My first flyback, Help!

George Herold · 2018-04-18T16:16:30+00:00

Hi all, well I went and moded JL's flyback with the LTC3803. I stuck the file in dropbox, but if someone can't access that I'll be happy to copy it here. For the inductor I picked one of the Versa-Pak inductors with 6 coils on one form. And made a 1:5 transformer. So I first assumed I'd be running in continuous conduction mode. (Which may be wrong.) And went ahead and calculated my duty cycle ratio. V_out(300)/V_in(24) = n*D_on/D_off.. or it's on ~30% of the time. and then the 'on' current from the 24V. ~150mA* So I picked an inductor with a saturation current which is twice this. (I have no idea how to pick the inductor.) Well that didn't work! I had to increase the current a lot to get the output up to 300V. I needed closer to 1 amp to get the thing to work. So A different inductor. (VPH5-0155-R) I must admit that if I just look at the inductor. V = L*di/dt that at 24V and ~24uH I expect the current to increase at about 1 amp/ usec. which is about what I see. So any advice about what I did wrong, or how to do this better would be appreciated. I should also note that there is lots of ringing in the inductor. I'm not sure what's causing this. George H. *This is just from 100% energy balance and is different from the equation in my SMPS text book.

Apr 18, 2018 42 Replies

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pcdhobbs 8 years ago

Yeah, I thought so too, which is why I glommed onto it.

Hey, there's value in ugly-but-simple. ;) You can right-click on it and set it invisible.

Cheers

Phil Hobbs

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John Larkin 8 years ago

That's even scarier.

John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com

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Lasse Langwadt Christensen 8 years ago

onsdag den 25. april 2018 kl. 19.44.36 UTC+2 skrev John Larkin:

increases the risk that one of the files will be lost to roughly 100%

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