I'm interested in a specific computer Graphics Processing Unit (GPU) that has a power limit fixed at 400W. I want to limit the GPU to around 200W while maintaining a stable 12V DC supply to it. Is there a "relatively simple" circuit design that can do this that I can install between the Power Supply Unit (PSU) and the GPU?

 

I'm interested in a specific computer Graphics Processing Unit (GPU) that has a power limit fixed at 400W. I want to limit the GPU to around 200W while maintaining a stable 12V DC supply to it. Is there a "relatively simple" circuit design that can do this that I can install between the Power Supply Unit (PSU) and the GPU?

Unfortunately not. The only way you can limit its current is by reducing the voltage.

 

Sorry, what you ask is not possible, either simply or with complexity.
If the voltage stays at 12V, then the GPU will take whatever power it wants/needs.
The only way to reduce its power at stay at 12V would be if there is an option to have it operate at less than its maximum capacity.

 

You can't do that.
If you limit the current, the voltage has to fall.
3 votes out of 3.

 

I'm interested in a specific computer Graphics Processing Unit (GPU) that has a power limit fixed at 400W. I want to limit the GPU to around 200W while maintaining a stable 12V DC supply to it. Is there a "relatively simple" circuit design that can do this that I can install between the Power Supply Unit (PSU) and the GPU?

What do you want the twelve volt supply to do when the load impedance demands more than 200 watts? The two obvious answers are shutdown and lower the voltage output. Which would you prefer, or did you have somethine else in mind?

 

Thank you all for quickly responding to my query. I do know ohm's law very well as I taught automotive electricity and electrical circuits in college for 20 years before retirement. But I was just curious about some things that I was not privy to other than in the 'replacement' end of it. Thanks again.

 

m interested in a specific computer Graphics Processing Unit (GPU) that has a power limit fixed at 400W. I want to limit the GPU to around 200W

On many computer boards there is a way to slow them down. That results in less power draw. Running at 1/2 speed will reduce the power to near the 200W. I do not know the commands for your project or if it can be done.

 

Since this has to do with a Computer,
the first question should be WHY You want to limit the Current to the Computer ?

Normally Computers require Power in very-VERY-short-bursts, and then sit mostly idle,
they usually do not draw their maximum Power continuously.
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Thank you all for quickly responding to my query. I do know ohm's law very well as I taught automotive electricity and electrical circuits in college for 20 years before retirement. But I was just curious about some things that I was not privy to other than in the 'replacement' end of it. Thanks again.

I was anticipating that you did indeed have something else in mind.

 

You can't do that.
If you limit the current, the voltage has to fall.
3 votes out of 3.

If you want to reduce power consumption, you need to reduce the operating voltage, not just the current.
This is why computer chip manufacturers have reduced the processor operating voltage from 5 V to 3.3 V, to 2.5 V, and to 1.2 V.

Power is proportional to the voltage squared. Hence power consumption goes down much faster when you reduce the voltage. A chip running at 5 V consumes 25 times more power than one operating at 1 V, keeping everything else the same.

 

It is a bit unclear to me just exactly what "(GPU) that has a power limit fixed at 400W." is actually telling me. Did it mean that it would draw up to that much power occasionally? Or that it was fused at 33 amps?? Or something else??
So I did not comment.
But the way to limit the maximum power from a 12 volt power supply is to use a "fold-back current limit" scheme so that at some point the voltage drops to hold the delivered power to that limit level.

 

Search "underclock GPU". Depending on the vintage of the card it may or may not be possible.

 

If this project is an Automotive application,
there is absolutely no need to limit anything.

The "average" Power-Consumption will be quite low.
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A Foldback current limiting circuit in LTSpice
https://forum.allaboutcircuits.com/threads/foldback-current-limiting.203932/post-1948165

 

Certainly "fold-back current limiting" will be an effective means of limiting the supplied power. BUT it works by reducing the supplied voltage to limit the current, and thus limit the power. That is how it works, as simply as I can describe it.
The bad news is that reducing the supplied voltage to the " specific computer Graphics Processing Unit (GPU) that has a power limit fixed at 400W. " will probably result in undesirable results.

(EDIT): See the next post for details!!

 

Most likely,
limiting the Current will result in a very slow oscillation,
or possibly cause the Computer to "lock-up" and crash.

A peak will come along and draw enough Current to cause the Voltage to drop
which will be too low to sustain normal operation of the Computer,
then it will try to Reboot and resume normal operation.
Rebooting causes a Current-Peak, and so the Voltage drops too low again.

Lather-Rinse-Repeat, Lather-Rinse-Repeat,
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