A power factor correction block diagram can be divided into three main blocks: the rectifier, which provides DC voltage to the PFC converter stage; the PFC converter, which provides the control over the current shape and phase lag while regulating the output voltage; and the controller block. The PFC converter can be implemented using different circuit topologies, each of them with their advantages and disadvantages. As shown in the block diagram, the input to the circuit is an AC supply, the output of the PFC is a DC voltage. An ideal PFC makes sure that its input impedance is purely resistive. This allows maximum use of usable power, or real power. The feedback signals needed for the control loop are the rectified AC voltage, input AC current and output DC voltage. The output of the control block is a Pulse Width Modulation (PWM) signal.