Matrix LED Dimmer Enables Accurate Color Control and
Pattern Production in RGBW LEDs
Keith Szolusha RGB LEDs are used in projector, architectural, display, stage and automotive lighting
systems that require efficient, bright output. To produce predictable colors from an
RGB LED, each of its component LEDs (red, green and blue) requires individual,
accurate dimming control. High end systems can use an optical feedback loop
to allow a microcontroller to adjust the LEDs for color accuracy. Adding a white
LED to an RGB LED to produce an RGBW LED extends the hue, saturation and
brightness values available in the color system. Each RGBW LED requires accurate
dimming of four component LEDs. Two RGBW LEDs require eight “channels.”
One way to drive and dim RGBW LEDs
is to use four separate LED drivers, one
for each color (R, G, B and W). In such a
system, the LED current, or PWM dimming,
of each individual LED or string is driven
by separate drivers and control signals.
In this solution, though, the number
of LED drivers increases quickly with
the number of RGBW LEDs. Any lighting system with a significant number
of RGBW LEDs requires a substantial
number of drivers and synchronization
of the control signals to those drivers. The LT3965 matrix LED dimmer enables
such a design, as shown in Figure 1. Each …