JP5461340B2 - Resonant type wireless power transmission device - Google Patents

Description

  The present invention relates to a resonance type wireless power transmission apparatus that feeds power from a power transmission side device to a power reception side device and transmits information from the power reception side to the power transmission side.

  A power feeding method that does not require a wired connection is used for charging a secondary battery such as a mobile phone or supplying power to a non-contact IC card, an RFID tag, or the like. A typical example of means for realizing this is an electromagnetic induction system. In the electromagnetic induction type wireless power transmission device, coils are arranged on the power transmission side and the power reception side, and when both are close to each other and the magnetic flux of the power transmission side coil passes through the power reception side coil, power is obtained on the power reception side. This detailed principle is described in Non-Patent Document 1. In general, in order to obtain a sufficient transmission efficiency, the electromagnetic induction method is a method in which the transmitting and receiving coils are close to each other to reduce the leakage magnetic flux.

  In such a wireless power transmission device, the power transmission side and the power reception side may communicate with each other for device authentication or the like. Here, a communication line from the power transmission side to the power reception side is called a downlink, and a communication line from the power reception side to the power transmission side is called an uplink. In order to configure a downlink using electromagnetic induction, a method of modulating transmission power is used. To configure an uplink using electromagnetic induction, load modulation is used in which power consumption is changed by connecting / disconnecting a load on the power receiving side, and the change is detected on the power transmission side.

FIG. 8 shows a configuration example of the wireless power transmission apparatus.
In FIG. 8, the power transmission side coil 13 connected to the power source 11 of the power transmission side device 10 and the power reception side coil 22 connected to the load 23 of the power reception side device 20 are electrically coupled by electromagnetic induction. Power is supplied to 23. Further, a switch 25 that is opened and closed by the control unit 26 is inserted between the power reception side coil 22 and the load 23, and the demodulation unit 12 is connected to the power transmission side coil 13. The control unit 26 opens and closes the switch 22 corresponding to the information bits transmitted on the uplink, so that the power consumed by the power receiving side device 20 changes. This is detected by the demodulator 12 of the power transmission side device 10 and the information bits sent from the power reception side device 20 are restored.

  In recent years, a resonance type wireless power transmission apparatus has been proposed that can obtain high power supply efficiency even when the transmission distance is at a certain level (for example, 1 m) (Non-Patent Document 2).

FIG. 9 shows a configuration example of a resonance type wireless power transmission apparatus.
In FIG. 9, the power transmission side resonance coil 14 that is electrically coupled to the power transmission side coil 13 of the power transmission side device 10 by electromagnetic induction, and the power reception side resonance that is electrically coupled to the power reception side coil 22 of the power reception side device 20 by electromagnetic induction. Electric power is transmitted by a resonance phenomenon with the coil 25. Resonance occurs only at specific frequencies. FIG. 10 shows an example of the S parameter (S21). From the figure, it can be seen that the frequency at which the peak is obtained is limited, and that the peak frequency varies depending on the load.

Hiroshi Isobe, “Introduction to contactless IC card design”, Nikkan Kogyo Shimbun. Aristeidis Karalis, J.D.Joannopoulos and Marin Soljacic, 'Efficient wireless non-radiative mid-range energy transfer,' Annals of Physics, Vol.323 Issue 1, pp.34-48, Apr 2007.

  In the resonance type wireless power transmission device of FIG. 9, in the configuration in which information is transmitted from the power receiving side to the power transmitting side, the load receiving device changes the load impedance so that the power receiving device continues to receive power supply even during communication. A load modulation method in which a change is detected by a power transmission side device is considered. Here, when the load impedance is in a plurality of states and the change in the load impedance is small, the information transmitted from the power receiving side device cannot be detected by the power transmitting side device. Further, when the load impedance changes greatly, the frequency at which resonance occurs changes, so that the power supplied to the load when load modulation is performed decreases.

  An object of the present invention is to provide a resonance type wireless power transmission apparatus that can appropriately set the amount of change in load impedance, improve the quality of information transmission, and increase the efficiency of power supply to the load.

The present invention includes a power transmission side resonance coil that is electrically coupled to a power transmission side coil of a power transmission side device by electromagnetic induction, and a power reception side resonance coil that is electrically coupled to a power reception side coil of the power reception side device by electromagnetic induction. In the resonance type wireless power transmission device that uses the resonance phenomenon between the power transmission side devices to transmit the power of the power source side device to the load of the power reception side device, the power reception side device changes the load impedance within a predetermined range by opening and closing the switch. A load impedance changing unit; and a control unit that controls the opening and closing of the switch by associating the change of the load impedance associated with the opening and closing of the switch with the information bit transmitted from the power receiving side device to the power transmitting side device. detecting a change in load impedance corresponding to the information bits to be transmitted from the side apparatus, a demodulation unit for restoring the information bit, the load impedance variation unit includes feeding As the amount of change in reflected power or power factor based on the change in impedance viewed power receiving apparatus from the side coils is within a prescribed value, a structure for varying the load impedance at a predetermined range.

The demodulator is connected in parallel to the power source, and measures the complex voltage and complex current to restore the information bits transmitted from the power receiving device.
The demodulator is connected in series to the power supply, and measures the current to restore the information bits transmitted from the power receiving device.
The demodulator is connected to the power supply via a directional coupler or circulator, and measures the reflected power from each coil to restore the information bits transmitted from the power receiving device.

  The load impedance changing means is configured such that the load impedance is set by increasing or decreasing the resistance connected to the load by opening and closing the switch.

  The load impedance changing means is configured such that the load impedance is set by increasing or decreasing the reactance connected to the load by opening and closing the switch.

  The resonance type wireless power transmission device of the present invention can transmit information bits by changing the load impedance according to the information bits transmitted from the power receiving side device and detecting the change as a current in the power transmission side device. is there. Further, by determining the change amount of the load impedance from the change amount and impedance of the current viewed from the power transmission side device, it is possible to achieve both the transmission quality of information bits and the power reachability. Moreover, the reachability of the power at the time of uplink information transmission can be improved by referring to the impedance viewed from the power transmission side device for each load impedance and determining the frequency and the characteristic impedance of the power source.

It is a figure which shows the structural example of the resonance type wireless power transmission apparatus of Example 1 of this invention. 4 is a diagram illustrating an example of a current at a point A of the power transmission side device 10. FIG. 4 is a diagram illustrating an imaginary part of impedance at A-A ′ of the power transmission side device 10. FIG. 6 is a diagram illustrating a real part of impedance at A-A ′ of the power transmission side device 10. FIG. It is a figure which shows the structural example of the resonance type wireless power transmission apparatus of Example 2 of this invention. It is a figure which shows the structural example of the resonance type wireless power transmission apparatus of Example 3 of this invention. It is a figure which shows the structural example of the resonance-type wireless power transmission apparatus of Example 4 of this invention. It is a figure which shows the structural example of a wireless power transmission apparatus. It is a figure which shows the structural example of a resonance type wireless power transmission apparatus. It is a figure which shows the example of S parameter (S21).

FIG. 1 shows a configuration example of a resonance type wireless power transmission apparatus according to a first embodiment of the present invention.
In FIG. 1, the resonance type wireless power transmission device includes a power transmission side device 10 that is responsible for power transmission and a power reception side device 20 that receives the transmitted power. An information bit is transmitted from the power reception side device 20 to the power transmission side device 10. This is a configuration for transmission. The flow of power and information bits from the power transmission side device 10 to the power reception side device 20 is called down, and the flow of information bits from the power reception side device 20 to the power transmission side device 10 is called up.

  The power transmission side device 10 includes a power source 11, a demodulation unit 12 that restores uplink information bits sent from the power reception side device 20, a power transmission side coil 13, and a power transmission side resonance coil 14. The power receiving side device 20 includes a power receiving side resonance coil 21, a power receiving side coil 22, a load 23, a resistor 24, a switch 25, and a control unit 26. The power transmission side coil 13 and the power transmission side resonance coil 14 are electrically coupled by electromagnetic induction. The power transmission resonance coil 14 and the power reception resonance coil 21 are electrically coupled by resonance. The power receiving side resonance coil 21 and the power receiving side coil 22 are electrically coupled by electromagnetic induction. Thereby, the power from the power source 11 can be transmitted to the load 23.

  The information bits transmitted on the uplink may be for authenticating the power transmission side device 10 and the power reception side device 20, or may be uplink data when the power reception side device 20 is a communication terminal. Here, for the sake of simplicity, the impedance of the load 23 alone is not changed, and the impedance when the right side is viewed from B-B ′ in the figure is referred to as load impedance. The load impedance can take two states by selecting whether or not the resistor 24 is passed by opening and closing the switch 25. The control unit 26 is configured to change the load impedance by opening and closing the switch 25 according to the information bit to be transmitted. However, in the configuration of the present embodiment, the connection to the load 23 is not released regardless of whether the switch 25 is open or closed, so that power supply to the load 23 is continued.

  In the configuration of FIG. 1, the resistor 24 and the switch 25 are connected in parallel, and the resistor 24 and the load 23 are connected in series. However, the resistor 24 and the switch 25 are connected in series, and the resistor 24 and the load 23 are connected. May be connected in parallel. However, the relationship between the information bits transmitted on the uplink and the opening / closing of the switch 25 is reversed.

  Since the power receiving side device 20 and the power transmitting side device 10 are electrically coupled, a change in the load impedance is a change in impedance when the power receiving side device 20 is viewed from AA ′ of the power transmitting side device 10, or a current change. appear. The demodulator 12 can detect this change and restore the information bits transmitted from the power receiving side device 20.

  In the power receiving side device 20, when the switch 25 is closed and the current does not pass through the resistor 24 (when the load impedance is high), the information bit to be transmitted is 0, and when the switch 25 is open and the current passes through the resistor 24 (load impedance Is 1). FIG. 2 shows a time waveform of the current at the point A of the power transmission side device 10, and the current changes in conjunction with the change of the information bit. The demodulator 12 detects this change and restores the information bits transmitted from the power receiving side device 20.

  Here, when the change in the load impedance with respect to the change in the information bits is minute, the change in the current at the point A is also minute, and there is a possibility that an error may occur in decoding due to external noise or the stability of the power source. Therefore, the amount of change in load impedance is determined so that the change in current at point A is at a level sufficient for demodulation.

  On the other hand, when the load impedance changes greatly in the case of information bit 1 under the condition that power can be transmitted without any problem in the case of information bit 0, the impedance when the power receiving side device 20 is viewed from AA ′ changes greatly. . This leads to reflection of power, and power does not reach the load 23. In this case, the amount of change in the load impedance is determined so that the reflected power or the power factor is equal to or less than the specified value. The reflected power can be directly measured using a directional coupler or the like, and the power factor when the power receiving side device 20 is viewed from AA ′ is obtained from the complex voltage between AA ′ and the complex current at point A. .

  The fact that the imaginary part of the impedance when the power receiving device 20 is viewed from A-A ′ is 0 means resonance. Therefore, it is desirable that the imaginary part of the impedance is close to 0 even when the load impedance is changed. It is desirable to set the frequency so that the sign of the imaginary part of the impedance changes between the information bit 0 and the information bit 1, and the imaginary part passes 0 during this time. FIG. 3 shows an example of the imaginary part of the impedance for each information bit in A-A ′. The frequency corresponding to the position of the arrow in the figure is an example in which the imaginary part passes 0 due to a change in information bits. Thereby, both the transmission quality of information bits and the reachability of power can be achieved.

  In addition, it is desirable to achieve impedance matching by making the real part of the impedance in A-A ′ and the characteristic impedance of the power source 11 and the power line equal or close to each other. FIG. 4 shows an example of the real part of the impedance for each information bit in A-A ′. When using the frequency corresponding to the position of the arrow in the figure, the real part of the impedance for each information bit may be set around 50 ohms in the middle. Thereby, both the transmission quality of information bits and the reachability of power can be achieved.

  As described above, uplink information bit transmission is possible while maintaining power supply to the load 23.

FIG. 5 shows a configuration example of the resonance type wireless power transmission apparatus according to the second embodiment of the present invention.
Compared with the first embodiment of FIG. 1, the resistor 24 is replaced with a reactance 27. Other configurations are the same as those of the first embodiment shown in FIG. The reactance 27 refers to a coil or a capacitor that is an element having a reactance component.

  In FIG. 5, the reactance 27 and the switch 25 are connected in parallel, and the reactance 27 and the load 23 are connected in series. However, the reactance 27 and the switch 25 are connected in series, and these are connected in parallel with the load 23. is there.

  Since the operation is the same as that of the first embodiment, a description thereof will be omitted. Note that the resistance component and the reactance component may be changed simultaneously as a change in the load impedance.

  Also in the configuration of the present embodiment, uplink information bit transmission is possible while maintaining power supply to the load 23.

FIG. 6 shows a configuration example of the resonance type wireless power transmission apparatus according to the third embodiment of the present invention.
Compared with the first embodiment of FIG. 1, the demodulator 12 is connected in series with the power supply 11. Other configurations are the same as those of the first embodiment shown in FIG. Note that the resistor 24 may be replaced with a reactance 27 as in the second embodiment.

  Since the operation is the same as that of the first embodiment, a description thereof will be omitted. However, in this configuration, since there is no impedance measurement means, demodulation is performed by detecting a change in current.

  Also in the configuration of the present embodiment, uplink information bit transmission is possible while maintaining power supply to the load 23.

FIG. 7 shows a configuration example of a resonance type wireless power transmission apparatus according to the fourth embodiment of the present invention.
Compared with the first embodiment of FIG. 1, the demodulator 12 is connected to measure the reflected power via the directional coupler 15 or the circulator. Other configurations are the same as those of the first embodiment shown in FIG. Note that the resistor 24 may be replaced with a reactance 27 as in the second embodiment.

  Since the operation is the same as that of the first embodiment, a description thereof will be omitted. However, in this configuration, power in only the reflection direction is extracted, so that demodulation with higher accuracy is possible.

  Also in the configuration of the present embodiment, uplink information bit transmission is possible while maintaining power supply to the load 23.

DESCRIPTION OF SYMBOLS 10 Power transmission side apparatus 11 Power supply 12 Demodulation part 13 Power transmission side coil 14 Power transmission side resonance coil 15 Directional coupler 20 Power reception side apparatus 21 Power reception side resonance coil 22 Power reception side coil 23 Load 24 Resistance 25 Switch 26 Control part

Claims (6)

A resonance phenomenon between a power transmission side resonance coil that is electrically coupled to the power transmission side coil of the power transmission side device by electromagnetic induction, and a power reception side resonance coil that is electrically coupled to the power reception side coil of the power reception side device by electromagnetic induction. In the resonance type wireless power transmission device that transmits the power of the power source of the power transmission side device to the load of the power reception side device,
The power receiving side device includes a load impedance changing means for changing a load impedance within a predetermined range by opening and closing a switch, an information bit transmitted from the power receiving side device to the power transmitting side device, and the load impedance associated with the opening and closing of the switch. A controller that controls the opening and closing of the switch in association with the change,
The power transmission side device includes a demodulator that detects a change in the load impedance corresponding to the information bit transmitted from the power reception side device and restores the information bit .
The load impedance changing means changes the load impedance within a predetermined range so that a change amount of reflected power or power factor based on a change in impedance when the power receiving side device is viewed from the power transmission side coil is within a specified value. resonance type radio power transmission apparatus, characterized in that the arrangement for. In the resonance type wireless power transmission device according to claim 1,
The resonance type wireless power transmission device, wherein the demodulation unit is connected in parallel to the power source, and measures a complex voltage and a complex current to restore the information bit transmitted from the power receiving side device. In the resonance type wireless power transmission device according to claim 1 ,
The resonance type wireless power transmission apparatus, wherein the demodulator is connected in series to the power supply, and measures the current to restore the information bits transmitted from the power receiving apparatus. In the resonance type wireless power transmission device according to claim 1 ,
The demodulator is connected to the power source via a directional coupler or circulator, and measures the reflected power from each coil to restore the information bits transmitted from the power receiving device. A resonance type wireless power transmission device. In the resonance type wireless power transmission device according to any one of claims 1 to 4 ,
The resonance type wireless power transmission device, wherein the load impedance changing means is configured to set the load impedance by increasing / decreasing a resistance connected to the load by opening / closing the switch. In the resonance type wireless power transmission device according to any one of claims 1 to 4 ,
The resonance type wireless power transmission device, wherein the load impedance changing means is configured to set the load impedance by increasing or decreasing reactance connected to the load by opening and closing the switch.

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