Circuit and method of operation for an adaptive charge rate power supply
First Claim
1. A battery charging circuit which adjusts to the parameters of an external power supply, to minimize charge time, comprising:
- a battery charge controller connected to said external power supply and electrifying a battery; and
a regulating circuit for maximizing the current drawn by said battery charge controller, while keeping the voltage to said battery charge controller above a preset minimum limit, said preset minimum limit corresponding to a low voltage shut off level for said battery charge controller.
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Abstract
A convenient source of charging power for portable communication devices is an integral power node of a computer data bus, such as a USB (universal serial bus) port. Unfortunately, USB ports have limited power capacity, making them generally incompatible with battery charge controllers (BCCs) which are designed to receive a steady, high capacity input. The invention provides a battery charging circuit which adjusts to the parameters of an external power supply such as a USB port by adding a regulating circuit to a standard BCC design. This regulating circuit maximizes the current drawn by the BCC, while keeping the voltage to the BCC above a preset minimum (the low voltage shut off level for the BCC). If the voltage to the BCC begins to drop, the regulating circuit reduces the current drawn, so the voltage rises and stays within the operating range of the BCC.
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Citations
16 Claims
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1. A battery charging circuit which adjusts to the parameters of an external power supply, to minimize charge time, comprising:
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a battery charge controller connected to said external power supply and electrifying a battery; and
a regulating circuit for maximizing the current drawn by said battery charge controller, while keeping the voltage to said battery charge controller above a preset minimum limit, said preset minimum limit corresponding to a low voltage shut off level for said battery charge controller. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A battery charger comprising:
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a battery charge controller whose current output varies with the voltage applied to a control signal input; and
a comparator for lowering the charge current when the voltage of the supply drops below a preset reference level.
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16. A method for charging a battery of a portable device via an external power supply, which adjusts to the parameters of said external power supply to minimize charge time, said method comprising the steps of:
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connecting a battery charge controller to said external power supply and to a rechargeable battery in said portable device;
determining a low voltage shut off level for said battery charge controller;
monitoring the voltage that said external power supply provides to said battery charge controller, and maximizing the current drawn by said battery charge controller, while keeping the voltage to said battery charge controller above said low voltage shut off level for said battery charge controller.
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Specification