Led + emitter follower regulator

[FOXYE]

Hello,
Trying to change the power supply circuit is based on the following:

An externally hosted image should be here but it was not working when we last tested it.

But instead of using a zener diode aim to use LEDs.

Edit:
Circuit works.

 

[Mooly]

Its normal because this is a "regulator" with no error correction or error amplifier.

 

[gianxdiy]

Way better the simple circuit with the zener, if you want i will post my implementation to that regulator, better regulation and noise but not useful for few mA's...

 

[Ketje]

Happely it's only simulation,otherwise those poor LED's, 250mA !
If you need 5V stabilised,why not use the LM117 with to resistors,that's it.
Mona

 

[FOXYE]

Thanks for the information,

Because of this:

Using 3-pin regulators off-piste: part 1

"For 5V output, a useful substitution is to use two green LEDs in series. These will drop about 1.94v each, or 3.9v across the two, with lower impedance than a 3.9v zener - which makes the output voltage setting more accurate, and with lower noise since the leds are forward-biased PN junctions. You also get bright green light to let you know the reg is working..."

 

[zakman35]

What is the max current this regulator can supply?
What demands has the circuit for heat dissipation?

gianxdiy can you post your implementation?

 

[martin clark]

Thanks for the information,

Because of this:

Using 3-pin regulators off-piste: part 1

That page was very specifically written (by me) for LM317 and similar adjustable 3-pin regulators.

Your circuit is not comparable; it will need informed revision to use LEDs instead, and infact in the circuit you post using LEDs would offer very minimal gains.

 

[Elvee]

With one additional transistor, you can retain the advantages of a LED, but with added benefits, like much better static and dynamic performance, approximate temperature compensation, flexibility in output voltage setting and low drop-out feature.
Note that a real life circuit will need some kind of start-up method for a deterministic behavior. The exact implementation depends on the context.