KX-UT670RU - Panasonic Telephone Service Manual (repair manual). Page 11

11

IC2(PoE IC) starts the PoE classification  when  connected with the switching hub with PoE.
After the PoE  classification ends, 8pin(VSS1) is connected with 9pin(GND) in IC2.

After that,the voltage supplied from hub is converted to the output voltage to the secondary side of T3 by IC2.
Output voltage is rectifiered to DC12V by D8,C22,C30 and C166.
Its voltage is generated as follows.

The rectifiered DC voltage is divided by R26 and R27.
Divided voltage is compared with reference voltage(2.465V) of IC4 pin 5.
 Its Comparative result is output to pin4 of IC4.
 Its result is tranfered to pin14 of IC2 through IC3(Photo-coupler).
 According to the signal(pin14),IC controls Q1 through pin 10 of IC2.
 Output voltage is fixed to 12V by these operation.

PoE_VSS

PoE_Pluse

D1

4

1

3

2

D2

4

1

3

2

Q1

1

2

3

4

5

6

7

8

IC3

1

2

3

4

L2 3.3u

C17

47u

80

R13 10k

C19

0.1u

16

R15

10k

R17 100

R19

NC

R20

52.3

C24

0.1u 25

R21 120k

R22 1.8k

C25

0.047u

16

C26

1000p

2000

R23

1k

C27

0.1u 25

R24 0

D7

PoE_G

PoE_AG

PoE_G

R71

0

PoE_G

PoE_G

PoE_G

C18 1u 100

C38

1u

100

PoE_G

D17

C124

1000p/100V

R69

100K

R14

68

L25

L24

L23

L22

PoE_VSS

C148

NC

C149

0.1u

16

PoE_G

R12

33k

C164

0.01u

50

C165

0.01u

50

C23

0.01u 50

R18 27k

C150

0.1u

16

T3

4

5

8

2

3

1

10

9

6

7

R16

1

R95

1

IC2

1

RT

2

SS

3

AUXII

4

VIN

5

RCLASS

6

AUXI_IRL

7

DCCL

8

VSS1

9

GND

10

GD

11

VCC

12

*PGD

13

CS

14

COMP

15

VFB

16

AGND

17

VSS2

F1

750m

D3

A

L32

LF1

1

4

32

C179

0.1u

1000

C180

0.1u

1000

C20

470p

50

L35

2.2u

L36

2.2u

C15

0.018u 100

IC4

1

NC1

2

A

3

NC2

5

REF

4

K

R25

15

C29

0.1u

25

R26 39k

R27

10k

R28

330

C32

4700p

50

C33 100p 50

R29 1.2k

DG

DG

DG

R30

3.3k

C28

1000p

50

L28 1

D8

V12_PoE

D9

C22

10u

25

C30

10u

25

C21

10u

25

Q5

DG

PoE_DET

R32

10k

3.3V

D15

R35 1k

DG

R36

NC

L29

L30

L31

L33

L34

C34

0.01u

50

C166

10u

25

DG

36-57V