Dual rail power supply for class A amplifiers

[Extreme_Boky]

Wanted setting is 30 Volt out , 3 Volt dropout across the darlington .
I simply can't reach the output voltage of 30 Volt while remaining 3 volt dropout.

What is the load? A class-A amp? Or something else..??

 

[Strong Believer]

The dropout depends on the regulator and the ripple on the input voltage at max current.
Maybe you can get to 3V, maybe you can get lower (unlikely), maybe you need 4V. It all depends.
It is not wise to get hooked on 3V and go around in circles with the regulator because it is not possible in this particular implementation.
As I said before, the smart thing to do is get the reg operating properly with a high input voltage, like 40V, so you are absolutely sure that Vin is not the limiting factor. Then if you get that right, lower Vin until the reg goes out of regulation and then you know the lowest possible Vi9n.
And then, mindful of the variation in mains voltage over the day, add 1 or 2 V to be sure that ypour reg doesn't drop out of regulation on saterday evening. Your transformer and rectifiers are maybe not identical with the original design. 😎
It is one thing to use an existing design as the starting point, but it is not smart to follow someones detailed design withpout thinking about it what it does for you.
You have all the building blocks to make this a succes. It's up to you, with help from your friends here.
But you need to think it through and be receptive to the posts here. Wish you success.

Edit - it's an adventure, enjoy it!

Jan

 

[mchambin]

I like schematics using a pass BJT with the emittor at the output side.

There are good reasons to replace the 1k resistor by a CCS ( made of 2 bjts or 1 bjt + diode...plus 2 resistors ).
This has no impact on stability, because of little change about the loop gain.
The 1k induces current ripple to the pass transistor control, the CCS doesn’t.
With a CCS it is easier to cope with voltage drop about mains 10% voltage accuracy at any output load.

 

[Strong Believer]

All true , and I will continue to figure one and other , i'm greatful to all help and support here ,
Of course 😀
If you read carefuly ... i did mention in one of my first posts here that I used different darlington transistors vs the original design from
Metanastis .
Anyhow , will share my results here as soon as I get this regulator working properly .
Huge thanks to everyone so far

 

[metanastis]

This is what National Instruments 12.0 "says" about this circuit.

In the first image, there is a regulation of about 31 volts using the trimpot. The second image shows the maximum regulated voltage from a transformer with a 30-volt secondary without load..

 

[mchambin]

I like schematics using a pass BJT with the emittor at the output side.

There are good reasons to replace the R2: 1.5 k resistor by a CCS ( made of 2 bjts or 1 bjt + diode...plus 2 resistors ).
This has no impact on stability, because of little change about the loop gain.
The 1k induces current ripple to the pass transistor control, the CCS doesn’t.
With a CCS it is easier to cope with voltage drop about mains 10% voltage accuracy at any output load.

This is to correct a mistake ( 1k resistor ) in my previous post ( 103 ). The considered resistor is R2 = 1.5 k in the original schematic ( R1 in the last schematic ).