CONTROLLING INDUCTIVE POWER TRANSFER SYSTEM
First Claim
1. A method of controlling inductive power transfer in an inductive power transfer system, the system comprising a primary unit operable to generate an electromagnetic field and at least one secondary device, separate from the primary unit, and adapted to couple with the field when the secondary device is in proximity to the primary unit so that power is received inductively by the secondary device from the primary unit without direct electrical conductive contacts therebetween, the method comprising:
- measuring, in the secondary device or devices therefrom, a characteristic of a secondary power being supplied to a load of the secondary device;
receiving, in the primary unit, power requirement information of the secondary device or devices therefrom, the power requirement information includes information relating to the measured characteristic of the secondary power;
determining, in the primary unit, in dependence upon the power requirement information of the secondary device a power supplied to the secondary device or, if there is more than one secondary device, a combined power supplied to the secondary devices;
measuring a primary power drawn from the primary unit, and determining if there is a substantial difference between, on the one hand, the measured primary power and, on the other hand, the power supplied; and
following such determination of a substantial difference, restricting or stopping the inductive power supply from the primary unit.
1 Assignment
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Accused Products
Abstract
An inductive power transfer system comprises a primary unit operable to generate an electromagnetic field and at least one secondary device, separable from the primary unit, and adapted to couple with the field when the secondary device is in proximity to the primary unit so that power can be received inductively by the secondary device from the primary unit without direct electrical conductive contacts therebetween. The system detects if there is a substantial difference between, on the one hand, a power drawn from the primary unit and, on the other hand, a power required by the secondary device or, if there is more than one secondary device, a combined power required by the secondary devices. Following such detection, the system restricts or stops the inductive power supply from the primary unit. Such a system can detect the presence of unwanted parasitic loads in the vicinity of the primary unit reliably.
13 Citations
20 Claims
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1. A method of controlling inductive power transfer in an inductive power transfer system, the system comprising a primary unit operable to generate an electromagnetic field and at least one secondary device, separate from the primary unit, and adapted to couple with the field when the secondary device is in proximity to the primary unit so that power is received inductively by the secondary device from the primary unit without direct electrical conductive contacts therebetween, the method comprising:
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measuring, in the secondary device or devices therefrom, a characteristic of a secondary power being supplied to a load of the secondary device; receiving, in the primary unit, power requirement information of the secondary device or devices therefrom, the power requirement information includes information relating to the measured characteristic of the secondary power; determining, in the primary unit, in dependence upon the power requirement information of the secondary device a power supplied to the secondary device or, if there is more than one secondary device, a combined power supplied to the secondary devices; measuring a primary power drawn from the primary unit, and determining if there is a substantial difference between, on the one hand, the measured primary power and, on the other hand, the power supplied; and following such determination of a substantial difference, restricting or stopping the inductive power supply from the primary unit.
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2. A method as claimed in claim 1, wherein the characteristic of the secondary power is at least one of a current and a voltage supplied to the load.
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3. A method as claimed in claim 1, wherein the power requirement information represents the amount of power used by the secondary device or devices therefrom.
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4. A method as claimed in claim 1, wherein the inductive power supply is restricted or stopped in the event that the measured primary power is greater than a threshold value.
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5. A method as claimed in claim 1, further comprising restricting or stopping the inductive power supply in the event that the measured primary power is less than a standby threshold value.
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6. A method as claimed in claim 1, wherein the inductive power supply from the primary unit is restricted or stopped in dependence upon a difference between the measured primary power and the power supplied to the secondary device or devices therefrom.
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7. A method as claimed in claim 6, wherein the inductive power supply is restricted or stopped in the event that the measured primary power exceeds the power supplied by more than a threshold value.
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8. A method as claimed in claim 1, wherein the or each secondary device transmits the power requirement information to the primary unit using a communication link that is separate from an inductive power transfer link between the primary unit and the secondary device concerned.
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9. A method as claimed in claim 1, wherein the or each secondary device transmits the power requirement information to the primary unit by varying a load imposed by the secondary device on the primary unit.
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10. A method as claimed in claim 9, wherein the load is varied to amplitude modulate or to pulse width modulate transmission of the power requirement information to the primary unit.
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11. A method as claimed in claim 10, wherein the power requirement information is transmitted as a series of bits or symbols.
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12. A method as claimed in claim 9, wherein the load is a dummy load.
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13. A method as claimed in claim 1, wherein the power requirement information transmitted includes information relating to a parasitic load imposed on the primary unit by the secondary device.
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14. A method as claimed in claim 1, wherein the power requirement information generated from at least one secondary device is representative of a sum of an amount of power supplied to the secondary device concerned and a parasitic load imposed on the primary unit by the secondary device concerned.
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15. An inductive power transfer system comprising:
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a primary unit operable to generate an electromagnetic field; at least one secondary device, separate from the primary unit, and adapted to couple with the field when the secondary device is in proximity to the primary unit so that power is received inductively by the secondary device from the primary unit without direct electrical conductive contacts therebetween; a load-measuring unit for determining information relating to a power requirement of the secondary device or devices therefrom; communication circuitry for receiving, in the primary unit, the power requirement of the secondary device or devices therefrom; power measuring circuitry; and a control unit for determining if there is a substantial difference between, on the one hand, the measured power and, on the other hand, the power requirement, and the control unit operable, following such determination of a substantial difference, to restrict or stop the inductive power supply from the primary unit.
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16. A system as claimed in claim 15, wherein the information relating to the power requirement is the voltage or current supplied to a load of the secondary device or devices therefrom.
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17. A system as claimed in claim 15, wherein the power requirement is an amount of power supplied to the secondary device or devices therefrom.
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18. A system as claimed in claim 15, wherein the power measuring circuitry is operable to measure a power drawn from the primary unit.
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19. A system as claimed in claim 15, wherein the at least one secondary device is adapted to transmit the power requirement information by modulating a load imposed on the primary unit.
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20. A system as claimed in claim 19, wherein amplitude modulation or pulse width modulation are used to transmit the power requirement information to the primary unit.
Specification