Sanyo VPC-GH2 Service Manual page 8

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)
Digital 3.25 V power output (L5041)
Digital 1.8 V power output (L5051)
Digital 1.1 V power output (L5021)
LCD backlight system power output (D5061, L5061)
Motor system 5.3 V power output (L5301)
CMOS 2.8 V output (L5031)
CMOS digital 1.8 V power output (Q5531, Q5532)
HDMI 5V power output (IC502)
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 six built-in channels, only CH1 (motor system),
CH2 (digital 1.1 V system), CH3 (CMOS 2.8 V system), CH4
(digital 3.25 V system), CH5 (digital 1.8 V system), and CH6
(LCD backlight system) are used.
Feedback from BOOST 5.3 V (CH1), VDD 1.1 (CH2), VAA
2.8 (CH3), VDD 3 (CH4), VDD 1.8 (CH5) and LCD backlight
system (CH6) are received, and the PWM duty is varied so
that each one is maintained at the correct voltage setting level.
Feedback for the backlight power (CH6) 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
IC501 monitors the feedback voltages from each channel, and
switches off output if a voltage is at the protection circuit de-
tection voltage or less for a continuous period of 1ms. To re-
set momentarily, set the control signal (P ON) to repeat con-
trol.
3. Digital 3.25 V Power Output
VDD3 is output. Feedback for the VDD3 is provided to the
swiching controller (Pin (15) of IC501) so that PWM control
can be carried out.
4. Digital 1.8 V Power Output
VDD 1.8 is output. Feedback for the VDD 1.8 is provided to
the switching controller (Pin (10) of IC501) so that PWM con-
trol to be carried out.
5. Digital 1.1 V Power Output
VDD 1.1 is output. Feedback for the VDD 1.1 is provided to
the switching controller (Pin (44) of IC501) so that PWM con-
trol to be carried out.
6. LCD 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 (28) of IC501) so that PWM control to be
carried out.
7. Motor System 5.3 V Power Output
BOOST 5.3 V is output. Feedback for the BOOST 5.3 V is
provided to the (Pin (B7) of IC501) so that PWM control to be
carried out.
8. CMOS Digital 1.8 V Power Output
+1.8 V (D) is output.
9. CMOS 2.8 V Power Output
VAA 2.8 is output. Feedback for the VAA 2.8 is provided to
the (Pin (53) of IC501) so that PWM control to be carried out.
10. HDMI 5V Power Output
VDD 5 is output. It is generated when the BOOST 5.3 V is
stepped down at IC502 to 5 V.
– 8 –