Current sharing for paralleled IGBTs using statistics method

Abstract

A mathematical analysis method is developed to model and calculate the deviation of the saturation voltage (Vce,sat) of IGBTs and the forward voltage (Vf) of the inverse diodes. In paralleled IGBT applications, it is important to predict the maximum current imbalance and maximum junction temperature deviation among the paralleled devices. This requires the knowledge of Vce,sat and Vf ranges at various operating conditions, such as junction temperature and current density. Since it is unrealistic to measure the parameters on 100 percent of production lots, the proposed technique uses statistical models requiring only sample measurements to provide a quantitative analysis for Vce,sat and Vf deviation. The adequacy of the modeling is tested to verify the assumption. Knowing the maximum and minimum Vce,sat and Vf values, a sample thermal model for paralleled IGBTs is presented and the maximum junction temperature deviation among paralleled IGBTs is calculated. The adequacy of the modeling is tested to verify the assumption.