Critical mode boost power factor correction converter with high efficiency and reduced input current distortion using variable inductor

In low-to-mid power applications, a critical mode (CRM) boost power factor correction (PFC) converter is widely used due to its simple control and low switching loss. In a CRM boost PFC converter, switching frequency fs varies over a wide range. In order to avoid audible noise small boost inductance LB is required. However small LB degrades efficiency and power quality by increasing fs. In this paper, a new method of improving efficiency and power quality for a CRM boost PFC converter is presented. This method uses a current-controlled variable inductor, where the inductance is adaptively changed according to the line input voltage Vin, rms. At nominal Vin, rms, where high efficiency and high power quality are required, the proposed method operates with large LB to reduce fs. On the other hand, at off-nominal Vin, rms, LB is changed to a smaller value to avoid the audible noise problem. The effectiveness of the proposed method is experimentally verified with 90–264 Vrms input voltage and 395 V/0.5 A output prototype.