Display backlight adjustment analytic solution

To make the cabin of the user at any time to get accurate and reliable information, using in cockpit display must have high reliability, at the same time, because the pilot to operate instruments with either hand, and to improve the legibility of cockpit display and alleviate visual fatigue, display the light intensity also should be able to according to the surrounding environment and user demand for automatic and manual adjustment, avoid the user can't see when the ambient light is very strong display content, or feel dazzling when ambient light is dark. Liquid crystal display backlight brightness directly decided to display the average brightness, by adjusting the backlight of liquid crystal display brightness to adjust the brightness of the display.

the author USES homebred STC12C5624AD MCU design a drive and control circuit, LCD backlight module can accurately measure the ambient light intensity of illumination, backlight brightness according to ambient light to realize the automatic and manual adjustment.

1 display backlight adjustment principle of

because of the particularity of the cockpit, the reliability, accuracy and intelligent of cockpit display higher requirements, the need to automatically adjust itself according to the variation of environmental light backlight brightness, make people see more comfortable, can also manually adjust the screen brightness in order to achieve the user's requirements. By studying the available ambient light xt and the relation between the brightness of the backlight panel yt.

when ambient light for the xt, automatically adjust the brightness to:

yt = KXT + b ( 1)

with b is when the ambient light is 0, the driver to see the screen display information to the minimum brightness; K is a proportionality constant, can be modified according to the user's habits, reflects human see the information on the screen in bright environment needed for the brightness and the ratio of the ambient light.

when users are not satisfied with automatic adjustment of brightness, artificial adjust brightness to yt 'under the call type calculation:

of b and k' replacement after checking (' 1) New formula to calculate the type b and k, in order to prevent the

the driver excessive regulation, set the bmin and bmax, only with a b 'between the two alternative b b ', factory system to set the initial value when the bs at the same time, the user can through the button to return to b bs, also for k set kmin, kmax and ks.

2 circuit of LCD backlight module circuit principle diagram is shown in figure 1, mainly including two pieces type PN23CV silicon photocell, single-chip microcomputer, the key circuit, with a core of DD313 LED backlight driving circuit, auxiliary circuit, etc. PN23CV type silicon photocell sensing ambient light intensity of illumination and the brightness of the LCD backlight, the signal is transmitted to the microcontroller by amplification, single-chip computer calculation theory of LCD backlight brightness, compared with the brightness of LCD backlight, determine whether need to adjust the brightness of the LCD backlight. If you need, then give DD313 signal as the core of backlight driving circuit, including DD313 13, 11, 6 pins respectively red, green and blue leds, control the LED brightness, then adjust the actual brightness of LCD backlight module. When users are not satisfied with the result of the automatic adjustment of, through the key circuit send signals to single chip microcomputer, microcomputer to determine whether to need to adjust the brightness of the LCD backlight. After the LCD backlight brightness adjustment, delay for a period of time, and modify b and k value. Circuit program flow chart is shown in figure 2 and figure 3.

when a user manually adjust the display brightness, button SW1 and SW2 respectively by single chip microcomputer STC12C5624AD interrupts 0 and 1. Press the button the output voltage of VCC, release the button, the output voltage of 0, press SW1 user requirements increase display brightness, press SW2 said user requirements to reduce the display brightness, SW1 and SW2 are press said back to the original factory and set the value of k and b bs and ks, SW1, SW2 respectively in the single chip microcomputer 8, 9 two pins.

3 software programming rely on software programming to implement the circuit function, using on STC microcontroller timer and interrupt to scan button pressed, do the corresponding processing.

4 conclusions in this paper, we use superior performance, the mature technology of 51 single chip microcomputer, through the MCU peripheral circuit design and the timer and interrupt programming to realize manual and automatic adjustment of cockpit display backlighting, in order to achieve the user satisfaction of comfortable screen brightness, cockpit display backlight adjustment at the same time, more intelligent and humanization of precise and reliable.