Buck Boost module hack?

Hi,

I need a Buck Boost converter to power my Arduino and projects so that I can use any kind of power source to run my projects.

I came across these cheap LM2577 based and XL6009 based Buck Boost converters like the ones in the picture. |500x375

However these modules have a minimum input voltage of 3v and 3.5v respectively. I want them to boost starting from 0.9v so that even a single AA battery can run my projects.

Is there anyway to modify these modules to boost from such a low voltage? maybe changing some component?

Or can you suggest me a decent Buck Boost module that takes input starting from 0.9v and has a 3A capabiltiy? I need them to be Buck Boost because I need an all in one power supply so I can also supply 19v into it sometimes or maybe even higher.

:)

1v-to-5v-dc-dc-step-up-converter

That module doesn't have Buck (step down) capability.

That module doesn't have Buck (step down) capability.

Well then you're out of luck, unless you want to put a buck converter between the stepup and the load.

Noobian: I need them to be Buck Boost because I need an all in one power supply so I can also supply 19v into it sometimes or maybe even higher.

What you want is possible but its asking rather a lot to expect it to be chinese cheap.

I think you need to post your Design Criteria. It’s getting too complicated to follow.

Yes.

This approaches what you need .

http://www.ebay.com/itm/DC-DC-Adjustable-Step-up-boost-Power-Converter-Module-XL6009-Replace-LM2577-/371054648639?hash=item5664949d3f:g:nx0AAOSwGvhUJ3NQ

Note however that at lower voltage the available power drops considerably Its possible to have high power from low voltage but the circuit has to be designed for it and is not suitable for the higher voltage ranges.

A 20 to 1 input range with very low voltage as well is asking an awful lot.

0.9v input voltage is asking a lot - they exist, though often with lower current specs… but those are generally boost converters - converters that go both directions are significantly more complicated and more expensive. They’re often a buck converter on the output of a boost converter, though the SEPIC topology is also not rare - note that either way, it’s 2 inductors. There’s a strong incentive for designers to stick with converters that go in one direction only.

So with that in mind, a converter with a 0.9v input voltage and the ability to do buck as well as boost would be strange indeed.

Your design criteria cry out for a separate buck converter connected to the external power input…

Boardburner2: Note however that at lower voltage the available power drops considerably

DrAzzy: 0.9v input voltage is asking a lot - they exist, though often with lower current specs....

I wouldn't mind lower current output when boosting from such a low voltage. I mentioned the high Amp rating for the chip because I didn't want it to explode if I input 19v 3.2A from a laptop charger. Anyways the project is gonna use 1-2W only, so "raschemmels" boost suggestion was a good idea but it didnt do buck.

Your design criteria cry out for a separate buck converter connected to the external power input...

I might consider that if it's not possible to modify/hack existing Buck Boost to accept low voltages.

Anyway, According to your suggestion is it possible to input to both seperate buck and boost from a single dc jack and then output at a single USB port? How will these converters decide which one gets to do the conversion?

My project is like ( Different types of power sources------> Step up/Step down------>Arduino )

You would have to use a different socket for 1S battery pack and the 19v charger, I think (at least without getting very fancy) - I think you’d have the low voltage coming into a boost converter, output of that into a schottky diode to the input of a second DC-DC converter, with the 19v input going right through a schottky diode and into that DC-DC converter.

To “hack” a buck/boost converter to accept a lower voltage, you would need to replace the switching regulator (that big black IC) with one that worked off a lower voltage and was pin compatible (since it’s layout sensitive - you can’t put in a different controller with a different pinout connected via wires; DC-DC converters need the high current path to be physically short). The thing that becomes hard at low voltages is that not only is higher input current needed, but you have less voltage available to operate the fet inside the switching regulator.

raschemmel: I think you need to post your Design Criteria. It's getting too complicated to follow.

I agree , do you really need the ability to work at such a low voltage.

A lithium cell with a sepic convertor will give just about anything you need.

Circuits which use single 1.5V cells for a supply tend to be application specific.

EDIT

If i had to do this i think i would use separate converters with voltage sensing and current steering transistors.

I might consider that if it's not possible to modify/hack existing Buck Boost to accept low voltages.

The fact that you would think it might be possible indicates you know more about talking about hacking and less about doing it. (ie: electronics)

It's a no brainer that if you start with 1 V and connect that to a stepUP converter, then you are in a position to connect that to a stepDOWN converter to get to where you want to be. Hacking a factory made converter with no documentation is just crazy. You can "hack" them to the extent of adding an external voltage to control the output with a uP but changing the input voltage minimum is a whole different ball game.

raschemmel: Hacking a factory made converter with no documentation is just crazy. You can "hack" them to the extent of adding an external voltage to control the output with a uP but changing the input voltage minimum is a whole different ball game.

We have the documentation. OP may not be well equipped to interpret it, as he's clearly new to electronics and DC-DC converter design isn't easy, but the datasheet for the chip is available, and you can trace out the circuit. The design of those cheapo buck/boost converters modules is largely cribbed from the application notes, some of which even recommend a layout. But you end up staring at the key part's minimum input voltage spec, and it's not low enough for you. Here the limiting factor is the LM2577 or XL6009 or whatever is filling that role (note that those are spec'ed for 3.5 and 5v minimum respectively - the chinese vendors selling them claiming they accept a wider range are relying on the parts working well enough outside their manufacturer specs) - at that point, unless there's a drop-in replacement that is will work, you can't do anything.

There's more potential to "hack" the bigger ones that use several IC's and external fet switches, but that's also a bigger deal, since you now have a more complicated circuit that you need to trace out and interpret, and more datasheets to study - which is something that you're probably not ready for.

So I guess modifying it is out of the question.

do you know any modules that accepts such a low voltage? I tried aliexpress and couldn't find one. Although they have Boost only converters that take 0.9 volts and up.

t’s a no brainer that if you start with 1 V and connect that to a stepUP converter, then you are in a position to connect that to a stepDOWN converter to get to where you want to be.

the only drawback of course is you need two module to get there.

I'm not sure the requirements that have been stated make much physical sense. From the bits we've been given, the OP is looking for 3 Amps at (presumably) 5 volts out possibly sourced by a single AA battery drained to 0.9 V which would imply something in excess of 15 Amps out of that nearly dead AA battery. Modern power converters are pretty amazing devices, but they don't do magic.

This means that you may not be able to predict how long your electronic device will run just by looking at the capacity rating of a battery. For example AA alkaline batteries typically have a capacity rating of over 2,500 mAh and AA NiMH batteries have rated capacities of only 1,200 to 1,900 mAh.

Clearly the math doesn't add up. The idea of starting with an egg and ending up with a chicken only works with eggs and chickens. It doesn't apply to batteries.

raschemmel: the only drawback of course is you need two module to get there.

Ok- the first Image I posted has only a single chip doing both Buck and Boost, but I have seen single board modules that have 2 separate chips for doing Boost and Buck. Like this one.

Still they show min input of 3V. Do you know of any such modules that take in from 1V? Because I know there are Boost only modules that accept 1V.

MrMark: I'm not sure the requirements that have been stated make much physical sense. From the bits we've been given, the OP is looking for 3 Amps at (presumably) 5 volts out possibly sourced by a single AA battery drained to 0.9 V which would imply something in excess of 15 Amps out of that nearly dead AA battery. Modern power converters are pretty amazing devices, but they don't do magic.

Nope I don't want 3A at 5V when boosting. I've already commented about that, The 3A I was asking was the max input rating for the buck chip so that it won't blow up if if step down 19V 2A to 5V 2A , The boost chip don't need that high amp rating for me because I know a AA battery doesn't have much power.

Noobian: Still they show min input of 3V. Do you know of any such modules that take in from 1V?

No , as i mentioned earlier they tend to be for specific applications.

I see no commercial reason for anyone to design one.

You may find something you can hack in a laser pointer or torch.

I already linked one.( a boost) which you rejected bexause it doesn't buck which is why I stated the "thd only draw back is you need TWO (1 boost +1 buck) to get there , which you ignored and continued to persist with your request for a module that does both but has a 1 V input voltage, despite repeated statements from others that no such mofule exists. Got it ?