X̶L̶6̶0̶0̶9̶ LM2577S-ADJ CC/CV SEPIC module (A.K.A. LM2577 CC/CV boost buck converter)

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Barkuti
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X̶L̶6̶0̶0̶9̶ LM2577S-ADJ CC/CV SEPIC module (A.K.A. LM2577 CC/CV boost buck converter)

Bought a couple of these recently:

 

https://www.aliexpress.com/item/LM2577-Automatic-Boost-Buck-Converter-4-35V-to-1-25-25V-CC-CV-Voltage-Regulator/32692428892.html

All of this “chip reference mangling” sucks imho

They're on the slow jet boat coming home. According to this XL6009 datasheet @ Sunrom it seems like the board is using a SEPIC topology very close to the reference one listed (I have not fully checked it).

Anyone using them?

My plan for one of them is to drive a 4S emitter chain (2 quad boards with 2P LH351B emitters in series with an LH351D each) at up to 1.5A, being fed from an AC transformer with 13VAC effective output + diode bridge + 4400µF of capacitance. Hope it works good.

 

Cheers Party 

Edited by: Barkuti on 05/10/2019 - 07:06
Lightbringer
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Wtf’s with the red/green charging indicator and other stuff? Sounds more like a battery charger…

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Kame Sennin
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Lightbringer wrote:
Wtf's with the red/green charging indicator and other stuff? Sounds more like a battery charger...

 

Even if they are frequently advertised as battery charger, the end of charge detection on CC/CV dc converters like this one usually doesn't do more than lighting the led so they can be used for any other purpose.

They are very handy as (bulky !) one mode led driver with good efficiency and easily ajustable current.

One thing to be careful though is that the current sense resistor is usually tied on the negative output so beware not to short it to ground

 

Lightbringer
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Unno, I got just regular boost modules. Settable Vout ≥ Vin + 2V or so. No weirdness on the output end or anything.

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Barkuti
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Just read the SEPIC Wiki article a bit. The XL6009 integrates an up to 4A rating switching MOSFET, however the output schottky looks stingy, maybe a 3A SS34 or so. For the love of god the smaller and cheaper XL4015 buck modules carry 5A schottkys now, what gives? Also, the article emphasizes the diode must be super fast switching, is every schottky a super fast switcher?

Two beefy surface mount ceramic capacitors can be seen in the middle as C1:

 

 

Once I get it I'll know what the fuss are they actually shipping on the board, of course.

By the way, replacing the current setting trimpot with a logarithmic taper potentiometer allows easy and handy light output adjustment. Successfully tried it in XL4015 modules already.

 

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Question to Kame Sennin or whoever knowledgeable, I am thinking in limiting the maximum current output somehow to match input power or power handling limitations. The most obvious way I see would be to briefly check maximum output current by measuring voltage drop at the sense resistor with the current potentiometer pedal to the metal with a short-circuited output or some small load, then swap the sense resistor value with a bigger one to fit my maximum current output needs. I also thought in messing with the potentiometer by installing some resistor in series with it at one of its terminals, does this makes sense? 

Lightbringer, how about the Tian Mu grey goo thermal glue plus copper filings fruitcake? Big Smile

 

Lightbringer
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Barkuti wrote:
Lightbringer, how about the Tian Mu grey goo thermal glue plus copper filings fruitcake? Big Smile

Nothing new as far as tracking info since February(!).

Queried the guy, who just extended the due-date from April into May, and now a week later I said screw it and put in for a refund.

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Kame Sennin
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I don't know that particular board but if it's like the similar buck either should work.

Personnaly i would rather add a resistor close to the potentiometer than messing with the sense resistor that might as well be a simple wire or pcb track

Would you mind explaining why you choose to use a buck/boost ? When power source is a battery the voltage range might lead to that choice but here you seem to be using a supply from mains.

Lightbringer
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Yeah, that’s the ‘S’-shaped pcb trace that senses current. Nb the very very thin trace to the solder-point which wiggles its way back to the sensing circuit, too. No chip-resistors here! LOL

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I have used one like it with the XL6009. It’s generally limited to around 4-5 amps (I wouldn’t go over 30-40W depending on the voltage). It’s a general purpose DC-DC buck module and you can set the current limit with the trimmer all it is good for driving led or use it for charging batteries, etc anything needing a CC/CV power source. I used it to run an xhp50.2 6v off a 3S pack. I got 3A at 6.5V before I quit because the thing had no heatsink and the inductors were getting hot. If you have some little heatsinks, stick on the mosfet.

Here’s a pro tip, like pretty much all cheap Chinese electronics, do not hook it up reverse polarity on the input. It will release the magic smoke!

Kame Sennin
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@Sirstinky : Are you sure it's a buck module ? (or maybe when you say buck you mean "switching converter" ?)

Would make no sense to have two inductors and a serial capacitor as seems to be here for a buck while that's typical for non-coupled-inductors sepic

Sirstinky
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I call it a buck module or converter, but yes, switching converter is the proper terminology.

Barkuti
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Wow too bad Lightbringer (concerning the Tian Mu grey goo), maybe you should have selected some sort of tracked shipping. I myself do select it way more often now, although I understand the thrill of getting ludicrously cheap stuff.

Pssst! I recently ordered this: https://www.ebay.com/itm/282581779776

Yikes! Yes that is ten pieces USB micro-B to type-C adapters for $1.51/$1.60! Big Smile

Kame Sennin wrote:

Would you mind explaining why you choose to use a buck/boost ? When power source is a battery the voltage range might lead to that choice but here you seem to be using a supply from mains.

My input power supply will be hand made with an AC transformer plus diode bridge plus capacitors. I plan on allowing up to 1.5A of current to the emitters in series, this is P = V × I = 13V × 1.5A = 19.5W which, at ≈85% converter efficiency, equals ≈23W of power from the supply. According to the following calculator (changpuak.ch):

 

 

I have inputted some undershot/overshot figures for safety/reliability reasons. My transformer's actual output voltage is above 13VAC, but I have chosen a 12V figure. Since P = V² / R → R = V² / P = 144V / 23W = ≈6.261Ω load average. Yes I know the module is not a linear load but it should work pretty nicely given the capacitors. I will also use slightly bigger capacitance at the bridge's output, +10% at least.

With all of this I want to make sure the minimum input voltage at the module is always high enough for everything to work correctly, this includes the current regulation logic which at least needs close to 6.5V according to my experience with XL4015 modules.

 

Cheers Smile 

Barkuti
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Sirstinky wrote:

Here's a pro tip, like pretty much all cheap Chinese electronics, do not hook it up reverse polarity on the input. It will release the magic smoke!

Yes I Big Smile know! I once tested that in one of these: https://www.ebay.com/itm/1-2-5-10Pcs-Lithium-Charger-5A-CV-Buck-Step-Down-Power-Supply-Module-LED-Driver/191993567480

It made a loud noise tiny firecracker style upon blowing up, scared me LoL! Big Smile

Heck, there is an electrolytic cap straight at the input. What could I expect protection wise? 

 

Cheers Party 

Sirstinky
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Barkuti]<p>[quote=Sirstinky wrote:

Here’s a pro tip, like pretty much all cheap Chinese electronics, do not hook it up reverse polarity on the input. It will release the magic smoke!

Yes I Big Smile know! I once tested that in one of these: https://www.ebay.com/itm/1-2-5-10Pcs-Lithium-Charger-5A-CV-Buck-Step-Down-Power-Supply-Module-LED-Driver/191993567480


It made a loud noise tiny firecracker style upon blowing up, scared me LoL! Big Smile


Heck, there is an electrolytic cap straight at the input. What could I expect protection wise? 


 


Cheers Party 

[/quote

There is no protection aside from that diode near the positive input. I have a 150W boost converter that has a 10 or 15 amp automotive style fuse on the input! I don’t think I’ll kill that one. Overkill? The last victim was a power bank kit and accidentally reversed the polarity. The switch mode power IC started cracking and went up in smoke within seconds. You get what you pay for I guess.

Barkuti
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Your quote got messed due to a missing ending square bracket, Sirstinky. Wink

Diode at the input low side (negative, not positive). I see. If that is so I will remove it and bridge the path since there it reduces efficiency. Then I will reflow it side by side with the output one. This will net me a small increase in overall efficiency. Thanks.

Protection is only needed when there is some risk of clanger somewhere. No clangering, no need for protection hurdles. Big Smile

 

Party 

Sirstinky
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Oops! I’m typing on the phone so it gets wonky sometimes. That’s a good idea to get more efficiency out of these converters.

Barkuti
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Please edit your post and fix it Sirstinky (click Wink here if you will), add the closing bracket at the end of line 15 where you will find:

<p>Cheers ^:)&nbsp;</p>[/quote

 

If those schottky diodes are SS34s I'll probably remove them both and install a slightly different package SK54 or SB1040 at the output. Then I could use that SS34 pair to improve the current 2x SS34 + 2x SS24 bridge rectifier I made a year or two ago for testing with the transformer. Big Smile

 

Party 

Thu, 04/25/2019 - 10:49

Lightbringer
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Wellp, just for s&g I pulled the trigger on a few of these. Might work nicely for a desk light, if it dials down to 200mA but can also go up to 2A or so.

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Barkuti
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In my experience with XL4015 CC/CV buck modules they can dial down as much as you want Lightbringer, firefly levels or even lower. It is very important to use logarithmic taper potentiometers for this because we're adjusting perceived brightness out of drive current.

 

Lightbringer
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Yeh, you don’t want it to ramp like a RJ02… LOL

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Lightbringer
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When (if?) you get yours, lemme know if it’s true buck/boost. The 2577, well, I’ve only seen in plain boost config with a single inductor, and you’d need an actual transformer for buck/boost. Or, you end up with negative output from positive input (and both these grounds are in common and imply positive/positive).

And if you look at that .pdf, all the sample circuits have 12V-16V input for 18V output. And the only SEPIC circuits in there use transformers, not plain inductors.

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Barkuti
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The converter's topology looks like this one found in the manual, so I think it's buck boost no doubt.

By the way, a transformer basically are two coupled coils. An XL6009 can handle its coil pair for it to operate like variable transformer, or so I think.

Yeah, we'll see.

 

Smile 

Lightbringer
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But there’s zero coupling between the two coils.

Unno, maybe they’ve got some trick circuit that lets it be a buck/boost, but…

Like I said, when (if) I get mine, I’ll put it to the test. Would actually be nice if it were a true b-b. Lots lots lots more flexible for the stuff I could do with it.

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SEPIC doesn’t require coupling between the coils, although you can often reduce the space taken up by the coils if they are coupled (which increases their effective inductance) and thereby build a smaller conversion module.

See here:

http://www.simonbramble.co.uk/dc_dc_converter_design/buck_boost_converte...

and scroll down to “Using a Transformer”.

As usual with inexpensive Chinese modules, the simplest way to find out is to buy one and see what it does Smile

Lightbringer
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Wellp, mine are currently (haha, get it?) in “pre-shipment”, so maybe by June…

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Barkuti
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My modules were shipped already. It is a good thing that Correos (main Spanish postal operator by far) reached an agreement with Sinotrans Limited a few years ago, I can choose Ali Saver or Ali Standard and the majority of times this means Sinotrans - Correos which comes home quite fast.

I'll be able to take a quick peek at the modules next week. Wink

 

Smile 

Barkuti
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Well, a little faster than expected:

 

 

So it matches the title well, it is based on an LM2577-ADJ integrated circuit. The board layout is a little bit different, namely at the switcher's leads for obvious reasons. Whether it is buck boost or not it a mistery is to me until I try it with my PSU, but it should.

 

Smile 

Lightbringer
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I just got mine yesterday, too. Didn’t mess with them yet, though.

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Barkuti
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Underside pictures. Notice the current sense track, right at the voltage trimpot's feet.

I've quick tested one. Fed with 7.24V from my PSU I've been able to adjust the output all the way up to 26.9V, and all the way down to 1.237V according to my Bside/Zotek ZT102 multimeter. Voltage adjustment is sort of logarithmic, took a lot of turns down from 3V. Hence, whoever devised this module knows something. Wink

 

Barkuti
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The unmarked chip next to the 78L05 regulator must be an LF351 or LM351 amplifier for the current sense thing. Compared to other modules this thing is using a quite low resistance current sense track, like 10mΩ or so.

 

Party 

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