Kenwood TH-K2AT, K2E, K2ET ■Charging Circuit, ■Power Supply Switching Circuit, ■Battery Type Recognition Circuit, Fig. 10 Charging and Power supply switching circuit

TH-K2AT/K2E/K2ET

CIRCUIT DESCRIPTION

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	Q36
MPU
	2SJ347
BTEMP
	THERM

■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.

-

DCDET						DET
		Q41								T
VR1		RN2105
ENC	5MS	5MS SW				BTDET				+
				D35						BATT TERMINAL
				RB521S-30
										7.5V Norminal
				PROTECT						(6.0 - 9.0V)
		Q57		IC9		Q35		Q33		D33
		RN2105		TK11250					D30
IC1			5M			2SK1830		2SB1184
				CM					RB521S-30	RB051L-40
TCXO	5C	5C SW		AVR		DC-IN		(Q,R)
Q4,5,6								BATT		PROTECT
D40,41				5.0V		DET			PROTECT
								CHARGE
								D31	B
								DA221
IC5		Q53		IC12		Q37, Q38		CONSTANT
Q30	5MV	RN2701		TK11250		2SB1184		CURRENT		D32
				CUCB	IC6	(Q,R)		Q34
										RB051L-40
IC3,17		5R SW			D48,49	2SC4617(R)
		5MV SW		AVR	D42,43,46	AF/LAMP	B	2SK1830	CHARGE	PROTECT
D9,14	5R			5.0V	D47,44	AVR		CHARGE
Q16,17
Q22,23,24				D36				SW
Q59					AF AMP
				RB521S-30
										DC IN
				PROTECT						13.8V Norminal
		Q55				IC4				(12.0 - 16.0V)
Q9,10,13		CPH3317				XC6202PB			D80	J2
D8,10	5T					52FR			RB521S-30
TH1		5T SW				AVR				B
IC16									PROTECT
						11.5V
Q47

Fig. 10 Charging and Power supply switching circuit

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.

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.

					IC15		Timing chart
					EEPROM		Power	Power
		IC9	5C				ON	OFF
	D35			L63
		5V OUT R244	5M		IC8	5M	5V
BATT	IN
		AVR			MPU
			+
				R243
			IC11				0
		C303	IN	OUT
					RESET	RESET	5V
				C307
			IC10				0
			IN	OUT	INT
						INT	5V
							0

10 Fig. 11 Reset and Backup circuit