Where can I learn about how to design and make a 12V or 24V - 20A DC power supply adapter

Thread Starter

Dolmetscher007

Joined Mar 21, 2019
29
Do any of you guys know any online courses, (free or fee), that are designed for beginners to learn the process of how to design power supplies for delicate audio circuits as well as LED lights etc? You're probably thinking, "Dude... there're 500k videos on YouTube about it" That's true, and I have watched most of them. However... the majority of "DIY Power Supply" videos are about bench top power supplies for analysis of other circuits as you design stuff. That's not what I am after.

I recently built a super bright LED panel light for photography and video lighting. Sure, it was no big feat of science, but it was the first project I've ever built quasi from scratch. I used an off the shelf PS and a small dimmer board from eBay. The power supply that was rated for 12V with a max of 10A. As a test, I left the light panel on for ~half an hour to see if it would... I dunno... explode, melt, flip a breaker...? Sure enough... after half an hour or so, started to turn itself on/off at about a rate of once per second. When I touched the plastic power supply box, it was so hot, it literally felt like the plastic was softening from so much heat.

I did the math; there was no way my LED strips (wired in series OR parallel) could have been reaching even 5A, much less the 10A max current draw of the power supply. They are standard run of the mill 12V LED strips; the whole 5 meter strip doesn't go over 5 amps, and I only used about half of the strip. I read online that cheap oversees power supplies are sometimes garbage that may say 12V, 10A, but achieve no way near those values in reality. I have a really nice BK Precision 388B multi-meter, but... as embarrassing as it is for me to admit... I don't know how to use it to test the max capabilities of a DC power supply adapter.

So, I've heard terms like... switch mode... linear... and flyback topology... etc. but... I'm looking for a real resource or class that will explain to me, like the newbie I am...
  • How to test a wall socket to see exactly what voltage and current you are getting out of each outlet
  • I know you need a rectifier... but, full-bridge? half? and do you make it yourself using diodes, or are there ready-built "full bridge rectifier ICs, and if so, are they better, worse, or the same as using diodes yourself?
  • I know that rectified DC is bumpy as hell, and must be smoothed using a capacitor or capacitors, but how do you know which capacitor(s) to buy... like... how many Volts and micro-Farads as well as... the little can shaped ones vs. the rusty-brown coin-with-legs shape etc?
  • Same question(s) about MOSFETs
  • Oscillators (???)
  • Transformers... toroidal vs brick-shape and why... also... values... what to buy?
  • And resistors... I see resistors all over PCBs when I look at schematics. Sometimes I know why they are there... like with LEDs for example, to prevent the LED from drawing too much current and burning itself out. But... other than that... I am just not advanced enough to know when, where, and why circuit designers add resistors.
  • Shotky diodes... (?)
I think you guys get my drift. I know OF a lot of stuff... but... do not understand how it all fits together.
 

MaxHeadRoom

Joined Jul 18, 2013
21,628
If you do not need precise regulation I would go with a Linear supply rather than SMPS, more rugged and much easier to build.
You can also add regulation, if you wish, or leave as un-regulated if the load does not require it.
For some loads for e.g. you do not require Cap smoothing even, e.g. motors etc.
Max.
 

Papabravo

Joined Feb 24, 2006
14,684
The subject of power supplies is broad and deep. After getting their degree some engineers spend their entire career on such designs. My recommendation is that you consider what you are after as a large brick building and you need to acquire and place 100,000 bricks - one brick at a time. Start anywhere with the first brick, wash rinse repeat.
 

MrSoftware

Joined Oct 29, 2013
1,935
First kudos for jumping in! Second, in regards to figuring out what's wrong now; you have to take some measurements. LEDs themselves will not limit current. Some LED strips/panels have current limiting resistors built in, others don't and require an external current limiter. We don't know which LED panels you have, but in the case they are not self regulating then it is possible that your power supply is in fact putting more than 10A through them. So your first task is (1) figure out if your LED panels will limit current themselves or if they require something external to regulate the current, and (2) get a DC ammeter and measure the current that your power supply is actually putting out. You can get cheap clamp ammeters on Amazon, they won't be super precise but will get you what you need to know. With this information you can plan your next step.
 

Martin_R

Joined Aug 28, 2019
28
Hi, you have a decent multimeter, so first I would check the current the LEDS are consuming. You state that you're a newbie and aren't sure of how to use the meter to the maximum. I think your time at this moment is to become familiar with the meter functions and how to take voltage, current and resistance measurements. I can more or less guarantee that you'll forget to change the current probe back over to voltage and end up blowing the meter fuse!( Still do it sometimes!) Don't even think about building a SMPS, way to dangerous to play with, with high DC voltages present.
 

Irving

Joined Jan 30, 2016
1,068
I second (third?) that first you need to understand exactly what's happening with your current setup. The problem might be with the dimmer rather than the LED strips themselves...

Post links to all your components, PSU, dimmer and LEDs... so we can advise what to do next, and how to use your multimeter safely.

TBH, and IMHO, high current low voltage PSUs are so cheap on eBay/Amazon that I'd not bother to build one unless you really want to learn from the ground up and have some spare cash. A 12v 20A+ supply on eBay is $20 or so, it'll cost you three or four times that to build one, even a linear constant-current supply (which is what you need to drve LEDs & building a 20A SMPS is a step too far for now)..
 

dl324

Joined Mar 30, 2015
11,892
If the LEDs are rated for 12V, why are you considering a 24V supply?

Designing and building a 120-240W power supply isn't exactly a beginner's project. No standard parts are going to provide that type of current, so you'll need to add additional circuitry.

A 20A supply is going to require a big transformer, it will weight a lot, and it will cost a lot.

Have you done a make vs buy analysis? A computer power supply will easily provide 12V@10A and they're cheap. They're switching regulators, so they don't use a big transformer.
 

Thread Starter

Dolmetscher007

Joined Mar 21, 2019
29
First kudos for jumping in! Second, in regards to figuring out what's wrong now; you have to take some measurements. LEDs themselves will not limit current. Some LED strips/panels have current limiting resistors built in, others don't and require an external current limiter. We don't know which LED panels you have, but in the case they are not self regulating then it is possible that your power supply is in fact putting more than 10A through them. So your first task is (1) figure out if your LED panels will limit current themselves or if they require something external to regulate the current, and (2) get a DC ammeter and measure the current that your power supply is actually putting out. You can get cheap clamp ammeters on Amazon, they won't be super precise but will get you what you need to know. With this information you can plan your next step.
Thanks for the Kudos @MrSoftware. I know I brought up my LED panel light as the example I seemed to be basing my question(s) on. But really... I am not JUST looking to learn how to design and build AC to DC Power Supply Units to drive LED light panels. I want to learn electronics from the ground up, and I figured that learning power management is as fine a place as any to start. My main goal is to build a power supply that can power all my electric guitar effects pedals. And yes... I absolutely know there are plenty of power supply units on the market that are specifically for this purpose. But... again... I am not looking to just get some cheap kit. I want to learn. I know that audio circuits like guitar pedals probably require some very smooth and consistent DC current, so if I can learn how to design an an AD to DC power supply for audio applications... then building a power supply to drive LED strips would be much easier.

Your point about me learning how to use meters to measure things is very accurate and my hope is that whatever course, book, or resource will help me with that.

Hi, you have a decent multimeter, so first I would check the current the LEDS are consuming. You state that you're a newbie and aren't sure of how to use the meter to the maximum. I think your time at this moment is to become familiar with the meter functions and how to take voltage, current and resistance measurements. I can more or less guarantee that you'll forget to change the current probe back over to voltage and end up blowing the meter fuse!( Still do it sometimes!) Don't even think about building a SMPS, way to dangerous to play with, with high DC voltages present.
I've posted a link to the exact LEDs I used, and they do have resistors all along the strip/tape/PCB.
As to the, "way to [sic.] dangerous to play with..." this is why my entire thread is about me looking for a course, a resource, some form of structured learning plan... so that I am not just playing around. I have let the, "You can really hurt or even kill yourself," message scare me away from learning the things I want to learn my whole life. I appreciate the sentiment, I really do. But with all due respect, I know people who are a lot dumber and more careless than I am dive into things like this. If I get hurt... I just get hurt.

I second (third?) that first you need to understand exactly what's happening with your current setup. The problem might be with the dimmer rather than the LED strips themselves...

Post links to all your components, PSU, dimmer and LEDs... so we can advise what to do next, and how to use your multimeter safely.

TBH, and IMHO, high current low voltage PSUs are so cheap on eBay/Amazon that I'd not bother to build one unless you really want to learn from the ground up and have some spare cash. A 12v 20A+ supply on eBay is $20 or so, it'll cost you three or four times that to build one, even a linear constant-current supply (which is what you need to drve LEDs & building a 20A SMPS is a step too far for now)..
Here is a list of everything I used to build the LED panel
Dimmer Boards
LED Strips
5A Power Supply Adapter
10A Power Supply Adapter

I think you might have a point about the dimmer board being the problem. If you look at the list of features on the Amazon link for the above LED strips, it does say: "Please note: we suggest you use 10A or 15A dimmer to control this 95 LED Strip Light, not use 5A dimmer."

One thing that makes me question that theory though, is... when I was using the above 5A power supply, that was when the panel started to cut on/off after 30 min. When I bought a 10A power supply (also above) I was able to leave the panel on for hours, with no issue.
 

Irving

Joined Jan 30, 2016
1,068
The thing to note is that LED strips ideally should be driven from a constant-current supply, and 99% of power-bricks that were intended as laptop supplies are constant voltage with current-limiting. So your 5A supply may have been just on the limit and as things warmed up it dropped into current-limiting and effectively turned off until something cooled down enough to allow it switch back on. Your 10A supply didn't have that problem. The 5A dimmer may or may not have exacerbated the issue, its hard to say.
 

MrSoftware

Joined Oct 29, 2013
1,935
If your goal is to learn power supplies, one way to start is to buy an assemble-it-yourself power supply kit, study the schematic until you understand it and assemble it. Here is one example, I'm not sure if this is a good project kit or not, it was just top on the Amazon search results, but this is the general idea:

https://www.amazon.com/Elenco-Tripl...=bench+power+supply+kit&qid=1602468042&sr=8-8

Edit --> Here's an Amazon search result, there are a few kits in here to look at:

https://www.amazon.com/s?k=bench+power+supply+kit&ref=nb_sb_noss_2
 

Irving

Joined Jan 30, 2016
1,068
With respect, as nice as those kits are (and I've fixed a few that friends made that didn't work for various reasons) I don't think building one will help the TS learn much. And none come close to resolving his issue with LEDs and their power supply needs (or understanding what the problem is/was).
 

SamR

Joined Mar 19, 2019
2,789
Easiest way to learn is a fistful of 1N4007 diodes, some 1000uF electrolytic capacitors, and a transformer with a 12-28V center-tapped secondary. Always put a fuse in one leg of the 120/240V feeding the transformer and unplug it when not in use. And another fistful of 1/2A fuses for the XFMR feed. Then, if you want to get fancy, some T0-220 regulators and READ the PDF for them. Learn the various rectification models and which works where. A good idea to have an isolation XFMR to plug the power supply XFMR into so you don't get the shock of yer life! A scope would be handy to see exactly what is going on and what happens when you connect a load.
 

MrSoftware

Joined Oct 29, 2013
1,935
With respect, as nice as those kits are (and I've fixed a few that friends made that didn't work for various reasons) I don't think building one will help the TS learn much. And none come close to resolving his issue with LEDs and their power supply needs (or understanding what the problem is/was).
I think we all agree that the fastest solution to fixing the LED problem is to figure out what the problem is (bad power supply or lack of current regulation), then use appropriate off-the-shelf parts to resolve it. The kits were in response to his wanting to learn how to make power supplies. Just assembling a kit wouldn't be much more than soldering practice, but studying and understanding the schematic while assembling it, then trouble shooting any issues has the potential to be a good learning exercise. One of many possible ways to start learning. :)
 

jtn

Joined Mar 27, 2017
22
For a 200W power supply, my recommend is to design a Push Pull converter using UC2846 PWM IC, current mode control. you could read the UC2846 spec from TI.com. First convert the 110Vac to 160Vdc through a full bridge diode. I recommend to use Simetrix spice model to create an open loop circuit and study the power section. Second build a Push Pull power converter section. Third, build a controller circuit with UC2846. Then adding feedback control circuit, FET driver if needed... Later on with more experience, you could replace the input full bridge diode circuit with a PFC circuit. Start with a power supply with constant voltage source. Later on convert that to a current source to drive LED.
 

DickCappels

Joined Aug 21, 2008
6,649
As for the broader aspect of this thread, which seems to be that of how to learn circuits and (as I too wondered when looking at some of the first transistor radios) "What are all those resistors doing there if they don't really do anything?"

An introductory class in electronics at your local college, if offered, would be a great place to start. Other than that there is experience. Set out do to something then review everything you can find about what you are trying to to -most likely this has been done many times. Next, analyze the solutions (this is where you learn a lot about resistors) and when possible include application notes from device manufacturers. After 10 years or so you should be able to design some stuff in your sleep.

To get to designing state-of-the art circuit requires in-depth knowledge of the application and latest available components as well as a good grip on the related physics and math. Like most things that encompass a lot of detail to get it right, this takes time and experience.
 
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