JP7521938B2 - Wireless power transmission system and power wave reflection method - Google Patents

Description

This disclosure relates to a wireless power transmission system and a power wave reflection method.

In recent years, as the IoT advances, there is a demand to collect various information using a large number of information terminals, including sensors. However, as the number of such information terminals increases, it may become difficult to supply power to the terminals. Patent Document 1 discloses a power supply system that utilizes wireless power transmission technology. The wireless power transmission system of Patent Document 1 includes a power transmitter that transmits wireless power, and multiple power receivers that are the targets of power supply by wireless power. The power transmitter checks the charging status of the multiple power receivers by wireless communication, and by changing the direction of wireless power transmission to power receivers that are lacking in charging power, it is possible to prioritize power supply.

Special Publication No. 2016-512677

However, in the conventional technology of Patent Document 1, the power transmitter needs to change the power transmission direction for each power receiver, which makes the configuration of the power transmitter complex. Therefore, the conventional technology has room for improvement in terms of simplifying the configuration of the power transmitter while supplying power to multiple power receivers.

Non-limiting examples of the present disclosure contribute to providing a wireless power transmission system and a power wave reflection method that can supply power to multiple power receivers while simplifying the configuration of the power transmitter.

A wireless power transmission system according to one embodiment of the present disclosure includes a power transmitter that radiates a power wave and a plurality of power receivers each having an antenna that receives the power wave, and the power receiver switches between a power supply state in which power is supplied to a load based on the received power wave and a reflection state in which the received power wave is reflected , and in the reflection state, alternates between a first state in which the antenna is connected to ground and a second state in which the antenna is released from the ground .

A power wave path changing method according to one embodiment of the present disclosure includes the steps of transmitting a power wave radiated from a power transmitter to a power receiver, switching between a power supply state in which power is supplied to a load based on the power wave received by an antenna of the power receiver and a reflection state in which the received power wave is reflected, alternately switching in the reflection state between a first state in which the antenna is connected to ground and a second state in which the antenna is released from the ground, and receiving the power wave reflected by the power receiver by a power receiver other than the power receiver.

According to one embodiment of the present disclosure, it is possible to construct a wireless power transmission system and a power wave reflection method that can supply power to multiple power receivers while simplifying the configuration of the power transmitter.

Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and/or benefits are provided by the various embodiments and features described in the specification and drawings, respectively.

FIG. 1 illustrates an example of the configuration of a wireless power transmission system 100 according to an embodiment of the present disclosure. FIG. 2 shows an example of the configuration of a power transmitter 201. FIG. 2 is a diagram showing a configuration example of a power receiver 202 according to an embodiment of the present disclosure. 1 is a flowchart for explaining an operation of a power receiver 202 according to an embodiment of the present disclosure. 1 illustrates a modified example of the power receiver 202 according to an embodiment of the present disclosure. FIG. 1 shows a semi-closed space 102 for evaluating changes in the amount of received power. FIG. 1 is a diagram for explaining the evaluation results of the amount of received power.

A preferred embodiment of the present disclosure will be described in detail below with reference to the attached drawings. Note that in this specification and drawings, components having substantially the same functions are designated by the same reference numerals to avoid redundant description.

[Embodiment]
<Configuration example of wireless power transmission system 100>
1 is a diagram illustrating an example of a configuration of a wireless power transmission system 100 according to an embodiment of the present disclosure. The wireless power transmission system 100 includes a power transmitter 201 that transmits radio waves (high frequency power) to a semi-closed space, and a plurality of power receivers 202 that receive radio waves 204 emitted from the power transmitter 201 toward the semi-closed space. The power receiver 202 has a function of generating power based on the received radio waves 204 and supplying it to a load, and a function of emitting the received radio waves 204 to the semi-closed space as reflected waves 205. Details of the semi-closed space and the power receiver 202 will be described later.

<Power transmitter 201>
Next, a configuration example of the power transmitter 201 will be described with reference to Fig. 2. Fig. 2 is a diagram showing a configuration example of the power transmitter 201. The power transmitter 201 includes an oscillator 302, a controller 303, an antenna 301, and a power supply 304.

The oscillator 302 has an electric circuit composed of, for example, a quartz crystal oscillator, a phase-locked loop, an amplifier circuit, etc., and generates high-frequency power (power waves) by the electric circuit. The frequency band of the high-frequency power is, for example, a microwave band such as the 900 MHz band, the 2.45 GHz band, or the 5.8 GHz band. These frequency bands are selected according to the distance from the power transmitter 201 to the power receiver 202, the size of the power transmitter 201, etc.

The control unit 303 includes electrical circuits, such as a memory, a CPU (Central Processing Unit), and a communication device, and controls the amount of high-frequency power generated by the oscillator 302 and switches the frequency band of the transmitted high-frequency power, using the electrical circuits.

The antenna 301 radiates the high-frequency power generated by the oscillator 302 into the semi-closed space as radio waves 204. The types of antenna 301 include, for example, directional antennas and omnidirectional antennas. A directional antenna is used when it is necessary to transmit power long distances in a specific direction, and an omnidirectional antenna is used when it is necessary to transmit power over a wide area in a short distance. For example, a planar patch antenna in which a dielectric substrate is sandwiched between a GND plate and an antenna is used as a directional antenna. For omnidirectional antennas, a linear dipole antenna or monopole antenna in which an electric conductor is extended in a straight line is used.

The power supply unit 304 has the function of supplying power to operate the power transmitter 201, and is composed of a power conversion circuit that generates DC power from a commercial AC power source.

Next, a configuration example of the power receiver 202 will be described with reference to FIG. 3. FIG. 3 is a diagram showing a configuration example of the power receiver 202 according to an embodiment of the present disclosure. The power receiver 202 shown in FIG. 3 includes an antenna 401, a rectifier 402, a controller 403, a power storage unit 405, and a switch unit 406.

The antenna 401 has a function of receiving radio waves 204 emitted from the power transmitter 201, inputting the received radio waves 204 to the rectification unit 402 as high-frequency power, and radiating the radio waves 204 into a semi-closed space as reflected waves 205. The type of the antenna 401 is the same as that of the antenna 301 described above, and may be, for example, a directional antenna or an omnidirectional antenna.

The rectifier 402 converts the radio waves 204 received by the antenna 401 into DC power. The rectifier 402 is composed of, for example, a rectifier diode, an impedance matching circuit, a filter circuit, etc.

The control unit 403 controls the supply of radio waves 204 received by the antenna 401 to the load 404, controls charging of the power storage unit 405 by the radio waves 204, controls discharging of the power storage unit 405, and controls switching of the switch unit 406.

The load 404 is, for example, a sensor used in the Internet of Things (IoT). However, the load 404 is not limited to this.

The power storage unit 405 is a storage means for storing the power required to drive the control unit 403. The power storage unit 405 is, for example, a secondary battery. The power storage unit 405 stores the DC power output from the rectification unit 402 under charging control by the control unit 403. Furthermore, when the power consumption of the load 404 exceeds the DC power output from the rectification unit 402, the power storage unit 405 supplies the stored power to the load 404 under discharging control by the control unit 403.

The switch unit 406 is a switching means for switching the antenna 401 to an open or grounded state in the reflection mode, and for connecting the antenna 401 to the load 404 in the power supply mode.

The reflection mode is a mode in which the antenna 401 totally reflects the radio waves 204 received in phase or totally reflects the radio waves 204 in opposite phase by switching the impedance of the circuit side as seen from the antenna 401.

The power supply mode is a mode in which the rectifier 402 supplies DC power from the rectifier 402 to the load 404 with the rectifier 402 connected to the load 404 via the switch 406.

Open circuit refers to a state in which the antenna 401 is not connected to either the GND 407 or the load 404, and the impedance of the circuit connected to the antenna 401 is infinite.

Grounding refers to a state in which the impedance of the circuit connected to the antenna 401 becomes zero by connecting the antenna 401 to GND 407.

The rectification unit 402, the control unit 403, the power storage unit 405, and the switch unit 406 constitute the phase change unit 610. The phase change unit 610 changes the phase of the power wave received by the antenna 401, and radiates the power wave after the phase change from the antenna 401 as a reflected wave 205.

In addition, in the power receiver 202, a switch unit 406 is provided on the output side of the rectifier unit 402, so power loss can be reduced compared to when the switch unit 406 is provided between the antenna 401 and the rectifier unit 402.

Next, the operation of the power receiver 202 will be described with reference to FIG. 4. FIG. 4 is a flowchart for explaining the operation of the power receiver 202 according to an embodiment of the present disclosure.

First, the control unit 403 switches the connection destination of the switch unit 406 to the load 404 side using the power stored in the power storage unit 405, thereby setting the device in power supply mode (step S1). As a result, the radio waves 204 received by the antenna 601 are converted to DC power by the rectification unit 402 and supplied to the load 404. In the power supply mode, the control unit 403 charges the power storage unit 405 at the same time as supplying power to the load 404.

The control unit 403 determines whether sufficient power is being supplied to the load 404 in the power supply mode (step S2).

For example, if the power consumption of the load 404 exceeds the power converted by the rectifier 402, the controller 403 determines that sufficient power is not being supplied to the load 404 (step S2, NO), and repeats the processing from step S1 onward.

For example, if the power consumption of the load 404 is less than the power converted by the rectifier unit 402, the control unit 403 determines that sufficient power is being supplied to the load 404 (step S2, YES) and executes the processing of step S3.

Next, the control unit 403 uses the power stored in the power storage unit 405 to set the switch unit 406 to the reflective mode (step S3).

The control unit 403 controls the switch unit 406 to alternately switch the antenna 401 between an open state and a grounded state (step S4). This switching operation causes the radio waves 204 received when the antenna 401 is open to be totally reflected in phase, and causes the radio waves 204 received when the antenna 401 is grounded to be totally reflected in the opposite phase. The totally reflected radio waves 204 are radiated toward the semi-closed space as reflected waves 205. The reflected waves 205 radiated into the semi-closed space are received by one or more receivers 202 present around the receiver 202. The one or more receivers 202 receive the reflected waves 205 and the radio waves 204 radiated from the transmitter 201, and rectify them in the rectifier unit 402 to supply power to the load 404 and to the power storage unit 405.

The control unit 403 may control the switch unit 406 to alternate between open and grounded at a constant or random cycle. This allows the transmission of a reflected wave 205 whose phase changes over time (phase modulation), and the phase of the reflected wave 205 received by one or more power receivers 202 changes over time. For example, even if the position of the power receiver 202 changes, efficient power supply is possible without adjusting the impedance between the power receiver 202 that emits the reflected wave 205 and the power receiver 202 that receives the reflected wave 205.

The switching operation of the switch unit 406 reduces the stored power of the power storage unit 405, so the control unit 403 monitors whether the power storage unit 405 is in a state requiring charging (step S5).

For example, when the charge rate of the power storage unit 405 is equal to or higher than a predetermined value (e.g., 30%), or when a certain period of time has not elapsed since the power storage unit 405 started to discharge, the control unit 403 determines that the power storage unit 405 does not require charging (step S5, NO), and repeats the processing from step S3 onward.

For example, when the charge rate of the power storage unit 405 falls below a predetermined value (e.g., 30%) or a certain amount of time has elapsed since the power storage unit 405 started to discharge, the control unit 403 determines that the power storage unit 405 needs to be charged (step S5, YES). In this case, the control unit 403 executes the process of step S1 to set the power storage unit 405 in the power supply mode.

These processes may be performed in all of the multiple power receivers 202, or in a portion (one or more) of the multiple power receivers 202.

By executing these processes in all of the multiple receivers 202, radio waves 204 of stable strength can be received at any point within the semi-closed space.

By executing these processes in some of the multiple receivers 202, the power consumed by the switching operation of the switch unit 406, etc. is reduced, so that the power consumption of the entire wireless power transmission system 100 is reduced, and radio waves 204 of a more stable strength can be received compared to when these processes are not executed.

Note that these processes may be performed by all or some of the multiple power receivers 202 in synchronization with each other, or may be performed asynchronously.

By having all or some of the multiple power receivers 202 execute these processes in synchronization with each other, it is possible to receive radio waves 204 with a more stable strength than when these processes are not executed.

By having all or some of the multiple power receivers 202 execute these processes asynchronously, the circuitry and control required for synchronization is no longer necessary, simplifying the configuration of the power receivers 202 and improving reliability, while allowing radio waves 204 of stable strength to be received at any point within the semi-closed space.

By equipping all or some of the multiple power receivers 202 with, for example, a random number generator that randomly generates a switching clock for the switch unit 406, it is possible to make the switching timing of the switch unit 406 asynchronous. This eliminates the need to centrally control the multiple power receivers 202, and allows a radio wave environment with stable strength to be created with a simple configuration.

Figure 5 is a diagram showing a modified example of the power receiver 202 according to the embodiment of the present disclosure. In the power receiver 202 shown in Figure 5, the switch unit 406 and the rectifier unit 402 are arranged in reverse. By arranging the switch unit 406 on the input side of the rectifier unit 402, the switching operation is performed by the switch unit 406 connected to the antenna 401, improving the transmission efficiency of the reflected wave 205.

The phase change unit 610 according to this embodiment may be configured to include an impedance change unit instead of the switch unit 406. The impedance change unit is configured, for example, with a variable capacitor, a variable coil, a variable resistor, a phase shifter, etc., and changes the complex impedance of the circuit to which the antenna 401 is connected over time. By changing the impedance between the antenna 401 and GND 407, it is possible to alternate between a first state in which the antenna 401 is connected to GND 407 and a second state in which the antenna 401 is released from GND 407.

Next, we will explain the simulation results of the received power with reference to Figures 6 and 7.

Figure 6 is a diagram showing a semi-closed space 102 for evaluating changes in the amount of received power. In Figure 6, the X-axis direction, the Y-axis direction, and the Z-axis direction represent directions parallel to the X-axis, the Y-axis, and the Z-axis, respectively. The X-axis direction and the Y-axis direction are mutually orthogonal. The X-axis direction and the Z-axis direction are mutually orthogonal. The Y-axis direction and the Z-axis direction are mutually orthogonal. The XY plane represents an imaginary plane parallel to the X-axis direction and the Y-axis direction. The XZ plane represents an imaginary plane parallel to the X-axis direction and the Z-axis direction. The YZ plane represents an imaginary plane parallel to the Y-axis direction and the Z-axis direction.

The semi-closed space 102 is, for example, a space in which two XY planes and two XZ planes are radio wave reflecting surfaces (surfaces that reflect radio waves 204) and two YZ planes are radio wave non-reflecting surfaces (surfaces that do not reflect radio waves 204). In the semi-closed space 102, a power transmitter 201 and two power receivers 202 (a first power receiver 202-1 and a second power receiver 202-2) according to this embodiment are arranged.

The width A of the semi-closed space 102 in the X-axis direction is 3 [m], the height B of the semi-closed space 102 in the Z-axis direction is 1 [m], and the depth C of the semi-closed space 102 in the Y-axis direction is 1 [m]. The distance X in the X-axis direction from the power transmitter 201 to the two power receivers 202 (first power receiver 202-1 and second power receiver 202-2) is 2 [m]. The distance Y in the Y-axis direction from the first power receiver 202-1 to the second power receiver 202-2 is 0.325 [m]. A dipole antenna operating at a center frequency of 920 MHz is used as the antenna 401 of each of the first power receiver 202-1 and the second power receiver 202-2.

In the simulation of the received power, a prototype circuit was created with a switch unit 406 that switches between ground (GND connection) and short circuit (load connection), and the S parameters of the first power receiver 202-1 were obtained by simulation when the switch unit 406 of the second power receiver 202-2 was switched, and the change in the amount of received power was evaluated.

Figure 7 is a diagram for explaining the evaluation results of the amount of received power. Figure 7 shows the evaluation results of the amount of received power in the first power receiver 202-1 when the second power receiver 202-2 performs a power reflection operation in the semi-closed space 102 in Figure 6. The vertical axis of Figure 7 represents the S parameter, and the horizontal axis of Figure 7 represents the frequency.

The dotted line represents the S-parameter 1202 of the first power receiver 202-1 when the switch section 406 of each of the first power receiver 202-1 and the second power receiver 202-2 is in a short-circuit state (load connection).

The solid line shows the S-parameter 1203 of the first power receiver 202-1 when the switch section 406 of the first power receiver 202-1 is in a short-circuit state (load connection) and the switch section 406 of the second power receiver 202-2 is in a grounded state (GND connection).

When the second power receiver 202-2 performs a power reflection operation, the amount of power received by the first power receiver 202-1 can be calculated from the difference between S parameter 1202 and S parameter 1203.

For example, the difference between S-parameter 1203 and S-parameter 1202 at the frequency where S-parameter 1203 is maximum is 2.1 dB. This indicates that the received power of first power receiver 202-1 is approximately 1.9 times the received power before second power receiver 202-2 starts its power reflection operation. Figure 7 shows that the received power is improved by using a power receiver 202 with a power reflection function in semi-closed space 102.

As described above, the power receiver 202 according to this embodiment can radiate reflected waves 205 to the surrounding power receivers 202 by switching from a power supply state in which power is supplied to a load to a reflection state in which the power wave is reflected, thereby increasing the amount of power supplied to the surrounding power receivers 202.

In addition, according to the wireless power transmission system 100 of this embodiment, the power transmitter 201 does not need to control the direction of radiation of the radio waves 204 for each of the multiple power receivers 202. Therefore, the directivity of the radio waves 204 is increased, and the amount of power supplied to the surrounding power receivers 202 can be increased while suppressing radio wave interference with surrounding devices and effects on the human body.

In addition, since there is no need to control the direction of radiation of radio waves 204, there is no need for a function to avoid radio wave interference with peripheral devices, and this simplifies the configuration of the transmitter 201, suppressing increases in the manufacturing costs of the transmitter 201 and improving reliability.

In addition, since there is no need to control the radiation direction of the radio waves 204, the increase in power density in the radiation direction of the radio waves 204 can be suppressed, so the wireless power transmission system 100 can be constructed without being restricted by regulations such as the Radio Law.

In addition, by emitting reflected waves 205 from a specific power receiver 202 to surrounding power receivers 202, it is possible to prevent the radio waves 204 from being reflected by a wall or the like and not reaching the specific power receiver 202. It is also possible to prevent the radio waves 204 from passing through window glass in a building and not reaching the specific power receiver 202.

For example, it is understood that the following aspects also fall within the technical scope of this disclosure:

(1) A wireless power transmission system includes a power transmitter that emits a power wave and a plurality of power receivers that receive the power wave, and the power receivers switch between a power supply state in which they supply power to a load based on the received power wave and a reflection state in which they reflect the received power wave.

(2) The power receiver includes an antenna that receives the power wave, and a phase change unit that reflects the power wave in phase or in reverse phase by switching the impedance of the circuit seen from the antenna that receives the power wave in the reflection state.

(3) The phase change unit includes a rectifier that rectifies the power wave received by the antenna, and a switch unit that is connected to the output side of the rectifier and alternates between a first state in which the antenna is connected to ground and a second state in which the antenna is disconnected from ground.

(4) The phase change unit includes a switch unit that alternates between a first state in which the antenna is connected to ground and a second state in which the antenna is disconnected from the ground, and a rectifier unit that inputs the power wave received by the antenna via the switch unit and rectifies it.

(5) All switch units of the multiple power receivers alternate between the first state and the second state.

(6) Some of the switch units of the multiple power receivers alternate between the first state and the second state.

(7) The power wave reflection method includes a step of transmitting a power wave radiated from a power transmitter to a power receiver, a step of switching between a power supply state in which power is supplied to a load based on the power wave received by the power receiver and a reflection state in which the received power wave is reflected, and a step of receiving the power wave reflected by the power receiver by a power receiver other than the power receiver.

An embodiment of the present disclosure is suitable for a wireless power transmission system.

100: Wireless power transmission system 102: Semi-closed space 201: Power transmitter 202: Power receiver 202-1: First power receiver 202-2: Second power receiver 204: Radio wave 205: Reflected wave 301: Antenna 302: Oscillator 303: Controller 304: Power supply unit 401: Antenna 402: Rectifier 403: Controller 404: Load 405: Power storage unit 406: Switch unit 407: GND
601: Antenna 610: Phase change unit

Claims (9)

A power transmitter that emits power waves;
A plurality of power receivers each having an antenna for receiving the power wave;
Equipped with
the power receiver switches between a power supply state in which power is supplied to a load based on the received power wave and a reflection state in which the power receiver reflects the received power wave ;
In the reflecting state, the wireless power transmission system alternates between a first state in which the antenna is connected to ground and a second state in which the antenna is disconnected from the ground. 2. The wireless power transmission system according to claim 1 , wherein the power receiver comprises a phase change unit that reflects the power wave in the same phase in the second state or in the opposite phase in the first state by switching an impedance of a circuit seen from an antenna receiving the power wave in the reflection state. The wireless power transmission system according to claim 2 , wherein the phase change unit includes a rectification unit that rectifies the power wave received by the antenna , and a switch unit that alternates between the first state and the second state. 3. The wireless power transmission system according to claim 2, wherein the phase change unit includes a switch unit that alternates between the first state and the second state, and a rectifier unit that inputs the power wave via the switch unit and rectifies it. The wireless power transmission system according to claim 3 or 4, wherein all of the switch units of the multiple power receivers alternate between the first state and the second state. The wireless power transmission system according to claim 3 or 4, wherein some of the switch units of the multiple power receivers alternate between the first state and the second state. transmitting a power wave radiated from a power transmitter to a power receiver;
A step of switching between a power supply state in which power is supplied to a load based on a power wave received by an antenna of the power receiver and a reflection state in which the received power wave is reflected;
in the reflecting state, alternately switching between a first state in which the antenna is connected to a ground and a second state in which the antenna is released from the ground;
receiving the electric power wave reflected by the electric power receiver by a receiver other than the electric power receiver;
A power wave reflection method comprising: An antenna is provided for receiving the electric power wave radiated from the electric power transmitter,
switching between a power supply state in which power is supplied to a load based on the power wave and a reflection state in which the received power wave is reflected;
The power receiver alternately switches, in the reflecting state, between a first state in which the antenna is connected to ground and a second state in which the antenna is disconnected from the ground. receiving, by an antenna, a power wave radiated from a power transmitter;
switching between a power supply state for supplying power to a load based on the power wave and a reflection state for reflecting the received power wave;
in the reflecting state, alternately switching between a first state in which the antenna is connected to a ground and a second state in which the antenna is released from the ground;
A power wave reflection method for a power receiver comprising:

Images