Circuit Description
Samsung Electronics
4-7
4-5 Desk-Top Rapid Charger
4-5-1 SMPS
1ST SWITCHING CIRCUIT
The AC current from AC plug transfers to a high-
voltage DC through BD1, C2, and C3. TNR1 is AC
surge protector, and F1 is fuse to protect circuit
from overcurrent . The line filter composed of LF1
and C1 is used to protect from line noise and
switching noise.
The transferred DC voltage is switched by T1. 2nd
switching voltage is flattened into AC through D20
and C22, and filtered through L20 and C30.
The voltage is regulated through shunt regulator
U5, R28, R29.
2ND SWITCHING
The regulated voltage through 1st switching
circuit performs 2nd switching. Step-down
regulator is composed of Q20, U2, D22, L21, and
C25. Q20 performs high-speed switching
according to the output signal from U2. L21 stores
energy when the switching transistor turns on.
D22 is a fly-wheel diode and transfers the stored
energy when Q20 turns off.
Voltage mode PWM IC U2 controls duty cycle
between the switching on and off of Q20. C30 and
R34 are parameter to determine the switching
frequency of U2.
4-5-2 Constant Current Circuit
U2 (TL494) has two error-amps. VREF (+5V) is
supplied to INV terminal (pin 15) of amp 1 and
N.INV terminal (pin 16) is connected to ground. It
causes the amp 1 output to be zero. In amp 2, the
reference voltage 2.0V is supplied to INV terminal
(pin 15) through R37 and R38, and the voltage
obtained in proportion to constant current is
supplied N.INV terminal (pin 16). The constant
current circuit also includes the shunt resistor R40,
and Q21 and U7.
FAST CHARGING (MASTER MODE)
The fast charging formula is shown below.
<RR=330
ߟ
, V
REF
=2.0 V>
For standard battery, RR is set with 680 ohm, and
for slim battery, 1 kohm is used.
SLOW (SLAVE MODE) AND TRICKLE
CHARGING
If batteries are installed both on front and rear port
of the desktop charger, the one installed in
advance performs fast charging while the other
installed later performs slow charging. In slave
mode, Q23 turns off. In trickle charging mode, Q24
turns off. The slow charging formula is shown
below.
<V
REF
=2.0 V>
I
CHG
=
x
V
REF
(mA)
R39
R40
x
(R43 + RR)
I
CHG
=
x
V
REF
(mA)
R39
R40
x
(R42)
Summary of Contents for SCH-1900
Page 2: ...Samsung Electronics Co Ltd GH68 60620A Printed in Korea ...
Page 27: ...Samsung Electronics 6 1 6 Troubleshooting 6 1 Logic Section 6 1 1 No Power ...
Page 29: ...Samsung Electronics 6 3 Troubleshooting 6 1 3 Abnormal Backlight Operation ...
Page 30: ...Troubleshooting 6 4 Samsung Electronics 6 1 4 Abnormal Key Data Input ...
Page 31: ...Samsung Electronics 6 5 Troubleshooting 6 1 5 Abnormal Keytone ...
Page 32: ...Troubleshooting 6 6 Samsung Electronics 6 1 6 Abnormal Alert Tone ...
Page 33: ...Samsung Electronics 6 7 Troubleshooting 6 2 Transmitter Section ...
Page 34: ...Troubleshooting 6 8 Samsung Electronics ...
Page 35: ...Troubleshooting 6 9 Samsung Electronics 6 3 Receiver Section ...
Page 36: ...Troubleshooting 6 10 Samsung Electronics ...
Page 37: ...Samsung Electronics 6 11 Troubleshooting ...
Page 39: ...Troubleshooting 6 13 Samsung Electronics 6 4 2 No Power HHP PWR 5 8V 13 5V Supply ...
Page 40: ...Samsung Electronics 6 14 Troubleshooting 6 4 3 Hands Free RX Path ...
Page 41: ...Troubleshooting 6 15 Samsung Electronics 6 4 4 Hands Free TX Path ...
Page 42: ...Samsung Electronics 6 16 Troubleshooting 6 5 Desk Top Rapid Charger ...
Page 43: ...Troubleshooting 6 17 Samsung Electronics 6 6 Cigarette Lighter Adapter 6 6 1 Power Fault ...
Page 44: ...Troubleshooting 6 18 Samsung Electronics 6 6 2 LED On Fault ...
Page 45: ...Troubleshooting 6 19 Samsung Electronics 6 6 3 Charge Fault ...
Page 46: ...Troubleshooting 6 20 Samsung Electronics 6 7 Travel Charger ...
Page 48: ...Exploded View and its Parts List 7 2 Samsung Electronics 7 1 Main Set Exploded View ...
Page 50: ...Exploded View and its Parts List 7 4 Samsung Electronics 7 3 Hands Free Kit Exploded View ...
Page 58: ...Exploded View and its Parts List 7 12 Samsung Electronics 7 11 Main Set Packing Layout ...
Page 60: ...7 14 Samsung Electronics Exploded View and its Parts List 7 13 Hands Free Kit Packing Layout ...
Page 62: ...7 16 Samsung Electronics Exploded View and its Parts List ...
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Page 100: ...10 2 Hands Free Kit Block Diagram ...
Page 101: ...10 3 Desk Top Rapid Charger Block Diagram ...
Page 102: ...10 4 Cigarette Lighter Adapter Block Diagram ...
Page 103: ...10 5 Travel Charger Block Diagram ...
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