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lumanauw 11th May 2008 05:20 AM

Common choke in full bridge class D
2 Attachment(s)
What is the advantage and disadvantage of common chokes, used in full bridge classD, like pic. no.2?

theAnonymous1 11th May 2008 05:38 AM

Here, read this while your waiting for a response from someone who counts.;)

I remembered seeing the above article a few years ago. It took me a solid 15 minutes of searching to find it again.

lumanauw 11th May 2008 05:58 AM

Thanks, anonymous1 :D

I read this thread, I got confused.

lumanauw 11th May 2008 06:02 AM

2 Attachment(s)
What is the meaning of this picture?

Pafi 11th May 2008 06:51 AM


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.

lumanauw 11th May 2008 04:40 PM

Hi, Pafi,

Thanks :D So it's about class BD.

Workhorse 12th May 2008 07:04 AM

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.

lumanauw 12th May 2008 07:38 AM

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.

Workhorse 12th May 2008 07:50 AM

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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