0-30 Vdc Stabilized Power Supply

[ante1]

Hi Guys,

There are a few ways to achieve the multi winding changeover trick. These techniques greatly reduce the heat dissipation in any linear PSU.  I attach two examples of how it can be done, one circuit for a split winding and another one using a four pole winding. 

View attachment 38818

View attachment 38819

 

[jackrs]

Hi Ante.

Do you have the parts list of the 0-30V 0-10A PSU posted above?

It looks good... ;D

If you have the parts list, please post it here. ;D ;D

Thanks in advance.

Regards.

jackrs

 

[ante1]

Hi jackrs,

Wellcome to this forum!

Yes, the complete manual coming up right away!  ;D

Manual_K7200.pdf

 

[Multeri]

Thanks Audioguru.

Maybe it's better to stay with original setup and mods for it.
But I have to use BD243A transistors to place of TIP31A:s.
Second change I have to go is 3,9k resistor, 1W version isn't available, so, they give me a 5W version.

 

[audioguru2]

Maybe it's better to stay with original setup and mods for it.
But I have to use BD243A transistors to place of TIP31A:s.

Same TO-220 package and pins layout, same voltage rating, same current gain, better current rating and better heat dissipation. It is perfect.

Second change I have to go is 3,9k resistor, 1W version isn't available, so, they give me a 5W version.

A 5W resistor won't fit on the pcb. Use a 4.3k/1W or 4.7k/0.5W resistor instead and you won't notice that the LED is a little dimmer.

 

[MaT3LkO]

hi men, i got one big problem, i'm gonna do matricular exams 3 days later, and i choose this circuit, but, i dont have any voltage at the emmiter of q4...at the collector of q4 its 36V, and at the output pin of U2 its 36V too...please, advice me, or give me your ICQ number...i'm hopeless...  ??? ??? ??? ???

 

[audioguru2]

Hi Mat,
Welcome to our forum. ;D
Does "no voltage" mean a voltage of 0V at the output?
Then the negative feedback through R12 will normally cause the output of U2 to go high, so the voltage at both ends of R15 should also be high, then the emitter of Q2 should also be almost as high (minus about 0.7V), then the emitter of Q4 should also be almost as high (minus 0.7V to about 2V).

Did you substitute any parts?
Maybe you have the pins of Q2 or Q4 mixed-up? Look at their pics on their datasheets.

 

[MaT3LkO]

hi audioguru i'm sure i dont have mixed pins of any of parts.... i did little mistake  :-[ i connected cooler of q4(collector) and output...and it little bit twinkled....and now? at the output its 0.3V...at the emitter of q4 its 0.3V.... can you give me your ICQ number? thanx 4 help anyway...

 

[MaT3LkO]

emh, i forgot, its normally when the output voltage(pin6) on U2 is 36V?

 

[audioguru2]

Mistakes quickly blowup parts.

The output voltage of U2 will go as high as it can because of the negative feedback through R12. The opamp's negative feedback senses that the output voltage of the project is too low and is trying to correct it.

If the base voltage of Q2 is high but its emitter voltage is low then it is broken.
If the base voltage of Q4 is high but its emitter voltage is low then it is broken.
If the base voltage of Q2 is low then R15 is broken or its value is much too high.

 

[MaT3LkO]

ehm, i got little problems with english, but who gives a shit ok, actually, i will discribe how Q2 behaves.... at the base of the Q2 is about 33V, at the emitter of Q2 is 0.3V and at the collector of Q2 is 33V too....does it say you anything?

 

[audioguru2]

Q2 is broken. Replace it.

 

[MaT3LkO]

thanx man ! i'll do it tomorrow (european time) 

 

[MaT3LkO]

HI AudioGuru !!! you really saved my ass....i have replaced Q2 as you said me, and, all is allright !!!! really thanx man !  ;D ;D ;D ;D

 

[audioguru2]

Good, you fixed it. ;D

Be very carefull if Q2 is a 2N2219. If the project is set to a low output voltage and a high current then Q2 will melt.

 

[bongo4000]

for the first tests, i powered the circuit from a lab power supply with +25 v/ -5v. so it worked well.

now that i connected the transformator and rectifier, the negative voltage dropped to about -1v.

when i remove the OP U2, i again get the -5v.

any idea what could be wrong?

 

[audioguru2]

Hi Bongo,
Welcome to our forum.
maybe you damaged the project's negative supply when you connected the other supply.
U2 doesn't draw much negative current. If it did then it would be very hot.

The negative supply has only 7 parts. Check them.

 

[bongo4000]

hi audioguru
thanx for the quick response.
i checked the neg supply, and it seems to be fine.
btw: i always had 25v on the output, since i connected the trafo, although i had the voltage pots on 0v.
(before, with the current limiting lab power supply instead of the trafo, it all worked well)
so i removed the OP U1-3 to check the output stage by itself.
the base of the 3055 is always at vcc, what looks really citical to me.
so i pulled the signal, which is usually driven from U2 pin6, to low, which, i think, burnt up R15.
i.e. the base of Q2 is always at vcc.
is it possible that Q2 has been killed?
how can this be avoided?
would it be better to replace R15 by a resistor with higher impedance, to limit the current through Q2 for not killing it again?
thanx!
bongo

 

[audioguru2]

btw: i always had 25v on the output, since i connected the trafo, although i had the voltage pots on 0v.

Without any voltage control.

the base of the 3055 is always at vcc

That is a severe error.

the base of Q2 is always at vcc.

Now two transistors are defective.

is it possible that Q2 has been killed?

Yes, and since the base of Q4 is also always at Vcc then it is also killed.

how can this be avoided?

I don't know what is wrong to short the transistors. Are their pins connected correctly?
Is the rectifier bridge connected correctly?

would it be better to replace R15 by a resistor with higher impedance, to limit the current through Q2 for not killing it again?

No. The current through R15 is very small. The output transistors are wired as a darlington emitter-follower. So the voltage at R15 should appear at the project's output, minus two base-emitter voltage drops.

Did you make the original or the improved project?
Did you substitute any parts?
Is there a short or overload on the project's output?

 

[bongo4000]

yes, the 25V have been there with the voltage control to 0V, and current control to 0A.
so i connected a 1E resistor to the output, as i thought the voltage was because of a loaded cap.
so i think, there was some over current for a short time, until the 1E resistor burnt away.
i think this must have resulted in an over current through Q2, which burnt this one.
no idea why the current limiter did not reduce this current.

i think the base of Q4 is at vcc because it is pulled to vcc by Q2 ?

rectifier seems to be ok, as voltages before the regulation (over the big caps) is ok.

my idea to use a higher value for R15 was to limit the C-E current through Q2 to avoid that it burns down, when the output of the power supply is shorted.

attached, you find my schematic for the 6A version. the trafo is 24V/200W

thanx!
bongo

View attachment 38946