WIRELESS POWER TRANSMITTER

• US 20130002034A1
• Filed: 01/03/2012
• Published: 01/03/2013
• Est. Priority Date: 09/18/2009
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Onizuka, Kohei, Ueno, Takeshi
• Granted Patent: US 9,190,850 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• 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 50/80 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: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems

Abstract

According to one embodiment, a wireless power transmitter wirelessly transmits power to a power receiving apparatus which includes a first resonance circuit and a load circuit. The first resonance circuit includes a power receiving coil and a first capacitor. The wireless power transmitter comprises a second resonance circuit that includes a power transmission coil and a second capacitor and transmits the signal generated by a power supply to the power receiving apparatus, a measuring unit that measures a signal reflection coefficient, and a controller. The controller detects a value of an oscillation frequency of the power supply making the signal reflection coefficient smaller than or equal to a threshold value, calculates an electromagnetic coupling coefficient between the power transmission coil and the power receiving coil, and controls one of the oscillation frequency and a capacitance value of the second capacitor based on the electromagnetic coupling coefficient.

Claims

1. A wireless power transmitter for wirelessly transmittting a signal to a power receiving apparatus having a first resonance circuit and a load circuit, wherein the first resonance circuit includes a power receiving coil and a first capacitor, the wireless power transmitter comprising:

a power supply that has a variable oscillation frequency and generates a signal having the oscillation frequency;

a second resonance circuit that includes a power transmission coil and a second capacitor and transmits the signal to the power receiving apparatus;

a measuring unit that measures a signal reflection coefficient based on magnitude of the signal and magnitude of a signal reflected on the second resonance circuit to the power supply; and

a controller that detects a value of the oscillation frequency making the signal reflection coefficient smaller than or equal to a threshold value, calculates an electromagnetic coupling coefficient between the power transmission coil and the power receiving coil based on the detected value, and controls either one of an oscillation frequency and a capacitance value of the second capacitor based on the electromagnetic coupling coefficient.

2. The wireless power transmitter according to claim 1, further comprising:

a transmitter that transmits a control signal to the power receiving apparatus so that the control signal indicates change of a capacitance value for the first capacitor and/or a parameter for the load circuit, wherein the controller generates the capacitance value and/or the parameter based on the electromagnetic coupling coefficient.

3. The wireless power transmitter according to claim 2,

wherein the controller controls a capacitance value for one of the first capacitor and the second capacitor so that a frequency range includes the oscillation frequency making the signal reflection coefficient smaller than or equal to the threshold value.

4. The wireless power transmitter according to claim 3,

wherein the controller controls a parameter for the load circuit so as to increase a difference between a maximum value and a minimum value for the signal reflection coefficient.

5. The wireless power transmitter according to claim 2,

wherein the controller generates a second control signal before assigning values to the oscillation frequency so as to change resonance characteristics of a semiconductor device for power transmission and reception having a third resonance circuit and a second load circuit, the third resonance circuit being provided with a coil and a capacitor;

wherein the second control signal allows the semiconductor device to perform one of;

changing one of an inductance value for the coil and a capacitance value for the capacitor; and

one of short-circuiting and opening a switch provided for the coil; and

wherein the transmitter transmits the second control signal to the semiconductor device.