Any of you electronic's wizzards can tell what I am doing wrong?
I'm using a PWM with a MOSFET rated at 20A, my system pulls 6A but the MOSFET gets hot in about one minute of operation. It is installed on a big heatsink and I can't hold my finger on it for more than two seconds.
Thanks.
MOSFET rated at 20A gets hot at 6A.
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MOSFET rated at 20A gets hot at 6A.
by olympios » Sun Nov 19, 2006 7:42 am
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Re: MOSFET rated at 20A gets hot at 6A.
by Looking In » Sun Nov 19, 2006 8:51 am
Rich (Looking In)
((((Is it really so difficult to tell a good action from a bad one? I think one usually knows right away or a moment afterward, in a flash of regret.)))) BOOM
((((Is it really so difficult to tell a good action from a bad one? I think one usually knows right away or a moment afterward, in a flash of regret.)))) BOOM
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by Looking In » Sun Nov 19, 2006 8:55 am
Rich (Looking In)
((((Is it really so difficult to tell a good action from a bad one? I think one usually knows right away or a moment afterward, in a flash of regret.)))) BOOM
((((Is it really so difficult to tell a good action from a bad one? I think one usually knows right away or a moment afterward, in a flash of regret.)))) BOOM
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by nebbian » Tue Nov 21, 2006 1:28 am
Hi Olympios,
Using PWM is the problem. As the FET turns on and off it momentarily dissipates a lot of heat. If your PWM frequency is too high, then this switching happens a lot more than it should, meaning your FET heats up.
I had a similar problem back in my racing car days, we had a fan that was controlled by a dashboard computer with three different speed settings. I had to lower the frequency to around 5 Hz to keep the FET block cool.
What you need to do is lower the switching frequency. This should solve the problem.
Using PWM is the problem. As the FET turns on and off it momentarily dissipates a lot of heat. If your PWM frequency is too high, then this switching happens a lot more than it should, meaning your FET heats up.
I had a similar problem back in my racing car days, we had a fan that was controlled by a dashboard computer with three different speed settings. I had to lower the frequency to around 5 Hz to keep the FET block cool.
What you need to do is lower the switching frequency. This should solve the problem.
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by Danberman » Tue Dec 26, 2006 5:16 am
Also make sure you are driving the gate at a high enough voltage. If your not your mosfet may have to much on resistance causing it to dissipate tons of power. May i recoment the HUFxxxx series. They have some that are rated for 250+ watts that are only a few bucks on digikey. i am using them in a cnc motor controller to switch 21 amp 12 volts at resonably high speeds with NO noticiable heat. They are some of the best mosfets i have ever come across
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