Analysis of the negative Miller capacitance during switching transients of IGBTs

The negative Miller capacitance in an Insulated Gate Bipolar Transistor (IGBT) can lead to instability and failures. The cause of this phenomenon has conventionally been attributed to the voltage dependency of the Miller capacitance. This paper investigates the real origin of the negative Miller capacitance with a new method considering the transform of the Miller capacitance characteristics. The negative current is derived based on the concept of electric charge. The conditions for the negative Miller capacitance to occur are analyzed both theoretically and experimentally. The key to reduce this effect is clear after the analysis.