Very Low Power Switched Mode Power Supply

[[email protected]]

Hi,

Does anyone know of a Switched Mode Power Supply that will operate on
really low input voltage, say about 1 or volts and has no constraints
on power output?

Steve.

 

[[email protected]]

Hi,

Does anyone know of a Switched Mode Power Supply that will operate on
really low input voltage, say about 1 or volts and has no constraints
on power output?

This has been discussed here, albeit some time ago. The only difficult
part is getting the thing to start up. If you don't mind including a
rechargeable battery there's no real problem; otherwise you've got to
go for an inverter based on normally "on" parts, like junction FETs or
depletion mode MOSFETs.

I've not worked on the problem, so this is just what I remember, and
isn't all that reliable. Win Hill and Joerg might know more - they did
chime in on the 31 May 2006 thread "Low voltage step up design?"

 

[Joerg]

Hi,

Does anyone know of a Switched Mode Power Supply that will operate on
really low input voltage, say about 1 or volts and has no constraints
on power output?

There are plenty of step-up chips that start at less than a volt but
they usually have one thing in common: They do require a bit of
quiescent from the output side, mostly a few ten uA. That can be a
problem in battery apps where you have to guarantee a continuous and
stable output voltage. Browse National or TI, take a look around their
step-up switcher chips.

If power consumption is a really tough issue you are often back to the
old JFET and have to coax it into a burst mode where the length of the
bursts depend on whether the output voltage has dropped below a lower
window limit or not. IOW it's going to have hysteretic behavior.

 

[MooseFET]

Hi,

Does anyone know of a Switched Mode Power Supply that will operate on
really low input voltage, say about 1 or volts and has no constraints
on power output?

The basic two transistor multivibrator oscillator will start and run
as low as about 0.8V. Using one of those you can make a simple
booster supply to run the control electronics on. A cross coupled
pair of 2N2222s and a transformer can get you a 10V supply to run
stuff on.

The main supplies pass elements can be MOSFETS or BJTs.

 

[Vladimir Vassilevsky]

Hi,

Does anyone know of a Switched Mode Power Supply that will operate on
really low input voltage, say about 1 or volts and has no constraints
on power output?

Check L6920 from ST.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

 

[Mike Harrison]

Hi,

Does anyone know of a Switched Mode Power Supply that will operate on
really low input voltage, say about 1 or volts and has no constraints
on power output?

Steve.

Texas TPS61200 - 0.3v min input

 

[Tim Williams]

A chopper oscillator built with germanium transistors ( = not for
production these days!) will run as low as 0.4V.

There was an article in an old Electronics Now, by Fred Nachbaur, of such a
circuit for single photocell use. I have it around here somewhere, and it
might be referenced on Fred's website somewhere.

Tim

 

[Joerg]

Texas TPS61200 - 0.3v min input

But watch out, IIRC it's 70uA quiescent, taken from the output cap. I
wrote TI support a while ago about some tricks and whether they'd be
kosher. Well, that was a couple months ago and I could not even get tech
support to answer. Four (!) reminders, four promises to get back to me
"soon", then zilch. That tells me something I'd have to keep in mind for
future design decisions ...

Hello TI, anyone listening?

 

[Phil Allison]

Does anyone know of a Switched Mode Power Supply that will operate on
really low input voltage, say about 1 or volts and has no constraints
on power output?

** The heading and the Q are in direct contradiction.






....... Phil

 

[Joerg]

Well, if ter is a reasonable market for your improved design, get some
fab house to make them and then undersell TI and market as "!Banned by
TI!".

IMHO there isn't much of a market (yet). But there certainly won't be
one developing if you can't obtain important info on available chips.
Anyhow, most people in this field do that the old fashioned way. That
would be a small helper circuit with a JFET and then a traditional
switcher. If PHEMTs and stuff would be lower in cost we'd use them. But
they cost a lot so mostly it's jelly-bean JFETs.