I am working on a high-current MOSFET switch project. I would like to implement short-circuit/overcurrent protection, that would be fast enough to prevent MOSFETs from blowing up.
In the actual application, I am using a HAL sensor to measure current, but it won't allow me to take any action quickly because of its delay.
How should I realize this protection? Should I do it by using a shunt and a high-quality op-amp, or is there a better solution?
Use Vds detection with minimal dead time; drivers with short circuit protection use that methods.
EG for high voltage
https://gate-driver.power.com/products/scale-idriver-ic-family/sid11x2k/
If you have inductive loads or long cabling, detecting the current with a shunt is too slow and when you trigger the shutdown the current could take to much time to reverse. Specially with 5 Mosfet in parallel you can have problem to handle the energy in the circuit.
One cheap option is an in-PCB current transformer: run the output trace in an inner layer of the PCB, and use vias and perpendicular traces on top and bottom layers to form a solenoid around it. Load the secondary winding with a resistor, and use a fast comparator to detect overcurrent.
Given the currents involved, the output trace can end up as two parallel fairly wide traces on layers 2 and 3, with the current transformer wrapped around them on layers 1, 4 and the vias.
Of course this will only detect transient short circuits, not a slow increase in current - but should be enough for such a purpose.
VDS measurement with deadtime would be a more typical option.
