TRANSMITTER AND RECEIVER TUNING IN A WIRELESS CHARGING SYSTEM

• US 20120169133A1
• Filed: 06/01/2011
• Published: 07/05/2012
• Est. Priority Date: 12/29/2010
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Lisi, Gianpaolo, Socci, Gerard G., Kiaei, Ali, Mahmodieh, Kosha, Djabbari, Ali
• Granted Patent: US 9,077,192 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices

Abstract

A transmitter includes an alternating current power source with tunable parameters. A tunable parameter may be capacitance, inductance, or frequency.

A metric related to power transfer from the transmitter through a coil is used to determine an amount to modify a parameter. One metric is equal to |Vs|·|Is|·cos(φ), where |Vs| is magnitude of the power source voltage, |Is| is magnitude of the power source current, and φ is phase difference between the power source voltage and power source current. Another metric is equal to |Vs|·|Is|·cos(φ)·(Vcoil_ref/Vcoil), where |Vs| is magnitude of the power source voltage, |Is| is magnitude of the power source current, φ is phase difference between the power source voltage and power source current, Vcoil_ref is a normalization value, and Vcoil is voltage across the coil.

The transmitter may further include a phase tracking and adjustment loop; for example, a phase-locked loop (PLL).

Claims

1. An apparatus, comprising:

an alternating current power source including tunable parameters;

a metric heuristic for determining the value of a metric, the metric related to power transfer from the apparatus through a transmitter coil; and

a tuning heuristic which, based on the value of the metric, determines an amount to modify a parameter of the apparatus.

2. The apparatus of claim 1, the metric being equal to |Vs|·

|Is|·

cos(φ

), where |Vs| is the magnitude of the power source voltage, |Is| is the magnitude of the power source current, and φ

is the phase difference between the power source voltage and the power source current.

3. The apparatus of claim 2, the power source current being limited.

4. The apparatus of claim 1, the metric being equal to |Vs|·

|Is|cos(φ

)·

(Vcoil_ref/Vcoil), where |Vs| is the magnitude of the power source voltage, |Is| is the magnitude of the power source current, φ

is the phase difference between the power source voltage and power source current, Vcoil_ref is a normalization value, and Vcoil is the voltage across the transmitter coil.

5. The apparatus of claim 1, the tuning heuristic determining a capacitance value for tuning a capacitor of the power source.

6. The apparatus of claim 1, the tuning heuristic determining an inductance value for tuning an inductor of the power source.

7. The apparatus of claim 1, the tuning heuristic determining an inductance value for tuning the transmitter coil.

8. The apparatus of claim 1, the tuning heuristic determining a frequency value for tuning the frequency of the power source.

9. The apparatus of claim 1, further comprising:

an oscillator providing a periodic signal;

a pulse width modulator controlling the frequency of the power source based on the periodic signal provided by the oscillator;

a phase detector detecting the difference between the phase of the power source voltage and the phase of the power source current; and

a frequency tuning heuristic determining from the phase of the power source an amount to adjust the oscillator.

10. The apparatus of claim 9, the oscillator, the pulse width modulator, the phase detector, and the frequency tuning heuristic being implemented as a phase-locked loop (PLL).

11. The apparatus of claim 1, a tunable parameter of the power source being duty cycle of an output of the power source, the duty cycle being adjusted to control transmitter magnetic field intensity and thereby adjust the amount of power being transferred.

12. A method, comprising:

providing alternating current power to a transmitter with tunable parameters;

calculating the value of a metric, the metric being related to power transfer through a coil of the transmitter; and

determining an amount to modify a parameter of the transmitter.

13. The method of claim 12, the metric being equal to |Vs|·

|Is|·

cos(φ

), where |Vs| is the magnitude of the power source voltage, is the magnitude of the power source current, and φ

is the phase difference between the power source voltage and power source current.

14. The method of claim 13, further comprising limiting power source current.

15. The method of claim 12, the metric being equal to |Vs|·

|Is|·

cos(φ

)·

(Vcoil_ref/Vcoil), where |Vs| is the magnitude of the power source voltage, |Is| is the magnitude of the power source current, φ

is the phase difference between the power source voltage and power source current, Vcoil_ref is a normalization value, and Vcoil is the voltage across the transmitter coil.

16. The method of claim 12, further comprising determining a capacitance value for tuning a capacitor of the power source.

17. The method of claim 12, further comprising determining an inductance value for tuning an inductor of the power source.

18. The method of claim 12, further comprising determining an inductance value for tuning the transmitter coil.

19. The method of claim 12, further comprising determining a frequency value for tuning the frequency of the power source.

20. The method of claim 12, further comprising adjusting the frequency of the power source based on the difference between the phase of the power source voltage and the phase of the power source current.

21. The method of claim 20, adjusting the frequency of the power source using a phase-locked loop (PLL).

22. The method of claim 12, a tunable parameter being a duty cycle of an output of a power source, and adjusting the duty cycle being to control transmitter magnetic field intensity and thereby adjusting the amount of power being transferred.