MOSFET and IGBT : Gate Driver and Semi-conductor Monitoring

This article focuses on advanced control circuits for silicon MOSFET and IGBT power devices, commonly known as "drivers" or "gate drivers". After a brief review of the elementary function of close control, the article focuses on the structure of industrial drivers, analyzing in detail the advanced functions they contain. The proposed approach is highly pragmatic, drawing on a wealth of experimental data to provide an in-depth understanding of the many electronic schematics of drivers' internal functions. A structural analysis highlights the main functions, namely the transmission of control commands through a galvanic isolation barrier and the protection of power components. Subsequently, only the transformer-based transmission of control commands is studied. Four electronic schematics meeting these requirements are analyzed in depth. Two main gate drive stages, frequently used, are studied. The first contains two complementary MOSFETs, while the second uses a push-pull bipolar transistor stage. The advantages and disadvantages of these two structures are discussed, with detailed measurements showing their operating mechanisms. The second part of this article deals with the implementation of monitoring and protection functions for power components. The authors clearly show that the galvanic isolation of the control commands and the structure of the gate drive stages have a direct impact on the implementation of the drivers' internal protection mechanisms. Two electronic structures are presented for detecting a short circuit in a switching cell. This monitoring of rapid, abnormal current growth is based on measurement of the voltage across the power component. The detection of a conduction state or abnormal switching triggers various protection mechanisms. The soft shutdown function of the power component is analyzed for the two gate drive stage structures mentioned above. The implementation of gate resistance variation or Miller plateau duration control by constant current is studied. Finally, the protection of the power component by restoring conduction is discussed. The implementation of this function, called active clamping, is discussed for the bipolar transistor gate drive stage only.