An active voltage clamping method on series connected power semiconductors for pulsed hard switching application

Abstract

There are commonly and widely used snubber, voltage clamping, and gate control circuit in series connection of IGBTs (Insulated Gate Bipolar Transistor) to relieve switching stresses induced by unbalanced voltage sharing in each of the IGBTs and overvoltage while that are occurred by rapid load condition varying, stray inductance, and delayed switching behavior in the power semiconductor switches. Due to easy design with simple structure and effective characteristics to suppress overvotage in the IGBTs, snubber circuit is preferred. But, high voltage switch that is composed by series connected IGBTs with snubber circuit has limitation in switching condition such as load condition, pulse duration, and operating frequency because capacitor of the snubber circuit is fixed and has to change its capacitance in proportion to operating frequency with pulse duration. Thus, focus of this paper is introducing newly designed active voltage clamping control method with passive network that consists of passive network circuit that is similar to the snubber circuit, BJT, and capacitor which is connected to the BJT to overcome shortcomings of the snubber circuit in narrow modulation of operation frequency and pulse duration in the series connected IGBTs.