Power-receiving coil unit

Abstract

The objective of the present invention is to achieve downsizing of a power-receiving coil unit including a power-receiving coil.　A power-receiving coil unit (60) comprises: a first power-receiving coil (34a); a ferromagnetic first core member (65) having a first base part (65b) and a core part (65a) that protrudes to one side of the first base part and passes through the first power-receiving coil; a substrate (66) disposed on the other side of the first base part; and a transformer in which a primary-side coil is configured by wiring formed on the substrate. The first core member constitutes a part of the transformer core.

Description

Receiving coil unit

[0001] The present invention relates to a power receiving coil unit.

[0002] Patent Document 1 discloses a contactless power supply device. The power receiving device of this contactless power supply device includes a sub-coil arranged to be electromagnetically coupled to a receiving coil, a second rectifier circuit connected to the sub-coil, and a smoothing capacitor. The second rectifier circuit outputs power to the smoothing capacitor when the rectified voltage is higher than the voltage across the smoothing capacitor.

[0003] Japanese Patent Publication No. 2020-072604

[0004] In the configuration of Patent Document 1, under normal conditions, the voltage rectified by the second rectifier circuit needs to be lower than the voltage rectified by the first rectifier circuit. Therefore, to realize the configuration of Patent Document 1, the number of turns of the receiving coil needs to be very large, which poses a problem of increasing the size of the receiving coil unit including the receiving coil. Furthermore, due to the demand for miniaturization of the receiving coil unit, it is difficult to introduce large electrical components.

[0005] An object of one aspect of the present invention is to achieve miniaturization of a power receiving coil unit including a power receiving coil.

[0006] The receiving coil unit of aspect 1 of the present invention comprises a first receiving coil, a first core member made of a ferromagnetic material having a base and a core protruding to one side of the base and passing through the first receiving coil, a substrate arranged on the other side of the base, and a transformer having a primary coil formed by wiring formed on the substrate, wherein the first core member forms part of the core of the transformer.

[0007] According to the above configuration, a part of the first core member constituting the core of the first power receiving coil can function as the core of the transformer formed on the substrate, thereby making it possible to reduce the size of the power receiving coil unit.

[0008] The receiving coil unit of aspect 2 of the present invention may be configured in the above-mentioned aspect 1 to include a second core member made of a ferromagnetic material, and the second core member may be arranged so that the first core member and the second core member sandwich the substrate.

[0009] According to the above configuration, the transformer can be made thinner and smaller.

[0010] A receiving coil unit according to aspect 3 of the present invention may be configured such that, in the above-mentioned aspect 2, a first hole is formed in the substrate at a position corresponding to the center of the primary coil, and the first core member or the second core member has a first leg portion passing through the first hole.

[0011] According to the above configuration, a thin transformer can be formed by the wiring formed on the substrate and the first leg portion passing through the first hole.

[0012] A receiving coil unit according to aspect 4 of the present invention may be configured such that, in the above-mentioned aspect 2, a second hole is formed in the substrate at a position corresponding to the outside of the primary coil, and the first core member or the second core member has a second leg portion passing through the second hole.

[0013] A receiving coil unit according to aspect 5 of the present invention may be configured such that, in the above-mentioned aspect 1, a first hole is formed in the substrate at a position corresponding to the center of the primary coil, and the first core member has a first leg portion passing through the first hole.

[0014] According to the above configuration, the substrate can be positioned by the first leg portion.

[0015] A receiving coil unit according to aspect 6 of the present invention may be configured such that, in the above-mentioned aspect 2, the substrate has a first hole formed at a position corresponding to the center of the primary coil, a second hole and a third hole formed at positions corresponding to the outside of the primary coil, and the second core member is an E-shaped core having a first leg passing through the first hole, a second leg passing through the second hole, and a third leg passing through the third hole.

[0016] According to the above configuration, the degree of coupling of the transformer can be increased and the transformer can be made smaller.

[0017] A power receiving coil unit according to Aspect 7 of the present invention may be configured in any one of Aspects 1 to 6 above, wherein the base portion has a plate shape that is larger than the first power receiving coil in the radial direction of the first power receiving coil.

[0018] With this configuration, most of the magnetic flux generated in the core by the first power receiving coil passes through the base and exits from the side surface of the base, thereby preventing the magnetic flux generated by the first power receiving coil from affecting the transformer.

[0019] The receiving coil unit according to Aspect 8 of the present invention may be configured as in any one of Aspects 1 to 6 above, wherein the primary coil of the transformer is connected across both ends of the first receiving coil.

[0020] The receiving coil unit according to Aspect 9 of the present invention may be configured in any one of Aspects 1 to 6 above, further comprising a first resonant capacitor disposed on the substrate and connected in series to the first receiving coil.

[0021] The receiving coil unit of aspect 10 of the present invention may be configured as in aspect 9 above, further comprising a second receiving coil connected in series to the first receiving coil, and a second resonant capacitor connected between the first receiving coil and the second receiving coil, and the core portion may pass through the second receiving coil.

[0022] The receiving coil unit of aspect 11 of the present invention may be configured in the above-mentioned aspect 9, further comprising a first external connection terminal connected to the first resonant capacitor and a second external connection terminal connected to the secondary coil of the transformer.

[0023] According to the above configuration, it is possible to reduce the absolute value of the voltage at the first external connection terminal and the second external connection terminal that connect the power receiving coil unit to an external circuit.

[0024] A receiving coil unit according to aspect 12 of the present invention may be configured as in any of aspects 1 to 6 above, including an auxiliary coil electromagnetically coupled to the first receiving coil, and the primary coil connected between both ends of the auxiliary coil.

[0025] A receiving coil unit according to aspect 13 of the present invention may be configured such that, in any of aspects 1 to 6 above, the substrate has a first wiring layer on which the primary coil is formed, a second wiring layer on which wiring connected to the primary coil is formed, and a third wiring layer on which the secondary coil of the transformer is formed.

[0026] According to one aspect of the present invention, the power receiving coil unit can be made smaller.

[0027] FIG. 1 is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present invention. FIG. 2 is a top view showing the configuration of a power receiving coil unit according to one embodiment of the present invention. FIG. 3 is a cross-sectional view showing the configuration of the power receiving coil unit along the A-A section line in FIG. 2. FIG. 4 is a bottom view showing the configuration of the power receiving coil unit. FIG. 5 is a bottom view showing the detailed configuration of a substrate. FIG. 6 is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present invention. FIG. 7 is a cross-sectional view showing the configuration of a power receiving coil unit according to one embodiment of the present invention.

[0028] [First Embodiment] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter also referred to as "the present embodiment") will be described with reference to the drawings.

[0029] 1 is a circuit diagram showing the configuration of a contactless power supply system 1 according to this embodiment. The contactless power supply system 1 includes a power transmitting device 2 and a power receiving device 3. The power transmitting device 2 supplies power to the power receiving device 3 in a contactless manner.

[0030] Before power feeding starts, the smoothing capacitor 37 of the power receiving device 3 is not charged. When power is fed from the power transmitting device 2 at the resonant frequency of the resonant circuit 33 while the smoothing capacitor 37 is not charged, extremely large voltages are generated due to resonance across both ends of the first power receiving coil 34a, both ends of the second power receiving coil 34b, both ends of the first resonant capacitor 35a, and both ends of the second resonant capacitor 35b.

[0031] The contactless power transfer system 1 includes a transformer 38 connected in parallel to the first power receiving coil 34a. When the smoothing capacitor 37 is not sufficiently charged, the voltage stepped down by the transformer 38 is output to the smoothing capacitor 37 via the second rectifier circuit 39. This changes the resonant frequency of the resonant circuit 33. This prevents the voltages generated in the first power receiving coil 34a and the second power receiving coil 34b from increasing excessively. The ability to step down the voltage using the transformer 38 also increases the degree of freedom in designing the power receiving coil 34.

[0032] In the power receiving coil unit 60, the core of the first power receiving coil 34a forms part of the core of the transformer 38. This allows the transformer 38 to be miniaturized, and therefore the power receiving coil unit 60 including the first power receiving coil 34a and the transformer 38 can be miniaturized.

[0033] §2 Configuration Example (Configuration of Power Transmission Device 2) The power transmission device 2 includes a first communication unit 21, a power transmission control unit 22, a power source 23, an inverter 24, a coil 25, a first capacitor 26, a second capacitor 27, and a power transmission coil 28. The power source 23 is a DC power source. The inverter 24 is connected to the power source 23 and converts DC voltage into AC voltage. The inverter 24 includes a plurality of switching elements 24a to 24d.

[0034] One end of the coil 25 is connected to one output terminal of the inverter 24. One end of the first capacitor 26 is connected to the other end of the coil 25, and the other end of the first capacitor 26 is connected to the other output terminal of the inverter 24. One end of the second capacitor 27 is connected to the other end of the coil 25.

[0035] One end of the power transmission coil 28 is connected to the other end of the second capacitor 27, and the other end of the power transmission coil 28 is connected to the other output terminal of the inverter 24. The power transmission coil 28 generates an AC magnetic field to supply power to the power receiving device 3 in a wireless manner.

[0036] The first communication unit 21 performs wireless communication with the second communication unit 32 of the power receiving device 3. The first communication unit 21 receives operation information of the power receiving device 3 from the power receiving device 3. The first communication unit 21 outputs the operation information received from the power receiving device 3 to the power transmission control unit 22.

[0037] The power transmission control unit 22 controls the frequency and / or power of the AC voltage output by the inverter 24 by controlling the multiple switching elements 24a to 24d based on operation information of the power receiving device 3. For example, the power transmission control unit 22 controls the average voltage applied to the power transmitting coil 28 by performing phase shift control. In this way, the power transmission control unit 22 controls the power supplied from the power transmitting coil 28 to the power receiving device 3.

[0038] (Configuration of power receiving device 3) The power receiving device 3 includes a voltage determination unit 31, a second communication unit 32, a power receiving coil unit 60, a first rectifier circuit 36, a smoothing capacitor 37, a second rectifier circuit 39, a switching circuit 40, and a load 90. The power receiving coil unit 60 includes a resonant circuit 33 and a transformer 38. The power receiving coil unit 60 includes a first external connection terminal 61 a, a second external connection terminal 61 b, a third external connection terminal 62 a, and a fourth external connection terminal 62 b for connection to an external circuit.

[0039] The resonant circuit 33 includes a first power receiving coil 34a, a second power receiving coil 34b, a first resonant capacitor 35a, and a second resonant capacitor 35b. The first power receiving coil 34a and the second power receiving coil 34b receive power from the power transmitting coil 28 of the power transmitting device 2. The first power receiving coil 34a and the second power receiving coil 34b share a common core. The first power receiving coil 34a, the second power receiving coil 34b, the first resonant capacitor 35a, and the second resonant capacitor 35b are connected in series with each other. The first resonant capacitor 35a is connected between the first power receiving coil 34a and the second power receiving coil 34b. The second power receiving coil 34b is connected between the first resonant capacitor 35a and the second resonant capacitor 35b. One end of the second resonant capacitor 35b is connected to the first external connection terminal 61a. One end of the first power receiving coil 34a is connected to the second external connection terminal 61b.

[0040] The transformer 38 has a primary coil and a secondary coil. The number of turns in the secondary coil is smaller than the number of turns in the primary coil. The transformer 38 is a transformer that transforms a voltage input to the primary coil to a lower voltage and outputs the resulting voltage to the secondary coil. The primary coil of the transformer 38 is connected in parallel to the first power receiving coil 34a, which is part of the power receiving coil of the power receiving device 3. In other words, the primary coil is connected between one end and the other end of the first power receiving coil 34a. One end of the secondary coil of the transformer 38 is connected to the third external connection terminal 62a. The other end of the secondary coil of the transformer 38 is connected to the fourth external connection terminal 62b.

[0041] The first rectifier circuit 36 ​​rectifies the AC voltage generated in the resonant circuit 33 into a DC voltage. Here, the first rectifier circuit 36 ​​is a bridge circuit including multiple diodes, but is not limited to this and may be a circuit including multiple switching elements. The first rectifier circuit 36 ​​has a first AC terminal 36a connected to the first external connection terminal 61a, a second AC terminal 36b connected to the second external connection terminal 61b, a positive terminal 36c, and a negative terminal 36d. The first rectifier circuit 36 ​​outputs a full-wave rectified DC (pulsating) voltage from the positive terminal 36c and the negative terminal 36d.

[0042] The smoothing capacitor 37 is connected between the positive terminal 36c and the negative terminal 36d of the first rectifier circuit 36. The smoothing capacitor 37 smoothes the voltage output from the first rectifier circuit 36. The smoothing capacitor 37 outputs the smoothed output voltage to the load 90.

[0043] The second rectifier circuit 39 rectifies the AC voltage on the secondary side of the transformer 38 into a DC voltage. The second rectifier circuit 39 is connected to the secondary coil of the transformer 38. Here, the second rectifier circuit 39 is a bridge circuit including multiple diodes, but is not limited to this and may be a circuit including multiple switching elements. The second rectifier circuit 39 has a first AC terminal 39a connected to one end of the secondary coil of the transformer 38, a second AC terminal 39b connected to the other end of the secondary coil of the transformer 38, a positive terminal 39c, and a negative terminal 39d. The positive terminal 39c is connected to one end of the smoothing capacitor 37. The negative terminal 39d is connected to the other end of the smoothing capacitor 37. The second rectifier circuit 39 outputs a full-wave rectified DC (pulsating) voltage to the smoothing capacitor 37 from the positive terminal 39c and the negative terminal 39d.

[0044] The switching circuit 40 is connected across the secondary coil of the transformer 38. The switching circuit 40 switches between a cutoff state (non-conducting) and a short-circuit state (conducting) across the secondary coil of the transformer 38. For example, the switching circuit 40 includes a first switching element 41, which is a transistor, and a second switching element 42, which is also a transistor. The first switching element 41 and the second switching element 42 are connected in series. One end of the first switching element 41 is connected to one end of the secondary coil of the transformer 38. The other end of the first switching element 41 is connected to one end of the second switching element 42. The other end of the second switching element 42 is connected to the other end of the secondary coil of the transformer 38. A node between the first switching element 41 and the second switching element 42 is connected to the negative terminal 36d of the first rectifier circuit 36.

[0045] The voltage determination unit 31 detects the output voltage output from the smoothing capacitor 37 to the load 90 and determines whether the output voltage is equal to or greater than a voltage threshold. The voltage determination unit 31 (short-circuit control circuit) shorts (conducts) the switching circuit 40 based on the output voltage. For example, if the output voltage is equal to or greater than the voltage threshold, the voltage determination unit 31 switches the first switching element 41 and the second switching element 42 to a conductive state. If the output voltage is less than the voltage threshold, the voltage determination unit 31 switches the first switching element 41 and the second switching element 42 to a non-conductive state.

[0046] If the output voltage is less than the voltage threshold, the voltage determination unit 31 notifies the second communication unit 32 that no overvoltage is occurring. If the output voltage is equal to or greater than the voltage threshold, the voltage determination unit 31 notifies the second communication unit 32 that an overvoltage is occurring. The voltage determination unit 31 may notify the second communication unit 32 of the output voltage.

[0047] The second communication unit 32 performs wireless communication with the first communication unit 21 of the power transmission device 2. Based on the notification from the voltage determination unit 31, the second communication unit 32 generates operation information of the power reception device 3 indicating whether an overvoltage is occurring in the power reception device 3. The second communication unit 32 wirelessly transmits the operation information of the power reception device 3 to the power transmission device 2. The operation information may include information on the output voltage.

[0048] (Operation of Contactless Power Transfer System 1) Before power transfer begins, the smoothing capacitor 37 of the power receiving device 3 is not charged. As power transfer begins, charging of the smoothing capacitor 37 begins, and the output voltage rises. Therefore, immediately after power transfer begins, current from the first rectifier circuit 36 ​​flows into the smoothing capacitor 37, so the load resistance seen from the resonant circuit 33 is close to zero. In the case of a series resonant circuit in which the first power receiving coil 34a, the second power receiving coil 34b, the first resonant capacitor 35a, and the second resonant capacitor 35b are connected in series, the smaller the load resistance of the resonant circuit, the larger the Q value, which represents the sharpness of the resonance peak. When power is transferred from the power transmitting device 2 at the resonant frequency of the resonant circuit 33 with the load resistance of the power receiving device 3 close to zero, resonance generates extremely large voltages across each of the first power receiving coil 34a, the second power receiving coil 34b, the first resonant capacitor 35a, and the second resonant capacitor 35b. To prevent this overvoltage from occurring, the power transmission device 2 starts power supply at a frequency different from the resonant frequency at the start of power supply, and gradually brings the frequency closer to the resonant frequency, or controls the amount of phase shift to gradually increase the voltage applied to the power transmission coil 28.

[0049] However, there may be cases where the power transmitter 2 supplies power at the resonant frequency of the resonant circuit 33 when the load resistance of the power receiver 3 is close to zero for some reason. For example, this may occur when (i) the relative positions of the power transmitter 2 and the power receiver 3 change, (ii) the switching circuit in the power receiver 3 is short-circuited and then cut off again for overvoltage protection, or (iii) a short circuit occurs in the load 90.

[0050] In the contactless power transfer system 1 of this embodiment, when power transfer from the power transmission device 2 begins, a voltage is generated across the first power receiving coil 34a and the second power receiving coil 34b. The same voltage across the first power receiving coil 34a is applied to the primary coil of the transformer 38. The voltage across the primary coil is stepped down in accordance with the turns ratio of the transformer 38 and output from the secondary coil. The second rectifier circuit 39 outputs the stepped-down voltage to the smoothing capacitor 37. When the smoothing capacitor 37 is not sufficiently charged immediately after power transfer begins, the voltage output from the second rectifier circuit 39 is higher than the output voltage of the smoothing capacitor 37. Therefore, a current flows from the secondary coil of the transformer 38 to the smoothing capacitor 37 via the second rectifier circuit 39. That is, a current corresponding to the current flowing through the secondary coil also flows from the first power receiving coil 34a to the primary coil of the transformer 38. In this state, the path of the transformer 38 and the second rectifier circuit 39 is added to the resonant circuit 33, so the resonant frequency of the resonant circuit 33 deviates from the original resonant frequency of the resonant circuit 33 itself. Therefore, even if the power transmitter 2 supplies power at the resonant frequency of the resonant circuit 33 when the smoothing capacitor 37 is not sufficiently charged, resonance does not occur in the resonant circuit 33. Therefore, the contactless power transfer system 1 can appropriately suppress an excessive increase in the voltage generated across the first power receiving coil 34a and the second power receiving coil 34b.

[0051] Adjustment of the supplied power via communication involves a delay (for example, about 10 ms) due to the communication. In the contactless power transfer system 1, although the power transmission device 2 controls the amount of power to be supplied, the occurrence of overvoltage can be prevented by control on the power receiving device 3 side without waiting for adjustment of the supplied power by the power transmission device 2. Therefore, the occurrence of failures due to overvoltage can be reduced.

[0052] After a certain period of time has elapsed since the start of power supply, the smoothing capacitor 37 is sufficiently charged, and the power receiving device 3 performs normal constant voltage output operation to the load 90. When the smoothing capacitor 37 is sufficiently charged, the winding ratio of the transformer 38 is set so that the secondary voltage stepped down by the transformer 38 is lower than the output voltage of the smoothing capacitor 37. Therefore, during constant voltage output operation, power is not supplied from the second rectifier circuit 39 to the smoothing capacitor 37, and power is supplied only from the first rectifier circuit 36 ​​to the smoothing capacitor 37. Therefore, no current flows through the secondary coil of the transformer 38. If the inductance of the primary coil of the transformer 38 is sufficiently larger than the inductance of the first power receiving coil 34a, the transformer 38 has almost no effect on the resonant frequency of the resonant circuit 33. The inductance of the primary coil of the transformer 38 may be 10 times or more the inductance of the first power receiving coil 34a. More preferably, the inductance of the primary coil of the transformer 38 may be 100 times or more the inductance of the first power receiving coil 34a.

[0053] When the output voltage of the smoothing capacitor 37 is less than the voltage threshold, the voltage determination unit 31 turns off the first switching element 41 and the second switching element 42. That is, the switching circuit 40 is in the cut-off state while the normal constant voltage output operation is being performed immediately after the start of power supply.

[0054] On the other hand, a change in the relative position between the power transmitting coil 28 and the power receiving coil 34, for example, may increase the output of the resonant circuit 33, causing an overvoltage in the smoothing capacitor 37. When the output voltage is equal to or greater than a voltage threshold, the voltage determination unit 31 switches the first switching element 41 and the second switching element 42 to a conductive state. This allows the switching circuit 40 to short-circuit both ends of the secondary coil of the transformer 38. The voltage threshold is set to a value higher than the output voltage during constant voltage output operation.

[0055] When both ends of the secondary coil of the transformer 38 are short-circuited, the resonant frequency of the resonant circuit 33 changes. This reduces the power received by the power receiving device 3 from the power transmitting device 2, and also reduces the voltage output from the resonant circuit 33 to the smoothing capacitor 37. This reduces the output voltage of the smoothing capacitor 37, making it possible to suppress overvoltage. In the contactless power transfer system 1, the transformer 38 is connected in parallel to the first power receiving coil 34a. Therefore, the power receiving device 3 can reliably change the resonant frequency of the resonant circuit 33 by using the switching circuit 40 provided on the secondary side of the transformer 38.

[0056] Furthermore, when the output voltage of the smoothing capacitor 37 is equal to or greater than the voltage threshold, the second communication unit 32 transmits, to the power transmission device 2 , operation information indicating that an overvoltage is occurring in the power reception device 3 .

[0057] When the first communication unit 21 receives operation information indicating that an overvoltage has occurred, the power transmission control unit 22 reduces the voltage applied to the power transmission coil 28 or shifts the frequency from the resonant frequency. As a result, the power transmission control unit 22 reduces the power supplied to the power receiving device 3. This makes it possible to prevent an overvoltage from occurring again when the voltage determination unit 31 of the power receiving device 3 returns the switching circuit 40 to the cut-off state.

[0058] (Configuration of power receiving coil unit 60) Fig. 2 is a top view showing the configuration of the power receiving coil unit 60. Fig. 3 is a cross-sectional view showing the configuration of the power receiving coil unit 60 taken along the line A-A in Fig. 2. Fig. 4 is a bottom view showing the configuration of the power receiving coil unit 60. The power receiving coil unit 60 includes a first power receiving coil 34a, a second power receiving coil 34b, a first core member 65, a substrate 66, and a second core member 67.

[0059] The first core member 65 is a ferromagnetic member having a core portion 65a and a first base portion 65b. The first base portion 65b is plate-shaped, and in this case, is disk-shaped. The first base portion 65b is larger than the first power receiving coil 34a in the radial direction of the first power receiving coil 34a. The core portion 65a protrudes to one side of the first base portion 65b, and in this case, is cylindrical. The core portion 65a passes through the first power receiving coil 34a and the second power receiving coil 34b. The first core member 65 functions as the core of the first power receiving coil 34a and the second power receiving coil 34b.

[0060] The first power receiving coil 34a and the second power receiving coil 34b are wound around the core portion 65a. The second power receiving coil 34b is arranged so as to be stacked on top of the first power receiving coil 34a.

[0061] The substrate 66 is a printed circuit board. The substrate 66 is disposed on the other side of the first base portion 65b. The substrate 66 has a plurality of wiring layers. The primary coil and the secondary coil of the transformer 38 are formed by wiring formed on the substrate 66.

[0062] The second core member 67 is a ferromagnetic member having a second base portion 67a, a first leg portion 68a, a second leg portion 68b, and a third leg portion 68c. The second base portion 67a is rod-shaped. The first leg portion 68a, the second leg portion 68b, and the third leg portion 68c protrude from one side of the second base portion 67a and are rectangular prism-shaped in this example. The first leg portion 68a passes through the primary and secondary coils of the transformer 38. The second leg portion 68b and the third leg portion 68c pass outside the primary and secondary coils of the transformer 38. In this example, the second core member 67 is an E-shaped core. The second core member 67 is bonded to the first core member 65 so that the first leg portion 68a, the second leg portion 68b, and the third leg portion 68c are in close contact with the first core member 65. The second core member 67 and the first core member 65 form a closed magnetic circuit.

[0063] Fig. 5 is a bottom view showing the detailed configuration of the substrate 66. In Fig. 5, wiring formed on the surface (bottom surface) of the substrate 66 is represented by solid lines, and wiring formed in a wiring layer inside the substrate 66 is represented by dotted lines. The substrate 66 includes a transformer 38, a first resonant capacitor 35a, a second resonant capacitor 35b, a first external connection terminal 61a, a second external connection terminal 61b, a third external connection terminal 62a, and a fourth external connection terminal 62b. The substrate 66 has a first hole 66a, a second hole 66b, and a third hole 66c formed therein as through holes.

[0064] The primary coil 38a of the transformer 38 is formed on the substrate 66 by spiral wiring formed on the underside of the substrate 66. The first hole 66a is formed at a position corresponding to the center of the primary coil 38a. The second hole 66b and the third hole 66c are formed at positions corresponding to the outside of the primary coil 38a.

[0065] Both ends of the primary coil 38a are connected to both ends of the first power receiving coil 34a via a plurality of lead wires 73, 74. One end of the primary coil 38a is connected to one end of the first resonant capacitor 35a via a wiring 71. One end of the primary coil 38a is connected to a lead wire 73 via the wiring 71. The other end of the primary coil 38a is connected to a lead wire 74 and the second external connection terminal 61b via a wiring 72 formed on a wiring layer inside the substrate 66. The other end of the primary coil 38a is connected to the wiring 72 via an interlayer wiring.

[0066] One end of the second resonant capacitor 35b is connected to the first external connection terminal 61a. The other end of the first resonant capacitor 35a and the other end of the second resonant capacitor 35b are connected to opposite ends of the second power receiving coil 34b via a plurality of lead wires 75 and 76. The plurality of lead wires 73, 74, 75, and 76 pass outside the first base portion 65b and extend toward the first power receiving coil 34a and the second power receiving coil 34b.

[0067] Fig. 6 is a top view showing the detailed configuration of the substrate 66. In Fig. 6, the wiring formed on the back surface (top surface) of the substrate 66 is represented by solid lines, and the wiring formed in the wiring layer inside the substrate 66 is represented by dotted lines. The secondary coil 38b of the transformer 38 is formed on the substrate 66 by spiral wiring formed on the top surface of the substrate 66. The first hole 66a is formed at a position corresponding to the center of the secondary coil 38b. The second hole 66b and the third hole 66c are formed at positions corresponding to the outside of the secondary coil 38b.

[0068] One end of the secondary coil 38b is connected to the third external connection terminal 62a via a wiring 77. The other end of the secondary coil 38b is connected to the fourth external connection terminal 62b via a wiring 78 formed in a wiring layer inside the substrate 66. The first external connection terminal 61a, the second external connection terminal 61b, the third external connection terminal 62a, and the fourth external connection terminal 62b are formed on the lower surface of the substrate 66 (the surface opposite the first base portion 65b) to facilitate external wiring. The third external connection terminal 62a is connected to the wiring 77 via an interlayer wiring. The fourth external connection terminal 62b is connected to the wiring 78 via an interlayer wiring.

[0069] The first leg 68a passes through the first hole 66a. The second leg 68b and the third leg 68c pass through the second hole 66b and the third hole 66c, respectively. The primary coil 38a and the secondary coil 38b share the first leg 68a as a common core. The transformer 38 is disposed at a position corresponding to the center of the core 65a.

[0070] The second core member 67 and a portion of the first base portion 65b of the first core member 65 (the portion facing the second core member 67) form a closed magnetic circuit. The outer diameter of the first base portion 65b is larger than the outer diameters of the first power receiving coil 34a and the second power receiving coil 34b. The outer diameter of the core portion 65a is larger than the longitudinal dimension of the second core member 67. In a plan view, the second leg portion 68b and the third leg portion 68c are located inside the core portion 65a. Most of the magnetic flux generated in the core portion 65a by the first power receiving coil 34a and the second power receiving coil 34b passes through the first base portion 65b and exits from the side surface of the first base portion 65b. Therefore, the magnetic flux generated by the first power receiving coil 34a and the second power receiving coil 34b does not substantially affect the transformer 38. On the other hand, the magnetic flux generated in the first leg 68a by the primary coil 38a passes through the second core member 67 and the portion of the first core member 65 that faces the second core member 67. Therefore, the second core member 67 and the portion of the first core member 65 that faces the second core member 67 function as the core of the transformer 38.

[0071] The second base portion 67a of the second core member 67 has a thin rod shape that is aligned with the substrate 66. The second core member 67 and the first core member 65 are arranged to sandwich the substrate 66 and function as the core of the transformer 38. This allows the transformer 38 to be made thinner and smaller. Furthermore, the core of the first power receiving coil 34a and the core of the transformer 38 can be integrally formed by the first core member 65 and the second core member 67 that are connected to each other. This allows the power receiving coil unit 60 to be made smaller.

[0072] The substrate 66 is provided with a first resonant capacitor 35a, a second resonant capacitor 35b, and a transformer 38. The voltage across the first power receiving coil 34a and the voltage across the first resonant capacitor 35a are in opposite phase. Therefore, the absolute value of the voltage across the first power receiving coil 34a and the first resonant capacitor 35a is smaller than the absolute value of the voltage across the first power receiving coil 34a. Similarly, the absolute value of the voltage across the second power receiving coil 34b and the second resonant capacitor 35b is smaller than the absolute value of the voltage across the second power receiving coil 34b. This reduces the maximum voltage in the resonant circuit 33. The first external connection terminal 61a is connected to the second resonant capacitor 35b. This reduces the absolute value of the voltage between the first external connection terminal 61a and the second external connection terminal 61b. The third external connection terminal 62a and the fourth external connection terminal 62b are connected to the secondary coil 38b of the transformer 38. Because the voltage on the secondary side is stepped down by the transformer 38, the absolute value of the voltage between the third external connection terminal 62a and the fourth external connection terminal 62b can be reduced. This makes it possible to reduce the absolute value of the voltage on the wiring extending from the power receiving coil unit 60 to the outside. This makes the power receiving coil unit 60 easy to handle and improves the degree of freedom in the wiring design of the peripheral circuitry.

[0073] (Modification) The substrate 66 has a first wiring layer on which the primary coil 38a is formed, a second wiring layer on which the wiring 72 or the wiring 78 is formed, and a third wiring layer on which the secondary coil 38b is formed. The order in which the multiple wiring layers are stacked may be arbitrary. The substrate 66 may also be a multilayer substrate having four or more wiring layers.

[0074] The second power receiving coil 34b and the second resonant capacitor 35b may be omitted. However, by providing two separate power receiving coils and resonant capacitors as in the above embodiment, the voltage applied to the primary side of the transformer 38 can be reduced. This makes it possible to prevent breakdown of the transformer 38. Furthermore, when the switching circuit 40 is brought into a conductive state and both ends of the secondary coil 38b of the transformer 38 are short-circuited, the current flowing through the switching circuit 40 and the secondary coil can be reduced. This makes it possible to prevent breakdown of the switching circuit 40.

[0075] [Embodiment 2] Another embodiment of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0076] 7 is a circuit diagram showing the configuration of a contactless power supply system 1a according to this embodiment. The contactless power supply system 1a includes a power transmitting device 2 and a power receiving device 3a.

[0077] The power receiving device 3a includes a voltage determination unit 31, a second communication unit 32, a power receiving coil unit 60a, a first rectifier circuit 36, a smoothing capacitor 37, a second rectifier circuit 39, and a load 90. The power receiving coil unit 60a includes a resonant circuit 33a, an auxiliary coil 44, a switching circuit 40, and a transformer 38. The power receiving coil unit 60a includes a first external connection terminal 61a, a second external connection terminal 61b, a third external connection terminal 62a, a fourth external connection terminal 62b, a fifth external connection terminal 63, and a sixth external connection terminal 64 for connection to an external circuit.

[0078] The resonant circuit 33a has a power receiving coil 34 and a resonant capacitor 35. The power receiving coil 34 receives power from the power transmitting coil 28 of the power transmitting device 2. The resonant capacitor 35 is connected in series to the power receiving coil 34. The first rectifier circuit 36 ​​rectifies the AC voltage generated in the resonant circuit 33a to a DC voltage. One end of the resonant capacitor 35 is connected to the first external connection terminal 61a. One end of the power receiving coil 34 is connected to the second external connection terminal 61b.

[0079] The primary coil of the transformer 38 is connected between one end and the other end of the auxiliary coil 44. The number of turns of the secondary coil is smaller than the number of turns of the primary coil. The second rectifier circuit 39 is connected to the secondary coil of the transformer 38.

[0080] The switching circuit 40 is connected across the auxiliary coil 44. A node between the first switching element 41 and the second switching element 42 is connected to a fifth external connection terminal 63. The fifth external connection terminal 63 is connected to the negative terminal 36d of the first rectifier circuit 36. Control terminals (gate terminals) of the first switching element 41 and the second switching element 42 are connected to a sixth external connection terminal 64. The sixth external connection terminal 64 is connected to the voltage determination unit 31.

[0081] The auxiliary coil 44 is electromagnetically coupled to the power receiving coil 34. The auxiliary coil 44 and the power receiving coil 34 share a core. That is, at least a portion of the magnetic flux generated in the power receiving coil 34 by the power transmitting coil 28 passes through the auxiliary coil 44. The number of turns of the auxiliary coil 44 is smaller than the number of turns of the power receiving coil 34. Therefore, the voltage generated in the auxiliary coil 44 by the power transmitting coil 28 is lower than the voltage generated in the power receiving coil 34.

[0082] When a voltage is generated in the auxiliary coil 44 by the AC magnetic field generated by the power transmitting coil 28, the voltage is further reduced by the transformer 38. If the voltage rectified by the second rectifier circuit 39 is higher than the voltage of the smoothing capacitor 37, a current flows from the secondary coil of the transformer 38 to the smoothing capacitor 37 via the second rectifier circuit 39. A current corresponding to the current flowing through the secondary coil also flows from the auxiliary coil 44 to the primary coil of the transformer 38. The auxiliary coil 44 is electromagnetically coupled to the power receiving coil 34. Therefore, in this state, the path of the auxiliary coil 44, the transformer 38, and the second rectifier circuit 39 is added to the resonant circuit 33a, and the resonant frequency of the resonant circuit 33a deviates from the original resonant frequency of the resonant circuit 33a itself. Therefore, even if the power transmitting device 2 supplies power at the resonant frequency of the resonant circuit 33a when the smoothing capacitor 37 is not sufficiently charged, no resonance occurs in the resonant circuit 33a. Therefore, according to the contactless power supply system 1a, it is possible to appropriately prevent the voltage generated across the power receiving coil 34 from increasing excessively.

[0083] In the contactless power transfer system 1a, a voltage lower than that of the power receiving coil 34 is generated by the electromagnetically coupled auxiliary coil 44, and this voltage is further stepped down by the transformer 38 and supplied to the smoothing capacitor 37. Because the voltage can be stepped down by the transformer 38, it is not necessary to make the turns ratio between the power receiving coil 34 and the auxiliary coil 44 extremely large. This makes it possible to prevent the power receiving coil 34 from becoming too large.

[0084] In the contactless power transfer system 1a, the switching circuit 40 is connected across the auxiliary coil 44. When the output voltage of the smoothing capacitor 37 is equal to or greater than the voltage threshold, the voltage determination unit 31 switches the first switching element 41 and the second switching element 42 to a conductive state. This allows the switching circuit 40 to short-circuit the auxiliary coil 44. When the auxiliary coil 44 is short-circuited, the resonant frequency of the resonant circuit 33a, which includes the power receiving coil 34 electromagnetically coupled to the auxiliary coil 44, changes. This also reduces the voltage output from the resonant circuit 33a to the smoothing capacitor 37. This makes it possible to suppress overvoltage applied to the smoothing capacitor 37. In the contactless power transfer system 1a, the voltage across the auxiliary coil 44 is lower than the voltage across the power receiving coil 34 (e.g., several kV), so it is possible to short-circuit the auxiliary coil 44 with a semiconductor switch.

[0085] The switching circuit 40 may be provided across the secondary coil of the transformer 38, as in the above embodiment.

[0086] In order to suppress the influence on the resonant frequency of the resonant circuit 33a during normal constant voltage output operation, the inductance of the primary coil of the transformer 38 may be made sufficiently larger than the inductance of the auxiliary coil 44. The inductance of the primary coil of the transformer 38 may be 10 times or more the inductance of the auxiliary coil 44. More preferably, the inductance of the primary coil of the transformer 38 may be 100 times or more the inductance of the auxiliary coil 44.

[0087] As in the above-described embodiment, the absolute value of the voltage at each external connection terminal of the power receiving coil unit 60a can be reduced.

[0088] 8 is a cross-sectional view showing the configuration of the power receiving coil unit 60a. The power receiving coil unit 60a includes the power receiving coil 34, the auxiliary coil 44, a first core member 65c, a substrate 66, and a second core member 67b.

[0089] The first core member 65c is a ferromagnetic member having a core portion 65a, a first base portion 65b, a first leg portion 68a, a second leg portion 68b, and a third leg portion 68c. The core portion 65a passes through the power receiving coil 34 and the auxiliary coil 44. The first core member 65c functions as a core for the power receiving coil 34 and the auxiliary coil 44. The second core member 67b is a plate-shaped or rod-shaped ferromagnetic member.

[0090] The power receiving coil 34 and the auxiliary coil 44 are wound around the core portion 65a. The auxiliary coil 44 is arranged so as to be stacked on top of the power receiving coil 34.

[0091] The transformer 38 is formed on the substrate 66. In addition to the resonant capacitor 35, the switching circuit 40 is also provided on the substrate 66.

[0092] In the power receiving coil unit 60a, a first core member 65c is formed with a first leg 68a, a second leg 68b, and a third leg 68c. The first leg 68a, the second leg 68b, and the third leg 68c protrude from the other side of the first base 65b (the side opposite the core 65a). The first leg 68a passes through the primary coil and the secondary coil of the transformer 38. The second leg 68b and the third leg 68c pass outside the primary coil and the secondary coil of the transformer 38. The second core member 67b is bonded to the first core member 65b so that the first leg 68a, the second leg 68b, and the third leg 68c are in close contact with the second core member 67b.

[0093] In this way, the first leg 68 a, the second leg 68 b, and the third leg 68 c may be formed as part of the first core member 65 c. In the power receiving coil unit 60 a, the first leg 68 a, the second leg 68 b, and the third leg 68 c can also be used to position the substrate 66. This makes assembly easy.

[0094] (Modification) Note that some of the first leg portion 68 a, the second leg portion 68 b, and the third leg portion 68 c may be formed on the first core member, and the remaining portions may be formed on the second core member. In this case, the first leg portion 68 a, the second leg portion 68 b, and the third leg portion 68 c can determine the position of both the substrate 66 and the second core member.

[0095] Also, the second leg 68b or the third leg 68c may be omitted.

[0096] If the first core member 65c has the first leg portion 68a, the second core member 67b may be omitted. As long as there is at least the first leg portion 68a, it can function as the core of the transformer 38.

[0097] [Example of implementation by software] The functions of the contactless power supply system 1, 1a (hereinafter referred to as "device") can be realized by a program for causing a computer to function as the device, and a program for causing a computer to function as each control block of the device (in particular, the first communication unit 21, the power transmission control unit 22, the voltage determination unit 31, and the second communication unit 32).

[0098] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The functions described in each of the above embodiments are realized by executing the program using the control device and storage device.

[0099] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0100] Furthermore, some or all of the functions of the control blocks can be realized by logic circuits. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention. In addition, the functions of the control blocks can also be realized by, for example, a quantum computer.

[0101] [Summary] The receiving coil unit of aspect 1 of the present invention comprises a first receiving coil, a first core member made of a ferromagnetic material having a base and a core protruding to one side of the base and passing through the first receiving coil, a substrate arranged on the other side of the base, and a transformer having a primary coil formed by wiring formed on the substrate, and the first core member forms part of the core of the transformer.

[0102] The receiving coil unit of aspect 2 of the present invention may be configured in the above-mentioned aspect 1 to include a second core member made of a ferromagnetic material, and the second core member may be arranged so that the first core member and the second core member sandwich the substrate.

[0103] A receiving coil unit according to aspect 3 of the present invention may be configured such that, in the above-mentioned aspect 2, a first hole is formed in the substrate at a position corresponding to the center of the primary coil, and the first core member or the second core member has a first leg portion passing through the first hole.

[0104] A receiving coil unit according to aspect 4 of the present invention may be configured such that, in the above-mentioned aspects 2 or 3, a second hole is formed in the substrate at a position corresponding to the outside of the primary coil, and the first core member or the second core member has a second leg portion passing through the second hole.

[0105] A receiving coil unit according to aspect 5 of the present invention may be configured such that, in aspect 1 or 2 above, a first hole is formed in the substrate at a position corresponding to the center of the primary coil, and the first core member has a first leg portion passing through the first hole.

[0106] A receiving coil unit according to aspect 6 of the present invention may be configured such that, in the above-mentioned aspect 2, the substrate has a first hole formed at a position corresponding to the center of the primary coil, a second hole and a third hole formed at positions corresponding to the outside of the primary coil, and the second core member is an E-shaped core having a first leg passing through the first hole, a second leg passing through the second hole, and a third leg passing through the third hole.

[0107] A power receiving coil unit according to Aspect 7 of the present invention may be configured in any one of Aspects 1 to 6 above, wherein the base portion has a plate shape that is larger than the first power receiving coil in the radial direction of the first power receiving coil.

[0108] The receiving coil unit according to Aspect 8 of the present invention may be configured as in any one of Aspects 1 to 7 above, wherein the primary coil of the transformer is connected across both ends of the first receiving coil.

[0109] The receiving coil unit according to Aspect 9 of the present invention may be configured in any one of Aspects 1 to 8 above, further comprising a first resonant capacitor disposed on the substrate and connected in series to the first receiving coil.

[0110] The receiving coil unit of aspect 10 of the present invention may be configured as in aspect 9 above, further comprising a second receiving coil connected in series to the first receiving coil, and a second resonant capacitor connected between the first receiving coil and the second receiving coil, and the core portion may pass through the second receiving coil.

[0111] The receiving coil unit of aspect 11 of the present invention may be configured in the above-mentioned aspects 9 or 10, further comprising a first external connection terminal connected to the first resonant capacitor and a second external connection terminal connected to the secondary coil of the transformer.

[0112] A receiving coil unit according to aspect 12 of the present invention may be configured as in any of aspects 1 to 7 above, including an auxiliary coil electromagnetically coupled to the first receiving coil, and the primary coil connected between both ends of the auxiliary coil.

[0113] A receiving coil unit according to aspect 13 of the present invention may be configured such that, in any of aspects 1 to 12 above, the substrate has a first wiring layer on which the primary coil is formed, a second wiring layer on which wiring connected to the primary coil is formed, and a third wiring layer on which the secondary coil of the transformer is formed.

[0114] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0115] REFERENCE SIGNS LIST 1, 1a Wireless power transfer system 2 Power transmitting device 3, 3a Power receiving device 21 First communication unit 22 Power transmission control unit 28 Power transmitting coil 31 Voltage determination unit 32 Second communication unit 33, 33a Resonant circuit 34 Power receiving coil 34a First power receiving coil 34b Second power receiving coil 35 Resonant capacitor 35a First resonant capacitor 35b Second resonant capacitor 36 First rectifier circuit 37 Smoothing capacitor 38 Transformer 38a Primary side coil 38b Secondary side coil 39 Second rectifier circuit 40 Switching circuit 44 Auxiliary coil 60, 60a Power receiving coil unit 61a, 61b, 62a, 62b, 63, 64 First external connection terminal to sixth external connection terminal 65, 65c First core member 65a Core portion 65b First base portion 66: Substrate; 66a to 66c: First to third holes; 67, 67b: Second core member; 67a: Second base portion; 68a to 68c: First to third legs; 90: Load

Claims

1. A receiving coil unit comprising: a first receiving coil; a first core member made of ferromagnetic material having a base and a core protruding from one side of the base and passing through the first receiving coil; a substrate arranged on the other side of the base; and a transformer having a primary coil formed by wiring formed on the substrate, wherein the first core member forms part of the core of the transformer.

2. A receiving coil unit as described in claim 1, further comprising a second core member made of a ferromagnetic material, the second core member being arranged so that the first core member and the second core member sandwich the substrate.

3. A receiving coil unit as described in claim 2, wherein a first hole is formed in the substrate at a position corresponding to the center of the primary coil, and the first core member or the second core member has a first leg portion that passes through the first hole.

4. A receiving coil unit as described in claim 2, wherein a second hole is formed in the substrate at a position corresponding to the outside of the primary coil, and the first core member or the second core member has a second leg portion that passes through the second hole.

5. The receiving coil unit according to claim 1, wherein a first hole is formed in the substrate at a position corresponding to the center of the primary coil, and the first core member has a first leg portion that passes through the first hole.

6. A receiving coil unit as described in claim 2, wherein the substrate has a first hole formed at a position corresponding to the center of the primary coil, and a second hole and a third hole formed at positions corresponding to the outside of the primary coil, and the second core member is an E-shaped core having a first leg passing through the first hole, a second leg passing through the second hole, and a third leg passing through the third hole.

7. The receiving coil unit according to any one of claims 1 to 6, wherein the base portion has a plate shape that is larger than the first receiving coil in the radial direction of the first receiving coil.

8. A receiving coil unit according to any one of claims 1 to 6, wherein the primary coil of the transformer is connected across the first receiving coil.

9. A receiving coil unit according to any one of claims 1 to 6, comprising a first resonant capacitor disposed on the substrate and connected in series to the first receiving coil.

10. A receiving coil unit as described in claim 9, comprising: a second receiving coil connected in series to the first receiving coil; and a second resonant capacitor connected between the first receiving coil and the second receiving coil, wherein the core portion passes through the second receiving coil.

11. The receiving coil unit according to claim 9, comprising: a first external connection terminal connected to the first resonant capacitor; and a second external connection terminal connected to the secondary coil of the transformer.

12. A receiving coil unit according to any one of claims 1 to 6, comprising an auxiliary coil electromagnetically coupled to the first receiving coil, and the primary coil is connected across both ends of the auxiliary coil.

13. A receiving coil unit as described in any one of claims 1 to 6, wherein the substrate has a first wiring layer on which the primary coil is formed, a second wiring layer on which wiring connected to the primary coil is formed, and a third wiring layer on which the secondary coil of the transformer is formed.

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