Snubber failure in Sparkle auxiliary flyback circuit
I encountered an unusual failure in a Fortron/Sparkle FSP280-60 PSU for a 2U Pentium-III class machine. The secondary caps were a mix of Fuhjyyu and Teapo, were OK, but I recapped them anyway as a matter of routine.
However, the auxiliary flyback converter had a failure - the switching device (a Fairchild 1H0165R integrated SenseFET/current-mode controller) and its snubber network (back-to-back FR106 and a PSK 180v Transient Voltage Supressor from Taiwan Semiconductor) had all shorted.
A quick analysis (from circuit topology alone) reveals that even if a switch breakdown occurs and it shorts drain to source, there's no way the snubber network should breakdown and short. Therefore, the failure initially
must have happened in the snubber, either in the FR106 fast-recovery rectifier or the 180v TVS, shorted each of them progressively, and then the SenseFET switch failed, followed finally by the fuse.
Has anybody else seen snubber-network failures of this kind?
However, the auxiliary flyback converter had a failure - the switching device (a Fairchild 1H0165R integrated SenseFET/current-mode controller) and its snubber network (back-to-back FR106 and a PSK 180v Transient Voltage Supressor from Taiwan Semiconductor) had all shorted.
A quick analysis (from circuit topology alone) reveals that even if a switch breakdown occurs and it shorts drain to source, there's no way the snubber network should breakdown and short. Therefore, the failure initially
must have happened in the snubber, either in the FR106 fast-recovery rectifier or the 180v TVS, shorted each of them progressively, and then the SenseFET switch failed, followed finally by the fuse.
Has anybody else seen snubber-network failures of this kind?
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