Low Parasitic Repackaging and Integration of Multiple GaN HEMT Devices

The wide bandgap semiconductor GaN HEMT device performs faster switching speed, which brings the advantage of high switching frequency and the challenge of switching stability for high power density of power converter. Besides, the current rating of the GaN HEMT discrete device is insufficient for industrial applications, so as that the high capacity multi-chip parallel GaH HEMT power module with innovative packaging structure is pursued. However, the traditional wire-bonding packaging with high parasitic is not suitable for the GaH HEMT power module with voltage overshooting and ringing issues. Due to the low threshold voltage of GaN HEMT, the unbalanced current sharing also challenge the multi-chip power module. In this paper, a low parasitic repackaging concept is proposed for a 650 V / 120 A GaN HEMT power module integrated with multiple GaN HEMT discrete devices and gate driver. A novel self-powered isolated gate driver is employed to simplify the parallel paths and shorten the power loop. Compared to the packaging with conventional layout, the measured parasitic inductance of the proposed multi-chip GaN HEMT power module is 4.75 nH, which is reduced by 46.7% benefit from the optimized symmetric layout. Furthermore, the experiments also present the overshooting voltage is only 7.3% under 400 V and 80 A during turn-off transient. The experimental results also ensure the outstanding current sharing performance of the proposed power module layout.