High Frequency ZVS GaN-Inverter with Adaptive Dead Time

This paper presents a zero voltage switching (ZVS) inverter and the corresponding modulation scheme, which uses variable and fixed switching frequency operation during the sinusoidal period to limit the switching frequency range. It is suitable for generating sinusoidal output waveforms and ensuring lossless switching over the entire fundamental period. ZVS requires a sufficiently long dead time during both switches are turned off. Typically, standard modulation schemes apply a fixed dead time. First experiments operate the ZVS inverter with a fixed dead time. Despite achieving lossless switching, unexpected high device temperatures of the Gallium Nitride half-bridge switches occur. The origin of these high temperatures need to be figured out in order to minimize the losses of the power stage. A study shows that significant reverse conduction losses occur during the half-bridge’s dead time. Thus, this paper introduces an adaptive dead time method, which shows its effectiveness at an experimental setup by reducing the semiconductor’s device case temperature by 10 K. Since the computational effort for this optimal procedure is relatively high, the paper finally presents a simplified, computationally less costly variant that achieves almost the same improvements regarding the device temperatures.