Philips PCL304 - Power Board; Power Supply Assembly; Connector Pin Assignment

8-30
8.2 Power Board
8.2.1 Power Supply Assembly
The
power
supply
consists
of
charge
control
circuit
on
the
power
board
and
some
other
control
circuits
on
the
main
board.
It
receives
power
from
adapter
(5.6V,
6.1V,
7.15V))
or
battery
(4.8V
nominal)
and
supplies
power
to:
(1)
The
main
board
(+5V,
PG,
BTW,
BUP,
LCDE)
(2) The LCD (VDD, VEE)
(3) The backlight (CCFT)
(4)
Battery
power
indicator
(PGR,
PRD,
CHRG,
CHRG)
Please
refer
to
the
block
diagram
on
the
following
page
for
the
operation
concept.
The
power
board
consists
of
four
blocks
as
follows:
1. Charge control circuit
The
power
controller
87C51
can
detect
the
battery
whe-
ther
charging
is
completed
(charge
LED
off)
by
sensing
the
battery
voltage.
It
is
because,
after
battery
is
fully
charged,
further
charging
will
cause
the
reduction
of
its
voltage.
2. Voltage detector
The
87C51
reads
the
voltage
of
main
battery,
+5V
from
ADC0833
and
manages
the
power
of
the
whole
system.
a.
When
switch
on
the
unit,
firstly,
it
detects
the
input
volt-
age
is
enough
or
not,
the
turn
on
the
control
circuit
to
ge-
nerate 5V, send PG (POWER GOOD) signal for main
board, and light up green power LED.
When
the
output
voltage
is
lower
than
4.6V,
it
will
change
to battery low mode. Under thismode, the buzzer will
beep twice every 15 seconds. Upon using battery and the
output voltage being lower than 4.5V, it will change to bat-
tery
warning
mode,
the
buzzer
will
beep
four
times
every
10
seconds.
a
. Power supply circuit
The transformer can transform the input voltage 5.0V to
15V, which supports the MOSFET as bias voltage. The
output MOSFET is regulated to 5V.
. Power supply of LCD circuit
It generates VDD and VEE for LCD when the signal
Py
LCDE
is
high.
The
circuit
uses
5V
to
generate
VDD.
The
VEE depends on the signal from keyboard controller
87C51 on the main board. When the duty of the signal in-
creases, the VEE de-creases.
5. Power Supply for Backlight (CCFT)
jt generates VBL for CCFT when the signal BLE is low.
The circuit uses VSW to generate VBL. The VBL de-
pends on the signal from keyboard controller 87C51 on
the main board. When the duty of the sigan! increases,
the VBL increase.
CS 55 846
8.2.2 Connector pin assignment
CN1 4-pin Voltage Adapter connector
Pin.no Signal
1 VA
2 VB
3 POK
4 GND
J2 2-pin battery connector
Pin.no Signal
1 +VM
2 GND
J3 5-pin backlight connector
Pin.no Signal
VCFF (AC)
anon
z oO
VCFF (AC)