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| 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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