Boost Converter

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Circuit design schematic or commercial product both welcome.
Specific specs not needed beyond these.

Boost converter.
input:0.4VDC to 1.0VDC;  Output:  3VDC +/- something
Output current 20ma or more
Any frequency
No regulation requirements

Don't get hung up on any of the following since they are a wish list  
but are in order of importance:
Maximum efficiency  i.e. if there are multiple ways of doing this then  
the most efficient one.
Minimum parts count
Small size




Re: Boost Converter
wrote:

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0.4VDC ???
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: Boost Converter
On Sun, 25 Oct 2015 11:10:36 -0700, OldGuy wrote:

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DigiKey -> product index -> integrated circuits -> PMIC - Voltage  
Regulators - DC DC Switching Regulators

Then search on a minimum voltage from 0 to 0.4V.

You'll be disappointed -- I only found two part numbers.

0.4V is an obnoxiously low voltage for this -- it's hard to get  
transistors that'll work at this voltage, much less work well.  I kind of  
have the notion you're doing this from solar cells -- can you run two in  
series?

--  
www.wescottdesign.com

Re: Boost Converter
wrote:

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I think Jan P has posted some inverters that run from millivolt
inputs. Jfets, I think.

Somebody, maybe LTC, has a low voltage booster chip.

I'd consider using a lithium primary battery to bootstrap the startup
of a simple boost converter. The battery might last several decades.



Re: Boost Converter
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I designed a little boost converter a while back that used one of
 those ISDN transformers that could operate from a very low
 voltage - it used a single transistor blocking oscillator wired
 to part of the primary to get the thing started, and then the
 main converter was like one of those things where you switch the
 center tap of a transformer, where the other two taps are
 connected in series with the load.

I don't think it ever made it out of LTSpice, but I think I still
 have the file around here somewhere.


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Re: Boost Converter
On Sun, 25 Oct 2015 19:26:11 -0400 (EDT), bitrex

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The ISDNs are great little xfmrs. We use thousands of a Talema
1:1:2:2, which has  all sorts of uses. Did you get a bipolar
transistor oscillator to start at 0.4 volts?

A small PHEMT would be cool, even better than Jan's jfet maybe.


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Boost Converter
On 10/26/2015 1:40 PM, John Larkin wrote:
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I think I used a depletion mode MOSFET. I bet a germanium bipolar would  
work! There's a local electronics store that still stocks real parts -  
they have a ton of NTE replacement PNP germanium transistors just siting  
around.

Re: Boost Converter
wrote:

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Such low input voltages are a common problem for energy harvesting and
self powered sensor systems.  Googling for these buzzwords,
<https://www.google.com/#q=energy+harvesting+low+voltage
I found:

"Ultra-Low-Voltage Input Power Converters Support Energy Harvesting"
<http://cds.linear.com/docs/en/article/LTC3108EnergyHarvest.pdf
<http://www.linear.com/product/LTC3107
<http://www.linear.com/product/LTC3108
etc...  20 mv input voltage.  Ok, I'm impressed.

--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Boost Converter
On 2015-10-25 3:24 PM, Jeff Liebermann wrote:
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Harvesting is the right keyword here. Or fuel cell converter. There are  
enough ICs available to get 20mA done.

If it has to be cheap: A JFET oscillator makes several volts as a  
control voltage, to operate a regular run-of-the-mills switcher and  
house-keeping stuff or maybe milk the whole 20mA out of it by  
paralleling JFETs. I got a BF862 in an oscillator hook-up to reliably  
start around 300-400mV. If not enough oomph and you don't want to  
parallel too many JFETs follow this with an "intermediate" helper  
converter that is switched by this oscillator. OldGuy would be done  
latest at this stage.

For those who need more power:

That drives a classic converter IC with some big old FETs and you can  
create almost any voltage at high power levels. Years ago we had a bet  
going on a German NG that you can get >90% efficiency. I put my bet in  
the "Yes, we can" hat, others said "impossible". Help in all shapes and  
forms was allowed. Then the OP did most of the design and prototype but  
it was in modern speak a "crowd design" with most of us pitching in. He  
got well over 90% out of it. One of the guys (who had bet against it)  
said if he loses he'll do a kegger at his company. I am sure he would  
have but most of us were just too far away.

Hey, how old is "Old"? Isn't 60 the new 40?

--  
Regards, Joerg

http://www.analogconsultants.com/

Re: Boost Converter
wrote:

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75 is the new 50 ;-)

(In that 3-month chip gig on Long Island a few years ago, a
co-contractor thought I was 55~60... he was astonished when I said
72.)
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: Boost Converter
72 here also.

I remember a ~0.4 VDC boost converter circuit shown in Electronic  
Design or EDN many years ago.
That used a single germanium transistor.
Anybody got a link for that. (as a curiosity)

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Re: Boost Converter
Google "germanium transistor" price - heaps of them.

Hul

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Re: Boost Converter
On Sunday, October 25, 2015 at 11:11:00 AM UTC-7, OldGuy wrote:
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The easiest design for 0.4V (or less) will not involve semiconductors.
It's a vibrator (electromechanical chopper), just like Model T spark
systems and vacuum-tube battery radios used to use.

Can you use a high-voltage battery for control circuitry?  Something
like a lithium coin cell can control and bias commutating switches
for a solid-state non-buzzing converter, if you don't mind replacing it
every year.

Re: Boost Converter
wrote:

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The "trick" exhibited in some of the LT products is that an auxiliary
battery is used to start the operation then the boosted output takes
over... thus consumption from battery is nil.

Another approach is to use a battery being charged as the
kick-starter.  This means you mustn't let the battery discharge too
low between charging operations.
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: Boost Converter
wrote:

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Some of the Tadiran lithium batteries have 40 year shelf lives. Makes
energy harvesting seem silly.

The battery just needs to start up the converter.  


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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