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1-3. CP1 POWER CIRCUIT DESCRIPTION
1. Outline
This is the main power circuit, and is comprised of the follow-
ing blocks.
Switching controller (IC501)
Digital 5 V and analog system power output (T5001, Q5001)
Digital 2.5 V system power supply (Q5007)
Digital 3.4 V system power supply (Q5018)
LCD system power supply (Q5008, T5002)
Backlight power supply output (Q5013)
Inverter output (T5003, Q5017)
2. Switching Controller (IC501)
This is the basic circuit which is necessary for controlling the
power supply for a PWM-type switching regulator, and is pro-
vided with five built-in channels, only CH2 (digital 5 V, analog
system), CH4 (LCD system), CH3 (digital 2.5 V), CH1 (digital
3.4 V) and CH5 (backlight system) are used. Feedback from
5 V (D) (CH2), 2.5 V (D) (CH3) , 12.4 V (L) (CH4), 3.4 V (D)
(CH1) and 7 V (L) (CH5) power supply outputs are received,
and the PWM duty is varied so that each one is maintained at
the correct voltage setting 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 (29) of IC501, all
output is turned off. The control signal (P ON) are recontrolled
to restore output.
3. Digital 3.4 V Power Output
3.4 V (D) is output. Feedback is sent to pin (41) of the switch-
ing controller (IC501) for PWM control to be carried out.
4. Digital 5 V and Analog System Power Output
5.1 V (D) , 26.4 V (A), 20 V (A), 13 V (A) and 5.1 V (A) are
output. Feedback for the 5.1 V (D) is provided to the switch-
ing controller (Pins (35) of IC501) so that PWM control can
be carried out.
5. Digital 2.5 V System Power Output
2.5 V (D) is output. Feedback is provided to the swiching con-
troller (Pin (23) of IC501) so that PWM control can be carried
out.
6. LCD System Power Output
12.4 V (L) is output. Feedback for the 12.4 V (L) is provided
to the switching controller (Pins (22) of IC501) so that PWM
control can be carried out.
7. Backlight Power Supply output
7.0 V (L) is output. Feedback is sent to pin (17) of the switch-
ing controller (IC501) for PWM control to be carried out.
8. Inverter Output
The backlight uses a flat picture tube. When INV CLK is in-
put, Q5017 carries out switching operations, so that T5003 is
energized and a high-voltage pulse is generated between pins
(3) and (4) of T5003. This high-voltage pulse is applied to the
backlight to make it illuminate.
– 6 –
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