In a voltage feedback network, where the input voltage is 300V, how can you protect against an overvoltage fault, or a fault in the high value R1 resistor?
I have de-rated the feedback resistor so that the voltage across the resistor is at most 65% less than the resistor voltage rating. I am using a 1kV 2Meg resistor for a max fault voltage of 350V. Would it be safe to assume that because resistors usually fail open, that the low voltage feedback circuitry would be safe?
Or would I need to add something additional, such as possibly a Zener diode, in case the resistor does happen to fail short? Are there other ways better to do this? I don't want to have to worry about having issues with creepage and clearance in the low voltage circuits or where the safety ground connections are.
See image attached.
SiC
I have de-rated the feedback resistor so that the voltage across the resistor is at most 65% less than the resistor voltage rating. I am using a 1kV 2Meg resistor for a max fault voltage of 350V. Would it be safe to assume that because resistors usually fail open, that the low voltage feedback circuitry would be safe?
Or would I need to add something additional, such as possibly a Zener diode, in case the resistor does happen to fail short? Are there other ways better to do this? I don't want to have to worry about having issues with creepage and clearance in the low voltage circuits or where the safety ground connections are.
See image attached.
SiC
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