How to Kill a SiC MOSFET - Errors in Gate Circuit Design

Martin Warnke, Mehrdad Baghaie Yazdi, ON Semiconductor:
Using SiC MOSFETs in various topologies can lead to great improvements in performance and efficiency, however if not used correctly engineers can quickly find themselves frustrated with failures. These failures are often, quite in contrast to the perception of the customers, no intrinsic weaknesses of the SiC MOSFET technology but in the design choices around the gate loop. Particularly the lack of attention to the turn-on interactions between the high side and low side device can result in catastrophic failures excited by wrong circuit choices. In this presentation, we show that classical dampening efforts using gate source capacitors in the gate circuit loop are a great hazard and an often hidden killer of SiC MOSFET gates. This practice of dampening oscillations on the gate, in order to improve switching transients actually results in heavy stress on the gate. This stress is not easily visible through measurements, as they occur on the internal gate node and not on the external measurable one, which thanks to the CGS seems nicely dampened. We show in simulation and test how these errors can be mitigated and where conceptual mistakes of “dampening” can be omitted.

[@Dc_tech386]

Hi I am trying to understand why mosfet damaged in a inverter dc to ac circuit a simple circuit showing 2npn mosfet connected to a half bridge inverter with only Shockley diodes to drain and source and diner diodes to gate and source but the mosfet switching convert dc to ac for only 1 minutes and mosfet failed this action happened with all 20 mosfet tested the mosfet is switching hard start but igbt turn on the transformer easy and smoothly converting and work perfectly for hours and still work but when replaced with mosfet irfz44n and irf 3710 the mosfet all fail even with a sic circuit inplace so con you explain to me why this is happening with the mosfet with no low but igbt work but mosfet fail

[@ilyasboujraf6051]

hello brother i hope you are fine please i would like you to help me in this topic SiC power devices characterization and modeling for embedded power converters

[@lo2740]

This is an OnSemi presentation, is not the place to seek help for your specific repair issue.

[@Dc_tech386]

@@lo2740 it’s ok I get pass that along time ago and my answer to why and fix it everything is ok

[@thomasmaughan4798]

MOSFET has rather high capacitance and a sharp transient especially turn-off will pulse the gate. This can make turn-off fail and in a totem-pole arrangement, the top and bottom MOSFET can turn on simultaneously which is a short circuit from battery. Also, MOSFET has very low "on" resistance which can allow high current flow if feeding a capacitor (for instance). Abrupt turn-off can produce high voltage if feeding into inductance even if you have a snubber diode if the diode is not fast enough (or able to handle high impulse current).