JP2018170819A - Wireless power transmission apparatus and wireless power transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless power transmission apparatus and wireless power transmission system, having a self-excited oscillation circuit in a simple circuit configuration and capable of achieving cost reduction, high quality and high efficiency.SOLUTION: A wireless power transmission system 1 includes: a wireless power transmission apparatus 10; and a wireless power reception apparatus 20 for receiving electric power transmitted from the wireless power transmission apparatus 10. The wireless power transmission apparatus 10 includes a power transmission coil Lfor executing power transmission and a self-excited oscillation circuit 15 for inverting a DC voltage applied between a pair of DC input terminals 12a, 12b into an AC voltage and supplying the voltage to the power transmission coil L. The power transmission coil Lis constituted of a single coil.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wireless power transmission apparatus and a wireless power transmission system that transmit power wirelessly.

  Wireless power transmission technology that supplies power without using a power cable or power cord has attracted attention. Wireless power transmission technology can supply power wirelessly from the power transmission side to the power reception side, so it can be applied to various products such as transportation equipment such as trains and electric cars, home appliances, electronic equipment, wireless communication equipment, toys, and industrial equipment. Is expected.

  In the wireless power transmission technology, similar to other electronic devices, a simple configuration with low cost and high efficiency is required. In order to realize this requirement, a device using a self-excited oscillation circuit that can be configured with a simple circuit has been proposed.

  For example, Patent Document 1 describes that in a non-contact power feeding device that supplies power from a power transmission side resonance unit to a power reception side resonance unit via a transformer in a contactless manner, the power transmission side resonance unit includes a self-excited oscillation circuit. ing. The self-excited oscillation circuit includes a reference circuit that applies a DC voltage to a middle point terminal of a power transmission side primary coil of the transformer, a first switching element, a second switching element, and a power transmission side primary coil in order to secure a reference of the transformer. And a capacitor connected in parallel. At both ends of the power transmission side primary coil, a voltage having a resonance frequency included in the resonance circuit of the power transmission side primary coil and the capacitor is generated, and induced voltages generated in the power transmission side secondary coil based on this voltage are first and second. The drain voltage obtained by amplifying this induced voltage is applied to both ends of the power transmission side primary coil by applying the feedback to the gate side of the switching element, and self-excited oscillation is performed by repeating such an operation.

  Patent Document 2 describes a push-pull resonant converter that performs self-excited oscillation. This resonant converter includes a parallel circuit of an exciting coil L0 and a capacitor C0, and a series circuit of two transistors Q1 and Q2 connected in parallel to this parallel circuit. The bases of the two transistors Q1 and Q2 are connected to the negative terminal of the DC input via resistors R1 and R2, respectively, and the base of one transistor Q1 is connected via a parallel circuit of a capacitor C1 and a resistor R3. The other transistor Q2 is connected to the collector of the other transistor Q2, and the base of the other transistor Q2 is connected to the collector of one transistor Q1 through a parallel circuit of a capacitor C2 and a resistor R4. The emitters of the two transistors Q1 and Q2 are connected in common and connected to the negative terminal of the DC input, and the positive terminal of the DC input is connected to the intermediate connection point of the exciting coil L0 via the coil L1.

JP 2012-175880 A JP-A-9-19078

  However, in the technique disclosed in Patent Document 1, a power transmission side primary coil is formed by two coils connected in series via a midpoint terminal, and further includes a power transmission side secondary coil as a feedback winding. There is a problem that the configuration of the power transmission coil unit becomes complicated and the cost increases. In addition, it is ideal that the primary coil on the power transmission side formed by two coils has the same inductance value and a coupling coefficient of 1, but in practice, the inductance value of each coil differs due to the structure, Furthermore, the coupling coefficient is smaller than ideal. Therefore, the current waveforms of the first and second switching elements that are self-oscillating are asymmetric, and there is a problem that switching loss increases and efficiency decreases.

  Moreover, although the technique disclosed in Patent Document 2 does not use a feedback winding, the exciting coil L0 is formed by two coils connected in series via a midpoint connection point, and the configuration of the power transmission coil unit is as follows. There was a problem that it would become complicated and costly. In addition, it is ideal that the exciting coil L0 formed of two coils has the same inductance value and a coupling coefficient of 1, but in reality, the inductance values of the two coils are different due to the structure. The coupling coefficient is also smaller than ideal. Therefore, the current waveforms of the two transistors Q1 and Q2 that are self-excited oscillate are asymmetrical, resulting in increased switching loss and reduced efficiency.

  The present invention has been made in view of the above problems, and provides a wireless power transmission apparatus and a wireless power transmission system that have a simple circuit configuration and include a low-cost, high-quality, and high-efficiency self-oscillation circuit. The purpose is to do.

  In order to solve the above-described problems, a wireless power transmission device according to the present invention includes a power transmission coil that performs power transmission, and converts a DC voltage applied between a pair of DC input terminals into an AC voltage and supplies the AC voltage to the power transmission coil. An excitation oscillation circuit is provided, and the power transmission coil is formed of a single coil.

  According to the present invention, since it is not necessary to use a power transmission coil composed of two coils connected via a feedback winding or an intermediate tap, a wireless power transmission device including a high-quality and high-efficiency self-excited oscillation circuit is provided. It can be realized at low cost.

  In the present invention, the self-excited oscillation circuit is connected to a resonance capacitor that forms a resonance circuit together with the power transmission coil, a first switch element connected to one end of the power transmission coil, and the other end of the power transmission coil. A second switching element; a first inductor connected between one end of the power transmission coil and one of the pair of DC input terminals; the other end of the power transmission coil and one of the pair of DC input terminals; And a second inductor connected between the two. According to this configuration, a wireless power transmission apparatus including a high-quality and high-efficiency self-excited oscillation circuit can be realized at a low cost. The first and second switch elements may be directly connected to one end and the other end of the power transmission coil, respectively, or may be indirectly connected via elements or the like constituting the resonance circuit.

  In the present invention, the self-excited oscillation circuit includes a first impedance element connected between a control electrode of the first switch element and the other end of the power transmission coil, and a control electrode of the second switch element. And a second impedance element connected between the power transmission coil and one end of the power transmission coil. In this case, the first impedance element has at least one of a first resistor and a first capacitor, and the second impedance element has at least one of a second resistor and a second capacitor. It is preferable. Further, the first impedance element further includes a first diode having a cathode connected to the other end of the power transmission coil, and the second impedance element has a cathode connected to one end of the power transmission coil. It is preferable to further have a second diode. As a result, it is possible to reduce the loss of the switch element, so that a more efficient self-excited oscillation circuit can be realized. The first and second impedance elements may be directly connected to the other end and one end of the power transmission coil, respectively, or may be indirectly connected via elements or the like constituting the resonance circuit.

  In the present invention, the number of turns of the power transmission coil is preferably one turn. Thereby, the further simplification of the structure of a power transmission coil can be achieved.

  In this invention, it is preferable that the said power transmission coil has a magnetic body and the conducting wire wound by the main surface of the said magnetic body spirally. Thereby, high-efficiency and low-noise power transmission is possible.

  A wireless power transmission system according to the present invention includes the wireless power transmission device according to the present invention having the above characteristics, and a wireless power reception device that wirelessly receives power transmitted from the wireless power transmission device, and the wireless power reception device. Includes a power receiving coil that is magnetically coupled to the power transmitting coil, and a rectifier circuit that converts an AC voltage generated in the power receiving coil into a DC voltage. According to the present invention, it is possible to provide a wireless power transmission system including a wireless power transmission device that uses a self-excited oscillation circuit having a simple circuit configuration and low cost, high quality, and high efficiency.

  ADVANTAGE OF THE INVENTION According to this invention, it is a simple circuit structure, Comprising: A low-cost, high quality, highly efficient self-excited oscillation circuit provided with the wireless power transmission apparatus and wireless power transmission system can be provided.

FIG. 1 is a circuit diagram showing a configuration of a wireless power transmission system according to a first embodiment of the present invention. FIG. 2 is a schematic perspective view showing an example of the structure of the power transmission coil _LTX . FIGS. 3A and 3B are operation explanatory diagrams of the wireless power transmission device. 4A and 4B are operation explanatory diagrams of the wireless power transmission device. FIG. 5 is a voltage waveform diagram for explaining the operation of the self-excited oscillation circuit 15. FIG. 6 is a circuit diagram showing a configuration of a wireless power transmission system according to the second embodiment of the present invention. FIG. 7 is a circuit diagram showing a modification of the wireless power transmitting apparatus 10. FIG. 8 is a circuit diagram showing a modified example of the wireless power transmitting apparatus 10. FIG. 9 is a circuit diagram showing a modification of the wireless power receiving apparatus 20.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a circuit diagram showing a configuration of a wireless power transmission system according to a first embodiment of the present invention.

  As shown in FIG. 1, the wireless power transmission system 1 is a combination of a wireless power transmission device 10 and a wireless power reception device 20, and wirelessly transmits power from the wireless power transmission device 10 to the wireless power reception device 20.

Wireless power transmission device 10 includes a power transmission coil L _TX perform power transmission, the pair of DC input terminals 12a, the self-oscillating circuit and supplying the converted AC voltage to a DC voltage applied between 12b to the power transmission coil L _TX 15, and an input capacitor C _in is connected between the pair of DC input terminals 12a, 12b.

The power transmission coil L _TX is composed of a single coil. Note that a single coil means that there are two terminals and no intermediate tap. As shown in FIG. 2, the power transmission coil L _TX according to the present embodiment is preferably a spiral coil in which a single conductive wire 11 is spirally wound around the main surface of a flat magnetic body 13. With this configuration, high-efficiency and low-noise power transmission is possible. The number of turns of the power transmission coil L _TX is not particularly limited, and may be about 1 turn. When the power transmission coil L _{TX is set} to one turn, the configuration of the power transmission coil can be further simplified.

Self-oscillating circuit 15, a first inductor and the resonant capacitor C _p1 connected in parallel to the power transmission coil L _TX, is connected between the positive terminal 12a of the one end 11a and a pair of DC input terminals of the power transmission coil L _TX L ₁ , a second inductor L ₂ connected between the other end 11 b of the power transmission coil L _TX and the plus terminal 12 a of the pair of DC input terminals, and a first connected to one end 11 a of the power transmission coil L _TX . the switch element Q _1, the second switch element Q ₂ to which is connected to the other end 11b of the power transmission coil L _TX, between the other end 11b of the first gate and the power transmission coil L _TX switching element Q ₁ The first impedance element Z ₁ to be connected and the second impedance element Z ₂ connected between the gate of the second switch element Q ₂ and one end 11a of the power transmission coil L _TX are provided.

The resonance capacitor C _p1 forms a resonance circuit together with the power transmission coil L _TX and the first and second inductors L ₁ and L ₂ . As will be described in detail later, the resonance capacitor C _p1 may be connected in series to the power transmission coil L _TX , or two or more capacitors may be connected in series and parallel.

In the present embodiment, the first and second switch elements Q ₁ and Q ₂ are NMOS transistors. The drain of the first switch element Q ₁ is connected to the plus terminal 12a which is one of the pair of DC input terminals via the first inductor L _1, and the drain of the second switch element Q ₂ is the second through the inductor L ₂ is connected to the positive terminal 12a of the pair of DC input terminals. The sources of the first and second switch elements Q ₁ and Q ₂ are connected to the negative terminal 12b which is the other of the pair of DC input terminals. Further, the gate (control electrode) of the _first switch element Q ₁ is connected to the plus terminal 12a of the pair of DC input terminals via the second inductor L _2, and the gate of the _second switch element Q ₂ is the _second one. It is connected to the positive terminal 12a of the pair of DC input terminals via the first inductor L _1.

The configuration of the first and second impedance elements Z ₁ and Z ₂ is not particularly limited. For example, a parallel circuit of a diode, a capacitor, and a resistor can be used as shown in the figure. Thus, the first impedance element Z ₁ preferably has a resistor or a capacitor, and the cathode (the anode on the gate side of the _first switch element Q ₁ ) is connected to the other end 11 b side of the power transmission coil L _TX. It is further preferable to have a diode. Second impedance element Z ₂ also preferably has a resistance or a capacitor, the cathode to one end 11a of the power transmission coil L _TX (anode to the second gate of the switching element Q ₂₎ has a diode connected More preferably.

Configuration of the wireless power receiving apparatus 20 is not particularly limited, for example, a receiving coil L _RX to the power transmission coil L _TX magnetically coupled during power transmission, the resonant capacitor C _s1 connected in series to the receiving coil L _RX, the receiving coil L _RX The rectifier circuit 21 converts the AC voltage generated at the DC voltage into a DC voltage and outputs it to the load 22, and the smoothing capacitor C _out connected between the pair of output terminals of the rectifier circuit 21. Although details will be described later, the resonance capacitor C _s1 may be connected in parallel to the power receiving coil L _RX , or two or more capacitors may be connected in series and parallel.

  Next, the operation of the wireless power transmitting apparatus 10 will be described with reference to FIGS. 3 and 4.

First pair of DC input terminals 12a, a DC voltage between 12b is applied, or the second switching element Q ₂ is turned on via the first inductor L ₁ and the second impedance element Z _2, the The first switch element Q ₁ is turned on via the _second inductor L ₂ and the first impedance element Z ₁ . Usually, since the symmetry of the circuit is lost due to variations in the characteristics of the electronic components, _{one of} the switch elements Q ₁ and Q ₂ is turned on first. In order to ensure the asymmetry of the circuit, the impedance of the first impedance element Z ₁ may be intentionally set smaller than that of the second impedance element Z ₂ , and the switch element Q ₁ may be turned on _first .

As shown in FIG. 3A, for example, when the first switch element Q ₁ is turned on, a current I ₁ flows from the first inductor L ₁ to the first switch element Q ₁ . Further, the current I ₂ flows from the second inductor L ₂ to the first switch element Q ₁ through the parallel circuit of the power transmission coil L _TX and the resonance capacitor C _p1 . Further, when the first switching element Q ₁ is turned on, so with the first drain voltage V _ds1 of the switching element Q ₁ becomes the second switching element Q ₂ of the gate voltage V _gs2 substantially zero [V], the second The off state of the switch element Q ₂ is maintained.

When the current I ₂ flows, the drain voltage V _ds2 of the second switch element Q ₂ increases, but when the voltage reaches a certain voltage level by the operation of the resonance circuit including the power transmission coil L _TX and the resonance capacitor C _p1 , Going down. When the drain voltage V _{ds2 of} the second switch element Q ₂ drops to near zero [V], the gate voltage V _{gs1 of the first} switch element Q ₁ also becomes substantially zero [V], and the first switch element Q ₁ Turns off.

Thus, as shown in FIG. 3B, the first and second switch elements Q ₁ and Q ₂ are both turned off, but the first inductor L ₁ tries to keep the current I ₁ flowing, and the power transmission coil L since _TX also tries to keep supplying a current I _2, the first drain voltage V _ds1 and the second gate voltage V _gs2 of the switching element Q ₂ of the switch element Q ₁ is increased, thereby the second switching element Q ₂ turns on.

As shown in FIG. 4A, when the second switch element Q ₂ is turned on, a current I ₂ flows from the second inductor L ₂ to the second switch element Q ₂ . Further, a current I ₁ flows from the first inductor L ₁ to the second switch element Q ₂ through the parallel circuit of the power transmission coil L _TX and the resonance capacitor C _p1 . Further, when the second switch element Q ₂ is turned on, the gate voltage V _{gs1 of the first} switch element Q ₁ together with the drain voltage V _{ds2 of the second} switch element Q ₂ becomes _{substantially} zero [V]. The switch element Q ₁ is kept off.

When the current I ₁ flows, the drain voltage V _ds1 of the first switch element Q ₁ increases, but when the voltage reaches a certain voltage level by the operation of the resonance circuit including the power transmission coil L _TX and the resonance capacitor C _p1 , Going down. When the drain voltage V _{ds1 of} the first switch element Q ₁ drops to near zero [V], the gate voltage V _{gs2 of the second} switch element Q ₂ also becomes substantially zero [V], and the second switch element Q ₂ Turns off.

Thus, as shown in FIG. 4B, the first and second switch elements Q ₁ and Q ₂ are both turned off, but the second inductor L ₂ tries to keep the current I ₂ flowing, and the power transmission coil L since _TX is tries to keep supplying a current I _1, the drain voltage V _ds2 and the first gate voltage V _gs1 switching element Q ₁ of the second switching element Q ₂ is increased, thereby the first switching element Q ₁ is turned on again (see FIG. 2A).

The first and second switching elements Q ₁ and Q ₂ are in a steady state while repeating the above-described on / off operation, and currents I ₁ and I ₂ having the same magnitude in opposite directions flow alternately in the power transmission coil L _TX . An AC voltage having a predetermined oscillation frequency is generated at both ends of the power transmission coil _LTX .

  FIG. 5 is a voltage waveform diagram for explaining the operation of the self-excited oscillation circuit 15.

FIG as shown in 5, the first and second switching elements Q _1, Q ₂ repeats on and off alternately operated, but the first drain voltage V _ds1 of the switching element Q ₁ is a first switching element Q ₁ When V is on, it is zero [V], and when it is off, it is a half-cycle sine wave. The second drain voltage V _ds2 of the switching element Q ₂ is also zero [V] becomes when the second switching element Q ₂ is turned on, a sine wave of the half cycle when off.

The first gate voltage V _gs1 switching element Q ₁ is a first switching element Q ₁ is in the on a sine wave half cycle, in particular the first impedance element Z ₁ voltage drop by the second a smaller peak level than the drain voltage V _ds2 of the switching element Q _2. When the first switch element Q ₁ is off, it is almost zero [V]. Similarly, the second gate voltage V _gs2 of the switching element Q ₂ is, the second switching element Q ₂ is in the on a sine wave half cycle, the voltage drop by the first particular of the second impedance element Z ₂ The peak level is lower than the drain voltage V _ds1 of the switch element Q ₁ . When the second switch element Q ₂ is off, it becomes almost zero [V].

Therefore, the voltage V _out across the power transmission coil L _TX becomes a first switching element to Q ₁ drain voltage V _ds1 and second AC output voltage and the drain voltage V _ds2 synthesized switching element Q _2, V it can be shown as _out = V _ds1 -V _ds2.

In a conventional self-excited oscillation circuit that performs an oscillating operation by feeding back an output voltage taken out from an intermediate tap (middle point terminal) of a power transmission coil, the switching element is caused by the asymmetry of two coils connected via the intermediate tap. The current waveforms of Q ₁ and Q ₂ are also asymmetric, and the efficiency is reduced due to an increase in switching loss. However, in this embodiment, the power transmission coil L _TX is constituted by a single coil, since the oscillation operation without using the output voltage self-oscillating circuit 15 is taken out from the intermediate tap, switching element Q _1, The symmetry of the current waveform of Q ₂ can be increased, switching loss can be reduced, and power conversion efficiency can be increased.

As described above, the wireless power transmission system 1 according to the present embodiment includes the wireless power transmission device 10 and the wireless power reception device 20, and the wireless power transmission device 10 _applies an AC voltage to the power transmission coil _LTX and the power transmission coil _LTX. Since the self-excited oscillation circuit 15 is provided and the power transmission coil L _TX is formed of a single coil having no intermediate tap, the first and second switching elements Q ₁ constituting the self-excited oscillation circuit 15 are provided. , Q ₂ current waveform becomes asymmetric, switching loss can be reduced and power conversion efficiency can be increased. Further, the self-excited oscillation circuit 15 according to the present embodiment has a simple circuit configuration in which the power transmission coil L _TX is configured by a single coil and does not have a feedback winding or the like. The power transmission device 10 and the wireless power transmission system 1 can be realized at low cost.

  FIG. 6 is a circuit diagram showing a configuration of a wireless power transmission system according to the second embodiment of the present invention.

As shown in FIG. 6, the wireless power transmission system 2 is characterized in that PMOS transistors are used as the first and second switch elements Q ₁ and Q ₂ constituting the self-excited oscillation circuit 15 instead of NMOS transistors. is there. Therefore, one end 11a of the power transmission coil L _TX, via a first inductor L ₁ is connected to the negative terminal 12b is one of the pair of DC input terminals, the other end 11b of the power transmission coil L _TX, the second It is connected to the negative terminal 12b of the pair of DC input terminals through the inductor L _2.

In the present embodiment, the drains of the first and second switch elements Q ₁ and Q ₂ are connected to the plus terminal 12a which is the other of the pair of DC input terminals, and the source of the _first switch element Q ₁ is the first It is connected to the negative terminal 12b of the pair of DC input terminals via the first inductor L _1, a second source of the switching element Q ₂ is the negative terminal of the pair of DC input terminals through a second inductor L ₂ 12b. Further, the gate of the first switch element Q ₁ is connected to the minus terminal 12 b via the first impedance element Z ₁ and the second inductor L _2, and the gate of the second switch element Q ₂ is the second switch element Q 2. The impedance element Z ₂ and the first inductor L ₂ are connected to the minus terminal 12b.

The wireless power transmission system 2 having the above configuration can achieve the same operational effects as the first embodiment. That is, the self-excited oscillation circuit 15 according to the present embodiment has a simple circuit configuration in which the power transmission coil L _TX is configured by a single coil and does not have a feedback winding, so that high-quality and high-efficiency wireless communication is achieved. The power transmission device 10 and the wireless power transmission system 2 can be realized at a low cost.

  7 and 8 are circuit diagrams illustrating modifications of the wireless power transmitting apparatus 10. 7 and 8 show a modification of the wireless power transmission device 10 in the wireless power transmission system 1 according to the first embodiment, the wireless power transmission in the wireless power transmission system 2 according to the second embodiment. The present invention can also be applied to the device 10.

A feature of the wireless power transmission apparatus 10 shown in FIG. 7A is that a resonance capacitor C _p1 that forms a resonance circuit together with the power transmission coil L _TX and the first and second inductors L ₁ and L ₂ is connected in series with the power transmission coil L _TX. It is in the point. Further, the wireless power transmission device 10 shown in FIG. 7B includes two resonance capacitors C _p1 and C _p2 that form a resonance circuit together with the power transmission coil L _TX and the first and second inductors L ₁ and L _2. The first resonance capacitor C _p1 is connected in series to the one end 11a side of the power transmission coil L _TX , and the second resonance capacitor C _p2 is connected in series to the other end 11b side of the power transmission coil L _TX. .

A feature of the wireless power transmission device 10 shown in FIGS. 8A and 8B is that three resonance capacitors C _p1 and C that constitute a resonance circuit together with the power transmission coil L _TX and the first and second inductors L ₁ and L _2. comprising a _p2, C _p3, first resonant capacitor C _p1 is connected in parallel to the power transmission coil L _TX, and a second resonance capacitor C _p2 is serially connected to one end 11a of the power transmission coil L _TX, a 3 of the resonant capacitor C _p3 is in that it is connected in series to the other end 11b of the power transmission coil L _TX.

Among these, the second and third resonance capacitors C _p2 and C _p3 in the wireless power transmission device 10 shown in FIG. 8A transmit power more than the connection points of the first and second switch elements Q ₁ and Q _2. It is provided near the coil _LTX . Therefore, the drain of the first switching element Q ₁ is are connected via the second resonant capacitor C _p2 to one end 11a of the power transmission coil L _TX, a second drain of the switching element Q ₂ is, third through the resonant capacitor C _p3 it is connected to the other end 11b of the power transmission coil L _TX. As described above, the first and second switch elements Q ₁ and Q ₂ may be indirectly connected to the one end 11 a and the other end 11 b of the power transmission coil L _TX via the constituent elements of the resonance circuit.

In addition, the second and third resonance capacitors C _p2 and C _p3 in the wireless power transmitting apparatus 10 shown in FIG. 8B are input from the DC of the connection points of the first and second switch elements Q ₁ and Q _2. It is provided near the terminal (close to the first and second inductors L ₁ and L ₂ ). Therefore, the drain of the first switching element Q ₁ is, power transmission is connected coil L _TX directly to one end 11a of the second drain of the switching element Q ₂ are directly connected to the other end 11b of the power transmission coil L _TX ing. In this way, the first and second switch elements Q ₁ and Q ₂ may be directly connected to the one end 11a and the other end 11b of the power transmission coil _LTX . Further, the first and second switch elements Q ₁ and Q ₂ may be indirectly connected to the first and second inductors L ₁ and L ₂ via components of the resonance circuit.

  FIG. 9 is a circuit diagram showing a modification of the wireless power receiving apparatus 20.

Features of the wireless power receiving apparatus 20 shown in FIG. 9 (a) is that the resonant capacitor C _s1 constituting the resonant circuit together with the power receiving coil L _RX is connected in parallel to the power receiving coil L _RX. Further, the wireless power receiving device 20 shown in FIG. 9B is characterized in that it includes two resonant capacitors C _s1 and C _s2 that form a resonant circuit together with the power receiving coil L _RX , and the first resonant capacitor C _s1 is the power receiving coil L _RX. The second resonance capacitor C _s2 is connected in parallel to the power receiving coil L _RX . Furthermore, the wireless power receiving device 20 shown in FIG. 9C is characterized in that the resonance capacitor is omitted. As described above, the wireless power receiving apparatus 20 can employ various configurations of resonance circuits.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in the above embodiment, the DC voltage between the pair of DC input terminals 12 a and 12 b is directly supplied to the self-excited oscillation circuit 15. A circuit may be provided.

1, 2 Wireless power transmission system 10 Wireless power transmission device 11 Spiral conductive wire 11a One end of power transmission coil L _TX (one end of conductive wire)
11b The other end of the power transmission coil L _TX (the other end of the conducting wire)
12a DC input plus terminal 12b DC input minus terminal 13 Magnetic body 15 Self-excited oscillation circuit 20 Wireless power receiving device 21 Rectifier circuit 22 Load C _in Input capacitor C _out Smoothing capacitor C _p1 , C _p2 , C _p3 Resonance capacitor C _s1 , C _s2 resonant capacitor I ₁ first current I ₂ second current L ₁ first inductor L ₂ second inductor L _RX power receiving coil L _TX power transmitting coil Q ₁ first switch element (transistor)
Q ₂ Second switch element (transistor)
V _ds1 first switching element to Q ₁ drain voltage V _ds2 second switching element Q ₂ of the drain voltage V _gs1 first gate voltage V of the switching element Q _{1 gs2} second gate voltage V _out of _the switching element Q ₂ Voltage Z ₁ first impedance element Z ₂ second impedance element across power transmission coil L _TX

Claims (8)

A self-excited oscillation circuit that includes a power transmission coil that performs power transmission, converts a DC voltage applied between a pair of DC input terminals into an AC voltage, and supplies the AC voltage to the power transmission coil;
The wireless power transmission apparatus, wherein the power transmission coil is formed of a single coil. The self-excited oscillation circuit is
A resonance capacitor that constitutes a resonance circuit together with the power transmission coil;
A first switch element connected to one end of the power transmission coil;
A second switch element connected to the other end of the power transmission coil;
A first inductor connected between one end of the power transmission coil and one of the pair of DC input terminals;
The wireless power transmission apparatus according to claim 1, further comprising a second inductor connected between the other end of the power transmission coil and one of the pair of DC input terminals. The self-excited oscillation circuit is
A first impedance element connected between a control electrode of the first switch element and the other end of the power transmission coil;
The wireless power transmission apparatus according to claim 2, further comprising a second impedance element connected between a control electrode of the second switch element and one end of the power transmission coil. The first impedance element has at least one of a first resistor and a first capacitor;
The wireless power transmission apparatus according to claim 3, wherein the second impedance element has at least one of a second resistor and a second capacitor. The first impedance element further includes a first diode having a cathode connected to the other end of the power transmission coil,
The wireless power transmission apparatus according to claim 4, wherein the second impedance element further includes a second diode having a cathode connected to one end of the power transmission coil.   The wireless power transmission device according to any one of claims 1 to 5, wherein the number of turns of the power transmission coil is one turn.   The wireless power transmission device according to any one of claims 1 to 6, wherein the power transmission coil includes a magnetic body and a conductive wire wound in a spiral shape on a main surface of the magnetic body. A wireless power transmission device according to any one of claims 1 to 7,
A wireless power receiving device that wirelessly receives power transmitted from the wireless power transmitting device, and
The wireless power receiving device is:
A power receiving coil magnetically coupled to the power transmitting coil;
A wireless power transmission system comprising: a rectifier circuit that converts an alternating voltage generated in the power receiving coil into a direct voltage.

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