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METHOD OF DRIVING A FLASH DEVICE AND A NUMBER OF LOADS POWERED BY A BATTERY AND HANDHELD ELECTRONIC DEVICE INCLUDING THE SAME

  • US 20120068599A1
  • Filed: 11/24/2011
  • Published: 03/22/2012
  • Est. Priority Date: 02/26/2009
  • Status: Active Grant
First Claim
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1. A method of driving a flash device of a handheld electronic device including a number of loads powered by a battery having a voltage, said flash device including a flash current, said method comprising:

  • determining a temperature operatively associated with said battery;

    determining a plurality of different voltage values corresponding to a plurality of different combinations of said number of loads as a function of said determined temperature;

    starting said flash device at a predetermined value of said flash current;

    selecting a corresponding one of the plurality of different voltage values as a function of;

    (a) a determined number of said number of loads which are active, or (b) a current flowing from said battery;

    determining the voltage of said battery;

    if the voltage of said battery is less than or equal to said corresponding one of said plurality of different voltage values, then reducing said flash current below the predetermined value of said flash current until the voltage of said battery is greater than said corresponding one of said plurality of different voltage values;

    determining said determined number of said number of loads which are active;

    selecting said corresponding one of said plurality of different voltage values as the function of said determined number of said number of loads which are active;

    employing T as said temperature operatively associated with said battery;

    determining each of said plurality of different voltage values from Vmin=Vlow-sys+I(hl)*ESR(T);

    employing Vlow-sys as a voltage at which said handheld electronic device will reset or shutdown;

    employing I(hl) as the sum of a plurality of different current loads that could occur after said starting said flash device; and

    employing ESR(T) from a look-up table of equivalent series resistance of said battery versus temperature operatively associated with said battery.

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