On the Maximum Permissible Working Voltage of Commercial Power Silicon Diodes and Thyristors

Most of commercial high voltage/current diodes and thyristors cannot operate without risk of failure, even for short time, above of a specified value of the blocking voltage, towards the breakdown region. Only for controlled-avalanche diodes, the maximum value of the working reverse voltage specified for steady-state operation can be overcome in specified conditions, so that, the breakdown region to be reached. Typical electrical characteristics are shown and analyzed for silicon diodes and thyristors. For ordinary rectifier diodes and thyristors, deviation of the leakage blocking current from linear voltage dependence takes place around the specified value of the working voltage, due to uncontrolled phenomena at the PN junction edge. For controlled-avalanche diodes, such deviation is not visible at the maximum specified working voltage value and linear variation is exhibited, practically, up to the breakdown region. Pulsed current-voltage characteristics exhibiting the breakdown region are shown for controlled-avalanche devices. Surge power limited to 100 kW for 10 mus in the breakdown region is specified for commercial high voltage controlled-avalanche diodes although junction temperature increase induced by such energy is not significant. This limitation of low power in the breakdown region is also related to the PN junction edge leakage current.