POWER TRANSMISSION SYSTEM AND POWER TRANSMISSION DEVICE USED FOR POWER TRANSMISSION SYSTEM

• US 20140375251A1
• Filed: 09/09/2014
• Published: 12/25/2014
• Est. Priority Date: 03/26/2012
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Tsuchiya, Takanori, SAKAI, HIRONORI
• Granted Patent: US 9,948,144 B2
• Time in Patent Office: Days
• US Class Current: 320/107
• CPC Class Codes: H02J 50/05 using capacitive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/50 using additional energy repeaters between transmitting devices and receiving devices
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters

Abstract

A power transmission device wirelessly transmits power to a power receiving device rectifying a voltage received and supplying the voltage to a load circuit. The power transmission device includes a power transmitter that makes capacitance or electromagnetic coupling to the power receiver and transmits electric power to the power receiver, a power supply unit that generates electric power to be transmitted to the power receiving device and supplies the electric power to the power transmitter, a load impedance detector that detects a load impedance of the power receiving device based on an electric signal detected in the power transmission device, and a controller that controls the electric power to be generated by the power supply unit such that an output voltage of the rectifying circuit of the power receiving device is equal to or lower than a predetermined voltage based on a detection result of the load impedance detector.

Claims

1. A power transmission device that wirelessly transmits electric power to a power receiving device having a power receiver with a rectifying circuit that supplies a voltage to a load circuit, the power transmission device comprising:

a power supply unit that generates electric power;

a power transmitter that transmits the electric power to the power receiver by capacitance coupling or electromagnetic coupling;

a load impedance detector configured to detect a load impedance of the power receiving device based on an electric signal detected in the power transmission device; and

a controller configured to control the power supply unit to generate the electric power such that the voltage supplied by the rectifying circuit to the load circuit is equal to or less than a predetermined voltage based on a signal output by the load impedance detector.

2. The power transmission device according to claim 1, wherein the power supply unit includes:

a direct-current (DC) power supply that supplies DC power having a predetermined voltage; and

a power converter that converts the DC power to alternating-current (AC) power and supplies the AC power to the power transmitter.

3. The power transmission device according to claim 2,

wherein the load impedance detector detects a current value of a DC current flowing through the power converter, and

wherein the controller controls a power conversion mode in the power converter to supply the AC power based on the current value detected by the load impedance detector.

4. The power transmission device according to claim 3,

wherein the rectifying circuit supplies DC power to the load circuit of the power receiving device,

wherein the power converter switches ON/OFF the DC voltage supplied by the DC power supply periodically so as to generate an AC voltage, and

wherein the controller controls a duty ratio of the power converter based on the current value detected by the load impedance detector.

5. The power transmission device according to claim 4, wherein the controller determines the duty ratio based on a relation previously defined between a current value of the DC current and the duty ratio.

6. The power transmission device according to claim 1,

wherein the power receiver includes a power receiving-side first electrode and a power receiving-side second electrode, and

wherein the power transmitter includes a power transmission-side first electrode that generates capacitance coupling with the power receiving-side first electrode and a power transmission-side second electrode that generates capacitance coupling with the power receiving-side second electrode.

7. The power transmission device according to claim 6, wherein a voltage of the power transmission-side first electrode is greater than a voltage of the power transmission-side second electrode during power transmission.

8. The power transmission device according to claim 7, wherein the power transmission device further includes a booster transformer with a secondary winding connected to and interposed between the power transmission-side first electrode and the power transmission-side second electrode and a primary winding connected to an output of the power converter.

9. A power transmission system comprising:

a power receiving device including a power receiver and a load circuit; and

a power transmission device including;

a power supply unit that generates electric power;

a power transmitter that transmits the electric power to the power receiver by capacitance coupling or electromagnetic coupling;

a load impedance detector configured to detect a load impedance of the power receiving device based on an electric signal detected in the power transmission device; and

a controller configured to control the power supply unit to generate the electric power such that the voltage supplied to the load circuit is equal to or less than a predetermined voltage based on a signal output by the load impedance detector.

10. The power transmission system according to claim 9, wherein the power receiving device further comprises a rectifying circuit that supplies DC power to the load circuit.

11. The power transmission system according to claim 10, wherein the power supply unit includes:

a direct-current (DC) power supply that supplies DC power having a predetermined voltage; and

a power converter that converts the DC power to alternating-current (AC) power and supplies the AC power to the power transmitter.

12. The power transmission system according to claim 11,

wherein the load impedance detector detects a current value of a DC current flowing through the power converter, and

wherein the controller controls a power conversion mode in the power converter to supply the AC power based on the current value detected by the load impedance detector.

13. The power transmission system according to claim 12,

wherein the power converter switches ON/OFF the DC voltage supplied by the DC power supply periodically so as to generate an AC voltage, and

wherein the controller controls a duty ratio of the power converter based on the current value detected by the load impedance detector.

14. The power transmission system according to claim 13, wherein the controller determines the duty ratio based on a relation previously defined between a current value of the DC current and the duty ratio.

15. The power transmission system according to claim 9, wherein the load circuit includes a voltage stabilization circuit and a secondary battery connected to a secondary side of the voltage stabilization circuit.

16. The power transmission system according to claim 9,

wherein the power receiver includes a power receiving-side first electrode and a power receiving-side second electrode, and

wherein the power transmitter includes a power transmission-side first electrode that generates capacitance coupling with the power receiving-side first electrode and a power transmission-side second electrode that generates capacitance coupling with the power receiving-side second electrode.

17. The power transmission system according to claim 16, wherein a voltage of the power transmission-side first electrode is greater than a voltage of the power transmission-side second electrode during power transmission.

18. The power transmission system according to claim 17, wherein the power transmission device further includes a booster transformer with a secondary winding connected to and interposed between the power transmission-side first electrode and the power transmission-side second electrode and a primary winding connected to an output of the power converter.

19. A power transmission method for wirelessly transmitting electric power from a power transmission device to a power receiving device having a power receiver that supplies a voltage to a load circuit, the method comprising:

generating electric power by a power supply unit;

supplying the electric power to a power transmitter;

detecting a load impedance of the power receiving device based on an electric signal detected in the power transmission device; and

controlling the power supply unit to generate the electric power such that the voltage supplied by the rectifying circuit to the load circuit is equal to or less than a predetermined voltage based on the load impedance.

20. The power transmission method according to claim 19, further comprising:

detecting detects a current value of a direct-current (DC) current flowing through a power converter of the power transmission device; and

controlling a power conversion mode in the power converter to supply alternating-current (AC) power to the power transmitter based on the detected current value of the DC current.