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Old 25th June 2012, 02:52 PM   #1
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Question PSU choke

How to calculate the inductive & resistive value for a PSU choke?
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Old 25th June 2012, 03:01 PM   #2
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In which configuration, input choke or input cap?
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Old 25th June 2012, 03:59 PM   #3
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Input cap.
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Old 25th June 2012, 06:39 PM   #4
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Do you mean how to calculate the inductance and resistance of a particular choke, or how to determine the required values for a PSU design? I assume you mean the latter.

PSU current, voltage, acceptable ripple, half or full-wave or doubler, any subsonic issues? Once you understand the issues, you will be almost there for calculating the values.
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Old 25th June 2012, 07:26 PM   #5
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Inductance: the most you can given a certain resistance in the wire, and core size. Be aware the gap in the core regarding the DC in it.
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Old 25th June 2012, 08:11 PM   #6
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Quote:
Originally Posted by DF96 View Post
Do you mean how to calculate the inductance and resistance of a particular choke, or how to determine the required values for a PSU design? I assume you mean the latter.

PSU current, voltage, acceptable ripple, half or full-wave or doubler, any subsonic issues? Once you understand the issues, you will be almost there for calculating the values.
Yes the latter.

I'm a newbie, I know target voltage & current but I need to understand how implement the PSU to get the lower ripple possible to sound the best possible.

For example I know that before diodes I have to put a RC snubber, first question: how measure with scope if values are correct & how to calculate the values of RC.

Why the resistor in series with choke have to be 0R47 or low value?

Why not choke & resistor in ground rail?

Choke is better alone or common mode if used also for ground?

etc.
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Old 25th June 2012, 08:38 PM   #7
DF96 is offline DF96  England
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"Lowest ripple possible" is not a useful criterion. It is quite normal for a newbie to want to over-engineer a circuit, so you are in good company!

The choke and smoothing cap act as a low pass filter, as the choke and cap act as an AC potential divider. You need to calculate/measure/simulate the ripple on the first (reservoir) cap, then consider your amp circuit PSRR. Taken together these tell you how much the PSU has to suppress ripple. This is of course is elementary PSU design theory which you can find in a book or on the internet.

The choke needs no resistor in series. On the contrary, often the choke resistance itself is larger than we would like. The choke could be put in the negative rail - it might even help people get their grounding right by forcing them to avoid the common mistakes.

Common mode chokes eliminate common-mode noise. Ripple is usually differential mode.
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Old 25th June 2012, 10:07 PM   #8
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I assume that choke don't need resistor in series for tube PSU not for SS, how can be calculate inductance & resistor for SS?

I use PSUDII to simulate but sorry my ignorance could you post a pic with ideal graphics to understand what I have to look for?

Last edited by merlin el mago; 25th June 2012 at 10:09 PM.
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Old 26th June 2012, 09:13 AM   #9
DF96 is offline DF96  England
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Do some searching and reading on PSU design. Gain some understanding; don't just look for a formula.
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Old 26th June 2012, 09:36 AM   #10
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I will do thanks.
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