I need a variable current source as part of a power supply for an experiment I'm building. This part should heat up a filament, so the load is pretty constant. Timing is not a factor either.
So what I'm looking for is a pretty simple solution, much simpler than a lot of circuits I find online. But all the simple circuits, like the ones attached are often calculated for small currents.
I need a regulation between 1.5A and 2.5A and my question is if someone has experience with such simple circuits and higher currents. Of course I would use other parts like power transistor and other resistors but heat and efficiency could be problems, but I don't know to which degree. I study physics, so I'm no expert in electrical engineering.
I hope someone could give some intuitive answer. Thanks
Best Answer
Something like this should work for you. With the values shown, R3 needs to be rated for about 1W and M1 needs a heat sink for up to 30W if RL can be shorted. The current sink has a compliance of the supply voltage minus about 0.5V so don't use excessive voltage for V1 (needs to be about 7V minimum for U1 to work properly) if you want to keep the heat sink reasonable. Or you can add a resistor in series with RL to move some of the power dissipation off the transistor.
"Or you can add a resistor in series with RL to move some of the power dissipation off the transistor." You mean from the Drain to GND, Right?
simulate this circuit – Schematic created using CircuitLab