Junction temperature monitoring for cascode GaN devices using the Si MOSFET's body diode voltage drop

In this paper, a new online junction temperature monitoring method is proposed for cascode GaN devices using the body diode of Si MOSFET. The reverse current during soft-switching mode is utilized to extract the voltage drop of the Si MOSFET's body diode. It is pointed out that, to accurately obtain the voltage drop of Si MOSFET's body diode, the VDS voltage of cascode GaN device should be measured when the reverse current is small during the dead-time period. An experimental platform has been designed to validate the proposed method. The proposed method exhibits an accuracy within 0.6 °C and a R2 = 0.99 goodness of linear fit on a test Buck converter, showing that this method is practical for real applications.