Circuit and method of operation for an adaptive charge rate power supply
First Claim
1. A portable communication device, comprising:
- a rechargeable battery; and
a battery charging circuit coupled to the rechargeable battery and configured to receive power from an external power source and use the power from the external power source to charge the rechargeable battery, the battery charging circuit including;
a battery charge controller configured to receive an input voltage form the external power source and use the input voltage to charge the rechargeable battery, the battery charge controller requiring that the input voltage remain above a low voltage threshold when charging the rechargeable battery, the battery charge controller having a current control input; and
a regulating circuit configured to regulate the input voltage to maintain the input voltage above the low voltage threshold, said regulating circuit being operable to respond to deviations in the input voltage by adjusting a current drawn by the battery charge controller to maintain the input voltage above the low voltage threshold.
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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
15 Claims
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1. A portable communication device, comprising:
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a rechargeable battery; and a battery charging circuit coupled to the rechargeable battery and configured to receive power from an external power source and use the power from the external power source to charge the rechargeable battery, the battery charging circuit including; a battery charge controller configured to receive an input voltage form the external power source and use the input voltage to charge the rechargeable battery, the battery charge controller requiring that the input voltage remain above a low voltage threshold when charging the rechargeable battery, the battery charge controller having a current control input; and a regulating circuit configured to regulate the input voltage to maintain the input voltage above the low voltage threshold, said regulating circuit being operable to respond to deviations in the input voltage by adjusting a current drawn by the battery charge controller to maintain the input voltage above the low voltage threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A portable communication device, comprising:
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a rechargeable battery; means for connecting the portable communication device to an external power source; means for charging the rechargeable battery using an input voltage from the external power source; and means for maintaining the input voltage above a low voltage shut-off level below which the portable communication device stops charging the rechargeable battery by adjusting a current drawn by the means for charging in response to deviations in the input voltage.
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Specification