Author Topic: RPS with from 0-30V and Current variable up to 3 A design Circuit Please....  (Read 8162 times)

0 Members and 1 Guest are viewing this topic.

Offline BravoV

  • Super Contributor
  • ***
  • Posts: 7549
  • Country: 00
  • +++ ATH1
With all excellent replies, advises, tips and even circuit, I guess the OP will not create, yet another new thread nagging for a new 723 based 30V 3A psu again, as this is the 5th one or 6th already ?  :-//

Its just sad to see all goodwills and helps going to be wasted again if this happened.
« Last Edit: January 11, 2019, 10:13:30 am by BravoV »
 

Offline j395

  • Contributor
  • Posts: 10
  • Country: 00
why not use something like LD1085 - much more robust for beginners due to built-in overcurrent/overheat protection ?
to decrease heating, use cheap buck or buck/boost module as pre-regulator, LD1085 works at 1.3V dropout - only 4W wasted at 3A
 

Offline rstofer

  • Super Contributor
  • ***
  • Posts: 9963
  • Country: us
why not use something like LD1085 - much more robust for beginners due to built-in overcurrent/overheat protection ?
to decrease heating, use cheap buck or buck/boost module as pre-regulator, LD1085 works at 1.3V dropout - only 4W wasted at 3A

It doesn't meet the "spec" in that the minimum output voltage is around 1.8V - see Vo Table 3  or it could be as high as 2.5V from Table 4 but I didn't pursue the difference in #18 versus #25.  In any event, the device can't get anywhere near the "spec" of 0V.

Without a pre-regulator and in the situation where Vi-Vo is about 25V, the device can only deliver about 0.5A based on Short Circuit Current.  But we want, perhaps, 35V as Vi and 0.1 as Vo so call it 35V across the regulator.  The maximum output current won't be much = Figure 7.

With a pre-regulator that can get Vi down to a reasonable level, the device can deliver the full 3A required by the "spec".  But that adds a bit of complication.  Transformer taps would be better (in my view).

https://www.st.com/resource/en/datasheet/cd00001883.pdf

"Specs" have consequences.  It's a lot easier to write 0-30V than it is to achieve the 0V end of the spec.  Same with the 0-3A.  It's hard to deliver 0.1V at 3A from a fixed secondary transformer that is delivering enough voltage to produce 3A at 30V.  I haven't seen a circuit for a linear supply served by a switching mode pre-regulator but I haven't really looked.
 

Offline rstofer

  • Super Contributor
  • ***
  • Posts: 9963
  • Country: us
With all excellent replies, advises, tips and even circuit, I guess the OP will not create, yet another new thread nagging for a new 723 based 30V 3A psu again, as this is the 5th one or 6th already ?  :-//

Its just sad to see all goodwills and helps going to be wasted again if this happened.

But maybe some of the responders, like myself, are learning something about the problems created by the "specs".  Yes, I have spent some time wandering around, bouncing off of other schematics and different approaches to the problem and, as a result, I have a new appreciation for the problem.

If there was a simple design that had a decent bill of material, it would be a 'sticky' and served up as the universal answer to a DIY power supply.  Alas, it isn't simple!

As I see it, there are two choices:  First, come up with a more realistic spec or, second, plan on finding a transformer with secondary taps.  I don't know how hard it would be to wind a custom toroid.  Maybe buy one, unwind the secondary and then rewind it with taps.

There are a lot of commercial supplies that advertise to meet the spec and they tend to be in the $50-$60 range.  I don't know that they actually meet the spec but I would tend to just buy one rather than try to build one.


 

Offline dmills

  • Super Contributor
  • ***
  • Posts: 2093
  • Country: gb
Hum, 2 * 9V dual secondary transformers, 4 bridge rectifiers and filter caps (That will only need to be 16V or so rated), and 4 NPN pass transistors plus 4 diodes and some small beer stuff, build an output stage class G style, almost right out of Doug Selfs book on audio power amplifiers (You only need half of it!)?

At 3A with 12V across the pass device (more or less worst case with zero output voltage) you are looking at only 36W in the heatsink which is easily within the SOA of a single TO3P pass device, I would have thought a 1.5C/W convection cooled job would be fine.

I think you could even wrap this around a 723 as the controller if you really wanted to, but there is nothing really wrong with a long tailed pair, Vas and some passives.   

The trick is that you hang a current source (a few mA or so) off the highest rail, then use a string of zenners to switch on the higher taps as the voltage comes up.

I am not sure it is economic given what you can find a lab supply for on the used market, but I don't really see the difficulty, I might design if for shits and giggles.

This is the basic concept :



Zenners are 3.1V, transistors are probably darlingtons, current source is a few mA via the usual PNP transistor and a couple of diodes and resistors sort of affair.

Regards, Dan.
« Last Edit: January 11, 2019, 11:38:03 pm by dmills »
 

Offline Kleinstein

  • Super Contributor
  • ***
  • Posts: 15151
  • Country: de
The kind of linear cross over between separate transformer taps is a good option at intermediate power.

It can be done even simpler, especially if the floating regulator circuit is used and only 2 taps.
It may not be the most economic way, thought not that bad (mainly more filter caps). On the positive side it's simple and about half the worst case heat compared to the single tap way. So it's about as good as using relays for 3 transformer taps as one can go closer to the edge.
It depends wether the reduced (about half) heat sink can make up for about 1.5 times the filter caps.

There is a lab supply project using this system, though with MOSFETs:
https://www.eevblog.com/forum/projects/diy-bench-power-supply-psl-3604/

This supply could be a good option - at least a good point to learn from. For simplification one could use classical rectifier if a little more loss is acceptable.
 

Offline rstofer

  • Super Contributor
  • ***
  • Posts: 9963
  • Country: us

There is a lab supply project using this system, though with MOSFETs:
https://www.eevblog.com/forum/projects/diy-bench-power-supply-psl-3604/

This supply could be a good option - at least a good point to learn from. For simplification one could use classical rectifier if a little more loss is acceptable.

It might be a little over the top for a newcomer.
If we had a sticky thread for PSs, this should certainly be a candidate.
 

Offline techguruTopic starter

  • Regular Contributor
  • *
  • Posts: 83
  • Country: in
I do not think there is a lack of such schematic diagrams neither that it would be more difficult to design than e.g. a 0-15V 1A PSU.
4 large heatsinks and 8 TO3 BJTs can work for more than 120W of wasted power even without the help of fans.
It just does make little sense and would be more expensive than using a suitable multi-tap transformer based PSU.
Go on, post your design. . .

He's right. It's not so much the current, but the voltage which is the problem. At 15V, an ordinary op-amp can be run from the unfiltered rectifier voltage. With 30V something more elaborate is required. The absolute maximum voltage rating of most standard op-amps is under 44V, which would be an AC voltage of just over 30V on the transformer secondary. A lower voltage transformer could be used, but that doesn't leave much headroom for voltage ripple.

You must be kidding... nothing easier than that.  ;D

I made this from a quick copy & paste from other .asc files so there are likely some problems although it works flawlessly in the simulator.

BTW to play with it you need TL431 and BD140 models.



Sir,
             How to analyse this schematic. Where to start my analysis to understand the circuit?
What is the book to learn to develop Understanding skill for Discrete or Integrated circuit?
 

Offline BravoV

  • Super Contributor
  • ***
  • Posts: 7549
  • Country: 00
  • +++ ATH1
With all excellent replies, advises, tips and even circuit, I guess the OP will not create, yet another new thread nagging for a new 723 based 30V 3A psu again, as this is the 5th one or 6th already ?  :-//

Its just sad to see all goodwills and helps going to be wasted again if this happened.

But maybe some of the responders, like myself, are learning something about the problems created by the "specs".  Yes, I have spent some time wandering around, bouncing off of other schematics and different approaches to the problem and, as a result, I have a new appreciation for the problem.

If there was a simple design that had a decent bill of material, it would be a 'sticky' and served up as the universal answer to a DIY power supply.  Alas, it isn't simple!

As I see it, there are two choices:  First, come up with a more realistic spec or, second, plan on finding a transformer with secondary taps.  I don't know how hard it would be to wind a custom toroid.  Maybe buy one, unwind the secondary and then rewind it with taps.

There are a lot of commercial supplies that advertise to meet the spec and they tend to be in the $50-$60 range.  I don't know that they actually meet the spec but I would tend to just buy one rather than try to build one.

I am a electronics hobbyist, totally understand your point above, nothing against it what so ever.

Its just you don't realize what the OP's have been done here, hint, just read from the bottom the list of threads created since the beginning, no need to read the thread's content, just the title ...

The OP's created threads list -> https://www.eevblog.com/forum/profile/?area=showposts;sa=topics;u=154644

Actually the current nick is his second, as he re-registered here to get a fresh new nick, as before, his old nick where he felt no one could give him satisfaction, btw, he admitted it already.  :palm:

Again, just read the thread's title to get a clue ...

Previous abandoned nick threads list , started from mid 2017  :palm:-> https://www.eevblog.com/forum/profile/?area=showposts;sa=topics;u=138516

The point, he will nag until someone come with a full schematic that uses 723 with 30V 3A capable, and also must utilizes components that are available in his drawer, if not, he will make another thread again, or re-register as new user when most "helpful & friendly" people exhausted on his nick.


He does not have technical problem at all, nor language barrier, he has really bad netiquette and bad attitude.

« Last Edit: January 12, 2019, 05:48:17 pm by BravoV »
 

Offline techguruTopic starter

  • Regular Contributor
  • *
  • Posts: 83
  • Country: in
With all excellent replies, advises, tips and even circuit, I guess the OP will not create, yet another new thread nagging for a new 723 based 30V 3A psu again, as this is the 5th one or 6th already ?  :-//

Its just sad to see all goodwills and helps going to be wasted again if this happened.

But maybe some of the responders, like myself, are learning something about the problems created by the "specs".  Yes, I have spent some time wandering around, bouncing off of other schematics and different approaches to the problem and, as a result, I have a new appreciation for the problem.

If there was a simple design that had a decent bill of material, it would be a 'sticky' and served up as the universal answer to a DIY power supply.  Alas, it isn't simple!

As I see it, there are two choices:  First, come up with a more realistic spec or, second, plan on finding a transformer with secondary taps.  I don't know how hard it would be to wind a custom toroid.  Maybe buy one, unwind the secondary and then rewind it with taps.

There are a lot of commercial supplies that advertise to meet the spec and they tend to be in the $50-$60 range.  I don't know that they actually meet the spec but I would tend to just buy one rather than try to build one.

I am a electronics hobbyist, totally understand your point above, nothing against it what so ever.

Its just you don't realize what the OP's have been done here, hint, just read from the bottom the list of threads created since the beginning, no need to read the thread's content, just the title ...

The OP's created threads list -> https://www.eevblog.com/forum/profile/?area=showposts;sa=topics;u=154644

Actually the current nick is his second, as he re-registered here to get a fresh new nick, as before, his old nick where he felt no one could give him satisfaction, btw, he admitted it already.  :palm:

Again, just read the thread's title to get a clue ...

Previous abandoned nick threads list , started from mid 2017  :palm:-> https://www.eevblog.com/forum/profile/?area=showposts;sa=topics;u=138516

The point, he will nag until someone come with a full schematic that uses 723 with 30V 3A capable, and also must utilizes components that are available in his drawer, if not, he will make another thread again, or re-register as new user when most "helpful & friendly" people exhausted on his nick.


He does not have technical problem at all, nor language barrier, he has really bad netiquette and bad attitude.


Mr Bravo,

              I totally deny you. may be my specification may be to high for a beginner and Now i feel There is no need to built a circuit which can deliver 100W of power. Neither i could go for LT3080 which could control both voltage and Control regulation with dissipation of Nearly 30W. This is what i would understand from this forum.I cannot analyse big circuit. I donot know where to start my analysis.

Here i could not get the component which we have discussed in this thread. What ever is available here i could use it.I could not order from online website because i am student of electronic engineering. my economy wont allow me.

A simple LM723 cost ten rupee which is affordable my me. So i was searching for circuit with LM723. This is the reason for those those thread.

I respect every one in this forum, Sorry If i hurted you all. Thank you all .
 

Offline BravoV

  • Super Contributor
  • ***
  • Posts: 7549
  • Country: 00
  • +++ ATH1
              I totally deny you. may be my specification may be to high for a beginner and Now i feel There is no need to built a circuit which can deliver 100W of power. Neither i could go for LT3080 which could control both voltage and Control regulation with dissipation of Nearly 30W. This is what i would understand from this forum.I cannot analyse big circuit. I donot know where to start my analysis.

You've been told, gently assisted, repeatedly mentioned, yet, you are stubbornly deny any good intentions and helps offered, and keep spamming again and again ... oh ... again.


Here i could not get the component which we have discussed in this thread. What ever is available here i could use it.I could not order from online website because i am student of electronic engineering. my economy wont allow me.

Yep, again .. you've been told, explained and "sympathized" on the limitation of common Indian's budget limitation, with circuit designs that of course limited, but fit into your budget and component availability, and very likely available to you at your country as they're common jellybean components, yet, you ignored and stubbornly create another same identical request at new thread ... again.. again.. and again.

.. oh ... forgot ... again.


A simple LM723 cost ten rupee which is affordable my me. So i was searching for circuit with LM723. This is the reason for those those thread.

Again ... geezz... I'm tired typing this word, you've been assisted, gently informed (as people were aware of price sensitive for Indians and worry that might offend you) for "alternative" circuits that don't use 723, but still ...

... you keep spamming with new thread asking to people to spoon feed you in "designing" a 723 based pcu .. oh .. again..again ... and again.


I respect every one in this forum, Sorry If i hurted you all. Thank you all .

Whatever, just DO NOT make a new same new discussion thread, or worst re-register a new nick and launch the same nagging again.

Show appreciation for those generous people who helped you, don't just ignore and abandon the ongoing thread when every times you don't like it, and create another identical thread ... again.

Offline techguruTopic starter

  • Regular Contributor
  • *
  • Posts: 83
  • Country: in
              I totally deny you. may be my specification may be to high for a beginner and Now i feel There is no need to built a circuit which can deliver 100W of power. Neither i could go for LT3080 which could control both voltage and Control regulation with dissipation of Nearly 30W. This is what i would understand from this forum.I cannot analyse big circuit. I donot know where to start my analysis.

You've been told, gently assisted, repeatedly mentioned, yet, you are stubbornly deny any good intentions and helps offered, and keep spamming again and again ... oh ... again.


Here i could not get the component which we have discussed in this thread. What ever is available here i could use it.I could not order from online website because i am student of electronic engineering. my economy wont allow me.

Yep, again .. you've been told, explained and "sympathized" on the limitation of common Indian's budget limitation, with circuit designs that of course limited, but fit into your budget and component availability, and very likely available to you at your country as they're common jellybean components, yet, you ignored and stubbornly create another same identical request at new thread ... again.. again.. and again.

.. oh ... forgot ... again.


A simple LM723 cost ten rupee which is affordable my me. So i was searching for circuit with LM723. This is the reason for those those thread.

Again ... geezz... I'm tired typing this word, you've been assisted, gently informed (as people were aware of price sensitive for Indians and worry that might offend you) for "alternative" circuits that don't use 723, but still ...

... you keep spamming with new thread asking to people to spoon feed you in "designing" a 723 based pcu .. oh .. again..again ... and again.


I respect every one in this forum, Sorry If i hurted you all. Thank you all .

Whatever, just DO NOT make a new same new discussion thread, or worst re-register a new nick and launch the same nagging again.

Show appreciation for those generous people who helped you, don't just ignore and abandon the ongoing thread when every times you don't like it, and create another identical thread ... again.

Hi..

           I forgot my Old login password ,So i created my New account. Thats all.I have not used both login in parrallel. A college boy will not mature enough to accept things. But From now onwards i will use single thread to get advices. thanks Bravo sir.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf