In this presentation several electronic concepts are developed in connection with the TCON board in a TFT LCD TV and the operation of the gate driver. The electronic content of this chip is detailed. Thus we find a bi-directional shift register, a level shifter, a voltage follower and logic gates including NAND. The operation of this assembly requires various voltages either in logic form such as the CPV, CKV, CKVB, STV, STVP, OE, XAO, R/L, U/D signal, or in analog voltage form such as VGH and VGL.
Introduction to T-CON and maintenance matters
T-CON board is also called logic board or control board. T-CON is the English abbreviation of Timing Controller, which means timing control circuit. At present, there are not many T-CON boards in China, CRT TV has a history of several decades. The traditional CRT TV works by scanning, and the signals are serial. The current TV standard is based on CRT TV, so the TV signal passes through the TV main board. The output after decoding is also a serial signal. We know that the liquid crystal display works in a matrix display mode, and it processes parallel signals. That is to say, if the TV signal decoded by the motherboard is sent directly to the LCD display, the LCD display can't be displayed. There must be a device that converts serial signals into parallel signals so that the LCD can display TV signals, so there is a T-CON board, which is a device that converts serial signals into parallel signals. The TV signal output by the main board is disassembled and recombined in the T-CON board to finally form the control signal and data signal required for the row and column drive of the liquid crystal display. The general T-CON board circuit can be roughly divided into three parts: signal processing circuit (main IC and its peripheral circuits), gray-scale forming circuit (GMA forming circuit), and power supply circuit (DC/DC circuit). The signal processing circuit mainly converts the TV signal transmitted from the motherboard into the control signal, pixel signal, auxiliary signal, etc. required for the LCD display; the gray-scale forming circuit mainly forms the gray-scale signal required for the LCD display (the grayscale can make the display of the LCD screen is more layered, making the display richer and more vivid). The power supply circuit mainly forms the signal processing IC, the power supply voltage of the row drive and the column drive, and the switching voltage of the TFT (TFT turn-on voltage VGH, TFT turn-off voltage VGL) and so on.
Common faults and analysis of T-CON board:
1. The color of the display screen is abnormal
Generally speaking, the abnormal color of the LCD screen has a lot to do with the signal processing IC. The internal structure of the signal processing is complicated and the integration is high, and it is easy to be damaged by static electricity, sudden strong voltage and high current. Most of the picture abnormalities are caused by the damage of the signal processing IC. The IC outputs the control signals and pixel signals needed for the LCD display. After the IC is damaged, the control signals cannot complete the orderly arrangement of the pixel signals, so the picture is abnormal. In addition, damage to the FFC (flexible cable) or improper connection will also cause screen abnormalities.
2. There is no picture on the display screen
There is no image on the display screen, which means that the IC has no control signal and pixel signal output. There are several reasons that cause the display to have no picture: 1. The IC is seriously damaged, resulting in no control signal and pixel signal output, and the display is not available for display. The input image is not displayed; 2. The IC does not work due to the damage of the voltage regulator chip to the IC, so there is no image; 3. The failure of the power supply circuit (DC/DC circuit) causes the voltage required for the operation of the IC cannot be provided, so there is no image.
3. The grayscale picture on the display screen is abnormal
The abnormal gray scale picture has a lot to do with the GMA forming circuit. The GMA voltage is formed by a series of VS voltage signals collected by the resistor divider array after being amplified by the integrated operational amplifier and then outputting a series of GMA voltage signals. In the process, the GMA voltage signal is used as the reference standard, and the abnormal GMA voltage will cause the grayscale picture to be abnormal.
Repair method of control panel
1. No diagrams and circuit diagrams with power supply parts caused by faults in the power supply circuit of the control board:
The power supply part mainly provides working voltage for signal processing IC, row drive circuit, and column drive circuit. Except for GMA voltage, almost all voltages are generated by this circuit. Failure of the power supply part will inevitably cause other circuits to fail to work due to abnormal power supply,
In this presentation several electronic concepts are developed in connection with the TCON board in a TFT LCD TV and the operation of the gate driver. The electronic content of this chip is detailed. Thus we find a bi-directional shift register, a level shifter, a voltage follower and logic gates including NAND. The operation of this assembly requires various voltages either in logic form such as the CPV, CKV, CKVB, STV, STVP, OE, XAO, R/L, U/D signal, or in analog voltage form such as VGH and VGL.
Introduction to T-CON and maintenance matters
T-CON board is also called logic board or control board. T-CON is the English abbreviation of Timing Controller, which means timing control circuit. At present, there are not many T-CON boards in China, CRT TV has a history of several decades. The traditional CRT TV works by scanning, and the signals are serial. The current TV standard is based on CRT TV, so the TV signal passes through the TV main board. The output after decoding is also a serial signal. We know that the liquid crystal display works in a matrix display mode, and it processes parallel signals. That is to say, if the TV signal decoded by the motherboard is sent directly to the LCD display, the LCD display can't be displayed. There must be a device that converts serial signals into parallel signals so that the LCD can display TV signals, so there is a T-CON board, which is a device that converts serial signals into parallel signals. The TV signal output by the main board is disassembled and recombined in the T-CON board to finally form the control signal and data signal required for the row and column drive of the liquid crystal display. The general T-CON board circuit can be roughly divided into three parts: signal processing circuit (main IC and its peripheral circuits), gray-scale forming circuit (GMA forming circuit), and power supply circuit (DC/DC circuit). The signal processing circuit mainly converts the TV signal transmitted from the motherboard into the control signal, pixel signal, auxiliary signal, etc. required for the LCD display; the gray-scale forming circuit mainly forms the gray-scale signal required for the LCD display (the grayscale can make the display of the LCD screen is more layered, making the display richer and more vivid). The power supply circuit mainly forms the signal processing IC, the power supply voltage of the row drive and the column drive, and the switching voltage of the TFT (TFT turn-on voltage VGH, TFT turn-off voltage VGL) and so on.
Common faults and analysis of T-CON board:
1. The color of the display screen is abnormal
Generally speaking, the abnormal color of the LCD screen has a lot to do with the signal processing IC. The internal structure of the signal processing is complicated and the integration is high, and it is easy to be damaged by static electricity, sudden strong voltage and high current. Most of the picture abnormalities are caused by the damage of the signal processing IC. The IC outputs the control signals and pixel signals needed for the LCD display. After the IC is damaged, the control signals cannot complete the orderly arrangement of the pixel signals, so the picture is abnormal. In addition, damage to the FFC (flexible cable) or improper connection will also cause screen abnormalities.
2. There is no picture on the display screen
There is no image on the display screen, which means that the IC has no control signal and pixel signal output. There are several reasons that cause the display to have no picture: 1. The IC is seriously damaged, resulting in no control signal and pixel signal output, and the display is not available for display. The input image is not displayed; 2. The IC does not work due to the damage of the voltage regulator chip to the IC, so there is no image; 3. The failure of the power supply circuit (DC/DC circuit) causes the voltage required for the operation of the IC cannot be provided, so there is no image.
3. The grayscale picture on the display screen is abnormal
The abnormal gray scale picture has a lot to do with the GMA forming circuit. The GMA voltage is formed by a series of VS voltage signals collected by the resistor divider array after being amplified by the integrated operational amplifier and then outputting a series of GMA voltage signals. In the process, the GMA voltage signal is used as the reference standard, and the abnormal GMA voltage will cause the grayscale picture to be abnormal.
Repair method of control panel
1. No diagrams and circuit diagrams with power supply parts caused by faults in the power supply circuit of the control board:
The power supply part mainly provides working voltage for signal processing IC, row drive circuit, and column drive circuit. Except for GMA voltage, almost all voltages are generated by this circuit. Failure of the power supply part will inevitably cause other circuits to fail to work due to abnormal power supply,
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