Wireless power transmission system and power transmission device of wireless power transmission system

Patent metadata

Field	Value
Publication number	US-10097047-B2
Application number	US-201715628772-A
Country	US
Kind code	B2
Filing date	Jun 21, 2017
Priority date	May 27, 2014
Publication date	Oct 9, 2018
Grant date	Oct 9, 2018

Abstract

A power transmission device includes an inverter using a frequency f11 lower than a frequency f0 between a first resonator and a second resonator or a frequency f12 higher than the frequency f0 to generate a first power; an oscillator using a frequency f10 lower than a frequency fr between the first resonator and the second resonator or a frequency f20 higher than the frequency fr to generate a second power; and a power transmission control circuitry setting a foreign object detection period between first and second transmission periods, using the frequency f11 or frequency f12 in the first transmission period, using the frequency f10 or frequency f20 in the foreign object detection period, and if it is determined that a substance is present in the foreign object detection period, transmitting power in the second transmission period at a frequency different from the frequency used in the first transmission period.

First claim

What is claimed is:

1. A power transmission device that transmits first AC power wirelessly to a power receiving device having a first resonator, the first resonator receiving the first AC power, the power transmission device comprising:
a second resonator that electromagnetically couples with the first resonator to transmit the first AC power to the first resonator;
an inverter that generates the first AC power by using either a frequency f11 or a frequency f12, the frequency f11 being lower than a first resonance frequency f0 between the first resonator and the second resonator, and the frequency f12 being higher than the first resonance frequency f0;
an oscillator that generates second AC power by using either a frequency f10 or a frequency f20, the frequency f10 being lower than a second resonance frequency fr between the first resonator and the second resonator, the frequency f20 being higher than the second resonance frequency fr;
a foreign object detector that determines whether or not a foreign object is present between the first resonator and the second resonator based on a physical quantity in the second resonator that changes according to the second AC power of either the frequency f10 or the frequency f20; and
a power transmission control circuitry configured to:
set a foreign object detection period in which the foreign object is detected by the foreign object detector, between i) a first power transmission period in which the first AC power is transmitted from the second resonator to the first resonator and ii) a second power transmission period subsequent to the first power transmission period;
set, to the inverter, one of the frequency f11 or the frequency f12 in the first power transmission period; and
set, to the inverter, other of the frequency f11 or the frequency f12 in the second power transmission period if it is determined that the foreign object is present in the foreign object detection period.

2. The power transmission device according to claim 1 , wherein,
if it is determined that the foreign object is not present in the foreign object detection period, the power transmission control circuitry sets to the inverter, in the second power transmission period, the frequency f11 or the frequency f12 that is same frequency as frequency used in the first power transmission period, and causes the inverter to start to transmit the first AC power at the set one of the frequency f11 and the frequency f12.

3. The power transmission device according to claim 1 , wherein,
if it is determined that the foreign object is present in the foreign object detection period when the frequency f11 is used in the first power transmission period and the frequency f10 is used in the foreign object detection period, the power transmission control circuitry sets to the inverter, the frequency f12 in the second power transmission period, and causes the inverter to start to transmit the first AC power at the frequency f12.

4. The power transmission device according to claim 2 , wherein,
if it is determined that the foreign object is not present in the foreign object detection period when the frequency f11 is used in the first power transmission period and the frequency f10 is used in the foreign object detection period, the power transmission control circuitry sets to the inverter, the frequency f11 in the second power transmission period, and causes the inverter to start to transmit the first AC power at the frequency f11.

5. The power transmission device according to claim 1 , wherein,
if it is determined that the foreign object is present in the foreign object detection period when the frequency f12 is used in the first power transmission period and the frequency f20 is used in the foreign object detection period, the power transmission control circuitry sets to the inverter, the frequency f11 in the second power transmission period, and causes the inverter to start to transmit the first AC power at the frequency f11.

6. The power transmission device according to claim 2 , wherein,
if it is determined that the foreign object is not present in the foreign object detection period when the frequency f12 is used in the first power transmission period and the frequency f20 is used in the foreign object detection period, the power transmission control circuitry sets to the inverter, the frequency f12 in the second power transmission period, and causes the inverter to start to transmit the first AC power at the frequency f12.

7. The power transmission device according to claim 1 , wherein
the foreign object detector measures the physical quantity in the second resonator that changes according to the second AC power, and determines that a foreign object is present between the first resonator and the second resonator when a difference between the physical quantity after having changed and a prescribed reference value is greater than a preset threshold value.

8. The power transmission device according to claim 1 , wherein
the foreign object detector measures the physical quantity in the second resonator, and determines whether or not a foreign object is present, based on a value calculated from the measured physical quantity.

9. The power transmission device according to claim 8 , wherein
the physical quantity in the second resonator is i) a voltage that is applied to the second resonator, ii) a current that flows in the second resonator, iii) a frequency that is applied to the second resonator, iv) an input impedance value of the second resonator, or v) an input inductance value of the second resonator.

10. The power transmission device according to claim 1 , wherein
the first resonator has a parallel resonance circuit including a coil and a capacitor, and,
if the physical quantity in the second resonator is an input inductance of the second resonator,
the foreign object detector is configured to;
measure i) an input inductance value Lin(f10) of the second resonator that is produced when the oscillator is oscillating at the frequency f10 and ii) an input inductance value Lin(f20) of the second resonator that is produced when the oscillator is oscillating at the frequency f20;
calculate a coupling coefficient k according to an expression k 2 =1−Lin(f20)/Lin(f10): and
determine whether or not the foreign object is present based on the calculated coupling coefficient k.

11. The power transmission device according to claim 1 , wherein
the first resonator has a parallel resonance circuit including a coil and a capacitor, and,
if the physical quantity in the second resonator is an input inductance value of the second resonator,
the foreign object detector is configured to:
measure i) an input inductance value Lin(f10) of the second resonator that is produced when the oscillator is oscillating at the frequency f10 and ii) an input inductance value Lin(f20) of the second resonator that is produced when the oscillator is oscillating at the frequency f20;
calculate a ratio between the Lin(f10) and the Lin(f20); and
determine whether or not the foreign object is present based on the calculated ratio.

12. The power transmission device according to claim 1 , wherein
the first resonator has a parallel resonance circuit including a coil and a capacitor,
squaring of an oscillation frequency of the oscillator is inversely proportional to an input inductance value of the second resonator, when the oscillator is a self-exciting oscillator and when the physical quantity in the second resonator is the input inductance value of the second resonator, and
the foreign object detector is configured to:
measure the frequency f10 and the frequency f20 at which the oscillato

Assignees

• Panasonic Ip Man Co Ltd

Inventors

• Yamamoto Hiroshi
• Asanuma Kenichi
• Sakata Tsutomu
• Kanno Hiroshi

Classifications

• H02J50/12 Primary

  of the resonant type · CPC title

• H02J50/60

  responsive to the presence of foreign objects, e.g. detection of living beings · CPC title

• H02J50/70

  involving the reduction of electric, magnetic or electromagnetic leakage fields · CPC title

• G01V3/101

  by measuring the impedance of the search coil; by measuring features of a resonant circuit comprising the search coil (measuring impedance or characteristics derived therefrom G01R27/00, e.g. quality factor G01R27/26) · CPC title

• G01V3/10

  using induction coils · CPC title