High-voltage GaN HEMT evaluation in micro-inverter applications

The purpose of this work is to identify potential problems through an initial implementation and testing of an in-house designed GaN device based micro-inverter. The switching performance of high-voltage gallium nitride devices was first characterized to ensure successful implementation of a full-bridge micro-inverter. The inverter phase-leg output voltage before filter was evaluated with two different pulse-width-modulation schemes: dual modulation and discontinuous modulation. A 500-W full-bridge micro-inverter prototype was designed and tested to verify the performance of the two modulation schemes. With 100-kHz effective switching frequency, harmonic spectra and power stage efficiency were evaluated. Although the device operating condition is different, these two schemes show identical switching loss and harmonic performance when their effective switching frequency is the same. Experimental results in this implementation indicate that the circuit design and layout are critical as the parasitic inductance and capacitance coupling may cause shot-through fault and impact the switching efficiency. More efforts are needed in circuit design and layout to fully exploit the advantage of the ultrafast switching GaN devices.