Method and apparatus for maximizing the sustainable flash of a handheld portable electronic device
First Claim
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1. A method for adjusting a flash current of a flash in a handheld electronic portable device powered by a battery, the method comprising:
- determining any high current load from sources other than the flash during measurement of the voltage across the battery prior to initiation of the flash;
determining any high current load from sources other than the flash during measurement of the voltage across the battery after initiation of the flash;
determining a maximum current based on an equivalent series resistance (ESR) value for a predetermined flash current pulse duration, the equivalent series resistance (ESR) value determined as a function of an ESR of the battery after initiation of the flash, any high current loads that occurred during measurement of the voltage across the battery prior to initiation of the flash, any high current loads that occurred during measurement of the voltage across the battery after initiation of the flash, and potential high current loads due to variable loads placed on the battery; and
adjusting the flash current to approximate the maximum current to maintain a maximum sustainable flash current over the predetermined flash current pulse duration.
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Abstract
A method and apparatus for maintaining a maximum sustained flash current over the whole length of a flash using a programmable current drive in a handheld portable device powered by a battery. The method involves measuring the battery voltage before and after a flash is initiated and calculating the equivalent series resistance (ESR) of the battery. The calculated ESR is then used to adjust the flash current. The process may be repeated to correct for errors in the flash current.
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Citations
18 Claims
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1. A method for adjusting a flash current of a flash in a handheld electronic portable device powered by a battery, the method comprising:
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determining any high current load from sources other than the flash during measurement of the voltage across the battery prior to initiation of the flash; determining any high current load from sources other than the flash during measurement of the voltage across the battery after initiation of the flash; determining a maximum current based on an equivalent series resistance (ESR) value for a predetermined flash current pulse duration, the equivalent series resistance (ESR) value determined as a function of an ESR of the battery after initiation of the flash, any high current loads that occurred during measurement of the voltage across the battery prior to initiation of the flash, any high current loads that occurred during measurement of the voltage across the battery after initiation of the flash, and potential high current loads due to variable loads placed on the battery; and adjusting the flash current to approximate the maximum current to maintain a maximum sustainable flash current over the predetermined flash current pulse duration. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A handheld portable electronic device powered by a battery, the device comprising:
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a flash device; a programmable current drive to initiate the flash device at an initial flash current; at least one voltage measuring device for measuring, prior to initiating the flash, the voltage across the battery, under normal system load, and for measuring the voltage across the battery with flash after the flash device is initiated; at least one recording device for recording any high current load from sources other than the flash during measurement of the voltage across the battery prior to initiation of the flash and for recording any high current load from sources other than the flash during measurement of the voltage across the battery after initiation of the flash; and a microprocessor configured to adjust the flash current of the flash device by; determining a maximum current that can be drawn from the battery based on an equivalent series resistance (ESR) value for the predetermined flash current pulse duration, the equivalent series resistance (ESR) value determined as a function of an ESR of the battery after initiation of the flash, any high current loads that occurred during measurement of the voltage across the battery prior to initiation of the flash, any high current loads that occurred during measurement of the voltage across the battery after initiation of the flash, and potential high current loads due to variable loads placed on the battery; and causing the programmable current drive to adjust the flash current to approximate the maximum current to maintain a maximum sustainable flash current over the predetermined flash current pulse duration. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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Specification