Dont use normal mosfets, use a proper automotive rated high side driver IC. Something like the VN5E010
The VN5E010 has...
- Low on resistance so doesn't get very hot.
- Operating voltage 4.5 V to 28 V
- Internal back EMF clamping for inductive loads (it has a limit but can handle most stuff)
- High current capability (85A max, internally limited) but you probably wont want to switch more than 20A per chip anyway.
- Internally protected form short circuit to power and ground (it just shuts off if it gets too hot from a short)
- Reverse polarity protection (It's internal fet turns on under reverse polarity, so the body diode doesn't explode
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)
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- Analog current sense output. So you can measure the current with a mcu ADC. (You can also chain lots of the chips together so they all share 1 ADC channel. Then you just need 1 digital output per chip to enable its sense output so you can read its current in sequence)
- Fault detection output (part of the current senses line, it goes high if the chip goes into protection mode)
- Simple CMOS compatible on/off input. So you can drive it directly from a MCU output pin.
And it's rated to be used in automotive applications.
Costs $2.85 each in qty of 10 from digikey.
It's SMD though, so if you want TH you'll need to find different brand/version. (There's a range of these sort of chips available, eg BTS6133 google "automotive high side driver")
I like the VN5E range because the switching time is fast enough to do slow PWM without too much extra heat.
You could strobe your headlights with 100Hz pwm
![Laughing :-DD](https://www.eevblog.com/forum/Smileys/default/smiley_laughing.gif)
Be aware though, different lamps respond differently to brightness control. Some lamps will actually fail if you don't run them at full power. If i remember correctly halogen lamps dont like running at under 80% of their rated voltage. Not sure if this would apply to PWM.