Power receiving device and radio power transmission system

Abstract

To detect abnormality even when a light load is connected to a power receiving circuit.SOLUTION: A power receiving device of the present invention wirelessly receives electric power from a power transmitting device, and has: a power receiving antenna; a plurality of power receiving circuits that each have a switching element and that are connected in parallel to each other; a plurality of current detection means that are arranged respectively in the plurality of power receiving circuits and that each output a detection value; comparison means that compares the detection values output from the plurality of current detection means to each other; and abnormality determination means that determines whether abnormality occurs on the basis of a result of the comparison made by the comparison means.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power receiving device that wirelessly receives power from a power transmitting device, and a wireless power transmission system. [Background technology]

[0002] In recent years, wireless power transmission systems that wirelessly supply power of several kW or more to devices such as EVs (electric vehicles) have been researched and developed. In wireless power transmission systems of several kW or more, a large current flows through the switching elements of the power transmission circuit and the power receiving circuit. For example, Patent Document 1 describes a system in which multiple power transmission circuits are connected in parallel to distribute the current flowing through the switching elements. In addition, in wireless power transmission systems, it is necessary to promptly detect an abnormal state when it occurs. For example, Patent Document 2 describes a configuration that detects when the current value of the current flowing through the power receiving circuit exceeds a threshold value and determines an abnormality. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2016-038737A1 [Patent Document 2] JP 2016-220532 A Summary of the Invention [Problem to be solved by the invention]

[0004] This paper describes a wireless power transmission system in which multiple power receiving circuits are connected in parallel to distribute the current flowing through the switching elements of the power receiving circuits. In the above system, for example, when one of the switching elements in the power receiving circuits becomes abnormal and the ON resistance increases or becomes open, the prior art described in Patent Document 2 may not be able to detect the abnormality.

[0005] Specifically, when the load connected to the power receiving circuit is light (high resistance), the current flowing through the power receiving circuit is small, so even if an abnormality occurs in the switching element, the current does not exceed the threshold and the abnormality in the switching element cannot be detected.It is only when the load changes from a light to a heavy (low resistance) state that the current exceeds the threshold and the abnormality can be detected.

[0006] In view of the above problems, an object of the present invention is to detect an abnormality even when the load connected to a power receiving circuit is light. [Means for solving the problem]

[0007] The present invention provides a power receiving device that wirelessly receives power from a power transmitting device, a power receiving antenna; and a plurality of power receiving circuits each having a switching element and connected in parallel with each other; The power supply circuit is characterized in having a plurality of current detection means arranged in each of the plurality of power receiving circuits and outputting detected values, a comparison means for comparing the detection values ​​output from the plurality of current detection means with each other, and an abnormality determination means for determining whether or not an abnormality has occurred based on the comparison result of the comparison means. Effect of the Invention

[0008] According to the present invention, it is possible to detect an abnormality even when the load connected to the power receiving circuit is light. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a wireless power transmission system according to a first embodiment. [Diagram 2] Configuration diagram of a power receiving circuit according to the first embodiment [Diagram 3] Configuration diagram of a determination unit according to the first embodiment [Figure 4] Current waveform diagram according to embodiment 1 [Diagram 5] Anomaly detection flow chart according to the first embodiment [Figure 6] 1 is a schematic diagram of a wireless power transmission system according to a second embodiment. [Figure 7] Current waveform diagram according to the second embodiment [Figure 8] 1 is a schematic diagram of a wireless power transmission system according to a third embodiment. [Figure 9] 13 is a diagram showing the configuration of a determination unit according to the third embodiment. [Figure 10] Table of Simulation Results for the Third Embodiment [Figure 11] Anomaly detection flow chart according to the third embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Embodiment 1] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] In addition, the wireless power transmission system of the present invention will be described as an example of a method called electromagnetic induction / magnetic resonance, which transmits power using a magnetic field or both an electric field and a magnetic field, but it is also applicable to an electric field coupling method, which transmits power mainly using an electric field.

[0012] A configuration diagram of a wireless power transmission system described in this embodiment is shown in Fig. 1. The wireless power transmission system 100 is composed of a power transmitting unit 101 having a power transmitting antenna 110, a power transmitting circuit 111, and a DC power supply 112, a power receiving antenna 120, power receiving circuits 121 and 122, a determination unit 123, a power receiving unit 102 having a smoothing capacitor 124, and a load 103.

[0013] The power transmitting circuit 111 is configured with a known switching circuit used when an electromagnetic induction or magnetic resonance method is adopted. The power transmitting circuit 111 converts a DC voltage supplied from a DC power source 112 into an AC voltage having a frequency of a clock signal (hereinafter referred to as CLK) generated by a clock generating circuit (not shown) and outputs the AC voltage to the power transmitting antenna 110. The power receiving antenna 120 is coupled to the power transmitting antenna 110 and receives the AC voltage. The power receiving circuits 121 and 122 are also configured with a known rectifier circuit used when an electromagnetic induction or magnetic resonance method is adopted, and convert the received AC voltage into a DC voltage and supply it to the load 103.

[0014] Next, the configuration of the power receiving circuits 121 and 122 will be described by taking as an example a full-wave rectifier circuit using diodes as switching elements. Note that this is also applicable to synchronous rectification using MOSFETs or GAN-FETs. Figure 2 shows the configuration of the power receiving circuit described in this embodiment. The power receiving circuit is composed of switching elements 201, 202, 203, and 204, capacitors 205, 206, 207, and 208, and current sensors 209, 210, 211, and 212.

[0015] The current sensor is connected in series with each switching element, detects the current flowing through each switching element, and outputs a voltage value proportional to the current. Specifically, the current sensor 209 in the power receiving circuit 121 outputs Sense_out1, the current sensor 210 outputs Sense_out2, the current sensor 211 outputs Sense_out3, and the current sensor 212 outputs Sense_out4. The current sensor 209 in the power receiving circuit 122 outputs Sense_out5, the current sensor 210 outputs Sense_out6, the current sensor 211 outputs Sense_out7, and the current sensor 212 outputs Sense_out8. Here, the current sensor outputs a voltage value as the detection value, but it is also possible to output a value proportional to the current value or a value indicating the current value as the detection value. Each of the multiple current sensors is mounted at approximately the same position of each power receiving circuit connected in parallel, and it is desirable that the wiring pattern is the same for the power receiving circuits if possible. The capacitor connected in parallel with the switching element is for adjusting the ON time of the switching element, and the constant is determined according to the value of the rated load. If the parasitic capacitance of the switching element is sufficiently large, or if there is no need to adjust the ON time of the switching element, the capacitor does not need to be connected.

[0016] The configuration of the determination unit 123 described in this embodiment is shown in FIG. 3. The determination unit 123 is composed of comparison units 301, 302, 303, 304, and an abnormality determination unit 305. The comparison unit 301 compares the values ​​of Sense_out1 and 5, the comparison unit 302 compares the values ​​of Sense_out2 and 6, the comparison unit 303 compares the values ​​of Sense_out3 and 7, and the comparison unit 305 compares the values ​​of Sense_out4 and 8. Based on the comparison result, the abnormality determination unit determines whether an abnormality has occurred, and if an abnormality has occurred, an alert signal (not shown) is output. Note that the signal input to the comparison unit may be the instantaneous value of Sense_out1 to 8, or may be a value obtained by taking a time average. The following describes the case where a time average is obtained, but detection is possible in the same way when an instantaneous value is obtained.

[0017] A part or all of the above-mentioned functional units can be configured as circuits within the power receiving circuits 121 and 122.

[0018] FIG. 4 shows the results of a simulation of the waveform of the current flowing through the current sensor 209 in the power receiving circuits 121 and 122 in the configurations of FIG. 1 and FIG. 2. Note that in the simulation of FIG. 4, it is assumed that the switching elements 202, 203, and 204 in the power receiving circuit 121 and the switching elements 201, 202, 203, and 204 in the power receiving circuit 122 are all operating normally. The simulation was performed by changing only the operation of the switching element 201 in the power receiving circuit 121. Note that normal operation of a switching element means that the forward voltage or ON resistance is at a standard value. Also, this simulation was performed using a simple method of changing the ON resistance of a diode.

[0019] Fig. 4(a) shows the simulation result of the current waveform when the switching element 201 of the power receiving circuit 121 is operating normally. As shown in Fig. 4(a), a current flows while the switching element is ON, and it can be seen that the waveforms of the currents flowing through the current sensors 201 in the power receiving circuits 121 and 122 overlap and are completely identical.

[0020] When comparing the current values ​​during the period when current flows through current sensor 209 in power receiving circuit 121 and current sensor 209 in power receiving circuit 122, the difference is 0. Also, when comparing the average current values ​​during the period when current flows through current sensor 209, the divided value is 1.

[0021] 4(b) shows the results of a simulation in which the ON resistance of the switching element 201 of the power receiving circuit 121 is larger within the range of manufacturing variation than that of the switching element 201 of the power receiving circuit 122. The waveform of the current flowing through the current sensor 201 of the power receiving circuit 121 is shown as 401, and the waveform of the current flowing through the current sensor 209 of the power receiving circuit 122 is shown as 402.

[0022] Comparing the current values ​​of the current sensor 209 in the power receiving circuit 121 and the current sensor 209 in the power receiving circuit 122, it is found that less current flows through the switching element with a large ON resistance. The average current value during the period when the switching element is ON and current flows is 5.41 A for 401 and 4.71 A for 402, and comparing the average values ​​reveals that the division value is approximately 0.87 (=4.71 / 5.41).

[0023] 4(c) shows the results of a simulation in which an abnormality occurs in the switching element 201 of the power receiving circuit 121 and the switching element 201 goes into an open state. 403 shows the waveform of the current flowing through the current sensor 201 of the power receiving circuit 121, and 404 shows the waveform of the current flowing through the current sensor 209 of the power receiving circuit 122. It can be seen that the current waveform of 403 is always approximately 0 A. Comparing the current values ​​of the current sensor 201 of the power receiving circuit 121 and the current sensor 209 of the power receiving circuit 122, the difference is a very large value of approximately 20 A at most. Also, comparing the average value of the current during the period when it flows through the current sensor 209, the division value is a very small value of less than 1 / 1000.

[0024] Therefore, as can be seen from the simulation results in FIG. 4, it is possible to detect an abnormality in the power receiving circuit by comparing the current values ​​flowing through the current sensors. In addition, in this embodiment, the simulation results when the load resistance is 10Ω are shown. The absolute value of the current flowing through the current sensor 209 of the power receiving circuit 121 and the current sensor 209 of the power receiving circuit 122 is inversely proportional to the magnitude of the load resistance. However, the ratio of the current values ​​flowing through the current sensor 209 of the power receiving circuit 121 and the current sensor 209 of the power receiving circuit 122 does not change substantially even if the load changes. For example, the ratio of the average current when the load is 10Ω in FIG. 4(b) is 0.87, while the ratio when the load is 20Ω is 0.88, which is almost the same. Therefore, if a predetermined value is set as a threshold and the ratio between the current sensors falls below the threshold, it is possible to determine that an abnormality has occurred regardless of the magnitude of the load.

[0025] In this embodiment, the configuration is described for the case where the number of power receiving circuits is two, but the number of power receiving circuits may be three or more. In this case, the maximum and minimum current values ​​of each current sensor are selected, and the minimum value is used as the numerator and the maximum value is used as the denominator. If the divided value is equal to or greater than a threshold value, it is determined to be normal, and if it is less than the threshold value, it is determined to be abnormal.

[0026] Even if the ON resistance of the switching elements varies within the range of normal manufacturing variations, as the number of power receiving circuits increases, the minimum and maximum current values ​​of each current sensor tend to become smaller.

[0027] For example, in the configuration of Figure 1, when five power receiving circuits are connected in parallel, the minimum / maximum current value is approximately 0.6. When the number of power receiving circuits is 10, the minimum / maximum current value is approximately 0.58. Considering a practical system, a maximum of 10 power receiving circuits is appropriate. Also, considering that there may be large manufacturing variations depending on the type of switching element, a threshold value of 0.5 is appropriate.

[0028] Figure 5 shows the flow from when the wireless power transmission system starts up, to when an abnormality is detected and when it is notified to the user. First, the user or an external device turns on the power supply to the wireless power transmission system, and the comparison unit acquires an output value proportional to the current value flowing through each current sensor implemented in the power receiving circuit. The comparison unit calculates the minimum and maximum output values ​​of each current sensor and sends them to the abnormality detection unit. If all output values ​​of the comparison unit are equal to or greater than the threshold, it is determined to be normal, and if even one output value is below the threshold, it is determined to be abnormal. The comparison unit with an output below the threshold is identified, and the switching element connected in series to the current sensor with the smallest output value among the current sensors connected to that comparison unit is determined to be abnormal. Finally, the user is notified of the abnormal switching element.

[0029] [Embodiment 2] In the first embodiment, a system in which current sensors are arranged in series with all switching elements is described, but in this embodiment, a configuration in which current sensors are connected between a power receiving circuit and a load is described. With this configuration, the number of current sensors can be reduced compared to the first embodiment.

[0030] A configuration diagram of a wireless power transmission system described in this embodiment is shown in Fig. 6. The same components as those in Fig. 1 are assigned the same reference numerals, and current sensors 601, 602, 603, and 604 are connected to the output parts of the power receiving circuits 121 and 122 and to GND, respectively.

[0031] In this embodiment, the multiple current sensors are mounted in approximately the same position on each of the parallel-connected power receiving circuits, and it is desirable that the wiring patterns are the same for the power receiving circuits if possible. Current sensor 601 outputs Sense_out9, current sensor 602 outputs Sense_out10, current sensor 603 outputs Sense_out11, and current sensor 604 outputs Sense_out12. The specific configuration of power receiving circuits 121 and 122 is the configuration of the power receiving circuit in Fig. 2 shown in embodiment 1 except that current sensors 209, 210, 211, and 212 are removed. The configuration of determination unit 123 is the configuration of Fig. 3 shown in embodiment 1 except that comparison units 303 and 304 are removed.

[0032] Fig. 7 shows the results of a simulation of the waveforms of the currents flowing through the current sensors 601 and 603 in the configuration of Fig. 6. As in the simulation of embodiment 1, it is assumed that the switching elements 202, 203, and 204 in the power receiving circuit 121 and the switching elements 201, 202, 203, and 204 in the power receiving circuit 122 are all operating normally. The simulation was performed by changing only the operation of the switching element 201 in the power receiving circuit 121.

[0033] FIG. 7(a) shows the state when the switching element 201 in the power receiving circuit 121 is normal. It can be seen that the current waveforms flowing through the current sensors 601 and 603 overlap and are completely identical. Also, unlike the simulation result in FIG. 4, it can be seen that a current flows through the current sensor 601 during both the period when the switching element 201 is ON and the period when the switching element 204 is ON. FIG. 7(b) shows the state when the ON resistance of the switching element 201 in the power receiving circuit 121 is large within the range of manufacturing variations. The current waveform flowing through the current sensor 601 is shown in 701, and the current waveform flowing through the current sensor 603 is shown in 702. It can be seen that the current waveforms flowing through the current sensors 601 and 603 are different only during the period when the switching element 201 is ON, and the waveforms overlap and are completely identical during the period when the switching element 204 is ON, as in FIG. 7(a). Furthermore, FIG. 7(c) shows the state when an abnormality occurs in the switching element 201 in the power receiving circuit 121 and the ON resistance becomes abnormally large. The waveform of the current flowing through current sensor 601 is shown as 703, and the waveform of the current flowing through current sensor 603 is shown as 704. It can be seen that the current waveform 703 is approximately 0 only during the period when switching element 201 is ON, which is different from the normal case. Also, as in Fig. 7(b), it can be seen that the waveforms overlap and are completely identical during the period when switching element 204 is ON.

[0034] As can be seen from the simulation results in FIG. 7, different switching elements are turned on depending on the period. Therefore, in order to detect an abnormality in a switching element, it is necessary to detect which switching element is turned on during which period. For example, detection is possible by placing a high resistance in parallel with the switching element and transmitting the voltage value generated across the high resistance to the MCU. Therefore, even in the configuration shown in this embodiment, it is possible to minimize the number of current sensors and detect an abnormality in a switching element by comparing the minimum and maximum current values ​​acquired by the current sensors.

[0035] [Embodiment 3] In this embodiment, a configuration that can detect even when there are multiple abnormal power receiving circuits will be described. Note that, as in the first and second embodiments, this embodiment can also be applied to a case where there are two power receiving circuits and one of them is abnormal.

[0036] FIG. 8 shows the configuration in FIG. 6 when there are three power receiving circuits. The same components as in FIG. 6 are given the same reference numerals, and the power receiving circuit 181 and current sensors 805 and 806 are added. The current sensor 805 outputs Sense_out13, and the current sensor 806 outputs Sense_out14. FIG. 9 shows the configuration of the determination unit 123 of this embodiment. It is composed of average value calculation units 901 and 902, comparison units 903 and 904, and an abnormality determination unit 305. The same components as in FIG. 3 shown in the first embodiment are given the same reference numerals.

[0037] The average value calculation unit 901 calculates the average value of Sense_out9, 11, and 13, and 902 calculates and outputs the average values ​​AVG_ALL1 and AVG_ALL2 of Sense_out10, 12, and 14. The comparison unit 903 compares Sense_out9, 11, and 13 with AVG_ALL1, and the comparison unit 904 compares Sense_out10, 12, and 14 with AVG_ALL2, and the abnormality determination unit determines whether or not an abnormality has occurred based on the comparison result. If an abnormality has occurred, an alert signal (not shown) is output. The output signal of the current sensor input to the comparison unit and the average value calculation unit may be an instantaneous value or a value obtained by acquiring a time average. The following describes the case where a time average is acquired, but detection is possible in the same way when an instantaneous value is acquired.

[0038] It is assumed that the switching elements 201, 202, 203, and 204 in the power receiving circuit 121 and the switching elements 202, 203, and 204 in the power receiving circuits 122 and 181 are all operating normally. A simulation was performed by changing only the operation of the switching element 201 in the power receiving circuits 122 and 181. Regarding the current flowing through the current sensors 601, 603, and 805, the simulation results of the average current during the period when the switching element 201 is ON are shown in the table of Fig. 10. In addition, the average value (AVG_ALL1) of the average current flowing through each current sensor is shown.

[0039] First, case 1 is a simulation result when the switching element 201 in the power receiving circuits 121 and 181 is operating normally, and the current value flowing through the three current sensors matches AVG_ALL1. Case 2 is a simulation result when the switching element 201 in the power receiving circuits 121 and 181 has a large ON resistance within the range of manufacturing variation. Comparing the value with AVG_ALL1, "average current of current sensor 603 or 805 / AVG_ALL1" is approximately 0.86. Case 3 is a simulation result when the switching element 201 in the power receiving circuit 121 is within the range of manufacturing variation, an abnormality occurs in the switching element 201 in the power receiving circuit 181, and the ON resistance is abnormally large. Here, the simulation result is shown when the switching element in the power receiving circuit 181 has a larger ON resistance than the switching element in the power receiving circuit 121. Comparing the values ​​with AVG_ALL1, "average current of current sensor 603 / AVG_ALL1" is 1.02, and "average current of current sensor 805 / AVG_ALL1" is 0.30. Case 4 is a simulation result in which an abnormality occurs in both switching element 201 in power receiving circuit 121 and switching element 201 in power receiving circuit 181, resulting in an abnormally large ON resistance. Comparing the values ​​with AVG_ALL1, "average current of current sensor 603 or 805 / AVG_ALL1" is approximately 0.28.

[0040] As in the first embodiment, when the number of power receiving circuits increases, the value of each current sensor average current ÷ AVG_ALL1 or 2 tends to decrease even if the ON resistance of the switching elements varies within the range of normal manufacturing variations. For example, when the number of power receiving circuits is 10, the value of each current sensor average current ÷ AVG_ALL1 or 2 is 0.67. Considering a practical system, a maximum of about 10 power receiving circuits is appropriate, and considering that manufacturing variations are large depending on the type of switching element, the threshold value of each current sensor average current ÷ AVG_ALL1 or 2 is appropriate to be 0.6.

[0041] FIG. 11 shows a flow of the wireless power transmission system from starting up to detecting an abnormality and notifying the user. First, the user or an external device turns on the power supply of the wireless power transmission system, and the comparison unit acquires an output value proportional to the current value flowing through each current sensor implemented in the power receiving circuit. The average value (AVG_ALL) of the acquired values ​​is calculated, and the calculation result is compared with the output value of each current sensor and transmitted to the abnormality detection unit. If all output values ​​of the comparison unit are greater than the threshold, it is determined to be normal, and if even one output value is smaller, it is determined to be abnormal. The current sensor with an output smaller than the threshold is identified, and it is determined that an abnormality has occurred in the power receiving circuit to which the current sensor is connected. Furthermore, it is determined that an abnormality has occurred in the switching element connected in series with the current sensor. At this time, two switching elements are candidates, so the switching element can be identified by monitoring the voltage value generated across the high resistance shown in the second embodiment. Finally, the user is notified of the switching element in which an abnormality has occurred.

[0042] In the first, second and third embodiments, the simulation results are shown as current waveforms, but the output value of the current sensor is, for example, an analog voltage value proportional to the current value. The voltage value can be converted to digital data by an AD converter in the MCU and processed.

[0043] In the first, second and third embodiments, the comparison unit determines that an abnormality has occurred when the division of the output values ​​of the current sensors or the division of the output of each current sensor and the average value is greater than a threshold value. However, it is not limited to division, and an abnormality may also be determined when the difference is greater than a threshold value.

[0044] In the first, second and third embodiments, the sampling period for acquiring the output value of the current sensor is set to a period shorter than about 1 / 40 of the period of the CLK frequency, so that an accurate output value can be acquired.

[0045] In the first, second and third embodiments, simulation results are shown for a case where the power receiving circuit is a full-wave rectifier circuit. However, abnormalities can also be detected using the above concept with other circuit configurations, such as a half-wave rectifier circuit or a voltage doubler rectifier circuit.

Claims

1. A power receiving device that wirelessly receives power from a power transmission device, Receiving antenna and Multiple power receiving circuits connected to the aforementioned power receiving antenna and connected in parallel to one another, Each of the aforementioned multiple power receiving circuits is provided with a plurality of current detection means for detecting the current flowing through the power receiving circuit, Multiple output means that output values ​​related to the current detected by the multiple detection means, A comparison means for comparing the values ​​output from the plurality of output means with each other, A power receiving device characterized by having an abnormality determination means that determines whether or not an abnormality has occurred in at least one of the power receiving circuits based on the comparison results of the comparison means.

2. The power receiving device according to claim 1, characterized in that the abnormality determination means determines that an abnormality has occurred when the values ​​output from the plurality of output means, which are arranged at substantially the same position in the plurality of power receiving circuits, are different from each other.

3. The abnormality determination means calculates a division value using the smaller value and the larger value as the denominator from the values ​​output from the plurality of current detection means arranged at substantially the same position in each of the plurality of power receiving circuits, and determines that the abnormality has occurred if the division value is less than a threshold value, as described in claim 2.

4. The power receiving device according to claim 3, characterized in that the threshold value is 0.

5.

5. An average value calculation means for calculating the average value of the values ​​output from the multiple current detection means arranged at substantially the same position in each of the multiple power receiving circuits, The power receiving device according to claim 1, characterized in that the abnormality determination means determines that an abnormality has occurred when the average value and at least one of the values ​​output from the plurality of current detection means are different.

6. The power receiving device according to claim 5, characterized in that the abnormality determination means calculates a division value with at least one of the values ​​output from the plurality of current detection means as the numerator and the average value as the denominator, and determines that the abnormality has occurred if the division value is less than a threshold.

7. The power receiving device according to claim 6, characterized in that the threshold value is 0.

6.

8. The power receiving device according to any one of claims 1 to 7, characterized in that the plurality of current detection means are arranged in the output section of the power receiving circuit and GND.

9. Each of the plurality of power receiving circuits has a switching element, The power receiving device according to any one of claims 1 to 7, characterized in that the plurality of current detection means are connected in series with the switching element.

10. A power transmission device that transmits electricity wirelessly, A power receiving device that wirelessly receives power from the aforementioned power transmission device, Receiving antenna and Multiple power receiving circuits connected to the aforementioned power receiving antenna and connected in parallel to one another, Each of the aforementioned multiple power receiving circuits is provided with a plurality of current detection means for detecting the current flowing through the power receiving circuit, Multiple output means that output values ​​related to the current detected by the multiple detection means, A comparison means for comparing the values ​​output from the plurality of output means with each other, A power receiving device characterized by having an abnormality determination means that determines whether or not an abnormality has occurred in at least one of the power receiving circuits based on the comparison result of the comparison means, A wireless power transmission system characterized by having the following features.

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