Kenwood TH-D74E Service Manual page 11

2.1.6.2 Lithium-ion Battery charging control circuit
The IC585 will charge the lithium battery by receiving the charge control instruction from the main MPU. The IC585 will detect the
battery voltage and the battery charging current, and operate as shown below.
If the battery voltage is less than 6.0 V, the IC585 and Q580 will supply a constant voltage of 6.0 V to the +B power supply, and control
the gate voltage of the Q581 and perform pre-charging at a charging current of 128 mA.
If the battery voltage is 6.0 V or higher and less than 8.4 V, the Q581 will be turned ON. Then the IC585 and Q580 will perform
switching (constant current charging) so that the charging current will be a constant current as specified, and supply a voltage
almost the same as the battery voltage to the +B power supply.
When the voltage battery rises to 8.4 V, the Q581 will be kept turned ON, and the IC585 and Q580 will provide the +B power supply
with a constant voltage of 8.4 V and perform the constant voltage charging of the battery.
During the constant voltage charging of the battery, the charging current will gradually decrease. The battery will be deemed to be fully
charged when the charging current reaches 128 mA or below, and the Q581 will be turned OFF, and the charging will be completed.
If the charging of the battery is completed while the transceiver is in signal reception or a standby state, the IC585 and Q580 will
continue providing a constant voltage of 8.4 V to the +B power supply.
If the charging of the battery is completed while the transceiver is in a standby state, the main MPU will send a charge stop
instruction to the IC585, and the IC585 will stop charging the battery. The main MPU will set the 40CS to a low level, thus stopping
the operation of the IC584 to block the 40C power supply. Then the main MPU will stop operating, and the transceiver will be turned off.
If the transceiver starts transmission while the battery is charged, the main MPU will send a charge stop instruction to the IC585 to
stop charging the battery. Upon completion of transmission, the main MPU will transmit a charge control instruction to the IC585 to
resume charging the battery.
2.1.6.3 Protection circuit
The main MPU monitors the temperature detected by the thermistor (TH700). If the temperature is out of an optimal temperature range
of 0°C to 40°C, the main MPU will transmit a charge stop instruction to the IC585 to stop charging the battery.
The main MPU monitors the DC-IN JACK voltage. If an overvoltage beyond guarantee is applied, the main MPU will stop the operation
of the transceiver and protect the circuits.
11.0~16.0V
3.15A FUSE
DC IN
F577
J576
D577
4A FUSE
F576
7.4V
+BATT
GND D576
BAT_DET
S
(To MAIN MPU)
THERMISTOR
TH700
CHG_TH
TH
(To MAIN MPU)
FET SW FET SW
Q579 Q580
R615
VIN RBDRV ACSP ACSN SW
HSDRV
LSDRV
IC585
VBAT BATDRV BCSN BCSP VINOK
R618
FET SW
Q581
D578
3.1V_AVR
IC586
ONE SHOT
OR CIRCUIT
IC588
IC592
POW SW
INVERTER
Q584
40CS
(From MAIN MPU)
Fig.8 Power supply circuit (TXRX PCB)
+B
4.7V_AVR
IC584
40C
4.0V_DC/DC
IC584
Q582 SW
EN 47RA
AUS AVS
Q9 SW
45PDT
COMPARATOR IC
IC591 CKY
VTX1
(From
SUB MPU)
SW
Q10,D29-30
INVERTER
Q585 Q577 SW
144T
144TS
Q578 SW
220T
AND CIRCUIT
IC587 220TS
Q576 SW
430T
430TS
Q14 SW
ATT
144TS 430TS
VDCIN
(To CONT PCB)
(To CONT PCB)
(To CONT PCB)
IC582 3.3V_AVR
33S
33SS
IC581 3.3V_AVR
33CA
33CAS
IC578 3.3V_AVR
33CB
RIPPLE F
Q375
33CBS
33CBF
Q388 SW
33TX
IC580 3.3V_AVR VTX1
33C
33CS
IC576 3.3V_AVR
33BU
33BUS
IC577 3.3V_AVR
33BV
33BVS
IC579 3.3V_AVR
33RA
33RAS
IC583 3.3V_AVR
33RB
33RBS
IC593 3.3V_AVR
33RAD
BFMS
IC590 3.3V_AVR
33IF
33IFS
IC365 CHARGE P
IC363 5.3V_AVR
5C
33CS
(No.RA044<Rev.001>)1-11
+B
47C
40C