The FL7930B is an active power factor correction (PFC) controller for boost PFC applications that operate in critical conduction mode (CRM). It uses a voltage-mode PWM that compares an internal ramp signal with the error amplifier output to generate a MOSFET turn-off signal. Because the voltage-mode CRM PFC controller does not need rectified AC line voltage information, it saves the power loss of an input voltage sensing network necessary for a current-mode CRM PFC controller.FL7930B provides over-voltage protection (OVP), open-feedback protection, over-current protection (OCP), input-voltage-absent detection, and under-voltage lockout protection (UVLO). The additional OVP pin can be used to shut down the boost power stage when output voltage exceeds OVP level due to the resistors that are connected at INV pin are damaged. The FL7930B can be disabled if the INV pin voltage is lower than 0.45 V and the operating current decreases to a very low level. Using a new variable on-time control method, total harmonic distortion (THD) is lower than in conventional CRM boost PFC ICs.