WIRELESS CHARGING SYSTEMS, DEVICES, AND METHODS

• US 20140266019A1
• Filed: 03/13/2013
• Published: 09/18/2014
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: John M. Pigott
• Inventors: PIGOTT, JOHN M.
• Granted Patent: US 9,667,084 B2
• Time in Patent Office: Days
• US Class Current: 320/108
• CPC Class Codes: H01M 2220/30 Batteries in portable systems, e.g. mobile phone, laptop
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/007192 in response to temperature
• CPC Class Codes: H02J 7/04 Regulation of charging current or voltage
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A wireless charging system includes a power transmitting device and a power receiving device. In the transmitting device, a transmitting coil converts a drive signal from a drive signal circuit into an alternating magnetic field. In the receiving device, a receiving coil produces an alternating waveform from the magnetic field, and a rectifier rectifies the alternating waveform to deliver power having a rectified voltage. A modulation circuit causes a loading circuit to be coupled to and uncoupled from the receiving coil at a pre-determined modulation rate when, for example, the rectified voltage is greater than a threshold voltage. Back in the transmitting device, a modulation detector circuit detects modulation of the load impedance, and when the load impedance is modulating at the pre-determined modulation rate, causes the drive signal circuit to adjust a characteristic of the drive signal, resulting in an adjustment in an intensity of the magnetic field.

Claims

1. A power receiving device comprising:

a receiving coil configured to produce an input alternating waveform from a received alternating magnetic field emanating from a source external to the power receiving device;

a rectifier coupled to the receiving coil and configured to rectify the input alternating waveform in order to deliver, at an output of the rectifier, power having a rectified voltage;

a loading circuit configured to be selectively coupled to the receiving coil, wherein the power receiving device presents a first load impedance when the loading circuit is uncoupled from the receiving coil, and the power receiving device presents a different, second load impedance when the loading circuit is coupled to the receiving coil; and

a modulation circuit coupled to the output of the rectifier, wherein the modulation circuit is configured to cause the loading circuit to be coupled to and uncoupled from the receiving coil at a pre-determined modulation rate when the rectified voltage and a first threshold voltage have a first inequality relationship.

2. The device of claim 1, wherein the modulation circuit is further configured to compare the rectified voltage with one or more threshold voltages, to cause the loading circuit to be coupled to and uncoupled from the receiving coil at the pre-determined modulation rate when the rectified voltage and the first threshold voltage have the first inequality relationship, and to refrain from causing the loading circuit to be coupled to and uncoupled from the receiving coil at the pre-determined modulation rate when the rectified voltage and a second threshold voltage have a different second inequality relationship, wherein the first and second threshold voltages may be a same voltage or different voltages.

3. The device of claim 1, wherein:

the modulation circuit produces a modulation signal at the pre-determined modulation rate when the rectified voltage is greater than the first threshold voltage, and the modulation circuit refrains from producing the modulation signal when the rectified voltage is less than the first threshold voltage; and

the loading circuit includes a switch that functions to couple and uncouple impedance affecting components of the loading circuit with the receiving coil in response to the modulation signal.

4. The device of claim 3, wherein the impedance affecting components include one or more components selected from one or more capacitors, one or more inductors, one or more resistors, and one or more diodes.

5. The device of claim 1, wherein a reference voltage equal to the first threshold voltage is provided to the modulation circuit, and wherein the modulation circuit comprises:

a comparator configured to compare the rectified voltage with the first threshold voltage, and to produce a modulation enable signal having a state that reflects whether the rectified voltage is greater than or less than the first threshold voltage; and

a modulator configured to produce a modulation signal that oscillates between first and second signal levels at the pre-determined modulation rate when the modulation enable signal indicates that the rectified voltage is greater than the first reference voltage, and to refrain from producing the modulation signal when the modulation enable signal indicates that the rectified voltage is less than the first reference voltage, wherein the loading circuit is coupled to the receiving coil when the modulation signal has the first signal level, and the loading circuit is not coupled to the receiving coil when the modulation signal has the second signal level.

6. The device of claim 5, wherein the power receiving device further comprises:

a voltage regulator coupled to the output of the rectifier, wherein the voltage regulator is configured to regulate the rectified voltage to a regulation voltage at an output node when the regulator is operating in a regulated operational region, and wherein the regulation voltage is less than the first threshold voltage.

7. The device of claim 6, wherein the regulation voltage is in a range of 4.5 volts to 5.5 volts, and the first threshold voltage is in a range of 5.5 volts to 10 volts.

8. The device of claim 6, wherein the power receiving device is a portable device, and the power receiving device further comprises:

a battery charging system, wherein the output terminal is coupled to the battery charging system to provide charge to a battery coupled to the battery charging system.

9. The device of claim 1, wherein the power receiving device further comprises:

a temperature sensor configured to detect a temperature within the power receiving device, and to provide a control signal to the modulation circuit when the temperature exceeds a temperature threshold, and

wherein the modulation circuit causes the loading circuit to be coupled to and uncoupled from the receiving coil at a second modulation rate in response to receiving the control signal from the temperature sensor, where the second modulation rate may be the same as or different from the pre-determined modulation rate.

10. The device of claim 1, wherein the power receiving device is a portable device that receives operational power from a battery, and the power receiving device is selected from a hearing aid, wireless headphones, a wireless speaker, a wireless earbud device, an in-ear headphone, a remote control device, a joystick, a wireless keyboard, a wireless cursor control device, a watch, a keyfob, and a portable consumer device.

11. A power transmitting device comprising:

a drive signal circuit configured to produce a time-varying drive signal;

a transmitting coil coupled to the drive signal circuit, and configured to receive the time-varying drive signal and to convert the time-varying drive signal into an alternating magnetic field that emanates from the power transmitting device; and

a modulation detector circuit coupled to the transmitting coil and to the drive signal circuit, wherein the modulation detector circuit is configured to detect modulation of a load impedance that is magnetically coupled with the transmitting coil, to determine whether the load impedance is modulating at a pre-determined modulation rate, and when the load impedance is modulating at the pre-determined modulation rate, to cause the drive signal circuit to adjust a characteristic of the time-varying drive signal, which results in an adjustment in an intensity of the magnetic field emanating from the power transmitting device.

12. The device of claim 11, wherein the modulation detector circuit is configured to detect the modulation of the load impedance by detecting a type of modulation selected from modulation of a load current through the transmitting coil, modulation of a relative phase shift of the load current with respect to the time-varying drive signal, and modulation of a resonant amplitude of the time-varying drive signal.

13. The device of claim 11, wherein, in order to adjust the intensity of the magnetic field, the drive signal circuit adjusts a characteristic of the time-varying drive signal that is selected from a duty cycle of the time-varying drive signal, a frequency of the drive signal, and a voltage level of the time-varying drive signal.

14. The device of claim 11, wherein, when the load impedance is modulating at the pre-determined modulation rate, the modulation detector circuit is configured to cause the drive signal circuit to adjust the characteristic in a manner that causes a decrease the intensity of the magnetic field emanating from the power transmitting device.

15. The device of claim 14, wherein:

as long as the load impedance is modulating at the pre-determined modulation rate, the modulation detector circuit is configured to cause the drive signal circuit to adjust the characteristic of the time-varying drive signal by an increment upon expiration of each of a series of sequential time periods in order incrementally to decrease the intensity of the magnetic field down to a minimum value.

16. A system comprising:

a power transmitting device, which includes

a drive signal circuit configured to produce a time-varying drive signal,

a transmitting coil coupled to the drive signal circuit, and configured to receive the time-varying drive signal and to convert the time-varying drive signal into an alternating magnetic field that emanates from the power transmitting device, and

a modulation detector circuit coupled to the transmitting coil and to the drive signal circuit, wherein the modulation detector circuit is configured to detect modulation of a load impedance that is magnetically coupled with the transmitting coil, to determine whether the load impedance is modulating at a pre-determined modulation rate, and when the load impedance is modulating at the pre-determined modulation rate, to cause the drive signal circuit to adjust a characteristic of the time-varying drive signal, which results in an adjustment in an intensity of the magnetic field emanating from the power transmitting device; and

a power receiving device, which includes

a receiving coil configured to produce an input alternating waveform from the alternating magnetic field emanating from the power transmitting device,

a rectifier coupled to the receiving coil and configured to rectify the input alternating waveform in order to deliver power at an output of the rectifier,

a loading circuit configured to be selectively coupled to the receiving coil, wherein the power receiving device presents a first load impedance when the loading circuit is uncoupled from the receiving coil, and the power receiving device presents a different, second load impedance when the loading circuit is coupled to the receiving coil, and

a modulation circuit coupled to the output of the rectifier, wherein the modulation circuit is configured to cause the loading circuit to be coupled to and uncoupled from the receiving coil at the pre-determined modulation rate when the rectified voltage and a first threshold voltage have a first inequality relationship.

17. A wireless charging method performed by a power receiving device, the method comprising:

producing, by a receiving coil, an input alternating waveform from a received alternating magnetic field emanating from a source external to the power receiving device;

rectifying the input alternating waveform in order to deliver power having a rectified voltage;

comparing the rectified voltage with a first threshold voltage; and

causing a loading circuit to be coupled to and uncoupled from the receiving coil at a pre-determined modulation rate when the rectified voltage and a first threshold voltage have a first inequality relationship, wherein the power receiving device presents a first load impedance when the loading circuit is uncoupled from the receiving coil, and the power receiving device presents a different, second load impedance when the loading circuit is coupled to the receiving coil.

18. The method of claim 17, further comprising:

comparing the rectified voltage with a second threshold voltage, wherein the first and second threshold voltages may be a same threshold voltage or different threshold voltages; and

refraining from causing the loading circuit to be coupled to and uncoupled from the receiving coil at the pre-determined modulation rate when the rectified voltage and the second threshold voltage have a different second inequality relationship.

19. The method of claim 17, further comprising:

producing a modulation signal that oscillates between first and second signal levels at the pre-determined modulation rate when the rectified voltage is greater than the first threshold voltage; and

refraining from producing the modulation signal when the rectified voltage is less than the first threshold voltage, wherein

the loading circuit includes a switch that functions to couple impedance affecting components of the loading circuit to the receiving coil when the modulation signal has the first signal level, and to uncouple the impedance affecting components from the receiving coil when the modulation signal has the second signal level.

20. The method of claim 17, further comprising:

detecting a temperature within the power receiving device;

determining whether the temperature exceeds a temperature threshold; and

causing the loading circuit to be coupled to and uncoupled from the receiving coil at a second modulation rate in response to determining that the temperature exceeds the temperature threshold, where the second modulation rate may be the same as or different from the pre-determined modulation rate.

21. A wireless charging method performed by a power transmitting device, the method comprising:

providing a time-varying drive signal to a transmitting coil;

converting, by the transmitting coil, the time-varying drive signal into an alternating magnetic field that emanates from the power transmitting device;

detecting modulation of a load impedance that is magnetically coupled with the transmitting coil;

determining whether the load impedance is modulating at a pre-determined modulation rate; and

when the load impedance is modulating at the pre-determined modulation rate, adjusting a characteristic of the time-varying drive signal that results in an adjustment in an intensity of the magnetic field that emanates from the power transmitting device.

22. The method of claim 21, wherein detecting modulation of the load impedance comprises detecting a type of modulation selected from modulation of a load current through the transmitting coil, modulation of a relative phase shift of the load current with respect to the time-varying drive signal, and modulation of a resonant amplitude of the time-varying drive signal.

23. The method of claim 21, wherein adjusting the characteristic of the time-varying drive signal comprises adjusting a characteristic of the time-varying drive signal that is selected from a duty cycle of the time-varying drive signal, a frequency of the drive signal, and a voltage level of the time-varying drive signal.

24. The method of claim 21, wherein, when the load impedance is modulating at the pre-determined modulation rate, adjusting the characteristic of the time-varying drive signal comprises adjusting the characteristic in a manner that causes a decrease in the intensity of the magnetic field emanating from the power transmitting device.

25. The method of claim 24, wherein as long as the load impedance is modulating at the pre-determined modulation rate, adjusting the characteristic of the time-varying drive signal comprises adjusting the characteristic by an increment upon expiration of each of a series of sequential time periods in order incrementally to decrease the intensity of the magnetic field emanating from the power transmitting device down to a minimum value.