Evaluation of Surge Reduction Performance of a SiC Avalanche Diode with Mesa Structure in a Switching Power Supply

A p-n junction diode with mesa structure by silicon carbide (SiC) has been developed to utilize the avalanche breakdown in an excessed reverse bias condition to clamp the surge voltage in switch-mode power supplies. Static voltage-current correlation by pulsed reverse voltage has been measured. The increase of the breakdown voltage was measured to be 32 volts with increased current density up to 3900 A/cm 2 . The operational performance in suppressing the surge voltage in a step-down DC/DC converter has been evaluated. A superior performance in suppressing the surge voltage by the SiC p-n junction diode has been confirmed. It was also found that a resonant oscillation induced during clamping period limits the performance. By a circuit analysis with an equivalent circuit model, it was found that a parasitic wiring inductance between the diode and switching element induces the resonance. It was also found that a promising way to mitigate the disturbing effect is to minimize the inductance.