JP2019205296A - Power reception apparatus and wireless power transmission system - Google Patents

Abstract

To suppress the occurrence of an overvoltage in a power reception apparatus.SOLUTION: A power reception apparatus according to an embodiment includes a resonant circuit that wirelessly receives power from a power transmission device, a rectifier circuit that rectifies an output current of the resonant circuit, and an overvoltage detection circuit connected between the rectifier circuit and a load, and the overvoltage detection circuit includes a first switch element connected between the rectifier circuit and the load, a first capacitive element connected in parallel with the first switch element, a second capacitive element connected in parallel with the load, and a control circuit that turns off the first switch element when the output voltage of the overvoltage detection circuit is equal to or higher than a first threshold voltage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power receiving apparatus and a wireless power transmission system.

  Conventionally, in a wireless power transmission system, wireless communication such as Bluetooth (registered trademark) is used to feed back a state of a power receiving device to a power transmitting device. By adjusting the power transmitted by the power transmission device based on feedback from the power reception device, it is possible to suppress the occurrence of overvoltage in the power reception device.

JP 2017-5991 A

  However, the communication frequency of wireless communication cannot cope with a sudden change in the state of the power receiving device due to load fluctuation or the like, and there is a possibility that an overvoltage occurs in the power receiving device.

  The present invention has been made in view of the above problems, and an object thereof is to suppress the occurrence of overvoltage in a power receiving apparatus.

  A power receiving device according to an embodiment includes a resonance circuit that wirelessly receives power from a power transmission device, a rectification circuit that rectifies an output current of the resonance circuit, and an overvoltage detection circuit that is connected between the rectification circuit and a load. And the overvoltage detection circuit includes a first switch element connected between the rectifier circuit and the load, a first capacitor element connected in parallel with the first switch element, and the load. A second capacitance element connected in parallel; and a control circuit that turns off the first switch element when an output voltage of the overvoltage detection circuit is equal to or higher than a first threshold voltage.

  According to each embodiment of the present invention, it is possible to suppress the occurrence of overvoltage in the power receiving device.

The figure which shows an example of a wireless power transmission system. FIG. 9 illustrates a specific example of a power receiving device. The timing chart which shows an example of operation | movement of a wireless power transmission system. FIG. 9 illustrates a specific example of a power receiving device. FIG. 9 illustrates a specific example of a power receiving device. FIG. 9 illustrates a specific example of a power receiving device. FIG. 9 illustrates a specific example of a power receiving device. FIG. 9 illustrates a specific example of a power receiving device.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, regarding the description of the specification and the drawings according to each embodiment, constituent elements having substantially the same functional configuration are denoted by the same reference numerals and overlapping description is omitted.

<First Embodiment>
A wireless power transmission system 100 according to the first embodiment will be described with reference to FIGS. The wireless power transmission system 100 according to the present embodiment is a system that wirelessly transmits power from the power transmission device 1 to the power reception device 2 by a magnetic resonance method.

  FIG. 1 is a diagram illustrating an example of a wireless power transmission system 100. A wireless power transmission system 100 in FIG. 1 includes a power transmission device 1, a power reception device 2, and a load 3.

  The power transmission device 1 is a device that wirelessly transmits power to the power reception device 2, and includes a resonance circuit 11, a drive circuit 12, a power source 13, and a control circuit 14.

  The resonance circuit 11 is a circuit that generates an alternating magnetic field, and includes a capacitive element C1 and a coil L1. The capacitive element C1 includes a first terminal and a second terminal. The first terminal of the capacitive element C1 is connected to the first output terminal of the drive circuit 12, and the second terminal of the capacitive element C1 is connected to the first terminal of the coil L1. The coil L1 is a power transmission coil and generates an alternating magnetic field. The coil L1 includes a first terminal and a second terminal. The first terminal of the coil L1 is connected to the second terminal of the capacitive element C1, and the second terminal of the coil L1 is connected to the second output terminal of the drive circuit 12.

  The drive circuit 12 is a circuit that supplies an alternating current I1 to the resonance circuit 11 and generates an alternating magnetic field in the resonance circuit 11, and includes switch elements S1 and S2. The switch elements S1 and S2 are elements that can open and close the circuit, and each include a first terminal, a second terminal, and a control terminal. The first terminal of the switch element S1 is connected to the first terminal of the power supply 13, the second terminal of the switch element S1 is connected to the first terminal of the switch element S2, and the control terminal is connected to the control circuit 14. The first terminal of the switch element S2 is connected to the second terminal of the switch element S1, the second terminal of the switch element S2 is connected to the second terminal of the power supply 13, and the control terminal is connected to the control circuit 14. A connection point between the second terminal of the switch element S1 and the first terminal of the switch element S2 corresponds to the first output terminal of the drive circuit 12. The second terminal of the switch element S2 corresponds to the second output terminal of the drive circuit 12.

  The alternating current I1 is supplied to the resonance circuit 11 by alternately opening and closing the switch elements S1 and S2. The switch elements S1 and S2 are, for example, bipolar transistors or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), but are not limited thereto. As the switch elements S1 and S2, any element capable of opening and closing a circuit can be used.

  The power source 13 is a constant voltage source and includes a first terminal and a second terminal. The first terminal (high voltage side terminal) of the power source 13 is connected to the first terminal of the switch element S1, and the second terminal (low voltage side terminal) of the power source 13 is connected to the second terminal of the switch element S2.

  The control circuit 14 is a circuit that controls the frequency of the alternating current I1 supplied to the resonance circuit 11 by controlling the opening and closing of the switch elements S1 and S2, and the frequency of the alternating magnetic field generated by the resonance circuit 11. The control circuit 14 detects an overvoltage generated in the power receiving device 2 based on the alternating current I1 flowing through the resonance circuit 11. When detecting an overvoltage, the control circuit 14 turns off at least one of the switch elements S1 and S2 and stops power transmission. The control circuit 14 may be a microcomputer or hardware.

  In addition, the structure of the power transmission apparatus 1 is not restricted to the example of FIG. For example, the power transmission device 1 may include a wireless communication module for wirelessly communicating with the power receiving device 2 by a predetermined communication method such as Bluetooth or Wi-Fi (registered trademark), or power is supplied from an external power source. Also good.

  The power receiving device 2 includes a resonance circuit 21, a rectifier circuit 22, an overvoltage detection circuit 23, and a control circuit 24.

  The resonance circuit 21 is a circuit that wirelessly receives power from the resonance circuit 11. The resonance circuit 21 includes a capacitive element C2 and a coil L2. The capacitive element C2 includes a first terminal and a second terminal. The first terminal of the capacitive element C2 is connected to the first terminal of the coil L2, and the second terminal of the capacitive element C2 is connected to the first input terminal of the rectifier circuit 22. The coil L <b> 2 is a power receiving coil, and an alternating current is generated by the alternating magnetic field generated by the coil L <b> 1 and is input to the rectifier circuit 22. The coil L2 includes a first terminal and a second terminal. The first terminal of the coil L2 is connected to the first terminal of the capacitive element C2, and the second terminal of the coil L2 is connected to the second input terminal of the rectifier circuit 22.

  The rectifier circuit 22 is a circuit that rectifies the alternating current input from the resonance circuit 21 and outputs the voltage of the output current obtained by the rectification as the output voltage V1 from the first output terminal. The output voltage V1 is input to the overvoltage detection circuit 23. The rectifier circuit 22 includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input terminal of the rectifier circuit 22 is connected to the first terminal of the capacitive element C2, and the second input terminal of the rectifier circuit 22 is connected to the second terminal of the coil L2. The first output terminal of the rectifier circuit 22 is connected to the first input terminal of the overvoltage detection circuit 23, and the second output terminal of the rectifier circuit 22 is connected to the second input terminal of the overvoltage detection circuit 23. The rectifier circuit 22 is, for example, a diode bridge, but is not limited thereto. As the rectifier circuit 22, any circuit capable of rectifying an alternating current can be used.

  The overvoltage detection circuit 23 is a circuit that detects an overvoltage. The overvoltage here means that the output voltage V2 of the overvoltage detection circuit 23 becomes equal to or higher than the threshold voltage Vth1 (first threshold voltage). The overvoltage detection circuit 23 includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input terminal of the overvoltage detection circuit 23 is connected to the first output terminal (high voltage side output terminal) of the rectifier circuit 22, and the second input terminal of the overvoltage detection circuit 23 is connected to the second output terminal (low voltage) of the rectifier circuit 22. Side output terminal). The first output terminal of the overvoltage detection circuit 23 is connected to the first terminal (high voltage side terminal) of the load 3, and the second output terminal of the overvoltage detection circuit 23 is the second terminal (low voltage side terminal) of the load 3. Connected to. That is, the overvoltage detection circuit 23 is connected between the rectifier circuit 22 and the load 3. The overvoltage detection circuit 23 outputs an output voltage V2 corresponding to the output voltage V1 input from the rectifier circuit 22. The output voltage V2 is input to the load 3. The overvoltage detection circuit 23 includes a switch element S3 (first switch element), a capacitive element C3 (first capacitive element), a capacitive element C4 (second capacitive element), and a control circuit 24.

  The switch element S3 is an element that can open and close a circuit, and includes a first terminal, a second terminal, and a control terminal. The first terminal of the switch element S3 is connected to the first output terminal of the rectifier circuit 22 and the first terminal (high-voltage side terminal) of the capacitive element C3. The second terminal of the switch element S3 is the first terminal of the load 3, The second terminal (low voltage side terminal) of the capacitive element C3 and the first terminal (high voltage side terminal) of the capacitive element C4 are connected. That is, the switch element S3 is connected in series between the rectifier circuit 22 and the load 3. A control signal for controlling opening and closing of the switch element S3 is input to the control terminal of the switch element S3. The first terminal of the switch element S3 corresponds to the first input terminal of the overvoltage detection circuit 23, and the second terminal of the switch element S3 corresponds to the first output terminal of the overvoltage detection circuit 23. Hereinafter, a connection point between the first terminal of the switch element S3 and the first terminal of the capacitive element C3 is referred to as a node N1. A connection point of the second terminal of the switching element S3, the second terminal of the capacitive element C3, and the first terminal of the capacitive element C4 is referred to as a node N2. The voltage at the node N1 corresponds to the output voltage V1 of the rectifier circuit 22, and the voltage at the node N2 corresponds to the output voltage V2 of the overvoltage detection circuit 23. The switch element S3 is, for example, a bipolar transistor or a MOSFET, but is not limited thereto. As the switch element S3, any element that can open and close a circuit can be used.

  The capacitive element C3 includes a first terminal and a second terminal. A first terminal of the capacitive element C3 is connected to the node N1, and a second terminal of the capacitive element C3 is connected to the node N2. That is, the capacitive element C3 is connected in parallel with the switch element S3.

  The capacitive element C4 includes a first terminal and a second terminal. The first terminal of the capacitive element C4 is connected to the node N2, and the second terminal (low voltage side terminal) of the capacitive element C4 is connected to the second output terminal of the rectifier circuit 22 and the second terminal of the load 3. That is, the capacitive element C4 is connected in parallel with the load 3. The second terminal of the capacitive element C4 corresponds to the second input terminal and the second output terminal of the overvoltage detection circuit 23. Hereinafter, the connection point of the second terminal of the capacitive element C4, the rectifier circuit 22, and the load 3 is referred to as a node N3. The node N3 may be connected to the ground.

  The control circuit 24 is a circuit that notifies the power transmission device 1 of the detection result of the overvoltage by detecting the overvoltage and controlling the opening and closing of the switch element S3. The control circuit 24 normally turns on the switch element S3, and turns off the switch element S3 when an overvoltage is detected. When the switch element S3 is turned off, the load capacity of the overvoltage detection circuit 23 decreases, and the output voltage V1 rises rapidly. When the output voltage V1 rises, the alternating current I1 supplied by the power transmission device 1 rapidly increases. Therefore, the power transmission device 1 can detect the overvoltage generated in the power reception device 2 based on the magnitude of the alternating current I1. The control circuit 24 may be a microcomputer or hardware.

  Note that the configuration of the power receiving device 2 is not limited to the example of FIG. For example, the power receiving device 2 may include a wireless communication module, a filter circuit, an amplifier circuit, and the like for wirelessly communicating with the power transmitting device 1 using a predetermined communication method such as Bluetooth or Wi-Fi.

  The load 3 is supplied with the power received by the power receiving apparatus 2 wirelessly. The load 3 includes a first terminal and a second terminal. A first terminal of the load 3 is connected to the node N2, and a second terminal of the load 3 is connected to the node N3. The load 3 is, for example, an IC (Integrated Circuit), a battery, or a sensor, but is not limited thereto.

  FIG. 2 is a diagram illustrating a specific example of the power receiving device 2. In the example of FIG. 2, the switch element S3 is a P-channel MOSFET (hereinafter referred to as “PMOS”), a source terminal (first terminal), a drain terminal (second terminal), and a gate terminal (control terminal). And comprising. The source terminal of the switch element S3 is connected to the node N1, the drain terminal of the switch element S3 is connected to the node N2, the gate terminal of the switch element S3 is the second terminal of the resistor element R1, the first terminal of the resistor element R2, and The drain terminal of the switch element S4 (second switch element) is connected. Hereinafter, a connection point of the gate terminal of the switch element S3, the second terminal of the resistor element R1, the first terminal of the resistor element R2, and the drain terminal of the switch element S4 is referred to as a node N4. A voltage corresponding to the output voltage V1 (the voltage at the node N4) is input to the gate terminal of the switch element S3.

  In the example of FIG. 2, the control circuit 24 includes resistance elements R1 to R6, a switch element S4, and a switch element S5 (third switch element).

  The resistance elements R1 and R2 each include a first terminal and a second terminal. A first terminal of resistance element R1 is connected to node N1, and a second terminal of resistance element R1 is connected to node N4. A first terminal of resistance element R2 is connected to node N4, and a second terminal of resistance element R2 is connected to node N3. That is, the resistance elements R1 and R2 are connected in series between the node N1 and the node N3, and the voltage obtained by dividing the output voltage V1 (the voltage at the node N4) is input to the gate terminal of the switch element S3. A pressure circuit (first voltage dividing circuit) is configured.

  The switch element S4 is a PMOS and includes a source terminal (first terminal), a drain terminal (second terminal), and a gate terminal (control terminal). The source terminal of the switch element S4 is connected to the node N1, the drain terminal of the switch element S4 is connected to the node N4, and the gate terminal of the switch element S4 is connected to the second terminal of the resistor element R3 and the first terminal of the resistor element R4. Has been. Hereinafter, a connection point between the second terminal of the resistor element R3 and the first terminal of the resistor element R4 is referred to as a node N5. A voltage corresponding to the output voltage V1 (the voltage at the node N5) is input to the gate terminal of the switch element S4 when the switch element S5 is on.

  The resistance elements R3 and R4 each include a first terminal and a second terminal. A first terminal of resistance element R3 is connected to node N1, and a second terminal of resistance element R3 is connected to node N5. The first terminal of the resistor element R4 is connected to the node N5, and the second terminal of the resistor element R4 is connected to the drain terminal of the switch element S5. That is, the resistance elements R3 and R4 are connected in series between the node N1 and the drain terminal of the switch element S5, and a voltage (node N5) obtained by dividing the difference between the output voltage V1 and the drain voltage of the switch element S5. Voltage divider circuit (second voltage divider circuit) is input to the gate terminal of the switch element S4.

  The switch element S5 is an N-channel MOSFET (hereinafter referred to as “NMOS”), and includes a drain terminal (first terminal), a source terminal (second terminal), and a gate terminal (control terminal). The drain terminal of the switch element S5 is connected to the second terminal of the resistor element R4, the source terminal of the switch element S5 is connected to the node N3, and the gate terminal of the switch element S5 is the second terminal of the resistor element R5 and the resistor element R6. Connected to the first terminal. Hereinafter, a connection point between the second terminal of the resistor element R5 and the first terminal of the resistor element R6 is referred to as a node N6. A voltage corresponding to the output voltage V2 (the voltage at the node N6) is input to the gate terminal of the switch element S5.

  Resistor elements R5 and R6 each include a first terminal and a second terminal. A first terminal of resistance element R5 is connected to node N2, and a second terminal of resistance element R5 is connected to node N6. A first terminal of resistance element R6 is connected to node N6, and a second terminal of resistance element R6 is connected to node N3. That is, the resistance elements R5 and R6 are connected in series between the node N2 and the node N3, and the voltage obtained by dividing the output voltage V2 (the voltage at the node N6) is input to the gate terminal of the switch element S5. A pressure circuit (third voltage dividing circuit) is configured.

  Next, the operation of the wireless power transmission system 100 will be described. FIG. 3 is a timing chart showing an example of the operation of the wireless power transmission system 100.

  First, the power transmission device 1 starts power transmission wirelessly. Specifically, the control circuit 14 starts driving of the drive circuit 12 (opening / closing control of the switch elements S1 and S2). As a result, an alternating current I1 having a predetermined frequency is supplied to the resonance circuit 11 as shown in FIG. When the alternating current I1 is supplied to the resonance circuit 11, the coil L1 generates an alternating magnetic field having the same frequency as the alternating current I1.

  When the power receiving device 2 approaches the power transmitting device 1 during power transmission, the coil L2 generates an alternating current by an alternating magnetic field and inputs the alternating current to the rectifier circuit 22. When an alternating current is input, the rectifying circuit 22 rectifies the alternating current, and generates an output voltage V1 by flowing an output current obtained by the rectification to the resistance elements R1 and R2. When the output voltage V1 is input from the rectifier circuit 22, the overvoltage detection circuit 23 outputs an output voltage V2 corresponding to the output voltage V1. This output voltage V2 is applied to the load 3, and power corresponding to the output voltage V2 is supplied to the load 3.

  Here, the operation of the overvoltage detection circuit 23 of FIG. 2 will be described in detail. When the output voltage V2 is not output, the switch elements S1 to S3 of the overvoltage detection circuit 23 are all off until the power receiving device 2 starts to receive power. When the power receiving device 2 starts to receive power, the capacitive elements C3 and C4 are charged, and the output voltages V1 and V2 increase as shown in FIG.

  When the output voltage V1 becomes equal to or higher than the threshold voltage Vth3 (third threshold voltage), the gate-source voltage of the switch element S3 (potential difference between the nodes N1 and N4) becomes equal to or higher than the gate threshold voltage, and as shown in FIG. Element S3 is turned on. Thereby, the capacitive element C3 is removed from the load capacitance of the overvoltage detection circuit 23, and the load capacitance is increased. The threshold voltage Vth3 is set lower than the threshold voltages Vth1 and Vth2 by the resistance elements R1 and R2.

  On the other hand, when the output voltage V2 becomes equal to or higher than the threshold voltage Vth2 (second threshold voltage), the gate-source voltage (potential difference between the nodes N3 and N6) of the switch element S5 becomes equal to or higher than the gate threshold voltage, as shown in FIG. The switch element S5 is turned on. As a result, current starts to flow through the resistance elements R3 and R4 and the switch element S5, and the voltage at the node N5 decreases. The threshold voltage Vth2 is set lower than the threshold voltage Vth1 by the resistance elements R5 and R6.

  Thereafter, output voltages V1, V2 corresponding to the load 3 are output from the rectifier circuit 22 and the overvoltage detection circuit 23, respectively. The output voltage V2 varies with the output voltage V1 while the switch element S3 is on.

  When the load 3 fluctuates during power reception by the power receiving device 2 and the output voltage V2 becomes equal to or higher than the threshold voltage Vth1 (overvoltage is detected), the gate-source voltage of the switch element S4 (potential difference between the nodes N1 and N5) Becomes equal to or higher than the gate threshold voltage, and the switch element S4 is turned on as shown in FIG. As a result, current starts to flow through the switch element S4, the gate-source voltage of the switch element S3 (potential difference between the nodes N1 and N4) becomes less than the gate threshold voltage, and the switch element S3 is turned off as shown in FIG. Become. Thereafter, the switch element S4 is designed so that the switch element S3 cannot be turned on while the switch element S4 is turned on.

  When the switch element S3 is turned off, the capacitive element C3 is connected in series to the capacitive element C4, so that the load capacity of the overvoltage detection circuit 23 is reduced, and the output voltage V1 rapidly increases as shown in FIG. . When the output voltage V1 rises, the alternating voltage of the resonance circuit 21 rises, and as shown in FIG. 3, the alternating current I1 supplied by the power transmission device 1 rapidly increases. At this time, the output voltage V2 output to the load 3 rises more gently than the output voltage V1 in accordance with the capacitance ratio of the capacitive elements C3 and C4, so that overvoltage to the load side is suppressed. Note that the capacitance of the capacitive element C3 is set to be smaller than the capacitance of the capacitive element C4.

  When the control circuit 14 of the power transmission device 1 detects that the alternating current I1 is equal to or greater than the threshold current Ith, the control circuit 14 determines that an overvoltage has occurred in the power reception device 2, turns off at least one of the switch elements S1 and S2, and transmits power. To stop. The power transmission from the power transmission device 1 is preferably stopped until the output voltage V2 is at least less than the threshold voltage Vth1. Specifically, the stop of power transmission may be canceled when the output voltage V2 becomes equal to or lower than the threshold voltage Vth2. Note that the power transmission device 1 may reduce the amount of power supplied to the power receiving device 2 by changing the power transmission frequency or lowering the voltage of the power source 13 instead of stopping the power transmission.

  When power transmission from the power transmission device 1 is stopped, the output voltages V1 and V2 of the power reception device 2 decrease. Thereafter, while the output voltage V2 is equal to or higher than the threshold voltage Vth2, the switch element S3 remains off, and the switch elements S4 and S5 remain on.

  When the output voltage V2 becomes less than the threshold voltage Vth2, the gate-source voltage of the switch element S5 (potential difference between the nodes N3 and N6) becomes less than the gate threshold voltage, and the switch element S5 is turned off as shown in FIG. . When the switch element S5 is turned off, no current flows through the resistance elements R3 and R4, so that the gate-source voltage (potential difference between the nodes N1 and N5) of the switch element S4 becomes 0 (less than the gate threshold voltage). As shown, the switch element S4 is turned off.

  When the switch element S4 is turned off, the switch element S3 can be turned on. Therefore, when the threshold voltage Vth3 is set lower than the threshold voltage Vth2, when the switch element S4 is turned off, the switch element S3 is turned on as shown in FIG.

  When the power transmission device 1 detects an overvoltage generated in the power reception device 2 and stops power transmission, the power transmission device 1 may automatically resume power transmission after a predetermined time, or the power reception device 2 is requested to transmit power by wireless communication. The power transmission may be resumed in the event of a failure. When the output voltage V2 is higher than the threshold voltage Vth1 when power transmission is resumed, as described above, the alternating current I1 increases rapidly, and thus the power transmission device 1 detects the overvoltage again.

  As described above, when the power receiving device 2 according to the present embodiment detects an overvoltage, the power receiving device 2 turns off the switch element S3, reduces the load capacity of the overvoltage detection circuit 23, and sets the output voltage V2 output to the load 3 to the threshold voltage. The power transmission device 1 is notified of the occurrence of an overvoltage by suppressing the voltage from becoming Vth1 or higher, increasing the output voltage V1, and increasing the alternating current I1. Thereby, the power receiving apparatus 2 can notify the power transmission apparatus 1 of the occurrence of overvoltage instantaneously (in a time shorter than the communication interval of wireless communication). As a result, when an overvoltage occurs in the power receiving device 2, the power transmitting device 1 can quickly stop power transmission and suppress the occurrence of the overvoltage in the power receiving device 2.

  In the example of FIG. 2, the control circuit 24 is realized by hardware. However, as described above, the control circuit 24 may be realized by a microcomputer that executes a program.

  Further, the resistance element R1 may be a single resistance element or a combination of a plurality of resistance elements connected in series or in parallel. The same applies to the resistance elements R2 to R6.

  Further, the capacitive element C1 may be a single capacitive element or a combination of a plurality of capacitive elements connected in series or in parallel. The same applies to the capacitive elements C2 to C4.

  In the example of FIG. 2, the switch elements S3 to S5 are MOSFETs, but may be bipolar transistors. In this case, the above “N channel”, “P channel”, “source”, “drain”, and “gate” are respectively referred to as “NPN type”, “PNP type”, “emitter”, “collector”, and “collector”. It may be read as “base”.

  In the example of FIG. 2, the switch element S3 is provided on the high voltage side, but may be provided on the low voltage side. FIG. 4 is a diagram illustrating a modification of the power receiving device 2 of FIG. As shown in FIG. 4, when the switch element S3 is provided on the low voltage side, the switch elements S3 and S4 are NMOS and the switch element S5 is PMOS while maintaining the connection relationship between the elements of the power receiving device 2 of FIG. And Further, the node N1 is connected to the second output terminal (low voltage side output terminal) of the rectifier circuit 22, the node N2 is connected to the second terminal (low voltage side terminal) of the load 3, and the node N3 is connected to the first terminal of the rectifier circuit 22. Connect to the output terminal (high voltage side output terminal) and the first terminal (high voltage side terminal) of the load 3. Further, the high voltage side and the low voltage side of each terminal of each element of the overvoltage detection circuit 23 are such that the first terminal of the capacitive element C4 is the low voltage side terminal and the second terminal of the capacitive element C4 is the high voltage side terminal. Replace. The overvoltage detection circuit 23 receives the output voltage V3 from the second output terminal of the rectifier circuit 22, and the overvoltage detection circuit 23 outputs an output voltage V4 corresponding to the output voltage V3 from the node N2. With such a configuration, according to the power receiving device 2 of FIG. 4, the same effects as those of the power receiving device 2 of FIG. In the example of FIG. 4, the node N2 may be connected to the ground instead of the node N3.

Second Embodiment
A wireless power transmission system 100 according to the second embodiment will be described with reference to FIGS. 5 and 6. In the present embodiment, another example of the control circuit 24 will be described. FIG. 5 is a diagram illustrating a specific example of the power receiving device 2. In the example of FIG. 5, the control circuit 24 includes resistance elements R7 and R8, a switch element S6, and comparators Cmp1 and Cmp2. Other configurations are the same as those of the control circuit 24 of FIG.

  The resistance elements R7 and R8 each include a first terminal and a second terminal. The first terminal of the resistor element R7 is connected to the node N1, and the second terminal of the resistor element R7 is connected to the first terminal of the resistor element R8, the drain terminal of the switch element S6, and the ratio inverting input terminal of the comparator Cmp1. . Hereinafter, a connection point of the second terminal of the resistance element R7, the first terminal of the resistance element R8, and the non-inverting input terminal of the comparator Cmp1 is referred to as a node N7. The first terminal of the resistor element R8 is connected to the node N7, and the second terminal of the resistor element R8 is connected to the node N3. That is, the resistance elements R7 and R8 are connected in series between the node N1 and the node N3, and a voltage obtained by dividing the output voltage V1 (voltage of the node N7) is input to the non-inverting input terminal of the comparator Cmp1. A voltage dividing circuit is configured.

  The switch element S6 is an NMOS and includes a drain terminal (first terminal), a source terminal (second terminal), and a gate terminal (control terminal). The drain terminal of the switch element S6 is connected to the node N7, the source terminal of the switch element S6 is connected to the node N3, and the gate terminal of the switch element S6 is connected to the output terminal of the comparator Cmp2.

  The comparator Cmp1 is configured by a comparator and is driven by the auxiliary power supply voltage Vcc of the power receiving device 2. The comparator Cmp1 includes a non-inverting input terminal, an inverting input terminal, and an output terminal. The non-inverting input terminal of the comparator Cmp1 is connected to the node N7, the inverting input terminal of the comparator Cmp1 is supplied with the reference voltage Vref1, and the output terminal of the comparator Cmp1 is connected to the gate terminal of the switch element S5. The comparator Cmp1 compares the voltage at the node N7 with the reference voltage Vref1, and outputs a comparison result. The comparator Cmp1 outputs 1 (auxiliary power supply voltage Vcc) when the voltage of the node N7 is higher than the reference voltage Vref1, and 0 (voltage of the node N3 (for example, ground) when the voltage of the node N7 is lower than the reference voltage Vref1. Voltage)). The comparison result (output signal of 1 or 0) of the comparator Cmp1 is input to the gate terminal of the switch element S5. The switch element S5 is turned on when 1 is input from the comparator Cmp1, and is turned off when 0 is input from the comparator Cmp1.

  The comparator Cmp2 includes a comparator and is driven by the auxiliary power supply voltage Vcc of the power receiving device 2. The comparator Cmp2 includes a non-inverting input terminal, an inverting input terminal, and an output terminal. The inverting input terminal of the comparator Cmp2 is connected to the node N6, the non-inverting input terminal of the comparator Cmp2 is input with the reference voltage Vref2, and the output terminal of the comparator Cmp2 is connected to the gate terminal of the switch element S6. The comparator Cmp2 compares the voltage at the node N6 with the reference voltage Vref2, and outputs a comparison result. The comparator Cmp2 outputs 1 (auxiliary power supply voltage Vcc) when the voltage at the node N6 is lower than the reference voltage Vref2, and 0 (voltage at the node N3 (for example, ground) when the voltage at the node N6 is higher than the reference voltage Vref2. Voltage)). The comparison result (output signal of 1 or 0) of the comparator Cmp2 is input to the gate terminal of the switch element S6. The switch element S6 is turned on when 1 is input from the comparator Cmp2, and is turned off when 0 is input from the comparator Cmp2.

  With the configuration as described above, according to the present embodiment, the threshold voltages Vth1 and Vth2 can be set more accurately than in the first embodiment.

  The resistance element R7 may be a single resistance element or a combination of a plurality of resistance elements connected in series or in parallel. The same applies to the resistance element R8.

  In the example of FIG. 5, the switch element S6 is a MOSFET, but may be a bipolar transistor.

  In the example of FIG. 5, the switch element S3 is provided on the high voltage side, but may be provided on the low voltage side. FIG. 6 is a diagram illustrating a modification of the power receiving device 2 of FIG. As shown in FIG. 6, when the switch element S3 is provided on the low voltage side, the switch elements S3 and S4 are PMOS while maintaining the connection relationship between the elements of the power receiving device 2 of FIG. Further, the node N1 is connected to the second output terminal (low voltage side output terminal) of the rectifier circuit 22, the node N2 is connected to the second terminal (low voltage side terminal) of the load 3, and the node N3 is connected to the first terminal of the rectifier circuit 22. Connect to the output terminal (high voltage side output terminal) and the first terminal (high voltage side terminal) of the load 3. Further, the high voltage side and the low voltage side of each terminal of each element of the overvoltage detection circuit 23 are such that the first terminal of the capacitive element C4 is the low voltage side terminal and the second terminal of the capacitive element C4 is the high voltage side terminal. Replace. The overvoltage detection circuit 23 receives the output voltage V3 from the second output terminal of the rectifier circuit 22, and the overvoltage detection circuit 23 outputs an output voltage V4 corresponding to the output voltage V3 from the node N2. The overvoltage detection circuit 23 includes resistance elements R9 to R12, switch elements S7, S8, and a comparator Cmp3 instead of the resistance elements R3, R4, R7, R8, the switch elements S5, S6, and the comparator Cmp1. .

  The resistance elements R9 and R10 each include a first terminal and a second terminal. The first terminal of the resistor element R9 is connected to the node N1, and the second terminal of the resistor element R9 is connected to the first terminal of the resistor element R10 and the non-inverting input terminal of the comparator Cmp3. Hereinafter, a connection point of the second terminal of the resistor element R9, the second terminal of the resistor element R10, and the non-inverting input terminal of the comparator Cmp3 is referred to as a node N8. The first terminal of the resistor element R10 is connected to the node N8, and the second terminal of the resistor element R10 is connected to the source terminal of the switch element S7.

  The switch element S7 is an NMOS and includes a drain terminal (first terminal), a source terminal (second terminal), and a gate terminal (control terminal). The drain terminal of the switch element S7 is connected to the node N3, the source terminal of the switch element S7 is connected to the second terminal of the resistor element R10, and the gate terminal of the switch element S7 is the second terminal of the resistor element R11 and the resistor element R12. Connected to the first terminal. Hereinafter, a connection point between the second terminal of the resistor element R11 and the first terminal of the resistor element R12 is referred to as a node N9.

  The comparator Cmp3 is constituted by a comparator and is driven by the auxiliary power supply voltage Vcc of the power receiving device 2. The comparator Cmp3 includes a non-inverting input terminal, an inverting input terminal, and an output terminal. The non-inverting input terminal of the comparator Cmp3 is connected to the node N8, the inverting input terminal of the comparator Cmp3 is input with the reference voltage Vref3, and the output terminal of the comparator Cmp3 is connected to the gate terminal of the switch element S4. The comparator Cmp3 compares the voltage at the node N8 with the reference voltage Vref3 and outputs a comparison result. The comparator Cmp3 outputs 1 (auxiliary power supply voltage Vcc) when the voltage at the node N4 is higher than the reference voltage Vref3, and outputs 0 (voltage at the node N1) when the voltage at the node N4 is lower than the reference voltage Vref3. . The comparison result (output signal of 1 or 0) of the comparator Cmp3 is input to the gate terminal of the switch element S4. The switch element S4 is turned on when 1 is input from the comparator Cmp3, and is turned off when 0 is input from the comparator Cmp3.

  The resistance elements R11 and R12 each include a first terminal and a second terminal. The first terminal of the resistor element R11 is connected to the drain terminal of the switch element S8, and the second terminal of the resistor element R11 is connected to the node N9. A first terminal of resistance element R12 is connected to node N9, and a second terminal of resistance element R12 is connected to node N3.

  The switch element S8 is an NMOS and includes a drain terminal (first terminal), a source terminal (second terminal), and a gate terminal (control terminal). The source terminal of the switch element S8 is connected to the node N2, the drain terminal of the switch element S8 is connected to the first terminal of the resistor element R11, and the gate terminal of the switch element S8 is connected to the output terminal of the comparator Cmp2. That is, in the example of FIG. 6, the output terminal of the comparator Cmp2 is connected to the gate terminal of the switch element S8 instead of the gate terminal of the switch element S6.

  With such a configuration, according to the power receiving device 2 of FIG. 6, the same effect as that of the power receiving device 2 of FIG. 5 can be obtained.

<Third Embodiment>
A wireless power transmission system 100 according to the third embodiment will be described with reference to FIGS. 7 and 8. In the present embodiment, another example of the control circuit 24 will be described. FIG. 7 is a diagram illustrating a specific example of the power receiving device 2.

  The control circuit 24 in FIG. 7 corresponds to the control circuit 24 in FIG. 5 in which the resistance elements R5 and R6, the switch element S6, and the comparator Cmp2 are removed. In other words, the control circuit 24 of FIG. 7 corresponds to the control circuit 24 of FIG. 2 in which the resistance elements R5 and R6 are removed and the resistance elements R7 and R8 and the comparator Cmp1 are added.

  With the configuration as described above, according to the present embodiment, the threshold voltages Vth1 and Vth2 can be set more accurately than in the first embodiment. Even in the configuration as described above, after detecting the overvoltage, by stopping the power transmission from the power transmission device 1 and discharging the charges accumulated in the capacitive element C3 within the power transmission stop period by R1 to R8, The overvoltage detection circuit 23 can be reset to the initial state before power reception. Thus, the same effect can be obtained even if the resistance elements R5 and R6, the switch element S6, and the comparator Cmp2 are removed from the control circuit 24 of FIG. Since the output voltage V1 and the output voltage V2 become the same potential by discharging the capacitive element C3, detecting the output voltage V1 is equivalent to detecting the output voltage V2. Therefore, the power transmission device 1 may cancel the stop of power transmission after the output voltage V1 becomes less than the threshold voltage Vth1. In other words. The power transmission device 1 may resume power transmission when the time corresponding to the time when the output voltage V1 becomes less than the threshold voltage Vth1 has elapsed since the power transmission was stopped.

  In the example of FIG. 7, the switch element S3 is provided on the high voltage side, but may be provided on the low voltage side. FIG. 8 is a diagram illustrating a modification of the power receiving device 2 of FIG.

  The control circuit 24 in FIG. 8 corresponds to the control circuit 24 in FIG. 6 from which the resistance elements R5, R6, R11, and R12, the switch elements S7 and S8, and the comparator Cmp2 are removed. In other words, the control circuit 24 in FIG. 8 corresponds to the control circuit 24 in FIG. 4 in which the resistance elements R3 to R6 and the switch element S5 are removed and the resistance elements R9 and R10 and the comparator Cmp3 are added.

  With such a configuration, according to the power receiving device 2 of FIG. 8, the same effects as those of the power receiving device 2 of FIG. 7 can be obtained.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. Further, for example, a configuration in which some components are deleted from all the components shown in each embodiment is also conceivable. Furthermore, you may combine suitably the component described in different embodiment.

1: Power transmission device 2: Power reception device 3: Load 11: Resonance circuit 12: Drive circuit 13: Power supply 14: Control circuit 21: Resonance circuit 22: Rectifier circuit 23: Overvoltage detection circuit 24: Control circuit S: Switch element R: Resistance Element C: Capacitance element L: Coil N: Node

Claims (10)

A resonant circuit that wirelessly receives power from the power transmission device;
A rectifier circuit for rectifying the output current of the resonant circuit;
An overvoltage detection circuit connected between the rectifier circuit and a load;
With
The overvoltage detection circuit
A first switch element connected between the rectifier circuit and the load;
A first capacitive element connected in parallel with the first switch element;
A second capacitive element connected in parallel with the load;
A control circuit that turns off the first switch element when an output voltage of the overvoltage detection circuit is equal to or higher than a first threshold voltage;
A power receiving apparatus comprising: After the control circuit turns off the first switch element, the control circuit disables the first switch element until an output voltage of the overvoltage detection circuit becomes lower than a second threshold voltage lower than the first threshold voltage. The power receiving device according to claim 1. The control circuit, when the first switch element can be turned on, turns on the first switch element when an output voltage of the rectifier circuit becomes equal to or higher than a third threshold voltage lower than the first threshold voltage. The power receiving device according to claim 1 or claim 2. The first switch element includes a first terminal connected to the rectifier circuit, a second terminal connected to the load, and a control terminal to which a voltage corresponding to the output voltage of the rectifier circuit is input. The power receiving device according to any one of claims 1 to 3. The power receiving device according to claim 4, wherein the control circuit includes a first voltage dividing circuit that inputs a voltage corresponding to an output voltage of the rectifier circuit to a control terminal of the first switch element. The control circuit includes a first terminal connected to the rectifier circuit, a second terminal connected to the control terminal of the first switch element, and a control terminal to which a voltage corresponding to the output voltage of the rectifier circuit is input. The power receiving device according to claim 4, further comprising: a second switch element including: The control circuit includes:
A second voltage dividing circuit for inputting a voltage corresponding to an output voltage of the rectifier circuit to a control terminal of the second switch element;
A third terminal comprising: a first terminal connected to the second voltage dividing circuit; a second terminal connected to the rectifier circuit; and a control terminal to which a voltage corresponding to the output voltage of the overvoltage detection circuit is input. A switch element;
A power receiving device according to claim 6. The power receiving device according to claim 7, wherein the control circuit includes a third voltage dividing circuit that inputs a voltage corresponding to an output voltage of the overvoltage detection circuit to a control terminal of the third switch element. A wireless power transmission system including a power transmission device and a power reception device,
The power receiving device is:
A resonant circuit that wirelessly receives power from the power transmission device;
A rectifier circuit for rectifying the output current of the resonant circuit;
An overvoltage detection circuit connected between the rectifier circuit and a load;
With
The overvoltage detection circuit
A first switch element connected between the rectifier circuit and the load;
A first capacitive element connected in parallel with the first switch element;
A second capacitive element connected in parallel with the load;
A control circuit that turns off the first switch element when an output voltage of the overvoltage detection circuit is equal to or higher than a first threshold voltage;
A wireless power transmission system comprising: The wireless power transmission system according to claim 10, wherein after the first switch element is turned off, the power transmission device stops power transmission until an output voltage of the rectifier circuit becomes less than the first threshold voltage.

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