Samsung PS42D51SX/XEC, Service Manual

Page: 109 / 118

Circuit Description
13-24 Samsung Electronics
Ambient Light Sensor
(TSL2550 Lux Calculation IC)
13-3-1 Power Saving Modes (Standard, Automatic, Super Power Saving)
1. Objective
To enhance a sensible visual quality by maintaining an appropriate screen brightness according to the ambient brightness and to
reduce power consumption.
2. Circuit Architecture
The CPU PW318 of the Video Board takes the current ambient brightness (in Lux units), stored in the Ambient Light Sensor of
Power Assy., which is attached at the front of the PDP, at given intervals through SMBUS communication (identical to I2C) and
controls the PDP module to operate with the appropriate illuminance. The I2C bus is used to communicate with the PDP module,
and the communication method is the same as the existing communication method.
3. Descriptions of Each Mode
1) Standard Mode
Standard Mode is set as standard visual quality.
2) Auto Power Saving Mode (Ambient Light Sensor)
This uses the TAOS 4 pin TSL2550 and is currently being used in
LCD TVs. It also uses SMBUS, which is the same type as I2C, for
communication. The Ambient Light Sensor can detect up to 1846
Lux in normal mode. The data of the sensor can be measured for
Lux operations once every 800ms.
Control is implemented by using R_ASL_GAIN. The number of
sustain pulses moves left or right as shown in the figure on the right.
For a low gradation condition, the change by R_ASL_GAIN has
been minimized considering the degradation of the visual quality.
That is, the Auto Power Saving mode screen controlled by the
ambient light sensor aims at normal video of medium gradation.
※
The following values are for a normal air signal with 80 Watt attenuation at maximum
Number of Sustain Pulses
Detected Lux R_ASL_GAIN (Address 0xE9) Remarks
0 ~ 8 250
- Read the Lux value once per second and change it the target
R_ASL_GAIN value by 5 per second according to the changed Lux
value.
- If more than 3 communication errors or saturation (count1>count0) is
detected, the default value is set (R_ASL_GAIN=128).
9 ~ 22 210
23 ~ 35 170
Else 128 (default)
13-3 New Circuit Description