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Does anyone know of a simple circuit to establish an upper limit for a high load variable supply?

Don Murphy

Mar 14, 2017
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Mar 14, 2017
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I have a slightly unusual application which involves a generator that's being deliberately shorted across a resistor with some mosfets. The purpose is to create a controlled variable mechanical load. I need to limit the output of the generator to 30 volts to prevent damage to some of the machine's sensitive components (which burn about 70W). It's well past the limits for a simple zener diode set-up. I was thinking that an open looped op amp comparator driving some transistors might work but it's a complicated option. If there's a simpler way, that would be great. I don't care what the generator is producing up to the thirty volts......I just can't exceed the thirty volts. If anyone knows of a simple solution to this, I'd appreciate all the feedback I can get.
 

(*steve*)

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The simple solution is to place a zener diode from the MOSFETs drain to it's gate. If the drain voltage gets too high this will turn the MOSFET on.

You need to be careful that this gate voltage doesn't interfere with your gate driver. Typically all you need is judiciously placed resistors.
 

Don Murphy

Mar 14, 2017
5
Joined
Mar 14, 2017
Messages
5
The simple solution is to place a zener diode from the MOSFETs drain to it's gate. If the drain voltage gets too high this will turn the MOSFET on.

You need to be careful that this gate voltage doesn't interfere with your gate driver. Typically all you need is judiciously placed resistors.
Clever and simple, outstanding! That will definitely get the job done. Thanks.
 
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