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DC Variable supply design help

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jami007

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[/COLOR]yes I changed the value of V2 but output remains constant
 

goldsmith

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can you attach the circuit that right now you have tested it ? or can you simulate it with PSpice ?

---------- Post added at 20:53 ---------- Previous post was at 20:48 ----------

Perhaps your simulator cant consider some things . to break that consideration use a 10 k ohm resistor in parallel with BE of PNP .

---------- Post added at 21:04 ---------- Previous post was at 20:53 ----------

SO with top changes , what is the result?
 

jami007

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yes i changed the v2 but it still shows 48v output
 

goldsmith

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No my mean was the other changes . it appear that your simulator can not consider some things . to break that consideration , add a 10 k resistor in parallel with BE of PNP transistor.
 

goldsmith

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By the way , i forgot to say , that you should connect the vcc and gnd to both of op amps . and you forgot it it will not consider that they are connected with together .
 

jami007

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here are the simulation results, I'm simulating it in Proteus

output-02.jpg
output-01.jpg
output-03.jpg
 

jami007

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here is the result by connecting 10k resistor across PNP

output-04.jpg
 

goldsmith

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Did you read things that i told you at top ? Read Post #25 and #24 carefully ! why you didn't do them in your simulation ?
 

jami007

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and about pin 8 and 4, it works fine because it is a single ic, so dont need to supply voltage independently
 

goldsmith

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Why you didn't connect the vcc of the current limiter op amp ( at simulator it need ground and vcc however both of them are in one IC )

---------- Post added at 16:33 ---------- Previous post was at 16:32 ----------

And i said in parallel with BE not BC why you did it with BC ??????

---------- Post added at 16:35 ---------- Previous post was at 16:33 ----------

Try post 31 please

---------- Post added at 16:38 ---------- Previous post was at 16:35 ----------

when i disconnected the supply of the other op amp it didn't work , and it destroyed the behavior of circuit . and you should connect it's supply voltage and GND and again i have to say that those resistance should connect between BE not BC ( see my top posts please!)
 

jami007

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here it is in parallel with BE

output-05.jpg

In proteus you dont need to connect vcc and ground to every op-amp of a single IC, see this

output-06.jpg
 

goldsmith

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decrease your input voltage from 50 volt to 30 volt and then try to change the vref .
I have this circuit in my home and it works very well and i don't no why you can not get success . i hate proteus because 6years ago when i used it it occurs some problem for me .
 

jami007

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it has only one change which is 28v instead of 48v at output...... -:) , ok I'll redraw the circuit in Multisim and then post the results again...

Best Regards
 

dselec

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40V 2A LM317 & TIP42 Power Supply

Did you read all info in link ?
changing ratio of r3-r4 will give u what u want cheap.
"
A very good and powerful Regulated Power Supply section was implemented by simply adding a PNP power transistor to the excellent LM317T adjustable regulator chip. In this way this circuit was able to deliver much more than the power required to drive two Mini-MosFet amplifiers to full output (at least 2Amp @ 40V into 4 Ohm load) without any appreciable effort."

---------- Post added at 17:55 ---------- Previous post was at 17:45 ----------

What r u using for load .
U must attach load or 500 ohm at least to get u starting.
and where is the bias resistor for all the drive transistors ?

---------- Post added at 18:03 ---------- Previous post was at 17:55 ----------

jami post with q6 pnp emitter at left will work.

---------- Post added at 18:06 ---------- Previous post was at 18:03 ----------

google this and get ready for a "stunami" of supplys
"lm317 adjustabe pwr supply"
 

goldsmith

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Dear Dselec
Hi
No it is not good idea . because when you put a transistor to increase the current , in fact you helped to the ripples to go into the transistor and go to the load.
Respect
Goldsmith

---------- Post added at 21:58 ---------- Previous post was at 21:55 ----------

so LM317 has no current limiter and it will be ok for currents up to 0.5 A
 

nobeel

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Helpful discussion, Its all is very true and I was looking for some this type of information. So its my pleasure to have this thread. Thanks man.
 

dselec

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Improved version by goldsmith will work fine
notice that the load is part of feed back route so load always connected or add paralel to load another resistor.
the out put should always be there with/out load.
about lm317 by adding 2 resistors it can be variable.
 

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