日本語が上手くないので英語を書きます。 MOSFET/IGBT have to work in saturation mode only fully on or fully open , the Gate voltage have to connect to high enough to make sure the MOSFET / IGBT go into saturation not in linear region.. During Linear region the MOSFET dissipation alot power and over heat... So when you slowly increase the power supply voltage like 5V the MOSFET didnt fully turn on and in linear region cause the MOSFET burn.