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53

KX-FC965RU-T

The following is an overview of how the power supply unit is controlled. 
The control method of this power supply unit is pulse width modulation.

When Q

1

 is ON, the energy is charged in the transfer primary coil according to E

1

. When Q

1

 is OFF, the energy is output from the

secondary transfer as follows.
    L 

→ D

1

 

→ Load → L

Then the power is supplied to the Load. When Q

1

 is ON, power is not output from the secondary side. The output voltage is fed

back in the control IC according to the error amp rectifier. Then depending on how T

ON

 is controlled, stabilization occurs. Also,

when the current load becomes too large, in order to decrease the voltage output, the increase in 

 is controlled and the output

voltage is stabilized.
Therefore, basically the timing: Ton/Toff of Q1 controls the output voltage.

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KX-FC965RU-T

[Surge Absorber Circuit] 
This circuit is for absorbing surge voltage generated by the transformer.

[Control Circuit and Detecting Circuit] 
The control circuit amplifies the output with increased voltage detected in the error detecting circuit. Then it drives the main transis-
tor.
In this power supply, the duty ratio is defined by changing the ON period of the main transistor.
This is shown as follows.
When the output voltage of the 24V circuit increases, the current of the photo coupler PC101 increases, the pulse width of the out-
put control IC becomes narrower and the ON period of Q101 becomes shorter.

[Over Current Limiter (O.C.L)]
The highest drain current (Q101) is limited by a limiter circuit (IC101) of 24V. The 24V output is limited by this circuit.

[Over Voltage Circuit]
If the 24V output increases because the error detecting circuit or control circuit is broken, IC101 will recognize this signal and output
becomes 0V.

Refer to Power Supply Board Section (P.136).

55

KX-FC965RU-T

Cordless handset consists of the following ICs as shown in Block Diagram (P.55).

• DECT BBIC (Base Band IC): IC1

- All data signals (forming/analyzing ACK or CMD signal)
- All interfaces (ex: Key, Detector Circuit, Charge, DC/DC Converter, EEPROM, LCD, RF Power Amp.)
- PLL Oscillator
- Detector
- Compress/Expander
- Reception

• RF Power Amp: IC801

- Amplifier for transmission

• EEPROM: IC3

- Temporary operating parameters (for RF, etc.)

SPEAKER

RECEIVER

MIC

CHARGE
CIRCUIT

Q4, Q9, R7

Q4, Q9, R7

CHARGE
CONTACTS

CHARGE(+)

CHARGE(-)

CHARGE_CTRL

CHARGE

EEPROM

SCL

SDA

BATTERY
TERMINAL

D7

VBAT

J1

J2

1.8 V

Q2

Q2

1.8 V

LCD

CD

RESET

CSB

SDA

 SCL

CPU

Analog

Front

End

D/A

A/D

33

35

15

16
19

20

32

31

57

58

 36

13

43

42

63

54

55

66

ADPCM

Codec

Filter

DSP

Speech

Decoding

Speech

Encoding

BMC

Burst

Decoding

RF PA

ANT1

Burst

Encoding

RF

PLL

MOD/DEMOD

5

3

4

3

6
7

8

9

2

77

78

75

RXn

RXon

ANT1

DA801

RXp

TXp

TXn

Pon
PSEL

TXon

VDD-PADRY

9

10

XTAL

X1

10.368
MHz

BATTERY

44

ON SWITCH

KEYPAD

Charge

Pump

ROWS

COLUMNS

CP3.0 V CP4.0 V

48, 49, 50, 51

22, 23, 24, 25, 26

BBIC

 56

LCD-BACK  LIGHT

KEY   LED

BELL  LED

52

68

73
74

80

LDO_CTRL

KX-FC965RU: CORDLESS HANDSET BLOCK DIAGRAM

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KX-FC965RU-T

When power on the cordless handset, the voltage is as follows;
BATTERY(2.2 V ~ 2.6 V: BATT+) 

→ F1 → Q2 (1.8 V), IC1-43pin (2.5V)

The Reset signal generates IC1 (61 pin) and 1.8 V.

When charging the cordless handset on the Base Unit, the charge current is as follows;
DC+(6.5 V) 

→ D1 → R56 → R55 → D22 → CHARGE+(Base) → CHARGE+(Handset) → Q4 → D7→ F1 → BATTERY+... Bat-

tery... 
BATTERY- 

→ R45 → GND → CHARGE-(Handset)→ CHARGE-(Base) → GND → DC-(GND)

In this way, the BBIC on cordless handset detects the fact that the battery is charged.
The charge current is controlled by switching Q9 of cordless handset.

“Battery Low” and “Power Down” are detected by BBIC which check the voltage from battery.
The detected voltage is as follows;

• Battery Low

Battery voltage: V(Batt)   2.25 V ± 50 mV

The BBIC detects this level and 

 starts flashing.

• Power Down

Battery voltage: V(Batt)   2.0 V ± 50 mV
The BBIC detects this level and power down.

The hands-free loudspeaker at SP+ and SP- is used to generate the ring alarm.

The power supply is as shown.