inductor for HV flyback supply

On Friday, August 5, 2016 at 12:24:37 PM UTC-4, John Larkin wrote:
> On 5 Aug 2016 05:53:42 -0700, Winfield Hill <hill@rowland.harvard.edu>
> wrote:
> 
> >bill.sloman@ieee.org wrote...
> >>
> >> Too many people make a habit of avoiding custom magnetics.
> >> The Rowland Institute ought to have a simple coil winder -
> >> there are cheap ones available from China if it doesn't -
> >> and you don't need much of a range of RM cores, formers,
> >> mylar tape and enamelled wire to do useful stuff.
> >
> > We have a winder, but need an fixture for small bobbins.
> > I have the full range of materials, including my favorite
> > Kapton tape, in various widths.  It's the painful magnet-
> > wire enamel removal and soldering to tiny bobbin pins
> > that slows me down.  That'd be an even worse issue with
> > extra windings.   But I heard a rumor about a special
> > magnet wire with disappearing enamel at soldering temps.
> 
> Beldsol, thermal strip. I got a high-temp Metcal clone tip from
> Amazon, 
> 
We get "solderable" magnet wire from MWS.  Stripped and tinned in a 
solder pot.  Nice stuff.  

George H. 
> https://www.amazon.com/Thermaltronics-S75CH015-Chisel-interchangeable-SSC-738A/dp/B00NS4E0YW
> 
> that solders this stuff great. 
> 
> https://dl.dropboxusercontent.com/u/53724080/Parts/Inductors/TEM1_Xfmr_Proto.JPG
> 
> 
> I hate custom magnetics. Expensive, boring hassle. The technical
> challenge of designing transformers is to NOT design transformers.
> 
> 
> -- 
> 
> John Larkin         Highland Technology, Inc
> 
> lunatic fringe electronics

On Friday, August 5, 2016 at 9:45:40 PM UTC+10, bill....@ieee.org wrote:
> On Friday, August 5, 2016 at 9:05:33 PM UTC+10, Winfield Hill wrote:
> > bill.sloman@ieee.org wrote...
> > >
> > >On Friday, August 5, 2016 at 1:07:26 PM UTC+10, Winfield Hill wrote:
> > >> I've created all kinds of HV circuits in the last
> > >>  5 years,** and each one needs an external HV supply.
> > >>  So I really need some simple HV-supply circuits to
> > >>  plop onto these PCB's to make them self-sufficient.
> > >> 
> > >>  Today's circuit is a basic flyback, to convert a
> > >>  12V,1A wallwort source to 500V max, at 5-10W load.
> > >> 
> > >>  I used a UC3843B running at 100kHz ...
> > 
> >   https://www.dropbox.com/s/cwo10wm5upehvrw/PWR_s.jpg
> > 
> > > Why futz around with flyback supplies when you can
> > > use a Baxandall Class-D oscillator?
> > >
> > > Peter Baxandall invented it to deal with the problem
> > > of getting a kV or so for photomultiplier supplies,
> > > and Jim Williams used it to generate even higher
> > > voltages for the cold cathode back-lights that used
> > > to be popular in lap-top computers.
> > >
> > >http://sophia-elektronica.com/Baxandall_parallel-resonant_Class-D_oscillator1.htm
> > >
> > > http://sophia-elektronica.com/0344_001_Baxandal.pdf
> > >
> > > It's two pot cores - transformer and inductor -
> > > rather than just one, but it's a lot tidier, you
> > > should be able to get away with smaller pot cores.
> > 
> >  Thanks for the suggestion Bill, I know you love
> >  that circuit, and resonance is good.  Indeed for
> >  higher power and voltages it'd be the right idea. 
> > 
> >  But the uc3843 and other parts are small, SO-8,
> >  etc., mounted on the underside of the PCB, and
> >  in the beginning I had hoped to use a single
> >  simple commercial off-the-shelf inductor, and
> >  avoid any custom magnetics.  May still do so.
> 
> Too many people make a habit of avoiding custom magnetics. The Rowland Institute ought to have a simple coil winder - there are cheap ones available from China if it doesn't - and you don't need much of a range of RM cores, formers, mylar tape and enamelled wire to do useful stuff.
> 
> Printed windings are neater, but you've got to talk to a specialist printed circuit shop to get useful copper fill factors. I talked to one in the Netherlands, but didn't get to the point of having anything made - that would have been for a better electric piano keyboard, but I couldn't get the Linux mechanical drafting program to do anything useful, and tossed it all into the too-hard basket.
>  
> >  Anyway, even with having to wind 22 turns on an
> >  RM8, the result is still simple, small and cheap.
> > 
> >  BTW, some of your web article links are broken.
> 
> That's been on the to-do list for a while. I seem to be coming out of jet-lag today, and my wife won't be back until Monday, so I might get it done over the weekend.
> 
> I've had a some help with the Baxandall article and it should look a little better in the next few hours.

I finally seem to have fixed all the links on my web-site. The obvious problem was that several of them were linking back to my old Dutch web-site, but when I corrected that I seem to have managed to get the file names subtly wrong - spaces where there should have been under-scores, and one file with the extension .html where I'd named it .hmt when I'd called it.

Nothing difficult, but tedious. And the better scan of the 1959 Baxandall article is there too.

-- 
Bill Sloman, Sydney

On Thursday, August 4, 2016 at 11:07:26 PM UTC-4, Winfield Hill wrote:
> I've created all kinds of HV circuits in the last
>  5 years,** and each one needs an external HV supply.
>  So I really need some simple HV-supply circuits to
>  plop onto these PCB's to make them self-sufficient.
> 
>  Today's circuit is a basic flyback, to convert a
>  12V,1A wallwort source to 500V max, at 5-10W load.
> 
>  I used a UC3843B running at 100kHz driving a MOSFET
>  switching a 47uH inductor (dI = dt V/L = 2A in 8us).
>  This can provide up to 100uJ each cycle, to charge
>  a say 2000uF storage cap to 400V in 16 seconds.
>  
>  I settled on an ES1J fast-recovery output diode
>  (after rejecting an MRA4007),  After rejecting
>  an STP7NB60 as too lossy, I experimented and
>  picked an Infineon IPP65R225C7 superjunction
>  MOSFET: Rds(on) = 0.2 ohms (0.5 ohms max at Tj 
>  = 150C), and Coss = 14pF at 400V (20pF at 100V).
>  Nice.
> 
>  But the flyback inductor was an issue.  See photo
> https://www.dropbox.com/s/cwo10wm5upehvrw/PWR-741_flyback_350V-inductors_small.jpg?dl=0
> 
>  I started with an older 1A part from the drawer:
>  a Mouser 47uH, 0.1 ohms, rated 1.3A, see photo,
>  lower right.  With this part my circuit had 2.2W
>  of wasted power at 5W out.  Heating was bad, the
>  inductor melted a soldered lead and disconnected
>  itself from the circit!  Whew, ugly!  I needed a
>  beefier part.  Enter a Coilcraft PCV-0-473-05L,
>  photo lower left.  Those fat wires, this had to
>  be the answer.  Rated 0.035 ohms and 6A.  But it 
>  increased my wasted power to 3.7W, double ouch!
> 
>  Giving up on my commercial inventory, I made
>  an inductor using an RM8 bobbin and core.
>  (See photo, upper part, mounted on the PCB.)
> 
>  I selected a large gap core, A_L = 100nH/t^2.
>  N = sqrt(L / A_L) = 22 turns.  With #20 wire,
>  Rdc=0.036 ohms.  I measured Q=39 at 100kHz,
>  esr = 2pi f L/Q = 0.75 ohms.  Q=80 at 1MHz.
>  Looking pretty good, ignoring coreloss at
>  full power (the ckt uses 40mW at no load). 
> 
>  Yeah!  With the RM8 inductor, total losses
>  dropped to 1.1 watts.  Note, the MOSFET,
>  sense resistor, diode and capacitor share
>  in the loss generation, so I don't know
>  the inductor loss.  Everything runs cool,
>  which wasn't the case at the beginning.
> 
>  ** more on that later ...
> 
> 
> -- 
>  Thanks,
>     - Win

Win, small world--looks like I have a similar requirement.

I did a bit of magnetics-scrounging, finding hits under 'coupled inductors,'
and 'flyback transformers.'

Interesting specimens: (DigiKey)
 Pulse PA0367A: 9x9mm (case) 12x12 footprint, SMD, 1:12, 18uH, 500V, $2
 TDK ATB322524-0110-T000: 1210 SMD, 1:10.2, 7uH, 500V insulation, $1 qty 1

Other candidates:
o CCFL transformers are quasi-interesting for forward converters.
o Xenon strobe transformers are classic flybacks roughly in this ballpark.
o Coilcraft Hexa-Path, http://www.coilcraft.com/hexa-path.cfm
o PoE (power over ethernet) transformers

Cheers,
James Arthur

In article <no228m01d1m@drn.newsguy.com>,
Winfield Hill  <hill@rowland.harvard.edu> wrote:
>bill.sloman@ieee.org wrote...
>>
>> Too many people make a habit of avoiding custom magnetics.
>> The Rowland Institute ought to have a simple coil winder -
>> there are cheap ones available from China if it doesn't -
>> and you don't need much of a range of RM cores, formers,
>> mylar tape and enamelled wire to do useful stuff.
>
> We have a winder, but need an fixture for small bobbins.
> I have the full range of materials, including my favorite
> Kapton tape, in various widths.  It's the painful magnet-
> wire enamel removal and soldering to tiny bobbin pins
> that slows me down.  That'd be an even worse issue with
> extra windings.   But I heard a rumor about a special
> magnet wire with disappearing enamel at soldering temps.

I use aspirin to melt the enamel, and solder 0.1 mm wires no
problem. It looks like you don't know that trick.
(You must use acetyl salicic acid, the brand. just any
pain killer won't do. No mixins.)

>--
> Thanks,
>    - Win

Groetjes Albert
-- 
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- being exponential -- ultimately falters.
albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst

On Sun, 1 Jan 2017 19:56:52 +0100 (CET),
albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) wrote:

>In article <no228m01d1m@drn.newsguy.com>,
>Winfield Hill  <hill@rowland.harvard.edu> wrote:
>>bill.sloman@ieee.org wrote...
>>>
>>> Too many people make a habit of avoiding custom magnetics.
>>> The Rowland Institute ought to have a simple coil winder -
>>> there are cheap ones available from China if it doesn't -
>>> and you don't need much of a range of RM cores, formers,
>>> mylar tape and enamelled wire to do useful stuff.
>>
>> We have a winder, but need an fixture for small bobbins.
>> I have the full range of materials, including my favorite
>> Kapton tape, in various widths.  It's the painful magnet-
>> wire enamel removal and soldering to tiny bobbin pins
>> that slows me down.  That'd be an even worse issue with
>> extra windings.   But I heard a rumor about a special
>> magnet wire with disappearing enamel at soldering temps.
>
>I use aspirin to melt the enamel, and solder 0.1 mm wires no
>problem. It looks like you don't know that trick.
>(You must use acetyl salicic acid, the brand. just any
>pain killer won't do. No mixins.)
>
>>--
>> Thanks,
>>    - Win
>
>Groetjes Albert

Use Beldsol enameled wire. Just solder it with a hot iron.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

In article <0gki6c97s9h9bn65pq52fo8s52ud51ccog@4ax.com>,
John Larkin  <jjlarkin@highlandtechnology.com> wrote:
>On Sun, 1 Jan 2017 19:56:52 +0100 (CET),
>albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) wrote:
>
>>In article <no228m01d1m@drn.newsguy.com>,
>>Winfield Hill  <hill@rowland.harvard.edu> wrote:
>>>bill.sloman@ieee.org wrote...
>>>>
>>>> Too many people make a habit of avoiding custom magnetics.
>>>> The Rowland Institute ought to have a simple coil winder -
>>>> there are cheap ones available from China if it doesn't -
>>>> and you don't need much of a range of RM cores, formers,
>>>> mylar tape and enamelled wire to do useful stuff.
>>>
>>> We have a winder, but need an fixture for small bobbins.
>>> I have the full range of materials, including my favorite
>>> Kapton tape, in various widths.  It's the painful magnet-
>>> wire enamel removal and soldering to tiny bobbin pins
>>> that slows me down.  That'd be an even worse issue with
>>> extra windings.   But I heard a rumor about a special
>>> magnet wire with disappearing enamel at soldering temps.
>>
>>I use aspirin to melt the enamel, and solder 0.1 mm wires no
>>problem. It looks like you don't know that trick.
>>(You must use acetyl salicic acid, the brand. just any
>>pain killer won't do. No mixins.)
>>
>>>--
>>> Thanks,
>>>    - Win
>>
>>Groetjes Albert
>
>Use Beldsol enameled wire. Just solder it with a hot iron.

I've a similar litze wire for my Boehm self built organ.
Use Weller 8 tips instead of 7, and tin-lead solder.
It was 17 guilders at the time (1980) for 90 meter.
Boehm had all kind of secondary supplies (meters, resistors,
etc.) for cheap, and unbranded. Maybe this was Beldsol.
It is litze, enamelled and then wrapped in secondary isolation.

Got 61*10+61*10+30*10 solder points in that organ and then some.
This clearly was for easy connection not wire for transformers,
with small added benefit for soldering.

I still have a spool, which will last my life time, unless
I dream up some weird project.

>John Larkin         Highland Technology, Inc

Groetjes Albert
-- 
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- being exponential -- ultimately falters.
albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst

On 1/1/2017 12:56 PM, Albert van der Horst wrote:
> In article <no228m01d1m@drn.newsguy.com>,
> Winfield Hill  <hill@rowland.harvard.edu> wrote:
>> bill.sloman@ieee.org wrote...
>>>
>>> Too many people make a habit of avoiding custom magnetics.
>>> The Rowland Institute ought to have a simple coil winder -
>>> there are cheap ones available from China if it doesn't -
>>> and you don't need much of a range of RM cores, formers,
>>> mylar tape and enamelled wire to do useful stuff.
>>
>> We have a winder, but need an fixture for small bobbins.
>> I have the full range of materials, including my favorite
>> Kapton tape, in various widths.  It's the painful magnet-
>> wire enamel removal and soldering to tiny bobbin pins
>> that slows me down.  That'd be an even worse issue with
>> extra windings.   But I heard a rumor about a special
>> magnet wire with disappearing enamel at soldering temps.
>
> I use aspirin to melt the enamel, and solder 0.1 mm wires no
> problem. It looks like you don't know that trick.
> (You must use acetyl salicic acid, the brand. just any
> pain killer won't do. No mixins.)
>
>> --
>> Thanks,
>>    - Win
>
> Groetjes Albert
>

How is that accomplished? How do you coat the wire with the aspirin? Do 
you melt the aspirin with your iron first? What is your process?

Thanks.

On 02/01/2017 09:58, John S wrote:
> On 1/1/2017 12:56 PM, Albert van der Horst wrote:
>> In article <no228m01d1m@drn.newsguy.com>,
>> Winfield Hill  <hill@rowland.harvard.edu> wrote:
>>> bill.sloman@ieee.org wrote...
>>>>
>>>> Too many people make a habit of avoiding custom magnetics.
>>>> The Rowland Institute ought to have a simple coil winder -
>>>> there are cheap ones available from China if it doesn't -
>>>> and you don't need much of a range of RM cores, formers,
>>>> mylar tape and enamelled wire to do useful stuff.
>>>
>>> We have a winder, but need an fixture for small bobbins.
>>> I have the full range of materials, including my favorite
>>> Kapton tape, in various widths.  It's the painful magnet-
>>> wire enamel removal and soldering to tiny bobbin pins
>>> that slows me down.  That'd be an even worse issue with
>>> extra windings.   But I heard a rumor about a special
>>> magnet wire with disappearing enamel at soldering temps.
>>
>> I use aspirin to melt the enamel, and solder 0.1 mm wires no
>> problem. It looks like you don't know that trick.
>> (You must use acetyl salicic acid, the brand. just any
>> pain killer won't do. No mixins.)
>>
>>> --
>>> Thanks,
>>>    - Win
>>
>> Groetjes Albert
>>
>
> How is that accomplished? How do you coat the wire with the aspirin? Do
> you melt the aspirin with your iron first? What is your process?
>
> Thanks.


Beware reading posts on the internet about using Aspirin as flux, and 
they trying it out! I did those things, and the stink was incredible. I 
had a sore throat for a while after that. If you do try it, use fume 
extraction!

On 02/01/2017 06:01, John Larkin wrote:
> On Sun, 1 Jan 2017 19:56:52 +0100 (CET),
> albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) wrote:
>
>> In article <no228m01d1m@drn.newsguy.com>,
>> Winfield Hill  <hill@rowland.harvard.edu> wrote:
>>> bill.sloman@ieee.org wrote...
>>>>
>>>> Too many people make a habit of avoiding custom magnetics.
>>>> The Rowland Institute ought to have a simple coil winder -
>>>> there are cheap ones available from China if it doesn't -
>>>> and you don't need much of a range of RM cores, formers,
>>>> mylar tape and enamelled wire to do useful stuff.
>>>
>>> We have a winder, but need an fixture for small bobbins.
>>> I have the full range of materials, including my favorite
>>> Kapton tape, in various widths.  It's the painful magnet-
>>> wire enamel removal and soldering to tiny bobbin pins
>>> that slows me down.  That'd be an even worse issue with
>>> extra windings.   But I heard a rumor about a special
>>> magnet wire with disappearing enamel at soldering temps.
>>
>> I use aspirin to melt the enamel, and solder 0.1 mm wires no
>> problem. It looks like you don't know that trick.
>> (You must use acetyl salicic acid, the brand. just any
>> pain killer won't do. No mixins.)
>>
>>> --
>>> Thanks,
>>>    - Win
>>
>> Groetjes Albert
>
> Use Beldsol enameled wire. Just solder it with a hot iron.

There are many brands of polyurethane insulated winding wire that can be 
soldered through, but it helps if the iron is a little hotter than 
usual. The hotter iron and longer soldering time can damage things if 
you are trying to simultaneously tin the winding wire and also solder it 
to a pin of a plastic coil former that can melt easily. Pre-tinning the 
winding wire would be one option. If the wire is thick enough that you 
can scratch the enamel with a blade before tinning it, that works more 
quickly as the hot solder can heat the copper of the wire directly. Also 
it is quicker to tin the end of a wire than the middle, because again 
the hot solder can contact the copper at the cut end and heat it more 
easily.

Beware the TDI (Toluene Di-isocyanate) from the burning enamel. It hurts 
your eyes and is generally nasty. Use fume extraction if you are doing a 
lot of it.

Albert van der Horst <albert@cherry.spenarnc.xs4all.nl> wrote:
>>Use Beldsol enameled wire. Just solder it with a hot iron.
>
> I've a similar litze wire for my Boehm self built organ.
> Use Weller 8 tips instead of 7, and tin-lead solder.
> It was 17 guilders at the time (1980) for 90 meter.
> Boehm had all kind of secondary supplies (meters, resistors,
> etc.) for cheap, and unbranded. Maybe this was Beldsol.
> It is litze, enamelled and then wrapped in secondary isolation.

In the Netherlands similar wire was known as "Posijndraad", I'm not
sure if Posijn was a manufacturer and where it was based.
I made quite some digital circuits in the past with this wire and
breadboard-type PCB (1/10" spaced holes with a copper island per hole).
Indeed it was easy to solder with a number 8 tip, without having to
pre-tin the ends of the wire.  I just wrapped the wire 1 turn around
the IC pin (continuing to the next pin when required) and soldered those
junctions.