Color Management System Feedback Controller

TechOnline (01/24/2006 12:00 AM ET)

The HDJD-J822 is a CMOS mixedsignal IC designed to be the optical feedback controller of an LED-based lighting system. A typical system consists of an array of red, green and blue LEDs, LED drivers, a tri-color photosensor that samples the light output, and the HDJD-J822.The IC interfaces directly to the photosensor, processes the color information and adjusts the light output from the LEDs until the desired color is achieved. To achieve this, the IC integrates a high-accuracy 10-bit analog-to-digital converter front-end, a color data processing logic core, and a high-resolution 12-bit PWM output generator.

By employing a feedback system and the HDJD-J822, the light output produced by the LED array maintains its color over time and temperature. In addition, the desired color can be specified using a standard CIE color space.

In addition, by incorporating a standard I2C serial interface, specifying the color of the LED array's light output is as simple as picking the color coordinates from the CIE color space and writing several bytes of data to the device.

The output PWM signals are connected directly to the LED drivers as enable signals. The PWM signals control the on-time duration of the red, green and blue LEDs. That duration is continually adjusted in real-time to match the light output from the LED array to the specified,desired color.

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