eBay special boost converter recommendation

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Can anyone recommend a China Special high voltage boost converter
 module? I'm looking for perhaps 12 volts in, ~300 volts out at
 around 100 mA. So I'm guessing it's going to be flyback.
 Isolation not important.

-150/ +150 would actually be ideal. If they're cheap I guess I can
 just get two.

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Re: eBay special boost converter recommendation
bitrex wrote...
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 The "DC-DC 600W 10-60V to 12-80V Boost Converter"
 selling for $11 + $1.50 shipping can be modified
 for up to 300 volts.

 BTW, the 600W rating is totally bogus.

 The mod requires replacing the MOSFET, the output
 rectifier and caps, some passive components, and
 maybe adding some turns to the coil.

 I reverse-engineered the PCB, see on dropbox:
https://www.dropbox.com/s/l1osx7frwtnwkyt/uc3843A_boost_eBay-600W.pdf

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 Boost to +150V is better, only 12.5 times.  Then
 you can add a simple second winding, diode & cap
 for the negative voltage.


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 Thanks,
    - Win

Re: eBay special boost converter recommendation
Den tirsdag den 29. december 2015 kl. 17.39.02 UTC+1 skrev Winfield Hill:
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a cap and two diodes might do

http://www.ti.com/lit/ug/sluu176/sluu176.pdf


-Lasse

Re: eBay special boost converter recommendation
Lasse Langwadt Christensen wrote...
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 Indeed, nice to avoid an extra winding.

 One issue with either scheme: Since Vout + rides
 on top of the +12 input, you get 12V less than
 you might expect on the negative side.


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 Thanks,
    - Win

Re: eBay special boost converter recommendation
Winfield Hill wrote:
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   Waited 5 min and still "loading"...

Re: eBay special boost converter recommendation
Robert Baer wrote...
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 dropbox isn't working for you!??!!


--  
 Thanks,
    - Win

Re: eBay special boost converter recommendation
On Tuesday, December 29, 2015 at 11:39:02 AM UTC-5, Winfield Hill wrote:
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The regulator supplying the IC seems bit complicated. Does the UC3843 need all that?

-RS

Re: eBay special boost converter recommendation
Rich S wrote...
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 It doesn't need any of that if Vin < 28 volts.  
 But if Vin can be as high as say 75 volts, and
 if you must be able to supply more than 12V at
 50mA for switching drivers, etc, then some form
 of a serious HV power regulator is required.  
 The designer also selected very low-cost parts.


--  
 Thanks,
    - Win

Re: eBay special boost converter recommendation
"Rich S"  wrote in message  
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Normally, an aux winding is used, with a ~100k pullup for startup current.  
For intermediate input voltages, a regulator can be worthwhile.

Tim

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Electrical Engineering Consultation and Contract Design
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Re: eBay special boost converter recommendation
On Tue, 29 Dec 2015 11:19:28 -0500 (EST), bitrex

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  You 100mA output is not a reasonable figure.  At least not in a
compact form factor..

  and that size would likely have to be custom, not off the shelf.

  Look at these.

http://www.hitekpower.com/eng/Product/1/324/SERIES-MPM

Re: eBay special boost converter recommendation
 message:
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A 30 watt flyback isn't reasonable and can't be put in a compact
 form factor?

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Re: eBay special boost converter recommendation
On Tue, 29 Dec 2015 12:23:24 -0500 (EST), bitrex

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  Did you even look at the link?  Those were about 3 cubic inch modules.

  HV supplies at ten watts per cubic inch are not easy.  At least not at
that form factor.

  Getting into hundreds of watts, maybe a bit easier per cubic inch, but
not at the PCB mount DC to DC convertor level.

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