Passive PFC Circuit for 250W PC Power Supply

The circuit show here is input circuitry of the power supply with passive PFC. Note the line voltage range switch connected to the center tap of the PFC inductor. In the 230V position (switch Open) both halves of the inductor winding are used and the rectifier functions as a full wave bridge. in the 115V ( switch closed) position only the left half of the inductor and left half of the rectifier bridge are used, placing the circuit in the half wave double mode. As in the case of the full wave rectifier with 230V AC input, this produces 325V DC at the output of the rectifier. This 325 VDC bus is , of course, unregulated and move up and down with i9nput line voltage.

Circuit Courtesy www.onsemi.com