8A photo flash driver exploits supercapacitors to produce 4x brighter flash light
The chip can drive up to 8A current through an LED flash system, enabling mobile phone cameras to take pin-sharp images. Pictures of fast-moving objects in dark conditions that previously would have suffered from motion artifacts may now be captured in precise detail. At the same time, glare and discomfort can be avoided because even short flash durations as low as 10ms provide sufficient light.
Compared to today’s LED flash drivers in mobile phones typically providing a maximum 2A output, the AS3630 is rated for an output four times higher and supports substantially faster shutter speeds. The LED flash driver uses an innovative, patent-pending architecture that fully exploits the energy stored inside a supercap (Electric Double Layer Capacitor, or EDLC). Driving two LEDs in series, the output of the supercap is always boosted from 5.5V to typically higher than 9V, to match the forward voltage of the LEDs. The boost topology employed also keeps the flash illuminated longer when the output from the unassisted capacitor would fall below the LEDs’ forward voltage. This architecture enables the use of the smallest capacitors.
The AS3630 photo flash driver also combines power from the EDLC with power from the phone battery, increasing the power available to the flash light system and supporting additional functions such as pre-flash and video light even when the supercap is discharged. Driving two flash LEDs in series also provides for consistent light output.
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