Utilizing a white LED driver to cost-effectively drive power-limited xenon flashes in digital cameras, camera Phones

Over the last several years, the digital cameras and camera-equipped cell phones has migrated from exotic specialty items to a mainstream offerings. The digital image sensors within these products can be either CCD or CMOS technology based. To support the image sensor in low light conditions a flash circuit is mainstream for a digital camera and becoming more common for camera phones. The primary light source to address the flash requirement are xenon bulbs (commonly used in film and digital cameras today) and the now emerging high brightness white LEDs.

The primary advantage of xenon is the high light output power generated during the flash pulse. The LED approach, however, has the advantage of being relatively small and thin and can be turned on for extended periods of time for video capture albeit with a modest light output compared to xenon. Specifically, xenon lamps provide very short flash bursts, capable of freezing the picture captured by the camera. They do require a special driver to generate a high voltage as well as a large reservoir capacitor to store the energy.

We have found that a white LED driver provides a cost-effective option for driving power-limited xenon flash light to illuminate a photographic scene. This paper depicts the basics of the xenon concept and details a typical low power/low cost flash application.

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