Electronics > Projects, Designs, and Technical Stuff
I want to built a Power Supply
(1/4) > >>
Alexandros81:
Hi! I want to built my own power supply.

It should be:

-Dual Tracking
-Adjustable
-Go down to 0V
-Current Limiting

Voltage adjustable range 0-30V 3A, and -30-0V 3A

I have been studying some theory on voltage regulation and i know that a switching power supply is more efficient.

Please provide any help like ideas schematics etc.
kizzap:
One thing you will find on this forum (and others I suspect too) is that people generally won't straight out give you the answer to the problem you pose. This is great because it really forces you to learn about the ins and outs of the project you are making.  :-+

A good way(best way?) to design a product is to start with a set of end goals (which you have  :-+) and slowly expand on how you will need to get to the required solution.

For Example, your goal is to have a dual tracking ±0-30V 0-3A adjustable Lab power supply with current limiting. Your next question would be output regulation- how much ripple, etc. do you want on the output? If you want a low noise supply, you should consider linear. If you can tolerate some ripple, switching might be a good option. If you want improved efficiency, maybe you could consider a switch-mode pre-regulator feeding into a linear regulator.

Do you need to use a Linear regulator? Can you use a power transistor?

Then consider where you are getting the power to be able to feed 180W through both outputs. are you going to be using some form of battery, or rectified AC from a transformer? if you go the transformer route, will you need one transformer (centre-tapped) or one for each output? make sure you consider that you will also need to use power in the control circuitry, so your transformer will need to be able to provide over 180W.

You mentioned Current limiting. That means you will need to measure the current flowing, in both the +ive and -ive outputs. How are you going to do that?

How are you going to control the output voltage and current limit? are you going to use potentiometers, or do you want to use rotary encoders, and MCU and DACs to drive the outputs?

How are you going to display  :bullshit: the output voltage/current? are you going to read them to an MCU, or use panel meters?

At this point you can start to consider physical issues. First, identify what parts will be hot. These parts will need to placed on sinks that will be large and bulky. Consider your transformer. It will be the largest component you have to house. You will also need to be able to place all the displays, output control circuitry, and output connections on the front, and you will need it all to fit. You will also need to consider that your control circuitry might be bulky, so you will need to leave space for that.

Now we come to PCB layout. First, you need to find what limits your board will need to adhere to. Things such as the maximum allowable board size, and importantly how the board will be mounted. Will the board be in rails, or will it be mounted on standoffs/screwed down. Either of these is going to mean that there are regions on the boards that will be off limits, which you will need to account for.

Before you consider component placement, take a moment to think track size. Some tracks-especially any carrying high currents-will require thicker tracks. There is also the trend to go to the smallest track size possible too. Do your tracks need to be at the bleeding edge of circuit design, or could you possibly get away with 16mil tracks?

Now we can start placing components, using a logical manner, I.E. keep parts of a circuit within the same function together. Again, keep an eye out for clearance or heat issues. And don't forget those decoupling caps!

Once you have laid out the board, go back and review all you have done so far. If anything needs to be tweaked or changed, do it.  :-/O

So this is just a start: Every little thing you need to decide will have a number of flow-on considerations that you will have to take into account. Its also ALL OF THIS that all of us electronics enthusiasts love about our hobby/job. You will also find that for every question, you will find 5+ solutions. So take heart young Padawan! You have a long way to go yet!  :scared:

-kizzap

(as an aside, make sure you go watch a lot of the earlier videos our humble leader has uploaded to youtube. There is a wealth of information there that will help you on your journey.)
Alexandros81:

--- Quote ---For Example, your goal is to have a dual tracking ±0-30V 0-3A adjustable Lab power supply with current limiting. Your next question would be output regulation- how much ripple, etc. do you want on the output? If you want a low noise supply, you should consider linear. If you can tolerate some ripple, switching might be a good option. If you want improved efficiency, maybe you could consider a switch-mode pre-regulator feeding into a linear regulator.
--- End quote ---

This power supply I'll use it for embedded systems designs and RF TXs & RXs designs. So really I don't know If I could get away with a switching voltage regulator. The switch-mode pre-regulator feeding into a linear regulator sounds as a great idea.


--- Quote ---Do you need to use a Linear regulator? Can you use a power transistor?
--- End quote ---


--- Quote ---Then consider where you are getting the power to be able to feed 180W through both outputs. are you going to be using some form of battery, or rectified AC from a transformer? if you go the transformer route, will you need one transformer (centre-tapped) or one for each output? make sure you consider that you will also need to use power in the control circuitry, so your transformer will need to be able to provide over 180W.
--- End quote ---

I am thinking of using rectified AC from a transformer. Is there a draw-back if a use a single transformer(centre-tapped)?


--- Quote ---You mentioned Current limiting. That means you will need to measure the current flowing, in both the +ive and -ive outputs. How are you going to do that?
--- End quote ---

By using a)short-circuit or Overload protection
               b)Fold back current Limiting
               c)or a regulator with two transistors

see attached images


--- Quote ---How are you going to control the output voltage and current limit? are you going to use potentiometers, or do you want to use rotary encoders, and MCU and DACs to drive the outputs?
--- End quote ---

Both are interesting. I would like to use mcu's and DACs on my design. Is there a drawback?


--- Quote ---How are you going to display  :bullshit: the output voltage/current? are you going to read them to an MCU, or use panel meters?
--- End quote ---

Well if I use an mcu do i have to use an LCD display? Is there a preferable choice?


--- Quote ---At this point you can start to consider physical issues. First, identify what parts will be hot. These parts will need to placed on sinks that will be large and bulky. Consider your transformer. It will be the largest component you have to house. You will also need to be able to place all the displays, output control circuitry, and output connections on the front, and you will need it all to fit. You will also need to consider that your control circuitry might be bulky, so you will need to leave space for that.

Now we come to PCB layout. First, you need to find what limits your board will need to adhere to. Things such as the maximum allowable board size, and importantly how the board will be mounted. Will the board be in rails, or will it be mounted on standoffs/screwed down. Either of these is going to mean that there are regions on the boards that will be off limits, which you will need to account for.

Before you consider component placement, take a moment to think track size. Some tracks-especially any carrying high currents-will require thicker tracks. There is also the trend to go to the smallest track size possible too. Do your tracks need to be at the bleeding edge of circuit design, or could you possibly get away with 16mil tracks?

Now we can start placing components, using a logical manner, I.E. keep parts of a circuit within the same function together. Again, keep an eye out for clearance or heat issues. And don't forget those decoupling caps!

Once you have laid out the board, go back and review all you have done so far. If anything needs to be tweaked or changed, do it.  :-/O

So this is just a start: Every little thing you need to decide will have a number of flow-on considerations that you will have to take into account. Its also ALL OF THIS that all of us electronics enthusiasts love about our hobby/job. You will also find that for every question, you will find 5+ solutions. So take heart young Padawan! You have a long way to go yet!  :scared:
--- End quote ---

I am far behind for all of that.

Any suggestions for theory links or books related to power supplies are welcome.
What I have read so far is Electronic Devices by Floyd



phil:
To be honest, it sounds like you want too much at once. Why not begin with a PSU on a smaller scale with a single channel to learn how it works? There are many pitfalls to PSU design. And you can avoid most of them in your final design if you work your way up from a very basic one (opamp, transistor) to the more advanced ones.

Why not take a plug pack with 12V out and try to get a circuit to regulate from 0-10V with 0-1A current limit? Trust me, even that will be a challenge, especially if you want to do it right.
Doing it right means "stable under all possible loads", meaning BIG capacitive loads, inductive loads and dynamic loads. Expanding to MCU control, 30V/3A, dual tracking won't be very hard after that.

Phil
mariush:
Have a look at these schematics below to see what's involved in making such a power supply  (multiple taps on transformer, multiple relays, multiple transistors, opamp for feedback etc ).

With a switching preregulator you get around using multiple taps on a transformer but you still need some isolated input for each channel (maybe a 48v dc switching power supply for each channel? )

 
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod