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Old 11th May 2008, 05:20 AM   #1
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Default Common choke in full bridge class D

What is the advantage and disadvantage of common chokes, used in full bridge classD, like pic. no.2?
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Old 11th May 2008, 05:38 AM   #2
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Here, read this while your waiting for a response from someone who counts.

http://www.murata.com/emc/knowhow/pd...-1/26to28e.pdf

I remembered seeing the above article a few years ago. It took me a solid 15 minutes of searching to find it again.
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Old 11th May 2008, 05:58 AM   #3
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Thanks, anonymous1

I read this thread, I got confused.
A new (Stupid?) class d idea
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Old 11th May 2008, 06:02 AM   #4
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What is the meaning of this picture?
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Old 11th May 2008, 06:51 AM   #5
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lumanauw!

It means that in a Class BD (tri-state) amplifier the common choke shows a higher inductance for carrier (mainly common mode) then for the audio (differential mode). This also means that it can bear very high audio current without saturation.
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Old 11th May 2008, 04:40 PM   #6
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Hi, Pafi,

Thanks So it's about class BD.
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Old 12th May 2008, 07:04 AM   #7
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David , your inductor is wound in common-mode fashion, its good in class-BD when at idle, no signal conditions. But when the duty cycle variation begins with signal, it triggers the saturation very easily, because the flux charging discharging cycle time period is asymmetric......since carrier is in Phase, Audio is out of phase...................

if you wound a differential inductor and put it in bridged Class-D with AD modulation, it would not saturate and also provide more inductance with lesser number of turns.
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Old 12th May 2008, 07:38 AM   #8
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Hi, Kanwar,

I wanted to try a common choke in classAD (not BD). I also tought classBD needs a separate choke, I don't know if it can work with common choke.
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Old 12th May 2008, 07:50 AM   #9
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Common Choke in AD mode is not useful to that extent, because both carrier and audio signal are out of phase with each other
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