Electricity: battery or capacitor charging or discharging – Battery or cell charging – Time control
Reexamination Certificate
2001-05-18
2002-08-06
Toatley, Gregory (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell charging
Time control
C340S636210
Reexamination Certificate
active
06429625
ABSTRACT:
BACKGROUND
Handheld computing devices, “palmtops,” “palmhelds,” personal digital assistants (PDAs), or handheld computers typically weigh less than a pound and fit in a pocket. These handhelds generally provide some combination of personal information management, database functions, word processing, and spreadsheets as well as voice memo recording and telephony functions. Because of the small size and portability of handhelds, strict adherence to hardware constraints such as battery charge indicating hardware must be maintained. It is conventional to have lights and/or icons that indicate whether a battery is charged.
Handheld computing devices can include rechargeable batteries used to power the handheld computer and other on-board devices such as a wireless phone. The user must periodically recharge the rechargeable batteries by plugging the unit directly into a battery recharger or by placing the handheld computing device into a synchronization cradle that also functions as a battery charger.
Handheld computing devices typically have a battery charge indicator that informs the user whether the handheld computing device is currently being charged, and can indicate whether the battery is fully charged and may be removed from the charger.
To determine the status of the battery and therefore indicate to the user whether the battery has completed its charging process, both hardware and software are required. The handheld computing device must have hardware in the form of a battery voltage detector to measure the terminal voltage of the battery during charging. Additionally, a software algorithm is used to compare the measured voltage against a battery charge curve associated with the particular battery in the unit. The software algorithm can be complicated because the battery charge curve changes during the life of the battery as the maximum voltage changes.
The conventional methods of indicating whether the handheld computing device battery is fully charged are disadvantageous because the required hardware takes space and adds manufacturing cost to the unit, and the necessary software uses memory of the handheld unit that could otherwise be used for other functions.
Accordingly, there is a need for a handheld computing device that can indicate to the user when the rechargeable battery has been charged allowing the unit to be disconnected from the battery charger, but that does not require the hardware necessary to measure the battery voltage, as well as the software necessary to compute whether the battery is fully charged based on the output voltage of the battery. Further, there is a need for a handheld computing device including simplified and expense saving electronics that indicate whether a battery has been charged. Further still, there is a need for a handheld computing device including a simplified charging timer for indicating charge status.
The teachings hereinbelow extend to those embodiments that fall within the scope of the appended claims, regardless of whether they accomplish one or more of the above-mentioned needs.
SUMMARY
An exemplary embodiment relates to a method of indicating when a rechargeable battery of a handheld computer has been fully charged. The method includes the steps of determining an elapsed charging time and activating a charge completion indicator when the elapsed charging time exceeds a predetermined time and requiring no dependence on actual battery voltage or current.
Another exemplary embodiment relates to a handheld computer having a display, a rechargeable battery, and an operating system. The handheld computer also includes a battery charger and a timing routine that activates a charge completion indicator after the battery charger has been charging the rechargeable battery for a predetermined time the predetermined time being independent of a measured battery voltage or current.
Further, an exemplary embodiment relates to a method of indicating when a rechargeable battery has been fully charged. The method includes the steps of determining an elapsed charging time and activating a charge completion indicator when the elapsed charging time exceeds a predetermined time the predetermined time being independent of a measured battery voltage or current.
Further still, an exemplary embodiment relates to a method of charging a rechargeable battery of a handheld computer having a battery charger and a timer. The method includes the steps of electrically linking the battery and the battery charger thereby commencing battery charging and determining an elapsed charging time. Further, the method includes the step of indicating completion of battery charging when the elapsed charging time exceeds a predetermined time the predetermined time being independent of a measured battery voltage or current.
Yet further still, an exemplary embodiment relates to a synchronization cradle. The synchronization cradle includes a current source coupled to a battery charging circuit and a battery charge status indicator wherein the battery charge status indicator indicates that a rechargeable battery is fully charged after a predetermined charging time has elapsed the predetermined charging time being independent of a measured battery voltage or current.
REFERENCES:
patent: 5570025 (1996-10-01), Lauritsen et al.
patent: 5623193 (1997-04-01), Lang et al.
patent: 5663629 (1997-09-01), Hinohara
patent: 5764034 (1998-06-01), Bowman et al.
patent: 5973497 (1999-10-01), Bergk et al.
Linear Technology LTC 1732-4/LTC 1732-4.2: Lithium-Ion Linear Battery Charger Controller (Oct. 2000).
Kwok Alec
LeFevre John S.
Yamanaka Keith
Foley & Lardner
Palm Inc.
Toatley Gregory
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