Help me PSU with output of 0-12V 1A using only discrete components

[Splitfoot]

I have been trying to design a bench PSU using only discrete components. The input will be 16-20v and I need to output 0-12v 1A with current limiting.
So far I have managed to get

Q3 and R6 are supposed to control the current limit at 1A but I don't think it is working, where am I going wrong with this?
Thanks in advance for any possible help.

 

[goldsmith]

Re: PSU design, 0-12V 1A

Dear Splitfoot
Hi
You need to use a darlington pair at the out put . to be ensure that , that current will given . but here are better ways , with op amps and some simple transistors or etc , is it important to use that circuit exactly ?
Best Wishes
Goldsmith

 

[Splitfoot]

Re: PSU design, 0-12V 1A

It is not important that I use that exact circuit, the only requirements are that I only use discrete components to achieve the desired results.

 

[goldsmith]

Re: PSU design, 0-12V 1A

What do you mean by discrete component ? has op amp , any problem for you ? ( op amp will use at feed back loop and the series pass element is transistor ) .

 

[Splitfoot]

Re: PSU design, 0-12V 1A

An op amp would be no problem, I just can't use any ICs that have a built in current limiter or something like that.

 

[goldsmith]

Re: PSU design, 0-12V 1A


You can use top circuit , you can control the vout and iout simply .
Best Wishes
Goldsmith

 

[Splitfoot]

Re: PSU design, 0-12V 1A

Which area are you referring to when you say the "top circuit"?
I don't really understand how the circuit you posted works.

 

[goldsmith]

Re: PSU design, 0-12V 1A

Which area are you referring to when you say the "top circuit"?

What do you mean by that ?
And about the action of that circuit , i designed that circuit according to the LDO configuration .
Which section of that isn't clear for you ? I'll illustrate that section for you if you tell me .
Best Wishes
Goldsmith