What determines whether a switching supply will properly dri

  • Thread starter William Sommerwerck
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William Sommerwerck

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The following is unduly long -- especially as I want a short answer -- and
is partly an excuse for bragging about an expensive luxury I own. But the
question is serious, and the answer likely useful to many in this group.

The most-common external power supply (wall wart, if you like) ever made is
likely the Sony AC-E455D. This little black cube pumped out 4.5V at 500mA,
to power hundreds of thousands of Discmans and other portable devices.
They're so common that you can easily find them on eBay for a few bucks
each.

Jump to STAX. A few years back STAX introduced the SR-001 electrostatic
earphone (not headphone) system. These little gems are driven by a tiny
battery-operated amplifier/energizer that puts out 580V DC polarizing
voltage (!!!) and about 300V of AC drive signal. They aren't cheap, but the
sound justifies the price -- if you want really good sound when listening to
portable equipment.

http://www.audioreview.com/mfr/stax/headphones/sr-001-mk2-system/PRD_143823_2750crx.aspx

Now, the amplifier/energizer is powered by two AA cells. But there's a jack
on the back for 4.5V DC -- whose diameter and polarity just happen to match
the AC-E455D's. Though STAX sells its own terribly overpriced power supply,
one can't help but think that STAX was deliberately making the SR-001
compatible with a very common AC adapter.

Hang on, we're getting there...

Sony also produced a switching version of the AC-E455D, which operates from
100V to 240V, and puts out 1000mA. Two years ago I bought a dozen of these
on eBay for a buck apiece. As they were thinner and lighter than the
"linear" version, they became the power supplies I carried with my Discman
and STAX SR-001 system.

The interesting thing (finally!) is that most of the switching supplies
won't power the STAX energizer. The energizer's red "low voltage" light
comes on, the energizer tries to turn on (briefly flashing the green "good
voltage" light), but then drops back, and the cycle repeats, producing a
"thump-thump-thump" in the earphones.

Only one of the switching supplies I have will power the earphones -- and it
often has to struggle a bit to get going.

It's not an issue of voltage or current capacity, per se. What, exactly, is
going on?


--
"We already know the answers -- we just haven't asked the right
questions." -- Edwin Land
 
Just a wild guess .. a load resistor in parallel with the device
will fix the problem. It seems that some SMPS need a minimum
load to function as expected.
Click to expand...
That's what I suspected. However, the energizer is not a "light" load -- it
runs slightly warm. Whereas the CD player draws next to nothing, and the
supply has no problem with it.

Nevertheless, I might just stick a 200 ohm resistor across the power jack,
just to see what happens.
 
Just a wild guess ... a load resistor in parallel with the device will fix
the problem. It seems that some SMPS need a minimum load to function as
expected.
 
"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:hgjnk8$fvk$1@news.eternal-september.org...
Just a wild guess .. a load resistor in parallel with the device
will fix the problem. It seems that some SMPS need a minimum
load to function as expected.

That's what I suspected. However, the energizer is not a "light" load --
it
runs slightly warm. Whereas the CD player draws next to nothing, and the
supply has no problem with it.

Nevertheless, I might just stick a 200 ohm resistor across the power jack,
just to see what happens.


Perhaps a few hundred mF as well ??
Click to expand...

--
Regards .............. Rheilly P
 
"William Sommerwerck"

The interesting thing (finally!) is that most of the switching supplies
won't power the STAX energizer. The energizer's red "low voltage" light
comes on, the energizer tries to turn on (briefly flashing the green "good
voltage" light), but then drops back, and the cycle repeats, producing a
"thump-thump-thump" in the earphones.

Only one of the switching supplies I have will power the earphones -- and
it
often has to struggle a bit to get going.

It's not an issue of voltage or current capacity, per se. What, exactly,
is
going on?
Click to expand...

** The STAX energiser obviously contains a high frequency ( supersonic at
least ) inverter to generate the high DC voltage. Betya anything it draws a
heap of current when it first gets going.

Problem is, SMPSs usually have over-current protection which typically shuts
the supply down pronto - then it may try to re-start itself. Hence the
hiccupping noise.

OTOH - a battery supply or iron transformer supply can provide brief bursts
of high DC current that few small SMPSs can manage.



..... Phil
 
I agree with other comments WRT a high initial load causing the SMPS to
current-limit or shut down.

A couple of 12V 15A SMPSs I had recently, would fail to start up when a high
initial load was connected to them.
I was using a dual-beam halogen headlight lamp for a load, and the SMPS
would start up with either lamp connected, but not both.
They would try to restart after a brief pause, but not start up.

The load of the hot lamp filaments was about 5A and 3A, but higher with cold
filaments. The SMPS was able to power both lamps by starting with one lamp,
then adding the second (either one first) for extended periods with no
problems.

These were used SMPSs, and I have no way to know if new ones would operate
the same way, but I suspect that new ones would be the same.

Smart machines.. whaddaya gonna do?
The protected output keeps end users out of the supply (maybe), since
changing a fuse (or adjusting pots) won't change the rated output.

I don't know if adding a filtering electrolytic capacitor to the output
would help, I haven't tried it.
The solution may be to limit the inrush current to the STAX accessory.

Otherwise, get some over-2000 mAh NiMh AAs and a good charger, and carry
freshly-charged spares. This has been the only reasonable solution for
keeping my digital cameras portable.

--
Cheers,
WB
..............


"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:hgjm4j$9tk$1@news.eternal-september.org...
The following is unduly long -- especially as I want a short answer -- and
is partly an excuse for bragging about an expensive luxury I own. But the
question is serious, and the answer likely useful to many in this group.

The most-common external power supply (wall wart, if you like) ever made
is
likely the Sony AC-E455D. This little black cube pumped out 4.5V at 500mA,
to power hundreds of thousands of Discmans and other portable devices.
They're so common that you can easily find them on eBay for a few bucks
each.

Jump to STAX. A few years back STAX introduced the SR-001 electrostatic
earphone (not headphone) system. These little gems are driven by a tiny
battery-operated amplifier/energizer that puts out 580V DC polarizing
voltage (!!!) and about 300V of AC drive signal. They aren't cheap, but
the
sound justifies the price -- if you want really good sound when listening
to
portable equipment.

http://www.audioreview.com/mfr/stax/headphones/sr-001-mk2-system/PRD_143823_2750crx.aspx

Now, the amplifier/energizer is powered by two AA cells. But there's a
jack
on the back for 4.5V DC -- whose diameter and polarity just happen to
match
the AC-E455D's. Though STAX sells its own terribly overpriced power
supply,
one can't help but think that STAX was deliberately making the SR-001
compatible with a very common AC adapter.

Hang on, we're getting there...

Sony also produced a switching version of the AC-E455D, which operates
from
100V to 240V, and puts out 1000mA. Two years ago I bought a dozen of these
on eBay for a buck apiece. As they were thinner and lighter than the
"linear" version, they became the power supplies I carried with my Discman
and STAX SR-001 system.

The interesting thing (finally!) is that most of the switching supplies
won't power the STAX energizer. The energizer's red "low voltage" light
comes on, the energizer tries to turn on (briefly flashing the green "good
voltage" light), but then drops back, and the cycle repeats, producing a
"thump-thump-thump" in the earphones.

Only one of the switching supplies I have will power the earphones -- and
it
often has to struggle a bit to get going.

It's not an issue of voltage or current capacity, per se. What, exactly,
is
going on?


--
"We already know the answers -- we just haven't asked the right
questions." -- Edwin Land
Click to expand...
 
The STAX energiser obviously contains a high frequency
(supersonic at least ) inverter to generate the high DC voltage.
Betya anything it draws a heap of current when it first gets going.

Problem is, SMPSs usually have over-current protection which
typically shuts the supply down pronto -- then it may try to re-start
itself. Hence the hiccupping noise.

OTOH -- a battery supply or iron transformer supply can provide
brief bursts of high DC current that few small SMPSs can manage.
Click to expand...
That makes the most sense. Even with the supply that works, the red
(low-voltage) light comes on for quite some time before the energizer
switches to green, noticeably longer than batteries or the conventional
power supply.

Thanks for the info. I have to decide whether I want to accept things as
they are (I use the headphones fairly often, and am not sure want to carry
around a pile of rechargeable batteries), or modify the energizer with (say)
a 10-ohm series resistor.
 
Otherwise, get some over-2000 mAh NiMh AAs and a good
charger, and carry freshly-charged spares. This has been the
only reasonable solution for keeping my digital cameras portable.
Click to expand...
Actually, I have a bunch of 2500 and 2750mAh AA cells, from PowerEx (MAHA).
I use the MAHA C9000 charger, which I highly recommend. I have two, both of
which were purchased when Thomas Distributing had them on sale. There's an
(optional?) car-battery cable that permits "off line" recharging, a great
help for those "in the field".

The only thing wrong with this charger is that it won't take C or D cells
(MAHA refuses to produce adapters), so I use an Eveready nicad/NiMH charger
that takes all sizes from AAA to D, plus 9V. It works well, but it doesn't
have any of the C9000's features (choice of charging current, controlled
discharge and conditioning, capacity measurement, etc).

My first digital camera was the Olympus D-620L (still have it -- I'll sell
it for $100 to anyone who wants a cheap zoom DSLR for eBay shots, etc),
which used loose AA cells. My newer DSLRs take custom Li-ion battery packs.
I hope Olympus and Canon have the common decency to provide replacement
packs for at least the next decade. If not, may they (and other camera
companies) be struck with class-action lawsuits!

In case it hasn't been mentioned here... Do not purchase third-party Li-ion
battery packs, even from well-known companies (eg, DigiPower). They simply
do not last. Their capacities quickly decline and the charger starts
blinking or reporting "battery won't charge". The ones I bought for my Yaesu
VX-5R and Olympus E-500 "went bad" very quickly -- a complete waste of
money. (The OEM batteries for both still work fine.)
 
Some switching supplies do no do well in the presence
of a RF field. Does the STAX emit this type of interference
through the power lead?
Click to expand...
The STAX energizer is an audio product, and it's unlikely any switching
circuits in it operate above 50kHz or so.
 
On Sat, 19 Dec 2009 13:04:18 -0800, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

The following is unduly long -- especially as I want a short answer -- and
is partly an excuse for bragging about an expensive luxury I own. But the
question is serious, and the answer likely useful to many in this group.

The most-common external power supply (wall wart, if you like) ever made is
likely the Sony AC-E455D. This little black cube pumped out 4.5V at 500mA,
to power hundreds of thousands of Discmans and other portable devices.
They're so common that you can easily find them on eBay for a few bucks
each.

Jump to STAX. A few years back STAX introduced the SR-001 electrostatic
earphone (not headphone) system. These little gems are driven by a tiny
battery-operated amplifier/energizer that puts out 580V DC polarizing
voltage (!!!) and about 300V of AC drive signal. They aren't cheap, but the
sound justifies the price -- if you want really good sound when listening to
portable equipment.

http://www.audioreview.com/mfr/stax/headphones/sr-001-mk2-system/PRD_143823_2750crx.aspx

Now, the amplifier/energizer is powered by two AA cells. But there's a jack
on the back for 4.5V DC -- whose diameter and polarity just happen to match
the AC-E455D's. Though STAX sells its own terribly overpriced power supply,
one can't help but think that STAX was deliberately making the SR-001
compatible with a very common AC adapter.

Hang on, we're getting there...

Sony also produced a switching version of the AC-E455D, which operates from
100V to 240V, and puts out 1000mA. Two years ago I bought a dozen of these
on eBay for a buck apiece. As they were thinner and lighter than the
"linear" version, they became the power supplies I carried with my Discman
and STAX SR-001 system.

The interesting thing (finally!) is that most of the switching supplies
won't power the STAX energizer. The energizer's red "low voltage" light
comes on, the energizer tries to turn on (briefly flashing the green "good
voltage" light), but then drops back, and the cycle repeats, producing a
"thump-thump-thump" in the earphones.

Only one of the switching supplies I have will power the earphones -- and it
often has to struggle a bit to get going.

It's not an issue of voltage or current capacity, per se. What, exactly, is
going on?
Click to expand...
Some switching supplies do no do well in the presence of a RF field.
Does the STAX emit this type of interference through the power
lead?
 
William Sommerwerck wrote:
The following is unduly long -- especially as I want a short answer -- and
is partly an excuse for bragging about an expensive luxury I own. But the
question is serious, and the answer likely useful to many in this group.

The most-common external power supply (wall wart, if you like) ever made is
likely the Sony AC-E455D. This little black cube pumped out 4.5V at 500mA,
to power hundreds of thousands of Discmans and other portable devices.
They're so common that you can easily find them on eBay for a few bucks
each.

Jump to STAX. A few years back STAX introduced the SR-001 electrostatic
earphone (not headphone) system. These little gems are driven by a tiny
battery-operated amplifier/energizer that puts out 580V DC polarizing
voltage (!!!) and about 300V of AC drive signal. They aren't cheap, but the
sound justifies the price -- if you want really good sound when listening to
portable equipment.

http://www.audioreview.com/mfr/stax/headphones/sr-001-mk2-system/PRD_143823_2750crx.aspx

Now, the amplifier/energizer is powered by two AA cells. But there's a jack
on the back for 4.5V DC -- whose diameter and polarity just happen to match
the AC-E455D's. Though STAX sells its own terribly overpriced power supply,
one can't help but think that STAX was deliberately making the SR-001
compatible with a very common AC adapter.

Hang on, we're getting there...

Sony also produced a switching version of the AC-E455D, which operates from
100V to 240V, and puts out 1000mA. Two years ago I bought a dozen of these
on eBay for a buck apiece. As they were thinner and lighter than the
"linear" version, they became the power supplies I carried with my Discman
and STAX SR-001 system.

The interesting thing (finally!) is that most of the switching supplies
won't power the STAX energizer. The energizer's red "low voltage" light
comes on, the energizer tries to turn on (briefly flashing the green "good
voltage" light), but then drops back, and the cycle repeats, producing a
"thump-thump-thump" in the earphones.

Only one of the switching supplies I have will power the earphones -- and it
often has to struggle a bit to get going.

It's not an issue of voltage or current capacity, per se. What, exactly, is
going on?
Click to expand...
I would find it interesting that a supply of 1000ma would go into
current shutdown. If you had a peak hold DMM or some other way to
plot inrush current draw, it would be helpful to know what the device is
actually drawing peak. If it is an over current situation, maybe you can
get a NTC resistor to cut down the peak surge current. It might be
a challenge to find one with that low of rating.

on the flip side, if its shutting down from not enough load, you need
to put a small light bulb or such in parallel with the device for some
additional start up load.

bob
 
William Sommerwerck wrote:

The STAX energiser obviously contains a high frequency
(supersonic at least ) inverter to generate the high DC voltage.
Betya anything it draws a heap of current when it first gets going.


Problem is, SMPSs usually have over-current protection which
typically shuts the supply down pronto -- then it may try to re-start
itself. Hence the hiccupping noise.


OTOH -- a battery supply or iron transformer supply can provide
brief bursts of high DC current that few small SMPSs can manage.


That makes the most sense. Even with the supply that works, the red
(low-voltage) light comes on for quite some time before the energizer
switches to green, noticeably longer than batteries or the conventional
power supply.

Thanks for the info. I have to decide whether I want to accept things as
they are (I use the headphones fairly often, and am not sure want to carry
around a pile of rechargeable batteries), or modify the energizer with (say)
a 10-ohm series resistor.


If you would like, use a power PNP transistor on the (+) output and bias
Click to expand...
the base via the Hfe of the transistor to limit the max current of what
the supply can handle. The Collector would then be the output and the
Emitter to (+) of the power supply output. Base gets biased with
appropriate R to maybe just below the max current of the supply.

The beta will shift upward a bit when the transistor gets warm but
I don't think i'll matter after that..One could always place a Si diode
on top of the transistor to help clamp the bias voltage at the base to
stabilize it.

I've used simple PNP current limited circuits like that in many cases
to fix inrush currents on small circuits.

You can do this with a NPN if you want to float the (-) from the
collector.. Myself, I would go with the PNP..
 
"William Sommerwerck"

The STAX energizer is an audio product, and it's unlikely any switching
circuits in it operate above 50kHz or so.
Click to expand...

** Hang on a mo !!!

Current technology in audio power uses PWM amplification.

Switching frequencies are typically from 250 kHz up to over 1 MHz.

The A to Ds in most current audio uses sampling rates of 2.6 MHz.

Hi-fi FM radio is also audio - operates in the VHF range.

Radio microphones are considered part of "audio" too - frequencies used
range from VHF up to several GHz.



..... Phil
 
I would find it interesting that a supply of 1000mA would go into
current shutdown. If you had a peak hold DMM or some other
way to plot inrush current draw, it would be helpful to know what
the device is actually drawing peak. If it is an over current situation,
maybe you can get a NTC resistor to cut down the peak surge
current. It might be a challenge to find one with that low of rating.

On the flip side, if its shutting down from not enough load, you need
to put a small light bulb or such in parallel with the device for some
additional start up load.
Click to expand...
I think is the issue is "too much" load. The power supply operates a
Discman -- which draws 1/10 the current -- with no problem whatever. Ergo...

I don't have a peak-hold meter. However, I did measure the battery current
with a Fluke 87 -- it's around 180mA. But at the moment you connect the
battery, the digital bar-graph display goes WHAM!, all the way to the right
in a fraction of a second. I suspect the unit is drawing several times 180mA
at turn-on.

The AC adapter input is spec'd at 300mA -- presumably the maximum capacity
required, rather than the average drawn.

If I can find a matching plug/socket pair, I might experiment with small
series resistors (1 to 5 ohms) to see what happens. At the moment, it's not
a pressing issue.
 
The STAX energizer is an audio product, and it's unlikely
any switching circuits in it operate above 50kHz or so.

** Hang on a mo !!!
Current technology in audio power uses PWM amplification.
Click to expand...
Who said this was a PWM amplifier?

The design dates back to 1996. It's highly unlikely the unit uses PWM -- why
should it? The amp drives electrostatic earphones whose cross-sectional area
is a bit larger than 1 square inch -- plus the cable capacitance. You don't
need much current drive for that. What would be the advantage of PWM
amplification?

Now, it might use a switching power supply to get the 580V DC needed for the
polarizing voltage. But that's a different issue.
 
If you would like, use a power PNP transistor on the (+) output
and bias the base via the Hfe of the transistor to limit the max
current of what the supply can handle. The collector would then
be the output and the emitter to (+) of the power supply output.
Base gets biased with appropriate R to maybe just below the
max current of the supply.

The beta will shift upward a bit when the transistor gets warm
but I don't think it'll matter after that..One could always place
a Si diode on top of the transistor to help clamp the bias
voltage at the base to stabilize it.

I've used simple PNP current limited circuits like that in many
cases to fix inrush currents on small circuits.

You can do this with a NPN if you want to float the (-) from
the collector. Myself, I would go with the PNP...
Click to expand...
Thanks for the suggestion, but the amplifier is quite small, and I'm not
going to rip into it for a modification of this sort.
 
"William Sommerwanker"

** Hang on a mo !!!

Current technology in audio power uses PWM amplification.

Who said this was a PWM amplifier?
Click to expand...

** Read the WHOLE fucking post.

IDIOT !!
 
What makes you think I take anything you say seriously? Or that I'm bothered
that you so crudely disagree with anyone here, or am pleased when you do?

I couldn't care less. You are less than nothing, Mr. Allison.
 
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