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Dim an LED light bar with internal 10-40VDC driver

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Daloway
Riding on 13's
Posts: 1
Joined: February 27th, 2018, 2:35 am

Dim an LED light bar with internal 10-40VDC driver

Postby Daloway » February 27th, 2018, 3:33 am

I need to be able to dim an LED light bar with internal 10-40VDC driver to 50% (1/2 current) and switch it on and off - dimmed and at full current. I need to switch the high side. Am I better off using a P-Channel MOSFET or an N-Channel MOSFET with a high side driver? The light bar uses 14A at 10-40VDC (which will be the input to the high side switch) and the system controller will run at 3.3VDC but also have regulated 12VDC available.

To dim I was thinking of using this circuit I found on this site and setting the VRef with a DAC in the microcontroller I'm using. That way I could tweak the brightness of needed.

Image

I know heat will be unavoidable but I need a solution that generates minimal heat. Lower heat is more important than cost for this project.

I also intended to use a AUIR3315STRL found from kynix to as fast resettable overcurrent protection. Is that excessive or can overcurrent protection be baked into the switching and diming solution?

This will be used in an automotive environment and I keep reading about how important protection is against load dumps, ESD, etc. Being an output does this need those same protections like a TVS or Schottky diodes to the supply rails? The output will go to a connector that will be used quite a bit, not just installed and left alone.

Finally, what if anything do I need to do to protect the microcontroller against the high side switch always being at VBatt (10VDC-40VDC) when the rest of the controller only has power (3.3VDC) when the ignition is on?

Sorry for any dumb questions but this is new to me and I'm trying to do everything right or at least the most sensible way possible. Thanks.

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