TUNABLE RESONANT INDUCTIVE COIL SYSTEMS FOR WIRELESS POWER TRANSFER AND NEAR FIELD COMMUNICATIONS

• US 20160276877A1
• Filed: 03/17/2016
• Published: 09/22/2016
• Est. Priority Date: 03/17/2015
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: WEALE, Gareth Pryce
• Granted Patent: US 10,164,483 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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: H04B 5/26 using coils
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A tunable resonant inductive coil system includes an electrical circuit having an alternating current (AC) voltage source, a barium strontium titanate (BST) variable capacitor coupled in series with a first terminal of the AC voltage source, a coil coupled in series with the BST variable capacitor, and a return line coupling the coil with a second terminal of the AC voltage source and/or a ground. The electrical circuit forms an LC circuit (resonant circuit). The electrical circuit adjusts between two configurations. In the first configuration the resonant circuit has a first resonant frequency configured for wireless power transfer and in the second configuration it has a second resonant frequency configured for near field communication (NFC). An entire length of the coil is used for both resonant frequencies. Adjusting between the first and second configurations includes varying a capacitance of the BST variable capacitor in response to receiving a control signal.

Claims

1. A tunable resonant inductive coil system, comprising:

an electrical circuit comprising an alternating current (AC) voltage source, a barium strontium titanate (BST) variable capacitor coupled in series with a first terminal of the AC voltage source, a coil coupled in series with the BST variable capacitor, and a return line coupling the coil with one of a second terminal of the AC voltage source and a ground;

wherein the electrical circuit forms an LC circuit (resonant circuit);

wherein the electrical circuit is configured to, in response to receiving one or more electrical signals, adjust between a first configuration and a second configuration, wherein in the first configuration the resonant circuit has a first resonant frequency configured to be used for wireless power transfer and in the second configuration the resonant circuit has a second resonant frequency configured to be used for near field communication (NFC), wherein an entire length of the coil is used for both the first resonant frequency and the second resonant frequency, and;

wherein adjusting the electrical circuit between the first configuration and the second configuration comprises varying a capacitance of the BST variable capacitor in response to receiving a control signal at the BST variable capacitor.

2. The system of claim 1, wherein the coil comprises an antenna.

3. The system of claim 1, wherein adjusting the electrical circuit between the first configuration and the second configuration comprises one of opening and closing a switch of the electrical circuit to one of electrically couple a fixed capacitor with the resonant circuit and electrically isolate the fixed capacitor from the resonant circuit.

4. The system of claim 1, further comprising a second BST variable capacitor coupled in series with the coil on the return line.

5. The system of claim 4, further comprising a fixed capacitor coupled in parallel with the second BST variable capacitor and coupled in series between the coil and one of the second terminal of the AC voltage source and the ground.

6. The system of claim 1, further comprising a fixed capacitor coupled in series between the first terminal of the AC voltage source and the coil.

7. The system of claim 1, further comprising a fixed capacitor coupled in series between the coil and one of the second terminal of the AC voltage source and the ground.

8. The system of claim 1, further comprising a fixed capacitor coupled in parallel with the BST variable capacitor and in series between the first terminal of the AC voltage source and the coil.

9. The system of claim 1, wherein the first resonant frequency is between 5.800 MHz and 7.525 MHz and wherein the second resonant frequency is between 9.625 MHz and 14.850 MHz.

10. A tunable resonant inductive coil system, consisting of:

an electrical circuit consisting of an alternating current (AC) voltage source;

one or more barium strontium titanate (BST) variable capacitors, at least one of the one or more BST variable capacitors coupled in series with a first terminal of the AC voltage source;

a coil coupled in series with the first terminal of the AC voltage source;

a return line coupling the coil with one of a second terminal of the AC voltage source and a ground;

a switch coupled with the AC voltage source;

a direct current (DC) voltage source controlling the switch, and;

one or more additional passive electrical components;

wherein the electrical circuit forms an LC circuit (resonant circuit);

wherein the electrical circuit is configured to, in response to receiving one or more electrical signals, adjust between a first configuration and a second configuration by one of opening and closing the switch and by correspondingly varying a capacitance of the one or more BST variable capacitors, wherein in the first configuration the resonant circuit has a first resonant frequency configured to be used for wireless power transfer and in the second configuration the resonant circuit has a second resonant frequency configured to be used for near field communication (NFC), and;

wherein an entire length of the coil is used for both the first resonant frequency and the second resonant frequency.

11. A method of use of a tunable resonant inductive coil system, comprising:

providing an electrical circuit, the electrical circuit comprising an alternating current (AC) voltage source having a first terminal, a variable capacitor electrically coupled in series with the first terminal of the AC voltage source, a coil electrically coupled in series with the variable capacitor, and a return line electrically coupling the coil with one of a second terminal of the AC voltage source and a ground, the electrical circuit comprising an LC circuit (resonant circuit);

in response to the electrical circuit receiving a control signal at the variable capacitor, adjusting a capacitance of the variable capacitor to adjust a resonant frequency of the resonant circuit between a first resonant frequency configured to be used for wireless power transfer and a second resonant frequency configured to be used for near field communication (NFC), and;

using an entire length of the coil for both the first resonant frequency and the second resonant frequency.

12. The method of claim 11, wherein adjusting the resonant frequency between the first resonant frequency and the second resonant frequency comprises one of adjusting the resonant frequency from a lower value to a higher value and adjusting the resonant frequency from the higher value to the lower value, wherein the lower value is between 5.800 MHz and 7.525 MHz and wherein the higher value is between 9.625 MHz and 14.850 MHz.

13. The method of claim 11, wherein the variable capacitor comprises a barium strontium titanate (BST) variable capacitor.

14. The method of claim 11, wherein the coil comprises an antenna.

15. The method of claim 11, wherein the variable capacitor does not comprise a switched capacitor, does not comprise a varactor diode, and does not comprise a trimmer capacitor.

16. The method of claim 11, wherein adjusting the resonant frequency between the first resonant frequency and the second resonant frequency comprises one of opening and closing a switch of the electrical circuit.

17. The method of claim 16, wherein one of opening and closing the switch electrically couples a fixed capacitor in parallel with the coil.

18. The method of claim 11, further comprising tuning the capacitance of the variable capacitor to adjust one of the first resonant frequency and the second resonant frequency in response to the resonant circuit being out of resonance with a second resonant circuit of a computing device.

19. The method of claim 18, wherein tuning the capacitance of the variable capacitor comprises one of adjusting the first resonant frequency from a first value to a second value and adjusting the second resonant frequency from a third value to a fourth value, wherein the first value and the second value are between 5.800 MHz and 7.525 MHz and wherein the third value and the fourth value are between 9.625 MHz and 14.850 MHz.

20. The method of claim 11, wherein the electrical circuit comprises a near field communication (NFC) chip coupled with the resonant circuit and wherein adjusting the resonant frequency to the second resonant frequency protects the NFC chip from wireless power transfer signals from a power source by detuning the resonant circuit from the wireless power transfer signals.