On Wednesday, September 25, 2019 at 9:31:26 PM UTC+10, mook Jonhon wrote:
> Winfield Hill wrote:
>
> > bitrex wrote...
> > >
> > > Does this count as "custom":
> > >
> > > two multi winding power transformers (220 instead of 120, say)
> > >
> > >
> <https://www.dropbox.com/s/hv086gf97sgwuyz/Photo%20Mar%2019%2C%2011%2030%2008%20PM%20%28edited-Pixlr%29.jpg?dl=0>
> >
> > Why not both xfmr primaries to the 120, and their
> > four secondaries on series?
>
> I need it tiny 60Hz transformers are most definately out. :)
>
> think less than a half of a match box,
I was poking around on the Mouser site looking at their ferrites and found a TDK RM8 core - the B65811J0000R608122092 (Mouser part) using the new PC200 ferrite, which is good for 300kHz.
RM8 is bigger than half a match box, and you'd need two of them for a Baxandall inverter, but when I went through the transformer design for 45V to 2kV the turns ratios were low enough that it looked as if you could go directly from 45V to 2kV while running at 300kHz. The interwinding capacitance on the secondary wasn't as crippling as I'd feared.
A smaller core might work, but I lost interest at that point.
--
Bill Sloman, Sydney
Reply by Dimiter_Popoff●September 25, 20192019-09-25
On 8/21/2019 4:46, mook Jonhon wrote:
>
> Its been a while but once again looking at a HV pulser type application.
>
> It will charge up about 10nF to 2kV with about 1mA. Then keep it toped
> off as that cap discharges into another capacitive much smaller
> capacitive load. The 10nF will loose 100V or so then need to be
> recharged witn 1mA before the next burst.
>
> It need to be a custom approach due to environment constraints. Cost is
> not a strong consideration but must be reasonable I can use custom
> transformers etc.
>
> The voltage does need to be variable from 1K to 2K.
>
> no input to output ground isolation required. but sometime the load
> shorts and the supply must go into current limit and not damage itself
> when this happens.
>
> looking for small topologies to do this.
>
> 1) boost inductor feeding a voltage multiplier (8-10 stage)
> I have had 1A diodes blow when a previous VM design was shorted from
> 1.5kV. even with a 100K resistor in series with the output. never
> investigated jsut sured up the source of the arcing and moved on with
> fingers crossed.
>
> 2) flyback to do most of the boost with a doubler or tripler on the
> output. This should keep the turns ratio reasonable.
>
> 3) straight pushpull making use of the primary voltage doubling action
> to get soem volatge gain. PWM the center tap.
>
> any other physically small power stage topologies to look into?
>
> thanks
>
>
>
>
>
>
>
You do not need a multiplier, 2 kV is not much. Our HV sources go to
5kV directly out of the flyback (that for the HPGe versions, for NaI
we make them up to 1.5kV (more on request)/1mA (also more on request).
While the transformer for the 5kV takes a lot of details to know how
to make, the 1.5 kV version is more forgiving (not infinitely
of course).
They regulate from something like 100V up to the maximum, driving
them with some choice of a waverorm should be OK within some reasonable
BW limits (never tried that though on the netMCA it is a DAC driving
the analog input setting the HV value).
Dimiter
======================================================
Dimiter Popoff, TGI http://www.tgi-sci.com
======================================================
http://www.flickr.com/photos/didi_tgi/
Reply by mook Jonhon●September 25, 20192019-09-25
jlarkin@highlandsniptechnology.com wrote:
> On Mon, 23 Sep 2019 01:54:57 GMT, "mook Jonhon" <mook@mook.net> wrote:
>
> > DecadentLinuxUserNumeroUno@decadence.org wrote:
> >
> >> jlarkin@highlandsniptechnology.com wrote in
> >> news:hbpqlelas5jo4e929g3lemri8k9njthf8d@4ax.com:
> >>
> >> > https://www.dropbox.com/s/r6o5krfl5p86cp5/T840_A.JPG?raw=1
> >>
> >> Above 1000V it should be potted and no solder mask on the HV
> section. >>
> >> Potting boxes can be obtained or spec'd at just over the profile
> >> height of your multiplier section, which should be separated from
> the >> rest of that board. That minimizes the section size needing a
> pot >> shell slipped over it.
> >
> >
> > How does potting compare to conformal coating with a silicon based
> > coating spray. Not the thick goopy stuff but more like heavy
> > clearcoat.
>
> With healthy clearances, you don't need any of that stuff at 1KV or
> so. Coating is messy and potting is very messy.
I'm really pushing the size limits down so voltage clearances are being
pushed. I can slit the board in spots but not everywhere.
I've used confirmal coat for tolerance to surface contamination and
moisture in traditional voltage circuit boards but never depended on it
for HV insulation. Just looking for experience.
In theory, silicon should hold 500V/mil so 10 mil spacing should be
good for 5kV. :) RIGHT!! what would be a realistic number?
Reply by mook Jonhon●September 25, 20192019-09-25
Winfield Hill wrote:
> bitrex wrote...
> >
> > Does this count as "custom":
> >
> > two multi winding power transformers (220 instead of 120, say)
> >
> >
>DecadentLinuxUserNumeroUno@decadence.org wrote:
>
>> jlarkin@highlandsniptechnology.com wrote in
>> news:hbpqlelas5jo4e929g3lemri8k9njthf8d@4ax.com:
>>
>> > https://www.dropbox.com/s/r6o5krfl5p86cp5/T840_A.JPG?raw=1
>>
>> Above 1000V it should be potted and no solder mask on the HV section.
>>
>> Potting boxes can be obtained or spec'd at just over the profile
>> height of your multiplier section, which should be separated from the
>> rest of that board. That minimizes the section size needing a pot
>> shell slipped over it.
>
>
>How does potting compare to conformal coating with a silicon based
>coating spray. Not the thick goopy stuff but more like heavy
>clearcoat.
With healthy clearances, you don't need any of that stuff at 1KV or
so. Coating is messy and potting is very messy.
Reply by mook Jonhon●September 22, 20192019-09-22
DecadentLinuxUserNumeroUno@decadence.org wrote:
> jlarkin@highlandsniptechnology.com wrote in
> news:hbpqlelas5jo4e929g3lemri8k9njthf8d@4ax.com:
>
> > https://www.dropbox.com/s/r6o5krfl5p86cp5/T840_A.JPG?raw=1
>
> Above 1000V it should be potted and no solder mask on the HV section.
>
> Potting boxes can be obtained or spec'd at just over the profile
> height of your multiplier section, which should be separated from the
> rest of that board. That minimizes the section size needing a pot
> shell slipped over it.
How does potting compare to conformal coating with a silicon based
coating spray. Not the thick goopy stuff but more like heavy
clearcoat.
Reply by ●August 24, 20192019-08-24
jlarkin@highlandsniptechnology.com wrote in
news:hbpqlelas5jo4e929g3lemri8k9njthf8d@4ax.com:
Above 1000V it should be potted and no solder mask on the HV section.
Potting boxes can be obtained or spec'd at just over the profile
height of your multiplier section, which should be separated from the
rest of that board. That minimizes the section size needing a pot
shell slipped over it.
Why not both xfmr primaries to the 120, and their
four secondaries on series?
--
Thanks,
- Win
Reply by bitrex●August 22, 20192019-08-22
On 8/22/19 2:25 AM, bitrex wrote:
> On 8/21/19 8:19 AM, Winfield Hill wrote:
>> piglet wrote...
>>>
>>> On 21/08/2019 9:34 am, Winfield Hill wrote:
>>>> mook Jonhon wrote...
>>>>>
>>>>> 2) flyback to do most of the boost with a
>>>>> doubler or tripler on the output. This
>>>>> should keep the turns ratio reasonable.
>>>>
>>>> My flyback approach, previously detailed here
>>>> on s.e.d., is different. Three flyback stages,
>>>> each with its own MOSFET, all running from one
>>>> controller and gate driver. The DC input-V of
>>>> each stage is the previous stage's DC output.
>>>> Starting with say 12V, you need a 167x stepup.
>>>> Three 5.5x stages gets you to 2kV, and that's
>>>> a pretty mild step-up ratio. 66V, 363V, 2kV.
>>>> Stage currents and inductor values scale, since
>>>> they all run with the same time parameters.
>>>>
>>>> Three feedback taps, each with a diode to the
>>>> controller's FB pin. The highest one controls,
>>>> to prevent any one stage from going excessively
>>>> over its voltage limit, but the last stage gets
>>>> the controlling vote. Very simple. Except for
>>>> HV winding technique of the 3rd inductor. :-)
>>>
>>> But surely that triple cascaded flyback topology you
>>> suggest would need a MOSFET with 2000V Vds rating?
>>
>> Details, details ... The HV MOSFET table in the
>> x-Chapters goes up to 4kV. But they're expensive.
>> The idea makes more sense up to 1.2 or 1.5kV.
>>
>>
>
> Does this count as "custom":
>
> two multi winding power transformers (220 instead of 120, say)
>
> <https://www.dropbox.com/s/hv086gf97sgwuyz/Photo%20Mar%2019%2C%2011%2030%2008%20PM%20%28edited-Pixlr%29.jpg?dl=0>
>
>
> 48 volt DC to 220 AC inverter:
>
> <https://www.invertersupply.com/index.php?main_page=product_info&products_id=31043&gclid=CjwKCAjw1_PqBRBIEiwA71rmtUbYId5MEJqs7JBSBopoGTKSaxIOkUKkV6VA01VIocxgLAesoIymQRoCgboQAvD_BwE>
>
>
(hell no I've never built this in case you're wondering.)
Reply by bitrex●August 22, 20192019-08-22
On 8/21/19 8:19 AM, Winfield Hill wrote:
> piglet wrote...
>>
>> On 21/08/2019 9:34 am, Winfield Hill wrote:
>>> mook Jonhon wrote...
>>>>
>>>> 2) flyback to do most of the boost with a
>>>> doubler or tripler on the output. This
>>>> should keep the turns ratio reasonable.
>>>
>>> My flyback approach, previously detailed here
>>> on s.e.d., is different. Three flyback stages,
>>> each with its own MOSFET, all running from one
>>> controller and gate driver. The DC input-V of
>>> each stage is the previous stage's DC output.
>>> Starting with say 12V, you need a 167x stepup.
>>> Three 5.5x stages gets you to 2kV, and that's
>>> a pretty mild step-up ratio. 66V, 363V, 2kV.
>>> Stage currents and inductor values scale, since
>>> they all run with the same time parameters.
>>>
>>> Three feedback taps, each with a diode to the
>>> controller's FB pin. The highest one controls,
>>> to prevent any one stage from going excessively
>>> over its voltage limit, but the last stage gets
>>> the controlling vote. Very simple. Except for
>>> HV winding technique of the 3rd inductor. :-)
>>
>> But surely that triple cascaded flyback topology you
>> suggest would need a MOSFET with 2000V Vds rating?
>
> Details, details ... The HV MOSFET table in the
> x-Chapters goes up to 4kV. But they're expensive.
> The idea makes more sense up to 1.2 or 1.5kV.
>
>