Can I limit 12v 25A current to 18A without dropping that 12v?
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2Have you read Choosing power supply, how to get the voltage and current ratings? – The Photon Mar 10 '20 at 18:37
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1What is the load you are powering? – The Photon Mar 10 '20 at 18:38
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2When you say "limit", do you mean that the power supply is capable of 25A output, and the load is capable of >25A draw, but you want to limit it to 18A? When it hits the limit, what do you want it to do? Disconnect? Increase voltage? – Ron Beyer Mar 10 '20 at 18:49
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What does Ohm's Law tell you? Are you a student? Current is determined by load & supply. – Tony Stewart EE75 Mar 10 '20 at 20:07
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3Increase the load resistance. – Mar 10 '20 at 20:33
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It's not possible. You have a fixed voltage, 12V. You are attempting to enforce a current limit, 18A.
The trouble is, once you hit the set the current limit, if the load continues to try to draw more than that 18A limit, the only means left to keep the current down is to start dropping the output voltage.
In other words, any load resistance below 12V/18A = 0.66 ohm will begin to drag the voltage down. Think about it: taken to the extreme, if you had a dead short (load resistance = 0 ohm), any voltage above 0V would result in infinite current.
hacktastical
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