NCP1082

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4

SIMPLIFIED APPLICATION DIAGRAMS

Figure 4. Non−Isolated Fly−back with Extra Winding and Rear Auxiliary Support

NCP1082

Rcs

Cvddl

Cvddh

Cpd

Css

Rosc

M1

T1

Cload

LD1

Rd1

Rclass

Rilim1

Rinrush

Rslope

Voutput

D1

GATE

RTN

FB

VPORTN2

VDDH

VDDL

VPORTN1

CLASS

ARTN

ILIM1

INRUSH

TEST

AUX

UVLO

CS

VPORTP

Data

Pairs

Spare

Pairs

R1

R2

RJ−45

DB1

DB2

Raux1

VAUX(+)

VAUX(−)

Raux2

Raux3

D3

D4

Cline

Z_line

COMP

SS

OSC

R3

R4

C1comp

C2comp

Rcomp

R5

D2

Figure 4 shows the same non−isolated fly−back configuration as Figure 3, but adds a 12 V auxiliary bias winding on the

transformer to provide power to the NCP1082 DC−DC controller via its VDDH pin. This topology shuts off the current flowing

from VPORTP to VDDH and therefore reduces the internal power dissipation of the PD, resulting in higher overall power

efficiency.

Figure 5. Non−Isolated Forward Converter with Rear Auxiliary Support

NCP1082

Rcs

Cvddl

Cvddh

Cpd

Css

Rosc

M1

T1

Cload

LD1

Rd1

Rclass

Rilim1

Rinrush

Rslope

Voutput

D1

GATE

RTN

FB

VPORTN2

VDDH

VDDL

VPORTN1

CLASS

ARTN

ILIM1

INRUSH

TEST

AUX

UVLO

CS

VPORTP

Data

Pairs

Spare

Pairs

R1

R2

RJ−45

DB1

DB2

Raux1

VAUX(+)

VAUX(−)

Raux2

Raux3

D4

D5

Cline

Z_line

COMP

SS

OSC

R3

R4

C1comp

C2comp

Rcomp

D3

D2

L1

Figure 5 shows the NCP1082 used in a non−isolated forward topology.