Kenwood 144MHz FM TRANSCEIVER K2E Service Manual page 10

TH-K2AT/K2E/K2ET
Power Supply Circuit
Charging Circuit
When an external power supply is connected to the DC IN
terminal, the constant-current circuit consisting of Q33 and
D31 provides a constant current of approx. 110 mA to the Ni-
MH battery.
If no external power supply is connected to the DC IN
terminal, the constant-current circuit does not function.
IC8
MPU
BTEMP
DCDET
Q41
RN2105
VR1
ENC
5MS
5MS SW
Q57
RN2105
IC1
5M
TCXO
5C SW
5C
Q4,5,6
D40,41
IC5
Q53
Q30
5MV
RN2701
5R SW
IC3,17
5MV SW
D9,14
5R
Q16,17
Q22,23,24
Q59
Q55
CPH3317
Q9,10,13
D8,10
5T
TH1
5T SW
IC16
Q47
Control System
Reset and Backup Circuit
When power is supplied to the transceiver, the 5M voltage
goes "H" as C303 is charged.
A rising edge of the 5M voltage is detected by the voltage
detection IC (IC11) and when its output (RESET) goes "H",
the reset status of the MPU is released.
IC9
D35
IN
5V
BATT
AVR
10
CIRCUIT DESCRIPTION
BTDET
D35
RB521S-30
PROTECT
IC9
TK11250
CM
AVR
5.0V
IC12 Q37, Q38
2SB1184
TK11250
(Q,R)
IC6
CUCB
D48,49
2SC4617(R)
AVR D42,43,46
AF/LAMP
D47,44
5.0V
AVR
D36
RB521S-30 AF AMP
PROTECT
IC4
XC6202PB
Fig. 10 Charging and Power supply switching circuit
5C
R244
5M
OUT
IC11
C303
IN
IC10
IN
Fig. 11 Reset and Backup circuit
Power Supply Switching Circuit
The voltage supplied through the battery terminal or DC IN
terminal is branched in the power supply switching circuit as
shown in Fig.10 and then supplied to the required components.
Battery Type Recognition Circuit
When the battery pack is attached to the transceiver, the
battery type is recognized with the T terminal on the
transceiver. This battery type recognition activates charging
for the Ni-MH battery pack and displaying the battery meter.
Q36
2SJ347
THERM
DET
Q35
Q33
2SK1830
2SB1184
DC-IN
BATT
DET
CHARGE
D31
DA221
CONSTANT
CURRENT
Q34
2SK1830
B
CHARGE
SW
52FR
AVR
11.5V
If the supplied voltage to the transceiver is reduced and
the 5M voltage falls below the detection voltage of the voltage
detection IC (IC10), the MPU detects it by an interrupt
processing, backs up data in EEPROM (IC15) and turns the
power off.
EEPROM
L63
R243
OUT
RESET
C307
OUT INT
D33
D30
RB051L-40
RB521S-30
(Q,R)
PROTECT
PROTECT
B
D32
RB051L-40
CHARGE PROTECT
D80
RB521S-30
PROTECT
Timing chart
IC15
Power
ON
5M 5V
IC8
MPU
0
RESET 5V
0
INT 5V
0
-
T
+
BATT TERMINAL
7.5V Norminal
(6.0 - 9.0V)
DC IN
13.8V Norminal
(12.0 - 16.0V)
J2
B
Power
OFF