High-efficiency capacitive idling SEPIC PFC converter with varying reference voltage for wide range of load variations

The capacitive idling SEPIC converter can operate as a power supply with reduced line current harmonics and improved power factor, which features from the decoupling of the pre-stage and the second-stage feedback loops, while preserves the cost, size and simplicity of the conventional two-stage PFC converter. The additional degree of control freedom introduced by capacitor voltage idling operating status has been exploited through an easy control technique to achieve a sinusoidal input current at near unity power factor and maintain constant DC output voltage respectively. Compared with conventional SEPIC PFC converter, the proposed converter demonstrates much improved current handling capability with reduced current and voltage ripples. Besides, the reference voltage of the energy transfer capacitor is always slightly higher than the AC input voltage peak value, which reduces the loss of the pre-stage PFC converter and improves the overall efficiency of converter. Analysis and simulation results of the capacitive idling SEPIC converter have been presented. The proposed converter shows improved load capacity and higher efficiency over the existing converters.