Embedded Linux

In a handheld device, liquid crystal display is more and more widely used. Since the LCD itself is not luminous, it requires a strong light source to provide light, to clearly display information. Such a light source is a very power-hungry, copy movie to PSP usually liquid crystal display power often accounted for more than 60% total system power consumption. In group a 7 inch screen as an example, usually backlight power consumption is 2.5 W, while the LCD power consumption of only 0.825 W. Thus, the backlight source power consumption in the whole power proportion is very high. If the system is in no screen, also full power operation, system of battery energy will soon be exhausted. Therefore, regulating LCD backlight source, reduce the system without energy consumption when the display is very necessary work. In addition, the handheld device to changes in the work environment, also need according to the external light intensity changes, the backlight brightness to make corresponding adjustment, chinese herbal product dab6d23ck to fit the human eye viewing comfort.

Based on the above 2 reasons, considering the equipment to reduce the power consumption and convenience to use, based on the embedded Linux design, using a S3C2440 timer generates the PWM (Pulse Width Modulation ) signal according to the actual needs, equipment, and the external light intensity changes with button regulating LCD backlight brightness solutions.

1 based on the PWM backlight adjustment principle

In the medium and small size LCD, generally using white light LED as display backlight light source. PWM pulse width modulation, PWM dimming is using visual suspension principle, Google TV remotes with some frequency and duty cycle of the square wave to control the LED conduction. LED forward current at zero current and rated current to switch back and forth between, through the high-speed switch backlight, cycle to provide different duty cycle square wave, brightness adjustment. As long as the conduction of LED forward current size is constant, the white light will not happen as long as the frequency of color, and big 100Hz, the human eye will be continuous light source.

Assumption high level representative of open backlight, low level represents the backlight is turned off, online ups power manufacturer the backlight open and close time of different proportion will get different duty cycle of the square wave. The output from the waveform, the mean wave power is not the same, so we have obtained different luminance, achieve backlight adjustment.