A universal automatic and self-powered gate driver power supply for normally-ON SiC JFETs

Abstract

Normally-ON silicon carbide junction-field-effect transistors have a simple design and exhibit advantageous performance in terms of losses, elevated junction temperatures and high switching frequencies. However, under a loss of power to their gate, normally-ON junction-field-effect transistors are subject to a shoot-through situation, which might be severe for their survivability. This paper presents a universal concept for an automatic and self-powered gate driver power supply circuit for normally-ON silicon carbide junction- field-effect transistors employed in high input-impedance circuits. The power to the gate is supplied during start-up and steady-state operations through a mutually coupled induc- tor with the high input impedance inductor and by employing a typical low-voltage, power supply circuit. The performance of the proposed automatic and self-powered gate driver was evaluated on a DC/DC boost converter rated at 6 kW, as well as in a low-voltage solid- state DC circuit breaker. From experiments it is shown that using the proposed circuit, the start-up process requires approximately 350 s, while the steady-state switching process of the junction-field-effect transistor during steady-state is also shown. Using the proposed circuit in a low-voltage solid-state DC breaker, a fault current of 68 A is cleared within 155 s.