Coupling factor of common mode choke?

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treez

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Hello,
Do you know what is the coupling coefficient of this common mode choke?

SRF0504-191Y
https://www.bourns.com/data/global/pdfs/SRF0504.pdf

(We will use it on a 24vin, 19vout, 2a5=iout LED driver board.)
We need to evaluate ringing overvoltage between the leakage of the CMC and the input caps of the driver card, so we need to know leakage
 

It's essentially simple. You can
- ask the manufacturer for additional data
- measure the missing parameters yourself
 
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thankyou, I was also going to ask why these common mode chokes all have such low mutual inductance....but then I suppose this is because the frequencies dealt with by CMC's are very very high?
 


DCR is 20mΩ per line so if Vin is 24V the drop is only 50mV per line. 19Vout I assume is after PWM. Since this is common mode it suppresses radiated noise not differential conducted noise.

The effectiveness is based on ratio of impedance thru 0.6µH and impedance to ground plane. Thus if DC is floating, differential caps to ground provide additional suppression.

The differential inductance will be very small compared to each leg.
 
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thankyou, I was also going to ask why these common mode chokes all have such low mutual inductance
Click to expand...
There are essentially two types of common mode chokes, signal chokes with intentionally low leakage inductance respectively high coupling factor to get high signal bandwith along with the common mode filtering and power chokes with intentionally high leakage, to implement an additional filtering of differential noise.

I agree that it would be better to have complete specifications in the datasheets, but that's apparently asking too much.
 
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