JP5862844B2 - Wireless power transmission system - Google Patents

Description

  The present invention relates to a wireless power transmission system that transmits power from a power transmission device to a power reception device by an electric field coupling method.

  In an electric field coupling type wireless power transmission system, electrodes of a power transmission device and a power reception device are opposed to each other to cause electric field coupling between the electrodes, and electric power is transmitted from the power transmission device to the power reception device by the electric field coupling. In general, in a technique for increasing the transmission efficiency of a power transmission system, it is effective to incorporate a low-loss resonance circuit. This resonance circuit is composed of an electrostatic capacity and an inductor of a coupling portion between the power transmission device and the power reception device. When such resonance circuits are combined, the Q value of the resonance circuit is almost determined by the DCR of the inductor. Therefore, realization of a small and low-loss inductor becomes a problem.

  Therefore, it is conceivable to use a piezoelectric device (piezoelectric resonator, piezoelectric transformer) for the inductor. However, although the piezoelectric device is small and low loss, there is a problem that the frequency characteristic is steep and the transformation ratio (ratio between the power receiving device side voltage and the power transmitting device side voltage) varies greatly when the load fluctuates.

  Patent Document 1 discloses a wireless power transmission system that uses a piezoelectric transformer for voltage reduction in a power receiving apparatus. In the power transmission system according to Patent Document 1, the first resonance circuit and the second resonance circuit are configured in the power receiving device, and a high frequency high voltage frequency generated by the power transmission device is combined with the two resonance circuits. It is set between two resonance frequencies due to resonance. Thus, the ratio between the power receiving device side voltage and the power transmitting device side voltage when load variation or drive frequency variation of the power receiving device occurs can be stabilized.

International Publication 2012/172929 Pamphlet

  The power transmission device side voltage varies depending on the load variation of the power receiving device. For this reason, in Patent Document 1, the power transmission device side voltage is detected so that the power transmission device side voltage is constant, and the generated voltage of the high-frequency high voltage generated by the power transmission device is feedback-controlled. Therefore, in patent document 1, the voltage detection circuit which detects the power transmission apparatus side voltage, the controller for feedback control, etc. are needed. Moreover, when the fluctuation | variation of the power transmission apparatus side voltage is large, if feedback control is not operated normally, there exists a possibility that transmission efficiency may fall or the problem that a stable output voltage cannot be obtained will arise. Therefore, the present inventor has found a circuit configuration capable of suppressing the fluctuation of the power transmission device side voltage accompanying the load fluctuation.

  An object of the present invention is to provide a wireless power transmission system capable of suppressing fluctuations in the power transmission apparatus side voltage accompanying load fluctuations of a power receiving apparatus.

  The present invention includes an AC voltage generation circuit, a primary coil, and a secondary coil, and a first transformer that transmits a voltage from the AC voltage generation circuit, and a voltage induced by the first transformer is applied. A power transmission device including a power transmission side active electrode and a power transmission side passive electrode, a power reception side active electrode, a power reception side passive electrode, a power transmission side active electrode, and a voltage induced in the power reception side passive electrode. A power receiving device including two transformers and a load circuit for supplying a voltage induced by the second transformer, wherein the power transmission side active electrode and the power reception side active electrode are electrically coupled, and the power transmission side Power is transmitted from the power transmission device to the power reception device by electric field coupling or direct conduction between the passive electrode and the power reception side passive electrode. In the Yaless power transmission system, the power transmission device includes a first parallel resonance configured by the secondary coil and a power transmission side capacitance component generated or connected between the power transmission side active electrode and the power transmission side passive electrode. And the power receiving device includes a first series resonant circuit and a second parallel resonant circuit, and the first series resonant circuit includes a power receiving side active electrode and a power receiving side passive electrode. Including a configuration in which a first inductance component and a first capacitance component generated or connected in series are connected in series, and the second parallel resonant circuit includes a configuration in which a second capacitance component and a second inductance component are connected in parallel The first parallel resonance circuit, the first series resonance circuit, and the second parallel resonance circuit have the same resonance frequency, and Frequency of high frequency high voltage generated by the voltage generating circuit is characterized in that it is set to the resonant frequency.

  In this configuration, the first parallel resonance circuit, the first series resonance circuit, and the second parallel resonance circuit having the same resonance frequency are provided between the AC voltage generation circuit of the power transmission device and the load circuit of the power reception device. Are connected, and by setting the frequency of the high frequency high voltage to the resonance frequency of each resonance circuit, voltage fluctuation between the AC voltage generation circuit and the load circuit of the power receiving device can be suppressed. Thereby, the fluctuation | variation of the power transmission apparatus side voltage accompanying the load fluctuation | variation of a power receiving apparatus can be suppressed.

  The power transmission device includes a power transmission side capacitor connected in series to a primary coil of the first transformer, and a second series resonance circuit including the power transmission side capacitor and the primary coil, The resonance frequency of the second series resonance circuit is preferably the same as the resonance frequency of each of the first parallel resonance circuit, the first series resonance circuit, and the second parallel resonance circuit.

  In this configuration, a second series resonance circuit, a first parallel resonance circuit, a first series resonance circuit, having the same resonance frequency between the AC voltage generation circuit of the power transmission device and the load circuit of the power reception device, And the second parallel resonant circuit are connected, and the frequency fluctuation between the AC voltage generating circuit and the load circuit of the power receiving device is set by setting the frequency of the high frequency high voltage to the resonant frequency of each resonant circuit. Can be suppressed. Thereby, the fluctuation | variation of the power transmission apparatus side voltage accompanying the load fluctuation | variation of a power receiving apparatus can be suppressed.

  The second transformer includes a first input unit connected to the power receiving side active electrode, a second input unit connected to the power receiving side passive electrode, a first output unit, and a second output unit. The voltage applied between the first input unit and the second input unit is transmitted and output between the first output unit and the second output unit, and the first inductance component, A piezoelectric transformer including a first capacitance component and the second capacitance component, wherein the power receiving device includes a parallel inductor connected in parallel to the second capacitance component, and the second inductance component is a voltage of the parallel inductor. An inductance component is preferable.

  In this configuration, since the fluctuation of the output voltage of the piezoelectric transformer due to the load fluctuation can be suppressed, the input voltage range of the load connected to the subsequent stage can be narrowed.

  Further, in order to operate the piezoelectric transformer with high efficiency, it is necessary to remove harmonic components contained in the input voltage to the piezoelectric transformer. When a spurious frequency is applied to the piezoelectric transformer, there is a possibility that the efficiency is reduced (heat generation is generated) due to coupling with unnecessary resonance of the piezoelectric transformer. For this reason, it is possible to prevent the spurious frequency component from being applied to the piezoelectric transformer by setting the resonance frequency of each resonance circuit in the vicinity of the drive frequency.

  The power receiving device includes a current detection circuit that detects a current supplied to the load circuit, and a control circuit that cuts off the supply of current to the load circuit when the current detected by the current detection circuit exceeds a threshold value. Are preferably provided.

  With this configuration, overcurrent protection of the load circuit can be performed. Moreover, when a piezoelectric transformer is used, thermal runaway of the piezoelectric transformer can be prevented.

  ADVANTAGE OF THE INVENTION According to this invention, the fluctuation | variation of the power transmission apparatus side voltage accompanying the load fluctuation | variation of a power receiving apparatus can be suppressed, and the fluctuation | variation of the output voltage by the side of a power receiving apparatus can be suppressed.

1 is a circuit diagram of a wireless power transmission system according to a first embodiment. 1 is an equivalent circuit diagram of the wireless power transmission system shown in FIG. Diagram showing the characteristics of transmission voltage when the load is changed The figure which shows the characteristic of the output voltage when changing the load Circuit diagram of wireless power transmission system according to Embodiment 2 Diagram showing the characteristics of transmission voltage when the load is changed The figure which shows the characteristic of the output voltage when changing the load Circuit diagram of wireless power transmission system according to Embodiment 3 Circuit diagram of wireless power transmission system according to Embodiment 4 The figure which shows the characteristic of the power transmission voltage at the time of carrying out load fluctuation in the wireless power transmission system of FIG. The figure which shows the characteristic of the power transmission voltage when carrying out load change when the parallel resonance circuit is not constituted in the power transmission device Circuit diagram of wireless power transmission system according to Embodiment 5 Diagram showing the characteristics of transmission voltage when the load is changed

(Embodiment 1)
FIG. 1 is a circuit diagram of a wireless power transmission system 1 according to the first embodiment.

  The wireless power transmission system 1 includes a power transmission device 101 and a power reception device 201. A power receiving apparatus 201 is placed on the power transmitting apparatus 101. The power transmission device 101 and the power reception device 201 include the active electrodes 13 and 23 and the passive electrodes 14 and 24, respectively. When the power reception device 201 is placed on the power transmission device 101, the active electrodes 13 and 23, the passive electrode 14 and the like. , 24 face each other. In that state, the power transmission apparatus 101 transmits electric power to the power reception apparatus 201 using electric field coupling.

  The power transmission apparatus 101 includes a voltage generation circuit 11 and a step-up transformer T1. The voltage generation circuit 11 converts a DC voltage (for example, DC 19 V) converted from an AC voltage (AC 100 V to 230 V) by an AC adapter connected to a commercial power source into an AC voltage by a DC-AC inverter circuit, and outputs the AC voltage.

  The step-up transformer T1 includes a primary coil n11 and a secondary coil n12. The step-up transformer T1 corresponds to the first transformer of the present invention. The primary coil n11 is connected to the voltage generation circuit 11. The secondary coil n12 is connected to the active electrode 13 and the passive electrode 14. The step-up transformer T1 boosts the high-frequency voltage output from the voltage generation circuit 11 and applies it to the active electrode 13 and the passive electrode 14.

  A capacitor C1 is connected between the active electrode 13 and the passive electrode 14. The capacitor C1 includes a capacitance generated between the active electrode 13 and the passive electrode 14, a stray capacitance between windings of the step-up transformer T1, and the like. The capacitor C1 forms a parallel resonance circuit with the secondary coil n12 of the step-up transformer T1.

  The power receiving apparatus 201 includes a capacitor C2, a piezoelectric transformer 22, an inductor L1, and a load circuit RL1. The capacitor C <b> 2 is connected between the active electrode 23 and the passive electrode 24. The capacitor C2 includes a capacitance generated between the active electrode 23 and the passive electrode 24.

  The piezoelectric transformer 22 includes a first input unit E21 connected to the active electrode 23, a second input unit E22 connected to the passive electrode 24, a first output unit E23 connected to the load circuit RL1, and a second output unit. E24. The first input unit E21 is connected to the active electrode 23, the second input unit E22 is connected to the passive electrode 24, the first output unit E23 is connected to one end of the load RL1, and the second output unit E24 is connected to the other end of the load RL1. ing. When a voltage induced in the active electrode 23 and the passive electrode 24 is applied between the first input unit E21 and the second input unit E22, the piezoelectric transformer 22 steps down the voltage to generate a third output unit. Output from between E23 and the fourth output unit E24. Here, although the piezoelectric transformer has four electrodes E21, E22, E23, E24, the second input portion E22 and the second output portion E24 are connected (as a common electrode) to form a three-terminal structure. Also good.

  As will be described later, the piezoelectric transformer 22 has a capacitance component and an inductance component. The inductance component forms a series resonance circuit with the capacitor C2. The inductor L1 is connected to the third electrode E23 and the fourth electrode E24 of the piezoelectric transformer 22. The capacitance component of the piezoelectric transformer 22 forms a parallel resonant circuit with the inductor L1.

  The load circuit RL1 includes a rectifying / smoothing circuit, a charging circuit, a secondary battery, and the like. The load circuit RL1 is supplied with the voltage stepped down by the piezoelectric transformer 22, rectifies and smoothes the voltage, and charges the secondary battery.

  FIG. 2 is an equivalent circuit diagram of the wireless power transmission system 1 shown in FIG. In FIG. 2, illustration of a part of the voltage generation circuit 11 and the like of the power transmission apparatus 101 is omitted.

  The secondary coil n12 of the step-up transformer T1 forms a parallel resonance circuit RC1 with the capacitor C1. The capacitor C1 corresponds to a power transmission side capacitance component according to the present invention. The parallel resonant circuit RC1 corresponds to the first parallel resonant circuit according to the present invention.

  The piezoelectric transformer 22 is represented by an inductance component Lp, capacitance components Ci, Cp, C3, a resistor Rp, and an ideal transformer Tp. The capacitance component Ci is an equivalent input capacitance of the piezoelectric transformer 22. The capacitance component C3 is an equivalent output capacity of the piezoelectric transformer 22. The capacitance component Cp and the inductance component Lp are electromechanical parameters. The resonance frequency of the piezoelectric transformer 22 is determined mainly by the resonance of the resonance circuit due to the capacitance component Cp and the inductance component Lp. Since electrical energy conversion is via elastic vibration, the piezoelectric transformer 22 has a natural resonance frequency determined by the elastic wave propagation speed and dimensions of the piezoelectric ceramic.

  The inductance component Lp and the capacitance components Ci and Cp of the piezoelectric transformer 22 form a series resonance circuit RC2 with the capacitor C2. The resonance frequency of the series resonance circuit RC2 is determined by the circuit constant of the series resonance circuit RC2. The series resonance circuit RC2 corresponds to the first series resonance circuit according to the present invention. The capacitances of the capacitance components Ci and Cp and the capacitor C2 correspond to the first capacitance component according to the present invention. Further, the inductance component Lp corresponds to the first inductance component according to the present invention.

  The capacitance components constituting the parallel resonance circuit RC1 and the series resonance circuit RC2 include a parasitic capacitance generated between the electrodes (13, 23, 14, 24) contributing to the coupling (four electrodes 13, 23, 14,. Including all capacitor combinations between two of the 24 electrodes).

  The capacitance component C3 of the piezoelectric transformer 22 forms a parallel resonant circuit RC3 with the inductor L1. The resonance frequency of the parallel resonance circuit RC3 is determined by the capacitance of the capacitance component C3 and the inductance of the inductor L1. The parallel resonant circuit RC3 corresponds to the second parallel resonant circuit according to the present invention. The capacitance component C3 corresponds to the second capacitance component according to the present invention. The inductor L1 corresponds to a parallel inductor according to the present invention and a second inductance component.

  Each of the parallel resonance circuit RC1, the series resonance circuit RC2, and the parallel resonance circuit RC3 is set to have a constant resonance frequency. In the present embodiment, the resonance frequency is 550 kHz, and the frequency of the high frequency high voltage generated by the voltage generation circuit 11 is determined as the resonance frequency. It should be noted that the resonance frequencies of the parallel resonance circuit RC1, the series resonance circuit RC2, and the parallel resonance circuit RC3 can be regarded as the same as long as the numerical values are within a range of ± 10%. At the resonance frequency, the parallel resonance circuit RC1 and the parallel resonance circuit RC3 are high impedance (maximum), and the series resonance circuit RC2 is low impedance (minimum). For this reason, voltage fluctuations between the voltage generation circuit 11 and the load circuit RL1 to which the parallel resonance circuit RC1, the series resonance circuit RC2, and the parallel resonance circuit RC3 are connected are small. Therefore, the power transmission voltage ACV in the power transmission apparatus 101 can be made constant even when a load fluctuation occurs on the power reception apparatus 201 side. The transmission voltage ACV is a voltage between the active electrode 13 and the passive electrode 14.

  Since the resonance frequency is close to the drive frequency, the voltage waveform input to the piezoelectric transformer 22 approaches a sine wave shape. The parallel resonant circuit RC1, the active electrodes 13 and 23, and the passive electrodes 14 and 24 can suppress the voltage component voltage other than the driving frequency from being input to the piezoelectric transformer 22. Thereby, the loss by the distortion of the voltage waveform in the piezoelectric transformer 22 can be reduced, and voltage conversion (step-down) can be performed efficiently. Since the voltage conversion fluctuation between the transmission voltage ACV and the output voltage Vout is small, the output voltage Vout to the load circuit RL1 can be made constant by making the transmission voltage ACV constant. Further, since the parallel resonant circuit RC1 is a parallel resonant circuit, unlike the series resonant circuit RC2, an excessive voltage generated due to load fluctuation on the power receiving device 201 side is not applied to the piezoelectric transformer 22. Thereby, an excessive increase in the vibration speed of the piezoelectric transformer 22 can be suppressed.

  FIG. 3 is a diagram showing the characteristics of the transmission voltage ACV when the load is varied. FIG. 3 shows characteristics when the load is changed to 10, 21.5, 46, 100, 200, 215, 464, and 1000Ω with the driving frequency [kHz] on the horizontal axis and the transmission voltage ACV [V] on the vertical axis. Indicates. Since each characteristic is substantially the same, they are displayed overlapping in the figure. As shown in the figure, the fluctuation in the transmission voltage ACV is small even if there is a load fluctuation in the vicinity of a frequency of 550 kHz (dotted circle in the figure).

  FIG. 4 is a diagram showing the characteristics of the output voltage Vout when the load is varied. The output voltage Vout is a voltage supplied to the load circuit RL1. FIG. 4 shows characteristics when the load is changed to 10, 21.5, 46, 100, 200, 215, 464, and 1000Ω with the driving frequency [kHz] on the horizontal axis and the output voltage Vout [V] on the vertical axis. Indicates. As shown in the figure, the output voltage Vout is substantially constant even when there is a load fluctuation in the vicinity of a frequency of 550 kHz (dotted circle in the figure).

  Thus, the resonance frequency of each of the parallel resonance circuit RC1 of the power receiving device 201, the series resonance circuit RC2 and the parallel resonance circuit RC3 of the power transmission device 101 is made the same, and the frequency of the high frequency high voltage generated by the voltage generation circuit 11 is By setting the resonance frequency, fluctuations in the transmission voltage ACV can be reduced regardless of load fluctuations. Thereby, the output voltage Vout can be made substantially constant. In addition, the vibration waveform of the piezoelectric transformer 22 can be made substantially sinusoidal, and voltage conversion in the piezoelectric transformer 22 can be performed efficiently.

  When the input voltage to the piezoelectric transformer 22 includes a harmonic component (such as a square wave (pulse) waveform), a low-pass filter is further provided on the input side of the piezoelectric transformer 22 to remove the harmonic component of the input voltage. However, the spurious frequency may be applied to the piezoelectric transformer 22 due to the frequency characteristics of the low-pass filter. In this case, heat may be generated in the piezoelectric transformer 22. For this reason, it is possible to prevent the spurious frequency from being applied to the piezoelectric transformer 22 by setting the frequency of the high frequency high voltage generated by the voltage generation circuit 11 to the resonance frequency of each of the resonance circuits RC1, RC2, and RC3.

(Embodiment 2)
FIG. 5 is a circuit diagram of the wireless power transmission system 2 according to the second embodiment. The present embodiment is different from the first embodiment in that a series resonance circuit RC4 is further configured in the power transmission device 102. The power receiving apparatus 201 is the same as that in the first embodiment.

  A capacitor C4 is provided between the voltage generation circuit 11 of the power transmission device 102 and the primary coil n11 of the step-up transformer T1. The capacitor C4 corresponds to the power transmission side capacitor according to the present invention. The capacitor C4 forms a series resonance circuit RC4 by the primary coil n11 of the step-up transformer T1 (resonates with the inductance when the secondary coil n12 is short-circuited). The series resonance circuit RC4 is set to the same resonance frequency (550 kHz) as the parallel resonance circuit RC1, the series resonance circuit RC2, and the parallel resonance circuit RC3 described in the first embodiment.

  The frequency of the high frequency high voltage generated by the voltage generation circuit 11 is set to be the same as the resonance frequency of the parallel resonance circuit RC1, the series resonance circuit RC2, the parallel resonance circuit RC3, and the series resonance circuit RC4. In this case, at the resonance frequency, the parallel resonance circuit RC1 and the parallel resonance circuit RC3 have high impedance (approximately ∞), and the series resonance circuit RC2 and series resonance circuit RC4 have low impedance (approximately 0). For this reason, voltage fluctuations between the voltage generation circuit 11 and the load circuit RL1 to which the series resonance circuit RC4, the parallel resonance circuit RC1, the series resonance circuit RC2, and the parallel resonance circuit RC3 are connected are small. Therefore, even if a load fluctuation occurs on the power receiving apparatus 201 side, the fluctuation of the transmission voltage ACV in the power transmission apparatus 102 is small.

  FIG. 6 is a diagram showing the characteristics of the transmission voltage ACV when the load is varied. FIG. 7 is a graph showing the characteristics of the output voltage Vout when the load is varied. 6 is a diagram corresponding to FIG. 3, and FIG. 7 is a diagram corresponding to FIG. As shown in FIG. 6, the transmission voltage ACV is substantially constant even when there is a load fluctuation in the vicinity of a frequency of 550 kHz (dotted circle in the figure). Further, as shown in FIG. 7, the output voltage Vout is substantially constant even when there is a load fluctuation in the vicinity of the frequency of 550 kHz (dotted circle in the figure).

  As described above, in the present embodiment, the power transmission device 102 includes the series resonance circuit RC4 and the parallel resonance circuit RC1, and the power reception device 201 includes the series resonance circuit RC2 and the parallel resonance circuit RC3. The resonance frequencies of the parallel resonance circuit RC1, the series resonance circuit RC2, the parallel resonance circuit RC3, and the series resonance circuit RC4 are made the same, and the frequency of the high frequency high voltage generated by the voltage generation circuit 11 is set to the resonance frequency. ing. Thereby, the fluctuation | variation of the transmission voltage ACV can be made small irrespective of a load fluctuation | variation. Thereby, the output voltage Vout can be made constant. The voltage waveform input to the piezoelectric transformer 22 can be brought close to a sine wave shape, and voltage conversion in the piezoelectric transformer 22 can be performed efficiently.

(Embodiment 3)
FIG. 8 is a circuit diagram of the wireless power transmission system 3 according to the third embodiment. In the present embodiment, the power transmission apparatus 102 is the same as that in the second embodiment.

  The power receiving device 202 includes a piezoelectric transformer 22, an active electrode 23, and a passive electrode 24. The piezoelectric transformer 22 steps down the voltage induced in the active electrode 23 and the passive electrode 24. A resonance inductor L1 is connected to the piezoelectric transformer 22, and a rectification diode bridge DB, a smoothing inductor L2, and a capacitor C5 are further connected. The voltage rectified and smoothed by the diode bridge DB, the inductor L2, and the capacitor C5 is supplied to the load circuit RL2. The load circuit RL2 includes a charging circuit and a secondary battery.

  A switch element SW is provided between the output of the power receiving apparatus 202 and the load. The switch element SW is opened and closed by the control unit 25. The switch element SW and the control unit 25 correspond to a control circuit according to the present invention.

  A resistor R1 for current detection is provided on the reference potential side of the load circuit RL2. The control unit 25 detects the current flowing through the load circuit RL2 by the resistor R1. When the detected current exceeds the threshold value, the control unit 25 turns off the switch element SW. Thereby, the current flowing to the load circuit RL2 is interrupted, and an overcurrent in the power receiving device 202 can be prevented. Since the piezoelectric transformer 22 has a correlation between the vibration speed and the output current, the piezoelectric transformer 22 can be protected by preventing thermal overrun of the piezoelectric transformer 22 by preventing overcurrent. Note that the switch element SW may be arranged upstream of the rectifying diode bridge DB of the power receiving apparatus 202. In this case, an AC compatible switch element SW is provided.

(Embodiment 4)
FIG. 9 is a circuit diagram of the wireless power transmission system 4 according to the fourth embodiment. In the first embodiment, a piezoelectric transformer is used for the step-down unit of the power receiving device. However, in this embodiment, a winding transformer is used for the step-down unit of the power receiving device 203. The power transmission apparatus 101 is the same as that in the first embodiment.

The power receiving device 203 includes a step-down transformer T2 having a primary coil n21 and a secondary coil n22. The step-down transformer T2 corresponds to a second transformer according to the present invention. The primary coil n <b> 21 has one end connected to the active electrode 23 and the other end connected to the passive electrode 24. The leakage inductance L _leak of the primary coil n21 forms a series resonance circuit RC5 with the capacitor C2. The secondary coil n22 of the step-down transformer T2 is connected to the load circuit RL1. A capacitor C6 is connected in parallel to the secondary coil n22, and the secondary coil n22 and the capacitor C6 constitute a parallel resonance circuit RC6. In addition to leakage inductance, a series resonance coil may be inserted separately.

The capacitor C2 corresponds to the power receiving side first capacitor and the first capacitance component according to the present invention, and the capacitor C6 corresponds to the power receiving side second capacitor and the second capacitance component according to the present invention. The leakage inductance L _leak corresponds to the first inductance component according to the present invention. The secondary coil n22 corresponds to the second inductance component according to the present invention. The series resonance circuit RC5 corresponds to the first series resonance circuit according to the present invention. The parallel resonant circuit RC6 corresponds to the second parallel resonant circuit according to the present invention.

  Further, as described in the first embodiment, in the power transmission apparatus 101, the parallel resonance circuit RC1 is configured by the secondary coil n12 of the step-up transformer T1 and the capacitor C1.

  The parallel resonance circuit RC1, the series resonance circuit RC5, and the parallel resonance circuit RC6 of the power transmission apparatus 101 have the same resonance frequency. The frequency of the high frequency high voltage generated by the voltage generation circuit 11 is set to the resonance frequency (300 kHz). As a result, similarly to the first embodiment, the power transmission voltage ACV in the power transmission apparatus 101 can be made constant even when a load fluctuation occurs on the power reception apparatus 203 side.

  FIG. 10 is a diagram showing the characteristics of the transmission voltage ACV when the load is varied in the wireless power transmission system 4 of FIG. FIG. 11 is a diagram illustrating the characteristics of the transmission voltage ACV when the load is changed when the parallel transmission circuit is not configured in the power transmission apparatus 101. 10 and 11 show characteristics when the load is changed to 1, 2.15, 4.6, 10, 21.5, 46.4, and 100Ω.

  Comparing FIG. 10 and FIG. 11, when there is a load fluctuation, the fluctuation X1 of the transmission voltage ACV in the vicinity of the frequency of 300 kHz shown in FIG. 10 is smaller than the fluctuation X2 shown in FIG. That is, in the present embodiment, similarly to the first embodiment, even if a winding transformer is used for the step-down unit of the power receiving device 203, fluctuations in the transmission voltage ACV accompanying load fluctuations can be suppressed.

(Embodiment 5)
FIG. 12 is a circuit diagram of the wireless power transmission system 5 according to the fifth embodiment. As in the second embodiment, the power transmission apparatus 102 according to the present embodiment includes a parallel resonant circuit RC1 and a series resonant circuit RC4. Specifically, a capacitor C4 is provided between the voltage generation circuit 11 and the primary coil n11 of the step-up transformer T1. This capacitor C4 and the primary coil n11 of the step-up transformer T1 constitute a series resonance circuit RC4. Since the power receiving apparatus 203 is the same as that of Embodiment 4, description is abbreviate | omitted.

  The series resonance circuit RC4 and the parallel resonance circuit RC1 configured in the power transmission apparatus 102, and the series resonance circuit RC5 and the parallel resonance circuit RC6 configured in the power reception apparatus 203 are set to the same resonance frequency (300 kHz). The frequency of the high frequency high voltage generated by the voltage generation circuit 11 is set to be the same as this resonance frequency (300 kHz). As a result, similarly to the second embodiment, the power transmission voltage ACV in the power transmission apparatus 102 can be made constant even when a load fluctuation occurs on the power reception apparatus 203 side.

  FIG. 13 is a diagram illustrating the characteristics of the transmission voltage ACV when the load is changed. As shown in FIG. 13, even if there is a load fluctuation in the vicinity of a frequency of 300 kHz (dotted circle in the figure), the fluctuation of the transmission voltage ACV is small. Thus, in the present embodiment, the transmission voltage ACV can be made constant regardless of load fluctuations.

  In the above-described embodiment, the wireless power transmission system has a configuration in which the passive electrodes 14 and 24 are opposed to each other and are electrically coupled. Further, although the power transmission device includes a step-up transformer and the power reception device includes a step-down transformer, the present invention is not limited thereto. The power transmission device and the power reception device may include an insulating transformer that does not step up or down.

1, 2, 3, 4, 5 ... Wireless power transmission system 11 ... Voltage generation circuit (AC voltage generation circuit)
DESCRIPTION OF SYMBOLS 13, 23 ... Active electrode 14, 24 ... Passive electrode 22 ... Piezoelectric transformer 25 ... Control part 101, 102 ... Power transmission apparatus 201, 202, 203 ... Power receiving apparatus C1 ... Capacitor (power transmission side capacitance component)
C2 ... Capacitor (power-receiving-side first capacitor, first capacitance component)
C3: Capacitance component (second capacitance component)
C4 ... Capacitor (transmission side capacitor)
Ci: Capacitance component (first capacitance component)
Cp: Capacitance component (first capacitance component)
C5: Capacitor C6: Capacitor (power-receiving-side second capacitor, second capacitance component)
DB ... diode bridge E21 ... first input unit E22 ... second input unit E23 ... first output unit E24 ... second output units L1, L2 ... inductor L _leak ... leakage inductance (first inductance component)
Lp: Inductance component (first inductance component)
n11 ... primary coil n12 ... secondary coil n21 ... primary coil n22 ... secondary coil (second inductance component)
R1 ... resistance (current detection circuit)
RC1: parallel resonance circuit (first parallel resonance circuit)
RC2: Series resonance circuit (first series resonance circuit)
RC3: parallel resonance circuit (second parallel resonance circuit)
RC4: Series resonance circuit (second series resonance circuit)
RC5: Series resonance circuit (first series resonance circuit)
RC6: parallel resonance circuit (second parallel resonance circuit)
RL1, RL2 ... load circuit Rp ... resistor SW ... switch element T1 ... step-up transformer (first transformer)
T2: Step-down transformer (second transformer)
Tp ... Ideal transformer

Claims (4)

A first transformer having an AC voltage generation circuit, a primary coil and a secondary coil, for transmitting a voltage from the AC voltage generation circuit, and a power transmission side active electrode to which a voltage induced by the first transformer is applied , And a power transmission device comprising a power transmission side passive electrode,
A power receiving side active electrode, a power receiving side passive electrode, a power receiving side active electrode, a second transformer for transmitting a voltage induced in the power receiving side passive electrode, and a load for supplying a voltage induced by the second transformer A power receiving device comprising a circuit;
The power transmitting side active electrode and the power receiving side active electrode are electrically coupled, and the power transmitting side passive electrode and the power receiving side passive electrode are electrically coupled or directly connected to each other to receive the power from the power transmitting device. In a wireless power transmission system in which power is transmitted to a device,
The power transmission device is:
A first parallel resonance circuit configured by the secondary coil and a power transmission side capacitance component generated or connected between the power transmission side active electrode and the power transmission side passive electrode;
The power receiving device is:
A first series resonant circuit and a second parallel resonant circuit;
The first series resonant circuit includes:
A configuration in which a first inductance component and a first capacitance component generated or connected between the power receiving side active electrode and the power receiving side passive electrode are connected in series;
The second parallel resonant circuit is:
Including a configuration in which a second capacitance component and a second inductance component are connected in parallel;
The resonance frequency of each of the first parallel resonance circuit, the first series resonance circuit, and the second parallel resonance circuit is the same,
The frequency of the high frequency high voltage generated by the AC voltage generation circuit is set to the resonance frequency,
Wireless power transmission system. The power transmission device is:
A power transmission side capacitor connected in series to the primary coil of the first transformer;
A second series resonant circuit composed of the power transmission side capacitor and the primary coil;
With
The resonance frequency of the second series resonance circuit is the same as the resonance frequency of each of the first parallel resonance circuit, the first series resonance circuit, and the second parallel resonance circuit.
The wireless power transmission system according to claim 1. The second transformer is
A first input unit connected to the power receiving side active electrode; a second input unit connected to the power receiving side passive electrode; a first output unit; and a second output unit. And the voltage applied between the first output unit and the second output unit is transmitted between the first output component and the second output unit, and the first inductance component, the first capacitance component, and A piezoelectric transformer including the second capacitance component;
The power receiving device is:
A parallel inductor connected in parallel to the second capacitance component;
The second inductance component is an inductance component of the parallel inductor.
The wireless power transmission system according to claim 1 or 2. The power receiving device is:
A current detection circuit for detecting a current supplied to the load circuit;
A control circuit that cuts off the supply of current to the load circuit when the current detected by the current detection circuit exceeds a threshold;
The wireless power transmission system according to any one of claims 1 to 3, further comprising:

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