I want to built a Power Supply - Page 1
Forum section: electronics / projects

author: Alexandros81
author_rank: Regular Contributor
timestamp: January 28, 2014, 11:31:23 am
content: Hi! I want to built my own power supply.It should be:-Dual Tracking-Adjustable-Go down to 0V-Current LimitingVoltage adjustable range 0-30V 3A, and -30-0V 3AI 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.

author: kizzap
author_rank: Unknown
timestamp: January 28, 2014, 01:02:21 pm
content: 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 displaythe 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.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!-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.)

author: Alexandros81
author_rank: Regular Contributor
timestamp: January 28, 2014, 03:27:25 pm
content: QuoteThis 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.QuoteQuoteI am thinking of using rectified AC from a transformer. Is there a draw-back if a use a single transformer(centre-tapped)?QuoteBy using a)short-circuit or Overload protectionb)Fold back current Limitingc)or a regulator with two transistorssee attached imagesQuoteBoth are interesting. I would like to use mcu's and DACs on my design. Is there a drawback?QuoteWell if I use an mcu do i have to use an LCD display? Is there a preferable choice?QuoteI 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

author: phil
author_rank: Regular Contributor
timestamp: January 28, 2014, 06:16:20 pm
content: 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

author: mariush
author_rank: Super Contributor
timestamp: January 28, 2014, 07:07:05 pm
content: 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? )

author: Fluxed Matter
author_rank: Regular Contributor
timestamp: January 29, 2014, 12:11:13 am
content: Hi mariush, would you happen to have the schematic of the Circuit Specialist power supply CSI3303S? It is the older model 2X30V 3A with the LED displays. If so I would appreciate a copy if you would post it.Thanks!Flux

author: mariush
author_rank: Super Contributor
timestamp: January 29, 2014, 01:36:22 am
content: Unfortunately no, I don't have it.But it's just another Chinese rebadged power supply, probably made by the same company QJE as the power supplies I linked datasheets for above. Here's the manufacturer page:http://www.nbjiuyuan.cn/index.php/product/index/id/1/lang/enJust after a simple google search I found a similar one under Aktakom APS-3205 DC Power Supply 315W 30V / 5A 2CH+1Aux :http://www.tmatlantic.com/e-store/index.php?SECTION_ID=270&ELEMENT_ID=6189Or Atten ATTEN) APS3003S-3D :http://www.zhunce.cn/product/product_detail.asp?pid=50201069The insides should be very similar, maybe just other transistors used, just straight pots to adjust current and voltage instead of those switches to mix buttons as in the datasheets above, and the LED driver version of the multimeter chips instead of the LCD version (ICL7107 instead of ICL7106 or something like that). The basics of the psu operation should be the same.Maybe if you're lucky they'll send you the service schematics if you mail them at the contact address.

author: Alexandros81
author_rank: Regular Contributor
timestamp: January 29, 2014, 01:51:28 pm
content: QuoteI was watching Dave's videos on Lab Power Supply Design. Probably am gonna try and built something similar.What is a plug pack?Once again i am searching for books on power supplies design. Do you have any good in mind?Just after a quick search on amazon:http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3Dstripbooks&field-keywords=Power%20supply

author: nowlan
author_rank: Frequent Contributor
timestamp: January 29, 2014, 02:08:00 pm
content: Plug pack is a brick or wall wart.

author: GeoffS
author_rank: Unknown
timestamp: January 29, 2014, 02:12:13 pm
content: A plug pack.

author: phil
author_rank: Regular Contributor
timestamp: January 29, 2014, 05:18:00 pm
content: Quote from: Alexandros81 on January 29, 2014, 01:51:28 pmDo you have a scope? That would make things a lot easier. One of the big problems with linear supplies is that they tend to oscillate. The best way to find out about that is to use a scope. Especially discrete opamp designs have that problem, but it can also happen with a LM317 or similar ICs.Don't expect to get a fully working PSU with all the features you wanted with your first try. Start with a small project to learn about the quirks of these circuits.As with any other medium/high power devices: Layout matters! You can break even the best circuit with a bad layout. Switch mode supplys suffer even more from bad layouts than linear ones do. Read Dave's PCB guide to get a feel for what you need.Phil

author: Alexandros81
author_rank: Regular Contributor
timestamp: January 30, 2014, 10:22:18 am
content: QuoteThanks Phil. I'll check Dave's PCB guide. I don't yet have a scope.I have found a lot of free books inhttp://lib.freescienceengineering.orgAlex

author: Alexandros81
author_rank: Regular Contributor
timestamp: June 23, 2019, 02:42:58 pm
content: Where do I find Dave's PCB Guide?thanks

author: Alexandros81
author_rank: Regular Contributor
timestamp: June 23, 2019, 03:02:14 pm
content: Quote from: phil on January 28, 2014, 06:16:20 pmHi Phil.The plug pack will have a 12V out. What would be the current output of the plug pack?thanks

author: ggchab
author_rank: Frequent Contributor
timestamp: June 23, 2019, 03:45:27 pm
content: You might find some ideas in this threadhttps://www.eevblog.com/forum/beginners/lm324-power-supply-with-variable-voltage-and-current/msg2253243/#msg2253243

author: H713
author_rank: Regular Contributor
timestamp: June 24, 2019, 03:06:18 am
content: First question is to really look at what the requirements are for the projects you like to work on.Do you really need all of those requirements? Building a 1.2-30V @1.5A PSU is quite easy. Doubling that to 3A makes it a bit harder. Making it go down to 0 is harder still.I would forego the SMPS for your first go. In a bench application, the main advantage is cost, size and weight. You don't care that much about efficiency on the bench. Bear in mind however, that the transformer is going to be the most expensive part of this project. Antek will probably be the most economical supplier. The AS-2228 will be fine so long as you don't try to pull 3A on both your power rails for hours on end. Remember that when rectified and filtered a 28V RMS winding will give about 39V DC. You will also see a corresponding decrease in current capacity of about 40%. So while they list a 3.6A current rating on the site, that actually gets reduced to closer to 2A when rectified and filtered. That said, their transformers are quite tough. If, however, you plan to run this at high power continuously, then I would suggest you step up to the AS-3428. One nice thing about the Antek is that it actually has two separate secondary windings, rather than a center-tapped winding. It's easy to turn this into a center tap by wiring them in series, but having two separate windings gives you more flexibility. You can create two completely separate, electrically-isolated power supplies (in one chassis) that can be put together to make a +/- power supply. Lots of advantages of this.Digital controls add considerable complication, and aside from the "cool" factor, I see minimal advantage.A scope is highly recommended for this. With just a bone-stock LM317 you willprobablybe fine so long as you have a reasonable layout and have your .1uF caps on the inputs and outputs. If you're going to do more than that, oscillation is a very real problem.Another thread you might consider reading through- it's for a high-voltage bench supply, but I think there are some interesting schematics that have been posted that you may consider looking at. A lot of the concepts can be scaled down to lower output voltages.https://www.eevblog.com/forum/projects/high-voltage-bench-power-supply-design-165562/25/One other suggestion- Ihighlyrecommend playing around with LTspice if you haven't already. It's very helpful when you are learning to be able to quickly simulate ideas. It's not perfect, and a lot of things that are stable in spice will be great oscillators when you actually build them, but it's an excellent tool.It's easy to say you want all the features, but it is very easy for your "little power supply project" to balloon into something not-so-little.

author: austfox
author_rank: Regular Contributor
timestamp: June 24, 2019, 04:24:39 am
content: QuoteHuh? You are replying to a thread you started more than 5 years ago. This power supply you are building is certainly going at a snails pace...