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1-3. CA3 CIRCUIT DESCRIPTION
1. Outline
This is the main CA3 power block, and is comprised of the
following blocks.
Switching controller (IC511)
Lens system 3.4 V power output (L5101, Q5102, D5101,
C5114)
Backlight power output (L5103, Q5106, C5121)
Analog and LCD system power output (Q5112, T5101)
2. Switching Controller (IC511)
This is the basic circuit which is necessary for controlling the
power supply for a PWM-type switching regulator, and is pro-
vided with four built-in channels. They are CH1 (lens system
3.4 V), CH2 (backlight) and CH4 (analog and LCD system).
CH3 is not used. Feedback from 3.4 V (D) C (CH1), +15.0 V
(A) or +12.4 V (L) power supply output are received, and the
PWM duty is varied so that each one is maintained at the
correct voltage setting level. CH2 is feedback from 10 mA
power supply output are received, and the PWM duty is var-
ied so that each one is maintained at the correct voltage set-
ting level.
2-1. Short-circuit protection circuit
If output is short-circuited for the length of time determined
by the condenser which is connected to Pin (33) of IC511, all
output is turned off. The control signal (P(A) ON and LCD
ON) are recontrolled to restore output.
3. Lens system 3.4 V Power Output
3.4 V (D) C is output for lens. Feedback is provided to the
swiching controller (Pin (1) of IC511) so that PWM control
can be carried out. Also when this power output is ON and
OFF, Q5124 turns on and it rises to 3.7 V output.
4. Backlight Power Output
10 mA (L) is output. The backlighting turns on when current
flows in the direction from pin (1) to pin (2) of CN531. At this
time, a feedback signal is sent from pin (2) of CN531 to pin
(12) of IC511 through R5137 so that PWM control is carried
out to keep the current at a constant level (10 mA).
5. Analog and LCD System Power Output
15.0 V (A), –7.7 V (A), 12.4 V (L) and 15 V (L) are output.
Feedback for the 15.0 V (A) with view mode and 12.4 V (L)
with play mode is provided to the switching controller (Pin
(36) of IC511) so that PWM control can be carried out.
