24V 4A 100W LED Switching Power Supply - test, schematic & explanation

Today I tested and reverse engineered a 24V 4A 100W switching power supply module (XK-2412-DC) for LEDs or any other purpose. It also comes in 12V 8A version. This power supply works well an seems good, but I'm able to find some flaws in any device :). I have drawn a full schematic of it and explained how does it work. It's a flyback power supply with a MOSFET, CR6841S control chip, an optocoupler and a 431 voltage reference.
This switching power supply was donated to me by a kind viewer "Siana Gearz", so big thanks to you ;).
You can support me on Patreon:
/ diodegonewild
My Instagram:
/ savage_danyk

[@shiladityaray3137]

Mark my words......With this simple way of explaining, your vast knowledge and your beautiful accent this channel will become huge in the coming days.......Best of luck.....

[@taunteratwill1787]

A speech issue is not an accent! :-)

[@bamsuth9650]

@@taunteratwill1787 wdym ur racist u can't mess with a slavic electronic boi

[@johnrubensaragi4125]

@@taunteratwill1787 well, your first statement can easily be misinterpreted

[@windigo000]

@@taunteratwill1787 it's a heavy czech accent. this is not a speech impediment 😁 we all talk like that here 🤣

[@taunteratwill1787]

@@bamsuth9650 Talking about a white guy, talking about speech . . . . . racist?! Whahahahaaaaaaa! Find a shrink moron.

[@therealjammit]

About that backwards LED. I've run into many "sold as parts or scrap" pieces of equipment. What happens is the manufacturer might have made a good device, but messed up and put the LED in backwards. They made a few hundred devices backwards. The device may work fine with a backwards LED, but the customer (who might have ordered 20,000 devices) obviously wouldn't want that, and since it's too expensive to rework 100 devices (time wasted, power running a shop, hiring more people or taking workers from the assembly line and putting them on rework) they instead run a new production and sell the bad parts to hobbyists or reworkers to get some of their money back (even if they have to sell the device at below their cost).

[@Tremor244]

would it really cost more to rework than to sell at a lower price?

[@boblewis5558]

@@Tremor244 Absolutely, as you have to then setup a repair/rework line which is nowhere near optimised for production flow rates. WAY less costly to do as suggested. I worked for a number of large electronics corporations and they did this as common practice.

[@manickn6819]

Between my own experimenting and stripping and several teardowns (2 from you so far) I think power supplies are finally becoming less mysterious.

[@VivaMessico]

lol

[@bashaaksema94]

Yeah look at his video about the 800 or so whatt computer power supply then we will talk

[@dariofranco3051]

You have done a great job, helping us to understand how these types of power supplies work... they appeared to be so complicated before you expained them to us. Thank you very much.

[@crocellian2972]

Best SMPSU tear down I’ve seen. Love your variable load!

[@SianaGearz]

I have now received my power supply... and it's similar but different! The bottom side is empty, all SMD components are topside. The top carries the marking AC-DC24V. The bottom carries SKU:6724. The transformer body is smaller and wrapped in blue tape rather than yellow. There are no separation slots on the PCB, but they put a handful of holes under the transformer. The separation distance between primary and the secondary across the PCB is 6mm or more throughout. The capacitor across the transformer claims to be an XY capacitor and is correspondingly rather thick. All electrolyics are Taiwanese rather than Mainlandian, Cheng brand - not what anybody considers good, but hey, they're 'imported'. The logic IC is CR6842S.

[@vishftw]

Wow :D nice comment for kid beginners like me

[@matthiasbretonnier4015]

Moderator Zockt Aliexpress, Amazon or eBay :)

[@Bodragon]

Excellent. At first, I was like, annoyed by your strange voice but I soon got used to it. I have subscribed and a thumb up. You have a great and thorough way of explaining. Loved the reverse engineering part with the schematics. FIRST CLASS SIR!

[@hectorpascal]

Yes, interesting and well done! But despite the fact that this Vlogger REALLY knows his stuff, I found his odd sing-song phrasing SO distracting, I had to turn it off!

[@morthren]

Excellent video! You're very thorough with your commentary and circuit diagram. I really like that

[@jvandervyver]

"Let's cheat it" Haha amazing

[@MCSGproject]

legend lol

[@lupojacobo9892]

Lets try to cheat iiiiiiit 😄😃😄

[@spirit-teacher]

just because you test these power supplies so extensively I can buy them with peace of mind

[@jmtorres6710]

The manually operated pulse modulation.. I love that part :D

[@AThreeDogNight]

I knew I was missing something this time, your security officer was not on the scene allowing work to be done. LOL. A great explanation on this power supply regardless with or without kitty. Keep doing these videos please, I'm learning a lot from your explanations, best yet on all of the you tube channels I've watched, so thanks again.

[@electronresonator8882]

you know how to design a good circuit and also can reverse engineer it as well, nice !

[@PeterMilanovski]

Is it possible to modify the resistor divider for the 431 to make the output voltage adjustable? I need an output of 3.6 to 4.2V for charging batteries from 200V+ solar panels...

[@boblewis5558]

I have that exact same model but my LED is correctly fitted! Thanks for doing all the reverse engineering for me ! :)

[@scientistrazz480]

Thanks. I have some of those power supplies. I'm glad you gave a detailed analysis of it. keep up the good work.

[@cri8tor]

Using the same power supply to build my soldering station. Glad I watched you video before finishing the build. Cheers

[@Basement-Science]

I´m using one of these PSUs in combination with a cheap "10A" chinese CC CV boost converter. I mounted this together with an old CPU heatsink into the case of an ATX PSU. So far it looks like the 100W led will be the first thing to fail... The rest is working well.

[@resjandonero2221]

i have this power supply.. when connecting a load the voltage fluctuates like in this video and uaing the cheat.. it will work but when the load is diskonected or the power is removed.. i have to use the cheat again.. is there a fix solution to this?

[@wariskn7096]

Can anyone explain what happens to the dutycycle and frequency of the circuit when we increase the load.Some of the say dutycycle is fixed and frequency are varied according to load. Also under what circumstances we are giving a typical frequency for the circuit..I have gone through various IC which has capablity of delivering 500khz. But for eg if we going to design 12v 5a PS the frequency is set to 50khz.Can anyone please sort me with this issue?

[@stevenbliss989]

The CR6841 (which I assume is the same as the SG6841 - the datasheet for which is in English) is a very nice chip with built in: 1) soft start, 2) short circuit protect, 3) slope compensation, 4) leading edge blanking etc. Why the power supply has an RC leading edge blanking is wierd since that is already built into the CR6841? I know it's not your thing, but talking about the features of the CR/SG 6841 may be of interest to your viewers.

[@retiredjan4714]

The CR6841 is a (china) clone of the SG6841 not a copy. It's specs are NOT the same (sample: Irt= 70 uA Vs 100 uA and VOTP=1.06V Vs 0.62V so it needs a other NTC)

[@prakashsharma6186]

I love the way u explain in detail. Keep on going . Thx

[@vijaykumar-fb6yp]

yes

[@vijaykumar-fb6yp]

mujhe lga india me sirf m hi iski videos dekhta hu lekin yahan to boht sare indian hai

[@patrikjankovics2113]

9:36 "If you are deciding something, you should decide either to connect it or to leave some space in-between" xDDD

[@Zebra_Paw]

Designing*

[@Palmit_]

"...which, as you can see, is a bloody mess. So here is a better schematic which, doesn't fit my paper, but it's ok, because i have more papers and sticky tape." @DiodeGoneWild This is why i admire you so much. Instead of reducing the brilliant aid of 'visual learning' to fit the page, you make the page fit the learning. Thank you. Sincerely. 👍

[@moya9450]

I have used this PS about 3 years. The short circut current is about 8A. I used a high power loads which could draw 6A easily of it. It's so weird that your chip has 5.3A cut off limit. Also in the seller description is mentioned that the max output current is 6A and then need heatsink to cool it down

[@TAMIL-MUSIC]

how can you toch the primary side of the smps whole power is on

[@austinbrahma4671]

Very good explanation. I love your style

[@akonlyaman7593]

Thanks for the schematic will definitely support your channel

[@vampritt]

my power supply turn on and off without giving any power. the led red light turn on and shortly turn off again.. what is wrong ? tried tested the capacitor and the diode its still oke.

[@agustinguzman6375]

This video is Awesome!! great explanation. Been in the EE-field for quite some time now, on and off working on power supplies and this helps tremendously! Also, looks like this same style power supply (same Voltage controller and feedback loop) had a PCBA layout improvement. (Amazon) Purchase of "WX-DC2412" as a 24VDC 4A power supply and it's literally this same power supply BUT with all SMD components on top side (so no components on the bottom side). Same heat-sink setup though, so also expecting this one to run hot. Thanks again for the great video!

[@-yeme-]

Ive been using an identical supply for a couple of years in a Hakko clone T12 soldering station

[@28897manojk]

I love ur explanation

[@pierreuntel1970]

That trick though, never though of that

[@opera5714]

I like your videos. Sorry, I take a quick look at the board and go right to the schematic. I was thinking of buying one of these and converting it to 12V and powering at 70VDC. Video saves a lot of guess work before I buy. Keep making more.

[@repair5782]

I have the same bord, but the fuse on the AC side is blow out, and i cant read what is the fuse Amp Who can help me to find out

[@phonicwheel933]

Brilliant explanation- very useful as I am thinking of modifying one of these PSUs for a project.

[@buddhistsympathizer1136]

Thank you for your video - I enjoyed it, and the information was useful.

[@das250250]

Thank you for your video, you do a wonderful job . I used an identical power unit 240VAC to 24V Dc ( 5A) to replace a broken supply to power auxillary boards inside my TIG/PLASMA cutter welder. It worked succesfully for a year and then the board fuse blew so on checking it appears the primary FET blew up. Although I was not actually welding at the time I suspect the heat possibly affected this unit or transients from welding. I am motivated to try and solve the problem because everything else works fine on the welder unit. I am going to increase the thermal capacity of the system by adding better air flow and a better heat sink but I was curious if I could use the thermal shut down pin on the control chip. I'll look at the data sheet but if any body has experience on how to make this board more robust for my application I am all ears . Thanks in advance !!

[@rogerd4559]

they used screws for the older mosfets that dont have plastic on the metal mounting tab. the earlier mosfets, and were too lazy to upgrade the length of the screws

[@SODA-iz8lc]

Hi mate, Thanks for the upload. I always learns something here. Great explanation of this sm psu

[@aliahmed-gh1lu]

How lamps glow by sliding them with wire?

[@adamsucksatyt]

By interrupting the inrush current quickly, the power supply gets fooled cuz the inrush current won't exceed 5.3A (its limit)

[@jhuncamara3326]

Good day sir, i bought the same thing before. My question is can i use this to make a motorcycle battery charger? Please respond. Thank you in advance.

[@musicasrelaxbrasil]

thank you for your videos! you are just great! greetings from brazil

[@Doggies_rule]

Hello i have two ones very similar to this one and was wondering if there a way to bypass over load protection as i have them in parallel and cant use them to full power

[@SandeepKumar-jj7zi]

so it is a flyback transformer power supply?

[@tapashaldar1506]

Sir i have this power supply but output voltage is not fixed in24v.. .it is countie chenging between 16 to 24 v and led not glowing continue it also glow up down....why this occure pls help me....

[@alibehrouz9833]

in datasheet pin 5 is ground but you said it was over temperature protector whats the matter?

[@rashh77]

Very nice explaination. Thanks a lot.

[@sudhirdhanawade89]

u have a depth knowledge of smps. very nice explaination. but here wt is the X'er turn ration at primary n secondary side?

[@vvdb_fr]

To modify the output voltage, what must be modified? This module is also available in 12V. I deduce that some components need to change values. I would like a voltage of 3V3 to power ESP-01s, 25 units in total. Will the maximum output current be 30A? Thank you for your reply.

[@ramaswamyranganathan9171]

Sir 0.33ohms is very crucial because it sets the current for higher and lower voltages. I have checked if I use 0.1ohms it is giving a good current in 230v, but in lower voltages like 100v it is not giving that current. Why is it so?

[@vineethjose6514]

Hello Sir, Can I know how the polarity gets changed when the mosfet is in off state.?? Thanks in advance.

[@phbrinsden]

I believe the mosfet switching on then off causes the required flux change in the transformer. At a high frequency. That creates what I think of as “synthetic AC” for the transformer.

[@minazulkhan8287]

best video your catch on basics and everything thanks

[@resjandonero2221]

hi i have that problem with the testing of the light bulbs and it really works when using the cheat how ever if turn the supply off, it comes back again to flicker and i need again to use the cheat.. is there a fix on this?? pls anyone?

[@PhilXavierSierraJones]

Good ol' Xinrui strikes again!

[@AhmedAli-sn3ty]

how is the reference voltage 2.5V at output voltage divider ??

[@johnnytwotimez]

Pop a relay on the output for supervision and connect to an alarm relay and thats what controls horn strobes on a fire alarm

[@AxellTh]

What about noice. Does it make a lot of noise in the ac mains it is plugged in to?

[@scientisthadi]

I like mosfet based dc load....can you share its circuit..

[@naitikshailendrakumaryadav2824]

Hi, can we adjust output voltage of smps by replacing optocoupler with variable resistance. If yes please explain or make a video on this topic. Thank you....

[@Tegelane5]

Not optocoupler needs replacing but if this 20 kiloohm resistor at TL431 was with variable resistance then output voltage woul'd be adjustable.

[@muhsen61]

hi friend i can take out the 2 resistor for the 431 and put a variable 10 kilo OM TO make it adjustable?

[@saadrad9156]

Thanks a lot for explanation

[@EdwinFairchild]

@10:52 what is point of that huge 10k discharging resistor when there is a less resistive path through that diode connected at the gate which i thought was for discharging faster

[@Rogash11]

I haven't checked the IC but maybe it can't sink, only source current and the diode on that gate is unnecessary. More likely is that the mosfet is prevented from turning on while the device is powered up. When you don't have the resistor there and the output of the driver ic is high impedance the mosfet could turn on, due to noise or static charge, which may short the primary coil.

[@__MINT_]

Without that resistor, in case there is nothing at the output of a chip because it failed, the power supply is more likely to blow up.

[@victornyanga5447]

I have installed a similar power supply (WX-DC2412) on a turnstile gate, but the gate started to misbehave. It periodically start to open itself and lock again. I used a linear power supply on the same type of gate it works well. Original power supply has output of only 2.5A. I thought this 4A power power supply would even work better than the low current ones. I wonder if this might be the same effect displayed when you first test the module with halogen bulbs. I would like to know what you would do if you wanted the power supply to lit the bulb right away without you helping it. Will adding output capacitors work?

[@UpcycleElectronics]

11:35 what is the purpose of the inductor between the capacitors?

[@BlackopTN]

To smooth out the output current

[@DiodeGoneWild]

It's here to reduce the high frequency ripple at the output. With this inductor, the ripple is far lower than if you had just the two capacitors in parallel.

[@UpcycleElectronics]

DiodeGoneWild I need to find a practical reference for snubbers and filtering like this. Someone needs to explain things empirically, like X problem, is solved using Y, to achieve Z. All of the information I have found requires too much theory and math, and they don't make any attempt to create a practical relationship to real world circuits. By "they" I mean Sam-Ben Yaakov, and MIT OpencourseWare 6.002, on KZbin, or "The Art of Electronics" in print.

[@VivaMessico]

Upcycle Electronics unfortunately, engineering IS math.. but, if you know an inductor's impedance is proportional to its inductance, and a capacitor's impedance is inversely proportional to its capacitance, one way to look at it is.. they form a voltage divider. The capacitor shorts out higher frequencies to ground, the inductor also resists high frequencies. So there you have a filter. When you start seeing it like that it starts making sense. Unfortunately it's still more than that, it's also tank circuit with a resonance frequency.. something that's undesired in a filter and can cause nasty problems.

[@__MINT_]

@@UpcycleElectronics The formula for the cut-off frequency (-3,01dB) of a LC low pass filter is 1/(2*PI*sqrt(L*C))

[@amitarun3287]

Hi thanks for the informative review! How long could the output be allowed to stay short circuited without damaging the power supply?

[@dr.nadhimrasool2959]

very nice and perfect explanation

[@uwepolifka4583]

Very good plan and very good explained. But now I ask myself if it is possible to change the output voltage from 24V to 28Volts only by changing the feedback to the 431 chip but without changing the sek. winding. I thing I have to try it but if someone already knows please tell me.

[@__MINT_]

Just change the resistor(s)' value in the voltage divider (change the upper one to 24k ohm or add 12k ohm in parallel to the lower one), unless it will be tripping the overvoltage protection, if so add a zener diode between the auxiliary capacitor and the plus of the chip

[@felixcat4346]

Hi, excellent tutorial. Could you please post some information on the variable dummy load device. It looks extremely simple and useful, it seems to be using a single mosfet and no external power supply. I think everyone would like to know more about it! Thanks and happy new year.

[@FaysalKhalashi]

found in his website: danyk.cz/zatez_en.html

[@eddprst]

@@FaysalKhalashi thank you mate.

[@yudikusvianto9991]

can I just use this switching when i want to increase to 10 amp ? could I just re cable winding on trafo

[@hmjeon8609]

I have one of this. While it can provide 24V 4A but is really noisy. I bought this to power my DIY soldering station but when connected it behaved weirdly. It worked Ok with my other SMPS. Is there any way to reduce the HF noise?

[@hmjeon8609]

Do I need to connect the minus side of 24V output to the earth ground?

[@hopara4279]

I recently purchased same module from aliexpress china . But it is working up to 1.5 amp output above that the module switches off. Can any body help me to troubleshoot this module to get 4 amp current output.

[@doncgez1673]

Can you use this to power a mini spot welder.

[@CarlosFilmagem2008]

Muito obrigado!!!! ótimo video

[@mobilered2776]

Hi, I want to know how u have measured the Amphere (current) from out put by varying the control. Plz share me the details.

[@cisarvialpando7412]

16:20 And this is what I called is manually operated pulse modulation...💯💯💯

[@DrHouse-zs9eb]

Very interesting Video!

[@steffenk8955]

Thank you very much, i can understand it, now.👍🎅

[@EliteHEAD]

Hello, I have a silly question, what is the reason behind using a transformer, why not have it configured like a buck converter. Is it because of isolation, that you can’t have the output ground be the neutral wire of the AC input?

[@danielmantione]

The safety of buck converter design would be completely unacceptable. 230V rectified is 325V. If the MOSFET of the buck converter would be stuck in the ON-state by a defect, you would get 325V on the output of the power supply., which is obviously going to kill people. But a buck converter generally gets less efficiency the bigger the difference between input and output voltage. For example the datasheet of the XL4015 shows a peak efficiency of 93% with 8V in and 5 V out. At 36V in and 5V out, the efficiency drops below 85%. I can imagine that a buck converter with 325V in and 5V out would be very inefficient.

[@MrGuano11]

Why does the rectification happen BEFORE the transformer?

[@limks1980]

can you post the loading circuit that you use ?

[@Koolian.]

How many windedings does the Transformer have?

[@pedromiranda7701]

it may got hot due to the proximity to lamps, that are actually heaters for the winter ☃️

[@InssiAjaton]

I expected to see a constant current output device. This is constant voltage type, so not good for LEDs directly. Needs still some resistors or another converter before it is applicable for any LEDs. In other words, it is a run of mill 24 V power supply, not a LED driver.

[@DiodeGoneWild]

You're right, but for example LED strips usually have built in resistors so they use constant voltage (usually 5V, 12V or 24V). And of course, the chinese sellers put the "LED" keyword to almost every listing even if it's totally irrelevant :D. But the next time I will take a look at some constant current supply. I haven't opened any yet.

[@gelow1717]

Thanks, i am planning to buy that kind of power supply for my amplifer if it safe?

[@user-js7ip7hf1u]

Well done

[@prolawren6491]

how do we know to put two 820 kohm resistor in series for pin 3?

[@samueldavies646]

what is the turn ratio on the transformer?

[@Rogash11]

Can somebody explain to me why the B20200 diode is getting that hot? When looking into the datasheet of that diode it states a worst case forward voltage of 0.7V for 25°C at 4A. At higher temperatures the forward voltage even gets lower 0.5V at 150°C for 4A. Let's assume an absolute worst case scenario with a forward voltage of 1V at room temperature, there the diode has to dissipate 4W of heat. DiodeGoneWild mentioned that the heatsink attached to the diode is too hot to touch, which sounds to me like more than 50°C. However a temperature rise of more than 25 degrees sounds unreasonable to me for such a large heatsink. What am I missing here?

[@__MINT_]

Remember about the switching losses

[@hamcher]

Why you touch the wire many times to lamp before it light

[@siloton]

He said it in the video. Cold lamp overloads the PSU

[@hamcher]

@@siloton thanks

[@SomnathDas-ej3ve]

Is there a polarity in ac side in this board

[@power45118]

So this would not turn a dc motor, due to its high inrush current in the beginning 🤔?

[@mojojomo6750]

I've got an identical power supply, that this video inspired me to fire up and test. LED is right-way round too! What alarmed me was that a phase-tester, when touching the small heatsink on the primary side, lights up brightly. Checking when powered off, there is no electrical connection from it to anything in the circuit. Question, is this apparently 'Live' condition a result of the high switching frequency of the transistor?

[@muhammadluthfifauzan5811]

Transistor in 1947: "Exists" People before 1947: 16:16

[@bunch8]

Did you do a video on the electronic load ? Looks like a good design. Thanks for your videos !

[@DiodeGoneWild]

I didn't make a video on it, but a very long time ago I made a webpage on it. danyk.cz/zatez_en.html

[@zuliusderechter5841]

Hi, thank you so much for the schematic. Do you know what the part number on the coils are? I want to build it myself but I don't know which coils to get.Tahnks!

[@belaborbely2883]

PQ262524V4A

[@togitradinggroup2271]

I have a smart power supply that sells a lot in US market. How do I send you one for review. We have 75W - 150 or 250W versions 12 and 24V. Let me know :)

[@bashaaksema94]

I would like to see that

[@jean4756]

Good good very good i like. Tank you. Nice work

[@electronicspamore590]

i like your funny accent . it makes your videos interesting

[@alejandroperezkeogan8281]

Just a little suggestion, why don you teach us, how do you do inverse Ingenieri, it will be very helpful to us. That's