Electronic Design

Battery "Fuel Gauges," CCFL Trends

Battery ?Fuel Gauges?
Few of today's handheld devices incorporate a battery-status ?fuel-gauge? chip. But that will change as handheld devices grow into electronic Swiss Army knives. In fact, we're really going to need fuel-gauge chips that are tied a lot more tightly to the system CPU.

Imagine a cell phone that incorporates a still photo and video camera as well as audio-video personal media player functions. It would need a pretty smart fuel gauge, right? It would have to identify how much power remains, depending on the application.

For example, watching an episode of a favorite TV show would eat up a lot more power than a simple phone call. On screen, bars next to icons could indicate the time remaining per application. Users don't need to know the state of the battery charge. They just want to know how much stuff they can do before the battery goes kaput.

The Demise Of The CCFL
Future laptops can save power by switching from cold-cathode fluorescent lamps (CCFLs) to LEDs. It's not going to be easy, and the laptop makers won't do it cheerfully. But eventually, the EU will ban CCFLs. While they're exempted from the Restrictions on Hazardous Substances (RoHS) directives for now, because of their mercury content, that won't last forever.

Driving white LEDs is simpler than driving CCFLs. Several things have to happen, though, before LEDs become practical. First, we'll need a diffuser that spreads the light from multiple point sources evenly across the screen, the way today's diffusers spread the bars of light output by CCFLs. Second, the LED manufacturing process must be better controlled to minimize the variations in output and color temperature (and in forward voltage drop) found in today's batches of white LEDs.

TAGS: Components
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