0-30 Vdc Stabilized Power Supply

[MP1]

Thanks for the feedback neo,
It is very much appreciated.

MP

 

[audioguru2]

Hi Neo,
You were smart to use opamps rated for a 44V supply. ;D
The original opamps are rated for a max 36V supply but operate at 41V in the original project.

Mixos, the owner of this site built the original project and him and others reported that it won't give 30V at 3A, has a lot of ripple in its output and many parts overheat. Mixos's project failed before he finished measuring it and he hasn't talked about it since.

We have been discussing improvements in this thread so that the project can meet its spec's reliably, like Mixos said in the other thread before I joined this forum:

View attachment 38555

 

[MP1]

Actually, to keep the rumors down, I will interject here:

Mixos has mentioned to me recently that he put the project on hold due to a time constraint.  He has been doing other things and has not been able to put attention to it. Please do not exaggerate, audioguru.
I am not aware that his power supply has failed. Just did not give him the full 3 amps. The other thread is about improving the supply to be capable of 5 amps.

Again, thanks Neo for your valuable input. Others have successfully built this supply with minimal or no changes as well.

I tip my hat to those who are actually building this supply on the bench and who are not just building it in their heads or simulator. (I will not mention names).

MP

 

[audioguru2]

Actually, to keep the rumors down, I will interject here:

Mixos has mentioned to me recently that he put the project on hold due to a time constraint.View attachment 38558

 

[MP1]

No rumor, no exaggeration. The supply had original low-rated parts that over-heated and broke, and Mixos never mentioned the supply again. It has happened to a few people who made the original circuit.

Some who have made the original circuit also had success. You seem to be blinded to this because of the work you have done to make it better.
You also don't seem to understand what I mean by rumor and exaggeration. I have spoken with mixos on this subject within the past week. It is as I have posted. Nothing more.

Let's bring this thread back to constructive discussion on the power supply project and drop the argument and rumors of who did what.

MP

 

[ante1]

Hi all,

Unfortunately some projects in E-Labs collection are not quite up to standards! The power supply discussed here is one of them which no one could have missed to discover. I have received mail and messages about a few others too but the PSU project has been very popular and thus much discussed. Sometimes I try to figure out what’s wrong and sometimes I have to divert the person to another site with a better circuit to fill the needs. I hope this is not going to miss credit E-Lab. Earlier to day a post was made that is similar to many of the mails and messages I have received:  http://www.electronics-lab.com/forum/index.php?topic=5915.msg36593;topicseen#msg36593
Perhaps it’s time to decontaminate the project department; there is no reason to have many projects, much better to have a few good once!

 

[neo_himura]

i would like to add a fan to this power supply without adding another transformer...
the fan rating is 12V, 0.19A...
can i add this fan to the circuit?
how?

 

[audioguru2]

Hi Neo,
Using the recommended 30VAC transformer for this project, the unregulated positive voltage is about 40.4V which is much too high for a 12V fan. If a 5.4W resistor was added in series with the fan to reduce its supply voltage then there might not be enough extra current in the resistor to allow the fan to start running.

Make a two-resistors voltage divider of the 40.4V to reduce it to about 13.2V, then feed it to a darlington power transistor as an emitter-follower to drive the fan. The transistor will provide plenty of current for the fan to start if the current in the resistor divider is high enough.

 

[MP1]

You can use a capacitive divider at the AC. Capacitive dividers can be used with AC input signals.  A DC input voltage would not pass through the capacitors, so you would have to use this type of divider where there is still an AC component to the circuit. The formula for determining the AC output voltage of a capacitive divider is:
Vout = Vin*C1/(C1+C2)

The output voltage is not dependent on the input frequency.  However, if the reactance of the capacitors is not large at the frequency of interest (i.e. capacitance not large enough), the output current capability will be very low.


MP

View attachment 38582

 

[Dosster166]

I'm having trouble finding a few parts.

.47 ohm 10w
12,000uh / 63v electrolytic
47uf / 50v electrolytic  (found a 47uf / 35v)
100nf and 220nf Poyester
6-10a / 50v Diode bridge (is there another name for this?)
bzx79c5v6 5.6v zener
bc557
opa445ap

The site I ordered everything else from didn't have these. anyone know a good place to get them?

Also is there a difference between TIP31 and TIP31A (Sorry if that is a really dumb question, I'm a newbe.

Thanks to all ;D

 

[audioguru2]

Hi Dosster,
All parts are available online at www.digikey.com and www.newarkinone.com .

Corrected spelling or re-phrased:
0.47 ohm/10W
12,000uF/63V Electrolytic capacitor
47uF/50V or 47uF/63V Electrolytic capacitor
100nF and 220nF Polyester capacitor
6-10 Amp/50V (or 100V) rectifier bridge module
BZX79C5V6 zener diode
BC557 transistor
OPA445AP opamp

 

[audioguru2]

Also is there a difference between TIP31 and TIP31A (Sorry if that is a really dumb question, I'm a newbe.

Hi again,
You don't need to be a nooby if you look at datasheets for parts on www.datasheetarchive.com or other sites on the web. View attachment 38591

 

[Untitled_user]

Hello!  ;D

I am looking this power supply for some time and I was planning to build it; in fact I still am interessted in this project, but I need some answers, so, please:

1. I have a 30/30 V transformer 100VA total, 1.7/1.7A secondary output. Can I use     
    it? What for output I will get?
2. What can I use instead OPA445AP?  ???  Not availabile, and as I hear,    expensive.
    TL081? +-18V will be enough?
3. Wich partslist to use? Modified or original one?
    I saw a part of conversation about this PS, (not all 60+ sites ;D) and I am
    confused. I do not need high-end tip-top extreme power supply, but I even do not
    want PS crashes, overheating etc. Just a nice, good working and reliable PS.
4. I assume that 10000uF/50V as C1 is gonna be just nice.

So long...

 

[audioguru2]

1. I have a 30/30 V transformer 100VA total, 1.7/1.7A secondary output. Can I use     
    it? What for output I will get?

Unregulated will be 40.0VDC at 2.3A at full load to about 44VDC without a load. The negative 5.6V supply is additional for the supply to the opamps.

2. What can I use instead OPA445AP?  ???  Not availabile, and as I hear,    expensive.
    TL081? +-18V will be enough?

Your opamp's supply is 44V + 5.6V=49.6V. It is way too high for ordinary opamps with a 36V max rating and also too high for opamps with a 44V rating. Use OPA445AP opamps or get another transformer. Today, Digikey have 259 OPA445AP opamps in stock for $9.50US each.

3. Wich partslist to use? Modified or original one?

It doesn't matter. The voltage is too high for your opamps and the current is too small for the project.

I do not need high-end tip-top extreme power supply, but I even do not want PS crashes, overheating etc. Just a nice, good working and reliable PS.

If the project has enough voltage headroom, then the opamps will make its voltage and current regulation fantastic if you use the correct zener diode for its voltage reference.

4. I assume that 10000uF/50V as C1 is gonna be just nice.

Then it will easily reach 30VDC output at full current without ripple.

 

[Untitled_user]

Hi.

There is no way that this circuit will work with my transformer?
Adding a parrallel R to trafo output to drop voltage? Current will be too small?
Connecting together both trafo outputs is out of question, right?
Something else?
And I really cant afford 445 OPs to me... international shipping price + $30 for 445's is too much for me ???  :'(

There's really nothing to do? Only new transformer?

 

[audioguru2]

There is no way that this circuit will work with my transformer?
Adding a parrallel R to trafo output to drop voltage? Current will be too small?

A parallel R is an AC load on the transformer and will drop the voltage only when the current and heating is so high that the transformer is grossly overloaded.

Connecting together both trafo outputs is out of question, right?

You need to parallel the secondary windings to get 3.4A AC.

There's really nothing to do? Only new transformer?

A 20VAC transformer will give about 22VAC without a load and about 29.7VDC for the positive unregulated supply. Adding the 5.6V negative supply and ordinary 36V rated opamps will be operating at 35.3V
The max regulated output voltage will be only about 20V to 21VDC.

 

[Untitled_user]

OK. Lets mess it out!

I parallel transformer secondary windings and i get 30V 4.3A AC.
And ... I buy OPA445AP's. 
And thing is gonna work.

Will it? How?

And wich partslist to use? Need I change something more?

Cheers...  ;D

 

[audioguru2]

OK. Lets mess it out!

I parallel transformer secondary windings and i get 30V 4.3A AC.

No. Your transformer will provide only 3.4AAC, so the supply will provide only 2.4ADC instead of 3A.

And ... I buy OPA445AP's.

Yes.

And thing is gonna work.

Not yet. Your transformer doesn't have enough output current so the current setting pot should have a trimpot added in series with it and adjusted so that this project can supply a max current of only 2.4ADC.

And wich partslist to use?

Use the modified parts list.

It will perform very well and be very reliable. ;D

 

[Untitled_user]

Your transformer will provide only 3.4AAC, so the supply will provide only 2.4ADC instead of 3A.
Well, guess I gonna need satisfy with this...
If nothing else, there will be less heating problems...  8)

I will buy (or borrow, or steal  ;D) theese OP AMPs, add trimmer in series with current pot and use modified parts list.

And then...


And finaly, THANK YOU!!!
It was impressive and quick as always.

 

[neo_himura]

Make a two-resistors voltage divider of the 40.4V to reduce it to about 13.2V, then feed it to a darlington power transistor as an emitter-follower to drive the fan. The transistor will provide plenty of current for the fan to start if the current in the resistor divider is high enough.

Sorry, i'm a newbie...
can u please include the circuit with the values?..i'm not sure how to connect it.. and what kind of Darlington power transistor sould i use?
is 2n6036 ok?