Medium-Speed Isolated Power Switch
The isolated power switch presented here was built to do repeated power-up/power-down tests on a power supply. I basically needed a MOSFET that could be controlled by a PC. To keep the circuit universal, the following design goals were added:
- Isolation of the switched circuit from the PC, so the switch can be used in either supply line (no safety-rated isolation is required, the isolated side is assumed to be SELV).
- Moderately fast (switch-on/switch-off faster than 1us). This makes it possible to add an external power resistor and use the circuit as a stepped-load tester to test the loop response of DC/DC supplies
I used parts that I had available: a 6N136 optocoupler, BUZ10 MOSFET, and an isolated 5V->9V DC/DC converter module from an old ethernet card. An arduino nano provides the PC interface and generates repeatable pulses.
The circuit performance is close to what the simulation estimated: ~600ns rise/fall time at the MOSFET gate: