@Keno – “Yes, heart of the problem is % “the changing of voltage” Right. So stop beating around the bush and tell us what the voltages. Hi, Elektor – I might call- circuit is not bad. Couple of minor modifications made here. Check this out. Item, Type, Manufacturer, Date. Elektor – July/August , Magazine, Elektor – November , Magazine, Unknown. Elektor – October , Magazine.
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This is also my final school project. I made two of these PSU’s in one housing. First one works perfectly fine. But second one causes a problem on the output that couldn’t been solved yet.
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Me and my mentor professor did all kinds of measuring on the not-working PSU – measuring connections, short circuit possibilities, voltage measurement on specified components and with oscilloscope too. Elektog we found out is next – after turning on the PSU, the output voltage rises to certain level depends of voltage potentiometer and than starts to slowly descending til 3V.
Then the voltage changes slowly from 3V-5V. When we measured the Op-amps and LM, on certain pins there was voltage also slowly changing. And if I connect load on the output the voltage slowly descends till 0V eelektor seems like there should be a capacitor making these problems.
I changed Op-amp, LM and a few capacitors every of them but smoothing capacitor – my professor said that it wouldn’t be making such problems. I hope someone has any ideas or has worked on similar project so I can solve my problem which stayed unsolved till now. All of these measurements were measured to the common GND of circuit in that part of circuit stabilizer stage. TR2 is power stage of 26V.
So stop beating around the bush and tell us what the voltages ARE. And if the voltages are changing, then isolate the section by removing the 3 base drive components R9, D4 and D5and find out why the is acting up. Come 11982, this isn’t hard. Isolate the problem section, determine the error, and fix it. Stop beating around the bush with generalities.
I am from Brazil, I am also mounting this source 3 outputs: My LM regulator works well with stable 7. I saw through your measurements that elrktor voltages are way out of the way I would tell flektor Check some things:. If you can put more pictures, it may be easier for someone to see something wrong and find the defect. Be sure to comment on finding the defect.
Forgive me if I wrote some nonsense I do not speak English and I use google translator. Thus something is loading it. This old design uses external eelektor for 2nd order elekto which in closed loop Op Amps causes loss of phase margin and can cause oscillation is no margin.
A common issue is the thru hole lead inductance of cap and ground connections can cause phase shift and if not compensated properly will oscillate. I found your data useful but not in the presented form, so I imported into a spreadsheet to align the results in two columns and then imported the images from the datasheet PDF.
op amp – Precision Power Supply / Elektor, December, – Electrical Engineering Stack Exchange
And 9182 I connect load on the output the voltage slowly descends till 0V everything seems like there should be a capacitor making these problems I changed Op-amp, LM and a few capacitors every of them but smoothing capacitor – my professor said that it wouldn’t be making such problems. Keno 1 9 Since you have a working one, did you compare the non-working one to the working one? Most likely solder connection errors. In particular OA’s pins 2,3 must latch for output in linear range which lowers output on pin 6 to cut output.
Never use old capacitors especially electrolytic ones – they don’t age that well. Listen to what IgnacioVazquez-Abrams said too. Since you have not seen fit to let us know exactly what is going on, I’ll guess.
Start by removing the diode from the current limit op amp. If this 1928 it, you know where to look next.
And are you sure the – supply is properly isolated? How about contact of the heat sinks? How, exactly, are the two supplies connected? WhatRoughBeast 49k 2 28 I am surprised your Prof has not helped you isolate this trivial issue.
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I am also surprised you accepted this an answer. Any challenge with failures is a good experience to learn.
EEsince’75 – For what it’s worth, I’m surprised as well. I would elektlr you Check some things: Possible batch of fake Eleektor High ESR of electrolytic capacitors did you check this? Instability due to the use of lower voltage supply in the Since one PCB worked perfectly and the other one didn’t, I made another one with new board and all elements new. Now it works perfectly. I don’t really bother what went wrong there. Glad your circuit works. Mine still has trouble adjusting the voltage.
When I raise the voltage setting the voltage goes up to 32Vdc when it should go up to 47Vdc, when I reduce P1 the voltage goes up and the potentiometer works upside down min: I am grateful if you can help as I used google to translate this message before. I managed to solve it, the defect was because I replaced the original transistors T T5 with higher gain ones and this caused instability to the circuit. Increase the value of C4 until stable up to 10x. Warning this will affect loop bandwidth and step load response time.
Tony EE rocketscientist 62k 2 21 I don’t epektor get the point your compensation thing. If the first PCB works without this compensation then why would the not-working one need it.
Did you measure phase margin from step load? Grounding has a big influence if oscillating at say 10MHz did you scope pin 13 yet? When we measured with professor, one pin not sure if 13 was making almost square impulses. I myself don’t have the scope.
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