0-30V Stabilized Power Supply

[du.facc]

What about the multimeter? is there a link with a PIC or maybe a link from Redwire? Redwire is pretty good, it gives us tons of information.

 

[audioguru2]

What about the multimeter?

Why are you asking about a multimeter?

 

[du.facc]

I was wondering because I saw one of the multimeter in the documents that caught the tompa, but already got some information ...

could you tell me please how the VA is essential for the PSU work well? According to his part list, a transformer of 28V / 4.3A, I provide 120.6 VA correct? I read about 45 pages of the topic and saw that will warm the 120VA transformer .. I'm from Brazil and here there is no standard transformer of 28V, if I know the VA will be able to make a relationship volt / amp and find the ideal transformer am I correct?

 

[audioguru2]

I was wondering because I saw one of the multimeter in the documents that caught the tompa, but already got some information ...

Please translate "caught the tompa" into English.

 

[red_81]

First, Sorry for not introducing mysef, I registrated on forum just to say that this is probably one of the best circuits that I have built (Picmaters pcb, 5A version). Everything just works.
I almoast started to build 1st version...but fortunatly I didnt.
This 3rd rev. is great one. Big TNX to all here!!!

Greetengs from Croatia

 

[acristea]

Hi everybody. I'm a newbie. I've spent some time reading this topic, and for me was very helpful to understand the functioning of this power supply. It’s true that I didn't finished yet the entire topic, but I will do this in the next period. With your permission I will ask you a few questions about this project.

First of all, obvious I have started this project from the original faulty diagram, buying a kit of this PS, but without transformer. Now, I'm trying to finalize a good upgraded diagram for the 3A version. The questions are:

1. What do you think about using a MJE3055 instead of 2N3055. I intend to use two of them mounted on a PC processor heatsink with fan?

2. I know that in the latest version of this PS, U3 is powered through a 10V zener. Why we don't use the same method for powering the U2? Assuming a 30V transformer @ no load, we will have around 41V between pin 4 and 7, that is close to the 44V limit of opamp.

3. It is correct if I calculate the voltage drop, from transformer to the output, like this: 2V on the transformer, 2V on the rectifier bridge, 1.4V on R7, 2V on Q4/Q5 transistors? All losses are assumed for a 3A load.

4. Do you think it is possible to have a voltage ripple below 10mV using a 10000microF and a 28V @ 5,35A transformer.

Thank you

MJE3055T_ST.pdf

2N3055_ST.pdf

 

[audioguru2]

1. What do you think about using a MJE3055 instead of 2N3055. I intend to use two of them mounted on a PC processor heatsink with fan?

Two little MJE3055's are not good enough for this project. Maybe if you use four of them.

2. I know that in the latest version of this PS, U3 is powered through a 10V zener. Why we don't use the same method for powering the U2? Assuming a 30V transformer @ no load, we will have around 41V between pin 4 and 7, that is close to the 44V limit of opamp.

The output voltage of U3 goes only as high as about +14V so its collector voltage can be reduced by the zener diode.
But the output of U2 must go much higher than the maximum output voltage of +30V.

3. It is correct if I calculate the voltage drop, from transformer to the output, like this: 2V on the transformer, 2V on the rectifier bridge, 1.4V on R7, 2V on Q4/Q5 transistors? All losses are assumed for a 3A load.

U2 and the driver transistor also cause a voltage drop. The main filter capacitor also causes a voltage drop.

4. Do you think it is possible to have a voltage ripple below 10mV using a 10000microF and a 28V @ 5,35A transformer.

The ripple voltage that is about  3V p-p.

 

[du.facc]

What I meant was that I saw a multimeter in Tompa´s archives which was able for download, but It was in a folder called Redwire, I´ve already sent a MP to it and I got some information.
Once I´m posting again, one more question came up to me about my last request.
I read about those VA and found out that the energy wire is different for South America, USA and Europe, knowing this, how could I choose my transformer ?Could it be by the VA output? if so how many VA should i choose for a good performance? ( PS: in Brazil it is 110/220v 60Hz)

 

[audioguru2]

I am in Canada where nearly all electric things use 120V/60Hz but high power electric things like the electric stove, air conditioner and electric clothes dryer use 240V.
So I use 120V transformers.
In Brasil you probably use 110V transformers.
VA is how much power passes through the transformer.

If the power supply has a maximum output current of 3A then a 30V transformer must have a VA rating of 127VA.
If the power supply has a maximum output current of 5A then a 30V transformer must have a VA rating of 212VA.

 

[du.facc]

so, back to VA, i´d like to know how many VA is the best for the transformer, or maybe you´d tell me how many you used. Thank´s again

 

[Samu_s]

Just a quick question:

Is it possible to use larger transformer like: 2x38 VAC 272,5 VA.

Probably by lowering voltage to 30 V after diodes? Just asking becouse i might get one cheap.

 

[audioguru2]

A 38VAC transformer without a load might be 39.5VAC. When rectified and filtered the raw DC is 54.4VDC.
But the U2 opamp has an absolute max allowed supply of 44V so you have a lot of power to throw away.

 

[halcon671]

I can use a laptop charger instead of a transformer in this design, or any other design? Only for space in the housing that will use.

Thank you.

PS: excuse my bad English, I'm spanish.

 

[audioguru2]

A laptop charger has only 19V.
This project uses 40V.

 

[halcon671]

I know. I do not really need more than 20 volts, so I think a 24 volt charger fits my needs, could use this design with the charger I mentioned earlier?

 

[audioguru2]

I know. I do not really need more than 20 volts, so I think a 24 volt charger fits my needs, could use this design with the charger I mentioned earlier?

The resistors and voltage drops all must be re-calculated to use a much lower supply voltage.

 

[xristost]

I know. I do not really need more than 20 volts, so I think a 24 volt charger fits my needs, could use this design with the charger I mentioned earlier?

Part of the circuit will not work, because it use AC voltage to make negative supply voltage for U3. But charger will provide only DC voltage.

 

[audioguru2]

Part of the circuit will not work, because it use AC voltage to make negative supply voltage for U3. But charger will provide only DC voltage.

That is only one of hundreds of parts where the voltage is too low. What about the other hundreds of parts where the voltage is too low?

 

[du.facc]

Can I add two potentiometers to the "fine tuning"? From what I know, just add the potentiometer in series with the potentiometer in the circuit that already exists, but do not know if this circuit is possible to contain the RV2 and RV3. If possible, which would then potentiometers?

 

[audioguru2]

A coarse pot and a fine pot would be a nuisance. The fine would almost always be in the wrong position.
Use a bigger knob instead on one pot.