55%) (18%)
(0.12%)
(0.02%)
(0.035%)
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Power efficiency versus power delivery
0
20
40
60
80
100
0 50 100 150 200 250 300 350 400 450 500 550
Output power (mW)
η (
%)
(100%) (27%)
(85%)
* PLoss = 150mW ∙ 20% = 30mW/2.4mW (8%, TDA&encoder)
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EMI Spectrum of Multilevel Class-D Amplifier
0 250 500 750 1000
-100
-80
-60
-40
-20
0
Frequency (kHz)
Mag
nit
ude
(dB
)
0 250 500 750 1000
-100
-80
-60
-40
-20
0
Frequency (kHz)
Mag
nit
ude
(dB
) Conventional PWM Class-D Amplifier
Proposed Multilevel Class-D Amplifier
fc
fc
fc-2fsig fc+2fsig
fc-2fsig fc+2fsig
250
250
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Comparison to prior class-D audio amplifiers
Design [53] [54]§ [55] [56]§ [21] [22]
BMA/TMA [24] [57]
Proposed
Amplifier
CMOS
Process
(μm)
0.09 0.35 0.5 0.35 0.5 0.5 0.5 0.5 0.35
Supply
(V) 4.2 5.0 5.0 5.0 2.7 2.7 2.7 2.5 5.0
Load (Ω) 8 8 8 8 8 8 8 8 8
fs (kHz) 410 250 1000 280 380 450 500 >200 250
η (%) 76 88 70 89 84 89 / 90 91 92 85
Po,max
(mW) 700 1000 1000 1000 410 250 200 450 550
SNR (dB) 98 97 94 98 100 94 / 92 65 80 85
THD (%) 0.03 0.18 0.02 0.02 0.02 0.02 / 0.03 0.08 0.3 0.02
Area(mm²) 0.44 2.1 10.5 9.0 1.65 1.49 / 1.31 4.7 0.6 2.25
Levels 3 3 2 2 3 2 / 3 3 2 13
FOM 35.5 7.9 15.7 17.0 52.2 35.1 / 26.3 1.6 9.2 30.9
Topology PWM PWM ΔΣ ΔΣ SMC SMC SMC RWDM PWM
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Outline
Induction & background
Four switching power amplifier designs & results
High-fidelity multilevel filterless class-D audio amplifier
Multilevel amplifier with integrated protections
High-efficiency class-D amplifier power stages
Continuous-time LED dimming controller
Conclusions
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Multilevel Amplifier with Integrated Protections
Over-current (OC)
Over-voltage (OV)
Multilevel Technique
I. Pulse Density
Adjustment MLC
II. OC& OV & OT
Detection
III.
Control Logic
OV OC
+ ILim
− ILim
+ VLim
− VLim Adaptive Power Control Loop
MLSG
Chun-Wei Lin, Bing-Shiun Hsieh, “Multilevel filterless class-D amplifier with adaptive power control
protection,” Microelectronics Journal, under-review 2013.
The relationship between power loss PLoss and relative temperature difference ΔT
( ) ( )J A Loss Static DynamicH k T T W P t P P t
* k is heat coefficient of packages usually cause by OC or OV conditions
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Multilevel Amplifier Design
PWM modulator
Multilevel
Signal
Generator
(MLSG)
1 0 0
0 0 0
1 0 0
0 1 0
Encoder
Multilevel
Converter
(MLC)
1 0 0
0 0 0
1 0 0
0 1 0
audio pulse width
control code
Bin
ary
nu
meric
audio
I II
III
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before after pulse density adjustment
I. Pulse Density Adjustment Circuits 1/2
TS
PWM pulse width Multilevel output
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I. Pulse Density Adjustment Circuits 2/2
PWM
Modulator
Pre-amplifier
K ≥ 1
Pre-amplifier
K ≤ 1
Pulse-Adjustment
Control
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MXS
II. Over-Current (OC) Detection Circuits
–
+
OPA
…
MX
IOut
= N∙ ISense
ISense MFS
VTh
VDD VDD
VDD
Reset
CLK
D Q
𝐼𝑀𝑋
𝐼𝑀𝑋𝑆
= (𝑊
𝐿)𝑀𝑋
(𝑊
𝐿)𝑀𝑋𝑆
= N
𝑉𝐺𝑆,𝑀𝑋= 𝑉𝐺𝑆,𝑀𝑋𝑆
𝑉𝐷𝑆,𝑀𝑋= 𝑉𝐷𝑆,𝑀𝑋𝑆
Chun-Wei Lin, Bing-Shiun Hsieh, Chih-Wei Chung, “PWM-based multilevel class-D amplifier with
integrated over-current protection system,” IEEE ICIEA, pp.1394 - 1398, June 2010.
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II. Over-Voltage (OV) Detection Circuits
Multilevel output
t
LPF output
The maximum
output level
clock
MLS
G
Encoder
Flip
Flop
Counter
Ι
Previous
state
Present
state
Clipping
Chun-Wei Lin, Bing-Shiun Hsieh, “An anti-clipping protection system for multilevel class-D amplifier,”
IEEE ECTI-CON, pp.129 - 132, May 2011.
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II. Over-Temperature (OT) Detection
Tchip (°C)
VCTAT1
Vout (V)
VCTAT2
VZTC
25 125 100
CTAT
Bandgap
Zero TC
Bandgap
IZTC
ICTAT VCTAT1
VCTAT2
VZTC
VZTC
Thermal
Shutdown
(125°C)
Thermal
Protection
(100°C)
+
+
-
-
* CTAT: output current reduces with increasing temperature
* Zero TC: zero temperature coefficient
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III. Pulse Density Adjustment Control Logic
S 0
K = 1
S 1
K = 1 - 2/12 S 2
K = 1 - 4/12
S 3
K = 1 - 6/12
S 4
K = 1 - 8/12
S 5
K = 1 - 10/12
S 6
K = 0, PWM out = 0
( Short Circuit )
OC/OV/OT
= 0 OC/OV/OT = 1 OC/OV/OT = 1 OC/OV/OT = 1 OC/OV/OT = 1 OC/OV/OT = 1
OC/OV/OT = 1 OC/OV/OT = 0
OC/OV/OT = 0 OC/OV/OT = 0 OC/OV/OT = 0 OC/OV/OT = 0 OC/OV/OT = 0
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Output Signals before and after Protection
0 0.25 0.5 0.75 1-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
3
Time (ms)
Vo
lta
ge
(V
)
After 6-levels reduction
Before over-current protection
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10%
0
20
40
60
80
100
0 2 4 6 8 10
Po
wer
Eff
icie
ncy
(%
)
Reduced levels
0.01
0.1
1
10
0 2 4 6 8 10
TH
D (
%)
(RL=8Ω) (RL=4Ω)
fSIG = 1kHz
fTRI = 250kHz,
IO,MAX = 0.35mA
17dB
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Transient Response of OV Protections
0 0.5 1 1.5 2 2.5 3-15
-10
-5
0
5
10
Time (ms)
Ou
tpu
t V
olta
ge
(V
)
I
I II
II
Audio signal
Hard clipping
Soft clipping
Proposed anti-clipping
0 0.5 1 1.5 2 2.5 3-15
-10
-5
0
5
10
Time (ms)
Ou
tpu
t V
olta
ge
(V
)
I
I II
II
Audio signal
Hard clipping
Soft clipping
Proposed anti-clipping
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Representation of OV Condition
Expected sinusoidal signal
Clipping sinusoidal signal
II
2/sT
sV
tI
max_oV
III
IT IIT IIIT
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Clipping Ratio and Weight
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90 100
Cli
pp
ing w
eigh
t (%
)
Clipping ratio (%)
Hard-Clipping
Soft-Clipping
Anti-Clipping
35%
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Clipping Ratio and Weight
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90 100
Heat
Fact
or
(%
)
Clipping ratio (%)
Hard-Clipping
Soft-Clipping
Anti-Clipping
60 %
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Temperature estimation qJA : Junction-to-Ambient resistance
* TJ: temperature of chip junction
* TA: temperature of ambient
* PLoss: power-loss of chip
Thermal Resistance of Chip Packages 1/2
J AJA
Loss
T T
Pq
TJ
case
chip
board
TA
TA
θJC
θCA
θBA
≡
TA
TJ
θJA
(option)
Heat spreader
θJB
Radiation Convection Conduction
25 / 2( ) 4 (1 0.85%) 0.47W
4LossP
0.47 65 30
J A Loss JAT T T P
C
q
* Temperature difference on package!
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Thermal Resistance of Chip Packages 2/2
t (s)
TJ (°C)
100
25
TJ
TA
ΔTOT
ΔTOTP
OT condition after power-loss reduction (OTP)
( )J AJA
Loss
T T
Pq
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Control of OT Protection
PLoss (W)
TJ (°C)
25
125
100
PStatic ↓
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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Speaker
output
Transient Response of OT Protection
Multilevel
output
VMLT (V)
PLoss (W)
TJ (oC)
100
125
t OTP
t (ms)
t (ms)
t (ms)
… …
…
25
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Simulation Results
0 2 4 6 8 10
0 2 4 6 8 10
IO,RMS = 0.88mA
PO,MAX = 3.1W
PLoss,MAX = 0.47W
ΔTpackage ≒ 30°C
100
80
60
40
20
0
PL
oss
Red
uct
ion
(%
) P
ow
er E
ffic
ien
cy (
%)
100
80
60
40
20
0
Over-temperature Protection
Reduced levels
(15%
)
(50%)
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Outline
Introduction & background
Four switching power amplifier designs & results
High-fidelity filterless class-D audio amplifier
Multilevel amplifier with integrated protections
High-efficiency class-D amplifier power stages
Continuous-time LED dimming controller
Conclusions
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Design of full-bridge power stage 1/2
PWM
Modulator c(t)
s(t)
LC
filter
Gate
drivers
Full-bridge
power inverters
The power stage of class-D amplifier consume most of total
power loss because they are in charge to delivery heavy current
into speaker.
Proposed control method is applied to dynamically reduce the
power loss of power stages and enhance the power efficiency
of PWM class-D amplifier over a wide range of power demand.
Full-bridge Power stage
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Design of full-bridge power stage 2/2
0
20
40
60
80
100
0.0 0.2 0.4 0.6 0.8 1.0
Modulation index, D
Pow
er
loss
(m
W)
PS, D=0.1
PS, D=0.9
PS, D=0.3
PD, D=0.9
PD, D=0.3
PD, D=0.1
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Optimal design of efficient power stages 1/9
Chains of gate drivers CMOS inverters
The total power loss of power stages comprise the switching loss
on parasitic capacitance CSW of gate drivers and conduction loss
on on-resistance ron of inverter transistors.
Switching Power Stages
𝑻−(𝑵−𝟐)𝑪𝒑 𝑻−(𝑵−𝟏)𝑪𝒑 𝑻𝟎𝑪𝒑 𝑻−𝟏𝑪𝒑
𝑪𝑺𝑾
𝒓𝒐𝒏
𝒓𝒐𝒏
PWM
Modulator V𝐂
VS LC
Filter
𝒊𝒐𝒖𝒕
𝑻−(𝑵−𝟐)𝑪𝒑 𝑻−(𝑵−𝟏)𝑪𝒑 𝑻𝟎𝑪𝒑 𝑻−𝟏𝑪𝒑
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Optimal design of efficient power stages 2/9
𝑃𝐿𝑜𝑠𝑠 = 𝑃𝑐 + 𝑃𝑟 → 𝜂 % =𝑃𝑜𝑢𝑡
𝑃𝑜𝑢𝑡 + 𝑃𝐿𝑜𝑠𝑠⋅ 100% ≥ 85% 1.
1.1 𝑃𝑐 =1
2𝑉𝐷𝐷
2 ⋅ 𝑓𝑆𝑊 ⋅ 𝐶𝑆𝑊
=1
2𝑉𝐷𝐷
2 ⋅ 𝑓𝑆𝑊 ⋅ 2 𝑪𝒑 ⋅ 𝑇−𝑖
𝑁−1
𝑖=0
=1
2𝑉𝐷𝐷
2 ⋅ 𝑓𝑆𝑊 ⋅ 2 (𝑘1 + 𝑘2)𝒘𝒑 ⋅ 𝑇−𝑖
𝑁−1
𝑖=0
,where k1 and k2 are parasitic capacitance of Gate-Source and
Drain-Source in adjacent stages of gate driver chains.
minimization
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Cg,pi
Cg,ni
Cdb,pi
Cdb,ni
stage i stage i+1 stage i-1
k1 ∙ wp k2 ∙ wp
Optimal design of efficient power stages 3/9
T T
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𝑘1 = 2 1 +1
𝛼𝑪𝒐𝒙𝐿 + 𝐶𝐺𝐷𝑂 + 𝐶𝐺𝑆𝑂
𝑘2 = 2 𝐶𝐽𝑃 +𝐶𝐽𝑁
𝛼𝑳𝑫𝑺 + 1 +
1
𝛼𝐶𝐺𝐷𝑂 + 2𝐶𝐽𝑆𝑊
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Optimal design of efficient power stages 5/9
Full- (H-) bridge power inverters
𝑃𝑜𝑢𝑡 = 𝑖𝑜𝑢𝑡2 ⋅ 𝑅𝐿
𝑃𝑟= 𝑖𝑜𝑢𝑡2 ⋅ 2𝑟𝑜𝑛
𝑉𝑝𝑤𝑚+ 𝑉𝑝𝑤𝑚−
k4 / wp
k3 / wp
k3 / wp
4𝑘3 + 2𝑘4
𝒘𝒑 =
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1.2 𝑃𝑟 =1
𝑇𝑆 𝑖𝑜𝑢𝑡
2(𝑡) ⋅ 2𝒓𝒐𝒏𝑑𝑡
𝑇𝑆
0
≈1
2(𝐼𝑂𝑈𝑇 ⋅ 𝐷)2⋅ 2𝑟𝑜𝑛
𝑠𝑖𝑛𝑒
=1
2(
𝑉𝐷𝐷
𝑅𝐿 + 2𝑟𝑜𝑛⋅ 𝐷)2⋅ 2𝑟𝑜𝑛
≈1
2(𝑉𝐷𝐷
𝑅𝐿⋅ 𝐷)2⋅ 2𝒓𝒐𝒏
=1
2(𝑉𝐷𝐷
𝑅𝐿⋅ 𝐷)2⋅ 2
4𝑘3 + 2𝑘4
𝒘𝒑
,where k3 and k4 are contact resistances of Drain-Source diffusion
and on-resistance of power transistors.
→ 𝑅𝐿≫ 2𝑟𝑜𝑛
Optimal design of efficient power stages 6/9
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𝑘3,𝑝 = 𝑙1 + 2𝑙3 𝑅𝑝 + 2 𝑙1 + 𝑙2 𝑅𝑐𝑡𝑝
𝑘4 =𝐿
𝜇𝑝𝐶𝑜𝑥 𝑉𝐷𝐷 − 𝑉𝑡ℎ
𝑘3,𝑛 = 𝑙1 + 2𝑙3 𝑅𝑛 + 2 𝑙1 + 𝑙2 𝑅𝑐𝑡𝑛
: Contact resistances
of Drain-Source diffusion
: On-resistance of power transistors
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⇒ 𝑃𝐿𝑜𝑠𝑠 =1
2𝑉𝐷𝐷
2 ⋅ 𝑓𝑆𝑊 ⋅ 2 (𝑘1 + 𝑘2)𝒘𝒑 ⋅ 𝑇−𝑖
𝑁−1
𝑖=0
+
1
2(𝑉𝐷𝐷
𝑅𝐿⋅ 𝐷)2⋅ 2
4𝑘3 + 2𝑘4
𝒘𝒑
⇒𝜕𝑃𝐿𝑜𝑠𝑠
𝜕𝑤𝑝=
1
2𝑉𝐷𝐷
2 ⋅ 𝑓𝑆𝑊 ⋅ 2 (𝑘1 + 𝑘2) ⋅ 𝑇−𝑖
𝑁−1
𝑖=0
+
1
2(𝑉𝐷𝐷
𝑅𝐿⋅ 𝐷)2⋅ 2
0 ⋅ 𝑤𝑝 − 4𝑘3 + 2𝑘4 ⋅ 1
𝒘𝒑2
= 0
Optimal design of efficient power stages 8/9
𝑷𝑫,𝑮𝑫
𝑷𝑺,𝑻𝒓
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MSIC D&T Lab., Dept. of El. Eng., NYUST ~ CW Lin
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⇒ 𝑤𝑝 = 𝐷 ⋅4𝑘3 + 2𝑘4 /𝑅𝐿
2
𝑓𝑆𝑊 ⋅ 𝑘1 + 𝑘2 ⋅ 𝑇−𝑖𝑁−1𝑖=0
= 𝐷 ⋅𝐹1
𝐹2
The optimal design of driving capability wp of power stages
is proportional to current delivery by modulation index D.
The wp should be optimized to fit every D for minimal
average power loss and higher power efficiency
over a wide range of power demand!
Optimal design of efficient power stages 9/9
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Surface plot of total power loss
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130135140145 150
155160165170
175180 185190195200205210
Modulation Index (D)
wp
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
200
400
600
800
1000
1200
1400
Contour plot of total power loss 1/2
(0.9, 550)
(0.8, 490)
(0.7, 430)
(0.6, 370)
(0.5, 310)
(0.4, 250)
(0.3, 190)
(0.2, 130)
(0.1, 70)
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110
110
115
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120
120
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130135140145 150
155160165170
175180 185190195200205210
Modulation Index (D)
wp
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
200
400
600
800
1000
1200
1400
Contour plot of total power loss 2/2
Pc↑
Pr↑
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The power stage of amplifier is segmented into several small
stages and selectively enabled according to the optimal designs
respecting to different modulation indexes (i.e. power demands).
The driving capability of power stage is dynamically adjusted to
minimize the power loss and improve the power efficiency,
especially for small modulation index.
Control of efficient power stages
Dynamic Adjustment Unit
𝑉𝑀𝐿𝑆𝐺(𝑡) PWM
modulator Vc(t)
Vs(t)
LC
filter
proposed MLSG
Segmented
Power Inverters
𝑉𝑃𝑊𝑀(𝑡)
Segmented
Gate Drivers
Chun-Wei Lin, Bing-Shiun Hsieh, “Dynamic power efficiency improvement for PWM class-D amplifier,”
IEICE Electron. Express Letter (ELEX), vol. 10, no. 6, 2013.
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Control of segmented power stages 1/2
Up-PMOS
Up-NMOS
Dn-PMOS
Dn-NMOS
𝑽𝑷𝑾𝑴(𝒕)
Thermometer
decoder
𝑽𝑴𝑳𝑺𝑮′(𝒕)
𝑑𝑒(𝑡)
𝒕𝒄𝒉
𝑽𝑷𝑾𝑴(𝒕)
1100
0111
𝑽𝑴𝑳𝑺𝑮′(𝒕)
For VMLSG’(t) varies between 11 and 12, means large duty ratio of
PWM signal and great power demand from input signal.
The 6 segmented gate drivers and power inverters are all on duty.
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Control of segmented power stages 2/2
If 1≤VMLSG(t)≤(M+1)/2, VMLSG’=i, for VMLSG (t) varies between i and i+1
If (M+1)/2 ≤VMLSG (t)≤M, VMLSG’=i+1, for VMLSG (t) varies between i and i+1
1100
1011
0001
0000
1100
…..
0000
Up-PMOS
Up-NMOS
Dn-PMOS
Dn-NMOS
𝑽𝑷𝑾𝑴(𝒕)
Thermometer
decoder
𝑽𝑴𝑳𝑺𝑮′(𝒕)
𝑑𝑒(𝑡)
𝑽𝑴𝑳𝑺𝑮(𝒕) 𝑽𝑴𝑳𝑺𝑮′(𝒕)
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Transient Response
I o,max I o,min
Vsig
Ven5
Ven4
Ven3
Ven2
Ven1
Vpwm
Vout
I o,max
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Total Power Loss Reduction
0
10
20
30
40
50
0.0 0.2 0.4 0.6 0.8 1.0
I. Proposed method II. D = 0.9 III. [36]
Modulation Index, D
To
tal
po
wer
loss
(m
W)
Pavg = 23mW 28 mW 24.5 mW
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Power Efficiency Enhancement
0
20
40
60
80
100
0.0 0.2 0.4 0.6 0.8 1.0
I. Proposed method II. D = 0.9 III. [36]
Modulation Index, D
Po
wer
Eff
icie
ncy
(%
)
0.26 0.16
0
10
20
30
0.0 0.1 0.2 0.3 0.4 0.5
Diff1 = I - II Diff2 = I - III
Modulation Index, D
Pow
er E
ffic
ien
cy (
%)
27
13
13.5%
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0.01
0.1
1
10
TH
D (
%)
Output power (mW)
500 750 1000 1250
Proposed method + 1st feedback compensation
Conventional optimization of D=0.9
THD comparison
∆𝒓𝒐𝒏↑
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Outline
Introduction & background
Four switching power amplifier designs & results
High-fidelity filterless class-D audio amplifier
Multilevel amplifier with integrated protections
High-efficiency class-D amplifier power stages
Continuous-time LED dimming controller
Conclusions
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• Applications: Display backlight, indoor lighting, home theater…
• Techniques: I. linear and II. PWM dimming
• I. linear: simple structure, continuous-time control,
but its bad linearity results in “Hue shift”.
• II. PWM: precise adjustment of illuminations,
switching control,
but faster switching
increases PD & reduces
the life of LED devices.
• III. Continuous-time PWM dimming:
8-bits PWM control.
Voltage
Supply
Current
regulator
ILED
LED dimming techniques
I. Linear dimming
II. PWM dimming
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Driving
buffer
𝑉𝑠𝑖𝑛
ILED
• ΔILED is determined by ∆(VGS – VTn)
ILED is dimmable with Vsin (assume from light sensor)
• offset effect of current regulator and driving buffer
brings variation on bias current of LED
leads in “Hue shift (色相偏移)”.
“Color temperature (色溫)” v.s.“Hue”.
∆𝑉𝐺𝑆
+𝑉𝐷𝐷
−𝑉𝐷𝐷
I. Linear LED dimming technique 1/4
Amp.
Voltage
Supply
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“Color Temperature” v.s. “Hue” 1/2
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“Color Temperature” v.s. “Hue” 2/2
10°
11°
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1 1.5 2 2.5 3 3.5 40
2
4
6
8
10
V DIM
(V)
I L
ED
(m
A)
0.85 4.25
I. Linear LED dimming technique 2/4
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I. Linear LED dimming technique – 8bits 3/4
1 1.5 2 2.5 3 3.5 4-1
-0.5
0
0.5
1
DN
L
(LS
B)
1 1.5 2 2.5 3 3.5 4-10
-5
0
5
10
V DIM
(V)
INL
(L
SB
)
0.85 4.25
8.2
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I. Linear LED dimming technique 4/4
1 1.5 2 2.5 3 3.5 40
5
10
15
20
25
30
Po
wer
(m
W)
1 1.5 2 2.5 3 3.5 40
10
20
30
40
50
60
70
80
90
100
V DIM
(V)
Po
wer
Eff
icie
ncy
(%
)
Pavg of LED
Pavg of current regulation
0.85 4.25
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• Current regulator is switched on or off.
• TS ≥ 1/24s ~ 1/16s for “Persistence of Vision(視覺暫留)”
• Luminous intensity can be changed
by adjusting the duration of ton
(ILED is constant!)
• Precise control of luminous
intensity than linear
dimming control
• Large switching loss may
reduce the power efficiency
& life of LED devices.
Voltage
Supply
ILED
𝑽𝒔𝒊𝒏 +
– 𝑽𝒕𝒓𝒊
PWM modulator
𝑇𝑆
𝑡𝑜𝑛
𝑪𝒔𝒘
II. PWM LED dimming technique 1/4
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0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
2
4
6
8
10
V DIM
(D : duty ratio, %)
I L
ED
(m
A)
(100%)(80%)(40%) (60%)(20%)(0%)
II. PWM LED dimming technique 2/4
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II. PWM LED dimming technique 3/4
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
5
10
15
20
25
30
35
40
Po
wer
(m
W)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
10
20
30
40
50
60
70
80
90
100
V DIM
(D: duty ratio, %)
Po
wer
Eff
icie
ncy
(%
)
Pavg of LED
Pavg of current regulator
(40%) (60%) (80%) (100%)(20%)(0%)
ILED = C
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II. PWM LED dimming technique 4/4
* fPWM = 1kHz fPWM ≥ 200Hz
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PWM signal
Binary-weighted
current regulation
Proposed dimming
scheme
𝒘:𝟐𝟎 𝒘:𝟐𝟏 𝒘:𝟐𝒏−𝟏
III. Continuous-time LED dimming 1/12
4-bits
8-bits Digital
Filter
ILED ≠ C
1-bit Voltage
Supply
Chun-Wei Lin, Bing-Shiun Hsieh, Ying-Xu Tsai, “A continuous-time LED dimming technique,” IEICE
Electron. Express Letter (ELEX), vol. 10, no. 4, 2013.
Multilevel
Signal
Generator
(MLSG)
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III. Continuous-time LED dimming 3/12
Multilevel:
M levels
Interpolation:
n levels
𝑡𝑟
𝑇𝑆
𝑡𝑝
Ramp signal
rts
KsH
2
210
)(
• Transfer function of 1st order digital filter
• In discrete domain, ptzs /)1(
rp tt
z
KzH
2
210
)1()(
• If tr = 30ms, M = 12, n = 15 ( 180 levels)
4
1
1
1
1
1
1
0625.01
21047.01)(
i
i
z
Kzz
Kz
z
KzzH
, the multiplication can be implemented
by a simple right shift register.
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III. Continuous-time LED dimming 4/12
Subtractor Add/Sub
Delay
Shift
Register
Complement
Turn to
Binary
MSB
LSB
TDA Signal
8bits output
8bits 4bits
𝟏
𝟏 = 𝟎. 𝟎 𝟐
4
1
1
0625.01][
][)(
iz
Kz
nX
nYzH
z -1 X [n] Y [n] = a∙Y[n-1] + X[n]
-0.0625
integration
I II
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III. Continuous-time LED dimming 5/12
Multilevel
Signal
Generator
output
filter output
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FP
GA
8 p
ow
er
MO
S
mo
un
ted
on
PC
B
Proposed
MLSG
PWM signal from
Agilent 81110A (FPAA)
binary-weighted
current regulation
𝒘:𝟐𝟎 𝒘:𝟐𝟏 𝒘:𝟐𝟕
Digital
Filter
ILED
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0 100 200 3000
2
4
6
8
10
Time (ms)
I L
ED
(m
A)
III. Continuous-time LED dimming 7/12
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0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
2
4
6
8
10
V DIM
(D : duty ratio, %)
I L
ED
(m
A)
(100%)(80%)(40%) (60%)(20%)(0%)
III. Continuous-time LED dimming 8/12
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III. Continuous-time LED dimming – 8-bits 9/12
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
DN
L
(LS
B)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
V DIM
(V)
INL
(L
SB
)
2.2
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III. Continuous-time LED dimming – 8-bits 10/12
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1D
NL
(L
SB
)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-10
-8
-6
-4
-2
0
2
4
6
8
10
V DIM
(V)
INL
(L
SB
) Proposed method
Linear dimming
2.2
8.2
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1 1.5 2 2.5 3 3.5 40
2
4
6
8
10
V DIM
(V)
I E
RR
(%
)
0.01%
4.250.85
proposed Proposed LED dimming
Linear LED dimming
III. Continuous-time LED dimming 11/12
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III. Continuous-time LED dimming 12/12
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
5
10
15
20
25
30
35
Po
wer
(m
W)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
10
20
30
40
50
60
70
80
90
100
V DIM
(D: duty ratio, %)
Po
wer
Eff
icie
ncy
(%
)
Pavg of LED
Pavg of current regulator
(40%) (60%)(0%) (20%) (80%) (100%)
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Outline
Motivation & background
Four switching power amplifier designs & results
High-fidelity filterless class-D audio amplifier
Multilevel amplifier with integrated protections
High-efficiency class-D amplifier power stages
Continuous-time LED dimming controller
Conclusions
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Conclusions 1/4
The features of proposed multilevel class-D audio
amplifier
filterless
reduce distortion & noise
improve electromagnetic interference (EMI)
keep high power efficiency
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Conclusions 2/4
The features of proposed integrated protections for
multilevel audio amplifier
reduce excessive power consumption
prevent overheated damage (chip & PCB)
without shutting amplifier down
or involving in large signal distortion
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Conclusions 3/4
The features of proposed efficient class-D amplifier
power stages
less power consumption
higher power efficiency over a wide range of modulation
index (i.e. power demand)
without using complex package or extra heat-sink
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Conclusions 4/4
The features of proposed LED dimming controller
linear luminous intensity adjustment
luminous efficiency enhancement
extend the life of LED devices