Best voltage regulator for high current application?

Question

I have high-current devices (10 A) of variable resistance and I am researching their current-voltage behavior over time. I want to operate several devices in series using only a single power supply which delivers a constant DC current of 10 A. However, the voltage drop across each device may never exceed 2.5V as this would cause overheating.

So, here are the requirements for my circuit:

1. Ideally, 10 A runs through each device (whatever the voltage drop).
2. If the resistance of a device increases such that the voltage drop would exceed 2.5 V, it should be held at 2.5 V instead (still drawing current - but now less than 10 A).
3. I should be able to disconnect each device from the series circuit without affecting the others.

Below is a simple depiction of the desired circuit which I hope is helpful. I'm looking for circuit elements that are maybe something like a very-high-power Zener diode. Thank you!

Answer 1

I have a device that's directly connected to a power supply. The power supply is set to a 10A current limit and a 2.5V voltage limit. So, if the voltage drop across my device at 10A exceeds 2.5V, the device will be held at 2.5V instead and the current is reduced accordingly.

No. If the effective resistance is lower than V/I = 2.5 / 10 = 0.25 Ω then the PSU will limit the current to 10 A and the voltage will fall below 2.5 V.

Can I put my devices in series and replicate similar voltage controls for each device by using circuit elements?

This would generally be a bad idea as series-connected circuits would normally share the same current. You could do it using a "shunt regulator" around each of your loads but that would be difficult with only 2.5 V for the regulator circuit to go on.

Note that your Zener diodes are drawn backwards.

Let all current flow go through Device A if V1 < 2.5V If V1 would exceed 2.5V at 10A, hold it constant at 2.5V instead (whatever the current that flows through) Be able to disconnect Device A from the circuit without affecting Device B.

To power both devices you would need at least 5 V.

This sounds as though you are trying to run two different model LEDs in series. You'd get much better answers if you edit your question to explain the real problem you're trying to solve.

Answer 2

Here is something that seems to work as you require. The voltage across the variable load R2 (which tries to simulate your loads), is limited to 2.2 volts, which is the combined forward voltage of the two diodes D1 and D2, and the base-emitter junction of power transistor Q1. R1 limits current in the diodes to about 267 uA. Changing it to 10 ohms raises the maximum voltage to about 2.35 volts.