Partial Discharge Measurement of Power Module Packaging Insulation Under Square Wave with Short Transition Time Based on SHF-Down-Mixing Method

Exploring the partial discharge (PD) characteristics of power modules under square wave high electric fields with short rise and fall time is of great significance for improving the reliability of its packaging insulation. In this paper, a PD detection method based on super high frequency (SHF, 3-30 GHz) technique and signal down-mixing principle is applied to detect the PD under square wave. The power module packaging insulation specimen consisting of metal baseplate, direct bonding copper (DBC), substrate and housing is fabricated. A repetitive square wave generator is built to supply high voltage square waves with short transition time. PD experiments are performed under square wave and sinusoidal wave. Experimental results show that the SHF-down-mixing PD detection system can effectively suppress the electromagnetic interference (EMI) from the square wave and extract PD signals successfully. As the radius of the electrode corner increases, the partial discharge inception voltage (PDIV) values under the sinusoidal wave also gradually increases. The PDIV under square wave does not show a monotonically increasing and is usually higher than that under sinusoidal wave probably because of the effect of space charge accumulation.