DESCRIPTION OF BLOCK DIAGRAM
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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 and D904.
2)The control IC(IC901) starts switching and generates
switching pulses in the primary turns of the SMPS
transformer (T901).
3)The switching pulses of the primary turns are induced
the secondary turns of the transformer by the turn
ratio. These pulses are rectified by each diode (D920,
D922, D923, D924 and D926) .
4) Each rectified DC voltage (75V, 175V, 5V, 15V 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
22.5V(typical), 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, Q923
and Q930, are turned on and Q920, Q926 are turned
off. Then input power consumption is below 15 watts.
2)OFF mode
When no input of horizontal and vertical sync, Q923,
Q926, Q930 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, R734, R717,
R718, R719, R785, VR701, IC701 start operation to
shut down high voltage circuit.
5. Microprocessor Control Circuit.
The operating procedure is as follows :
1) Horizontal and Vertical sync signals are supplied to
the microprocessor(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 and 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. So output horizontal and vertical drive signal
control screen distortions.
8. Horizontal linearity 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
the 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 the G1.
13. Video Processor Circuit.
Video processor circuit consists of the video drive
output block. The video drive IC(IC302) receives the
video signal from PC. The gain of each channel is
controlled by the voltage of contrast pin. 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 on the screen information of the
monitor's status.