METHOD AND APPARATUS FOR MAXIMIZING THE SUSTAINABLE FLASH OF A HANDHELD PORTABLE ELECTRONIC DEVICE

• US 20100060178A1
• Filed: 11/17/2009
• Published: 03/11/2010
• Est. Priority Date: 01/08/2007
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Research In Motion Limited (Blackberry Limited)
• Inventors: Winger, Lyall, Drader, Marc, Geris, Ryan
• Granted Patent: US 8,040,069 B2
• Time in Patent Office: Days
• US Class Current: 315/200.A
• CPC Class Codes: H04M 2250/52 including functional features of a camera
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04W 52/0261 managing power supply demand, e.g. depending on battery level
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/395 Linear regulators
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

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.

Claims

1. A method for maintaining a maximum sustainable flash current over a whole length of a flash in a handheld electronic device powered by a battery of a given type, wherein the handheld electronic device places other variable loads on the battery in addition to the flash, comprising the steps of:

(a) calculating a first ESR of the battery based on a flash current at the battery following initiation of the flash at a given current;

(b) calculating a new ESR value for a pre-selected time period after step (a), within the length of the flash, based on the first ESR and known ESR characteristics for the given type of battery;

(c) calculating a new flash current based on the new ESR value; and

(d) adjusting the flash current upwards or downwards to approximate the new flash current.

2. The method of claim 1, further including the step of calculating the flash current at the battery following initiation of the flash at a given current based on a first voltage across the battery prior to initiation of the flash at a given current and a second voltage across the battery after initiation of the flash at the given current.

3. The method of claim 1, further including, during the length of the flash and after step (d), the steps of:

(e) measuring the voltage across the battery with flash plus normal system load;

(f) calculating the flash current at the battery following step (e);

(g) calculating an additional 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 in step (f);

(h) calculating an additional new ESR value for a pre-selected time period after step (g), within the length of the flash, based on known ESR characteristics for that type of battery;

(i) calculating an additional new flash current based on the additional new ESR value; and

(j) adjusting the flash current upwards or downwards to approximate the additional new flash current.

4. The method of claim 3 further including the step of repetitively repeating steps (e) through (j) during the length of the flash.

5. The method of claim 3, wherein steps (a) through (d) are performed approximately 2.5 ms from the start of the flash and steps (e) through (j) are performed at approximately 4 ms from the start of the flash.

6. The method of claim 3, including performing step (e) at a pre-selected time from the initiation of the flash and performing step (j) by adjusting the flash current with a ratio of the measured voltage across the battery from step (e) and a voltage value that is a predicted battery voltage at the pre-selected time.

7. The method of claim 6, wherein the predicted battery voltage is derived from the known ESR characteristics.

8. The method of claim 2, wherein the handheld portable device has a feature that when active applies a given operating load and step (a) takes into account the given operating load whether the feature is active or not.

9. The method of claim 8, wherein the given operating load is a WIFI TX/RX load and step (a) takes into account the WIFI TX/RX load whether active or not.

10. The method of claim 1, wherein the given current is approximately 500 mA.

11. The method of claim 1, wherein the flash current is adjusted in step (d) within 3 ms of initiating the flash.

12. The method of claim 1, including the step of sampling the battery voltage at pre-selected intervals throughout the flash duration to assure that a battery droop due to ESR follows a predicted path and does not reset the device.

13. The method of claim 12, wherein the pre-selected interval is approximately every 3 ms.

14. The method of claim 1, wherein the flash is an LED flash.

15. The method of claim 1, wherein the flash is an OLED flash

16. The method of claim 1, including the step of sampling the voltage across various points in a circuit in the handheld device to assure that operation of the handheld device is not compromised or all voltage rails remain within their operating specifications.

17. The method of claim 16, wherein the sampling step is performed at pre-selected time intervals.

18. The method of claim 17, wherein the pre-selected time intervals are approximately every 3 ms.

19. A handheld electronic device, comprising:

a battery of a given type;

a flash device; and

a processor, wherein the processor is programmed to;

(a) calculate a first ESR of the battery based on a flash current at the battery following initiation of the flash device at a given current;

(b) calculate a new ESR value for a pre-selected time period after calculating the first ESR, within the length of the flash of the flash device, based on the first ESR and known ESR characteristics for the given type of battery;

(c) calculate a new flash current based on the new ESR value; and

(d) adjust the flash current upwards or downwards to approximate the new flash current.

20. The handheld electronic device of claim 19, wherein the processor is programmed to calculate the flash current at the battery following initiation of the flash at a given current based on a first voltage across the battery prior to initiation of the flash at a given current and a second voltage across the battery after initiation of the flash at the given current.

21. A handheld electronic device, comprising:

a battery of a given type;

a flash device; and

a processor, wherein the processor is programmed to;

(a) determine the voltage across the battery under normal system load;

(b) initiate the flash device at a given current;

(c) measure the voltage across the battery with flash plus normal system load;

(d) calculate the flash current at the battery;

(e) calculate 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) calculate a new ESR value for a pre-selected time period after calculating the equivalent series resistance, within the length of the flash of the flash device, based on known ESR characteristics for the given type of battery;

(g) calculate a new flash current based on the new ESR value; and

(h) adjust the flash current upwards or downwards to approximate the new flash current.

22. The handheld electronic device of claim 21, wherein the processor is programmed to repeat (c) through (h) during the length of the flash.

23. The handheld electronic device of claim 21, wherein the processor is programmed to repetitively repeat (c) through (h) during the length of the flash.