双闭环控制反激变换器起动过程

Start Process of Flyback Converter in Double Close-Loop Control

变换器起动期间,由于低的输出电压导致过冲电流,将对变换器造成损坏。本文研究了电压电流双闭环控制反激(Flyback)变换器的起动过程,该变换器采用峰值电流控制芯片来实现。将Flyback变换器的起动过程分为电流过冲、电流调节器调节和电压调节器调节3个阶段。分别讨论了断续模式和连续模式下起动过程的3个阶段的特点,详细分析了影响起动过程电流过冲的因素。文中进行了仿真分析,并且通过对500W,200V/20V原理样机的研制,验证了仿真分析的正确性。

The low output voltage causes the control loop to call for maximum duty cycle and a large surge of input current when converter starts up, thus demaging the converter. The peak current mode PWM controller can limit the duty cycle. Flyback can deliver the stored energy in primary side to the output side in power switch off period. These two methods can alleviate the inrush current. This paper studies a voltage and current close-loop control flyback converter with peak current mode PWM controller. The start process of the flyback converter is divided into three stages： inrush current, current regulating and voltage regulating stages. The characteristics of three stages are discussed both in DCM mode and CCM mode. The critical factor effected by the inrush current is analyzed. Simulation and experimental results verify the theoretical analysis。