What does this capacitor do in this PSU?

[zane1978]

Thank you both for your advice. I acknowledge I made alot of mistakes and could not find certain symbols in easyEDA yet. I have I will try to do better and take more time to design/copy a circuit. Alot of users simulate their psu, maybe I should start with learning how to do that. I think it is more efficient to post my whole design+componentlist for the psu but also the amplifier/grounding/etcetc/ in a separate topic from now on.

1 question about the choke, is there a reason why you selected 1mH/10A? I found this chokecalculator and I could not get the answer to come close to your suggestion. thanks.

 

[DF96]

That is not a choke calculator, it is a Chebyshev filter calculator - used mainly for RF purposes.

 

[GoatGuy]

Is there a reason why you selected 1mH/10A?

Yes.

№ 1: modest cost
№ 2: ample current-output (10 amps)
№ 3: relatively small
№ 4: well regarded manufacturer
№ 5: low series resistance
№ 6: “just enough” inductance to suppress rectification buzz​

In other words, a compromise of compromises. But satisfactory.
GoatGuy

 

[PRR]

That is not a choke calculator, it is a Chebyshev filter calculator - used mainly for RF purposes.

It "works", if you hammer on it.

We want just C-L-C so set # components to 3.

Set F to the bottom of the audio band (you want to change the Units to Hz).

Our job is NOT an impedance-matched filter and the results will not be precise. I estimated one side of a totem-pole audio amp as ~~24 Ohms, decided the filter impedance would be much less, so I put "1 Ohm". We don't need 0.01dB flatness, but don't want 10dB lumps, and I know anything around 3dB will be much the same values.

The suggest result is in-sight of GoatGuy's 1mH: 2.3mH and a couple of our usual 10,000uFd caps. Small changes in these values will have even smaller changes in result. If GG says a 1mH is cheap and cheerful, I'd go with that. If I set the wild-guess "1 Ohm" to 0.444 Ohms it gives 1mH and 24,000uFd, also a super-reasonable flock of parts. Or 111Hz and 1 Ohm gives 1mH 4800uFd.

None of these gives much cut to the 100Hz/120Hz ripple. But they will reject 1KHz/1.2KHz ripple-buzz 40dB better than a simple fat cap. Since the ear low-level response rises more than 20dB from bass to midrange, this may be audibly cleaner.

 

[DF96]

Yes, you can use it to design a PSU filter but getting the parameters right requires more knowledge of filters than the average PSUD2 user. I think I managed to get something like 20mH and 5000uF, with an impedance of 10 ohms.