A Comprehensive Investigation on Short-Circuit Oscillation of p-GaN HEMTs

This article presents a study on the short-circuit (SC) instability of p-doped gate gallium nitride (p-GaN) high-electron-mobility transistors (HEMTs). Under SC condition, self-sustained oscillation occurs when a package stray inductance is introduced in a common source. The SC oscillation features some unique characteristics. With higher dc-bus voltage, the SC oscillation tends to be more unstable. The SC oscillation of p-GaN HEMTs is, thereby, a real threat to the converter operation. When the common-source inductance is eliminated or a larger gate resistor is utilized, the SC oscillation can be dampened. Due to the SPICE simulation, the self-sustained SC oscillation is reproduced. The analyses on the simulated waveforms reveal a positive feedback mechanism that excites the SC oscillation. An analytical model is, thereby, derived to analyze the instability of the positive feedback system. The analyses reveal that the SC oscillation becomes more unstable when the power loop or gate loop has smaller stray inductances, which makes some conventional oscillation suppression methods invalid. To avoid SC oscillation, some effective guidelines are proposed at the end of the article.