LCD monitor pixel clock signal dclk

As long as the digital signal processing circuit, there must be a clock signal. In the LCD panel, the pixel clock is a very important clock signal. The frequency of the pixel clock signal is related to the working mode of the LCD panel, the higher the resolution of the LCD panel, the higher the frequency of the pixel clock signal. Within a row, the number of pixel clocks is equal to the number of pixels in the LCD panel line. For example, for a 1024x768 LCD panel with a row of 1024 pixels, the number of pixel clocks in a row (corresponding to a valid video interval) is also 1024.

Regardless of the TTL interface LCD panel, or the LVDS interface panel, the pixel clock signal has the following two functions:
(1) The command RGB signal is transmitted sequentially. The pixel clock signal is like the command of the commander to send the password "one or two, one or two ...", the digital RGB signal in the pixel clock signal, in accordance with a certain sequence, driven by the drive plate transmission to the LCD panel, so that the circuit in accordance with a certain pace of coordination to work.

(2) Ensure the correctness of data transmission. Whether it is the driver board circuit, or the LCD panel circuit, when reading the digital RGB signal, are in the role and control of the pixel clock, the circuit only when the pixel clock falling edge (or rising edge) to the arrival of the digital RGB data to read, to ensure the correctness of reading data. Figure shows a schematic diagram of the corresponding relationship between the pixel clock and the digital RGB signal (1024x768 LCD panel).

Schematic diagram of the corresponding relationship between the pixel clock and the digital video signal

Liquid crystal Display Line sync signal (HS) and field Sync Signal (VS)

In the liquid crystal display, the function of the line synchronous signal (HS) is to select the effective line signal interval on the LCD panel, the function of the field synchronous signal (VS) is to select the effective field signal interval on the LCD panel, the interaction of the line-field synchronization signal, the effective video signal range of the LCD panel can be selected.

Note that the synchronization signal used in the LCD monitor is a two-level signal that does not contain the blanking signal, while the synchronous signal in the CRT display color TV is a three-level signal containing the blanking signal. This is because the LCD is processing digital signals, the digital signal can only have two levels, high Level 1 and low level 0.

In the circuit, the line synchronization signal commonly used HS or hsync, the field synchronization signal commonly used vs or vsync representation.

Summary of DCLK/HG/VS/DE signal of liquid crystal display

According to the previous introduction. In the LCD panel TTL and LVDS interface, including the main signal is the RGB data signal, pixel clock signal dclk, line synchronization signal HS, field synchronization signal vs and effectively display the data selected communication number DE. All LCD panels require input of RGB data and pixel clock dclk, but they use synchronous signals in different ways.

(1) Use only the de sync signal LCD panel
This LCD panel does not require the input line synchronization signal HS and the field sync signal vs, only need to enter the de as a synchronous signal to use the normal operation. The line synchronization signal of the LCD panel and the field synchronous signal end usually need to be low level, otherwise it will not work properly.

(2) Simultaneous use of De/hs/vs simultaneous signal LCD panel
This LCD panel needs to input a valid display data Select communication number DE, line synchronous signal HS, field synchronous signal vs to normal operation.

(3) LCD panel single pixel/odd idol data input mode and signal timing
The LCD driver board transmits the RGB data signal to the LCD panel in two ways: one for single-pixel mode and one for the odd-and-even double-pixel mode (two way), which divides the RGB data into odd pixel and even pixel two way LCD panel transfer. Figure 1 shows the timing relationship between the two-pixel (dual-channel) R (example of a 1024x768 LCD panel) for the station data transfer mode.

Figure 1 Two-pixel (two-way) RGB data transfer the timing relationship between each signal