Table of Contents
Advertisement
Circuit Description
STATIC VOLTAGE CIRCUIT (4.1V OUTPUT)
The secondary (cathod of D23) output voltage Vo
is separated by R50, VR1, R55, R79 and applied to
the comparator U24-B pin 6. Q41 turns off
(10k~33k) or on (0~5.1k) according to the resistance
value in V/F (front/rear) terminal of R50,R79.
In accordance, when Q41 turns on, the parallel
linked resistance value of R50 and R79 become
smaller, so that 4.1V comes out. The voltage will be
compared with the reference input voltage of pin
5, and feedback to the primary by U2(OPT).
U24-B output voltage is linked to U24-A output. It
turns Q36 off. Consequently, if either one of these
static voltage or static current overflows, it will
automatically turn U1 off. R45 and C36 are used to
compensate the phase difference caused by the
time delay.
R55
Vd =
(R50//R79 + VR21) + R55
Since, the Vd is maintained to be the same level as
the reference voltage Vr is,
(R50//R79 + VR21) +R55
Vo =
R55
STATIC VOLTAGE CIRCUIT (4.2V OUTPUT)
The secondary (cathod of D23) output voltage Vo is
separated by R50, VR21, R55, R79 and applied to
the comparator U24-B pin 6. Q41 turns off
(10k~33k) or on (0~5.1k) according to the resistance
value in V/F (front/rear) terminal of R50, R79.
In accordance, when Q41 turns off, only the
parallel linked resistance value of R50 is selected,
so that 4.2V comes out. The voltage will be
compared with the reference input voltage of pin
5, and feedback to the primary by U2.
U24-B output voltage is linked to U24-A output. It
turns Q36 off. Consequently, if either one of these
static voltage or static current overflows, it will
automatically turn U2 off. R45 and C36 are used to
compensate the phase difference caused by the
time delay.
R55
Vd =
(R50 + VR21) + R55
5-8
Vo
Vr
Vo
Since the Vd is maintained to be the same level as
the reference voltage Vr is,
(R50 + VR21) +R55
Vo =
R55
CHARGE SWITCHING CIRCUITRY
The rapid charger has two charge ports; front port
and rear port.
When the battery is charged in the front port, Q35
turns on. It turns Q34-A (P-CHANNEL FET) on.
When the battery is charged in the rear port, Q33
turns on. It turns Q34-B (P-CHANNEL FET) on.
When the battery level becomes low, this circuitry
will charge the battery until it reaches 2.7V with
Q26 and Q39.
5-4-2 Controller
MICRO-CONTROLLER
U21 is a 4-bit micro-controller which controls the
whole charging system. It contains I/O port, timer,
and A/D converter. 4 MHz clock is used for the
controller.
DETECTION OF CHARGE VOLTAGE
The battery voltage in the front port is detected by
R60 and R61, and measured at the pin 13 of the
MPU.
The battery voltage in the rear port is detected by
R58 and R59, and measured at the pin 14 of the
MPU through the analog switch U25. measured at
the pin 14 of the MPU through U25.
Vr
Samsung Electronics
Advertisement
Chapters
Table of Contents
