JP2008312357A - Inductive power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inductive power supply system using a resonant antenna system that matches at a relatively low impedance and efficiently transmits spacial power. <P>SOLUTION: At least either of a transmitting antenna and a receiving antenna transmits spacial energy via an endpoint having antenna obtained by winding a wire having both ends in a coil shape and connecting a feeder line to a midpoint of the wire. This makes it possible to match impedance with a slightly low value with which the impedance can be easily matched with the impedance of the power supply circuit of an electronic device connected to the antenna for energy transmission. The matched impedance can be controlled by adding an additional loop wire in parallel to the feeding point of the endpoint having antenna at which the feeder line is connected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inductive power supply system that supplies electric power to an electric device across a space via wireless induction means.

  An inductive power supply system transmits electric energy in the air from one device having a primary winding to another device spaced apart by generating electromagnetic induction in a secondary winding installed in the device. . The inductive power supply system transmits power without bringing the electrical terminals of these devices into contact with each other by supplying power to the secondary winding from the primary winding that is opposed across the space. There is an advantage that contact failure does not occur. Taking advantage of this advantage, inductive power supply systems are used for toothbrushes and mobile phones.

  In Patent Document 1, a conventional inductive power supply system transmits energy in a power supply device from a primary winding installed in a power supply device to a secondary winding installed in a power supplied device by electromagnetic induction. The secondary winding of the power supplied device is physically spaced from the primary winding of the power supply device and is inductively coupled through the atmosphere. The secondary winding of the power-supplied device uses a closed loop coil that connects both ends to the terminals of the electronic circuit.

  Further, in Patent Document 2, a spiral antenna is installed in a power-supplied device instead of a secondary winding, an electromagnetic wave having a wavelength four times the length is supplied from a power supply device, and the spiral antenna is resonated with the antenna. The effective area of was increased, and the spatial energy of the electromagnetic waves supplied from the power supply device was absorbed.

The known literature is described below.
JP-T-2006-517778 JP-T-2006-526979

  However, in the technique of Patent Document 1, when the center position of the primary winding and the secondary winding is deviated, a part of the magnetic flux generated by the primary winding does not pass through the secondary winding. There is a problem that the entire power supplied to the primary winding by the circuit cannot be supplied to the power-supplied device provided with the secondary winding. In addition, if the distance between the primary winding coil and the secondary winding coil is increased, a part of the magnetic flux generated by the primary winding does not pass through the secondary winding, and all of the electric power passes through the secondary winding. There is a problem that it becomes impossible to supply power to the installed power supplied device.

  Further, in the technique of Patent Document 2, since the spiral antenna has a power supply line connected to both ends of the wiring, the impedance of the power supply point where the power supply line is connected to the antenna increases when the spiral antenna resonates. Since the voltage of the power supplied to the feeder line becomes high, there is a problem that an electronic component used in the inductive power feeding system that transmits power with the spiral antenna requires a large withstand voltage characteristic.

  Therefore, the problem to be solved by the present invention is to obtain an induction power feeding system using a resonant antenna system that transmits spatial power with an efficiency that can be matched with a relatively low impedance.

  In order to solve this problem, the present invention provides a system for transmitting energy from a transmitting antenna to a receiving antenna, and at least either the transmitting antenna or the receiving antenna has a wire having both ends wound in a coil shape. An inductive power feeding system using an end point holding antenna formed by connecting a feeding line in the middle of the wiring.

  Further, the present invention is the above inductive power feeding system, wherein an additional loop wiring is added in parallel to a feeding point to which the feeding line of the end point holding antenna is connected.

  Further, the present invention is the above inductive power feeding system, wherein both electrodes of the capacitor are connected to the both ends of the end point holding antenna.

  The present invention provides a power supply circuit for an electronic device connected to an antenna by winding a wire having both ends in a coil shape and transmitting spatial energy using an antenna in which a feed line is connected to the middle of the wire. There is an effect that energy can be transmitted between antennas matched with a low impedance that is easily matched to the impedance. In addition, the present invention has an effect of freely adjusting the matching impedance at which the antenna transmits and receives energy with the maximum efficiency by adding an additional loop wiring in parallel to the connection portion of the feeder line of the antenna. . Thereby, there is an effect that the impedance of the energy transmission system using the antenna of the present invention can be easily matched with the impedance of the electronic device.

<First Embodiment>
FIG. 1 shows a block diagram of an inductive power supply system according to a first embodiment of the present invention. The inductive power supply system includes a power supply circuit 2 connected to the transmission antenna 1 and a load circuit 4 connected to the reception antenna 3, and supplies power from the non-contact power supply circuit 2 to the load circuit 4. FIG. 2 shows the shapes of the transmitting antenna 1 and the receiving antenna 3 and the arrangement structure. In FIG. 2, as the transmission antenna 1, the transmission antenna 1 that feeds power from the power supply circuit 2 to the center of the wiring of the coil of the three-winding coil of 41 mm in length and width is opened. The coil of the transmission antenna 1 is made of copper, and a coil having a wiring width of 1 mm and a thickness of 20 μm is used. The receiving antenna 3 is also formed of a coil having the same shape as the transmitting antenna 1, and power is taken out from the center of the coil wiring to the load circuit 4. The transmitting antenna 1 and the receiving antenna 3 are arranged in parallel with a distance of 10 mm.

  FIG. 3 shows a graph of the simulation result of the power transmission efficiency from the power supply circuit 2 to the load circuit 4 in this embodiment. The power transmission efficiency represents S21 in dB (decibel). In the case of 0 dB, 100% power is transmitted. In the case of -3 dB, 50% power is transmitted. In the case of -10 dB, 10% power is transmitted. FIG. 3 shows a graph of power transmission efficiency for various impedances Z when the output impedance Z1 of the power supply circuit 2 and the input impedance Z2 of the load circuit 4 are equal. In the present embodiment, power transmission is performed at 258 MHz, which is the frequency of the higher peak of the two peaks in the graph of FIG. The frequency of these two peak peaks changes by changing the distance between the transmitting antenna 1 and the receiving antenna 3. The response to the frequency change is by feeding back the resonance current of the transmission antenna 1 to a high-frequency oscillation circuit that supplies the transmission antenna 1, so that the power supply circuit 2 oscillates the frequency that matches the resonance frequency of the antenna pair to generate power. Can be supplied. From the simulation result graph, it can be seen that S21 having a frequency of 258 MHz is −1 dB when Z is 5Ω, and can transmit about 80% of power. When Z is 20Ω, -0.2 dB is about 95%, and when Z is 100Ω, it is -0.4 dB and about 91% is transmitted.

(Modification 1)
FIG. 4 is a graph showing the power transmission efficiency when the output impedance Z1 of the power supply circuit 2 is 30Ω, the input impedance Z2 of the load circuit 4 is 60Ω, and the impedances of the power supply circuit 2 and the load circuit 4 are different. . Thus, even if both impedances differ, S21 in the case of frequency 258MHz is -0.64dB, and about 86% of electric power can be transmitted.

  As described above, when power is transmitted at a high frequency of 258 MHz using the transmitting antenna 1 and the receiving antenna 3, the power is efficiently used if the impedances Z1 and Z2 of the power supply circuit 2 and the load circuit 4 are within a predetermined range. It can be transmitted well. This effect is an effect obtained when power is transmitted between a pair of antennas that are close to each other at a sufficiently short distance compared to the wavelength at which the antenna resonates. In the present embodiment, the wavelength of the electromagnetic field having a frequency of 258 MHz is a wavelength of about 1.2 m, the distance between the antenna pair resonating at that frequency is 10 mm, and the distance is about 1/100 of the wavelength. The interval is sufficiently shorter than that. In the present embodiment, power can be transmitted in a non-contact manner with a gap of 10 mm. For example, an in vitro power supply circuit is connected to the receiving antenna 24 embedded in the living body and the load circuit 4 of the apparatus with the living tissue separated. There is an effect that power can be supplied to an in-vivo device cordlessly across a living tissue having a thickness of 2 to 10 mm. Since the receiving antenna 24 embedded in the living body is a thin antenna having a length and width of 41 mm and a thickness of 20 μm, the volume occupied in the living body is small and the affinity to the living body is good.

<Second Embodiment>
In the second embodiment, as the transmission antenna 1, a transmission antenna 1 is used in which both end points of a wiring of seven coils of 470 mm in length and breadth are opened and power is supplied from the power supply circuit 2 to the center of the wiring of the coil. This coil is made of copper, and has a coil wiring width of 10 mm and a thickness of 50 μm. The receiving antenna 3 is also formed of a coil having the same shape as the transmitting antenna 1, and power is taken out from the center of the coil wiring to the load circuit 4. The transmitting antenna 1 and the receiving antenna 3 are arranged in parallel with a distance of 100 mm.

  FIG. 5 shows a graph of a simulation result of the power transmission efficiency from the power supply circuit 2 to the load circuit 4 in this embodiment. The power transmission efficiency represents S21 in dB (decibel). FIG. 5 shows a graph of power transmission efficiency for various impedances Z when the output impedance Z1 of the power supply circuit 2 and the input impedance Z2 of the load circuit 4 are equal. In the present embodiment, power is transmitted at 10.6 MHz which is the frequency of the lower peak of the two peaks in the graph of FIG. From the graph of the simulation result, it can be seen that S21 having a frequency of 10.6 MHz is −1 dB when Z is 4Ω, and can transmit about 80% of power. When Z is 30Ω, -0.2 dB is about 95%, and when Z is 120Ω, it is -1.06 dB and about 78% is transmitted.

  In the present embodiment, the wavelength of the electromagnetic field having a frequency of 10.6 MHz is a wavelength of about 28 m, the distance between the antenna pair resonating at the frequency is 100 mm, and the distance is about 1/300 of the wavelength. The interval is sufficiently shorter than that. In this embodiment, there is an effect that power can be efficiently transmitted in a non-contact manner with a gap of 100 mm. For example, a wall having a thickness of about 100 mm from the power circuit 2 in the house is connected to the load circuit 4 of an outdoor device such as a lighting device or a display device outside the house without making a hole for wiring on the wall of the house. There is an effect that power can be supplied in a contactless manner.

<Third Embodiment>
In the third embodiment, as shown in FIG. 6, the transmitting antenna 1 is configured by connecting both ends of a 37 mm □ one-turn coil wire with a 3 pF capacitor. The central portion of the wiring of the coil of the transmission antenna 1 is connected to the power supply circuit 2. The receiving antenna 3 is the same as the first embodiment, and uses the receiving antenna 3 in which both end points of the wiring of the three-winding coil of 41 mm in length and width are open. The one-turn coil of the transmission antenna 1 is shorter than the wiring length of the three-turn coil of the reception antenna 3, but resonates at the same frequency as the reception antenna 3 by connecting both ends of the transmission antenna 1 with 3 pF capacitors. Since the coil of the transmission antenna 1 is a single coil and the coil of the reception antenna 3 is three, the impedance of the load circuit 4 on the reception antenna 3 side is higher than the impedance on the transmission antenna 1 side. Has the effect of matching.

  In FIG. 7, the graph of the simulation result of the transmission efficiency of the electric power from the power supply circuit 2 to the load circuit 4 of this embodiment is shown. FIG. 7 shows a graph of power transmission efficiency for various impedances by changing the output impedance Z1 of the power supply circuit 2 and the input impedance Z2 of the load circuit 4. In the present embodiment, power is transmitted at 277 MHz, which is the frequency of the higher peak of the two peaks in the graph of FIG. From the simulation result graph, S21 having a frequency of 277 Hz has a good impedance match when Z1 is 0.2Ω and Z2 is 1.6Ω, and S21 at that time is −0.6 dB, which is about 87%. It can be seen that power can be transmitted. When Z1 is 4Ωm, Z2 matches 32Ω well, S21 is −0.07 dB and about 98% of power can be transmitted, and Z2 that matches when Z1 is 25Ω is 200Ω, and S21 at that time Is -0.63 dB, and about 86% of power can be transmitted. As described above, as a result of simulation, energy can be efficiently transmitted between the output impedance Z1 of the power supply circuit 2 and the input impedance Z2 of the load circuit 4 when Z2 = Z1 × 8. We obtained knowledge proportional to the square of the number of turns of the coil.

  FIG. 8 is a graph showing the value of S21 at 277 MHz when the horizontal axis represents impedance Z2 (which matches 8 times Z1 well). Symbols (a) to (c) in FIG. 8 represent the cases of FIGS. 7 (a) to (c). As shown in FIG. 8, this inductive power feeding system can perform efficient energy transmission by using a predetermined range of impedance for the power supply circuit 2 and the load circuit 4.

  In the present embodiment, by connecting both ends of the transmission antenna 1 with capacitors, the resonance frequency can be lowered, and the transmission antenna 1 having a short antenna length can be used by resonating at the same frequency as the reception antenna 3. There is. The resonance frequency of the receiving antenna 3 can also be lowered by connecting both ends of the coil wiring with capacitors. Thus, by connecting a capacitor to both ends of an antenna formed of coiled wiring, the resonant frequency of the antenna can be lowered. In this embodiment, the case where energy is transmitted from the power supply circuit 2 to the load circuit 4 in a non-contact manner using induction of an electromagnetic field of 277 MHz is shown. However, both ends of the reception antenna 3 are connected by a capacitor, and the transmission antenna By making the capacitance of the capacitor connecting both ends of 1 higher than 3 pF, the resonance frequency of the antenna is lowered by an order of magnitude, and there is an effect that energy can be transmitted by the electromagnetic field of the low frequency.

<Fourth Embodiment>
In the fourth embodiment, as shown in FIG. 9, as the transmitting antenna 1 and the receiving antenna 3, both end points of 14-winding coil wiring are opened on both sides of 47 mm in length and width, and the power circuit 2 is arranged at the center of the coil wiring. A transmission antenna 1 that feeds power and a reception antenna whose center is connected to the load circuit 4 are used. As shown in FIG. 9, the transmitting antenna 1 and the receiving antenna 3 are provided side by side at a distance of 20 mm. That is, the distance between the centers of both antennas is 67 mm, which is larger than the antenna size of 47 mm.

  In the present embodiment, when the output impedance Z1 of the power supply circuit 2 and the input impedance Z2 of the load circuit 4 are equal impedance Z = 7Ω, the efficiency of power transmission at the resonance frequency is maximized. FIG. 10 shows a graph of the simulation result of the power transmission efficiency from the power supply circuit 2 to the load circuit 4 in that case. In the present embodiment, power is transmitted at a peak frequency of 23.8 MHz in the graph of FIG. From the graph of the simulation result, S21 is -0.73 dB, and about 85% of power can be transmitted.

  In this embodiment, the wavelength of the electromagnetic field having a frequency of 23.8 MHz is a wavelength of about 13 m, and an antenna pair that resonates at that frequency is provided 20 mm laterally, and the center distance between both antennas is 67 mm. The interval is approximately 1/190 of that of the wavelength, and is sufficiently shorter than the wavelength. In the present embodiment, even when the coiled antennas are provided side by side as described above and the distance is larger than the dimension of the antenna, power can be transmitted with an efficiency of about 85%. In addition, as the distance between the antennas increases, in order to efficiently transmit power, it is necessary to lower the impedances of the power supply circuit 2 and the load circuit 4 for matching. Lowering the impedance has the effect of efficiently transmitting power.

<Fifth Embodiment>
In the fifth embodiment, as shown in FIG. 11, as a transmitting antenna 1 and a receiving antenna 3, an additional loop wiring of 13 mm □ is connected in parallel to the feeding point where the feeding line is connected in the central portion of the antenna of the sixth embodiment. Add By adding this wiring, the output impedance Z1 of the power supply circuit 2 that maximizes the efficiency of power transmission at the resonance frequency and the input impedance Z2 of the load circuit 4 become 16Ω, which is about twice that of the sixth embodiment. Become. By changing the length (size) of the additional loop wiring, the impedance that maximizes the efficiency of power transmission can be freely adjusted. In the fourth embodiment, the impedance that maximizes the efficiency of power transmission is 7Ω, which is a low value. However, in this embodiment, an additional loop wiring is connected in parallel to the feeding points of the transmitting antenna 1 and the receiving antenna 3. By adding, there is an effect that the impedance matching with the power transmission can be freely increased to an appropriate size that is easy to use.

  The present invention can be applied to an application for supplying inductive energy across a wall to a display device or the like. In addition, the non-invasive system configuration for a living body can be applied to an application for supplying energy to an electronic device embedded in the living body.

1 is a block diagram of an inductive power supply system according to a first embodiment of the present invention. It is the top view and side view of a transmitting antenna and a receiving antenna of the induction power feeding system of the 1st Embodiment of this invention. It is a graph of the frequency characteristic of the power transmission efficiency of the 1st Embodiment of this invention. It is a graph of the frequency characteristic of the power transmission efficiency of the modification 1 of the 1st Embodiment of this invention. It is a graph of the frequency characteristic of the power transmission efficiency of the 2nd Embodiment of this invention. It is the top view and side view of a transmitting antenna and a receiving antenna of the induction power feeding system of the 3rd Embodiment of this invention. It is a graph of the frequency characteristic of the power transmission efficiency of the 3rd Embodiment of this invention. It is a graph of the impedance characteristic of the power transmission efficiency of the 3rd Embodiment of this invention. It is a top view of the transmitting antenna and receiving antenna of the induction power feeding system of the 4th Embodiment of this invention. It is a graph of the frequency characteristic of the power transmission efficiency of the 4th Embodiment of this invention. It is a top view of the transmitting antenna and receiving antenna of the induction power feeding system of the 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transmission antenna 2 ... Power supply circuit 3 ... Reception antenna 4 ... Load circuit

Claims (3)

  In a system for transmitting energy from a transmission antenna to a reception antenna, at least one of the transmission antenna and the reception antenna is formed by winding a wire having both ends in a coil shape and connecting a feeding line in the middle of the wiring. An inductive power feeding system using an end-point holding antenna.   The induction power feeding system according to claim 1, wherein an additional loop wiring is added in parallel to a feeding point to which the feeding line of the end point holding antenna is connected.   The induction power supply system according to claim 1, wherein both electrodes of a capacitor are connected to the both ends of the end point holding antenna.

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