Wireless power transfer system

• US 10,243,406 B2
• Filed: 09/19/2014
• Issued: 03/26/2019
• Est. Priority Date: 05/14/2014
• Status: Active Grant

• Current Assignee: Wqc, Inc.
• Original Assignee: Wqc, Inc.
• Inventors: Ushijima, Masakazu, Yuasa, Hajime, Ogino, Go
• Primary Examiner(s): Shin, Jeffrey M
• Application Number:
  US15/310,222
• Publication Number:
  US 20170149285A1
• Time in Patent Office: 1,649 Days
• Field of Search: None
• CPC Class Codes: H02J 50/12 of the resonant type
• 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

In a wireless power transfer system, a resonant circuit is formed on the secondary coil side, phase information of a resonant current flowing in the resonant circuit is detected, and, based on this phase information, a driving frequency is determined so that the current phase of a driving current flowing in a primary coil slightly delays from the voltage phase, thereby driving the primary coil. A Q valued determined based on a leakage inductance of the secondary coil, a capacitance of a resonant capacitor, and an equivalent load resistance is set to a value greater than or equal to a value determined by Q=2/k² (k is a coupling coefficient).

Claims

1. A wireless power transfer system in which a primary coil connected to a high-frequency power source and a secondary coil connected to a load are disposed so as to be isolated from each other with a coupling coefficient k, thereby supplying power from the primary coil to the secondary coil in a non-contact manner, the system comprising:

a resonance current phase detection means forming a resonance circuit by connecting a resonance capacitor to the secondary coil and configured to detect phase information of a resonance current flowing through the resonance capacitor;

a phase information transfer means configured to transfer the detected phase information without phase delay; and

a driving circuit configured to determine, based on the phase information, a driving frequency so that a current phase of a driving current flowing in the primary coil slightly delays from a voltage phase of a driving voltage applied to the primary coil, thereby driving the primary coil,

wherein a Q value determined based on a leakage inductance of the secondary coil, a capacitance of the resonance capacitor, and an equivalent load resistance on the secondary coil side is set to a value greater than or equal to a value determined by Q=2/k².

5. The wireless power transfer system according to claim 1, comprising a filter configured to remove distortion included in a waveform of the resonance current and to extract only a fundamental wave.

6. The wireless power transfer system according to claim 1,

wherein the driving circuit includes a switching means configured to drive the primary coil, and

wherein the switching means performs power control by changing an on-off duty cycle thereof, turning on the switching means based on the phase information, and turning off the switching means after a lapse of a predetermined time.

7. The wireless power transfer system according to claim 1, wherein the resonance current phase detection means detects the phase information from a current flowing through a small-capacity capacitor connected in parallel to the resonance capacitor.

2. A wireless power transfer system in which a primary coil connected to a high-frequency power source and a secondary coil connected to a load are disposed so as to be isolated from each other with a coupling coefficient k, thereby supplying power from the primary coil to the secondary coil in a non-contact manner, the system comprising:

a resonance current phase detection means forming a resonance circuit by connecting a resonance capacitor to the secondary coil and configured to detect phase information of a resonance current flowing in the secondary coil;

a phase information transfer means configured to transfer the detected phase information without phase delay; and

a driving circuit configured to determine, based on the phase information, a driving frequency so that a current phase of a driving current flowing in the primary coil slightly delays from a voltage phase of a driving voltage applied to the primary coil, thereby driving the primary coil,

wherein a Q value determined based on a leakage inductance of the secondary coil, a capacitance of the resonance capacitor, and an equivalent load resistance on the secondary coil side is set to a value greater than or equal to a value determined by Q=2/k².

3. A wireless power transfer system in which a primary coil connected to a high-frequency power source and a secondary coil connected to a load are disposed so as to be isolated from each other with a coupling coefficient k, thereby supplying power from the primary coil to the secondary coil in a non-contact manner, the system comprising:

a resonance current phase detection means forming a resonance circuit by connecting a resonance capacitor to the secondary coil and configured to detect, from the primary coil, phase information of a resonance current flowing in the resonance circuit;

a phase information transfer means configured to transfer the detected phase information without phase delay; and

a driving circuit configured to determine, based on the phase information, a driving frequency so that a current phase of a driving current flowing in the primary coil slightly delays from a voltage phase of a driving voltage applied to the primary coil, thereby driving the primary coil,

wherein a Q value determined based on a leakage inductance of the secondary coil, a capacitance of the resonance capacitor, and an equivalent load resistance on the secondary coil side is set to a value greater than or equal to a value determined by Q=2/k².

4. A wireless power transfer system in which a primary coil connected to a high-frequency power source and a secondary coil connected to a load are disposed so as to be isolated from each other with a coupling coefficient k, thereby supplying power from the primary coil to the secondary coil in a non-contact manner, the system comprising:

a resonance current phase detection means forming a resonance circuit by connecting a resonance capacitor to the secondary coil and configured to detect phase information of a resonance current based on a waveform obtained by superimposing and combining one of a waveform of a resonance current flowing through the resonance capacitor, a waveform of a resonance current flowing in the secondary coil, and a waveform of a resonance current flowing in the primary coil, and an inverted integrated waveform of the one of the waveforms;

a phase information transfer means configured to transfer the detected phase information without phase delay; and

a driving circuit configured to determine, based on the phase information, a driving frequency so that a current phase of a driving current flowing in the primary coil slightly delays from a voltage phase of a driving voltage applied to the primary coil, thereby driving the primary coil,

wherein a Q value determined based on a leakage inductance of the secondary coil, a capacitance of the resonance capacitor, and an equivalent load resistance on the secondary coil side is set to a value greater than or equal to a value determined by Q=2/k².

8. A wireless power transfer system including a primary coil connected to a high-frequency power source, a secondary coil connected to a load, and a third coil disposed close to the secondary coil or including the secondary coil as an autotransformer and wound so as to step down a voltage induced in the secondary coil, wherein the primary coil and the secondary coil are disposed so as to be isolated from each other with a coupling coefficient k, thereby supplying power from the primary coil to the third coil via the secondary coil in a non-contact manner, the system comprising:

a resonance current phase detection means forming a resonance circuit by connecting a resonance capacitor to the secondary coil and configured to detect phase information of a resonance current flowing through the resonance capacitor;

a phase information transfer means configured to transfer the detected phase information without phase delay; and

a driving circuit configured to determine, based on the phase information, a driving frequency so that a current phase of a driving current flowing in the primary coil slightly delays from a voltage phase of a driving voltage applied to the primary coil, thereby driving the primary coil,

wherein a Q value determined based on a leakage inductance of the secondary coil, a capacitance of the resonance capacitor, and an equivalent load resistance on the secondary coil side is set to a value greater than or equal to a value determined by Q=2/k².

12. The wireless power transfer system according to claim 8, comprising a filter configured to remove distortion included in a waveform of the resonance current and to extract only a fundamental wave.

13. The wireless power transfer system according to claim 8,

wherein the driving circuit includes a switching means configured to drive the primary coil, and

wherein the switching means performs power control by changing an on-off duty cycle thereof, turning on the switching means based on the phase information, and turning off the switching means after a lapse of a predetermined time.

14. The wireless power transfer system according to claim 8, wherein the resonance current phase detection means detects the phase information from a current flowing through a small-capacity capacitor connected in parallel to the resonance capacitor.

9. A wireless power transfer system including a primary coil connected to a high-frequency power source, a secondary coil connected to a load, and a third coil disposed close to the secondary coil or included in an autotransformer including the secondary coil, the third coil being wound so as to step down a voltage induced in the secondary coil, wherein the primary coil and the secondary coil are disposed so as to be isolated from each other with a coupling coefficient k, thereby supplying power from the primary coil to the secondary coil in a non-contact manner, the system comprising:

a resonance current phase detection means forming a resonance circuit by connecting a resonance capacitor to the secondary coil and configured to detect phase information of a resonance current flowing in the secondary coil;

a phase information transfer means configured to transfer the detected phase information without phase delay; and

a driving circuit configured to determine, based on the phase information, a driving frequency so that a current phase of a driving current flowing in the primary coil slightly delays from a voltage phase of a driving voltage applied to the primary coil, thereby driving the primary coil,

wherein a Q value determined based on a leakage inductance of the secondary coil, a capacitance of the resonance capacitor, and an equivalent load resistance on the secondary coil side is set to a value greater than or equal to a value determined by Q=2/k².

10. A wireless power transfer system including a primary coil connected to a high-frequency power source, a secondary coil connected to a load, and a third coil disposed close to the secondary coil or included in an autotransformer including the secondary coil, the third coil being wound so as to step down a voltage induced in the secondary coil, wherein the primary coil and the secondary coil are disposed so as to be isolated from each other with a coupling coefficient k, thereby supplying power from the primary coil to the secondary coil in a non-contact manner, the system comprising:

a resonance current phase detection means forming a resonance circuit by connecting a resonance capacitor to the secondary coil and configured to detect, from the primary coil, phase information of a resonance current flowing in the resonance circuit;

a phase information transfer means configured to transfer the detected phase information without phase delay; and

a driving circuit configured to determine, based on the phase information, a driving frequency so that a current phase of a driving current flowing in the primary coil slightly delays from a voltage phase of a driving voltage applied to the primary coil, thereby driving the primary coil,

wherein a Q value determined based on a leakage inductance of the secondary coil, a capacitance of the resonance capacitor, and an equivalent load resistance on the secondary coil side is set to a value greater than or equal to a value determined by Q=2/k².

11. A wireless power transfer system including a primary coil connected to a high-frequency power source, a secondary coil connected to a load, and a third coil disposed close to the secondary coil or included in an autotransformer including the secondary coil, the third coil being wound so as to step down a voltage induced in the secondary coil, wherein the primary coil and the secondary coil are disposed so as to be isolated from each other with a coupling coefficient k, thereby supplying power from the primary coil to the secondary coil in a non-contact manner, the system comprising:

a resonance current phase detection means forming a resonance circuit by connecting a resonance capacitor to the secondary coil and configured to detect phase information of a resonance current based on a waveform obtained by superimposing and combining one of a waveform of a resonance current flowing through the resonance capacitor, a waveform of a resonance current flowing in the secondary coil, and a waveform of a resonance current flowing in the primary coil, and an inverted integrated waveform of the one of the waveforms;

a phase information transfer means configured to transfer the detected phase information without phase delay; and

a driving circuit configured to determine, based on the phase information, a driving frequency so that a current phase of a driving current flowing in the primary coil slightly delays from a voltage phase of a driving voltage applied to the primary coil, thereby driving the primary coil,

wherein a Q value determined based on a leakage inductance of the secondary coil, a capacitance of the resonance capacitor, and an equivalent load resistance on the secondary coil side is set to a value greater than or equal to a value determined by Q=2/k².