一种单级隔离恒流输出LED驱动电源的分析与设计

Analysis and Design of a Single-stage Isolated LED Driver With Constant Current Output

在交流输入LED照明应用领域,为降低成本,减小体积,可以采用单级驱动电源对LED进行恒流驱动。为此,提出一种由工作于电感电流断续模式的Buck-Boost功率因数校正单元和带倍压整流电路的隔离型DC/DC变换单元通过共用开关管复合而成的单级隔离型LED驱动电源。当开关工作占空比一定的条件下,功率因数校正单元能实现单位功率因数,DC/DC变换单元由于采用倍压整流电路,提高了变压器磁芯利用率,并降低了二极管的电压应力。首先阐述了其工作原理,然后对其性能进行了详细分析,并完成了主电路参数的定量设计,最后根据参数设计结果搭建了一台输出功率为120W的实验样机,并进行相关实验验证。实验结果验证了理论分析和参数设计的正确性。

In order to reduce cost and volume in the ac input LED lighting system applications, the single-stage LED driver is often used to drive LEDs with constant current. Therefore, a single-stage isolated LED driver is proposed in this paper, which integrates a Buck-Boost power factor correction unit operating in the discontinuous current mode into an isolated DC/DC conversion unit with a voltage doubler rectifier circuit by sharing a same power switch. The power factor correction unit can achieve unity power factor when the duty ratio of the switch keeps constant. Since there is a voltage doubler rectifier circuit in the isolated DC/DC conversion unit, the magnetic core utilization can be improved and the voltage stress of the secondary diodes can be decreased. Firstly, the operating principle of LED driver is analyzed in this paper. Then, the performance of the main circuit is selectively analyzed and all parameters are quantitatively designed in detail. Finally, a 120W experimental .prototype is built according to the results of parameter design, and the experimental results are presented, which have verified the correctness of the theoretical analysis and parameter design.