LM2577 DC-DC step-up converter module

[ontheset]

I got this of ebay. I'm using a AW 18650. Its suppose to boost up (i think).
Off load it works fine but when i put a atty on it gives me 3.2 steady reading.
Did i get the wrong part for a mod?

 

[TomCatt]

Do a search here for LM2577. I built a mod using a similar LM2577 module. I was able to get up to 4.9V under a 3.2 ohm load using a 'non-IMR' 18650.

What ohm atty/carto are you using?

If you're interested in 5V vaping, eBay has a '3V to 5V 3A' boost module which seemed to work OK. Search here for '3-2-5' for a mod I made with it.


Sent from my iPod touch using Tapa-tapa-tapa-tapatalk

 

[ninjaguy]

Hello,the LM2577 is made by National Semi which was purchased by TI.You can find the datasheet @ http://www.ti.com/lit/ds/symlink/lm2577.pdf.There is a possibility that the battery voltage might be a little lower then expected and the switcher might not turn on properly. According to the datasheet the device will take an input voltage as low as 3.5V . That should give you enough range to use up most of your Lithium Ion battery. Depending on the anode material used the useful voltage range fluctuates a little but nominal voltage should be around 3.6V to 3.7V. Fully charged voltage should be 4.2V or so.If we assume the switcher is working properly hook up a voltage meter on the output and try adjusting the multi-turn trimpot (the blue thing) until you get the desired voltage.

 

[ninjaguy]

Oh also,the undervoltage lockout is listed as 2.9V. Check out the Vin and see if it dips below that voltage. It is possible that it dips when the switcher is initially turned on and it turnes itself off. If you have an oscilloscope hook it up to the input side and trigger on the falling edge of the input signal and see how far it dips.If I were you I would hook it up to a stable 5V power supply (from lets say an old computer power supply) and see how it behaves.

 

[jhonutz]

it`s not good lm2577 for mods. have a lot drop down voltage under load.

 

[ontheset]

Yea, I figured as much....I got 2 and I dont know what to do with them now.

 

[jhonutz]

try to use step down convertor with 2 batts stacked, much better..Personal i don`t have good impression about booster. Or don`t works or works acceptable but it`s big module and under 2 ohm not works good.

 

[ontheset]

Actually I have made a lot of 04050 boost mods based on breaktru's mods.
I thought mayby this could be a cheaper way, but was wrong.
The thing that I wonder is y does it work without load. It actually goes up to 25V and some, but as soon as i put an atty on it regulates it at 3.2V steady, cant change a thing. Weird.

 

[CraigHB]

According to the specs for the controller, it "should" be able to output around 10W. If you try to ask more than that from it, it will go into shutdown which results in an output of battery voltage less about a half volt due to rectifier losses. Boosters do that. Unlike a linear regulator or buck converter, they go home to battery voltage when things go all to hell.

Your booster could be hitting the switching limit on current prematurely or just destabilizing. Switching converters destabilize when there's an issue either with a component or in the design. Most simply, that means they fail to control output voltage properly. Hard to say why you're seeing poor output performance off-hand, but it could be due to some issue with the design or possibly a faulty component.

 

[ontheset]

But on both of them? They act the same exact way.