lm2596 buck converter - Page 1
Forum section: electronics / projects

author: Arcamax
author_rank: Regular Contributor
timestamp: February 05, 2015, 06:31:11 am
content: i was wondering if this was miss labeled when it said Input current: 3A(maximum). Isn't it supposed to be the output maximum 3A

author: rx8pilot
author_rank: Super Contributor
timestamp: February 05, 2015, 06:33:15 am
content: Say what?

author: Arcamax
author_rank: Regular Contributor
timestamp: February 05, 2015, 06:38:26 am
content: opps sorry thishttp://www.ebay.ca/itm/1-Pcs-DC-DC-Buck-Converter-Step-Down-Module-LM2596-Power-Output-1-23V-30V-EK-/201126191001?pt=LH_DefaultDomain_0&hash=item2ed40e1f99was this miss labeled when it said Input current: 3A(maximum). Isn't it supposed to be the output maximum 3A

author: rx8pilot
author_rank: Super Contributor
timestamp: February 05, 2015, 06:57:41 am
content: Output ripple is stated in mA?$.99 seriously?Did they steal a batch of these things?Max input voltage of 35V with a 35V caps on in/out - that is bad.

author: mij59
author_rank: Frequent Contributor
timestamp: February 05, 2015, 07:11:43 am
content: Check the data sheet of the LM2596 :Capable of 1.2V to 37V ±4% Max Over Line and Load driving a 3A load.Search the EEVblog for more info about this modules.Tested a similar module with input voltage 20V and 5V 2.95A output.The LM2596 and the freewheel diode run within 1 minute very hot ( +/- 100 C )

author: peter.mitchell
author_rank: Super Contributor
timestamp: February 05, 2015, 07:19:26 am
content: No. 3A is the rated current of the switching transistor. Thus the input current maximum.Likely fake ICs with no name brand everything else. Garbage.For the same price in about 100x units quantity you could make something infinitely better - sync rectification, lower noise, better transient response, higher efficiency, higher current output.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 05, 2015, 07:31:25 am
content: this data sheet?http://www.ti.com/product/lm2596

author: sleemanj
author_rank: Super Contributor
timestamp: February 05, 2015, 08:20:54 am
content: Quote from: mij59 on February 05, 2015, 07:11:43 am5v@2.95A is 14.75W output, these things are circa 80 to 85% efficiency, so that could be like 3.6W you could be trying to dissipate out of the switching IC, without a heatsink other than the ground plane of the board, not surprising it gets hotYou need to add a reasonable heatsink if you're going to be pushing that kind of power through them.

author: mij59
author_rank: Frequent Contributor
timestamp: February 05, 2015, 08:42:08 am
content: Quote from: sleemanj on February 05, 2015, 08:20:54 amEven with a heat sink it's a bad idea, i don't use the module to its "rated" specs.

author: MrAl
author_rank: Super Contributor
timestamp: February 05, 2015, 09:36:54 am
content: Hi,I have two of these although i got them from a different web site.I tend to like these modules, but the current rating seems too high for the heat sink area on the board, and it's just the board clad as the heat sink and the data sheet suggests a larger area. This means i would not use it as the 3 amps output but only up to maybe 2 amps.You should also be aware that trim pots are not usually made for continuous everyday use like a good quality potentiometer is, but are usually made to adjust once or twice and then leave alone forever. So if you intend to use one as a variable power supply it would be good to swap out the trim pot for a regular pot keeping leads short. Find a pot with a good rating on the number of rotations before failure.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 05, 2015, 04:42:53 pm
content: so when this says in current 3A max. What is the output currenthttp://www.ebay.ca/itm/1-Pcs-DC-DC-Buck-Converter-Step-Down-Module-LM2596-Power-Output-1-23V-30V-EK-/201126191001?pt=LH_DefaultDomain_0&hash=item2ed40e1f99

author: suicidaleggroll
author_rank: Super Contributor
timestamp: February 05, 2015, 04:49:53 pm
content: I wouldn't use that in the first place. If I was forced to, I wouldn't use it past maybe a few hundred mA. If you want a reliable product where you can actually trust the specs, then don't buy $1 shit on ebay.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 05, 2015, 04:52:21 pm
content: but this just for a phone charger

author: Arcamax
author_rank: Regular Contributor
timestamp: February 05, 2015, 04:57:26 pm
content: is this good thenhttp://www.ebay.ca/itm/18V-2-5W-Solar-Panel-Module-Solar-System-Solar-Cells-Charger-DIY-120x194mm-Mini-/361099099137?pt=LH_DefaultDomain_0&hash=item54132efc01

author: suicidaleggroll
author_rank: Super Contributor
timestamp: February 05, 2015, 04:59:58 pm
content: Quote from: Arcamax on February 05, 2015, 04:52:21 pmAnd?If it goes tits up and dumps the full input voltage into the output, what do you think is going to happen to your phone?POS Chinese knockoff phone chargers can kill people too:http://rt.com/news/168772-faulty-usb-electrocutes-woman/And many more where that came from.Seriously, I willneverunderstand this fascination with buying knockoff Chinese electronic garbage on ebay.

author: MrAl
author_rank: Super Contributor
timestamp: February 05, 2015, 05:42:21 pm
content: Hi again,I tested mine up to at least 2 amps, but ran it at 1 amp most of the time.I could test again if anyone has a question about the output current or something.I also got mine from Amazon not eBay. Mine was more money too.I got two and tested them both and they both worked, although like i said when i checked the data sheet i found the heat sink area to be too small for the OUTPUT rating of 3 amps which was stated when i bought it.We could look at the data sheet again for more info.The circuit is as the data sheet says, except i dont think they put a compensating capacitor on it and heat sink too small. It's the same as any other person would build i think, with a double sided board.I bought my first one because i wanted to try this IC chip and so i did not have to build a board. For the price i paid (3 dollars each i think) i could never build one that cheap.It looks like the genuine part, but who knows.

author: sleemanj
author_rank: Super Contributor
timestamp: February 05, 2015, 06:02:27 pm
content: Quote from: Arcamax on February 05, 2015, 04:42:53 pmIgnore what they say. For constant operation, 2A out max unless you heatsink it. Other than that, these devices work well, reliably, and cheap.two things to be aware of, some do have 50v input caps, so try and get one of those if you can, and the HV ones up to 60v are indeed sometimes fake (normal ones remarked, and will fail miserably at 60v).

author: mij59
author_rank: Frequent Contributor
timestamp: February 05, 2015, 06:02:27 pm
content: Quote from: MrAl on February 05, 2015, 05:42:21 pmIf the switching frequency is 150 kHz its probably a LM2596.If the switching frequency is 50 kHz it could be a LM2576.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 05, 2015, 06:04:17 pm
content: Quote from: Arcamax on February 05, 2015, 04:52:21 pmMy smart phone costs about $500 to replace.A common failure mode for a buck converter is to pass the Vin to the Vout - which will most likely kill your phone.The specs are meaningless if these are counterfeit parts - and there is a HIGH likelihood of that.It could fail at any time for any reason.Just because one works does not allow you to jump to the conclusion that another one will also work.Seems like an expensive way to save money and support support shady counterfeit operations.

author: Zepnat
author_rank: Regular Contributor
timestamp: February 05, 2015, 08:59:23 pm
content: I wouldn't buy any more of these 'Chinese' lm2596 they are all garbage. they are numbered lm2596 but run at 52khz. Very likely to justexplode or short circuitwhen run anywhere near their specs and have awful output waveforms. They don't have temperature shutdown and dubious current limiting.Yeah they work ok for low power but push them and they fail. Buy a true lm2576/2596 and never look back.EDIT:Forgot to say the genuine lm2576 has been indestructible and I've tried very hard to blow it up. The output current limits at 5 amps at any voltage although it says 3A in the datasheet. With 44v on the input it will output 30v at 5 A continuously.Sorry for going on and on but I've a real loathing for these fake ICs when the genuine is fantastic and makes a nice power supply which I've been using for many months.Sorry for the rant!

author: Arcamax
author_rank: Regular Contributor
timestamp: February 05, 2015, 10:25:15 pm
content: well i want around 12-18v input from solar panel and charge controller and 5v output to charge my smartphone

author: Zepnat
author_rank: Regular Contributor
timestamp: February 05, 2015, 10:54:23 pm
content: It'll do that ok. I'd run the output through a low drop out 5v regulator though as extra protection.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 05, 2015, 11:18:13 pm
content: 5v regulator... would one of my lm317t's work, i have six but can only find three(not that that matters).

author: Arcamax
author_rank: Regular Contributor
timestamp: February 06, 2015, 07:38:38 am
content: would a lm317t work as a low drop out 5v regulator, or should i try salvage one off one of my spare boards i have laying around

author: MrAl
author_rank: Super Contributor
timestamp: February 06, 2015, 02:46:17 pm
content: Quote from: mij59 on February 05, 2015, 06:02:27 pmHi,Oh so you think that they may have substituted a LM2576 for an LM2596?That sounds like a reasonable suspicion so i'll check that very soon and get back here with some results. The part number stamped on top is the 96 version, but as i am sure you know that's not a guarantee. If they both come in the same package type then it is a possibility they swapped numbers.Unfortunately it is possible that this may occur on a case by case basis, so that mine may check out ok but others buying the same product may turn out to be the older chip (2576). Lets hope they dont do that.

author: Seekonk
author_rank: Super Contributor
timestamp: February 06, 2015, 03:18:36 pm
content: OR you could put a zener on the output. Panel can't provide much current if the regulator shorts.Still spinning, these guys have you all wound up.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 06, 2015, 04:55:10 pm
content: Quote from: Seekonk on February 06, 2015, 03:18:36 pmYeaaah i dont need it to complicated than it has to be (originally intended to be more simpler, but thanks for everyones input anyways).Yeah a zener should work.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 06, 2015, 05:25:06 pm
content: ok then i think ill get these items then1-step-down dc regulater, looks ok/genuine.http://www.ebay.ca/itm/DC-DC-LM2596-Step-Down-Adjustable-Buck-Converter-Power-Supply-Module1-5V-35V-/360672163864?pt=LH_DefaultDomain_2&hash=item53f9bc78182-probably my own diy charge controller3-this solar panel,http://www.ebay.ca/itm/18V-2-5W-Solar-Panel-Module-Solar-System-Solar-Cells-Charger-DIY-120x194mm-Mini-/361099099137?pt=LH_DefaultDomain_0&hash=item54132efc01(try the ones i have again first). it doesn't matter what buck converters input current from solar and controller does it, the panels i have now are low? mine supposed to be 80mA(max i think)4-zener in case of failure.

author: Kalvin
author_rank: Super Contributor
timestamp: February 06, 2015, 05:41:00 pm
content: Quote from: Arcamax on February 06, 2015, 05:25:06 pmIt would be a good idea to add a fuse, which will blow if the zener starts conducting. Maybe a resettable fuse will do.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 06, 2015, 06:26:00 pm
content: Quote from: Kalvin on February 06, 2015, 05:41:00 pmi dont know, maybe

author: Seekonk
author_rank: Super Contributor
timestamp: February 06, 2015, 09:41:15 pm
content: Fuse is an example of a suggestion that sounds logical at first but doesn't make sense when you think about it. One panel that was quoted was 180ma. If the buck converter is working properly, it can supply a half amp to the phone at 5V. Should the converter short out, less than 200ma would go to the zener. The fuse protects nothing.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 07, 2015, 12:38:56 am
content: how many mA minimum do you think would be required to charge my galaxy s3

author: rx8pilot
author_rank: Super Contributor
timestamp: February 07, 2015, 01:08:02 am
content: If you give a Galaxy S3 5v, it will slow charge at <500ma. if you have the controller or voltage divider setup on the data pins, it can go up to 2000ma, but more typically about 1400ma for a fast charge.I use the MAX14667 that works with Apple and Galaxy tablets to charge at full current.

author: DanielS
author_rank: Frequent Contributor
timestamp: February 07, 2015, 06:03:09 am
content: Quote from: suicidaleggroll on February 05, 2015, 04:59:58 pmYou can buy cheap electronic junk from China from Amazon, Best Buy, Future Shop, NewEgg, corner electronics shop, etc.Cheap Chinese junk is everywhere.The phenomenon is fairly understandable IMO: buying the official AC adapter for your phone/tablet costs $20-30 for a device that has maybe $4 worth of parts in it for a proper implementation while the Chinese knock-off costs $4 and contains $3 worth of parts. Of course, that is no excuse for criminally bad design where the device might be an imminent fire or shock hazard and a simple re-layout might have prevented the issues for $0.00. Mike and others have done tear-downs of cheap line-powered Chinese stuff and the PCB layouts often look like they have been done by someone with no clue about what the differences between 5V and 170V or 100mA and 10A are.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 07, 2015, 06:14:06 am
content: Quote from: DanielS on February 07, 2015, 06:03:09 amyeah i know... (what is IMO)

author: DanielS
author_rank: Frequent Contributor
timestamp: February 07, 2015, 06:31:39 am
content: Quote from: Arcamax on February 07, 2015, 06:14:06 amIn My Opinion

author: Arcamax
author_rank: Regular Contributor
timestamp: February 07, 2015, 07:27:41 am
content: so if i put another heatsink on this regulatorhttp://www.ebay.ca/itm/DC-DC-LM2596-Step-Down-Adjustable-Buck-Converter-Power-Supply-Module1-5V-35V-/360672163864?pt=LH_DefaultDomain_2&hash=item53f9bc7818does it go on the back side.

author: Seekonk
author_rank: Super Contributor
timestamp: February 07, 2015, 10:08:51 am
content: I grind down the pot leads and put a little tape over them. Then you can glue down the board to some metal. Then you can glue a heatsink to the top of the chip. That board is a little better than others because it has all the vias under the chip. Try as you will that only slightly improves the capability. The board is a thermal insulator and you are dealing with transfer rates not much better than air. The limiting factors are the diode and the inductor. And the coil will loose half its inductance when it heats up. It is what it is. Don't use it for more than a half amp.

author: Kalvin
author_rank: Super Contributor
timestamp: February 07, 2015, 10:19:42 am
content: Quote from: Seekonk on February 06, 2015, 09:41:15 pmThis is valid argument, until the panel is replaced with something more powerful. Fuse is quite cheap protection and Plan B when everything else fails.

author: MrAl
author_rank: Super Contributor
timestamp: February 07, 2015, 04:04:52 pm
content: Hi again,Some measurements on my unit turns up some interesting information.First, but dont jump to conclusions yet, the ripple frequency has its major harmonic (fundamental) at 58kHz. This is far from 150kHz, but the device is trying to switch three times during one major cycle, so it could be the right chip LM2596, but more about that. It could also be the LM2576 trying to switch more than one time during the major cycle. The reason for this problem looks like the output capacitor has an ESR that is far too high for a regulator of this type, so it could be that the feedback circuit is sensing a voltage which would lead to another switch cycle but as soon as it turns on it senses it should end the cycle right away, and so shuts off again.It's hard to tell for sure, but the one thing for sure is that the ripple is definitely very close to 58kHz and the scope was calibrated with a very accurate frequency standard before this test. The lowest possible was 57kHz.The waveshape indicates that the ESR of the capacitor is somewhere around 0.25 ohms, which is far too high for these kinds of regulators.Also, the regulator gets warm at 1 amp output but not hot by any standard.I could try a lower ESR on the output and see if the waveshape indicates a 150kHz major component, but i dont know if i will get to do this or not, and it has to be with short leads too.So the bottom line after doing the tests was that the ripple frequency is closer to 60kHz than it is to 150khz, so it could very well be the older part with a changed number. I cant say for sure yet though because the output cap they used is not as good as we would like to see. The output ripple at only 1 amp is 0.4v peak to peak, which is kinda high too, suggesting a high cap ESR also.The other thing though is that it does in fact work, and provide an output as a buck converter would do, and it seems to do it pretty well. It's just not as well as we would get with 150kHz. Still very useable though for non critical applications.If it was an LM2576 that would also easily explain why there is no compensation capacitor anywhere to be found on the board.Looking at the two data sheets, both chips come in the TO263(S) package.Also, there is a series protection diode on the input to help prevent damage from input reverse connection. This can be shorted out for higher efficiency, with the obvious added risk.Just for reference, the inductor is 33uH and the output cap is 220uf. The input also has a 200uf cap. Both caps rated (or at least stamped) for 35 volts.If anyone can think of another simple test let me know and i'll try to do it ASAP.

author: MrAl
author_rank: Super Contributor
timestamp: February 07, 2015, 05:02:50 pm
content: Hello again,Ok after my previous post with some of the specs and some speculation about what is going on here, i decided to connect a 1000uf low ESR cap to the output. The waveform cleaned up pretty well. Just one problem, it's showing a frequency of 57kHz to 58kHz. There's almost no question now, it's not an LM2596 but rather an LM2576. It is stamped with "LM2596" however, so it is either a fake or a mismarked part that was let through production, or picked up by a second party for use in equipment even though it's not marked correctly.Just to note again, the LM2596 switches at or near 150kHz while the LM2576 switches close to 50kHz. The 96 part would provide better output ripple with smaller components.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 07, 2015, 05:20:46 pm
content: Quote from: MrAl on February 07, 2015, 05:02:50 pmyeah ok thanksim using this one now (thought i would look for a input 50v caped one instead)(make sure i got a good one).Don't know if it matters for your tests or not but anyway thanks.

author: MrAl
author_rank: Super Contributor
timestamp: February 07, 2015, 07:37:26 pm
content: Hi there,Yes very good idea, i'll have to try that too. They use the same type cap on input and output.Maybe you can test your frequency too.Note that there may be boards that actually have the right chip, but i would have a hard time believing it now that i have seen this first hand.They do work however, even if a 'lowly' LM2576, so they are still useful.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 07, 2015, 09:10:58 pm
content: i dont think i have any equipment to test the frequency.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 07, 2015, 09:16:41 pm
content: :)i hope this one i ordered is like those green board pictures and not that blue board.

author: dannyf
author_rank: Super Contributor
timestamp: February 07, 2015, 10:21:43 pm
content: QuoteMine (a genuine knock-off) works at 155Khz.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 08, 2015, 02:46:35 am
content: Quote from: dannyf on February 07, 2015, 10:21:43 pmwhere did you get yours

author: radioFlash
author_rank: Regular Contributor
timestamp: February 08, 2015, 02:47:00 am
content: Mine runs at 150Khz. They're useful for driving LED strings. I test it at the expected load and check the temperature of the chip and inductor.I got mine in 2012 from here:http://www.ebay.com/itm/5PCS-NEW-LM2596-DC-DC-adjustable-power-step-down-module-/130704328176?Here's what the output of mine looks like.Input: 10 VOutput: 4.8V into a 10 Ohm resistive LoadBoth channels AC CoupledYellow: Output from Pin 2 of the LM2596Blue: Output at load, 100mV p-p ripple

author: jarrodhroberson
author_rank: Contributor
timestamp: February 08, 2015, 04:31:58 am
content: I have been using these very successfully for converting 9V batteries to power my 5V projects.They make the batteries last way longer and work great in 12V to 5V situations like adding a USB charger port in the back of my car.I would not try and pull any kind of real Amps through something like this but for microcontroller projects they are awesome and the price is right!I got 10 for $11.98 shipped! I do not think plain old 5V voltage regulators would be much cheaper!http://www.ebay.com/itm/10-pcs-DC-DC-LM2596-Step-Down-Adjustable-Converter-Power-Supply-Module1-3V-35V-/301120877446?hash=item461c33f386These have started popping up and are getting good reviews, they are much smaller and lighter for what I am doing, size and weight counts. So I got a handful of these to test out as well.http://www.ebay.com/itm/10PCS-3A-DC-DC-Converter-Adjustable-Step-down-Power-Supply-Module-replace-LM2596/400571751111All the ones I have used have tested out to spec so far.

author: Seekonk
author_rank: Super Contributor
timestamp: February 08, 2015, 09:27:37 am
content: Quote from: Arcamax on February 07, 2015, 09:16:41 pmThere must be something to it. When someone would call up with a car problem they would always ask what color the car was. As a manager once told me....The optics of a project are everything.

author: dannyf
author_rank: Super Contributor
timestamp: February 08, 2015, 10:25:57 am
content: Quoteebay, a couple years back.I have another that's more recent (over the last 6 months). I will test it when I find out where it is,

author: MrAl
author_rank: Super Contributor
timestamp: February 08, 2015, 03:31:01 pm
content: Hello again,Thanks for the pictures and notes from you all.I see now that there is a lot of variation in the product here. There are at least three different boards i have seen now. Mine does not have the compensation capacitor, while the ones on eBay in the link previously in this thread does have that capacitor. The capacitor is for compensation for certain operating conditions.I see the waveform too posted by RadioFlash (thanks), and mine is not like that. It is much slower, so i guess the chip i have is a fake, that's the only explanation. It is marked LM2596 and JM24RP, but it cant be that chip.

author: Arcamax
author_rank: Regular Contributor
timestamp: February 08, 2015, 05:58:40 pm
content: Quote from: Seekonk on February 08, 2015, 09:27:37 amIf your saying i should have checked/asked what it was, then yeah i should have done/thought that. wasn't thinking lol.http://www.ebay.ca/itm/DC-DC-LM2596-Step-Down-Adjustable-Buck-Converter-Power-Supply-Module1-5V-35V-/360672163864?pt=LH_DefaultDomain_2&hash=item53f9bc78185 out of 6 pictures are actually a green board but one blue, so it should be good

author: electrophiliate
author_rank: Regular Contributor
timestamp: February 10, 2015, 02:43:16 am
content: I have several of these cheap buck converters with the IC marked "LM2596S".I got these from here about a year ago:http://www.ebay.com/itm/3pcs-LM2596-1-23V-30V-Output-DC-DC-Buck-Converter-Step-Down-Module-Power-Supply-/400516985374So I did a brief test to compare with the results in the post by .Input: roughly 13V from SLA battery.Output: 5.00V into 100R and 10R loads.Both channels are AC coupled.Ch1 (yellow): pin 2 of the alleged "LM2596S".Ch2 (blue): output ripple.Mine are generally only running at about 56kHz, the ripple is comparatively much worse, and there is ringing on pin 2 (presumably indicative of discontinuous mode).See attached images below.I also have a few of the much smaller buck modules mentioned by , from the same supplier as in my previous link:http://www.ebay.com/itm/2pcs-DC-DC-4-5V-28V-to-0-8V-20V-Step-Down-Module-Power-Supply-Brand-New-/370965365951I did not want to spend too much time on all this but those performed much better than the bigger modules.With a 10R load at 5V output the ripple was under 50mV and the waveform suggested a switching frequency of 1MHz as claimed in the link posted by .

author: akis
author_rank: Frequent Contributor
timestamp: February 10, 2015, 08:15:34 am
content: Quote from: Arcamax on February 05, 2015, 06:38:26 amBe very very very very careful with these. I have bitter experiences with the bigger brother of the LM2596 the LM2679. When it blows, and it does, and I have blown a few, 50% of the time it goes closed circuit and lets the full input voltage to the output. Then you also fry everything downstream.In particular with these ebay LM2596 boards, I have used a lot, and have fried a lot, and those fried were mounted and working happily inside a closed box, and one day they decided they had enough. I did not draw anywhere near 3A from the output, more like 0.5A if that.

author: electrophiliate
author_rank: Regular Contributor
timestamp: February 10, 2015, 08:20:51 am
content: Quick update. Another capture of the "LM2596" (LM2576?) based buck converter modules described in the previous post.This time with a 2A load, which resulted in a minor voltage drop (I did not look at the transient response just a DMM), and quickly heated up the non-heatsinked IC.See attached image. Looks like it in now in continuous mode so the previous ringing is gone. Ripple is about the same as with the 10R load (500mA).[edit 1: It did not like that test and no longer wants to put out 2A @ 5V but still seems to work OK for lighter loads.][edit 2: It seemed to recover overnight and behaved better today and took at least 10 minutes of punishment but became hot.][edit 3: Updated the attached capture.]

author: Arcamax
author_rank: Regular Contributor
timestamp: February 11, 2015, 07:45:02 am
content: Quote from: akis on February 10, 2015, 08:15:34 amQuote from: electrophiliate on February 10, 2015, 08:20:51 amok so then should these good for 5volt and ~500mA output?

author: Kjelt
author_rank: Super Contributor
timestamp: February 11, 2015, 08:33:27 am
content: Use them for critical applications in a two stage design with failsafe. So for instance you have 18V input and want 5V output, let the 2596 do the 18 to 8V stepping down followed by a traditional 7805 do the 8 to 5V. Monitor the 7805 input if its higher then 10V shut the ps down.

author: electrophiliate
author_rank: Regular Contributor
timestamp: February 11, 2015, 12:20:36 pm
content: Quote from: Arcamax on February 11, 2015, 07:45:02 amYeah, that should be OK, but I would be reluctant to use them for critical applications, but  suggested a failsafe workaround in the above post. I have a handful of different cheap modules from Ebay but have never really used them much or left them running for long periods of time, so my experience with them is limited.Today for a test I let it run at 5.1V 510mA for 30 minutes and it seemed OK and the IC was only warm to the touch.I think I might order some genuine LM2596-ADJ and LM2576-ADJ ICs to build a few circuits and compare the performances with these cheap modules.

author: MrAl
author_rank: Super Contributor
timestamp: February 11, 2015, 12:31:51 pm
content: Hi,I am now reading around the web that other people have had problems with these regulator boards too. Not just this one, but with the LM2596HVS where the input is allowed to go up to something like 60 volts. The genuine chip takes 60 volts input no problem, but the fake HV version chip blows out at around 45 volts input. So there is clearly a difference and some fake chips floating around. Where they came from and how they worked their way into the parts stream is unknown at this time.I have had very good luck with the LM2576 TO220 package, building the entire circuit from scratch myself. I've built them on a regular PC board etched just for that circuit, and also on those little 2x3 perf boards with the dip patterns etched on them from sources like Radio Shack, wired by hand with small 22 gauge jumper wire. They all work just as expected. One had a 15v 1 amp output for use with a flat bed scanner.Someone suggested that i treat one of my 'fake' boards as a faulty circuit and just start replacing parts to see if the problem goes away with brand new parts. I have to wonder if a cheap inductor would cause this too if it saturates. It's not as likely now though, now that i have seen the fake HV version blow up. I guess it is worth a shot though. Swap out the inductor with a better quality unit first.

author: Seekonk
author_rank: Super Contributor
timestamp: February 11, 2015, 03:00:37 pm
content: I think many of the problems relate to relying on the on board capacitors alone. These are for localized use only to prevent the circuit from oscillating. They are of dubious quality chosen on cost and unlikely to handle ripple currents long term. Always parallel other capacitors with these for reliability. If that capacitor opens up, the chip will likely destroy itself in short order.

author: Zepnat
author_rank: Regular Contributor
timestamp: February 12, 2015, 11:01:40 pm
content: These findings are the same as mine. The fake IC is total garbage for anything other than light work.Please test a genuine lm2576. I blew (exploded) 20 fakes while the genuine one isstill working fine.

author: Saronni
author_rank: Contributor
timestamp: February 26, 2017, 04:25:17 am
content: I'm adding my LM2596 module story to this thread for the benefit of anyone searching the archives for these modules.I too picked up several modules with suspected "fake" ICs in June 2016 from this ebay sellerhttp://www.ebay.com.au/usr/shieldsfans. While the IC is clearly marked LM2596 it is only switching at 54kHz. In the scope picture below the yellow trace is the AC coupled ripple on the module output and the blue trace is pin 2 of the "LM2596" (also AC coupled).