0-30 Vdc Stabilized Power Supply

[Jeremy2]

Hello. This is my first post here. So HI!

im building this power supply, but I have ordered already premade board from eBay(the red ones). I have soldered and it's all working correctly (sort of). But I'm having trouble with current limiting. When the pot is turned all the way up the current can spike to 10-15 amps depending on the load and then fry the power transistor. I doo have a transformer that can supply more than 3a but that shouldn't work like that. So does anybody have an idea how to fix it?

Sorry if it has already been dicused in this forum, but google didn't provide answers and 75 pages is just too much. 

Hi all.

I have got the same issue.

The adjustment of current limiting from zero to max is on 1/4 of the range potentiometer.

It is looks for logarithmic regulation not linear. 

Any clues ?

 All checked two times.

Regards

 

[audioguru2]

The original circuit has many overloaded parts and cannot produce 30VDC at 3A. It is also missing the calibration trimpots that are used in the improved version that can be set to exact maximums of 30.0V and 3.0A.

 

[Jeremy2]

Hi.

 I add the trimpot 100 k and resistor 33 K instead 56k. Sensor resisor is the same 0.47 Om.

All rest is the same like basic version. It is look like there is not current protection, - minimal  adjustment is  at the minimum pitch of the potentiometer and after 1/4 range  current is not limited ( once Q2 was replaced -  was a short circuit)   It's probably PCB mistake . I have red one too from ebay (kit).

I build the same power supply  a few years ago with PCB by myself and it is working for today! Great construction!

Now I want smaller version, but from ebay or banggood (red version kit) doesn't work properly.

On the movie is mistake with current point. Value of the current is 2.7 A not 0.27 A - one more mistake from banggood - bigger range of panel

Regards.

 

[audioguru2]

I think the kit from Banggood and copies of it are selling at a clearance price today because it has been replaced with a better kit maybe with its errors corrected.

Of course the new kit costs much more and comes with voltage and current displays. 

 

[Jeremy2]

Ok, skip the voltage and current LCD panel

With R18 = 33 kOhm I have got 4,7 A on out...

U3 was replaced for another .

 

[audioguru2]

We talked about fixing the cheap Chinese Banggood kit on another website and I do not want to talk about it again.

 

[repairman2be]

@Jeremy

I have built a Power Supply according to Liquibyte post here:

"electronics-lab.com/community/index.php?/topic/40835-0-30v-0-3a-latest-data/&page=2#comment-156499"

I have had made PCB's from his gerber files he offered. The board has a size of 67x100mm. If you want one or more board leave a message here.

Regards, William

 

[Jeremy2]

@Jeremy

I have built a Power Supply according to Liquibyte post here:

"electronics-lab.com/community/index.php?/topic/40835-0-30v-0-3a-latest-data/&page=2#comment-156499"

I have had made PCB's from his gerber files he offered. The board has a size of 67x100mm. If you want one or more board leave a message here.

Regards, William

Hi.

How much is it cost? I haven't time to do it again from begining (PCB).

I think that my problem with banggod kit is easy to fix. With a 30 V or 15 V  on out  I making a  short circuit  , LED is blinking and current is  4,7 A.

Too bad .. .

They do not help  with ebay kits.

Regards

 

[repairman2be]

@Jeremy

You may have 2 PCB's for AU$5 plus shipping in an envelope. Two boards weigh about 44grams.

Email me if you would like some to: [email protected]

Cheere, William

PS. Seems your Kit has a problem to start with. Before I found this Forum I ordered two Banggood Kits. It is still not assembled and probably never will be. Anyway, over at this page there is a lengthy description on how to improve the Banggood kit.

"www.paulvdiyblogs.net/2015/05/tuning-030v-dc-with-03a-psu-diy-kit.html"

 

[Amiir]

hey guys. im new here.

i made this power supply for my small workshop and i have some question about it.

first Q : how can i add Fine volume for voltage and current! (Coarse and Fine)

second Q : this circuit cut off the output voltage when we take more than 3.0 Amperes. its ok. but my transformer can deliver 4.0 Amperes and i want to change this cutoff option to 4Amp.

third Q : can we use 24v 10a (or 30v 10a or 48v 10a) Switching power supply instead of transformer in input and make it more powerful ?

thanks guys. in attachments you can see my power supply v1.0

i make this one for my friend and now im about make another one for myself.

please answer my question. after completing the project i will upload Corel Draw files (Front and Rear Panel Plaxi Laser Cut)

* That "Made in IRAN" is just for fun all parts purchased from china :lol:

images are for v1.0. in this new one i made a lots of changes in front and rear panel.

this one has no volt/amp meter yet. but the rectangular cuts are place for them.

thanks guys and im sorry for my bad english

 

[audioguru2]

If you use fine and coarse controls then one will always be in the wrong position. Use larger knobs instead.

Higher output current will cause a heat problem in the output and driver transistors. The improved version of this project already uses two output transistors to share the heat produced at 3A. Use a huge heatsink and a fan for 4A output. Change R7 to be 0.35 ohms/10W.         

A 24VAC transformer is too low for this project to produce 30VDC output at 3A or 4A but the original TL081 opamps will have a voltage too high for them if the transformer voltage is increased. The improved version of this project uses TLE2141 opamps rated at a supply of 44V and a 28VAC or 30VAC transformer.

A transformer rated at 24V/4A has a limit of 24V x 3A= 72VA. But here the 24V is rectified to produce a peak voltage of 34V. Then if the load on this project is 3A the transformer produces 34V x 3A= 102VA. It must be rated for 102VA/24V= 4.25A. If the output of this project is 4A then the transformer must be rated for 5.7A. 

 

[Amiir]

If you use fine and coarse controls then one will always be in the wrong position. Use larger knobs instead.

Higher output current will cause a heat problem in the output and driver transistors. The improved version of this project already uses two output transistors to share the heat produced at 3A. Use a huge heatsink and a fan for 4A output. Change R7 to be 0.35 ohms/10W.         

A 24VAC transformer is too low for this project to produce 30VDC output at 3A or 4A but the original TL081 opamps will have a voltage too high for them if the transformer voltage is increased. The improved version of this project uses TLE2141 opamps rated at a supply of 44V and a 28VAC or 30VAC transformer.

A transformer rated at 24V/4A has a limit of 24V x 3A= 72VA. But here the 24V is rectified to produce a peak voltage of 34V. Then if the load on this project is 3A the transformer produces 34V x 3A= 102VA. It must be rated for 102VA/24V= 4.25A. If the output of this project is 4A then the transformer must be rated for 5.7A. 

thank you so much for your reply sir. :wub:

forget about using hi amp switching power supply instead of transformer. it was just a Curiosity question.

but about increasing the output amperes as you said for taking 4A from output i should change my transformer with 24v 5.7A.

so if i use 24v 4A transformer then how much amperes i can take from output?

cooling 2N3055 is not a problem. best heat sink and turbo fan used for that.

each 2N3055 can handle how much amperes in best cooling situation ?

If you use fine and coarse controls then one will always be in the wrong position. Use larger knobs instead.

in Chinese power supplies coarse and fine works well. they use same opamp and other parts for that.

volumes are :

Voltage Coarse : 50K - Voltage Fine : 5K

Current Coarse : 10K - Current Fine : 1K

Use larger knobs instead.

before i asking my questions here i decided to use larger knobs as you said. but fine volume works better.

*i just completed the rear panel laser cutting file Designed with extreme accuracy.

so if anyone use the box just like mine then he/she can use this files without any changes.

but of course you can change it as you like.

the front panel will be done soon.

ebay link for used parts will be placed here.

 

[audioguru2]

If you use a 24V/4A transformer then its maximum allowed output is 24 x 4= 96VA. Then the project maximum output current must be calculated with the 34V peak voltage (96VA/34VDC= 2.8A).

You can simply calculate how much heating (volts times Amps) a 2N3055 will survive by its thermal spec's and the heatsink thermal specs on their datasheets.  

 

[Amiir]

i dont  understand. in projects Bill Of Material said use 24v 3a Transformer for making 0-30v 0-30a power supply.

but u said if i use 24v 4a i will get 0-30v 2.8a !? how can its possible ?

so if we use 24v 3a transformer we will get less than 2.2a! so its not 0-30v 0-3a dc power supply!

the circuit current cutoff (short circuit protection) is 2a or 3a?

if its 3a and we use 3a transformer for making project (taking 2.1a) its never cutoff the output for short circuits!

anyway my heat sink were bought from local stores and they do not provide datasheet for this items!

 

[audioguru2]

The original Greek kit and the first Chinese copy wrongly said to use a 24V/3A transformer that does not work and becomes overloaded. Its voltage is too low for the project to produce 30VDC at 3A and its voltage is too high for the opamps with a low maximum supply voltage rating of only 36V. The original opamps also needed an additional negative supply with a fairly high voltage.

We corrected the circuit and used opamps with a 44V maximum supply voltage rating and a 28V/4.24A transformer (the peak of 28VAC is 39.6V). With an output current from the project of 3A then the transformer must supply 39.6V x 3A= 188.8VA. Then the current rating of the transformer must be 118.8VA/28VAC= 4.24A.

The improved circuit also works with a 30AC transformer and you can calculate its current rating needed.

The current limiting is variable from about 2mA to 3A and has excellent current regulation. If the output is shorted then the current will not cutoff, instead it will be at the current setting.

Many stores do not provide datasheets that are available online from the manufacturers. Wakefield is a heatsink manufacturer and has datasheets of all their heatsinks at their online site. 

 

[BobRob77]

So, anyone who is smarter than me: if what I have currently available is a 24V/3,33A transformer (2x12V) and I’d still like to build the supply using that (accepting less output), what would I need to change? 

 

[audioguru2]

You must change the values of the parts that try to produce volts and amps outputs higher than you will get. You can calculate the maximum regulated output voltage, maximum regulated current and maximum heat produced by the transformer then try adjusting the calibration pots to see if they will limit V, A and P low enough.

24VAC has a peak of 34VDC. Your 24V/3.33A transformer is overloaded with more than 80VA. The maximum output of the circuit will be about 25VDC at about 2.3A

 

[elctro123]

The original circuit has many overloaded parts and cannot produce 30VDC at 3A. It is also missing the calibration trimpots that are used in the improved version that can be set to exact maximums of 30.0V and 3.0A.

So Finally which version of schematic is correct  / flawless  to  build the PSU ? 

 

[audioguru2]

Since it was years ago I do not remember which page of which thread has version 6 or 7. I have the schematic and parts list of version 6 here:

 

[electron234]

Is it possible to charge 12V  18AH (Sealed Rechargeable UPS ) battery with this Charger ?

In past i have blown 0-30V / 0-3A LOADSTAR PSU while charging this battery.

Thanks Ahead

So Finally which version of schematic is correct  / flawless  to  build the PSU ? 

I have a 24V, 10A transformer. Will this do the job. 

Thanks audioguru