JP2012060730A - Resonant wireless power transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable transmission of information from the power receiving side to power transmitting side on a resonant wireless power transmission device that transmits power from a power supply of the power transmitting device to a load of the power receiving device.SOLUTION: A power receiving device has means of changing load impedance within a predetermined range by turning on and off a switch, and a controller that on-off controls the switch with association of transmission data to be transmitted from the power receiving device to a power transmitting device with the change of the load impedance. The power transmitting device has a demodulator that detects the change of a current or a voltage that occurs in response to change of the load impedance corresponding to the transmission data, and reconstructs the transmission data. The controller of the power receiving device transmits a signal known to the power receiving device and the power transmitting device. The demodulator of the power transmitting device detects the presence or absence of bit inversion from the reconstructed known signal, and outputs the following transmission data after bit inversion when bit inversion is detected.

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. In order to configure an uplink using electromagnetic induction, load modulation is used in which the load impedance is changed 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 changes the load impedance of the power receiving side device 20 by turning on and off the switch 25 in response to transmission data transmitted on the uplink. The demodulator 12 of the power transmission side device 10 detects this as a change in current or voltage, and restores the transmission data transmitted from the power reception side device 20.

  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) of the resonance coil. It can be seen from the figure that the frequency at which the peak is obtained is limited, and that the peak frequency varies depending on the load. Further, the peak frequency varies depending on the interval between the power transmission side device 10 and the power reception side device 20.

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.

  Also in the resonance type wireless power transmission apparatus shown in FIG. 9, transmission data can be transmitted from the power receiving side to the power transmitting side by load modulation that changes the load impedance on the power receiving side. At this time, it is necessary to match the power supply frequency on the power transmission side with the resonance frequency, but even in that case, depending on the installation conditions such as the distance between the power transmission side device and the power reception side device, the load impedance level due to load modulation and the power transmission side In some cases, the correspondence with the magnitude of the current or voltage detected in (1) is reversed (see FIGS. 2 and 3 to be described later). As a result, transmission data is received with bit inversion, and correct information transmission cannot be performed. That is, it is impossible to perform control such as authentication of the power receiving side device using the uplink and adjustment of the power supply frequency on the power transmitting side upon receiving the notification of the power receiving state from the power receiving side.

  An object of the present invention is to provide a resonance type wireless power transmission device that enables transmission of transmission data from a power receiving side to a power transmission side regardless of bit inversion of the transmission data.

  A first invention is a power transmission side resonance coil electrically coupled to a power transmission side coil of a power transmission side device by electromagnetic induction, and a power reception side resonance coil 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 transmits power from the power source of the power transmission side device to the load of the power reception side device using the resonance phenomenon between the power transmission side device and the power reception side device, the load impedance is set within a predetermined range by turning on and off the switch. A means for changing, and a control unit that controls on / off of the switch by associating a change in load impedance with a change in load impedance transmitted from the power receiving side device to the power transmission side device, and the power transmission side device has a load impedance corresponding to the transmission data A demodulator that detects a change in current or voltage that occurs in response to a change in power and restores transmission data, and the control unit of the power receiving side device includes a power receiving side device and a power transmitting side device. The demodulator of the power transmission side device detects the presence or absence of bit inversion from the reconstructed known signal, and if it is bit-inverted, the subsequent transmission data is bit-inverted and output. It is the structure to do.

  Here, the known signal may be a bit string of a plurality of bits, and the demodulator of the power transmission side device may be configured to detect the presence or absence of bit inversion by detecting the correlation between the restored signal and the known signal.

  In addition, the control unit of the power receiving side device is configured to transmit the transmission data as a burst signal and transmit a 1-bit signal as a known signal before starting transmission of the transmission data. The presence or absence of bit inversion is detected from the restored 1-bit known signal, and when the bit inversion is performed, the subsequent transmission data may be inverted and output.

  According to a second aspect of the present invention, there is provided a power transmission side resonance coil electrically coupled to the power transmission side coil of the power transmission side device by electromagnetic induction, and a power reception side resonance coil 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 power from the power source of the power transmission side device to the load of the power reception side device using the resonance phenomenon between the power transmission side device and the power reception side device, the load impedance is set within a predetermined range by turning on and off the switch. A means for changing, and a control unit that controls on / off of the switch by associating a change in load impedance with a change in load impedance transmitted from the power receiving side device to the power transmission side device, and the power transmission side device has a load impedance corresponding to the transmission data A demodulator that detects a change in current or voltage that occurs in response to a change in power and restores transmission data, and the control unit of the power receiving side device includes a power receiving side device and a power transmitting side device. A known bit string is used as transmission data, and a bit string obtained by inverting the known bit string is not used as transmission data.The demodulator of the power transmission side device performs a bit inverted signal and a signal that is not bit inverted with respect to the restored signal. In this configuration, a signal that is generated and matches a known bit string is output as transmission data.

  According to a third aspect of the present invention, there is provided a power transmission side resonance coil electrically coupled to the power transmission side coil of the power transmission side device by electromagnetic induction, and a power reception side resonance coil 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 power from the power source of the power transmission side device to the load of the power reception side device using the resonance phenomenon between A means for changing, and a control unit that controls on / off of the switch by associating a change in load impedance with a change in load impedance transmitted from the power receiving side device to the power transmission side device, and the power transmission side device has a load impedance corresponding to the transmission data A demodulator that detects a change in current or voltage that occurs in response to a change in power and restores transmission data, and the control unit of the power receiving side device includes a power receiving side device and a power transmitting side device. A configuration in which a known bit string is used as transmission data, a bit string obtained by inverting the known bit string is not used as transmission data, and a bit-inverted signal and a signal that is not bit-inverted are alternately output as transmission data, The demodulating unit of the power transmission side device is configured to output a signal that matches a known bit string for the restored signal as transmission data.

  The resonance type wireless power transmission device of the present invention corrects a bit string even when the correspondence between the level of load impedance by load modulation and the magnitude of the current or voltage detected on the power transmission side is reversed and outputs the bit string, Can be transmitted reliably. That is, the transmission accuracy of information by load modulation can be improved, and the power frequency on the power transmission side can be reliably adjusted based on the authentication or the power reception state notification from the power reception side.

It is a figure which shows the structural example of the resonance type wireless power transmission apparatus of this invention. It is a timing chart which shows example 1 of transmission data and a reception waveform. It is a timing chart which shows the example 2 of transmission data and a reception waveform. 3 is a diagram illustrating a first configuration example of a demodulation unit 12. FIG. 3 is a diagram illustrating a second configuration example of a control unit 26 and a demodulation unit 12. FIG. FIG. 10 is a diagram illustrating a third configuration example of the demodulation unit 12. It is a figure which shows the 4th structural example of the control part 26 and the demodulation part 12. FIG. 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) of a resonance coil.

FIG. 1 shows a configuration example of a resonance type wireless power transmission apparatus 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, and transmits transmission data from the power reception side device 20 to the power transmission side device 10. Includes a configuration for transmitting. The flow of power and transmission data from the power transmission side device 10 to the power reception side device 20 is downward, and the flow of transmission data from the power reception side device 20 to the power transmission side device 10 is upward.

  The power transmission side device 10 includes a power source 11, a demodulation unit 12 that restores uplink transmission data sent from the power reception side device 20, a power transmission side coil 13, a power transmission side resonance coil 14, and a frequency adjustment unit 15 that adjusts the power frequency of the power source 11. Is provided. 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. As a result, power can be supplied from the power source 11 to the load 23 and the control unit 26.

  The transmission data 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 when the switch 25 is turned on / off. The control unit 26 is configured to turn on and off the switch 25 in accordance with transmission data and change the load impedance. However, in the configuration of the present embodiment, the power supply to the load 23 is continued because the connection to the load 23 is not released regardless of whether the switch 25 is on or off.

  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.

  Since the power receiving side device 20 and the power transmitting side device 10 are electrically coupled, the 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, and the current or voltage is changed. Appears as a change. The demodulator 12 detects this change and restores the transmission data transmitted from the power receiving side device 20.

  FIG. 2 shows a waveform obtained by envelope detection of the current or voltage in the demodulator 12 of the power transmission side device 10, and it can be seen that the current or voltage changes in conjunction with the change of transmission data. This is an example in which the power supply frequency of the power transmission side device 10 and the resonance frequency coincide with each other. The transmission data 1 corresponds to the increase in the amplitude of the reception waveform, and the transmission data 0 corresponds to the decrease in the amplitude of the reception waveform. Corresponds. The demodulation unit 12 can restore the transmission data transmitted from the power receiving side device 20 by sampling this change at an appropriate timing.

  By the way, since there are a plurality of resonance frequencies, the load impedance due to load modulation depends on the power supply frequency of the power transmission side device 10 being a different resonance frequency or depending on the installation conditions such as the distance between the power transmission side device 10 and the power reception side device 20. There is a case where the correspondence between the height of the power supply and the magnitude of the impedance or the current or voltage detected on the power transmission side when the power reception side is viewed from the power transmission side may be reversed. FIG. 3 shows the relationship between the transmission bit and the reception waveform in this case. Here, 1 of the transmission data corresponds to a decrease in the amplitude of the reception waveform, and 0 of the transmission data corresponds to an increase in the amplitude of the reception waveform, which is the reverse of the case of FIG. That is, when the transmission data is restored assuming the reception waveform of FIG. 2, a signal with all bits inverted is obtained. However, it is impossible to determine whether or not the bit string is inverted only by referring to the obtained bit string. Therefore, this problem is solved by using the following means.

FIG. 4 shows a first configuration example of the demodulator 12.
In FIG. 4, the demodulation unit 12 includes a detection unit 120, an A / D conversion unit 121, a code determination unit 122, a correlation detection unit 123, a pattern storage unit 124, and a bit inversion unit 125.

  The detector 120 detects the received waveform, that is, the current or voltage in the power transmission side device 10. This can be realized by an AM detection circuit that extracts an envelope. The detection output is digitized by the A / D converter 121, and the bit is determined by the code determination unit 122 and output. Here, it is assumed that a known signal is added to the transmission data from the power receiving side device 20 on both the power transmission side and the power receiving side, and this is stored in the pattern storage unit 124. As this known signal, for example, a preamble signal added at the head of the burst signal or a pilot signal added at a specific timing in the continuous signal can be used.

  For example, the correlation detection unit 123 compares the output bit string of the code determination unit 122 at a timing corresponding to the preamble unit with a known signal held by the pattern storage unit 124. A positive correlation is obtained when the bits are not inverted, and a negative correlation is obtained when the bits are inverted. The bit inversion unit 125 that inputs the output bit string of the sign determination unit 122 outputs the sign of the positive correlation bit string without inverting the sign of the positive correlation bit string, and outputs the sign of the negative correlation bit string. Invert and output.

  Thereby, even when the correspondence between the level of the load impedance due to load modulation and the magnitude of the current or voltage detected on the power transmission side is reversed, the bit string can be corrected and a correct signal can be transmitted. That is, the transmission accuracy of information by load modulation can be improved.

FIG. 5 shows a second configuration example of the control unit 26 and the demodulation unit 12.
In FIG. 5, the control unit 26 includes a bit 1 output unit 261 and a switch 262. The demodulation unit 12 includes a detection unit 120, an A / D conversion unit 121, a code determination unit 122, and a burst detection unit 126. Here, the functions of the detection unit 120, the A / D conversion unit 121, and the code determination unit 122 are the same as those of the first configuration example shown in FIG.

  In order to use the control unit 26 and the demodulation unit 12 of this configuration example, uplink transmission data is assumed to be a burst signal generated intermittently. The switch 25 of the power receiving side device 20 shown in FIG. 1 performs only power reception when it is normally off, and does not transmit transmission data. When the transmission data is 1, the switch 25 is on, the transmission data is 0, the switch 25 is off, and the switch 25 is turned on and off, the transmission data is transmitted.

  The control unit 26 outputs the transmission data via the switch 262, but outputs only 0 that turns off the switch 25 in the initial state where the transmission data is not transmitted. Here, when transmission of transmission data as a burst signal is started, the switch 262 switches to the bit 1 output unit 261 to output bit 1, and after the switch 25 is turned on, the switch 262 is switched to transmission data. That is, bit 1 is the start of transmission data.

  The demodulator 12 restores the transmission data in the same manner as in the first configuration example, but the burst detector 126 detects a change (increase or decrease) in current or voltage corresponding to bit 1 that is the start of the transmission data, The code determination unit 122 is notified. Since the sign determination unit 122 is bit-inverted when the current or voltage corresponding to bit 1 that is the start of transmission data decreases, the sign determination unit 122 is 0 if the original current or voltage is generated for the subsequent received signal. If the current or voltage decreases, 1 is output. Similarly, when the current or voltage corresponding to bit 1 which is the start of transmission data increases, bit inversion is not performed, so that if the original current or voltage occurs for the subsequent received signal, 0, current or If the voltage increases, 1 is output. That is, this configuration example corresponds to the case where the known preamble in the first configuration example is 1 in 1 bit.

  Thereby, even when the correspondence between the level of the load impedance due to load modulation and the magnitude of the current or voltage detected on the power transmission side is reversed, the bit string can be corrected and a correct signal can be transmitted. That is, the transmission accuracy of information by load modulation can be improved.

FIG. 6 shows a third configuration example of the demodulation unit 12.
In FIG. 6, the demodulation unit 12 includes a detection unit 120, an A / D conversion unit 121, a code determination unit 122, a bit inversion unit 127, and an output selection unit 128. Here, the functions of the detection unit 120, the A / D conversion unit 121, and the code determination unit 122 are the same as those of the first configuration example shown in FIG.

  In order to use the demodulator 12 of this configuration example, a known bit string is prepared on both the power transmission side and the power reception side as transmission data transmitted from the power reception side device 20. For simplicity, the predetermined transmission data is composed of 4 bits, and the bit string is “1101”. When the demodulator 12 inverts the bit string, it becomes “0010”, so that the transmission data is configured so that the inverted bit string is not assigned as transmission data.

  The code determination unit 122 outputs the bit sequence (here, 4 bits) subjected to code determination to the bit inversion unit 127 and the output selection unit 128. The bit inversion unit 127 inverts the bit string output from the code determination unit 122 and outputs the inverted bit string to the output selection unit 128. The output selection unit 128 outputs, as transmission data, a bit string that matches a known bit string among the bit string output from the code determination unit 122 and the inverted bit string output from the bit inversion unit 127. Note that the output selection unit 128 uses a switch that alternately outputs the outputs of the sign determination unit 122 and the bit inversion unit 127, one of which is a bit string known as transmission data, so that it is output as significant transmission data. Since is not a known bit string, it may be discarded.

  Thereby, even when the correspondence between the level of the load impedance due to load modulation and the magnitude of the current or voltage detected on the power transmission side is reversed, the bit string can be corrected and a correct signal can be transmitted. That is, the transmission accuracy of information by load modulation can be improved.

FIG. 7 shows a fourth configuration example of the control unit 26 and the demodulation unit 12.
In FIG. 7, the control unit 26 includes a bit inversion unit 263 and a switch 262. The demodulation unit 12 includes a detection unit 120, an A / D conversion unit 121, a code determination unit 122, and an output selection unit 129. Here, the functions of the detection unit 120, the A / D conversion unit 121, and the code determination unit 122 are the same as those of the first configuration example shown in FIG.

  In order to use the control unit 26 and the demodulation unit 12 of this configuration example, as in the case of the second configuration example of the demodulation unit 12, transmission data to be transmitted from the power reception side device 20 on both the power transmission side and the power reception side. A known bit string is prepared, and transmission data is configured so that the inverted bit string is not assigned as transmission data.

  In the control unit 26, the bit string of the transmission data is input to the bit inverting unit 263 and the switch 262. The bit inverting unit 263 inverts the input bit string and outputs it to the switch 262. The switch 262 has a buffer function, and alternately outputs the input bit string and the inverted bit string output from the bit inverting unit 263, and controls the on / off of the switch 25 of the power receiving side device 20 illustrated in FIG. Accordingly, the power receiving side device 20 alternately transmits predetermined transmission data represented by a known bit string and a signal obtained by inverting the bit string.

  The demodulator 12 restores transmission data as in the first configuration example, but the output selector 129 compares the output of the code determination unit 123 with a known bit string. Here, even if bit inversion of transmission data occurs, one of them is a bit string known as transmission data, so it is output as significant transmission data, and the other is not a known bit string and is discarded.

  Thereby, even when the correspondence between the level of the load impedance due to load modulation and the magnitude of the current or voltage detected on the power transmission side is reversed, the bit string can be corrected and a correct signal can be transmitted. That is, the transmission accuracy of information by load modulation can be improved.

DESCRIPTION OF SYMBOLS 10 Power transmission side apparatus 11 Power supply 12 Demodulation part 120 Detection part 121 A / D conversion part 122 Code determination part 123 Correlation detection part 124 Pattern storage part 125 Bit inversion part 126 Burst detection part 127 Bit inversion part 128,129 Output selection part 13 Power transmission Side coil 14 Power transmission side resonance coil 20 Power reception side device 21 Power reception side resonance coil 22 Power reception side coil 23 Load 24 Resistance 25 Switch 26 Control unit 261 Bit 1 output unit 262 Switch 263 Bit inversion unit

Claims (5)

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 power from the power source of the power transmission side device to the load of the power reception side device,
The power receiving side device associates the change of the load impedance with the means for changing the load impedance in a predetermined range by turning the switch on and off, and the transmission data transmitted from the power receiving side device to the power transmitting side device. And a control unit for controlling
The power transmission side device includes a demodulator that detects a change in current or voltage generated according to a change in the load impedance corresponding to the transmission data, and restores the transmission data.
The control unit of the power receiving device is configured to transmit a known signal between the power receiving device and the power transmitting device,
The demodulator of the power transmission side device is configured to detect the presence or absence of bit inversion from the restored known signal, and when the bit is inverted, the subsequent transmission data is output after being bit inverted. Resonant type wireless power transmission device. In the resonance type wireless power transmission device according to claim 1,
The known signal is a bit string of a plurality of bits,
The resonance type wireless power transmission device, wherein the demodulator of the power transmission side device is configured to detect the presence or absence of bit inversion by performing correlation detection between the restored signal and the known signal. In the resonance type wireless power transmission device according to claim 1,
The control unit of the power receiving side device is configured to transmit the transmission data as a burst signal and transmit a 1-bit signal as the known signal before starting transmission of the transmission data,
The demodulator of the power transmission side device is configured to detect the presence or absence of bit inversion from the restored known signal of 1 bit, and when the bit inversion is performed, the subsequent transmission data is bit inverted and output. A resonance type wireless power transmission device characterized by the above. 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 power from the power source of the power transmission side device to the load of the power reception side device,
The power receiving side device associates the change of the load impedance with the means for changing the load impedance in a predetermined range by turning the switch on and off, and the transmission data transmitted from the power receiving side device to the power transmitting side device. And a control unit for controlling
The power transmission side device includes a demodulator that detects a change in current or voltage generated according to a change in the load impedance corresponding to the transmission data, and restores the transmission data.
The control unit of the power receiving side device uses a known bit string in the power receiving side device and the power transmitting side device as the transmission data, and does not use a bit string obtained by inverting the known bit string as the transmission data.
The demodulator of the power transmission side device is configured to generate a signal that is bit-reversed and a signal that is not bit-reversed with respect to the restored signal, and output a signal that matches the known bit string as the transmission data. Resonance type wireless power transmission device. 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 power from the power source of the power transmission side device to the load of the power reception side device,
The power receiving side device associates the change of the load impedance with the means for changing the load impedance in a predetermined range by turning the switch on and off, and the transmission data transmitted from the power receiving side device to the power transmitting side device. And a control unit for controlling
The power transmission side device includes a demodulator that detects a change in current or voltage generated according to a change in the load impedance corresponding to the transmission data, and restores the transmission data.
The control unit of the power receiving side device uses a known bit string in the power receiving side device and the power transmitting side device as the transmission data, and does not use a bit string obtained by inverting the known bit string as the transmission data, and It is a configuration that alternately outputs a bit-inverted signal and a signal that is not bit-inverted as transmission data,
The demodulator of the power transmission side device is configured to output a signal that matches the known bit string as the transmission data with respect to the restored signal.

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