AN-6067(2010_01) Ver la hoja de datos (PDF) - Fairchild Semiconductor

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AN-6067
(Rev.:2010_01)

Design and Application of Primary-Side Regulation (PSR) PWM Controller

Fairchild Semiconductor 

AN-6067

APPLICATION NOTE

Figure 27. Calculated System Parameter by Design Spreadsheet

The parameters in Figure 27 can be found in the corresponding components in Figure 28.

Vdc

Rin

- VFa +

Vdc

+ VF -

+

Naux Npri

Nsec

VO

R1

−

VDD

VS

VDD Cap. Vs Cap.

R2

+

Vds na : np : 1

-

RS

Figure 28. Application Circuit

Vin 1

6

Transformer Structure

As mentioned in the Constant Voltage Output Regulation

section, the PSR controller incorporates a proprietary

control design to achieve CV/CC regulations. A correct

sampling voltage of the auxiliary winding is critical to the

CV/CC performance. Therefore, the coupling of the

auxiliary winding and the secondary winding should be

precise. The suggested transformer structure is shown in

Figure 29 and Figure 30. The coupling coefficient between

the secondary winding and the auxiliary winding can be

effectively improved by sloughing off the EMI shielding

between auxiliary winding and secondary winding. Further

effectiveness is achieved by increasing the coupling area

through a well-paved the auxiliary winding on the top layer.

Primary

N1

Winding

MOS ' s 2

Drain

3

Auxiliary

N3

Winding

4

N2

Secondary

Winding

8

EMI Shielding

Figure 29. Transformer Winding

3

6

EMI Shielding

1

2

EMI Shielding

4

Auxiliary

Winding ( N 3)

Secondary

8

Winding(N 2)

(Insulated )

Primary

Winding ( N1)

Figure 30. Recommended Transformer Structure

© 2008 Fairchild Semiconductor Corporation

Rev. 1.0.1 • 1/26/10

12

www.fairchildsemi.com

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