Current Sharing During Unipolar and Bipolar Operation of SiC JBS Diodes

Commercial SiC JBS diodes operate as unipolar devices under standard conditions, allowing for uniform current sharing and easy paralleling. Under transient forward surge conditions, these diodes can transition into bipolar operation, where current sharing among paralleled diodes is not ensured by positive temperature coefficient behavior. This work utilized a new test fixture to evaluate the current sharing behavior of JBS diodes in parallel as they transitioned into bipolar mode. Uniform current sharing was observed after the initial transition to bipolar operation. The ability to maintain this sharing with increasing current was dependent upon die attach quality and thermal resistance. Parametric shifts were observed in those diodes that exceeded the datasheet rating for nonrepetitive surge current, suggesting possible damage to the devices. A new datasheet graph is proposed to identify safe operating area for current surge in these diodes.