Power receiving device and contactless power supply system

Abstract

To realize a power receiving device that can appropriately obtain a constant voltage or constant current output. [Solution] The power receiving device (3) comprises a resonant circuit (30) having a resonant coil (31) and a first resonant capacitor (32), a power receiving coil (43), a saturable reactor (44) connected to the power receiving coil, a rectifier circuit (45), a smoothing capacitor (46), and a reset unit (50) that adjusts the reset current flowing to the saturable reactor (44) according to the output voltage or output current.

Description

[Technical Field]

[0001] The present invention relates to a power receiving device and a contactless power supply system. [Background technology]

[0002] Patent Document 1 discloses a contactless power supply device. The power receiving device of this contactless power supply device includes a resonant circuit having a receiving coil and a variable capacitance circuit. The power receiving device reduces the capacitance of the variable capacitance circuit as the output voltage from the resonant circuit increases. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-148640 [Overview of the project] [Problems that the invention aims to solve]

[0004] In contactless power supply devices, the relative position between the power transmitting device and the power receiving device can change. Therefore, the power received by the power receiving device can fluctuate. In the configuration of Patent Document 1, the resonant frequency is discretely changed by changing the capacitance in steps. Therefore, in the configuration of Patent Document 1, it is difficult to keep the output voltage smoothly constant.

[0005] One aspect of the present invention aims to realize a power receiving device that can appropriately obtain a constant voltage or constant current output even when the relative position between the power transmitting device and the power receiving device changes. [Means for solving the problem]

[0006] A power receiving device for contactless power supply according to Embodiment 1 of the present invention comprises: a resonant circuit having a resonant coil and a first resonant capacitor connected in series with the resonant coil; a power receiving coil that is electromagnetically coupled to the resonant coil and receives power from a power transmitting device; a saturable reactor connected to the power receiving coil; a rectifier circuit connected to the saturable reactor; a smoothing capacitor connected to the rectifier circuit and smoothing the voltage output from the rectifier circuit; a first detection unit that detects the output voltage or output current of the smoothing capacitor; and a reset unit connected to the saturable reactor and adjusting the reset current flowing to the saturable reactor according to the output voltage or output current.

[0007] According to the above configuration, the charging period or amount of the smoothing capacitor can be adjusted according to the output voltage or output current of the smoothing capacitor. Therefore, even in situations where the receiving voltage of the power receiving device fluctuates due to changes in the relative position between the power transmitting device and the power receiving device, a constant voltage or constant current output can be appropriately obtained.

[0008] A power receiving device for contactless power supply according to aspect 2 of the present invention comprises a resonant circuit having a resonant coil for receiving power from a power transmission device and a first resonant capacitor connected in series with the resonant coil; a saturable reactor through which the received AC current flows; a rectifier circuit connected to the saturable reactor; a smoothing capacitor connected to the rectifier circuit for smoothing the voltage output from the rectifier circuit; a first detection unit for detecting the output voltage or output current of the smoothing capacitor; and a reset unit connected to the saturable reactor for adjusting the reset current flowing to the saturable reactor according to the output voltage or output current.

[0009] In the power receiving device according to embodiment 3 of the present invention, in embodiment 1 or 2 described above, the resonant circuit may be configured to include a second resonant capacitor connected in series or parallel with the first resonant capacitor, and a switching circuit that changes the resonant frequency of the resonant circuit by switching it on or off.

[0010] With the above configuration, even if the received voltage of the receiving device, which fluctuates due to changes in the relative position between the power transmitting device and the power receiving device, exceeds the range adjustable by the saturable reactor, the received voltage can be reduced by changing the resonant frequency of the resonant circuit. Therefore, the output voltage or output current can be adjusted by the saturable reactor. Thus, a constant voltage or constant current output can be appropriately obtained over a wide range of relative positions between the power transmitting device and the power receiving device.

[0011] In the power receiving device according to embodiment 4 of the present invention, in embodiment 3 described above, the second resonant capacitor may be connected in series with the first resonant capacitor, and the switching circuit may be connected in parallel with the second resonant capacitor.

[0012] In the power receiving device according to embodiment 5 of the present invention, in embodiment 3 described above, the second resonant capacitor may be connected in parallel with the first resonant capacitor, and the switching circuit may be connected in series with the second resonant capacitor.

[0013] The power receiving device according to embodiment 6 of the present invention may be configured as described in embodiment 3 above, comprising: a second detection unit for detecting the peak value of the power receiving voltage of the power receiving device; and a control unit for switching the switching circuit on or off according to the peak value of the power receiving voltage.

[0014] With the above configuration, the received voltage can be appropriately controlled based on the peak value of the received voltage before it is adjusted by the saturable reactor.

[0015] In the power receiving device according to embodiment 7 of the present invention, the control unit may be configured to perform hysteresis control so that the peak value of the power receiving voltage falls within a predetermined range, as described in embodiment 6 above.

[0016] With the above configuration, the received voltage can be controlled within a range adjustable by the saturable reactor.

[0017] The power receiving device according to aspect 8 of the present invention, in the above aspect 1 or 2, includes a battery connected to the smoothing capacitor, the first detection unit detects the output voltage and the output current, and the reset unit adjusts the reset current so that the output current becomes constant when the battery has a first charge rate, and adjusts the reset current so that the output voltage becomes constant when the battery has a second charge rate higher than the first charge rate.

[0018] According to the above configuration, charging suitable for the characteristics of the battery can be appropriately performed according to the charge rate of the battery.

[0019] The power receiving device according to aspect 9 of the present invention, in the above aspect 2, includes a transformer having a primary coil connected between one end and the other end of the resonance coil and a secondary coil having a number of turns less than that of the primary coil, and the saturable reactor may be connected to the secondary coil.

[0020] According to the above configuration, the high AC voltage generated in the resonance coil can be appropriately reduced in voltage and supplied to the saturable reactor.

[0021] The non-contact power supply system according to aspect 10 of the present invention includes the power receiving device in the above aspect 1 or 2 and a power transmission device including a power transmission coil that supplies power to the power receiving device.

Effects of the Invention

[0022] According to one aspect of the present invention, an output of constant voltage or constant current can be appropriately obtained.

Brief Description of the Drawings

[0023] [Figure 1] It is a circuit diagram showing the configuration of a non-contact power supply system according to an embodiment of the present invention. [Figure 2] It is a circuit diagram showing an example of the configuration of a second detection unit, a resonance control unit, and a resonance circuit. [Figure 3] This figure shows the peak value of the received voltage when the conditions change. [Figure 4] This figure shows the peak value of the received voltage when the conditions change. [Figure 5] This figure shows the peak value of the received voltage when the conditions change. [Figure 6] This is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present invention. [Figure 7] This is a circuit diagram showing the configuration of a contactless power supply system according to one embodiment of the present invention. [Modes for carrying out the invention]

[0024] [Embodiment 1] Hereinafter, an embodiment relating to one aspect of the present invention (hereinafter also referred to as "this embodiment") will be described based on the drawings.

[0025] §1 Examples of Application Figure 1 is a circuit diagram showing the configuration of the contactless power supply system 1 of this embodiment. The contactless power supply system 1 comprises a power transmission device 2 and a power receiving device 3. The power transmission device 2 supplies power to the power receiving device 3 in a contactless manner.

[0026] The reset unit 50 of the power receiving device 3 adjusts the reset current flowing through the saturable reactor 44 according to the output voltage or output current of the smoothing capacitor 46. This allows the charging period of the smoothing capacitor 46 to be adjusted. In addition, the resonance control unit 52 changes the power receiving voltage of the power receiving device 3 by changing the resonance frequency of the resonance circuit 30. Therefore, even in situations where the power receiving voltage of the power receiving device 3 fluctuates due to changes in the relative position between the power transmitting device 2 and the power receiving device 3, a constant voltage or constant current output can be appropriately obtained.

[0027] §2 Example Configuration (Configuration of power transmission device 2) The power transmission device 2 comprises a power transmission control unit 22, a power supply 23, an inverter 24, a coil 25, a first capacitor 26, a second capacitor 27, and a power transmission coil 28. The power supply 23 is a DC power supply. The inverter 24 is connected to the power supply 23 and converts the DC voltage to an AC voltage. The inverter 24 includes a plurality of switching elements 24a to 24d.

[0028] 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.

[0029] 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 supplies power to the power receiving device 3 in a non-contact manner by generating an alternating magnetic field.

[0030] The power transmission control unit 22 operates the inverter 24 by controlling multiple switching elements 24a to 24d.

[0031] (Configuration of power receiving device 3) The power receiving device 3 comprises a resonant circuit 30, a first detection unit 41, a power receiving coil 43, a saturable reactor 44, a rectifier circuit 45, a smoothing capacitor 46, a first resistive element 47, a reset unit 50, and a battery 80. The power receiving device 3 also comprises a second detection unit 51, a resonant control unit 52 (control unit), a first diode 53, and a detection capacitor 54.

[0032] The resonant circuit 30 comprises a resonant coil 31, a first resonant capacitor 32, a second resonant capacitor 33, and a switching circuit 34. The resonant coil 31 generates an AC voltage from the AC magnetic field from the power transmission coil 28 of the power transmission device 2. The first resonant capacitor 32 is connected in series with the resonant coil 31. The second resonant capacitor 33 is connected in series with the first resonant capacitor 32. The switching circuit 34 is connected in parallel with the second resonant capacitor 33. The switching circuit 34 switches between a short-circuit state and a disconnected state across the second resonant capacitor 33 by switching the switching circuit 34 on (conducting) / off (non-conducting). The switching circuit 34 includes, for example, a transistor.

[0033] The receiving coil 43 receives power from the transmitting coil 28 of the power transmission device 2. The receiving coil 43 is electromagnetically coupled to the resonant coil 31. For example, the receiving coil 43 and the resonant coil 31 share a core and are electromagnetically coupled with a high degree of coupling. The number of turns of the receiving coil 43 is less than the number of turns of the resonant coil 31.

[0034] One end of the saturable reactor 44 is connected to one end of the receiving coil 43. The saturable reactor 44 interrupts the alternating current while the magnetization is not saturated, and allows the alternating current to flow when the magnetization is saturated.

[0035] The rectifier circuit 45 rectifies the AC voltage output by the saturable reactor 44 into a DC voltage. In this case, the rectifier circuit 45 is a half-wave rectifier circuit with a diode, but it is not limited to this. One end of the rectifier circuit 45 is connected to the other end of the saturable reactor 44.

[0036] The smoothing capacitor 46 is connected between the other end of the rectifier circuit 45 and the other end of the power receiving coil 43. The smoothing capacitor 46 smooths the voltage output from the rectifier circuit 45. The smoothing capacitor 46 outputs the smoothed output voltage to the battery 80.

[0037] One end of the first resistive element 47 is connected to the other end of the rectifier circuit 45. The first resistive element 47 is a resistive element for measuring the output current.

[0038] Battery 80 is a rechargeable secondary battery. The positive terminal of battery 80 is connected to one end of the smoothing capacitor 46 and the other end of the rectifier circuit 45 via a first resistive element 47. The negative terminal of battery 80 is connected to the other end of the smoothing capacitor 46. Battery 80 is connected to the smoothing capacitor 46 without going through a DC-DC converter.

[0039] The first detection unit 41 detects the output voltage and output current that the smoothing capacitor 46 outputs to the battery 80. The first detection unit 41 detects the output current flowing to the battery 80 by measuring the voltage across the first resistor element 47. The first detection unit 41 outputs a signal indicating the values ​​of the output voltage and output current to the reset unit 50.

[0040] The reset unit 50 is connected to the other end of the saturable reactor 44 and the other end of the power receiving coil 43. The reset unit 50 supplies a reset current Ir to the saturable reactor 44. The reset unit 50 adjusts the reset current Ir supplied to the saturable reactor 44 according to the output voltage or output current indicated by the signal input from the first detection unit 41. The reset unit 50 adjusts the length of the period during which the reset current Ir is supplied and / or the magnitude of the reset current Ir.

[0041] Here, the reset unit 50 includes a reset control unit 42, a second diode 48, and a second resistive element 49. The cathode of the second diode 48 is connected to the other end of the saturable reactor 44. One end of the second resistive element 49 is connected to the anode of the second diode 48. The reset control unit 42 is connected to the other end of the second resistive element 49 and the other end of the power receiving coil 43. The reset control unit 42 receives signals from the first detection unit 41 indicating the values ​​of the output voltage and output current. The reset control unit 42 flows a reset current Ir for a period of time corresponding to the output voltage or output current.

[0042] The anode of the first diode 53 is connected to one end of the power receiving coil 43.

[0043] The detection capacitor 54 is connected between the cathode of the first diode 53 and the other end of the power receiving coil 43.

[0044] The second detection unit 51 detects the peak value of the power receiving voltage received by the power receiving coil 43 of the power receiving device 3. Here, the second detection unit 51 detects the peak value of the power receiving voltage (the voltage obtained by smoothing the power receiving voltage) by detecting the voltage across the detection capacitor 54. The second detection unit 51 outputs a signal indicating the peak value of the power receiving voltage to the resonance control unit 52.

[0045] The resonance control unit 52 switches the switching circuit 34 on or off according to the peak value of the received voltage. For example, if the peak value of the received voltage is greater than or equal to the first threshold, the resonance control unit 52 switches the switching circuit 34 on. If the peak value of the received voltage is less than or equal to the second threshold (which is less than the first threshold), the resonance control unit 52 switches the switching circuit 34 off. In this way, the resonance control unit 52 may perform hysteresis control based on the peak value of the received voltage at a predetermined switching frequency. Note that the first threshold and the second threshold are greater than the target value of the output voltage of the power receiving device 3.

[0046] (Operation of contactless power supply system 1) When the power transmission device 2 and the power receiving device 3 approach each other, the power transmission coil 28 and the resonant coil 31 are electromagnetically coupled, and power is supplied to the power receiving device 3. Resonance in the resonant circuit 30 generates an AC voltage in the resonant coil 31, and an AC voltage (receiving voltage) is also generated in the power receiving coil 43, corresponding to the degree of coupling with the resonant coil 31 and the turns ratio. The receiving voltage is considered positive when the voltage at one end of the power receiving coil 43 (the side connected to the saturable reactor 44) is higher than the voltage at the other end of the power receiving coil 43.

[0047] During periods when the receiving voltage is positive, current flows from the receiving coil 43 to the saturable reactor 44. As the magnetization of the saturable reactor 44 increases and saturates, the current from the receiving coil 43 passes through the saturable reactor 44 and the rectifier circuit 45 and flows to the smoothing capacitor 46. This charges the smoothing capacitor 46.

[0048] During periods when the receiving voltage is negative, the reset unit 50 supplies a reset current Ir to the saturable reactor 44. For example, the reset control unit 42 includes a switching element. The reset control unit 42 turns on (conducts) the switching element for a period of time corresponding to the output voltage or output current of the smoothing capacitor 46. As a result, the reset control unit 42 supplies a reset current Ir to the saturable reactor 44 from the other end of the receiving coil 43 via the second resistive element 49 and the second diode 48. This reduces the magnetization of the saturable reactor 44. The reduction in magnetization depends on the amount of the reset current Ir, i.e., the duration and magnitude of the reduction.

[0049] During the next period when the receiving voltage is positive, the saturable reactor 44 does not conduct current until its magnetization saturates, at which point it begins to conduct current. Therefore, the smoothing capacitor 46 is charged according to the period during which current flows through the saturable reactor 44.

[0050] The reset unit 50, for example, lengthens the reset period during which the reset current Ir flows as the output voltage or output current increases. When controlling the output voltage, the reset unit 50 may shorten the reset period when the output voltage is a second voltage (lower than the first voltage) compared to the reset period when the output voltage is a first voltage. If the decrease in magnetization of the saturable reactor 44 is small, the magnetization of the saturable reactor 44 will saturate quickly during the period when the receiving voltage is positive, and the charging period of the smoothing capacitor 46 will be extended. As a result, the output voltage will rise. This allows the power receiving device 3 to control the output voltage to the target voltage. The reset unit 50 can change the length of the reset period in multiple stages or continuously depending on the output voltage. As a result, the power receiving device 3 can smoothly maintain a constant output voltage. Therefore, even in situations where the receiving voltage of the power receiving device fluctuates due to changes in the relative position between the power transmitting device and the power receiving device, the power receiving device 3 can appropriately obtain a constant output voltage without communicating with the power transmitting device 2 and changing the control of the power transmitting device 2.

[0051] When controlling the output current, the reset unit 50 may shorten the reset period when the output current is a second current (which is smaller than the first current) compared to the reset period when the output current is a first current. This allows the power receiving device 3 to control the output current to a target current, similar to the case of voltage.

[0052] Adjusting the power supply via communication involves a delay due to the communication (e.g., about 10ms). In the contactless power supply system 1, although the power transmission device 2 controls the amount of power supplied, the power receiving device 3 can prevent overvoltage or overcurrent from occurring through its control. Therefore, the occurrence of failures due to overvoltage or overcurrent can be reduced.

[0053] Here, if the frequency of the transmission coil 28 of the power transmission device 2 matches the resonant frequency of the resonant circuit 30, which is a parallel resonant, a constant current characteristic is obtained. Therefore, as the load approaches zero, the voltage generated in the resonant coil 31 or the receiving coil 43 rises significantly. In addition, the voltage generated in the resonant coil 31 or the receiving coil 43 also rises as the degree of coupling between the transmission coil 28 and the resonant coil 31 increases. If the received voltage becomes too high, it may exceed the range that can be controlled (reduced) by the saturable reactor 44. Therefore, the power receiving device 3 changes the resonant frequency of the resonant circuit 30 so that the received voltage does not exceed the upper limit.

[0054] Figure 2 is a circuit diagram showing an example of the configuration of the second detection unit 51, the resonance control unit 52, and the resonance circuit 30. The second detection unit 51 has a third resistive element 61 and a fourth resistive element 62. The third resistive element 61 and the fourth resistive element 62 are connected in series with each other. The peak value Vo of the received voltage is input to one end of the third resistive element 61.

[0055] The resonance control unit 52 includes a comparator 63, a constant voltage source 64, a fifth resistor 65, a first transistor 66, and a second transistor 67. A divided received voltage is input to the non-inverting input terminal of the comparator 63 from the node between the third resistor 61 and the fourth resistor 62. A predetermined voltage is input to the inverting input terminal of the comparator 63 from the constant voltage source 64. One end of the fifth resistor 65 is connected to the non-inverting input terminal of the comparator 63. The other end of the fifth resistor 65 is connected to the output terminal of the comparator 63. One end of the first transistor 66 is connected to the power supply Vcc. The other end of the first transistor 66 is connected to one end of the second transistor 67. The other end of the second transistor 67 is connected to the other end of the resonant coil 31. The control terminals of the first transistor 66 and the second transistor 67 are connected to the output terminal of the comparator 63. The node between the other end of the first transistor 66 and one end of the second transistor 67 is connected to the control terminal of the switching circuit 34. Here, the first transistor 66 is an NPN bipolar transistor. The second transistor 67 is a PNP bipolar transistor.

[0056] The comparator 63, the constant voltage source 64, and the fifth resistor element 65 constitute a hysteresis control circuit. The first transistor 66 and the second transistor 67 constitute a push-pull circuit. When the peak value Vo of the received voltage exceeds the first threshold, the resonance control unit 52 switches the switching circuit 34 on. When the peak value Vo of the received voltage falls below the second threshold, the resonance control unit 52 switches the switching circuit 34 off.

[0057] The first resonant capacitor 32 and the second resonant capacitor 33 are connected in series with each other. Therefore, when the switching circuit 34 is off, the combined capacitance of the first resonant capacitor 32 and the second resonant capacitor 33 is smaller than the capacitance of the first resonant capacitor 32. Consequently, the capacitance (combined capacitance) in the resonant circuit 30 when the switching circuit 34 is off is smaller than the capacitance (combined capacitance) in the resonant circuit 30 when the switching circuit 34 is on. The switching circuit 34 changes the combined capacitance of the first resonant capacitor 32 and the second resonant capacitor 33 by switching it on and off. In this way, the switching circuit 34 changes the resonant frequency of the resonant circuit 30.

[0058] For example, suppose the capacitance of the first resonant capacitor 32 is 10 nF and the capacitance of the second resonant capacitor 33 is 100 nF. When the switching circuit 34 is on, the capacitance in the resonant circuit 30 is 10 nF, and when the switching circuit 34 is off, the capacitance in the resonant circuit 30 is 9.09 nF. In this case, a capacitance change of approximately 10% is obtained. When the switching circuit 34 is off, a voltage 0.0909 times the voltage generated across the resonant coil 31 is applied to the switching circuit 34. A voltage of 1 kV to several kV can be generated across the resonant coil 31, but even in this case, a MOSFET with a low voltage rating can be used in the switching circuit 34.

[0059] Figure 3 shows the peak value of the received voltage when the conditions change. The horizontal axis represents the frequency fq (Hz). The vertical axis represents the peak value of the received voltage Vo (V). The frequency of the transmission coil 28 is the frequency at the position indicated by the vertical line on the graph.

[0060] The load resistance of the power receiving device is RL, and the coupling degree between the power transmission coil 28 and the resonant coil 31 is k. 12 The peak value of the received voltage when the capacitance of the resonant circuit 30 is C2 is |Vo(w(fq),RL,k 12 The line ,C2)| is shown with a thick solid line. In this case, the resonant frequency of the resonant circuit 30 approximately matches the frequency of the transmission coil 28. The peak value of the received voltage matches the target voltage Vt.

[0061] The peak value of the received voltage when the transmission coil 28 and the resonant coil 31 are brought closer together and the degree of coupling doubles is |Vo(w(fq),RL,2k 12 The line ,C2)| is shown with a thick dashed line. In this case, the peak value of the received voltage is between the first threshold and the second threshold. If the peak value of the received voltage is less than or equal to the first threshold, the received voltage can be reduced by the saturable reactor 44, and the output voltage can be set to the target voltage Vt.

[0062] When the transmission coil 28 and the resonant coil 31 are brought closer together and the coupling degree becomes four times greater, the peak value of the received voltage is |Vo(w(fq),RL,4k 12 The line ,C2)| is shown as a thin solid line. In this case, the peak value of the received voltage exceeds the first threshold. In this case, the received voltage cannot be sufficiently reduced by the saturable reactor 44, and the output voltage becomes higher than the target voltage Vt. Therefore, the resonance control unit 52 changes the resonance frequency of the resonant circuit 30 by changing the capacitance of the resonant circuit 30.

[0063] The peak value of the received voltage when the coupling degree is 4 times and the capacitance of the resonant circuit 30 is 1.2 times is |Vo(w(fq),RL,4k 12 The line ,1.2C2)| is shown with a thin dotted line. As the capacitance increases, the resonant frequency of the resonant circuit 30 decreases, and the peak of the received voltage shifts to a lower frequency. As the resonant frequency deviates from the frequency of the transmitting coil 28, the peak value of the received voltage decreases and falls below the first threshold. If the peak value of the received voltage falls below the second threshold, the resonance control unit 52 returns the capacitance of the resonant circuit 30 to C2, increasing the peak value of the received voltage.

[0064] The peak value of the received voltage when the coupling degree is 4 times, the capacitance of the resonant circuit 30 is 1.2 times, and the load resistance is 100 times is |Vo(w(fq),100RL,4k 12 The line ,1.2C2)| is shown with a thin dashed line. Even when the load resistance is large (output load is small), the peak value of the received voltage decreases and falls below the first threshold because the resonant frequency is shifted.

[0065] Thus, the resonance control unit 52 performs hysteresis control so that the peak value of the received voltage falls within a predetermined range by changing the resonance frequency. By the hysteresis control, the peak value of the received voltage fluctuates within a range from approximately the first threshold value to the second threshold value. Thereby, the power receiving device 3 can reduce the received voltage by the saturable reactor 44 and set the output voltage to the target voltage Vt.

[0066] FIG. 4 is a diagram showing the peak value of the received voltage when the conditions change. The horizontal axis represents the frequency fq (Hz). The vertical axis represents the peak value Vo (V) of the received voltage. The frequency of the power transmission coil 28 is the frequency at the position indicated by the vertical line in the graph.

[0067] When the power transmission coil 28 approaches the resonance coil 31, the coupling degree increases, and usually the inductance L2 of the resonance coil 31 can also increase. The peak value of the received voltage |Vo(w(fq), RL, 4k 12 , C2, 1.1L2)| is shown by a thin solid line. The peak value of the received voltage |Vo(w(fq), RL, 4k 12 , 1.1C2, 1.1L2)| is shown by a thin dotted line. The peak value of the received voltage |Vo(w(fq), 100RL, 4k 12 , 1.1C2, 1.1L2)| is shown by a thin dashed line.

[0068] Due to the increase in the inductance L2, the resonance frequency decreases. Therefore, by changing (increasing) the capacitance of the resonance circuit 30 by 10%, the peak value of the received voltage can be sufficiently decreased.

[0069] Figure 5 shows the peak value of the received voltage when the conditions change. The horizontal axis represents the frequency fq (Hz). The vertical axis represents the peak value of the received voltage Vo (V). The frequency of the transmission coil 28 is the frequency at the position indicated by the vertical line on the graph. Here, when the peak value of the received voltage Vo exceeds the first threshold, the resonance control unit 52 switches the switching circuit 34 off. When the peak value of the received voltage Vo falls below the second threshold, the resonance control unit 52 switches the switching circuit 34 on. That is, when the switching circuit 34 is on, the resonant frequency of the resonant circuit 30 matches the frequency of the transmission coil 28. Also, when the peak value of the received voltage Vo exceeds the first threshold, the resonance control unit 52 reduces the capacitance of the resonant circuit 30.

[0070] The peak value of the received voltage when the coupling degree is 4 times and the capacitance of the resonant circuit 30 is 0.8 times is |Vo(w(fq),RL,4k 12 The line 0.8C2 is shown as a thin dotted line. As the capacitance decreases, the resonant frequency of the resonant circuit 30 increases, and the peak of the received voltage shifts to a higher frequency. As the resonant frequency deviates from the frequency of the transmitting coil 28, the peak value of the received voltage decreases and falls below the first threshold. Here, the peak value of the received voltage falls below the second threshold, so the resonance control unit 52 returns the capacitance of the resonant circuit 30 to C2 again, causing the peak value of the received voltage to increase again.

[0071] The peak value of the received voltage when the coupling degree is 4 times, the capacitance of the resonant circuit 30 is 0.8 times, and the load resistance is 100 times is |Vo(w(fq),100RL,4k 12 The line ,0.8C2)| is shown with a thin dashed line. Even when the load resistance is large (output load is small), the peak value of the received voltage remains below the first threshold. However, in this case, the peak value of the received voltage is as shown in Figure 4|Vo(w(fq),100RL,4k|. 12 (1.1C2, 1.1L2) is greater than. Considering the increase in inductance due to the approach of the transmission coil 28, when the peak value of the received voltage increases, increasing the capacitance to shift the resonant frequency to the same low-frequency side requires a smaller percentage change in capacitance.

[0072] The reset unit 50 switches between constant voltage control and constant current control depending on the charge level of the battery 80. When the charge level of the battery 80 is low, it is preferable that the current output to the battery 80 is constant. When the charge level of the battery 80 is high, it is preferable that the voltage output to the battery 80 is constant.

[0073] The reset unit 50 acquires information on the charge level of the battery 80. When the battery is at the first charge level, the reset unit 50 adjusts the reset current based on the detected output current to keep the output current constant. When the battery is at the second charge level, the reset unit 50 adjusts the reset current based on the detected output voltage to keep the output voltage constant. The second charge level is higher than the first charge level.

[0074] According to the contactless power supply system 1 of this embodiment, communication between the power receiving device 3 and the power transmitting device 2 is not required to adjust the supplied power. Therefore, the supplied power can be adjusted without delay in environments where the relative position of the power receiving device 3 with respect to the power transmitting device 2 changes. For this reason, the contactless power supply system 1 can also be used for wireless power supply while driving (DWPT), etc.

[0075] [Embodiment 2] Other embodiments of the present invention will be described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0076] Figure 6 is a circuit diagram showing the configuration of the contactless power supply system 1a of this embodiment. The contactless power supply system 1a comprises a power transmission device 2 and a power receiving device 3a. The power receiving device 3a comprises a resonant circuit 30, a transformer 55, a first detection unit 41, a saturable reactor 44, a rectifier circuit 45, a smoothing capacitor 46, a first resistive element 47, a reset unit 50, and a battery 80. The power receiving device 3a also comprises a second detection unit 51, a resonant control unit 52 (control unit), a first diode 53, and a detection capacitor 54.

[0077] The primary coil of transformer 55 is connected between one end and the other end of the resonant coil 31. One end of the secondary coil of transformer 55 is connected to one end of the saturable reactor 44. The other end of the secondary coil of transformer 55 is connected to the negative terminal of the battery 80 and the other end of the smoothing capacitor 46. The number of turns of the secondary coil of transformer 55 is less than the number of turns of the primary coil.

[0078] The anode of the first diode 53 is connected to one end of the secondary coil of the transformer 55.

[0079] The detection capacitor 54 is connected between the cathode of the first diode 53 and the other end of the secondary coil of the transformer 55.

[0080] (Operation of contactless power supply system 1a) In the power receiving device 3a, the resonant coil 31 receives power from the power transmitting device 2. Resonance in the resonant circuit 30 generates an AC voltage (receiving voltage) in the resonant coil 31. The receiving voltage generated in the resonant coil 31 is reduced in pressure by the transformer 55. The reduced receiving voltage is generated in the secondary coil of the transformer 55. An AC current (received AC current) due to the reduced receiving voltage flows through the saturable reactor 44. The power received by the resonant coil 31 is supplied to the load (battery 80) via the transformer 55. The second detection unit 51 detects the peak value of the receiving voltage reduced by a predetermined ratio by the transformer 55.

[0081] In Embodiment 1, the AC voltage to be received is reduced by a receiving coil 43 that is electromagnetically coupled to the resonant coil 31, but in Embodiment 2, the AC voltage to be received is reduced by a transformer 55 connected to the resonant coil 31. Other operations of the power receiving device 3a are the same as those of the power receiving device 3 in Embodiment 1.

[0082] [Embodiment 3] Other embodiments of the present invention will be described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0083] Figure 7 is a circuit diagram showing the configuration of the contactless power supply system 1b of this embodiment. The contactless power supply system 1b comprises a power transmission device 2 and a power receiving device 3b. The power receiving device 3b includes a resonant circuit 30b instead of the resonant circuit 30 of Embodiment 1. The other configurations of the power receiving device 3b are the same as those of the power receiving device 3 of Embodiment 1.

[0084] The resonant circuit 30b comprises a resonant coil 31, a first resonant capacitor 32, a second resonant capacitor 33, and a switching circuit 34. The first resonant capacitor 32 is connected in series with the resonant coil 31. The second resonant capacitor 33 is connected in parallel with the first resonant capacitor 32. The switching circuit 34 is connected in series with the second resonant capacitor 33.

[0085] The resonance control unit 52 switches whether the second resonant capacitor 33 contributes to the capacitance of the resonant circuit 30b by switching the switching circuit 34 on or off. The resonance control unit 52 changes the resonant frequency of the resonant circuit 30b by changing the capacitance of the resonant circuit 30b. Hysteresis control of the powered voltage is possible even in a resonant circuit 30b in which multiple resonant capacitors are connected in parallel.

[0086] (modified version) In each circuit, the second resonant capacitor 33, the switching circuit 34, the second detection unit 51, the resonant control unit 52, the first diode 53, and the detection capacitor 54 may be omitted. This is sufficient as long as the powered voltage is within a range controllable by the saturable reactor 44.

[0087] In the power receiving device 3a of Embodiment 2, the transformer 55 may be omitted. When the AC voltage generated in the resonant coil 31 and the target voltage of the output voltage are far apart, it is preferable to reduce the voltage using the transformer 55.

[0088] Instead of the battery 80, any load device may be connected to the power receiving device.

[0089] The power receiving device may be configured to perform only one of constant voltage control or constant current control. For example, the first detection unit 41 may not detect the output current, and the reset unit 50 may adjust the reset current to keep the output voltage output to the load device constant.

[0090] In the power receiving device 3a of Embodiment 2, the resonant circuit 30b of Embodiment 3 may be used instead of the resonant circuit 30.

[0091] In a resonant circuit, a resonant capacitor and a switching circuit may be added to allow the resonant frequency to be changed in three or more stages.

[0092] [Examples of implementation using software] The functions of the contactless power supply systems 1, 1a, and 1b (hereinafter referred to as "devices") are programs that cause a computer to function as the device, and these programs can be realized by programs that cause a computer to function as each control block of the device (especially the power transmission control unit 22, the first detection unit 41, the reset control unit 42, etc.).

[0093] 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., memory) as hardware for executing the program. By executing the program using this control device and storage device, the functions described in each of the embodiments are realized.

[0094] The above program may be recorded on one or more computer-readable recording media, not temporary ones. These recording media may or may not be provided by the above device. In the latter case, the program may be supplied to the above device via any wired or wireless transmission medium.

[0095] Furthermore, some or all of the functions of each of the above control blocks can also be realized by logic circuits. For example, an integrated circuit in which logic circuits functioning as each of the above control blocks are formed is also included in the scope of the present invention. In addition, it is also possible to realize the functions of each of the above control blocks by, for example, a quantum computer.

[0096] 〔summary〕 A power receiving device for contactless power supply according to Embodiment 1 of the present invention comprises: a resonant circuit having a resonant coil and a first resonant capacitor connected in series with the resonant coil; a power receiving coil that is electromagnetically coupled to the resonant coil and receives power from a power transmitting device; a saturable reactor connected to the power receiving coil; a rectifier circuit connected to the saturable reactor; a smoothing capacitor connected to the rectifier circuit and smoothing the voltage output from the rectifier circuit; a first detection unit that detects the output voltage or output current of the smoothing capacitor; and a reset unit connected to the saturable reactor and adjusting the reset current flowing to the saturable reactor according to the output voltage or output current.

[0097] A power receiving device for contactless power supply according to aspect 2 of the present invention comprises a resonant circuit having a resonant coil for receiving power from a power transmission device and a first resonant capacitor connected in series with the resonant coil; a saturable reactor through which the received AC current flows; a rectifier circuit connected to the saturable reactor; a smoothing capacitor connected to the rectifier circuit for smoothing the voltage output from the rectifier circuit; a first detection unit for detecting the output voltage or output current of the smoothing capacitor; and a reset unit connected to the saturable reactor for adjusting the reset current flowing to the saturable reactor according to the output voltage or output current.

[0098] In the power receiving device according to embodiment 3 of the present invention, in embodiment 1 or 2 described above, the resonant circuit may be configured to include a second resonant capacitor connected in series or parallel with the first resonant capacitor, and a switching circuit that changes the resonant frequency of the resonant circuit by switching it on or off.

[0099] In the power receiving device according to embodiment 4 of the present invention, in embodiment 3 described above, the second resonant capacitor may be connected in series with the first resonant capacitor, and the switching circuit may be connected in parallel with the second resonant capacitor.

[0100] In the power receiving device according to embodiment 5 of the present invention, in embodiment 3 described above, the second resonant capacitor may be connected in parallel with the first resonant capacitor, and the switching circuit may be connected in series with the second resonant capacitor.

[0101] The power receiving device according to embodiment 6 of the present invention may be configured to include, in any of embodiments 3 to 5 above, a second detection unit for detecting the peak value of the power receiving voltage of the power receiving device, and a control unit for switching the switching circuit on or off according to the peak value of the power receiving voltage.

[0102] In the power receiving device according to embodiment 7 of the present invention, the control unit may be configured to perform hysteresis control so that the peak value of the power receiving voltage falls within a predetermined range, as described in embodiment 6 above.

[0103] A power receiving device according to embodiment 8 of the present invention may be configured such that, in any of embodiments 1 to 7 above, it includes a battery connected to the smoothing capacitor, the first detection unit detects the output voltage and the output current, and the reset unit adjusts the reset current to keep the output current constant when the battery is at a first charge level, and adjusts the reset current to keep the output voltage constant when the battery is at a second charge level higher than the first charge level.

[0104] In the power receiving device according to embodiment 9 of the present invention, in embodiment 2 described above, a transformer is provided having a primary coil connected between one end and the other end of the resonant coil, and a secondary coil having fewer turns than the primary coil, and the saturable reactor may be connected to the secondary coil.

[0105] A contactless power supply system according to embodiment 10 of the present invention comprises the power receiving device according to any of embodiments 1 to 9 described above, and a power transmission device equipped with a power transmission coil that supplies power to the power receiving device.

[0106] The present invention is not limited to the embodiments described above, 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. [Explanation of Symbols]

[0107] 1, 1a, 1b Contactless power supply system 2 Power transmission equipment 3, 3a, 3b Power receiving device 22 Power transmission control unit 24 Inverters 28 Power transmission coil 30, 30b resonant circuit 31 Resonant coil 32. First resonant capacitor 33. Second resonant capacitor 34 Switching Circuits 41 First detection unit 42 Reset Control Unit 43 Power receiving coil 44 Saturable reactor 45 Rectifier circuit 46 Smoothing Capacitor 48. Second Diode 50 Reset section 51 Second detection unit 52 Resonance Control Unit (Control Unit) 53 First Diode 54 Detect Capacitor 55 transformers 80 batteries

Claims

1. A resonant circuit having a resonant coil and a first resonant capacitor connected in series with the resonant coil, The resonant coil is electromagnetically coupled to the receiving coil, which receives power from the power transmission device, A saturable reactor connected to the power receiving coil, A rectifier circuit connected to the aforementioned saturable reactor, A smoothing capacitor connected to the rectifier circuit, which smooths the voltage output from the rectifier circuit, A first detection unit for detecting the output voltage or output current of the smoothing capacitor, A power receiving device for contactless power supply, comprising: a reset unit connected to the saturable reactor, which adjusts the reset current flowing through the saturable reactor according to the output voltage or the output current.

2. A resonant circuit having a resonant coil that receives power from a power transmission device and a first resonant capacitor connected in series with the resonant coil, A saturable reactor through which the received AC current flows, A rectifier circuit connected to the aforementioned saturable reactor, A smoothing capacitor connected to the rectifier circuit, which smooths the voltage output from the rectifier circuit, A first detection unit for detecting the output voltage or output current of the smoothing capacitor, A power receiving device for contactless power supply, comprising: a reset unit connected to the saturable reactor, which adjusts the reset current flowing through the saturable reactor according to the output voltage or the output current.

3. The aforementioned resonant circuit is A second resonant capacitor connected in series or parallel to the first resonant capacitor, A power receiving device according to claim 1 or 2, comprising a switching circuit that changes the resonant frequency of the resonant circuit by switching it on or off.

4. The second resonant capacitor is connected in series with the first resonant capacitor. The power receiving device according to claim 3, wherein the switching circuit is connected in parallel with the second resonant capacitor.

5. The second resonant capacitor is connected in parallel with the first resonant capacitor. The power receiving device according to claim 3, wherein the switching circuit is connected in series with the second resonant capacitor.

6. A second detection unit detects the peak value of the power receiving voltage of the power receiving device, The power receiving device according to claim 3, further comprising a control unit that switches the switching circuit on or off according to the peak value of the power receiving voltage.

7. The power receiving device according to claim 6, wherein the control unit performs hysteresis control so that the peak value of the power receiving voltage falls within a predetermined range.

8. The battery is connected to the smoothing capacitor, The first detection unit detects the output voltage and the output current, The aforementioned reset unit When the battery is at a first charge level, the reset current is adjusted to keep the output current constant. The power receiving device according to claim 1 or 2, wherein the reset current is adjusted to keep the output voltage constant when the battery is at a second charge level higher than the first charge level.

9. The transformer comprises a primary coil connected between one end and the other end of the resonant coil, and a secondary coil having fewer turns than the primary coil, The power receiving device according to claim 2, wherein the saturable reactor is connected to the secondary coil.

10. A power receiving device according to claim 1 or 2, A contactless power supply system comprising a power transmission device equipped with a power transmission coil that supplies power to the power receiving device.

Images