Power receiving device, control method for power receiving device, and program

Abstract

To prevent proper communication from being disrupted during power transmission.SOLUTION: A power receiving device includes power receiving means for receiving power wirelessly from a power transmission device, communicating means for communicating with the power transmission device by load modulating the power received by the power receiving means, and control means for controlling the modulation of the load modulation by the communication means so that the modulation level of the load modulation is changed when no response signal from the power transmission device for a predetermined signal transmitted by the communication means is received within a predetermined time.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a power receiving device, a control method for a power receiving device, and a program. [Background technology]

[0002] In wireless power transmission, a load modulation method is known in which a power receiving device performs amplitude modulation on a transmitted power when communicating between the power receiving device and the power transmitting device. Patent Document 1 discloses a method of transmitting test signals with different modulation indices at the start of power transmission and determining the modulation indices to be used during power transmission. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-8763 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, according to Patent Document 1, even if the determined modulation depth is used, communication may not be performed properly due to factors such as an object other than the power receiving device being placed within the power transmission range of the power transmitting device during power transmission.

[0005] The present disclosure aims to prevent appropriate communication from being interrupted during power transmission. [Means for solving the problem]

[0006] The power receiving device of the present disclosure is A power receiving device, The power transmission device includes a power receiving means for wirelessly receiving power from a power transmitting device, a communication means for communicating with the power transmitting device by load modulating the power received by the power receiving means, and a control means for controlling so that a modulation degree of the load modulation by the communication means is changed when a response signal from the power transmitting device in response to a predetermined signal transmitted by the communication means is not received within a predetermined time. and when a response signal to the predetermined signal load-modulated based on the modulation factor changed by the control means is received from the power transmitting device, the communication means transmits a signal to the power transmitting device to request detection of an object different from the power receiving device. do. Effect of the Invention

[0007] According to the present disclosure, it is possible to prevent appropriate communication from being interrupted during power transmission. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram illustrating communication between a power transmitting device and a power receiving device. [Diagram 2] 2 is a block diagram showing a configuration example of a power receiving device; [Diagram 3] FIG. 2 is a diagram showing a communication flow between a power transmitting device and a power receiving device. [Figure 4] FIG. 4 is a diagram illustrating an example of the configuration of a load modulation signal modulation unit. [Diagram 5] FIG. 2 is a diagram showing a power transmission coil. [Figure 6] FIG. 4 is a diagram showing a load modulation signal. [Figure 7] 4 is a flowchart showing an operation of the power receiving device. [Figure 8] 1A and 1B are diagrams for explaining processing phases performed by a power transmitting device and a power receiving device; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (First embodiment) 1 is a diagram showing an example of the configuration of a power transfer system according to a first embodiment. The power transfer system includes a power transmitting device 101 and a power receiving device 102. The power transmitting device 101 performs wireless power transfer to the power receiving device 102. The wireless power transfer has an initial phase in which authentication and the like are performed between the power transmitting device 101 and the power receiving device 102, and a power transmission phase in which power is transmitted. During the power transmission phase, the power receiving device 102 transmits a load modulation signal 103 to the power transmitting device 101.

[0010] A case will be described in which a frequency modulation signal 104 is used for communication from the power transmitting device 101 to the power receiving device 102. The frequency modulation signal 104 is used for communication from the power transmitting device 101 to the power receiving device 102. A load modulation signal 103 is used for communication from the power receiving device 102 to the power transmitting device 101. The power receiving device 102 transmits the load modulation signal 103 to the power transmitting device 101. The power transmitting device 101 transmits the frequency modulation signal 104 to the power receiving device 102.

[0011] Fig. 2 is a block diagram showing an example of the configuration of the power receiving device 102 in Fig. 1. The power receiving device 102 includes a control unit 1021, a communication receiving unit 1022, a power receiving antenna 1023, a load modulation signal modulation unit 1024, a power receiving unit 1025, and a battery 1026. The power receiving device 102 in Fig. 2 shows a portion related to wireless power transmission.

[0012] The control unit 1021 controls the entire power receiving device 102 by executing a control program stored in a memory (not shown), for example. In one example, the control unit 1021 performs control necessary for device authentication and power reception in the power receiving device 102. The control unit 1021 may perform control for executing applications other than wireless power transmission. The control unit 1021 includes one or more processors, such as a CPU or an MPU. The control unit 1021 may include hardware dedicated to a specific process, such as an ASIC, or an array circuit, such as an FPGA, compiled to execute a predetermined process. The control unit 1021 stores information to be stored during execution of various processes in a memory (not shown). The control unit 1021 may also measure time using a timer.

[0013] The power receiving antenna 1023 receives the power wirelessly transmitted by the power transmitting device 101. The power receiving unit 1025 extracts necessary DC power from the power received by the power receiving antenna 1023 and charges a battery 1026. The communication receiving unit 1022 extracts a frequency modulation signal 104 including control information and status information from the power received by the power receiving antenna 1023, and outputs the frequency modulation signal 104 to the control unit 1021. Under the control of the control unit 1021, the load modulation signal modulating unit 1024 generates a load modulation signal 103 including control information addressed to the power transmitting device 101 and status information of the power receiving device 102, and wirelessly transmits the load modulation signal 103 to the power transmitting device 101 via the power receiving antenna 1023. After the power receiving antenna 1023 receives the power transmitted by the power transmitting device 101, the load modulation signal modulation unit 1024 controls the load to superimpose the load modulation signal 103 on the transmission power.

[0014] FIG. 8 is a diagram for explaining the process performed by the power transmitting device 101 and the power receiving device 102 according to the present embodiment. The power transmitting device 101 and the power receiving device 102 perform wireless power transmission in accordance with the WPC standard. FIG. 8 is a sequence diagram showing the flow of control of the power transmitting device 101 and the power receiving device 102 in accordance with the WPC standard v1.2.3. The sequence shown in FIG. 8 is not limited to the power transmitting device 101 having a plurality of power transmitting coils and a plurality of power transmitting units, but is a control executed by a power transmitting device having a configuration conforming to the WPC standard. In the following description, the power transmitting device 101 is described as transmitting power to the power receiving device 102 using an arbitrary power transmitting coil. Note that, in the following, a case will be described in which the power transmitting device 101 and the power receiving device 102 comply with the WPC standard v1.2.3, but is not limited thereto. That is, the power transmitting device 101 and the power receiving device 102 may comply with the WPC standard of a version after the WPC standard v1.2.3, or may comply with a version earlier than the WPC standard v1.2.3.

[0015] The WPC standard specifies multiple phases, including a power transfer phase in which power is transmitted for charging, and a phase before power is transmitted for charging. The phases before power transmission include (1) a selection phase, (2) a ping phase, (3) an identification and configuration phase, (4) a negotiation phase, and (5) a calibration phase. In the following, the identification and configuration phase is referred to as the I&C phase.

[0016] In the Selection phase, the power transmitting device 101 transmits an Analog Ping (hereinafter, referred to as an A-Ping) to detect an object existing in the vicinity of the power transmitting coil (F500). The control method of the A-Ping in this embodiment will be described later. The A-Ping is a pulsed power for detecting an object. Even if the power receiving device 102 receives the A-Ping, the power is so small that the control unit 1021 of the power receiving device 102 cannot be started. The power transmitting device 101 transmits the A-Ping intermittently. Here, the voltage and current applied to the power transmitting coil change depending on whether an object is placed within the power transmitting range of the power transmitting device 101 or not. Therefore, the control unit of the power transmitting device 101 detects at least one of the voltage value and the current value of the power transmitting coil when the A-Ping is transmitted. When the detected voltage value falls below a certain threshold or the detected current value exceeds a certain threshold, the control unit of the power transmitting device 101 determines that an object is present and transitions to the Ping phase.

[0017] In the Ping phase, when the power transmitting device 101 detects that an object has been placed by A-Ping, it measures the Q-factor (Quality Factor) of the power transmitting coil (F501). When the Q-factor measurement ends, the power transmitting device 101 starts transmitting a Digital Ping (hereinafter referred to as D-Ping) (F502). The D-Ping is power for starting the control unit 1021 of the power receiving device 102, and is a power greater than that of the A-Ping. After that, the power transmitting device 101 continues transmitting power equal to or greater than the D-Ping from the start of D-Ping transmission (F502) until it receives an End Power Transfer (EPT) packet requesting the stop of power transmission from the power receiving device 102 (F522). When the control unit 1021 of the power receiving device 102 receives the D-Ping and starts up, it transmits a Signal Strength packet, which is data storing the voltage value of the received D-Ping, to the power transmitting device 101 (F503). By receiving a Signal Strength packet from the power receiving device 102 that has received the D-Ping, the power transmitting device 101 recognizes that the object detected in the Selection phase is the power receiving device 102. Upon receiving the Signal Strength packet, the power transmitting device 101 transitions to the I&C phase.

[0018] In the I&C phase, the power receiving device 102 transmits data storing an ID including version information of the WPC standard to which the power receiving device 102 complies and device identification information (F504). The power receiving device 102 also transmits a Configuration packet to the power transmitting device 101 including information indicating the maximum value of power that the power receiving unit 1025 supplies to a load (F505). By receiving the ID and the Configuration packet, the power transmitting device 101 determines whether the version of the power receiving device 102 corresponds to the WPC standard to which the power receiving device 102 complies, and transmits an ACK. Specifically, when the power transmitting device 101 determines that the power receiving device 102 complies with an extended protocol of the WPC standard v1.2 or later (including processing in the negotiation phase to be described later), it responds with an ACK (F506). When the power receiving device 102 receives the ACK, it transitions to the Negotiation phase in which negotiations are performed regarding the power to be transmitted and received.

[0019] In the negotiation phase, the power receiving device 102 transmits FOD Status data to the power transmitting device 101 (F507). In this embodiment, the FOD Status data is expressed as FOD(Q). The power transmitting device 101 performs foreign object detection based on the Q value stored in the received FOD(Q) and the Q value measured by the Q value measurement, and transmits an ACK indicating that it has been determined that there is a high possibility that no foreign object is present to the power receiving device (F508).

[0020] When the power receiving apparatus 102 receives the ACK, the power receiving apparatus 102 transmits a General Request (Capability) packet, which is data inquiring about the capabilities of the power transmitting apparatus 101 and is one of the General Requests defined in the WPC standard (F535). Hereinafter, the General Request (Capability) packet is referred to as a GRQ (CAP) packet. When the power transmitting apparatus 101 receives the GRQ (CAP) packet, the power transmitting apparatus 101 transmits a Capability packet (hereinafter, referred to as CAP) storing capability information supported by the power transmitting apparatus 101 (F536).

[0021] The power receiving apparatus 102 negotiates Guaranteed Power (hereinafter, referred to as GP), which is the maximum value of the power value requested to receive power. Specifically, Guaranteed Power represents the amount of power available to the power receiving apparatus 102, agreed upon in negotiation with the power transmitting apparatus 101. In other words, GP is the maximum value of power (power consumed by the load) that can be used to supply to the load of the power receiving apparatus 102. The negotiation is realized by transmitting to the power transmitting apparatus 101 a packet that stores the value of Guaranteed Power requested by the power receiving apparatus 102, among Specific Request packets defined in the WPC standard (F509). In this embodiment, the data is expressed as an SRQ (GP) packet.

[0022] The power transmitting device 101 responds to the SRQ(GP) packet taking into consideration its own power transmitting capability and the like. When the power transmitting device 101 determines that the Guaranteed Power is acceptable, it transmits an ACK indicating that the request has been accepted (F510). When the power receiving device 102 finishes negotiation of a plurality of parameters including the Guaranteed Power, it transmits an SRQ(EN) of the Specific Request requesting the end of the negotiation (End Negotiation) to the power transmitting device 101 (F511). The power transmitting device 101 transmits an ACK in response to the SRQ(EN) packet (F512), ends the negotiation, and transitions to a calibration phase in which a criterion for performing foreign object detection based on a power loss method is created. Note that the foreign object detection is a process of determining whether or not an object other than the power receiving device 102 (hereinafter, referred to as a foreign object) is present or may be present within the power transmitting range of the power transmitting device 101.

[0023] In the calibration phase, the power receiving device 102 notifies the power transmitting device 101 of the received power value R1 when the power receiving device 102 receives a D-Ping in a state in which the power receiving unit 1025 is not connected to a load (battery 1026). At this time, the power receiving device 102 transmits a Received Power packet (mode1) (hereinafter referred to as RP1) storing the received power value R1 to the power transmitting device 101 (F513). Upon receiving RP1, the power transmitting device 101 transmits an ACK to the power receiving device 102 (F514). At this time, the power transmitting device 101 measures its own transmitted power value T1 and calculates a difference Δ1 between T1, which is the power loss, and R1. After receiving the ACK, the power receiving device 102, with the power receiving unit 1025 and the load connected, transmits to the power transmitting device 101 a Control Error packet (hereinafter referred to as CE) requesting the power transmitting device 101 to increase or decrease the receiving voltage. A code and a numerical value are stored in the CE, and if the code of the numerical value stored in the CE is positive, it indicates a request to increase the receiving voltage, if it is negative, it indicates a request to decrease the receiving voltage, and if the numerical value is zero, it indicates that the receiving voltage is to be maintained. Here, the power receiving device 102 transmits CE(+) to the power transmitting device 101, which indicates to increase the receiving voltage (F515).

[0024] When the power transmitting device 101 receives CE(+), it changes the setting value of the power transmitting unit and increases the transmission voltage (F516). When the power receiving device 102 responds to CE(+) and the received power increases, it supplies the received power to the load and transmits RP2 (Received Power packet (mode2) (hereinafter referred to as RP2) to the power transmitting device 101 (F517). Here, RP2 stores a received power value R2 in a state in which the power receiving device 102 supplies the output of the power receiving unit 1025 to the load (battery 1026).

[0025] When the power transmitting device 101 receives RP2, it transmits an ACK to the power receiving device 102 (F518). At this time, the power transmitting device 101 measures its own transmission power value T2 and calculates the difference Δ2 between T2, which is the power loss, and R2. The power transmitting device 101 performs foreign object detection based on the power loss, using as a reference the power loss Δ1 when the power receiving unit 1025 is not connected to a load and the power consumption of the load is zero, and the power loss Δ2 when the power receiving unit 1025 is connected to a load and the power consumption of the load is not zero. Specifically, the power transmitting device 101 can predict the power loss in a state where there is no foreign object at an arbitrary received power value from Δ1 and Δ2, and perform foreign object detection based on the actually received received power value and transmitted power value. When the power transmitting device 101 transmits an ACK to RP2, it transitions to the Power Transfer phase.

[0026] In the power transfer phase, the power transmitting device 101 transmits the power that the power receiving device 102 can receive up to 15 watts, which was negotiated in the negotiation phase. The power receiving device 102 periodically transmits to the power transmitting device 101 an RP0 (Received Power packet (mode 0) (hereinafter referred to as RP0) that stores a CE and a current received power value (F519, F520). When the power transmitting device 101 receives RP0 from the power receiving device 102, it predicts a power loss at an arbitrary received power from the above Δ1 and Δ2, and performs foreign object detection. If the power transmitting device 101 determines that there is a high possibility that there is no foreign object as a result of the foreign object detection, it transmits an ACK to the power receiving device 102 (F521). If it determines that there is a high possibility that there is a foreign object, the power transmitting device 101 transmits a NAK to the power receiving device 102.

[0027] When charging of the battery 1026 is completed, the power receiving apparatus 102 transmits an EPT (End Power Transfer) packet requesting the power transmitting apparatus 101 to stop power transmission (F522). The above is the flow of control of the power transmitting apparatus 101 and the power receiving apparatus 102 that complies with the WPC standard v1.2.3.

[0028] Fig. 4 is a diagram showing an example of the configuration of the load modulation signal modulation unit 1024 of Fig. 2. The load modulation signal modulation unit 1024 has switches 4011, 4012, 4013, 4014, and 4015, and capacitors 4021, 4022, 4023, 4024, and 4025.

[0029] The load modulation signal modulating unit 1024 changes the modulation degree of the load modulation signal 103 in Fig. 1. The capacitors 4021, 4022, 4023, 4024, and 4025 are connected to the power receiving antenna 1023 in Fig. 2 by closing the switches 4011, 4012, 4013, 4014, and 4015, respectively. The modulation degree of the load modulation signal 103 in Fig. 1 can be changed by repeatedly opening and closing one or more of the switches 4011, 4012, 4013, 4014, and 4015. The capacitances of the connected capacitors 4021 to 4025 may be the same or different. This is because the total capacitance changes depending on the number of opening and closing of the switches 4011 to 4015. For example, when the capacitors 4021-4025 have the same capacitance, turning on more switches 4011-4015 increases the capacitance of the load modulation signal modulation unit 1024, thereby increasing the modulation depth. Also, when the capacitors 4021-4025 have different capacitances, the modulation depth can be increased by switching on the switch to a capacitor with a larger capacitance.

[0030] FIG. 4 shows an example in which the modulation degree of the load modulation signal 103 is changed depending on the connection state of the capacitors 4021 to 4025, but the modulation degree can also be changed using resistors, coils, or a combination of these. Also, in FIG. 4, the capacitors 4021 to 4025 are connected in parallel, but the modulation degree can also be changed using a circuit configuration in which the capacitors are connected in series and switches are arranged to bypass each capacitor. In this embodiment, the description will be given assuming that the larger the capacity of the load modulation signal modulation unit 1024, the higher the modulation degree. However, depending on conditions such as the magnitude of the received power, the modulation degree may be increased by reducing the capacity. In this case, the power receiving device 102 switches the switch so that the capacity of the load modulation signal modulation unit 1024 becomes smaller.

[0031] 6(a) is a diagram showing an amplitude 601 of the load modulation signal 103 transmitted by the power receiving apparatus 102. FIG. 6(b) is a diagram showing an amplitude 602 of the load modulation signal 103 received by the power transmitting apparatus 101.

[0032] Fig. 6(a) shows the amplitude 601 of the load modulation signal 103 transmitted by the power receiving device 102. Thereafter, the amplitude of the load modulation signal 103 changes when a foreign object or the like approaches during power transmission. Due to the influence of the foreign object, the amplitude 602 of the load modulation signal 103 received by the power transmitting device 101 becomes smaller than the amplitude 601, as shown in Fig. 6(b). When this amplitude 602 drops to a level that makes it difficult to demodulate, the amplitude 602 becomes the same as fluctuating noise to the power transmitting device 101.

[0033] Fig. 3(a) is a diagram showing an example of a communication flow between the power transmitting device 101 and the power receiving device 102 during normal operation. Fig. 3(b) is a diagram showing an example of a communication flow between the power transmitting device 101 and the power receiving device 102 when a foreign object is placed within the power transmission range of the power transmitting device 101. Fig. 7 is a flowchart showing a method of controlling the power receiving device 102. The process shown in Fig. 7 is performed by the control unit 1021 executing a control program stored in a memory (not shown).

[0034] Hereinafter, a description will be given with reference to Fig. 3(a), (b) and Fig. 7. At the start of power transmission, the power receiving device 102 performs amplitude modulation of the load modulation signal 103 by repeatedly opening and closing only the switch 4011 of the load modulation signal modulation unit 1024. The "communication" in Fig. 3(a) and (b) is, for example, RP0 transmitted from the power receiving device 102 to the power transmitting device 101 in the power transmission phase. However, this is not limited to this. This embodiment can be applied to any communication in which a response is transmitted from the power transmitting device 101.

[0035] FIG. 3(a) is a diagram showing an example of a communication flow between the power transmitting device 101 and the power receiving device 102 during normal operation. During normal operation, as shown in FIG. 3(a), in step S701, the control unit 1021 of the power receiving device 102 transmits the load modulation signal 103 to the power receiving device 102 by load modulation using the load modulation signal modulation unit 1024 (S301). When the power transmitting device 101 receives the load modulation signal 103, it transmits a response signal to the power receiving device 102 (S302). In step S702, the control unit 1021 of the power receiving device 102 determines whether or not the response signal has been received using the communication reception unit 1022, and if it is determined that the response signal has been received, the process proceeds to step S704. In step S704, the control unit 1021 of the power receiving device 102 ends the process for the load modulation signal 103.

[0036] Fig. 3(b) is a diagram showing an example of a communication flow between the power transmitting device 101 and the power receiving device 102 when a foreign object is placed within the power transmission range of the power transmitting device 101. For example, if a foreign object is placed within the power transmission range of the power transmitting device 101 and the amplitude 602 of the load modulation signal 103 decreases, the power transmitting device 101 cannot demodulate the load modulation signal 103 from the power receiving device 102 and determines that the load modulation signal 103 has not been transmitted. As a result, the power transmitting device 101 cannot transmit a response signal. This state is shown in Fig. 3(b).

[0037] The flow of Fig. 3(b) will be described with reference to the flowchart of Fig. 7. In step S701, the control unit 1021 of the power receiving device 102 transmits the load modulation signal 103 to the power receiving device 102 by load modulation using the load modulation signal modulation unit 1024 (S311). When a foreign object is placed within the power transmission range of the power transmitting device 101 and the amplitude 602 of the load modulation signal 103 decreases, the power transmitting device 101 cannot demodulate the load modulation signal 103 from the power receiving device 102 and therefore does not transmit a response signal.

[0038] In step S702, the control unit 1021 of the power receiving apparatus 102 determines whether or not a response signal has been received within a predetermined period by the communication receiving unit 1022, and if a response signal has not been received, the process proceeds to step S703.

[0039] In step S703, the control unit 1021 simultaneously and repeatedly opens and closes the switches 4011 and 4012 of the load modulation signal modulation unit 1024 to change the modulation degree to a larger value, and retransmits the load modulation signal 103 to the power transmitting device 101 at the changed modulation degree (S312). At this time, the power transmitting device 101 determines that the load modulation signal 103 is not being transmitted from the power receiving device 102, so after a certain period of time (timeout period), the power transmitting device 101 times out and stops transmitting power to the power receiving device 102. Therefore, the power receiving device 102 changes the modulation degree and retransmits the signal before the timeout period at which the power transmitting device 101 stops transmitting power elapses, and returns to step S702.

[0040] Since the amplitude of the load modulation signal 103 transmitted with the changed modulation index is large, the power transmitting device 101 can demodulate the load modulation signal 103 and transmits a response signal to the power receiving device 102 (S313). In step S702, the control unit 1021 of the power receiving device 102 determines that the response signal has been received within a predetermined period of time by the communication receiving unit 1022. Since the reception was successful after changing the modulation index, the control unit 1021 of the power receiving device 102 determines that there may be a foreign object nearby, and transmits a foreign object detection request to the power transmitting device 101 (S314).

[0041] When the power transmitting device 101 receives the foreign object detection request, it transmits a response signal to the power receiving device 102 (S315), interrupts power transmission as necessary, and performs foreign object detection. The foreign object detection request may be a request packet or RP0. When a foreign object detection request in a request packet is transmitted from the power receiving device 102, the power transmitting device 101 can perform foreign object detection processing using any method. Furthermore, when a foreign object detection request of RP0 is transmitted from the power receiving device 102, the power transmitting device 101 can compare the magnitude of the power transmitted by the power transmitting device 101 with the power received by the power receiving device 102 to perform foreign object detection based on power loss.

[0042] As described above, the power receiving unit 1025 wirelessly receives power from the power transmitting device 101. In step S701, the control unit 1021 functions as a transmission unit, and transmits the load modulation signal 103 to the power transmitting device 101 by superimposing the load modulation signal 103 on the power using the load modulation signal modulation unit 1024. In step S703, if the control unit 1021 does not receive a response signal from the power transmitting device 101 within a predetermined time after the transmission of the load modulation signal 103, the control unit 1021 changes (increases) the modulation degree of the load modulation signal 103 using the load modulation signal modulation unit 1024. Specifically, in step 703, if the control unit 1021 does not receive a response signal from the power transmitting device 101 within a predetermined time after the transmission of the load modulation signal 103, the control unit 1021 changes (increases) the modulation degree of the load modulation signal 103 using the load modulation signal modulation unit 1024 and retransmits the load modulation signal 103. 6(a) and (b), the modulation depth of the load modulation signal 103 is represented based on, for example, the difference between the maximum value (high level) and the minimum value (low level) of the amplitude of the load modulation signal 103. The response signal may be, for example, a frequency modulation signal 104.

[0043] When the power transmitting device 101 detects the load modulation signal (S312) transmitted by the power receiving device 102, it superimposes a response signal (S313) on the power and transmits the response signal to the power receiving device 102. When the control unit 1021 obtains the response signal (S313) from the power transmitting device 101 after retransmission of the load modulation signal 103, it causes the load modulation signal modulation unit 1024 to superimpose a signal (S314) for requesting foreign object detection on the power and transmit the signal to the power transmitting device 101.

[0044] As described above, according to the present embodiment, when the power receiving device 102 does not receive a response signal from the power transmitting device 101, the power receiving device 102 increases the modulation degree and transmits the load modulation signal 103 to the power transmitting device 101 again. This allows the power receiving device 102 to transmit the load modulation signal 103 to the power transmitting device 101 more reliably, and also allows the power receiving device 102 to detect the possibility of the presence of a foreign object and transmit a request for a foreign object detection process to the power transmitting device 101. Note that the modulation degree can be set to an arbitrary value by the power receiving device 102 before the power transmission phase, so the modulation degree may be set to a large value from the beginning. However, as in the present embodiment, when there is no response signal from the power transmitting device 101, the power receiving device 102 has the effect of being able to detect the possibility of the presence of a foreign object by changing the modulation degree. In addition, the larger the modulation degree, the larger the noise during normal communication may be. Therefore, the power receiving device 102 has the effect of suppressing noise during communication by performing communication from a relatively small modulation degree state.

[0045] Second embodiment 5(a) is a diagram showing an example of the configuration of power transmitting coils 501-504 of the power transmitting device 101 according to the second embodiment. A case will be described where the power transmitting device 101 has a plurality of power transmitting coils 501-504. The plurality of power transmitting coils 501-503 are multi-coils. The power transmitting coil 501, the power transmitting coil 502, the power transmitting coil 503, and the power transmitting coil 504 overlap each other.

[0046] 5(b) to 5(d) are diagrams illustrating a case where the power receiving device 102 moves relative to the power transmitting coils 501 to 504 of the power transmitting device 101. The power receiving device 102 moves due to, for example, an impact. Among the power transmitting coils 501 to 504, the power transmitting coils indicated by dashed lines are power transmitting coils that are not transmitting power, and the power transmitting coils indicated by solid lines are power transmitting coils.

[0047] 5B shows a state in which the power receiving device 102 is placed on the power transmitting coil 501 and power transmission from the power transmitting coil 501 to the power receiving device 102 begins. The power transmitting coil 501 is being used for power transmission.

[0048] Fig. 5(c) shows a state in which the position of the power receiving device 102 is shifted due to an impact or the like during the power transmission in Fig. 5(b). The power receiving device 102 is about to come off the power transmitting coil 501 that is transmitting power. Therefore, as shown in Fig. 6(b), the amplitude 602 of the load modulation signal 103 received by the power transmitting device 101 from the power receiving device 102 becomes small, and the power transmitting device 101 cannot demodulate the load modulation signal 103 and cannot transmit a response signal.

[0049] In step S702, if the communication receiving unit 1022 of the power receiving device 102 does not receive a response signal, the control unit 1021 of the power receiving device 102 proceeds to step S703. In step S703, the control unit 1021 changes the modulation degree to a larger value by simultaneously repeatedly opening and closing the switch 4011 and the switch 4012, retransmits the load modulation signal 103 to the power transmitting device 101 with the changed modulation degree (S312), and returns to step S702.

[0050] Since the amplitude of the load modulation signal 103 transmitted with the changed modulation factor is large, the power transmitting device 101 can demodulate the load modulation signal 103 and transmits a response signal to the power receiving device 102 (S313). In step S702, the control unit 1021 of the power receiving device 102 determines that the response signal has been received within a predetermined period by the communication receiving unit 1022. Since the reception was successful after changing the modulation factor, the control unit 1021 of the power receiving device 102 determines that a position shift of the power receiving device 102 has occurred, and transmits a position detection request for the power receiving device 102 to the power transmitting device 101 (S314).

[0051] When the power transmitting device 101 receives the position detection request from the power receiving device 102, it transmits a response signal to the position detection request to the power receiving device 102 (S315), stops power transmission, and detects the position of the power receiving device 102. When the power transmitting device 101 detects, as a result of the detection, that the power receiving device 102 has moved to the position of the power transmitting coil 502, it starts power transmission by the power transmitting coil 502, as shown in Fig. 5(d). After detecting the position of the power transmitting device 101, the power receiving device 102 may lower the modulation degree by the load modulation signal modulation unit 1024 as necessary.

[0052] As described above, when the control unit 1021 receives a response signal (S313) from the power transmitting device 101 after retransmitting the load modulation signal (S312), the load modulation signal modulation unit 1024 superimposes a position detection request on the power and transmits the superimposed power to the power transmitting device 101. The position detection request is a signal for requesting power transmission according to the position of the power receiving device 102.

[0053] When the power transmitting device 101 receives the position detection request, it detects the position of the power receiving device 102, and wirelessly transmits power using a power transmitting coil corresponding to the detected position of the power receiving device 102. The power transmitting coil is a multi-coil having a plurality of power transmitting coils 501 to 504, or a moving coil in which the power transmitting coil is movable.

[0054] After power transmission according to the position of the power receiving device 102 is started, the control unit 1021 may cause the load modulation signal modulation unit 1024 to reduce the modulation degree of the load modulation signal 103 .

[0055] As described above, according to this embodiment, the power transmitting device 101 can detect the position of the power receiving device 102 and correct the positional deviation of the power receiving device 102 with respect to the power transmitting coil.

[0056] The power receiving device 102 can maintain communication with the power transmitting device 101 by changing the modulation degree of the load modulation signal 103. If the power transmitting device 101 has a multi-coil or a moving coil, it can be determined that the situation in which the load modulation signal cannot be communicated is due to a positional deviation of the power receiving device 102. The power receiving device 102 can retransmit the load modulation signal 103 with a changed modulation degree and transmit a position detection request to the power transmitting device 101. Furthermore, when the load modulation signal 103 becomes communicable, the power receiving device 102 can transmit a foreign object detection request to the power transmitting device 101.

[0057] In the first and second embodiments, if the power receiving device 102 does not receive a response signal from the power transmitting device 101 within a predetermined time after the transmission of the load modulation signal 103 in step S702, the power receiving device 102 determines that the amplitude of the load modulation signal is small and therefore the power transmitting device 101 cannot demodulate the load modulation signal. Then, the power receiving device 102 changes (increases) the modulation degree of the load modulation signal 103 by the load modulation signal modulation unit 1024. However, the present invention is not limited to this configuration. The power receiving device 102 may observe the amplitude 601 of the load modulation signal shown in FIG. 6(a) based on the voltage value or current value of the power receiving antenna, and predict the amplitude 602 of the load modulation signal at the power transmitting device. Then, the power receiving device 102 compares the predicted value of the amplitude 602 with a threshold value of the amplitude 602 that the power transmitting device 101 will be able to demodulate, and changes (increases) the modulation degree of the load modulation signal 103 when the predicted value is equal to or less than the threshold value (or close to the threshold value). With this configuration, the same effects as those of the first and second embodiments can be obtained.

[0058] In addition, the power receiving device 102 may predict the amplitude 602 on the power transmitting device 101 side from the coupling coefficient between the power transmitting antenna (not shown) and the power receiving antenna 1023 of the power transmitting device 101 and the power consumption of the load of the power receiving device 102 (such as a charging circuit for the battery 1026).

[0059] In the first and second embodiments, the power receiving device 102 is configured to change the modulation degree of its own load modulation signal modulation unit 1024, but this configuration can also be applied to the power transmitting device 101. That is, the power transmitting device 101 may be configured to change the modulation degree of its own frequency-modulated signal 104. Specifically, when the power transmitting device 101 cannot receive an expected response from the power receiving device 102 in response to the transmitted frequency-modulated signal 104, the power transmitting device 101 may change (increase) the modulation degree of the frequency modulation and transmit the frequency-modulated signal 104 again. With such a configuration, when the power transmitting device 101 determines that the power receiving device 102 cannot demodulate the frequency-modulated signal 104 due to a foreign object or the like, it has the effect of enabling demodulation.

[0060] Furthermore, the determination of whether demodulation is possible by the power transmitting device 101 may be made by the power transmitting device 101 observing the frequency-modulated signal 104 based on the voltage value or current value of the power transmitting antenna, and predicting the modulation depth of the frequency-modulated signal in the power receiving device 102. Then, the power transmitting device 101 compares the predicted value of the modulation depth with a threshold value of the modulation depth that the power receiving device 102 will be able to demodulate, and changes (increases) the modulation degree of the frequency-modulated signal 104 when the predicted value is equal to or less than the threshold value (or close to the threshold value). The same effect can be obtained with this configuration.

[0061] In addition, the prediction may predict the modulation depth on the power receiving device 102 side from the coupling coefficient between the power transmitting antenna and the power receiving antenna 1023 (not shown) of the power transmitting device 101 and the power consumption of the load of the power receiving device 102 (such as a charging circuit for the battery 1026).

[0062] In the above embodiment, the power transmitting device 101 is configured to transmit the frequency-modulated signal 104, but this may be amplitude-modulated. Specifically, when the power transmitting device 101 cannot receive an expected response from the power receiving device 102 in response to the transmitted amplitude-modulated signal, the power transmitting device 101 may change (increase) the modulation degree of the amplitude modulation and transmit the amplitude-modulated signal again. This configuration has the effect of enabling demodulation when the power transmitting device 101 determines that the amplitude-modulated signal cannot be demodulated by the power receiving device 102 due to a foreign object or the like.

[0063] Alternatively, the power transmitting device 101 may make the above judgment based on the voltage value or current value of the power transmitting antenna, by observing the amplitude-modulated signal and predicting the modulation depth of the amplitude-modulated signal in the power receiving device 102. The power transmitting device 101 may then compare the prediction of the modulation depth with a threshold value of the modulation depth that the power receiving device 102 will be able to demodulate, and if the prediction is equal to or less than the threshold value (or close to the threshold value), change (increase) the modulation degree of the amplitude-modulated signal, thereby obtaining the same effect.

[0064] The prediction may also predict the modulation depth on the power receiving device 102 side from a coupling coefficient between a power transmitting antenna (not shown) and a power receiving antenna 1023 of the power transmitting device 101 or power consumption of a load (such as a charging circuit for a battery 1026) of the power receiving device 102. The power consumption of the load may also be based on a received power value notified to the power transmitting device 101 by the power receiving device 102.

[0065] It should be noted that the above-described embodiments are merely illustrative of specific examples of implementing the present disclosure, and the technical scope of the present disclosure should not be interpreted as being limited by these embodiments. In other words, the present disclosure can be implemented in various forms without departing from its technical concept or main features.

[0066] (Other embodiments) The above-described first and second embodiments can also be implemented in combination. The present disclosure can also be realized by a process in which a program for implementing one or more functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that implements one or more functions. [Explanation of symbols]

[0067] 102 power receiving device, 1021 control unit, 1022 communication receiving unit, 1023 power receiving antenna, 1024 load modulation signal modulation unit, 1025 power receiving unit, 1026 battery

Claims

1. A power receiving device, A power receiving unit that wirelessly receives power from a power transmitting device; A communication means for communicating with the power transmitting device by load modulating the power received by the power receiving means; a control means for controlling the load modulation by the communication means so as to change a modulation degree when a response signal from the power transmitting device in response to a predetermined signal transmitted by the communication means is not received within a predetermined time, The communication means of the power receiving device is characterized in that when the communication means receives a response signal from the power transmitting device in response to the specified signal load-modulated based on the modulation index changed by the control means, the communication means transmits a signal to the power transmitting device requesting detection of an object other than the power receiving device.

2. A power receiving device, A power receiving unit that wirelessly receives power from a power transmitting device; A communication means for communicating with the power transmitting device by load modulating the power received by the power receiving means; a control means for controlling the load modulation by the communication means so as to change a modulation degree when a response signal from the power transmitting device in response to a predetermined signal transmitted by the communication means is not received within a predetermined time, The communication means of the power receiving device is characterized in that when the communication means receives a response signal from the power transmitting device in response to the specified signal load-modulated based on the modulation index changed by the control means, the communication means transmits a signal to the power transmitting device to request power transmission according to the position of the power receiving device.

3. The power receiving device according to claim 2, characterized in that the control means controls the modulation degree of the load modulation by the communication means to be smaller after the communication means transmits a signal to request power transmission according to the position of the power receiving device.

4. The power receiving device according to any one of claims 1 to 3, characterized in that the control means controls the modulation degree of the load modulation by the communication means to be larger when a response signal from the power transmitting device in response to a specified signal transmitted by the communication means is not received within a specified time.

5. The power receiving device according to any one of claims 1 to 4, characterized in that if a response signal from the power transmitting device to the specified signal is not received within a specified time, the communication means transmits the specified signal load modulated based on a modulation index changed by the control means.

6. 6. The power receiving device according to claim 1, wherein the modulation factor is expressed based on a difference between a maximum value and a minimum value of an amplitude of the predetermined signal that is load modulated.

7. 7. The power receiving device according to claim 1, wherein the communication means receives a frequency modulated signal as the response signal.

8. A power transmission device; The power receiving device according to any one of claims 1 to 7, A power transmission system comprising:

9. A method for controlling a power receiving device, comprising: a power receiving step of wirelessly receiving power from a power transmitting device; a communication step of communicating with the power transmitting device by load modulating the power received in the power receiving step; a control step of controlling so that a modulation degree of the load modulation by the communication step is changed when a response signal from the power transmitting device in response to the predetermined signal transmitted by the communication step is not received within a predetermined time, A control method for a power receiving device, characterized in that, in the communication step, when a response signal from the power transmitting device to the specified signal load-modulated based on the modulation index changed by the control step is received, a signal requesting detection of an object other than the power receiving device is transmitted to the power transmitting device.

10. A method for controlling a power receiving device, comprising: a power receiving step of wirelessly receiving power from a power transmitting device; a communication step of communicating with the power transmitting device by load modulating the power received in the power receiving step; a control step of controlling so that a modulation degree of the load modulation by the communication step is changed when a response signal from the power transmitting device in response to the predetermined signal transmitted by the communication step is not received within a predetermined time, A control method for a power receiving device, characterized in that, in the communication step, when a response signal from the power transmitting device to the specified signal load-modulated based on the modulation index changed by the control step is received, a signal for requesting power transmission according to the position of the power receiving device is transmitted to the power transmitting device.

11. A program for causing a computer to function as the power receiving device according to claim 1 .

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