JP2013106490A - Wireless power-feeding device, wireless power-feeding system, and transmission method of power signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a power signal in wide dynamic range.SOLUTION: A resonant antenna 30 includes a transmission coil Land a resonant capacitor Cfor transmitting a power signal S1 that are provided in series. A DC power supply 32 applies a DC voltage VDC between a first power-supply line LVDD and a second power-supply line LVSS. An H-bridge circuit 34 is provided between the first power-supply line LVDD and the second power-supply line LVSS. A control unit 36 switches a pair of a first switch SW1 and a second switch SW2 by a transmission frequency f, and switches a pair of a third switch SW3 and a fourth switch SW4 by the transmission frequency f. The control unit 36 adjusts a phase difference Δφ according to the strength of the power signal S1 to be transmitted.

Description

  The present invention relates to a wireless power feeding technique.

  In recent years, wireless (non-contact) power transmission has attracted attention as a power feeding technique for electronic devices such as mobile phone terminals and notebook computers, or electric vehicles. Wireless power transmission is mainly classified into three types: an electromagnetic induction type, a radio wave reception type, and an electric field / magnetic field resonance type.

  The electromagnetic induction type is used in a short distance (within several centimeters) and can transmit power of several hundred W in a band of several hundred kHz or less. The power use efficiency is about 60 to 98%. When power is supplied to a relatively long distance of several meters or more, a radio wave receiving type is used. In the radio wave reception type, power of several W or less can be transmitted in a medium wave to microwave band, but power use efficiency is low. An electric field / magnetic field resonance type is attracting attention as a method of supplying power at a relatively high efficiency over a medium distance of several meters (see Non-Patent Document 1).

A. Karalis, J.D. Joannopoulos, M. Soljacic, `` Efficient wireless non-radiative mid-range energy transfer '', ANNALS of PHYSICS Vol. 323, pp.34-48, 2008, Jan.

FIG. 1 is a diagram illustrating an example of a wireless power feeding system. The wireless power feeding system 100r includes a wireless power feeding device 200r and a wireless power receiving device 300r. Wireless power supply apparatus 200r includes a transmission coil _{L T,} a resonance capacitor _{C T} and the AC power source 10. The AC power supply 10 generates an electric signal S2 having a transmission frequency _fTX . Resonance capacitor C _T and the transmission coil L _T constitutes a resonance circuit, the resonance frequency is tuned to the frequency f _TX of the electrical signal S2. From the transmitter coil _{L T,} the power signal S1 is sent.

Wireless power receiving device 300r comprises a receiver coil _{L R,} resonance capacitor _{C R} and the load circuit 20. The resonance capacitor C _R , the reception coil L _R and the load circuit 20 constitute a resonance circuit, and the resonance frequency is tuned to the frequency f _TX of the power signal S1.

Depending on the positional relationship between the distance and orientation of the wireless power supply apparatus 200r and the wireless power receiving device 300 r, the degree of coupling receiving coil L _R and the transmission coil L _T changes with time. Therefore, AC power supply 10 needs to dynamically change the signal intensity of power signal S1 according to the positional relationship between wireless power supply apparatus 200r and wireless power reception apparatus 300r.

For example, when the AC power supply 10 generates a drive voltage of the transmission frequency f _TX as the electric signal S2, it is necessary to change the amplitude of the drive voltage in a dynamic range of 10 times or more according to the positional relationship. The dynamic range of the amplitude control of the output voltage of a general DC / DC converter or DC / AC converter (inverter) is several times at most, and it is difficult to use the wireless power supply apparatus 200r.

  SUMMARY An advantage of some aspects of the invention is to provide a wireless power feeding apparatus capable of controlling a power signal with a wide dynamic range.

  One embodiment of the present invention relates to a wireless power feeding apparatus that transmits a power signal having a transmission frequency including any one of an electric field, a magnetic field, and an electromagnetic field. A wireless power feeding apparatus includes a resonance antenna including a transmission coil and a resonance capacitor for transmitting a power signal provided in series, a DC power source that applies a DC voltage between a first power supply line and a second power supply line, A first switch provided between the first power supply line and one end of the resonant antenna; a second switch provided between the second power supply line and one end of the resonant antenna; and the other end of the first power supply line and the resonant antenna. An H bridge circuit including a third switch provided between the second power supply line and a fourth switch provided between the other end of the resonant antenna, and a pair of the first switch and the second switch, Switching at the transmission frequency in the first phase, switching the pair of the third switch and the fourth switch at the transmission frequency in the second phase, and transmitting the power signal to be transmitted Depending on the time, and a control unit for adjusting a difference between the first and second phases, the.

  Another aspect of the present invention is also a wireless power feeder. This wireless power feeder includes a resonance antenna including a transmission coil and a resonance capacitor for transmitting a power signal provided in series, and a high-level voltage and a low-level voltage at one end of the resonance antenna at a first phase. A first power source that applies a first rectangular voltage that switches between them at a transmission frequency, and a second rectangle that switches between a high level voltage and a low level voltage at a second phase at the other end of the resonant antenna at a transmission frequency. A second power source for applying a voltage; and a controller for adjusting a difference between the first phase and the second phase in accordance with the strength of the power signal to be transmitted.

  According to these aspects, by controlling the difference between the first phase and the second phase, the energy supplied to the resonant antenna can be controlled with a wide dynamic range, and as a result, the power signal can be controlled with a wide dynamic range. Can be controlled.

  Another aspect of the present invention includes the wireless power feeding apparatus according to any one of the above aspects that transmits a power signal including any one of an electric field, a magnetic field, and an electromagnetic field, and a wireless power receiving apparatus that receives the power signal.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other between methods and apparatuses are also effective as an aspect of the present invention.

  According to an aspect of the present invention, the power signal can be controlled with a wide dynamic range.

It is a figure which shows an example of a wireless electric power feeding system. It is a circuit diagram which shows the structure of the wireless electric power feeder which concerns on embodiment. It is a simulation waveform diagram which shows operation | movement of the wireless power supply apparatus of FIG. Figure 4 (a), (b) is a diagram showing the spectrum of the coil current _{I L.}

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, “the state in which the member A is connected to the member B” means that the member A and the member B are electrically connected to each other in addition to the case where the member A and the member B are physically directly connected. It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as their electric It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.

FIG. 2 is a circuit diagram showing a configuration of wireless power supply apparatus 200 according to the embodiment.
The wireless power feeding apparatus 200 forms a wireless power feeding system together with a wireless power receiving apparatus (not shown). The wireless power supply apparatus 200 transmits a power signal S1 having a transmission frequency f _{TX to} the wireless power receiving apparatus. The power signal S1 is a near field (an electric field, a magnetic field, or an electromagnetic field) of an electromagnetic wave that is not a radio wave.

The wireless power feeder 200 includes a resonant antenna 30, a DC power supply 32, an H bridge circuit 34, and a control unit 36.
Resonant antenna 30, arranged in series, including a transmission coil L _T and the resonance capacitor C _T for delivering power signal S1. Resistor R denotes wiring and transmission coil L _T, the DC resistance component of the resonance capacitor C _T.

  The DC power supply 32 applies a DC voltage VDC between the first power supply line LVDD and the second power supply line LVSS. Hereinafter, the potential of the first power supply line LVDD is referred to as a first power supply voltage VDD, and the potential of the second power supply line LVSS is referred to as a second power supply voltage VSS.

  The H bridge circuit 34 is provided between the first power supply line LVDD and the second power supply line LVSS, and its two output terminals are connected to the resonant antenna 30. The H bridge circuit 34 includes a first switch SW1 to a fourth switch SW4. The first switch SW1 is provided between the first power supply line LVDD and one end P1 of the resonant antenna 30, and the second switch SW2 is provided between the second power supply line LVSS and one end P1 of the resonant antenna 30. The third switch SW3 is provided between the first power supply line LVDD and the other end P2 of the resonance antenna 30, and the fourth switch SW4 is provided between the second power supply line LVSS and the other end P2 of the resonance antenna 30. The first switch SW1 to the fourth switch SW4 can be configured using transistors such as MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

  The control unit 36 switches the first switch SW1 to the fourth switch SW4 of the H-bridge circuit 34 to supply an electric signal (hereinafter also referred to as a drive voltage) S2 to both ends P1-P2 of the resonant antenna 30. .

Control unit 36, the first switch SW1 a pair of the second switch SW2, at the transmission frequency _{f TX,} is switched by the first phase .phi.1. As a result, the one end P1 of the resonance antenna 30, a first power supply voltage VDD and the second power supply voltage VSS is first rectangular voltage V1 for switching is applied at the transmission frequency _{f TX.} The ON times of the first switch SW1 and the second switch SW2 are equal, and therefore the first rectangular voltage V1 takes the first power supply voltage VDD in the half cycle and takes the second power supply voltage VSS in the remaining half cycle.

The control unit 36 includes a third switch SW3 pairs fourth switch SW4, at the transmission frequency _{f TX,} is switched by the second phase .phi.2. The other end P2 of the resonance antenna 30, a first power supply voltage VDD and the second power supply voltage VSS, a second rectangular voltage V2 for switching is applied at the transmission frequency _{f TX.} The on-times of the third switch SW3 and the fourth switch SW4 are equal, and therefore the second rectangular voltage V2 takes the first power supply voltage VDD in the half cycle and takes the second power supply voltage VSS in the remaining half cycle.

  The controller 36 adjusts the difference Δφ between the first phase φ1 and the second phase φ2 according to the strength of the power signal S1 to be transmitted.

  The above is the configuration of the wireless power supply apparatus 200. Next, the operation will be described. FIG. 3 is a simulation waveform diagram showing the operation of the wireless power supply apparatus 200 of FIG.

  In the waveforms of the first switch SW1 to the fourth switch SW4, the high level corresponds to on and the low level corresponds to off. Further, VDD = 3V and VSS = 0V. The first rectangular voltage V1 is switched at the first phase φ1, and the second rectangular voltage V2 is switched at the second phase φ2.

The drive voltage S2 applied between both ends of the resonant antenna 30 includes, in order, a first period T1 that takes −VDD, a second period T2 that takes 0V, a third period T3 that takes + VDD, and a fourth period T4 that takes 0V. repeat. The frequency of the drive voltage S2 is the transmission frequency _fTX , and the period is 1 / _fTX . The second period T2 and the fourth period T4 correspond to the phase difference Δφ = φ1-φ2.

When the drive voltage S <b> 2 is applied to the resonant antenna 30, a current _IL flows through the resonant antenna 30. When the resonance frequency _{f RES} of the resonant antenna 30 is tuned to the transmission frequency _{f TX,} the current _{I L} is a sine wave having a transmission frequency _{f TX,} power signal intensity corresponding to the current _{I L} from the transmitting coil _{L T} S1 is transmitted.

According to the wireless power supply apparatus 200, according to the phase difference [Delta] [phi, can control the amplitude of the current I _L, as a result, can control the intensity of the power signal S1. The reason will be explained qualitatively.

The rectangular voltages V1 and V2 are expressed by superposition of the fundamental wave and the odd-order harmonics. However, since the impedance of the resonant antenna 30 is sufficiently high in a band other than the resonance frequency, that is, the fundamental wave _fTX , It contributes little to the current _IL and the electrical signal S2 and can therefore be ignored.

When focusing only on the fundamental wave, the rectangular voltages V1 and V2 are expressed by the equations (1) and (2). However, φ1 = 0 and φ2 = Δφ.
V1 = sin (2πf _TX ) (1)
V2 = sin (2πf _TX + Δφ) (2)

Therefore, the drive voltage S2 is approximated by the equation (3).
S2 = V1-V2 = sin ( 2πf TX) -sin (2πf TX + Δφ) ... (3)

Equation (4) is obtained from the formula of the product of trigonometric functions.
S2 = 2 · cos (2πf _TX + Δφ / 2) · sin (Δφ / 2)
= A · cos (2πf _TX + Δφ / 2) (4)
However, A = 2 × sin (Δφ / 2)

That is, by changing Δφ, the voltage amplitude A of the drive voltage S2 can be controlled, and consequently the strength of the power signal S1 can be controlled. The term sin (Δφ / 2) can take a value from 0 to 1 depending on the phase difference Δφ. If the phase difference Δφ is controlled with high accuracy, a theoretically infinite dynamic range can be obtained. Can be realized.
The switching period 1 / f _TX is on the order of μs, whereas the time difference Δφ can be controlled with a few tens of ns or more precisely. Therefore, in practice, it is possible to realize a very wide dynamic range of the intensity of the electric signal S2.

For comparison, each switch is switched at the transmission frequency f _TX by so-called PWM (Pulse Width Modulation) control without controlling the phase difference Δφ as in the embodiment. ) Will be considered. In this case, when the duty ratio changes, the waveform of the drive voltage S2 becomes asymmetrical between positive and negative. As a result, in PWM control, harmonic energy that does not contribute to the electric signal S2 increases.

  In contrast to the comparative technique, the wireless power supply apparatus 200 according to the embodiment has a feature that the waveform of the drive voltage S2 is symmetric regardless of the phase difference Δφ. That is, according to the wireless power supply apparatus 200, the energy of the harmonic component can be reduced as compared with the comparative technique.

Figure 4 (a), (b) is a diagram showing the spectrum of the coil current _{I L.} FIG. 4B shows a spectrum when PWM control is performed. The amplitude of the component of the fundamental wave f _TX can be changed according to the duty ratio of the drive voltage S2.
FIG. 4A shows a spectrum when the phase difference Δφ is controlled. When the phase difference Δφ is changed to 22.5 °, 45 °, 90 °, and 180 °, the amplitude of the fundamental wave f _TX (1 MHz) can be changed similarly to the PWM control. Further, it can be seen that even-order harmonics are suppressed.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and various modifications may exist in each of those constituent elements, each processing process, and a combination thereof. Hereinafter, such modifications will be described.

The wireless power supply apparatus 200 in FIG. 2 can be grasped as follows.
The first switch SW1 and the second switch SW2 are provided at one end P1 of the resonance antenna 30 with a first rectangular voltage that switches between the high level voltage VDD and the low level voltage VSS at the first phase φ1 at the transmission frequency f _TX. It is the 1st power supply (half bridge circuit) which applies V1.
In addition, the third switch SW3 and the fourth switch SW4 are connected to the other end P2 of the resonant antenna 30 at the second phase φ2 between the high level voltage VDD and the low level voltage VSS at the transmission frequency _fTX . A second power supply (half-bridge circuit) that applies a rectangular voltage V2. The controller 36 adjusts the difference Δφ between the first phase φ1 and the second phase φ2 according to the strength of the power signal S1 to be transmitted.

  Those skilled in the art will understand that the first power supply and the second power supply can be configured in a topology different from that shown in FIG. 2, and such modifications are also included in the scope of the present invention. For example, the first power supply and the second power supply may include so-called inverters (logic inversion circuits).

  In the wireless power supply apparatus 200 of FIG. 2, the DC power source 32 is configured by a DC / DC converter so that the DC voltage VDC can be adjusted, so that the dynamic range of the intensity of the electric signal S2 can be further expanded.

  Although the present invention has been described based on the embodiments, the embodiments merely show the principle and application of the present invention, and the embodiments depart from the idea of the present invention defined in the claims. Many modifications and changes in the arrangement are allowed within the range not to be performed.

DESCRIPTION OF SYMBOLS 100 ... Wireless electric power feeding system, 200 ... Wireless electric power feeder, 300 ... Wireless electric power receiving apparatus, 10 ... AC power supply, LVDD ... 1st power supply line, LVSS ... 2nd power supply line, SW1 ... 1st switch, SW2 ... 2nd switch, SW3 3rd switch, SW4 4th switch, 30 ... Resonant antenna, 32 ... DC power supply, 34 ... H bridge circuit, 36 ... Control unit, VDD ... 1st power supply voltage, VSS ... 2nd power supply voltage, 40 ... 1st Power supply, 42 ... second power supply, L _T ... transmitting coil, C _T ... resonance capacitor, S1 ... power signal, S2 ... electric signal, V1 ... first rectangular voltage, V2 ... second rectangular voltage.

Claims (6)

A wireless power feeder that transmits a power signal having a transmission frequency including an electric field, a magnetic field, or an electromagnetic field,
A resonant antenna including a transmission coil for transmitting the power signal;
A DC power supply for applying a DC voltage between the first power supply line and the second power supply line;
A first switch provided between the first power supply line and one end of the resonant antenna; a second switch provided between the second power supply line and one end of the resonant antenna; and the first power supply line; An H-bridge circuit including a third switch provided between the other ends of the resonant antenna, and a fourth switch provided between the second power supply line and the other end of the resonant antenna;
The first switch and the second switch pair are switched at the transmission frequency in the first phase, and the third switch and the fourth switch pair are switched at the transmission frequency at the second phase. A controller that switches in phase and adjusts the difference between the first phase and the second phase according to the strength of the power signal to be transmitted;
A wireless power supply apparatus comprising: A wireless power feeder that transmits a power signal having a transmission frequency including any one of an electric field, a magnetic field, and an electromagnetic field,
A resonant antenna including a transmission coil for transmitting the power signal;
A first power source that applies a first rectangular voltage that switches between a high level voltage and a low level voltage at a first phase at the transmission frequency to one end of the resonant antenna;
A second power source that applies a second rectangular voltage that switches between a high level voltage and a low level voltage at a second phase at the transmission frequency to the other end of the resonant antenna;
A control unit that adjusts a difference between the first phase and the second phase according to the intensity of the power signal to be transmitted;
A wireless power supply apparatus comprising:   The wireless power feeder according to claim 2, wherein each of the first power source and the second power source includes a half-bridge circuit. The wireless power supply apparatus according to any one of claims 1 to 3, which transmits a power signal including any one of an electric field, a magnetic field, and an electromagnetic field;
A wireless power receiver for receiving the power signal;
A wireless power supply system comprising: A method of transmitting a power signal having a transmission frequency including any one of an electric field, a magnetic field, and an electromagnetic field from a resonant antenna including a transmission coil,
Applying a DC voltage between the first power line and the second power line;
A first switch provided between the first power supply line and one end of the resonant antenna; a second switch provided between the second power supply line and one end of the resonant antenna; and the first power supply line; Controlling an H-bridge circuit including a third switch provided between the other ends of the resonant antenna and a fourth switch provided between the second power supply line and the other end of the resonant antenna; ,
With
The controlling step includes
The first switch and the second switch pair are switched at the transmission frequency in the first phase, and the third switch and the fourth switch pair are switched at the transmission frequency at the second phase. A method of switching in phase and adjusting a difference between the first phase and the second phase according to the strength of the power signal to be transmitted. A method of transmitting a power signal having a transmission frequency including any one of an electric field, a magnetic field, and an electromagnetic field from a resonant antenna including a transmission coil,
Applying to the one end of the resonant antenna a first rectangular voltage that switches between a high level voltage and a low level voltage in a first phase at the transmission frequency;
Applying to the other end of the resonant antenna a second rectangular voltage that switches between a high level voltage and a low level voltage in a second phase at the transmission frequency;
Adjusting the difference between the first phase and the second phase according to the strength of the power signal to be transmitted;
A method comprising:

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