Improvement of Characteristics in CRM-PFC Using a Control Method based on Switching Frequency Limitation

This paper deals with efficiency improvement and noise reduction of a critical-conduction-mode power factor correction (CRM-PFC) circuit. In CRM-PFC, the switching frequency increases near the zero crossing of the input voltage. However, losses and conducted EMI increase with increase in the frequency. This paper proposes a control method which is based on limiting the switching frequency. Generally, limiting the switching frequency worsens the total harmonic distortion of the input current. The proposed method reduces the input current distortion as compared to the conventional method by compensating the on-time width of the switching device. Furthermore, with this method, the efficiency is improved and the conducted EMI is reduced while the temperature rise of the inductor is suppressed. Experimental results are presented to validate the efficacy of the proposed method.