具有高功率因数的原边反馈LED恒流电源的研究

Study on Primary-Controlled High-PF LED Driver

为了满足LED照明对低成本、小体积以及高功率因数的要求,采用了具有单级功率因数校正(PFC)和原边反馈(PSR)恒流控制功能的驱动电源方案。文章分析了在单级PFC拓扑下原边恒流控制的原理,提出一种新颖的去磁时间检测方法,并将其应用于芯片G7102;同时推导了在准谐振工作模式下单级PFC拓扑的电流和功率因素λ值的计算公式,提出该工作条件下变压器的设计方法;最后制作了24 V 350 mA输出的LED驱动电源。实验证明,该方案在全电压范围内,电源效率η为85%以上,功率因数0.9以上,恒流精度达到2%,在小功率LED照明中具有很高的应用价值。

Aiming at the low-cost,small size and high power factor requirements of the LED driver,the primary-side control and single-stage power factor correction were both integrated in the topology.The relationship between quantities on the primary side and output current of the high-PF flyback converter was analyzed,and a novel strategy of secondary diode conduction period detection was proposed and applied to controller G7102.Then a method of transformer designing was proposed after analyzing the current and power factor under quasi-resonant mode,and the design methods of several key parameters were included,finally produced 24 V 350 mA output LED drive was produced.Experiment results show that within the full voltage range,power efficiency more than 85％,power factor above 0.9,constant accuracy of 2％,has a higher application value in small power LED lighting.