A Novel Noiseless Burst Mode Control of Half-Bridge LCC Resonant Converter Based on Simplified State Trajectory

Abstract

When the half-bridge LCC resonant converter works in light load mode, its high switching frequency and large reactive power in the resonant circuit reduce the efficiency of the converter significantly. Burst mode is an effective method to improve the light load efficiency of the converter. However, the conventional burst mode will cause the voltage and current to oscillate and further increase the loss, and even cause the transformer to saturate. In this paper, the simplified state sub-trajectories of different modes of half-bridge LCC converter were derived, and the state trajectory control strategy of the burst mode for half-bridge LCC converter was derived. By controlling the switching time of the half-bridge, there is no oscillation during burst off time, which makes the half-bridge LCC converter work in high efficiency stably. Besides, considering the noise pollution problem of burst mode under extremely light load conditions, the improved control is proposed based on the simplified state trajectory to ensure that the LCC converter works outside the audible band to avoid noise. Finally, an experimental prototype was built. The experimental results show that the proposed method can significantly improve the light load efficiency of the half-bridge LCC converter, and eliminate the oscillation and noise pollution of the resonant circuit.