IECON2013
November 10-13, 2013, Vienna, Austria
Review
R
i
off Current
C
t Sh
Sharing
i
Techniques In LED Drivers
Presented by: Xiaohui QU
Southeast University,
Nanjing, CHINA
2013/11/26
1
IECON2013
VO
i1
i2
iN
LED Strings in Parallel
 Reliability
 Safe
S f tterminal
i l voltage
lt
2
LED Strings in Parallel
 Current Imbalance
• Brightness uniformity
• Fast degradation or even failure
IECON2013
Voltage Difference Absorption
VO
i1
i2
iN
• The additional component is needed to absorb the voltage difference
between the bus voltage and the voltage drops of LED string
• The additional component should be lossless
type
• The bus voltage can be in DC or AC type.
3
IECON2013
For DC Voltage Bus
• Resistor
• Linear regulator
• Switched-Mode
Current Regulator
4
IECON2013
Linear Regulator
Linear Mode Switch
• simple
• loss
To improve the efficiency,
minimize the Vo
5
IECON2013
Switching Mode Mosfet
I1
VO
i2
i1
i1
iN
I LED
D1TS
I2
i2
I LED
D2TS
IN
iN
Q1
Q2
I LED
QN
DN TS
I LED =I1D1 =I 2 D2 =...=I N DN
To improve the
luminous efficiency
6
Forwarrd Current
Pulse Width Modulation
IECON2013
Switching Mode Regulator
Individual circuit and logic
• Complexity, Efficiency
To improve the efficiency
7
IECON2013
For AC Voltage Bus
• Capacitor
p
• Inductor or Transformer
8
IECON2013
Capacitor
p
based
• Large voltage stresses
Capacitors isolation
with
ith inherent
i h
t currentt
sharing capacity
9
Auto-Balance Schemes
IECON2013
Auto-Balance Schemes
Coupled inductor based
• Complexity increases exponentially
2N
i1 =i2
vO1 -vO 2
v1 =v2 =
2
10
IECON2013
Auto-Balance Schemes
Coupled inductor based
To simplify， Daisy Chain structure with 2N
11
IECON2013
Summary
Current sharing scheme is used to compensate the current
imbalance due to variation of LED characteristics;
Each scheme has its pros and cons. Selection should depend on
the application requirement, such as cost, bulk, efficiency, reliability
and so on.
IECON2013
Reference Papers
[1] Q. Hu and R. Zane, Minimizing required energy storage in off-line LED drivers based on series-input converter
modules, IEEE Trans. on Power Electronics, vol. 26, no. 10, pp. 2887--2895, Oct. 2011.
[2] K.
K I.
I Hwu and Y.
Y T.
T Yau,
Yau Applying one-comparator
one comparator counter-based
counter based sampling to current sharing control of
multichannel LED strings, IEEE Trans. on Industry Applications, vol. 47, no. 6, pp. 2413--2421, Nov/Dec. 2011.
[3] D. Liu, A. Hu, G. Wang, and W. Hu, Current sharing schemes for multiphase interleaved DC/DC converter with
FPGA implementation, IEEE International Conf. on Electrical and Control Engineering, pp. 3512--3515, 2010.
[4] X.
X Qu,
Qu S.C.
S C Wong and C.K.
C K Tse,
Tse Non
Non-cascading
cascading structure for electronic ballast design for multiple LED lamps
with independent brightness control, IEEE Trans. on Power Electronics, vol. 25, no. 2, pp. 331--340, Feb. 2010.
[5] W. Chen and S. Y. R. Hui, A dimmble light-emitting diode driver with mag-amp postregualtors for multistring
applicaitons, IEEE Trans. on Power Electronics, vol. 26, no. 6, pp. 1714--1722, Jun. 2011.
[6] J.
J Zhang,
Zhang L.
L Xu,
Xu X.
X Wu,
Wu and Z.
Z Qian,
Qian A precise passive current balancing method for multioutput LED drivers,
drivers
IEEE Trans. on Power Electronics, vol. 26, no. 8, pp. 2149--2159, Aug. 2011.
[7] K. I. Hwu and S. C. Chou, A simple current-balancing converter for LED lighting,IEEE Applied Power
Electronics Conf, pp. 587--590, 2009.
[8] X.
X Wu,
Wu Z.
Z Wang,
Wang and J.
J Zhang,
Zhang Design considerations for dual-output
dual output quasi
quasi-resonant
resonant flyback LED driver with
current-sharing transformer, IEEE Trans. on Power Electronics, vol. 28, no. 10, pp. 4820--4830, Oct. 2013.
[9] K. H. Jung, J. W. Yoo, and C. Y. Park, A design of current balancing circuit for parallel connected LED strings
using balancing transformers, IEEE International Conf. on Power Electronics- ECCE Asia, pp. 528--535, 2011.
[10] R.
R Zhang and H.
H S.
S H.
H Chung,
Chung Daisy-chain
Daisy chain transformer structure for current-balancing
current balancing multiple LED strings,
strings
IEEE Energy Conversion Congress and Expo., pp. 3118--3125, 2013.
[11] S. N. Li, W. X. Zhong, W. Chen, and S. Y. R. Hui, Novel self-configurable current-miror techniques for
reducing current imbalance in parallel light-emitting diode(LED) strings, IEEE Trans. on Power Electronics, vol.
27 no
27,
no. 44, pp
pp. 2153
2153--2162,
2162 Apr
Apr. 2012.
2012
2013/11/26
13
IECON2013
Reference Papers
[12] Y. Hu and M. M. Jovanovic, LED driver with self-adaptive drive voltage, IEEE Trans. on Power
Electronics,, vol. 23, no. 6, pp. 3116--3125, Nov. 2008.
[13] H
H. JJ. Chiu
Chiu, Y
Y. K
K. Lo
Lo, J.
J T.
T Chen,
Chen S.
S J.
J Cheng,
Cheng C.
C Y.
Y Lin,
Lin and S.
S C.
C Mou,
Mou A high-efficiency
high efficiency dimmable LED
driver for low-power lighting applications, IEEE Trans. on Industrial Electronics, vol. 57, no. 2, pp. 735--743,
Feb. 2010.
[14] S. M. Baddela and D. S. Zinger, Parallel connected LEDs operated at high frequency to improve current
sharing IEEE Industry Applications Conf.,
sharing,
Conf pp.
pp 1677--1681,
1677 1681 2004
2004.
[15] S. Choi and T. Kim, Symmetric current-balancing circuit for LED backlight with dimming, IEEE Trans.
on Industrial Electronics, vol. 59, no.4, pp. 1698--1706, Apr. 2012.
[16] J. Zhang, J. Wang, and X. Wu, A capacitor-isolated LED driver with inherent current balance capability,
IEEE Trans.
Trans on Industrial Electronics,
Electronics vol.
vol 59,
59 no.4,
no 4 pp.
pp 1708--1716,
1708 1716 Apr
Apr. 2012.
2012
[17] H. Wu, S. Ji, F. C. Lee, and X. Wu, Multi-channel constant current ($MC^{3}$) LLC resonant LED
driver, IEEE Energy Conversion Congress and Expo., pp. 2568--2575, 2011.
[18] K. H. Loo, Y. M. Lai, and C. K. Tse, Design and analysis of LCC resonant network for quasi-lossless
current balancing in multistring AC-LED
AC LED array,
array IEEE Trans.
Trans on Power Electronics,
Electronics vol.
vol 28,
28 no.
no 2,
2 pp.
pp 1047-1047
1059, Feb. 2013.
[19] X. Wu, J. Zhang, and Z. Qian, A simple two-channel LED driver with automatic precise current sharing,
IEEE Trans. on Industiral Electronics, vol. 58, no. 10, pp. 4783--4788, Oct. 2011.
[20] S
S. Zhang
Zhang, Q
Q. Chen
Chen, JJ. Sun
Sun, M
M. Xu
Xu, and Y
Y. Qiu
Qiu, High accuracy passive current balancing schemes for
large-scale LED backlight system, IEEE Applied Power Electronics Conf. and Expo., pp. 723--727, 2011.
[21] C. Lin, T. Hung, C. Wang and K. Pai, A balancing strategy and implementation of current equalizer for
high power LED backlighting, IEEE Power Electronics and Drive Systems, pp. 1613--1617, 2007.
2013/11/26
14