LG 575N, 575C, CB575BN, CB575BC BLOCK DIAGRAM
BLOCK DIAGRAM
- 12 -
POW ER INPUT
100~240VAC
(50/60Hz)
Line Filter
Degaussing
Circuit
OSD
ON/OFF
SET
[OSD Control]
SMPS
TRANS
(T901)
SMPS
CONTROL
(IC901)
DPM
CONTROL
194V
75V
15V
6.3V
TILT
Controlt
6.3V
6.3V
EEPROM
(IC402)
H / V POSITION
H / V SIZE
SPCC
TRAPIZODE
PIN BALANCE
PARALLELOGRAM
ROTATION
RECALL
DEGAUSSING
DDC OPTION
COLOR CURVE
MOIRE
LANGUAGE
RECALL
INFORMATION
5V
OSD IC
(IC301)
H-Sync
V-Sync
I
2
C DATA(SDA)
I2C CLOCK(SCL)
VIDEO
PRE-AMP
(IC302)
Signal
Cable
R
G
B
VIDEO
MAIN AMP
(IC303)
KA7808
(IC304)
8V
15V
CUT-OFF
CONTROL
150V
8V
5V
H/V Sync Processor
( IC701 )
TDA4856
V-OUT
( IC601)
TDA4866
H-OUT
( Q706)
H-Linearity
Correction
DC/DC Convert er
X-RAY
Protection
FBT
( T701 )
ABL
Beam
Limit
V-Blanking,
Brightness
Control
-120V
40V
30V
15V
MICOM
(IC401)
12V
15V
194V
DY CDT
Heater ( 6.3V
)
I
2
C
I2C
I2C
H/V
Sync
kD/D Feed Bac
G1Screen
Focus
H.V
R/G/B Drive
R/G/B Cut-off
R/G/B Bias
H-DRV
B-DRV
B+
IC302
15V
POWER
I2C
VOLTAG E
FEEDBACK
V-DY
H-DY
KA7805
5V
150V
5V
SCL/SDA
H/V SYNC,
PWM CONTROL
DESCRIPTION OF BLOCK DIAGRAM
- 13 -
1. SMPS(Switching Mode Power Supply)
When you turn on the power switch, the operating procedure is as follows:
1) The AC line voltage is rectified by the bridge diodes
D901, D902, D903, D904
2) The control IC(IC901) starts switching and generates
switching pulses in the primary turn of the SMPS transformer (T901)
3) The switching pulses of the primary turns are induced
to the secondary turns of the transformer by the turn
ratio. This pulses are rectified by each diode(D922,
D923, D924, D926, D930)
4) Each rectified DC voltage(194V, 75V, 15V, 11V and
6.3V) is supplied to the main circuit.
2. Over Voltage Protection Circuit
When the input voltage of IC901 Vin(pin 4) is more
than 22V, all the secondary voltages of the SMPS
transformer (T901) down to low value.
3. Display Power Management Circuit
1) Stand-by and Suspend mode.
When no input of horizontal or vertical sync, Q922 and
Q923, Q924 are turned off and Q920, Q925 and Q926
are turned on. Then input power consumption is below
15 watts.
2) OFF mode
When no input of horizontal and vertical sync, Q922,
Q923, Q924, Q925, Q926 are turned off and Q920 is
turned on. Then input power consumption is below 5
watts.
4. X-ray Protection Circuit
When the high voltage reaches to 29kV in an abnormal
case, the high voltage detector circuit, R816, R818,
ZD801, C805, and Q807 start operation to shut down
high voltage circuit.
5. Microprocessor Control Circuit.
The operating procedure is as follows
1) Horizontal and Vertical sync signal are supplied to the
microcessor (IC401).
2) Microprocessor (IC401) discriminates the operating
mode from the sync polarity and resolution.
3) After microprocessor reads these adjusted mode data
stored at EEPROM, it controls operating mode data
through IIC.
4) Users can control screen condition by the OSD, SET,
UP, DOWN, RIGHT, LEFT buttons.
6. D/D Convert Circuit.
To obtain constant high voltage, this circuit supplies
controlled DC voltage for FBT and horizontal deflection
circuit according to the horizontal sync frequency.
7. Horizontal and Vertical Sync Processor Circuit.
The horizontal and vertical sync processor IC (IC701)
has a sync detector, a saw-tooth generator, and drive
function. And outputs horizontal and vertical drive signal to control screen distortions.
8. Horizontal S-correction Circuit.
This circuit corrects the horizontal linearity for each
horizontal sync frequency.
9. Horizontal drive and Output Circuit.
This circuit is a horizontal deflection amplifier for raster
scan.
10. ABL Circuit.
This circuit limits the beam-current for the reliability of
CDT.
11. Vertical Output Circuit.
This circuit takes the vertical ramp wave from the
TDA4856 (IC701) and performs the vertical deflection
by supplying the saw-tooth wave current to the vertical
deflection yoke.
12. Blanking and Brightness Control Circuit.
Blanking circuit eliminates the retrace line by supplying
a negative pulse wave to the G1 of the CDT.
Brightness control circuit is used for control of the
screen brightness by changing the DC level of G1.
13. Video Processor Circuit.
Video processor circuit consists of the video drive outputblock. The video drive IC(IC302) receives the video
signal from PC. The gain of each channel is controlled
by MICOM through IIC.
The cut-off circuit compensate different voltage of each
channel between the cathode and the G1 of the CDT.
14. OSD (On-Screen-Display) Circuit.
This circuit displays information of the montor’s status
on the screen.
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