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0-30 Vdc Stabilized Power Supply


Sallala
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Hi, does anybody know how to realize this circuit?


I had similar problem, but mine was with fluctuation of the panel all over. My solution was to power up the pannel on bipolar, i.e. +-5V with midpoint. I suppose your panels allow you to connect them this way, or hopefully they do. The good thing is that you only need few miliampers to power up the thingy. What I did is I used two zeners at 5.1V with resistors, and built basically the analogue scheme of voltage devider, but instead of 4 resistors, I used 2 resistors and 2 zeners. Zeners are connected together in series the resistors are connected again in series - one attached to each zenner. The midpoint between the zenners you can take as zero - it will be relative zero, so between the midpoint and the other pin of the zeners you will have relatively +5.1 and -5.1. The good thing is that you can take the power to power up the zener stabilizators from the rectifier bridge of the PSU, meaning no more transformers in the case. Resistor values will depend on the potential input - use ohm's law. This worked for me and hopefully it will work for you :)
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Hi Everybody,
i'm a french fan of thie famous forum and i'm newbie...
I'm just wondering about what kind of change i have to operate on the propsed schematic in order to be able to use a transformer which could deliver 6 A ? I would like to build a power supply with a max intensity of 6 A instead of 3 (that's because i have only one transformer).

I hope you will understand my request ...
Good Luck in all your project

SKAPPY

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Hi Skappy,
Welcome to our forum and greetings to France.
If you want this power supply to produce 0 to 30VDC at up to 6A, then it will need modifications similar to those we dicussed in the other forum about converting it for 5A. Near the end of the other forum is a good schematic with parts' values shown. The other forum is here:
http://www.electronics-lab.com/forum/index.php?board=13;action=display;threadid=196

The modifications that you need are:
1) A 30VAC/8.5A (255VA) transformer.
2) A larger heatsink since with a 6A low voltage load, or with the output shorted when the supply is set for 6A, the 3 output transistors must dissipate a total of 230W!
3) R7 will need to be changed to 0.22 ohms/15W

However, if your transformer is rated at only 30VAC/6A (180VA), then this power supply will produce only about 4.2ADC at the transformer's limit. The remainder of the parts for the 5A modification will be fine.

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Hi Skappy,
Since your transformer doesn't have a 30VAC output, your project that uses it won't be able to have a well-regulated output up to 30VDC, as I explain half-way down page 18 in the other post.
The rating of your 300VA transformer is probably for the total of its 3 outputs, so maybe each output is rated at only 100VA. Its voltage and current aren't enough.

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Hi Guys,
I just made another discovery to improve the 5A soup-up of this project on the other thread, and it also applies here.
The zener diode D8 is this project's voltage reference and must perform well. With R4 being 4.7K, D6 is operating at a current of only 1.2mA. Our project doesn't specify a part number for D8 and some guys have been using a 1W zener diode.
A 1W zener diode such as the 5.6V 1N4734A is rated and measured at a current of 45mA. At 1.2mA it just barely conducts and is about only 4.2V (the normally vertical voltage line has curved to be nearly diagonal, like an ordinary resistor).
A 500mW zener diode such as the 5.6V BZY79C5V6 (available worldwide) is rated and measured at a current of 5mA, where it performs very well. It also performs poorly at 1.2mA (5.3V) but is much better than a 1W zener diode.

Therefore we should change R4 to 1K (for a zener current of 5.6mA), and specify using BZY79C5V6 zener diodes for D7 and D8.
Edited Nov.6/04: in bold.

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Hi Marek,
Welcome to our forum.
Let us fix your jumpy power supply project.
First, some questions:
1) What are the output voltage and current or VA ratings of your transformer?
2) Did you build it like the original plans, or did you make any modifications that we discussed here?
3) Did you substitute any parts?
4) When the output voltage jumped when adjusted, did you have an output load?
5) When the output voltage jumped when adjusted, did the current regulating LED light?
6) Does the voltage at the slider of the voltage adjust pot adjust smoothly from 0V to 11.2V?
7) Does the voltage at the output of U2 (pin 6) adjust smoothly from about 1.3V to 27 or 28V?
8) Without a load, does anything get hot when you adjust the voltage?

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HI
1) 22 V AC (28 DC on capacitor C1) about 5A
2) I build standard project 0-30V 0-3A
3 )Yes i substitute Q3 with BC556,Q2 with BD243C and r15 with 100 ohm. I nowhere can find 2n2219 or Tip29, Tip31.
4) I didn't load output
5) No , LED is not light
6) voltage at the slider of the voltage adjust pot adjust from 0V to 11.2 without U2.(At 6 pin is the same voltage at pin3 on board without U2). If i insert U2 the voltage is about 25V at pot.
U2) is getting hot. If i solder off pin6 U2 the temperature is normal, but is all time 27V.
Regards and Thanks for interest.

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Hi Marek,
You made good transistor substitutions.
Your U2 is defective, replace it. It is feeding voltage to its input.
Wait a minute, it could be that you have U2's pin 3 (input) and pin 6 (output) reversed! The top of the IC looks like this:

1* 8
2 7
3 6
4 5

Wait a minute again. Without U2, its pin 6 follows its input? Then your circuit board is shorted from pin 3 to pin 6. ;D

Your transformer voltage is kinda low, so your project's maximum output voltage will also be low. If you use 10,000uF or more for C1, and a 10A or more bridge rectifier module then you will get a couple of volts more output at full load.

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Hi again.
I know that U2 is placed correctly. I changed U1,U2,U3
I use 22kOhm pot.
Maybe some measure points will help me?
On board beetwen 6 and 3 pin U2 i have 28 Kohm on multimeter, beetwen pin 2 and collector Q4 is 25Kohm.
Something is wrong, and I don't know what :(
Regards
Marek

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6) voltage at the slider of the voltage adjust pot adjust from 0V to 11.2 without U2.(At 6 pin is the same voltage at pin3 on board without U2). If i insert U2 the voltage is about 25V at pot.
U2) is getting hot. If i solder off pin6 U2 the temperature is normal, but is all time 27V.

Hi Marek,
Did you say that without U2, the voltage at its pin 6 is the same as its pin 3, that both pins adjust from 0V to 11.2V?
Pin 6 shouldn't do that without U2.

With U2 connected, it must be passing some of its output voltage of 27V to the pot to make it 25V instead of 0V to 11.2V.

Your resistance measurement of 28K between pins 3 and 6 of U2 depends on the output voltage of your ohm-meter. If its voltage is only about 0.3V or less, then it should measure more than 1M.

All of these observations point to leakage between pins 3 and 6 of U2. Try lifting D9 and R9 from pin 3 to see if you still have leakage from pin 3 to pin 6, or leakage from D9 or R9 to pin 6.
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Hi
Yes, I said without U2 the voltage at pin 6 is the same at is pin 3.
I agree from this that pin6 shouldn't do that.
I lifted D9 and r9, at pin 3 is 0V -good. Adjust at pin 6 is still from 0 to 11 V- and this is bad.
And i found solution. I had micro short-circuit at r8 and r15.
Thank You very much Audioguru for your time and help. Such trifle, and it be able to lead out with aim man. ;D
One more time Thank You.
Regards Marek.

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  • 1 month later...

Hi Zwieke,
I couldn't find a datasheet for a 2N6578, but got conflicking reports about its power dissipation ability, either 87.5W or 120W on an infinite size heatsink at 25 degrees C. So it might burn.
It's a darlington transistor so has an extra B-E voltage drop, which will reduce your project's maximum output voltage.
I wouldn't use it, 2N3055 transistors are very common and inexpensive.

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Hi all 1st post here
And to start quickly here are some questions...
1) On post #93 someone asked about higher Voltage rating Caps can be used (change a 50V to a 250V) but he went to sleep :P
So is it possible ? The voltage rating of caps refers to how quickly does the Cap releases its energy ?
2) IS there an updated PCB image yet ?
3) In a previous post you audioguru say
"Our project doesn't specify a part number for D6"
But i see on the project page that says D6=1N4148
In the end shall we use the BZY79C5V6 you suggest ?
Or you did a typo, and you meant changing D7 and D8 ??

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Hi Ngt,
Welcome to our forum.
1) The guy with the 250V caps did go to sleep when he realised that they were actually 450V ones and said, "forget it".
The voltage rating of a cap has nothing to do with the way it operates. Just how much voltage it can withstand without breakdown.
2) A few guys talked about making an updated PCB but nobody posted one.
3) OOOps, I did make a typo. Sorry!
D8 is this project's main voltage reference and should be a BZY79C5V6, and also D7 which is the voltage regulator for the negative supply. D6 is just a low current rectifier.
Also, R4 should be changed to 1K for 5.6mA throgh D8.
I have corrected my posts.

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