| Abstract |
In power modules with high current ratings where several devices are required for parallelconnection, electrothermal balance between the parallel devices is a very important consideration. Thispaper investigates the impact of electrothermal imbalance between parallel connected devices on thethermal stability of the parallel pair. Under investigation are parallel connected 600 V silicon PiN andsilicon carbide Schottky diodes. The electrothermal imbalance between the parallel devices wasintroduced by setting different initial junction temperatures and using different thermal boundaryconditions i.e. different case temperatures. The effect of the diode technology on the thermal stresses ofthe complementing transistor is also assessed. The results show that silicon PiN diodes operate at lowerjunction temperatures because of the higher zero-temperature coefficient points in the forward currentcharacteristics, however, the complementing MOSFETs are more thermally stressed since the reverserecovery of the diode causes current overshoots in the complementing transistor. It is also shown thatSiC Schottky diodes exhibit more electrothermally stable operation under electrothermal imbalancewhen connected in parallel. Parallel connected SiC Schottky diodes with different initial junctiontemperatures and different thermal boundary conditions (case temperatures) exhibit better temperatureconvergence/stability compared to silicon PiN diodes. The temperature convergence in parallel SiCSchottky diode pairs is due to the lower Zero-Temperature Coefficient (ZTC) point compared with thePiN diode pairs, which means more equal current sharing in parallel SiC diodes. |
