0-30V Stabilized Power Supply

[Holt]

I have not checked the circuit out but I hear what you say about RV1. What was it "supposed" to adjust ?

It was supposed to adjust 0 volt

Holt

 

[audioguru2]

If C7 (the output capacitor) is an electrolytic type then it has "dielectric absoption" where it stores a charge even if it is shorted. Then the output always has a voltage even if the voltage pot is turned down. It also messes up the setting of RV1 that should adjust the output offset voltage about plus and minus 50mV so that it is 0V when the voltage setting pot is turned down.

If C7 is changed to a film capacitor then the dielectric absorption problem will disappear.
A 10uF film capacitor is pretty big.

 

[Hero999]

Tantalum should be better than aluminium electrolytic.

If you want to go with film, choose polypropylene over Mylar.

 

[tesseract]

I built the original version about two years ago ( with the Voltmeter + Ammeter LCD panel ) and it works wery good, but now i need some more power and i decided to built the new version with the 5 A output ( it is possible to become 7A with more powertransistors ? I have a 30V~ / 10 A trafo ). I used EAGLE ( i don't make publicity for EAGLE !! ) to make a single PCB layer with only 3 wire on top of PCB. The C1 ( 2x10.000

30V_5A_PSU_Eagle.zip

Pictures.zip

 

[GrahamG]

tesseract

Brilliant. I think you are the first person that I have seen on this forum who has actually built the unit and made the associated comments about various parts that need to be changed or put off the PCB.

Did you suffer from this 0V adjust problem with the original cct or is it just the newer version that does this ?

Nice to see also that someone has published the EAGLE CAD files. A great help.

 

[tesseract]

tesseract

Did you suffer from this 0V adjust problem with the original cct or is it just the newer version that does this ?

oh...the 0V problem...i have not noticed it because i don't use lower voltage than 3 volt. If i go home i check this with the old version, the new one is not finished yet.

 

[Holt]

The PSU are not ready because i have problems to become the TLE2141 in Germany.

You can get them here: http://de.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6612000 or you can order samples from TEXAS INSTRUMENTS like i did, ordered them sunday and got them tuesday- pretty fast from USA to Denmark.
I dont know if it is possibel to buy from RS in Germany unless you are a registret compagny, it isent in Denmark, thats why i orderet the samples
If only you had postet the PCB design 2 weeks before, it was just what i was looking for, its looking really good

Holt

 

[Holt]

I improve a bit the bottom of PCB with a picture editor. If someone find some errors please tell me

you could easily get rid of one of the wires if you rotate D9 90 deg, and move a couple of tracs a bit

Holt

a bit like this, but i couldent rotate D930V_PSU_rev.zip

 

[tesseract]

I dont know if it is possibel to buy from RS in Germany unless you are a registret compagny.

Yes you have right, that is my problem, RS sell only to a company. But i found someone and he ordered it for me. I must wait only a few days and i have the parts.
You have right it is possible to rotate D9 and eliminate the wire, but it does not change much....

@GrahamG
i check the old version of PSU and and it is possible to adjust the voltage up to 0.0 volt.

 

[audioguru2]

@GrahamG
i check the old version of PSU and and it is possible to adjust the voltage up to 0.0 volt.

The original version uses a TL081 opamp as U2 and has the value of R10 completely wrong and it is connected to the wrong voltage.

 

[tesseract]

@audioguru,
I'll give you absolutely right, it may be the original PSU has errors, but i built it for about 2 years ?? ( with TL081, 1x2N3055 and i have used the shown PCB ) and it's work fine !

 

[audioguru2]

@audioguru,
I'll give you absolutely right, it may be the original PSU has errors, but i built it for about 2 years ?? ( with TL081, 1x2N3055 and i have used the shown PCB ) and it's work fine !

In addition to the errors of the offset adjustment, the opamps are operating at supply voltages above their absolute maximum allowed voltage, the transformer and many resistors are overloaded at full output, the tiny Q2 transistor and single 2N3055 transistor are very much overloaded when the current is 3A and the output voltage is set low or is shorted.
The voltage from the transformer is too low for an output of 30V at 3A and the value of the main filter capacitor C1 is much too low which causes ripple in the output at high current and high voltage. 

 

[mendimano1]

i want to say  thanks to tesseract for this god work, now im thinking to build this modified version.

 

[Barney1]

I have built a 5A version of this power supply. It seems it's working in some way but there is one 'load' problem. When I connect the 12V/60W lamp to PS and set both potentiometers to max. values I get around 11V at the output. This is somewhat strange so I think in theory this PS should burn out that kind of lamp. The problem is why is the voltage drop that big.

There is also another strange thing. I was measuring voltage levels in the circuit. Most values seem ok, except some values around  U2. When both potentiometers are set to min. there is few milivolts on the pin 2 and 3 but at the output pin (6) there is 10V. I don't know from where this voltage come from if the input pins are almost at zero value. In the other hand, when I set potentiometers to the max. the I measure around 3.5V at the pin 2 and 11.2V at the pin 3. At max. settings with no load connected I get 39V at pin 6.

I am using 30V/7A toroidal transformer and 3x2N3055 as output transistors.

 

[audioguru2]

I have built a 5A version of this power supply. It seems it's working in some way but there is one 'load' problem. When I connect the 12V/60W lamp to PS and set both potentiometers to max. values I get around 11V at the output.

60W/12V= 5A. So the current regulator reduces the output voltage so that the current is 5.0A. The warning LED should turn on to warn you that the current regulator is reducing the voltage.

There is also another strange thing. I was measuring voltage levels in the circuit. Most values seem ok, except some values around  U2. When both potentiometers are set to min. there is few milivolts on the pin 2 and 3 but at the output pin (6) there is 10V. I don't know from where this voltage come from if the input pins are almost at zero value.

Maybe opamp U2 is damaged from having its supply voltage too high for it.

In the other hand, when I set potentiometers to the max then I measure around 3.5V at the pin 2 and 11.2V at the pin 3.

The opamp is clipping with its output voltage as high as it can go. It is not regulating. Something is dragging down the output voltage so that the negative feedback to pin 2 has a voltage too low. U2 and the output transistors are supposed to have a voltage gain of 3.074 times and the output voltage will try to be 34.4V. The output of U2 will try to be 37V or more. Maybe the pins on the transistors are connected backwards.

 

[Barney1]

Thank you for reply.

LED doesn't light at this current but it is working with lower currents just fine. It is true that the lamp is using 5A but I still think there is some power left even if transformer is overloaded. I think this is the reason why LED doesn't light.

However I changed the OPAMPs a few times (i have spare ones) but the problem is still there. Pins on transistors are connected the right direction.

I'll keep searching for problem...

 

[DenFed]

Today finished assembling an updated power supply to the TLE2141.
I have the problem that HOLT.
In the zero position P1, I have the voltage at the output exactly 60 milivolt.
Situation RV1 result is not affected (not regulated).
Help please!!

 

[audioguru2]

Today finished assembling an updated power supply to the TLE2141.
I have the problem that HOLT.
In the zero position P1, I have the voltage at the output exactly 60 milivolt.
Situation RV1 result is not affected (not regulated).
Help please!!

Make sure that the output of P1 goes down to 0V.
The max offset voltage of the TLE2141 is only 1.4mV for the inexpensive one and the circuit amplifies it 3 times to only 4.2mV.
RV1 adjusts the output from negative 30mV to positive 30mV so the null should be 0.00V.
Like I said earlier, if the output capacitor C7 is an electrolytic type then it has "dielectric absorption" where it holds a charge even if it is shorted for a while. Use a film capacitor instead and add a resistor across the output to discharge it.

 

[tesseract]

Like I said earlier, if the output capacitor C7 is an electrolytic type then it has "dielectric absorption" where it holds a charge even if it is shorted for a while. Use a film capacitor instead and add a resistor across the output to discharge it.

is this capacitor Ok ?
http://www.reichelt.de/?;ACTION=3;LA=2;GROUP=B326;GROUPID=3155;ARTICLE=12380;START=0;SORT=artnr;OFFSET=100;SID=28HyyhlKwQARwAAAxcL@0017dd4cf916edddf0991c5990ba93c2d

 

[audioguru2]

is this capacitor Ok ? .....

10uf/20%/100V is fine but a 50V or 63V capacitor will also be fine, will be smaller and cost less.