Super Regulator

To quote personal messages probably not very nice but want to share finished and working project ant to thank you all for helpful advices. My reference voltages from GLED431 slightly off, at the positive rail 6.7V and at the negative 6.85V and leds on negative rail are a little bit lighter. But I put trimmers to have a possibility to adjust output voltage and I can set exactly 15V. Should I worry about these reference voltages?
View attachment 1289258
I would prefer that both references have almost the same voltages. Which LED did you use? Did you check that the reg oscillates? Try replacing R17 and R19 with 1K and increase the current through the reference. A long time ago, I made four such references and the differences were in tens of mV.
 

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Yes, it was my fault. I already noticed that. Just put a wrong resistor (instead of 390R I put 1k and opposite for another one). Now everything is fine. LED’s are from old stock green SMD and I do not remember exactly the type. But voltage drop across one is about 1.8V. So, chain is from 3 leds and one 1N4148 diode.
 
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I would prefer that both references have almost the same voltages. Which LED did you use? Did you check that the reg oscillates? Try replacing R17 and R19 with 1K and increase the current through the reference. A long time ago, I made four such references and the differences were in tens of mV.
Looks like I was happy too early :(
On my scope the picture is not very pleasant:
oscillation.jpg

c11/c12 caps are correct. What else can cause problems?
 
Looks like I was happy too early :(
On my scope the picture is not very pleasant:
That's what I was afraid of.
To begin with, put a small electrolyte or film parallel to the reference. Increase the value of C10 and C18(or put a small electrolyte in parallel). What type of tantal are you using? Also measure Vds on BSS169, I've never worked with those mosfets so I'm interested in those voltages.
As for the PCB, I would like it to be more compact and the lengths of the lines to be as short as possible especially around the op amp.
 
Thank you, grunf, things are worse than I thought. With GLED431 probably everything is ok. Before I assembled it on PCB I tested it on test board and tweaked resistors to get 6.9V. I will measure voltages around current source transistors and will post it later. But now I tried more simpler things. First of all I disconnected GLED431 current source with BSS169 mosfets and replaced it by 1.2K resistor to set current for GLED431 to about 6.7mA. Oscillation gets worse. Then I replaced GLED431 with an original LM329 voltage reference. And now oscillation at 2MHz frequency but it worse than before:
Oscillation 2MHz.jpg

My tantalum capacitors are from Farnell:
https://lt.farnell.com/kemet/t491x107k025at/cap-100-f-25v-10/dp/2321230
And for now I am not able to do symmetrical changes on -15V rail because had only one LM329. My power supply is loaded with a phono preamp and I made the mistake of not foreseeing an option to disconnect it from power supply. A simple 0R resistor would have solved a problem. If I disconnecting -15V rail things are changing and I do not see this very clear 2MHz oscillation just some garbage as on GND plane. My first thoughts were that PCB layout is bad but now I cautiously thinking that maybe oscillation on -15V rail might have an effect to +15V rail. Or with half of power load is changed. But maybe not. So, will try to do the same procedure with negative rail but need another LM329 :)
But any suggestions would be greatly appreciated.
And for now, I would like to congratulate everyone on the upcoming Easter 🐣
 
Some update:
As suggested changed C10/C18 from 0.1uF to 1.0uF and on negative rail removed GLED431 constant current source with Mosfets and instead added 1.2k resistor to supply 6.7mA current. So, positive rail with LM329 and negative with GLED431 and looks like oscillation gone. I only detecting the same signal as on ground plane:
GND.jpg

Understand that GND should be plain line but with such small signals and antique equipment and probably measurement technique I am getting such weird results. But anyway, prime suspect probably is GLED431 constant current source.
 
And here is voltages at different nodes but on my test board. It is pretty close to the LTSpice simulation. Except the value of R18 resistor. Drop across R28 resistor is about 1.52V, so current is about 5.6mA for GLED. But on PCB I had different values. Across R28 I measured about 4V and that probably too much. Probably I damaged mosfets by putting additional 470uF electrolytic capacitor across power rail. I did it by hand on working circuit and got some spark when connected it. It was not smart solution but I wanted to see changes on oscilloscope.
GLED431_voltages.JPG


Simulation.JPG
 
Good morning,
I would like to build a pair of + - 12v super regulators, using components I have at home (NE5534, BD139 etc), so i created the simulation with LTspice for the positive version.
For the Vref, since I can't find the lm329 on sale, I thought of the solution with 4 green LEDs (further adjusting the R15) or inserting the PM329 6.9V by W. Jung.
Could you advise me which of the two solutions is feasible, also considering that I have little space to include the reg in the supply?
Below is the diagram with PM329 applied.
Thank you so much.
Best regards
Dimitri
 

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Jan has said

Yes, when in doubt, screen the sense wires.
......the sense wiring itself has an induction and possibly a parasitic capacitance.


So....what is best practice?
Does each sense wire get its own individual screened cable?
Or do both sense wire share a 2 wire screened cable?
Or does the sense and force wires share a 2 wire screened cable?
Or do all 4 sense and force wires share the one 4 wire screened cable?
I understand that the screen should be connected to ground at the reg PCB
thanks
tim
 
I need help with this super regulator to get 5v output. Input 8,4 volts. After changing voltage reference to ADR510 with op amp OPA1641 it does not work. R7 is 1k ohm and R6 is 4k ohm. D2 is 2,4 v diode and R5 is 1.5k ohm. I started this circuit also without op amp. I forgot to put it in. If I turn on then led makes one blink and on the output I see max input voltage. Tested with higher input voltage also and it was the same. I used DMM to test diodes and transistors using diode function but these seems to by fine. What to check next or are the resistors values wrong? Please help 🙏
 
The problem with your setup could be due to the fact that your CM voltage of 2.4V is outside the OPA1641 device rating. This is 5V - 3.5V, which is 1.5V. Much less than 2.4V. You may not have damaged anything internal, but it wont work properly, unless you drop the reference voltage down to less than 1.5V. If the adr510 is OK, it should give you 1.0V, not 2.4V! This may need fixing. Your divider Rs should get a 5V output at 4K(top)/1K(bottom). If everything is well, you should then get a very nice 5V output. Not super quiet, unless you do some RC filtering between the ADR510 and the (+) input.

Look for a coming follow-up on my low noise/voltage LED references of Part1 (https://refsnregs.waltjung.org/LEDs_as_Audio_Voltage_References_P1.pdf). The part two is called "A 1V Reference with Mirrors".

Walt Jung
 
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