H-bridge heating problem

Thread Starter


Joined Jan 5, 2020
You can run a high drive charge pump with a couple of diodes and capacitors, and an NPN transistor or small mosfet, pulsed by a spare pin of the Microcontroller.

That will work very well if you are only running forward and reverse. If you are running PWM for speed control the High Side Drive will work harder to keep up. Pulsing makes it more complicated because you need to be sure it can keep the gates charging repeatedly instead of only once. It might still be easy enough.

It also depends on your 12Volt power supply. If your main supply drops to 9 Volts under a high motor load then the high side drive might drop to as low as 16Volts.

This kind of highside is just a charge pump that doubles the Power Rail voltage minus diodes and some droop.

IRFZ44N would probably survive with only 7 volts of drive overhead even if we are looking at highest load situations. You say your motor is 2 Amps, so assuming 10 Amps for stall is safe we can hope. At 7 Volts drive the FET would be 10 Amps and less than half a volt Drain to Source. 5 watts should be in its survival zone even without a heat sink.

But this is all quick look guesses and I am very frequently wrong.
Hi.. I'm using the circuit attached to control 2 nos. Of DC motors drawing 10amps each. One motor works fine & mosfet is cool like water. But the other motor works only in one direction and high side mosfet is heating in sometime.

Mosfet - IRF3205
Transistor - BC847