Power transmission device, wireless power feeding system, and control method

• US 10,075,025 B2
• Filed: 06/19/2013
• Issued: 09/11/2018
• Est. Priority Date: 06/19/2013
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Renesas Electronics Corporation
• Inventors: Ichikawa, Katsuei
• Primary Examiner(s): Gannon, Levi
• Application Number:
  US14/898,830
• Publication Number:
  US 20160141882A1
• Time in Patent Office: 1,910 Days
• Field of Search: 307104
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• 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 7/00045 Authentication, i.e. circuits for checking compatibility between one component, e.g. a battery or a battery charger, and another component, e.g. a power source
• CPC Class Codes: H03H 7/38 Impedance-matching networks
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

The present power transmission device performs a power transmission process for transmitting power in a wireless manner through electromagnetic field resonance coupling using a resonance circuit. In a case where a resonance frequency of the resonance circuit set to be the same as a frequency of a power transmission signal which is output as transmission power is deviated during transmission of the power, the present power transmission device detects a direction in which the resonance frequency is deviated and controls the power transmission process on the basis of a detection result thereof. Consequently, it is possible to determine not only whether or not a foreign substance is present in a power transmission region but also determines whether or not the foreign substance influences wireless power transmission with high accuracy, and thus reliability of the wireless power transmission system can be improved.

Claims

1. A power transmission device which performs a power transmission process for transmitting power in a wireless manner through electromagnetic field resonance coupling using a resonance circuit,

wherein, in a case where a resonance frequency of the resonance circuit set to be the same as a frequency of a power transmission signal which is output as transmission power is deviated during transmission of the power, the power transmission device detects a direction in which the resonance frequency is deviated and controls the power transmission process on the basis of a detection result thereof, and

wherein the power transmission device further determines whether the resonance frequency is deviated by a presence of a non-metallic object.

2. The power transmission device according to claim 1,

wherein whether or not transmission of the power is continued is controlled on the basis of the detection result.

3. The power transmission device according to claim 2,

wherein the power transmission device detects the extent of deviation of the resonance frequency in addition to the direction in which the resonance frequency is deviated.

4. The power transmission device according to claim 1,

wherein the power transmission device controls the power transmission process on the basis of a difference between an amount of reception power which is received by an external device as a power transmission target, and an amount of the transmission power which is transmitted in addition to the detection result.

5. The power transmission device according to claim 2,

wherein transmission of the power is continued in a case where the resonance frequency is deviated in a direction of being heightened, and transmission of the power is stopped in a case where the resonance frequency is deviated in a direction of being lowered.

6. The power transmission device according to claim 3,

wherein, in a case where the resonance frequency is deviated in a direction of being heightened, transmission of the power is stopped if the extent of deviation of the resonance frequency exceeds a predetermined threshold value, and transmission of the power is continued if the extent of deviation of the resonance frequency does not exceed the predetermined threshold value, and in a case where the resonance frequency is deviated in a direction of being lowered, transmission of the power is stopped.

7. The power transmission device according to claim 1, comprising:

a power source unit that generates an AC signal corresponding to the transmission power;

a primary side resonance circuit that includes a primary side resonance coil and a resonance capacitor as a power transmission antenna, and is supplied with power based on the AC signal generated by the power source unit;

a resonance frequency adjustment unit that is provided between the power source unit and the primary side resonance circuit, and adjusts a resonance frequency of the primary side resonance circuit;

a power amount detection unit that detects the magnitude of a reflected power amount of an AC signal which is supplied to the primary side resonance circuit from the power source unit; and

a control unit,

wherein the control unit changes the resonance frequency of the primary side resonance circuit by controlling the resonance frequency adjustment unit, and determines a direction in which the resonance frequency is deviated by determining a direction in which the reflected power amount detected by the power amount detection unit is changed.

8. The power transmission device according to claim 7,

wherein the control unit controls the resonance frequency adjustment unit so that the resonance frequency of the primary side resonance circuit is heightened, determines that the resonance frequency is deviated in a direction in which the resonance frequency becomes higher than the frequency of the power transmission signal in a case where the reflected power amount increases, and determines that the resonance frequency is deviated in a direction in which the resonance frequency becomes lower than the frequency of the power transmission signal in a case where the reflected power amount decreases.

9. The power transmission device according to claim 7,

wherein the control unit controls the resonance frequency adjustment unit so that the resonance frequency of the primary side resonance circuit is lowered, determines that the resonance frequency is deviated in a direction in which the resonance frequency becomes lower than the frequency of the power transmission signal in a case where the reflected power amount increases, and determines that the resonance frequency is deviated in a direction in which the resonance frequency becomes higher than the frequency of the power transmission signal in a case where the reflected power amount decreases.

10. The power transmission device according to claim 7,

wherein the control unit determines a deviation direction of the resonance frequency on the basis of a change direction of the reflected power amount when adjusting the resonance frequency adjustment unit so that the resonance frequency of the primary side resonance circuit is lowered, and a change direction of the reflected power amount when adjusting the resonance frequency adjustment unit so that the resonance frequency of the primary side resonance circuit is heightened.

11. The power transmission device according to claim 7,

wherein the power amount detection unit generates a voltage corresponding to an incident power amount of an AC signal which is supplied from the power source unit to the primary resonance circuit side and a voltage corresponding to a reflected power amount of the AC signal, and

wherein the control unit calculates a voltage standing wave ratio on the basis of the voltage corresponding to the incident power amount and the voltage corresponding to the reflected power amount, generated by the power amount detection unit, and determines a change direction of the reflected power amount on the basis of a calculation result thereof.

12. The power transmission device according to claim 11,

wherein the control unit performs a calculation process of controlling the resonance frequency adjustment unit so as to change the resonance frequency of the primary side resonance circuit in one direction for each unit adjustment amount, thereby sequentially calculating values of the voltage standing wave ratio and also sequentially comparing calculated values before and after the resonance frequency is changed, performs the calculation process by reversing a direction in which the resonance frequency is changed if a calculated value after the resonance frequency is changed is greater than a calculated value before the resonance frequency is changed, and stops the calculation process if a calculated value after the resonance frequency is changed is smaller than a calculated value before the resonance frequency is changed.

13. The power transmission device according to claim 7, further comprising:

a communication antenna; and

a communication unit that controls transmission and reception of data using the communication antenna.

14. A wireless power feeding system comprising:

the power transmission device according to claim 1; and

a power reception device that receives power supplied from the power transmission device in a wireless manner through electromagnetic field resonance coupling using a resonance circuit.

15. The wireless power feeding system according to claim 14,

wherein the power transmission device and the power reception device can perform data communication conforming to an NFC standard, and

wherein the power reception device can perform the data communication and power reception by using a single antenna.

16. A control method for controlling power transmission in a wireless power feeding system which includes a power transmission device and a power reception device and performs transmission and reception of power through electromagnetic field resonance coupling using power transmission side and power reception side resonance circuits which are respectively provided in the power transmission device and the power reception device, the method comprising:

performing by the power transmission device;

setting a resonance frequency of the power transmission side resonance circuit so that the resonance frequency is the same as a frequency of a power transmission signal which is output as transmission power;

starting transmission of the power after setting the resonance frequency; and

detecting a direction in which the resonance frequency is deviated in a case where the resonance frequency, after being set, is deviated during transmission of the power and to control a process related to transmission of the power on the basis of a detection result thereof;

and determining whether the resonance frequency is deviated by a presence of a non-metallic object.

17. The control method according to claim 16,

further comprising:

measuring a reflected power amount of an AC signal supplied to the resonance circuit while changing the resonance frequency of the power transmission side resonance circuit, thereby estimating a resonance frequency which causes the reflected power amount to be smallest, and generating information regarding deviation of the resonance frequency, including a deviation direction of the resonance frequency on the basis of the estimated resonance frequency;

determining the presence or absence of a foreign substance influencing wireless power transmission on the basis of the information regarding deviation of the resonance frequency; and

stopping transmission of the power in a case where it is determined that there is a foreign substance influencing the wireless power transmission, and to continue transmission of the power in a case where there is no foreign substance influencing the wireless power transmission.

18. The control method according to claim 17,

wherein the information regarding deviation includes the extent of deviation of the resonance frequency in addition to a deviation direction of the resonance frequency.

19. The control method according to claim 17,

further comprising:

receiving information, regarding an amount of reception power which is received, at the power transmission device, and

calculating a difference between the amount of reception power and an amount of transmission power which is transmitted from the power transmission device on the basis of the information regarding the reception power, transmitted from the power reception device, and determining the presence or absence of a foreign substance influencing wireless power transmission on the basis of the difference and the deviation information.

20. The control method according to claim 17,

further comprising:

determining that there is a foreign substance which does not influence wireless power transmission in a case where the resonance frequency is deviated in a direction of being heightened, and determining that there is a foreign substance which influences wireless power transmission in a case where the resonance frequency is deviated in a direction of being lowered.