I have the following circuit wired up:
Where 4 STP55NF06L MOSFETS are wired to 12V LED stripes, and one STP55NF06L MOSFET drain is wired to an ATX PSU green (PSU ON) wire.
When the whole system is unplugged from mains:
- MOSFETs Drain-Source resistance = 9Mohms.
- MOSFETs Gate-Drain resistance = 9Kohms.
When the whole system is plugged to mains but no MOSFET has been turned on yet:
- MOSFETs Drain-Source resistance = fluctuates every second between 3.5Kohms and Open Line.
When the whole system is plugged to mains, MOSFETs have been turned on before and now all the Gates are being pulled LOW:
- MOSFETs Drain-Source resistance = Open Line. (But LEDs shining and PSU still ON in spite of "PSU" MOSFET gate pulled LOW) Gate-Source voltage is 0.02V when LOW and 5.2V when HIGH.
I haven't managed to fix this myself in the last few days. There are many posts in the internet about MOSFETs not working properly but I don't understand why do MOSFETs work OK when the system is first plugged in and cease working once their gates have been turned HIGH at least once. I'd appreciate any suggestions. Please don't hesitate to ask me for any information I might have forgotten to post ! Thank you in advance.