LED display screens are very common in life and bring a lot of convenience to our lives. Since the brightness of the LED display screen cannot be changed with the ambient light, there is a problem of unclear display during the day or dazzling at night due to being too bright. If the brightness can be controlled, not only energy can be saved, but also the display effect of the display screen can be made clearer.
01led is a green light source, its main advantage is high luminous efficiency
With the development and progress of material science, the luminous efficiency will be greatly improved in the next 10 years; low energy consumption, long service life, recyclable materials, and no pollution to the environment. Although our country started late, in recent years it has also begun active research and development and industrial policies and support. Compared with the incandescent lamp, the LED has a significant difference: the brightness of the light is basically proportional to the size of the forward current flowing through the light-emitting diode. Using this feature, the brightness of the surrounding environment is measured by an optical sensor, the luminous brightness changes according to the measured value, and the influence of the brightness changes of the surrounding environment is maintained, and the construction transfers people to work happily. This not only creates a comfortable environment with constant brightness, but also makes full use of natural lighting and greatly saves energy. Therefore, the research on LED adaptive dimming technology is extremely important.
02 basic principles
This design uses the column to send data and the row scan method to realize the LED display text or image. This method is combined with the hardware circuit to achieve the purpose of relatively uniform overall brightness of the display screen. Utilize the sensitive characteristic of the photoresistor to ambient light, collect the change of ambient light, convert it into electrical signal and send it to the single-chip microcomputer, the single-chip processor performs signal processing, and controls the duty ratio of the output PWM wave according to a certain rule. A switch voltage regulator circuit is added between the single-chip microcomputer and the led display screen to realize the brightness adjustment of the display screen by the single-chip microcomputer. The adjusted PWM wave is used to control the switching voltage regulator circuit to adjust the input voltage of the display screen, and finally realize the brightness control of the display screen.
An adaptive brightness control circuit for a light emitting diode display screen, which is characterized by comprising: a duty cycle preset value input device, a counter and a magnitude comparator, wherein the counter and the duty cycle preset value input device respectively count a The value is compared with a preset value of the duty cycle into the size comparator to control the output value of the comparator.
04LED adaptive dimming system hardware design
The brightness of the LED is proportional to the current flowing through it in the forward direction, and the size of the forward current can be adjusted to adjust the brightness of the LED. Currently, the brightness of the LED is generally adjusted by adjusting the working current mode or the pulse width modulation mode. The former has a large adjustment range, good linearity, but high power consumption. So it is rarely used. The pulse width modulation method uses a higher frequency to switch the leds, the switching frequency is beyond the range that people can perceive, so that people do not feel the existence of stroboscopic. Realize LED adaptive dimming.