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Question about headlights relay in car.

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Thanks ()blivion
I'll get a few of those to play with in my next order.
 
Do you really believe that the TO-220 package can withstand 75A for longer than a second?

The current rating on mosfets is a calculated value.

It is based on the rdson value, and the thermal resistance of the package and die.

The rated current is that which will cause the die to run at its maximum temperature when the case is held at 25C with an infinite heatsink.

As such, it is not a usable value outside of a testing lab.
 
On some FETs, there is a "disclaimer" that states "Package limitation current is 75A"
Here's a simple circuit for on - off, high beam - low beam
 
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In most automobile forward view lighting, the "high beam" setting turns on the "low beam" as well.

Not sure over in the US but in the UK a lot of the cars were supplied with H4 (472) bulbs which were dual filament and you could only use one filament at a time for main / dip (low) beam. Using two at the same time could quickly melt the housing / plugs / loom etc if you weren't careful.
 
True, I shouldn't have generalized this so much. I speak of the US cars that I have worked on. I know nothing of auto manufacturers in other country's.
 
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