On the Influence of Temperature on Current Value.

[mikefenghao]

Hello, I have set up the basic hardware circuit. Due to the difficulty in obtaining the components, I used the LM324dt operational amplifier and the HY5110W NMOS. My test revealed that as the load is turned on and the temperature rises, the limiting current value also gradually increases. May I ask if you have experienced this kind of phenomenon? And how to solve it.

[Dominik-Workshop]

Hello,
I’ve seen current change with temperature too, but in my case it decreased as things warmed up. That was due to a large positive temperature coefficient in the shunt path (copper + a non-precision shunt), so the effective resistance increased with temperature and the regulated current fell. That was in a different project than this one.

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I see a few potential solutions for your problem:

• Use a more precise OpAmp, maybe the input offset voltage drifts too much with temperature in case of the LM324DT
• Maybe your voltage reference is not stable thermally? What do you use to generate the reference voltage?
• Your current shunt resistors may have a significant negative coefficent of resistance? If so, find ones with more thermally stable resistance.

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If you can share exact schematic of your circuit (shunt value/type, how Vref is generated), I could pinpoint which of these is most likely and suggest specific component changes.