I am designing a circuit where I want to protect Q1 from current overload and popping in the event that Rl is a short. The length of wire in a short circuit situation is 0.7 ohms. Usually Rl is 10 ohms (when it is not shorted) or so and thus 1.25A flows through it. RL has LED's in it so I need to keep 12VDC. I have looked at an LM513 as a current source but it looks like the voltage drop from Vin to Vout is too great.
A microcontroller is driving the base of Q1
I have designed the circuit below using 3A transistors, but I keep popping Q1. I have verified that the circuit works by changing out the Rs resistor value and verifying that it regulates the current correctly.
I chose the Rs to 0.5 so that I could run a max of 1.5A. With the transistors rated at 3A I thought this should be fine.
My thought is that Q1 is popping too quickly before it even has a chance of turning off with the instantaneous current of approximately 10A flowing through it.
Should I replace Q1 with a mosfet transistor?
Schematic is below.