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Flyback transformer tutorial: function and design
Posted:2009-10-06

This article discusses design parameters for the flyback or swinging choke type of transformer used ...[ View complete article ]


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Flyback transformer tutorial: function and design

 Post time:  2009-10-06
 

Author:para

Points:  15

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This article discusses design parameters for the flyback or swinging choke type of transformer used in flyback converters.
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Reply:Flyback transformer tutorial: function and design Post time:  2009-10-06
 

Author:para

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transformer tutorial for flyback converters
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Reply: Flyback transformer tutorial: function and design Post time:  2010-04-01 02:32
 

Author:Daniel_p

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Hello!
I read your articel and hope to get help with the following problem :

Flyback transformer in discontineous mode:

"Vin"=11-12V Dc
"Ipeak"(primary)=520mA, ton(turn-on time)=5us
"Lp"(primary inductance) is calculated by: Lp=(Vin*ton)/Ipeak

A EF20 core is used with "Ae"=31mm^2 and "AL"=1200nH.
Wire with "d"=0.38mm is used.

Air-gap calculated by: "Lg"=[0.4*3.14*Lp*Ipeak^2*10^8]/(Ae*Bmax^2)=0.02mm
"Bmax"=2000Gaus selected.
Primary number of turns by: "Np"=(Bmax*Lg)(0.4*3.14*Ipeak)=8 turns
------
Surprisingly the primary current taken from the power supply during the turn-on time is too small, about 100mA, expected 520mA!!
Questions:Why is the current so small?
Why is the inductance not equal to 100uH,it's about 80uH.
(In each case the current is too small for Lp=80uH or 100uH)

I'll be gratefull if you could help me with this problem!
thank you very much in advance
Daniel_p edited at 2010-04-01
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