fly3rman

You were right, it was a output transistor has died (2n3055). But they are on a huge cooler. I replaced them now, hooked up my multimeter for amper-measurement and ... one died again. So it seems only one of them route the power, and dies. They were from the same charge, so resistance and hfe shouldnt be that different. Ideas why they dont share the power not symmetrical.

Hey guys, as my power supply is finished and actually working, i was testing very heavy loads (2x12volt halogen lamps) with it. But something is gone wrong, my voltage regulation doesnt work anymore and i get fully 40 volts on my output. Also U2 is getting very hot, so i replaced it, still same problem. The current limiting is still working, i can turn current to zero and led is also showing that. Any idea where to start and which parts to check?

@ audioguru Ive calculated the working point on my circuit (42v plus, -1.6 volt minus) to a voltage divider of 10k ohm and 440 ohm. Already did a dirty testing with 10k and 470 ohm, its better, but still problematic. Still the d10 isnt in so far. I will do more testing with a potentiometer, but there is a flaw in the design with the voltage divider i think. If plus voltage is kept up and minus voltage drops, the q1 can work. But there will be a point, where plus voltage is also very low, so the needed base voltage cant be kept up and it will be conduct again. Still, this can kill an LED. The approach must be different, the complete ouput must be OFF as along as plus voltage is under 42V and minus voltage is over -1.3V. I will try followin approach (maybe in addition): a closing mechanic relais: http://www.produktinfo.conrad.com/datenblaetter/500000-524999/503605-da-01-en-RELAIS_ZETTLER_AZ762_1A_48DE.pdf "Must operate DC" for 60 DC Coil is 42V. The difference between our plus and minus lanes is ~43.5V. Connected to this and if one lane drop voltage (off behaviour), the relais is open and output is OFF.

Ive replaced C2 and C1 with 470uF. The negative voltage goed down to -1.6V now. But the behaviour is different from just drop too fast. It does oscilate. In my case it does go up to +3V, and after some quick flashes of connected leds it goed down again to -1.2 again and is slowly dropping. I am also testing Q1 solution right now. Used parts: Q1 BC548 R13 10kOhm R14 1.5kOhm I quicktested, the transistor is always on :/ But i also have to put D10 into. R14 value must be corrected too i think because of difference from -5.6V to -1.3V. I might use a potentiometer for testing.

Hey guys, sorry for putting pressure on this, but i/we do have fixing of this problem as a task on sunday ;] Can someone give me some input if he has the same problem and if it would help to reimplement q1 again and how to impelent it into the REV2 circuity? I need clean on/off behaviour on my supply.

Hi. Ive increased C3 to 47uF + 100uF. Same behaviour. Increased to 47uF + 470uF same. 47uF+2200uF is way better. But for this is took reduced the C3 for 2200uF, only a slight increase of voltage/current on OFF. Couldnt i feed C3 from C1? With 2200uF on C3: Negative Voltage of -1.5 on negative lane and it does not get higher than -1.1 while OFF process. So thats not the problem i think. Also nice: fast off/on doesnt produce this behaviour, because caps are still loaded then. So how to delay the output ON after ON of powersupply itself? Its not an option to fully go down with the potentiometers before on/off of the supply. The effect is still only there if i use current limit, not voltage. IF Voltagelimit is to zero, no flash of led on start or off. Could be in next design update. Iam also thinking a on/off switch for the output is a must. But mechanical it would be a problem, because we want an OFF state for Output for each ON of the supply. Also maybe q1 should find his way back into the circuit because of the dont-have-to-wait-cap thing: "It is a great advantage in experimental work to be able to kill the output of a power supply without having to wait for the capacitors to discharge and there is also an added protection because the output of many stabilised power supplies tends to rise instantaneously at switch off with disastrous results." If someone provide me a reasonable R15 value for the REV2 Circuit, i could implement the Q1 into my actually cirtcuit for testing if whished Is actually the ON behaviour (no limiting for a short time) normal? Cany anyone test it pease? Btw i have to replace the rectifier bridge (600v, 4A at the moment, getting too hot).

Hmm. Okay still it does happen, and i do use TI Sampled tle2141, so they should be fine. Can anyone else who build the supply test this behaviour? Redwire maybe? I dont think its something in the circuit like the multimeter? I will test further later today. Will see what happens on U3 pins. EDIT: Btw it does only affect current control. It does not overcome the set maximum voltage. But if voltage is to max and current is limited, i still has the effect. Ive uploaded a video showing the effect, also very interresting is the flickering effect, no idea where thats from. http://share.ovi.com/media/fly3rman.videos/fly3rman.10007 Also at ON of the supply there is kind of the same effect: current limit jumps in after a flash of led (so its conducting for a short time) EDIT2: testing with dc trafo now, i think the effect isnt there with it. Must be the big transformer, maybe i DO need the full 12000uF wrong EDIT3: Exchanged u3, no effect.

Yep, i came also to the same calculations. There are heatsinks with 0.8K/W, but they are too huge and its not really possible to mount the 2n3055 on it. I will later check my local dealer, ive got an idea .... Today i was playing around a little bit with the Powersupply and burned some leds. Why: If you set the current to ~10mA and turn off the supply, u get a short, huge peak of current which kills your leds. My slow multimeter shows up to 30-40mA for a setting of 10mA. Because the multimeter is slow and averaing, i think its way more for a short time. At the moment ive got like 3000uF only on my caps, so if i got up to 12000uF the peak will be longer and higher. Is there any solution to keep up the current control "till the end"? Also possible solution: Switch for output and switch for the supply itself. Or maybe i get a multiple-pole-switch (never saw it with more than 2) switch turn off the output and 220v input at the same time. One switch and 2 relays would be an idea too ...

One more picture:

Hi audoguru, I have no idea how you could find that problem but you was right, again! I actually double/three time checked all the parts, but this one slipped through ... R12 was a 56 Ohm instead of 56K Ohm. No wonder it wasnt working. Now it does freaking work. Voltage goes up to 30+something, i successfully trimmed it down to 30. Shorted Amper measurement was showing 5 Amp, then i stopped turning up =). Trimmed it down successfully to 3Amp! Zero Voltage is something of 0.33mV. Cant trim it down, but will recheck values around RV1. But actually that Voltage is ok for me first. Now i will build in the additional fine potentiometers. Do some heatshrink ... And then i will think about heating problems, my heatsinks are way not enough ( 3,5'K/W, http://www.segor.de/#Q=SK 63-37,5SA 3S) For thins i thinking about follwing: placing these heatsinks inside on the aluminium backplate (se picture), and outside another one big heatsink, conencted with screws/nuts and silicon heatpaste. Maybe a problem: the whole backplate gets hot? Other idea: on the bottom inside on the airholes i just place a 40x40 or 50x50 airfan, maybe controlled with a temperature-sensor. I posted some pictures of my work so far. Thanks man, you rock!

@ audioguru, thanks for the input, you were right. It was the Q2. I put in a new one and now its working like it was before, but still not right. I can: Set voltage from zero to 11.1 Control current and also turn it off completely (led lights on) Now some data: - i used redwires pcb with latest values (see picture) - power is supplied by 2x15 (series) 160VA transformer - ac voltage is fine: 30v - dc voltage after rectifier and supplied to 2n3055`s: 42v - q3 is a bc327, collector:32v, emitter: zero aslong no c.c, base ~32v - q2: zero to 11v on emitter (reacts on base voltage), 42v on collector, base zero to 11.9v - negative rail is @ -1.3 - R1 is 2200 Ohm, R2 is 82 Ohm, both 2W, still getting extreme instant-fingerburn hot - u1 pin7 voltage: 42v, pin6: constant 10.8 - p12: 0-10.9v, p10: zero constant, p5 10.9 constant - p13:0-0.9v?, p11: zero constant, p6:0.9v - u3: pin7: 32v, 6:zero to 32 - u2: pin7: 42v, 6: zero to 11.7 - trimmers seem to have no effect at all It really seems that is dont get the voltage gain of 2.68 times. i start thinking about faulty opamps? they are hard soldered, so not fun to exchange them, but i wanted to put in sockets anyway .... I hope you can provide some more help.

Arghs. Crap. Mixed up Base and Emitter of 2n3055 and now somethin weird is happening, but its not working. Output of maximal 3V and extreme hot R1 and R2. But iam able (in a small range) to control voltage and current. extreme strange. Test everything will be fun :/ I think i saw some picture of "as it should be" voltages and differente places. will look into that. update: u1 and u2 (tle2141) do have 42.6 volts on pin 7. u3 does have zero. when shorten the output, ~1.5 amper are flowing and 2n3055s heat up very well, so far working, but cant control current then. But when i set voltage to zero on voltage poti, its no current flowing anymore -> working. Led isnt lighten up. I think i should replace u3, but maybe its something next to it. Ideas please =)

Iam aware of that. Also on the other side, one 18v/1.5VA transformer couldnt blow anything up, and still possible that it works ;] Yep, got that. 3mA is fine enough. Redesigning is a little bit problematic at the moment because of the lack of overview and compelte understanding of the cirtcuit, but time will come ;] But its possible without any problems in stability or something? If i trim down to lets say 1A max Output? (This, as i mentioned, would allow a later upgrade to a highpower transformer) This is fine. Iam actually gonna use it in region of <1A most of the time. Ive used the latest version. Nice. Thanks for the input so far. UPDATE: My Circuit works! Had wrong wiring on current / voltage control, but now it works. With lower voltage and current transformer i am able to set voltage and current! Tested on 2 leds. Will show pictures later. Of course hard to set the current/voltage on this potis because of wrong dimensions. But now iam aware its working i can get the expensive transofmer i think =)

1) Still it should work or will it not? I meant this transformators just for testing so far. Is it possible to trim it down with RV2? What is the minimum voltage needed for correct working of the voltagecontrol? Putting them in series with 36v is also a little high then :/ 2) Yes, but only for higher currents right? 3) thanks, put a wrong on it, will replace. Questions: For understanding: So this always need the 3A current and atleast 28V AC and heat up everything not used by the consuming load? Otherwise the control doenst work? Is it possible to trim it down to lets say 2A? As written before : "RV3 is to set the maximum current to 3 or 5 amps". And actually i want to use an 120VA Trafo instead of 160VA because its 1/4 cheaper. It should can handle the missing 0.2A right? (someone ask before also) and another one: Can anybody say something to the stability and possibility to control the current of this powersupply?

Thanks alot redwire, it seems it got it then. Here my toner-selfmade-double-side-etched-pcb. I hope you can see it on the pictures. I will test it tomorrow with the small 18v trafo. If everyone finds any wiring problems ...

Redwire? Could you please exlain the offboard wiring? Points 7a 7 8 3 and 1. Also what it is with D7 Diode and if d2+d3 are replacing it? Or are they needed? 4 and 4a are ground? Current outputis wired from Output Transistor?

just to check: this one ok as bridge? (asking because of the glass) http://diodes.com/datasheets/ds21221.pdf 25A GLASS PASSIVATED BRIDGE RECTIFIER 600V 4700 or 6800uF/63VDC should be enough for stable voltage at low currents right?

Thanks for answering and thanks for the PCB. I also crosschecked it yesterday and and seems to be fine, only some values differs. Alignments its a little bit tricky but there is still some leeway. Ill finish the toner transfer to the 2nd side today and etch this one.

@audioguru, wolud you please approve the files i posted here: http://www.electronics-lab.com/forum/index.php?topic=19066.msg100521#msg100521 before i start to build i have to know =)

Exactly. Thanks. But it would only overheat if i set the current limiter HIGHER than 2.1A DC and also consume it. Fine. Cool i also can go with lower voltage then. nice. Wonderfull, exactly what i wanted to hear. Because this way i can first use a weak Trafo and after i found a strong and cheap one, ill switch. Thanks you. Will try to double etch the board with my toner method ;] EDIT: I gonna use this files, are they compatible? are there newer? because in part list it says rev3:

Hi guys, i am really interested into building this one. Only thing is: What if my transformator doesnt supply 3A? Does the current regulation still work? Will there be a voltage Dropoff if current regulation is set to higher than the current supplied by the transformator? Should i "redesign" some parts to stay in my range of current control? And which parts do i have to recalculate?