Low cost battery sensing technique
First Claim
1. A battery sensing circuit which includes a pair of input terminals, a pair of output terminals, and a power supply, the battery sensing circuit comprising;
- a first feedback loop, coupled between said pair output terminals and said power supply, for use in a first mode of operation when no load is present;
a second feedback loop, coupled between said pair of output terminals and said power supply, for use in a second mode of operation when a load is present; and
an indicating circuit coupled to said first and second feedback loops for indicating the presence of a battery in said second mode of operation.
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Accused Products
Abstract
A low cost load sensing technique that is suitable for use in sensing batteries in a battery charging circuit is disclosed. The circuit is adapted to be utilized in conjunction with a power supply which may include a primary converter and a voltage feedback circuit. A transformer with a dual secondary winding is connected between the primary converter and the output terminals of the charging circuit. When no load or battery is present, a first feedback loop is utilized with both of the secondary transformer windings in series, which supplies a constant output voltage at the output terminals. When a load is present, a second feedback loop is utilized which includes one of the secondary windings to provide the voltage of the output terminals. A capacitor is connected in parallel with the other secondary winding. When a load is present, a step increase in voltage occurs across the capacitor due to the fact that the both secondary windings are in phase when a load is present. The voltage across the capacitor is used to drive an indicating circuit which provides an indication of a battery when the voltage across the capacitor exceeds a predetermined value. The indicating circuit may include a voltage divider and a Zener diode, configured to drive a transistor. The configuration of the indicating circuit as well as the feedback loops enable the circuit to detect a load, such as a battery, over a relatively wide dynamic range.
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Citations
17 Claims
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1. A battery sensing circuit which includes a pair of input terminals, a pair of output terminals, and a power supply, the battery sensing circuit comprising;
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a first feedback loop, coupled between said pair output terminals and said power supply, for use in a first mode of operation when no load is present; a second feedback loop, coupled between said pair of output terminals and said power supply, for use in a second mode of operation when a load is present; and an indicating circuit coupled to said first and second feedback loops for indicating the presence of a battery in said second mode of operation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A load detection circuit which includes a pair of input terminals and a pair of output terminals, the load detection circuit comprising:
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a transformer having a primary winding and first and secondary windings, said primary winding coupled to said input terminals; a first feedback loop which includes said first and second secondary windings, coupled to said output terminals, said first feedback loop being active in a first mode of operation; a second feedback loop which includes one of said first and secondary windings, coupled to said output terminals, and second feedback loop being active in a second mode of operation; and an indication circuit for detecting one of said first mode of operation or said second mode of operation. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification