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

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_GS) is 0 V. There are applications where the MOSFET´ intrinsic diode is used while V_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_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_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 RG 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_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.