JP2017225232A - Non-contact power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact power supply device that can suppress a reduction in the amount of energy transmission power even when the distance between a coil on a power transmission side and a coil on a power reception side is changed.SOLUTION: A non-contact power supply device 1 comprises: a power transmission device 10 that includes a power transmission resonance circuit 14 including a power transmission coil 141 transmitting power in a non-contact manner; and a power reception device 20 to which a power is transmitted from the power transmission device 10. The power reception device 20 includes a power reception capacitor 212, a power reception coil 211 that is connected to one end of the power reception capacitor 212 and can receive a power transmitted from the power transmission coil 141, and a load circuit voltage detector 25 that detects a load circuit voltage output to a load circuit 26 connected to the power reception device 20. The power reception device 20 further includes a resonant frequency changing circuit 22 that, when the load circuit voltage is equal to or larger than a first threshold voltage, changes a resonant frequency of the power reception device 20. When a first changing capacitor and the power reception coil and power reception capacitor are electrically connected, the resonant frequency is changed, and thereby a voltage gain is reduced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a non-contact power feeding device.

  2. Description of the Related Art Conventionally, so-called non-contact power feeding (also called wireless power feeding) technology that transmits power through a space without using a metal contact has been studied.

  As one of non-contact power feeding techniques, a magnetic field resonance (also called magnetic resonance coupling or magnetic resonance) method is known (see, for example, Patent Document 1). In the magnetic field resonance method, a resonance circuit including a coil is provided on each of the power transmission side and the power reception side, and the resonance frequency of the resonance circuit is tuned so that magnetic resonance occurs between the power transmission side coil and the power reception side coil. A coupling state of magnetic fields capable of transmitting energy occurs. Thereby, electric power is transmitted from the coil on the power transmission side to the coil on the power reception side through the space. In the non-contact power feeding by the magnetic field resonance method, it is possible to achieve an energy transmission efficiency of about several tens of percent, and the distance between the power transmission side coil and the power reception side coil can be made relatively large. . For example, when each coil has a size of about several tens of centimeters, the distance between the coil on the power transmission side and the coil on the power reception side can be several tens cm to 1 m or more.

  On the other hand, in the magnetic field resonance method, when the distance between the coil on the power transmission side and the coil on the power reception side is closer than the optimum distance, it is known that the amount of energy transmission power decreases (for example, see Patent Document 2). . This is because the degree of coupling between the two coils changes according to the distance between the two coils, and the resonance frequency between the two coils changes. When the distance between the two coils is appropriate, the resonance frequency between the two coils is one, and the resonance frequency is determined by the inductance of the coil and the capacitance of the capacitor. Equal to the resonance frequency. However, when the distance between the two coils becomes close and the degree of coupling increases, two resonance frequencies appear between the two coils. One is a frequency higher than the resonance frequency of each resonance circuit itself, and the other is a frequency lower than the resonance frequency of each resonance circuit itself. As described above, when the degree of coupling increases, the resonance frequency between the two coils and the resonance frequency of each resonance circuit itself do not match. Therefore, AC power having the resonance frequency of the resonance circuit is supplied to the resonance circuit on the power transmission side. Even if it supplies to, since the resonance between coils does not arise well, energy transmission electric energy falls.

  Therefore, the power transmission device disclosed in Patent Document 2 has a resonance point different from that of the power reception resonance coil that transmits power supplied from the power supply unit as magnetic field energy to the power reception resonance coil that resonates at a resonance frequency that causes magnetic field resonance. It has a coil. Thereby, this power transmission device enables power transmission / reception between the power transmission coil and the power reception resonance coil without using magnetic field resonance.

  Further, in Patent Document 3, when the output voltage of the power reception side resonance circuit is higher than a predetermined value, the protection switch is turned on to form a closed loop including a coil and a capacitor, and the resonance frequency of the power reception side resonance circuit is shifted, Preventing the occurrence of overvoltage in the power receiving device is described.

  Also, in Patent Document 4, in order to prevent theft, when the power receiving side cord does not correspond to the power transmission side cord, the capacity of the variable capacitor is changed, and sufficient power cannot be obtained on the power receiving device side. It is described that the resonance frequency is set to such a value.

Special table 2009-501510 International Publication No. 2011-064879 JP2015-208136A JP 2011-2111895 A

  In the method shown in Patent Document 3, since the protection switch is turned on to form a closed loop including a coil and a capacitor to shift the resonance frequency, the current flowing in the closed loop while the protection switch is turned on does not contribute to power transmission. May reduce efficiency. Further, in the method shown in Patent Document 3, when a state in which the output voltage of the power reception side resonance circuit is higher than a predetermined value frequently occurs, an overcurrent frequently flows in a coil and a capacitor that form a closed loop, There is a risk of overheating and damage.

  Further, in the method shown in Patent Document 4, the change in the voltage gain with respect to the change in the capacitance of the variable capacitor becomes small under a predetermined condition such as in a light load circuit, so that it may not be possible to sufficiently prevent the occurrence of overvoltage. .

  Therefore, an object of the present invention is to provide a non-contact power feeding device that can prevent the occurrence of overvoltage regardless of changes in conditions such as the size of a load circuit.

  As one form of this invention, the non-contact electric power feeder which has a power transmission apparatus which has a power transmission resonance circuit containing the power transmission coil which transmits electric power non-contactingly, and the power receiving apparatus which transmits electric power from a power transmission apparatus is provided. The power receiving device includes a power receiving resonance circuit having a power receiving capacitor and a power receiving coil connected to one end of the power receiving capacitor and capable of transmitting power to and from the power transmitting coil, and a load circuit output to a load circuit connected to the power receiving device A load circuit voltage detector for detecting a voltage. The power receiving apparatus further includes a resonance frequency changing circuit connected to the power receiving resonance circuit. The resonance frequency changing circuit includes: a first changing capacitor having one end connected to the other end of the receiving capacitor and the other end connected to the receiving coil; and the first changing capacitor and the receiving coil when an ON instruction signal is input. And a first change switch that cuts off the electrical connection between the first change capacitor and the power reception coil and the power reception capacitor when the ON instruction signal is not input. And an overvoltage determination circuit that outputs an ON instruction signal to the first change switch when the load circuit voltage is equal to or higher than the first threshold voltage. In the non-contact power supply device, when the first change capacitor, the power receiving coil, and the power reception capacitor are electrically connected, the resonance frequency is changed by the resonance frequency change circuit, thereby reducing the voltage gain.

  In this case, the first change switch is preferably an n-channel MOSFET whose source is grounded.

  In this non-contact power feeding device, the resonance frequency changing circuit includes a second changing capacitor connected in parallel to the power receiving capacitor, and between the second changing capacitor, the power receiving coil, and the power receiving capacitor when the ON instruction signal is input. And a second change switch that cuts off the electrical connection between the second change capacitor and the receiving coil and the receiving capacitor when the ON instruction signal is not input, The overvoltage determination circuit preferably further outputs an ON instruction signal to the second change switch when the load circuit voltage is equal to or higher than the first threshold voltage.

  In this case, the first change switch and the second change switch are preferably n-channel MOSFETs whose sources are grounded.

  In this contactless power supply device, the power receiving device further includes an overvoltage signal transmission circuit that transmits an overvoltage signal indicating that the load circuit voltage is overvoltage when the load circuit voltage is equal to or higher than the first threshold voltage. A power supply circuit that supplies an AC voltage to the power transmission resonance circuit, an overvoltage signal receiver circuit that receives an overvoltage signal, and a control that lowers the operating frequency of the power supply circuit when an overvoltage signal is input from the overvoltage signal receiver circuit It is preferable to have a circuit.

  The non-contact power feeding device according to the present invention has an effect that it is possible to prevent the occurrence of overvoltage regardless of changes in conditions such as the size of the load circuit.

It is a schematic block diagram of the non-contact electric power feeder which concerns on 1st Embodiment. It is a figure which shows the change of the load circuit voltage when changing the capacity | capacitance of a receiving capacitor. It is a figure which shows the relationship between the operating frequency of the non-contact electric power supply shown in FIG. 1, and a load circuit voltage, (a) is a figure which shows the relationship between the operating frequency and load circuit voltage in the state where the 1st change switch was turned off. (B) is a diagram showing the relationship between the operating frequency and the load circuit voltage when the first change switch is turned on when the load circuit is relatively heavy, and (c) when the load circuit is relatively light. It is a figure which shows the relationship between the operating frequency of the state in which the 1st change switch was turned on, and load circuit voltage. It is a schematic block diagram of the non-contact electric power feeder which concerns on 2nd Embodiment. It is a figure which shows the relationship between the operating frequency of the non-contact electric power supply shown in FIG. 4, and a load circuit voltage, (a) is a figure which shows the relationship between the operating frequency and load circuit voltage in the state where the 1st change switch was turned off. (B) is a diagram showing the relationship between the operating frequency and the load circuit voltage when the first change switch is turned on when the load circuit is relatively heavy, and (c) when the load circuit is relatively light. It is a figure which shows the relationship between the operating frequency of the state in which the 1st change switch was turned on, and load circuit voltage. It is a schematic block diagram of the non-contact electric power feeder which concerns on 3rd Embodiment. (A) is a figure which shows the control signal output to a gate driver from the control circuit shown in FIG. 6 when an overvoltage signal is input, (b) shows an example of the drain current of the switching element shown in FIG. FIG. It is a schematic block diagram of the non-contact electric power feeder which concerns on 4th Embodiment. FIG. 9 is an equivalent circuit diagram of a power transmission circuit including the power transmission resonance circuit and the power reception resonance circuit illustrated in FIG. 8. It is a figure which shows an example of the frequency characteristic of the impedance of the equivalent circuit shown in FIG. It is a schematic block diagram of the non-contact electric power feeder which concerns on 5th Embodiment. 12 is a timing chart in a state where a power receiving device (not shown) that does not have an identification number is disposed in proximity to the power transmitting device illustrated in FIG. 11. (A) is a timing chart when the degree of coupling between the power transmission coil and the power reception coil shown in FIG. 11 is 0.3, and (b) is a power transmission detected by the power transmission current detection circuit in the state shown in (a). It is a figure which shows an example of the measured value of an electric current and the load circuit voltage which a load circuit voltage detector detects. 14 is a timing chart in a state where the power receiving device shown in FIG. 11 further approaches the power transmission device and the degree of coupling changes from 0.3 to 0.5 from the state shown in FIG. FIG. 15 is a timing chart in a state where the load circuit of the power receiving device illustrated in FIG. 11 is smaller than the state illustrated in FIG. 14. It is a schematic block diagram of the non-contact electric power feeder by which the 1st change capacitor and the 1st change switch are arrange | positioned between a receiving coil and a receiving capacitor. (A) is an equivalent circuit diagram of the power transmission circuit of the non-contact power feeding device shown in FIG. 1, and (b) is an equivalent circuit diagram of the power transmission circuit of the non-contact power feeding device shown in FIG. (A) is a figure which shows the relationship between the operating frequency and load circuit voltage of the state which the 1st change switch turned on when the load circuit is comparatively heavy in the non-contact electric power feeder shown in FIG. 16, (b) is a figure. 16 is a diagram illustrating a relationship between an operating frequency and a load circuit voltage in a state where a first change switch is turned on when the load circuit is relatively light in the contactless power supply device illustrated in FIG.

  Hereinafter, a non-contact power feeding device and a control method thereof according to an embodiment of the present invention will be described with reference to the drawings. As described above, in non-contact power feeding using resonance between a power transmission side coil and a power reception side coil, a power transmission side coil (hereinafter referred to as a power transmission coil) and a power reception side coil (hereinafter referred to as a power reception coil). The degree of coupling changes according to the distance between them. As the distance between the power transmission coil and the power reception coil becomes shorter, the power reception voltage received by the power reception device increases as the degree of coupling increases. On the other hand, when the distance between the power transmission coil and the power reception coil increases, the power reception voltage received by the power reception device decreases as the degree of coupling decreases. This contactless power supply device suppresses the maximum voltage that can be received by the power receiving device by changing the resonance frequency of the power receiving resonant circuit when the coupling degree increases and the power receiving voltage received by the power receiving device exceeds a predetermined voltage. To do. More specifically, the resonance frequency changing circuit includes a first changing capacitor, a first changing switch, and an overvoltage determination circuit, and is connected to the power receiving resonance circuit. The first change capacitor has one end connected to the other end of the power receiving capacitor and the other end connected to the power receiving coil. The first change switch electrically connects the first change capacitor, the power receiving coil, and the power receiving capacitor when the ON instruction signal is input. Further, the first change switch cuts off the electrical connection between the first change capacitor, the power receiving coil, and the power receiving capacitor when the ON instruction signal is not input. The overvoltage determination circuit outputs an ON instruction signal to the first change switch when the load circuit voltage is equal to or higher than the first threshold voltage.

  FIG. 1 is a schematic configuration diagram of a contactless power feeding device according to a first embodiment of the present invention. As illustrated in FIG. 1, the contactless power supply device 1 includes a power transmission device 10 and a power reception device 20 that transmits power from the power transmission device 10 via a space. The power transmission device 10 includes a power supply circuit 11, a power transmission resonance circuit 14 including a power transmission coil 141 and a power transmission capacitor 142, a power transmission voltage detection circuit 15, a gate driver 16, and a control circuit 17. On the other hand, the power receiving device 20 includes a power receiving resonance circuit 21, a resonance frequency changing circuit 22, a rectifier circuit 23, a smoothing capacitor 24, a load circuit voltage detector 25, and a load circuit 26. The power receiving resonance circuit 21 includes a power receiving coil 211 and a power receiving capacitor 212. The resonance frequency changing circuit 22 includes a first changing capacitor 221, a first changing switch 222, and an overvoltage determination circuit 223. The rectifier circuit 23 includes a first rectifier diode 231 and a second rectifier diode 232.

First, the power transmission device 10 will be described.
The power supply circuit 11 supplies AC power having an adjustable operating frequency to the power transmission resonance circuit 14. For this purpose, the power supply circuit 11 includes a DC power supply 12 and a pair of switching elements 13-1 and 13-2.

  The DC power supply 12 supplies DC power having a predetermined voltage. Therefore, the DC power supply 12 may have a battery, for example. Alternatively, the DC power source 12 may be connected to a commercial AC power source, and may include a full-wave rectifier circuit and a smoothing capacitor for converting AC power supplied from the AC power source into DC power.

  The pair of switching elements 13-1 and 13-2 are connected in series between the positive terminal and the negative terminal of the DC power supply 12. In the present embodiment, the switching element 13-1 is connected to the positive electrode side of the DC power supply 12, while the switching element 13-2 is connected to the negative electrode side of the DC power supply 12. Each of the switching elements 13-1 and 13-2 can be an n-channel MOSFET, for example. The drain of the switching element 13-1 is connected to the positive terminal of the DC power source 12, and the source of the switching element 13-1 is connected to the drain of the switching element 13-2. The source of the switching element 13-2 is connected to the negative terminal of the DC power supply 12. Furthermore, the source of the switching element 13-1 and the drain of the switching element 13-2 are directly connected to one end of the power transmission coil 141, and the source of the switching element 13-2 is connected to the power transmission coil 141 via the power transmission capacitor 142. Connected to the other end.

  The gates of the switching elements 13-1 and 13-2 are connected to the control circuit 17 through the gate driver 16. In addition, the gates of each switching element 13-1 and 13-2 are sourced through resistors R1 and R2, respectively, to ensure that the switching element is turned on when a turn-on voltage is applied. Connected. Each switching element 13-1 and 13-2 is alternately turned on / off at a desired operating frequency by a control signal from the control circuit 17. As a result, the DC power supplied from the DC power supply 12 is converted into AC power through charging / discharging by the power transmission capacitor 142 and supplied to the power transmission resonance circuit 14 including the power transmission capacitor 142 and the power transmission coil 141.

  The power transmission resonance circuit 14 is an LC resonance circuit formed by the power transmission coil 141 and the power transmission capacitor 142.

  One end of the power transmission coil 141 is connected to the source of the switching element 13-1 and the drain of the switching element 13-2, and the other end of the power transmission coil 141 is connected to one end of the power transmission capacitor 142. The other end of the power transmission capacitor 142 is connected to the negative terminal of the DC power supply 12 and the source of the switching element 13-2. The power transmission coil 141 generates a magnetic field corresponding to the current flowing through the power transmission coil 141 itself by the AC power supplied from the power supply circuit 11. When the distance between the power transmission coil 141 and the power reception coil 211 is close enough to resonate, the power transmission coil 141 resonates with the power reception coil 211 and transmits power to the power reception coil 211 through the space.

  The power transmission voltage detection circuit 15 detects an AC voltage applied between both terminals of the power transmission coil 141 at predetermined intervals. The predetermined cycle is longer than, for example, a cycle corresponding to an assumed minimum value of the operating frequency of the AC power supplied to the power transmission coil 141, and is set to, for example, 50 msec to 1 sec. The transmission voltage detection circuit 15 measures, for example, the peak value or effective value of the AC voltage as the AC voltage to be detected. The power transmission voltage detection circuit 15 outputs a voltage detection signal representing the AC voltage to the control circuit 17. Therefore, the power transmission voltage detection circuit 15 can be any of various known voltage detection circuits that can detect an AC voltage, for example.

  The gate driver 16 receives a control signal for switching on / off of the switching elements 13-1 and 13-2 from the control circuit 17, and the gates of the switching elements 13-1 and 13-2 according to the control signal. The voltage applied to is changed. That is, when the gate driver 16 receives the control signal for turning on the switching element 13-1, the switching element 13-1 is turned on at the gate of the switching element 13-1, and the current from the DC power source 12 is changed to the switching element 13-1. A relatively high voltage is applied so that it flows through -1. On the other hand, when the gate driver 16 receives the control signal for turning off the switching element 13-1, the switching element 13-1 is turned off at the gate of the switching element 13-1, and the current from the DC power source 12 is changed to the switching element 13-1. A relatively low voltage is applied so that -1 does not flow. Similarly, the gate driver 16 controls the voltage applied to the gate of the switching element 13-2.

  The control circuit 17 includes, for example, a nonvolatile memory circuit and a volatile memory circuit, an arithmetic circuit, and an interface circuit for connecting to other circuits, and is applied to the power transmission coil 141 indicated by the voltage detection signal. The operating frequency of the power supply circuit 11, that is, the operating frequency of the AC power supplied from the power supply circuit 11 to the power transmission resonance circuit 14 is adjusted according to the AC voltage to be applied.

  Therefore, in the present embodiment, the control circuit 17 is configured such that the switching element 13-1 and the switching element 13-2 are alternately turned on, and the switching element 13-1 is turned on within one cycle corresponding to the operating frequency. The switching elements 13-1 and 13-2 are controlled so that the period during which the switching element 13-2 is on is equal to the period during which the switching element 13-2 is on. Note that the control circuit 17 prevents the switching element 13-1 and the switching element 13-2 from being turned on at the same time and the DC power supply 12 is short-circuited. When switching on / off, a dead time during which both switching elements are turned off may be provided.

Next, the power receiving device 20 will be described.
The power reception resonance circuit 21 is an LC resonance circuit including a power reception coil 211 and a power reception capacitor 212. One end of the power receiving coil 211 is connected to the power receiving capacitor 212, and the other end of the power receiving coil 211 is connected to the rectifier circuit 23 via the resonance frequency changing circuit 22.

  The power reception coil 211 resonates with the power transmission coil 141 by resonating with a magnetic field generated by an alternating current flowing through the power transmission coil 141 of the power transmission device 10, and receives power from the power transmission coil 141. The power receiving coil 211 outputs the received power to the rectifier circuit 23 via the power receiving capacitor 212. Note that the number of turns of the power receiving coil 211 and the number of turns of the power transmission coil 141 of the power transmission device 10 may be the same or different. Moreover, it is preferable that the inductance of the power receiving coil 211 and the capacitance of the power receiving capacitor 212 are set so that the resonance frequency of the power receiving resonance circuit 21 is equal to the resonance frequency of the power transmission resonance circuit 14 of the power transmission device 10.

  One end of the power receiving capacitor 212 is connected to the power receiving coil 211, and the other end of the power receiving capacitor 212 is connected to the rectifier circuit 23 via the resonance frequency changing circuit 22. The power receiving capacitor 212 outputs the power received by the power receiving coil 211 to the rectifier circuit 23 via the resonance frequency changing circuit 22.

  The resonance frequency changing circuit 22 changes the resonance frequency of the power receiving device 20 by turning on the first changing switch 222 and connecting the first changing capacitor 221 in parallel to the power receiving coil 211 and the power receiving capacitor 212. The first change switch 222 is an n-channel MOSFET, for example. The first change switch 222 is turned on while the ON instruction signal is input from the overvoltage determination circuit 223 to electrically connect the power receiving resonance circuit 21 and the first change capacitor 221. Further, the first change switch 222 is turned off when the on instruction signal is not input from the overvoltage determination circuit 223, and the electrical connection between the power receiving resonance circuit 21 and the first change capacitor 221 is cut off. One end of the first change capacitor 221 is connected to the other end of the power receiving capacitor and is connected to the rectifier circuit 23 via the resonance frequency change circuit 22, and the other end of the first change capacitor 221 is the drain of the first change switch 222. Connected to. The gate of the first change switch 222 is connected to the overvoltage determination circuit 227, and the source of the first change switch 222 is connected to the other end of the power receiving coil 211 and the rectifier circuit 23. The source of the first change switch 222 is grounded.

The overvoltage determination circuit 223 receives the load circuit voltage signal from the load circuit voltage detector 25. The overvoltage determination circuit 223 outputs an ON instruction signal to the first change switch 222 when the load circuit voltage _VL corresponding to the load circuit voltage signal is equal to or higher than a predetermined first threshold voltage. When the over instruction determination circuit 223 outputs the on instruction signal to the first change switch 222, the over voltage determination circuit 223 outputs the on instruction signal until the load circuit voltage _VL becomes equal to or lower than the second threshold voltage lower than the first threshold voltage. Keep doing. The overvoltage determination circuit 223 stops outputting the ON instruction signal when the load circuit voltage V _L becomes equal to or lower than a predetermined second threshold voltage. In one example, the first threshold voltage is 300 [V], and the second threshold voltage is 100 [V].

  The rectifier circuit 23 rectifies the power received by the power receiving coil 211 and the power receiving capacitor 212, and the smoothing capacitor 24 smoothes the rectified power, converts it to DC power, and outputs it to the load circuit 26. The rectifier circuit 23 includes, for example, a full wave rectifier circuit and a smoothing capacitor. The anode of the first rectifier diode 231 is connected to one end of the power receiving coil 211 via the resonance frequency changing circuit 22, and the cathode of the first rectifier diode 231 is connected to the load circuit 26. The anode of the second rectifier diode 232 is connected to the other end of the power receiving coil via the resonance frequency changing circuit 22, and the cathode of the second rectifier diode 232 is connected to one end of the power receiving coil 211 and the anode of the first rectifier diode 231. .

One end of the load circuit voltage detector 25 is connected to one end of the load circuit 26, and the other end of the load circuit voltage detector 25 is connected to the other end of the load circuit 26. The load circuit voltage detector 25 detects the load circuit voltage output to the load circuit 26 and outputs a load circuit voltage signal indicating the load circuit voltage V _L to the overvoltage determination circuit 227.

FIG. 2 is a diagram illustrating a change in the load circuit voltage V _L when the capacitance of the power receiving capacitor is changed. In FIG. 2, the horizontal axis indicates the capacitance [F] of the power receiving capacitor 212, and the vertical axis indicates the load circuit voltage V _L in arbitrary units.

The magnitude of the load circuit voltage V _L when the capacity of the power receiving capacitor 212 is 40 [nF] is about ¼ of the magnitude of the load circuit voltage V _L when the capacity of the power receiving capacitor 212 is 100 [pF]. is there. When the capacity of the power receiving capacitor 212 is Cr and the capacity of the first change capacitor 221 is Cc, the combined capacity Ct when the first change switch 222 is turned on is

Indicated by When the capacitance Cr of the power receiving capacitor 212 is 100 [pF] and the capacitance Cc of the first change capacitor 221 is 20 [nF], the load circuit voltage V _L becomes equal to or higher than the first threshold voltage and the first change switch 222 is The combined capacitance Ct when turned on is approximately 20 [nF]. Assuming that the capacitance Cr of the power receiving capacitor 212 is 100 [pF] and the capacitance Cc of the first change capacitor 221 is 20 [nF], the load voltage circuit becomes higher than the first threshold voltage and the first change switch 222 is turned on. The magnitude of the voltage V _L can be reduced to about ¼.

FIG. 3A is a diagram illustrating a relationship between the operating frequency and the load circuit voltage V _L when the first change switch 222 is turned off. FIG. 3B is a diagram showing the relationship between the operating frequency and the load circuit voltage V _L when the first change switch 222 is turned on when the load circuit 26 is relatively heavy. FIG. 3C is a diagram showing the relationship between the operating frequency and the load circuit voltage V _L when the first change switch 222 is turned on when the load circuit 26 is relatively light. In the example shown in FIG. 3B, the resistance of the load circuit 26 is 1 [kΩ], and in the example shown in FIG. 3C, the resistance of the load circuit 26 is 100 [kΩ]. 3A to 3C, the horizontal axis represents the operating frequency [kHz], and the vertical axis represents the load circuit voltage V _L in arbitrary units.

As shown in FIG. 3A, when the first change switch 222 is turned off, the operating frequency is about 80 [kHz] and the load circuit voltage V _L is maximized. On the other hand, as shown in FIGS. 3B and 3C, when the operating frequency is about 80 [kHz] regardless of the size of the load circuit 26 with the first change switch 222 turned on, the load The circuit voltage V _L is lowered. In the non-contact power feeding device 1, since the first change switch 222 changes the resonance frequency of the on to the power receiving device 20 when the load circuit voltage V _L becomes equal to or higher than the first threshold voltage, the load circuit voltage V _L Can be lowered.

Further, in the non-contact power feeding device 1, since the rectifier circuit 23 is rectified by the first rectifier diode 231 and the second rectifier diode 232 connected in series, the load circuit extends over a relatively wide frequency band centering on 80 [kHz]. The voltage V _L can be increased.

  FIG. 4 is a schematic configuration diagram of a contactless power supply device according to the second embodiment.

  The non-contact power feeding device 2 is different from the non-contact power feeding device 1 in that the power receiving device 30 is arranged instead of the power receiving device 20. The power receiving device 30 is different from the power receiving device 20 in that a power receiving resonance circuit 31 and a resonance frequency changing circuit 32 are arranged instead of the power receiving resonance circuit 21 and the resonance frequency changing circuit 22. The configurations and functions of the constituent elements of the non-contact power feeding device 2 other than the power receiving resonance circuit 31 and the resonance frequency changing circuit 32 are the same as the configurations and functions of the constituent elements of the non-contact power feeding device 1 denoted by the same reference numerals. Detailed description is omitted.

  The power receiving resonance circuit 31 is different from the power receiving resonance circuit 21 in the position where the power receiving capacitor 212 is disposed. In the power receiving resonance circuit 21, the power receiving capacitor 212 is disposed between the power receiving coil 211 and the first change capacitor 221, whereas in the power receiving resonance circuit 31, the power reception capacitor 212 includes the power receiving coil 211 and the first change switch. Arranged between.

  The resonance frequency changing circuit 32 is different from the resonance frequency changing circuit 22 in that it includes a second changing capacitor 224 and a second changing switch 225. The resonance frequency changing circuit 32 is different from the resonance frequency changing circuit 22 in that an overvoltage determination circuit 226 is arranged instead of the overvoltage determination circuit 223.

  For example, the second change switch 225 is an n-channel MOSFET. The second change switch 225 is turned on while the on instruction signal is input from the overvoltage determination circuit 226, and is turned off when the on instruction signal is not input from the overvoltage determination circuit 226. One end of the second change capacitor 224 is connected to one end of the power receiving coil 211 and the power reception capacitor 212, and the other end of the second change capacitor 224 is connected to the drain of the second change switch 225. The gate of the second change switch 225 is connected to the overvoltage determination circuit 227. The source of the second change switch 225 is connected to the other end of the power receiving coil 211 and the rectifier circuit 23 together with the source of the first change switch 222. The sources of the first change switch 222 and the second change switch 225 are grounded.

The overvoltage determination circuit 226 receives the load circuit voltage signal from the load circuit voltage detector 25 in the same manner as the overvoltage determination circuit 223. The overvoltage determination circuit 226 outputs an ON instruction signal to the first change switch 222 and the second change switch 225 when the load circuit voltage _VL corresponding to the load circuit voltage signal is equal to or higher than a predetermined first threshold voltage. . When the overvoltage determination circuit 223 outputs the on instruction signal to the first change switch 222 and the second change switch 225, the load circuit voltage V _L becomes lower than the second threshold voltage lower than the first threshold voltage. Continue to output the ON instruction signal. The overvoltage determination circuit 223 stops outputting the ON instruction signal when the load circuit voltage V _L becomes equal to or lower than a predetermined second threshold voltage.

FIG. 5A is a diagram illustrating a relationship between the operating frequency and the load circuit voltage V _L when the first change switch 222 and the second change switch 225 are turned off. FIG. 5B is a diagram illustrating the relationship between the operating frequency and the load circuit voltage V _L when the first change switch 222 and the second change switch 225 are turned on when the load circuit 26 is relatively heavy. FIG. 5C is a diagram showing the relationship between the operating frequency and the load circuit voltage V _L when the first change switch 222 and the second change switch 225 are turned on when the load circuit 26 is relatively light. In the example shown in FIG. 5B, the resistance of the load circuit 26 is 1 [kΩ], and in the example shown in FIG. 5C, the resistance of the load circuit 26 is 100 [kΩ]. 5A to 5C, the horizontal axis indicates the operating frequency [kHz], and the vertical axis indicates the load circuit voltage V _L in arbitrary units.

As shown in FIG. 5A, when the first change switch 222 and the second change switch 225 are turned off, the operating frequency is about 100 [kHz] and the load circuit voltage _VL becomes maximum. On the other hand, as shown in FIGS. 5B and 5C, when the first change switch 222 and the second change switch 225 are turned on, the operating frequency is 100 [kHz] regardless of the size of the load circuit 26. If so, the load circuit voltage _VL becomes very low. In the non-contact power feeding device 2, when the load circuit voltage V _L becomes equal to or higher than the first threshold voltage, the first change switch 222 and the second change switch 225 are turned on to set the resonance frequency of the power receiving device 20 to the non-contact power feeding device. By changing it to 1 or more, the load circuit voltage V _L can be lowered.

  FIG. 6 is a schematic configuration diagram of a non-contact power feeding device according to the third embodiment.

  The non-contact power supply device 3 is different from the non-contact power supply device 2 in that the power transmission device 40 is arranged instead of the power transmission device 10. Further, the non-contact power feeding device 3 is further different from the non-contact power feeding device 2 in that the power receiving device 50 is arranged instead of the power receiving device 30. The power transmission device 40 is different from the power transmission device 10 in that an overvoltage signal reception circuit 41 is arranged. Further, the power transmission device 40 is further different from the power transmission device 10 in that the control circuit 47 is arranged instead of the control circuit 17. The power receiving device 50 is different from the power receiving device 30 in that the resonance frequency changing circuit 52 is arranged instead of the resonance frequency changing circuit 32. The resonance frequency changing circuit 52 is different from the resonance frequency changing circuit 32 in that it has an overvoltage determination circuit 227 instead of the overvoltage determination circuit 226. The resonance frequency changing circuit 52 is further different from the resonance frequency changing circuit 32 in having an overvoltage signal transmission circuit 228. The components and functions of the contactless power feeding device 3 other than the overvoltage determination circuit 227, the overvoltage signal transmission circuit 228, the overvoltage signal reception circuit 41, and the control circuit 47 are components of the contactless power feeding device 2 denoted by the same reference numerals. Since the configuration and function are the same, detailed description is omitted here.

The overvoltage determination circuit 227 executes determination processing similar to that of the overvoltage determination circuit 226. Overvoltage determining circuit 227, when the load circuit voltage V _L corresponding to the load circuit voltage signal is first threshold voltage or more predetermined, overvoltage signal an overvoltage signal indicating that the load circuit voltage V _L is in an overvoltage state The output to the transmission circuit 228 is different from the overvoltage determination circuit 226.

  The overvoltage signal transmission circuit 228 is a communication circuit capable of wireless communication with the overvoltage signal reception circuit 41. For example, the overvoltage signal transmission circuit 228 communicates with the overvoltage signal reception circuit 41 by performing wireless communication in a frequency band of 130 to 135 kHz. The overvoltage signal transmission circuit 228 transmits the overvoltage signal input from the overvoltage determination circuit 227 to the overvoltage signal reception circuit 41.

  The overvoltage signal reception circuit 41 receives the overvoltage signal transmitted from the overvoltage signal transmission circuit 228 and outputs the received overvoltage signal to the control circuit 47.

  Similarly to the control circuit 17, the control circuit 47 adjusts the operating frequency of the AC power that the power supply circuit 11 supplies to the power transmission resonance circuit 14. The control circuit 47 is different from the control circuit 17 in that when the overvoltage signal is input from the overvoltage signal receiving circuit 41, the operation of alternately switching the switching element 13-1 and the switching element 13-2 on is intermittent. To do.

  FIG. 7A shows a control signal output from the control circuit 47 to the gate driver 16 when an overvoltage signal is input, and FIG. 7B shows an example of the drain current of the switching element 13-1. FIG. In FIG. 7A, a waveform 701 indicates a control signal output from the control circuit 47 to the gate driver 16. In FIG.7 (b), the waveform 702 shows the electric current which flows between the source | sauce and drain of the switching element 13-1.

  In the example illustrated in FIG. 7, the control circuit 47 controls the switching elements 13-1 and 13-2 to be turned on and off 100 times per second when an overvoltage signal is input. The power transmitted to is greatly reduced. When switching elements 13-1 and 13-2 are turned on and off 100 times per second, the transmission power can be reduced to 1/1300 compared to when switching elements 13-1 and 13-2 are turned on and off at 130 kHz. it can.

  FIG. 8 is a schematic configuration diagram of a contactless power feeding device according to the fourth embodiment.

  The non-contact power supply device 4 is different from the non-contact power supply device 3 in that the power transmission device 60 is arranged instead of the power transmission device 40. The power transmission device 60 is different from the power transmission device 40 in that an auxiliary capacitor 61, a current detection resistor 62, and a power transmission current detection circuit 63 are arranged. The power transmission device 60 is further different from the power transmission device 40 in that the control circuit 67 is arranged instead of the control circuit 47. The components and functions of the contactless power supply device 4 other than the auxiliary capacitor 61, the current detection resistor 62, the power transmission current detection circuit 63, and the control circuit 67 are the components of the contactless power supply device 3 with the same reference numerals. Since it is the same as the function, the detailed description is omitted here.

  The auxiliary capacitor 61 is connected in parallel to the power transmission capacitor 142 and preferably has a capacity smaller than that of the power transmission capacitor 142. The current detection resistor 62 is connected in series to the auxiliary capacitor 61. The transmission current detection circuit 63 detects the transmission current flowing through the current detection resistor 62 and outputs a transmission current signal indicating the detected transmission current to the control circuit 67.

  The control circuit 67 outputs to the gate driver 16 a control signal for controlling the operating frequency of each of the switching elements 13-1 and 13-2 so that the transmission current corresponding to the transmission current signal does not exceed a predetermined threshold current. To do.

  Moreover, the control circuit 67 controls the operating frequency of each switching element 13-1 and 13-2 based on the power transmission voltage which the power transmission voltage detection circuit 15 detected so that the non-contact electric power feeder 4 performs soft switching operation | movement. A control signal is output to the gate driver 16.

FIG. 9 is an equivalent circuit diagram of the power transmission circuit 100 including the power transmission resonance circuit 14 and the power reception resonance circuit 31. Here, L ₁ and L ₃ are leakage inductances on the power transmission side and the power reception side, respectively, and L ₂ is a mutual inductance. Assuming that the self-inductance of the power transmission coil 141 and the power reception coil 211 is L ₀ , and the degree of coupling between the power transmission coil 141 and the power reception coil 211 is k, L ₁ = L ₃ = (1−k) L ₀ , L ₂ = kL ₀ Become. For example, if L ₀ = 30.5 μH and k = 0.731028, then L ₁ = L ₃ = 8.205 μH and L ₂ = 22.3 μH. In general, the degree of coupling k increases as the distance between the power transmission coil 141 and the power reception coil 211 decreases. In this case, the transmission matrix A (f) expressed by F parameter analysis is expressed by the following equation.

Here, f _s is the operating frequency of the power supply circuit 11, and s (f) = jω and ω = 2πf. C1 and C2 are capacitances on the power transmission side and the power reception side, respectively. R1 and R2 are impedances on the power transmission side and the power reception side. Rac is the impedance of the load circuit.

FIG. 10 is a diagram illustrating an example of frequency characteristics of impedance of the equivalent circuit illustrated in FIG. 9. In FIG. 10, the horizontal axis represents frequency, and the vertical axis represents impedance. Note that the impedance of the equivalent circuit is calculated as the absolute value of the ratio of the upper left element to the lower left element in the transmission matrix A (f) of the equation (2) represented by 2 rows and 2 columns. A graph 300 represents frequency characteristics of impedance. The graph 300 was calculated based on the equation (2) with L ₀ = 30.5 μH, k = 0.731028, C1 = C2 = 180 nF, and R1 = R2 = 270 mΩ.

As shown in FIG. 10, when the degree of coupling k is a relatively large value as described above, the frequency characteristic of the impedance is the first resonance frequency f _p1 and the resonance smaller than the resonance frequency f _s of the power transmission resonance circuit 14. It has two local minimum values at the second resonance frequency f _p2 that is greater than the frequency f _s . That is, there are two frequencies at which the power transmission coil 141 and the power reception coil 211 resonate, and the impedance is minimum at each resonance frequency, that is, the energy transmission power amount is maximum. The resonance frequency f _s of the power transmission resonance circuit 14 is

Indicated by Here, L is the inductance of the power transmission coil 141, and C is the capacitance of the power transmission capacitor 142. The first resonance frequency f _p1 and the second resonance frequency f _p2 are

  Indicated by Here, k is the degree of coupling between the power transmission coil 141 and the power reception coil 211.

As the operating frequency f _{s of} AC power supplied to the power transmission resonance circuit 14 of the power transmission device 60 is closer to the first resonance frequency f _p1 or the second resonance frequency f _p2 , the impedance between the power transmission side and the power reception side decreases. To do. When the operating frequency f _{s of} AC power approaches the first resonance frequency f _p1 or the second resonance frequency f _p2 and the impedance between the power transmission side and the power reception side decreases, the energy transmitted from the power transmission coil 141 to the power reception coil 211 The amount of transmission power increases. Therefore, the closer the operating frequency f _{s of the} AC power supplied to the power transmission resonance circuit 14 is to any one of the resonance frequencies, the higher the AC voltage between both terminals of the power receiving coil 211 on the power receiving side.

In FIG. 10, the frequency region higher than the first resonance frequency f _p1 and lower than the resonance frequency f _s of the power transmission resonance circuit 14 and the frequency region higher than the second resonance frequency f _p2 are inductance regions. The contactless power supply device 1 is included in a frequency region that is higher than the first resonance frequency f _p1 and lower than the resonance frequency f _s of the power transmission resonance circuit 14 and an inductance region that is a frequency region higher than the second resonance frequency f _p2. It operates at the operating frequency f _s . Since the reactance region is a region in which the alternating current is delayed from the alternating voltage, the alternating current has a negative value when the phase of the alternating voltage becomes 0 degrees and the switching elements 13-1 and 13-2 are switched. When the switching elements 13-1 and 13-2 are switched, the AC current becomes a negative value, so that the contactless power supply device 4 can perform soft switching.

Table 1 is a table showing the relationship between the degree of coupling k and the second resonance frequency f _p2 .

The control circuit 67 reduces the gain of the transmitted power by setting the operating frequency at the time of startup to be higher than the second resonance frequency f _p2 . For example, when the maximum value of the degree of coupling k is 0.7, the maximum value of the second resonance frequency f _p2 is 148.9 [kHz]. Therefore, the control circuit 67 sets the operating frequency at startup to 160 [kHz]. May be set. By setting the operating frequency at startup to 160 [kHz] by the control circuit 67, the non-contact power feeding device 4 can reduce the gain of transmitted power and perform soft switching.

  FIG. 11 is a schematic configuration diagram of a non-contact power feeding device according to the fifth embodiment.

  The non-contact power feeding device 5 is different from the non-contact power feeding device 4 in that the power transmission device 70 is arranged instead of the power transmission device 60. The power receiving device 80 is further different from the power receiving device 50 in that the power receiving device 80 is arranged instead of the power receiving device 50. The power transmission device 70 is different from the power transmission device 60 in that an identification signal receiving circuit 71 is disposed. The power transmission device 70 is further different from the power transmission device 60 in that a control circuit 77 is arranged instead of the control circuit 67. The power receiving device 80 is different from the power receiving device 50 in that an identification signal transmission circuit 81 is disposed. The configuration and function of the constituent elements of the non-contact power feeding device 5 other than the identification signal receiving circuit 71 and the identification signal transmitting circuit 81 are the same as the configuration and function of the constituent elements of the non-contact power feeding device 4 assigned the same reference numerals. Then, detailed explanation is omitted.

  The identification signal receiving circuit 71 receives an identification signal indicating the identification number of the power receiving device 80 from the identification signal transmitting circuit 81. The identification signal transmission circuit 81 is an RFID in one example, and transmits the identification signal to the identification signal reception circuit 71.

  In a state where the power transmitting device 70 and the power receiving device 80 are not arranged close to each other, the control circuit 77 sends a control signal for intermittently turning on the switching elements 13-1 and 13-2 to the gate driver 16. Output to. The transmission voltage is a predetermined magnitude while the switching elements 13-1 and 13-2 are alternately turned on at a predetermined operating frequency, but is zero while the switching elements 13-1 and 13-2 are not turned on. . In the state where the power transmission device 70 and the power reception device 80 are not arranged close to each other, the operation in which the switching elements 13-1 and 13-2 are alternately turned on is intermittent, so that the power consumption of the power transmission device 70 is reduced. The

  FIG. 12 is a timing chart in a state where a power receiving device (not shown) that does not have an identification number is arranged in the vicinity of the power transmitting device 70. In FIG. 12, a waveform 1201 indicates a control signal output from the control circuit 77 to the gate driver 16, a waveform 1202 indicates a transmission voltage detected by the transmission voltage detection circuit 15, and a waveform 1203 does not have an identification number. The load circuit voltage of the power receiving device is shown.

  In a state where a power receiving device (not shown) that does not have an identification number is arranged in the vicinity of the power transmission device 70, the control circuit 77 does not receive an identification signal indicating the identification number. Since the identification signal indicating the identification number is not input, the control circuit 77 outputs a control signal for intermittently turning on the switching elements 13-1 and 13-2 to the gate driver 16. In a state where a power receiving device (not shown) that does not have an identification number is disposed in the vicinity of the power transmission device 70, the operation in which the switching elements 13-1 and 13-2 are alternately turned on is intermittent. The power received by a power receiving device (not shown) that is not provided, that is, the power that is stolen, is reduced.

FIG. 13A is a timing chart when the degree of coupling k between the power transmission coil 141 and the power reception coil 211 is 0.3. FIG. 13B shows an example of measured values of the transmission current detected by the transmission current detection circuit 63 and the load circuit voltage _VL detected by the load circuit voltage detector 25 in the state shown in FIG. It is. In FIG. 13A, a waveform 1301 indicates a control signal output from the control circuit 77 to the gate driver 16, a waveform 1302 indicates a transmission voltage detected by the transmission voltage detection circuit 15, and a waveform 1303 indicates a load circuit voltage detector. 25 shows the load circuit voltage V _L detected. In FIG. 13B, a waveform 1304 indicates a transmission current detected by the transmission current detection circuit 63, and a shape 1305 indicates a load circuit voltage _VL detected by the load circuit voltage detector 25.

At time t131, when the power receiving device 80 is arranged close to the power transmitting device 70, the identification signal transmitting circuit 81 transmits an identification signal to the identification signal receiving circuit 71, and the identification signal receiving circuit 71 controls the received identification signal. Output to circuit 77. The control circuit 77 refers to the identification number corresponding to the identification signal and authenticates that the power receiving device 80 is a regular power receiving device. When the control circuit 77 authenticates that the power receiving device 80 is a regular power receiving device, the control circuit 77 outputs a control signal to the gate driver 16 that turns on the switching elements 13-1 and 13-2 alternately. In the example shown in FIG. 13, the operating frequency is 130 [kHz], the transmission current is 1.6 [A], and the load circuit voltage V _L is 150 [V].

FIG. 14 is a timing chart in a state where the power receiving device 80 is further closer to the power transmitting device 70 and the coupling degree k is changed from 0.3 to 0.5 from the state shown in FIG. In FIG. 14, a waveform 1401 indicates a control signal output from the control circuit 77 to the gate driver 16, and a waveform 1402 indicates the load circuit voltage V _L detected by the load circuit voltage detector 25.

At time t141, when the power receiving device 80 approaches the power transmitting device 70 and the coupling degree k increases, the second resonance frequency f _p2 shifts to the high frequency side as shown in Table 1. When the second resonance frequency f _p2 is shifted to the high frequency side, the transmission voltage detected by the transmission voltage detection circuit 15 and the transmission current detected by the transmission current detection circuit 63 increase. The control circuit 77 adjusts the control signal so that the transmission voltage detected by the transmission voltage detection circuit 15 and the transmission current detected by the transmission current detection circuit 63 have desired values.

FIG. 15 is a timing chart in a state where the size of the load 27 of the load circuit 26 of the power receiving device 80 becomes lighter than the state shown in FIG. In FIG. 15, a waveform 1501 indicates a control signal output from the control circuit 77 to the gate driver 16, a waveform 1502 indicates the load circuit voltage _VL detected by the load circuit voltage detector 25, and a waveform 1503 indicates the magnitude of the load 27. It shows. A waveform 1504 indicates the gate voltages of the first change switch 222 and the second change switch 225. In the example shown in FIG. 15, the first threshold voltage is 300 [V], and the second threshold voltage is 100 [V].

When the size of the load 27 becomes light at time t151, the load circuit voltage V _L rapidly increases from 280 [V]. When the load circuit voltage V _L reaches 300 [V], which is the first threshold voltage, at time t152, the overvoltage determination circuit 223 outputs an ON instruction signal to the first change switch 222 and the second change switch 225. . When the ON instruction signal is input, the gate voltage of the first change switch 222 and the second change switch 225 becomes equal to or higher than the ON voltage, the first change switch 222 and the second change switch 225 are turned ON, and the resonance of the power receiving device 80. The frequency changes. The control circuit 77 receives an overvoltage signal from the overvoltage determination circuit 227 via the overvoltage signal transmission circuit 228 and the overvoltage signal reception circuit 41. When the overvoltage signal is input from the overvoltage signal receiving circuit 41, the control circuit 77 intermittently turns on the switching element 13-1 and the switching element 13-2. When the resonance frequency of the power receiving device 80 changes, the load circuit voltage V _L decreases. When the load circuit voltage V _L drops to 100 [V], which is the second threshold voltage, the overvoltage determination circuit 223 stops outputting the on instruction signal.

  In the contactless power supply device according to the embodiment, the load circuit voltage is lowered by changing the resonance frequency of the power receiving device when the load circuit voltage indicating the voltage of the load circuit of the power receiving device is equal to or higher than the first threshold voltage. Thus, the load circuit voltage can be prevented from becoming an overvoltage. That is, the non-contact power feeding device according to the embodiment is configured such that when the first change capacitor, the power receiving coil, and the power receiving capacitor are electrically connected, the resonance frequency is changed by the resonance frequency changing circuit, whereby the voltage at the time of power supply is changed. Gain can be reduced.

  In the contactless power supply device according to the embodiment, since the first change capacitor and the first change switch are arranged between the power reception capacitor and the load circuit, the resonance frequency of the power reception device when the first change switch is turned on. The amount of change can be increased.

  FIG. 16 is a schematic configuration diagram of a non-contact power feeding device in which a first change capacitor and a first change switch are arranged between a power receiving coil and a power receiving capacitor.

  The non-contact power feeding device 6 is different from the non-contact power feeding device 1 in that a power receiving device 90 is arranged instead of the power receiving device 20. The power receiving device 90 is different from the power receiving device 90 in that the resonance frequency changing circuit 22 is disposed between the power receiving coil 211 and the power receiving capacitor 212. Since the configuration of the non-contact power feeding device 6 other than the position of the resonance frequency changing circuit 22 is the same as the configuration of the non-contact power feeding device 1, detailed description thereof is omitted here.

  FIG. 17A is an equivalent circuit diagram of the power transmission circuit of the non-contact power feeding apparatus 1 including the power transmission resonance circuit 14, the power reception resonance circuit 21, and the resonance frequency change circuit 22 when the first change switch 222 is turned on. FIG. 17B is an equivalent circuit diagram of the power transmission circuit of the non-contact power feeding device 6 including the power transmission resonance circuit 14, the power receiving coil 211, the power receiving capacitor 212, and the resonance frequency changing circuit 22 when the first change switch 222 is turned on. is there.

17A and 17B, L ₁ and L ₃ are leakage inductances on the power transmission side and the power reception side, respectively, and L ₂ is a mutual inductance. Assuming that the self-inductance of the power transmission coil 141 and the power reception coil 211 is L ₀ , and the degree of coupling between the power transmission coil 141 and the power reception coil 211 is k, L ₁ = L ₃ = (1−k) L ₀ , L ₂ = kL ₀ Become. For example, if L ₀ = 30.5 μH and k = 0.731028, then L ₁ = L ₃ = 8.205 μH and L ₂ = 22.3 μH.

  A transmission matrix A (f) of the power transmission circuit when the first change switch 222 of the contactless power supply device 1 is turned on is expressed by the following equation.

  On the other hand, the transmission matrix A (f) of the power transmission circuit when the first change switch 222 of the non-contact power feeding device 6 is turned on is expressed by the following equation.

Here, f _s is the operating frequency of the power supply circuit 11, and s (f) = jω and ω = 2πf. C1 and C2 are capacitances on the power transmission side and the power reception side, respectively. C3 is the capacitance of the first change capacitor. R1 and R2 are impedances on the power transmission side and the power reception side.

FIG. 18A is a diagram illustrating a relationship between the operating frequency and the load circuit voltage V _L when the first change switch 222 is turned on when the load circuit 26 is relatively heavy in the contactless power supply device 6. FIG. 18B is a diagram illustrating the relationship between the operating frequency and the load circuit voltage V _L when the first change switch 222 is turned on when the load circuit 26 is relatively light in the contactless power supply device 6. In the example shown in FIG. 18A, the resistance of the load circuit 26 is 1 [kΩ], and in the example shown in FIG. 18B, the resistance of the load circuit 26 is 100 [kΩ]. 18A to 18B, the horizontal axis indicates the operating frequency [kHz], and the vertical axis indicates the load circuit voltage V _L in an arbitrary unit.

  As shown in FIGS. 3B and 3C, in the non-contact power feeding device 1, regardless of the size of the load circuit 26, the non-contact power feeding device 6 shown in FIGS. Compared with the case, the change of the resonance frequency in the state where the first change switch 222 is turned on is large.

  In the contactless power supply device according to the embodiment, since one end of the change switch that is turned on / off to change the resonance frequency of the power receiving device is grounded, the gate voltage can be easily controlled when the change switch is a MOSFET. .

  In the contactless power supply device according to the embodiment, since the power transmitted to the power receiving device is rectified by a pair of diodes connected in series, the load circuit voltage can be increased over a relatively wide frequency band. it can.

  In addition, since the non-contact power feeding device according to the second embodiment includes the second change capacitor that can be connected in parallel to the power receiving capacitor, the resonance frequency of the power receiving device is set when the load circuit voltage reaches the first threshold voltage. By making a large change, the load circuit voltage can be lowered.

  In addition, the contactless power supply device according to the third embodiment more reliably lowers the load circuit voltage by intermittently switching the power transmission device when the load circuit voltage reaches the first threshold voltage. Can be made.

  Further, the non-contact power feeding device according to the fourth embodiment is such that the control circuit of the power transmission device can change the operating frequency of the switching element according to the power transmission voltage and the power transmission current. It is possible to prevent the voltage from becoming an overvoltage state. Moreover, in the non-contact electric power feeder which concerns on 4th Embodiment, since the control circuit of a power transmission apparatus can change the operating frequency of a switching element according to a power transmission voltage and a power transmission current, it can perform soft switching operation | movement.

  In the non-contact power feeding device according to the fifth embodiment, the power transmission device intermittently performs the switching operation until it authenticates that the power reception device is a regular power reception device with reference to the identification number of the power reception device. The magnitude of the power transmitted to the power receiving device that does not have the identification number can be reduced.

  In the non-contact power feeding devices 1 to 6, the first change switch 222 and the second change switch 225 are configured by MOSFETs. However, in the non-contact power feeding device according to the embodiment, the first change switch and the second change switch may be configured by other elements capable of high-speed switching operation such as an insulated gate bipolar transistor.

  As described above, those skilled in the art can make various modifications in accordance with the embodiment to be implemented within the scope of the present invention.

1-6 Non-contact power supply device 10, 40, 60, 70 Power transmission device 11 Power supply circuit 12 DC power supply 13-1 and 13-2 Switching element 14 Power transmission resonance circuit 141 Power transmission coil 142 Power transmission capacitor 15 Power transmission voltage detection circuit 16 Gate driver 17, 47, 67, 77 Control circuit 20, 30, 50, 80, 90 Power receiving device 21, 31 Power receiving resonance circuit 211 Power receiving coil 212 Power receiving capacitor 22, 32, 52 Resonance frequency changing circuit 221 First changing capacitor 222 First change Switch 223, 226, 227 Overvoltage determination circuit 224 Second change capacitor 225 Second change switch 23 Rectifier circuit 24 Smoothing capacitor 25 Load circuit voltage detector 26 Load circuit

Claims (5)

A non-contact power feeding device having a power transmission resonance circuit including a power transmission coil that transmits power in a contactless manner, and a power receiving device that transmits power from the power transmission device,
The power receiving device is:
A power receiving resonance circuit having a power receiving capacitor and a power receiving coil connected to one end of the power receiving capacitor and capable of transmitting power to and from the power transmitting coil;
A load circuit voltage detector for detecting a load circuit voltage output to a load circuit connected to the power receiving device;
A resonance frequency changing circuit connected to the power receiving resonance circuit,
The resonance frequency changing circuit is:
A first changing capacitor having one end connected to the other end of the power receiving capacitor and the other end connected to the power receiving coil;
When the on instruction signal is input, the first change capacitor is electrically connected to the power receiving coil and the power reception capacitor. When the on instruction signal is not input, the first change capacitor is electrically connected. And a first change switch for cutting off an electrical connection between the power receiving coil and the power receiving capacitor;
An overvoltage determination circuit that outputs the ON instruction signal to the first change switch when the load circuit voltage is equal to or higher than a first threshold voltage;
The contactless power feeding, wherein when the first change capacitor, the power receiving coil, and the power reception capacitor are electrically connected, a voltage gain is reduced by changing a resonance frequency by the resonance frequency changing circuit. apparatus.   The contactless power supply device according to claim 1, wherein the first change switch is an n-channel MOSFET whose source is grounded. The resonance frequency changing circuit is:
A second changing capacitor connected in parallel to the power receiving capacitor;
When the ON instruction signal is input, the second change capacitor is electrically connected to the power receiving coil and the power receiving capacitor. When the ON instruction signal is not input, the second change capacitor is electrically connected. A second change switch for cutting off an electrical connection between a capacitor and the power receiving coil and the power receiving capacitor;
The contactless power supply device according to claim 1, wherein the overvoltage determination circuit further outputs the ON instruction signal to the second change switch when the load circuit voltage is equal to or higher than a first threshold voltage.   The contactless power supply device according to claim 3, wherein the first change switch and the second change switch are n-channel MOSFETs whose sources are grounded. The power receiving device further includes an overvoltage signal transmission circuit that transmits an overvoltage signal indicating an overvoltage state when the load circuit voltage is equal to or higher than the first threshold voltage,
The power transmission device is:
A power supply circuit for supplying an AC voltage to the power transmission resonance circuit;
An overvoltage signal receiving circuit for receiving the overvoltage signal;
A control circuit for lowering an operating frequency of the power supply circuit when the overvoltage signal is input from the overvoltage signal receiving circuit;
The non-contact electric power feeder as described in any one of Claims 1-4 which has these.

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