This article will discuss LEDs and their associated driver circuits that are widely used in portable devices such as mobile phones and PDAs. In addition to focusing on the latest LED applications, the development of white LEDs will also be examined. Finally, LCD backlighting and decoration will be used. Graphical descriptions of the structure and up-to-date functions of the lighting and instructions and the drive circuitry such as the flash on the camera phone.
Due to its high illumination efficiency, long-term efficiency and small size, LED has become the first choice for portable devices such as mobile phones and PDAs. The low-power white LEDs of about 0.1W are currently widely used. In the backlight and keyboard illumination of the LCD display panel, it is of course also possible to connect a plurality of LEDs to provide higher brightness for temporary lighting or flashlight applications. High-power LEDs up to 1W are used in camera phones with 2 million pixels or even higher resolution to support photography in dark environments.
In addition to white LEDs, RGB (red, green, blue) LEDs are often used to enhance the texture of mobile phones. By accurately and appropriately mixing these three colors, RGBLED can create a rich variety of color performance. In the indicator application, when a call or message arrives, the color LED can be flashed, or the color can be used to display the identity of the caller, such as a friend, family member, or a call from a business call, such as a self-defined group. It brings personalization to your phone and is also very useful when the user is in a very noisy environment.
In order to further enhance the user's audio and video experience, RGBLED is also used to generate a lot of attractive lighting effects, one example is to synchronize the RGB lighting action with the ringing melody or MP3 music, another interesting application of RGB lighting It is the Feel*Talk function of Panasonic. Since the RGBLED is arranged under the casing of the mobile phone, it can display different colors according to the user's mood.
Major white LED suppliers
Currently used in the portable device LCD and keyboard backlight white LED, was introduced by Nichia Chemical Company in 1996, through the coating of gallium nitride (GaN) with pale yellow fluorescent material. A blue LED of indium gallium nitride (InGaN) is used to achieve a white light effect. In addition, the development of blue and green LEDs has expanded the richness of LED color output.
However, in the late 1990s, multiple patent infringement issues between major LED manufacturers in Japan, the United States, and Europe prevented new manufacturers from entering the market. Fortunately, these legal proceedings were gradually resolved through mutual authorization negotiations, and some manufacturers such as Nichia, ToyodaGosei, Cree, Philips Lumileds and OSRAM established their leading position at that time. In addition, newcomers in Taiwan and South Korea began to rise a few years ago, and in the past two years they have gradually tasted the fruits of high turnover.
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