Others - Sony BVM-L230 Service Manual

(3) Sensor gain switching
To obtain the output signal of an RGB color sensor, this
model uses a 12-bit precision A/D converter. However,
the dynamic range in 12-bit precision is difficult to use
when the LED luminance of backlight is lowered. By
switching Vref (reference voltage) of an A/D converter
when a PWM ratio is low, precision can be secured even in
the case where luminance is lowered. Therefore, the D/A
port output signal of an H8 microcomputer on the LMD2
board is connected to the S1, S2, and S3 boards so that a
Vref voltage can be controlled from the H8
microcomputer.
The VRHI/VRLO signal shown in Figure 3 means the high
and low levels during Vref switching. In other words, it
corresponds to the SENSCNT signal in the block diagram
of Figure 2. The dynamic range of an A/D converter can
be secured by switching the level of a SENSCNT signal to
high (approx. 3 V) and low (approx. 1 V). However,
assume that high and low levels may be changed
depending on the design. The A/D conversion value
during Vref switching is calculated by the relational
expression of an A/D output level described in 2.1.1
Measurement circuit operation.
2. Digital temperature sensor measurement
circuit
LED temperature information is required for backlight
control. Therefore, digital temperature sensors (LM75) are
mounted on the S1, S2, and S3 boards located near LED so
as to measure the temperature of LED. LM75 is a I
compatible temperature sensor that has a delta-sigma-type
A/D converter and digital abnormal temperature detection
2
function. An I C sub address can be set by setting pins 5,
6, and 7. Six LM75s in all are mounted on the S1, S2, and
S3 boards. Their addresses are set differently. The
relation between digital temperature sensors (LM75) and
2
I C sub addresses is shown in Table 1.
Board IC reference
S1 IC206
S1 IC356
S2 IC1206
S2 IC1356
S3 IC2206
S3 IC2356
2
LM75 and I
BVM-L230
2
C bus-
IIC sub address
0x90
0x92
0x94
0x96
0x98
0x9A
C sub addresses

2-4-3. Others

1. Sensor location
(1) RGB color sensor location
This model has twelve RGB color sensors (S9702) in all.
Four RGB color sensors are each mounted on the S1, S2,
and S3 boards. Numbers are assigned to each RGB color
sensor as shown in Figure 5. During service display, the
position of each RGB color sensor can be confirmed based
on these numbers.
SENS_R00 SENS_R01
SENS_G00 SENS_G01
SENS_B00 SENS_B01
SENS_R03 SENS_R04
SENS_G03 SENS_G04
SENS_B03 SENS_B04
S1 S2
SENS_R06 SENS_R07
SENS_G06 SENS_G07
SENS_B06 SENS_B07
SENS_R09 SENS_R10
SENS_G09 SENS_G10
SENS_B09 SENS_B10
RGB color sensor (Front panel of unit)
RGB color sensor location
(Viewed from the front panel of the unit.)
Figure 5
2. Digital temperature sensor location
This model has fix digital temperature sensors (LM75) in
all in a backlight unit. Two digital temperature sensors are
each mounted on the S1, S2, and S3 boards. Numbers are
assigned to each digital temperature sensor as shown in
Figure 6. During service display, the position of each
digital temperature sensor can be confirmed based on these
numbers.
TEMP1[LT] TEMP3[CT]
S1 S2
TEMP2[LB] TEMP4[CB]
Digital temperature sensor (Rear panel of unit)
Digital temperature sensor location
(Viewed from the front panel of the unit.)
Figure 6
SENS_R02
SENS_G02
SENS_B02
SENS_R05
SENS_G05
SENS_B05
S3
SENS_R08
SENS_G08
SENS_B08
SENS_R11
SENS_G11
SENS_B11
TEMP5[RT]
S3
TEMP6[RB]
2-15