At a previous employer, we had an issue where some of our power supplies would brown-out when turned off, and this destroyed some hardware. By 'brown-out' I mean they acted like there was a capacitor connected directly across the output terminals (probably because there was), and the output voltage would drop gradually from the set-point to zero over the course of a few seconds. Under certain conditions, this relatively slow drop in voltage could result in unexpected conduction paths that permanently broke things.
It seems to me that an ideal power supply should open the circuit when output is disabled, e.g. via relay-like action. Thus, it would be like pulling a plug from the wall. Is that desired behavior, or am I missing something?
If that is desired behavior, how can I achieve that without resorting to a solid state relay? I can't imagine the contact bounce on a mechanical relay would be good. If I connected a thyristor in series with the load, would that eliminate the bounce when the relay is opened? When enabling output, I'm thinking close the relay, then trigger the thyristor. When disabling output, I'm thinking the thyristor will choke the current as soon as it first drops, and then it will stay closed during subsequent bouncing of the relay.
If I recall correctly, the issue was with peripheral hardware remaining at least partially functional after the main hardware shut down. The main hardware involved an FPGA, and the peripheral continued to apply a voltage to one of the FPGA's I/O pins. And it so happens that when an FPGA is unpowered, applying a voltage to an I/O pin can fry the chip by creating a short between the power rail for the pin's I/O bank and ground. So the FPGA becomes a solid state heater.