WO2019176359A1

WO2019176359A1 - Power reception device

Info

Publication number: WO2019176359A1
Application number: PCT/JP2019/003570
Authority: WO
Inventors: 宮崎　英樹; 城杉　孝敏; 孝徳山添
Original assignee: 日立オートモティブシステムズ株式会社
Priority date: 2018-03-14
Filing date: 2019-02-01
Publication date: 2019-09-19
Also published as: JP2021083142A

Abstract

In order to enable suppression of occurrence of unnecessary leakage flux even when power feeding to a battery is forcedly blocked, this power reception device for wirelessly receiving power feeding upon receiving an AC magnetic field emitted from a power transmission device being set on the ground side and including a primary coil, is provided with: a secondary coil; a resonance element that is connected to the secondary coil and that constitutes, along with the secondary coil, a resonance circuit having a prescribed resonance frequency; a power conversion unit that includes a plurality of switching elements and that controls AC current flowing through the resonance circuit by causing the plurality of switching elements to respectively execute switching operations; a closed circuit element that selectively forms a closed circuit including the secondary coil but being different from the resonance circuit; a battery to which power is supplied from the power conversion unit via a transfer unit; a communication unit that outputs, to the power transmission device, an instruction relating to emission of an AC magnetic field; and a power reception control unit that, when determining, after elapse of a prescribed time period after the instruction, that the emission of an AC magnetic field does not conform to the instruction, blocks the transfer unit so as to stop power supply to the battery.

Description

Power receiving device

The present invention relates to a power receiving device used in wireless power feeding.

In recent years, in an electric vehicle or the like, a wireless power feeding system that feeds power wirelessly from a power transmitting device provided on the ground side to a power receiving device provided on the vehicle side is being realized. In such a wireless power feeding system, a wireless power feeding technique using magnetic field resonance or magnetic field induction has attracted attention. In magnetic field induction, a magnetic field (magnetic flux) is generated by flowing an alternating current through a coil provided in a ground-side power transmission device, and this magnetic field is received by a coil provided in a vehicle-side power receiving device to generate an alternating current. By doing so, wireless power feeding from the power transmitting device to the power receiving device is realized. On the other hand, magnetic resonance is the same as magnetic field induction in that a coil is provided in each of the power transmission device and the power reception device, but by matching the frequency of the current flowing in the coil of the power transmission device with the resonance frequency of the coil of the power reception device, Resonance is generated between the power transmission device and the power reception device. As a result, the coil of the power transmission device and the coil of the power reception device are magnetically coupled to achieve highly efficient wireless power feeding.

Regarding the wireless power feeding technology described above, the following Patent Document 1 is known. Patent Document 1 discloses an AC power source, a power supply side facility including a primary side resonance coil that receives power from the AC power source, a secondary side resonance coil that receives power from the primary side resonance coil, A resonance type non-rectifier comprising: a rectifier that rectifies the power received by the secondary resonance coil; a charger that is supplied with the power rectified by the rectifier; and a mobile unit that includes a power storage device connected to the charger. In the contact power supply system, the moving body side equipment includes a matching unit provided between the secondary resonance coil and the rectifier, and power supply determination means for determining whether power is being supplied from the power supply side equipment. A power reception determination means for determining whether or not to receive power, and, based on the determination information of the power supply determination means and the power reception determination means, in a state where power reception should be rejected but power is being supplied, the matching unit is Control to make inconsistent state Resonance type non-contact power supply system characterized in that it comprises a stage is disclosed.

Japanese Patent Application No. 2011-244533

In the system described in Patent Document 1, the magnetic coupling between the power transmitting apparatus and the power receiving apparatus is disturbed, and unnecessary leakage magnetic flux may be generated.

A power receiving device according to the present invention is a power receiving device that receives an alternating magnetic field emitted from a power transmitting device including a primary coil installed on the ground side and is wirelessly powered, and is connected to a secondary coil and the secondary coil. A resonance circuit having a resonance circuit having a predetermined resonance frequency together with the secondary coil and a plurality of switching elements, and controlling the alternating current flowing through the resonance circuit by switching each of the plurality of switching elements. A power conversion unit, a closed circuit element that selectively forms a closed circuit that includes the secondary coil and is different from the resonance circuit, a battery that is supplied with power from the power conversion unit via a transmission unit, A communication unit that outputs an instruction regarding the release of the AC magnetic field to the power transmission device, and determines that the release of the AC magnetic field is different from the instruction after a predetermined time has elapsed since the instruction. When, and a power reception control unit stopping the supply of power to the battery to cut off the transmission unit.

According to the present invention, it is possible to suppress generation of unnecessary leakage magnetic flux even when power supply to the battery is forcibly cut off.

1 is a diagram illustrating a configuration of a wireless power feeding system according to an embodiment of the present invention. It is a figure which shows the structural example of the power receiving apparatus which concerns on one Embodiment of this invention. It is an equivalent circuit diagram of a resonance circuit and a closed circuit. It is a figure which shows the processing flow of the wireless power feeding system which concerns on one Embodiment of this invention. It is a figure which shows the processing flow of an electric current monitoring process.

Hereinafter, embodiments of a power receiving device according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a wireless power feeding system 1 according to an embodiment of the present invention. A wireless power feeding system 1 shown in FIG. 1 is used in wireless power feeding to a vehicle such as an electric vehicle, and includes a power transmission device 100 installed on the ground side in the vicinity of the vehicle and a power receiving device respectively mounted on the vehicle side. 200, battery 300, load 400 and transmission unit 500, and battery monitoring device 600.

The power transmission device 100 includes a power transmission control unit 110, a communication unit 120, an AC power source 130, a power conversion unit 140, and a primary coil L1. The power transmission control unit 110 controls the power transmission apparatus 100 as a whole by controlling the operations of the communication unit 120 and the power conversion unit 140. As will be described later, the power transmission control unit 110 controls the operation of the power conversion unit 140 in consideration of information received by the communication unit 120 from the power receiving device 200. In other words, the power transmission control unit 110 operates in response to an instruction regarding the release of the alternating magnetic field from the power receiving device 200.

The communication unit 120 is a communication module corresponding to, for example, IEEE 802.11 or Bluetooth (registered trademark). The communication unit 120 performs wireless communication with the communication unit 220 included in the power receiving device 200 under the control of the power transmission control unit 110. Various information necessary for wireless power feeding is exchanged between the power transmitting apparatus 100 and the power receiving apparatus 200 by wireless communication between the communication unit 120 and the communication unit 120. For example, information such as the frequency of the alternating current flowing through the primary coil L1, that is, the frequency of the alternating magnetic field emitted from the primary coil L1, is transmitted from the communication unit 120 to the communication unit 220. In addition, information such as the state of charge (SOC) and deterioration state of the battery 300, the allowable current during charging, and a power transmission stop command are transmitted from the communication unit 220 to the communication unit 120.

Therefore, if a problem occurs in communication between the communication unit 120 and the power receiving device 200, the power transmitting device 100 cannot obtain the above-described information from the power receiving device 200, and the operation of the power transmitting device 100 emits an alternating magnetic field output by the power receiving device 200. May diverge from the instructions.

AC power supply 130 is a commercial power supply, for example, and supplies predetermined AC power to the power conversion unit 140. The power conversion unit 140 outputs an alternating current having a predetermined frequency and current value to the primary coil L <b> 1 using the alternating current power supplied from the alternating current power supply 130 under the control of the power transmission control unit 110. Primary coil L1 is installed on the ground side located under the vehicle, and emits an alternating magnetic field corresponding to the alternating current flowing from power conversion unit 140 toward the vehicle. Thereby, wireless power feeding to the vehicle is performed.

The power receiving apparatus 200 includes a power reception control unit 210, a communication unit 220, an alternating current detection unit 230, a drive control unit 240, a power conversion unit 250, a secondary coil L2, a resonance coil Lx, a resonance capacitor Cx, and a buffer coil Ly. Two resonant coils Lx and two resonant capacitors Cx are connected to the secondary coil L2, respectively, and constitute a resonant circuit together with the secondary coil L2. The resonance frequency of the resonance circuit is determined according to the inductances of the secondary coil L2 and the resonance coil Lx and the capacitance value of the resonance capacitor Cx. Note that the resonance coil Lx and the resonance capacitor Cx may each be composed of one or three or more elements. Further, part or all of the resonance coil Lx may be substituted by the inductance of the secondary coil L2.

The buffer coil Ly acts to alleviate a change in the magnetic field generated in the secondary coil L2 when the alternating current flowing through the resonance circuit including the secondary coil L2 is suddenly interrupted. One end of the buffer coil Ly is connected between one resonance coil Lx and the resonance capacitor Cx, and the other end of the buffer coil Ly is connected between the other resonance coil Lx and the resonance capacitor Cx. In other words, the buffer coil Ly is connected to both ends of the secondary coil L2 with the two resonance capacitors Cx interposed therebetween without passing through the power converter 250. Thereby, according to the operation state of the power converter 250, a closed circuit including the secondary coil L2 and the buffer coil Ly is selectively formed. The selective formation of the closed circuit by the buffer coil Ly will be described later in detail with reference to FIG.

The power reception control unit 210 controls the power reception apparatus 200 as a whole by controlling the operations of the communication unit 220 and the drive control unit 240. The power reception control unit 210 also controls the operation of the transmission unit 500. The communication unit 220 is a communication module that supports, for example, IEEE 802.11 or Bluetooth (registered trademark). The communication unit 220 is controlled by the power reception control unit 210, performs wireless communication with the communication unit 120 included in the power transmission device 100, and stores various kinds of information described above exchanged between the power transmission device 100 and the power reception device 200. Send and receive. Information such as the frequency of the alternating current flowing through the primary coil L1 received by the communication unit 220 is output from the communication unit 220 to the power reception control unit 210.

The alternating current detection unit 230 detects the alternating current flowing through the resonance circuit including the secondary coil L2 when the secondary coil L2 receives the alternating magnetic field emitted from the primary coil L1. Then, an AC voltage whose frequency and amplitude change according to the detected AC current is generated and output to the drive control unit 240. The drive control unit 240 can acquire the frequency and magnitude of the alternating current flowing through the resonance circuit based on the alternating voltage input from the alternating current detection unit 230. The power reception control unit 210 acquires the magnitude of the current detected by the alternating current detection unit 230, that is, the current value.

The drive control unit 240 controls the switching operations of the plurality of switching elements included in the power conversion unit 250 under the control of the power reception control unit 210. At this time, the drive control unit 240 changes the timing of the switching operation of each switching element based on the alternating current flowing through the resonance circuit detected by the alternating current detection unit 230. A specific method for changing the timing of the switching operation will be described later.

The power conversion unit 250 has a plurality of switching elements, and controls the AC current flowing through the resonance circuit and rectifies by switching each of the plurality of switching elements, thereby converting AC power to DC power. Do. A battery 300 that can be charged and discharged is connected to the power conversion unit 250 via the transmission unit 500, and the battery 300 is charged using DC power output from the power conversion unit 250. Note that a smoothing capacitor C0 for smoothing an input voltage to the battery 300 is connected between the power conversion unit 250 and the battery 300.

Battery 300 is supplied with power from power conversion unit 250 via transmission unit 500. A load 400 is connected to the battery 300. The load 400 provides various functions related to the operation of the vehicle using the DC power charged in the battery 300. The load 400 includes, for example, an AC motor for driving a vehicle, an inverter that converts DC power of the battery 300 into AC power, and supplies the AC power to the AC motor. The transmission unit 500 is a switch that can be opened and closed in response to an operation command from the power reception control unit 210, for example, an electromagnetic switch. The transmission unit 500 is normally in a “closed” state in which the power conversion unit 250 and the battery 300 are connected. When receiving an operation command from power reception control unit 210, transmission unit 500 transitions to an “open” state and interrupts the supply of power to battery 300.

The battery monitoring device 600 is connected to the battery 300 and acquires information for monitoring the state of charge (SOC) of the battery 300 from the battery 300. For example, the battery monitoring apparatus 500 detects the voltage of the battery 300, outputs the detection result to the drive control unit 240, and the drive control unit 240 transmits the detection result to the power reception control unit 210. However, the battery monitoring unit 600 may directly output the acquired information to the power reception control unit 210. That is, the route of information is arbitrary, and it is sufficient that the power reception control unit 210 obtains the state of charge (SOC) of the battery 300 necessary for processing to be described later.

Next, details of the power receiving apparatus 200 to which the present invention is applied in the wireless power feeding system 1 of FIG. 1 will be described. FIG. 2 is a diagram illustrating a configuration example of the power receiving device 200 according to an embodiment of the present invention.

As shown in FIG. 2, the alternating current detection unit 230 is configured using, for example, a transformer Tr. When the magnetic flux generated by the alternating magnetic field emitted from the primary coil L1 is linked to the secondary coil L2, an electromotive force is generated in the secondary coil L2, and an alternating current i flows through the resonance circuit including the secondary coil L2.
When this alternating current i flows through the primary coil of the transformer Tr, an alternating voltage Vg whose frequency and amplitude change according to the alternating current i is generated at both ends of the secondary coil of the transformer Tr. Thereby, the alternating current detection part 230 can detect the alternating current i. Note that the AC current detection unit 230 may be configured by using a device other than the transformer Tr as long as the AC current i flowing through the resonance circuit can be detected.

The power conversion unit 250 includes two MOS transistors (MOSFETs) Q1 and Q2 connected in series, and two MOS transistors Q3 and Q4 connected in series. The series circuit of the MOS transistors Q1, Q2 and the series circuit of the MOS transistors Q3, Q4 are connected in parallel to the smoothing capacitor C0. The MOS transistors Q1 to Q4 perform a switching operation for switching between the source and the drain from the conductive state to the disconnected state or from the disconnected state to the conductive state in accordance with the gate drive signal from the drive control unit 240. By this switching operation, the MOS transistors Q1 and Q3 can function as switching elements for the upper arm, and the MOS transistors Q2 and Q4 can function as switching elements for the lower arm, respectively. A resonance circuit including the secondary coil L2 is connected to a connection point O1 between the MOS transistors Q1 and Q2 and a connection point O2 between the MOS transistors Q3 and Q4. Therefore, the alternating current i flowing through the resonance circuit can be controlled and rectified by switching the MOS transistors Q1 to Q4 at appropriate timings.

The drive control unit 240 includes a voltage acquisition unit 241, a drive signal generation unit 243, and a gate drive circuit 244.

The voltage acquisition unit 241 acquires the AC voltage Vg output from the AC current detection unit 230 (transformer Tr) and outputs the AC voltage Vg to the drive signal generation unit 243.

The drive signal generation unit 243 receives the basic drive signal Sr from the power reception control unit 210 in addition to the AC voltage Vg acquired by the voltage acquisition unit 241. The basic drive signal Sr is an AC signal that is output from the drive control unit 240 to the power conversion unit 250 and is a source of a gate drive signal that controls the switching operation of the MOS transistors Q1 to Q4. It is determined according to the frequency of the current flowing through the coil L1. Specifically, when the communication unit 220 receives information representing the frequency f of the alternating current flowing through the primary coil L1 of the power transmission device 100 from the communication unit 120, the communication unit 220 outputs the information to the power reception control unit 210. When the information on the frequency f is input from the communication unit 220, the power reception control unit 210 generates a basic drive signal Sr corresponding to the frequency f and outputs it to the drive control unit 240. The basic drive signal Sr is, for example, a combination of four rectangular waves respectively corresponding to the MOS transistors Q1 to Q4, and has an H level corresponding to ON (conducting state) and an L level corresponding to OFF (disconnected state). Are alternately repeated at the frequency f. However, in order to prevent the MOS transistors Q1 and Q2 and Q3 and Q4 from being turned on at the same time, a predetermined protection period is provided between the H levels of the two rectangular waves in each combination of the rectangular waves corresponding thereto.

The drive signal generation unit 243 adjusts the phase of the basic drive signal Sr input from the power reception control unit 210 based on the AC voltage Vg input from the power reception control unit 210, and generates the charge drive signal Sc. Then, the generated charge drive signal Sc is output to the gate drive circuit 244.

The gate drive circuit 244 outputs a gate drive signal based on the charge drive signal Sc input from the drive signal generation unit 243 to the gate terminals of the MOS transistors Q1 to Q4, respectively, and causes the MOS transistors Q1 to Q4 to perform a switching operation. As a result, in the power conversion unit 250, the MOS transistors Q1 to Q4 function as switching elements, respectively, and control of the alternating current i flowing in the resonance circuit according to the alternating magnetic field emitted from the primary coil L1, or the alternating current power to the direct current power. Conversion to

The power receiving device 200 of the present embodiment can charge the battery 300 by receiving wireless power feeding from the power transmitting device 100 by performing the operation described above.

Here, it is assumed that the transmission unit 500 is cut off when the alternating current i flows through the resonance circuit including the secondary coil L2. In this case, since the connection points O1 and O2 are disconnected regardless of the states of the MOS transistors Q1 to Q4, the current flowing through the resonance circuit including the resonance coil Lx is cut off, but the buffer coil Ly is connected to the secondary coil L2. It acts to keep the current flowing through. That is, a closed circuit including the secondary coil L2 and the buffer coil Ly is selectively formed without using the power conversion unit 250. Since this closed circuit does not include the resonance coil Lx, it is different from the resonance circuit formed when the power conversion unit 250 is operating.

When the above closed circuit is formed, the buffer coil Ly continues to flow current to the secondary coil L2 according to a time constant corresponding to the inductance. Therefore, by appropriately setting the inductance of the buffer coil Ly, the buffer coil Ly is made to act as a constant current source that maintains a substantially constant current flowing in the closed circuit formed when the transmission unit 500 is cut off. Can do.

FIG. 3 is an equivalent circuit diagram of the above-described resonant circuit and closed circuit. However, the transmission unit 500 is also shown on the right end of FIG. In the equivalent circuit diagram of FIG. 3, the switch SW corresponds to the MOS transistors Q1 to Q4, and the constant current source VCS corresponds to the buffer coil Ly. The variable coil LM and the AC power source Vc correspond to the secondary coil L2. That is, the switch SW described in this equivalent circuit is different from the transmission unit 500.

Next, the flow of wireless power feeding using the wireless power feeding system 1 will be described. FIG. 4 is a diagram showing a processing flow of the wireless power feeding system 1 according to the embodiment of the present invention. When the vehicle on which the power receiving device 200, the battery 300, and the load 400 are mounted is parked at a predetermined charging position, the processing flow of FIG.

In step S10, the ground-side power transmission device 100 issues a charge inquiry to the vehicle-side power reception device 200. Here, for example, charging is inquired by transmitting a predetermined communication message from the communication unit 120 of the power transmission device 100 to the communication unit 220 of the power reception device 200.

In step S20, the power receiving device 200 that has received the charge inquiry in step S10 notifies the power transmitting device 100 of the allowable current of the battery 300 during charging. At this time, the power receiving apparatus 200 determines the allowable current based on, for example, the charge state or deterioration state of the battery 300 measured in advance, and transmits information indicating the value of the allowable current from the communication unit 220 to the communication unit 120 of the power transmission apparatus 100. Send. Note that, when charging is unnecessary, the power receiving apparatus 200 may notify the power transmitting apparatus 100 to that effect. In this case, the process flow of FIG. 3 is complete | finished, without performing the process after step S30.

In step S30, the power transmission device 100 determines the amount of current and starts power transmission to the power reception device 200. At this time, the power transmitting apparatus 100 compares the output current value corresponding to the allowable current notified from the power receiving apparatus 200 in step S20 and its own rated current value, and selects the smaller one to determine the current amount. . Then, the power transmission control unit 110 controls the power conversion unit 140 to cause an alternating current corresponding to the determined current amount to flow through the primary coil L1, thereby generating an alternating magnetic field in the primary coil L1 and starting power transmission. At this time, by further transmitting information representing the frequency f of the alternating current flowing through the primary coil L1 from the communication unit 120 to the communication unit 220 of the power reception device 200, the power reception control unit 210 of the power reception device 200 sets the frequency f to It is preferable that the above-described basic drive signal Sr can be generated. Alternatively, the frequency f may be notified from the power transmitting apparatus 100 to the power receiving apparatus 200 when an inquiry for charging is made in step S10.

In step S40, the power receiving device 200 performs drive control processing of the power conversion unit 250 according to the alternating current i that flows through the resonance circuit including the secondary coil L2 by receiving the alternating magnetic field emitted from the primary coil L1. Here, drive control of the power conversion unit 250 according to the alternating current received from the power transmission device 100 is performed by performing the above-described processing in each unit of the drive control unit 240. Thereby, the battery 300 is charged in the constant current (CC) mode.

In step S50, the power receiving apparatus 200 performs a current monitoring process described later. In step S60, in power receiving device 200, it is determined whether or not the state of charge (SOC) of battery 300 has reached a predetermined value, for example, 80% or more. As a result, if the SOC is less than 80%, the processes in steps S40 and S50 are repeated. If the SOC becomes 80% or more, the constant current mode is changed to the constant voltage (CV) mode, and the process proceeds to step S70.

In step S <b> 70, the power receiving device 200 notifies the power transmitting device 100 of a charging current corresponding to the current charging state of the battery 300. At this time, the power receiving apparatus 200 determines a charging current with a value smaller than the allowable current notified in step S20 based on the current charging state of the battery 300, and receives information indicating the value of the charging current from the communication unit 220. It transmits to the communication part 120 of the power transmission apparatus 100. That is, in step S <b> 70, the power receiving device 200 gives an instruction to weaken the AC magnetic field to be emitted to a value corresponding to the determined charging current.

In step S80, the power receiving device 200 performs the drive control process similar to that in step S40, thereby charging the battery 300 in the constant voltage (CV) mode. In step S90, a current monitoring process described later is performed in the same manner as in S50.

In step S100, the power receiving device 200 determines whether or not the state of charge (SOC) of the battery 300 has reached 100% of full charge. As a result, if the SOC is less than 100%, the process returns to step S70 to continue charging the battery 300, and if the SOC reaches 100%, the process proceeds to step S110.

In step S110, the power receiving device 200 transmits a predetermined communication message indicating power transmission stop from the communication unit 220 of the power receiving device 200 to the communication unit 120 of the power transmitting device 100 to instruct to stop power transmission, that is, stop the release of the AC magnetic field. To do. In the power transmission device 100, power transmission is stopped by interrupting the energization of the primary coil L1 in response to the power transmission stop instruction.

In step S120, the power receiving apparatus 200 determines whether power transmission by the power transmitting apparatus 100 is stopped. The power reception control unit 210 of the power reception device 200 can determine whether or not power transmission is stopped based on whether or not the current detected by the AC current detection unit 230 is zero. When it is determined that the power transmission is stopped, the processing flow of FIG. 4 is terminated, and when it is determined that the power transmission is not stopped, the process proceeds to step S130. In step S130, in the power receiving device 200, the power reception control unit 210 interrupts the transmission unit 500 to stop the power supply to the battery 300, and the processing flow of FIG. However, the command to stop power transmission is not necessarily transmitted instantaneously, and a slight time delay can ignore the adverse effect on the battery 300. Therefore, in step S130, this determination is made after a predetermined time, for example, 5 seconds after the power transmission stop command. Do.

FIG. 5 is a flowchart showing the current monitoring process in step S50 and step S90 in FIG. In step S210, the power reception control unit 210 acquires a current value detected by the alternating current detection unit 230. In subsequent step S220, power reception control unit 210 determines whether or not the current value acquired in S210 is larger than the current value notified to power transmission device 100. For example, the current monitoring process in step S50 of FIG. 4 compares with the allowable current notified in S20, and the current monitoring process in step S90 of FIG. 4 compares with the charging current notified in S70.

In addition, the current notification is not necessarily transmitted instantaneously, and a slight time delay can ignore the adverse effect on the battery 300. Therefore, this determination is made after a predetermined time has elapsed since the current was notified, for example, 5 seconds later. . For example, when the process shown in FIG. 5 is started, a 5-second waiting operation may be performed before step S210 is executed, in other words, a 5-second sleep operation may be performed. When it is determined that the current value acquired in step S220 is larger than the notified current value, the process proceeds to step S230, the transmission unit 500 is shut off, and the charging ends. When it is determined that the current value acquired in step S220 is equal to or less than the notified current value, the process illustrated in FIG. 5 is terminated and the process returns to FIG. The above is the description of the processing flow shown in FIG.

According to the embodiment of the present invention described above, the following operational effects are obtained.

(1) The power receiving device 200 is wirelessly powered by receiving an alternating magnetic field emitted from the primary coil L1 installed on the ground side. The power receiving apparatus 200 includes a secondary coil L2, a resonance coil Lx and a resonance capacitor Cx, which are resonance elements that are connected to the secondary coil L2 and constitute a resonance circuit having a predetermined resonance frequency together with the secondary coil L2. A resonance circuit including MOS transistors Q1 to Q4 which are switching elements and including a secondary coil L2 and a power conversion unit 250 that controls an alternating current i flowing through the resonance circuit by switching the MOS transistors Q1 to Q4. A buffer coil Ly that is a closed circuit element that selectively forms a closed circuit different from the above, a battery 300 that is supplied with power from the power conversion unit 250 via the transmission unit 500, and an AC magnetic field emission to the power transmission device 100 The communication unit 220 that outputs the instruction, and determines that the release of the AC magnetic field is different from the instruction after a predetermined time has elapsed from the instruction. , And a power reception control unit 210 to stop the power supply to the battery 300 to interrupt the transmission unit 500. Since it did in this way, when abnormality occurs in communication or when a problem occurs in the operation of the power transmission device 100, the transmission unit 500 can be cut off to prevent overcharging of the battery 300. Generation of unnecessary magnetic flux leakage can be suppressed.

(2) When the communication unit 220 instructs the power transmission device 100 to stop the release of the alternating magnetic field when the communication unit 220 instructs the power transmission apparatus 100 to stop, the power reception control unit 210 blocks the transmission unit 500 when the current flowing through the resonance circuit is not zero (S130 in FIG. 4). : N, S140). Therefore, safe charging and unnecessary leakage magnetic flux can be suppressed at the end of charging.

(3) When the communication unit 220 instructs the communication unit 220 to weaken the AC magnetic field emitted to the power transmission device 100 to a predetermined value, the power reception control unit 210 transmits the current when the current flowing through the resonance circuit is larger than a value corresponding to the predetermined value. Block part 500. Therefore, it is possible to safely charge and suppress unnecessary leakage magnetic flux during constant voltage charging that gradually weakens the intensity of the AC magnetic field.

In the embodiment described above, each component of the drive control unit 240 and the power reception control unit 210 may be realized by software executed by a microcomputer or the like, or an ASIC or FPGA (Field-Programmable Gate Array ) Or the like. These may be used in combination.

In the above-described embodiment, the wireless power feeding system 1 used for wireless power feeding to a vehicle such as an electric vehicle has been described. However, the present invention is not limited to wireless power feeding to a vehicle, but is applied to a wireless power feeding system for other uses. May be.

The embodiment and various modifications described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired. Moreover, although various embodiment and the modification were demonstrated above, this invention is not limited to these content. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Wireless power supply system 100 Power transmission apparatus 200 Power reception apparatus 210 Power reception control part 220 Communication part 230 AC current detection part 240 Drive control part 300 Battery 400 Load 500 Transmission part L1 Primary coil L2 Secondary coil Lx Resonance coil Ly Buffer coil Cx Resonance capacitor Tr Transformer Q1, Q2, Q3, Q4 MOS transistor

Claims

A power receiving device that receives an alternating magnetic field emitted from a power transmitting device including a primary coil installed on the ground side and is wirelessly powered,
A secondary coil;
A resonant element connected to the secondary coil to form a resonant circuit having a predetermined resonant frequency together with the secondary coil;
A power converter that has a plurality of switching elements and controls the alternating current flowing in the resonance circuit by switching the plurality of switching elements, respectively;
A closed circuit element that selectively forms a closed circuit that includes the secondary coil and is different from the resonant circuit;
A battery to which power is supplied from the power conversion unit via a transmission unit;
A communication unit that outputs an instruction regarding the release of the alternating magnetic field to the power transmission device;
A power reception device comprising: a power reception control unit configured to shut off the transmission unit and stop power supply to the battery when it is determined that the release of the AC magnetic field is different from the command after a predetermined time has elapsed from the command.
The power receiving device according to claim 1,
The power reception control unit is configured to interrupt the transmission unit when a current flowing through the resonance circuit is not zero when the communication unit instructs the power transmission device to stop the emission of the AC magnetic field.
The power receiving device according to claim 1 or 2,
The power reception control unit, when the communication unit instructs to weaken the AC magnetic field emitted to the power transmission device to a predetermined value, the current flowing through the resonance circuit is greater than a value corresponding to the predetermined value A power receiving device that cuts off the transmission section.