I am looking to design a low-level safety override. This override can be represented as a three terminal device that is electrically a switch.
In normal operation,
OUTPUT are shorted together and
OVERRIDE pin is floating. It is important that there is complete isolation (Up to 1KV) between
OUTPUT as the voltages present on
400VDC. A blocking diode may not be sufficient.
During a rescue/safety event, the user applies an override pulse to the override port when the device is turned off. This should permanently connect
OUTPUT. Allowing an external device to take over the
OUTPUT device, and not allowing any further normal function. It is important that there is total non-resetable isolation of
OVERRIDE/OUTPUT, as the circuit may interfere and damage the rescue box. (However, a resetable solution can be considered if it is a significantly simpler design)
Is there a circuit that I can use as an example for this type of functionality, or is there a discrete device that serves this fusable purpose. I would appreciate any input on how to approach this design.