controlling 7amp 12Vdc Heater with PWM using MOSFET?

Thread Starter


Joined Apr 9, 2019
Hello everyone,

I'm working on a project that controls 12Vdc 7Amp silicon heater pad using MOSFET.
I tried HA210N06 MOSFET with a heatsink but it doesn't work correctly, the heater doesn't get hot but the MOSFET is getting very hot, I tried another lower amper heater it's work but also not get very hot with a 100% duty cycle as I connect it directly to the power supply.

I'm using dual output power supply 5v for microcontroller and 12v 15A for the heater.
PWM frequency is 500hz.
I'm using pic 18f4685 and programming with MikroC.

The circuit is attached.

my question is this MOSFET could work correctly but I have some connections problem or coding problem?

Thank you.



Joined Mar 10, 2018
No way is that MOSFET going to work. Its not a logic level MOSFET.

You select a part with low Rdson at the availabel; gate drive V out of the micro.

Then you have problem that micro cannot drive a high C load, which a MOSFET gate is. So MOSFET switches slowly, thereby buring a lot of power in its active region. You should have a gate driver when using a PWM for MOSFET control.

Regards, Dana.

Thread Starter


Joined Apr 9, 2019
Thank you Dana for the fast answer.
I'm very new using MOSFET so I can't recognize that. so the problem now is the kind of MOSFET that will work well.
Can you please tell me the characteristics of the best one?

John P

Joined Oct 14, 2008
I'm skeptical that at 500Hz, there will be much heating due to the slow rise and fall of the MOSFET gate voltage. If the transistor is heating up, the first thing I'd consider is whether it's being fully turned on. And of course it needs a low channel resistance to begin with!

Not mentioned yet, but can the power source adequately deal with pulses of 7 amps being drawn 500 times a second?


Joined Mar 14, 2008
I agree with John that it's probably the MOSFET not turning fully ON that's the problem, not the gate drive for the capacitive gate load.
I did a simulation at 7A and 500Hz using a MOSFET with similar gate capacitance to the IRL640.
Even with a 10kΩ source driver (likely higher than the micro output), the total MOSFET dissipation was <1W.