Method of driving a flash device and a number of loads powered by a battery and handheld electronic device including the same

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.

2. The method of claim 1 further comprising employing about 900 mA as said predetermined value of said flash current.

3. The method of claim 1 further comprising:

determining that the voltage of said battery is less than said corresponding one of said plurality of different voltage values;

stopping said flash device responsive to the voltage of said battery being less than said corresponding one of said plurality of different voltage values; and

alerting said processor of said stopping.

4. 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;

employing as said number of loads powered by the battery at least two different loads powered by said battery;

selecting at least four of said plurality of different voltage values; and

after said starting said flash device, determining which number of said at least two different loads are active and 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.

5. The method of claim 4 further comprising employing about 900 mA as said predetermined value of said flash current.

6. The method of claim 4 further comprising:

determining that the voltage of said battery is less than said corresponding one of said plurality of different voltage values;

stopping said flash device responsive to the voltage of said battery being less than said corresponding one of said plurality of different voltage values; and

alerting said processor of said stopping.

7. The method of claim 4 further comprising:

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

employing I(hl) as a possible current from said battery corresponding to a number of said number of loads powered by said battery;

employing ESR from: (a) a look-up table of equivalent series resistance of said battery versus temperature operatively associated with said battery, or (b) the determined voltage of said battery divided by the current flowing from said battery; and

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

8. The method of claim 7 further comprising:

employing a current sensor to provide a sensed current from said current flowing from said battery; and

determining said corresponding one of said plurality of different voltage values from said sensed current and from said plurality of said plurality of different voltage values.

9. The method of claim 8 further comprising comparing the voltage of said battery to said determined corresponding one of said plurality of different voltage values.

10. 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 a plurality of said plurality of different voltage values from Vmin(I(hl))=Vlow-sys+I(hl)*ESR;

employing I(hl) as a possible current from said battery corresponding to a number of said number of loads powered by said battery;

employing ESR from: (a) a look-up table of equivalent series resistance of said battery versus temperature operatively associated with said battery, or (b) the determined voltage of said battery divided by the current flowing from said battery; and

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

11. The method of claim 10 further comprising employing about 900 mA as said predetermined value of said flash current.

12. The method of claim 10 further comprising employing as said number of loads powered by the battery up to about three different radios powered by said battery.

13. The method of claim 10 further comprising:

determining that the voltage of said battery is less than said corresponding one of said plurality of different voltage values;

stopping said flash device responsive to the voltage of said battery being less than said corresponding one of said plurality of different voltage values; and

alerting said processor of said stopping.

14. The method of claim 10 further comprising:

employing as said number of loads powered by the battery at least two different loads powered by said battery;

selecting at least four of said plurality of different voltage values; and

after said starting said flash device, determining which number of said at least two different loads are active and 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.

15. The method of claim 10 further comprising:

employing a current sensor to provide a sensed current from said current flowing from said battery; and

determining said corresponding one of said plurality of different voltage values from said sensed current and from said plurality of said plurality of different voltage values.

16. The method of claim 15 further comprising comparing the voltage of said battery to said determined corresponding one of said plurality of different voltage values.

17. A handheld electronic device comprising:

a processor;

a battery having a voltage;

a flash device including a flash current;

a number of loads powered by said battery; and

a flash driver structured to output said flash current to said flash device,

wherein said processor is structured to determine a temperature operatively associated with said battery, determine 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, and start said flash device at a predetermined value of said flash current,

wherein said flash driver is structured to select 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; determine the voltage of said battery, and if the voltage of said battery is less than or equal to said corresponding one of said plurality of different voltage values, then reduce 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,

wherein a temperature sensor is operatively associated with said battery to determine said temperature operatively associated with said battery and output a corresponding analog signal,

wherein said processor comprises an analog to digital converter structured to input said analog signal and output a digital value corresponding to said temperature operatively associated with said battery.

18. The handheld electronic device of claim 17 wherein said flash driver is further structured, after said flash device is started, to repetitively repeat said determine the voltage (Vbat) of said battery and repetitively repeat said reduce said flash current if the voltage (Vbat) of said battery is less than or equal to said corresponding one of said plurality of different voltage values and wherein said flash driver is further structured to said repetitively repeat said determine the voltage (Vbat) of said battery and said repetitively repeat said reduce said flash current until stopping said flash device.

19. The handheld electronic device of claim 17 wherein said flash driver is external to said processor.

20. The handheld electronic device of claim 19 wherein said flash driver is a hardware circuit structured to input a number of:

(a) said plurality of different voltage values from said processor;

(b) the predetermined value of said flash current from said processor; and

(c) a synchronization signal from a camera.

21. The handheld electronic device of claim 17 wherein said processor is structured to save said plurality of different voltage values in said flash driver.

22. The handheld electronic device of claim 17 wherein said flash driver comprises a comparator circuit structured to compare the voltage of said battery with said corresponding one of said plurality of different voltage values.