Current Ripple Reduction with Enhanced ZVS Operation Based on Off-time Discrete Control for DCM Inverters to Achieve High Efficiency

This paper proposes an enhanced modulation strategy based on a discontinuous current mode (DCM) for single-phase full-bridge inverters. The DCM inverter with an off-time discrete control can achieve zero-voltage switching (ZVS) by discretely adjusting the oscillation cycles during the zero current period. Based on the off-time discrete control, a new control strategy is proposed to improve the efficiency. The triangular inductor currents with high peak values in conventional modulations are reshaped into trapezium-like waveforms by rearranging turn-on duty ratios for the two legs in the full-bridge inverter. Furthermore, the conditions to achieve minimum peak current with ensuring ZVS operation are analyzed and an optimized operation strategy is shown. With the proposed strategy, higher efficiency can be achieved since the peak and rms current flowing through the semiconductor devices and inductors are reduced. A 400-W prototype using GaN-HEMTs was built to verify the feasibility and effectiveness of the proposed strategy. The loss reduction by the proposed strategy was verified in the experiments, and it was confirmed that the experimentally measured loss reduction agreed with the estimated loss reduction well.