High Voltage isolated DC-DC converter

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hi,

I am developing flyback dc-dc converter using UC3843
first prototype targeting for the output voltage 100V to 200V, 10 to 50mA from 12V input
This circuit may be used for tube preamp or other purposes

attached schematic with 120V output voltage has been tested in prototype using a 10K resistor
schematic for variable output voltage (usingTL431) is in the simulation process

next time i will post pcb files, but I can not promise to update quickly

note:
-I only have 1 MHz oscilloscope, it's not too accurate displaying waveform
-RCD snubber is not installed in this test
 

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Snubber across secondary diode might further ease stress...
I mean (cap in series with a resistor) in parallel to your D3.

There are other controller options that offer much closer to
zero voltage valley switching and can estimate the secondary
flyback voltage by watching what the primary does during the
open half cycle. May be possible to cut the zeniers and opto...
 
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