功率因数校正电路轻载工况下的效率优化

Efficiency Optimization of Power Factor Correction Circuit Under Light Load Conditions

单级式LLC功率因数校正(PFC)变换器由于保留了LLC软开关特性,并具有电路简单、成本低以及Buck-Boost功率转换能力强的优势而被广泛应用。但是在轻载工况下,该变换器使用传统的电压电流双环控制方案会出现效率降低、输出电压失调的问题。针对轻载工况产生的这些问题,提出最少脉冲下均匀脉冲密度调制。该方法能够实现在不同负载下,系统自动选择合适的脉冲密度,通过均匀地关断驱动信号,减少初级输入的能量,从而改善轻载工况下产生的问题。采用该调制方法在额定功率为500 W的实验样机上测试,结果表明最少脉冲下的均匀脉冲密度调制能够有效提高系统效率,稳定输出电压。

The single-stage LLC power factor correction(PFC)converter is widely used because it retains LLC softswitching characteristics,has the advantages of simple circuit,low cost and strong Buck-Boost power conversion capability.However,under light load conditions,the converter using the traditional voltage and current dual-loop control scheme will have problems of reducing efficiency and output voltage misaligned.Aiming at these problems caused by light load conditions,uniform pulse density modulation with minimal pulses is proposed.Using this method,under different loads,the system automatically selects the appropriate pulse density and reduces the energy input by the primary side by uniformly turning off the driving signals to improve the problems under light load conditions.This modulation method is tested on an experimental prototype with a rated power of 500 W.The results show that the uniform pulse density modulation with minimal pulses can effectively improve the system efficiency and stabilize the output voltage.