Driver IC is an important component of TFT display, responsible for converting digital signals into electrical signals that control liquid crystal pixels to display image content. The following is a detailed process and key principles of how driver IC drives TFT display:
1.Introduction to driver IC functions
The core tasks of driver IC are to achieve:
- Receive and process display data from the main control device (such as CPU).
- Convert digital signals into analog voltage signals that can be used by TFT liquid crystal display.
- Control the switching and brightness of each pixel in time sequence.
Driver IC usually consists of two parts:
- Row driver (Gate Driver): Controls the scan line and determines which row of pixels is activated.
- Column driver (Source Driver): Provides column signal voltage to determine the grayscale value of each pixel in the activated row.
2.Driving process
Driver IC drives TFT display through the following steps:
(1) Data reception and analysis
Driver IC receives display data from the main control chip, mainly including:
- Image data: Represents the color or grayscale information of each pixel.
- Control signal: including clock signal (CLK), synchronization signal (HSYNC, VSYNC), etc., used to coordinate data transmission.
Common data interface: - Parallel interface (such as RGB interface): data of each pixel is transmitted simultaneously through multiple data lines.
- Serial interface (such as SPI, MIPI DSI): data is transmitted in time sequence through a small number of cables.
(2) Row scan control
The row driver (Gate Driver) activates the gate line of the display screen row by row according to the row scan signal.
- When a row of pixels is activated, the TFT transistors of the row are turned on, so that the pixels of the row can receive the signal provided by the column driver.
(3) Grayscale signal output
The column driver (Source Driver) converts color or grayscale data into analog voltage signals and transmits them to each pixel of the activated row.
- These analog voltage signals control the rotation angle of the liquid crystal molecules, thereby adjusting the transmittance to form the corresponding color or brightness.
(4) Storage and retention
The charge of each pixel is provided by the TFT transistor and maintained by the storage capacitor until the next refresh.
- During the charge retention period, the display state of the pixel does not change.
(5) Backlight and light transmission control
- Liquid crystal itself does not emit light, and the backlight LED provides the light source.
- The TFT display screen controls the light transmittance of each pixel by rotating the liquid crystal molecules, thereby displaying different brightness and colors.
- Key technologies of driver IC
3.Gamma correction
- The color and brightness of the display screen usually change nonlinearly.
- The gamma correction circuit inside the driver IC ensures that the displayed color is close to natural reality by adjusting the output voltage.
(1) Timing control
- The driver IC contains a complex timing control circuit to coordinate the operation of the row driver and column driver to ensure the synchronization of data transmission and display.
(2) Power management
- The driver IC is responsible for generating gate drive voltage, source signal voltage, etc. for the TFT display screen, and providing different power levels.
- Interface example between driver IC and TFT display screen
RGB interface
- Red, green, and blue data lines: transmit image pixel information.
- Clock signal (CLK): controls the speed of data transmission.
- Line synchronization (HSYNC) and field synchronization (VSYNC): mark the start of each line and each frame.
3.Driver IC architecture
- Main control chip: responsible for the generation and transmission of display data.
- Driver IC: responsible for data processing and output control.
- TFT panel: converts electrical signals into visual images.
- Backlight module: provides lighting.
The following is part of the driver IC code 4.3-inch display MIPI interface
WriteComm (0xFF);
WriteData (0x77);
WriteData (0x01);
WriteData (0x00);
WriteData (0x00);
WriteData (0x13);
WriteComm (0xEF);
WriteData (0x08);
WriteComm (0xFF);
WriteData (0x77);
WriteData (0x01);
WriteData (0x00);
WriteData (0x00);
WriteData (0x10);
WriteComm (0xC0);
WriteData (0x63);
WriteData (0x00);
WriteComm (0xC1);
WriteData (0x0A);
WriteData (0x0C);
WriteComm (0xC2);
WriteData (0x31);
WriteData (0x08);
WriteComm (0xCC);
WriteData (0x18);
WriteComm (0xB0);
WriteData (0x00);
WriteData (0x08);
WriteData (0x10);
WriteData (0x0E);
WriteData (0x11);
WriteData (0x07);
WriteData (0x08);
WriteData (0x08);
WriteData (0x08);
WriteData (0x25);
WriteData (0x04);
WriteData (0x12);
WriteData (0x0F);
WriteData (0x2C);
WriteData (0x30);
WriteData (0x1F);
WriteComm (0xB1);
WriteData (0x00);
WriteData (0x11);
WriteData (0x18);
WriteData (0x0C);
WriteData (0x10);
WriteData (0x05);
WriteData (0x07);
WriteData (0x09);
WriteData (0x08);
WriteData (0x24);
WriteData (0x04);
WriteData (0x11);
WriteData (0x10);
WriteData (0x2B);
WriteData (0x30);
WriteData (0x1F);
WriteComm (0xFF);
WriteData (0x77);
WriteData (0x01);
WriteData (0x00);
WriteData (0x00);
WriteData (0x11);
WriteComm (0xB0);
WriteData (0x4D);
WriteComm (0xB1);
WriteData (0x39);
WriteComm (0xB2);
WriteData (0x87);
WriteComm (0xB3);
WriteData (0x80);
WriteComm (0xB5);
The driver IC is the core component of the TFT display screen. It analyzes the display data and controls the row and column signals in time sequence to provide the correct voltage for each pixel to achieve image display.