Electronics > Projects, Designs, and Technical Stuff

SMPS for vacuum tube power amplifiers.(status: back at it)

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MagicSmoker:

--- Quote from: SK_Caterpilar_SK on September 16, 2019, 10:03:34 pm ---2x 56uF 450V and one 10uF low ESR all in parallel (perhaps a SMD high voltage cap to bypass it a little better. I dont know if that makes it any better but I expect it will ;D )

Max output power I expect is 70W peak 50W nominal.

--- End quote ---

70W output max, so estimate about 100W input and I assume this is a flyback, but is it just for operation at your mains voltage (220VAC/50Hz) or "universal" (typically 90VAC to 260VAC or thereabouts), and so the input capacitance needs to be designed for the low-end of the voltage range?

High frequency bypass of the input capacitance to a buck or flyback is always a good idea, but something like a 100nF film capacitor placed right across the power loop (e.g. - top of flyback primary and input ground) would be more appropriate; there's no help - and sometimes harm in the form of ringing - from placing the low-ESR bypass capacitor right next to the electrolytics doing the low-frequency ripple filtering and reservoir duty.


T3sl4co1l:
It really won't matter because as long as the electrolytic is placed where the film bypass would be placed, it'll perform just as well.  Bypass isn't critical on a flyback anyway, leakage inductance acts in series with the supply.  The switch snubber is the only required low-inductance path.

Tim

MagicSmoker:

--- Quote from: T3sl4co1l on September 17, 2019, 12:05:24 pm ---It really won't matter because as long as the electrolytic is placed where the film bypass would be placed, it'll perform just as well. ...

--- End quote ---

Bolded the key part; my point wasn't dissimilar, just more that 10uF of "low-ESR" (unspecified, but assumed film) capacitance directly in parallel with the bulk elkos located some distance away from the switching loop would be kind of a waste of money here.

m3vuv:
stick an hf transceiver near it if you think its noise free!!

SK_Caterpilar_SK:
Low ESR electrolitic (low impedance caps)

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