One-Step Method of Dynamic Capacitances Extraction From a SiC Power MOSFET in a Half-Bridge Package for EMI Analysis

The electromagnetic interference (EMI) and dynamic capacitance characteristics of metal-oxide-semiconductor field-effect transistors (mosfets) are essential considerations in circuit design and electromagnetic compatibility. A mosfet is a semiconductor widely used in switching applications. The dynamic capacitance characteristics of a mosfet are closely related to the switching behavior of the circuit and EMI generation. Therefore, for EMI analysis and to control power conversion systems, the capacitances of the mosfets have to be accurately known. The capacitance of a mosfet changes depending on the dc bias voltage. In other words, this means that EMI characteristics may vary depending on operating conditions, so capacitance must be obtained based on the dc voltage. Much research has been conducted on the capacitance extraction of a single mosfet. However, the complexity of the half-bridge structure increases as the number of terminals increases, so conventional research has limitations. This article proposes a method to extract the half-bridge mosfet dynamic capacitances simply using a one-step measurement. By changing the terminal connection of the half-bridge mosfet, the dynamic capacitances were obtained through two-port S-parameter measurement. The proposed method was verified through simulation and experiment, and a switching test was performed for EMI analysis.