1-3. PW1 POWER CIRCUIT DESCRIPTION

1. Outline

This is the main power circuit, and is comprised of the following blocks.Switching controller (IC501)

Digital and analog system and LCD 5.0 V system power output (L5010, Q5002, D5013, C5061)

Digital 3.3 V system power supply (L5017, Q5009, D5007, C5062)

Analog and LCD system power supply (Q5007, T5001) Backlight power supply output (L5005, Q5008, D5014, C5005)

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 provided with four built-in channels, only CH1 (digital 3.3 V), CH2 (5 V system), CH3 (analog and LCD system) and CH4 (back- light system) are used. Feedback from 3.3 V (D) (CH1) ,5.0 V

(D)(CH2), +15.0 V (A), +12.4 V (L) (CH3) and 5.8 V (L) (CH4) power supply outputs 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 (17) of IC501, all output is turned off. The control signal (P ON, P(A) ON and LCD ON) are recontrolled to restore output.

3. Digital 3.3 V Power Output

3.3V (D) is output. Feedback for the 3.3 V (D) is provided to the switching controller (Pins (1) of IC501) so that PWM con- trol can be carried out.

4. 5 V System Power Output

5 V (D), 5.1 V (A) and 5 V (L) are output. Feedback for the 5 V (D) is provided to the switching controller (Pin (12) of IC501) so that PWM control can be carried out.

5. Analog and LCD System Power Output

15.0V (A), -7.5 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 (25) of IC501) so that PWM control can be carried out.

6. Backlight Power Supply output

5.8V (L) is output. Feedback is sent to pins (36) of the switch- ing controller (IC501) for PWM control to be carried out.

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