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 f_s varies over a wide range. In order to avoid audible noise small boost inductance L_B is required. However small L_B degrades efficiency and power quality by increasing f_s. 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 V_{in, rms}. At nominal V_{in, rms}, where high efficiency and high power quality are required, the proposed method operates with large L_B to reduce f_s. On the other hand, at off-nominal V_{in, rms}, L_B is changed to a smaller value to avoid the audible noise problem. The effectiveness of the proposed method is experimentally verified with 90–264 V_rms input voltage and 395 V/0.5 A output prototype.