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# 0-30V Stabilized Power Supply

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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?

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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.

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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.

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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.

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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.

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

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

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Load - car 60 watt lamp.

It draws 5A at 12V when hot and it draws maybe 50A when cold.
The moment that you connect it then it will try to draw 50A but the current-regulation will limit its current to only 3A by limiting or reducing the voltage.

If you turn the current-setting to maximum and the voltage to zero, connect the light bulb then slowly turn up the voltage it should work up to maybe 10V at 3A.

Your video shows that the warning LED lights when there is no load and the current-setting pot is turned down which is wrong. It is due to an input offset voltage of U3. Increase the value of R17 (it is now 33 ohms) to maybe 47 ohms or 68 ohms until the LED does not light when the current-setting pot is at minimum.
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But what about if you want to charge a batterry with thats say for example 12 Volts and 2.5 amps....when battery  draws 5 amps...and you want to limit the current for a beater charging...when the gurrent limiter is activated...you cant regulate the voltage to 12 volts....
It draws 5A at 12V when hot and it draws maybe 50A when cold.
The moment that you connect it then it will try to draw 50A but the current-regulation will limit its current to only 3A by limiting or reducing the voltage.

If you turn the current-setting to maximum and the voltage to zero, connect the light bulb then slowly turn up the voltage it should work up to maybe 10V at 3A.

Your video shows that the warning LED lights when there is no load and the current-setting pot is turned down which is wrong. It is due to an input offset voltage of U3. Increase the value of R17 (it is now 33 ohms) to maybe 47 ohms or 68 ohms until the LED does not light when the current-setting pot is at minimum.
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But what about if you want to charge a batterry with thats say for example 12 Volts and 2.5 amps....when battery   draws 5 amps...and you want to limit the current for a beater charging...when the gurrent limiter is activated...you cant regulate the voltage to 12 volts....

Set the voltage to 13.8V to 14.4V and set the current to 2.5A if you want. The current regulation will reduce the voltage to whatever the battery needs when it draws 2.5A. The voltage will slowly rise as the battery charges and the current will stay at 2.5a until the battery becomes near fully charged when the battery will reduce the current.
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Let me inform you that i have changed the value of R17 from 33 Ohm to 47 Ohm, and now  the warning LED of an current limiter does not light when there is no load, thank you Audioguru.

Your video shows that the warning LED lights when there is no load and the current-setting pot is turned down which is wrong. It is due to an input offset voltage of U3. Increase the value of R17 (it is now 33 ohms) to maybe 47 ohms or 68 ohms until the LED does not light when the current-setting pot is at minimum.

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I measured the voltage of the project with a 10k resistor since that resistor was in hand, and the min voltage was 1.1V and the max was 30V, without it, it the min was 6.4V and the max 30V;with the output shorted,the min was 0.0V, but the max was 0.3V. And the two 2n3055 transistors that I use are connected with the right pins

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I forgot to mention that I connected a light bulb from a car which had approx.  1ohm resistance, and the project was working normally(min voltage 0.0V, max voltage 30.0V and max load 3A), so I'm totally out of guesses what is wrong...

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Hello and Sorry for Bad English ..

i draw this circuit with Orcad 16.3 & multisim 11 But Output is 0v !! why ??

I Need It ...

Thanks

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i draw this circuit with Orcad 16.3 & multisim 11 But Output is 0v !! why ??

Many things will cause the output to always be 0V.
Post a PNG file of your schematic so I can see if something is wrong.
Maybe your SIM software does not know the details of the special opamps that are used in the fixed version.
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Many things will cause the output to always be 0V.
Post a PNG file of your schematic so I can see if something is wrong.
Maybe your SIM software does not know the details of the special opamps that are used in the fixed version.

I cant use Rv1 Pot because Orcad TL081 Not supported !
See this images :

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I cant use Rv1 Pot because Orcad TL081 Not supported !

You have sketched part of tthe original schematic but transistor Q3 is missing. It drives an LED that warns when the current regulator is reducing the output voltage. The current regulator does not do anything when there is no load so it is not reducing the output voltage.

The original project has many errors and is not reliable because many parts are overloaded.
We have fixed it a few times for about 6 years.

You should use the latest version of the schematic that has been posted in this thread many times (see page #55 of this thread on Jan 27/2011).
You should also use modern SIM software that supports modern opamps.
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Hi audioguru .

I Create this New circuit with Multisim 11 But Not Work !!

0-30-Power_Supply-Multisim-11.rar

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Hi audioguru .

I Create this New circuit with Multisim 11 But Not Work !!

I don't have Multisim so I can't see your schematic.
Post your schematic as a screen save PNG file type.
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Thanks PNG Attached

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Thanks PNG Attached

Your Multisim schematic is a nightmare of crossed wires going all over the place. You changed all the parts designation numbers so it is too time-consuming to see if anything is wrong.

If you SIM it in Multisim then it probably will not work.
But if you build it from the corrected schematic then it will work perfectly.

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Hello.

I also tried to simulate circuit in multisim 11 and couldn't make it work.
Could someone have a look at the circuit if its ok?

Has any one managed to simulete circuit using any simulation software and got it worked correctly??
If yes could you tell what software you used and could you upload simulation file please.

Many thanks!

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