China special boost converters

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Got a couple of these from our friends in Shenzen:

<https://www.dropbox.com/s/fltwl455j6c0e85/20170721_114608.jpg?dl=0

<https://www.dropbox.com/s/la6amaowd0avf9c/20170721_114631.jpg?dl=0

It claims 8-32 Vin for 45-390 Vout at 40 watts (70 watts peak.)

The power MOSFET is an "RU7088":

<http://www.junyi-ic.com/upfiles/video/20121113155055.pdfhttp://www.junyi-ic.com/upfiles/video/20121113155055.pdf

The ICs on the underside from left to right are a no-name-branded SMD  
78L0(illegible), a ST-branded UC3843B, and a TI-branded LM358.

The electrolytics on top are 10uF 450V 105 degree "Chong" brand "LOW  
ESR", which are of course my favorites.

$10 each delivered

Re: China special boost converters
On 07/21/2017 11:56 AM, bitrex wrote:

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Sorry, try this:

<http://www.junyi-ic.com/upfiles/video/20121113155055.pdf

Re: China special boost converters
bitrex wrote...
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 There's quite a range of these on eBay, apparently
 the same PCB, but with varying assembly options,
 prices ranging from $5 + $0.85 shipping to $7.75.
 Some say the circuit is ZVS.  Some mention a dual
 bipolar output available.  To my mind the most
 interesting part is the transformer.  

 An eBay flyback boost circuit rated at 200W (600W
 claimed) may be similar, but uses a toroid inductor.
https://www.dropbox.com/s/l1osx7frwtnwkyt/uc3843A_boost_eBay-600W.pdf?dl=0

 One has to supply a 12 to 24V input == so starting
 at 120 or 230Vac, we make 100W low-voltage dc, and
 then step it up again.   It'd be convenient to have
 an AC-line supply, with an adjustable HV DC output.


--  
 Thanks,
    - Win

Re: China special boost converters
On 07/21/2017 01:57 PM, Winfield Hill wrote:
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It looks like I got the one with the bipolar output as it seems the  
output terminal block has three lugs; I can't recall if that's what I  
ordered but looks like that's what they shipped. Is that option what  
makes the transformer interesting? It should be straightforward enough  
to draw up a schematic from inspecting the traces on this one; I think  
it's only double-sided.

I think I have an appropriate set of power resistors to use as a dummy  
load to run it up to near full load at max output voltage, I'd like to  
see if it does meet its specs and what the output ripple is like towards  
the limit.

Re: China special boost converters
On Fri, 21 Jul 2017 14:03:06 -0400, the renowned bitrex

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It's a voltage doubler on the output with the center grounded, so if
your load is grounded you can pick either +380 or -380 max. Probably
the feedback is from the +.  

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--  
Best regards,  
Spehro Pefhany

Re: China special boost converters
On Fri, 21 Jul 2017 11:56:09 -0400, the renowned bitrex

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I got one of those to play around with some Soviet GM tubes. I think I
paid a bit less, but whatever.  

Current draw is weird- huge current with little load, then settles
down.  

--sp  


--  
Best regards,  
Spehro Pefhany

Re: China special boost converters
On Fri, 21 Jul 2017 11:56:09 -0400, the renowned bitrex

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BTW, sorry if this is obvious, but you need to move that jumper on the
bottom to get below 10V- that bypasses the 78L09 regulator for input
voltages between 8V and 16V.  

Thanks for identifying the other two chips. The numbers have been
scraped off the SO8's on mine.  

--sp  



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--  
Best regards,  
Spehro Pefhany

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