WIRELESS POWER TRANSMISSION SYSTEM

• US 20120274149A1
• Filed: 04/23/2012
• Published: 11/01/2012
• Est. Priority Date: 04/26/2011
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Management Co., Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: KANNO, Hiroshi, YAMAMOTO, Hiroshi
• Granted Patent: US 9,620,995 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 50/20 using microwaves or radio frequency waves
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices

Abstract

A wireless power transmission system according to the present disclosure includes: a pair of antennas, between which power is transmissible wirelessly by resonant magnetic coupling at a frequency f0, one of which is a series resonant circuit, and the other of which is a parallel resonant circuit; and a control section, which controls a transmission frequency according to the magnitude of the power being transmitted between the antennas. If the power transmitted between the antennas is greater than a reference value P1, the control section sets the transmission frequency to be a value that falls within a first level range that is higher than the frequency f0. But if the power is smaller than the reference value P1, then the control section sets the transmission frequency to be a value that falls within a second level range that is lower than the first level range.

Claims

1. A wireless power transmission system comprising:

a pair of antennas configured to transmit power wirelessly by resonant magnetic coupling at a frequency f0, one of the pair of antennas being a series resonant circuit, and the other of the pair of antennas being a parallel resonant circuit; and

a control section configured to control a transmission frequency according to the magnitude of the power being transmitted between the antennas,

wherein if the power is greater than a reference value P1, the control section sets the transmission frequency to be a value that falls within a first level range that is higher than the frequency f0, and if the power is smaller than the reference value P1, the control section sets the transmission frequency to be a value that falls within a second level range that is lower than the first level range.

2. The wireless power transmission system of claim 1, wherein if the power has changed from a value that is greater than the reference value P1 into a value that is smaller than the reference value P1, or if the power has changed from a value that is smaller than the reference value P1 into a value that is greater than the reference value P1, the control section makes the transmission frequency hop between a value falling within the first level range and a value falling within the second level range.

3. The wireless power transmission system of claim 2, wherein when making the transmission frequency hop, the control section changes the modes of a resonant magnetic field that couples the pair of antennas from an even mode into an odd mode, and vice versa.

4. The wireless power transmission system of claim 1, wherein if the power to be transmitted is smaller than the reference value P1 and greater than a second reference value P2 that is smaller than the reference value P1, the control section sets the transmission frequency to be equal to or lower than a frequency f2 that is lower than the frequency f0, and if the power to be transmitted is smaller than the second reference value P2, the control section sets the transmission frequency to be higher than the frequency f2.

5. The wireless power transmission system of claim 1, wherein the first level range starts at the frequency f0 and ends at the resonant frequency fH of the even mode, and

wherein the second level range starts at the resonant frequency fL of the odd mode and ends at the frequency f0.

7. The wireless power transmission system of claim 1, wherein the resonant frequency formed by the pair of antennas is equal to the frequency f0.

8. The wireless power transmission system of claim 1, wherein the coupling coefficient k of the pair of antennas is kept constant while the power is being transmitted.

9. The wireless power transmission system of claim 1, wherein the reference value P1 is set to be 60% through 80% of a maximum transmission power Pmax.

10. The wireless power transmission system of claim 1, wherein if the maximum value of the transmission frequency is identified by ftrmax and the resonant frequency of the even mode is identified by fH and if the power is greater than the reference value P1,

then the control section sets the maximum value ftrmax of the transmission frequency so that Rhigh defined by the equation

Rhigh=(ftrmax−

f0)÷

(fH−

f0)×

100

falls within the range of 18% to 56%.

11. The wireless power transmission system of claim 1 wherein if the minimum value of the transmission frequency is identified by ftrmin and the resonant frequency of the odd mode is identified by fL and if the power is smaller than the reference value P1,

then the control section sets the minimum value ftrmin of the transmission frequency so that Rlow defined by the equation

Rlow=(f0−

ftrmin)=(f0−

fL)×

100

falls within the range of 21% to 45%.

12. The wireless power transmission system of claim 1, wherein when one of the two antennas that is located at a power receiving end has its output terminal connected to a load that follows the antenna, the output impedance Zoc of an oscillator that applies RF energy to the other antenna at a power transmitting end and the input impedance Zin of the antenna at the power transmitting end are equal to each other.

13. The wireless power transmission system of claim 1, wherein when the output terminal of an oscillator that applies RF energy to one of the two antennas that is located at a power transmitting end is connected to the input terminal of the antenna at the power transmitting end, the output impedance Zout of the other antenna at a power receiving end and the input impedance of a load that follows the antenna are equal to each other.

6. The wireless power transmission system of claim wherein if the power to be transmitted is equal to the reference value P1, the control section sets the transmission frequency to be equal to the frequency f0.