Wireless power supply apparatus

• US 8,217,535 B2
• Filed: 03/24/2010
• Issued: 07/10/2012
• Est. Priority Date: 03/31/2009
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Uchida, Akiyoshi, Taguchi, Masakazu
• Primary Examiner(s): Wallis, Michael Rutland
• Application Number:
  US12/730,459
• Publication Number:
  US 20100244580A1
• Time in Patent Office: 839 Days
• Field of Search: 307/104, 320/108
• US Class Current: 307/104
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment

Abstract

A wireless power supply includes: a power transmitting coil resonant at a first resonant frequency that generates a magnetic field resonance, a power receiving coil resonant at the first resonant frequency, a power receiving unit that outputs energy received by the power receiving resonant coil; a distance detector that detects a distance between the power transmitting resonant coil and the power receiving resonant coil; a power transmitting frequency controller that changes the first resonant frequency to a second resonant frequency on the basis of the distance detected by the distance detector; and a power receiving frequency controller that changes the first resonant frequency of the power receiving resonant coil from the first resonant frequency to a second resonant frequency on the basis of the distance detected by the distance detector.

Claims

1. A wireless power supply apparatus, comprising:

a power supply unit configured to supply electric power;

a power transmitting resonant coil configured to be able to resonate in a magnetic field with a power receiving resonant coil at a first resonant frequency that generates a magnetic field resonance, and transmit the electric power supplied from the power supply unit as a magnetic field energy by using the magnetic field resonance;

a power receiving resonant coil configured to be able to resonate in a magnetic field with the power transmitting resonant coil at the first resonant frequency, and receive the magnetic field energy transmitted from the power transmitting resonant coil by using the magnetic field resonance;

a power receiving unit configured to output the magnetic field energy received by the power receiving resonant coil as electric power;

a distance detector configured to detect a distance between the power transmitting resonant coil and the power receiving resonant coil;

a power transmitting frequency controller configured to change the first resonant frequency of the power transmitting resonant coil from the first resonant frequency to a second resonant frequency on the basis of the distance detected by the distance detector, the power transmitting frequency controller being provided for the power transmitting resonant coil; and

a power receiving frequency controller configured to change the first resonant frequency of the power receiving resonant coil from the first resonant frequency to a second resonant frequency on the basis of the distance detected by the distance detector, the power receiving frequency controller being provided for the power receiving resonant coil.

2. The wireless power supply apparatus according to claim 1 comprising a switch that inhibits resonance, wherein the wireless power supply apparatus transmits the electric power between the power supply unit and the power transmitting resonant coil by using electromagnetic induction, and transmits the electric power between the power receiving resonant coil and the power receiving unit by using electromagnetic induction.

3. The wireless power supply apparatus according to claim 1,

wherein, when the electric power is transmitted over the distance between the power transmitting resonant coil and the power receiving resonant coil, and when the distance is in an area in which transmission efficiency increases as the distance increases,

the power transmitting frequency controller sets the second resonant frequency of the power transmitting resonant coil to a value determined on the basis of the distance, and the power receiving frequency controller sets the second resonant frequency of the power receiving resonant coil to a value determined on the basis of the distance, which is the same value as that of the second resonant frequency of the power transmitting resonant coil, and

thereby the wireless power supply apparatus transmits the electric power as a magnetic field energy between the power transmitting resonant coil and the power receiving resonant coil by using the magnetic field resonance.

4. The wireless power supply apparatus according to claim 3,

wherein the power transmitting frequency controller sets the second resonant frequency of the power transmitting resonant coil to a value selected from a plurality of values set in advance on the basis of the distance, and

the power receiving frequency controller sets the second resonant frequency of the power receiving resonant coil to a value selected from a plurality of values set in advance on the basis of the distance, which is the same value as that of the second resonant frequency of the power transmitting resonant coil.

5. The wireless power supply apparatus according to claim 1,

wherein, when the electric power is transmitted over the distance between the power transmitting resonant coil and the power receiving resonant coil, and when the distance is in an area in which transmission efficiency decreases as the distance increases,

the power transmitting frequency controller sets the resonant frequency of the power transmitting resonant coil to the first resonant frequency, and the power receiving frequency controller sets the resonant frequency of the power receiving resonant coil to the first resonant frequency, and thereby the wireless power supply apparatus transmits the electric power as a magnetic field energy between the power transmitting resonant coil and the power receiving resonant coil by using the magnetic field resonance.

6. The wireless power supply apparatus according to claim 1,

wherein, the power transmitting resonant coil includes an inductor and a capacitor,

the power receiving resonant coil includes an inductor and a capacitor, and

when the distance between the power transmitting resonant coil and the power receiving resonant coil is in an area in which the electric power may be transmitted between the power transmitting resonant coil and the power receiving resonant coil by using electromagnetic induction,

the power transmitting frequency controller sets a capacitance of the capacitor of the power transmitting resonant coil to 0, and the power receiving frequency controller sets a capacitance of the capacitor of the power receiving resonant coil to 0, and thereby the wireless power supply apparatus transmits the electric power between the power transmitting resonant coil and the power receiving resonant coil by using the electromagnetic induction.

7. A wireless power supply apparatus, comprising:

a power supply unit configured to supply electric power with a first resonant frequency;

a power transmitting coil configured to transmit the electric power by converting the electric power into magnetic field energy;

a power transmitting resonant circuit configured to be able to change a power transmitting resonance characteristic, the power transmitting resonant circuit including the power transmitting coil;

a power transmitting frequency controller configured to change the power transmitting resonance characteristic of the power transmitting resonant circuit;

a power receiving coil configured to receive the magnetic field energy and convert the magnetic field energy into electric power;

a power receiving resonant circuit configured to be able to change a power receiving resonance characteristic, the power receiving resonant circuit including the power receiving coil;

a power receiving frequency controller configured to change the power receiving resonance characteristic of the power receiving resonant circuit; and

a detector configured to detect a relative relationship between the power transmitting coil and the power receiving coil,

wherein the power transmitting resonance characteristic and the power receiving resonance characteristic have a plurality of resonance characteristics which include a first resonating characteristic that resonates at the first resonant frequency and a second resonating characteristic that resonates at a second resonant frequency different from the first resonant frequency, and

the power transmitting frequency controller and the power receiving frequency controller switch the resonance characteristics of the power transmitting resonant circuit and the power receiving resonant circuit between the first resonating characteristic and the second resonating characteristic.