skmdmasud
Member
No.
The diode from drain to source is not needed because it would block the drain from going negative which never happens and the Mosfet has a diode there anyway as part of its construction.
The drain does not go negative, instead it goes POSITIVE when the Mosfet turns off then the diode in the Mosfet has avalanche breakdown from the high voltage which causes heating. The diode must be parallel to the motor to prevent the positive voltage spike at the drain of the Mosfet. The cathode of the new diode connects to +VDD and its anode connects to the drain of the Mosfet. If its wires are long (far away from the motor) then it might cause oscillation ringing.
Ok so finally i had some time to open up the dashboard of my car, located the blower and installed a snubber diode in the blower. After testing my mosfet is still heating up like before which means i need to built the driver circuit.
One question do i remove the diode which is across my mosfet or leave it there?
Regards.