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switchers -- input range

D

David Lesher

Jan 1, 1970
0
In another group; there's a discussion about PC switcher inputs
ranges. This came up after a poster suffered from an open neutral,
and lost a lot of equipment.


A) Are their any switchers that automagicly sense the input and
change ranges? Some older Mac's are labeled "110-130 or 220-250"
vice the "110-250" of newer ones. Note I am NOT talking about units
with a {manual} voltage selector switch.

B) What's the gotcha on having a wider input range: More design
effort, to be sure, but do you also lose in efficiency, watts/cc^3,
power factor, etc? I've only read a little on switcher design &
never soldered on one. I'd assume you need to worry about the ratings
on the input L, C and other items, and the one limit is high-input
voltage, low load, [vs low, high...] cases. Other things?
 
L

legg

Jan 1, 1970
0
A) Are their any switchers that automagicly sense the input and
change ranges? Some older Mac's are labeled "110-130 or 220-250"
vice the "110-250" of newer ones. Note I am NOT talking about units
with a {manual} voltage selector switch.

Yes. These will describe themselves as 'universal input' and list one
wide input range of voltages. Sometimes this is achieved through an
automatic switching between ranges (auto-ranging), sometimes through
preregulation that may include power factor correction, and in some
lower-powered applications simply by operating over the wider range
(with the added stress absorbed by adequately rated parts).
B) What's the gotcha on having a wider input range: More design
effort, to be sure, but do you also lose in efficiency, watts/cc^3,
power factor, etc? I've only read a little on switcher design &
never soldered on one. I'd assume you need to worry about the ratings
on the input L, C and other items, and the one limit is high-input
voltage, low load, [vs low, high...] cases. Other things?

For your requirements (none stated), its just a matter of cost and
availability. For consumer PCs the most likely parts available will be
power-factor corrected supplies in PC form-factor, produced to comply
to newer EN61000 harmonic limits. As they are not yet commodities,
their pricing reflects the lower volume, rather that the component
cost.

For lower-powered projects or those not requiring PC clone
form-factor, there are wide-range, pfc corrected or auto-ranging input
supplies that are commodities reflecting the requirements of the
marketplace listed in didtributor catalogs for your inspection (Power
One, Condor and Kaga in the Digikey catalog, as examples).

RL
 
D

David Lesher

Jan 1, 1970
0
Yes. These will describe themselves as 'universal input' and list one
wide input range of voltages. Sometimes this is achieved through an
automatic switching between ranges (auto-ranging), sometimes through
preregulation that may include power factor correction, and in some
lower-powered applications simply by operating over the wider range
(with the added stress absorbed by adequately rated parts).


Err, that's not what I am asking. I am contrasting units that state
either of two input voltages vs those that have one WIDE (2-1)range.

What do the 'either' units actually do? I know (as the other responder
noted, perhaps a simple full-wave/half wave choice) such is possible
-- my question is what is/was built/sold.

(Or are the "either" units really just wide range ones with
a different label?)
For your requirements (none stated), its just a matter of cost and
availability.

Here my query is more theory-based. I know manufacturing costs
predominate, and create the bias for the "Any Voltage" design;
but I am curious where the piper gets paid when you do so....
(TANSTAAFL.)
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that David Lesher <[email protected]>
Err, that's not what I am asking. I am contrasting units that state
either of two input voltages vs those that have one WIDE (2-1)range.

What do the 'either' units actually do? I know (as the other responder
noted, perhaps a simple full-wave/half wave choice) such is possible --
my question is what is/was built/sold.

AIUI, they have/had a relay which opens its contacts very quickly if
subjected to the higher voltage and puts the rectifier into the bridge
mode (no voltage-doubling). A 120 V a.c. relay in series with a bridge
rectifier with a 120 V zener string across the d.c terminals might be
one way to do that.
 
R

Rich Grise

Jan 1, 1970
0
I read in sci.electronics.design that David Lesher <[email protected]>


AIUI, they have/had a relay which opens its contacts very quickly if
subjected to the higher voltage and puts the rectifier into the bridge
mode (no voltage-doubling). A 120 V a.c. relay in series with a bridge
rectifier with a 120 V zener string across the d.c terminals might be
one way to do that.

In fact, I once worked for a guy who did exactly that - well, not
exactly. He used a 220V relay, that pulled in and switched the dual
primaries from parallel to series. I thought it was a really flaky
design - kind of a klooge, actually - a diode and cap and resistor,
and it depended on a "calibrated" pull-in voltage for the relay, but
he sold a lot of them. But that wasn't a switcher - it was a 24V,
40A ferroresonant battery charger. You might have one if you have
a SkyJack scissors lift. :)

Cheers!
Rich
 
L

legg

Jan 1, 1970
0
Err, that's not what I am asking. I am contrasting units that state
either of two input voltages vs those that have one WIDE (2-1)range.

Your question was explicitly stated, and answered.
What do the 'either' units actually do? I know (as the other responder
noted, perhaps a simple full-wave/half wave choice) such is possible
-- my question is what is/was built/sold.

Most dual range units work(ed) on the simple single-link-selection of
full-wave or full-wave voltage doubler input rectification. Other
topologies that switched points in the converter stage were also
developed at various times.

The opportunity of using more complicated mechanical switching (dp/dt)
or manual plug/link assemblies, allowed the use of linear magnetics
and simpler AC air movers, without further design. Some ingenuity was
employed getting AC magnetics to move air and power housekeeping based
on the single link method, including the use of tapped-winding fan
motors being used as autotransformers.

Automatic switchover is typically achieved using a triac in the single
link position, or a relay in the complex switch situation. Sanken even
manufactured a dedicated smart-power IC with an internal triac for the
first technique (from memory the STK8900 and STK8901).

What is/was built/sold? ..... Everything you might think of.

RL
 
L

legg

Jan 1, 1970
0
On Thu, 23 Dec 2004 19:02:22 +0000 (UTC), David Lesher

Refreshed memory. Sanken part was STR80145, STR81145 and other
variations.

RL
 
P

przemek klosowski

Jan 1, 1970
0
In another group; there's a discussion about PC switcher inputs ranges.
This came up after a poster suffered from an open neutral, and lost a lot
of equipment.

A) Are their any switchers that automagicly sense the input and change
ranges? Some older Mac's are labeled "110-130 or 220-250" vice the
"110-250" of newer ones. Note I am NOT talking about units with a {manual}
voltage selector switch.

B) What's the gotcha on having a wider input range: More design effort, to
be sure, but do you also lose in efficiency, watts/cc^3, power factor,
etc? I've only read a little on switcher design & never soldered on one.
I'd assume you need to worry about the ratings on the input L, C and other
items, and the one limit is high-input voltage, low load, [vs low,
high...] cases. Other things?

I always thought that the basic principle is very simple: the input
voltage is double-wave rectified and charges a 500V cap; then, it is
chopped up at 100 kHz or so, step-down transformed (high freq->smaller
core) and rectified. Voltage control by PWM. In principle, such design
doesn't care about voltage or even AC/DC (I'd swear I have seen a power
supply rated something like 24-240V, DC/50Hz/60Hz).

Nobody else seemed to suggest this approach---am I off-base here?
 
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