power supply woes

[glinjik]

Hi I have built the diagram below all works fine max voltage and current work etc but although I'm feeding in 24v I cannot get more than 3v out checked all connections all seems fine for the life of me cant figure this out I'm suspicious of the 2 zener diodes an was thinking maybe a tl314 would be better any ideas?

[inse]

This looks like an Elektor circuit, do you have the entire article?
Usually the circuit is explained.

[glinjik]

no just this diagram

[bob91343]

The diagram is poorly drawn in that the crossovers and the connections are unclear.  Perhaps you got one or more of them wrong.

Having said that, the output voltage is compared to the zener voltage with a differential amplifier.  Are the two inputs to that amplifier equal?

[glinjik]

TBH I think I'm gonna look for a different circuit, I've spent too much time faffing with it lol

[magic]

For up to 36V input voltage and 2.5V or higher output there is a fairly simple way to combine TL431 for regulation and a pass transistor for power, shown in the datasheet.

I have used it with LM317 configured for constant current in place of the transistor to also get current limiting, but potentially some other solution could be devised for output currents in excess of what 317 can provide. Variable current limit would be harder to do, unless you are OK with doing it by swapping resistors

I'm not sure how stable such circuit would be with capacitive load.

There is also a thread here in "beginners" about a fully tested, but somewhat more complex lab PSU using LM324 and a bunch of power transistors.

[Zero999]

That input-output voltage differential is too high to be practical. Is this running off a transformer? If so, tap switching should be implemented, so the input voltage is reduced, for lower output voltage settings.