Study on False Turn-On in IGBT With Floating p-Well and Comparing With Improved Structures

In a half bridge circuit, one OFF-state insulated gate bipolar transistor (IGBT) can be turned on falsely if its overshoot of gate voltage ( ${V}_{\text {GE}}$ ) exceeds the threshold voltage ( ${V}_{\text {th}}$ ) during the turn-on period of the another IGBT. In this article, the mechanism of false turn-on in the IGBT with floating p-well [i.e., injection-enhanced IGBT (IEGT)] is studied based on theoretical analysis, simulation, and experiment. Main factors determining the overshoot of ${V}_{\text {GE}}$ are Miller capacitance ( ${C}_{\text {GC}}$ ), collector voltage change rate ( $\textit {dV}_{\text {CE}}/\textit {dt}$ ), gate-emitter capacitance ( ${C}_{\text {GE}}$ ), and gate resistance ( ${R}_{\text {G}}$ ). It is found that the peak overshoot of ${V}_{\text {GE}}$ [ ${V}_{\text {GE(max)}}$ ] occurs after the time with peak $\textit {dV}_{\text {CE}}/\textit {dt}$ due to the ${R}_{\text {G}}~{C}_{\text {GE}}$ network, which is beneficial for reducing ${V}_{\text {GE(max)}}$ to some extent. Reducing ${C}_{\text {GC}}$ is the most effective way to suppress the false turn-on and improve the tradeoff between turn-on loss ( ${E}_{\text {on}}$ ) and ${V}_{\text {GE(max)}}$ , which is verified by comparing the IEGT with three improved structures, i.e., IGBT with floating p-well separated from the trench gate, micropattern trench (MPT) IGBT, and split gate (SG) IGBT. Experimental results show that ${V}_{\text {GE}(\max)}$ in MPT IGBT is reduced by 39% even under a higher peak $\textit {dV}_{\text {CE}}/\textit {dt}$ .