Data expansion:
Screen specification information-backlight control mode and PWM frequency setting
The brightness change of screen backlight is realized by controlling the voltage or current of backlight power supply by software. At present, there are two control modes: DC level control and PWM pulse width control. The performance of DC level control and PWM pulse width control in software is pulse width control. The difference between DC level control and hardware lies in the need to add PWM wave rectifier circuit to rectify PWM wave into DC, and the output frequency of PWM wave is high, generally 50KHz, so that better rectification effect can be achieved with smaller capacitance in hardware. PWM pulse width control is to directly output PWM wave to backlight power supply to control the brightness of backlight. The frequency of PWM wave is low, generally 50Hz~240Hz. When it is necessary to replace the movement to repair the machine, it is best to confirm the backlight control mode of the screen first to see if the rectifier circuit on the board is needed. The picture on the right shows the PWM circuit of one of the movements. DIM_OUT is the PWM signal output by the main chip. Through this circuit, PWM pulse width signal or DC signal can be output from DIM_PWM.
Source: Baidu -Screen