JP2022142090A - Power transmission device and wireless power transmission system - Google Patents

Abstract

To appropriately determine the timing to start power transmission to a power receiving device.SOLUTION: A power transmission device comprises: a voltage switching circuit capable of switching and outputting a first DC voltage and a second DC voltage smaller than the first DC voltage: an inverter circuit which converts the first DC voltage or the second DC voltage outputted from the voltage switching circuit into an AC voltage; a control circuit which controls the voltage switching circuit; and a plurality of power transmitting electrodes for wirelessly transmitting power to a plurality of power receiving electrodes of a power receiving device. In a detection mode, the control circuit causes the voltage switching circuit to output the second DC voltage. In a case where a predetermined condition including that (a) a phase difference between the AC voltage and an AC current measured by a measurement instrument is within a first range is satisfied, the control circuit switches the voltage outputted from the voltage switching circuit from the second DC voltage to the first DC voltage and shifts to a transmission mode.SELECTED DRAWING: Figure 16

Description

The present disclosure relates to a power transmission device and a wireless power transmission system.

2. Description of the Related Art In recent years, the development of wireless power transmission technology for transmitting power wirelessly, that is, in a contactless manner, to mobile devices such as mobile phones and electric vehicles is underway. Wireless power transmission technology includes various methods such as a magnetic field coupling method and an electric field coupling method.

In a magnetic field coupling wireless power transmission system, power is wirelessly transmitted from a power transmission coil to a power reception coil while the power transmission coil and the power reception coil face each other. For example, Patent Literatures 1 and 2 disclose examples of wireless power transmission systems using the magnetic field coupling method.

On the other hand, in a wireless power transmission system using an electric field coupling method, power is wirelessly transmitted from power transmission electrodes to power reception electrodes in a state in which two or more power transmission electrodes and two or more power reception electrodes face each other. A wireless power transmission system based on the electric field coupling method can be used, for example, for supplying power from a plurality of power transmission electrodes provided on the floor to a moving object having a load such as a battery. For example, Patent Literature 3 discloses an example of an electric field coupling type wireless power transmission system.

WO2011/099071 JP 2011-223860 A WO2020/241677

The present disclosure provides a novel technique for detecting with higher accuracy a state in which a power receiving electrode of a power receiving device faces a power transmitting electrode, and appropriately determining timing to start power transmission to the power receiving device.

A power transmitting device according to an embodiment of the present disclosure wirelessly transmits power to a power receiving device including a plurality of power receiving electrodes. The power transmission device includes a voltage switching circuit capable of switching and outputting a first DC voltage and a second DC voltage lower than the first DC voltage, and the first DC voltage output from the voltage switching circuit. Alternatively, an inverter circuit that converts the second DC voltage into an AC voltage and outputs it, a measuring device that measures the AC voltage and the AC current output from the inverter circuit, and the voltage based on the measured value of the measuring device A control circuit that controls a switching circuit, and a plurality of power transmission electrodes that transmit power based on the AC voltage output from the inverter circuit to the plurality of power reception electrodes of the power reception device. The control circuit operates in a detection mode for detecting the approach of the power receiving device and a transmission mode for transmitting power based on the first DC voltage to the power receiving device. The control circuit causes the voltage switching circuit to output the second DC voltage in the detection mode, and (a) the phase difference between the AC voltage and the AC current measured by the measuring device is within a first range. is satisfied, the detection mode is switched to the transmission mode by switching the voltage output from the voltage switching circuit from the second DC voltage to the first DC voltage.

General or specific aspects of this disclosure may be implemented in a system, apparatus, method, integrated circuit, computer program, or recording medium. Alternatively, they may be embodied in any combination of systems, devices, methods, integrated circuits, computer programs and recording media.

According to the embodiments of the present disclosure, it is possible to detect with higher accuracy the state in which the power receiving electrode of the power receiving device faces the power transmitting electrode, and appropriately determine the timing of starting power transmission to the power receiving device.

FIG. 1 is a diagram schematically showing an example of a wireless power transmission system using an electric field coupling method. FIG. 2 is a diagram showing a schematic configuration of the wireless power transmission system shown in FIG. 1. As shown in FIG. FIG. 3 is a diagram schematically showing another example of a wireless power transmission system using the electric field coupling method. FIG. 4 is a diagram showing a schematic configuration of the wireless power transmission system shown in FIG. 3. As shown in FIG. FIG. 5 is a diagram schematically showing a usage example of the wireless power transmission system. FIG. 6 is a diagram illustrating an example of a circuit configuration of a wireless power transmission system; FIG. 7A is a first diagram for explaining an example of power transmission control when moving body 200 travels along power transmission electrode sheet 120S. FIG. 7B is a second diagram for explaining an example of power transmission control when moving body 200 travels along power transmission electrode sheet 120S. FIG. 7C is a third diagram for explaining an example of power transmission control when moving body 200 travels along power transmission electrode sheet 120S. FIG. 8 is a diagram showing an example of relative positions between power receiving electrodes and power transmitting electrodes in a mobile body. FIG. 9A is a graph showing an example of the relationship between the electrode overlap ratio and the input current Iin of the inverter circuit. FIG. 9B is a graph showing another example of the relationship between the electrode overlap ratio and the input current Iin of the inverter circuit. FIG. 10 is a graph showing an example of temporal changes in the output voltage Vout and the output current Iout of the inverter circuit. FIG. 11 is a graph showing an example of the relationship between the phase difference between the output voltage Vout and the output current Iout in the demonstrator and the electrode overlap ratio. FIG. 12 is a diagram illustrating the configuration of a wireless power transmission system according to an exemplary embodiment of the present disclosure; FIG. 13 is a block diagram showing a configuration example of a voltage switching circuit. FIG. 14 is a diagram schematically showing a configuration example of an inverter circuit. FIG. 15 is a diagram schematically showing a configuration example of a rectifier circuit. FIG. 16 is a flow chart showing an example of operation in the detection mode by the power transmission control circuit. FIG. 17 is a flow chart showing an example of the operation of determining the transition timing to the transmission mode based only on the phase difference. FIG. 18 is a flow chart showing an example of processing for determining the timing of transition to the transmission mode based on the amount of noise contained in the waveform of the output voltage or current of the inverter circuit. FIG. 19 is a block diagram showing a configuration example of a system that determines the transition timing to the transmission mode based on the input current of the inverter circuit. 20 is a flow chart showing the operation of the power transmission control circuit in the example of FIG. 19. FIG. FIG. 21 is a diagram showing a configuration example of a moving object capable of adjusting load impedance. FIG. 22 is a diagram illustrating an example of a method of controlling a resistor circuit by a power reception control circuit; FIG. 23 is a diagram illustrating another example of a method of controlling the resistor circuit by the power reception control circuit. FIG. 24 is a diagram illustrating still another example of a method of controlling the resistor circuit by the power reception control circuit. FIG. 25 is a diagram illustrating still another example of a method of controlling the resistance circuit by the power reception control circuit. FIG. 26A is a diagram showing an example in which power transmission electrodes are laid on the side surface of a wall or the like. FIG. 26B is a diagram showing an example in which the power transmission electrodes are installed on the ceiling. FIG. 10 is a diagram schematically showing another example of a wireless power transmission system using an electric field coupling method; FIG. 28 is a diagram schematically showing configurations of a power receiving device and a power transmitting device in the example shown in FIG. 27; FIG. 10 is a diagram showing still another example of a power receiving device;

(Findings on which this disclosure is based)
Prior to describing the embodiments of the present disclosure, knowledge on which the present disclosure is based will be described.

FIG. 1 is a diagram schematically showing an example of a wireless power transmission system using an electric field coupling method. “Electric field coupling method” refers to electric field coupling (also referred to as “capacitive coupling”) between a power transmitting electrode group including a plurality of power transmitting electrodes and a power receiving electrode group including a plurality of power receiving electrodes, thereby A transmission method in which power is transmitted wirelessly (that is, contactless) to a group. For simplicity, first, an example in which each of the power transmitting electrode group and the power receiving electrode group is configured by a pair of two electrodes will be described.

The wireless power transmission system shown in FIG. 1 is a system that wirelessly transmits power to a mobile object 200 . The moving body 200 in this example is an automated guided vehicle (AGV). The mobile body 200 can be used for transporting goods, for example, in factories or warehouses. In this system, a pair of flat power transmission electrodes 120 a and 120 b are arranged on a floor surface 30 . The pair of power transmission electrodes 120a and 120b has a shape extending in the first direction (the Y direction in FIG. 1). AC power is supplied from the power transmission circuit to the pair of power transmission electrodes 120a and 120b.

The moving body 200 includes a pair of power receiving electrodes facing the pair of power transmitting electrodes 120a and 120b. The moving body 200 receives the AC power transmitted from the power transmitting electrodes 120a and 120b by a pair of power receiving electrodes. The received electric power is supplied to a load such as a motor, a secondary battery (battery), or a capacitor for power storage provided in the moving body 200 . Thereby, charging or driving of the moving body 200 is performed.

FIG. 1 shows XYZ coordinates indicating mutually orthogonal X, Y, and Z directions. The following description uses the XYZ coordinates shown. The direction in which the power transmission electrodes 120a and 120b extend is the Y direction, the direction perpendicular to the surfaces of the power transmission electrodes 120a and 120b is the Z direction, and the direction perpendicular to the Y and Z directions is the X direction. The X direction is the direction in which the power transmission electrodes 120a and 120b are arranged. It should be noted that the orientations of the structures shown in the drawings of the present application are set in consideration of the clarity of explanation, and do not limit the orientations when the embodiments of the present disclosure are actually implemented. Also, the shape and size of all or part of the structures shown in the drawings are not intended to limit the actual shape and size.

FIG. 2 is a diagram showing a schematic configuration of the wireless power transmission system shown in FIG. 1. As shown in FIG. The wireless power transmission system includes a power transmission device 100 and a mobile object 200 that is a power reception device.

The power transmission device 100 includes a pair of power transmission electrodes 120a and 120b and a power transmission circuit 110 that supplies AC power to the power transmission electrodes 120a and 120b. The power transmission circuit 110 is, for example, an AC output circuit including an inverter circuit. The power transmission circuit 110 converts the power supplied from the power source 400 into AC power for power transmission, and outputs the AC power to the pair of power transmission electrodes 120a and 120b. The power supply 400 can be, for example, a commercial AC power supply that outputs AC power with a frequency of 50 Hz or 60 Hz and a voltage of 100V, 120V, 200V, or 240V. Power transmission circuit 110 may include a converter circuit that converts AC power supplied from power supply 400 into DC power, and an inverter circuit that converts DC power output from the converter circuit into AC power for transmission. The power transmission circuit 110 may include a matching circuit for impedance matching between the power transmission electrodes 120a and 120b and the inverter circuit.

The moving body 200 includes a pair of power receiving electrodes 220 a and 220 b, a power receiving circuit 210 and a load 230 . The power receiving circuit 210 converts the AC power received by the power receiving electrodes 220 a and 220 b into another form of power required by the load 230 and supplies the load 230 with the power. Power receiving circuit 210 outputs DC power of a predetermined voltage or AC power of predetermined frequency and voltage required by load 230 . Power receiving circuit 210 may include various circuits such as, for example, a rectifying circuit and an impedance matching circuit. The load 230 may include devices that consume or store power, such as motors, storage capacitors, or secondary batteries, and circuits that control those devices. Due to the electric field coupling between the pair of power transmission electrodes 120a and 120b and the pair of power reception electrodes 220a and 220b, power is wirelessly transmitted while the two electrodes face each other.

Each of the power transmitting electrodes 120a, 120b and the power receiving electrodes 220a, 220b may be divided into two or more portions. For example, configurations as shown in FIGS. 3 and 4 may be adopted.

3 and 4 are diagrams showing examples of wireless power transmission systems in which each of the power transmitting electrode group and the power receiving electrode group includes four electrodes. In this example, the power transmission device 100 includes two first power transmission electrodes 120a and two second power transmission electrodes 120b. The two first power transmission electrodes 120a and the two second power transmission electrodes 120b are alternately arranged along the second direction (the X direction in FIG. 3). The moving body 200 similarly includes two first power receiving electrodes 220a and two second power receiving electrodes 220b. The two first power receiving electrodes 220a and the two second power receiving electrodes 220b are also alternately arranged. During power transmission, the two first power receiving electrodes 220a face the two first power transmitting electrodes 120a, respectively, and the two second power receiving electrodes 220b face the two second power transmitting electrodes 120b, respectively.

The power transmission circuit 110 has two terminals for outputting AC power. One terminal is connected to the two first power transmission electrodes 120a, and the other terminal is connected to the two second power transmission electrodes 120b. When power is transmitted, the power transmission circuit 110 applies a first voltage to the two first power transmission electrodes 120a and applies a second voltage opposite in phase to the first voltage to the two second power transmission electrodes 120b. Apply voltage. Thus, electric power is wirelessly transmitted by electric field coupling between a power transmitting electrode group including four power transmitting electrodes and a power receiving electrode group including four power receiving electrodes. According to such a configuration, it is possible to obtain the effect of suppressing the leakage electric field on the boundary between any two adjacent power transmission electrodes. Thus, in each of power transmission device 100 and moving body 200, the number of electrodes that transmit or receive power is not limited to two.

In the following embodiments, as shown in FIGS. 1 and 2, a configuration in which the power transmission device 100 includes two power transmission electrodes and the moving body 200 includes two power reception electrodes will be mainly described. In each of the embodiments below, each of the power transmitting electrode group and the power receiving electrode group may include more than two electrodes, as illustrated in FIGS. In either case, the electrodes to which the first voltage is applied at a given moment and the electrodes to which the second voltage having the opposite phase to the first voltage are applied are arranged alternately. Here, the term "opposite phase" is defined to include not only the case where the phase difference is 180 degrees, but also the case where the phase difference is within the range of 90 degrees to 270 degrees. In the following description, the plurality of power transmission electrodes included in the power transmission device 100 may be referred to as “power transmission electrodes 120” without distinction, and the plurality of power reception electrodes included in the moving object 200 may be referred to as “power reception electrodes 220” without distinction. be.

According to the wireless power transmission system as described above, the moving object 200 can wirelessly receive power while moving along the power transmission electrode 120 . The moving body 200 can move along the power transmitting electrode 120 while maintaining the state in which the power transmitting electrode 120 and the power receiving electrode 220 face each other in close proximity. As a result, the moving body 200 can move while charging a power storage device such as a battery or a capacitor.

FIG. 5 is a diagram schematically showing a usage example of the wireless power transmission system. The wireless power transfer system in this example is utilized within a warehouse. This system includes multiple power transmission devices 100 and multiple moving bodies 200 . Each power transmission device 100 includes a power transmission electrode sheet 120S including two power transmission electrodes 120, and a power transmission circuit 110 shown in FIG. A warehouse is provided with a plurality of shelves 40 forming a plurality of rows. A plurality of power transmission electrode sheets 120S are arranged between rows of shelves 40 . AC power is supplied from the power transmission circuit 110 to the two power transmission electrodes 120 in each power transmission electrode sheet 120S. Each moving body 200 automatically travels along a predetermined route in the warehouse, picks up an article stored on the shelf 40, and carries it to a predetermined location. Each moving body 200 includes, for example, a secondary battery and an electric motor for driving. Each moving body 200 runs by driving an electric motor for driving with electric energy stored in a secondary battery. Each moving body 200 charges a secondary battery when traveling in an area where the power transmission electrode sheet 120S is arranged (hereinafter referred to as "power transmission area"). That is, each moving object 200 receives power sent from the power transmitting electrode 120 at the power receiving electrode 220, and runs while charging the secondary battery with the power. As a result, the transportation work can be continued without being unable to travel due to insufficient power storage.

In such a system, the moving body 200 repeatedly enters and exits the power transmission area in which the power transmission electrode sheet 120S is arranged. Therefore, each power transmission device 100 operates by switching between two modes, the detection mode and the transmission mode. The power transmission device 100 operates in a detection mode that outputs weak power from the power transmission electrode 120 and detects the approach of the mobile body 200 when the mobile body 200 does not exist in the power transmission area. The power transmission device 100 can detect the approach of the moving object 200 based on the measured values such as the current flowing through the power transmission circuit 110 . When the power transmission device 100 detects the approach of the mobile body 200 , the power transmission device 100 increases the power output from the power transmission electrode 120 and shifts to a transmission mode in which power is transmitted to the mobile body 200 . While the moving body 200 is running on the power transmission electrode sheet 120S, the power transmission device 100 operates in transmission mode. When the mobile body 200 leaves the power transmission area, the power transmission device 100 switches from the transmission mode to the detection mode and waits for the arrival of the next mobile body 200 .

FIG. 6 is a diagram illustrating an example of a circuit configuration of a wireless power transmission system capable of switching between detection mode and transmission mode. The power transmission circuit 110 shown in FIG. 6 includes a voltage switching circuit 130, an inverter circuit 160, and a matching circuit 180. In FIG. Power receiving circuit 210 includes a matching circuit 280 and a rectifying circuit 260 .

Voltage switching circuit 130 includes a first DC power supply 131 , a DC-DC converter circuit 135 and a switch 132 . The DC-DC converter circuit 135 converts a relatively high DC voltage (eg, 200 V) output from the first DC power supply 131 into a lower DC voltage (eg, 3.3 V to 12 V). The DC-DC converter circuit 135 is also called a second DC power supply. The switch 132 is a switch for switching between detection mode and transmission mode, and is connected to the first DC power supply 131 and the DC-DC converter circuit 135 . The switch 132 is a semiconductor switch such as a MOSFET (Metal Oxide Semiconductor Field-Effect Transistor), and is controlled by a control circuit including a gate driver. In the detection mode, the switch 132 is opened (turned off), and a relatively low DC voltage output from the DC-DC converter circuit 135 is applied to the inverter circuit 160 . On the other hand, in the transmission mode, the switch 132 is closed (on), and a relatively high DC voltage output from the first DC power supply 131 is applied to the inverter circuit 160 .

The inverter circuit 160 converts the DC voltage output from the voltage switching circuit 130 into an AC voltage and outputs the AC voltage. Matching circuit 180 matches the impedance between inverter circuit 160 and power transmission electrode 120 . The matching circuit 180 is arranged as required, and its circuit configuration can be modified in various ways.

The matching circuit 280 in the power receiving circuit 210 matches the impedance between the power receiving electrode 220 and the rectifier circuit 260 . The matching circuit 280 is also arranged as required, and its circuit configuration can be modified in various ways. Rectifier circuit 260 converts the AC voltage output from matching circuit 280 into a DC voltage and outputs the DC voltage to load 230 .

7A to 7C are diagrams for explaining an example of power transmission control when moving body 200 travels along power transmission electrode sheet 120S. FIG. 7A shows a situation in which the moving object 200 is traveling toward the power transmission area where the power transmission electrode sheet 120S is arranged. FIG. 7B shows a situation where the power receiving electrode 220 of the moving object 200 has started to face the power transmitting electrode 120. FIG. FIG. 7C shows the situation after the mobile object 200 has passed through the power transmission area.

As shown in FIG. 7A, when the moving body 200 is traveling toward the power transmission electrode sheet 120S, the power transmission device 100 operates in detection mode. In sensing mode, power transmission circuit 110 supplies weak power to power transmission electrode 120 . For example, the power transmission circuit 110 applies a relatively low voltage (eg, 12 V) output from the DC-DC converter circuit 135 to the power transmission electrode 120 by opening the switch 132 shown in FIG. In this state, the power transmission circuit 110 can measure, for example, the input current Iin to the inverter circuit 160, and detect the approach of the moving object 200 based on the fluctuation of the measured value.

As shown in FIG. 7B , when power receiving electrode 220 of moving object 200 begins to face power transmitting electrode 120, input current Iin to inverter circuit 160 increases as the coupling capacitance between power transmitting electrode 120 and power receiving electrode 220 increases. increases. The power transmission circuit 110 detects that the power receiving electrode 220 of the moving object 200 faces the power transmitting electrode 120 based on the change in the input current Iin. For example, when the measured value of the input current Iin exceeds a predetermined threshold, it can be determined that the power receiving electrode 220 of the moving body 200 has faced the power transmitting electrode 120 . When the power transmission circuit 110 detects that the power receiving electrode 220 faces the power transmission electrode 120, the power transmission circuit 110 switches from the detection mode to the transmission mode. In the transmission mode, the power transmission circuit 110 outputs AC power (eg, 1.5 kW) of relatively high voltage (eg, 200 V) to the power transmission electrode 120 . Switching from the sensing mode to the transmission mode can be done, for example, by switching the switch 132 shown in FIG. 6 from off (non-conducting state) to on (conducting state). Thereafter, power transmission in the transmission mode is performed until the moving object 200 passes through the power transmission area. While the moving body 200 is traveling in the power transmission area, the power transmission circuit 110 determines whether the moving body 200 has passed through the power transmission area based on the measured value of the input current Iin. For example, when the measured value of the input current Iin is below a predetermined threshold, it can be determined that the moving object 200 has passed through the power transmission area.

As shown in FIG. 7C, when the moving object 200 passes through the power transmission area, the power transmission circuit 110 switches from the transmission mode to the detection mode. The power transmission circuit 110 switches from the transmission mode to the sensing mode by switching the switch 132 in the power transmission circuit 110 from on to off to reduce the output voltage, for example, from 200V to 12V. Thereafter, the power transmission circuit 110 operates in the detection mode and waits for the arrival of the moving body 200 until the next moving body 200 approaches the power transmission area.

In the system as described above, the power transmission circuit 110 operates in a state in which the power receiving electrode 220 of the moving body 200 is sufficiently opposed to the power transmitting electrode 120, in other words, in a state in which the coupling capacitance between the power transmitting electrode 120 and the power receiving electrode 220 is sufficiently high. It is important that switch 132 is turned on. This is because matching circuits 180 and 280 are designed such that impedance matching is achieved with sufficiently high coupling capacitance such that power is transferred with high efficiency in transmission mode.

FIG. 8 is a diagram showing an example of relative positions between the power receiving electrode 220 and the power transmitting electrode 120 in the mobile body 200. As shown in FIG. FIG. 8 shows how the moving object 200 runs on the power transmission electrode 120 in the order of (a), (b), and (c). (a) of FIG. 8 shows a state in which the power receiving electrode 220 does not face the power transmitting electrode 120 at all. (b) of FIG. 8 shows a state in which the power receiving electrode 220 slightly faces the power transmitting electrode 120 . (c) of FIG. 8 shows a state in which the power receiving electrode 220 completely faces the power transmitting electrode 120 . When the sensing mode is shifted to the transmission mode in the state shown in (a) or (b) of FIG. Reflection of the transmitted power increases within the power transmission device 100 . As a result, problems such as destruction of circuit elements in power transmission circuit 110 may occur. In order to avoid such a problem, switching from the detection mode to the transmission mode may be performed in a state where the power receiving electrode 220 and the power transmitting electrode 120 are sufficiently opposed to each other, as shown in FIG. 8(c). desirable.

However, it is not easy to detect with high accuracy the state in which the power receiving electrode 220 and the power transmitting electrode 120 are sufficiently opposed to each other. In the example shown in FIGS. 7A to 7C , power transmission circuit 110 estimates the degree of overlap between power reception electrode 220 and power transmission electrode 120 based on input current Iin of inverter circuit 160 . However, as a result of verification by the present inventors, it was found that there are cases where the input current Iin significantly increases and exceeds the threshold even though the power receiving electrode 220 is not sufficiently opposed to the power transmitting electrode 120 .

This problem will be described with reference to FIGS. 9A and 9B. FIG. 9A shows an example of the relationship between the ratio of the overlapping area of the power transmitting electrode 120 and the power receiving electrode 220 to the area of the power receiving electrode 220 (hereinafter referred to as "electrode overlap ratio") and the input current Iin to the inverter circuit 160. is a graph showing The overlapping area of the power transmitting electrode 120 and the power receiving electrode 220 means the area of the portion of the surface of the power receiving electrode 220 that overlaps with the power transmitting electrode 120 when viewed in a direction perpendicular to the surface. FIG. 9A shows an ideal example in which the input current Iin increases as the electrode overlap ratio increases. In such a case, the above method of determining that the power receiving electrode 220 has sufficiently overlapped the power transmitting electrode 120 when the input current Iin exceeds the threshold value is effective. The threshold may be set to the value of the input current Iin when 70% or more of the power receiving electrodes 220 overlap the power transmitting electrodes 120, for example.

However, in practice, the characteristics shown in FIG. 9A are not necessarily obtained. FIG. 9B is a graph showing an example of the relationship between the electrode overlap ratio and the input current Iin in a demonstrator. In the example of FIG. 9B, the input current Iin does not monotonically increase as the electrode overlap ratio increases. In this example, the input current Iin is remarkably high when the electrode overlap ratio is in the range of approximately 0.55 to 0.8. When the electrode overlap ratio is in the range of approximately 0.4 to 0.5, the input current Iin is approximately the same value as when the electrode overlap ratio is 1. In such a case, even if the electrode overlap ratio is approximately 0.4, the input current Iin exceeds the threshold, and it may be erroneously determined that the power receiving electrode 220 sufficiently overlaps the power transmitting electrode 120 . The characteristic shown in FIG. 9B is an example, and depending on the configuration of the matching circuit 180 and the like, the relationship between the input current Iin and the electrode overlap ratio can vary greatly.

Therefore, in the method based on comparison between the input current Iin of the inverter circuit 160 and the threshold, it is difficult to detect the state in which the power transmitting electrode 120 and the power receiving electrode 220 are sufficiently opposed to each other. In order to detect with higher accuracy, for example, a method in which the power transmission circuit 110 detects that the power reception electrode 220 has sufficiently opposed the power transmission electrode 120 based on feedback information transmitted from the moving object 200 is also conceivable. However, the method of using the feedback information from the mobile unit 200 requires a relatively long time for communication, so detection takes time and the shift to the transmission mode may be delayed. In a system that charges the mobile object 200 while it is running, it is required to shorten the time until the start of charging as much as possible in order to secure the charging time as long as possible. Moreover, having a separate communication means also increases the cost. Therefore, it is desirable to be able to detect that the power receiving electrode 220 and the power transmitting electrode 120 have sufficiently opposed each other based on the behavior of the circuit in the power transmitting device 100 without using feedback information from the mobile body 200 .

Based on the above considerations, the inventors considered introducing an indicator other than the input current Iin in order to detect that the power receiving electrode 220 is sufficiently opposed to the power transmitting electrode 120 . The present inventors have investigated the phase difference between the output voltage Vout and the output current Iout (see FIG. 6) of the inverter circuit 160, the temporal variation of the phase difference, or the amount of noise in the output voltage Vout or the output current Iout, and the power transmission electrode 120 and the coupling capacitance with the power receiving electrode 220 have a correlation, and arrived at the technique of the present disclosure.

Fluctuations in the coupling capacitance between power transmitting electrode 120 and power receiving electrode 220 cause variations in the input impedance of circuits subsequent to inverter circuit 160 . A change in the input impedance causes a change in the phase difference between the output voltage Vout and the output current Iout of the inverter circuit 160 . In the wireless power transmission system as described above, when the coupling capacitance between the power transmitting electrode 120 and the power receiving electrode 220 is high, the current lags behind the voltage, resulting in low circuit loss and high transmission efficiency. Conversely, when the coupling capacitance between the power transmitting electrode 120 and the power receiving electrode 220 is low, the phase lag of the current with respect to the voltage is small and the current may lead the voltage.

FIG. 10 is a graph showing an example of temporal changes in output voltage Vout and output current Iout of inverter circuit 160 . In this example, the phase of the output current Iout lags the phase of the output voltage Vout by Δθ=2πΔt/T. Here, Δt is the time difference between the waveform of the output voltage Vout and the waveform of the output current Iout, and T is the period of the output voltage Vout and the output current Iout. In this specification, it is assumed that the phase difference Δθ and the time difference Δt take positive values in a lagging state in which the output current Iout lags behind the output voltage Vout. In the following description, not only Δθ but also Δt may be referred to as "phase difference".

FIG. 11 is a graph showing an example of the relationship between the phase difference between the output voltage Vout and the output current Iout and the electrode overlap ratio in a demonstrator. In FIG. 11, the time difference Δt is represented as a phase difference. For comparison, FIG. 11 also shows the waveform of the input current Iin shown in FIG. 9B. As the electrode overlap ratio approaches 1 (100%), the coupling capacitance increases. As can be seen from this graph, the phase difference Δt increases as the electrode overlap ratio increases. Therefore, it can be determined that power receiving electrode 220 has sufficiently opposed power transmitting electrode 120 based on phase difference Δt or Δθ. For example, the range of Δt or Δθ when the electrode overlap ratio exceeds 0.7 is recorded in advance, and based on whether the value of Δt or Δθ during operation is within the recorded range, the power receiving electrode It can be determined whether 220 is sufficiently opposed to the power transmitting electrode 120 .

Furthermore, when the state fluctuation of the device on the power receiving side is large (for example, when the electrode overlap ratio is small and the coupling capacitance changes greatly over time) or when the input current Iin is small, the waveforms of the output voltage Vout and the output current Iout It was found that a large amount of noise was generated and the variation in the detected phase difference increased. Therefore, it is also possible to determine whether or not the power receiving electrode 220 sufficiently faces the power transmitting electrode 120 based on the amount of noise in the waveform of the output voltage Vout or the output current Iout or the amount of temporal variation in the phase difference. is. The amount of noise in the waveform of the output voltage Vout or the output current Iout can be evaluated, for example, by Fourier transforming each waveform and extracting high frequency components. Also, the amount of variation in the phase difference can be evaluated by, for example, repeatedly calculating the phase difference at short time intervals and calculating an index value indicating the degree of variation, such as the variance or standard deviation of the obtained phase difference.

An outline of the embodiments of the present disclosure will be described below.

A power transmitting device according to an exemplary embodiment of the present disclosure wirelessly transmits power to a power receiving device comprising a plurality of power receiving electrodes. The power transmission device includes a voltage switching circuit capable of switching and outputting a first DC voltage and a second DC voltage lower than the first DC voltage, and the first DC voltage output from the voltage switching circuit. Alternatively, an inverter circuit that converts the second DC voltage into an AC voltage and outputs it, a measuring device that measures the AC voltage and the AC current output from the inverter circuit, and the voltage based on the measured value of the measuring device A control circuit that controls a switching circuit, and a plurality of power transmission electrodes that transmit power based on the AC voltage output from the inverter circuit to the plurality of power reception electrodes of the power reception device. The control circuit operates in a detection mode for detecting the approach of the power receiving device and a transmission mode for transmitting power based on the first DC voltage to the power receiving device. 2 outputting a DC voltage, and if a predetermined condition including (a) a phase difference between the AC voltage and the AC current measured by the measuring device being within a first range, the voltage switching; The detection mode is switched to the transmission mode by switching the voltage output from the circuit from the second DC voltage to the first DC voltage.

Here, the "phase difference" refers to a value obtained by subtracting the phase of the AC current from the phase of the AC voltage. Phase is typically expressed in units of radians (rad) or degrees (°), but values converted to time may also be treated as phase. The "first range" may be a range defined by a lower limit value θmin and an upper limit value θmax. Alternatively, the first range may be defined only by the lower limit θmin without defining the upper limit θmax. In this case, with θmin as a threshold, it is determined that the phase difference is within the first range when the phase difference is equal to or greater than θmin.

According to the above configuration, it is possible to switch from the detection mode to the transmission mode at an appropriate timing based on the phase difference between the AC voltage and the AC current output from the inverter circuit. As described above, the phase difference between the AC voltage and the AC current output from the inverter circuit has a correlation with the overlapping area ratio of the power transmitting electrode and the power receiving electrode. By switching to the transmission mode based on the phase difference, it is possible to switch to the transmission mode at an appropriate timing when the power receiving electrode faces the power transmitting electrode.

In the detection mode, the control circuit performs the voltage switching when the conditions (a) and (b) an amount of variation indicating the degree of temporal variation of the phase difference is within a second range. The detection mode may be switched to the transmission mode by switching the voltage output from the circuit from the second DC voltage to the first DC voltage. In addition to the phase difference, it is possible to detect the state in which the power receiving electrode faces the power transmitting electrode with higher accuracy by considering the amount of temporal variation in the phase difference.

The "second range" may be a range defined by a lower limit value σmin and an upper limit value σmax. Alternatively, the second range may be defined only by the upper limit value σmax without defining the lower limit value σmin. In this case, with σmax as a threshold, if the amount of variation is equal to or less than σmax, it is determined that the amount of variation is within the second range.

The control circuit, in the detection mode, satisfies the conditions (a) and (c) that the amount of noise contained in the waveform of the AC voltage and/or the AC current is within a third range, the The detection mode may be switched to the transmission mode by switching the voltage output from the voltage switching circuit from the second DC voltage to the first DC voltage. By considering the amount of voltage or current noise in addition to the phase difference, the state in which the power receiving electrode faces the power transmitting electrode can be detected with higher accuracy.

The "third range" may be a range defined by a lower limit nmin and an upper limit nmax. Alternatively, the third range may be defined only by the upper limit value nmax without defining the lower limit value nmin. In this case, nmax is used as a threshold, and when the amount of noise is equal to or less than nmax, it is determined that the amount of variation is within the third range.

In the detection mode, the control circuit satisfies the conditions (a) and (b) that the variation amount indicating the degree of temporal variation of the phase difference is within a second range, and (c) the AC voltage and /or switching the voltage output from the voltage switching circuit from the second DC voltage to the first DC voltage when the amount of noise included in the waveform of the AC current is within a third range. may be switched from the detection mode to the transmission mode by. By considering the amount of temporal variation in the phase difference and the amount of voltage or current noise in addition to the phase difference, the state in which the power receiving electrode faces the power transmitting electrode can be detected with even higher accuracy.

The control circuit repeatedly calculates the phase difference between the alternating voltage and the alternating current based on the measured values of the alternating voltage and the alternating current measured by the measuring device, and calculates the phase difference within a unit time. may be calculated as the variation amount. By determining the timing of switching to the transmission mode based on such variations, erroneous determination can be easily prevented.

The control circuit controls a voltage zero crossing at which the measured value of the AC voltage output from the inverter circuit becomes zero, and/or the measured value of the AC current output from the inverter circuit becomes zero. A current zero-crossing point is detected at a time, and an amount corresponding to the frequency of the voltage zero-crossing point and/or the current zero-crossing point detected during a half cycle of the driving frequency of the inverter circuit is calculated as the noise amount. You may By using such a noise amount, it becomes easier to prevent erroneous determination.

The power transmission device may further include a current measuring device that measures an input current of the inverter circuit. The control circuit changes the voltage output from the voltage switching circuit to the The detection mode may be switched to the transmission mode by switching from a second DC voltage to the first DC voltage. Further consideration of the input current of the inverter circuit makes it easier to prevent erroneous determination. In this case, at least one of the above conditions (b) and (c) may be included in the conditions for mode switching.

The "fourth range" may be a range defined by the lower limit value Imin and the upper limit value Imax. Alternatively, the upper limit value Imax may not be defined, and the fourth range may be defined only by the lower limit value Imin. In this case, with Imin as a threshold, it is determined that the value of the input current is within the fourth range when the measured value of the input current is equal to or greater than Imin.

A wireless power transmission system according to an embodiment of the present disclosure includes any of the power transmitting devices described above and the power receiving device.

The power receiving device operates by a rectifying circuit that converts AC power received by the plurality of power receiving electrodes into DC power and outputs the DC power, and the DC power that is output from the rectifying circuit. a load that is activated when a starting voltage is exceeded; a resistor circuit connected between the rectifier circuit and the load, the resistor circuit including a resistor connected in parallel to the load; and the power receiving device. a power reception control circuit that controls the impedance of the resistance circuit so as to suppress fluctuations in the load impedance of the rectifier circuit caused by the approach of the power transmission device and the activation of the load. According to such a configuration, in the process of shifting from the detection mode to the transmission mode, fluctuations in the load impedance can be suppressed, and fluctuations in the output voltage and output current of the inverter circuit can be suppressed. Therefore, it is possible to reduce errors in determination based on the phase difference or the amount of noise.

The “power receiving device” in the present disclosure is not limited to mobile objects, and may be any device that can be moved or carried. The power receiving device may be mounted on a portable electronic device, such as a mobile phone, or on a movable outlet (charging pole), for example.

A "moving object" in this disclosure is not limited to vehicles such as the aforementioned automatic guided vehicle (AGV), but means any movable object driven by electric power. A mobile object includes, for example, an electric vehicle having an electric motor and one or more wheels. Such vehicles can be, for example, the aforementioned AGVs, transport robots, electric vehicles (EV), electric carts, electric wheelchairs. A "moving object" in the present disclosure also includes a movable object that does not have wheels. For example, bipedal walking robots, unmanned aerial vehicles (UAVs, so-called drones) such as multicopters, manned electric aircraft, and elevators are also included in the “mobile body”. Hereinafter, more specific embodiments of the present disclosure will be described. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid unnecessary verbosity in the following description and to facilitate understanding by those skilled in the art. It is noted that the inventors provide the accompanying drawings and the following description for a full understanding of the present disclosure by those skilled in the art and are not intended to limit the claimed subject matter thereby. do not have. In the following description, constituent elements having the same or similar functions are given the same reference numerals.

(embodiment)
FIG. 12 is a diagram illustrating the configuration of a wireless power transmission system according to an exemplary embodiment of the present disclosure; This wireless power transmission system is a system for wirelessly transmitting power to mobile bodies, like the examples shown in FIGS. 1 to 7C. A wireless power transmission system includes one or more power transmission devices and one or more moving bodies.

The wireless power transmission system shown in FIG. 12 includes a power transmission device 100 and a mobile object 200. Also shown in FIG. 12 is an AC power supply 400, which is an external element of the wireless power transfer system.

The power transmission device 100 includes a power transmission circuit 110 , two power transmission electrodes 120 , a measuring instrument 140 that measures current and voltage, and a power transmission control circuit 150 . The power transmission circuit 110 includes a voltage switching circuit 130 , an inverter circuit 160 and a matching circuit 180 .

The voltage switching circuit 130 is a circuit that switches the voltage input to the inverter circuit 160 . FIG. 13 is a block diagram showing a configuration example of the voltage switching circuit 130. As shown in FIG. The voltage switching circuit 130 shown in FIG. 13 includes a transmission mode first DC power supply 131 , a switch 132 , a detection mode second DC power supply 136 , a diode 137 and an electrolytic capacitor 139 . First DC power supply 131, second DC power supply 136, and electrolytic capacitor 139 are connected in parallel with each other. Diode 137 is connected in series with second DC power supply 136 to prevent reverse current flow to second DC power supply 136 . Switch 132 is a semiconductor switch and is connected between first DC power supply 131 and second DC power supply 136 . Electrolytic capacitor 139 is connected in parallel between second DC power supply 136 and inverter circuit 160 . The electrolytic capacitor 139 smoothes the DC voltage output from the first DC power supply 131 or the second DC power supply 136 and supplies a constant DC voltage to the inverter circuit 160 .

The first DC power supply 131 and the second DC power supply 136 may be AC-DC converter circuits that convert AC power output from the external AC power supply 400 into DC power and output the DC power. First DC power supply 131 and second DC power supply 136 may include, for example, a rectifier circuit connected to AC power supply 400 and a DC-DC converter circuit. The second DC power supply 136 may be a DC-DC converter circuit that steps down the voltage output from the first DC power supply 131, like the DC-DC converter circuit 135 shown in FIG. The first DC power supply 131 outputs DC power with a relatively high voltage V1 (for example, 200 V) for transmission mode. The second DC power supply 136 outputs DC power with a relatively low voltage V2 (for example, 12V) for detection mode. A switch 132 is a switch for switching between a detection mode and a transmission mode. The switch 132 shown in FIG. 13 is an N-channel MOSFET. The source of switch 132 is connected to diode 137 , electrolytic capacitor 139 and inverter circuit 160 . A drain of the switch 132 is connected to the first DC power supply 131 . A gate of the switch 132 is connected to the power transmission control circuit 150 . The power transmission control circuit 150 includes a gate driver. The switch 132 is controlled by a gate drive signal input from the gate driver. Note that the switch 132 is not limited to an N-channel MOSFET, and may be another type of semiconductor switch such as a P-channel MOSFET or an IGBT (Insulated-Gate Bipolar Transistor).

The gate driver in the power transmission control circuit 150 outputs a gate drive signal that opens (off) the switch 132 in the detection mode and closes (on) the switch 132 in the transmission mode. Accordingly, in the detection mode, a relatively small DC current flows from second DC power supply 136 to electrolytic capacitor 139 and inverter circuit 160 . On the other hand, in the transmission mode, a relatively large DC current flows from first DC power supply 131 to electrolytic capacitor 139 and inverter circuit 160 .

The inverter circuit 160 converts the DC power output from the voltage switching circuit 130 into AC power and outputs the AC power. FIG. 14 is a diagram schematically showing a configuration example of the inverter circuit 160. As shown in FIG. In this example, the inverter circuit 160 is a full-bridge inverter circuit including four switching elements. Each switching element can be realized by an IGBT, MOSFET, or a transistor such as GaN, for example. Each switching element is controlled by a power transmission control circuit 150 . The power transmission control circuit 150 includes a gate driver that outputs a control signal for controlling the on (conduction) and off (non-conduction) states of each switching element, and a processor such as a microcontroller (MCU) that causes the gate driver to output a drive signal. and Power transmission control circuit 150 causes inverter circuit 160 to output AC power having a desired frequency and voltage by controlling the ON and OFF states of each switching element. Instead of the illustrated full-bridge inverter circuit, a half-bridge inverter circuit or other types of oscillator circuits, such as class E, may be used.

The frequency of power transmission may be set, for example, between 50 kHz and 300 GHz, in some examples between 20 kHz and 10 GHz, in other examples between 20 kHz and 20 MHz, and in still other examples between 80 kHz and 14 MHz. However, it is not limited to these frequency ranges.

Matching circuit 180 matches the impedance between inverter circuit 160 and power transmission electrode 120 . The matching circuit 180 may have the same configuration as the matching circuit 180 shown in FIG. 6, for example. The matching circuit 180 may have a configuration different from that shown in FIG.

Measuring instrument 140 measures the current and voltage output from inverter circuit 160 . The power transmission control circuit 150 can detect the approach of the moving object 200 based on the phase difference between the current and the voltage measured by the measuring device 140, and shift from the detection mode to the transmission mode.

The moving body 200 includes a plurality of power receiving electrodes 220 , a power receiving circuit 210 , a charge/discharge control circuit 310 , an electric motor 320 and an electricity storage device 330 . Power receiving circuit 210 includes a matching circuit 280 and a rectifying circuit 260 .

The matching circuit 280 matches the impedance between the power receiving electrode 220 and the rectifier circuit 260 . The matching circuit 280 may have the same configuration as the matching circuit 280 shown in FIG. 6, for example. The matching circuit 280 may have a configuration different from that shown in FIG.

Rectifier circuit 260 converts the AC power output from matching circuit 280 into DC power. FIG. 15 is a diagram schematically showing a configuration example of the rectifier circuit 260. As shown in FIG. Rectifier circuit 260 in this example is a full-wave rectifier circuit including a diode bridge and a smoothing capacitor. Rectifier circuit 260 may have other configurations, such as, for example, a half-wave rectifier circuit. Rectifier circuit 260 converts the AC energy it receives into DC energy that can be used by loads such as storage device 330 and motor 320 .

Charge/discharge control circuit 310 is connected between power reception circuit 210 and power storage device 330 and controls charging and discharging of power storage device 330 .

The electric motor 320 is connected to the charge/discharge control circuit 310 and driven by the energy stored in the electrical storage device 330 . Motor 320 may be any motor, such as a DC motor, permanent magnet synchronous motor, induction motor, stepper motor, or reluctance motor. The motor 320 rotates the wheels of the moving body via shafts, gears, and the like to move the moving body 200 . Depending on the type of motor, various circuits such as a rectifier circuit, an inverter circuit, an inverter control circuit, etc. may be provided in front of the motor 320 .

The power storage device 330 may be, for example, a secondary battery or a capacitor for power storage. For example, a lithium ion battery or a nickel hydrogen battery can be used as the secondary battery. The storage capacitor can be a high-capacity and low-resistance capacitor such as an electric double layer capacitor or a lithium ion capacitor. The moving body 200 moves by driving the motor 320 with electric power stored in a capacitor or a secondary battery.

The sizes of the housing of the moving body 200, the power transmitting electrode 120, and the power receiving electrode 220 in this embodiment are not particularly limited, but can be set to the following sizes, for example. The length (that is, the size in the Y direction) of each power transmitting electrode 120 can be set within a range of 50 cm to 20 m, for example. The width (that is, the size in the X direction) of each power transmission electrode 120 can be set within a range of 5 cm to 2 m, for example. Each size in the movement direction and the lateral direction of the housing of the moving body 200 can be set within a range of 20 cm to 5 m, for example. The size of the housing of the moving body 200 in the moving direction may be set to be less than half the length of each power transmitting electrode 120 so that power can be supplied to two or more moving bodies 200 from the power transmitting electrode 120 at the same time. The length of the power receiving electrode 220a (that is, the size in the movement direction) can be set within a range of 5 cm to 2 m, for example. The width (that is, the size in the lateral direction) of the power receiving electrode 220a can be set within a range of 2 cm to 2 m, for example. The gap between the power transmitting electrodes 120 and the gap between the power receiving electrodes 220 can be set within a range of 1 mm to 40 cm, for example. However, it is not limited to these numerical ranges.

Next, the operation of the power transmission device 100 detecting the approach of the moving object 200 in the detection mode and switching to the transmission mode will be described in more detail.

FIG. 16 is a flow chart showing an example of the operation of the power transmission control circuit 150 in the detection mode. In this example, in the detection mode, the power transmission control circuit 150 performs operations from steps S101 to S105 shown in FIG.

In step S<b>101 , the power transmission control circuit 150 acquires the phase difference between the output voltage and the output current based on the measured values of the output voltage and the output current of the inverter circuit 160 measured by the measuring device 140 . The measuring instrument 140 measures the output voltage and the output current with a period sufficiently shorter than the period of the output voltage and the output current, and records waveform data of the voltage and the current as illustrated in FIG. The power transmission control circuit 150 calculates the phase difference from the waveform data. Here, the current measurement is the t-th measurement, and the phase difference obtained by the t-th measurement is written as Δθt. The phase difference Δθt can be calculated from the time difference Δt between when the measured value of the output voltage Vout becomes zero and when the measured value of the output current Iout becomes zero, as shown in FIG. 10, for example. The power transmission control circuit 150 detects the zero crossings at which the values of the output voltage Vout and the output current Iout become zero, and records the times when the respective zero crossings are detected to calculate the time difference Δt and the phase difference Δθt. can. Note that the phase difference may be calculated based on the time of the peak point instead of the zero crossing point. Note that the time difference Δt may be used as the phase difference instead of the phase difference Δθt.

In step S102, the power transmission control circuit 150 determines whether or not the phase difference Δθt is within a preset first range. The first range is defined by the lower limit value θmin and the upper limit value θmax. The lower limit value θmin and the upper limit value θmax can be determined in advance by calibration, for example, and recorded in a recording medium within power transmission control circuit 150 . The power transmission control circuit 150 determines whether or not θmin≦Δθt≦θmax. If this determination is Yes, the process proceeds to step S103. If this determination is No, the process returns to step S101. Alternatively, the first range may be defined only by the lower limit θmin without defining the upper limit θmax. In that case, it is determined whether or not Δθt is equal to or greater than θmin using θmin as a threshold.

In step S103, the power transmission control circuit 150 acquires the phase difference variation amount σt. The phase difference variation amount σt is an amount representing the degree of variation in the phase differences (Δθt−n, . The phase difference variation amount σt is calculated by a predetermined function f(Δθt−n, . . . , Δθt). As the function f, for example, variance or standard deviation can be used, but not limited to them, any function representing the degree of dispersion can be used as the function f.

In step S104, the power transmission control circuit 150 determines whether or not the phase difference variation amount σt is within a predetermined second range. The second range is defined by the lower limit value σmin and the upper limit value σmax. The lower limit value σmin and the upper limit value σmax can be determined in advance by calibration, for example, and recorded on a recording medium within the power transmission control circuit 150 . The power transmission control circuit 150 determines whether or not σmin≦σt≦σmax. If this determination is Yes, the process proceeds to step S105. If this determination is No, the process returns to step S101. The second range may be defined only by the upper limit value σmax without the lower limit value σmin being defined. In that case, it is determined whether or not σt is equal to or less than σmax using σmax as a threshold.

In step S105, the power transmission control circuit 150 transitions from the detection mode to the transmission mode. Specifically, the power transmission control circuit 150 sends a signal to turn on the switch 132 in the voltage switching circuit 130 . This causes the switch 132 to be turned on, that is, to be in a conductive state. After that, a relatively large voltage V1 is applied to the inverter circuit 160 from the first DC power supply 131, and transmission of large power to the moving object 200 is started.

By the above operation, it is possible to appropriately determine the transition timing to the transmission mode based on the phase difference between the output voltage and the output current of the inverter circuit 160 and the variation in the phase difference. According to the above operation, for example, when the phase difference Δθt is too small or the phase difference variation amount σt is too large, it is estimated that the moving body 200 has not yet reached the power transmission electrode 120, and the detection mode is changed to maintained. Therefore, it is possible to avoid shifting to the transmission mode when the coupling capacitance between the power transmission electrode 120 and the power reception electrode 220 is low. As a result, damage to circuit elements in the power transmission device 100 can be reduced.

In the above example, the operations of steps S101 and S102 and the operations of steps S103 and S104 may be reversed in order or performed in parallel. Alternatively, steps S103 and S104 may be omitted, and the timing to shift to the transmission mode may be determined based only on the phase difference. FIG. 17 is a flow chart showing an example of the operation of determining the transition timing to the transmission mode based only on the phase difference. In the example of FIG. 17, when it is determined as Yes in step S102, the mode shifts to the transmission mode without evaluating the phase difference variation amount.

The power transmission control circuit 150 may determine the transition timing to the transmission mode based on the zero crossing variation instead of or in addition to the phase difference variation in the example of FIG. When the coupling capacitance between the power transmitting electrode 120 and the power receiving electrode 220 is small, the noise included in the waveforms of the measured output voltage and output current becomes large, and the respective zero crossings occur during the half period of the driving frequency of the inverter circuit 160. may be detected multiple times in Therefore, the zero-crossing variation of one or both of the output voltage and output current can be used instead of the phase difference variation described above. For example, for one or both of the output voltage and the output current, the number of zero crossings detected during the half period is counted as the amount of variation or the amount of noise, and only when the amount of variation is within the third range, the transmission mode , and the detection mode may be continued if the amount of variation is not within the third range. In addition, the amount of noise included in the waveform of the output voltage or output current may be evaluated by any method other than the amount of variation at the zero crossing point of the waveform of the measured output voltage or output current. For example, the amount of high frequency components of a predetermined order or higher extracted by performing fast Fourier transform on the waveform of the output voltage or output current may be used as the amount of noise.

FIG. 18 shows an example of processing for determining the transition timing to the transmission mode based on the amount of noise contained in the waveform of the output voltage or current of the inverter circuit 160 instead of the amount of phase difference variation in the example of FIG. It is a flow chart. This flowchart replaces steps S103 and S104 in the flowchart shown in FIG. 16 with steps S113 and S114, respectively. The operations of steps S101 and S102 are the same as those in FIG.

In step S<b>113 , the power transmission control circuit 150 acquires the noise amount n in at least one of the waveforms of the output voltage and the output current of the inverter circuit 160 measured by the measuring instrument 140 by calculation. The amount of noise can be, for example, the number of zero crossings detected during a half cycle of the drive frequency of inverter circuit 160 . Alternatively, the amount of high-frequency components of a predetermined order or higher obtained by fast Fourier transform may be used as the amount of noise.

In step S114, the power transmission control circuit 150 determines whether or not the noise amount n is within a preset third range. The third range is defined by the lower limit nmin and the upper limit nmax. The lower limit value nmin and the upper limit value nmax can be determined in advance by calibration, for example, and recorded in a recording medium within the power transmission control circuit 150 . The power transmission control circuit 150 determines whether or not nmin≦n≦nmax holds. If this determination is Yes, the process proceeds to step S105. If this determination is No, the process returns to step S101. Note that the third range may be defined only by the upper limit value nmax without defining the lower limit value nmin. In that case, it is determined whether or not n is less than or equal to σmax using nmax as a threshold.

In the above example, the operations of steps S101 and S102 and the operations of steps S113 and S114 may be reversed in order or performed in parallel. Alternatively, steps S101 and S102 may be omitted, and the timing to shift to the transmission mode may be determined based only on the amount of noise.

The power transmission control circuit 150 in each of the above examples determines the transition timing to the transmission mode based only on the output voltage and/or the output current of the inverter circuit 160 . In addition to such an operation, for example, the measurement value of the input current of the inverter circuit 160 may also be used to determine the transition timing to the transmission mode.

FIG. 19 is a block diagram showing a configuration example of a system that determines the transition timing to the transmission mode based on the input current of the inverter circuit 160. As shown in FIG. In the example of FIG. 19 , the power transmission device 100 further includes a current measuring device 142 that measures the input current of the inverter circuit 160 . The power transmission control circuit 150 in this example determines the transition timing to the transmission mode based on not only the measured value of the measuring device 140 but also the measured value of the current measuring device 142 in the detection mode.

FIG. 20 is a flow chart showing the operation of the power transmission control circuit 150 in the example of FIG. The flowchart shown in FIG. 20 is obtained by adding steps S121 and S122 before step S101 in the flowchart shown in FIG.

In step S<b>121 , the power transmission control circuit 150 acquires the measured value of the input current Iin of the inverter circuit 160 measured by the current measuring device 142 .

In step S122, the power transmission control circuit 150 determines whether or not the input current Iin is within a preset fourth range. The fourth range is defined by the lower limit value Imin and the upper limit value Imax. The lower limit value Imin and the upper limit value Imax may be determined in advance by calibration, for example, and recorded in a recording medium within power transmission control circuit 150 . The power transmission control circuit 150 determines whether or not Imin≤Iin≤Imax. If this determination is Yes, the process proceeds to step S101. If this determination is No, the process returns to step S121. Note that the fourth range may be defined only by the lower limit value Imin without the upper limit value Imax being defined. In that case, it is determined whether or not Iin is equal to or greater than Imin using Imin as a threshold. Imin can be set to a value that allows the phase difference Δθt to be obtained with a relatively high degree of accuracy.

The operations from steps S101 to S105 thereafter are the same as those shown in FIG. However, if it is determined No in steps S102 and S104, the process returns to step S121.

By the operation described above, the timing to shift to the transmission mode can be appropriately determined based on the phase difference between the output voltage and the output current of the inverter circuit 160 and the variation in the phase difference, as well as the input current of the inverter circuit 160. can be done. According to the above operation, for example, when the input current Iin is too small, the phase difference Δθt is too small, or the phase difference variation amount σt is too large, the moving object 200 has not yet reached the power transmitting electrode 120. is assumed to be absent and detection mode is maintained. Therefore, it is possible to avoid shifting to the transmission mode when the coupling capacitance between the power transmission electrode 120 and the power reception electrode 220 is low. As a result, damage to circuit elements in the power transmission device 100 can be reduced.

In the above example, the order of the operations of steps S121 and S122, the operations of steps S101 and S102, and the operations of steps S103 and S104 may be changed, or these operations may be performed in parallel. Also, steps S103 and S104 may be omitted, and the timing of transition to the transmission mode may be determined based only on the input current of the inverter circuit 160 and the phase difference. Further, the power transmission control circuit 150 determines the transition timing to the transmission mode based on the amount of noise such as the amount of variation in the zero crossing point or the amount of high frequency components as described above instead of or in addition to the amount of variation in the phase difference. may

In each example shown in FIGS. 16, 17, 18, and 20, the timing of transition from the detection mode to the transmission mode is determined based on the phase difference between the output voltage and the output current of the inverter circuit 160. FIG. The phase difference between the output voltage and the output current of inverter circuit 160 fluctuates as the load impedance in moving body 200 fluctuates. In order to accurately detect the phase difference, it is desirable that the load impedance is nearly constant. However, the load impedance fluctuates greatly according to the operating state of the moving body 200 . For example, when the moving body 200 approaches the power transmission electrode 120 and a voltage above a certain level is applied to the load inside the moving body 200, various electronic circuits included in the load are activated, and the load impedance fluctuates greatly before and after. do. In that state, the phase difference between the output voltage and the output current of the inverter circuit 160 also fluctuates greatly. Furthermore, in this state, losses in power transmission circuit 110 and power reception circuit 210 increase, the output voltage of power reception circuit 210 increases, and there is a possibility of causing heat generation or damage to circuit elements.

Therefore, the moving body 200 may have a configuration that suppresses variations in load impedance. A configuration example of such a moving body 200 will be described below. In the following description, activation of an electronic circuit included in a load is expressed as "activation of the load".

FIG. 21 is a diagram showing a configuration example of a moving body 200 capable of adjusting load impedance. This moving body 200 includes a plurality of power receiving electrodes 220 , a power receiving circuit 210 , a resistance circuit 270 , a power receiving control circuit 250 and a load 230 . Power receiving circuit 210 may include matching circuit 280 and rectifying circuit 260 shown in FIG. Load 230 may include charge/discharge control circuit 310, electric motor 320, and storage device 330 shown in FIG. The moving body 200 shown in FIG. 21 can be used in combination with the power transmission device 100 shown in FIG. 12 or 19, for example.

Resistance circuit 270 is connected between power receiving circuit 210 and load 230 . Resistive circuit 270 includes a resistor 272 and a switch 274 connected in series with each other. Resistor 272 and switch 274 are connected in parallel with load 230 . Although one resistor 272 is shown in FIG. 21, resistor 272 may be a collection of multiple resistors.

When mobile object 200 is away from power transmission device 100, the impedance of mobile object 200 seen from power transmission device 100 is substantially infinite. In this state, the power transmission device 100 operates in the detection mode and outputs less power than it outputs in the transmission mode. When the moving object 200 approaches the power transmission device 100, the power supplied to the load 230 gradually increases. When the input voltage of load 230 exceeds a predetermined starting voltage, electronic circuits such as charge/discharge control circuit 310 and DC-DC converter included in load 230 start to start. During load startup, the impedance of the load 230 drops while fluctuating. After start-up is complete, the impedance of load 230 will be a certain value. As described above, the load impedance of the power receiving circuit 210 decreases as the electronic circuit included in the load 230 is activated. The power reception control circuit 250 controls the impedance of the resistance circuit 270 so as to suppress fluctuations in the load impedance of the power reception circuit 210 caused by activation of the electronic circuit. Power reception control circuit 250 controls the impedance of resistance circuit 270 so that the load impedance of power reception circuit 210 is maintained within a preset range regardless of the state of load 230 . With such control, the voltage inside the moving body 200 can be maintained within an appropriate range. The impedance of resistive circuit 270 may be controlled by controlling switch 274, for example.

The power reception control circuit 250 turns on the switch 274 before the load 230 is activated, and after the load 230 is activated, controls the switch 274 so that the impedance of the resistance circuit 270 increases. After power is applied, switch 274 is turned off. The power reception control circuit 250 turns on the switch 274 again after the power transmission from the power transmission device 100 to the mobile body 200 is completed. The resistance value of the resistor 272 can be set to a value substantially equal to the resistance value of the load 230 when power for transmission is being supplied from the power transmission device 100 to the moving object 200 . By such operation, the load impedance of power receiving circuit 210 can be maintained within an appropriate range.

Next, some examples of methods for controlling the resistance circuit 270 will be described with reference to FIGS. 22 to 25. FIG.

FIG. 22 is a diagram showing an example of a control method for the resistance circuit 270 by the power reception control circuit 250. As shown in FIG. In this example, switch 274 is a semiconductor switch such as a MOSFET and resistor 272 has a fixed resistance value. The power reception control circuit 250 controls the resistance value, ie the impedance, of the resistance circuit 270 by adjusting the voltage input to the gate of the semiconductor switch.

FIG. 23 is a diagram showing another example of a control method of the resistance circuit 270 by the power reception control circuit 250. As shown in FIG. In this example, the power reception control circuit 250 controls the impedance of the resistance circuit 270 by adjusting the ON/OFF duty ratio of the switch 274, that is, the ratio between the ON time and the period.

FIG. 24 is a diagram showing still another example of a control method of resistance circuit 270 by power reception control circuit 250. In FIG. In this example, resistive circuit 270 includes a variable resistor 273 connected in parallel with load 300 . The power reception control circuit 250 controls the impedance of the resistance circuit 270 by controlling the resistance value of the variable resistor 273 . In this example as well, the power reception control circuit 250 may turn on the switch 274 before starting the load 300 and turn off the switch 274 after starting the main power transmission. Alternatively, the switch 274 may be omitted and the same function may be realized only by adjusting the resistance value of the variable resistor 273 .

FIG. 25 is a diagram showing still another example of a control method of resistance circuit 270 by power reception control circuit 250. In FIG. In this example, resistive circuit 270 comprises a plurality of modules each including resistor 272 and switch 274 and connected in parallel with load 300 . The power reception control circuit 250 controls the switch 274 in each module in the same manner as in the example of FIG. 22 or 23, thereby adjusting the combined resistance, ie, combined impedance, of all modules. Thereby, the combined impedance of the entire resistance circuit 270 is controlled. As in the example of FIG. 24, variable resistors 273 may be provided instead of the resistors 272, and the combined impedance of the resistance circuit 270 may be controlled by adjusting the resistance value of each variable resistor 273. FIG. In that case, switch 274 may be omitted.

With the above configuration, fluctuations in the load impedance of the moving body 200 can be suppressed, and as a result, fluctuations in the measured values of the output voltage and output current of the inverter circuit 160 can be suppressed.

In the above embodiment, the power transmission electrodes 120 are laid on the ground or the floor, but the power transmission electrodes 120 may be laid on the side surfaces such as walls or the top surfaces such as ceilings. The arrangement and orientation of power receiving electrode 220 of moving body 200 are determined according to the location and orientation where power transmitting electrode 120 is laid.

FIG. 26A shows an example in which power transmission electrodes 120 are laid on the side surface of a wall or the like. In this example, the power receiving electrode 220 is arranged on the side of the moving body 200 . FIG. 26B shows an example in which the power transmission electrodes 120 are installed on the ceiling. In this example, the power receiving electrode 220 is arranged on the top plate of the moving body 200 . As in these examples, there are various variations in the arrangement of power transmitting electrode 120 and power receiving electrode 220 .

The wireless power transmission system according to the embodiments of the present disclosure can be used, as described above, as a system for transporting goods in warehouses or factories, for example. The moving body 200 has a carrier on which articles are loaded, and functions as a cart that autonomously moves within the factory and conveys articles to required locations. However, the wireless power transmission system and mobile object according to the present disclosure are not limited to such uses, and can be used for various other uses. For example, the moving body is not limited to AGVs, but may be other industrial machines, service robots, electric vehicles, multicopters (drones), and the like. The wireless power transmission system can be used not only in factories or warehouses, but also in shops, hospitals, homes, roads, runways, and other places. Also, the power receiving device is not limited to a mobile object, and can be any portable device such as a charging pole, a smart phone, a tablet computer, or a laptop computer.

An example of a wireless power transmission system in which the power receiving device does not have a power device for movement will be described below.

FIG. 27 is a perspective view schematically showing an example of a wireless power transmission system that supplies power to a portable power receiving device 500. As shown in FIG. FIG. 28 is a schematic cross-sectional view of this system.

As shown in FIG. 27 , in this system, a portable power receiving device 500 receives power from a power transmitting device 100 and operates instead of a mobile object. Although two power receiving devices 500 are illustrated in FIG. 27, the number of power receiving devices 500 is arbitrary. Power receiving device 500 may be, for example, a portable charging pole. The power receiving device 500 is placed on the power transmission electrode sheet 120S included in the power transmission device 100 and used. The power transmission electrode sheet 120S includes a pair of power transmission electrodes 120 extending in one direction. The power receiving device 500 includes a power receiving electrode sheet 220S that faces the power transmitting electrode sheet 120S during use. The power receiving electrode sheet 220</b>S includes a pair of power receiving electrodes 220 . Power is wirelessly transmitted in a state in which the pair of power receiving electrodes 220 face the pair of power transmitting electrodes 120 respectively. Power receiving device 500 is portable and can be slid along the direction in which power transmitting electrode 120 extends. The dimension of power receiving device 500 in the direction in which power transmitting electrode 120 extends is less than half the length of power transmitting electrode 120 . Therefore, two or more power receiving devices 500 can be placed on the power transmitting electrode sheet 120S at the same time.

As shown in FIG. 28 , the pair of power transmission electrodes 120 are connected to the power transmission circuit 110 . As in the previous embodiment, the power transmission circuit 110 supplies AC power to a pair of power transmission electrodes 120 . Thereby, alternating current energy is sent out from the power transmission electrode 120 to space. Power receiving device 500 includes power receiving circuit 210, power storage device 330, and load 350 in addition to power receiving electrode sheet 220S. The power receiving circuit 210 is connected to a pair of power receiving electrodes 220, converts AC power received by the power receiving electrodes 220 into DC power, and outputs the DC power. Power storage device 330 stores the DC power output from power receiving circuit 210 . The load 350 is connected to the power storage device 330 and operates by power stored in the power storage device 330 . Load 350 is any device that operates on electrical power and may include, for example, an electric motor, power unit, or lighting device. If powered device 500 is a charging pole, powered device 500 may include one or more outlets for powering other devices. Although not shown in FIG. 28, the power receiving device 500 may have a function of adjusting impedance, similar to the examples shown in FIGS. 21 to 25 and the like.

FIG. 29 is a diagram showing another example of the power receiving device 500. As shown in FIG. As shown in FIG. 29, power receiving device 500 may be smart phone 400A, tablet computer 400B, or laptop computer 400C. The power receiving device 500 is not limited to these examples, and may be any portable device. By applying the technology of the present disclosure, it is possible to appropriately determine the timing of starting power transmission to the power receiving device 500 regardless of the type of the power receiving device 500 .

The technology of the present disclosure can be used for wireless power transmission. For example, it can be used as a power transmission device that wirelessly transmits electric power to an electric moving body such as an automatic guided vehicle (AGV).

30 floor surface 40 shelf 100 power transmission device 110 power transmission circuit 120 power transmission electrode 120S power transmission electrode sheet 130 voltage switching circuit 131 first DC power supply 132 switch 135 DC-DC converter 136 second DC power supply 137 diode 139 electrolytic capacitor 140 measuring instrument 150 power transmission control Circuit 160 Inverter circuit 180 Matching circuit 200 Moving body 210 Power receiving circuit 220 Power receiving electrode 230 Load 260 Rectifier circuit 270 Resistance circuit 280 Matching circuit 310 Charge/discharge control circuit 320 Electric motor 330 Electricity storage device 350 Load 400 Power supply 500 Power receiving device

Claims (9)

A power transmitting device that wirelessly transmits power to a power receiving device that includes a plurality of power receiving electrodes,
a voltage switching circuit capable of switching and outputting a first DC voltage and a second DC voltage lower than the first DC voltage;
an inverter circuit that converts the first DC voltage or the second DC voltage output from the voltage switching circuit into an AC voltage and outputs the AC voltage;
a measuring instrument for measuring the alternating voltage and the alternating current output from the inverter circuit;
a control circuit that controls the voltage switching circuit based on the measured value of the measuring instrument;
a plurality of power transmitting electrodes that transmit power based on the alternating voltage output from the inverter circuit to the plurality of power receiving electrodes of the power receiving device;
with
The control circuit is
operating in a detection mode for detecting the approach of the power receiving device and a transmission mode for transmitting power based on the first DC voltage to the power receiving device;
In the detection mode,
causing the voltage switching circuit to output the second DC voltage;
(a) the phase difference between the AC voltage and the AC current measured by the measuring instrument is within a first range;
When a predetermined condition including
transmission device. In the detection mode, the control circuit satisfies the conditions (a) and (b) that the amount of variation indicating the degree of temporal variation in the phase difference is within a second range;
is satisfied, switching the voltage output from the voltage switching circuit from the second DC voltage to the first DC voltage to switch from the detection mode to the transmission mode;
The power transmission device according to claim 1 . In the detection mode, the control circuit satisfies the conditions (a) and (c) that the amount of noise contained in the waveform of the AC voltage and/or the AC current is within a third range;
is satisfied, switching the voltage output from the voltage switching circuit from the second DC voltage to the first DC voltage to switch from the detection mode to the transmission mode;
The power transmission device according to claim 1 . In the detection mode, the control circuit satisfies the conditions (a) and (b) that the variation amount indicating the degree of temporal variation of the phase difference is within a second range, and (c) the AC voltage and / or that the amount of noise included in the waveform of the alternating current is within a third range;
is satisfied, switching the voltage output from the voltage switching circuit from the second DC voltage to the first DC voltage to switch from the detection mode to the transmission mode;
The power transmission device according to claim 1 . The control circuit is
repeatedly calculating the phase difference between the alternating voltage and the alternating current based on the measured values of the alternating voltage and the alternating current measured by the measuring instrument;
calculating an amount according to the variance of the phase difference value calculated within a unit time as the amount of variation;
The power transmission device according to claim 2 or 4. The control circuit is
A voltage zero crossing at which the measured value of the AC voltage output from the inverter circuit becomes zero, and/or a zero current at which the measured value of the AC current output from the inverter circuit becomes zero. detect intersections,
calculating, as the noise amount, an amount corresponding to the frequency of the voltage zero crossings and/or the current zero crossings detected during a half cycle of the drive frequency of the inverter circuit;
The power transmission device according to claim 3 or 4. The power transmission device further includes a current measuring device that measures the input current of the inverter circuit,
The control circuit changes the voltage output from the voltage switching circuit to the switching from the sensing mode to the transmission mode by switching from a second DC voltage to the first DC voltage;
The power transmission device according to claim 1 . a power transmission device according to any one of claims 1 to 7;
the power receiving device;
A wireless power transfer system comprising: The power receiving device
a rectifier circuit that converts the AC power received by the plurality of power receiving electrodes into DC power and outputs the DC power;
a load operated by the DC power output from the rectifier circuit and activated when the voltage of the DC power exceeds a predetermined activation voltage;
a resistor circuit connected between the rectifier circuit and the load, the resistor circuit including a resistor connected in parallel with the load;
a power reception control circuit that controls the impedance of the resistance circuit so as to suppress fluctuations in the load impedance of the rectifier circuit that occur when the power reception device approaches the power transmission device and the load is activated;
The wireless power transfer system of claim 8, comprising:

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