Dynamic gate resistance control for current balancing in parallel connected IGBTs

In high power applications, switching devices such as MOSFETs and IGBTs must often be connected in parallel in order to provide higher current capability. However, the current imbalance of parallel connected IGBTs due to stray inductance, variations in device characteristics and asymmetric PCB layout, necessitates de-rating of the IGBTs. This deliberate de-rating is required in order to ensure the IGBTs function within their Safe-Operating-Area. Unfortunately, de-rating also leads to an increase in cost, size and complexity of the overall power electronics system. A current balancing method for parallel connected IGBTs using a dynamically adjustable gate driving resistance (Rg_dyanmic) is presented in this paper. Experimental results are achieved by measuring the current distribution between two parallel connected IGBTs (rated at 600V, 90A). These experimental results indicate an improvement in average current imbalance of 74% and 65% for the turn on and off periods, respectively.