整合式单开关两路恒流输出LED驱动电源

提出了一种整合式单开关两路恒流输出LED驱动电源.该LED驱动电源由非隔离Buck-Boost和Buck变换器通过一个有源开关整合而成,简化了控制环路.采用恒导通时间COT(constant on-time)控制,消除了Buck功率因数校正PFC(power factor correction)变换器输入电流的死区.因...

Integrated Single-switch Dual-string LED Driver with Constant Current Output

In this paper, an integrated single-switch dual-string LED driver with constant current output is proposed, which is composed of a non-isolated Buck-Boost converter and a Buck converter by using only one active switch, thus simplifying the control loop. With the constant on-time(COT) control, the dead zone of input current of the Buck power factor correction(PFC) converter is eliminated. Therefore, the input current harmonics of the proposed LED driver can easily meet the IEC61000-3-2 Class C limits. By means of the passive current-balancing network, the control of current in only one string can realize the current-balancing control of the other string, thus simplifying the control circuit. By combining the advantages of the Buck-Boost converter(e.g., high power factor) and the Buck converter(e.g., high efficiency), the proposed LED driver can achieve a high efficiency and a high power factor in universal-input applications. Finally, a 56 W dual-string prototype with 93.5% peak efficiency was built, and results verified the theoretical analysis.