Reducing the variation range of the switching frequency for CRM boost PFC converter by injecting 3rd harmonic into the input current

CRM Boost PFC converter features zero-current turn-on for the switch and no reverse recovery in diode. However, its switching frequency varies over a wide range, which leads to the efficiency deterioration and the EMI filter design complexity. In this paper, a minimum switching frequency variation range control (MFVC) strategy is proposed by injecting the optimal 3rd harmonic into the input current. Compared to that with the traditional control (TC), the proposed MFVC strategy achieves a minimum variation range of the switching frequency, an output voltage ripple reduction and a higher efficiency. A 60W input prototype has been fabricated and tested in the laboratory. The experimental results are given to verify the effectiveness of the proposed method.