基于升降压的高效率低纹波LED驱动芯片设计
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摘要
设计了一款基于同相Buck-Boost变换器的LED驱动控制芯片.设计的控制电路实现了从降压模式到升压模式的平滑切换,从而保证了系统的稳定性并减小了输出电流纹波;在Buck-Boost过渡模式工作状态下,控制电路降低了平均电感电流,因而提高了系统转换效率.此外,控制电路中设计了一种自动调零的误差放大器,减小了放大器的输入失调电压和闪烁噪声,输出电流的精度得以提高.在180 nm CMOS工艺上流片的测试结果表明:当输入电压为2.7～5.0 V,输出电流为850 mA时,纹波率不超过3%;当负载电流为150 mA、输入电压为5 V时,驱动电路的转换效率高达95%.
The LED driver control circuit was designed and implemented based on noninverting buck-boost converter.The control circuit not only achieved the smooth modes transition from Buck to Boost,but also reduced the average inductor current in the Buck-Boost transition mode and improved system efficiency.Furthermore,an auto zeroing error amplifier was designed to reduce input offset voltage and flicker noise,which improved output current accuracy.The driver,implemented in a 180 nm CMOS technology,achieves percentage output current ripple of less than 3% when output current is 850 mA and the input voltage ranges from 2.7 V to 5 V,and gets the maximal efficiency of 95% when load current is 150 mA and input voltage is 5 V.
The LED driver control circuit was designed and implemented based on noninverting buck-boost converter.The control circuit not only achieved the smooth modes transition from Buck to Boost,but also reduced the average inductor current in the Buck-Boost transition mode and improved system efficiency.Furthermore,an auto zeroing error amplifier was designed to reduce input offset voltage and flicker noise,which improved output current accuracy.The driver,implemented in a 180 nm CMOS technology,achieves percentage output current ripple of less than 3% when output current is 850 mA and the input voltage ranges from 2.7 V to 5 V,and gets the maximal efficiency of 95% when load current is 150 mA and input voltage is 5 V.
引文
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[2]WEI C L,CHEN C H,WU K C,et al.Design of an average-current-mode noninverting buck-boost dc-dc converter with reduced switching and conduction losses[J].IEEE Transactions on Power Electronics,2012,27(12):4934-4943.
[3]JU Y M,SHIN S U,HUH Y,et al.A hybrid inductor-based flying-capacitor-assisted step-up/stepdown DC-DC converter with 96.56%efficiency[C]//Proc of 2017 IEEE International Solid-State Circuits Conference(ISSCC).San Francisco:IEEE,2017:184-185.
[4]REN X,RUAN X,QIAN H,et al.Three-mode dual-fequency two-edge modulation scheme for fourswitch buck-boost converter[J].IEEE Transactions on Power Electronics,2009,24(2):499-509.
[5]HONG X E,WU J F,WEI C L.98.1%-Efficiency hysteretic-current-mode noninverting buck-boost dc-dc converter with smooth mode transition[J].IEEE Transactions on Power Electronics,2017,32(3):2008-2017.
[6]RAO S,KHAN Q,BANG S,et al.A 1.2-A buck-boost LED driver with on-chip error averaged sensefet-based current sensing technique[J].IEEE Journal of Solid-State Circuits,2011,46(12):2772-2783.
[7]MA Y,WANG H,CHEN G,et al.A novel method for smooth transition in step-up/step-down DC-DC converter[C]//Proc of 2009 IEEE International Conference of Electron Devices and Solid-State Circuits(EDSSC).Xi’an:IEEE,2010:95-98.
[8]ENZ C C,TEMES G C.Circuit techniques for reducing the effects of op-amp imperfections:autozeroing,correlated double sampling,and chopper stabilization[J].Proceedings of the IEEE,1996,84(11):1584-1614.
[9]PHILLIP E A.CMOS analog circuit design[M].3rd Edition.NewYork:Oxford University Press,2012.
[10]DANCHIV A,BODEA M,DAN C.Design considerations and residual offset analysisfor an autozero transconductance amplifier topology[C]//Proc of 2006 International Semiconductor Conference.Sinaia:IEEE,2006:409-412.