JP7623196B2 - Non-contact power supply system and power transmission device - Google Patents

Description

The present invention relates to a non-contact power supply system and a power transmission device.

As a conventional non-contact power supply system, for example, Patent Document 1 describes a non-contact power transmission system that includes a charging station having a power transmission circuit that transmits power and a primary communication device capable of wireless communication, and an electric vehicle having a power receiving circuit that receives power transmitted from the power transmission circuit and a secondary communication device capable of wireless communication with the primary communication device. When transmitting power to an electric vehicle parked at the charging station, this non-contact power transmission system transmits power from the power transmission circuit to the power receiving circuit after confirming the power receiving circuit of the electric vehicle by communicating between the primary communication device and the secondary communication device.

Patent No. 6458084

However, in the non-contact power transmission system described in Patent Document 1, when transmitting power from the power transmission circuit of the charging station to the power receiving circuit of the electric vehicle, it is necessary to confirm the power receiving circuit of the electric vehicle through communication, and there is room for further improvement in this regard.

Therefore, the present invention has been made in consideration of the above, and aims to provide a non-contact power supply system that can properly supply power non-contactly.

In order to solve the above-mentioned problems and achieve the object, the contactless power supply system according to the present invention comprises a power transmission device including an AC power source that supplies AC power, a power transmission unit that transmits the AC power supplied from the AC power source in a contactless manner, a voltage detection unit that detects the voltage of the power transmission unit, and a power transmission side control unit that controls the AC power source based on the voltage detected by the voltage detection unit, and a power receiving device that is mounted on a vehicle and includes a power receiving unit that receives the AC power transmitted from the power transmission device in a contactless manner, and the power transmission unit includes a power transmission coil that transmits power to the power receiving unit, a power transmission capacitor that is connected in series with the power transmission coil, and a power transmission capacitor that has one end connected to the power transmission coil. The power transmission side control unit has a resonant coil connected on the opposite side of the power transmission coil and the other end connected to the AC power source, and a resonant capacitor connected between the power transmission capacitor and the resonant coil and the other end connected to the opposite side of the power transmission coil from the power transmission capacitor, and the power transmission side control unit controls the AC power source to supply standby AC power from the AC power source to the power transmission unit, and when the voltage detection unit detects a change in the voltage of the resonant capacitor while the standby AC power is being supplied, it determines that the power transmission unit and the power receiving unit are opposed to each other, and controls the AC power source to supply supply AC power greater than the standby AC power to the power transmission unit.

The power transmission device according to the present invention includes an AC power source that supplies AC power, a power transmission unit that transmits the AC power supplied from the AC power source, a voltage detection unit that detects the voltage of the power transmission unit, and a power transmission side control unit that controls the AC power source based on the voltage detected by the voltage detection unit. The power transmission unit includes a power receiving unit that is mounted on a vehicle and receives the AC power transmitted from the power transmission unit in a non-contact manner. The power transmission unit includes a power transmission coil that transmits power to the power receiving unit of the power receiving device, a power transmission capacitor that is connected in series to the power transmission coil, one end of the power transmission capacitor is connected to the opposite side to the power transmission coil and the other end of the power transmission capacitor is connected to the AC power. The power transmission side control unit controls the AC power source to supply standby AC power from the AC power source to the power transmission unit, and when the voltage detection unit detects a change in the voltage of the resonant capacitor while the standby AC power is being supplied, the power transmission side control unit determines that the power transmission unit and the power receiving unit are opposed to each other and controls the AC power source to supply supply AC power greater than the standby AC power to the power transmission unit.

The contactless power supply system and power transmission device according to the present invention determine that the power transmission unit and power receiving unit are facing each other based on a voltage change in the resonant capacitor of the power transmission unit, eliminating the need to determine that the power transmission unit and power receiving unit are facing each other by communication as in the past. As a result, power can be supplied appropriately without contact.

FIG. 1 is a circuit diagram showing a configuration example of a contactless power supply system according to an embodiment. FIG. 2 is a diagram showing the voltage of the resonant capacitor during standby according to the embodiment. FIG. 3 is a diagram showing the voltage of the resonant capacitor when detecting the power receiving device according to the embodiment. FIG. 4 is a diagram showing an input current and an output voltage of an inverter when supplying power to a power receiving device according to the embodiment. FIG. 5 is a diagram showing the input current and output voltage of the inverter when no power is supplied to the power receiving device according to the embodiment (when the power receiving section is in a return current state). FIG. 6 is a diagram showing an input current and an input voltage of the rectifier according to the embodiment. FIG. 7 is a flowchart illustrating an example of the operation of the power transmitting device according to the embodiment. FIG. 8 is a flowchart illustrating an example of the operation of the power receiving device according to the embodiment. FIG. 9 is a circuit diagram illustrating a configuration example of a contactless power supply system according to a modified example of the embodiment. FIG. 10 is a flowchart illustrating an example of the operation of a power transmitting device according to a modification of the embodiment. FIG. 11 is a flowchart illustrating an example of the operation of a power receiving device according to a modification of the embodiment.

The following describes in detail the form (embodiment) for carrying out the present invention with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. The components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Various omissions, substitutions, or modifications of the configuration can be made without departing from the spirit of the present invention.

[Embodiment]
A contactless power supply system 100 according to an embodiment will be described with reference to the drawings. The contactless power supply system 100 supplies power contactlessly to a power receiving device 1B mounted on a vehicle, and in particular, supplies power instantaneously to a vehicle that is running. The contactless power supply system 100 will be described in detail below. Here, the vehicle includes, for example, electric vehicles such as EVs (Electric Vehicles), HEVs (Hybrid Electric Vehicles), and PHEVs (Plug-in Hybrid Electric Vehicles).

The non-contact power supply system 100 includes, for example, a power transmission device 1A and a power receiving device 1B, as shown in FIG. 1.

The power transmission device 1A supplies power to the power receiving device 1B in a non-contact manner, and includes a DC power source 10A, an inverter 20A as an AC power source, a current detection unit 30A, a voltage detection unit 40A, a power calculation unit 50A, a power transmission unit 60A, a voltage detection unit 70A, an opposing determination unit 80A, and an inverter control unit 90A as a power transmission side control unit.

The DC power supply 10A is a storage battery capable of storing and discharging DC power. The DC power supply 10A is connected to the inverter 20A and supplies the stored DC power to the inverter 20A.

The inverter 20A converts DC power into AC power. The inverter 20A includes switching elements (e.g., FETs; Field Effect Transistors) Q1 to Q4, forming a full bridge circuit. The inverter 20A has a first series circuit formed by connecting the switching elements Q1 and Q2 in series, and a second series circuit formed by connecting the switching elements Q3 and Q4 in series. The first series circuit and the second series circuit are connected in parallel to each other. In the inverter 20A, the positive electrode of the DC power source 10A is connected between the switching elements Q1 and Q3, and the negative electrode of the DC power source 10A is connected between the switching elements Q2 and Q4. In addition, in the inverter 20A, one end of the power transmission coil L1a described below is connected between the switching elements Q1 and Q2, and the other end of the power transmission coil L1a is connected between the switching elements Q3 and Q4. The inverter 20A is connected to an inverter control unit 90A, and turns on and off the switching elements Q1 to Q4 based on the control signal of the inverter control unit 90A, converts the DC power supplied from the DC power source 10A into AC power, and supplies the AC power to the transmission coil L1a.

The current detection unit 30A detects the current. The current detection unit 30A is provided between the positive electrode of the DC power supply 10A and the inverter 20A, and detects the current flowing from the DC power supply 10A to the inverter 20A. The current detection unit 30A is connected to the power calculation unit 50A, and outputs the detected current to the power calculation unit 50A.

The voltage detection unit 40A detects voltage. The voltage detection unit 40A is connected between the positive and negative electrodes of the DC power supply 10A and detects the voltage of the DC power supply 10A. The voltage detection unit 40A is connected to the power calculation unit 50A and outputs the detected voltage to the power calculation unit 50A.

The power calculation unit 50A calculates the power. The power calculation unit 50A is connected to the current detection unit 30A and the voltage detection unit 40A, and calculates the power from the detected current output from the current detection unit 30A and the detected voltage output from the voltage detection unit 40A. The power calculation unit 50A is connected to the inverter control unit 90A, and outputs the calculated power to the inverter control unit 90A.

The power transmission unit 60A transmits power, for example, AC power supplied from the inverter 20A to the power receiving device 1B in a non-contact manner. The power transmission unit 60A includes a power transmission coil L1a, a power transmission capacitor C1a, a resonant coil L2a, and a resonant capacitor C2a.

The power transmission coil L1a transmits power to the power receiving unit 10B. One end of the power transmission coil L1a is connected between the switching element Q1 and the switching element Q2 of the inverter 20A via the power transmission capacitor C1a and the resonant coil L2a, and the other end is connected between the switching element Q3 and the switching element Q4 of the inverter 20A. The power transmission capacitor C1a is provided between the power transmission coil L1a and the resonant coil L2a, and is connected in series to the power transmission coil L1a and the resonant coil L2a. One end of the resonant coil L2a is connected to the side of the power transmission capacitor C1a opposite to the power transmission coil L1a, and the other end is connected to the inverter 20A. In this example, the other end of the resonant coil L2a is connected between the switching element Q1 and the switching element Q2 of the inverter 20A. One end of the resonant capacitor C2a is connected between the power transmission capacitor C1a and the resonant coil L2a, and the other end is connected to the side of the power transmission coil L1a opposite to the power transmission capacitor C1a.

The power transmission unit 60A has a configuration in which an immittance conversion circuit composed of a resonant coil L2a and a resonant capacitor C2a is added to a resonant power transmission circuit composed of a power transmission coil L1a and a power transmission capacitor C1a. Here, the power transmission unit 60A is supplied with standby AC power (standby power) or supply AC power (normal power) larger than the standby AC power by the inverter 20A. Here, the standby AC power (standby power) is power supplied to the power transmission unit 60A in the case of a standby mode in which the power transmission unit 60A waits until the power receiving device 1B to be supplied is present, and is a relatively small power that does not interfere with determining the opposing state with the power receiving device 1B. The supply AC power (normal power) is power supplied to the power transmission unit 60A in the case of a normal mode in which the power receiving device 1B to be supplied is present and actually supplies power to the power receiving device 1B, in other words, in the case of a normal mode in which the power receiving device 1B to be supplied is supplied with power to charge the power storage unit 70B of the power receiving device 1B, and is a relatively large power that can correspond to the required power of the power receiving device 1B. In the above-mentioned immittance conversion circuit, when standby power is supplied by the inverter 20A and the power receiving device 1B is not present, the power transmitting coil L1a is energized with standby power by generating a double resonance state using the power transmitting coil L1a and the immittance conversion circuit. Then, when the power receiving coil L1b of the power receiving device 1B faces the energized power transmitting coil L1a, the power transmitting coil 60A causes a current of power (standby power) to flow from the power transmitting coil L1a to the power receiving coil L1b.

The voltage detection unit 70A detects the voltage. The voltage detection unit 70A is connected to both ends of the resonant capacitor C2a and detects the voltage of the resonant capacitor C2a. Here, in the standby mode, when the receiving coil L1b of the power receiving device 1B does not face the transmitting coil L1a, for example, a standby power voltage is applied to the resonant capacitor C2a as shown in FIG. 2. On the other hand, in the standby mode, when the receiving coil L1b of the power receiving device 1B faces the transmitting coil L1a, a current of power (standby power) flows from the transmitting coil L1a to the receiving coil L1b, so that the voltage of the resonant capacitor C2a becomes almost zero as shown in FIG. 3. Here, when the power receiving coil L1b of the power receiving device 1B approaches the power transmitting coil L1a and the power transmitting coil L1a and the power receiving coil L1b begin to be magnetically coupled, the double resonance state created by the power transmitting coil L1a and the immittance conversion circuit is no longer maintained, and as a result, the voltage of the resonant capacitor C2a drops significantly, as shown in Figure 3. The voltage detection unit 70A is connected to the opposing determination unit 80A and outputs the detected voltage of the resonant capacitor C2a to the opposing determination unit 80A.

The opposing determination unit 80A determines the opposing of the power receiving device 1B. The opposing determination unit 80A is connected to the voltage detection unit 70A, and the voltage of the resonant capacitor C2a is output from the voltage detection unit 70A. The opposing determination unit 80A determines the opposing of the power receiving device 1B based on the voltage of the resonant capacitor C2a output from the voltage detection unit 70A. For example, the opposing determination unit 80A compares the voltage of the resonant capacitor C2a with a predetermined reference voltage, and if the voltage of the resonant capacitor C2a is equal to or higher than the reference voltage (for example, in the case of the voltage shown in FIG. 2), it determines that the power receiving coil L1b of the power receiving device 1B is not opposed to the power transmitting coil L1a, and if the voltage of the resonant capacitor C2a is less than the reference voltage (for example, in the case of the voltage shown in FIG. 3), it determines that the power receiving coil L1b of the power receiving device 1B is opposed to the power transmitting coil L1a. The opposing determination unit 80A is connected to the inverter control unit 90A and outputs a determination result indicating the opposing state to the inverter control unit 90A.

The inverter control unit 90A controls the inverter 20A. The inverter control unit 90A controls the inverter 20A by changing the duty ratio for turning on and off the switching elements Q1 to Q4 of the inverter 20A based on the power of the DC power source 10A output from the power calculation unit 50A and the judgment result (judgment result indicating the opposing of the power receiving device 1B) output from the opposing judgment unit 80A. For example, when the judgment result output from the opposing judgment unit 80A does not indicate the opposing of the power receiving device 1B, the inverter control unit 90A sets the on-duty for turning on the switching elements Q1 to Q4 to be smaller than the normal mode described above and sets the mode to standby mode. On the other hand, when the judgment result output from the opposing judgment unit 80A indicates the opposing of the power receiving device 1B, the inverter control unit 90A sets the on-duty for turning on the switching elements Q1 to Q4 to be larger than the standby mode and sets the mode to normal mode, and supplies power to the opposing power receiving device 1B.

When the storage unit 70B of the power receiving device 1B is fully charged, as described below, a current reflux occurs in the power receiving unit 10B of the power receiving device 1B, and in this case, the input current to the inverter 20A suddenly decreases as a result of the operation of the immittance conversion circuit. The inverter control unit 90A detects this current change and transitions from normal mode to standby mode. For example, when the input current to the inverter 20A is less than a predetermined reference current, the inverter control unit 90A determines that the storage unit 70B of the power receiving device 1B is fully charged and current is being refluxed in the power receiving unit 10B, sets the duty ratio of the inverter 20A to a minimum value, and transitions from normal mode to standby mode. On the other hand, when the input current to the inverter 20A is equal to or greater than a predetermined reference current, the inverter control unit 90A determines that there is no return current due to full charging of the power storage unit 70B, even if there is a return current for voltage adjustment in the power receiving unit 10B, and maintains the duty ratio of the inverter 20A at the duty ratio in the normal mode. Here, the input current Ia (see FIG. 5) to the inverter 20A when there is a return current due to full charging of the power storage unit 70B is smaller than the input current Ia (see FIG. 4) to the inverter 20A when power is supplied to the power receiving device 1B in the normal mode. The reference current is a current that can determine the change from the input current Ia shown in FIG. 4 to the input current Ia shown in FIG. 5. Here, when the voltage is converted by refluxing the current in the power receiving unit 10B, the inverter control unit 90A determines that there is no reflux due to full charging of the power storage unit 70B because the input current Ia to the inverter 20A is equal to or greater than a predetermined reference current, and maintains the duty ratio of the inverter 20A at the duty ratio in normal mode. Note that the output current Va of the inverter 20A is the same voltage when power is supplied to the power receiving device 1B in normal mode (see FIG. 4) and when reflux occurs due to full charging in the power receiving unit 10B (see FIG. 5). FIG. 4 is a diagram showing the input current and output voltage of the inverter 20A when power is supplied to the power receiving device 1B according to the embodiment. FIG. 5 is a diagram showing the input current and output voltage of the inverter 20A when power is not supplied to the power receiving device 1B according to the embodiment (when refluxing the power receiving unit 10B).

The inverter control unit 90A sets the power to be supplied to the power receiving device 1B within an optimal range, taking into account the positional deviation between the power transmitting device 1A and the power receiving device 1B. Here, in this embodiment, the voltage of the power transmitting device 1A needs to be the highest when the coupling coefficient and the load voltage of the power receiving device 1B (the voltage of the power storage unit 70B) are the smallest within the design range, and the power of the power transmitting device 1A is highest when the coupling coefficient and the load voltage of the power receiving device 1B are the largest within the design range. Therefore, in this embodiment, the voltage of the power transmitting device 1A is set based on when the coupling coefficient and the load voltage of the power receiving device 1B are the smallest, and the upper limit of the power supplied from the power transmitting device 1A is determined based on when the coupling coefficient and the load voltage of the power receiving device 1B are the largest, and the output of the power transmitting device 1A, i.e., the duty ratio of the inverter 20A is controlled so as not to exceed that limit.

Next, the power receiving device 1B will be described. The power receiving device 1B receives power supplied contactlessly from the power transmitting device 1A, and includes a power receiving unit 10B, a current detection unit 20B, a rectifier 30B, a smoothing capacitor 40B, a current detection unit 50B, a voltage detection unit 60B, a power storage unit (load unit) 70B, a phase detection unit 80B, and a rectifier control unit 90B as a power receiving side control unit.

The power receiving unit 10B receives power, for example, AC power transmitted from the power transmitting unit 60A in a non-contact manner. The power receiving unit 10B includes a power receiving coil L1b, a power receiving capacitor C1b, a resonant coil L2b, and a resonant capacitor C2b.

The receiving coil L1b receives power from the receiving unit 10B. One end of the receiving coil L1b is connected between the diode D1 and diode D2 of the rectifier 30B described below via the receiving capacitor C1b and the resonant coil L2b, and the other end is connected between the diode D3 and diode D4 of the rectifier 30B. The receiving capacitor C1b is provided between the receiving coil L1b and the resonant coil L2b, and is connected in series to the receiving coil L1b and the resonant coil L2b. The resonant coil L2b has one end connected to the opposite side of the receiving coil L1b of the receiving capacitor C1b, and the other end connected to the rectifier 30B. In this example, the resonant coil L2b has the other end connected between the diode D1 and diode D2 of the rectifier 30B. One end of the resonant capacitor C2b is connected between the power receiving capacitor C1b and the resonant coil L2b, and the other end is connected to the side of the power receiving coil L1b opposite the power receiving capacitor C1b.

The power receiving unit 10B has a configuration in which an immittance conversion circuit consisting of a resonant coil L2b and a resonant capacitor C2b is added to a power receiving circuit consisting of a power receiving coil L1b and a power receiving capacitor C1b. When the power receiving coil L1b faces the power transmitting coil L1a of the power transmitting device 1A, the power receiving unit 10B magnetically couples with each other, and the power supplied from the power transmitting coil L1a is received by the power receiving coil L1b in a non-contact manner.

The current detection unit 20B detects the current. The current detection unit 20B is provided between the power receiving unit 10B and the rectifier 30B, and detects the current flowing from the power receiving unit 10B to the rectifier 30B. The current detection unit 20B is connected to the phase detection unit 80B, and outputs the detected current to the phase detection unit 80B.

The rectifier 30B rectifies AC power to DC power. The rectifier 30B includes diodes D1 to D4, a short-circuit switch SW1, a short-circuit switch SW2, a smoothing inductor 31B, and a smoothing inductor 32B, forming a full bridge circuit. The rectifier 30B forms a first series circuit by connecting diodes D1 and D2 in series, and forms a second series circuit by connecting diodes D3 and D4 in series. The first series circuit and the second series circuit are connected in parallel to each other. In the rectifier 30B, one end of the receiving coil L1b is connected between diodes D1 and D2, and the other end of the receiving coil L1b is connected between diodes D3 and D4. In the rectifier 30B, the positive electrode of the storage unit 70B is connected between diodes D1 and D3, and the negative electrode of the storage unit 70B is connected between diodes D2 and D4. Rectifier 30B rectifies the AC power received by power receiving unit 10B into DC power using diodes D1 to D4, and supplies the DC power to power storage unit 70B.

The short-circuit switch SW1 passes or cuts off current. The short-circuit switch SW1 is connected in parallel to the diode D2 of the rectifier 30B, and shorts out the diode D2. The short-circuit switch SW1 is connected to the rectifier control unit 90B, and turns the short-circuit switch SW1 on and off based on a control signal output from the rectifier control unit 90B. The short-circuit switch SW1 shorts out the diode D2 when turned on, and does not short out the diode D2 when turned off.

The short-circuit switch SW2 passes or cuts off current. The short-circuit switch SW2 is connected in parallel to the diode D4 of the rectifier 30B, and shorts out the diode D4. The short-circuit switch SW2 is connected to the rectifier control unit 90B, and turns the short-circuit switch SW2 on and off based on a control signal output from the rectifier control unit 90B. The short-circuit switch SW2 shorts out the diode D4 when turned on, and does not short out the diode D4 when turned off.

The smoothing inductor 31B smoothes the current and is provided between the diodes D1 and D2. The smoothing inductor 31B smoothes the current flowing between the diodes D1 and D2.

The smoothing inductor 32B smoothes the current and is provided between the diodes D3 and D4. The smoothing inductor 31B smoothes the current flowing between the diodes D3 and D4.

The smoothing capacitor 40B smoothes the current and is provided between the rectifier 30B and the power storage unit 70B, and is connected in parallel to the rectifier 30B (power storage unit 70B). The smoothing capacitor 40B smoothes the DC power rectified by the rectifier 30B, and supplies the smoothed DC power to the power storage unit 70B.

The current detection unit 50B detects the current. The current detection unit 50B is provided between the rectifier 30B and the positive electrode of the power storage unit 70B, and detects the current flowing from the rectifier 30B to the power storage unit 70B. The current detection unit 50B is connected to the rectifier control unit 90B, and outputs the detected current to the rectifier control unit 90B.

The voltage detection unit 60B detects voltage. The voltage detection unit 60B is connected between the positive and negative electrodes of the power storage unit 70B, and detects the voltage applied to the power storage unit 70B. The voltage detection unit 60B is connected to the rectifier control unit 90B, and outputs the detected voltage to the rectifier control unit 90B.

The power storage unit 70B is capable of charging and discharging power, and is composed of, for example, a lithium-ion battery. The power storage unit 70B is connected to the rectifier 30B, and stores the DC power supplied from the rectifier 30B.

The phase detection unit 80B detects the phase origin of the input current input to the rectifier 30B. For example, as shown in FIG. 6, the phase detection unit 80B detects the phase origin of the input current Ib to the rectifier 30B from the timing when the input current Ib input to the rectifier 30B crosses zero. The phase detection unit 80B is connected to the rectifier control unit 90B, and outputs the detected phase origin of the input current Ib to the rectifier 30B to the rectifier control unit 90B.

The rectifier control unit 90B controls the rectifier 30B. The rectifier control unit 90B controls the short-circuit switches SW1 and SW2 of the rectifier 30B based on the detected current (current flowing from the rectifier 30B to the power storage unit 70B) output from the current detection unit 50B, the detected voltage (voltage applied to the power storage unit 70B by the rectifier 30B) output from the voltage detection unit 60B, and the phase information (phase origin of the input current Ib to the rectifier 30B) output from the phase detection unit 80B. For example, when the detected current output from the current detection unit 50B or the detected voltage output from the voltage detection unit 60B is equal to or greater than the required value required by the power storage unit 70B, the rectifier control unit 90B relatively increases the on-duty of the short-circuit switches SW1 and SW2 to relatively increase the current flowing back to the power receiving unit 10B, thereby reducing the power charged to the power storage unit 70B. On the other hand, when the detected current output from the current detection unit 50B or the detected voltage output from the voltage detection unit 60B is less than the required value required by the power storage unit 70B, the rectifier control unit 90B relatively reduces the on-duty of the short-circuit switches SW1 and SW2 to relatively reduce the current flowing back to the power receiving unit 10B, thereby increasing the power charged to the power storage unit 70B. At this time, as shown in FIG. 6, the rectifier control unit 90B raises the on-duty pulse at the timing when the input current Ib input to the rectifier 30B crosses zero based on the phase information output from the phase detection unit 80B. This allows the rectifier control unit 90B to stably supply the input current Ib input to the rectifier 30B. FIG. 6 is a diagram showing the input current Ib and input voltage Vb of the rectifier 30B according to the embodiment.

When the detected voltage output from the voltage detection unit 60B is equal to or higher than the reference voltage representing the full charge of the power storage unit 70B, the rectifier control unit 90B causes all current of the AC power received by the power receiving unit 10B to flow back through the power receiving unit 10B, and does not supply the AC power received by the power receiving unit 10B to the power storage unit 70B. Here, the rectifier control unit 90B turns on the short-circuit switches SW1 and SW2 to form a closed circuit in the power receiving unit 10B including the power receiving coil L1b, and causes the current of the power received by the power receiving coil L1b to flow through the closed circuit, thereby causing the current to flow back, and does not supply the power received by the power receiving coil L1b to the power storage unit 70. On the other hand, when the detected voltage output from the voltage detection unit 60B is less than the reference voltage representing the full charge of the power storage unit 70B, the rectifier control unit 90B adjusts the amount of current that is circulated from the power receiving unit 10B according to the state of the power storage unit 70B, and then supplies the power receiving unit 10B with the power storage unit 70B.

Next, an example of the operation of the power transmission device 1A will be described. FIG. 7 is a flowchart showing an example of the operation of the power transmission device 1A according to the embodiment. As shown in FIG. 7, the inverter control unit 90A of the power transmission device 1A sets the duty ratio of the inverter 20A to a minimum value and transitions to a standby mode (step S1). For example, the inverter control unit 90A sets the on-duty of the inverter 20A to 5% and supplies a small amount of power to the power transmission unit 60A that does not interfere with determining the facing state with the power receiving device 1B. Next, the facing determination unit 80A determines whether the voltage of the resonant capacitor C2a is less than the reference voltage for facing determination (step S2). Here, when the power receiving coil L1b of the power receiving device 1B faces the power transmitting coil L1a, the voltage of the resonant capacitor C2a becomes almost zero as shown in FIG. 3 because a current of power (standby power) flows from the power transmitting coil L1a to the power receiving coil L1b. When the voltage of the resonant capacitor C2a is less than the reference voltage for the facing judgment (step S2; Yes), the facing judgment unit 80A judges that the power receiving coil L1b of the power receiving device 1B faces the power transmitting coil L1a, and outputs the judgment result indicating the facing state to the inverter control unit 90A. When the judgment result indicating the facing state is output from the facing judgment unit 80A, the inverter control unit 90A increases the on-duty for turning on the switching elements Q1 to Q4 of the inverter 20A to be greater than that in the standby mode, transitions to the normal mode, and supplies power to the facing power receiving device 1B. At this time, the inverter control unit 90A judges whether the input power to the inverter 20A is less than a predetermined upper limit threshold (step S3). When the input power to the inverter 20A is less than a predetermined upper limit threshold (step S3; Yes), the inverter control unit 90A increases the on-duty of the inverter 20A, and increases the power supplied in the normal mode (step S4). On the other hand, if the input power to the inverter 20A is equal to or greater than the predetermined upper threshold (step S3; No), the inverter control unit 90A reduces the on-duty of the inverter 20A to reduce the power supplied in the normal mode (step S9). Next, the inverter control unit 90A determines whether the input current to the inverter 20A is less than a predetermined reference current (step S5). If the input current to the inverter 20A is less than a predetermined reference current (step S5; Yes), the inverter control unit 90A determines that the power storage unit 70B of the power receiving device 1B is fully charged and current is being circulated in the power receiving unit 10B, sets the duty ratio of the inverter 20A to a minimum value, and transitions from the normal mode to the standby mode (step S6). Next, the opposing determination unit 80A determines whether the voltage of the resonant capacitor C2a is equal to or greater than the reference voltage for detachment determination (step S7). Here, when the power receiving coil L1b of the power receiving device 1B is not facing the power transmitting coil L1a and is separated, no power (standby power) current flows from the power transmitting coil L1a to the power receiving coil L1b, so the voltage of the resonant capacitor C2a rises. If the voltage of the resonant capacitor C2a is equal to or higher than the reference voltage for separation determination (step S7; Yes), the opposing determination unit 80A determines that the power receiving coil L1b of the power receiving device 1B is not facing the power transmitting coil L1a and is separated. Next, the inverter control unit 90A determines whether or not to end the power transmission process (step S8), and if the power transmission process is not to be ended (step S8; No), the inverter control unit 90A returns to the above-mentioned step S2 and determines the opposing state by the opposing determination unit 80A.

In addition, in the above-mentioned step 2, if the voltage of the resonant capacitor C2a is equal to or higher than the reference voltage for the opposing judgment (step S2; No), the opposing judgment unit 80A again compares it with the reference voltage for the opposing judgment. In the above-mentioned step S5, if the input current to the inverter 20A is equal to or higher than the predetermined reference current (step S5; No), the inverter control unit 90A returns to step S3 and judges whether the input power to the inverter 20A is less than the predetermined upper threshold value. In the above-mentioned step S7, if the voltage of the resonant capacitor C2a is less than the reference voltage for the separation judgment (step S7; No), the opposing judgment unit 80A again compares it with the reference voltage for the separation judgment.

Next, an example of the operation of the power receiving device 1B will be described. FIG. 8 is a flowchart showing an example of the operation of the power receiving device 1B according to the embodiment. The rectifier control unit 90B of the power receiving device 1B sets the duty ratio for short circuit to a minimum value (step T1). For example, the rectifier control unit 90B sets the on-duty of the short-circuit switches SW1 and SW2 of the rectifier 30B to 0%, so that the power receiving unit 10B is in a state in which no current flows back. Next, the rectifier control unit 90B determines whether the load voltage or load current of the power storage unit 70B is less than the required value (step T2). For example, if the detected current output from the current detection unit 50B or the detected voltage output from the voltage detection unit 60B is less than the required value required by the power storage unit 70B (step T2; Yes), the rectifier control unit 90B relatively reduces the on-duty of the short-circuit switches SW1 and SW2 to relatively reduce the current flowing back to the power receiving unit 10B, thereby increasing the received power (step T3). On the other hand, when the detected current output from the current detection unit 50B or the detected voltage output from the voltage detection unit 60B is equal to or greater than the required value required by the power storage unit 70B (step T2; No), the rectifier control unit 90B relatively increases the on-duty of the short-circuit switches SW1 and SW2 to relatively increase the current flowing back to the power receiving unit 10B, thereby reducing the received power (step T8). Next, the rectifier control unit 90B determines whether the load voltage of the power storage unit 70B is equal to or greater than a predetermined reference voltage (step T4). For example, when the detected voltage output from the voltage detection unit 60B is equal to or greater than the reference voltage indicating the full charge of the power storage unit 70B (step T4; Yes), the rectifier control unit 90B sets the on-duty for short-circuiting to a maximum value (step T5). The rectifier control unit 90B, for example, sets the on-duty of the short-circuit switches SW1 and SW2 to 100%, causes all current of the AC power received by the power receiving unit 10B to flow back through the power receiving unit 10B, and does not allow the AC power received by the power receiving unit 10B to be supplied to the power storage unit 70B. Next, the rectifier control unit 90B determines whether the input current to the rectifier 30B is less than a predetermined reference current for separation (step T6). If the input current to the rectifier 30B is less than the predetermined reference current for separation (step T6; Yes), the rectifier control unit 90B determines that the power transmitting device 1A and the power receiving device 1B have separated without facing each other, and determines whether the load voltage of the power storage unit 70 is equal to or higher than a predetermined reference voltage (step T7). If the load voltage of the power storage unit 70 is equal to or greater than the predetermined reference voltage (step T7; Yes), the rectifier control unit 90B determines that the power storage unit 70 is fully charged and ends the process. On the other hand, if the load voltage of the power storage unit 70 is less than the predetermined reference voltage (step T7; No), the rectifier control unit 90B determines that the power storage unit 70 is not fully charged, returns to the above-mentioned step T1, sets the short-circuit duty ratio to a minimum value (e.g., 0%), and puts the power receiving unit 10B in a state where no current flows back.

In the above-mentioned step T4, if the detected voltage output from the voltage detection unit 60B is less than the reference voltage representing the full charge of the power storage unit 70B (step T4; No), the rectifier control unit 90B returns to step T2 and determines whether the load voltage or load current of the power storage unit 70B is less than the required value. In the above-mentioned step T6, if the input current to the rectifier 30B is equal to or greater than the predetermined reference current for disconnection (step T6; No), the rectifier control unit 90B determines that the power transmission device 1A and the power receiving device 1B are opposed to each other and have not been disconnected, and again compares the reference current for disconnection.

As described above, the contactless power supply system 100 according to the embodiment includes a power transmission device 1A and a power receiving device 1B. The power transmission device 1A includes an inverter 20A, a power transmission unit 60A, a voltage detection unit 70A, and an inverter control unit 90A. The inverter 20A supplies AC power. The power transmission unit 60A transmits the AC power supplied from the inverter 20A in a contactless manner. The voltage detection unit 70A detects the voltage of the power transmission unit 60A. The inverter control unit 90A controls the inverter 20A based on the voltage detected by the voltage detection unit 70A. The power receiving device 1B is mounted on a vehicle and includes a power receiving unit 10B that receives AC power transmitted from the power transmission device 1A in a contactless manner. In the power transmission device 1A and power receiving unit 10B configured in this manner, the power transmission unit 60A includes a power transmission coil L1a that transmits power to the power receiving unit 10B, a power transmission capacitor C1a connected in series to the power transmission coil L1a, a resonant coil L2a having one end connected to the side of the power transmission capacitor C1a opposite the power transmission coil L1a and the other end connected to the inverter 20A, and a resonant capacitor C2a having one end connected between the power transmission capacitor C1a and the resonant coil L2a and the other end connected to the side of the power transmission coil L1a opposite the power transmission capacitor C1a. The inverter control unit 90A controls the inverter 20A to supply standby AC power from the inverter 20A to the power transmission unit 60A, and when the voltage detection unit 70A detects a change in the voltage of the resonant capacitor C2a while standby AC power is being supplied, it determines that the power transmission unit 60A and the power receiving unit 10B are opposed to each other, and causes the inverter 20A to supply supply AC power that is greater than the standby AC power to the power transmission unit 60A.

With this configuration, the contactless power supply system 100 determines that the power receiving unit 10B faces the power transmitting unit 60A based on a change in the voltage of the resonant capacitor C2a, so there is no need to determine the facing state between the power transmitting unit 60A and the power receiving unit 10B by communicating between the power transmitting device 1A and the power receiving device 1B as in the past. As a result, the contactless power supply system 100 can determine the facing state in a short time compared to when the facing state is determined by communication with the other side. As a result, the contactless power supply system 100 can ensure a longer time for transmitting power than in the past when supplying power contactlessly to a traveling vehicle, for example, and can supply more power from the power transmitting device 1A to the power receiving device 1B. As a result, the contactless power supply system 100 can properly supply power contactlessly even while the vehicle is traveling.

In the contactless power supply system 100, the power receiving device 1B includes a rectifier 30B that rectifies the AC power received by the power receiving unit 10B and supplies the rectified DC power to the power storage unit 70B, and a rectifier control unit 90B that controls the rectifier 30B. When the voltage of the power storage unit 70B is equal to or higher than a reference voltage indicating full charge, the rectifier control unit 90B controls the rectifier 30B to return the current of the AC power received by the power receiving unit 10B to the power receiving unit 10B, and does not supply the AC power received by the power receiving unit 10B to the power storage unit 70B. With this configuration, the contactless power supply system 100 can end the charging of the power storage unit 70B by returning the current of the AC power received by the power receiving unit 10B to the power receiving unit 10B.

In the above-mentioned non-contact power supply system 100, the power receiving device 1B includes a rectifier 30B that rectifies the AC power received by the power receiving unit 10B and supplies the rectified DC power to the power storage unit 70B, and a rectifier control unit 90B that controls the rectifier 30B. The rectifier control unit 90B controls the rectifier 30B and returns the current of the AC power received by the power receiving unit 10B to the power receiving unit 10B, thereby converting the voltage of the AC power supplied from the power transmitting unit 60A to the voltage of the power storage unit 70B, and supplies the voltage-converted AC power received by the power receiving unit 10B to the power storage unit 70B. With this configuration, the non-contact power supply system 100 can eliminate the need for a DC/DC converter when converting the voltage of the power transmitted from the power transmitting device 1A to the voltage of the power storage unit 70B.

[Modifications]
Next, a modified example of the embodiment will be described. In the modified example, the same components as those in the embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Fig. 9 is a circuit diagram showing a configuration example of a non-contact power supply system 100A according to a modified example of the embodiment. The non-contact power supply system 100A is different from the non-contact power supply system 100 according to the embodiment in that the power receiving unit 10C does not have an immittance conversion circuit composed of a resonant coil L2a and a resonant capacitor C2a as in the above embodiment.

The power receiving unit 10C receives power, for example, AC power transmitted from the power transmitting unit 60A in a non-contact manner. The power receiving unit 10C includes a power receiving coil L1b and a power receiving capacitor C1b, and does not include an immittance conversion circuit configured from a resonant coil L2a and a resonant capacitor C2a.

The receiving coil L1b receives power from the receiving unit 10C. One end of the receiving coil L1b is connected between the diodes D1 and D2 of the rectifier 30B via the receiving capacitor C1b, and the other end is connected between the diodes D3 and D4 of the rectifier 30B. The receiving capacitor C1b is provided between the receiving coil L1b and the rectifier 30B, and is connected in series to one end of the receiving coil L1b. When the receiving coil L1b faces the transmitting coil L1a of the power transmitting device 1A, the receiving coil L1b and the receiving coil L1b are magnetically coupled to each other, and the power supplied from the transmitting coil L1a is received by the receiving coil L1b in a non-contact manner.

Next, an operation example of the power transmission device 1A according to the modified embodiment will be described. FIG. 10 is a flowchart showing an operation example of the power transmission device 1A according to the modified embodiment. As shown in FIG. 10, the inverter control unit 90A of the power transmission device 1A sets the duty ratio of the inverter 20A to a minimum value and transitions to a standby mode (step S1a). Next, the opposing determination unit 80A determines whether the voltage of the resonant capacitor C2a is less than the reference voltage for opposing determination (step S2a). If the voltage of the resonant capacitor C2a is less than the reference voltage for opposing determination (step S2a; Yes), the opposing determination unit 80A determines that the power receiving coil L1b of the power receiving device 1B is opposing the power transmitting coil L1a, and outputs a determination result indicating the opposing state to the inverter control unit 90A. When the opposing state is output from the opposing determination unit 80A, the inverter control unit 90A increases the on-duty for turning on the switching elements Q1 to Q4 of the inverter 20A to be greater than that of the standby mode, transitions to normal mode, and supplies power to the opposing power receiving device 1B. At this time, the inverter control unit 90A determines whether the input power to the inverter 20A is less than a predetermined upper threshold (step S3a). When the input power to the inverter 20A is less than a predetermined upper threshold (step S3a; Yes), the inverter control unit 90A increases the on-duty of the inverter 20A to increase the power supplied in the normal mode (step S4a). On the other hand, when the input power to the inverter 20A is equal to or greater than the predetermined upper threshold (step S3a; No), the inverter control unit 90A decreases the on-duty of the inverter 20A to decrease the power supplied in the normal mode (step S9a). Next, the inverter control unit 90A determines whether the input current to the inverter 20A is equal to or greater than a predetermined reference current (step S5a). When the input current to the inverter 20A is equal to or greater than a predetermined reference current (step S5a; Yes), the inverter control unit 90A determines that the power storage unit 70B of the power receiving device 1B is fully charged and current is being circulated in the power receiving unit 10B, and sets the duty ratio of the inverter 20A to a minimum value to transition from normal mode to standby mode (step S6a). Here, since the power receiving unit 10C is not an immittance conversion circuit, when the power storage unit 70B is fully charged and current is being circulated in the power receiving unit 10B, the input current to the inverter 20A increases rapidly. Next, the opposing determination unit 80A determines whether the voltage of the resonant capacitor C2a is equal to or greater than a reference voltage for detachment determination (step S7a). When the voltage of the resonant capacitor C2a is equal to or greater than a reference voltage for detachment determination (step S7a; Yes), the opposing determination unit 80A determines that the power receiving coil L1b of the power receiving device 1B is not opposed to the power transmitting coil L1a and is detached. Next, the inverter control unit 90A determines whether or not to end the power transmission process (step S8a), and if the power transmission process is not to be ended (step S8a; No), the inverter control unit 90A returns to step S2a described above and determines the opposing state using the opposing determination unit 80A.

In addition, in the above-mentioned step 2a, if the voltage of the resonant capacitor C2a is equal to or higher than the reference voltage for the opposing judgment (step S2a; No), the opposing judgment unit 80A compares it again with the reference voltage for the opposing judgment. In the above-mentioned step 5a, if the input current to the inverter 20A is less than the predetermined reference current (step S5a; No), the inverter control unit 90A returns to step S3a and judges whether the input power to the inverter 20A is less than the predetermined upper limit threshold. In the above-mentioned step S7a, if the voltage of the resonant capacitor C2a is less than the reference voltage for the separation judgment (step S7a; No), the opposing judgment unit 80A compares it again with the reference voltage for the separation judgment.

Next, an operation example of the power receiving device 1C according to the modified embodiment will be described. FIG. 11 is a flowchart showing an operation example of the power receiving device 1C according to the modified embodiment. The rectifier control unit 90B of the power receiving device 1C sets the duty ratio for short circuit to a maximum value (e.g., 100%) (step T1a). This allows the rectifier control unit 90B to receive standby power transmitted from the power transmitting device 1A. Next, the rectifier control unit 90B determines whether the input current of the rectifier 30B is equal to or greater than a predetermined reference current (step T2a). If the input current of the rectifier 30B is equal to or greater than a predetermined reference current (step T2a; Yes), the rectifier control unit 90B determines that charging has started and sets the duty ratio for short circuit to a minimum value (e.g., 0%) (step T3a). Next, the rectifier control unit 90B determines whether the load voltage or load current of the power storage unit 70B is less than a required value (step T4a). For example, when the detected current output from the current detection unit 50B or the detected voltage output from the voltage detection unit 60B is less than the required value required by the power storage unit 70B (step T4a; Yes), the rectifier control unit 90B relatively reduces the on-duty of the short-circuit switches SW1 and SW2 to relatively reduce the current flowing back to the power receiving unit 10B, thereby increasing the received power (step T5a). On the other hand, when the detected current output from the current detection unit 50B or the detected voltage output from the voltage detection unit 60B is equal to or greater than the required value required by the power storage unit 70B (step T4a; No), the rectifier control unit 90B relatively increases the on-duty of the short-circuit switches SW1 and SW2 to relatively increase the current flowing back to the power receiving unit 10B, thereby decreasing the received power (step T11a). Next, the rectifier control unit 90B determines whether the load voltage of the power storage unit 70B is equal to or greater than a predetermined reference voltage (step T6a). For example, when the detected voltage output from the voltage detection unit 60B is equal to or higher than the reference voltage representing the full charge of the power storage unit 70B (step T6a; Yes), the rectifier control unit 90B sets the on-duty for short circuiting to a maximum value (e.g., 100%) (step T7a). Next, the rectifier control unit 90B determines whether the input current to the rectifier 30B is less than a predetermined reference current for separation (step T8a). When the input current to the rectifier 30B is less than a predetermined reference current for separation (step T8a; Yes), the rectifier control unit 90B determines that the power transmission device 1A and the power receiving device 1C have separated without facing each other, and sets the duty ratio for short circuiting to a minimum value (e.g., 0%) (step T9a). Next, the rectifier control unit 90B determines whether the load voltage of the power storage unit 70 is equal to or higher than a predetermined reference voltage (step T10a). If the load voltage of the storage unit 70 is equal to or greater than the predetermined reference voltage (step T10a; Yes), the rectifier control unit 90B determines that the storage unit 70 is fully charged and ends the process. On the other hand, if the load voltage of the storage unit 70 is less than the predetermined reference voltage (step T10a; No), the rectifier control unit 90B determines that the storage unit 70 is not fully charged, returns to the above-mentioned step T1a, and sets the short-circuit duty ratio to the maximum value (e.g., 100%) (step T1a).

In addition, in the above step T6a, if the detected voltage output from the voltage detection unit 60B is less than the reference voltage representing the full charge of the power storage unit 70B (step T6a; No), the rectifier control unit 90B returns to step T4a and determines whether the detected current output from the current detection unit 50B or the detected voltage output from the voltage detection unit 60B is equal to or greater than the required value required by the power storage unit 70B. In the above step T8a, if the input current to the rectifier 30B is equal to or greater than the predetermined reference current for separation (step T8a; No), the rectifier control unit 90B again determines whether the input current to the rectifier 30B is less than the predetermined reference current for separation.

In the contactless power supply system 100 according to the embodiment, the smoothing inductors 31B and 32B are provided between the diodes of the rectifier 30B, but this is not limited thereto. For example, as in the contactless power supply system 100A according to the modified embodiment, the smoothing inductor 33B may be provided between the rectifier 30B and the power storage unit 70B.

In the above explanation, an example of controlling the power supplied from the power transmission device 1A by controlling the duty ratio of the inverter 20A has been described, but this is not limiting. For example, the input voltage to the inverter 20A may be made variable, or the inverter 20A may be made a multilevel inverter, thereby lowering the output power of the inverter 20A and further reducing power consumption during standby.

An example has been described in which the amount of power received by the power receiving device 1B is adjusted by shorting the diodes D2 and D4 of the rectifier 30B, but this is not limiting. For example, a switching element that shorts the input section of the rectifier 30B may be provided, or another power adjustment section (e.g., a DC/DC converter) may be provided in front of the power storage section 70B.

The rectifier 30B may be configured with diodes D1 and D3 as switching elements such as FETs, and may be configured as synchronous rectifiers that are turned on and off according to the direction of current flow.

100 Non-contact power supply system 1A Power transmission device 1B Power receiving device 20A Inverter (AC power source)
60A Power transmission unit 70A Voltage detection unit 90A Inverter control unit (power transmission side control unit)
L1a Power transmission coil C1a Power transmission capacitor L2a Resonant coil C2a Resonant capacitor 10B Power receiving unit 30B Rectifier (rectification unit)
70B Power storage unit (load unit)
90B Rectifier control unit (power receiving side control unit)

Claims (4)

a power transmitting device including an AC power source that supplies AC power, a power transmitting unit that wirelessly transmits the AC power supplied from the AC power source, a voltage detection unit that detects a voltage of the power transmitting unit, and a power transmitting side control unit that controls the AC power source based on the voltage detected by the voltage detection unit;
a power receiving device including a power receiving unit mounted on a vehicle and configured to contactlessly receive the AC power transmitted from the power transmitting device;
the power transmitting unit includes a power transmitting coil that transmits power to the power receiving unit, a power transmitting capacitor connected in series to the power transmitting coil, a resonant coil having one end connected to the side of the power transmitting capacitor opposite to the power transmitting coil and the other end connected to the AC power source, and a resonant capacitor having one end connected between the power transmitting capacitor and the resonant coil and the other end connected to the side of the power transmitting coil opposite to the power transmitting capacitor,
the power transmission side control unit controls the AC power source to supply standby AC power from the AC power source to the power transmission unit, and when the voltage detection unit detects a change in voltage of the resonant capacitor while the standby AC power is being supplied, determines that the power transmission unit and the power receiving unit are opposed to each other, and controls the AC power source to supply supply AC power that is greater than the standby AC power to the power transmission unit. The power receiving device includes a rectification unit that rectifies AC power received by the power receiving unit and supplies the rectified DC power to a power storage unit, and a power receiving side control unit that controls the rectification unit,
2. The contactless power supply system according to claim 1, wherein, when a voltage of the power storage unit is equal to or higher than a reference voltage representing a full charge, the power receiving side control unit controls the rectification unit to return a current of the AC power received by the power receiving unit to the power receiving unit and not supply the AC power received by the power receiving unit to the power storage unit. The power receiving device includes a rectification unit that rectifies AC power received by the power receiving unit and supplies the rectified DC power to a power storage unit, and a power receiving side control unit that controls the rectification unit,
3. The contactless power supply system according to claim 1, wherein the power receiving side control unit controls the rectification unit and returns the current of the AC power received by the power receiving unit to the power receiving unit, thereby converting a voltage of the AC power supplied from the power transmitting unit to a voltage of a load unit, and supplies the AC power after voltage conversion to the load unit. an AC power source for supplying AC power;
a power transmitting unit that transmits the AC power supplied from the AC power source;
A voltage detection unit that detects a voltage of the power transmission unit;
a power transmission side control unit that controls the AC power supply based on the voltage detected by the voltage detection unit,
the power transmission unit includes a power transmission coil that transmits power to the power receiving unit of a power receiving device that is mounted on a vehicle and includes a power receiving unit that receives the AC power transmitted from the power transmission unit in a wireless manner, a power transmission capacitor that is connected in series to the power transmission coil, a resonance coil having one end connected to the opposite side of the power transmission capacitor to the power transmission coil and the other end connected to the AC power source, and a resonance capacitor having one end connected between the power transmission capacitor and the resonance coil and the other end connected to the opposite side of the power transmission coil to the power transmission capacitor,
the power transmission side control unit controls the AC power source to supply standby AC power from the AC power source to the power transmission unit, and when the voltage detection unit detects a change in voltage of the resonant capacitor while the standby AC power is being supplied, determines that the power transmission unit and the power receiving unit are opposed to each other, and controls the AC power source to supply supply AC power that is greater than the standby AC power to the power transmission unit.

Images