I am currently building variable voltage/variable current (lab) power supply out of an ATX switching power supply. I have done voltage regulation tweak of the TL494 so now it gave me variable voltage of approx 2V-15V.
Now, I want to add some current limiting capability as it is in lab power supplies (the other function of this will be short circuit protection because by tweaking the TL494, power supply lost its short circuit protection). Regulation range from 0-5A will be sufficient. (original rating on 12V rail was 15A).
I searched a lot, but all i can find is circuits using bipolar transistors and low value sensing resistors sometimes with opamps.
My idea is to use simple circuit - P-channel MOSFET connected as high side switch and potentiometer to set required current limit. I have chosen high side switch, because i require common ground, e.g. ground will be connected to chassis.
Here is scheme:
It will be kind of difficult to set desired current by potentiometer (because hreshold opening voltage is approx 4V and then the current will be climbing rapidly till full open transistor. I think multiturn potentiometer will be partly solution.
Is there any cons of this circuit? Is there any better options to do current limiting with MOSFET? Eventually, how can i add current limit signalization?