Limitation of switching frequency to improve characteristics and suppression of input current distortion for critical mode PFC

In critical mode power factor correction (PFC), the switching frequency is varied to achieve a sinusoidal input current waveform. Under certain conditions, a higher frequency increases the loss and noise. Meanwhile, the limitation of the switching frequency leads to an increase in input current distortion. This paper proposes a method to prevent an increase in distortion by compensating the pulse width at a limited frequency. Using this control method, critical mode PFC with a limited maximum switching frequency was evaluated. As a result, the total harmonic distortion of the input current was lower than that before the frequency limitation. Furthermore, the improvement in efficiency and the reduction in conducted EMI were confirmed.