What is a dot-matrix LCD screen and what is the driving method of a dot-matrix LCD screen? The following editor will take you to understand, I hope it can be helpful to everyone.
The liquid crystal display is due to the application of an electric field on the display pixel, which is a combination of the potential signals on the two electrodes before and after the display pixel. Since the DC electric field tends to reduce the life of the liquid crystal, generally only an AC electric field with a very small DC component is established. The direct current component is usually less than 50mV. The driving of the liquid crystal display establishes a driving electric field by adjusting the phase, peak value, frequency, etc. of the potential signal applied to the electrode of the liquid crystal display to realize the display.
1. Dynamic drive method
When the liquid crystal display displays a large number of pixels, such as a dot matrix, in order to save a huge hardware drive circuit, the production and arrangement of the liquid crystal display electrodes are processed, and a matrix structure is implemented: that is, the back electrodes of a horizontal group of display pixels are connected Leading out together is called the row electrode; connecting the segment electrodes of the vertical display pixels are all drawn together and called the column electrode. Each pixel on the display is uniquely determined by its row and column position. The dynamic driving method of the liquid crystal display is to cyclically apply selection pulses to the row electrodes, and at the same time apply selective or non-selective driving pulses to all the column electrodes, so as to realize the display function of all pixels in a certain row. This scanning is carried out sequentially line by line, and the cycle period is very short, so that a stable image appears on the LCD screen.
The selection time of each row in a frame is equal. Assuming that the number of scanning lines in a frame is N and the scanning time is 1, then the selection time occupied by one line is 1/N of the time of one frame. This is the duty cycle coefficient of the liquid crystal display drive, also known as the duty cycle.
2. Overcoming crossover effects
In the dynamic driving mode, to make a certain position such as (i, j) point display, it is necessary to apply a selection voltage on the i-th column and j-th row at the same time to maximize the variable electric field intensity at this point, but at this time, except Except for the (i, j) point, the remaining points in the i-th column and the j-th row are also subjected to a certain voltage, and these points are called semi-selected points. If the effective voltage at the half-selection point is greater than the threshold voltage, an undesirable display will appear on the screen and the contrast will decrease, which is the crossover effect. The solution to the cross effect is the average voltage method, that is, to average the voltages of the half-selected point and the non-selected point, and moderately increase the voltage of the non-selected point to offset a part of the voltage at the half-selected point, so that the voltage at the half-selected point drops, thereby Increase the display contrast.
