LG 795FT, FB795BE BLOCK DIAGRAM

BLOCK DIAGRAM

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Power

OSD

SETUPDOWN

LEFT

RIGHT

Power Off

STBY & SUS

USB-

USB+

SOG

SOG OFF

H-SIZE

H-SIZE MAX

HSTC

VSTC

IIC-SDA

IIC-SCL

DDC-SDA

DDC-SCL

CS1

CS2

CS3

CS4

CS0

TILT

ST-IN

PURITY SUB-BRT C-BRT ABL DPM OFF

28V

15V

12V

-12V

78V

198V

12V

6.3V

AFC SCL SDA

F/V

28V

X-RAY

15V

H-DRV

15V

198V

HD FBP

H/V DETECT

DF B+

X-RAY

15V

DYNAMIC

FOCUS VR

STATIC

FOCUS VR

SCREEN VR

CS1

CS2

CS3

CS4

CS5

CS0

AFC

15V

-12V

15V

MUTE H-SIZE

R/G/B

BIAS

115V

78V

12V

IIC-SDA

IIC-SCL

IIC-SDA

H-STC

TILT

SIGNAL

PURITY

SIGNAL

V-STC

12V

15V

-12V

15V

-12V

6.3V

IIC-SDA

IIC-SCL

R/G/B

CLAMP

CONTRAST

DDC-SDA

DDC-SCL

IIC

SIGNAL

H/V STC COIL

CDT

OSD Signal

(R/G/B)

V-SYNC

H-SYNC

V-SAW

KEY

CONTROL

(IC101, IC102,

IC103)

HEF4013BF

SEL

BUZZ

STBY

SCL SDA

POWER

& DPM

LED

PWM IC

(IC901)

RECTIFIER

D901

LED

DEG

12V

Switching

Regulator

(IC902)

6.3V

(IC912)

MICOM

(IC202)

H-SYNC

V-SYNC

D-SUB

(SIGNAL CABLE)

EEPROM

24C08

(IC207)

STC CONTROL

AN5769

(IC304)

TILT CONTROL

(IC603)

PURITY CONTROL

(IC603)

VIDEO PRE-AMP

M52743BSP

(IC302)

POWER AMP

VPS13

(IC303)

OSD

PROCESSOR

LSC4515

(IC301)

CLAMP

CONTROL

V-OUTPUT

TDA8172

(IC601)

AFC

H-LINRARITY

CORRECTION

(Q712, 713, 714,

715, 718)

DYNAMIC FOCUS

OUTPUT

LF353

(IC209)

D-FOCUS AMP

FLY

BACK

TRANS

(T703)

HIGH VOLTAGE

DYNAMIC FOCUS

STATIC FOCUS

SCREEN

FBT DRIVE

& SWITCHING

(Q502, 506, 507)

HIGH VOLTAGE

PWM IC

M62501P

(IC501)

H-Drive Trans

(T701)

H-Drive Trans

B+ Control

(T701)

D/D CONVER

(Q503)

H-OUTPUT

2SC5047

(Q707)

H-CENYERING

COIL

DUMMY FBT

(T702)

D/D

CONVERTER

(Q404)

D/D DRIVE

(IC402, Q411,

412, 413, 414)

SPCC &

H-SIZE MIXING

(IC401)

SMPS

MAIN

(T901)

SMPS

SUB

(T902)

H/V SYNC

PROCESSOR

UPC1884ACT

(IC701)

POWER INPUT

90~132Vac

198~264Vac

LINE

FILTER

(LF901)

DEGAUSSING

COIL

DEGAUSSING

CIRCUIT

(RL902)

SUB

MICOM

(IC1004)

MC68HC705

BDIA

DESCRIPTION OF BLOCK DIAGRAM

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1. Line Filter & Associated Circuit.

This is used for suppressing noise of power input line flowing into the monitor and/or some noise generated in this monitor flowing out through the power input line. That is to say, this circuit prevents interference between the monitor and other electric appliances.

2. Degaussing Circuit & Coil.

The Degauss circuit consists of the degaussing coil, the PTC (Positive Temperature Coefficient thermistor, TH901), and the relay(RL902). This circuit eliminates abnormal color of the screen automatically by degaussing the slot mask in the CRT when turn on the power switch. When you need to degauss while using the monitor select (DEGAUSS) in the OPTION SELECT on the OSD menu.

3. SMPS (Switching Mode Power Supply) Circuit.

This circuit works with power of 90~132Vac/180~264Vac (50/60Hz).

The operation procedure is as follows:

1) AC input voltage is rectified and smoothed by the bridge diode (D901) and capacitors (C912, C913).

2) The rectified voltage (DC voltage) is applied to the primary coil of the transformer (T901, T902).

The control IC (IC901) generates switching pulse to turn on and off the primary coil of the transformer (T901) repeatedly.

4) Depending on the turn ratio of the transformer, the secondary voltages appear at the secondary coil of the transformer (T901).

5) These secondary voltages are rectified by each diode (D921, D922, D924, D925, D926, D931, D932, D927) and operate the other circuits. (Deflection, Video

Amplifier ,..... etc.)

The switching IC(IC903) controls input-pulse-width and generates secondary voltages by sub-transformer (T902).

4. Display Power Management Circuit.

This circuit control power consumption of the monitor by detecting H and V sync signal. There are Stand-by and suspend, OFF mode. When no horizontal or vertical sync signal input, the circuit consists of Q903 and IC916 becomes stand-by and suspend mode. It’s power consumption is below 8W without USB function.

5. X-ray Protection.

This circuit detects the rectified DC voltage comes from the FBT pin 4. If the high voltage of the FBT reaches up to about 29kV (abnormal state), high voltage control PWM IC (IC501) detects it. And PWM IC (IC501) prevent output voltage to the gate of high-voltage-D/D-convert-transistor (Q503). It stops B+ voltage supplied to the FBT (T703), and high voltage is not be generated. (In the normal state, the high voltage is about 26kV.)

6. Micom (Microprocessor) Circuit.

The operating procedure of Micom (Microprocessor) and its associated circuit is as follows:

1) H and V Sync signal is supplied from the D-sub to the Micom (IC202).

2) The Micom (IC202) distinguishes polarity and frequency of H and V sync.

3) The Micom controls each OSD function signals.(H-size, H-position, V-size, etc.)

4) The controlled data of each mode is stored in itself. User can adjust screen condition by each OSD function. The data of the adjust screen condition is stored automatically.

7. Horizontal and Vertical Synchronous Processor.

This circuit generates the horizontal drive pulse and the vertical drive pulse by taking sync-signal form the D-SUB (P202). This circuit consists of the UPC1884ACT (IC701) and the associated circuit.

8. Oscillating Circuit for D/D Converter.

This circuit generates the saw-tooth wave which has the horizontal period by taking the output of the UPC1884ACT (IC701) .

9. D/D (DC to DC) Converter.

This circuit supplies DC voltage to the horizontal deflection output circuit by decreasing DC 198V which is the secondary voltage of the SMPS in accordance with the input horizontal sync signal.

10. Side-Pincushion Correcting Circuit.

This circuit improves the side-pincushion of the screen by mixing east-west wave to the output of the horizontal deflection D/D converter which is used for the supply voltage source (B+) of the deflection circuit.

11. D/D Drive & Convert Circuit.

This circuit is used for supplying B+voltage to horizontal deflection output transistor (Q707). This circuit makes to add side-pincushion correcting signal to B+voltage.

12. Horizontal Deflection Output Circuit.

This circuit makes the horizontal deflection by supplying the saw-tooth current to the horizontal deflection yoke.

13. High Voltage Output & FBT (Flyback Transformer).

The high voltage output circuit is used for generating pulse wave to the primary coil of the FBT (Flyback Transformer (T703). A boosted voltage (about 26kV) appears at the secondary of the FBT and it is supplied to the anode of the CDT. And there are another output voltages such as the dynamic focus frequency.

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