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 a 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:
- (a) measuring a voltage across the battery (Vb1) under normal system load;
(b) determining if a high current load (Ihighload1) occurred during the measurement taken in (a);
(c) initiating the flash at a given current;
(d) measuring a voltage across the battery with flash (Vb2) after a first pre-selected period after the flash is initiated;
(e) determining if the high current load (Ihighload2) occurred during the measurement taken in (d);
(f) calculating an equivalent series resistance (ESR) of the battery at the end of the first pre-selected period, from the voltages measured across the battery under normal system load and under normal system load plus flash using the formula—
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(g) calculating a new ESR value for a second pre-selected period after calculating the ESR in (f), within the length of the flash, based on known ESR characteristics for that type of battery;
(h) calculating a maximum current allowed from the battery (IMax) and subtracting any high current loads that can occur during the flash using the formula—
where ESR2nd is the ESR calculated for the end of the second pre-selected period; and
(i) adjusting the flash current upwards or downwards to approximate the IMax.
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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 maintaining a maximum sustainable flash current over a 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:
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(a) measuring a voltage across the battery (Vb1) under normal system load; (b) determining if a high current load (Ihighload1) occurred during the measurement taken in (a); (c) initiating the flash at a given current; (d) measuring a voltage across the battery with flash (Vb2) after a first pre-selected period after the flash is initiated; (e) determining if the high current load (Ihighload2) occurred during the measurement taken in (d); (f) calculating an equivalent series resistance (ESR) of the battery at the end of the first pre-selected period, from the voltages measured across the battery under normal system load and under normal system load plus flash using the formula—
;(g) calculating a new ESR value for a second pre-selected period after calculating the ESR in (f), within the length of the flash, based on known ESR characteristics for that type of battery; (h) calculating a maximum current allowed from the battery (IMax) and subtracting any high current loads that can occur during the flash using the formula— where ESR2nd is the ESR calculated for the end of the second pre-selected period; and (i) adjusting the flash current upwards or downwards to approximate the IMax. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A handheld portable device powered by a battery of a given type comprising:
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a flash device; a programmable current drive; a voltage measuring device for measuring a voltage across the battery under normal system load when a flash command is first initiated and before the flash is initiated (Vb1); a device for determining if a high current load (Ihighload1) occurred during the measurement of Vb1; a voltage measuring device for measuring a voltage across the battery under normal system load plus flash at first pre-selected period after the flash is initiated (Vb2); a device for determining if the high current load (Ihighload2) occurred during the measurement of Vb2; a calculating device for calculating a first equivalent series resistance (ESR) of the battery at the end of the first pre-selected period from the voltages measured across the battery under normal system load Vb1 and under normal system load plus flash (Vb2) using the following formula— a calculating device for calculating a new ESR value for a second pre-selected period after the ESR calculated at the end of the first pre-selected period is calculated, within the length of the flash, based on known ESR characteristics for that type of battery; a calculating device for calculating a maximum current allowed from the battery (IMax) and subtracting any high current loads that can occur during the flash using the formula— wherein ESR2nd is the ESR calculated for the end of the second pre-selected period; and wherein the programmable current drive is programmed to adjust the flash current upwards or downwards to approximate IMax. - View Dependent Claims (17, 18)
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Specification