Gallium nitride (GaN) field-effect transistors have low ON resistance and switching losses in high-frequency (>MHz) resonant wireless power transfer systems. Nevertheless, their performance in the system is determined by their characteristics and operation mode. A particular operating mode in a 6.78-MHz magnetic resonant wireless transfer system that employs class-D GaN power amplifiers in the zero-voltage switching mode is studied. Two operation modes, the forward mode and the reverse mode, are investigated. The nonideal effect under the device-level dynamic resistance and thermal effect are also analyzed. The dynamic resistance under different operation modes is demonstrated to have different generation mechanisms. Finally, the device characteristics with system operating conditions are combined, and the effects of temperature and dynamic resistance under different operating conditions are evaluated.
A wireless power transfer system using commercial lateral gallium nitride (GaN)‐based high electron mobility transistor (HEMT) is studied. Waveform distortions from an ideal class‐D zero‐voltage switching topology are observed. A special method is presented to accurately measure the dynamic resistance in the nanosecond scale. The origin of distortions is traced back to both the circuit and device levels. The receiver‐side condition and dynamic ON resistance of the GaN devices, as well as the thermal effects are responsible for the waveform distortion. The severity of deterioration of the GaN device is influenced by the circuit performance. Herein, the influence of the nonideal effects of the device on the system under different working conditions is studied. It is found that such influence can be reduced by adjusting the circuit design.
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