Method and apparatus for maximizing the sustainable flash of a handheld portable electronic device
First Claim
1. A method for maintaining a maximum sustainable flash current over the whole length of a flash using a programmable current drive in a handheld portable device powered by a battery of a given type, that places other variable loads on the battery, in addition to the flash, comprising the steps of:
- (a) measuring the voltage across the battery under normal system load;
(b) initiating the flash at a given current;
(c) measuring the voltage across the battery with flash plus normal system load;
(d) calculating the flash current at the battery;
(e) calculating an equivalent series resistance (ESR) of the battery from the voltages measured across the battery under normal system load and under normal system load plus flash and the current calculated at the battery;
(f) calculating a new ESR value for a pre-selected time period after step (e), within the length of the flash, based on known ESR characteristics for that type of battery;
(g) calculating a new flash current based on the new ESR value; and
(h) adjusting the flash current upwards or downwards to approximate the new flash current.
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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.
8 Citations
20 Claims
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1. A method for maintaining a maximum sustainable flash current over the whole length of a flash using a programmable current drive in a handheld portable device powered by a battery of a given type, that places other variable loads on the battery, in addition to the flash, comprising the steps of:
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(a) measuring the voltage across the battery under normal system load; (b) initiating the flash at a given current; (c) measuring the voltage across the battery with flash plus normal system load; (d) calculating the flash current at the battery; (e) calculating an equivalent series resistance (ESR) of the battery from the voltages measured across the battery under normal system load and under normal system load plus flash and the current calculated at the battery; (f) calculating a new ESR value for a pre-selected time period after step (e), within the length of the flash, based on known ESR characteristics for that type of battery; (g) calculating a new flash current based on the new ESR value; and (h) adjusting the flash current upwards or downwards to approximate the new flash current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A handheld portable device powered by a battery of a given type comprising:
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a flash device; a programmable current drive; means for measuring the voltage across the battery; means for calculating the flash current at the battery from voltage measured across the battery under normal system load and from voltage measured across the battery under normal system load plus flash; means for calculating a first equivalent series resistance (ESR) of the battery from the voltages measured across the battery under normal system load and under normal system load plus flash and the current calculated at the battery; means for calculating a new ESR value for a pre-selected time period after the first ESR is calculated, within the length of the flash, based on known ESR characteristics for that type of battery; means for calculating a new flash current based on the new ESR value; and wherein the programmable current drive is programmed to adjust the flash current upwards or downwards to approximate the new flash current. - View Dependent Claims (19, 20)
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Specification