Briefly Describe The LED Three Primary Color PWM Dimming.
- Jan 11, 2019 -

Briefly describe the LED three primary color PWM dimming.

PWM Dimming (Pulse Width Modulation, Pulse Width Modulation) is a common gamma adjustment method that is currently used in LEDs. The easy-to-understand PWM theory is to control the proportion of time that the LED is on and off. The ratio of the time of opening and closing is divided into several levels, and the LED will display the corresponding number of gray levels.

As for the PWM frequency, just said that PWM is the ratio of the time to open and close the LED, but the number of switches can not be too low, at least to deceive the eyes. The experience of drawing on TV sets is generally greater than 100Hz. Some LED display screens will be taken by the camera. Under the conditional recommendation, the design is more reasonable at 300-500Hz.

In the three primary color design applications, the white balance and the maximum desired brightness are achieved by adjusting the LED current, and the gray level is achieved by controlling the PWM. The number of gray levels in the LED field is 7 steps, 8 steps, 16 steps, 32 steps, 64 steps, 128 steps, 256 steps, 512 steps, and so on. It can also be a different order of magnitude, which is mainly for the convenience of digital line data processing. For example, if you want to divide it into 100 steps, that is ok.

The gray level product of the three primary colors is the number of colors that the product theory can reproduce, and we usually say how many colors. For example: monochrome is 256 colors, red 256 (level) × green 256 (level) × blue 256 (level) = 16777216 (16KK colors).

Monochrome 256-level grayscale has fully met the color gamut of the eye. This is the case with current LCD liquid crystal displays, and it is also one of the most supported gray scales in the current IC. Due to the large difference in LED color, 512-step gray scale is used, and the corrected partial gray scale display is actually used. Representative ICs of 512 gray scale are MBI5030, TLC5940, DM137, DM133, DM412 and so on. Point correction design method. This method is used to calibrate each pixel in a large display. After the calibration is completed, or after the point correction is completed, each pixel can provide the same brightness level when the display is adjusted to a certain brightness.

Other low-gray levels can be selected as needed during design. For example, 32 steps on commercial decorative lighting is enough, and the text symbols will be lower. Monochrome illumination brightness adjustment of 16 steps can meet the requirements.


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