Sanyo VPC-WH1W Service Manual page 6

1-3. PWA POWER CIRCUIT DESCRIPTION
1. Outline
This is the main power circuit, and is comprised of the follow-
ing blocks.
Switching controller (IC501)
Motor system power output (L5301)
Digital 3.25 V power output (L5002)
Digital 1.2 V power output (L5003)
Backlight power output (Q5007, L5007)
Digital and CMOS 1.8 V power output (IC504, L5006)
CMOS analog 2.8 V power output (IC503, L5005)
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 seven built-in channels, only CH1 (motor system),
CH2 (digital 3.25 V), CH3 (digital 1.2 V) and CH7 (backlight)
are used.
Each power supply output is received, and the PWM duty is
varied so that each one is maintained at the correct voltage
setting level.
Feedback for the backlight power (CH7) is provided to the
both ends voltage of registance so that regular current can
be controlled to be current that was setting.
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 (A6) of IC501, all
output is turned off. To reset, momentarily set the control sig-
nal (P ON) to repeat control, or temporarily disconnect the
input power supply.
3. Motor System Power Output
BOOST 5 V is output. Feedback for the 5.0 V output is pro-
vided to the switching controller (Pin (B7) of IC501) so that
PWM control can be carried out.
4. Digital 3.25 V Power Output
VDD3 is output. Feedback for the VDD3 is provided to the
swiching controller (Pin (F3) of IC501) so that PWM control
can be carried out.
5. Digital 1.2 V Power Output
VDD 1.2 is output. Feedback for the 1.2 V is provided to the
switching controller (Pin (C3) of IC501) so that PWM control
to be carried out.
6. Backlight Power Supply output
Regular current is being transmitted to LED for LCD back-
light. Feedback for the both ends voltage of registance that is
being positioned to in series LED are provided to the switch-
ing controller (Pin (C4) of IC501) so that PWM control to be
carried out.
7. Digital and CMOS 1.8 V Power Output
VDD 1.8 is output. Feedback for the VDD 1.8 is provided to
the switching controller (Pin (3) of IC504) so that PWM con-
trol to be carried out.
8. CMOS Analog 2.8 V Power Output
VAA 2.8 is output. Feedback for the VAA 2.8 is provided to the
switching controller (Pin (3) of IC503) so that PWM control to
be carried out.
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