0-30V Stabilized Power Supply

[VittoYi]

Hi guys,
I was just wondering if a transformer with 4.17A would make a big difference instead of the one which is suggested in the scheme (4.3A).
The transformer I've got can supply 30V while the scheme says 28V are enough. The power supplied is pretty much the same. So is a 4.17A - 30V transformer suitable?
Thanks to everyone.

 

[audioguru2]

Your 30V transformer supplies a voltage of 30V and its rated current is 4.17A. Then its maximum allowed power output is 30V x 4.17A= 125.1VA. 
The power supply constantly charges its main filter capacitor to the peak voltage 30V x 1.414= 42.4V. The rated output of the power supply is 3.0A plus maybe 0.1A for its circuitry so it uses a maximum power of 42.4V x 3.1A= 131.4VA.

Then your transformer will be a little overloaded but probably not enough to smoke or to catch on fire.

 

[junee_bal]

Hai...

        I would like to design the same for a 0-30V / 5A power supply with the changes below.

        30V/5A transformer.
        2N3055 transistor 2nos parallel with Q4 and Q5 with same design.
        RV3 with 500K trimpot.

        Is it enough to make a 5A 30V power supply or please suggest a necessary changes.

 

[audioguru2]

A 30A/5A transformer is overloaded when the output of this power supply is 5A because the rectifiers charge the main filter capacitor to almost the peak voltage of 42.4V. The circuit draws about 0.1A. Then the power from the transformer is 42.4V x 5.1A= 216VA. A 30VAC/7.2A transformer is needed to provide 216VA.

We use two 2N3055 power transistors for a 3A output and they get pretty hot when the output voltage is low. THREE of them are needed for an output of 5A.
Here is a fairly old parts list for a 5A power supply:

View attachment 42121

 

[junee_bal]

I have doubt on transformer that the current ratting mentioned in my transformer is correct.
So I need to reconfirm it by testing.
I want to know the correct testing procedure of transformer.
For example explain with a 30V/2A.

Please help me to find out.

 

[audioguru2]

I have one small very cheap Chinese AC/DC adapter that has no safety certification markings and is rated at 9VDC/100mA. It produces a little more than 18VDC with no load and gets hot. With a load of 100mA its output is 8V with a lot of AC ripple and it is dangerously hot so I do not use it.

An overloaded transformer gets hot. A transformer with safe ratings gets pretty warm but not hot. Simply find a safe name-brand transformer with the ratings you need and compare its size with the unknown transformer. If the unknown transformer is smaller then it might be overloaded at its rating.

A 2A load on a 30VAC transformer is resistance that is 30V/2A= 15 ohms at 30V x 2A= 60W. If you find this resistor then load it on the transformer and feel if the transformer gets hot. 

 

[junee_bal]

Shall I use TL081 instead of TLE2141 or MC34071

What are the changes need.

 

[audioguru2]

Shall I use TL081 instead of TLE2141 or MC34071

What are the changes need.

The original circuit used TL081 opamps. Its maximum supply voltage is only 36V and it needs a negative supply so it cannot produce +30V without risking damaging it with a supply voltage too high for it. It also has a problem called Opamp Phase Inversion that causes its output to go high when its negative supply voltage drops too low when the power is turned off. So transistor Q1 was added to short its output to ground when the power was turned off.

The MC34071 is not available anymore in a DIP package. It and the TLE2141 have a maximum supply of 44V and they do not need a negative supply so they work fine producing an output of +30V.

If you use TL081 opamps then they need a -5.6V negative supply as shown in the original circuit. But the positive supply in the original circuit was too high for them since it used a 24V AC transformer and without a load the positive supply was about +34V or more, then the opamps are powered with a total of 40V or more. If the transformer is 20V then without a load the positive supply will be about +28 but then the maximum output from the project will be only about +20V if you are lucky. 

 

[deepak.roy.alchemist]

hello audioguru! i am a newbie in electronics. i want to know that why the opamps like CA3140, CA3240 etc do not work at all in this circuit though they are capable of operating with single supply. i know they have a max operating voltage of only 36 volts but still if i require a low o/p voltage from the supply, the circuit does'nt work at all with these opamps.

 

[audioguru2]

hello audioguru! i am a newbie in electronics. i want to know that why the opamps like CA3140, CA3240 etc do not work at all in this circuit though they are capable of operating with single supply. i know they have a max operating voltage of only 36 volts but still if i require a low o/p voltage from the supply, the circuit does'nt work at all with these opamps.

The circuit might work with CA3140 opamps if the supply voltage is reduced by using a custom made 22V AC transformer but then the maximum output will be only about +22.5V DC at 3A if you are lucky. You might need to re-calculate a lower value many of its resistors so that the currents in the circuit are adequate. 

 

[OO7O]

Hi everyone.

I Draw this circuit with PROTEUS-ISIS but cant simulate because a error, can someone help me to find the problem pls.

Final.zip

 

[audioguru2]

I Draw this circuit with PROTEUS-ISIS but cant simulate because a error, can someone help me to find the problem pls.

Very few people use your Proteus program. For us to see if there is something wrong with your schematic then please post it as a normal PNG file type that everybody can see.

Maybe you can "copy screen" then paste the schematic into a picture viewer like Paint program then save it as a PNG file type.

 

[OO7O]

Hi again

There is the circuit in ".png" Format.

 

[audioguru2]

Your schematic looks fine. I do not know what error Proteus is giving but maybe it knows nothing about the opamps.

 

[mvs sarma]

Hi again There is the circuit in ".png" Format.

hi James Bond O ,
you may have to indicate the  error image and  to members.
Otherwise, getting some error message doesn't appear a good way of reporting.
you can capture the screen and  upload as  .png.
it helps  proteous gurus to study and comment.

 

[thiagoas]

Would NE5532 work in this circuit? I have no LME2141 in my country.

I also simulate the circuit in proteus, and it works, just have to change SPICE options for better convergence.

 

[audioguru2]

Would NE5532 work in this circuit? I have no LME2141 in my country.

The LME2141 is not available anywhere because nobody makes it. You have the wrong letters.

The TLE2141 is made by the world's largest semiconductor manufacturer, Texas Instruments, and should be available everywhere.
It was selected because its maximum supply is 44V, its inputs work at 0V without a negative supply and its output goes down to almost 0V.

The NE5532 also has a maximum 44V supply but its inputs do not work below 3V and its output does not go below 2V so the circuit and spec's for the project must be changed for it to be used. 

 

[thiagoas]

Ops, sorry, I was thinking in another piece at the time. 

Not even farnell have this one in DIP socket here.

I will have to find something similar to this.


Edit.
I requested samples from TI, let's see what I get.

 

[redwire]

Ops, sorry, I was thinking in another piece at the time. 

Not even farnell have this one in DIP socket here.

I will have to find something similar to this.

Then build it with the SOIC 8 package.  You will have a choice between  the TLE2141 or the MC34071.

 

[rvendrame]

Hello all,

That's a very nice initiative + community + development here in this post.  Congratulations to all of you!!!

I will start to build my PS soon, and I have a quick question.  In case I make two of them, as liquibyte did  ---  Does the short-circuit protection will still working across the + 0 - outputs?  Or will it blow up in case of short-circuit between the + and - output, or even between the +/- and the zero?

Thanks
Ricardo