一种减小PFC变换器电容规格的方法

常规的由Boost和DC/DC变换器级联构成的两级式PFC变换器,在Boost电路输出端要接高耐压等级的电解电容作为储能电容,不仅体积大、价格高,而且寿命短,为此本文研究了一种低压输出的Boost/半桥组合式软开关谐振PFC变换器。该变换器利用半桥电路输出端的低压电解电容平衡瞬时功率,Boost电路输出端电容与变压器漏感谐振,并不大量储能,由此减小了Boost电路电容的规格,提高了工作可靠性。讨论了该变换器的控制策略,前后级共用一套控制电路,实现功率管的软开关和能量的传递。分析了降低电容容值的可行性,指出采用小容值非电解电容替代Boost电路输出端的大容量电解电容后,变换器具有良好的性能。给出了Boost和半桥电路输出端电容的设计方法,进行了实验验证。

Method for Reducing Capacitor Size of PFC Converter

In a conventional two-stage PFC converter cascaded from the Boost and DC/DC converters,the output of the Boost circuit needs high voltage level electrolytic capacitor to storage energy,which has a large volume,short lifetime and high price.A Boost/half-bridge combined soft-switching resonant PFC converter is studied.It uses the low voltage electrolytic capacitor in the output of the half-bridge circuit to balance the instantaneous power,and greatly reduces the capacitor of a PFC converter.The Boost circuit output capacitor is resonant with the leakage inductance of the transformer.The control logic using a common circuit to control the two-stage converter is discussed.Good performance of the converter with small capacitance in the output of the Boost converter improves the feasibility of the reduction in capacitance.The capacitor design methods are given.The experimental results verify the theoretical analysis.