JP2015136274A - Non-contact power transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem of a non-contact power transmission device that when the voltage of a transmission section is varied, resonance frequency between the transmission section and a reception section varies, and the power transmission efficiency is reduced.SOLUTION: Since a non-contact power transmission device determines an optimum power transmission efficiency based on the transmission supply voltage, and controls the frequency and electric energy of power of a transmission section by the optimum power transmission efficiency, resonance state between a transmission resonance circuit and a reception resonance circuit can be maintained in a high state, and power can be transmitted with high efficiency even if the power requested on the power reception side varies.

Description

  The present invention relates to a non-contact power transmission device that performs non-contact (wireless) power transmission via a power transmission coil provided in a power transmission device and a power reception coil provided in the power reception device.

  As a method of transmitting power in a non-contact manner, an electromagnetic induction type by electromagnetic induction (several hundreds of kHz), an electric field / magnetic field resonance type by transmission between LC resonances via electric field or magnetic field resonance, a microwave power transmission type by radio waves (several GHz), Alternatively, a laser power transmission type using electromagnetic waves (light) in the visible light region is known. Among them, the electromagnetic induction type has already been put into practical use. This has the advantage that it can be realized with a simple circuit (transformer system), but there is also a problem that the transmission distance is short.

  Therefore, recently, electric field / magnetic field resonance type power transmission capable of short-distance transmission (up to 2 m) has attracted attention. Among these, in the case of the electric field resonance type, when a hand or the like is put in the transmission path, the human body is a dielectric, so that energy is absorbed as heat and dielectric loss occurs. On the other hand, in the case of the magnetic resonance type, the human body hardly absorbs energy, and dielectric loss can be avoided. From this point of view, attention to the magnetic resonance type has been increasing.

  In general, the magnetic field resonance type includes a power transmission device and a power reception device. The power transmission device includes a power transmission resonator including at least a power transmission coil and a resonance capacitor, and a power transmission unit that supplies power to the power transmission resonator. The power receiving device includes a power receiving resonator including at least a power receiving coil and a resonant capacitor.

  Patent Document 1 discloses that when the power transmission resonator of the power transmission device and the power reception resonator of the power reception device resonate at the drive frequency of the power transmission unit of the power transmission device, power can be transmitted from the power transmission device to the power reception device with high efficiency. ing.

  In Patent Document 2, in a non-contact power transmission device that performs power transmission by electromagnetic induction, a power transmission frequency is sequentially changed to find a specific frequency that maximizes the current amplitude of the power transmission coil, and high-efficiency power is generated at this specific frequency. A technique for transmitting is disclosed.

JP 2010-130878 A JP 2010-136464 A

  In the non-contact power transmission device, the present inventors have found a problem that when the transmission power changes, the resonance frequencies of the power transmission resonance circuit and the power reception resonance circuit also change. This problem will be described in detail later. When the resonance frequency of the power transmission resonance circuit and the power reception resonance circuit is changed, power transmission efficiency is reduced if power is transmitted at a constant frequency. Therefore, in a non-contact power transmission device that needs to change the transmission power each time according to the request from the power receiving side, the change in the resonance frequency that occurs when the transmission power is changed leads to a reduction in power transmission efficiency. It becomes a problem.

  In addition, in the method of finding the specific frequency that maximizes the current amplitude of the power transmission coil by sequentially changing the transmission frequency, it takes time until the specific frequency is found, and the transmission power is changed in response to a sudden power change request on the receiving side. There is a problem that the frequency cannot be switched at high speed.

  A non-contact power transmission device of the present invention includes a power transmission device having a power transmission resonator configured by a power transmission coil and a resonance capacitor, and a power reception device having a power reception resonator configured by a power reception coil and a resonance capacitor, the power transmission In a non-contact power transmission device that transmits power from the power transmission device to the power reception device via an action between a coil and the power reception coil, the power transmission device further includes a power transmission unit that applies high-frequency power to the power transmission resonator; A power transmission voltage control unit that controls a power transmission supply voltage of the power transmission unit; and a power transmission frequency control unit that controls a power transmission frequency of the power transmission unit, wherein the power transmission frequency control unit is controlled by the power transmission voltage control unit. A power transmission frequency of the power transmission unit is controlled based on a power transmission supply voltage of the power transmission unit.

  According to the present invention, the optimum power transmission frequency is determined based on the power transmission supply voltage, and the power frequency and power amount of the power transmission unit are controlled by the optimum power transmission frequency. However, since the power transmission frequency can be changed as appropriate, the resonance state between the power transmission resonance circuit and the power reception resonance circuit can always be kept high, and power can be transmitted with high efficiency.

The block diagram which shows the structure of the non-contact electric power transmission apparatus in Embodiment 1 of this invention. The circuit diagram which shows the outline of the power transmission part in Embodiment 1 of this invention Diagram showing the relationship between transmission frequency and transmission power with transmission supply voltage as parameter The figure for calculating | requiring a power transmission frequency from the power transmission supply voltage in Embodiment 1 of this invention The block diagram which shows the structure of the non-contact electric power transmission apparatus in Embodiment 2 of this invention.

  FIG. 1 shows a configuration of a non-contact power transmission apparatus according to the present invention. The non-contact power transmission device includes a power transmission device 1 and a power reception device 2. The power transmission device 1 includes a power transmission coil 4 for non-contact transmission of high-frequency power. The power receiving device 2 includes a power receiving coil 10 for receiving high frequency power supplied from the power transmitting coil 4. The non-contact power transmission apparatus having the configuration of FIG. 1 can be configured to transmit power from the power transmission apparatus 1 to the power reception apparatus 2 via magnetic field resonance between the power transmission coil 4 and the power reception coil 10, for example. Note that the coupling form of the power transmission coil 4 and the power reception coil 10 can be appropriately employed such as electromagnetic induction, radio wave, electric field or magnetic field sharing. Below, the case where electric power is transmitted from the power transmission apparatus 1 to the power receiving apparatus 2 via the magnetic field resonance between the power transmission coil 4 and the power receiving coil 10 is demonstrated as an example.

  In the power transmission device 1, the power transmission coil 4 and the power transmission resonance capacitor 5 constitute a power transmission resonator. In the power reception device 2, the power reception coil 10 and the power reception resonance capacitor 11 constitute a power reception resonator. The power transmission unit 3 supplies high-frequency power to the power transmission resonator. Electric power is transmitted from the power transmission coil 4 to the power reception coil 10 through magnetic field resonance between the power transmission coil 4 constituting the power transmission resonator and the power reception coil 10 constituting the power reception resonator. The power converter 12 is connected to the power receiving resonator. The power conversion unit 12 performs detection and smoothing of the high-frequency power received by the power receiving coil 10 and converts it into a power format required by the load connected to the power output terminal 13.

  The power transmission unit 3 of the power transmission device 1 supplies relatively large AC power to the power transmission resonator. Therefore, a power circuit using a semiconductor switching element is used for the power transmission unit 3, and direct current is converted into alternating current by switching. FIG. 2 shows a half bridge circuit using two FETs 21 and 22 as switching elements. Below, the case where the half bridge circuit shown in FIG. 2 comprises the power transmission part 3 is demonstrated. The power transmission unit 3 may use a full bridge circuit using four FETs. The voltage during power transmission is determined by the power transmission supply voltage Vc in FIG. 2, and the frequency during power transmission is determined by the power transmission frequency f0 of the switching control power supply 20 in FIG. Vc is set based on a command from the power transmission voltage control unit 6, and f0 is set based on a command from the power transmission frequency control unit 7.

  By the way, in order to realize high-efficiency power transmission, the power transmission resonator by the power transmission coil 4 and the power transmission resonance capacitor 5, the resonance frequency between the power reception resonator by the power reception coil 10 and the power reception resonance capacitor 11, and the power transmission unit 3 It is preferable to substantially match the transmission frequency of the high-frequency power supplied to the power transmission resonator.

  However, the resonance frequency between the power transmission resonator and the power reception resonator may fluctuate. FIG. 3 is a graph obtained by measuring the relationship between the transmission frequency f0 and the transmission power using the transmission supply voltage Vc as a parameter. The inductance of the power transmission coil 4 is 425 μH, and the capacitance of the resonance capacitor 5 is 4950 pF. When these values of the power transmission coil and the resonant capacitor are connected in series, the calculated resonant frequency is about 110 kHz. However, the obtained resonance frequency was 102.5 kHz when the power transmission supply voltage Vc was 24V, and 105.5 kHz when it was 60V.

  The reason why the resonance frequency is different between the power transmission supply voltage Vc of 24V and 60V is that the impedance matching on the power transmission side and the power reception side changes between Vc of 24V and 60V.

  First, on the power transmission side, in the present embodiment, the power transmission unit 3 of the power transmission device 1 includes a half bridge circuit using FETs 21 and 22 as switching elements, and the half bridge circuit is configured by a power transmission coil 4 and a power transmission resonance capacitor 5. Directly connected to the power transmission resonator. The impedance of the power transmission circuit by the switching element is theoretically 0Ω, which is actually very low impedance, so that the impedance changes due to fluctuations in the transmission power. The impedance of the power transmission side resonator composed of the power transmission coil 4 and the power transmission resonance capacitor 5 also varies with the frequency.

  Further, also on the power receiving side, the impedance of the power receiving side resonator constituted by the power receiving coil 10 and the power receiving resonance capacitor 11 varies depending on the frequency, and the power receiving circuit of the power conversion unit 12 that performs detection and smoothing of the high frequency power is also received power. Impedance varies due to.

  As described above, it is considered that the resonance frequency differs when the impedances on the power transmission side and the power reception side change according to the power transmission supply voltage.

  Incidentally, as is apparent from FIG. 3, high-efficiency non-contact power transmission cannot be performed unless the power transmission frequency f0 is set to an appropriate frequency in accordance with the power transmission supply voltage Vc. Therefore, when the received power required by the power receiving device 2 varies depending on the state of the load connected to the power output terminal 13 of the power receiving device 2, the power transmission device 1 changes the power transmission supply voltage Vc of the power transmission unit 3. Therefore, it is necessary to set the power transmission frequency f0 to an appropriate value.

  The contactless power transmission device of the present invention is characterized in that the power transmission device 1 controls the transmission voltage and the transmission frequency in association with each other. The value of the power transmission supply voltage Vc is transmitted from the power transmission voltage control unit 6 to the power transmission unit 3 and also transmitted to the power transmission frequency control unit 7. The power transmission frequency control unit 7 transmits the optimum power transmission frequency f0 to the power transmission unit 3 based on the value of the power transmission supply voltage Vc. The power transmission unit 3 sets the value of the power transmission supply voltage Vc based on the command from the power transmission voltage control unit 6, and sets the value of the power transmission frequency f0 based on the command from the power transmission frequency control unit 7.

  In addition, although it is preferable to comprise the power transmission voltage control part 6 and the power transmission frequency control part 7 with a microcomputer, it can also be comprised with FPGA and an electronic circuit.

Below, the non-contact power transmission apparatus in which the transmission voltage and the transmission frequency of the present invention are associated will be described in detail by dividing them into embodiments.
<Embodiment 1>
FIG. 1 shows a configuration of a non-contact power transmission apparatus according to Embodiment 1 of the present invention. The power transmission voltage control unit 6 controls the power transmission supply voltage Vc supplied to the switching element of the power transmission unit 3. In the first embodiment, the power transmission supply voltage to be supplied is switched between 24 V and 60 V, but it may be switched between three or more voltage values or may be continuous voltage control.

  FIG. 4 is a table in which the optimum power transmission frequency f0 frequency corresponding to the power transmission supply voltage Vc is determined when the power transmission supply voltage Vc is 24V and 60V, respectively. This table can be obtained in advance, for example, by performing the measurement of FIG. 3 during the initial operation before shipping of the non-contact power transmission apparatus. The measurement of FIG. 3 may use the method of the cited reference 2 for every power transmission supply voltage Vc, for example. Since the relationship of the optimal power transmission frequency f0 corresponding to the power transmission supply voltage Vc may fluctuate due to changes in the environmental temperature or the like, the relationship of the optimal power transmission frequency f0 frequency corresponding to the power transmission supply voltage Vc shown in FIG. May be appropriately calibrated during operation of the non-contact power transmission apparatus. For the calibration, for example, the method of the cited document 2 may be used for each power transmission supply voltage Vc.

  The power transmission frequency control unit 7 controls the power transmission frequency f0 of the high frequency power output from the power transmission unit 3 based on the table of FIG. The power transmission frequency control unit 7 receives the value of the power transmission supply voltage Vc from the power transmission voltage control unit 6 and controls the power transmission frequency f0 of the switching control power source 20 of the power transmission unit 3 with the power transmission frequency f0 corresponding to the power transmission supply voltage Vc. The power transmission frequency control unit 7 controls the power transmission frequency f0 of the switching control power supply 20 in the power transmission unit 3 to 102.5 kHz when the power transmission supply voltage Vc is 24 V based on the table of FIG. At the time, the power transmission frequency f0 of the switching control power supply 20 in the power transmission unit 3 is controlled to 105.5 kHz.

  As a result, in the power transmission device 1, power transmission is performed at a power transmission frequency f0 of 102.5 kHz when the power transmission supply voltage Vc is 24V, and power transmission is performed at a power transmission frequency f0 of 105.5 kHz when the power transmission supply voltage Vc is 60V. That is, in the present embodiment, control is performed so that the power transmission frequency f0 increases as the power transmission supply voltage Vc increases.

With the above operation, power transmission can be performed in a state where the resonance state is high regardless of whether the power transmission supply voltage Vc is 24 V or 60 V. Therefore, contactless power transmission can be realized with high efficiency regardless of the voltage value of the power transmission supply voltage Vc. In this embodiment, the case where the power transmission supply voltage is switched between 24 V and 60 V has been described as an example for the sake of simplicity. However, switching between three or more voltages may be performed, and continuous voltage control may be performed. good.
<Embodiment 2>
In the first embodiment, the power transmission supply voltage Vc and the power transmission frequency f0 are controlled only by the power transmission device 1, but in the second embodiment, the power transmission device 1 uses the power transmission supply voltage Vc and the power transmission frequency f0 based on information from the power receiving device 2. To control.

  FIG. 5 shows a configuration of a non-contact power transmission apparatus according to Embodiment 2 of the present invention. The required power calculation unit 14 of the power reception device 2 determines the transmission power required for the power transmission device 1 based on the output power of the power conversion unit 12 or information input from the outside of the power reception device 2. As for the requested transmission power, for example, when the power output from the power output unit 13 to the load is large, the required power to the power transmission device 1 is small, and when the power output from the power output unit 13 to the load is small, the power is transmitted. The power required for the device 1 can be increased. The required power calculation unit 14 sends the requested transmission power information to the communication transmission unit 15. The required power calculation unit 14 is preferably configured by a microcomputer, but may be configured by an FPGA or an electronic circuit.

  The communication transmission unit 15 transmits the requested transmission power information to the power transmission device 1 by wireless communication.

  The communication reception unit 8 of the power transmission device 1 receives the transmission power information transmitted from the communication transmission unit 15 of the power reception device 2 by wireless communication.

  As communication means for realizing the communication transmitter 15 and the communication receiver 8, for example, ZigBee (registered trademark) or Bluetooth (registered trademark) can be used, or a low-power radio station or weak radio is used. Also good.

  The communication receiving unit 8 instructs the power transmission voltage control unit 6 on the power transmission supply voltage Vc based on the power transmission power information received from the power receiving device by wireless communication. Since the subsequent operations of the power transmission voltage control unit 6, the power transmission frequency control unit 7, and the power transmission unit 3 in the power transmission device 1 are the same as those in the first embodiment, detailed description thereof is omitted.

  Hereinafter, non-contact power transmission can be performed in a state where the resonance state is high, according to the power required by the power receiving device, by the same operation as in the first embodiment.

  With the above operation, the power transmission supply voltage Vc can be determined based on the information on the power receiving side and the optimum power transmission frequency f0 can be obtained, so that highly efficient non-contact power transmission based on the power demand of the load can be realized.

  In FIG. 5, the transmission power requested to the power transmission device 1 is determined based on the output power of the power conversion unit 12. However, the transmission power requested to the power transmission device 1 based on the input power of the power conversion unit 12. May be determined.

  The contactless power transmission device of the present invention is capable of highly efficient power transmission even when the transmission voltage fluctuates, and is suitable for contactless power transmission when the power required on the power receiving device side fluctuates.

DESCRIPTION OF SYMBOLS 1 Power transmission apparatus 2 Charging apparatus 3 Power transmission part 4 Power transmission coil 5 Resonance capacity 6 Power transmission voltage control part 7 Power transmission frequency control part 8 Communication receiving part 10 Power receiving coil 11 Resonance capacity 12 Power conversion part 13 Power output part 14 Required power calculation part 15 Communication Transmitter 20 Switching control power supply 21 Switching element 22 Switching element 23 Coil

Claims (7)

A power transmission device having a power transmission resonator composed of a power transmission coil and a resonant capacitor;
A power receiving device having a power receiving resonator composed of a power receiving coil and a resonant capacitor;
In the non-contact power transmission device that transmits power from the power transmission device to the power reception device through the action between the power transmission coil and the power reception coil,
The power transmission device further includes:
A power transmission unit that applies high-frequency power to the power transmission resonator;
A power transmission voltage control unit for controlling a power transmission supply voltage of the power transmission unit;
A power transmission frequency control unit for controlling a power transmission frequency of the power transmission unit,
The non-contact power transmission device, wherein the power transmission frequency control unit controls a power transmission frequency of the power transmission unit based on a power transmission supply voltage of the power transmission unit controlled by the power transmission voltage control unit. The power receiving device, a required power calculation unit that calculates transmission power information to be transmitted by the power transmission device,
A communication transmission unit that transmits the transmission power information output by the required power calculation unit to the power transmission device in a contactless manner;
The power transmission device includes a communication reception unit that receives information transmitted by the communication transmission unit and transmits transmission power information to the frequency control unit,
The power transmission frequency control unit determines a power transmission supply voltage of the power transmission unit based on transmission power information received by the communication reception unit,
The contactless power transmission according to claim 1, wherein the power transmission frequency control unit controls a power transmission frequency of the power transmission unit based on a power transmission supply voltage of the power transmission unit controlled by the power transmission voltage control unit. apparatus.   The non-contact power transmission apparatus according to claim 1, wherein the power transmission frequency control unit performs control so that the power transmission frequency is increased when the power transmission supply voltage is increased.   4. The contactless power transmission apparatus according to claim 1, wherein an optimum relationship of the transmission frequency corresponding to the power transmission supply voltage is measured during an initial operation of the contactless power transmission apparatus. 5.   The contactless power transmission apparatus according to claim 4, wherein the optimum relationship between the power transmission frequencies corresponding to the power transmission supply voltage is appropriately calibrated during operation of the contactless power transmission apparatus. The power receiving device includes a power conversion unit that inputs power received by the power receiving coil, converts the power into a predetermined format, and outputs power.
3. The required power calculation unit calculates transmission power information based on input power of the power conversion unit, output power of the power conversion unit, and information input from the outside of the power receiving apparatus. The non-contact power transmission device described in 1.   The contactless power transmission device according to claim 1, wherein magnetic resonance is used as an action between the power transmission coil and the power reception coil.

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