0-30V Stabilized Power Supply

[audioguru2]

Hi Ultima,
The input bias current of a TLE2141 opamp is 2uA max. Then its current in R21 (10k ohms) causes an input offset voltage of 20mV at U3.
R17 is only 33 ohms which produces a voltage of only 4mV so increase its value to up to 200 ohms to fix your problem.

 

[audioguru2]

Hi Audioguru,
I don't find the solution of my problem. I checked all the components again and the voltage still remain 54Vdc( measured at C1 pins). If I disconnect R2 the voltage found is normal, 39Vdc. What is wrong? Please help me.

I do not see how you can measure a voltage as high as +54VDC. View attachment 41351

 

[adyhansolo]

It's very strange for me. Maybe if you see this photos with the measurements you can give me the solution.

The second is with the circuit interrupt (rectifier bridge- R2).

 

[audioguru2]

Measure the voltage with a portable voltmeter (not connected to earth).

 

[adyhansolo]

Measure the voltage with a portable voltmeter (not connected to earth).

I measured the voltage with a portable digital multimeter (a good one). Any idea?

 

[audioguru2]

Your voltmeter does not measure correctly.

 

[adyhansolo]

Your voltmeter does not measure correctly.

I appreciate you waste your time with my problem.
I measured with two multimeters, including a new one, with the same result. Why the measurements it's correctly in the second circuit ( without negative voltage)?

 

[lighty]

Audioguru / Adyhansolo

I might be way off of here, but learning from my last problem (previous page)

I didn't have the header pins for the off board LED soldered in place when I testing, this cause the C7 (rated 50V) to pop within a few sesconds of powering up. I assume it is due to the one pin is acting as a "via" to gound some of the circuit, could this not be Adyhansolos' problem?

Just a guess :-\

Image attached.

View attachment 41352

 

[surubel]

How about if we replace the bd139 with tip112, and so we could drive 4 x 2N3055?

 

[audioguru2]

The BD139 is a very fast transistor which is why it was selected. The TIP112 is far too slow and will cause the output amplifier to oscillator or have very poor transient response.

Years ago I replaced the little 2N2219 with a TIP31 transistor and another member showed that its slow speed caused ringing and a poor transient response. the BD139 was tried and worked well but cannot be heatsinked for driving 4 power transistors.

 

[fikic]

Audioguru / Adyhansolo

I might be way off of here, but learning from my last problem (previous page)

I didn't have the header pins for the off board LED soldered in place when I testing, this cause the C7 (rated 50V) to pop within a few sesconds of powering up. I assume it is due to the one pin is acting as a "via" to gound some of the circuit, could this not be Adyhansolos' problem?

Just a guess :-\

Image attached.

Your PCB is very negligent drawn.. Don't use autorouter, where you can draw PCB on your own. This one is really easy, especially if you have double-sided board like you..Just for an advice, your PCB could be much smaller for double-sided board, and much more accurate..

 

[lighty]

Your PCB is very negligent drawn.. Don't use autorouter, where you can draw PCB on your own. This one is really easy, especially if you have double-sided board like you..Just for an advice, your PCB could be much smaller for double-sided board, and much more accurate..

Fikic, this it the PCB done by Audioguru, not mine. Which in my optinion is perfectly fine.

 

[fikic]

audioguru says, that he doesn't use Eagle..so I doubt that it is his..

 

[lighty]

Sorry you right, it is Redwires'

 

[surubel]

the BD139 was tried and worked well but cannot be heatsinked for driving 4 power transistors.

Even if we use 2 x BD139 in Darlington connection?
Or you can i replace BD139 with BD681 ?

 

[audioguru2]

Even if we use 2 x BD139 in Darlington connection?
Or you can i replace BD139 with BD681?

A darlington transistor or two fast transistors connected as a darlington are too slow.
Why do you want four 2N3055 output transistors? To have a max output current of 6A?
Then each has a max current of 1.5A when the minimum current gain of a 2N3055 transistor is about 41 then the max current in the driver transistor is 6A/41= 146mA.
One BD139 driver transistor can easily be used and if the output is shorted and set to 6A then the single BD139 driver transistor can dissipate 34V x 146mA= 5W with a medium size heatsink.

 

[surubel]

Yes, I want to have 6 A at the output but I also want to reduce the heat dissipated by transistors.

 

[audioguru2]

With the output current set to 6A and the output is shorted then the output transistors must dissipate a total of 39V x 6A= 234W of heat.
You can use two powerful transistors with a fan or use hundreds of little transistors each with a little heatsink.

The amount of heat dissipated is the same.

 

[surubel]

Ok. Thanks for the clarification. I'll gather the components for PSU. 

 

[redwire]

Hi lighty,

In in my eagle file that you posted  I noticed that you don't have the ground plane filled under the power resistor  (blue outline on left hand side).  In the Eagle program, hit the ratsnest button and it will fill automatically.  Without it filled there are a few connections that may not be connected.  I should remind users because the standard default for Eagle is to not fill these areas when the file is first opened.