# Can a DC CC power supply be used for current limiting in a circuit with a battery in series

In circuit #1 I showed typical adjustable power supply usage it can limit voltage and current, all good.

It got me thinking. Let's say due to some reasons I can't replace battery with a power supply but I can connect it in series like showed in circuit #2. If I set power supply voltage to 0V (to keep same voltage) and current limit to some value.

Would it limit the current? Can I damage power supply by doing it? If I set positive or negative voltage would it still work the same?

• Yes, quite possibly and no. – Andy aka Aug 22 '20 at 18:29
• That's about it..... no Specs, no idea. Maybe if you put Python in series with C++ you get a vitamin snake. – Tony Stewart EE75 Aug 22 '20 at 19:56

• A current source is defined as high impedance has no voltage regulation with the load.

• A battery is defined as a voltage source with low impedance has no current regulation with the load.

• When the two are in series, you still have a current source ( or sink if on the low side)

• Unless the current is limited and voltage limited to match the load exactly, you have no regulation. But this is done with LED strings designed for the CC source.

Conceptually, yes. But if you want to do this with a real DC-DC, then you would need to verify whether it is capable of operating the way you describe. I have not seen DC-DC converters that were designed to operate at 0V. But it should be possible to design one that does that. It would need to have connection to Batt+ and Batt- in order to bias up its internal circuitry.

It seems like it would be better to just design a current limiter circuit. Maybe put some kind of microprocessor in there to control everything.

• Can you clarify what do you mean by saying "It would need to have connection to Batt+ and Batt-". Does it mean that is has to be connected in parallel? If so do I connect Batt+ to DCDC+ or DCDC-? "it would be better to just design a current limiter circuit" so if I understand correctly in circuit #2 if I change power supply with electronic load in constant current mode it should limit the current as expected? – Combinacijus Aug 25 '20 at 19:40