JP5456625B2 - 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. 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. 7 shows a configuration example of the wireless power transmission apparatus.
In FIG. 7, 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. 8 shows a configuration example of a resonance type wireless power transmission apparatus.
In FIG. 8, 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 21 . Resonance occurs only at specific frequencies. FIG. 9 shows an example of the S parameter (S21) of the resonance coil. 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. 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.

  In the resonance type wireless power transmission apparatus shown in FIG. 8, when the power frequency on the power transmission side is set to a frequency different from the resonance frequency, sufficient power does not reach the power receiving side. In addition, when the power frequency on the power transmission side is significantly different from the resonance frequency, if transmission data is transmitted from the power receiving side by load modulation that changes the load impedance on the power receiving side, the load impedance of the power receiving side on the power transmission side A change in current or voltage due to the change cannot be detected, and uplink information transmission fails. For example, even if an attempt is made to transmit information requesting the power transmission side to change the power supply frequency because the power supplied to the power receiving side is not sufficient, it does not reach the power transmitting side, and consequently power is supplied from the power transmitting side to the power receiving side. I can't do that.

  The present invention enables transmission of transmission data from the power receiving side to the power transmission side even when the power frequency on the power transmission side is different from the resonance frequency, and further, the frequency corresponding to the power frequency on the power transmission side by the notification from the power receiving side. It is an object of the present invention to provide a resonance type wireless power transmission device that can be adjusted to the above.

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 device and the power to the load of the power reception device, the power reception device changes the load impedance in a predetermined range by turning on and off the switch. And a control unit that controls on / off of the switch by associating the transmission data transmitted from the power receiving side device to the power transmission side device with a change in the load impedance, and the power transmission side device includes a change in the load impedance corresponding to the transmission data. detecting a transient response of the current or voltage generated in accordance with, a demodulation unit that restores the transmission data by the transient response, the control unit of the power receiving side apparatus, transmission de If the data is 0, the switch is maintained in the previous state, and if the transmission data is 1, the switch is inverted from the previous state. 1 for negative transient response, Ru configuration der to output 0 for no transient response.

In the resonance type wireless power transmission device of the present invention, the control unit of the power receiving side device is configured to transmit the power receiving state as transmission data to the power transmission side device, and the power transmission side device transmits the transmission data restored by the demodulation unit. A frequency adjustment unit that detects a power reception state from the power supply and adjusts the power supply frequency of the power supply so as to approach the resonance frequencies of the power transmission resonance coil and the power reception resonance coil.

In the resonance type wireless power transmission device of the present invention, the power receiving side device provides a control signal for adjusting the power source frequency of the power source so as to approach the resonance frequency of the power transmitting side resonance coil and the power receiving side resonance coil according to the power receiving state. The control unit of the power receiving side device is configured to transmit the control signal as transmission data to the power transmission side device, and the power transmission side device detects the control signal from the transmission data restored by the demodulation unit. The power supply frequency of the power supply is adjusted according to the control signal .

  The resonance type wireless power transmission device of the present invention changes the load impedance according to transmission data transmitted from the power receiving side device, and detects it from the transient response of the current or voltage by the power transmission side device, thereby Even when the frequency is different from the resonance frequency, transmission data can be transmitted from the power receiving side to the power transmitting side.

  Also, even when the power frequency on the power transmission side is different from the resonance frequency, transmission data can be transmitted from the power receiving side to the power transmission side. The frequency can be adjusted to approach the resonant frequency. Thereby, the power transmission efficiency can be further increased.

It is a figure which shows the structural example of the resonance type wireless power transmission apparatus of Example 1 of this invention. It is a figure which shows the example 1 of transmission data and a received waveform. It is a figure which shows the example 2 of transmission data and a received waveform. It is a figure which shows the example 3 of transmission data and a received waveform. 3 is a diagram illustrating a configuration example of a demodulation unit 12. 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 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 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, 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. 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, when the power supply frequency of the power transmission side device 10 is different from the resonance frequency, a reception waveform as shown in FIG. 3 is obtained. The average reception level (reception power) not only decreases compared to the case of FIG. 2, but also changes in the amplitude of the signal waveform are reduced. Furthermore, when the power supply frequency of the power transmission side device 10 is greatly different from the resonance frequency, the change in the amplitude of the signal waveform becomes very small, and it is difficult to restore the transmission data.

  On the other hand, the demodulator 12 of the power transmission side device 10 can observe a transient response of current or voltage corresponding to a change in transmission data as shown in FIG. Here, the transient response of the current or voltage observed in the power transmission side device 10 is a part where the switch 25 is turned on / off according to transmission data and the current or voltage rises and falls according to the change in the load impedance accompanying it. This is a phenomenon in which the waveform changes greatly. The control unit 26 of the power receiving side device 20 operates the switch 25 so that the transmission data corresponds to the occurrence of the transient response, and the demodulation unit 12 of the power transmission side device 10 restores the transmission data from the presence of the occurrence of the transient response. To do.

FIG. 5 shows a configuration example of the demodulation unit 12.
In FIG. 5, the demodulation unit 12 includes a detection unit 121, an A / D conversion unit 122, and a code determination unit 123. The detector 121 detects the received waveform, that is, the current or voltage in the power transmission side device 10. The detection output is digitized by the A / D converter 122, and the bit is determined by the code determination unit 123 and output.
The code determination unit 123 has two code determination logics. The sign determination logic 1 outputs “1” when a positive transient response is determined from the received waveform, and outputs “0” when a negative transient response is determined, and determines a steady state (no transient response). If it does, the previous determination result is output. The code determination for the steady state may be configured such that the previous determination result is stored in a storage unit connected to the code determination unit 123 and read from the storage unit when the steady state is determined. The configuration may be such that the previous determination result is output until a positive or negative transient response is determined.

  The control unit 26 of the power receiving device 20 corresponding to the code determination unit 123 operates the switch 25 so as to correspond to the transmission data as it is. That is, if the transmission data is 1, the switch 25 is turned on, and if the transmission data is 0, the switch 25 is turned off. The sign determination unit 123 determines the bit at the timing when the transmission data is inverted and a transient response occurs, and outputs the same bit as the bit immediately before the transient response occurs at the timing when the transient response does not occur, thereby restoring the transmission data. To do.

  Here, the state of the switch 25 for transmission data (0: off, 1: on), reception waveform (1: positive transient response, 0: steady state, −1: negative transient response), determination by the sign determination unit 123 Table 1 shows the data relationship. However, the received waveform at the first time is not shown because it depends on the previous state.

  In this example, if the bit determination is wrong at the timing when the transient response occurs, the bit at the timing when the transient response does not occur next becomes an error depending on the immediately preceding bit. Therefore, when a control signal is transmitted from the power receiving side device 20, the use of a bit string with many bit inversions increases the chances of bit determination by a transient response, and the error rate of the control signal can be reduced. That is, by using a bit string with many bit inversions including a known preamble as the control signal, transmission to the power transmission side device 10 can be performed reliably.

  Further, in the code determination logic 2 of the code determination unit 123, “1” is output when a positive or negative transient response is determined from the received waveform, and “0” is determined when a steady state (no transient response) is determined. You may make it output. The control unit 26 of the power receiving side device 20 corresponding to the code determination unit 123 maintains the switch 25 in the previous state if the transmission data is 0, and reverses the switch 25 from the previous state if the transmission data is 1. Perform the operation. At this time, if the transmission data is 01 and the switch 25 changes from off (0) to on (1), the reception waveform shows a positive transient response, the transmission data is 11, and the switch 25 is on (1) to off. If the received waveform changes to (0), the received waveform indicates a negative transient response. Therefore, the sign determining unit 123 determines that the determination data is “inverted” when the positive or negative transient response is determined from the received waveform. If the received waveform is in a steady state, the determination data is set to “0” and the transmission data is restored.

  Here, the state of the switch 25 for transmission data (0: off, 1: on), reception waveform (1: positive transient response, 0: steady state, −1: negative transient response), bit of the sign determination unit 123 Table 2 shows the output relationship. However, the received waveform at the first time is not described because it depends on the previous state.

  As described above, two examples of the operation of the switch 25 with respect to the transmission data and the determination method of the sign determination unit 123 have been shown. However, the power supply frequency of the power transmission side device 10 is slightly deviated from the resonance frequency by detecting the presence or absence of a transient response. In addition, it can be seen that the transmission data transmitted from the power receiving device 20 can be restored by the power transmitting device 10.

  Therefore, when the power receiving side device 20 detects a shift in power source frequency of the power transmitting side device 10 with respect to the resonance frequency due to a decrease in received power, the control unit 26 generates a corresponding control signal and switches the switch 25 to the above pattern. , The control signal is restored by the demodulator 12 of the power transmission side device 10, and the deviation of the power supply frequency of the power transmission side device 10 with respect to the resonance frequency can be notified. However, since the power receiving side device 20 does not know the direction or amount of deviation of the power source frequency of the power transmitting side device 10 with respect to the resonance frequency, for example, a power receiving power value is transmitted as a control signal. The demodulator 12 of the power transmission side device 10 reads the received power value from the control signal, and adjusts the power frequency of the power source 11 via the frequency adjuster 15 when it is less than the specified received power value. At this time, the power supply frequency can be adjusted so as to approach the resonance frequency by feedback control of the shift direction and shift amount of the power supply frequency from the change in the received power value with respect to the shift of the power supply frequency.

FIG. 6 shows a configuration example of a resonance type wireless power transmission apparatus according to the second embodiment of the present invention.
The feature of the present embodiment is that the frequency adjustment unit 15 of the power transmission side device 10 is provided as a frequency adjustment unit 27 in the preceding stage of the control unit 26 of the power reception side device 20 in Example 1 shown in FIG. 1 and corresponds to the received power value. The power frequency control signal is transmitted. Thereby, the demodulator 12 of the power transmission side device 10 can adjust the power supply frequency of the power supply 11 using the restored control signal. However, as described in the first embodiment, since the shift direction and shift amount of the power supply frequency cannot be directly set as the control signal, adjustment is performed so that the power supply frequency of the power supply 11 approaches the resonance frequency by feedback control.

DESCRIPTION OF SYMBOLS 10 Power transmission side apparatus 11 Power supply 12 Demodulation part 121 Detection part 122 A / D conversion part 123 Code | symbol determination part 13 Power transmission side coil 14 Power transmission side resonance coil 15 Frequency adjustment part 20 Power reception side apparatus 21 Power reception side resonance coil 22 Power reception side coil 23 Load 24 resistance 25 switch 26 control unit 27 frequency adjustment unit

Claims (3)

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 transient response of current or voltage generated according to a change in the load impedance corresponding to the transmission data, and restores the transmission data by the transient response ,
Controller of the receiving side apparatus, if the transmission data is 0 to maintain the switch to its previous state, a configuration to invert the previous state said switch when said transmission data is 1, the power transmission The resonance type wireless power transmission apparatus according to claim 1, wherein the demodulator of the side apparatus outputs 1 as a positive or negative transient response and 0 as no transient response as the transmission data to be restored . 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 power receiving state of the power to the power transmitting side device as the transmission data,
The power transmission side device detects the power reception state from the transmission data restored by the demodulation unit, and adjusts the power supply frequency of the power supply so as to approach the resonance frequencies of the power transmission side resonance coil and the power reception side resonance coil. A resonance type wireless power transmission device comprising a frequency adjustment unit. In the resonance type wireless power transmission device according to claim 1,
The power receiving device includes a frequency adjustment unit that generates a control signal for adjusting a power supply frequency of the power supply so as to approach a resonance frequency of the power transmission resonance coil and the power reception resonance coil according to a power reception state of the power. Prepared,
The control unit of the power receiving side device is configured to transmit the control signal to the power transmission side device as the transmission data ,
The resonance type wireless power transmission device, wherein the power transmission side device is configured to detect the control signal from the transmission data restored by the demodulation unit and adjust a power supply frequency of the power source according to the control signal. .

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