Here is an application example for a CCM PFC with separate auxiliary standby power supply, as might be used in a PC supply or other consumer applications. The auxiliary supply can be implemented with a CoolSET MOSFET which is always in operation and operates off the main bus voltage. Even when the PFC isn’t running, the rectified input line will be present at capacitor C2. In standby mode, both the PFC and the PWM can be turned off. The controller supply for the PFC and the PWM supply are derived from the Auxiliary supply, operating on a common ground.