Efficiency Improvement With Off-Time Discrete Control for GaN-Based MHz-Operated Discontinuous Current Mode Grid-Tied Inverter

This article proposes to apply an improved modulation based on a discontinuous current mode (DCM) to grid-tied inverters for efficiency improvement. The losses caused by the parasitic capacitance of the devices can be nonnegligible in MHz-operated converters even with Gallium Nitride high-electron-mobility transistors (GaN-HEMTs). The proposed off-time discrete control can achieve ZVS by discretely adjusting the oscillation period. This article reviews the principles of the proposed modulation, and the mechanism of the losses caused by the parasitic capacitance of semiconductor devices and printed circuit board. This article also reports some experimental verification with a 400-W fabricated converter, which consists of GaN-HEMT devices and is operated at 1 MHz. The loss reduction by the proposed off-time discrete control was verified in the experiments, and it was confirmed that the experimentally measured loss reduction agreed with the estimated loss reduction based on the model and device characteristics.