Precharge switch based on metal–oxide–semiconductor-controlled thyristor for power relay assembly of battery electric vehicles

Abstract

The power relay assembly (PRA) is an essential component to ensure the safety of an electric vehicle. We propose a semiconductor-based precharge switch to overcome the shortcomings of the conventional mechanical relay, which is currently used as the precharge switch in the PRA. The gate-driving circuit uses a photocoupler instead of a gate-driving integrated circuit to reduce complexity and cost. Five devices, namely, two insulated-gate bipolar transistors (IGBTs), two silicon carbide metal–oxide–semiconductor field-effect transistors (SiC MOSFETs), and one metal–oxide–semiconductor-controlled thyristor (MCT) are tested as candidate precharge switches. Each device is analyzed under varying battery voltage and fixed measurement conditions. The IGBT and SiC MOSFET burn below 600 V, while the MCT exhibits normal operation up to 800 V. The MCT precharge switch can solve shortcomings of the conventional mechanical relay and increase the performance with a simple gate-driving circuit. Furthermore, the PRA with an MCT precharge switch can reduce the volume, weight, and cost while improving reliability.