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Maxim > Design Support > Technical Documents > Application Notes > Display Drivers > APP 4317
Maxim > Design Support > Technical Documents > Application Notes > LED Lighting > APP 4317
Maxim > Design Support > Technical Documents > Application Notes > Power-Supply Circuits > APP 4317
Keywords: RGB LED Driver
APPLICATION NOTE 4317
Multicolor Lighting Employs High-Power Drivers for
RGB LEDs
By: Anil Baby, Senior Member of the Technical Staff
Jul 26, 2010
Abstract: This article looks at the design of high-power LED drivers suitable for powering multicolor
lighting systems that include high-brightness LEDs (HB LEDs). The circuit presented as an example
drives the RGB LEDs found in decorative, architectural, entertainment, and stage lighting.
A similar article appeared in Korea in the March, 2009, issue of Display magazine.
Next-generation architectural and decorative lighting achieves a wide range of color by mixing
appropriate proportions of output from red, green, and blue LED chips. The series-connected chips in
such high-brightness, multichip LEDs feature typical forward voltage drops of 22V to 36V, while drawing
1A to 2A currents. The LED driver featured in Figure 1 delivers 2A to a multichip LED module whose
forward voltage can range up to 36V. This circuit drives only one color of the RGB LEDs, so three such
drivers are needed to drive all three colors.
Because the light output from an LED is not a linear function of its forward current, brightness levels are
adjusted via PWM control rather than by controlling the LED's current amplitude. That is, each LED is
driven with a constant current that is pulse-width modulated to control the light output. The IC controller
shown uses average-current-mode control to implement this LED drive with a minimum of external
components.
More detailed image (PDF, 264kB)
Figure 1. This circuit drives one high-brightness LED of an RGB chipset. Three such circuits drive a
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