Magnetic resonance wireless power supply device

Abstract

[Problem] To keep transmission power constant even when the location of a power-receiving-side coil L2 with respect to a power-supplying-side coil L1 is changed. [Solution] A magnetic resonance wireless power supply device comprises: a power-supplying-side circuit 100 in which a power-supplying-side resonance circuit 110 is connected to an inverter 120 and a frequency command means 131; and a power-receiving-side circuit 200 which has a power-receiving-side resonance circuit 210. The power-supplying-side circuit 100 includes: a feedback circuit 140 which causes a current flowing in the power-supplying-side resonance circuit 110 to be positively fed back to the inverter 120; a self-excitation / separate-excitation changeover switch 150 which switches between a self-excitation mode in which the inverter 120 and the feedback circuit 140 are connected and a separate-excitation mode in which the inverter 120 and the frequency command means 131 are connected; and a switch control means 132 which performs change-over control of the self-excitation / separate-excitation changeover switch 150. Immediately after the start of power supply, the self-excitation / separate-excitation changeover switch is switched to the self-excitation mode, and the oscillation frequency of the inverter 120 is recorded in the frequency command means 131. When a prescribed period of time passes after the start of the power supply, the self-excitation / separate-excitation changeover switch is switched to the separate-excitation mode.

Description

Magnetic resonance type wireless power supply device

[0001] The present invention relates to a magnetic resonance type wireless power feeder that feeds power in a contactless manner by magnetically resonating a power feeding coil and a power receiving coil.

[0002] Wireless power feeders that supply power to electronic devices in a non-contact (wireless) manner without using a power cord, etc. Known power feed methods for wireless power feeders include electromagnetic induction and magnetic resonance.

[0003] In an electromagnetic induction type wireless power feeder (electromagnetic induction type wireless power feeder), an alternating current is passed through the power feed coil, changing the magnetic flux passing through the power feed coil, thereby changing the magnetic flux passing through the power receiving coil located near the power feed coil, and an induced current is passed through the power receiving coil, thereby transferring power from the power feed coil to the power receiving coil.

[0004] However, as shown in FIG. 1( a), electromagnetic induction wireless power transfer devices have the drawback that the transmitted power decreases significantly as the transmission distance increases. Therefore, while the electromagnetic induction method can be adopted for applications (such as charging a mobile terminal) in which a power receiving device incorporating a power transmitting coil can be placed in close proximity to a power transmitting device incorporating a power receiving coil, it is difficult to adopt the electromagnetic induction method for applications in which the power receiving device cannot be placed in close proximity to the power transmitting device. For example, when charging an electric vehicle wirelessly, the power transmitting device is installed at a charging station and the power receiving device is installed on the body of the electric vehicle. However, it is practically difficult to park the electric vehicle in a position where the power receiving device is placed in close proximity to the power transmitting device. For this reason, magnetic induction wireless power transfer devices are difficult to adopt for applications in which the power transmitting device is charged.

[0005] In contrast, in a wireless power feeder using a magnetic resonance method (magnetic resonance type wireless power feeder), as shown in FIG. 2 , a power feeding side resonant circuit 110 provided in a power feeding side device (power feeding side circuit 100) and a power receiving side resonant circuit 210 provided in a power receiving side device (power receiving side circuit 200) are resonated to form a power feeding side coil L １to the power receiving coil L of the power receiving side resonant circuit 210 ２ The power supply side circuit 100 is provided with an inverter 120 and a frequency command means 130. The frequency command means 130 outputs a frequency (command value) to the inverter 120 (signal S １０ ) and the inverter 120 outputs the signal S １０ ) to oscillate the power supply side resonant circuit 110. The frequency command means 130 is usually configured by a microcontroller.

[0006] Compared with electromagnetic induction wireless power feeders, magnetic resonance wireless power feeders have the advantage of being able to transmit power with high efficiency even over long transmission distances. Therefore, magnetic resonance wireless power feeders can be suitably employed in applications where the power-receiving device cannot be placed in close contact with the power-supplying device. Currently, the WiTricity system is the mainstream for wireless charging of electric vehicles, and this WiTricity system also falls under the magnetic resonance system.

[0007] However, as shown in Fig. 1(b), magnetic resonance-type wireless power feeders have the drawback that the transmitted power drops significantly if the transmission distance deviates from the point where the transmitted power peaks. Therefore, magnetic resonance-type wireless power feeders have the problem that highly efficient power transmission cannot be achieved unless the power receiving device (power receiving coil) is accurately positioned relative to the power supplying device (power supply coil). Taking the wireless charging of electric vehicles mentioned above as an example, even a slight deviation from the designated parking position of the electric vehicle relative to the charging stand prevents highly efficient power transmission.

[0008] In this way, although the magnetic resonance type wireless power feeder has a longer transmission distance than the electromagnetic induction type wireless power feeder, it is the same as the electromagnetic induction type wireless power feeder in that the power receiving device cannot be moved relative to the power feeding device. In order to make wireless power feeding more useful, it is necessary to change the power feeding device (power feeding coil L) by changing the transmission distance, etc. １ ) to the power receiving device (power receiving coil L ２Even if the position of the power supply coil L changes, the transmitted power must be kept approximately constant. １ The receiving coil L ２ The property of maintaining a constant transmission power even when the position of the antenna changes is called "robustness."

[0009] In this regard, even in a magnetic resonance type wireless power feeder, if control is performed using a computer or the like, the power feed coil L １ The receiving coil L ２ It is theoretically possible to keep the transmission power constant (maintain robustness) even when the position of the antenna changes. However, this raises other problems, such as the need to use a high-performance computer and the problem of high power consumption.

[0010] Japanese Patent Application Laid-Open No. 2022-121324

[0011] S. Assawaworrarit, X. Yu, and S. Fan, “Rоbust wireless power transfer using a nonlinear parity-time symmetric circuit” Nature, 546, 387 (2017)

[0012] Incidentally, in recent years, magnetic resonance wireless power feeders based on the principle of PT (Parity-Time) symmetry have been proposed (see Non-Patent Document 1) and have attracted attention. Here, PT symmetry refers to a combination of two symmetries: spatial inversion symmetry, which means that the laws of physics do not change even when spatial coordinates are inverted, and time reversal symmetry, which means that the laws of physics do not change even when the direction of time progresses is inverted. Hereinafter, a magnetic resonance wireless power feeder based on the principle of PT symmetry will be referred to as a "PT symmetric wireless power feeder," and a magnetic resonance wireless power feeder that is not based on the principle of PT symmetry will be referred to as a "non-PT symmetric wireless power feeder."

[0013] 3 shows an example of the circuit configuration of a PT symmetrical type wireless power feeder. As shown in FIG. 3, the PT symmetrical type wireless power feeder is composed of a power feeding side device and a power receiving side device. The power feeding side device is provided with a circuit in which a power feeding side resonant circuit 110 is connected to an inverter 120, and the power receiving side device is provided with a load R Ｌ A circuit is provided in which a power receiving-side resonant circuit 210 is connected to a load (such as a battery or a motor that consumes power). A self-oscillating inverter (called a "self-oscillating inverter") is used as the inverter 120. The power supply-side resonant circuit 110 and the power receiving-side resonant circuit 210 are configured by combining a coil and a capacitor. In all of Figures 3(a) to 3(c), the power supply-side resonant circuit 110 has a coil and a capacitor connected in series, and while there is no difference in the power supply-side resonant circuit 110, the power receiving-side resonant circuit 210 is different.

[0014] That is, in the power receiving side resonant circuit 210 shown in FIG. 3(a), a coil and a capacitor are connected in parallel. Also, in the power receiving side resonant circuit 210 shown in FIG. 3(b), a coil and a capacitor connected in series are connected in parallel to another capacitor. Furthermore, in the power receiving side resonant circuit 210 shown in FIG. 3(c), a coil and a capacitor are connected in series. The circuit configuration shown in FIG. 3(a) is called an "S-P topology," the circuit configuration shown in FIG. 3(b) is called an "S-SP topology," and the circuit configuration shown in FIG. 3(c) is called an "S-S topology."

[0015] Whether to adopt the S-P topology (FIG. 3(a)), S-SP topology (FIG. 3(b)), or S-S topology (FIG. 3(c)) depends on the application of the wireless power supply device. When a self-oscillating inverter is used to configure a PT symmetric wireless power supply device, immittance conversion is performed in the S-P topology (FIG. 3(a)) and S-SP topology (FIG. 3(b)), whereas immittance conversion is not performed in the S-S topology (FIG. 3(c)). That is, in the S-S topology (FIG. 3(c)), when a constant voltage power supply is used to supply power to the inverter, the load R ＬA constant voltage is supplied to the SS topology (Fig. 3(c)). For this reason, in applications where power is supplied at a constant voltage and received at a constant voltage (such as wireless charging of electric vehicles), the SS topology (Fig. 3(c)) is the basis.

[0016] An example of a circuit diagram of a PT symmetrical wireless power feeder using an S-S topology is shown in Fig. 4. In the PT symmetrical wireless power feeder, as shown in Fig. 4, a power feeding side resonant circuit 110 provided in a power feeding side device (power feeding side circuit 100) and a power receiving side resonant circuit 210 provided in a power receiving side device (power receiving side circuit 200) are resonated to form a power feeding side coil L １ to the power receiving coil L of the power receiving side resonant circuit 210 ２ , a feedback circuit 140 is provided instead of the frequency command means 130 (FIG. 2). The feedback circuit 140 detects the current flowing through the power supply side resonant circuit 110 with a current sensor (signal S ２０ ), and the current is fed back to the inverter 120 (signal S ４０ ) causes the inverter 120 to self-oscillate. The inverter 120 continues to self-oscillate as long as it is initially supplied with a trigger signal. Hereinafter, a PT symmetric wireless power feeder may be referred to as a "self-oscillation wireless power feeder." In contrast, a non-PT symmetric wireless power feeder may be referred to as a "separately excited wireless power feeder."

[0017] The principle of the PT symmetric type wireless power feeder is explained in detail in Patent Document 1 as well as the above Non-Patent Document 1, and therefore a detailed explanation of the principle will be omitted in this specification. However, in the PT symmetric type wireless power feeder, the power feeder device (power feeder coil L １ ) to the power receiving device (power receiving coil L ２ ) position changes, the oscillation frequency of the inverter 120 (signal S ４０ ) is automatically adjusted. Therefore, as shown in FIG. 1(c), high transmission power can be obtained over a wide transmission distance without incorporating a computer as described above.

[0018] Therefore, if a PT symmetric wireless power transfer device is used for wireless charging of electric vehicles, highly efficient power transfer can be achieved even if the electric vehicle is parked at a different position from the designated parking position relative to the charging station. However, as already mentioned, the WiTricity system (corresponding to a "non-PT symmetric wireless power transfer device") is currently the mainstream for wireless charging of electric vehicles. To increase the robustness of this WiTricity system requires detecting the positions of the power source coil and the power receiver coil using a sensor or the like and then performing complex corrections using a digital correction device or the like, which increases costs. Furthermore, replacing an already installed non-PT symmetric wireless power transfer device with a PT symmetric wireless power transfer device is not very realistic from an economic standpoint.

[0019] The present invention has been made to solve the above-mentioned problems, and provides a magnetic resonance type wireless power feeder that can utilize existing facilities related to a non-PT symmetric type wireless power feeder, and can maintain constant transmitted power even when the position of the power receiving side coil relative to the power feeding side coil changes, without performing complex correction using a sensor that detects the change, a digital correction device, etc. Another object of the present invention is to provide a power feeding side circuit to be used for the magnetic resonance type wireless power feeder.

[0020] The above problem is solved by a magnetic resonance type wireless power feeder including: a power feeding side circuit in which an inverter and frequency command means for outputting a frequency to the inverter are connected to a power feeding side resonant circuit including a power feeding side coil; and a power receiving side circuit having a power receiving side resonant circuit including a power receiving side coil, wherein the power feeding side circuit is provided with: a feedback circuit for positively feeding back a current flowing through the power feeding side resonant circuit to the inverter; a self-excitation / separately excited changeover switch for switching between a self-excitation mode in which the inverter and the feedback circuit are connected and the inverter is self-oscillated by the feedback circuit, and an other-excitation mode in which the inverter is connected to the frequency command means and the inverter is other-excited to oscillate at a frequency output from the frequency command means; and switch control means for controlling the self-excitation / other-excitation changeover switch, wherein immediately after power feeding starts, the self-excitation / other-excitation changeover switch is switched to the self-excitation mode by the switch control means and the inverter performs self-oscillation, and the oscillation frequency of the inverter at that time is recorded in the frequency command means, This problem is solved by providing a magnetic resonance type wireless power supply device, characterized in that when a predetermined time has elapsed since the start of power supply, the self-excitation / separately excited changeover switch is switched to the separate excitation mode by the switch control means, and the inverter is made to oscillate with the separate excitation at the oscillation frequency stored in the frequency command means.

[0021] In the magnetic resonance type wireless power feeder of the present invention, in the self-excitation mode executed immediately after the start of power feeding, the inverter oscillation frequency that can transmit power while maintaining the transmission power is searched for, and thereafter, the inverter is separately excited at the oscillation frequency. Therefore, even if the position of the power receiving device (power receiving coil) relative to the power feeding device (power feeding coil) varies, the inverter can be oscillated at an appropriate oscillation frequency depending on the position of the power receiving device (power receiving coil) at that time, thereby transmitting power. Therefore, highly efficient power transmission is possible even in applications where the position of the power receiving device (power receiving coil) relative to the power feeding device (power feeding coil) is not fixed. In particular, in applications where electric vehicles are wirelessly charged, the position of the power receiving device (electric vehicle) relative to the power feeding device (charging stand) is fixed when the electric vehicle is parked, and the power receiving device (electric vehicle) does not move during charging. Therefore, the magnetic resonance type wireless power feeder of the present invention can be advantageously employed.

[0022] Furthermore, the magnetic resonance type wireless power feeder of the present invention can be realized simply by adding a feedback circuit, a self-excited / separately excited selector switch, and a switch control means to a non-PT symmetrical wireless power feeder. The power feeder circuit (power feeder resonant circuit, inverter, and frequency command means) provided in the non-PT symmetrical wireless power feeder can be used as is. As already mentioned, the frequency command means is usually configured with a microcontroller, and this microcontroller can also be used as the switch control means in the magnetic resonance type wireless power feeder of the present invention. In addition, no changes are required to the power receiver circuit in the non-PT symmetrical wireless power feeder. Therefore, even in situations where a conventional non-PT symmetrical wireless power feeder such as the WiTricity system is already installed, the equipment can be easily converted to the magnetic resonance type wireless power feeder of the present invention without wasting the existing equipment.

[0023] However, even if the inverter is separately excited at the oscillation frequency found in self-excitation mode immediately after the start of power supply, the optimal oscillation frequency may subsequently change. For example, in an application for wirelessly charging an electric vehicle, even if the position of the power receiving device (electric vehicle) relative to the power supplying device (charging stand) remains unchanged after power supply starts, the optimal oscillation frequency may change if rain or snow starts falling, or if foreign objects such as fallen leaves or debris get between the power supplying device (charging stand) and the power receiving device (electric vehicle). In such a case, if the inverter continues to oscillate separately at the oscillation frequency found immediately after power supply starts, even if power transmission can be performed highly efficiently at first, power transmission will become inefficient over time. For this reason, it is preferable to periodically update the oscillation frequency at which the inverter is separately excited.

[0024] Specifically, even after a predetermined time has elapsed since the start of power supply, it is preferable that the switch control means intermittently switches the self-excitation / separately-excitation changeover switch from the separate excitation mode to the self-excitation mode, thereby intermittently operating the self-excitation mode, and the oscillation frequency recorded in the frequency command means is updated with the oscillation frequency of the inverter in the self-excitation mode that is intermittently operated. This makes it possible to keep the inverter separately excited at an optimal oscillation frequency depending on the situation, even if the situation changes after the start of power supply, and to maintain efficient power transmission.

[0025] The magnetic resonance type wireless power feeder of the present invention preferably includes an error output means for outputting an error when the oscillation frequency of the inverter in self-excitation mode falls outside a predetermined range. This allows an error to be output when the initial position of the power receiving device (power receiving coil) relative to the power feeding device (power feeding coil) deviates from a range where efficient power transfer is possible, or when an obstacle that prevents efficient power transfer subsequently appears between the power feeding device (power feeding coil) and the power receiving device (power receiving coil). For example, in an application for wirelessly charging an electric vehicle, if the parking position of the electric vehicle (power receiving device) relative to the charging stand (power feeding side device) deviates from an appropriate range, an alert can be issued to move the electric vehicle (power receiving side device) to an appropriate position, or if an obstacle appears between the charging stand (power feeding side device) and the electric vehicle (power receiving side device), an alert can be issued to remove the obstacle.

[0026] In the magnetic resonance type wireless power feeder of the present invention, power transmission is mainly performed when the separate excitation mode is being executed, and little emphasis is placed on power transmission when the self-excitation mode is being executed. The self-excitation mode is executed not for the purpose of power transmission, but to find the optimal oscillation frequency of the inverter. For this reason, if the same inverter power supply that supplies DC power to the inverter is used in both the self-excitation mode and the separate excitation mode, power will be wasted in the self-excitation mode. Therefore, it is preferable to switch the inverter power supply used when executing the self-excitation mode and the separate excitation mode.

[0027] Specifically, the power supply side circuit preferably includes a first inverter power supply, a second inverter power supply having a higher output than the first inverter power supply, and a power supply selector switch for switching the power supply connected to the inverter between the first inverter power supply and the second inverter power supply, and the switch control means preferably switches the power supply selector switch to the first inverter power supply side in a self-excitation mode in which the inverter self-oscillates, and switches the power supply selector switch to the second inverter power supply side in a separate-excitation mode in which the inverter separately oscillates. In this way, by using a high-output inverter power supply (for the second inverter) only in the separate-excitation mode, in other words, by using a low-output inverter power supply (first inverter power supply) in the self-excitation mode, it is possible to reduce the power consumption of the magnetic resonance type wireless power supply device.

[0028] As described above, the present invention makes it possible to provide a magnetic resonance type wireless power feeder that can maintain constant transmission power even when the position of the power receiving coil relative to the power feeding coil changes, while utilizing existing facilities related to a non-PT symmetric type wireless power feeder, without performing complex correction using a sensor that detects the change, a digital correction device, etc. It also makes it possible to provide a power feeding circuit used for the magnetic resonance type wireless power feeder.

[0029] 1 is a graph showing the relationship between transmission distance and transmission power in (a) an electromagnetic induction type wireless power feeder, (b) a magnetic resonance type wireless power feeder (non-PT symmetric type wireless power feeder), and (c) a magnetic resonance type wireless power feeder (PT symmetric type wireless power feeder). FIG. 1 is a circuit diagram showing an example of a magnetic resonance type wireless power feeder (non-PT symmetric type wireless power feeder). FIG. 2 is a circuit diagram showing an example of a circuit configuration of a PT symmetric type wireless power feeder, illustrating (a) an S-P topology, (b) an S-SP topology, and (c) an S-S topology. FIG. 3 is a circuit diagram showing an example of a magnetic resonance type wireless power feeder (PT symmetric type wireless power feeder) using an S-S topology. FIG. 4 is a circuit diagram showing an example of a magnetic resonance type wireless power feeder of the present invention. FIG. 5 is a flowchart explaining an example of the operation of the magnetic resonance type wireless power feeder of the present invention. FIG. 6 is a circuit diagram showing an example of a filtering circuit. FIG. 7 is a graph showing the relationship between the input voltage and output voltage of a voltage limiting circuit. FIG. 8 is a circuit diagram showing an example of a frequency ω ｈ and frequency ω ｌ 10 is a graph showing the relationship between the frequency and the transmission distance. When the self-excitation mode is executed, as the transmission distance changes, the oscillation frequency of the inverter decreases to a frequency ω ｈ and frequency ω ｌ 1 is a diagram illustrating the switching between (a) an ideal state and (b) an actual state after filtering the inverter oscillation frequency. Ｌ ) and the voltage detected by the shunt resistor (V ｉｎ ) and the voltage detected by the super-barrier rectifier diode (V ＳＢＲ ) is a graph showing the relationship between

[0030] Specific embodiments of the magnetic resonance type wireless power feeder of the present invention will be described in more detail with reference to the drawings. However, the configurations described below are merely preferred embodiments, and the technical scope of the magnetic resonance type wireless power feeder of the present invention is not limited to the configurations described below. The magnetic resonance type wireless power feeder of the present invention can be modified as appropriate within the scope that does not detract from the spirit of the invention.

[0031] 1. Circuit Structure of a Magnetic Resonance-Type Wireless Power Feeder First, the circuit structure of a magnetic resonance-type wireless power feeder of this embodiment will be described. FIG. 5 is a circuit diagram showing an example of a magnetic resonance-type wireless power feeder of the present invention. As shown in FIG. 5, the magnetic resonance-type wireless power feeder of this embodiment includes a power feeding circuit 100 and a power receiving circuit 200. The power feeding circuit 100 is provided in a power feeding device, and the power receiving circuit 200 is provided in a power receiving device. The specific specifications of the power feeding device and the charging device vary depending on the application of the magnetic resonance-type wireless power feeder. The magnetic resonance-type wireless power feeder of this embodiment is intended for applications such as wireless charging of electric vehicles, and a charging station is intended as the power feeding device and an electric vehicle is intended as the power receiving device.

[0032] 1.1 Power Supply Side Circuit The power supply side circuit 100 includes a power supply side resonant circuit 110, an inverter 120, a microcontroller 130, a feedback circuit 140, a self-excited / separately excited selector switch 150, an inverter power supply 160, and a power supply selector switch 170.

[0033] The power supply side resonant circuit 110 includes a power supply side coil L １ and the power supply capacitor C １ The power supply side resonant circuit 110 wirelessly transmits power to the power receiving side circuit 200 by interacting (resonating) with a power receiving side resonant circuit 210 (described later).

[0034] The inverter 120 is a self-excited inverter including a gate driver 121 and two switching elements (two field effect transistors (FET1 and FET12) in this embodiment). The inverter 120 receives an input signal S １０ , S ４０ In response to this, a signal S is input to the gates of FET1 and FET2. １１ , S １２ By switching between these, the DC voltage of the inverter power supply 160 is converted into AC. In the magnetic resonance type wireless power feeder of this embodiment, the inverter 120 is used as a constant voltage source.

[0035] The microcontroller 130 is a very small computer that combines a central processing unit (CPU), storage devices such as RAM and ROM, input / output ports, etc. into a single integrated circuit (IC). The microcontroller 130 is programmable. In the magnetic resonance type wireless power feeder of this embodiment, programming causes the microcontroller 130 to function as frequency command means 131, switch control means 132, error output means 133, etc. The microcontroller 130 is also provided with a timer 134.

[0036] The frequency command means 131 outputs the oscillation frequency stored in the storage device (not shown) of the microcontroller 130 to the gate driver 121 of the inverter 120 (signal S １０ ) The switch control means 132 switches the self-excited / separately excited changeover switch 150 and the power supply changeover switch 170 at a predetermined timing. The error output means 133 will be described later. The timer 134 detects the timing at which the switch control means 132 switches the self-excited / separately excited changeover switch 150 and the power supply changeover switch 170.

[0037] The feedback circuit 140 detects the AC current flowing through the power supply side resonant circuit 110 and positively feeds back the frequency of the AC current to the inverter 120 via the self-excited / separately excited changeover switch 150 (signal S ２０ , S ３０ , S ４０ ) The frequency of the AC current flowing through the power supply resonant circuit 110 is detected by a current detection circuit 180. This feedback circuit 140 allows the inverter 120 to self-oscillate in a self-excited mode, which will be described later, and maintains PT symmetry between the power supply circuit 100 and the power receiving circuit 200 (the magnetic resonance type wireless power feeder operates as a PT symmetric wireless power feeder). Therefore, even if the position of the power receiving device relative to the power supplying device changes, such as the transmission distance changes, the oscillation frequency of the inverter 120 is automatically adjusted so that the transmitted power is always kept constant.

[0038] The self-excited / separately excited changeover switch 150 is used to switch between a state in which the inverter 120 is connected to the feedback circuit 140 and a state in which the inverter 120 is connected to the frequency command means 131 of the microcontroller 130. A relay is usually used for the self-excited / separately excited changeover switch 150. The relay used for the self-excited / separately excited changeover switch 150 may be either a contact relay such as an electromagnetic relay or a contactless relay such as a solid-state relay. In the magnetic resonance type wireless power feeder of this embodiment, the self-excited / separately excited changeover switch 150 is configured using a solid-state relay in consideration of responsiveness and lifespan.

[0039] The self-excited / separately excited changeover switch 150 is switched by a control signal S output from the switch control means 132 of the microcontroller 130. ５１ When the self-excited / separately excited changeover switch 150 is connected to the feedback circuit 140 and the inverter 120 is connected to the feedback circuit 140, the frequency (signal S ４０ On the other hand, when the self-excited / separately excited changeover switch 150 is set to the frequency command means 131 side and the inverter 120 is connected to the frequency command means 131, the frequency (signal S １０ ) the inverter 120 enters a separately excited mode in which it oscillates separately.

[0040] The inverter power supply 160 is for supplying a DC voltage to the inverter 140. The DC voltage from this inverter power supply 160 is converted to AC by turning on and off switching elements (FET1 and FET12) of the inverter 140, and is supplied to the power supply-side resonant circuit 110. In the magnetic resonance type wireless power feeder of this embodiment, two types of inverter power supplies 160 are provided: a first inverter power supply 161 and a second inverter power supply 162. The first inverter power supply 161 has a low output voltage of DC 10 V, and the second inverter power supply 162 has a high output voltage of DC 200 V.

[0041] The power supply selector switch 170 is used to switch the power supply 160 connected to the inverter 120 between a first inverter power supply 161 and a second inverter power supply 162. As with the self-excited / separately excited selector switch 150, a relay is usually used for the power supply selector switch 170. The relay used for the power supply selector switch 170 may be either a contact relay such as an electromagnetic relay or a contactless relay such as a solid-state relay. In the magnetic resonance type wireless power feeder of this embodiment, the power supply selector switch 170 is configured using a solid-state relay in consideration of responsiveness and lifespan.

[0042] The power supply changeover switch 170 is switched by a control signal S output from the switch control means 132 of the microcontroller 130. ５２ When the power supply changeover switch 170 is set to the first inverter power supply 161 side, the inverter 120 is supplied with a DC voltage (DC 10 V) output from the first inverter power supply 161. On the other hand, when the power supply changeover switch 170 is set to the second inverter power supply 162 side, the inverter 120 is supplied with a DC voltage (DC 200 V) output from the second inverter power supply 162.

[0043] 1.2 Power Receiving Side Circuit The power receiving side circuit 200 includes a power receiving side resonant circuit 210, an AC-DC converter 220, a DC-DC converter 230, and a load R Ｌ It is equipped with the following.

[0044] The power receiving side resonant circuit 210 includes a power supply side coil L ２ and the power supply capacitor C ２ As already mentioned, the power supply side coil L of the power supply side resonant circuit 110 １ and the power supply capacitor C １are also connected in series, the magnetic resonance type wireless power feeder of this embodiment forms an S-S topology (FIG. 3(c)). The power receiving side resonant circuit 210 interacts (resonates) with the power feeding side resonant circuit 110 to receive power wirelessly from the power feeding side circuit 100. Because of the S-S topology, the constant voltage power supplied by the inverter 120 is Ｌ The signal is transmitted at a constant voltage.

[0045] The AC-DC converter 220 converts the AC power received by the power receiving side resonant circuit 210 into DC power. As the AC-DC converter 220, various known circuits can be used.

[0046] The DC-DC converter 230 converts the DC power output from the AC-DC converter 220 into a target voltage (load R Ｌ As the DC-DC converter 230, various known circuits can be used.

[0047] Load R Ｌ is an electric device that consumes power, such as a battery or a motor. Ｌ The type of the load R varies depending on the application of the magnetic resonance type wireless power feeder. In this embodiment, which is intended for wireless charging of an electric vehicle, Ｌ is used as a battery for electric vehicles.

[0048] 2. Operation of the Magnetic Resonance Type Wireless Power Supply Apparatus Next, the operation of the magnetic resonance type wireless power supply apparatus of this embodiment will be described. Fig. 6 is a flowchart illustrating the operation of the magnetic resonance type wireless power supply apparatus of this embodiment. When power supply (power transmission) is started using the magnetic resonance type wireless power supply apparatus of this embodiment, the steps shown in Fig. 6 are executed. Power supply is started by placing a power receiving device near a power supplying device and performing a predetermined operation on the power supplying device, etc. The magnetic resonance type wireless power supply apparatus of this embodiment is intended for wireless charging of electric vehicles, and power supply is started by parking the electric vehicle (power receiving device) in a predetermined position near a charging stand (power supplying side device) and operating a button or the like on a touch panel provided on the charging stand (power supplying side device).

[0049] Immediately after power supply is started, the self-excitation mode is first executed (step P1 in FIG. 6). This self-excitation mode is initiated by sending a control signal S ５１ (FIG. 5) is output, the self-excited / separately excited changeover switch 150 is switched to the feedback circuit 140 side, and the microcontroller 130 sends the trigger signal S ５３ At the same time, the switch control means 132 outputs a control signal S ５２ (FIG. 5) is output, and the power supply changeover switch 170 is turned on to the first inverter power supply 161. As already mentioned, in the self-excited mode, the inverter 120 self-oscillates. In order to make the inverter 120 self-oscillate, the trigger signal S ５３ First, the trigger signal S ５３ After that, the signal S from the feedback circuit 140 ４０ (FIG. 5) causes the inverter 120 to maintain self-oscillation.

[0050] When the self-excitation mode is being executed (step P1 in FIG. 6), the output signal S from the feedback circuit 140 ４０The inverter 120 self-oscillates at this frequency, and the PT symmetry between the power supply circuit 100 and the power receiving circuit 200 is maintained. Therefore, the magnetic resonance type wireless power feeder behaves as a PT symmetric wireless power feeder. Therefore, even if the position of the power receiving device relative to the power supply device (the parking position of the electric vehicle relative to the charging station) is deviated from the predetermined position, the oscillation frequency of the inverter 120 is automatically adjusted to an optimal value.

[0051] When self-excitation mode is executed, the power supply coil L １ From the receiving coil L ２ Power is transmitted to the load R of the power receiving device. Ｌ power is supplied to the inverter 120 (the battery of the electric vehicle is charged). However, because the inverter 120 is connected to a low-output inverter power supply 160 (first inverter power supply 161), the transmitted power during execution of the self-excitation mode is not very large. Since the self-excitation mode is executed with emphasis on finding the oscillation frequency of the inverter 120 in the separate-excitation mode that is executed later, rather than on power transmission, the inverter power supply 160 (first inverter power supply 161) during execution of the self-excitation mode can be low-output. This makes it possible to reduce the power consumption of the magnetic resonance type wireless power feeder.

[0052] The self-excitation mode (step P1 in FIG. 6) is performed for a predetermined time t １ (a predetermined time t １ The self-excitation mode is continued until a predetermined time t has elapsed ("no" in step P2 of FIG. 6). １ When the time elapses ("yes" in step P2 in FIG. 6), the oscillation frequency of the inverter 120 in the self-excitation mode is stored (step P3 in FIG. 6). In the magnetic resonance type wireless power feeder of this embodiment, the feedback circuit 140 sends a frequency signal S ５４ (Fig. 5) is output, and the frequency signal S ５４is stored in the storage device of the microcontroller 130 as the oscillation frequency of the inverter 120. This oscillation frequency is an optimum value according to the conditions of the power supplying device (charging stand) and the power receiving device (electric vehicle) at that time.

[0053] The oscillation frequency of the inverter 120 when the self-excitation mode is executed is stored (step P3 in FIG. 6), and then the separately-excitation mode is executed (step P4 in FIG. 6). This separately-excitation mode is executed by sending a control signal S ５１ (FIG. 5) is output, the self-excited / separately excited changeover switch 150 is switched to the frequency command means 131 side, and the switch control means 132 sends the control signal S ５２ (FIG. 5) is output, and the power supply changeover switch 170 is switched to the second inverter power supply 162 side.

[0054] When the separately excited mode is being executed (step P4 in FIG. 6), the output signal S from the frequency command 131 of the microcontroller 130 １０ The inverter 120 is then separately excited. That is, the inverter 120 is separately excited at the oscillation frequency stored in the microcontroller 130. However, although the inverter 120 is separately excited, the oscillation frequency is the one adjusted in the self-excited mode (step P1 in FIG. 6 ). Therefore, as long as the position of the power receiving device relative to the power supplying device (the parking position of the electric vehicle relative to the charging station) has not changed since the self-excited mode, the oscillation frequency remains at an optimal value even when the inverter 120 is separately excited.

[0055] Even when the separate excitation mode is executed, the power supply coil L １ From the receiving coil L ２ Power is transmitted to the load R of the power receiving device. Ｌ (The battery of the electric vehicle is charged.) Since the inverter 120 is connected to the high-output inverter power supply 160 (second inverter power supply 162), the transmitted power during execution of the separate excitation mode is greater than that during execution of the self-excitation mode.

[0056] When a completion signal is detected during execution of the separate excitation mode ("yes" in step P5 in FIG. 6), power supply ends. This completion signal is output, for example, when the supply of power preset on the touch panel of the power supplying device (charging stand) has finished, or when the power supplying device (charging stand) can no longer transmit power to the power receiving device (electric vehicle) (when the battery of the electric vehicle is fully charged).

[0057] The separate excitation mode may be continuously executed until a completion signal is detected, but in the magnetic resonance type wireless power feeder of this embodiment, even after the separate excitation mode is executed, the self-excitation mode is executed periodically to update the optimum oscillation frequency of the inverter 120. As a result, even if the weather changes or foreign objects such as fallen leaves or debris get between the power supply side device and the power receiving side device while the separate excitation mode is executed, the oscillation frequency can be updated to one appropriate for the situation, and the transmission power can be maintained. Specifically, after a predetermined time t has elapsed since the separate excitation mode was started, ２ (step P6 in FIG. 6) to determine whether a predetermined time t ２ When the time has elapsed ("yes" in step P6 in FIG. 6), the magnetic resonance type wireless power feeder is switched from the separate excitation mode to the automatic mode (step P1 in FIG. 6). The subsequent flow is as described above.

[0058] In the flow shown in FIG. 6, the time t １ However, the time t １ If the time t is too short, the separately excited mode may be executed before the oscillation frequency of the inverter 120 is stabilized in the self-excited mode, and power transmission in the separately excited mode may not be performed efficiently. １ is usually set to 1 second or more, and preferably set to 5 seconds or more. However, if the time t is set to a value that significantly exceeds the time required for the oscillation frequency of the inverter 120 to stabilize in the self-excited mode, １ Even if the time t is increased, it will only increase the power supply time (the time from when power supply starts to when it ends), and is therefore not very meaningful. １ The time t is usually set to 3 minutes or less, and preferably set to 1 minute or less.１ can be measured by a timer 134 provided in the microcontroller 130.

[0059] In the flow shown in FIG. 6, the time t ２ However, the time t ２ If the time t is set too long, it will take a long time for the magnetic resonance type wireless power feeder to adapt to changes in the power feeding environment due to changes in the weather, the intrusion of foreign objects, etc. ２ is usually 30 minutes or less, and preferably 20 minutes or less. ２ If is too short, the self-excitation mode will be executed frequently, which may lengthen the power supply time (the time from when power supply starts to when it ends). In addition, in an application where wireless charging is performed on an electric vehicle, it is unlikely that the weather or other conditions will change frequently, so there is little point in switching to the self-excitation mode frequently. For this reason, it is recommended to set the time t ２ The time t is usually 3 minutes or more, and preferably 5 minutes or more. ２ The time can also be measured by the timer 134 provided in the microcontroller 130.

[0060] However, if the position of the power receiving device (electric vehicle) relative to the power supplying device (charging stand) is significantly deviated from the predetermined position, or if an obstacle occurs between the power supplying device (charging stand) and the power receiving device (electric vehicle) during power supply, efficient power transmission from the power supplying device to the power receiving device may not be achieved even if the inverter 120 is separately excited at the oscillation frequency found in the self-excitation mode. Although not shown in the flowchart of FIG. 6 , the magnetic resonance type wireless power supply device of this embodiment outputs an error and stops power supply if the oscillation frequency of the inverter 120 in the self-excitation mode (the oscillation frequency stored in step P3) is outside a predetermined range. This error is output by the error output means 133 in the microcontroller 130. When an error is output, a message such as "Please place the power receiving device in an appropriate position (park the electric vehicle in an appropriate position)" can be displayed on the display device of the power receiving device (charging stand).

[0061] 3. Feedback Circuit The feedback circuit 140 will be described in more detail. As already mentioned, the feedback circuit 140 detects the AC current flowing through the power supply side resonant circuit 110 using the current detection circuit 180 and positively feeds back the frequency of the detected AC current to the inverter 120 via the self-excited / separately excited selector switch 150. While it is theoretically possible for this feedback circuit 140 to be configured using a digital circuit, this would require a computer with high processing power, which is not practical. For this reason, in the magnetic resonance type wireless power feeder of this embodiment, the feedback circuit 140 is configured using an analog circuit.

[0062] When the feedback circuit 140 is configured as an analog circuit, the feedback circuit 140 can be realized by a single operational amplifier. However, in the magnetic resonance type wireless power feeder of this embodiment, the feedback circuit 140 is configured by a filtering circuit 141 and a phase shift circuit 142, as shown in FIG. 5 .

[0063] 3.1 Filtering Circuit The filtering circuit 141 filters the input signal S (oscillation frequency of the inverter 120) to the inverter 120 to prevent the inverter 120 from oscillating outside a predetermined frequency range. ４０ 7 shows an example of the configuration of the filtering circuit 141. As shown in FIG. 7, the filtering circuit 141 includes a frequency-to-voltage conversion circuit 141a, a loop filter 141b, a voltage limiting circuit 141c, and a voltage-controlled oscillator (VCO) 141d.

[0064] The filtering circuit 141 receives the frequency signal S of the AC current generated in the power supply side resonant circuit 110 (FIG. 5). ２０ is input, the frequency-voltage conversion circuit 141a converts this frequency signal S ２０ In the magnetic resonance type wireless power feeder of this embodiment, the frequency-voltage conversion circuit 141a converts the frequency of the power supply into a voltage proportional to the frequency and outputs the voltage. １ and a charge pump (CP) 141a ２ The phase detector 141a is configured as follows: １ is the frequency signal S input to the filtering circuit 141 ２０ and the signal S fed back from the voltage-controlled oscillator 141d. ２５ The phase difference is detected and the phase difference is output as a signal S ２１ The charge pump 141a outputs the signal as ２ is the phase detector 141a １ The phase difference (signal S ２１ ) into a DC voltage. ２ From there, signal S ２１ A DC voltage proportional to the frequency of the signal S ２２ is output as

[0065] The above-mentioned frequency-voltage conversion circuit 141a (phase detector 141a １ and charge pump 141a ２ ) is a commercially available phase-locked loop circuit (PLL circuit) including a voltage-controlled oscillator 141d, which will be described later.２５ phase detector 141a １ In this type of feedback circuit, the signal S ２５ The phase of the signal S ２０ For signal S ２５ If the phase of the charge pump 141a is reversed, the circuit will not operate as designed. ２ The output signal S ２２ In the magnetic resonance type wireless power feeder of this embodiment, as shown in FIG. 7, a loop filter 141b is configured by a resistor and a grounded capacitor.

[0066] The voltage limiting circuit 141c limits the voltage (signal S ２３ ), the voltage outside the predetermined range is cut off, while the voltage within the predetermined range is output as is. In the magnetic resonance type wireless power feeder of this embodiment, the voltage limiting circuit 141c limits the input voltage (signal S ２３ ) is the threshold voltage V Ｔｈ If the input voltage does not reach the output voltage (signal S ２４ ) and the threshold voltage V Ｔｈ while outputting the input voltage (signal S ２３ ) is the threshold voltage V Ｔｈ If the input voltage is equal to or greater than the output voltage (signal S ２４ 8 shows the input voltage (signal S ２３ ) and output voltage (signal S ２４ ) is a graph showing the relationship between the threshold voltage V Ｔｈ is the resonant frequency ω ０ (See FIG. 9 below) is set to a value corresponding to the above.

[0067] In the magnetic resonance type wireless power feeder of this embodiment, as shown in FIG. 7, a voltage limiting circuit 141c is provided as a buffer amplifier 141c. １ and ideal diode 141c ２ and Zener diode 141c３ The buffer amplifier 141c is configured by combining the above. １ is the output signal S of the loop filter 141b ２３ The Zener diode 141c isolates the power supply and extracts only the voltage signal. ２ The part indicates the threshold voltage V Ｔｈ It may be replaced by various devices that can fix a voltage corresponding to the reference voltage IC, a reference voltage diode, a shunt regulator, etc.

[0068] The voltage controlled oscillator 141d receives a voltage (signal S ２４ ) is the frequency proportional to the output signal S ３０ The voltage (signal S ２４ ) is the frequency (signal S ２０ ), the signal S output from the voltage controlled oscillator 141d ３０ The frequency of the signal S input to the filtering circuit 141 ２０ and the frequency of the signal S ２５ and signal S ２０ The phase difference between the signals S ３０ is generated by the voltage controlled oscillator 141d, and the signal S ３０ is electrically a signal S ２０ Therefore, the signal S ３０ So, signal S ２０ The noise contained in the

[0069] In this way, the filtering circuit 141 converts the oscillation frequency of the inverter 120 into a voltage, filters it, and then converts it back into a frequency. The filtering circuit 141 is provided for the following reasons.

[0070] That is, when the magnetic resonance type wireless power feeder of this embodiment is driven in the self-excitation mode, the inverter 120 generates a power at a frequency ω ｈThe self-oscillation mode and the frequency ω ｌ In the following equations 1 and 2, ０ is the resonant frequency of the power supply resonant circuit and the power receiving resonant circuit, κ is the coupling rate between the couplers, and Γ ２０ is the intrinsic loss rate of the receiving resonant circuit, and Γ Ｌ is the load loss rate.

[0071] These frequencies ω ｈ , ω ｌ The relationship between the frequency ω and the transmission distance is shown in a graph in FIG. ｈ is the resonant frequency ω ０ is higher than the frequency ω ｌ is the resonant frequency ω ０ In order to achieve high-efficiency power transmission in the self-excited mode, PT symmetry must be maintained. ｈ and frequency ω ｌ and the resonant frequency ω ０ However, this PT symmetry is not preserved even if the transmission distance becomes infinitely long, and is no longer preserved once a certain transmission distance (critical transmission distance) is exceeded. In order to achieve highly efficient power transmission in self-oscillating mode, power transmission must be performed within the critical transmission distance.

[0072] However, in the self-excitation mode, even if power transmission is performed within the critical transmission distance, as shown in FIG. 10, the oscillation frequency of the inverter 120 is ｈ and frequency ω ｌ 3(d) in Non-Patent Document 1, the oscillation frequency changes from ω ｌ From ω ｈ As in Non-Patent Document 1, when the transmission power is as small as 0.01 W, the oscillation frequency is switched to the frequency ω ｌ and frequency ω ｈEven if the oscillation frequency is switched between 1 and 2, no major problems will occur in terms of hardware. However, if the transmission power is large and such a switch in the oscillation frequency occurs, the switching frequency of the inverter 120 will change suddenly, causing a short-circuit current to flow through the inverter 120, which may damage the switching elements (FET1 and FET12 in FIG. 5 ) that make up the inverter 120. Even if no damage occurs, the transmission power will fluctuate each time the oscillation frequency is switched, thereby defeating the original purpose of the wireless power supply device.

[0073] This problem can be solved by, for example, incorporating a high-pass filter in the inverter 120 to reduce the resonant frequency ω ０ 11(a), it seems that this problem can be solved by preventing the inverter 120 from oscillating within a range where the oscillation frequency does not reach the resonant frequency ω ０ The inverter 120 is filtered to have a resonant frequency ω ０ It may seem that the above problem can be solved by oscillating only above this threshold. However, since the gain of a high-pass filter has a frequency gradient, in an actual high-pass filter, as shown in Figure 11(a), the threshold (resonant frequency ω ０ ) cannot be clearly filtered, and as shown in FIG. 11(b), the threshold (resonant frequency ω ０ ) filtering becomes ambiguous near the high-pass filter. Therefore, this method cannot reliably prevent switching of the oscillation frequency. In addition, when a high-pass filter is incorporated, a phase difference occurs in the waveforms on the input and output sides of the high-pass filter. This phase difference causes a change in the output power of the inverter 120, defeating the original purpose of the wireless power supply device.

[0074] In contrast, if the oscillation frequency of the inverter 120 is converted into a voltage, filtered, and then converted back into a frequency, as in the magnetic resonance type wireless power feeder of this embodiment, clear filtering can be performed as shown in FIG. 11( a). This is because it is easy to clearly filter a voltage using a threshold value. For example, by using a Zener diode, a reference voltage diode, a shunt regulator, an ideal diode, or the like, clear filtering can be performed using the threshold voltage as a boundary. Therefore, even if the relative position of the power receiving device with respect to the power supplying device changes, such as when the transmission distance changes, the oscillation frequency of the inverter 120 is prevented from switching, and the above frequency ω ｈ and frequency ω ｌ The target frequency (in the magnetic resonance type wireless power feeder of this embodiment, the frequency ω ｈ ) allows the inverter to oscillate stably.

[0075] Incidentally, the current detection circuit 180 that detects the AC current flowing through the power supply side resonant circuit 110 is often configured with a shunt resistor, but in the magnetic resonance type wireless power supply device of this embodiment, the current detection circuit 180 is configured with a pair of super barrier rectifier diodes (SBR diodes) as shown in FIG. 5 .

[0076] This is because, when a shunt resistor is used in the current detection circuit 180, the current (i Ｌ ) and the voltage (V ｉｎ ) generates a slight phase difference. This phase difference is caused by the inductance component contained in the shunt resistor. If the frequency changes, the current (i Ｌ The phase difference between the current (i Ｌ It becomes difficult to generate a voltage signal that is in phase (zero phase difference) with the current (i Ｌ ) with respect to voltage (V ｉｎ) phase shift, the transmitted power fluctuates, and the purpose of wireless power supply is lost. On the other hand, if a pair of super-barrier rectifier diodes is used in the current detection circuit 180, as shown in FIG. 12(b), the current (i Ｌ ) and the same phase voltage (V ＳＢＲ ) can be detected. Ｌ ) and the same phase voltage (V ＳＢＲ ) can be detected, the voltage (V ＳＢＲ ) the voltage signal V ＰＬＬ 5. Then, the gate signal S shown in FIG. 12(d) is generated. １１ The voltage V used as Ｇ１ , and the gate signal S in FIG. １２ The voltage V used as Ｇ２ ) can be produced, and the above problems can be solved.

[0077] Furthermore, the forward voltage of a super-barrier rectifier diode is lower than that of other diodes. Therefore, if a super-barrier rectifier diode is used in the current detection circuit 180, the power loss in the current detection circuit 180 can be reduced. Furthermore, what is desired to be detected by the current detection circuit 180 is the current (i Ｌ ) but the magnitude of the current (i Ｌ ) is the timing of zero crossing, the voltage (V ＳＢＲ ) is the amplitude of the current (i Ｌ ) is not significantly affected by the magnitude of the current (i Ｌ ) can be small or large, allowing the circuit to operate over a wide range.

[0078] 3.2 Phase Shift Circuit The phase shift circuit 142 (FIG. 5) shifts the frequency signal S ４０ In this case, the signal S output from the filtering circuit 141 is adjusted so as to generate an inductive state in which the phase of the voltage waveform is slightly ahead of the phase of the current waveform. ３０The phase shift circuit 142 shifts the phase of the voltage waveform of the inverter 120. This phase shift circuit 142 enables soft switching in the inverter 120. Therefore, even when the transmission power is large (for example, 1 kW or more), not only can power loss be reduced and efficient power transmission be achieved, but also heat generation in the switching elements (FET1 and FET2 in FIG. 5) constituting the inverter 120 can be reduced, making the inverter 120 less likely to be damaged. A voltage-controlled phase shifter can be suitably used as the phase shift circuit 142.

[0079] However, the inductive state described above is caused by the oscillation frequency of the inverter 120 (signal S ４０ The frequency of ０ (FIG. 9). In other words, when the oscillation frequency of the inverter 120 is higher than the resonant frequency ω ０ Therefore, in order to create an inductive state and realize soft switching, the oscillation frequency of the inverter 120 must be set to a value lower than the frequency ω ｌ (Fig. 9) but at frequency ω ｈ In this regard, in the magnetic resonance type wireless power feeder of this embodiment, as described above, the frequency ω ｈ Since the filtering circuit 141 is configured so that the PT symmetry can be preserved and soft switching can be performed at the same time.

[0080] 4. Applications The magnetic resonance type wireless power feeder of this embodiment can be used in various applications in which power is transmitted wirelessly. In particular, the magnetic resonance type wireless power feeder of this embodiment can transmit power even when the transmission power is large, and therefore can be suitably employed when the transmission power is large. For example, it can be suitably employed when the transmission power is 100 W or more, 500 W or more, or 1 kW or more. Furthermore, the magnetic resonance type wireless power feeder of this embodiment is also highly robust, and therefore can be suitably employed in applications in which the relative position of the power receiving device with respect to the power supplying device is not fixed. An example of such an application is wireless charging of electric vehicles.

[0081] REFERENCE SIGNS LIST 100 Power supply side circuit 110 Power supply side resonant circuit 120 Inverter 121 Gate driver 130 Microcontroller (frequency command means) 131 Frequency command means 132 Switch control means 133 Error output means 134 Timer 140 Feedback circuit 141 Filtering circuit 141a Frequency-voltage conversion circuit 141a １ Phase Detector (PFD) 141a ２ Charge pump (CP) 141b Loop filter 141c Voltage limiting circuit 141c １ Buffer amplifier 141c ２ Ideal diode 141c ３ Zener diode 141d Voltage controlled oscillator (VCO) 142 Phase shift circuit 150 Self-excited / separately excited changeover switch 160 Inverter power supply 161 First inverter power supply 162 Second inverter power supply 170 Power supply changeover switch 180 Current detection circuit 200 Power receiving side circuit 210 Power receiving side resonant circuit 220 AC-DC converter 230 DC-DC converter

Claims

1. A magnetic resonance type wireless power supply device comprising: a power supply side circuit in which an inverter and a frequency command means for outputting a frequency to the inverter are connected to a power supply side resonant circuit including a power supply side coil; and a power receiving side circuit having a power receiving side resonant circuit including a power receiving side coil, wherein the power supply side circuit is provided with: a feedback circuit that positively feeds back the current flowing through the power supply side resonant circuit to the inverter; a self-excitation / separately excited changeover switch that switches between a self-excitation mode in which the inverter and the feedback circuit are connected and the inverter is self-oscillated by the feedback circuit, and an other-excitation mode in which the inverter and the frequency command means are connected and the inverter is other-excited to oscillate at a frequency output from the frequency command means; and switch control means that controls the self-excitation / other-excitation changeover switch; immediately after power supply starts, the self-excitation / other-excitation changeover switch is switched to the self-excitation mode by the switch control means, and the inverter performs self-oscillation, and the oscillation frequency of the inverter at that time is recorded in the frequency command means, a switch control means for switching a self-excited / separately excited changeover switch to the separate excitation mode when a predetermined time has elapsed since the start of power supply, so that the inverter is separately excited and oscillated at the oscillation frequency stored in the frequency command means.

2. A magnetic resonance type wireless power feeder as claimed in claim 1, wherein even after a predetermined time has elapsed since the start of power feeding, the switch control means intermittently switches the self-excitation / separately-excitation changeover switch from the separate-excitation mode to the self-excitation mode, thereby intermittently generating the self-excitation mode, and the oscillation frequency recorded in the frequency command means is updated with the oscillation frequency of the inverter in the self-excitation mode that is generated intermittently.

3. The wireless power supply device according to claim 2, further comprising error output means for outputting an error when the oscillation frequency of the inverter in the self-excitation mode falls outside a predetermined range.

4. A wireless power supply device as claimed in claim 3, wherein the power supply side circuit is provided with: a first inverter power supply; a second inverter power supply having a higher output than the first inverter power supply; and a power supply changeover switch for changing over the power supply connected to the inverter between the first inverter power supply and the second inverter power supply, wherein in a self-excitation mode in which the inverter self-oscillates, the power supply changeover switch is changed over to the first inverter power supply side by the switch control means, and in a separate excitation mode in which the inverter separately oscillates, the power supply changeover switch is changed over to the second inverter power supply side by the switch control means.

5. A power supply circuit for a magnetic resonance type wireless power feeder in which an inverter and frequency command means for outputting a frequency to the inverter are connected to a power supply resonant circuit including a power supply coil, the power supply circuit comprising: a feedback circuit for positively feeding back a current flowing through the power supply resonant circuit to the inverter; a self-excitation / separately-excited changeover switch for switching between a self-excitation mode in which the inverter is connected to the feedback circuit and the feedback circuit causes the inverter to self-oscillate, and an other-excitation mode in which the inverter is connected to the frequency command means and the inverter oscillates separately at a frequency output from the frequency command means; and switch control means for controlling the self-excitation / separately-excitation changeover switch; wherein immediately after power supply starts, the switch control means switches the self-excitation / separately-excitation changeover switch to the self-excitation mode, causing the inverter to self-oscillate, and the oscillation frequency of the inverter at that time is recorded in the frequency command means; and when a predetermined time has passed since power supply starts, the switch control means switches the self-excitation / separately-excitation changeover switch to the other-excitation mode, causing the inverter to oscillate separately at the oscillation frequency stored in the frequency command means. A power supply side circuit for a magnetic resonance type wireless power supply device.

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