Research on Mechanism and Suppression Method of Current Unbalance of Parallel IGBTs

To study the influence mechanism of asymmetric parameters on current sharing, the appropriate approximation is taken to solve the time-domain expression of the current difference when the parameters are inconsistent. From the expression, the factors that contribute to current imbalance are analyzed. By comparing the expression of current difference caused by different parameters that result in static or dynamic current imbalance, the sensitivity of different parameters of chip, packaging and driver to the current distribution is analyzed. The theoretical analysis is verified by experiment, partly. Based on the expression of current difference, a method of reducing the current difference is discussed and experimentally verified. The improvement of current imbalance due to mismatched Delta L-com decreasing from 46% to 21% is achieved. By this method, the current distribution in a Press-Pack IGBT module could be successfully improved by 50%.