Briefly describe the LED three primary colors PWM dimming

PWM Dimming (Pulse Width Modulation) is currently the most common and optimal grayscale adjustment method used in LEDs. PWM is easier to understand. It controls the ratio of the on and off time of the LED. By dividing the on and off time ratio into several levels, the LED will display a corresponding number of grayscales.

As for PWM frequency, as I just said, PWM is achieved by the ratio of the time of turning on and off the LED, but the number of on and off times cannot be too low, at least it must deceive the eyes. Drawing on the experience of TV, it is generally greater than 100 Hz. Some LED display screens will be filmed by cameras. If conditions permit, it is recommended to design at 300-500 Hz.

In the application of three-primary color design, the white balance and the maximum expected brightness are usually achieved by adjusting the LED current, and the grayscale is achieved by controlling the PWM. The number of grayscale levels in the LED field includes 7 levels, 8 levels, 16 levels, 32 levels, 64 levels, 128 levels, 256 levels, 512 levels, etc. It can also be a different number of levels, which is mainly for the convenience of digital line data processing. For example, if it must be divided into 100 levels, that is also possible.

The product of the gray levels of the three primary colors is the number of colors that the product can theoretically reproduce. We usually say how many colors there are. For example, a single color is 256 colors, red 256 (levels) × green 256 (levels) × blue 256 (levels) = 16777216 (16KK colors).

The monochrome 256-level grayscale has fully met the color gamut needs of the eyes. This is the case with current LCD displays, and it is also one of the grayscales that ICs support the most. Due to the large color difference of LEDs, 512-level grayscale is used, and the corrected partial grayscale is actually used for display. The more representative ICs of 512 grayscale are MBI5030, TLC5940, DM137, DM133, DM412, etc. 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, when the display is adjusted to a certain brightness, each pixel can provide the same brightness level.

Other low grayscale levels can be selected according to different needs during design. For example, 32 levels are enough for commercial decorative lighting, and even lower levels are needed for text and symbols. Adjusting the brightness of monochromatic lighting to 16 levels can meet the requirements.