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The digital light projector (DLP) display technology developed by Texas Instruments uses an optical semiconductor to manipulate light digitally. An all-digital device, the DLP chip delivers a high-quality picture across a broad range of products, including large-screen digital HDTVs; projectors for business, home and professional venues; and digital cinema. These applications present unique power design challenges because of the power requirements posed by the light source, which may be a high-intensity discharge (HID) lamp or an LED array, as well as standards-based requirements for power factor correction (PFC) and energy efficiency.

To satisfy these power requirements, designers need to understand the basic operation of the DLP chips and the options for providing power in the application.

DLP Operation

The DLP chip is a sophisticated light switch that contains a rectangular array of up to 2 million hinge-mounted microscopic mirrors. Each of these micromirrors measures 16 microns × 16 microns. When a DLP chip is coordinated with a digital video or graphic signal, a light source and a projection lens, its mirrors can reflect an all-digital image onto a screen or other surface.

A DLP chip's micromirrors are mounted on tiny hinges that enable them to tilt either toward the light source in a DLP projection system (when it is turned on) or away from it (when it is turned off) — creating a light or dark pixel on the projection surface. The bit-streamed image code entering the semiconductor directs each mirror to switch on and off up to several thousand times per second. When a mirror is switched on more frequently than off, it reflects a light gray pixel; a mirror that's switched off more frequently reflects a darker gray pixel. In this way, the mirrors in a DLP projection system can reflect pixels in up to 1,024 shades of gray to convert the video or graphic signal entering the DLP chip into a highly detailed gray-scale image.

The white light generated by the lamp in a DLP projection system passes through a red, green and blue color filter as it travels to the surface of the DLP chip. After passing through this filter, the colored light then falls sequentially onto the DLP chip to create an image with up to 16.7 million colors. Some DLP projection systems include a three-chip architecture capable of producing up to 35 trillion colors.

The on and off states of each micromirror are coordinated with these three basic building blocks of color. For example, a mirror responsible for projecting a purple pixel will only reflect red and blue light to the projection surface. Our eyes then blend these rapidly alternating flashes to see the intended hue in a projected image (Fig. 1).

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