A Comparative Performance Study of a 1200 V Si and SiC MOSFET Intrinsic Diode on an Induction Heating Inverter

摘要

This paper presents a comparison of the behavior of the intrinsic diode of silicon (Si) and silicon carbide (SiC) MOSFETs. The study was done for 1200 V Si and SiC MOSFETs. The data sheet from manufacturers shows the characteristics of MOSFET’ intrinsic diode when gate source voltage $(V_{rm GS})$ is 0 V. There are applications where the MOSFET’ intrinsic diode is used while $V_{rm GS}$ is different than 0 V. One of these applications is induction heating, where depending on the load and the regulation system, the diode can conduct a significant part of the inverter current. In most applications which use the MOSFET’ intrinsic diode, the turn ON of the intrinsic diode happens at $V_{rm GS}$ = 0 V. After a blanking time, the MOSFET’ gate is activated waiting for the direction change of current in the circuit. Therefore, most of the current through the MOSFET’ intrinsic diode occurs with a $V_{rm GS}$ different of 0 V. This paper shows the direct output characterization of Si and SiC MOSFET’ intrinsic diode under different gate voltages. The gate resistor $(R_{G})$ is an important parameter of the characterization. Depending on the input capacitance of the Si or SiC MOSFET, different $R_{G}$ are needed. The turn-on and turn-off behaviors are obtained when $R_{G}$ is optimized for each Si and SiC MOSFET. This has result in the turn-off robustness of intrinsic diode with optimum $R_{G}$. This paper presents a surprising result for the reverse characteristic of Si and SiC MOSFETs for the same current at different $V_{rm GS}$. The technology of Si MOSFET has different behavior depending on the manufacturer. The technology of SiC MOSFET presents a very similar behavior to low-voltage Si MOSFETs.