Wireless power transmission system and power transmission device

Patent metadata

Field	Value
Publication number	US-9595834-B2
Application number	US-201514711788-A
Country	US
Kind code	B2
Filing date	May 14, 2015
Priority date	May 27, 2014
Publication date	Mar 14, 2017
Grant date	Mar 14, 2017

Abstract

In a first power transmission period, a power transmission device holds, in a memory, a value indicating a frequency f 0 corresponding to an actual voltage value that matches a requested voltage value, then causes first AC power to be transmitted by using the frequency f 0 , and uses a foreign substance detector to determine whether or not a foreign substance is present. When it is determined that no foreign substance is present, in a second power transmission period, the power transmission device causes the power transmission of the first AC power to be resumed by using the value indicating the frequency f 0 , the value being held in the memory.

First claim

What is claimed is:

1. A power transmission device that transmits first AC power in a noncontact manner to a first resonator of a power receiving device including a power receiving circuit, the first resonator receiving the first AC power, the power receiving circuit converting the first AC power received by the first resonator to first DC power and supplying the first DC power to a load, the power transmission device comprising:
a memory that stores a requested voltage value of the first DC power supplied to the load;
a receiving circuit that receives, from the power receiving device, an actual voltage value of the first DC power supplied to the load;
an inverter that generates and transmits the first AC power to the first resonator via a second resonator;
an oscillator that generates second AC power smaller than the first AC power and transmits the second AC power to the first resonator via a third resonator;
a foreign substance detector that determines whether or not a foreign substance is present between the first resonator and the third resonator based on a physical quantity in the third resonator that changes according to the second AC power; and
power transmission control circuitry operative to:
set a foreign substance detection period in which foreign substance is detected by the foreign substance 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 sequentially to the inverter, in the first power transmission period, frequencies i) from a frequency f 1 of a power transmission voltage in an initial state ii) to a frequency f 2 of the requested voltage value;
cause the inverter to transmit the first AC power at each of the set frequencies;
compare the requested voltage value with the actual voltage value of each of the frequencies, received by the receiving circuit;
store a value indicating a frequency f 0 of the actual voltage value in the memory if the actual voltage value equals to the requested voltage value;
cause the inverter to transmit the first AC power at the frequency f 0 if the actual voltage value equals to the requested voltage value;
cause the inverter to stop the first AC power temporarily after the elapse of a predetermined period of time;
cause the foreign substance detector to determine whether or not the foreign substance is present in the foreign substance detection period; and
cause the inverter to resume a transmission of the first AC power in the second power transmission period by the value indicating the frequency f 0 in the memory if it is determined that the foreign substance is not present within a predetermined period that starts from the stopping of the first AC power and that is regulated to cause the inverter to resume a transmission of the first AC power from the frequency f 1 .

2. The power transmission device according to claim 1 ,
wherein the frequency f 1 is higher than the frequency f 2 .

3. The power transmission device according to claim 1 ,
wherein the frequency f 1 is lower than the frequency f 2 .

4. The power transmission device according to claim 1 ,
wherein, when it is determined that the foreign substance is not present after the predetermined period, the power transmission control circuitry resumes the transmission of the first AC power at the frequency f 1 in the second power transmission period.

5. The power transmission device according to claim 1 ,
wherein the predetermined period is 350 milliseconds specified in a Qi standard of a wireless power consortium (WPC).

6. The power transmission device according to claim 1 ,
wherein the power transmission control circuitry is operative to:
store, in the first power transmission period i) a value indicating a duty ratio of a voltage output from the inverter circuit and ii) the value indicating the frequency f 0 in the memory;
cause the first AC power to be transmitted at the frequency f 0 ; and
cause in the second power transmission period, the transmission of the first AC power to be resumed by using i) the value indicating the frequency f 0 , and ii) the value indicating the duty ratio in the memory.

7. The power transmission device according to claim 1 ,
wherein the foreign substance detector measures the physical quantity in the third resonator that changes according to the second AC power, and determines that a foreign substance is present between the first resonator and the third 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 substance detector measures the physical quantity in the third resonator, and determines whether or not a foreign substance 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 third resonator is i) a voltage that is applied to the third resonator, ii) a current that flows in the third resonator, iii) a frequency that is applied to the third resonator, iv) an input impedance value of the third resonator, or v) an input inductance value of the third resonator.

10. The power transmission device according to claim 1 ,
wherein the first resonator has a parallel resonant circuit including a coil and a capacitor, and
if the physical quantity in the third resonator is an input inductance of the third resonator,
the foreign substance detector is operative to:
measure i) an input inductance value Lin(f 10 ) of the third resonator that is produced when the oscillator is oscillating at the frequency f 10 , and ii) an input inductance value Lin(f 20 ) of the third resonator that is produced when the oscillator is oscillating at the frequency f 20 ;
calculate a coupling coefficient k according to an expression k 2 =1−Lin(f 20 )/Lin(f 10 ): and
determine whether or not the foreign substance 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 resonant circuit including a coil and a capacitor, and
if the physical quantity in the third resonator is an input inductance value of the third resonator,
the foreign substance detector is operative to:
measure i) an input inductance value Lin(f 10 ) of the third resonator that is produced when the oscillator is oscillating at the frequency f 10 , and ii) an input inductance value Lin(f 20 ) of the third resonator that is produced when the oscillator is oscillating at the frequency f 20 ;
calculate a ratio between the Lin(f 10 ) and the Lin(f 20 ); and
determine whether or not the foreign substance 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,
the square of an oscillation frequency of the oscillator is inversely proportional to the input inductance value of the third resonator, when the oscillator is a self-exciting oscillator and when the physical quantity in the third resonator is an input inductance value of the third resonator, and
the foreign substance detector is operative to:
measure the frequency f 10 and the frequency f 20 at which the oscillator is oscillating;
calculate a coupling coefficient k according to an expression k 2 =1−f 10 2 /f 20 2 ; and
determine whether or not a foreign substance is pr

Assignees

• Panasonic Ip Man Co Ltd

Inventors

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

Classifications

• 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

• 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

• H02J50/12 Primary

  of the resonant type · CPC title

• G01V3/10

  using induction coils · CPC title