Power receiving device

Abstract

A power receiving device (100) for receiving first AC power in a non-contact manner comprises: a first resonance circuit (110); a power conversion circuit (120); a battery (130); a second resonance circuit (140) connected to an AC power input unit in the power conversion circuit; a battery sensor (160); a power receiving sensor (180); and a control circuit (150). In the power conversion circuit, first AC power (AC1) supplied from the first resonance circuit (110) can be converted to first DC power and supplied to the battery, and second DC power supplied from the battery can be converted to second AC power and supplied to the second resonance circuit. The control circuit performs the conversion of the second DC power and the supply of the result to the second resonance circuit if the temperature detected by the battery sensor is included in a predetermined first range.

Description

Powered Device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from Patent Application No. 2023-209740, filed December 13, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a power receiving device.

[0003] Batteries may have a temperature suitable for use. For example, lithium ion batteries are preferably used at around 20 degrees Celsius. Lithium ion batteries are prone to deterioration when used in low-temperature conditions below approximately 0 degrees Celsius. For this reason, there is a technology for raising the temperature of a battery to a temperature suitable for use. In Patent Document 1, an AC power supply is connected to a battery serving as a load in a contactless power transfer system. The AC power supply in Patent Document 1 raises the temperature of the battery by applying current to the battery. However, Patent Document 1 does not disclose any specific application examples of the AC power supply connected to the battery in the contactless power transfer system.

[0004] Patent No. 4081855

[0005] However, adding an AC power supply poses the problem of increased cost and size for the circuit that heats the battery.

[0006] The present disclosure can be realized as the following aspects. According to a first aspect of the present disclosure, there is provided a power receiving device that receives first AC power in a contactless manner using a magnetic field. The power receiving device includes: a first resonant circuit including a power receiving coil that receives the first AC power, the first resonant circuit having a first resonant frequency; a power conversion circuit that bidirectionally converts AC power to DC power; a battery that is charged with first DC power supplied via the power conversion circuit; a second resonant circuit connected to an input section of AC power in the power conversion circuit, the second resonant circuit having a second resonant frequency different from the first resonant frequency; a battery sensor that measures the temperature of the battery; a power receiving sensor that detects reception of the first AC power; and a control circuit that controls the power receiving device. The power conversion circuit converts the first AC power supplied from the first resonant circuit into the first DC power by controlling the power conversion circuit in accordance with the first resonant frequency. and supplying the converted second DC power to the battery, and by controlling the power conversion circuit in accordance with the second resonant frequency, the second DC power supplied from the battery can be converted into second AC power and supplied to the second resonant circuit, and the control circuit performs the conversion of the second DC power and the supply of the second DC power to the second resonant circuit when the power receiving sensor is not receiving the first AC power and the temperature detected by the battery sensor is within a predetermined first range, and does not perform the conversion of the second DC power and the supply of the second DC power to the second resonant circuit when the power receiving sensor is not receiving the first AC power and the temperature detected by the battery sensor is within a second range higher than the first range.

[0007] In this configuration, when the battery temperature is within a first range while the battery is not receiving the first AC power, the power conversion circuit converts power between the battery and the second resonant circuit. When the battery is energized, the battery temperature increases. That is, the power receiving device of the present disclosure can control the battery temperature increase using the power conversion circuit. For example, when the second resonant circuit is composed only of a reactor and a capacitor, the power receiving device of the present disclosure can be configured more simply than a configuration in which an AC power source is used to increase the battery temperature. Furthermore, the power receiving device of the present disclosure increases the battery temperature using a second resonant frequency that is different from the first resonant frequency of the first resonant circuit that receives power, thereby preventing the power receiving coil from emitting a magnetic field. Therefore, the power receiving device of the present disclosure can prevent an increase in cost and size of the circuit that increases the battery temperature.

[0008] According to a second aspect of the present disclosure, there is provided a power receiving device that receives AC power contactlessly using a magnetic field, the power receiving device including: a resonant circuit including a power receiving coil that receives the AC power; a power conversion circuit that converts the AC power to DC power; a battery that charges the DC power; a smoothing capacitor connected in parallel between the power conversion circuit and the battery; a switch connected in series to the smoothing capacitor; a battery sensor that measures the temperature of the battery; and a control circuit that controls the power receiving device, wherein the control circuit controls the switch to an off state when the battery sensor detects a first temperature that is within a predetermined first range for the temperature, and controls the switch to an on state when the battery sensor detects a second temperature that is within a second range higher than the first range.

[0009] With this configuration, the power receiving device of the present disclosure smooths the current flowing through the battery using the smoothing capacitor when the switch is on. The power receiving device of the present disclosure does not smooth the current flowing through the battery when the switch is off. That is, when the switch is off, a current including frequency components of AC power flows through the battery. The battery is heated more by the current including frequency components than by the current not including frequency components. Therefore, by adding only a switch to the smoothing capacitor, the power receiving device of the present disclosure has a simpler configuration than a configuration using an AC power source to heat the battery. That is, the power receiving device of the present disclosure can prevent an increase in cost and size of the circuit that heats the battery.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an explanatory diagram showing the configuration of a contactless power transfer system according to a first embodiment, Fig. 2 is an explanatory diagram showing the operation of a power receiving device that charges a battery, Fig. 3 is an explanatory diagram showing the operation of a power receiving device that charges a battery, Fig. 4 is an explanatory diagram showing the operation of a power receiving device that heats up the battery, Fig. 5 is an explanatory diagram showing the operation of a power receiving device that heats up the battery, Fig. 6 is a flowchart showing a control method for a power receiving device, and Fig. 7 is an explanatory diagram showing a contactless power transfer system according to a second embodiment.

[0011] A. First Embodiment: A-1. Device Configuration: A contactless power transfer system 10 shown in Fig. 1 supplies power to a battery 130 in a contactless manner using a magnetic field. The contactless power transfer system 10 includes a power transmitting device 200 and a power receiving device 100. The contactless power transfer system 10 supplies power from the power transmitting device 200 to the power receiving device 100 in a contactless manner. The contactless power transfer system 10 supplies power in a contactless manner to a battery 130 mounted on a vehicle, for example.

[0012] The power transmitting device 200 uses a magnetic field to contactlessly supply AC power to the power receiving device 100. The power transmitting device 200 includes an AC power supply device 210 and a power transmitting resonant circuit 220.

[0013] The AC power supply device 210 supplies AC power of a predetermined operating frequency to the power transmission resonant circuit 220. The AC power supply device 210 includes a power supply circuit and a power transmission circuit. The power supply circuit is, for example, an AC / DC converter circuit, and converts AC power supplied from a power grid into DC power. The power transmission circuit is an inverter that converts DC power supplied from the power supply circuit into AC power at the operating frequency. The operating frequency is, for example, 85 kHz, and is set using a predetermined power transmission frequency stipulated by the Radio Law and the like. Note that the operating frequency is also a frequency corresponding to the resonant frequency of the power transmission resonant circuit 220, which will be described later.

[0014] In a resonant state, the power transmitting resonant circuit 220 is magnetically coupled to the power receiving coil 111. The power transmitting resonant circuit 220 includes a power transmitting coil 222 and a power transmitting resonant capacitor 221 connected in series to the power transmitting coil 222.

[0015] The power transmitting resonant capacitor 221 resonates the power transmitting resonant circuit 220 with AC power at the operating frequency when the power transmitting coil 222 and the power receiving coil 111 are magnetically coupled. That is, the capacitance of the power transmitting resonant capacitor 221 is set so that when the power transmitting coil 222 and the power receiving coil 111 are magnetically coupled, the operating frequency of the AC power supply device 210 and the resonant frequency of the power transmitting resonant circuit 220 approximately match.

[0016] The power transmitting coil 222 generates a magnetic field corresponding to the operating frequency of the AC power supply device 210. Furthermore, the power transmitting coil 222 transmits AC power to the power receiving coil 111 by magnetically coupling with the power receiving coil 111. In other words, the power transmitting coil 222 transmits power contactlessly by utilizing the electromagnetic induction phenomenon.

[0017] The power receiving device 100 receives AC power from the power transmitting device 200 in a contactless manner using a magnetic field. The AC power received by the power receiving coil 111 included in the power receiving resonant circuit 110 is referred to as first AC power AC1. The power receiving device 100 includes the power receiving resonant circuit 110, a power conversion circuit 120, a battery 130, a temperature raising circuit 140, a battery sensor 160, a control circuit 150, a smoothing capacitor 170, and a power receiving sensor 180.

[0018] The power receiving resonant circuit 110 includes a power receiving coil 111 and a power receiving resonant capacitor 112 connected in series to the power receiving coil 111. The power receiving resonant circuit 110 has a first resonant frequency. In this specification, the power receiving resonant circuit 110 is also referred to as a first resonant circuit 110.

[0019] The power receiving coil 111 is magnetically coupled to the power transmitting coil 222 by receiving the magnetic field emitted by the power transmitting coil 222. The power receiving coil 111 is used in a state facing the power transmitting coil 222, and is subjected to the magnetic field emitted by the power transmitting coil 222. As a result, the power receiving coil 111 receives the first AC power AC1 in a wireless manner.

[0020] The power receiving resonant capacitor 112 resonates the power receiving resonant circuit 110 with the first AC power AC1 when the power receiving coil 111 and the power transmitting coil 222 are magnetically coupled. That is, the capacitance of the power receiving resonant capacitor 112 is set so that when the power transmitting coil 222 and the power receiving coil 111 are magnetically coupled, the frequency of the first AC power AC1 and the first resonant frequency of the power receiving resonant circuit 110 approximately match.

[0021] In this embodiment, the power receiving resonant capacitor 112 includes a first capacitor 112P on the positive side and a second capacitor 112N on the negative side. By providing resonant capacitors on both the positive and negative sides, common mode noise can be suppressed.

[0022] The temperature raising circuit 140 is used to raise the temperature of the battery 130. The function of the temperature raising circuit 140 will be described in detail later. The temperature raising circuit 140 is composed of a reactor 141 and a capacitor 142 connected in series. The temperature raising circuit 140 has a second resonant frequency that is higher than the first resonant frequency of the power receiving resonant circuit 110. For example, the second resonant frequency is five times higher than the first resonant frequency. In other words, the temperature raising circuit 140 has a second resonant frequency that is different from the first resonant frequency of the power receiving resonant circuit 110. In this specification, the temperature raising circuit 140 is also referred to as the second resonant circuit 140.

[0023] The heating circuit 140 is connected in parallel between the power receiving resonant circuit 110 and the power conversion circuit 120. That is, the heating circuit 140 is connected to the output part of the power receiving resonant circuit 110 and to the input part of the AC power in the power conversion circuit 120.

[0024] The power conversion circuit 120 converts AC power and DC power bidirectionally. More specifically, the power conversion circuit 120 is a full-bridge circuit that uses four MOSFETs (metal-oxide-semiconductor field-effect transistors) as switching elements. The power conversion circuit 120 includes two leg circuits: a first leg circuit 121 and a second leg circuit 122. The switch Sw is driven by receiving a voltage at its gate in response to a command from the control circuit 150. In this specification, the power conversion circuit 120 is also referred to as a synchronous rectification circuit 120.

[0025] In the leg circuit, two switches Sw are connected in series. Furthermore, the leg circuit connects the positive line Lp and negative line Ln of the DC power. One of the output terminals of the temperature raising circuit 140 is connected between the two switches Sw of the leg circuit. In other words, the position of the input terminal of the power conversion circuit 120 is between the two switches Sw of the leg circuit. Note that with regard to the input terminal of the power conversion circuit 120, the leg circuit having terminal P1 is the first leg circuit 121. The leg circuit having terminal P2 is the second leg circuit 122.

[0026] As described above, the power conversion circuit 120 converts AC power and DC power bidirectionally. The conversion by the power conversion circuit 120 will be described in detail later.

[0027] The smoothing capacitor 170 is connected in parallel between the output of the power conversion circuit 120 and the battery 130. The smoothing capacitor 170 smoothes the DC current and DC voltage supplied to the battery 130.

[0028] The power receiving sensor 180 detects the reception of the first AC power AC1. The power receiving sensor 180 detects the reception of the first AC power AC1 by detecting the current at the output section of the power conversion circuit 120. More specifically, the power receiving sensor 180 detects the current flowing to the battery 130 between the output section of the power conversion circuit 120 and the battery 130. In other words, the power receiving sensor 180 is a current sensor that measures the current value of the DC power.

[0029] The battery 130 is charged by the first DC power DC1 supplied via the power conversion circuit 120. Furthermore, the battery 130 outputs the stored power as the second DC power DC2. The function of the battery 130 will be described in detail later.

[0030] The battery 130 is, for example, a lithium-ion battery. Lithium-ion batteries are prone to deterioration when used in low-temperature conditions below approximately 0 degrees Celsius. Lithium-ion batteries are preferably used at around 20 degrees Celsius. The heating circuit 140 heats up the battery 130 to a temperature suitable for use.

[0031] The battery sensor 160 measures the temperature of the battery 130. For example, if the battery 130 is a lithium ion battery, the battery sensor 160 measures the temperature of the cells of the lithium ion battery. The battery sensor 160 is connected to the control circuit 150. The temperature obtained by the battery sensor 160 is output to the control circuit 150.

[0032] The control circuit 150 controls the power receiving device 100. The control circuit 150 includes a control unit 151 and a drive circuit 152.

[0033] The drive circuit 152 drives the switch Sw. More specifically, the drive circuit 152 outputs power required to drive the switch Sw in response to a command from the control unit 151. The drive circuit 152 is connected to the gates of all the switches Sw in the power conversion circuit 120. That is, the drive circuit 152 drives the switch Sw by applying a gate voltage required to turn the switch Sw on and off to the gate of the switch Sw. Note that in FIG. 1 , the connection between the drive circuit 152 and the gate is omitted to facilitate understanding of the technology.

[0034] The control unit 151 generates a signal that controls the on / off operation of the switch Sw. The control unit 151 is mainly configured, for example, by a microcomputer, and includes a CPU, ROM, RAM, etc. (not shown). The control unit 151 is connected to a battery sensor 160. The control by the control unit 151 will be described in detail later.

[0035] A-2. Charging and temperature increase of the battery by the power receiving device: A method for charging the battery 130 in the power receiving device 100 will be described using Figures 2 and 3. To facilitate understanding of the technology, the power transmitting device 200 is omitted from Figures 2 and 3. The power receiving device 100 receives first AC power AC1 via the power receiving coil 111. The arrow AC1 in Figure 2 indicates the direction in which the first AC power AC1 is supplied.

[0036] The power conversion circuit 120 performs rectification according to the first resonant frequency. Arrow Ic in FIG. 2 represents the flow of positive current in one cycle of the first AC power AC1. Arrow Ic in FIG. 3 represents the flow of negative current in one cycle of the first AC power AC1. That is, the power conversion circuit 120 rectifies the current of the first AC power AC1 at the first resonant frequency via the switches Sw in each of the two leg circuits. As a result, the first AC power AC1 is converted into first DC power DC1. Arrow DC1 in FIG. 2 indicates the direction in which the first DC power DC1 is supplied. The battery 130 is charged with the first DC power DC1.

[0037] That is, by controlling the power conversion circuit 120 according to the first resonant frequency, the power conversion circuit 120 can convert the first AC power AC1 supplied from the first resonant circuit 110 into first DC power DC1 and supply it to the battery 130.

[0038] A method for raising the temperature of the battery 130 in the power receiving device 100 will be described using Figures 4 and 5. As with Figures 2 and 3, the power transmitting device 200 is omitted from Figures 4 and 5. The temperature of the battery 130 is raised in a state in which the first AC power AC1 is not being received. The battery 130 outputs stored power as second DC power DC2. The arrow DC2 in Figures 4 and 5 indicates the direction in which the second DC power DC2 is supplied.

[0039] The power conversion circuit 120 converts power according to the second resonant frequency. The heating current Ir indicated by the arrow in FIG. 4 is the flow of current output from the battery 130, and represents the flow when the second AC power AC2 becomes a positive current. The heating current Ir indicated by the arrow in FIG. 5 is the flow of current output from the battery 130, and represents the flow when the second AC power AC2 becomes a negative current. The heating circuit 140 resonates at the second resonant frequency. Therefore, the power conversion circuit 120 operates the switch Sw at a drive frequency corresponding to the second resonant frequency. That is, the power conversion circuit 120 converts the second DC power DC2 into second AC power AC2 corresponding to the second resonant frequency via the switch Sw, which is driven at a drive frequency corresponding to the second resonant frequency. Therefore, the second AC power AC2 is supplied to the heating circuit 140. Since the second AC power AC2 corresponding to the second resonant frequency is not supplied to the power receiving resonant circuit 110 having the first resonant frequency, the power receiving coil 111 does not radiate a magnetic field.

[0040] Note that the heating circuit 140 does not consume power because it does not include a resistive element. Therefore, during one cycle of the second AC power AC2, the second AC power AC2 supplied to the heating circuit 140 returns to the battery 130. The current returning to the battery 130 flows in the opposite direction to the direction of the heating current Ir.

[0041] That is, by controlling the power conversion circuit 120 according to the second resonant frequency, the power conversion circuit 120 can convert the second DC power DC2 supplied from the battery 130 into second AC power AC2 and supply it to the heating circuit 140.

[0042] A-3. Control Method of Power Receiving Device: A control method of the power receiving device 100 will be described with reference to Fig. 6. The control circuit 150 detects the reception of the first AC power AC1 using the power receiving sensor 180. Furthermore, the control circuit 150 acquires the temperature of the battery 130 using the battery sensor 160. The control circuit 150 starts processing, for example, when the temperature of the battery 130 is acquired, provided that the first AC power AC1 is not being received.

[0043] In step S100 of FIG. 6 , the control circuit 150 determines whether or not the temperature of the battery 130 needs to be increased. More specifically, if the temperature detected by the battery sensor 160 is within a predetermined first range, the control circuit 150 proceeds to step S200. If the temperature detected by the battery sensor 160 is within a second range higher than the first range, the control circuit 150 terminates the process. The second range being higher than the first range means that the lower limit of the second range is higher than the upper limit of the first range. For example, in the case of a lithium-ion battery, the first range of temperatures is a range of temperatures lower than 0 degrees Celsius. The second range is a range of temperatures equal to or higher than 0 degrees Celsius.

[0044] In step S200 of FIG. 6 , the control circuit 150 performs or continues heating of the battery 130. Specifically, the control circuit 150 converts the second DC power DC2 and supplies it to the heating circuit 140. That is, the control circuit 150 controls the power conversion circuit 120 according to the second resonant frequency, thereby converting the second DC power DC2 into second AC power AC2 and supplying it to the heating circuit 140, as shown in FIGS. 4 and 5 . By passing a current through the battery 130, the battery 130 is heated. If the control circuit 150 is already heating the battery 130, it continues the heating. After heating the battery 130, the control circuit 150 returns the process to step S100. The control circuit 150 determines whether heating is necessary based on the heated temperature of the battery 130, and thereby heats the battery 130 to a temperature suitable for use of the battery 130.

[0045] In this configuration, when the battery 130 is not receiving the first AC power AC1 and the temperature of the battery 130 is within the first range, the power conversion circuit 120 converts power between the battery 130 and the second resonant circuit 140. When the battery 130 is energized, the temperature of the battery 130 increases. That is, the power receiving device 100 of the present disclosure can control the temperature increase of the battery 130 using the power conversion circuit 120. For example, when the second resonant circuit 140 is configured only with a reactor 141 and a capacitor 142, the power receiving device 100 of the present disclosure has a simpler configuration than a configuration in which an AC power source is used to increase the temperature of the battery 130. Furthermore, the power receiving device 100 of the present disclosure does not emit a magnetic field from the power receiving coil 111 by increasing the temperature at a second resonant frequency different from the first resonant frequency of the first resonant circuit 110 that receives power. Therefore, the power receiving device 100 according to the present disclosure can prevent an increase in cost and size of the circuit that raises the temperature of the battery 130 .

[0046] Furthermore, because the second resonant frequency is greater than the first resonant frequency, when raising the temperature of the battery 130 that is less likely to deteriorate in the case of a high-frequency current, such as a lithium-ion battery, the power receiving device 100 of the present disclosure can raise the temperature at a frequency more suitable for the battery 130. Furthermore, the higher the frequency, the smaller the passive elements of the reactor 141 and capacitor 142 that make up the circuit can be.

[0047] B. Second Embodiment In a contactless power supply system 10x of the second embodiment, the power receiving device 100x further includes a switch Swx connected in series to the smoothing capacitor 170. The switch Swx is, for example, a semiconductor relay. A control circuit 150x of the second embodiment controls the switch Swx connected in series to the smoothing capacitor 170. However, the power receiving device 100x of the second embodiment does not include the temperature raising circuit 140 or the power receiving sensor 180. Furthermore, in a power conversion circuit 120x of the second embodiment, the switch Sw in the power conversion circuit 120 of the first embodiment is replaced with a rectifier diode. That is, the power conversion circuit 120x converts AC power to DC power but does not convert AC power and DC power bidirectionally. The other configuration of the contactless power supply system 10x of the second embodiment is the same as the configuration of the contactless power supply system 10 of the first embodiment. In the configuration of the contactless power supply system 10x of the second embodiment, components that are different from the configuration of the contactless power supply system 10 of the first embodiment are designated with an "x" at the end of their reference numerals.

[0048] The processing of the control circuit 150x will be described. The control circuit 150x starts processing, for example, when the temperature of the battery 130 is acquired. When the battery sensor 160 detects a first temperature of the battery 130 that falls within a predetermined first range, the control circuit 150x controls the switch Swx to be in an off state. Specifically, the control circuit 150x does not smooth the DC power using the smoothing capacitor 170. As a result, a current called a ripple current or a pulsating current flows through the battery 130. In other words, a current containing frequency components of AC power flows through the battery 130. The control circuit 150x continues to heat the battery 130 until the temperature of the battery 130 reaches a temperature suitable for use.

[0049] The control circuit 150x controls the switch Swx to the on state when the battery sensor 160 detects a second temperature that is included in a second range that is higher than the first range. That is, the control circuit 150x smoothes the DC power output from the power conversion circuit 120x using the smoothing capacitor 170. As a result, a more stable DC current flows through the battery 130 than when the DC power is not smoothed by the smoothing capacitor 170. Note that the first and second ranges are the same as those in the first embodiment.

[0050] With this configuration, the power receiving device 100x of the present disclosure smoothes the current flowing to the battery 130 using the smoothing capacitor 170 when the switch Swx is in the on state. The power receiving device 100x of the present disclosure does not smooth the current flowing to the battery 130 when the switch Swx is in the off state. That is, when the switch Swx is in the off state, a current including frequency components of AC power is passed through the battery 130. The battery 130 is heated more by passing a current including frequency components than by passing a current without frequency components. Therefore, by adding only the switch Swx to the smoothing capacitor 170, the power receiving device 100x of the present disclosure has a simpler configuration than a configuration in which an AC power source is used to heat the battery 130. That is, the power receiving device 100x of the present disclosure can prevent an increase in cost and size of the circuit that heats the battery 130.

[0051] Furthermore, since there is no need to smooth the current used to raise the temperature of the battery 130, the power receiving device 100x of the present disclosure can be designed more easily than in a configuration in which the current used to raise the temperature of the battery 130 is smoothed.

[0052] C. Modification 1: In the first embodiment, the power receiving device 100 may further include a current sensor 185 at the input of the power conversion circuit 120. In FIG. 1 , the current sensor 185 is indicated by a dashed line. The control circuit 150 controls the power conversion circuit 120 based on the detection value of the current sensor 185 so that the heating current Ir based on the second resonant frequency becomes a predetermined reference current. The predetermined reference current is, for example, a current value based on the rated current of the battery 130. Note that the current sensor 185 may be the power receiving sensor 180 at the output of the power conversion circuit 120 in the first embodiment.

[0053] More specifically, the control circuit 150 adjusts the heating current Ir to the reference current in the following manner.

[0054] The control circuit 150 may adjust the heating current Ir by providing a period during one cycle of the second AC power AC2 in which the battery 130 and the heating circuit 140 are disconnected from each other by turning off the switch Sw of the power conversion circuit 120. That is, the control circuit 150 can adjust the heating current Ir by adjusting the ratio between the period during which the battery 130 and the heating circuit 140 are disconnected from each other and the period during which the battery 130 and the heating circuit 140 are connected to each other in one cycle of the second AC power AC2.

[0055] By adopting such a configuration, the power receiving device 100 of the present disclosure can control the temperature rise of the battery 130 without adding a circuit for adjusting the temperature rise current Ir.

[0056] D. Modification 2: In the second embodiment, all of the rectifying elements of the power conversion circuit 120x are rectifying diodes. However, the power conversion circuit 120x only needs to be able to convert AC power to DC power. That is, some of the rectifying elements of the power conversion circuit 120x may be switches, or all of the rectifying elements may be switches, as in the first embodiment.

[0057] E. Modification 3: (1) In the above embodiment, the power receiving resonant circuit 110 includes a power receiving resonant capacitor 112 connected in series to the power receiving coil 111. However, the power receiving resonant circuit 110 may include a resonant capacitor connected in parallel to the power receiving coil 111. That is, the power receiving resonant circuit 110 may be a parallel resonant circuit. (2) In the above embodiment, the temperature raising circuit 140 has a second resonant frequency that is higher than the first resonant frequency. However, the temperature raising circuit 140 may have a second resonant frequency that is lower than the first resonant frequency. For example, the second resonant frequency is one-fifth the frequency of the first resonant frequency. (3) In the above embodiment, the switch Sw of the power conversion circuit 120 is a MOSFET. However, the switch Sw of the power conversion circuit 120 may be another switching element. The switch Sw may be, for example, a BJT (Bipolar Junction Transistor) or an IGBT (Insulated Gate Bipolar Transistor). (4) In the above embodiment, the power receiving sensor 180 is a current sensor that measures the current value of DC power. The power receiving sensor 180 may be another sensor. For example, the power receiving sensor 180 may be a voltage sensor that measures the voltage of DC power. Furthermore, the power receiving sensor 180 may be composed of multiple sensors. For example, the power receiving sensor 180 may be composed of a sensor that detects the reception of AC power and a sensor that detects power consumption of the battery 130 using DC power. (5) In the above embodiment, the battery 130 is, for example, a lithium-ion battery. However, the battery 130 may be another type of battery 130. The battery 130 may be a lead battery, a nickel-metal hydride battery, or the like. (6) In the first embodiment, the power conversion circuit 120 drives the switch Sw in accordance with the first resonant frequency to rectify the first AC power AC1. However, the power conversion circuit 120 does not have to drive the switch Sw in accordance with the first resonant frequency to rectify the first AC power AC1. If the switch Sw of the power conversion circuit 120 includes a parallel diode, the first AC power AC1 may be rectified only by the parallel diode.

[0058] The present disclosure is not limited to the above-described embodiments and modifications, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments and modifications corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0059] F. Other Aspects: The features of the present disclosure are as follows: (Aspect 1) A power receiving device (100) that receives first AC power (AC1) in a contactless manner using a magnetic field, comprising: a first resonant circuit (110) including a power receiving coil (111) that receives the first AC power, the first resonant circuit having a first resonant frequency; a power conversion circuit (120) that bidirectionally converts AC power to DC power; a battery (130) that is charged with first DC power (DC1) supplied via the power conversion circuit; a second resonant circuit (140) connected to an input section of AC power in the power conversion circuit, the second resonant circuit having a second resonant frequency different from the first resonant frequency; a battery sensor (160) that measures the temperature of the battery; a power receiving sensor (180) that detects the reception of the first AC power; and a control circuit (150) that controls the power receiving device. the power conversion circuit can convert the first AC power supplied from the first resonant circuit into the first DC power and supply it to the battery by controlling the power conversion circuit in accordance with the first resonant frequency, and can convert the second DC power (DC1) supplied from the battery into second AC power (AC2) and supply it to the second resonant circuit by controlling the power conversion circuit in accordance with the second resonant frequency, the control circuit performs the conversion of the second DC power and the supply to the second resonant circuit when the power receiving sensor is not receiving the first AC power and the temperature detected by the battery sensor is within a predetermined first range, and does not perform the conversion of the second DC power and the supply to the second resonant circuit when the power receiving sensor is not receiving the first AC power and the temperature detected by the battery sensor is within a second range higher than the first range. (Form 2) The power receiving device according to Form 1, wherein the second resonant frequency is higher than the first resonant frequency.(Mode 3) The power receiving device according to Mode 1, further comprising a current sensor at the input section or the output section of the power conversion circuit, wherein the control circuit controls the power conversion circuit based on a detected value of the current sensor so that the heating current based on the second resonant frequency becomes a predetermined reference current. (Feature 4) A power receiving device (100x) that receives AC power contactlessly by a magnetic field, comprising: a resonant circuit (110) including a power receiving coil (111) that receives the AC power; a power conversion circuit (120x) that converts the AC power into DC power; a battery (130) that charges the DC power; a smoothing capacitor (170) connected in parallel between the power conversion circuit and the battery; a switch (Swx) connected in series to the smoothing capacitor; a battery sensor (160) that measures the temperature of the battery; and a control circuit (150x) that controls the power receiving device, wherein the control circuit controls the switch to an off state when the battery sensor detects a first temperature that is included in a predetermined first range for the temperature, and controls the switch to an on state when the battery sensor detects a second temperature that is included in a second range that is higher than the first range.

Claims

1. A power receiving device (100) that receives a first AC power (AC1) in a non-contact manner by a magnetic field, comprising: a first resonant circuit (110) including a power receiving coil (111) that receives the first AC power, the first resonant circuit having a first resonant frequency; a power conversion circuit (120) that converts AC power and DC power in both directions; a battery (130) that is charged with first DC power (DC1) supplied via the power conversion circuit; a second resonant circuit (140) that is connected to an input section of AC power in the power conversion circuit, the second resonant circuit having a second resonant frequency different from the first resonant frequency; a battery sensor (160) that measures the temperature of the battery; a power receiving sensor (180) that detects the reception of the first AC power; and a control circuit (150) that controls the power receiving device, the power conversion circuit is capable of converting the first AC power supplied from the first resonant circuit into the first DC power and supplying it to the battery by controlling the power conversion circuit in accordance with the first resonant frequency, and is capable of converting the second DC power (DC1) supplied from the battery into second AC power (AC2) and supplying it to the second resonant circuit by controlling the power conversion circuit in accordance with the second resonant frequency; and the control circuit performs the conversion of the second DC power and the supply to the second resonant circuit when the first AC power is not being received by the power receiving sensor and the temperature detected by the battery sensor is within a predetermined first range, and does not perform the conversion of the second DC power and the supply to the second resonant circuit when the first AC power is not being received by the power receiving sensor and the temperature detected by the battery sensor is within a second range that is higher than the first range.

2. A power receiving device according to claim 1, wherein the second resonant frequency is greater than the first resonant frequency.

3. A power receiving device as described in claim 1, further comprising a current sensor (185) at the input section or the output section of the power conversion circuit, and the control circuit controls the power conversion circuit based on the detection value of the current sensor so that the heating current based on the second resonant frequency becomes a predetermined reference current.

4. A power receiving device (100x) that receives AC power contactlessly by a magnetic field, comprising: a resonant circuit (110) including a power receiving coil (111) that receives the AC power; a power conversion circuit (120x) that converts the AC power into DC power; a battery (130) that charges the DC power; a smoothing capacitor (170) connected in parallel between the power conversion circuit and the battery; a switch (Swx) connected in series to the smoothing capacitor; a battery sensor (160) that measures the temperature of the battery; and a control circuit (150x) that controls the power receiving device, wherein the control circuit turns the switch off when the battery sensor detects a first temperature that is included in a predetermined first range for the temperature, and turns the switch on when the battery sensor detects a second temperature that is included in a second range higher than the first range.

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