Need a big transformer...

On Mar 24, 5:23 pm, Joerg <notthisjoerg...@removethispacbell.net>
wrote:

mrdarr...@gmail.com wrote:
On Mar 24, 2:26 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
mrdarr...@gmail.com wrote:
On Mar 24, 2:14 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
mrdarr...@gmail.com wrote:
On Mar 24, 1:29 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
[...]
I just don't know where such a place would be near Sacramento, I don't
think the guys at Kiefer Blvd run such sales. The Bay Area should be
better, I guess John Larkin would know a place or two.
I went to the Kiefer Blvd place, and they didn't have large center-
tapped 48V transformers, but I called again today and they have a box
full of 24V stuff... time to pay them another visit...
Thanks, good to know they do such sales.
[...]
--
Regards, Joerg
http://www.analogconsultants.com/
Actually we went to the Surplus Stuff place on Folsom Blvd (it's not
Kiefer after all - or is there another one on Kiefer Blvd itself?)
because my wife and I wanted to take a look at the flea market going
on next door. They had a lot of old low-power stuff (reel-to-reel
tape players, VCRs) at the flea market but nothing that looked like it
could handle several hundred watts.
Lots of car audio amplifiers for sale, too. But that's no fun...
already built...
Kiefer is the waste and recycling collection site for Sacramento.

Where is that surplus place on Folsom Blvd?

--
Regards, Joerg

http://www.analogconsultants.com/

!!! Oh I hadn't realized the Kiefer Landfill had stuff for people to
grab. I thought you pay a fee to get in and dump your stuff, only.

Well, I don't know, it was just a thought. All I know is that the guys
up here don't let people cart things away but some places do.

Surplus Stuff...
http://maps.google.com/maps?f=q&hl=en&geocode=&q=surplus+stuff,+95826...

Here are pictures from inside the store:http://daviswiki.org/Surplus_Stuff

Wish those places had their stuff listed somewhere.

--
Regards, Joerg

http://www.analogconsultants.com/

I remember going there last year for a pcmcia wifi thingie; he wanted
more than eBay sellers charge.

When we went last Sat, I got a cd-rom drive for $5. (to get my kids'
computer working.)

They have lots of motherboards and older laptops (toughbooks I think).

I saw a few scopes there, but they looked old... not sure they're
calibrated...

What're you looking for in particular? Give 'em a call...

Michael

 

[Joerg]

mrdarrett@gmail.com wrote:

On Mar 24, 5:23 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
mrdarr...@gmail.com wrote:
On Mar 24, 2:26 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
mrdarr...@gmail.com wrote:
On Mar 24, 2:14 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
mrdarr...@gmail.com wrote:
On Mar 24, 1:29 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
[...]
I just don't know where such a place would be near Sacramento, I don't
think the guys at Kiefer Blvd run such sales. The Bay Area should be
better, I guess John Larkin would know a place or two.
I went to the Kiefer Blvd place, and they didn't have large center-
tapped 48V transformers, but I called again today and they have a box
full of 24V stuff... time to pay them another visit...
Thanks, good to know they do such sales.
[...]
--
Regards, Joerg
http://www.analogconsultants.com/
Actually we went to the Surplus Stuff place on Folsom Blvd (it's not
Kiefer after all - or is there another one on Kiefer Blvd itself?)
because my wife and I wanted to take a look at the flea market going
on next door. They had a lot of old low-power stuff (reel-to-reel
tape players, VCRs) at the flea market but nothing that looked like it
could handle several hundred watts.
Lots of car audio amplifiers for sale, too. But that's no fun...
already built...
Kiefer is the waste and recycling collection site for Sacramento.
Where is that surplus place on Folsom Blvd?
--
Regards, Joerg
http://www.analogconsultants.com/
!!! Oh I hadn't realized the Kiefer Landfill had stuff for people to
grab. I thought you pay a fee to get in and dump your stuff, only.
Well, I don't know, it was just a thought. All I know is that the guys
up here don't let people cart things away but some places do.

Surplus Stuff...
http://maps.google.com/maps?f=q&hl=en&geocode=&q=surplus+stuff,+95826...
Here are pictures from inside the store:http://daviswiki.org/Surplus_Stuff

Wish those places had their stuff listed somewhere.

--
Regards, Joerg

http://www.analogconsultants.com/


I remember going there last year for a pcmcia wifi thingie; he wanted
more than eBay sellers charge.

When we went last Sat, I got a cd-rom drive for $5. (to get my kids'
computer working.)

They have lots of motherboards and older laptops (toughbooks I think).

I saw a few scopes there, but they looked old... not sure they're
calibrated...

What're you looking for in particular? Give 'em a call...

Nothing right now but once in a while I am looking around for clients.
Tek 2465 and such, or the occasional 7L12 or 7L13 analyzer modules (but
without fried mixers).

--
Regards, Joerg

http://www.analogconsultants.com/

 

On Mar 24, 1:29 pm, Joerg <notthisjoerg...@removethispacbell.net>
wrote:

mrdarr...@gmail.com wrote:
On Mar 22, 3:34 pm, "Paul E. Schoen" <pst...@smart.net> wrote:
mrdarr...@gmail.com> wrote in message

news:37c1b825-37ff-4042-8c36-e5a294c4b4bb@s12g2000prg.googlegroups.com...

So let's say I want to build an LM3886 amplifier.
http://www.national.com/mpf/LM/LM3886.html
At 68W RMS, assuming 50% efficiency, I'd need at least, what, a 150W
transformer, right?
And if I build two for stereo, that would be 300W required. 70V
secondary, center-tapped, to get +/- 35V.
Those things are expensive on Mouser ($60+). Especially considering
the LM3886 only costs $7 or so.
Any suggestions where I can get such a large transformer for cheap?
Thanks,
Michael
Why do you need a transformer? The amplifier has direct output drive with
+/- 28 VDC supplies. You can use two inexpensive 100 watt switchers, and
add a little series inductor and a really big capacitor on each, to take
care of HF switching noise and short burst peak power requirements. You
could even use 24 VDC supplies, which might be more common, and available
very cheap surplus or used.

Paul

24VDC supplies are commonly used for...?

Mostly for industrial gear. Meaning that 12V supplies at a scrap yard
that sells to hobbyists cost a whole lot more than 24V supplies of which
they often have a lot. 48V is also popular, can be found in scrapped
telco gear.

I just don't know where such a place would be near Sacramento, I don't
think the guys at Kiefer Blvd run such sales. The Bay Area should be
better, I guess John Larkin would know a place or two.



Or do you mean regular computer ATX supplies, -12-0-12?

Could I take two ATX supplies, and tie them like this to get -24-0-24?

---------- ----------
| ATX | | ATX |
| Supply 1 | | Supply 2 |
| | | |
---------- ----------
| | | |
-12V +12V -12V +12V
| |___________| |
| | |
| | |
-24V 0 +24V

That can get noisy, their -12V is too weak and often they misbehave when
going underneath their minimum load. You'd have to keep listening to
AC-DC or Meat Loaf where the audio will be at max all the time ;-)

Another source would be, you guessed it, a big old stereo amp.

--
Regards, Joerg

http://www.analogconsultants.com/

Hopefully I'll go to Surplus Stuff today at lunch.

If worst comes to worst, I can always take an old AT power supply, and
put this DC-DC switcher between +12V and ground, right?

(for practice) http://sound.westhost.com/project69.htm
(the real deal) http://sound.westhost.com/project89.htm

Michael

 

[Paul E. Schoen]

<mrdarrett@gmail.com> wrote in message
news:60efae89-cd05-4a8f-9325-b1bbb02ded19@h11g2000prf.googlegroups.com...

Hopefully I'll go to Surplus Stuff today at lunch.

If worst comes to worst, I can always take an old AT power supply, and
put this DC-DC switcher between +12V and ground, right?

(for practice) http://sound.westhost.com/project69.htm
(the real deal) http://sound.westhost.com/project89.htm

Michael

That seems like an awful lot of trouble to save a few dollars. If cost is a
big issue, just get four (or six) similar old computer supplies and series
the +12V outputs which have at least 3 or 4 amps. I'm not sure if the
common is connected to the case, but you could always mount them on
insulators. Biggest problem might be running with no load on the 5 VDC
output, but you could add a resistor or a lamp or something if necessary,
and if efficiency and heat are not problems.

If you just need +/- 36 VDC from a 12 VDC source, try the simple circuit at
the end. It provides a total of about 70 watts at 88% efficiency. The
LT1170 is about $10, but the other parts are pretty cheap, and you only
need one inductor.

You could get more power by using a switchmode controller and an external
MOSFET.

Paul

========================================================================================

Version 4
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pn="UPL1J221MRH" type="Al electrolytic" ppPkg=1
TEXT 760 832 Left 0 !.tran 150m startup

 

[Joerg]

mrdarrett@gmail.com wrote:

On Mar 24, 1:29 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
mrdarr...@gmail.com wrote:
On Mar 22, 3:34 pm, "Paul E. Schoen" <pst...@smart.net> wrote:
mrdarr...@gmail.com> wrote in message
news:37c1b825-37ff-4042-8c36-e5a294c4b4bb@s12g2000prg.googlegroups.com...
So let's say I want to build an LM3886 amplifier.
http://www.national.com/mpf/LM/LM3886.html
At 68W RMS, assuming 50% efficiency, I'd need at least, what, a 150W
transformer, right?
And if I build two for stereo, that would be 300W required. 70V
secondary, center-tapped, to get +/- 35V.
Those things are expensive on Mouser ($60+). Especially considering
the LM3886 only costs $7 or so.
Any suggestions where I can get such a large transformer for cheap?
Thanks,
Michael
Why do you need a transformer? The amplifier has direct output drive with
+/- 28 VDC supplies. You can use two inexpensive 100 watt switchers, and
add a little series inductor and a really big capacitor on each, to take
care of HF switching noise and short burst peak power requirements. You
could even use 24 VDC supplies, which might be more common, and available
very cheap surplus or used.
Paul
24VDC supplies are commonly used for...?
Mostly for industrial gear. Meaning that 12V supplies at a scrap yard
that sells to hobbyists cost a whole lot more than 24V supplies of which
they often have a lot. 48V is also popular, can be found in scrapped
telco gear.

I just don't know where such a place would be near Sacramento, I don't
think the guys at Kiefer Blvd run such sales. The Bay Area should be
better, I guess John Larkin would know a place or two.



Or do you mean regular computer ATX supplies, -12-0-12?
Could I take two ATX supplies, and tie them like this to get -24-0-24?
---------- ----------
| ATX | | ATX |
| Supply 1 | | Supply 2 |
| | | |
---------- ----------
| | | |
-12V +12V -12V +12V
| |___________| |
| | |
| | |
-24V 0 +24V
That can get noisy, their -12V is too weak and often they misbehave when
going underneath their minimum load. You'd have to keep listening to
AC-DC or Meat Loaf where the audio will be at max all the time ;-)

Another source would be, you guessed it, a big old stereo amp.

--
Regards, Joerg

http://www.analogconsultants.com/



Hopefully I'll go to Surplus Stuff today at lunch.

If worst comes to worst, I can always take an old AT power supply, and
put this DC-DC switcher between +12V and ground, right?

(for practice) http://sound.westhost.com/project69.htm
(the real deal) http://sound.westhost.com/project89.htm

Just make sure to stay above frequencies that can still bother animals.
Occasionally the shepherd here leaves the lab and she can clearly signal
disgust just by one look at me. The rottie is usually quite unfazed by
any kind of noise.

Also, preventing noise into the audio won't be trivial. The PSRR of
audio amps might be great at 120Hz but not at a sub-harmonic of several kHz.

--
Regards, Joerg

http://www.analogconsultants.com/

 

On Mar 26, 2:25 pm, Joerg <notthisjoerg...@removethispacbell.net>
wrote:

....

Hopefully I'll go to Surplus Stuff today at lunch.

If worst comes to worst, I can always take an old AT power supply, and
put this DC-DC switcher between +12V and ground, right?

(for practice) http://sound.westhost.com/project69.htm
(the real deal)http://sound.westhost.com/project89.htm

Just make sure to stay above frequencies that can still bother animals.
Occasionally the shepherd here leaves the lab and she can clearly signal
disgust just by one look at me. The rottie is usually quite unfazed by
any kind of noise.

Also, preventing noise into the audio won't be trivial. The PSRR of
audio amps might be great at 120Hz but not at a sub-harmonic of several kHz.

--
Regards, Joerg

http://www.analogconsultants.com/

Bleah... the 24V transformers at Surplus Stuff are switchers similar
to laptop power supplies.

If I go the SG3525 switching route, it looks like the most expensive
part will be the ultrafast bridge. I Mousered those, and those prices
make a toroid transformer start to look cheap...

Any suggestions? 35A at 200V looks like overkill anyway...

Michael

 

[Paul E. Schoen]

<mrdarrett@gmail.com> wrote in message
news:ddafd50e-99bd-4472-9518-2b0727e4e499@i29g2000prf.googlegroups.com...

On Mar 26, 2:25 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:

...

Hopefully I'll go to Surplus Stuff today at lunch.

If worst comes to worst, I can always take an old AT power supply, and
put this DC-DC switcher between +12V and ground, right?

(for practice) http://sound.westhost.com/project69.htm
(the real deal)http://sound.westhost.com/project89.htm

Just make sure to stay above frequencies that can still bother animals.
Occasionally the shepherd here leaves the lab and she can clearly signal
disgust just by one look at me. The rottie is usually quite unfazed by
any kind of noise.

Also, preventing noise into the audio won't be trivial. The PSRR of
audio amps might be great at 120Hz but not at a sub-harmonic of several
kHz.

--
Regards, Joerg

http://www.analogconsultants.com/


Bleah... the 24V transformers at Surplus Stuff are switchers similar
to laptop power supplies.

If I go the SG3525 switching route, it looks like the most expensive
part will be the ultrafast bridge. I Mousered those, and those prices
make a toroid transformer start to look cheap...

Any suggestions? 35A at 200V looks like overkill anyway...

Michael

If you really want to use a 60 Hz transformer and the usual rectifiers,
capacitors, etc., here's one that should work (28 VAC, 6A), for $14.50:

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=HAR&Product_Code=TM95XFR2765&Category_Code=XFR

Or get two of these 24VAC at 4A jobs for $6.50 each.

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=HAR&Product_Code=TM99XFR3396&Category_Code=XFR

Or use two of these 65 watt 27VDC 2.4 amp switchers for $28 each:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=201946

Here's 24 VDC at 4 amps for $10. These guys have some cool stuff:

http://www.fairradio.com/catalog.php?mode=viewitem&item=2994

And here's a list of transformers. They have a toroid assembly with dual
24VCT at 8A for $40, and 36V 3A for $8:

http://www.fairradio.com/catalog.php?mode=view&categoryid=1546

Paul

 

On Mar 27, 12:05 am, "Paul E. Schoen" <pst...@smart.net> wrote:

mrdarr...@gmail.com> wrote in message

news:ddafd50e-99bd-4472-9518-2b0727e4e499@i29g2000prf.googlegroups.com...



On Mar 26, 2:25 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:

...

Hopefully I'll go to Surplus Stuff today at lunch.

If worst comes to worst, I can always take an old AT power supply, and
put this DC-DC switcher between +12V and ground, right?

(for practice) http://sound.westhost.com/project69.htm
(the real deal)http://sound.westhost.com/project89.htm

Just make sure to stay above frequencies that can still bother animals.
Occasionally the shepherd here leaves the lab and she can clearly signal
disgust just by one look at me. The rottie is usually quite unfazed by
any kind of noise.

Also, preventing noise into the audio won't be trivial. The PSRR of
audio amps might be great at 120Hz but not at a sub-harmonic of several
kHz.

--
Regards, Joerg

http://www.analogconsultants.com/

Bleah... the 24V transformers at Surplus Stuff are switchers similar
to laptop power supplies.

If I go the SG3525 switching route, it looks like the most expensive
part will be the ultrafast bridge. I Mousered those, and those prices
make a toroid transformer start to look cheap...

Any suggestions? 35A at 200V looks like overkill anyway...

Michael

If you really want to use a 60 Hz transformer and the usual rectifiers,
capacitors, etc., here's one that should work (28 VAC, 6A), for $14.50:

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=H...

Or get two of these 24VAC at 4A jobs for $6.50 each.

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=H...

Or use two of these 65 watt 27VDC 2.4 amp switchers for $28 each:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId...

Here's 24 VDC at 4 amps for $10. These guys have some cool stuff:

http://www.fairradio.com/catalog.php?mode=viewitem&item=2994

And here's a list of transformers. They have a toroid assembly with dual
24VCT at 8A for $40, and 36V 3A for $8:

http://www.fairradio.com/catalog.php?mode=view&categoryid=1546

Paul

Wow, thanks a bunch! Good thing I asked. Now I know where to shop...

Michael

 

On Mar 27, 12:05 am, "Paul E. Schoen" <pst...@smart.net> wrote:

mrdarr...@gmail.com> wrote in message

news:ddafd50e-99bd-4472-9518-2b0727e4e499@i29g2000prf.googlegroups.com...



On Mar 26, 2:25 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:

...

Hopefully I'll go to Surplus Stuff today at lunch.

If worst comes to worst, I can always take an old AT power supply, and
put this DC-DC switcher between +12V and ground, right?

(for practice) http://sound.westhost.com/project69.htm
(the real deal)http://sound.westhost.com/project89.htm

Just make sure to stay above frequencies that can still bother animals.
Occasionally the shepherd here leaves the lab and she can clearly signal
disgust just by one look at me. The rottie is usually quite unfazed by
any kind of noise.

Also, preventing noise into the audio won't be trivial. The PSRR of
audio amps might be great at 120Hz but not at a sub-harmonic of several
kHz.

--
Regards, Joerg

http://www.analogconsultants.com/

Bleah... the 24V transformers at Surplus Stuff are switchers similar
to laptop power supplies.

If I go the SG3525 switching route, it looks like the most expensive
part will be the ultrafast bridge. I Mousered those, and those prices
make a toroid transformer start to look cheap...

Any suggestions? 35A at 200V looks like overkill anyway...

Michael

If you really want to use a 60 Hz transformer and the usual rectifiers,
capacitors, etc., here's one that should work (28 VAC, 6A), for $14.50:

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=H...

Or get two of these 24VAC at 4A jobs for $6.50 each.

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=H...

Or use two of these 65 watt 27VDC 2.4 amp switchers for $28 each:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId...

Here's 24 VDC at 4 amps for $10. These guys have some cool stuff:

http://www.fairradio.com/catalog.php?mode=viewitem&item=2994

And here's a list of transformers. They have a toroid assembly with dual
24VCT at 8A for $40, and 36V 3A for $8:

http://www.fairradio.com/catalog.php?mode=view&categoryid=1546

Paul

Say... if I do go the switcher route here:
http://sound.westhost.com/project89.htm

is it ok to parallel smaller (1A) ultrafast bridges?
http://www.vishay.com/docs/88577/edf1am.pdf

Michael

 

[Joerg]

mrdarrett@gmail.com wrote:

On Mar 27, 12:05 am, "Paul E. Schoen" <pst...@smart.net> wrote:
mrdarr...@gmail.com> wrote in message

news:ddafd50e-99bd-4472-9518-2b0727e4e499@i29g2000prf.googlegroups.com...



On Mar 26, 2:25 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
...
Hopefully I'll go to Surplus Stuff today at lunch.
If worst comes to worst, I can always take an old AT power supply, and
put this DC-DC switcher between +12V and ground, right?
(for practice) http://sound.westhost.com/project69.htm
(the real deal)http://sound.westhost.com/project89.htm
Just make sure to stay above frequencies that can still bother animals.
Occasionally the shepherd here leaves the lab and she can clearly signal
disgust just by one look at me. The rottie is usually quite unfazed by
any kind of noise.
Also, preventing noise into the audio won't be trivial. The PSRR of
audio amps might be great at 120Hz but not at a sub-harmonic of several
kHz.
--
Regards, Joerg
http://www.analogconsultants.com/
Bleah... the 24V transformers at Surplus Stuff are switchers similar
to laptop power supplies.
If I go the SG3525 switching route, it looks like the most expensive
part will be the ultrafast bridge. I Mousered those, and those prices
make a toroid transformer start to look cheap...
Any suggestions? 35A at 200V looks like overkill anyway...
Michael
If you really want to use a 60 Hz transformer and the usual rectifiers,
capacitors, etc., here's one that should work (28 VAC, 6A), for $14.50:

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=H...

Or get two of these 24VAC at 4A jobs for $6.50 each.

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=H...

Or use two of these 65 watt 27VDC 2.4 amp switchers for $28 each:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId...

Here's 24 VDC at 4 amps for $10. These guys have some cool stuff:

http://www.fairradio.com/catalog.php?mode=viewitem&item=2994

And here's a list of transformers. They have a toroid assembly with dual
24VCT at 8A for $40, and 36V 3A for $8:

http://www.fairradio.com/catalog.php?mode=view&categoryid=1546

Paul


Say... if I do go the switcher route here:
http://sound.westhost.com/project89.htm

is it ok to parallel smaller (1A) ultrafast bridges?
http://www.vishay.com/docs/88577/edf1am.pdf

Usually that works, especially if from the same batch. Just keep in mind
that the current won't distribute equally, so don't load five of them
with exactly five times the current. Maybe three times ...

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Paul E. Schoen]

<mrdarrett@gmail.com> wrote in message
news:ee556ff4-6f89-47ce-a3a6-6982b6d6054e@d4g2000prg.googlegroups.com...

On Mar 27, 12:05 am, "Paul E. Schoen" <pst...@smart.net> wrote:
mrdarr...@gmail.com> wrote in message

news:ddafd50e-99bd-4472-9518-2b0727e4e499@i29g2000prf.googlegroups.com...



On Mar 26, 2:25 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:

...

Hopefully I'll go to Surplus Stuff today at lunch.

If worst comes to worst, I can always take an old AT power supply,
and
put this DC-DC switcher between +12V and ground, right?

(for practice) http://sound.westhost.com/project69.htm
(the real deal)http://sound.westhost.com/project89.htm

Just make sure to stay above frequencies that can still bother
animals.
Occasionally the shepherd here leaves the lab and she can clearly
signal
disgust just by one look at me. The rottie is usually quite unfazed
by
any kind of noise.

Also, preventing noise into the audio won't be trivial. The PSRR of
audio amps might be great at 120Hz but not at a sub-harmonic of
several
kHz.

--
Regards, Joerg

http://www.analogconsultants.com/

Bleah... the 24V transformers at Surplus Stuff are switchers similar
to laptop power supplies.

If I go the SG3525 switching route, it looks like the most expensive
part will be the ultrafast bridge. I Mousered those, and those prices
make a toroid transformer start to look cheap...

Any suggestions? 35A at 200V looks like overkill anyway...

Michael

If you really want to use a 60 Hz transformer and the usual rectifiers,
capacitors, etc., here's one that should work (28 VAC, 6A), for $14.50:

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=H...

Or get two of these 24VAC at 4A jobs for $6.50 each.

http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=H...

Or use two of these 65 watt 27VDC 2.4 amp switchers for $28 each:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId...

Here's 24 VDC at 4 amps for $10. These guys have some cool stuff:

http://www.fairradio.com/catalog.php?mode=viewitem&item=2994

And here's a list of transformers. They have a toroid assembly with dual
24VCT at 8A for $40, and 36V 3A for $8:

http://www.fairradio.com/catalog.php?mode=view&categoryid=1546

Paul


Say... if I do go the switcher route here:
http://sound.westhost.com/project89.htm

is it ok to parallel smaller (1A) ultrafast bridges?
http://www.vishay.com/docs/88577/edf1am.pdf

Michael

There's really no need to go to all the trouble of that complicated circuit
just to get +/- 35 VDC from 12 VDC, which you have to generate from line
voltage anyway (unless you really want a battery powered amp). I posted a
schematic for a switching supply that will generate at least +/- 34 volts
at 1 amp, using a single power IC, a single inductor, and three Schottky
diodes. You can use the same principle to generate as much voltage and
current as you want by using a single high power MOSFET and a switchmode
controller (even the SG3525 or SG3526), but much better would be one of
Linear Technology's controllers that are designed to drive a MOSFET
directly, or add a driver.

Look at the circuit provided by LTSpice for the 1247 PWM controller. It
will provide 24 volts into 10 ohms, or 62 watts, from 12 VDC input. I
modified the circuit to get 38 volts into 12 ohms, or 117 watts out, at 92%
efficiency. It's a $3 IC, a $1 MOSFET, a $1 diode, a $1 capacitor, and
maybe a $3 inductor. You can add two more diodes and two more capacitors to
get a negative voltage. Everything you need, maybe $15.

The circuit follows. You do have LTspice (SwitcherCAD), don't you?

Paul

==========================================================================

Version 4
SHEET 1 2984 1720
WIRE 2000 1200 1792 1200
WIRE 2384 1200 2000 1200
WIRE 1792 1216 1792 1200
WIRE 2384 1216 2384 1200
WIRE 1792 1312 1792 1296
WIRE 2384 1312 2384 1296
WIRE 2448 1312 2384 1312
WIRE 2560 1312 2512 1312
WIRE 2672 1312 2560 1312
WIRE 2784 1312 2672 1312
WIRE 2560 1328 2560 1312
WIRE 2784 1328 2784 1312
WIRE 2000 1344 2000 1200
WIRE 2672 1344 2672 1312
WIRE 2336 1392 2144 1392
WIRE 1856 1424 1760 1424
WIRE 2560 1424 2560 1408
WIRE 2560 1424 2464 1424
WIRE 2672 1424 2672 1408
WIRE 2784 1424 2784 1408
WIRE 1760 1440 1760 1424
WIRE 2560 1440 2560 1424
WIRE 2384 1456 2384 1408
WIRE 2384 1456 2144 1456
WIRE 2208 1472 2176 1472
WIRE 2304 1472 2208 1472
WIRE 2384 1472 2384 1456
WIRE 2304 1488 2304 1472
WIRE 2176 1520 2176 1472
WIRE 2176 1520 2144 1520
WIRE 2208 1520 2208 1472
WIRE 2560 1536 2560 1520
WIRE 1760 1552 1760 1520
WIRE 1856 1552 1760 1552
WIRE 2384 1568 2384 1552
WIRE 1760 1584 1760 1552
WIRE 2176 1584 2144 1584
WIRE 2304 1584 2304 1568
WIRE 1760 1664 1760 1648
WIRE 2176 1664 2176 1584
WIRE 2208 1664 2208 1584
WIRE 2208 1664 2176 1664
WIRE 2304 1664 2304 1648
WIRE 2304 1664 2208 1664
WIRE 2464 1664 2464 1424
WIRE 2464 1664 2304 1664
WIRE 2000 1680 2000 1632
FLAG 2384 1568 0
FLAG 2000 1680 0
FLAG 1792 1312 0
FLAG 2672 1424 0
FLAG 2560 1536 0
FLAG 1760 1664 0
FLAG 2784 1424 0
FLAG 2784 1312 OUT
FLAG 1792 1200 IN
SYMBOL NMOS 2336 1312 R0
WINDOW 0 -8 16 Right 0
WINDOW 3 36 108 Right 0
SYMATTR InstName Q1
SYMATTR Value STD30NF06L
SYMBOL RES 2368 1456 R0
SYMATTR InstName R1
SYMATTR Value .05
SYMBOL res 1744 1424 R0
SYMATTR InstName R2
SYMATTR Value 6.2K
SYMBOL cap 1744 1648 M180
WINDOW 0 24 64 Left 0
WINDOW 3 24 8 Left 0
SYMATTR InstName C1
SYMATTR Value 500p
SYMBOL cap 2192 1520 R0
SYMATTR InstName C2
SYMATTR Value 22p
SYMBOL ind 2368 1200 R0
SYMATTR InstName L1
SYMATTR Value 10ľ
SYMATTR SpiceLine Ipk=10.5 Rser=0.0129 Rpar=84445 Cpar=9.8p mfg="Wurth
Elektronik" pn="7447709100 WE-PD XXL"
SYMBOL VOLTAGE 1792 1200 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL schottky 2448 1296 M90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName D1
SYMATTR Value MBR20100CT
SYMBOL polcap 2656 1344 R0
SYMATTR SpiceLine V=63 Irms=1.34 Rser=0.055 MTBF=5000 Lser=0 mfg="Nichicon"
pn="UPL1J271MRH" type="Al electrolytic" ppPkg=1
SYMATTR InstName C3
SYMATTR Value 270ľ
SYMBOL res 2544 1312 R0
SYMATTR InstName R3
SYMATTR Value 35k
SYMBOL res 2544 1424 R0
SYMATTR InstName R4
SYMATTR Value 2.5k
SYMBOL cap 2288 1584 R0
SYMATTR InstName C4
SYMATTR Value 470p
SYMBOL res 2288 1472 R0
SYMATTR InstName R5
SYMATTR Value 3K
SYMBOL PowerProducts\\LT1247 2000 1488 R0
SYMATTR InstName U1
SYMBOL res 2768 1312 R0
SYMATTR InstName Rload
SYMATTR Value 12
TEXT 2520 1624 Left 0 !.tran 4m startup

 

On Mar 28, 1:02 am, "Paul E. Schoen" <pst...@smart.net> wrote:

....

There's really no need to go to all the trouble of that complicated circuit
just to get +/- 35 VDC from 12 VDC, which you have to generate from line
voltage anyway (unless you really want a battery powered amp). I posted a
schematic for a switching supply that will generate at least +/- 34 volts
at 1 amp, using a single power IC, a single inductor, and three Schottky
diodes. You can use the same principle to generate as much voltage and
current as you want by using a single high power MOSFET and a switchmode
controller (even the SG3525 or SG3526), but much better would be one of
Linear Technology's controllers that are designed to drive a MOSFET
directly, or add a driver.

Look at the circuit provided by LTSpice for the 1247 PWM controller. It
will provide 24 volts into 10 ohms, or 62 watts, from 12 VDC input. I
modified the circuit to get 38 volts into 12 ohms, or 117 watts out, at 92%
efficiency. It's a $3 IC, a $1 MOSFET, a $1 diode, a $1 capacitor, and
maybe a $3 inductor. You can add two more diodes and two more capacitors to
get a negative voltage. Everything you need, maybe $15.

The circuit follows. You do have LTspice (SwitcherCAD), don't you?

Paul

Yep, I've got SwitcherCAD on my laptop at home.

1 MHz switching frequency, huh?

Mouser doesn't have it, but Jameco does. (Come to think of it, I
don't recall Mouser having any National Semi stuff, either.)

I was thinking of using an AT power supply, but the old ones I've got
at home have all the power in the 5V side (10A), not so much the 12V
side (2A).

It would make a nice car amp, though. Plus I could drive to the
middle of nowhere to do the Sound Tests. (Neighbors might not
appreciate that so much.)

Thanks,

Michael

 

[Paul E. Schoen]

<mrdarrett@gmail.com> wrote in message
news:b14a55cc-84ad-4967-8062-7afcdeb28510@s12g2000prg.googlegroups.com...

On Mar 28, 1:02 am, "Paul E. Schoen" <pst...@smart.net> wrote:

...

There's really no need to go to all the trouble of that complicated
circuit
just to get +/- 35 VDC from 12 VDC, which you have to generate from line
voltage anyway (unless you really want a battery powered amp). I posted
a
schematic for a switching supply that will generate at least +/- 34
volts
at 1 amp, using a single power IC, a single inductor, and three Schottky
diodes. You can use the same principle to generate as much voltage and
current as you want by using a single high power MOSFET and a switchmode
controller (even the SG3525 or SG3526), but much better would be one of
Linear Technology's controllers that are designed to drive a MOSFET
directly, or add a driver.

Look at the circuit provided by LTSpice for the 1247 PWM controller. It
will provide 24 volts into 10 ohms, or 62 watts, from 12 VDC input. I
modified the circuit to get 38 volts into 12 ohms, or 117 watts out, at
92%
efficiency. It's a $3 IC, a $1 MOSFET, a $1 diode, a $1 capacitor, and
maybe a $3 inductor. You can add two more diodes and two more capacitors
to
get a negative voltage. Everything you need, maybe $15.

The circuit follows. You do have LTspice (SwitcherCAD), don't you?

Paul


Yep, I've got SwitcherCAD on my laptop at home.

1 MHz switching frequency, huh?

Mouser doesn't have it, but Jameco does. (Come to think of it, I
don't recall Mouser having any National Semi stuff, either.)

I was thinking of using an AT power supply, but the old ones I've got
at home have all the power in the 5V side (10A), not so much the 12V
side (2A).

It would make a nice car amp, though. Plus I could drive to the
middle of nowhere to do the Sound Tests. (Neighbors might not
appreciate that so much.)

Thanks,

Michael

Mouser has the TI equivalent part, UC1843a, which is what I used in my
recent design. You can also get a sample or order small quantities on the
www.linear.com website. You might need to prsent yourself as a company, but
you *are* an independent design consultant, aren't you?

The circuit I showed has a switching frequency of 500 kHz. For that you
need very careful board layout. You can probably use 100 kHz and get by
with a perfboard layout. My previous design used a PIC16F684 with PWM
output, but I had to use a gate driver for the MOSFET. I was able to get at
least 40 watts from a 1" x 2" board.

Also, here's another power amplifier I came up with. It's basically a power
op-amp, and it is flat 40 dB (100x gain) from DC to 100 kHz, but there is
more crossover distortion at higher frequencies. It has output current
limiting, and a boost circuit that allows the output to reach within about
1 volt of the supply rails, even with both high and low side N-channel
MOSFETs.

It is insensitive to supply voltage variations. I even added several volts
of AC ripple to the simulated supplies, and all it did was cause clipping
when the supply dipped below the peak of the output signal. It works into
light loads as well as down to 3 ohms, and will theoretically provide 100
watts or more, depending on power supply, load, output MOSFETs, and
overcurrent sense resistor values, with efficiency approaching 68%.

I added a trim resistor which can be adjusted to provide some quiescent
output stage current, which reduced crossover distortion at the expense of
efficiency. I'm not sure how the temperature stability will be, and thermal
runaway might be a problem. But that might be cured by adding a thermistor
to the bias circuit.

I also am thinking about adding a "smart" bias circuit controller by using
a PIC to sense some of the characteristics of the amplifier, and make
adjustments accordingly. It might be able to sense power supply current at
the zero crossing point of the output, and dynamically adjust bias current
accordingly.

Another thing it might be able to do is sense the input signal and adjust
the supply rails accordingly (by controlling the switching regulator), and
keep them just above the peaks of the output signal. Of course, there would
be some clipping during brief high power surges for music that changes very
abruptly from soft to loud, but maybe it could also be adjusted to the
volume control position, so you would only set the supply rails high when
you want maximum volume. This would greatly increase efficiency without
going to a PWM class D amplifier, which is more difficult to design and
build.

I will probably build this amplifier, and I'll post the completed design if
and when I do.

Good luck,

Paul

=====================================================================================

Version 4
SHEET 1 1304 744
WIRE 432 -320 -624 -320
WIRE 720 -272 -560 -272
WIRE -864 -208 -992 -208
WIRE -688 -208 -864 -208
WIRE -624 -208 -624 -320
WIRE -624 -208 -688 -208
WIRE -480 -208 -624 -208
WIRE -304 -208 -480 -208
WIRE -80 -208 -240 -208
WIRE 80 -208 -80 -208
WIRE 176 -208 80 -208
WIRE 256 -208 176 -208
WIRE 992 -208 256 -208
WIRE 80 -192 80 -208
WIRE 256 -176 256 -208
WIRE 656 -176 352 -176
WIRE 176 -128 80 -128
WIRE 432 -128 432 -320
WIRE -992 -112 -992 -208
WIRE 80 -112 80 -128
WIRE -560 -96 -560 -272
WIRE -560 -96 -624 -96
WIRE -480 -96 -480 -208
WIRE -80 -80 -80 -128
WIRE 16 -80 -80 -80
WIRE 656 -80 656 -176
WIRE -560 -64 -560 -96
WIRE 256 -64 256 -96
WIRE -864 -48 -864 -208
WIRE -624 -48 -624 -96
WIRE -240 -48 -272 -48
WIRE -80 -48 -80 -80
WIRE 176 -48 176 -128
WIRE 208 -48 176 -48
WIRE 352 -48 352 -176
WIRE 384 -48 352 -48
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WIRE 992 16 960 16
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WIRE 352 32 256 32
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WIRE -352 144 -560 144
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WIRE -80 160 -128 160
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WIRE -784 176 -800 176
WIRE -752 176 -784 176
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WIRE -992 192 -992 -48
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WIRE -864 192 -928 192
WIRE 32 192 32 160
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WIRE -80 208 -80 160
WIRE 432 208 432 160
WIRE -480 224 -480 112
WIRE -480 224 -528 224
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WIRE -400 224 -480 224
WIRE -928 240 -928 192
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WIRE 176 240 176 208
WIRE 176 240 80 240
WIRE 80 272 80 240
WIRE -800 288 -800 176
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WIRE -800 400 -864 400
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WIRE -672 400 -800 400
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WIRE -864 592 -992 592
WIRE -704 592 -864 592
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WIRE -480 592 -704 592
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WIRE -80 592 -480 592
WIRE 80 592 80 560
WIRE 80 592 -80 592
WIRE 256 592 256 560
WIRE 256 592 80 592
WIRE 432 592 432 560
WIRE 432 592 256 592
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WIRE 656 592 656 464
WIRE 656 592 576 592
FLAG -928 240 0
FLAG -784 176 Vin
FLAG 688 144 Vout
FLAG 32 192 0
FLAG 720 304 0
FLAG -688 -208 ps+
FLAG -704 592 ps-
SYMBOL voltage -864 -64 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 44 Left 0
SYMATTR SpiceLine Rser=.1
SYMATTR InstName V2
SYMATTR Value SINE(24 .1 120 0 0 0 1000)
SYMBOL voltage -800 272 R0
WINDOW 3 -107 382 Left 0
WINDOW 123 24 44 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value SINE(0 230m 10000 1u 0 0 5000)
SYMATTR Value2 AC 1
SYMATTR InstName V1
SYMBOL nmos 384 -128 R0
WINDOW 0 56 -3 Left 0
WINDOW 3 53 36 Left 0
SYMATTR InstName M1
SYMATTR Value STD30NF06L
SYMBOL nmos 384 208 R0
SYMATTR InstName M2
SYMATTR Value STD30NF06L
SYMBOL pmos 208 32 M180
SYMATTR InstName M3
SYMATTR Value IRF7205
SYMBOL res 64 368 R0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL res 704 176 R0
SYMATTR InstName R8
SYMATTR Value 8
SYMBOL res 64 -128 R0
SYMATTR InstName R4
SYMATTR Value 1k
SYMBOL res -112 144 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R1
SYMATTR Value 10
SYMBOL Opamps\\LT1037A -304 96 R0
WINDOW 3 9 107 Left 0
SYMATTR InstName U1
SYMBOL res -656 160 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R12
SYMATTR Value 1k
SYMBOL zener -384 352 R180
WINDOW 0 24 72 Left 0
WINDOW 3 -47 -78 Left 0
SYMATTR InstName D6
SYMATTR Value BZX84C15L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res -496 -112 R0
SYMATTR InstName R5
SYMATTR Value 1k
SYMBOL polcap -496 288 R0
SYMATTR InstName C4
SYMATTR Value 100ľ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=63 Irms=900m Rser=0.1 MTBF=20000 Lser=0 mfg="Nichicon"
pn="UPH1J101MRH" type="Al electrolytic" ppPkg=1
SYMBOL res -576 -80 R0
SYMATTR InstName R7
SYMATTR Value 100k
SYMBOL res -608 224 R0
SYMATTR InstName R9
SYMATTR Value 1k
SYMBOL res -688 224 R0
SYMATTR InstName R11
SYMATTR Value 100k
SYMBOL cap -640 -48 R0
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SYMATTR Value 8.2p
SYMBOL npn 16 -32 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL pnp 16 368 M180
SYMATTR InstName Q2
SYMATTR Value 2N3906
SYMBOL voltage -864 416 R0
WINDOW 123 0 0 Left 0
WINDOW 39 24 132 Left 0
SYMATTR SpiceLine Rser=.1
SYMATTR InstName V3
SYMATTR Value SINE(24 .1 120 0 0 0 1000)
SYMBOL res -496 416 R0
SYMATTR InstName R3
SYMATTR Value 1k
SYMBOL diode -96 48 R0
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL diode -96 304 R0
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL res -96 -224 R0
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SYMATTR Value 4.7k
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SYMBOL res 64 144 R0
WINDOW 0 38 51 Left 0
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SYMBOL zener 96 560 R180
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SYMATTR Value BZX84C15L
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SYMBOL zener 96 -128 R180
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SYMBOL schottky 576 576 R90
WINDOW 0 0 32 VBottom 0
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SYMATTR Value 1N5818
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res 608 400 R90
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SYMATTR InstName R22
SYMATTR Value 10
SYMBOL zener -384 128 R180
WINDOW 0 24 72 Left 0
WINDOW 3 -18 115 Left 0
SYMATTR InstName D7
SYMATTR Value BZX84C15L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL polcap -496 48 R0
SYMATTR InstName C3
SYMATTR Value 100ľ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=63 Irms=900m Rser=0.1 MTBF=20000 Lser=0 mfg="Nichicon"
pn="UPH1J101MRH" type="Al electrolytic" ppPkg=1
SYMBOL res 416 -16 R0
SYMATTR InstName R23
SYMATTR Value .1
SYMBOL res 576 -48 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R15
SYMATTR Value 10
SYMBOL npn 592 -80 R0
SYMATTR InstName Q4
SYMATTR Value 2N3904
SYMBOL schottky 576 80 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName D8
SYMATTR Value 1N5818
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res 240 -192 R0
SYMATTR InstName R24
SYMATTR Value 100
SYMBOL res -256 -64 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R26
SYMATTR Value 100
SYMBOL diode -96 208 R0
SYMATTR InstName D9
SYMATTR Value 1N4148
SYMBOL diode -96 -48 R0
SYMATTR InstName D10
SYMATTR Value 1N4148
SYMBOL res 160 112 R0
SYMATTR InstName R20
SYMATTR Value 4.2k
SYMBOL polcap -1008 -112 R0
WINDOW 3 24 64 Left 0
SYMATTR InstName C5
SYMATTR Value 2700ľ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=35 Irms=2.9 Rser=0.021 MTBF=2000 Lser=0 mfg="Panasonic"
pn="ECA1VFQ272" type="Al electrolytic" ppPkg=1
SYMBOL polcap -1008 432 R0
WINDOW 3 24 64 Left 0
SYMATTR InstName C6
SYMATTR Value 2700ľ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=35 Irms=2.9 Rser=0.021 MTBF=2000 Lser=0 mfg="Panasonic"
pn="ECA1VFQ272" type="Al electrolytic" ppPkg=1
SYMBOL polcap 784 0 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C7
SYMATTR Value 100ľ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=63 Irms=900m Rser=0.1 MTBF=20000 Lser=0 mfg="Nichicon"
pn="UPH1J101MRH" type="Al electrolytic" ppPkg=1
SYMBOL diode 880 80 R180
WINDOW 0 40 6 Left 0
WINDOW 3 24 -29 Left 0
SYMATTR InstName D11
SYMATTR Value MURS120
SYMBOL diode 896 32 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D12
SYMATTR Value MURS120
SYMBOL polcap 976 16 R0
SYMATTR InstName C8
SYMATTR Value 100ľ
SYMATTR Description Capacitor
SYMATTR Type cap
SYMATTR SpiceLine V=63 Irms=900m Rser=0.1 MTBF=20000 Lser=0 mfg="Nichicon"
pn="UPH1J101MRH" type="Al electrolytic" ppPkg=1
SYMBOL zener -304 -192 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D13
SYMATTR Value BZX84C6V2L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res 768 32 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R21
SYMATTR Value 20
TEXT -176 688 Left 0 !.tran 0 .5 .01 startup uic
TEXT 40 696 Left 0 !;ac oct 5 10 100000

 

On Mar 28, 11:51 am, "Paul E. Schoen" <pst...@smart.net> wrote:

....

Mouser has the TI equivalent part, UC1843a, which is what I used in my
recent design. You can also get a sample or order small quantities on thewww.linear.comwebsite. You might need to prsent yourself as a company, but
you *are* an independent design consultant, aren't you?

Um, yeah, sure. Independent Design Consultant In Training. ;-)

The circuit I showed has a switching frequency of 500 kHz. For that you
need very careful board layout. You can probably use 100 kHz and get by
with a perfboard layout. My previous design used a PIC16F684 with PWM
output, but I had to use a gate driver for the MOSFET. I was able to get at
least 40 watts from a 1" x 2" board.

Yeah, I was wondering about clocking it down some. The datasheet has
an ominous warning:

"Do not attempt to use Proto-boards or wire-wrap techniques to
breadboard high speed switching regulator circuits. They will not work
properly."


Thanks for the info...

Michael

 

[Joerg]

mrdarrett@gmail.com wrote:

On Mar 28, 11:51 am, "Paul E. Schoen" <pst...@smart.net> wrote:

...

Mouser has the TI equivalent part, UC1843a, which is what I used in my
recent design. You can also get a sample or order small quantities on thewww.linear.comwebsite. You might need to prsent yourself as a company, but
you *are* an independent design consultant, aren't you?


Um, yeah, sure. Independent Design Consultant In Training. ;-)


The circuit I showed has a switching frequency of 500 kHz. For that you
need very careful board layout. You can probably use 100 kHz and get by
with a perfboard layout. My previous design used a PIC16F684 with PWM
output, but I had to use a gate driver for the MOSFET. I was able to get at
least 40 watts from a 1" x 2" board.


Yeah, I was wondering about clocking it down some. The datasheet has
an ominous warning:

"Do not attempt to use Proto-boards or wire-wrap techniques to
breadboard high speed switching regulator circuits. They will not work
properly."

Oh well. I have a photo that would make your toe nails curl. A switcher
proto that looks worse than a coughed-up hairball yet works. But it's a
client's design so I can't post it.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Paul E. Schoen]

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:_utHj.22891$0o7.6120@newssvr13.news.prodigy.net...

mrdarrett@gmail.com wrote:
On Mar 28, 11:51 am, "Paul E. Schoen" <pst...@smart.net> wrote:

...

Mouser has the TI equivalent part, UC1843a, which is what I used in my
recent design. You can also get a sample or order small quantities on
thewww.linear.comwebsite. You might need to prsent yourself as a
company, but
you *are* an independent design consultant, aren't you?


Um, yeah, sure. Independent Design Consultant In Training. ;-)


The circuit I showed has a switching frequency of 500 kHz. For that you
need very careful board layout. You can probably use 100 kHz and get by
with a perfboard layout. My previous design used a PIC16F684 with PWM
output, but I had to use a gate driver for the MOSFET. I was able to
get at
least 40 watts from a 1" x 2" board.


Yeah, I was wondering about clocking it down some. The datasheet has
an ominous warning:

"Do not attempt to use Proto-boards or wire-wrap techniques to
breadboard high speed switching regulator circuits. They will not work
properly."


Oh well. I have a photo that would make your toe nails curl. A switcher
proto that looks worse than a coughed-up hairball yet works. But it's a
client's design so I can't post it.

I received 108 pieces of my switcher power supply board from
www.pcbcart.com in China. I got them for just a little under $1.50 each,
including tooling, setup, and shipping. But I requested 2 oz copper and
they are only 1 oz (according to my testing), so I will not be able to use
them for the high power version (40-50W) of my design. There is also a
minor design change I need to add, which can be done on the existing board,
but will be much better if I make the artwork changes (there were also a
couple of minor decal errors), so I will have a lot of them as surplus. It
uses the UC1843a, and it works OK up to about 30-35 watts out with 12VDC
in, with output voltage to 50V, and runs nicely at least up to 200 kHz. If
anyone is interested, I could send you one or more boards. I'd rather give
them to someone who could use them rather than have them go to waste.
Contact me by email if interested.

Paul

 

[Joerg]

Paul E. Schoen wrote:

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:_utHj.22891$0o7.6120@newssvr13.news.prodigy.net...
mrdarrett@gmail.com wrote:
On Mar 28, 11:51 am, "Paul E. Schoen" <pst...@smart.net> wrote:

...

Mouser has the TI equivalent part, UC1843a, which is what I used in my
recent design. You can also get a sample or order small quantities on
thewww.linear.comwebsite. You might need to prsent yourself as a
company, but
you *are* an independent design consultant, aren't you?

Um, yeah, sure. Independent Design Consultant In Training. ;-)


The circuit I showed has a switching frequency of 500 kHz. For that you
need very careful board layout. You can probably use 100 kHz and get by
with a perfboard layout. My previous design used a PIC16F684 with PWM
output, but I had to use a gate driver for the MOSFET. I was able to
get at
least 40 watts from a 1" x 2" board.

Yeah, I was wondering about clocking it down some. The datasheet has
an ominous warning:

"Do not attempt to use Proto-boards or wire-wrap techniques to
breadboard high speed switching regulator circuits. They will not work
properly."

Oh well. I have a photo that would make your toe nails curl. A switcher
proto that looks worse than a coughed-up hairball yet works. But it's a
client's design so I can't post it.

I received 108 pieces of my switcher power supply board from
www.pcbcart.com in China. I got them for just a little under $1.50 each,
including tooling, setup, and shipping. But I requested 2 oz copper and
they are only 1 oz (according to my testing), so I will not be able to use
them for the high power version (40-50W) of my design. There is also a
minor design change I need to add, which can be done on the existing board,
but will be much better if I make the artwork changes (there were also a
couple of minor decal errors), so I will have a lot of them as surplus. It
uses the UC1843a, and it works OK up to about 30-35 watts out with 12VDC
in, with output voltage to 50V, and runs nicely at least up to 200 kHz. If
anyone is interested, I could send you one or more boards. I'd rather give
them to someone who could use them rather than have them go to waste.
Contact me by email if interested.

That would be a nice solution for someone who wants to run and charge a
laptop off a lead-acid battery. Or for hams, since they can often get
28V RF power transistors for a lot less money compared to 12V versions.

I wonder why the UC1843 is still so expensive. At production quantities
$3 is a lot of money for a simple PWM controller.

--
Regards, Joerg

http://www.analogconsultants.com/