一种带原边电流控制的单级LED驱动电源的设计

在输入输出需要隔离的LED照明应用中,传统控制环路中均用到体积较大的光耦元件传递副边反馈信息,但这种控制降低了电路的响应速度,增大了LED驱动电源的体积,降低了功率密度,同时光耦的电流传输比易受到外界温度的影响。为了减小电路尺寸、降低成本以及降低温度对驱动电源的影响,采用基于无光耦原边控制的带漏感能量回馈支路的Buck-Boost-Flyback单级功率因数校正(PFC)变换器作为LED的驱动电源,这样既降低了成本,又提升了驱动电源的性能。分析了该单级PFC变换器的关键工作过程,并对核心元件参数值进行了具体的数学推导,设计了输入市电在85~265 V、50 V输出的8 W原理样机,通过实验证实了分析的正确性。

Design of single-stage LED driver power supply based on primary-side-current regulation

In some LED lighting applications,which needed isolation between input and output,the photo-coupler was needed to transfer the feedback signal from secondary side to primary side in the conventional control loop.The traditional control strategy decreased the response speed and the power density in cause of the large size of the photo-coupler and increased the cost of the components.Worse still,the current transfer ratio of the photo-coupler was susceptible to the environment temperature.To avoid the aforementioned problems,a primary-side-regulation strategy without the photo-coupler was studied to control the LED driver power supply,which integrated a Buck-Boost converter owning a leakage inductance energy recycling path with a flyback converter.The performance of the LED driver power supply was improved by this control strategy and the converter.The operating principle of the converter during a period was presented,as well as the crucial circuit parameters.At last,the analysis was verified by the experiment on a prototype of an 8 W driver circuit with 50 V DC output voltage,which operated at the line voltage varying between 85 V and 265 V.