JP2019180121A - Power transmission device - Google Patents

Abstract

To reduce generation of a current to flow to an antenna in a case where the antenna and a power transmission circuit are disconnected.SOLUTION: A power transmission device comprises: a power transmission antenna; a power transmission circuit for transmitting power by using a carrier in a predetermined frequency; and a switch for switching whether to connect or disconnect the power transmission antenna and the power transmission circuit, the switch including a semiconductor element and a coil connected in parallel with the semiconductor element. The power transmission device is characterized in that, in a state where the power transmission antenna and the power transmission circuit are disconnected by the switch, a capacitor component of the semiconductor element and an inductor component of the coil are resonated in the predetermined frequency.SELECTED DRAWING: Figure 7

Description

  The present invention relates to wireless power transmission.

  In recent years, wireless power transmission systems for supplying power to mobile objects wirelessly have been developed. Patent Document 1 proposes a wireless power transmission system that switches a power transmitting antenna to be fed in accordance with the position of an automatic guided vehicle traveling on a plurality of power transmitting antennas.

JP 2017-93181 A

  In the wireless power transmission system described in Patent Document 1, a general semiconductor element is used as a switch for switching a power transmission antenna. However, when the switch is configured only by the semiconductor element, an alternating current flows due to the parasitic capacitance of the semiconductor element when the switch is turned off and the antenna and the power transmission circuit are disconnected. Therefore, a current is also generated in the power transmission antenna with the switch turned off, and there is a problem that the efficiency of wireless power transmission is deteriorated due to the loss.

  In view of the above problems, an object of the present invention is to reduce generation of a current flowing through an antenna when the antenna and a power transmission circuit are disconnected.

A power transmission antenna;
A power transmission circuit for transmitting power using a carrier wave of a predetermined frequency;
A switch for switching between connecting or disconnecting the power transmission antenna and the power transmission circuit, comprising: a semiconductor element; and a switch having a coil connected in parallel with the semiconductor element,
The capacitance component of the semiconductor element and the inductor component of the coil resonate at the predetermined frequency in a state where the power transmission antenna and the power transmission circuit are disconnected by the switch.

  ADVANTAGE OF THE INVENTION According to this invention, when an antenna and a power transmission circuit are made non-connection, generation | occurrence | production of the electric current which flows into an antenna can be reduced.

1 is a system configuration diagram of a wireless power transmission system according to a first embodiment. Diagram showing equivalent circuit of semiconductor element Equivalent circuit diagram when a conventional switch is connected to a wireless power transmission system Equivalent circuit diagram when connected to the wireless power transmission system when the SPST switch is turned ON / OFF Power transmission simulation results in the equivalent circuit of FIG. Diagram showing the configuration of the switch section Equivalent circuit diagram of the wireless power transmission system when the switch unit according to the present embodiment is turned ON / OFF The figure which shows the electric power transmission simulation result in the equivalent circuit of FIG. System configuration diagram of wireless power transmission system according to Embodiment 2 The figure which shows the electric power transmission simulation result which concerns on Embodiment 2. Circuit diagram with matching circuit connected

(Embodiment 1)
Embodiments of the present invention will be described below with reference to the drawings. The wireless power transmission system of the present embodiment performs wireless power transmission using a system called electromagnetic induction or magnetic field resonance that transmits power using a magnetic field or both electric and magnetic fields. However, wireless power transmission may be performed using other methods.

  In this embodiment, an example will be described in which the wireless power transmission system is applied to a printer that ejects ink while moving an ink head along a rail. However, the application example of the wireless power transmission system is not limited to this. For example, the wireless power transmission system according to the present embodiment can be applied to all mobile objects that move in a certain direction and require power supply, such as an automated guided vehicle (AGV) used in a factory.

  FIG. 1 is a system configuration diagram of a printer to which a wireless power transmission system described in this embodiment is applied. 1 is a diagram when viewed from the Y-axis direction of the coordinate axes described in FIG. The printer 100 includes a power transmission unit 101 including power transmission antennas 110, 111, and 112, a power transmitter 113, and three switch units 114. The printer 100 also includes a power reception unit 102 including a power reception antenna 120 and a power receiver 121, a control unit 103, an ink head 104, a position detection unit 105, a drive unit 106, and a power supply unit 107. Although there are three power transmission antennas, two or four or more power transmission antennas may be used.

  The power transmitter 113 is configured by a power transmission circuit used when electromagnetic induction or a magnetic field resonance method is adopted. The power transmitter 113 converts the DC voltage supplied from the power supply unit 107 into a predetermined frequency (hereinafter referred to as a carrier frequency) used for conveyance using an inverter circuit, and outputs the DC voltage to the power transmission antenna 110 via the switch unit 114. That is, the power transmission unit 101 converts direct current to alternating current with the power transmitter 113 and generates an alternating magnetic field using one of the power transmission antennas 110, 111, and 112. In the present embodiment, the carrier frequency is described as 1.7 MHz, but other frequency bands may be used as the carrier frequency. The power transmission unit 101 is a power transmission device that transmits power wirelessly. In addition, you may comprise the power transmission part 101 as one module.

  In addition, when the printer 100 is viewed from the Z-axis direction of the coordinate axis illustrated in FIG. 1, the power receiving antenna 120 is disposed so as to overlap any one of the power transmitting antennas 110, 111, and 112. The length of the power receiving antenna 120 in the Y-axis direction may be approximately the same as the length of the power transmitting antennas 110, 111, and 112 in the Y-axis direction from the viewpoint of increasing the coupling coefficient between the power transmitting and receiving antennas.

  The power receiver 121 includes a power receiving circuit used when electromagnetic induction or a magnetic field resonance method is employed. The power receiver 121 converts an AC voltage generated in the power receiving antenna 120 by an AC magnetic field generated by any one of the power transmitting antennas 110, 111, and 112 into direct current using a rectifier circuit. The power receiver 121 converts the DC voltage converted by the rectifier circuit into a voltage used by the ink head 104 by the voltage conversion circuit. The power receiver 121 supplies the voltage converted by the voltage conversion circuit to the ink head 104 via the power supply path 161. That is, the power receiving unit 102 converts the voltage generated in the power receiving antenna 120 by the AC magnetic field from the power transmitting antenna 110 from AC to DC in the power receiver 121 and outputs the converted voltage. With the above configuration, power is supplied to the ink head 104 wirelessly. The power receiver 121 is mechanically coupled to the ink head 104 and slides together with the ink head 104. The power receiving unit 102 is a power receiving device that receives power transmitted wirelessly. Note that the power receiving unit 102 may be configured as one module.

  The control unit 103 is connected to the ink head 104, the drive unit 106, and the switch unit 114 via the transmission lines 130, 131, and 132, and controls each operation. The ink head 104 ejects ink using the power supplied from the power receiving unit 102 based on the control signal transmitted from the control unit 103 transmitted via the transmission path 130. The transmission path 130 may be wired, but may be wireless from the viewpoint of eliminating wear due to movement of the wire. When the transmission path 130 is wireless, a standard such as a wireless LAN or Bluetooth (registered trademark) may be used as a wireless communication method, or an original wireless communication method may be used. The position detection unit 105 detects the position of the ink head 104 and notifies the control unit 103 of it. The drive unit 106 slides the ink head 104 along the rail 150 based on a control signal from the control unit 103 transmitted via the transmission path 131.

  The switch unit 114 switches whether the corresponding power transmission antenna and the power transmitter 113 are connected or not. The switch unit 114 includes a semiconductor element and a coil connected in parallel with the semiconductor element. In a state where the power transmission antenna and the power transmitter 113 are not connected, the capacitance component of the semiconductor element of the switch unit 114 and the inductor component of the coil resonate at the carrier frequency. The semiconductor element is, for example, a field effect transistor.

  The control unit 103 controls ON / OFF of the switch unit 114 by the control unit 103 based on information indicating the position transmitted from the position detection unit 105 via the transmission path 130. That is, the control unit 103 selects an antenna to be used for power transmission from the power transmission antennas 110, 111, and 112 in accordance with the position of the ink head 104 that is a power receiving device that receives power. And the control part 103 turns ON the switch part 114 corresponding to the antenna used for the selected power transmission, and connects a power transmission antenna and the power transmission device 113. FIG. Further, the switch unit 114 corresponding to the selected antenna is turned OFF, and the power transmission antenna and the power transmitter 113 are disconnected.

  The power supply unit 107 generates a DC voltage used by each of the power transmission unit 101, the control unit 103, and the drive unit 106 from a commercial power source (not shown), and supplies the generated DC voltage to each unit via the power supply path 160.

  From the viewpoint of reducing power energy, efficient transmission is required when wireless power transmission is performed in a sliding system such as the present embodiment. In order to transmit power efficiently, it is necessary to suppress loss in the power transmission / reception antenna.

  An equivalent circuit of a semiconductor element used in a conventional switch is shown in FIG. The equivalent circuit shown in FIG. 2 includes a stray capacitance 201, a resistor 202, and an SPST switch 203. FIG. 3 shows an equivalent circuit of a wireless power transmission system using a conventional switch. In FIG. 3, the power transmission antenna is represented by an inductor component 301, a resistance component 302, and a power transmission capacitor 303 that is in series resonance with the inductor at the carrier frequency. In FIG. 3, the power receiving antenna is indicated by an inductor component 304, a resistance component 305, and a power receiving capacitor 306 that resonates in series with the inductor at the carrier frequency. In FIG. 3, the input impedance of the power receiver is indicated by 307 and the power transmitter is indicated by 308.

  FIG. 3 illustrates a case where the power receiving antenna 120 is positioned on the power transmitting antenna 111. When the power receiving antenna 120 is positioned on the power transmission antenna 111, only the SPST switch connected to the power transmission antenna 111 is turned on, and the two SPST switches corresponding to the power transmission antennas 110 and 112 are turned off. FIG. 4 shows an equivalent circuit when only the SPST switch connected to the power transmission antenna 111 is turned on. In FIG. 4, when the SPST switch is ON, the resistor is connected in series with the power transmission antenna, and when the SPST switch is OFF, the stray capacitance 201 is shown as an equivalent circuit connected in series with the power transmission antenna. FIG. 5 shows a simulation result of the relationship between the transmission coefficient and the frequency in the equivalent circuit of FIG.

  In FIG. 5, the vertical axis represents the transmission coefficient of the power transmitter and the power receiver, and the horizontal axis represents the frequency. FIG. 5 shows the results when the carrier frequency of the power transmitter is set to 1.7 MHz. In FIG. 5, the transmission coefficient at 1.7 MHz is −0 · 676 dB, which is about 85.5% in terms of efficiency. Since the Q value of the power transmitting antenna and the power receiving antenna is about 100 and the coupling coefficient is approximately 0.35, the maximum theoretical efficiency is 94%. However, the conventional circuit configuration is significantly lower than the theoretical efficiency. This is because an excess current flows through the power transmission antennas 110 and 112 whose switches are turned off, causing loss.

  In order to solve the above problems, a circuit configuration of the switch unit 114 in the present embodiment is shown in FIG. It is the structure which connected the coil in parallel with the conventional switch. The inductance value of the coil is set so as to resonate with the stray capacitance 201 of the semiconductor element at the carrier frequency.

  FIG. 7 shows an equivalent circuit of a wireless power transmission system using the switch unit 114. The equivalent circuit shown in FIG. 7 is an equivalent circuit in the case where the power receiving antenna 120 is positioned on the power transmitting antenna 111, as in FIG. In FIG. 7, only the SPST switch connected to the antenna 111 is turned on, and the two SPST switches corresponding to the power transmission antennas 110 and 112 are turned off.

  FIG. 8 shows a simulation result of the relationship between the transmission coefficient and the frequency in the equivalent circuit of FIG. In FIG. 7, the vertical axis represents the transmission coefficient of the power transmitter 113 and the power receiver 121, and the horizontal axis represents the frequency. FIG. 7 shows the result when the carrier frequency of the transmitter 308 is set to 1.7 MHz. The transmission coefficient at 1.7 MHz is -0.34 dB, which is about 92.4% in terms of efficiency. The circuit configuration of FIG. 7 improves the efficiency by about 7% compared to the circuit configuration shown in FIG. 4 using the conventional switch configuration. That is, the current flowing through the power transmission antennas 110 and 112 can be reduced as compared with the case where a conventional switch is used. Since current is reduced in the power transmission antennas 110 and 112, there is an effect of suppressing noise. This is because the amount of noise depends on the aperture area of the antenna through which current flows. In this way, the generation of current in the power transmission antenna with the switch unit 114 turned off is reduced, and loss is less likely to occur. This also improves the efficiency of wireless power transmission.

  In the present embodiment, the case where the position of the power receiving antenna 120 is on the power transmitting antenna 111 has been described, but the same effect can be obtained when the power receiving antenna 120 is positioned on the power transmitting antenna 110 or 112. That is, the same effect can be obtained even when the switch unit 114 corresponding to the power transmission antenna 110 is in the ON state and the other switch units 114 are OFF. The same effect can be obtained even when the switch unit 114 corresponding to the power transmission antenna 112 is in the ON state and the other switch units 114 are OFF. Although three power transmission antennas have been described, two or more power transmission antennas may be used.

(Embodiment 2)
In the first embodiment, the switch unit 114 switches whether the power transmission antenna and the power transmission circuit are connected. In the second embodiment, the switch unit 114 switches whether to connect the power transmission antenna and the matching circuit.

  In the second embodiment, the description of the same contents as in the first embodiment will be omitted, and different points from the first embodiment will be described in detail. Unless otherwise specified, the configuration using the same name has the same function as that of the first embodiment.

  FIG. 9 is a system configuration diagram of a printer to which the wireless power transmission system described in the present embodiment is applied. FIG. 9 is a diagram of the printer 900 viewed from the Y-axis direction of the coordinate axes illustrated in FIG.

  The printer 900 includes a power transmission unit 901 including a power transmission antenna 910, a power transmitter 911, three switch units 912, and three matching circuits 913. The printer 900 includes a power receiving antenna 920, a power receiving unit 902 including a power receiver 921, a control unit 103, an ink head 104, a position detection unit 105, a driving unit 106, and a power supply unit 107. The three matching circuits 913 have different impedance values. When the printer 900 is viewed from the X-axis direction of the coordinate axes illustrated in FIG. 9, the power receiving antenna 920 is disposed so as to overlap the power transmitting antenna 910. From the viewpoint of increasing the coupling coefficient between the power transmitting and receiving antennas, the power transmission antenna and the power receiving antenna 920 may have the same outer diameter as viewed from the X-axis direction. The three matching circuits 913 may be capacitors.

  The power receiver 921 is mechanically coupled to the ink head 104 and slides together with the ink head 104. That is, as the ink cartridge slides, the distance between the power transmitting and receiving antennas in the X-axis direction changes.

In order to efficiently transmit power in the system as described above, it is necessary to match the impedance with the load regardless of the distance between the power transmitting and receiving antennas. Therefore, it is necessary to switch the matching circuit according to the distance between the antennas. This is because the coupling coefficient changes when the distance between the antennas is changed.

  When the coupling coefficient is changed to 0.35, 0.5, and 0.9, the simulation result of the relationship between the transmission coefficient and the frequency when the matching circuit is switched by the switch unit 912 having the configuration shown in FIG. As shown in FIG. In FIG. 10, the transmission coefficient when the coupling coefficient is 0.35 is 1001, the transmission coefficient when the coupling coefficient is 0.5 is 1002, and the transmission coefficient when the coupling coefficient is 0.9 is 1003. The transmission coefficient at 1.7 MHz is -0.31 dB in all coupling coefficients, and is about 92.6% in terms of efficiency. That is, even if the distance fluctuates, sufficiently high-efficiency power transmission is possible.

  In the first and second embodiments, the case where the capacitor 303 matching with the antenna resonates in series with the inductance component 301 of the antenna as shown in FIG. 3 has been described, but as shown in FIGS. A simple circuit configuration may be used. The antennas of the first and second embodiments may be configured on a dielectric substrate such as FR4, or may be an antenna wound in a coil shape with a copper wire such as a litz wire. The switch unit 114 and the switch unit 912 may be relays that are mechanical switches. Moreover, you may combine Embodiment 1 and 2 suitably.

(Other embodiments)
Although the example in which the power transmission unit 101 and the power reception unit 102 are in the casing of the same device has been described, the present invention is not limited to this. The power transmission unit 101 may be configured as a power transmission device, and the power reception unit 102 may be configured as a separate device as a power reception device.

  The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions. Further, the program may be provided by being recorded on a computer-readable recording medium.

Claims (7)

A power transmission antenna;
A power transmission circuit for transmitting power using a carrier wave of a predetermined frequency;
A switch for switching between connecting or disconnecting the power transmission antenna and the power transmission circuit, comprising: a semiconductor element; and a switch having a coil connected in parallel with the semiconductor element,
The power transmission device, wherein the capacitance component of the semiconductor element and the inductor component of the coil resonate at the predetermined frequency in a state where the power transmission antenna and the power transmission circuit are disconnected by the switch.   The power transmission device according to claim 1, wherein the power transmission device includes a plurality of power transmission antennas and a plurality of the switches corresponding to the plurality of power transmission antennas. Selecting means for selecting a power transmission antenna to be connected to the power transmission circuit from the plurality of power transmission antennas;
The power transmission apparatus according to claim 2, wherein the switch corresponding to the power transmission antenna selected by the selection unit connects the power transmission antenna and the power transmission circuit.   The power transmission apparatus according to claim 3, wherein the selection unit selects a power transmission antenna to be connected to the power transmission circuit according to a position of a moving power reception antenna.   The power transmission device according to claim 4, wherein the power receiving antenna is an antenna for receiving power supplied to an ink head that ejects ink.   The power transmission device according to any one of claims 1 to 4, wherein the semiconductor element is a field effect transistor.   A switching unit that switches between connecting or disconnecting the power transmission antenna and the power transmission circuit between the power transmission antenna and a matching circuit for impedance matching of the power transmission antenna, the semiconductor element, and the semiconductor element The power transmission device according to any one of claims 1 to 6, further comprising a switching unit having a coil connected in parallel with the coil.

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