The Description of Turn-Off Process and Evaluation of Switching Power Losses in the Ultra Fast Power Mosfet

The article presents an analytical description of the turn-off process of the power MOSFET suitable for use in high-frequency converters. The purpose of this description is to explain the dynamic phenomena occurring inside the transistor and contributing to the switching power losses. The detailed description uses the results of simulation studies carried out using a very precise model of the CoolMOS transistor manufactured by Infineon (IPW60R070C6). The theoretical analysis has been verified in experimental measurements of power dissipated during turn-off transient of MOSFET operating in a full bridge converter with switching frequency of 100 kHz. To estimate these switching losses an original thermovision method based on the measurement of heat dissipated in the power semiconductor switches has been used. The obtained results confirm the correctness of the conclusions drawn from the theoretical analysis presented in this paper.