Simplified single stage PFC including peak current mode control in a flyback converter

The flyback-converter is suitable for low-cost single-stage power factor correction up to 300 W. If there are requirements for very low THD, the input current needs to be controlled to follow a sine wave reference signal by an inner current feed back control loop. Peak-current-mode control can be the choice for controlling the input current to achieve low THD. This can be achieved by a proper choice of the transformer's primary inductance. The inner control loop is however, dependent on a large output capacitor to have enough loop gain. Precautions must be taken to avoid sub-harmonic oscillations, which otherwise will have a negative effect on the conducted EMI-noise at the AC-inlet.