Wireless inductive power transfer
A power transmitter ( 101 ) transfers power to a power receiver ( 105 ) using a wireless inductive power signal. The power transmitter ( 101 ) comprises an inductor ( 103 ) for providing the power signal and a power signal generator ( 207 ) for driving the inductor ( 103 ) to provide the power signal. The power receiver ( 105 ) comprises an inductor ( 107 ) for receiving the power signal and a transmitter ( 305 ) which transmits data messages to the power transmitter ( 101 ). The data are communicated by load modulation of the power signal in repeating load modulation intervals which are separated by intervening time intervals. The power transmitter ( 101 ) transmits data to the power receiver ( 105 ) by modulating the power signal with a message during the intervening time intervals and the power receiver demodulates the data in these time intervals. The power transmitter ( 101 ) transmits single bit of the message by modulating it across a plurality of intervening time intervals and the power transmitter ( 101 ) receives it by demodulating over these time intervals.
1. A power transmitter for transferring power to a power receiver using a wireless inductive power signal, the power transmitter comprising:
an inductor for providing the power signal;
a power signal generator for driving the inductor to provide the power signal;
a receiver for receiving data messages from the power receiver;
a transmitter for transmitting data to the power receiver by modulating the power signal with a message;
wherein the data messages are communicated by load of the power signal in repeating load modulation intervals, the repeating load modulation intervals being separated by intervening time intervals, and
wherein the transmitter is arranged to modulate a single bit of the message across a plurality of the intervening time intervals in accordance with a predetermined modulation pattern, the modulation pattern defining modulation deviations to apply to the power signal in each of the plurality of intervening time intervals.
2. The power transmitter of claim 1 , wherein the predetermined modulation pattern comprises one modulation value for each of the plurality of intervening time intervals, each modulation value defining a modulation offset for the power signal for a value of the single bit.
3. The power transmitter of claim 2 , wherein each modulation offset is a constant offset for the corresponding intervening time interval.
4. The power transmitter of claim 2 , wherein each modulation offset is a non-constant predetermined pattern for the corresponding intervening time interval.
5. The power transmitter of claim 1 , wherein the predetermined modulation pattern corresponds to an average deviation of the power signal due to modulation of the single bit of no more than a maximum deviation between two of the plurality of intervening time intervals.
6. The power transmitter of claim 1 , the predetermined modulation pattern corresponds to a maximum deviation of the power signal due to the modulation of the single bit of no more than 5%.
7. The power transmitter of claim 1 , wherein the predetermined modulation pattern corresponds to a series of step changes between constant deviations in each intervening time interval, the predetermined pattern comprising step changes of opposite signs.
8. The power transmitter of claim 1 , the predetermined modulation pattern corresponds to a deviation of the power signal due to modulation of the single bit of less than a tolerance value for the power signal.
9. The power transmitter of claim 1 , wherein the modulation pattern corresponds to applying an offset to the power signal formed by a series of smaller changes to the power signal, each change corresponding to one intervening time interval.
10. The power transmitter of claim 1 , wherein the transmitter is arranged to generate a modulation offset for a first intervening time interval by determining a sign value of the modulation offset in response to the single bit and an amplitude of the modulation offset in response to the predetermined modulation pattern corresponding to the first intervening time interval, and to apply the modulation offset to the power signal in the first intervening time interval.
11. The power transmitter of claim 1 , wherein the predetermined modulation pattern represents an amplitude offset pattern for the power signal.
12. The power transmitter of claim 1 , wherein the predetermined modulation pattern represents voltage variations applied to the power signal.
13. The power transmitter of claim 1 , wherein the predetermined modulation pattern represents a frequency offset pattern for the power signal.
14. The power transmitter of claim 1 wherein the transmitter is arranged to transmit the message during a configuration phase performed by the power transmitter and the power receiver.
15. A power receiver for receiving power from a power transmitter using a wireless inductive power signal, the power receiver comprising:
an inductor for receiving the power signal;
a transmitter for transmitting data messages to the power transmitter;
a receiver for receiving a message from the power transmitter;
wherein the data messages being communicated by load modulation of the power signal in repeating load modulation intervals, the repeating load modulation intervals being separated by intervening time intervals, and
wherein the receiver is arranged to demodulate a single bit of the message across a plurality of the intervening time intervals in accordance with a predetermined modulation pattern, the modulation pattern defining modulation deviations to match to the power signal in each of the plurality of intervening time interval.
16. A power transfer system, comprising:
a power transmitter for transferring power to a power receiver using a wireless inductive power signal, the power transmitter comprising:
an inductor for providing the power signal;
a power signal generator for driving the inductor to provide the power signal;
a receiver for receiving data messages from the power receiver;
a transmitter for transmitting data to the power receiver by modulating the power signal with a message, wherein the data messages are communicated by load modulation of the power signal in repeating load modulation intervals, the repeating load modulation intervals being separated by intervening time intervals, and wherein the transmitter is arranged to modulate a single bit of the message across a plurality of the intervening time intervals in accordance with a predetermined modulation pattern, the modulation pattern defining modulation deviations to apply to the power signal in each of the plurality of intervening time intervals; and
the power receive for receiving power from the power transmitter using a wireless inductive power signal, the power receiver comprising:
an inductor for receiving the power signal;
a transmitter for transmitting data messages to the power transmitter;
a receiver for receiving a message from the power transmitter; wherein the data messages being communicated by load modulation of the power signal in repeating load modulation intervals, the repeating load modulation intervals being separated by intervening time intervals, and wherein the receiver is arranged to demodulate a single bit of the message across a plurality of the intervening time intervals in accordance with a predetermined modulation pattern, the modulation pattern defining modulation deviations to match to the power signal in each of the plurality of intervening time interval.
17. A method of operation for a power transmitter arranged to transfer power to a power receiver using a wireless inductive power signal, the power transmitter comprising an inductor for providing the power signal, and a power signal generator for driving the inductor to provide the power signal, the method comprising:
receiving data messages from the power receiver;
transmitting data to the power receiver by modulating the power signal with a message;
wherein the data messages are communicated by load modulation of the power signal in repeating load modulation intervals, the repeating load modulation intervals being separated by intervening time intervals,
wherein the transmitting data comprises modulating a single bit of the message across a plurality of the intervening time intervals, and
wherein transmitting comprises modulating the single bit in accordance with a predetermined modulation pattern, the modulation pattern defining modulation deviations to apply to the power signal in each of the plurality of intervening time intervals.
18. A method of operation for a power receiver arranged to receive power from a power transmitter using a wireless inductive power signal, the power receiver comprising an inductor for receiving the power signal, and the method comprising:
transmitting data messages to the power transmitter; and
receiving a message from the power transmitter by demodulating the power signal;
wherein the data messages are communicated by load modulation of the power signal in repeating load modulation intervals, the repeating load modulation intervals being separated by intervening time intervals, and
wherein receiving comprises demodulating a single bit of the message across a plurality of the intervening time intervals and comprises demodulating the single bit in accordance with a predetermined modulation pattern, the modulation pattern defining modulation deviations to match to the power signal in each of the plurality of intervening time interval.