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Old 17th Sep 2019, 7:55 am   #29
MrBungle
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Join Date: Jun 2016
Location: London, UK.
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Default Re: Adjustable voltage 15 amp power supply

Agreed. One of the killers isn’t actually the circuit which is quite easy but the thermal design. Consider shorting out the supply at 15A with an output voltage of 2V and input of 24V, both reasonable values. You’ve got to lose 360W somewhere which is quite difficult. Big supplies don’t do that - they use preregulation.

This is a problem with LM317 designs you see everywhere. A typical specification is 1.2-20V at 1.5A. Which is fine until you ask 3.3V at 1.5A of it. Min spec that’s 23V in and 3V out so 30 watts going out in that little LM317 on a tiny chinesium heatsink. Bang it goes! Not immediately either as they sort of work outside their SOA for a bit then go floppy and then explode.

I’ve got a meaty HP 6286A here that can shift 0-20V at 10A which is less than prescribed. It’s large, heavy and complicated!
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