Ugh. Sorry for the short not-very helpful title, but the "Bug when creating a NEW THREAD" is biting and 20-characters is not much....
I'm using a MOSFET to power a resistive load with a PWM input on the MOSFET gate. The application is a heater strip for my camera/telescope. My nice commercial unit had no short-circuit protection and is now a source for parts
The PWM part is easy. I can even use a comparator to decide when the load is shorted by looking at the voltage drop across the MOSFET. What I don't understand is how to use this to turn it off. All the short-circuit protection schematics I find don't use PWM on the MOSFET gate which creates this "funny" situation; when the gate is off, there's no short detected.
Attached is the schematic I have so far. R9 is the load resistance. Small resistances will cause the comparator output to go high, but even normal resistances (> 10Ω or so) will have the comparator go high when the MOSFET is off.
I'm using a MOSFET to power a resistive load with a PWM input on the MOSFET gate. The application is a heater strip for my camera/telescope. My nice commercial unit had no short-circuit protection and is now a source for parts
The PWM part is easy. I can even use a comparator to decide when the load is shorted by looking at the voltage drop across the MOSFET. What I don't understand is how to use this to turn it off. All the short-circuit protection schematics I find don't use PWM on the MOSFET gate which creates this "funny" situation; when the gate is off, there's no short detected.
Attached is the schematic I have so far. R9 is the load resistance. Small resistances will cause the comparator output to go high, but even normal resistances (> 10Ω or so) will have the comparator go high when the MOSFET is off.