0-30V Stabilized Power Supply

[audioguru2]

If you add another output transistor to the output of an old LM723 regulator IC then each one needs its own 0.33 ohm emitter resistor like is used in the 0V to 30V, 3A project. The emitter resistors for the output transistors will reduce the max output voltage by about 0.33V.

 

[arman92]

If you add another output transistor to the output of an old LM723 regulator IC then each one needs its own 0.33 ohm emitter resistor like is used in the 0V to 30V, 3A project. The emitter resistors for the output transistors will reduce the max output voltage by about 0.33V.

Thanks for reply.

If I add another Transistor (with .33 Ohm emitter resistor) would it increase the Max. Current? Or a change in other resistors is needed?
You didn't tell me your own view about http://www.electronics-lab.com/projects/power/004/index.html power supply,
is that alright? or it need some changes ( as 0V to 30V 3 A needs)?

I really need to have a power supply and I'd like to do it myself!
thanks

 

[audioguru2]

The old and simple LM723 regulator circuit needs a 6.8k resistor to ground at the base of the output transistor.
It does not have variable current regulation, it has only fixed current limiting that varies a little when the chip tyemperature changes.
Its minimum output is 3V, not 0V.

 

[arman92]

The old and simple LM723 regulator circuit needs a 6.8k resistor to ground at the base of the output transistor.

sorry if I ask silly questions, I'm amateur in electronics...
so it does not have a variable current and it's fixed at 2.5Amps.
there is no problem with minimum output (3V)

I'm confused and don't know what to do!
Can you suggest me a good power supply with available(familiar) components please?
Thanks

 

[audioguru2]

Can you suggest me a good power supply with available(familiar) components please?

I am in North America where any part is available. I don't know what is available for you so you should make whatever you can find parts for.

 

[arman92]

I simulated 3-30 V/2.5 A Stabilized power supply in Protues,

but there was only 15VDC Output...
I don't know if I am doing something wrong in Schematics...

Would somebody please check it out and tell me what part is wrong?

here is the file...

Power_Supply_Simple.rar

 

[audioguru2]

There are hundreds of SIM programs. I never heard about yours.

 

[arman92]

There are hundreds of SIM programs. I never heard about yours.

Ohh Really?

I thought Proteus is a very famous Simulation software (something as famous as Photoshop!!)

well... seems I'm not very lucky!

 

[audioguru2]

You said you used the SIM program called Protues, not Proteus.
Most of us use the newer SIM program called LTspice IV.

 

[arman92]

You said you used the SIM program called Protues, not Proteus.
Most of us use the newer SIM program called LTspice IV.

OK, so the problem was about an "e" and an "u" !!
I just downloaded the LTspice IV, seems to be a very simple software and to have a poor component library!
In my Proteus project, I changed the generator (AC) phase delay to 60 degrees,

and unbelievably when I run the project, the output voltage was 29.249 VDC which is what I wanted to have, but when the phase delay is zero, the output is 15 VDC
can you explain why these things happen?!
thanks a lot

 

[audioguru2]

I just downloaded the LTspice IV, seems to be a very simple software and to have a poor component library!

There is a Yahoo users group where they make models for any part

In my Proteus project, I changed the generator (AC) phase delay to 60 degrees, and unbelievably when I run the project, the output voltage was 29.249 VDC which is what I wanted to have, but when the phase delay is zero, the output is 15 VDC
can you explain why these things happen?!

I don't know why you are simulating this simple power supply, I don't know what you havew a "phase delay" and I don't know why its voltage is wrong. Simply build it and measure it.

 

[arman92]

I don't know why you are simulating this simple power supply, I don't know what you havew a "phase delay" and I don't know why its voltage is wrong. Simply build it and measure it.

I simulated this power supply so that I can see if there is any problem, before creating this. I'm a little pernickety in my works  ;D .
OK , so I'll create it!! I'm so thankful for your support, like you!

 

[audioguru2]

Does your SIM program see parts smoking or failing that are overloaded?
Does it know about the electrolytic absorption in the electrolytic output capacitor that causes the output voltage to rise when there is no load?
Does it know about the input offset voltages of opamps?
Does it know that each part has a tolerance?
I think it knows about none of these problems.

 

[jrhodes]

hey guys ive posted here a couple times this time  i think i got it right.  need help on my progect ive built the newest version of the supply and for the most part it works. my problem is the output of u1 ( this is the picmaster version so follow his print) ive got 34v at the rails but my output at u1 doesnt drop below 17 volts and it goes up to 34 volts  i thought this was a lower voltage output not maxed at 34v to drive the transisters. also i noticed when looking at the scope as im increasing or decreasing p2 that pin 2 and pin 3 will follow each other from ov up to about 5 to 6 volts then pin 3 will rise on its own (as i increase pot) and output will then start to rise from 16v to 34v switched chips so i know its good. hey guys i know you love this stuff please help ive got a couple months on this progect and would like to see it work. also this is all with 2 series 56k resister conn at output.

 

[audioguru2]

need help on my progect ive built the newest version of the supply and for the most part it works. my problem is the output of u1 ( this is the picmaster version so follow his print)

I think PicMaster changed all the parts designation numbers so we don't know which opamp is U1.
Please post the schematic you used.

ive got 34v at the rails but my output at u1 doesnt drop below 17 volts and it goes up to 34 volts  i thought this was a lower voltage output not maxed at 34v to drive the transisters. also i noticed when looking at the scope as im increasing or decreasing p2 that pin 2 and pin 3 will follow each other from ov up to about 5 to 6 volts then pin 3 will rise on its own (as i increase pot) and output will then start to rise from 16v to 34v switched chips so i know its good. this is all with 2 series 56k resister conn at output.

If the emitter and collector of the driver or output transistor are wired backwards then the emitter-base becomes a 7V zener diode preventing the output of the output opamp from going less than about +27V.
Only one 56k resistor is used for negative feedback, not two of them.
Which opamps did you use?

 

[jrhodes]

yes of course my picmaster version U1 is your march 11 rev2 U2. the one emmiting to the driver base emitter which im using tip3055 to-220 also i using the mc34071 chips which none of them are really even getting warm. im using 2 56k resisters at the output terminal to add a 112k load. question: the negative feedback coming through r12 and c6 (your version) this signal is stable is it not or does it drop and raise as i adjust p1(your version) on my board the output of u2 goes as high as 34v but only drops as low as 16volts and these voltages seem high driving tip3055 isnt the base emitter voltage of tip3055  only 7 volts. my output never drops  below 16v my inverting and noniverting pins 2-3 follow each other up from 0v to 7v then only the inverting pin 2 continues to rise to 11.15 volts.  why isnt the noninverting pin 3 continuing to rise due to its connection to p1 instead my negitive feedback cirtcuit through r12 and 6c voltage rises to 11.15volts is this due to the 3x gain. which brings me back to why doesnt my voltage drop below 16volts with the pot all the way down. i check my pinouts thought they looked good cant see them being a problem do you still think i have one switched around ill send pickmaster pdf its pretty thurow i used his eagle design printed it with laser and irond it and eched it the traces wernt perfect they all look good now

EL_power_supply.pdf

 

[morpheous87]

I've made 2 PicMaster's version PCBs. They are working well. Since now I had a transformer only for one PCB, so I ordered a new transformer, which can supply both power supplies. The ordered transformer should be with 2 secondaries without common on 31 without load (so approximately 29-30V with load). Now I got it, but the company did a mistake as I see. The transformer have 33,5V without load, I think they did it on 31V with load. I tried one PCB with it. The input voltage is between 32-33,5V ( tried it with a DC motor on 13V 1,5A). There weren't any problems, but should I make some changes on the schematic to use this transformer. May be if I turn on both PCBs the input voltage will drop more, but still it will be over 30V I think. What to do?

 

[audioguru2]

the driver base emitter which im using tip3055

The driver transistor is supposed to be a high frequency BD139, not a low frequency TIP3055 for good transient response.

question: the negative feedback coming through r12 and c6 (your version) this signal is stable is it not or does it drop and raise as i adjust p1(your version)

In an opamp circuit that has negative feedback and no output clipping, both inputs have the same voltage.

isnt the base emitter voltage of tip3055  only 7 volts?

No, it is 0.6V to 1.5V depending on the current.

my output never drops  below 16v .....  why doesnt my voltage drop below 16volts with the pot all the way down?

I think beause you have the pins on a transistor or all of them connected backwards.
PicMaster probably used a BD139 driver transistor. If you used a TIP3055 then its pins are backwards.View attachment 41520

 

[audioguru2]

I ordered a new transformer, ..... it has 33,5V without load.

Simple arithmatic shows that the unregulated voltage will be 46V which is too high since the absolute max voltage for the TLE2141 or MC34071 opamps is 44V.
Reduce the 46V to 41.3V with a 4.7V zener diode in series with the positive supply pin of my U1 and U2.

 

[morpheous87]

PicMaster's version has 3 OAMPs, so I need 3 zener diodes on their positive pins?