Nonlinear Output Capacitance of Bidirectional Gallium Nitride Power Switches

In this work, the characterization of the non-linear output capacitance of bidirectional GaN transistors is presented for the first time. An experimental characterization in an Unclamped Inductive Switching Circuit of the nonlinear output characterization of a discrete bidirectional GaN transistor consisting of two 650 V anti-serial unidirectional GaN transistors in common-drain and common-source configuration is shown. Besides the evaluation of the dissipated energy due to the non-linear output capacitance the influence of the negative gate source voltage is investigated. While the dissipated energy decreases with a more negative gate source voltage for a unidirectional switch the shows the inverse behavior. At 400 V the common drain configuration has with 17 μJ almost twice as much dissipated energy as the common source counterpart. Furthermore, an analysis into the origin of the losses will be given, which can be used to improve the modeling of bidirectional GaN transistors. Thus, a better understanding for the switched operation of a bidirectional switch is gained.