Wireless Power Receiver

Abstract

A wireless power reception device (10) comprises a power reception interruption circuit and an impedance adjustment circuit. The power reception interruption circuit causes a rectification circuit to execute a rectification operation if a smoothed voltage is smaller than a first voltage. The power reception interruption circuit causes the rectification circuit to stop the rectification operation if the smoothed voltage is equal to or greater than the first voltage, and protects a power reception DC circuit from an excessive voltage by causing the rectification circuit to stop the rectification operation. The impedance adjustment circuit suppresses increase in voltage at both ends of a power reception coil, and protects a power reception AC circuit from an excessive voltage when the power reception interruption circuit causes execution of the rectification operation and also when same causes stoppage of the rectification operation. The impedance adjustment circuit protects both the power reception AC circuit and the power reception DC circuit irrespective of whether the power reception interruption circuit causes execution or stoppage of the rectification operation.

Description

[Technical Field]

[0001] The present invention relates to a wireless power receiving device that receives power using electromagnetic coupling or electromagnetic resonance coupling. [Background technology]

[0002] Conventionally, various techniques have been devised for controlling the receiving voltage of a power receiving device in a wireless power supply system.

[0003] In Patent Document 1, switching control is performed by a synchronous rectification controller to adjust the rectified voltage output to the load. In Patent Document 2, surplus received power is processed using a power storage element. In Patent Document 3, a resonance suppression coil is used to suppress an excessive rise in the output voltage of the power receiving device.

[0004] In Patent Document 4, an excessive rise in voltage occurring in the receiving resonant circuit is suppressed by using a sub-coil on the receiving side. In Patent Document 5, the receiving voltage is adjusted by a Q-value matching circuit that properly matches the Q-value of the receiving coil. In Patent Document 6, overvoltage protection is achieved by an overvoltage protection circuit that includes a switch connected in series to a capacitor.

[0005] In Patent Document 7, a resonant modulation circuit is used to protect against overcurrent and overvoltage. In Patent Document 8, a receiving-side filter equipped with a reactor is controlled to protect the receiving-side resonant circuit. In Patent Document 9, a receiving-side cutoff circuit is used to protect against overvoltage. In Patent Document 10, a clamp circuit is provided after the rectifier circuit, and the clamp circuit controls the voltage. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-178442 [Patent Document 2] Japanese Patent Application Publication No. 2020-150699 [Patent Document 3] Japanese Patent Publication No. 2020-120434 [Patent Document 4] Japanese Patent Publication No. 2020-072604 [Patent Document 5] Japanese Patent Application Publication No. 2019-071705 [Patent Document 6] Patent No. 6890379 specification [Patent Document 7] Patent No. 6427983 specification [Patent Document 8] Patent No. 6252334 specification [Patent Document 9] Patent No. 6379660 specification [Patent Document 10] Patent No. 5998905 specification Summary of the Invention [Problem to be solved by the invention]

[0007] However, with the conventional configuration described above, it was difficult to continue operating properly even when the strength of the external magnetic field coupled to the receiving coil changed, and to protect the AC circuit and DC circuit when the external magnetic field became excessively strong.

[0008] Therefore, an object of the present invention is to provide a wireless power receiving device that can suppress the influence of changes in an external magnetic field, continue to operate properly, and protect a power receiving AC circuit and a power receiving DC circuit. [Means for solving the problem]

[0009] A wireless power receiving device according to one aspect of the present invention includes a power receiving circuit, a load circuit, and a power receiving coil. The load circuit is electrically connected to the power receiving circuit. The power receiving coil is electrically connected to the power receiving circuit.

[0010] The power receiving circuit includes an impedance adjustment circuit, a rectifier circuit, a smoothing circuit, and a power receiving cutoff circuit. The impedance adjustment circuit adjusts the input impedance seen from the power receiving coil toward the load circuit. The rectifier circuit rectifies the AC current flowing through the power receiving coil. The smoothing circuit is electrically connected to the rectifier circuit. The power receiving cutoff circuit switches between performing and stopping the rectification operation of the rectifier circuit using the result of comparing the smoothed voltage of the smoothing circuit with a predetermined first voltage.

[0011] The receiving coil, impedance adjustment circuit, and rectifier circuit constitute a receiving AC circuit, while the smoothing circuit and load circuit constitute a receiving DC circuit.

[0012] The first voltage is set based on the magnitude of an external magnetic field acting on the receiving coil and the magnitude of power of the load circuit. The impedance adjustment circuit suppresses an increase in the output voltage of the receiving coil.

[0013] The power receiving cutoff circuit performs the rectification operation of the rectifier circuit when the smoothed voltage is less than the first voltage, and stops the rectification operation of the rectifier circuit when the smoothed voltage is equal to or greater than the first voltage, thereby protecting the power receiving AC circuit and the power receiving cutoff circuit from overvoltage by the impedance adjustment circuit and the power receiving cutoff circuit.

[0014] In this configuration, if an external magnetic field causes a voltage equal to or greater than the first voltage to be applied to the power receiving DC circuit, the power receiving cutoff circuit protects the power receiving DC circuit from overvoltage. In addition, the impedance adjustment circuit suppresses the voltage across the power receiving coil, so the power receiving AC circuit and power receiving DC circuit are protected regardless of the operating state of the power receiving cutoff circuit. [Effects of the Invention]

[0015] According to this invention, the power receiving cutoff circuit can protect the power receiving DC circuit from overvoltage, and the impedance adjustment circuit can protect the power receiving AC circuit and the power receiving DC circuit regardless of the operating state of the power receiving cutoff circuit. [Brief explanation of the drawings]

[0016] [Figure 1]FIG. 1 is a circuit diagram showing the configuration of a wireless power receiving device according to the first embodiment. [Figure 2] FIG. 2 is a functional block diagram illustrating an example of a power transmitting device according to this embodiment. [Figure 3] Figure 3(A) is a diagram showing an example of variation in external magnetic field strength in the configuration of the present application, and Figure 3(B) is a diagram showing an example of variation in external magnetic field strength in a comparison configuration (a configuration that does not have the impedance adjustment circuit of the configuration of the present application). [Figure 4] FIG. 4 is a circuit diagram showing an example of the configuration of a wireless power receiving device according to the second embodiment. [Figure 5] FIG. 5 is a circuit diagram showing an example of the configuration of a wireless power receiving device according to the third embodiment. [Figure 6] FIG. 6 is a circuit diagram showing an example of the configuration of a wireless power receiving device according to the fourth embodiment. [Figure 7] FIG. 7 is a circuit diagram showing an example of the configuration of a wireless power receiving device according to the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] [First embodiment] A wireless power receiving device according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a circuit diagram showing an example of the configuration of the wireless power receiving device according to the first embodiment.

[0018] As shown in FIG. 1, the wireless power receiving device 10 includes a receiving coil 20P, a communication antenna 20T, a capacitor C31, a capacitor C32, a resistive element R41, a diode D51, a diode D52, a diode D53, a diode D54, a switch element S62, a switch element S64, a capacitor C70, a capacitor C79, an LDO 21, a voltage detection circuit 22, a short-range wireless communication IC 23, and a load circuit 24.

[0019] (receiving coil, receiving resonance circuit, impedance adjustment circuit) The power receiving coil 20P is, for example, a loop coil. A capacitor C31 is connected to both ends of the power receiving coil 20P. One terminal of a capacitor C32 is connected to a first terminal of the power receiving coil 20P. The other terminal of the capacitor C32 is connected to the node between the diodes D53 and D54. A second terminal of the power receiving coil 20P is connected to the node between the diodes D51 and D52.

[0020] The power receiving coil 20P, capacitor C31, and capacitor C32 form a power receiving resonant circuit. The resonant frequency of the power receiving resonant circuit is approximately the same as the resonant frequency of the power transmitting resonant circuit of the power transmitting device 90, which will be described later, and this resonant frequency becomes the frequency of the external magnetic field. Capacitor C31 corresponds to the "first resonant capacitor" of the present invention, and capacitor C32 corresponds to the "second resonant capacitor" of the present invention.

[0021] The resistive element R41 is connected to both ends of the receiving coil 20P. One end of the resistive element R41 is connected to a position closer to the first end of the receiving coil 20P than the capacitor C32. The other end of the resistive element R41 is connected to the second end of the receiving coil 20P. The resistive element R41 adjusts the input impedance seen from the receiving coil 20P toward the load circuit (details of which will be described later) to a predetermined value. The resistive element R41 corresponds to the "impedance adjustment circuit" of the present invention.

[0022] (Rectification circuit, power interruption circuit, smoothing circuit) Diode D51 and diode D52 are connected in series. More specifically, the anode of diode D51 and the cathode of diode D52 are connected. The cathode of diode D51 is connected to the high-side wiring pattern, and the anode of diode D52 is connected to the low-side wiring pattern. The low-side wiring pattern is connected to a reference potential.

[0023] Diode D53 and diode D54 are connected in series. More specifically, the anode of diode D53 and the cathode of diode D54 are connected. The cathode of diode D53 is connected to the Hi-side wiring pattern, and the anode of diode D54 is connected to the Low-side wiring pattern.

[0024] The node of the anode of diode D51 and the cathode of diode D52 is connected to the second end of power receiving coil 20P, as described above. The node of the anode of diode D53 and the cathode of diode D54 is connected to the other terminal of capacitor C32, as described above.

[0025] The circuit made up of multiple diodes D51-D54 corresponds to the "rectifier circuit" of the present invention. The power receiving coil 20P, impedance adjustment circuit, and rectifier circuit described above, more specifically, the power receiving resonant circuit, constitute the "power receiving AC circuit" of the present invention.

[0026] The switch element S62 is connected in parallel to the diode D52. More specifically, the switch element S62 is, for example, an n-channel FET. The drain of the switch element S62 is connected to the cathode of the diode D52. The source of the switch element S62 is connected to the anode of the diode D52.

[0027] Switch element S64 is connected in parallel to diode D54. More specifically, switch element S64 is, for example, an n-channel FET. The drain of switch element S64 is connected to the cathode of diode D54. The source of switch element S64 is connected to the anode of diode D54. It is preferable that switch element S62 and switch element S64 have the same characteristics.

[0028] The gate of switch element S62 and the gate of switch element S64 are connected to the output terminal of voltage detection circuit 22. Switch element S62 and switch element S64, which operate in response to the output from voltage detection circuit 22, correspond to the "power receiving cutoff circuit" of the present invention.

[0029] The capacitor C70 is connected between the Hi-side wiring pattern and the Low-side wiring pattern on the output end side of the rectifier circuit. The capacitor C70 corresponds to the "smoothing circuit" of the present invention.

[0030] (After the smoothing circuit) The LDO 21 is a low-loss linear regulator and has an input terminal, an output terminal, and a reference terminal. The input terminal of the LDO 21 is connected to the high-side wiring pattern. The reference terminal of the LDO 21 is connected to the low-side wiring pattern. The output terminal of the LDO 21 is connected to the voltage detection circuit 22 and the load circuit 24.

[0031] The voltage detection circuit 22 includes a high-side power supply terminal, a reference terminal, a detection voltage input terminal, and a control signal output terminal. The high-side power supply terminal of the voltage detection circuit 22 is connected to the output terminal of the LDO 21. The low-side power supply terminal of the voltage detection circuit 22 is connected to the low-side wiring pattern.

[0032] The detection voltage input terminal of voltage detection circuit 22 is connected to a position on the Hi-side wiring pattern after the smoothing circuit on the input terminal side of LDO 21 (a position on the Hi-side wiring pattern at the same potential as the node of capacitor C70). The control signal output terminal of voltage detection circuit 22 is connected to the gates of switch elements S62 and S64, as described above.

[0033] The power supply terminal of the load circuit 24 is connected to the output terminal and the low-side wiring pattern of the LDO 21. A capacitor C79 is connected in parallel to the power supply terminal of the load circuit 24.

[0034] The smoothing circuit and the load circuit 24, more specifically, including the LDO 21, form a power receiving DC current circuit.

[0035] (Circuit configuration of communication system) The communication antenna 20T is, for example, a loop coil. However, the communication antenna 20T is not limited to a loop coil. A capacitor C39 is connected to both ends of the communication antenna 20T. The communication antenna 20T and the capacitor C39 form a receiving resonant circuit.

[0036] Both ends of the communication antenna 20T are connected to a short-range wireless communication IC 23. The short-range wireless communication IC 23 is, for example, an NFCIC, and is connected to a load circuit 24.

[0037] (Example of operation of wireless power receiving device 10) The wireless power receiving device 10 receives power from an external power transmitting device 90 and performs a predetermined operation using a load circuit 24. Fig. 2 is a functional block diagram showing an example of a power transmitting device according to this embodiment.

[0038] The power transmitting device 90 includes a voltage conversion circuit 91, a power transmission control circuit 92, and a power transmitting coil 900. The voltage conversion circuit 91 converts the voltage level of an input voltage from an external power supply 99 and supplies the converted voltage to the power transmitting control circuit 92. The power transmitting control circuit 92 converts the DC voltage supplied from the voltage conversion circuit 91 into an AC voltage of a predetermined frequency and applies it to the power transmitting coil 900. The power transmitting coil 900 is, for example, a loop coil. The power transmitting coil 900 passes an AC current corresponding to the applied AC voltage and generates an alternating magnetic field.

[0039] The wireless power receiving device 10 is arranged so that the power receiving coil 20P is coupled to the alternating magnetic field generated by the power transmitting coil 900. As a result, the power receiving coil 20P is electromagnetically coupled or electromagnetically resonantly coupled to the alternating magnetic field generated by the power transmitting coil 900, and generates an alternating current of a predetermined frequency.

[0040] In this case, the resonant frequency of the power receiving resonant circuit of the wireless power receiving device 10 matches the frequency of the alternating magnetic field (external magnetic field), thereby achieving a magnetic resonance state between the power receiving coil 20P and the power transmitting coil 900, enabling highly efficient power reception. This resonant frequency is, for example, 13.56 MHz or 6.78 MHz in the ISM band. This resonant frequency is just an example, and other frequencies may be used, but using a frequency in the ISM band makes it possible to tolerate electromagnetic interference. Furthermore, by setting the resonant frequency to 6.78 MHz, it is possible to reduce power loss while tolerating electromagnetic interference, and it is also possible to reduce the size and weight of the wireless power receiving device 10.

[0041] The output current from the power receiving resonant circuit is rectified and output by a rectifier circuit composed of multiple diodes D51-D54. This converts the AC current into DC current. The smoothing circuit smoothes the output current and output voltage of the rectifier circuit and outputs it to the LDO 21. This provides a constant DC voltage to the LDO 21. The output voltage of this smoothing circuit corresponds to the "smoothed voltage" of this invention.

[0042] The LDO 21 converts the input DC voltage (smoothed voltage) into an output DC voltage of a desired value, and outputs it as a power supply for the voltage detection circuit 22 and the load circuit 24.

[0043] The load circuit 24 is driven by the output DC voltage of the LDO 21 and performs predetermined data processing and the like.

[0044] The communication antenna 20T performs communication by electromagnetically coupling with a transmitting antenna (not shown). When the transmitting antenna is also used as the power transmitting coil 900, the communication antenna 20T performs short-range wireless communication by electromagnetically coupling with the power transmitting coil 900. This short-range wireless communication is controlled by a short-range wireless communication IC 23 connected to the communication antenna 20T. The short-range wireless communication IC 23 and the load circuit 24 are capable of mutual data communication. The short-range wireless communication IC 23 controls the short-range wireless communication using the communication antenna 20T based on the result of data communication with the load circuit 24.

[0045] In this configuration, the wireless power receiving device 10 further performs the following control.

[0046] Resistance element R41, which is an impedance adjustment circuit, is connected in parallel to the output terminal of power receiving coil 20P. With this configuration, part of the current generated when power receiving coil 20P is coupled to an external magnetic field flows through resistance element R41. Therefore, a configuration including resistance element R41 can suppress the voltage across power receiving coil 20P (input voltage of the rectifier circuit) compared to a configuration without resistance element R41, even with the same external magnetic field strength.

[0047] Therefore, the range of high external magnetic field strength that can be protected by a configuration including the resistive element R41 is expanded compared to the range of high external magnetic field strength that cannot be protected by a configuration without the resistive element R41. This allows the wireless power receiver 10 to increase the withstand voltage for circuits subsequent to the rectifier circuit, i.e., the power receiving AC circuit and power receiving DC circuit, to a higher external magnetic field strength. Therefore, the wireless power receiver 10 can achieve more reliable overvoltage protection for the power receiving AC circuit and power receiving DC circuit.

[0048] The voltage detection circuit 22 generates a control signal for the switch element S62 and the switch element S64 based on the smoothed voltage (the output voltage of the smoothing circuit). The voltage detection circuit 22 is driven by the output DC voltage of the LDO 21.

[0049] The voltage detection circuit 22 compares the smoothed voltage with the first voltage and generates a control signal based on the comparison result. If the smoothed voltage is less than the first voltage, the voltage detection circuit 22 generates a control signal to turn off the switch elements S62 and S64.

[0050] When the switching elements S62 and S64 are controlled to be OFF, the rectifier circuit performs a rectifying operation, whereby the rectified DC current is supplied to the smoothing circuit, and DC power of a predetermined voltage is supplied to the load circuit 24.

[0051] If the smoothed voltage is equal to or higher than the first voltage, the voltage detection circuit 22 generates a control signal that turns on the switch elements S62 and S64. When the switch elements S62 and S64 are turned on, the rectifier circuit stops rectifying. As a result, no current flows through the smoothing circuit, and the supply of DC power to the load circuit 24 is stopped.

[0052] Here, the first voltage is set based on the strength (magnitude) of the external magnetic field acting on the power receiving coil and the magnitude of the power of the load circuit (the withstand voltage of the circuit components that make up the load circuit).

[0053] More specifically, the first voltage is determined by the upper limit voltage that can protect the DC receiving circuit when the resistor element R41 is connected. The voltage when the resistor element R41 is connected corresponds to the external magnetic field strength. Therefore, the first voltage is set based on the external magnetic field strength.

[0054] Furthermore, the upper limit voltage of the power receiving DC circuit is determined by the power and withstand voltage of the power receiving DC circuit, particularly the power of load circuit 24 and the withstand voltage of the circuit components that make up load circuit 24. Therefore, the first voltage is set based on the magnitude of the power of the load circuit (the withstand voltage of the circuit components that make up the load circuit).

[0055] The first voltage thus set is used to operate the power receiving cutoff circuit described above, whereby, within a range of external magnetic field strength where an overvoltage does not affect the power receiving DC circuit, the wireless power receiving device 10 can perform the operation of the rectifier circuit and supply power at an appropriate voltage to the power receiving DC circuit including the load circuit 24.

[0056] On the other hand, in the range of external magnetic field strength where an overvoltage may be applied to the receiving DC circuit, the wireless power receiving device 10 stops the operation of the rectifier circuit and stops the power supply to the receiving DC circuit including the load circuit 24, thereby protecting the receiving DC circuit from the overvoltage.

[0057] As described above, by including the configuration of this embodiment, the wireless power receiver 10 can suppress an increase in the voltage across the power receiving coil 20P using the impedance adjustment circuit, and can protect the power receiving AC circuit from overvoltage both when the power receiving cutoff circuit is on and off rectifying. Furthermore, the wireless power receiver 10 can supply appropriate power to the power receiving DC circuit using the power receiving cutoff circuit in a range where the power receiving DC circuit is not affected by overvoltage, and can protect the power receiving DC circuit from overvoltage in a range where the power receiving DC circuit is affected by overvoltage. This allows the wireless power receiver 10 to extend the range of external magnetic field strength at which power can be received appropriately to a higher level, and achieve appropriate overvoltage protection.

[0058] Furthermore, by including the above-mentioned impedance adjustment circuit and power receiving cutoff circuit, the wireless power receiving device 10 can also achieve the following effects. Fig. 3(A) is a diagram showing an example of variation in external magnetic field strength in the configuration of the present invention, and Fig. 3(B) is a diagram showing an example of variation in external magnetic field strength in a comparative configuration (a configuration without the impedance adjustment circuit of the present invention). Figs. 3(A) and 3(B) show a case where the external magnetic field strength is within the range of magnetic field strength at which the power receiving cutoff circuit operates in a configuration without an impedance adjustment circuit. Figs. 3(A) and 3(B) show the envelope of the magnetic field strength when no data communication is occurring (when only power is being supplied).

[0059] First, in the comparative configuration, the power receiving cutoff circuit operates every time an overvoltage is reached. This causes a change in the current flowing through the power receiving coil 20P, which in turn changes the envelope of the external magnetic field strength, as shown in Figure 3(B). This change depends on the switching period of the switching element.

[0060] Such a change in the envelope of the external magnetic field strength becomes noise during communication using the envelope of the magnetic field strength. That is, the amplitude of the communication current of the communication device depends on the magnitude of the external magnetic field. Therefore, a change in the envelope causes an unintended change in the amplitude of the communication current. As a result, the communication device may erroneously detect the change in the envelope as communication data.

[0061] However, by incorporating the configuration of the present invention (impedance adjustment circuit), the power receiving cutoff circuit is prevented from operating until the magnetic field reaches a certain strength, and the envelope of the external magnetic field strength remains constant, as shown in Figure 3(A). Therefore, the only change in the envelope is due to the communication data, and the communication device can more reliably detect the communication data.

[0062] Thus, by having the above-described configuration, the wireless power receiving device 10 can more reliably execute and continue data communication in a predetermined range (a range that can be set by the impedance adjustment circuit) of higher magnetic field strength than a comparative configuration (conventional configuration) that does not have an impedance adjustment circuit. As a result, the wireless power receiving device 10 can perform data communication more stably while receiving wireless power than a comparative configuration (conventional configuration) that does not have an impedance adjustment circuit.

[0063] Furthermore, in the wireless power receiving device 10, the resistive element R41, which is an impedance adjustment circuit, is connected closer to the power receiving coil 20P than the capacitor C32, which is a series resonant capacitor. This allows the current generated in the power receiving coil 20P to flow directly to the resistive element R41, thereby achieving a more effective impedance adjustment effect.

[0064] [Second embodiment] A wireless power receiving device according to a second embodiment of the present invention will be described with reference to the drawing. Fig. 4 is a circuit diagram showing an example of the configuration of the wireless power receiving device according to the second embodiment.

[0065] 4, the wireless power receiving device 10A according to the second embodiment differs from the wireless power receiving device 10 according to the first embodiment in that it includes a common coil 20 for both power reception and reception. Other configurations of the wireless power receiving device 10A are the same as those of the wireless power receiving device 10, and a description of similar parts will be omitted.

[0066] The wireless power receiver 10A includes a coil 20. The other end of the capacitor C32 and a second end of the coil 20 are connected to a short-range wireless communication IC 23. In this configuration, the resonant frequency for power reception and the resonant frequency for reception are the same, and the power receiving resonant circuit also serves as the receiving resonant circuit.

[0067] With this configuration, the wireless power receiver 10A can achieve the same operational effects as the wireless power receiver 10. Furthermore, since the wireless power receiver 10A uses a common coil 20 for both power reception and power reception, it can be further miniaturized. Also, with this configuration, it is more susceptible to the effects of the change in the envelope of the magnetic field strength described above during power reception. Therefore, the wireless power receiver 10A has the above operational effects more effectively.

[0068] [Third embodiment] A wireless power receiving device according to a third embodiment of the present invention will be described with reference to the drawing. Fig. 5 is a circuit diagram showing an example of the configuration of the wireless power receiving device according to the third embodiment.

[0069] 5, the wireless power receiver 10B according to the third embodiment differs from the wireless power receiver 10 according to the first embodiment in the configuration of the impedance adjustment circuit. Other configurations of the wireless power receiver 10B are the same as those of the wireless power receiver 10, and a description of similar parts will be omitted.

[0070] The wireless power receiver 10B includes a series circuit of a Zener diode TZ41 and a Zener diode TZ42 as an impedance adjustment circuit. The cathode of the Zener diode TZ41 and the cathode of the Zener diode TZ42 are connected together. The anode of the Zener diode TZ41 is connected to the second end of the power receiving coil 20P, and the anode of the Zener diode TZ42 is connected to the first end of the power receiving coil 20P.

[0071] The Zener voltages of the Zener diodes TZ41 and TZ42 are set based on a voltage at which no overvoltage is applied to the power receiving AC circuit.

[0072] In this configuration, when the external magnetic field strength is low and less than the Zener voltage, a large current does not flow through the Zener diodes TZ41 and TZ42, regardless of the external magnetic field strength. Therefore, the wireless power receiver 10B can maintain proper power receiving operation and suppress adverse effects on communication characteristics.

[0073] Furthermore, when the external magnetic field strength is high and equal to or greater than the Zener voltage, a large current flows through Zener diodes TZ41 and TZ42, causing a drop in the voltage across power receiving coil 20P. Therefore, wireless power receiving device 10B can protect the power receiving AC circuit and power receiving DC circuit. Since communication antenna 20T is provided separately from power receiving coil 20P, adverse effects on communication characteristics can be suppressed.

[0074] [Fourth embodiment] A wireless power receiving device according to a fourth embodiment of the present invention will be described with reference to the drawing. Fig. 6 is a circuit diagram showing an example of the configuration of the wireless power receiving device according to the fourth embodiment.

[0075] 6, a wireless power receiving device 10C according to the fourth embodiment differs from the wireless power receiving device 10 according to the first embodiment in that an overvoltage protection circuit is added. Other configurations of the wireless power receiving device 10C are similar to those of the wireless power receiving device 10, and a description of similar parts will be omitted.

[0076] The wireless power receiving device 10C includes a Zener diode TZ80 and a resistor R80. The Zener diode TZ80 and the resistor R80 are connected in series. Specifically, the anode of the Zener diode TZ80 is connected to one terminal of the resistor R80. The cathode of the Zener diode TZ80 is connected between a node of the smoothing circuit in the Hi-side wiring pattern and the input terminal of the LDO 21. The other terminal of the resistor R80 is connected to the Low-side wiring pattern. The Zener diode TZ80 and the resistor R80 constitute an "overvoltage protection circuit" of the present invention.

[0077] The Zener voltage of the Zener diode TZ80 is set to a voltage lower than the first voltage.

[0078] With this configuration, the wireless power receiver 10C can achieve two-stage overvoltage protection for the load circuit 24. More specifically, the wireless power receiver 10C protects the load circuit 24 from overvoltage at a predetermined voltage lower than the first voltage using an overvoltage protection circuit (Zener diode TZ80 and resistor element R80). Because the overvoltage protection circuit does not cause fluctuations in the external magnetic field strength, at this point, the wireless power receiver 10C can properly perform power receiving and communication operations while protecting the load circuit 24. Furthermore, when the first voltage is reached, the wireless power receiver 10C activates a power receiving cutoff circuit to protect the load circuit 24 from overvoltage.

[0079] [Fifth embodiment] A wireless power receiving device according to a fifth embodiment of the present invention will be described with reference to the drawing. Fig. 7 is a circuit diagram showing an example of the configuration of the wireless power receiving device according to the fifth embodiment.

[0080] 7, the wireless power receiving device 10D according to the fifth embodiment differs from the wireless power receiving device 10C according to the fourth embodiment in the detected voltage of the voltage detection circuit. Other configurations of the wireless power receiving device 10D are similar to those of the wireless power receiving device 10C, and a description of similar parts will be omitted.

[0081] In the wireless power receiving device 10D, the detection voltage input terminal of the voltage detection circuit 22 is connected to the node between the Zener diode TZ80 and the resistive element R80. As a result, the voltage detection circuit 22 detects the voltage associated with the resistive element R80 when a current flows through the resistive element R80, i.e., when a Zener current flows through the Zener diode TZ80.

[0082] When the voltage is low enough that no Zener current flows through Zener diode TZ80, voltage detection circuit 22 detects this voltage and turns off switch elements S62 and S64 (generates an OFF control signal). In other words, when the overvoltage protection circuit is not operating, voltage detection circuit 22 turns off switch elements S62 and S64.

[0083] When a Zener current flows through Zener diode TZ80, voltage detection circuit 22 detects this voltage and turns on switch elements S62 and S64 (generates an on control signal). In other words, when the overvoltage protection circuit is operating, voltage detection circuit 22 turns on switch elements S62 and S64.

[0084] In this way, the wireless power receiver 10D can operate the power reception cutoff circuit based on the operation of the overvoltage protection circuit using the Zener diode TZ80. This allows the wireless power receiver 10D to protect the Zener diode TZ80 from overcurrent.

[0085] The configurations and controls of the above-described embodiments can be combined as appropriate, and effects corresponding to each combination can be achieved. [Explanation of symbols]

[0086] 10, 10A, 10B, 10C, 10D: Wireless power receiving device 20: Coil 20P: Receiving coil 20T: Communication antenna 21: LDO 22: Voltage detection circuit 23: Near field wireless communication IC 24:Load circuit 90: Power transmission equipment 91: Voltage conversion circuit 92: Power transmission control circuit 99: Power supply 900: Transmission coil C31, C32, C39, C70, C79: Capacitors D51, D52, D53, D54: Diodes R41, R80: Resistor elements S62, S64: Switch elements TZ41, TZ42, TZ80: Zener diodes

Claims

1. A receiving circuit; a load circuit electrically connected to the power receiving circuit; a receiving coil electrically connected to the receiving circuit; Equipped with a power receiving resonant circuit including the power receiving coil, a first resonant capacitor connected in parallel to the power receiving coil, and a second resonant capacitor connected in series to the power receiving coil; The power receiving circuit includes: an impedance adjustment circuit that adjusts the input impedance when viewed from the receiving coil toward the load circuit; a rectifier circuit that rectifies the AC current flowing through the power receiving coil; a smoothing circuit electrically connected to the rectifier circuit; a power receiving cutoff circuit that switches between performing and stopping the rectification operation of the rectifier circuit using a comparison result between the smoothed voltage of the smoothing circuit and a predetermined first voltage; Equipped with the impedance adjustment circuit is connected to the power receiving coil side of the second resonant capacitor, the receiving coil, the impedance adjustment circuit, and the rectifier circuit constitute a receiving AC circuit, the smoothing circuit and the load circuit constitute a power receiving DC circuit, the first voltage is set based on the magnitude of an external magnetic field acting on the power receiving coil and the magnitude of power of the load circuit; the impedance adjustment circuit suppresses an increase in voltage across the receiving coil; The power receiving cutoff circuit includes: When the smoothed voltage obtained by the voltage suppressed by the impedance adjustment circuit is less than the first voltage, the rectifier circuit performs a rectification operation; When the smoothed voltage is equal to or higher than the first voltage, the rectification operation of the rectifier circuit is stopped; the impedance adjustment circuit and the power receiving cutoff circuit protect the power receiving AC circuit and the power receiving DC circuit from overvoltage; Wireless power receiving device.

2. the power receiving cutoff circuit protects the power receiving DC circuit from an overvoltage by stopping the rectification operation of the rectifier circuit; the impedance adjustment circuit suppresses an increase in the voltage across the power receiving coil and protects the power receiving AC circuit from overvoltage both when the power receiving cutoff circuit is performing and stopping a rectification operation; and protecting both the power receiving AC circuit and the power receiving DC circuit regardless of whether the rectification operation of the power receiving cutoff circuit is performed or stopped. The wireless power receiving device according to claim 1 .

3. the first voltage is set to an upper limit voltage that can protect the power receiving DC circuit by cutting off the power receiving by the power receiving cutoff circuit in a state where the impedance adjustment circuit is connected; The wireless power receiving device according to claim 1 .

4. A communication circuit; a communication antenna electrically connected to the communication circuit; Equipped with The communication antenna is a coil common to the power receiving coil. The wireless power receiving device according to claim 1 .

5. A communication circuit; a communication antenna electrically connected to the communication circuit; Equipped with The communication antenna is configured with a coil different from the receiving coil. The wireless power receiving device according to claim 1 .

6. the impedance adjustment circuit is configured using a resistive element; The wireless power receiving device according to claim 1 .

7. The impedance adjustment circuit is configured using a Zener diode. The wireless power receiving device according to claim 1 .

8. The impedance adjustment circuit is configured by using two Zener diodes connected in series in opposite directions. The wireless power receiving device according to claim 1 .

9. The power receiving cutoff circuit includes: a switch element connected in parallel to the rectifier element of the rectifier circuit; The wireless power receiving device according to claim 1 .

10. an overvoltage protection circuit connected between the smoothing circuit and the load circuit; The overvoltage protection circuit includes: a Zener diode connected in parallel to the smoothing circuit and operating at a voltage lower than the first voltage; The wireless power receiving device according to claim 1 .

11. The power receiving cutoff circuit includes: Operates based on the voltage of the overvoltage protection circuit; The wireless power receiving device according to claim 10.

12. The frequency of the external magnetic field is 13.56 MHz. The wireless power receiving device according to claim 1 .

13. The frequency of the external magnetic field is 6.78 MHz. The wireless power receiving device according to claim 1 .

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