Ambient Light; Inverter Board; Cycle Generator; Light Sensor - Philips 42PF9731D Service Manual

EN 168 9. BJ2.4U/BJ2.5U LA
The primary and secondary QVCP each contain a series of
layers and mixers. The QVCP creates a series of display data
layers (pixel streams) and mixes them logically from back to
front to create the composite output picture.
Some of the features the QVCP provides are:
• Video Quality Enhancement.
• Luminance Transient Improvement.
• Color Dependent Sharpening.
• Horizontal Dynamic Peaking.
• Histogram Modification.
• Digital Color Transient Improvement.
• Black Stretch.
• Skin Tone Correction.
• Blue Stretch and Green Enhancement.
• Video and Graphics horizontal up scaling.
• Color space unification of all the display surfaces.
• Contrast and Brightness Control.
• Screen timing generation adopted to the connected display
requirements (SD-TV standards, HD-TV standards,
progressive, interlaced formats).
9.14 Ambient Light (if present)
9.14.1 Introduction
At the rear left and right side of the TV-set, three gas
discharging lamps are mounted. With the red, green, and blue
lamps, each color can be made.
• Ambient light is adjustable with three variables: Hue,
Saturation, and Brightness.
• Hue and saturation are controlled via menu control or via
smart settings.
• The brightness is controlled via menu or via a cycle
generator.
• The light sensor influences the brightness.
• Switching "on" or "off" goes via a ramp up or down.
• The ambient light may be active or passive.
In the user set up menu the following items are added:
•

Ambient Light.

• Lights "On/Off".
• Ambient Light: "Personal/Normal/Warm/Cool".
Two extra keys are added on the Remote Control:
• ON/OFF: A (normal) press on this key switches the
Ambient Light "On/Off".
• MODE: In case the set is "On", to toggle the smart modes.
Specifications:
• Lamp current frequency= 43 kHz.
• Lamp dimming frequency= 85 Hz.
• PWM duty cycle range= 30%
• Each lamp is only driven one third of the period to avoid
crosstalk (drive lamps at 33.3% to have no losses in
output).
9.14.2 Block Diagram
All mentioned blocks (from "Cycle Generator" to "HSV-to-RGB
Converter" are implemented in the main software. Via I
RGB values are sent to the Pacific 3 (where a selection is made
between "active" and "passive" mode) and again via I
Inverter board is addressed.
In "passive" mode, the RGB values from the "HSV-to-RGB
Converter" are used, while in "active" mode the picture content
is used to steer the ambient lights.

Cycle Generator

The Cycle Generator (for fade in/out) starts with a long press
on the "On/Off" button on the RC. It stops when the button is
released.
Circuit Descriptions, Abbreviation List, and IC Data Sheets

9.14.3 Inverter Board

2
C, the
2
C the

Light Sensor

The light sensor influences the Brightness: when the room is
darker, the ambient light is reduced. The amount of dimming is
set according to an algorithm in the Auto TV software. In
"active" Ambient Light mode, the light sensor does not
influence the Brightness.
Ramp Up/Down
The Brightness is changing with a speed from min. to max. in
2 s.
HSV to RGB Converter
The HSV (Hue, Saturation, Value) values are converted to
RGB values.
Outputs
The outputs are RGB values and can individually be
decreased.
Pacific 3
In this chassis, no MOP is implemented. Instead, the Pacific 3
performs the signal processing to the screen. The Pacific 3
performs additional signal improvement. The AmbiLight units
are also driven by the Pacific 3.
This board is for Service a "Black Box". This means that it is not
repairable on component level, but when found defective, the
board must be swapped. See the Spare Parts List for the order
code.
Some specifications:
• There are three inverters to drive the lamps, each inverter
drives a lamp for one color.
• DC-to-AC converter: 2.3 kV.
• Able to drive Cold Cathode Fluorescent Lamps (CCFL).
There are two lamp units, three lamps (RGB) per unit= six
lamps.
• The lamps are driven with Pulse Width Modulation (PWM).
• The inverters and lamps are supplied with 12V from main
supply.