Design and Implementation of a Half-Bridge Resonant Converter with Light Load Efficiency Improvement

The paper describes the design of a half-bridge resonant converter that addresses the efficiency degradation issue caused by increasing switching losses at light loads during half-bridge resonant converter operation. The method used in this situation is burst-mode control with series resonant frequency operation. When the converter enters burst mode, the switching frequency is decreased to the series resonant frequency, and set the constant burst-frequency for output voltage regulation. This control method let the efficiency at the best point of this converter. An experimental prototype circuit with an input voltage of 400 V, output voltage of 12 V, rated power of 360 W, and series resonant frequency of 200 kHz is built to confirm the theoretical analysis in this study. In order to put the converter control methods into practice, a digital signal controller called the dsPIC33CK256MP506 is utilized. Under light load, it used burst-mode control that switch frequency is reduced to series resonant frequency functioning. The efficiency of the burst-mode control with switching frequency reduction is greater than other controls, according to experimental data. The best efficiency of converter is 93.7% at 50% load. At light loads, delivering a maximum efficiency improvement of up to 2.6% for load situations ranging from 1% to 8%.