Powered Device

Abstract

To provide a power receiving device capable of improving power receiving performance.SOLUTION: A power receiving device 20 is used in radio wave type wireless power supply. The power receiving device 20 includes a power receiving antenna 21, a rectifier circuit 40, and a bias circuit. The power receiving antenna 21 receives a radio wave for power supply. The rectifier circuit 40 includes rectifier diodes 41A and 41B. The rectifier circuit 40 converts the radio wave received by the power receiving antenna 21 into DC power. The bias circuit 50 applies a DC bias to the rectifier diodes 41A and 41B.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a power receiving device used in wireless power supply using radio waves. [Background technology]

[0002] Conventionally, so-called wireless power supply, which supplies power to electronic devices in a non-contact manner, has been proposed (see Patent Document 1). Patent Document 1 describes wireless power supply using a radio wave method. A power transmitting device used in radio wave wireless power feeding has a power transmitting antenna. Radio waves (e.g., microwaves) for power feeding are emitted from this power transmitting antenna. A power receiving device used in radio wave wireless power feeding has a power receiving antenna and a rectifier circuit. The power receiving antenna receives the radio waves emitted from the power transmitting device. The rectifier circuit is a circuit having a rectifier diode. The rectifier circuit converts the radio waves received by the power receiving antenna into DC power. The converted DC power is then used as a power source for an electrical device, or to charge a storage battery built into the electrical device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6725531 Summary of the Invention [Problem to be solved by the invention]

[0004] Radio waves used in wireless power transfer attenuate during spatial propagation. Therefore, even if a power transmitting device emits radio waves of the same strength, the strength of the radio waves received by the receiving antenna of a power receiving device decreases as the transmission distance of power in wireless power transfer (specifically, the propagation distance of the radio waves) increases.

[0005] Due to the circuit structure, the rectifier circuit of the power receiving device cannot convert the radio waves received by the power receiving antenna into DC power when the strength of the radio waves falls below a certain level. The performance limits of the rectifier circuit of the power receiving device also determine the limits of the power receiving performance (more specifically, the range in which power can be received). [Means for solving the problem]

[0006] The power receiving device for solving the above problem is a power receiving device used in radio wave wireless power supply, and includes a power receiving antenna that receives radio waves for power supply, a rectifier circuit that has a rectifier diode and converts the radio waves received by the power receiving antenna into DC power, and a bias circuit that applies a DC bias to the rectifier diode.

[0007] Normally, when using a rectifier circuit having a rectifier diode, the forward voltage Vf of the rectifier diode makes it impossible to convert the radio waves received by the receiving antenna into DC power in areas where the strength of the radio waves is low (low-intensity area).

[0008] According to the above configuration, when the power receiving device receives radio waves, a DC bias can be applied to the rectifier diode. This allows a DC voltage (more specifically, a forward bias voltage) equivalent to the forward voltage Vf to be applied across the rectifier diode. This makes it possible to suppress the influence of the forward voltage Vf on the power conversion by the rectifier circuit. This allows a current to flow through the rectifier diode even in the low intensity region, so that the rectifier circuit can convert the radio waves into DC power. Therefore, the range of positions where DC power can be obtained by the power conversion by the rectifier circuit, that is, the range of positions where power can be received by the power receiving device, can be widened to the extent that power conversion by the rectifier circuit is possible in the low intensity region. Therefore, according to the above configuration, the power receiving performance of the power receiving device can be improved.

[0009] In the above-mentioned power receiving device, it is preferable to include a judgment unit that judges whether the radio waves are being received by the power receiving antenna, and a switching unit that switches the mode of application of the DC bias, such that when the judgment unit judges that the situation is met, the DC bias is applied, and when the judgment unit does not judge that the situation is met, the DC bias is not applied.

[0010] According to the above configuration, when radio waves are received by the power receiving antenna, i.e., when power conversion is performed by the rectifier circuit, a DC bias is applied to the rectifier diode, thereby improving the power receiving performance of the power receiving device. On the other hand, when radio waves are not received by the power receiving antenna, i.e., when power conversion is not performed by the rectifier circuit, a DC bias is not applied to the rectifier diode, thereby reducing unnecessary power consumption.

[0011] In the above power receiving device, the bias circuit includes a voltage divider resistor circuit having a first resistor and a second resistor, the first resistor is a resistor that connects a power supply of the rectifier circuit and an anode of the rectifier diode, and the second resistor is a resistor that connects a ground of the rectifier circuit and an anode of the rectifier diode.

[0012] According to the above configuration, a predetermined DC voltage can be generated by utilizing the power supply of the rectifier circuit and the voltage dividing resistor circuit, and the voltage can be applied to the rectifier diode as a DC bias. In the power receiving device, at least one of the first resistor and the second resistor is preferably a thermistor.

[0013] The forward voltage Vf of a rectifier diode changes according to the temperature of the rectifier diode, and therefore the DC bias required to improve the power receiving performance also changes according to the temperature of the rectifier diode.

[0014] According to the above configuration, since at least some of the resistors constituting the voltage dividing resistor circuit are constituted by thermistors, the DC bias generated by the voltage dividing resistor circuit can be changed according to the temperature of the rectifier diode (more specifically, the thermistor). Therefore, a DC bias suitable for improving the power receiving performance can be applied to the rectifier diode in a form according to the temperature of the rectifier diode.

[0015] In the above power receiving device, it is preferable that the bias circuit has a detection unit that detects a temperature index value of the rectifier diode, and a control unit that sets the DC bias based on the temperature index value detected by the detection unit.

[0016] According to the above configuration, a DC bias voltage suitable for improving the power receiving performance can be applied to the rectifier diode in a manner according to the temperature of the rectifier diode. Effect of the Invention

[0017] According to the present invention, it is possible to improve the power receiving performance of a power receiving device. [Brief description of the drawings]

[0018] [Figure 1] 2 is a schematic diagram illustrating a relationship between a power receiving device and a power transmitting device according to an embodiment. [Diagram 2] 2 is a block diagram showing a schematic configuration of a power receiving device and a power transmitting device. FIG. [Diagram 3] 4 is a circuit diagram showing an electric circuit structure of a power receiving conversion unit of the power receiving device. FIG. [Figure 4] FIG. 4 is an explanatory diagram for explaining the operation of the embodiment. [Diagram 5] FIG. 11 is a circuit diagram showing an electric circuit structure of a power receiving and converting unit according to a modified example. [Figure 6] FIG. 11 is a circuit diagram showing an electric circuit structure of a power receiving and converting unit according to a modified example. [Figure 7] FIG. 11 is a circuit diagram showing an electric circuit structure of a power receiving and converting unit according to a modified example. [Figure 8]FIG. 11 is a circuit diagram showing an electric circuit structure of a power receiving and converting unit according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An embodiment of the power receiving device will be described below. 1, a power receiving device 20 of this embodiment is charged by power transmitted from a power transmitting device 10. The power transmitting device 10 supplies power to the power receiving device 20 by wireless power supply using a radio wave method. More specifically, radio waves for power supply (microwaves in this embodiment) are transmitted and received between a power transmitting antenna 11 of the power transmitting device 10 and a power receiving antenna 21 of the power receiving device 20.

[0020] The power receiving device 20 transmits a beacon signal including location information to the power transmitting device 10 at a predetermined time interval. When the power receiving device 20 is within its power transmitting range AR, the power transmitting device 10 receives the beacon signal from the power receiving device 20. When the power transmitting device 10 receives the beacon signal from the power receiving device 20, the power transmitting device 10 identifies the location of the power receiving device 20 based on the beacon signal. The power transmitting device 10 wirelessly supplies power to the power receiving device 20 by transmitting radio waves (power transmission signals) toward the identified location. This allows efficient power supply to the power receiving device 20 depending on the orientation of the power receiving device 20 relative to the power transmitting device 10, the distance between the power transmitting device 10 and the power receiving device 20, etc.

[0021] <Power transmission device 10> As shown in FIG. 2, the power transmitting device 10 includes a power transmitting antenna 11 and a control unit 12. The power transmitting antenna 11 is used for various communications with the power receiving device 20. The power transmitting antenna 11 is used for transmitting a power transmission signal and receiving a beacon signal.

[0022] The control unit 12 may be, for example, a microcontroller unit. The control unit 12 includes a processor and a storage unit. The storage unit includes a ROM (Read Only Memory) and a RAM (Random Access Memory). The control unit 12 executes various controls related to communication with the power receiving device 20. The control unit 12 controls the power transmitting antenna 11 to receive a beacon signal transmitted by the power receiving device 20. The control unit 12 converts power supplied from a power supply device (not shown) into a power transmission signal, and transmits the power transmission signal using the power transmitting antenna 11.

[0023] <Power receiving device 20> The power receiving device 20 of this embodiment includes the power receiving antenna 21, a power receiving conversion unit 22, a storage battery 23, an output unit 24, and a control unit 25.

[0024] The power receiving antenna 21 and the power receiving conversion section 22 constitute a section that receives power transmitted from the power transmitting device 10 by wireless power feeding using a radio wave method. <Receiving antenna 21> The power receiving antenna 21 is used for various communications with the power transmitting device 10. More specifically, the power receiving antenna 21 is used for receiving a power transmission signal transmitted from the power transmitting device 10 and for transmitting a beacon signal to the power transmitting device 10.

[0025] <Power receiving conversion unit 22> The power receiving conversion unit 22 constitutes a part that converts the power transmission signal received by the power receiving antenna 21 into DC power. In the power receiving device 20 of the present embodiment, the DC power converted by the power receiving conversion unit 22 is supplied to the storage battery 23, whereby the storage battery 23 is charged.

[0026] As shown in FIG. 3, the power receiving conversion unit 22 includes a balun transformer 30, a rectifier circuit 40, and a bias circuit 50. <Balun transformer 30> The balun transformer 30 is a transformer for converting a power transmission signal (unbalanced signal) received by the power receiving antenna 21 into a balanced signal. The power receiving antenna 21 is connected to the input of the balun transformer 30. The rectifier circuit 40 is connected to the output of the balun transformer 30. The balun transformer 30 realizes impedance matching between the power receiving antenna 21 and the rectifier circuit 40.

[0027] <Rectifier circuit 40> The rectifier circuit 40 is a circuit for converting the radio waves received by the power receiving antenna 21 (more specifically, the output of the balun transformer 30) into DC power. As the rectifier circuit 40, a single-phase full-wave rectifier circuit is adopted.

[0028] The rectifier circuit 40 includes two rectifier diodes 41A and 41B, two capacitors 43A and 43B, and a smoothing capacitor . The first capacitor 43A and the first rectifier diode 41A are provided to connect the first output tap 31 of the balun transformer 30 and the positive output part 45 of the rectifier circuit 40. The first capacitor 43A and the first rectifier diode 41A are connected in series and arranged in the order of the first capacitor 43A and the first rectifier diode 41A from the first output tap 31 side.

[0029] The second capacitor 43B and the second rectifier diode 41B are provided to connect the second output tap 32 and the positive output section 45 of the balun transformer 30. The second capacitor 43B and the second rectifier diode 41B are arranged in series connection in the order of the second capacitor 43B and the second rectifier diode 41B from the second output tap 32 side.

[0030] The smoothing capacitor 44 is provided in a manner that connects the positive output portion 45 (more specifically, the cathodes of the rectifier diodes 41A and 41B) and the ground output portion 46 of the rectifier circuit 40. The ground output portion 46 is connected to the center tap 33 of the balun transformer 30.

[0031] The output terminals (positive output section 45 and ground output section 46) of the rectifier circuit 40 are connected to the storage battery 23 via a charging circuit 231. The charging circuit 231 is a circuit that adjusts the power (more specifically, the charging current and the charging voltage) supplied to the storage battery 23. In this embodiment, the DC power converted by the rectifier circuit 40 is supplied to the storage battery 23 via the charging circuit 231, thereby charging the storage battery 23.

[0032] <Bias circuit 50> The bias circuit 50 is a circuit for applying a DC bias to the rectifier diodes 41A and 41B.

[0033] The bias circuit 50 includes a voltage dividing resistor circuit having a first resistor 51A and a second resistor 52A. The first resistor 51A and the second resistor 52A are fixed resistors. The first resistor 51A is provided in a manner that connects the power supply 47 of the rectifier circuit 40 and the anode 411A of the first rectifier diode 41A. The second resistor 52A is provided in a manner that connects the ground of the rectifier circuit 40 (specifically, the ground output section 46) and the anode 411A of the first rectifier diode 41A.

[0034] In this embodiment, the power supply voltage is divided by this voltage dividing resistor circuit (first resistor 51A and second resistor 52A). Then, this divided voltage is applied to the anode 411A of the first rectifier diode 41A as a DC bias voltage V1. In this embodiment, the relationship between the power supply voltage and the resistance value of the first resistor 51A and the resistance value of the second resistor 52A is determined so that the DC bias voltage V1 and the forward voltage Vf of the first rectifier diode 41A are equal to each other.

[0035] The bias circuit 50 also includes a voltage dividing resistor circuit having a first resistor 51B and a second resistor 52B. The first resistor 51B and the second resistor 52B are fixed resistors. The first resistor 51B is provided in a manner that connects the power supply 47 of the rectifier circuit 40 and the anode 411B of the second rectifier diode 41B. The second resistor 52B is provided in a manner that connects the ground of the rectifier circuit 40 (specifically, the ground output section 46) and the anode 411B of the second rectifier diode 41B.

[0036] In this embodiment, the power supply voltage is divided by this voltage dividing resistor circuit (first resistor 51B and second resistor 52B). Then, this divided voltage is applied to the anode 411B of the second rectifier diode 41B as a DC bias voltage V2. In this embodiment, the relationship between the power supply voltage and the resistance value of the first resistor 51B and the resistance value of the second resistor 52B is determined so that the DC bias voltage V2 and the forward voltage Vf of the second rectifier diode 41B are equal to each other.

[0037] <Selector switch 53> The bias circuit 50 has a changeover switch 53. Through this changeover switch 53, the power supply 47 and each voltage dividing resistance circuit (specifically, first resistors 51A and 51B) are connected.

[0038] When the changeover switch 53 is turned on, the power source 47 and each voltage-dividing resistance circuit are connected. At this time, the power source voltage is applied to each voltage-dividing resistance circuit, so that the DC bias voltages V1 and V2 are applied to each rectifier diode 41A and 41B. On the other hand, when the changeover switch 53 is turned off, the connection between the power source 47 and each voltage-dividing resistance circuit is cut off. At this time, the power source voltage is not applied to each voltage-dividing resistance circuit, so that the DC bias voltages V1 and V2 are not applied to each rectifier diode 41A and 41B. In this embodiment, the changeover switch 53 is operated to control the operation of the changeover switch 53, so that the rectifier diodes 41A and 41B can be switched between a state in which a DC bias is applied (on state) and a state in which a DC bias is not applied (off state).

[0039] <Output section 24> 2, the output unit 24 constitutes a part that outputs the power stored in the storage battery 23 to an electric device 26 to be charged. This electric device 26 is assumed to be a smartphone, a tablet terminal, a wireless earphone, or the like.

[0040] The output unit 24 has a DC-DC conversion circuit 241 and a connection unit 242. The DC-DC conversion circuit 241 is connected to the storage battery 23. DC power stored in the storage battery 23 is input to the DC-DC conversion circuit 241. The DC-DC conversion circuit 241 boosts the voltage of the DC power input from the storage battery 23 to a voltage suitable for output from the output unit 24. The DC-DC conversion circuit 241 is connected to the connection unit 242. The connection unit 242 is a connection cable for electrically connecting the DC-DC conversion circuit 241 and the electric device 26.

[0041] When the electric device 26 is charged by the power receiving device 20, the electric device 26 is connected to the connection unit 242. The DC-DC conversion circuit 241 boosts the DC power input from the storage battery 23, and outputs the boosted DC power to the electric device 26 via the connection unit 242. The electric device 26 (more specifically, the built-in storage battery) is charged by the DC power thus output.

[0042] <Control unit 25> The control unit 25 may be, for example, a microcontroller unit. The control unit 25 includes a processor and a storage unit. The storage unit includes a ROM and a RAM. The control unit 25 executes various controls related to the operation control of the power receiving device 20. The control unit 25 controls the power receiving antenna 21 to transmit a beacon signal to the power transmitting device 10. The control unit 25 controls the power receiving antenna 21 to receive a power transmission signal transmitted from the power transmitting device 10. The control unit 25 executes operation control of the change-over switch 53. The control unit 25 executes operation control of the output unit 24.

[0043] The control unit 25 has a determination unit 251 and a switching unit 252 as its functional units. <Judgment part 251> The determination unit 251 determines whether or not it is a situation where radio waves can be received by the power receiving antenna 21 (reception situation). Specifically, when the operation mode of the power receiving antenna 21 is a reception mode for receiving the radio waves, the determination unit 251 determines that it is in the above-mentioned reception situation. On the other hand, when the operation mode of the power receiving antenna 21 is an operation mode other than the reception mode, such as a transmission mode for transmitting the beacon signal, the determination unit 251 does not determine that it is in the above-mentioned reception situation, but determines that it is not in the above-mentioned reception situation. The result of the determination by the determination unit 251 is stored in the memory unit of the control unit 25.

[0044] <Switching unit 252> The switching unit 252 switches the mode of applying the DC bias to each of the rectifier diodes 41A, 41B depending on the result of the judgment by the judgment unit 251. Specifically, when the judgment unit 251 judges that the above-mentioned reception state exists, the switching unit 252 turns on the changeover switch 53. As a result, the DC bias voltages V1, V2 are applied to each of the rectifier diodes 41A, 41B of the rectifier circuit 40. On the other hand, when the judgment unit 251 judges that the above-mentioned reception state does not exist, the switching unit 252 turns off the changeover switch 53. As a result, the DC bias voltages V1, V2 are not applied to each of the rectifier diodes 41A, 41B of the rectifier circuit 40.

[0045] <effect> The operation of the power receiving device 20 of this embodiment will be described below. 1, the power receiving device 20 controls the power receiving antenna 21 to transmit a beacon signal. The power transmitting device 10 controls the power transmitting antenna 11 to receive the beacon signal transmitted by the power receiving device 20. Then, upon receiving the beacon signal, the power transmitting device 10 controls the power transmitting antenna 11 to transmit a power transmission signal to the power receiving device 20.

[0046] When the power transmitting device 10 is in a state in which it transmits a power transmission signal, the power receiving device 20 switches the operation mode of the power receiving antenna 21 to the power receiving mode. When the operation mode of the power receiving antenna 21 is in the power receiving mode, the changeover switch 53 of the bias circuit 50 (FIG. 3) is turned on, so that the DC bias voltages V1, V2 are applied to the rectifier diodes 41A, 41B of the rectifier circuit 40.

[0047] The power receiving device 20 receives the power transmission signal by controlling the operation of the power receiving antenna 21 while applying DC bias voltages V1, V2 to the rectifier diodes 41A, 41B. Then, the power transmission signal is converted into DC power by the power receiving conversion unit 22 of the power receiving device 20, and the DC power is supplied to the storage battery 23 via the charging circuit 231. The storage battery 23 is charged by the DC power supplied in this manner.

[0048] When the electric device 26 is connected to the connection unit 242 of the power receiving device 20, the power receiving device 20 transforms the DC power stored in the storage battery 23 and outputs the transformed DC voltage to the electric device 26. The electric device 26 (more specifically, the built-in storage battery) is charged by the DC power thus output.

[0049] <Effects> According to this embodiment, the following advantageous effects can be obtained. (1) The power receiving device 20 is used in radio wave wireless power supply. The power receiving device 20 includes a power receiving antenna 21, a rectifier circuit 40 having rectifier diodes 41A and 41B, and a bias circuit 50 that applies DC bias voltages V1 and V2 to the rectifier diodes 41A and 41B.

[0050] Normally, when using a rectifier circuit having a rectifier diode, the forward voltage Vf of the rectifier diode makes it impossible to convert the radio waves received by the receiving antenna into DC power in areas where the strength of the radio waves is low (low-intensity area).

[0051] According to this embodiment, when the power receiving device 20 receives radio waves, the DC bias voltages V1 and V2 can be applied to the rectifier diodes 41A and 41B. This makes it possible to apply a DC voltage equivalent to the forward voltage Vf (more specifically, a forward bias voltage) to both ends of the rectifier diodes 41A and 41B. This makes it possible to suppress the effect of the forward voltage Vf on the power conversion by the rectifier circuit 40.

[0052] As a result, even in the low intensity region, a current flows through the rectifier diodes 41A and 41B. Therefore, as shown in FIG. 4, even in the low intensity region, the rectifier circuit 40 can convert radio waves into DC power. Note that FIG. 4 shows an example of a power conversion mode by the rectifier circuit 40 that does not have a smoothing capacitor 44 in order to facilitate understanding of power conversion in the low intensity region. The solid line in FIG. 4 shows an example of a power conversion mode by the rectifier circuit 40 of this embodiment. The two-dot chain line in FIG. 4 shows an example of a power conversion mode by a rectifier circuit of a comparative example that does not have a bias circuit 50.

[0053] According to the present embodiment, since power conversion by the rectifier circuit 40 is possible in the low intensity region, DC power can be obtained by power conversion by the rectifier circuit 40 even at a position far from the power transmitting device 10. Therefore, it is possible to widen the range of positions where DC power can be obtained by power conversion by the rectifier circuit 40, that is, the range of positions where power can be received by the power receiving device 20. According to the present embodiment, it is possible to improve the power receiving performance of the power receiving device 20 in this way.

[0054] (2) The control unit 25 of the power receiving device 20 has, as its functional units, a determination unit 251 and a switching unit 252. The determination unit 251 determines whether or not a reception state exists in which radio waves can be received by the power receiving antenna 21. When the determination unit 251 determines that a reception state exists, the switching unit 252 brings the rectifier diodes 41A, 41B into a state in which the DC bias voltages V1, V2 are applied. When the determination unit 251 determines that a reception state does not exist, the switching unit 252 brings the rectifier diodes 41A, 41B into a state in which the DC bias voltages V1, V2 are not applied.

[0055] According to this embodiment, when radio waves are received by the power receiving antenna 21, that is, when power conversion is performed by the rectifier circuit 40, the DC bias voltages V1 and V2 can be applied to the rectifier diodes 41A and 41B. This can improve the power receiving performance of the power receiving device 20. Moreover, when radio waves are not received by the power receiving antenna 21, that is, when power conversion is not performed by the rectifier circuit 40, unnecessary power consumption can be suppressed by not applying the DC bias voltages V1 and V2 to the rectifier diodes 41A and 41B.

[0056] (3) The bias circuit 50 has a voltage dividing resistor circuit having a first resistor 51A and a second resistor 52A. The first resistor 51A is provided in a manner to connect the power supply 47 of the rectifier circuit 40 and the anode 411A of the first rectifier diode 41A. The second resistor 52A is provided in a manner to connect the ground output section 46 of the rectifier circuit 40 and the anode 411A of the first rectifier diode 41A. The bias circuit 50 also has a voltage dividing resistor circuit having a first resistor 51B and a second resistor 52B. The first resistor 51B is provided in a manner to connect the power supply 47 and the anode 411B of the second rectifier diode 41B. The second resistor 52B is provided in a manner to connect the ground output section 46 and the anode 411B of the second rectifier diode 41B. According to this embodiment, a predetermined DC voltage is generated by utilizing the power supply 47 of the rectifier circuit 40 and each voltage dividing resistor circuit, and this voltage can be applied to the rectifier diodes 41A and 41B as the DC bias voltages V1 and V2.

[0057] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0058] At least one of the first resistors 51A, 51B and the second resistors 52A, 52B may be configured by a thermistor. Here, the forward voltage Vf of the rectifier diodes 41A, 41B changes depending on the temperature of the rectifier diodes 41A, 41B. Therefore, it can be said that the DC bias required to improve the power receiving performance also changes depending on the temperature of the rectifier diodes 41A, 41B.

[0059] According to the above configuration, since some of the resistors constituting the voltage dividing resistor circuit are constituted by thermistors, the DC bias voltage generated by the voltage dividing resistor circuit can be changed according to the temperature of the rectifier diodes 41A, 41B (specifically, thermistors). This makes it possible to apply to the rectifier diodes 41A, 41B a DC bias voltage suitable for improving the power receiving performance in a form according to the temperature (specifically, the temperature characteristic of the forward voltage Vf) of the rectifier diodes 41A, 41B. In the above configuration, it is preferable to employ a thermistor having a temperature characteristic that satisfies the following [Condition]. [Condition] Even if the temperature of the rectifier diodes 41A, 41B changes, the forward voltage Vf of the rectifier diodes 41A, 41B and the voltage divided by the voltage dividing resistor circuit (i.e., the DC bias voltage) become equal.

[0060] An example of the above configuration is shown in Fig. 5. In Fig. 5, the same components as those of the power receiving conversion unit 22 of the above embodiment shown in Fig. 3 are denoted by the same reference numerals (or corresponding reference numerals), and detailed description of these components will be omitted below.

[0061] 5, the first resistors 61A and 61B of the bias circuit 60 are constituted by PTC thermistors, and the second resistors 52A and 52B of the bias circuit 60 are constituted by fixed resistors.

[0062] Here, the forward voltage Vf of the rectifier diodes 41A, 41B decreases as the temperature of the rectifier diodes 41A, 41B increases. In contrast, in this example, as the temperature of the first resistors 61A, 61B (PTC thermistors) increases, the resistance of the first resistors 61A, 61B increases, and the voltage (DC bias voltage) divided by the voltage-dividing resistor circuit decreases. Therefore, according to this example, a DC bias voltage that matches the temperature of the rectifier diodes 41A, 41B (more specifically, the temperature characteristic of the forward voltage Vf) can be applied to the rectifier diodes 41A, 41B.

[0063] Fig. 6 shows another example of the configuration. In Fig. 6, the same components as those of the power receiving conversion unit 22 of the embodiment shown in Fig. 3 are denoted by the same reference numerals (or corresponding reference numerals), and detailed description of these components will be omitted below.

[0064] 6, the first resistors 51A and 51B of the bias circuit 70 are configured with fixed resistors, and the second resistors 72A and 72B of the bias circuit 70 are configured with NTC thermistors.

[0065] As described above, the forward voltage Vf of the rectifier diodes 41A, 41B decreases as the temperature of the rectifier diodes 41A, 41B increases. In contrast, in this example, as the temperature of the second resistors 72A, 72B (NTC thermistors) increases, the resistance values ​​of the second resistors 72A, 72B decrease, and the voltage (DC bias voltage) divided by the voltage-dividing resistor circuit decreases. Therefore, according to this example, a DC bias voltage that matches the temperature of the rectifier diodes 41A, 41B (more specifically, the temperature characteristics of the forward voltage Vf) can be applied to the rectifier diodes 41A, 41B.

[0066] 7, a matching circuit 80 may be provided between the balun transformer 30 and the rectifier circuit 40. By providing the matching circuit 80, impedance matching with higher power conversion efficiency may be achieved between the power receiving antenna 21 and the rectifier circuit 40.

[0067] A detection unit for detecting a temperature index value TD of the rectifier diodes 41A, 41B may be provided. Furthermore, a process for setting a DC bias based on the temperature index value TD may be executed by the control unit 25. In this process, the DC bias voltage may be set so that the DC bias voltage decreases as the temperature index value TD indicates a higher temperature. According to the above configuration, a DC bias voltage suitable for improving the power receiving performance can be applied to the rectifier diodes 41A, 41B in accordance with the temperature (more specifically, the temperature characteristics of the forward voltage Vf) of the rectifier diodes 41A, 41B.

[0068] Fig. 8 shows an example of the above configuration. In Fig. 8, the same components as those of the power receiving conversion unit 22 of the above embodiment shown in Fig. 3 are denoted by the same reference numerals (or corresponding reference numerals), and detailed description of these components will be omitted below.

[0069] As shown in Fig. 8, the control unit 25 has a voltage dividing resistor circuit 90 in which an NTC thermistor 91 and a fixed resistor 92 are connected in series. In this voltage dividing resistor circuit 90, the NTC thermistor 91 constitutes a resistor on the ground side, and the fixed resistor 92 constitutes a resistor on the power supply side. The voltage value divided by this voltage dividing resistor circuit 90 is detected as a temperature index value TD of the rectifier diodes 41A, 41B. In this example, the temperature index value TD is a value according to the temperature of the control unit 25, more specifically, a value indicating a lower voltage as the temperature of the control unit 25 is higher. In this example, the voltage dividing resistor circuit 90 corresponds to the detection unit.

[0070] The control unit 25 is connected to each voltage dividing resistor circuit (specifically, the first resistors 51A, 51B). In this example, the voltage applied to the voltage dividing resistor circuit can be adjusted by the control unit 25. In this example, the control unit 25 sets the voltage applied to the voltage dividing resistor circuit to a lower voltage as the temperature index value TD indicates a lower voltage. This makes it possible to set the DC bias voltage so that the DC bias voltage becomes lower as the temperature index value TD indicates a higher temperature.

[0071] In the above configuration, a voltage dividing resistor circuit in which a fixed resistor and a PTC thermistor are connected in series may be provided instead of the voltage dividing resistor circuit 90. For example, this voltage dividing resistor circuit may be a circuit in which a fixed resistor constitutes the resistor on the ground side and a PTC thermistor constitutes the resistor on the power supply side. In this configuration, the voltage dividing resistor circuit corresponds to the detection unit.

[0072] In the above configuration, a temperature sensor for detecting the temperature index value TD of the rectifier diodes 41A, 41B may be provided instead of the voltage dividing resistor circuit 90. This temperature sensor may be provided in any position, such as in the control unit 25 or in the vicinity of the rectifier diodes 41A, 41B.

[0073] The changeover switch 53 of the bias circuit 50 may be omitted. In other words, a DC bias voltage may be constantly applied to the rectifier diodes 41A and 41B. The power receiving device according to the above embodiment can be applied to any power receiving device as long as it is equipped with a rectifier circuit having a rectifier diode. Examples of the rectifier circuit include a full-wave rectifier circuit, a half-wave rectifier circuit having only one rectifier diode, and a full-wave rectifier circuit having four rectifier diodes. [Explanation of symbols]

[0074] 10...Power transmission device 11...Transmission antenna 12...Control section 20...Power receiving device 21…Receiving antenna 22...Power receiving converter 23…Battery 24...Output section 231…Charging circuit 241...DC-DC conversion circuit 242…Connection 25...Control section 251...judgment department 252…Switching section 26...Electrical equipment 30…Balun transformer 31…1st output tap 32…Second output tap 33…Center tap 40... Rectifier circuit 41A…First rectifier diode 411A…Anode 41B…Second rectifier diode 411B…Anode 43A…First capacitor 43B…Second capacitor 44…Smoothing capacitor 45…Positive output section 46…Ground output section 47…Power supply 50,60,70...Bias circuit 51A, 52A, 61A, 61B…1st resistor 52A, 52B, 72A, 72B…Second resistor 53...Selector switch 80…matching circuit 90…Voltage divider circuit 91...NTC thermistor 92...Fixed resistor

Claims

1. A power receiving device used in wireless power supply using a radio wave method, A receiving antenna for receiving radio waves for power supply; a rectifier circuit having a rectifier diode and converting the radio waves received by the power receiving antenna into DC power; a bias circuit that applies a DC bias to the rectifier diode; the bias circuit includes a voltage divider circuit having a first resistor and a second resistor; the first resistor is a resistor that connects a power supply of the rectifier circuit and an anode of the rectifier diode, the second resistor is a resistor that connects a ground of the rectifier circuit and an anode of the rectifier diode, At least one of the first resistor and the second resistor is a thermistor.

2. A power receiving device used in radio wave wireless power supply, A receiving antenna for receiving radio waves for power supply; a rectifier circuit having a rectifier diode and converting the radio waves received by the power receiving antenna into DC power; a bias circuit that applies a DC bias to the rectifier diode; The bias circuit is a power receiving device having a detection unit that detects a temperature index value of the rectifier diode, and a control unit that sets the DC bias based on the temperature index value detected by the detection unit.

3. A determination unit that determines whether the radio waves can be received by the power receiving antenna; The power receiving device according to claim 1 or 2, further comprising a switching unit that switches the mode of application of the DC bias such that the DC bias is applied when the judgment unit judges that the situation exists, and the DC bias is not applied when the judgment unit does not judge that the situation exists.

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