Manufacturers are starting to turn to new high power to provide a photoflash function for these low-light conditions called white-light LEDs. These LEDs output is a wide light spectrum and it’s compact and easy to control. Unlike Xenon gas-discharges tubes which require hundreds of volts to flash, white-light LEDs can be operated in very low voltages. Additionally, to provide lighting for digital movie photography, white-light LEDs can be left on continuously.
3.2-4.8 V is the range of white-light LED forward voltage. This is drops in the middle of most battery input-voltage ranges, it’s mean the converter needs to be able to step up or step down the input voltage to maintain the forward voltage of the LED. Here’s the circuit diagram:
In movielight mode, the efficiency of TPS6105 can reach up to 93%, and 81% in high-current photoflash mode. The device completely disconnect the LED from the input source to prevent draining the battery and consumes a low 100 nA of quiescent current during shutdown.
This device has some additional features such as integrated-circuit protection for soft start, thermal shutdown, open or shorted LEDs, and an integrated anti-ring power switch for low-EMI operation in noise-sensitive applications. All of this is packaged in a 10-pin QFN, which a total solution size of less than 80 mm2 is allowed. [Source: Texas Instruments Application Note]