Impedance matching device and control method

• US 9,276,553 B2
• Filed: 04/22/2015
• Issued: 03/01/2016
• Est. Priority Date: 06/07/2011
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Pioneer Corporation
• Inventors: Suzuki, Masami
• Primary Examiner(s): Lee, Benny
• Assistant Examiner(s): Dieujuste, Albens
• Application Number:
  US14/692,790
• Publication Number:
  US 20150229289A1
• Time in Patent Office: 314 Days
• Field of Search: 333/17.1, 333/17.3, 333/32, 455/41.1
• US Class Current: 1/1
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 50/10 using inductive coupling
• 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: H03H 7/40 Automatic matching of load impedance to source impedance
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

In an impedance matching device, a storage unit stores a control value representing a load value and a value equivalent to input impedance in advance. The control value identifies inductance and capacitance values matching a predetermined impedance value by use of either a first or second matching circuit. An impedance estimation unit estimates input impedance of the power transmission antenna. The load value estimation unit estimates load value of a circuit connected to a power reception antenna and consuming transmitted electric power. A circuit selection unit electrically connects the first matching circuit, the second matching circuit, or a through circuit per the load value and the input impedance equivalent value. A control value output unit reads out the control value stored in the storage unit based on the load value and the input impedance equivalent value, and outputs the control value to the circuit selected by the circuit selection unit.

Claims

1. An impedance matching device included in a wireless electric power transmission system in accordance with electromagnetic field resonant coupling, the impedance matching device being provided between a power transmission circuit and a power transmission antenna, the impedance matching device comprising:

a matching circuit configured to perform impedance matching between the transmission circuit and the transmission antenna;

an impedance measuring unit configured to measure impedance of the transmission antenna;

a storage unit configured to store control values determined based on a locus of variation of an impedance of the transmission antenna in a condition that a coupling state between the transmission antenna and a reception antenna is changed, the reception antenna receiving a wireless electric power signal sent from the transmission antenna, the locus of the variation of the impedance being specific to the electromagnetic field resonant coupling;

a readout position determination unit configured to read out one of the control values stored on the storage unit based on an output of the impedance measuring unit; and

a control value output unit configured to apply the control value read out by the readout position determination unit to the matching circuit.

2. The impedance matching device according to claim 1,

wherein the matching circuit includes a first matching circuit, a second matching circuit, a switch unit and a matching circuit selection unit, the first matching circuit including a first variable inductor element and a first variable capacitor element, the first variable inductor element being connected in series between the transmission circuit and the transmission antenna, the first variable capacitor element being shunted closer to the transmission antenna than the first variable inductor element, the second matching circuit including a second variable inductor element and a second variable capacitor element, the second variable inductor element being connected in series between the transmission circuit and the transmission antenna, the second variable capacitor element being shunted closer to the transmission circuit than the second variable inductor element, the switch unit electrically connecting either the first matching circuit or the second matching circuit to the transmission circuit and the transmission antenna, the matching circuit selection unit controlling the switch unit based on the output of the impedance measuring unit.

3. The impedance matching device according to claim 2, further comprising:

a through circuit connected in series between the power transmission circuit and the power transmission antenna,

wherein the switch unit electrically connects one circuit selected from the group consisting of the first matching circuit, the second matching circuit, and the through circuit to the power transmission circuit and the power transmission antenna.

4. A control method executed by an impedance matching device included in a wireless electric power transmission system in accordance with electromagnetic field resonant coupling, the impedance matching device being provided between a power transmission circuit and a power transmission antenna, the impedance matching device being equipped with a matching circuit and a storage unit, the matching circuit being configured to perform impedance matching between the transmission circuit and the transmission antenna, the storage unit being configured to store control values determined based on a locus of variation of an impedance of the transmission antenna in a condition that a coupling state between the transmission antenna and a reception antenna is changed, the locus of the variation of the impedance being specific to the electromagnetic field resonant coupling, the control method comprising:

an impedance measuring process to measure the impedance of the transmission antenna;

a readout position determination process to read out one of the control values stored on the storage unit based on an output of the impedance measuring process; and

a control value output process to apply the control value read out by the readout position determination process to the matching circuit.