Electronics > Beginners

Simple go-to constant current/current limit circuit?

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Deku Tree:
I'm trying to come up with a quick and simple way to limit current to a nichrome burn wire. The wire resistance is about half an ohm. Depending on the wire length it looks like I need around 3-4A. The circuit is powered by a battery of my choice (most likely a small LiPo or Li-ion because that's what I have on hand).
Ideas I've looking in to so far:

* USB current limiting IC
* Other current limited switches like the TPS6528
* Using an op amp like in this article: http://www.bristolwatch.com/ccs/index.htm
The current regulating switches and protection ICs all drop the output voltage when hitting the current threshold. A lot of the other circuits I could find, such as placing a resistor between the output of a 3-terminal linear regulator require a resistor in series with the load.

I'm more or less looking for an "off the shelf" solution, however the current source ICs I could find all stopped about 1A in output. Any guidance would be greatly appreciated.

mikerj:

--- Quote from: Deku Tree on August 27, 2019, 10:03:07 pm ---
The current regulating switches and protection ICs all drop the output voltage when hitting the current threshold.

--- End quote ---

Because that is the only way you can reduce the current, you can't escape ohms law.  With a heating application like this PWM is a more efficient method of controlling current.

T3sl4co1l:
Get a switching buck regulator that specifies current mode operation or current-limited output.  Even if it's not an accurate current limit, you should be able to find one that's exactly in your range I think.

Tim

Deku Tree:
Makes sense, will do! Thank you both your for help.

HackedFridgeMagnet:
If you can use 2 cells, so between 6-8 volts.

you could use this.
 
the FET was logic level and you would have to think about power dissipation.

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