升压型Boost-PFC电路的频率反走临界电流控制

Frequency reverse method in boundary current control of Boost-PFC circuits

临界导通工作模式下的Boost PFC电路在交流输入电压过零点附近出现开关频率过高和过零点交越失真,导致电路开关损耗增加和总谐波失真增大,为此在恒定导通时间控制基础上,提出了一种电流控制频率反走的控制策略。通过在交流输入电压过零点附近将电路从临界工作模式切换到断续工作模式的方式,降低电路在交流输入电压过零点附近开关管的工作频率,提高变换器效率;并增大交流输入电压过零点附近时电路的开关管导通时间,增加电感储能,使得二极管在交流输入过零点附近仍能导通,改善过零点交越失真。仿真和实验结果表明:运用电流控制频率反走控制策略后,在交流输入电压过零点附近,电路通过切换到断续工作模式,降低了工作频率,增大了开关管导通时间。Boost PFC电路效率得到提高,电路的总谐波失真减小。

Aiming at the problem of high switching frequency and zero-crossing distortion in the Boost-PFC(power factor correction) circuit near the zero-crossing of AC input voltage in critical conduction mode, which leads to the increase of circuit switching loss and total harmonic distortion, on the basis of constant on-time control, a current control strategy of frequency foldback is proposed. By switching the circuit from the critical working mode to the discontinuous working mode near the AC input voltage zero crossing, the switching frequency of the circuit near the AC input voltage zero crossing was reduced, and the efficiency of the converter was improved. The switching tube conduction time of the circuit was increased when the AC input voltage was near zero crossing, and the inductive energy storage was increased, so that the diode can still conduct near the AC input zero crossing and the zero crossing distortion was improved. The simulation and experimental results show that the circuit can reduce the working frequency and increase the on time by switching to discontinuous mode when the AC input voltage crosses zero. The efficiency of the Boost-PFC circuit is improved, and the total harmonic distortion of the circuit is reduced.