0-30V Stabilized Power Supply

[rajabi]

The original project has many errors so it does not work properly and it is not reliable. therefore we fixed it in this thread and in another thread in the forum.

If the positive unregulated supply from your 24V transformer is 32VDC and the output to the load is 5V then the output transistors have 27V across them. If the load current is 1A then each of your two output transistors dissipates 13W so they will need a pretty big finned heatsink to get rid of that much heat.

The 24V transformer voltage is too high for the opamps in the original project. The 35V transformer is also too high for the opamps in our fixed circuit.

Thank you a lot for your answer
It is so difficult for me to find the final version of your project in this thread and in another thread in the forum because my English is too weak and it take so mach time therefor if it is possible give me the final version of circuit or link me in to it.
about the 35V transformer can I use some Zener diode for limit op amps IC to solve the problem and how can I do it

best regards
thanks again for your kind attention and corporation

 

[audioguru2]

It is so difficult for me to find the final version of your project in this thread

The latest schematic and parts list is on page 55 of this thread.

about the 35V transformer can I use some Zener diode for limit op amps IC to solve the problem and how can I do it

Then the output transistors must dissipate a maximum of 49W more heat than with a 28V transformer.
The driver transistor will also get too hot.

 

[redwire]

morpheous87 ,

Arduino ground is  TB4 pin 2

Connect the Arduino's ADC pin  to TB4 Pin 1 on your power supply.    Note that you are simply measuring the voltage drop across the 0.47 ohm resistor.  If you had a 3 amp load on the PS then your voltage drop across the resistor would be 0.47x3 = 1.41 V.    You should be able to measure this with your multimeter. 

 

[rajabi]

The latest schematic and parts list is on page 55 of this thread.


Then the output transistors must dissipate a maximum of 49W more heat than with a 28V transformer.
The driver transistor will also get too hot.

hello
thanks a lot for your answer as soon as possible but I can not found the op-amp IC you mention in your new circuit. Do you know any other IC's that I can put in the new circuit?

About the 35V Transformer except of 28V Transformer it is Important for me because I most pay money again for new transformer and it is a little bit difficult...

Best Regards

 

[audioguru2]

The two opamps selected for the modified and fixed project are made by two of the largest semiconductor manufacturers in the world.
The MC34071 is made by Motorola/ON Semi/ Freescale Semi and the TLE2141 is made by Texas Instruments. You can choose which of these opamps to use.

In North America and Europe they are available at hundreds of semiconductor distributors and in 30 to 50 countries at Farnell.

You don't say your country. Did you look to see if Farnell has an office/warehouse there?

Your 35V transformer is wrong for this project.

 

[sparky666]

Hi guys!
I have recently built the supply, but I have two major problems: Firstly I could set the upper limit of the voltage to 30 V, but the lower limit stays at 5.6V no mater what I do, and at this voltage the LED is on, and if I switch to the max current limit, then the voltage jumps from 5.6 to 12V. The second problem is that the voltage regulator pot is a 10k heli pot, and at the half way the voltage is at max, and furthermore I can't raise the upper limit.
The supply itself works great at higher voltages then 5.6V, so I can't figure out what is wrong.
Any help would be appreciated.

 

[audioguru2]

Hi guys!
I have recently built the supply, but I have two major problems

Which version did you make? The original one with TL081 opamps? The first modification with OPA445 opamps? The latest modification with MC34071 or TLE2141 opamps?

What is the voltage of the negative supply at pin 4 of U3?
Did you connect the voltage-setting pot correctly? What is a "heli" pot? Its input is the 11.2V reference made by U1 and its output goes from 0V to 11.2V. It feeds the output amplifier that has a gain of 2.68.
The output of the project should be 0V when the voltage setting pot is minimum and should be 30.0V when the pot is at maximum. When the pot is halfway is output should be 5.6V and the output of the project should be 15V.

The current regulation should not do anything until the output current exceeds the setting of the current-setting pot, then it should turn on the LED as a warning that it is reducing the output voltage to limit the output current. 

 

[sparky666]

Hi again!
The supply is the latest version with mc34071. The voltage at U3's pin4 is -1.5V. In my region, we call heli pot a potentiometer with multiple turns(12 turns for me).

 

[falkratz]

First of all sorry for my english... I'm from Brazil and here power supplyes are too expensive for my pocket

I found in page 55 the new schematic and I want to build one for me. I have here a 25-0-25 5A transformer, so I belive it can get a DC voltage of about 50V

I think it can't handle the 0-30V 5A modification (or can??), but is it OK to make de 3A version?? Do I need to make any modification to use my transformer to this application?

Thank's

 

[audioguru2]

Hi again!
The supply is the latest version with mc34071. The voltage at U3's pin4 is -1.5V. In my region, we call heli pot a potentiometer with multiple turns(12 turns for me).

With the voltage-setting pot at zero, the current setting pot at maximum and no load, measure the output voltage of each opamp and measure the output voltage of the project and report them here.

 

[audioguru2]

First of all sorry for my english... I'm from Brazil and here power supplyes are too expensive for my pocket

I found in page 55 the new schematic and I want to build one for me. I have here a 25-0-25 5A transformer, so I belive it can get a DC voltage of about 50V

I think it can't handle the 0-30V 5A modification (or can??), but is it OK to make de 3A version?? Do I need to make any modification to use my transformer to this application?

The voltage from your transformer is much too high and will blow up most parts. It is 50VAC which makes 68.7VDC. If you use it as a 25V transformer then its voltage is too low but it could allow the project to have a max output of about 26VDC at 3.5A.
The minimum transformer voltage for the latest version of this project is 28V and the maximum voltage is 30V.
The current from the transformer will be 4.2A when the project has a 3ADC load and the transformer's current will be 7.1A when the project's output is 5ADC.

 

[falkratz]

The voltage from your transformer is much too high and will blow up most parts. It is 50VAC which makes 68.7VDC. If you use it as a 25V transformer then its voltage is too low but it could allow the project to have a max output of about 26VDC at 3.5A.
The minimum transformer voltage for the latest version of this project is 28V and the maximum voltage is 30V.
The current from the transformer will be 4.2A when the project has a 3ADC load and the transformer's current will be 7.1A when the project's output is 5ADC.

I really don't need a 30V output, 26VDC is more than enough. So I can make 2 independent power supplies of 26VDC at 3.5A with my transformer??? There is a way to make it synchronous?

 

[audioguru2]

So I can make 2 independent power supplies of 26VDC at 3.5A with my transformer???

No you cannot make two independent supplies because the transformer does not has two completely separate secondary windings.
Connect the transformer to make one supply like this:

There is a way to make it synchronous?

It is not synchronous.View attachment 41457

 

[sparky666]

Audioguru! I made the measurements as you said. With the voltage pot set to 0, and the current pot at max, the output voltage of the project is 6.1-6.2V, the voltages at U1 : pin1,4,5 0V, pin2 1.9V, pin3 -0.5V, pin6 0.01V, pin7 36V. The voltages at U2:  pin1,2,3,4 0V, pin6 0.01V, pin7 36V. The voltages at U3: pin1 -1.4V, pin2,3 0V, pin4 -1.4V, pin5 -1.5V, pin6 -1.1V and at pin7 26.2V.

 

[audioguru2]

Audioguru! I made the measurements as you said. With the voltage pot set to 0, and the current pot at max, the output voltage of the project is 6.1-6.2V, the voltages at U1 : pin1,4,5 0V, pin2 1.9V, pin3 -0.5V, pin6 0.01V, pin7 36V. The voltages at U2:  pin1,2,3,4 0V, pin6 0.01V, pin7 36V. The voltages at U3: pin1 -1.4V, pin2,3 0V, pin4 -1.4V, pin5 -1.5V, pin6 -1.1V and at pin7 26.2V.

The output of U1 pin6 should be +11.2V all the time. Pin2 and pin3 of U1 should be +5.6V all the time.

Since the output of U2 pin6 is almost at 0V then the output voltage of the project should also be at 0V because the driver and output transistors are simply emitter-followers with no voltage gain. Maybe a transistor is connected backwards. Try connecting a 1k resistor from the output of the project to 0v to discharge the output capacitor C7.

Pin3 of U3 should be plus a couple of volts but its output voltage is correct.

 

[mrk86]

Hi! I apologize for my English. Assembled power supply 3A version. No-load, current is not regulated, only voltage. When I connect the load, lights LED, can regulate the current, but does not regulate voltage.

Please, help me! :-[ :'(

 

[audioguru2]

Hi! I apologize for my English. Assembled power supply 3A version. No-load, current is not regulated, only voltage. When I connect the load, lights LED, can regulate the current, but does not regulate voltage.

It cannot regulate the voltage when it is regulating the current.
It regulates the current by reducing the output voltage until the current is at the same low value as the setting of the current-regulation pot. For example when you short the output to 0V then the output voltage goes to 0V and the current is regulated to the setting of the current-regulation pot.
If you turn up the current-regulation pot so that the actual output current is less than the setting of the pot then the output will have voltage regulation.

 

[mrk86]

But why can not I regulate the voltage when connecting the load, current only.

 

[audioguru2]

But why can not I regulate the voltage when connecting the load, current only.

You need to turn up the current-setting pot so that the load current is less than its setting. Then the red warning light turns off and you can vary the voltage regulation voltage with the voltage-setting pot.
What is the resistance of your load?

 

[mrk86]

Load - car 60 watt lamp. If I understand the question