Placement of resonant capacitor in a LLC converter

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zhuxiaozhu
Level 1
Level 1
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Dear all

in almost every LLC evaluation boart , the resonant capacitor Cr is not series with resonant inductor Lr,

but parallel , connect with transformer and Both ends of the power supply,

SO I am interested in why is this? What's the advantage ?

thank you for attention ,hope you a nice day!1.jpg

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1 Solution
Shiva_C
Moderator
Moderator
Moderator
25 solutions authored 50 replies posted 100 sign-ins

Hi,

Connecting Cr in series with Lr is a conventional LLC Resonant Converter. In the above configuration, the Cr is rearranged into a split capacitor Half-Bridge Configuration.

This configuration enhances the extended power handling capacity of Half Bridge Resonant converter when compared with conventional LLC (single Cr connected in series with Lr).

Split Cap. HB LLC having below benefits over single Cr LLC HB.

1. Lower RMS ripple current demand from DC bus capacitor

2. Since half of the RMS currents flow into split capacitor the capacitor will have long life.

3. Typical LLC HB start-up issue due to Cr will be improved in split cap. concept since it will take less time to charge (However it is function of multiple factors please refer to below attached document to understand benefits of Split Cap. HB LLC)

https://www.infineon.com/dgdl/Infineon-Application%20Note%20Design%20of%20a%20600%20W%20HB%20LLC%20C...

BR,

SC

 

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2 Replies
Shiva_C
Moderator
Moderator
Moderator
25 solutions authored 50 replies posted 100 sign-ins

Hi,

Connecting Cr in series with Lr is a conventional LLC Resonant Converter. In the above configuration, the Cr is rearranged into a split capacitor Half-Bridge Configuration.

This configuration enhances the extended power handling capacity of Half Bridge Resonant converter when compared with conventional LLC (single Cr connected in series with Lr).

Split Cap. HB LLC having below benefits over single Cr LLC HB.

1. Lower RMS ripple current demand from DC bus capacitor

2. Since half of the RMS currents flow into split capacitor the capacitor will have long life.

3. Typical LLC HB start-up issue due to Cr will be improved in split cap. concept since it will take less time to charge (However it is function of multiple factors please refer to below attached document to understand benefits of Split Cap. HB LLC)

https://www.infineon.com/dgdl/Infineon-Application%20Note%20Design%20of%20a%20600%20W%20HB%20LLC%20C...

BR,

SC

 

got it!

 

Thank you very much!

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