The FAN7528 is an active power factor correction (PFC) controller for boost PFC applications which operates in the critical conduction mode (CRM). It uses the voltage mode PWM that compares an internal ramp signal with the error amplifier output to generate MOSFET turn-off signal. Because the voltage mode CRM PFC controller does not need the rectified AC line voltage information, it can save the power loss of the input voltage sensing network that is necessary for the current mode CRM PFC controller.