Thank you. I'd need two regulators for constant current and constant voltage, in series? For the constant voltage part, would my original schematic work (minus Rsense)?Here's the simulation with the unneeded parts removed (you can't regulate current and voltage at the same time):
As stated by Ian0, note the high power dissipation of the regulator (red trace) from the ≈3A through the LED (yellow trace).
View attachment 290323
Trying to build a constant current/constant voltage adjustable power supply, but I may need to use two identical regulator for that.R1 is shorted out, and the potential divider Rsense/R2 isn’t going to do much. What were you hoping to adjust?
I hope you’ve got a big heatsink. 9V loss x 2.95A =26.5watts.
That is unlikely to handle 29W.And I do have a small heatsink for the TO-220 regulator.
Yes, you can put two in series for that (constant current first, feeding the constant voltage).Trying to build a constant current/constant voltage adjustable power supply, but I may need to use two identical regulator for that.
Does this look right?That is unlikely to handle 29W.
For that power dissipation a heat-sink with a fan may be needed.
Yes, you can put two in series for that (constant current first, feeding the constant voltage).
Note that the constant-current is only readily adjustable over only a small range with a potentiometer for the shunt resistor due to current limitations of available pots.
For a larger adjustment range, there are better circuits.
What will be your DC raw power source for the supply?
Does that make much sense?Yes, you can put two in series for that (constant current first, feeding the constant voltage).
Yes. But notice that neither of those diagrams have a wire that goes from one side of R1 to the other side. Yours does.
oops, fixed it.
my goal is to build a multi-purpose adjustable power supply with constant current & voltage limit that I can use to power LEDs and laser diodes, charge batteries and power external peripherals.Does that make much sense?
What would you expect to happen if you drive a constant voltage source with a constant current source?
Within it's compliance limits, the constant current source is going to try to FORCE the constant voltage source to consume the programmed current. But what if the load that the constant voltage source is driving either doesn't need that much current or needs more than that current?
If the constant current source succeeds, it will have done that by forcing the constant voltage source to output a different voltage -- one that results in the load accepting the programmed current. But that means that the constant voltage source has failed to hold it's programmed voltage. If the constant voltage source succeeds, it will have done so by either limiting the amount of current from the constant current source, or drawing more from it. In either case, the constant current source has failed to hold it's programmed current.
It makes no sense to try to control both the current and the voltage -- you control one and the circuit dictates the other.
THIS is where the discussion needed to start.my goal is to build a multi-purpose adjustable power supply with constant current & voltage limit that I can use to power LEDs and laser diodes, charge batteries and power external peripherals.
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