Impedance transformation network for improved driver circuit performance

• US 10,122,214 B2
• Filed: 10/19/2015
• Issued: 11/06/2018
• Est. Priority Date: 03/25/2011
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Low, Zhen Ning, Wheatley, III, Charles Edward
• Primary Examiner(s): Poos, John
• Application Number:
  US14/887,049
• Publication Number:
  US 20160043574A1
• Time in Patent Office: 1,114 Days
• Field of Search: 307104
• CPC Class Codes: H02J 5/00 Circuit arrangements for transfer of electric power between ac networks and dc networks H02J3/36 takes precedence
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• 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
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H03H 11/28 Impedance matching networks
• CPC Class Codes: H03H 3/00 Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
• CPC Class Codes: H03H 7/38 Impedance-matching networks
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer
• CPC Class Codes: Y02D 30/70 in wireless communication networks
• CPC Class Codes: Y10T 29/49016 Antenna or wave energy "plumbing" making

Abstract

This disclosure provides systems, methods and apparatus for reducing harmonic emissions. One aspect of the disclosure provides a transmitter apparatus. The transmitter apparatus includes a driver circuit characterized by an efficiency and a power output level. The driver circuit further includes a filter circuit electrically connected to the driver circuit and configured to modify the impedance of the transmit circuit to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit when the impedance is within the complex impedance range. The filter circuit is further configured to maintain a substantially constant power output level irrespective of the reactive variations within the complex impedance range. The filter circuit is further configured to maintain a substantially linear relationship between the power output level and the resistive variations within the impedance range.

Claims

1. A transmitter device, comprising:

a driver circuit characterized by an efficiency, the driver circuit electrically connected to a transmit circuit having an impedance, the impedance of the transmit circuit within a complex impedance range including resistive and reactive variations, the complex impedance range defined by a minimum real impedance value, and a maximum real impedance, a ratio between the minimum and maximum real impedance value being at least two to one; and

a filter circuit electrically connected to the driver circuit and configured to modify the impedance of the transmit circuit to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit when the impedance is within the complex impedance range, the filter circuit further configured to maintain a substantially constant power output level irrespective of the reactive variations within the complex impedance range.

2. The transmitter device of claim 1, wherein the ratio is one of at least five to one and at least ten to one.

3. The transmitter device of claim 2, wherein the minimum real impedance value comprises 8 ohms and the maximum real impedance value comprises 80 ohms.

4. The transmitter device of claim 1, wherein the ratio is a first ratio, wherein the range is further defined by a first imaginary impedance value and a second imaginary impedance value, wherein a second ratio of a first magnitude of a difference between the first imaginary impedance and the second imaginary impedance value to a second magnitude of a difference between the minimum real impedance value and the maximum real impedance value is substantially equal to at least one of one to two, two to three, one to one, three to two, and two to one.

5. The transmitter device of claim 4, wherein the minimum real impedance value is substantially four ohms, wherein the maximum real impedance value is substantially forty ohms, wherein the first imaginary impedance value is substantially negative four ohms, and wherein the second imaginary impedance value is substantially 50 ohms.

6. The transmitter device of claim 1, wherein the transmit circuit comprises a transmit coil electrically connected to the output of the filter circuit, the transmit coil configured to wirelessly transmit power to charge or power a receiver device.

7. The transmitter device of claim 1, wherein the transmit circuit is configured to wirelessly transmit power to charge or power a plurality of receiver devices, wherein each of the plurality of receiver devices is configured to cause a change in the impedance when positioned to wirelessly receive power from the transmit circuit.

8. The transmitter device of claim 1, wherein the driver circuit comprises a class E amplifier circuit.

9. The transmitter device of claim 1, wherein the impedance of the transmit circuit comprises a reactance that is substantially zero before the impedance is modified.

10. A method of adjusting an impedance of a driver circuit characterized by an efficiency, the driver circuit electrically connected to a transmit circuit having an impedance, the impedance of the transmit circuit within a complex impedance range including resistive and reactive variations, the complex impedance range defined by a minimum real impedance value and a maximum real impedance, a ratio between the minimum and maximum real impedance value being at least two to one, the method comprising:

modifying the impedance to maintain the efficiency of the driver circuit at a level that is within 20% of a maximum efficiency of the driver circuit when the impedance is within the complex impedance range, and to maintain a substantially constant power output level irrespective of the reactive variations within the complex impedance range.

11. The method of claim 10, wherein a value of the modified impedance comprises a complex value comprising a real part corresponding to a resistance value and an imaginary part corresponding to a non-zero reactance value.

12. The method of claim 10, wherein modifying comprises modifying using a filter circuit comprising at least one of a low pass filter, a high pass filter, or any combination thereof.

13. The method of claim 12, wherein the low pass filter comprises a 3-pole Butterworth filter with a 3 dB bandwidth of an operating frequency of the driver circuit.

14. The method of claim 12, wherein a cutoff frequency of the filter circuit is higher or lower than an operating frequency of the driver circuit.

15. The method of claim 10, further comprising substantially removing harmonic components of the signal generated by the driver circuit operating at an operating frequency.

16. The method of claim 10, wherein an amount of power provided to the transmit circuit increases as an amount of a resistive portion of the impedance increases.

17. The method of claim 10, wherein a first magnitude of the impedance at which a maximum power amount is output by the driver circuit is higher than a second magnitude of the impedance at which maximum efficiency of the driver circuit is provided.

18. The method of claim 10, wherein modifying the impedance comprises modifying using a filter circuit comprising a ladder network of reactive circuits, each of the reactive circuits comprising a combination of reactive components.

19. The transmitter device of claim 10, wherein modifying comprises modifying using a filter circuit and an impedance adjustment element configured to cause a reactive shift of a transformed impedance produced by the filter circuit.

20. A transmitter device, comprising:

means for driving characterized by an efficiency, the means for driving electrically connected to a transmit circuit having an impedance, the impedance of the transmit circuit within a complex impedance range including resistive and reactive variations, the complex impedance range defined by a minimum real impedance value, and a maximum real impedance, a ratio between the minimum and maximum real impedance value being at least two to one; and

means for filtering electrically connected to the means for driving and configured to modify the impedance to maintain the efficiency of the driving means at a level that is within 20% of a maximum efficiency of the driving means when the impedance is within the complex impedance range, the means for filtering further configured to maintain a substantially constant power output level irrespective of the reactive variations within the complex impedance range.

21. An apparatus for wirelessly transmitting power, comprising:

a transmit circuit characterized by a first impedance and configured to generate a magnetic field for wirelessly transferring power to one or more receiver devices to power or charge respective loads of the one or more receiver devices positioned within the magnetic field, the first impedance varying over a first range in response at least in part to changes in a number of the one or more receiver devices positioned within the magnetic field;

a driver circuit configured to drive the transmit circuit with a time-varying signal to cause the transmit circuit to generate the magnetic field;

a passive filter circuit comprising one or more reactive components having respective reactance values selected to transform the first impedance presented to the passive filter circuit by the transmit circuit within the first range to a second impedance presented to the driver circuit by the passive filter circuit that has a complex impedance value that is within a second range of complex impedance values corresponding to a range of complex impedance values that maintains an efficiency level of the driver circuit above a threshold efficiency value, the passive filter circuit further configured to maintain a substantially constant power output level irrespective of the reactive variations within the complex impedance range.

22. The apparatus of claim 21, wherein the threshold efficiency value corresponds to an efficiency level that is within 20% of a maximum efficiency of the driver circuit.

23. The apparatus of claim 21, wherein the first range corresponds to a range of real impedance values between 8 ohms and 80 ohms.

24. The apparatus of claim 21, wherein the first range corresponds to a range of complex impedance having a real impedance range between four ohms and forty ohms and an imaginary impedance range between negative 4j ohms and substantially 50j ohms.

25. The apparatus of claim 21, wherein the driver circuit comprises a class E amplifier circuit.

26. The apparatus of claim 21, wherein the complex impedance value comprises a real part corresponding to a resistance value and an imaginary part corresponding to a non-zero reactance value.

27. The apparatus of claim 21, wherein the passive filter circuit comprises a 3-pole Butterworth filter with a 3 dB bandwidth of an operating frequency of the driver circuit.

28. The apparatus of claim 21, wherein the passive filter circuit is further configured to substantially remove harmonic components of a signal generated by the driver circuit operating at an operating frequency.

29. The apparatus of claim 21, further comprising an impedance adjustment element configured to cause a reactive shift between the driver circuit and the passive filter circuit.