Electronics > Projects, Designs, and Technical Stuff
Simple DIY Linear PSU
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panoss:
I 'm in the process of building the circuit and I thought of trying something in the simulation.
BUT I found out that I had made a mistake:

On Reply #32 I had written that I made the simulation with D45H11.
Well...that 's not true...I had not connected the D45H11 model to the transistor. :palm:
So the simulator used a 'Generic PNP transistor' and not a D45H11...

So, I connected the model to the transistor and run it, but it wouldn't run because of errors.
So, for Q2 I thought of using a Darlington transistor (BDX54), because of it 's high gain.

I changed the value of R10 (from 300 Ohms) back to it's original value, 1k.
And looks like working fine!
xavier60:
If you are adding one of those cheap Volt Amp panel meters to the project, it should not be powered directly from the 9V rail. A shunt regulator should be added to prevent the LEDs from causing current fluctuations through the CS resistor.
panoss:
Ok, I built it!
But, I 've made some modifications because these are the parts I had in hand.
I avoided getting out of the house (corona virus, you know).

So, I replaced Q2 with a DIY darlington pair, with BC557 & S8550.
Q3=Q4=D209L.
D5=BAT41 (instead of BAT85)

I did some tests, with no current limit:
RL= no load, Vout=16.79V
RL= 20 Ohms, Vout=14.93V, Iout=0.71A
RL= 10 Ohms, Vout=13.59V, Iout=1.26A
xavier60:

--- Quote from: panoss on March 14, 2020, 09:49:32 am ---Ok, I built it!
But, I 've made some modifications because these are the parts I had in hand.
I avoided getting out of the house (corona virus, you know).

So, I replaced Q2 with a DIY darlington pair, with BC557 & S8550.
Q3=Q4=D209L.
D5=BAT41 (instead of BAT85)

I did some tests, with no current limit:
RL= no load, Vout=16.79V
RL= 20 Ohms, Vout=14.93V, Iout=0.71A
RL= no load, Vout=13.59V, Iout=1.26A

--- End quote ---
Both of those PNP transistors have fairly high gain.
The CV loop is likely oscillating, can you check?
Use just one PNP transistor.

Extra; The D209L has very low gain so a lot of load will be placed on the undersized PNP driver. So don't power anything valuable with it yet.
xavier60:
Do you have any scrapped audio power amplifiers? They might have suitable transistors.
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