一种单相降压型PFC电路及其非线性控制

以Buck为基础的单相功率因数校正(power factor correction,PFC)电路,器件电压应力小,输入、输出电流控制能力强;但输入电流存在固有死区,造成输入电流畸变。提出一种双电路模式的单相降压型PFC电路,通过加入1个辅助开关和1个二极管,在传统Buck PFC变换器的输入电流死区时间段,使电路工作于Buck-Boost模式,消除电流死区。对于Buck与Buck-Boost之间的切换控制问题,基于单周期控制,推导出一种非线性控制策略,不同工作模式具有相同的电流控制律,消除了模式切换造成的电流畸变,从而实现单位功率因数。设计了1台开关频率为50 k Hz、输出为100 V/1 A的实验样机,在175~265 V输入电压范围内,输入电流保持较低的总谐波畸变率(total harmonic distortion,THD)。电路实现2个开关管共地,驱动电路设计简单;且不同电路模式采用相同的电流控制律,简化了控制,有利于实际的工程应用。

Single-phase step-down PFC converter and its nonlinearcontrol

Buck-type power factor correction ( PFC ) converters have low voltage stress and strong input and output current control ability , but the input current has naturally dead zones in traditional single-phase Buck-type PFC converter ,which leads to high current distortion .A novel Buck PFC converter was proposed ,by adding an auxiliary switch and a diode .The dead zones were eliminated when the converter operated in Buck-Boost mode during the dead time .Based on one cycle control ,a nonlinear control was deduced to solve the transfer problem between Buck and Buck-Boost operating modes .The two operating modes have the same control strategy ,which smoothes the modes transfer and nearly unit power factor can be achieved.The circuit operating modes and control strategy were analyzed in detail ,verified by experi-mental results on a 50 kHz,100 V/1 A prototype .The total harmonic distortion ( THD) of input current keeps low in the input voltage range of 175~265 V.Both the two switches are grounded ,simplifying the driving circuits,and the two operating modes have the same control strategy ,which make the proposed converter suitable for practical application .