Compared to the passive power factor correction circuit composed of bulky inductors and capacitor filters, this solution adopts an active power factor correction circuit with better power factor correction performance and higher power density, which has been widely applied. The active power factor correction circuit incorporates a DCDC switch-mode converter between the rectifier and the load, using control techniques to automatically track the input current waveform with the AC input sine voltage waveform, thereby reducing THD and improving power factor.