One cell power supply

[Chasm]

Hi,

I want to tinker with more up to date ways to power a device.
In particular a relatively simple AVR Board with LCD display and SD card.


There are various one (and two) cell SMPS controllers out there, but which make actually sense?

[Simon]

well it depends on what you want

[Mr J]

try this http://www.sparkfun.com/products/8466

1.2 Volts to 5 Volt INPUT @ 100mA

[tyblu]

SMPS controllers vary as widely as power requirements, which is all of the place. Best to just find a cheap one that fits your immediate needs and go for it. No better way to learn than "why the %E@) doesn't this work!?"

[NiHaoMike]

Are you working with Lithium or NiMH?

[Chasm]

What do I want?
The cake and eat it too.

No, actually some idea which controllers are actually used for this application - if there is such a thing as a widely used SMPS controller.
I did not have the NCP1400 on my list, just some LT and Maxim stuff so far.
Maybe some hints what is actually important, the switching frequencies vary widely.

I want to use a NiMH AA battery, Lithium Ion is something for another day.
3.3V or 5V, 100mA sounds about right, writing the SD Card takes most of it.
3.3V for the card, but I have a heap of 5V displays. Seems to be cheaper to add another switcher than to buy a 3V LCD

[Chasm]

Looking around a bit, what about the MCP1624?

0.90 Euro is not too bad, for something likely to blow up on the first tries.

Ok, obvious question time:
A "power choke" inductor is used as a filter, it is not the kind of inductor I need. Right?

[qno]

If you want a single cell power supply check out Collin Mitchels work at

http://www.talkingelectronics.com/projects/LEDTorchCircuits/LEDTorchCircuits-P1.html

He has a good description of a flyback converter.

All done with 2 transistors.

(o dear, transistors, does that show my age....)

[Zero999]

Colin's circuit is not regulated but that should be easy to fix.

[coderkevin]

I'm in the selection process for a similar circuit.  I've put together a spreadsheet of promising ICs for this purpose with some key variables from the datasheet.  Note that the max current comes from the actual graphs and not from the formulas on the datasheet.  Hope this helps you out!

I have a couple of SparkFun's NCP1400 breakouts, and I've made one of my own for the Seiko chip, but since then I've decided I want to try to maintain about 100mA all the way down to the 0.9V level of the battery for maximum usage.

I'll be making breakouts for the Sipex and Microchip ICs to evaluate their performance next as it seems they're the pick of the litter here...or at least they're the best I've found so far!

--Kevin

[Chasm]

I've decided to try the MPC1640, it is the cheapest chip I can easily get at the moment and seems to fit my requirements.
If necessary I can add more cells to boost the power output. Actually using it seems almost foolproof.