0-30V Stabilized Power Supply

[PicMaster]

Here it is:

Looking at your PCB the output tracks are still not big enough to take the current for 5A and yes the pads need upgrading.

Here is the modified version this will either do the 3A or 5A version, For the 3A just leave out Q3A & R20A
For the 5A change R7 must be 0.27 ohms/10W (TB4 or the 2 holes either side), I have not updated the BOM yet but should be easy to workoutEL3-_5A_PSU.pdf

 

[fikic]

Nice PCB you have there. But mine is made just for 3A version, so I think the thickness of output tracks is good. Here is final version:

pcb.pdf

 

[audioguru2]

Hi Fikic,
On your pcb layout you have a few tracks too close together. Many traces under the ICs do not carry much current so they do not need to be as wide as you made them.

View attachment 41293

 

[morpheous87]

How much VAa should be the transformer for 2x5A power supplies?

 

[audioguru2]

How much VAa should be the transformer for 2x5A power supplies?

The peak voltage from the transformer is 39.6V from a 28V transformer and is 42.4V for a 30V transformer.
So 39.6V x 10A= 396VA and 42.4V x 10A= 424VA.

The windings must be completely separate if you are making a +/- power supply or if you are adding them to get up to 60VDC.
You cannot connect these power supplies in parallel.

 

[bg8dmy]

Hello, audioguru ,
I have one question
I have a two-winding transformer, rectifier whether the Department can use full-wave rectifier?
My English is poor, thanks for your answer ~

 

[audioguru2]

Hello, audioguru ,
I have one question
I have a two-winding transformer, rectifier whether the Department can use full-wave rectifier?
My English is poor, thanks for your answer ~

I do not know what you are asking.
Many transformers have 4 windings so they can be used with 115VAC or 230VAC and can be 15V at high current or 30V at lower current.

 

[Hero999]

A transformer either an inductor or an autotransformer.

You need a transformer with at least two windings (primary and secondary) for this project. Never use an autotransformer because it doesn't provide isolation form the mains.

 

[bg8dmy]

I do not know what you are asking.
Many transformers have 4 windings so they can be used with 115VAC or 230VAC and can be 15V at high current or 30V at lower current.

I did not express clearly
I have a two-winding transformer secondary, double winding with center tap voltage 2X25V, I can use full-wave rectifier rectifier? Means that this part of the rectification circuit using only two rectifier diodes, rather than the full-bridge rectifier
In addition, the circuit is able to use CA3140 LM741  operational amplifier?View attachment 41301

 

[audioguru2]

I have a two-winding transformer secondary, double winding with center tap voltage 2X25V, I can use full-wave rectifier rectifier? Means that this part of the rectification circuit using only two rectifier diodes, rather than the full-bridge rectifier
In addition, the circuit is able to use CA3140 LM741  operational amplifier?

You are trying to make the original circuit that does not work properly and has many overloaded parts.
We fixed it and changed it and the new schematic and new parts list have been posted here many times.

Your 25VAC transformer produces a positive unregulated voltage of only 34VDC which is too low. Your supply will produce a maximum regulated output of pnly 26VDC at 3A, not 30VDC.
The new parts list has a 28VAC or 30VAC transformer and new 44V opamps. The new opamps work with no negative supply and a low voltage negative supply.

Your idea has a positive 34VDC supply and a negative 5.6V supply which is a total of 39.6VDC when there is a full 3A load and a total of maybe 43VDC when there is no load.
But the original TL081 opamps and the ones you are talking about have an absolute maximum allowed total supply of only 36VDC.

The new circuit has a positive supply that is +37.6V to +42.4V. It has a negative -1.3V supply for one opamp. Then its maximum total is less than the 44V max of the new TLE2141 or MC34071 opamps.
The old opamp and the opamps you are talking about do not work without a negative supply or a negative supply as low as -1.3V.

 

[fikic]

I built it (3A version) and I have a few issues:
- current limiting LED is always on (if I turn current pot to max value it even lights more)
- I just can adjust minimum voltage to 50mV with voltage trimmer
- what can I adjust with other two trimmers?

However, PSU woks fine, the maximum output voltage with no load is 40V.

 

[audioguru2]

I built it (3A version)

Which version? Which opamps?

I have a few issues:
1) current limiting LED is always on (if I turn current pot to max value it even lights more)

Opamp U3 us used as a comparator with a voltage gain of about 200,000. Its output switches on and off, not as a linerar fader. It turns Q3 off when the output current is less than the setting of the current-setting pot.

I just can adjust minimum voltage to 50mV with voltage trimmer

If there is a load then the voltage setting pot should adjust the voltage to 0.0V. The offset adjust trimpot sets the offset so the output can go to 0.0V when there is a load.
C7 is an electrolytic type that produces "dielectric absorption" which produces an output voltage when there is no load. A film type of capacitor for C7 fixes it.

what can I adjust with other two trimmers?

I told about the offset adjust trimpot. There is a voltage trimpot that sets 30.0V when the voltage pot is at max and there is a current trimpot that sets 3.0A when the current setting pot is max and there is enough load.

However, PSU works fine, the maximum output voltage with no load is 40V.

You should adjust the voltage trimpot so that the max output voltage is 30.0V so that the circuit regulates properly without ripple when it has a load.

 

[fikic]

Which version? Which opamps?

The newest version with mc34071 opamps.

Opamp U3 us used as a comparator with a voltage gain of about 200' date='000. Its output switches on and off, not as a linerar fader. It turns Q3 off when the output current is less than the setting of the current-setting pot.[/quote']
I don't understand this part.. ???


With RV2, I can set the maximum output voltage. If current pot is set to maximum, I can regulate it to minimum 30V. But If I turn current pot to minimum, I can regulate it to minimum 40V. Something is wrong here...

 

[audioguru2]

I don't understand this part.. ???

Opamp U3 is a comparator. It compares the voltage at its inputs and its output is either high at about +24V or low at about -0.6V.
When its output is low then it reduces the output voltage through D9 until the current is the same as the setting on the current-setting pot P2. It also turns on Q3 which lights the LED.
When its output is high then it does nothing.

Its (-) input measures the voltage across R7 produced by load current on the circuit. Its (+) input voltage is set by the current-setting pot. When the (-) input voltage exceeds the (+) input voltage then the output of U3 goes low.

With RV2, I can set the maximum output voltage.

But RV2 on my latest schematic adjusts the output offset voltage a little. P1 adjusts the voltage and P2 adjusts the current.
Whose schematic did you use?

 

[fikic]

You've disunderstood me. I am also adjusting voltage with P1 and current with P2, but with RV2 I can set the maximum output voltage.

I used schematic that you posted it one page back.
PS.: I still don't know, why LED is always on. What is the reason, what can I do?

 

[fikic]

I've noticed something new:
If I have pot for voltage adjustment set to maximum value and I am changing current limit pot value from minimum to maximum, something strange happens. At it's minimum, output voltage is 40.5V. Then I am slowly raising it. The output voltage stays 40.5V for about 1/4 of a circle, then it starts to fall to 30V, and then again raising to 35V, and than finally falls to 24V at maximum value of pot for current adjustment. I don't understand. Is my pot broken?

PS.: And I am using 24V/250VA transformer.

 

[audioguru2]

Maybe c8 is shorted.

 

[PicMaster]

I've noticed something new:
If I have pot for voltage adjustment set to maximum value and I am changing current limit pot value from minimum to maximum, something strange happens. At it's minimum, output voltage is 40.5V. Then I am slowly raising it. The output voltage stays 40.5V for about 1/4 of a circle, then it starts to fall to 30V, and then again raising to 35V, and than finally falls to 24V at maximum value of pot for current adjustment. I don't understand. Is my pot broken?

So you have used Audio's schematic ?, Did you redraw the schematic and then transfered the design over to the PCB package then once you laid it out you ran the DRC rule checker ?
or Who's PCB layout you used ?,
The only reason I ask is if you have just laid out the PCB yourself just from the schematic then you could have errors in your PCB.
When I did mine I redrew the schematic check it and double check it against the orginal then transfered the design internally to the PCB package, Then Laid out then design then ran the DRC rule checker this tells me that it is 100% routed and error free.  Mine worked first time has it should whenI built mine.

 

[fikic]

I think, there is no problem with this schematic and PCB..
@audioguru, C8 isn't shorted..

sch.pdf

pcb.pdf

 

[gogo2520]

boy I swear
        This thread is starting to read like a Linux man page with all the misinformation floating  around, can some please post the right schematic and parts list for the 3amp supply.  I think audio's is the right one but with all the European influence its hard telling ( just like Linux ).  Not the 5amp just the 3amp.  **I thought a 5amp thread was started years ago.**

gogo