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'[EE] Design challenge - boost converter'
2005\04\28@105514 by Russell McMahon

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I'm looking for the cheapest design in semi volume production (say
1000 at a time) for a buck-boost converter that meets the specs below.
I can think of a few zillion circuits that would do this - I thought
people may enjoy the challenge, and some excellent ideas are sure to
come out of it. NO prize but much adulation for the best design :-).
I'll put any useful designs on my website.

Application is to run a "Polar" type heartbeat receiver at 5 volts
while the battery pack ages from about 6.5 volts down to about 4 volts
over its lifetime. Receiver is commercial prepotted unit with fixed
expectations/specs. Many other applications will suggest themselves
for such a supply.

- will accept input from 4 alkaline cells over 6.5v to 4v range and
- provide 5 volts output
- at a few mA.
- Regulation for load or input voltage need not be flash - probably
+/- 0.25v OK but I'd expect we could do better.
- Efficiency not a major issue. 60% would do! - rather better
expected.
- Isolation not needed.
- Probably through-hole construction.

I would expect that a suitable design could be implemented for a
component cost of tens of cents in say 1,000 volume. Assembly costs
and PCB area are liable to be approximately the same for a range of
solutions and are not liable to be a major issue.

Starters for 10 points:

- Use could be made of a commercial buck-boost IC. Easy. Compact. Low
parts count. Liable to be expensive.

- One (or 2 or 3) transistor self oscillating converter with eg zener
clamp regulator. Cheap. Compact. Tapped inductor or dual inductors may
be needed.

- Std cheap smps IC with suitable glue -  OK. Better regulation etc
than 2. Dearer.
   Ye olde MC34063 would do and is cheapish. (Digikey $0.26/1000).
   Could do SEPIC or std buck boost.

- As 3 but use cheap commodity IC - 74C14/40106 or LM339/390 or ...
(even a 555 :-) )
   An extremely viable approach. A "single gate" SMT component would
do the job if SMT was being used.

- A diode pump doubler with post regulator would meet the spec but is
annoyingly energy wasteful. Could use existing processor line for
drive frequency to reduce cost. eg LCD drive or whatever. Heath
Robinson but practical. Could be very cheap.

Thoughts ???




       Russell McMahon


2005\04\28@114909 by Bob Blick

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> - will accept input from 4 alkaline cells over 6.5v to 4v range and
> - provide 5 volts output
> - at a few mA.
> - Regulation for load or input voltage need not be flash - probably
> +/- 0.25v OK but I'd expect we could do better.
> - Efficiency not a major issue. 60% would do! - rather better
> expected.

That's easy, just throw away one of the cells and do boost-only.
Seriously. I regularly have to deal with a 4 cell spec, and it's crazy. It
always takes huge effort to convince others that an odd number of cells is
not satanic or something.

Also, don't run Duracells down below 1.1 volts or some of them will leak.

Cheerful regards,

Bob


2005\04\28@122615 by Spehro Pefhany

picon face
At 08:49 AM 4/28/2005 -0700, you wrote:

> > - will accept input from 4 alkaline cells over 6.5v to 4v range and
> > - provide 5 volts output
> > - at a few mA.
> > - Regulation for load or input voltage need not be flash - probably
> > +/- 0.25v OK but I'd expect we could do better.
> > - Efficiency not a major issue. 60% would do! - rather better
> > expected.
>
>That's easy, just throw away one of the cells and do boost-only.
>Seriously. I regularly have to deal with a 4 cell spec, and it's crazy. It
>always takes huge effort to convince others that an odd number of cells is
>not satanic or something.
>
>Also, don't run Duracells down below 1.1 volts or some of them will leak.
>
>Cheerful regards,
>
>Bob

Why not go to 2 cells? For only a few mA output, and it's less Satanic
than three. I had a car with 5 cylinders, and seriously considered
another vehicle with 3, but there's something "not right" about it. ;-)

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spam_OUTspeffTakeThisOuTspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com




2005\04\28@124611 by Mike Hord

picon face
> >That's easy, just throw away one of the cells and do boost-only.
> >Seriously. I regularly have to deal with a 4 cell spec, and it's crazy. It
> >always takes huge effort to convince others that an odd number of cells is
> >not satanic or something.
> >
> >Also, don't run Duracells down below 1.1 volts or some of them will leak.
> >
> >Cheerful regards,
> >
> >Bob
>
> Why not go to 2 cells? For only a few mA output, and it's less Satanic
> than three. I had a car with 5 cylinders, and seriously considered
> another vehicle with 3, but there's something "not right" about it. ;-)

It's along the lines of buns and sausages coming in packs of 6 and 8,
respectively (although that's not the case so much anymore).  One must
either purchase 24 of each OR be left with excess buns/wieners at the
end of the picnic.  Or eat bare sausages (because who eats just a bun?).

Spehro, did you find yourself frequently in posession of a single spark
plug?  When I put 3 cells in things, I find myself with an extra battery
lying about the place for months until, having forgotten whether it's the
last of a new pack or a stray dead cell, I toss it.

Not that it's entirely inappropriate, mind you.  It just has other
considerations.

Mike H.

2005\04\28@124858 by Bob Blick

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Of course 4 cells is reasonable in this case since it is an add-on to your
existing device. So since you don't need super efficiency, do a sepic
regulator. By adding one more inductor and a capacitor to this circuit:
http://bobblick.com/3cell/
you could do it very cheaply. Voltage regulation is not great, you could
either use a zener and waste a lot of current or add an LM431 for the
reference.

Cheers,

Bob

{Quote hidden}

2005\04\28@130619 by Mike Harrison

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On Thu, 28 Apr 2005 12:30:30 -0400, you wrote:

{Quote hidden}

2 cells is aesthetically more attractive, but significantly increases potential losses due to the
higher current - bettery contacts in particular, although at the 'a few mA' level this is probably
not too much of a problem.
And of course you have less than half the total juice compared to 4 cells.

Another thing that may be worth considering - do you _really_ need 5V, as opposed to, for example,
4.5 or 4.0V ? A simple micropower LDO (e.g. 78LC/FC40 from Onsemi) would then do the trick with
reasonable efficiency and low cost.


2005\04\28@131012 by Dave Tweed

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Russell McMahon <.....apptechKILLspamspam@spam@paradise.net.nz> wrote:
> I'm looking for the cheapest design in semi volume production (say
> 1000 at a time) for a buck-boost converter that meets the specs below.

Lately, I've been looking into building a universal wall-wart replacement,
and I realized that an inverting DC-DC converter (positive in, negative
out, or vice-versa) has the same complexity as a regular buck converter,
but does not have the restriction that Vin > Vout. Why not hook up your
battery pack in a positive-ground configuration and use an inverting
converter to generate your +5.0 V?

I'd probably do it by using a PIC10F204 as a controller, an NPN transitor
as the switch, and a PNP transistor to translate the feedback voltage
for the PIC's comparator. Something like this:


                +-----------------------+-----+---o +
                |                       |     |
                R                       |     |
                R                       K     |     5.0V
                R                     diode  ---    output
                |                       A    ---
                E                       |     |
            PNP  B---+                  |     |
                C    |                  |     |
          +-----|----+--+----------+----|-----+---o -
      +   |     |       |          |    |
        -----   |    +-----+       |    |
 4.0 to  ---    |    |     |       L    |
 6.5 V  -----   +----| PIC |--+    L    |
 input   ---    |    | 10F |  |    L    |
        -----   R    |     |  R    L    |
         ---    R    |     |  R    |    |
      -   |     R    +-----+  R    |    |
          |     |       |     |    |    |
          |     |       |     B    |    |
          +-----+-------+----E C---+----+

                             NPN

The upper resistor in the feedback path sets the current through the PNP
as a function of output voltage. The lower resistor converts this current
into a voltage suitable for the PIC's comparator.

Not shown is a way to limit the supply voltage to the PIC to no more than
5.5V. One obvious answer would be to use a 3-cell pack instead of four, but
then you could just use a regular boost converter topology to begin with.

A pulse generator based on discrete transistors or a comparator wouldn't
have this restriction.

-- Dave Tweed

2005\04\28@131856 by Russell McMahon

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> That's easy, just throw away one of the cells and do boost-only.
> Seriously. I regularly have to deal with a 4 cell spec, and it's
> crazy. It
> always takes huge effort to convince others that an odd number of
> cells is
> not satanic or something.

Alas there are other constraints not relevant to the converter. The 4
cells operate equipment with an end pouint voltage of 4
volts.Efficiency of supply matters more there and the design exists
and is unchangeable.



       RM

2005\04\28@132643 by Harold Hallikainen
face picon face


>
> Why not go to 2 cells? For only a few mA output, and it's less Satanic
> than three. I had a car with 5 cylinders, and seriously considered
> another vehicle with 3, but there's something "not right" about it. ;-)
>


That, of course, is why 5 phase power is so common...

Harold


--
FCC Rules Updated Daily at http://www.hallikainen.com

2005\04\28@133419 by Russell McMahon

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> Of course 4 cells is reasonable in this case since it is an add-on
> to your
> existing device. So since you don't need super efficiency, do a
> sepic
> regulator. By adding one more inductor and a capacitor to this
> circuit:
> http://bobblick.com/3cell/
> you could do it very cheaply. Voltage regulation is not great, you
> could
> either use a zener and waste a lot of current or add an LM431 for
> the
> reference.

Yes. I mentioned a SEPIC as one of the options. The two inductors is
annoying but not necessarily a killer. And it needs a semi formal
controller, unlike some options.

You could run a SEPIC entirely open loop, designed to make enough
power and voltage and zener shunt the excess when needed. Mayhaps open
loop except with basic regulation turning it on and off. Aim
throughout is cheapness. Not a lot of power involved - probably about
15 mW ! -)

I wonder if CUK has anything to add here.



       RM

2005\04\28@134014 by Spehro Pefhany

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At 11:46 AM 4/28/2005 -0500, you wrote:
{Quote hidden}

No, but I have not changed my own plugs for a very long time. ;-)

>When I put 3 cells in things, I find myself with an extra battery
>lying about the place for months until, having forgotten whether it's the
>last of a new pack or a stray dead cell, I toss it.

Yes, that's a consideration.

BTW, unless there's a good reason not to, I'd also try to allow for
NiMH cells. I have not yet run into a product that won't work with them,
even if only alkalines are suggested.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamKILLspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com




2005\04\28@134540 by Russell McMahon

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Happened across this interesting and useful power converter page.

       http://www.national.com/nationaledge/feb03/article2.html

The most interesting (to me) idea is in fig 3. It shows the
retrospectively obvious addition of a slaved boost prestage to a buck
converter to turn it into a boost-buck converter with a minimum of
extraparts. As the boost stage is slaved to the buck stage it needs no
PWM control of its own.

I could eg add this to my GSR buck converter thereby making it a boost
buck converter and requiring only 3 additional parts - a FET, an
inductor and a diode. May not be optimum for the present application,
but adds to the armoury. Also could add to Roman's BLACK converter in
the same way.

Quite a lot of other good material on that page and on linked pages


       RM



2005\04\28@140055 by Russell McMahon

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While I find the "why don't you do something completely different than
the challenge" interesting, it's not useful for what I'm trying to
achieve. There is a larger context and the challenge specified the
desired task. Think of it as an exam question where you are required
to answer the question rather than show your lateral thinking skills
:-).

Briefly, the battery exists and cannot be changed. Other things run
off the battery. The 5v is required to make a potted circuit work
stably as intended. I want to generate the 5v from the battery.


       RM




2005\04\28@141223 by Bob Ammerman

picon face
>
> BTW, unless there's a good reason not to, I'd also try to allow for
> NiMH cells. I have not yet run into a product that won't work with them,
> even if only alkalines are suggested.
>
I once bought a set of FRS (license free short range voice) radios that ran
on three alkaline AA cells. Didn't work very well at all on NiMH.

Bob Ammerman
RAm Systems

2005\04\28@141709 by Bob Blick

face picon face

> Yes. I mentioned a SEPIC as one of the options. The two inductors is
> annoying but not necessarily a killer. And it needs a semi formal
> controller, unlike some options.
>

No, it does not. As I said, this circuit:
http://bobblick.com/3cell/

or ANY boost controller, can be a sepic circuit with the addition of a cap
and inductor.

Cheers,

Bob


2005\04\28@190738 by Bob Blick

face picon face
part 1 410 bytes content-type:text/plain; charset="iso-8859-1" (unknown type 8bit not decoded)

Here you go. Switches up and down. Three transistors, 4 to 6.5 volts in
and 5 volts out. Sorry about the funky schematic, I "built" it in
SwitcherCAD. It simulates just fine. Some adjusting of values to suit your
particulars if needed is allowed, for instance right now it is optimized
for higher current.

(small gif file attached)

Cheers,

Bob


part 2 6517 bytes content-type:image/gif; name="3_transistor_sepic.gif" (decode)


part 3 35 bytes content-type:text/plain; charset="us-ascii"
(decoded 7bit)

2005\04\28@193510 by Alexandre Guimaraes

face picon face
Hi, Bob

   Could you give a little explanation about the operating principles ? The
2 inductors with the series cap are too much for my small brain :-)

----- Original Message -----
From: "Bob Blick" <.....bblickKILLspamspam.....sonic.net>


{Quote hidden}

2005\04\28@194328 by Russell McMahon

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>> Why not go to 2 cells? For only a few mA output, and it's less
>> Satanic
>> than three. I had a car with 5 cylinders, and seriously considered
>> another vehicle with 3, but there's something "not right" about it.
>> ;-)

> That, of course, is why 5 phase power is so common...

One of my car's has 3 cylinders (by design, not just happenstance
:-) ).


       RM

2005\04\28@195844 by Russell McMahon

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> Here you go. Switches up and down. Three transistors, 4 to 6.5 volts
> in
> and 5 volts out. Sorry about the funky schematic, I "built" it in
> SwitcherCAD. It simulates just fine. Some adjusting of values to
> suit your
> particulars if needed is allowed, for instance right now it is
> optimized
> for higher current.

Yes - essentially as per your website Less Than Perfect (tm) example.
An excellent entry to the fray.

Similarly worth a look as a starter for 10 points is this IC based CUK
converter

      http://cache.national.com/ds/LM/LM2611.pdf

Inverting polarity but a good idea starter.


       Russell McMahon

2005\04\28@200404 by Spehro Pefhany

picon face
At 08:34 PM 4/28/2005 -0300, you wrote:
>Hi, Bob
>
>    Could you give a little explanation about the operating principles ?
> The 2 inductors with the series cap are too much for my small brain :-)

I take it that the output voltage is proportional to Vbe, so -0.3%/K tempco?

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
EraseMEspeffspam_OUTspamTakeThisOuTinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com




2005\04\28@205050 by Bob Blick

face picon face
On 28 Apr 2005 at 20:08, Spehro Pefhany wrote:

> I take it that the output voltage is proportional to Vbe, so -0.3%/K tempco?

Something like that. Use an LM431, or if you can afford the current
required for proper zenering, a zener instead of R5.

Cheers,

Bob

2005\04\28@205550 by Richard.Prosser

flavicon
face





> That, of course, is why 5 phase power is so common...

One of my car's has 3 cylinders (by design, not just happenstance
:-) ).


       RM

As does mine.
And you _really_  notice the difference when a sparkplug lead falls off !.

RP





2005\04\28@210018 by Bob Blick

face picon face
On 28 Apr 2005 at 20:34, Alexandre Guimaraes wrote:
>     Could you give a little explanation about the operating principles ? The
> 2 inductors with the series cap are too much for my small brain :-)

The average voltage across each inductor is zero.
The voltage across C5 is equal to the input voltage.
C5 couples from L1, centered around Vin, to L2, centered around Gnd.
By varying the duty cycle, the positive peak voltage at L2 changes
and is routed to the output by D1.

Cheerful regards,

Bob



2005\04\28@210926 by Dave VanHorn

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>
>As does mine.
>And you _really_  notice the difference when a sparkplug lead falls off !.


Try it in a Fiat 500.


2005\04\28@221332 by Russell McMahon

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>>     Could you give a little explanation about the operating
>> principles ? The
>> 2 inductors with the series cap are too much for my small brain :-)

> The average voltage across each inductor is zero.
> The voltage across C5 is equal to the input voltage.
> C5 couples from L1, centered around Vin, to L2, centered around Gnd.
> By varying the duty cycle, the positive peak voltage at L2 changes
> and is routed to the output by D1.

Or another perspective.

Q1 & L1 form a positive boost converter.
C5 is charged from this.
When Q1 goes low it drives C5 output negative.
L2 is a negative to positive flyback converter which is driven
negative by C5 when Q1 is on and C5 not discharged and will ring
positive when Q1 is off or as C5 discharges.


       RM

2005\04\28@221332 by Russell McMahon

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>>As does mine.
>>And you _really_  notice the difference when a sparkplug lead falls
>>off !.

> Try it in a Fiat 500.

See my OT relabelling for this change in thread topic.

   [OT] Unusual configurations <- Re: [EE] Design challenge - boost
converter

       RM

2005\04\29@034818 by Alan B. Pearce

face picon face
>Yes. I mentioned a SEPIC as one of the options. The two
>inductors is annoying but not necessarily a killer. And
>it needs a semi formal controller, unlike some options.

have you looked at the recently introduced 16F series device designed for
power supply use? 16F785 IIRC. I do not know what its own power supply
rating is, but considering the supposed end use it might go up to the 6V
range.

2005\04\29@052320 by Russell McMahon

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> >Yes. I mentioned a SEPIC as one of the options. The two
>>inductors is annoying but not necessarily a killer. And
>>it needs a semi formal controller, unlike some options.

> have you looked at the recently introduced 16F series device
> designed for
> power supply use? 16F785 IIRC. I do not know what its own power
> supply
> rating is, but considering the supposed end use it might go up to
> the 6V
> range.

No.
Worth adding to the list of possibilities but almost certainly
overkill.
Would have to be extremely cheap to compete with other options.


       Russell McMahon

2005\04\30@043925 by ThePicMan

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At 11.30 2005.04.29 +1200, you wrote:
>>>Why not go to 2 cells? For only a few mA output, and it's less Satanic
>>>than three. I had a car with 5 cylinders, and seriously considered
>>>another vehicle with 3, but there's something "not right" about it. ;-)
>
>>That, of course, is why 5 phase power is so common...
>
>One of my car's has 3 cylinders (by design, not just happenstance :-) ).

Also my Skoda Fabia City. :D


2005\04\30@043932 by ThePicMan

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face
At 20.10 2005.04.28 -0500, you wrote:


>>As does mine.
>>And you _really_  notice the difference when a sparkplug lead falls off !.
>
>
>Try it in a Fiat 500.

The old or the new? The old had just 2 cylinders. :P



'[EE] Design challenge - boost converter'
2005\05\29@230455 by Russell McMahon
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I solicited suggestions for a converter which would meet all of the
following without alteration (regardless of why it may be a good idea
to alter them)

>> - will accept input from 4 alkaline cells over 6.5v to 4v range and
>> - provide 5 volts output
>> - at a few mA.
>> - Regulation for load or input voltage need not be flash - probably
>> +/- 0.25v OK but I'd expect we could do better.
>> - Efficiency not a major issue. 60% would do! - rather better
>> expected.
>> Probably through hole construction / ie DIP package if ICs used.

As output current is a few mA (say 5 mA max) the quiescent current
needs to be low to achieve OK efficiency. ie parts that draw 3 mA
quiescent aren't really acceptable.

Low manufactured cost is a key factor but possibly not originally
mentioned.

There were various suggestions.
At present I'm looking at either a TL499 design or one based on a
CD40106 hex Schmitt trigger plus a few transistors. It has a high
parts count but excellent performance and component cost is low.

Various self oscillating transistor designs proved less than ideal for
various reasons. (Voltage range, efficiency at low load current,
startability, ...). (I'm sure a fully transistor based design could do
a good job with refinement but the 40106 design is not a lot dearer
and very effective). CD40106 is about $US0.15/1000 Digikey and TL499
is about $US0.45/1000 Digikey. TL499 has a nasty high current mode
when the power supply rises slowly - not mentioned in any data sheet
or app note (of course).

The TL499 is very old but an effective solution. Much more modern
boost converter ICs exist but they are usually much dearer. Most
suitable Maxim parts are more like $2/1000 or more from Digikey. The
LM2578/LM3578 is cheaper (about $US0.50) but not in DIP.

Has anyone got any other suggested IC that may do the job that is also
well priced - probably not over $US0.50/1000 quantity. Anything this
'dear' would want a minimum of 'glue' components.



       RM

2005\05\30@010535 by PicDude

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On Sunday 29 May 2005 09:53 pm, Russell McMahon scribbled:
> ...  The
> LM2578/LM3578 is cheaper (about $US0.50) but not in DIP.

Where did you find these for $0.50?  I was looking at these National parts
recently, and Digikey has the LM3578AM for US$0.80/1k.  Would really
appreciate a lower-cost source.

I believe the MC33063/MC34063 can do what you want, and is much lower-cost at
~US$0.28/1000.

BTW, aren't you on the other side of the planet?  Curious why you check
pricing at Digikey -- do you buy from here and have them ship to you, or does
Digikey have a branch over yonder?

Cheers,
-Neil.



2005\05\30@031845 by Russell McMahon

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n> Where did you find these for $0.50?  I was looking at these
National
> parts
> recently, and Digikey has the LM3578AM for US$0.80/1k.  Would really
> appreciate a lower-cost source.

I may have got that wrong - was from (recent) memory.

> I believe the MC33063/MC34063 can do what you want, and is much
> lower-cost at
> ~US$0.28/1000.

I tried it. Alas, it has a poor quiescent current drain - about 3 mA
at
no load in a typical configuration.  Usually this would not be a major
issue but as my load current is in that range it badly hurts the
total current draw. Also, its switch is an internal Darlington and
unless you can get very creative the voltage drop is an appreciable
part of the 4v minimum supply and further hurts efficiency. One way to
get creative is to use it to drive an external FET switch (which is
what I did in the inverter I did for Jinx a few months ago) BUT that
adds to parts count and cost which are at a premium here.

I'm about to try an LM393 design to see if I can get it all entirely
internal - no transistors at all - use an inverter section or two as
the switch. It will be close to its capabilities probably and I have
to watch typical versus worst case/min parameters.

I tried a capacitor pump but the CD40106 boost converter was better
overall.

> BTW, aren't you on the other side of the planet?  Curious why you
> check
> pricing at Digikey -- do you buy from here and have them ship to
> you, or does
> Digikey have a branch over yonder?

Digikey are a good universal reference - many people know them, they
have a good range of prices and you can say that in real volume the
prices won't be worse than they charge :-). I do in fact buy SOME
parts from them when there's no better easy source and even the
Taiwanese company who build some stuff I design, buy from Digikey on
occasion! But they have no branch here. When I want it soonish and
Farnell & RS haven't got it and /or charge far too much (as they do)
in volume then Digikey are a good source.

The other side of the planet is only a few days away once they get it
shipped. Or a week or two at much better rates.


       RM


2005\05\30@090305 by Mark Jordan

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face
On 30 May 2005 at 19:07, Russell McMahon wrote:

>
> I tried a capacitor pump but the CD40106 boost converter was better
> overall.

       I would like to see that circuit. Was it posted already?

       Thanks.
       Mark

2005\05\30@141212 by PicDude

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On Monday 30 May 2005 02:07 am, Russell McMahon scribbled:
> I tried it. Alas, it has a poor quiescent current drain - about 3 mA
> ...

Ah yes -- I had not checked the DS for that spec before recommending.

> I'm about to try an LM393 design to see if I can get it all entirely
> ...

You mean the comparator?  Interesting.  Would never have thought of that.


> Digikey are a good universal reference - many people know them, they
> ...

So true.  The ability to search by parameters over a large set of
manufacturers is awesome, so my designs are largely based on what they have,
unless I need something specific.  But admittedly, prior to placing an order
with them, I end up checking mouser as well, since pricing generally works
out better, especially for low volumes.


> The other side of the planet is only a few days away once they get it
> shipped. Or a week or two at much better rates.

I do need to get over my fear of purchasing internationally, though it's not a
totally unfounded fear.  Example: I purchased from Jaycar recently.  On the
order, I asked to email me a tracking #, but never heard back.  Emailed them
about it a couple weeks later, but no response.  A couple more weeks later I
was emailing trying to find out what happened with my order.  Once I finally
got a hold of them by phone, they were pretty casual as if this is normal.  A
week later I got the order.  Another week or so after that, they responed to
my email saying that it went out already.  Arrrggghhh!  All worked out in the
end, but being in the dark about where my order was was totally frustating,
and not being here, it was a helpless feeling.

Cheers,
-Neil.



2005\05\30@142529 by Spehro Pefhany

picon face
At 01:15 PM 5/30/2005 -0500, you wrote:


>So true.  The ability to search by parameters over a large set of
>manufacturers is awesome

All the parameters *except* price. ;-)

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamspam_OUTinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\05\30@144621 by PicDude

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On Monday 30 May 2005 01:30 pm, Spehro Pefhany scribbled:
> At 01:15 PM 5/30/2005 -0500, you wrote:
> >So true.  The ability to search by parameters over a large set of
> >manufacturers is awesome
>
> All the parameters *except* price. ;-)


Somewhat.  The rightmost column shows price.  Comparing the 1-pc and
multiple-thousand-piece (tape & reel) prices gives a decent ballpark price
indication.  And often, I will click on the part to see the full price
levels.  Much better than having to get on multiple manufacturers websites
and pull up datasheets or get quotes from distributors.  What would be really
nice is if it let me specify how much I need, then sorted by that price.

Cheers,
-Neil.


2005\05\30@150419 by phil B

picon face
>
> All the parameters *except* price. ;-)
>

There are a number of params they don't put up.  Like
Rds on MOSFETs for example.  Or spectrum for LEDs
(color doesn't have a standardized meaning).  Still, I
wish mouser would get with the program here.  With
that and their project manager SW plus good prices,
they would be unstoppable.

Phil


               
__________________________________
Do you Yahoo!?
Yahoo! Small Business - Try our new Resources site
http://smallbusiness.yahoo.com/resources/

2005\05\30@151738 by Spehro Pefhany

picon face
At 12:04 PM 5/30/2005 -0700, you wrote:
> >
> > All the parameters *except* price. ;-)
> >
>
>There are a number of params they don't put up.  Like
>Rds on MOSFETs for example.

That would be useful, but only if they indicated the Vgs
it was measured at.

>  Or spectrum for LEDs
>(color doesn't have a standardized meaning).

nm wavelength ranges would do for me, in most cases.

>  Still, I
>wish mouser would get with the program here.  With
>that and their project manager SW plus good prices,
>they would be unstoppable.
>
>Phil

Yup. Digikey obviously have people there that understand how the
components are broadly classified, and allow you to distinguish
between, say, X7R and X5R dielectric on a ceramic cap. It's not
perfect, but it's pretty good.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
@spam@speffKILLspamspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\05\30@173616 by William Chops Westfield

face picon face

On May 30, 2005, at 11:49 AM, PicDude wrote:

>> All the parameters *except* price. ;-)
>
> Somewhat.  The rightmost column shows price.

But you can't sort by price or use price as a parameter in the
(otherwise
pretty good) parametric search functions. :-(  (still, this is much
better
than the major distributer sites that won't even let you LOOK at the
price
until you're deep within a single device branch of the product tree.)


> Comparing the 1-pc and multiple-thousand-piece (tape & reel) prices
> gives a decent ballpark price indication.

One of the nice things about digikey is that their first (and usually
pretty significant) price break occurs at the 25 count level.  That's
rather rare, and ideal for the smallish user...

BillW


2005\05\31@052431 by Chen Xiao Fan

face
flavicon
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The problem with the low cost SMPS controllers is the
quiescent current. This was true 5 years ago and is less
true now. MC34063 is a quite an old product anyway.

The problem with those nice SMPS controllers from
Intersil/Maxim/AD/Linear/TI is the relative high cost.
OnSemi/Fairchild/National/IR may produce some cheaper
product. There are some new players from Asia whose
product are less know to the public though.

Xiaofan

{Original Message removed}

2005\05\31@063804 by Russell McMahon

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flavicon
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I'm probably about to offer the manufacturer both TL499 and CD40106
based design and let them choose the one which works out cheapest
overall. I'll publish versions of them both with a pointer here as
they may be useful to others. The CD40106 (hex Schmitt inverter) has a
nasty parts count but the IC is the dearest single part at about
$US0.15 or less.  The TL499 design uses far less parts but the IC is
several times dearer. Both give good quiescent current and OK overall
performance. The CD40106 is probably more efficient due to the full
CMOS oscillator. Potentially VERY low quiescent  with great care. I
have also tried various discrete and IC approaches but all are either
too high quiescent or too dear or too flaky under questionable startup
conditions or samples not available to me here right now.

> The problem with the low cost SMPS controllers is the
> quiescent current. This was true 5 years ago and is less
> true now. MC34063 is a quite an old product anyway.

Very old. Excellent for higher power levels where leading edge
effciency is not an issue. Driver stage is not at all nice inside with
its darlington driver BUT using it to drive a FET removes the
saturation issue and transforms it. Driving a FET was not something
the makers ever envisaged "way back then".

> The problem with those nice SMPS controllers from
> Intersil/Maxim/AD/Linear/TI is the relative high cost.

Typically 5 times as much as a MC34063 :-(.

> OnSemi/Fairchild/National/IR may produce some cheaper
> product. There are some new players from Asia whose
> product are less know to the public though.

These I'd be interested in but I need samples here NOW and they also
need to be available in Taiwan soonish.
Next time round maybe.


               RM


'[EE] Design challenge - boost converter'
2005\06\01@122734 by PicDude
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Hey Russell,

Never heard of these guys until a mfgr's rep recently told me about them.  
Perhaps one of their products might fit your needs...  http://www.semtech.com .

Cheers,
-Neil.



On Tuesday 31 May 2005 05:37 am, Russell McMahon scribbled:
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