Research On Passive Lossless Snubber For CCM PFC

Power factor correction technology has been widely applied in switch mode power supply to reduce the harmonic pollution to the grid. However the added energy conversion decreases the efficiency of it. Small size and high power density are the tendencies and requirements of SMPS all the time and how to improve the efficiency and performance of converters is the key point for power electronics. Based on the deep investigation, the passive lossless snubber is applied in power factor corrector and snubber topologies are deeply researched especially in this paper.This paper analyzed the Boost converter power loss breakdown firstly, and founded the power loss mathematical models. Using MathCAD software, the efficiency of Boost type PFC was calculated. The calculation result showed that the percent of switch turning-on power loss caused by reverse recovery of diode was 1.2%. So the efficiency and performance of PFC could be improved if the switch realizes soft switching.Minimum voltage stress cell and Non-minimum voltage stress cell were researched in detail. The operating principle was analyzed and passive components parameters design method was presented also. Experimental results showed that both the two snubbers could improve the efficiency of PFC. Unfortunately, some drawbacks were followed, such as extra voltage or current stress, complex parameters design process.In this paper, a novel passive lossless snubber based on magnetic coupling was proposed through summarizing the structure characteristics of coupling passive lossless snubbers. Simple structure, brief parameters design process and wide soft switching realizing range were the evident advantages. Besides, the introduction of it did not introduce the extra voltage stress to switch. Comparing some passive lossless snubbers, the proposed snubber overcame the following defects: high voltage or current stress, complex parameters design and soft switching conditions are difficult to be satisfied.The 500 W prototype was designed and built at the basics of principle analysis and parameters calculation. The tested results showed that when the PFC with the proposed snubber operated in 220 V input and half load output, the efficiency was 96.7%, the total harmonic distortion of input current was 4.0% and the power factor was 0.986.