0-30V Stabilized Power Supply

[audioguru2]

"- Ripple maximum: 0.5mV RMS"

The ripple is what I'm interested in

With an output current of 5A and even if the main filter capacitor is huge the positive unregulated supply will have plenty of ripple that might be coupled to the 11.2V reference voltage or to the output amplifier.
Careful wiring layout will avoid coupling and the addition of a constant current source to power the voltage reference will reduce the ripple to almost nothing.

 

[singonn2]

thx guru

 

[audioguru2]

guru did u get my msg ? the pm msg

One minute ago I answered your PM.
Tell us the voltage measurement of C1, the output voltage of U1 and the -5.6V voltage and we will fix your power supply circuit. Does the LED light up?

 

[singonn2]

i using 24VAC with 3A isn't can replace TL081with741? , the led is no light up , isn't the leb light up while DC output short circuit ? the C1 voltage is 33VDC the output of U1 is 11VDC and the -5.6V voltage there is -5.6VDC also it's correct?the point i check the voltage of -5.6V is between R3 , D7,U3/U2 -V there.

U1/2/3 and +V there is 33VDC mean after bridge rectifier is 33VDC and the R1 and R2 (1W) resistor will start heat up quickly but Q4Q1 seen not working cos did't heat


what problem is it

 

[audioguru2]

i using 24VAC with 3A isn't can replace TL081with741?

The original project used a 24v/3A transformer. Without a load on the project the transformer will probably be 25v and have a peak voltage of 35.4V then the rectifier bridge will reduce it to 34v which will be the positive unregulated supply. since opamps U2 and u3 also use the negative -5.6V supply then their total supply voltage is 39.6V which is higher than their 36V max allowed supply voltage. they might fail.

the led is no light up , isn't the leb light up while DC output short circuit ?

It is good that the LED does not light. It lights to indicate that the current regulator is reducing the output voltage.

the C1 voltage is 33VDC

Good.

the output of U1 is 11VDC

It is a little low. If R4 is changed to 1k and zener diode D8 is changed to a 5mA BZX79V5V6 part number then the voltage will be a little higher and the reference voltage will be regulated better.

the -5.6V voltage there is -5.6VDC

Good.

U1/2/3 and +V there is 33VDC

Good.

R1 and R2 (1W) resistor will start heat up quickly

They heat too much because they are too small. Use 2W resistors.

but Q4Q1 seen not working cos did't heat

Q4 gets hot only when the load current is high and the voltage at the output is low.
q1 is normally turned off. it turns on for a moment only when the power to the project is turned off so it shorts the output of U2 to ground to keep the output voltage from rising when the negative -5.6V supply disappears quickly but the positive supply is still discharging C1 slowly.

Measure and report the voltage at the input pin 3 of U2 and its output pin 6 when the voltage setting pot is turned up then is turned down.
Double-check the pins on Q1, Q2 and Q4.

 

[singonn2]

thx guru the fringe problem is fix reason was a ic741 was burned , from original circuit U3 output voltage is about 30VDC and U2 output voltage along with the supply voltage change isn't correct?

the ripple can check with electric meter ? if the digital electric meter show the voltage is fix at 0.01xVDC mean low ripple ?

this circuit have auto protect function ? mean when the output voltage is short circuit will have a signal ?what the function of D12 LED ? when it will light up ?

when i supply to 20VDC + 2A  the Q4 2N3055 is heat up too much can i use 2x 2N3055 like the new circuit for relief it heat up ? and the R7 also heat up quickly should i change to it 10W resistor ?

 

[audioguru2]

thx guru the fringe problem is fix reason was a ic741 was burned

Do you mean that the problem where the output voltage was always -0.5V is fixed because a 741 opamp was burned?

from original circuit U3 output voltage is about 30VDC and U2 output voltage along with the supply voltage change isn't correct?

I don't know what you are asking. It is normal for the output voltage of U3 to be +30V when it is not regulating the current. The output voltage of U2 is about 1.5V higher than the project's output voltage.

the ripple can check with electric meter ? if the digital electric meter show the voltage is fix at 0.01xVDC mean low ripple ?

Ripple is not DC, it is AC at double the mains frequency. If the value of C1 is only 3300uF like in the original project then the ripple voltage on C1 is about 6V p-p (2.1V RMS) when the output current is 3A.
then the output of the project will also have ripple if its output voltage is more than about 22V at 3A.

this circuit have auto protect function ? mean when the output voltage is short circuit will have a signal ?what the function of D12 LED ? when it will light up ?

I explained the current regulation in my last post.
The max amount of output current is set by the current adjust pot. The current regulator reduces the output voltage so that the current is not more than the setting of the pot. When the current regulator is reducing the output voltage then it lights the warning LED.

when i supply to 20VDC + 2A  the Q4 2N3055 is heat up too much can i use 2x 2N3055 like the new circuit for relief it heat up ? and the R7 also heat up quickly should i change to it 10W resistor ?

Your 2N3055 transistor has 33V on its collector and its emitter is 20V. Then it has 13V across it.
The amount of heat it is dissipating is 13V x 2A= 26W. It needs a heatsink big enough so that it does not get too hot when it dissipates 26W. A very big heatsink will allow it to dissipate about 70W but then it and the heatsink will be very hot.

The 0.47 ohm/5W resistor R7 has a current of 2A so it is dissipating 2A squared x 0.47 ohms= 1.88W.
A 5W resistor can easily dissipate only 1.88W. Space it up a little away from the pcb.

 

[singonn2]

ya,one of it,after i replace U2 with TL081 the voltage is like my notion as u say higher voltage than output voltage,isn't TL081 can replace with TL082 ?sry for my bad english.

the LED is always light up now


i see , i had put the Q4 on a heatsink + a fan on it , 26W wont reach 200*C is enough.
the cement resistor i use is heat up very much although not more than 5W.

thx for your guide guru.

 

[audioguru2]

ya,one of it,after i replace U2 with TL081 the voltage is like my notion as u say higher voltage than output voltage,isn't TL081 can replace with TL082?
The TL081 has one opamp but the TL082 has two opamps and its pins are completely different. Look on the datasheet.


Then the output current is higher than the setting of the current regulation pot or U3 is not working properly.


200 degrees C is the max allowed internal temperature of the 2N3055 power transistor. You cannot measure the temperature inside it.


A 5w resistor that dissipates only 1.88W is hot but it is fine.

 

[bugmenot1]

Hey RedWire, where is the zip file with all files of PS? I'll appreciate if you put the most recent files including the Eagle files too (.sch and .brd). The double side PCB is easy with the tonner transfer method. And thanks again for the support.
Audioguru, thanks to you too.
...
When I first saw this project the link for the forum doesn't work, so I make the PCB and search for the components for the original version.
Now I will make the RedWire most up to date project.
But my transformer (the only I have in the moment) is 24V 3A. I only need 0-15V in the output.
I ask you if I can use the Redwire Project to obtain 0-15V in the output without any problems?
Best Regard to all.
Here some pictures of a case of my project.

View attachment 40791

 

[karthikeid]

i have a problem with the current limit indicator it was glowing before but not now what  should i check?

 

[ali_kaffi]

Hello
I finish build this power supply, but output volatage is very low (0-2v). ???
please help me!!
Thanks

 

[nxt02]

I have made the older version of this power supply and i made the whole pcb the wrong direction by not mirroring it before printing. I do not want to make another pcb is there a way to make this? ???
Thanks

 

[audioguru2]

i have a problem with the current limit indicator it was glowing before but not now what  should i check?

The LED lights and current regulation happens when U3 detects the voltage across R7 caused by load current is more than the voltage set at the current regulation pot.
3A in 0.47 ohms causes a voltage of 1.41V. The slider of the current setting pot should go from almost 0V to +1.41V.

 

[audioguru2]

Hello
I finish build this power supply, but output volatage is very low (0-2v). ???
please help me!!
Thanks

The output voltage of U1 should be +11.2V.
The slider of the voltage setting pot should go from 0V to +11.2V.
U2 and the output transistors form an amplifier with a voltage gain of (56k/27k) + 1= 3.074 so the 11.2V input to U2 creates 34.4V at the output if the unregulated supply voltage is high enough.

Check the datasheets for the pins on the driver and output transistors.
Check that R11 is 27k and R12 is 56k.

 

[effenberg0x0]

Audioguru,
You obviously have a very detailed understanding of the circuit and expected behaviors. Do you use Spice or other software for these analysis?

 

[audioguru2]

Audioguru,
You obviously have a very detailed understanding of the circuit and expected behaviors. Do you use Spice or other software for these analysis?

This power supply circuit is very simple. I fixed it so that it meets its spec's and is reliable.

I use LTspice IV software for analysing audio amplifiers but have never used it on this power supply.
I never built this power supply.

 

[Biggy Boy]

Hello everyone!
I built this power supply two days ago from the original site, and found this link today.
I have just spent about two hours reading every post in this thread.

LOL too funny!
Seriously that web page should be corrected or pulled down.
Anyway very entertaining.

@Audioguru Do you not get tired of answering the same questions over and over again in the same thread?
I don't understand why people don't just read the thread instead of asking questions that have been answered multiple times.

Glen  

 

[audioguru2]

@Audioguru Do you not get tired of answering the same questions over and over again in the same thread?
I don't understand why people don't just read the thread instead of asking questions that have been answered multiple times.

Glen  

we had a thread about fixing this power supply project that was about 155 pages long but it got deleted when this site crashed. The same questions over and over and over and ....

 

[singonn2]

i think need make a FAQ about this power supply project because it's a lot newbie doing it.

guru can i put a cooler on U1 output ? or other ways without using 2 power supply
for add the cooler.