JP5545341B2 - Wireless power supply device - Google Patents

Description

  The present invention relates to a wireless power feeding apparatus for transmitting power wirelessly.

  Wireless power supply technology that supplies power without a power cord is drawing attention. Current wireless power transfer technologies are (A) a type that uses electromagnetic induction (for short distance), (B) a type that uses radio waves (for long distance), and (C) a type that uses magnetic field resonance (medium distance). Can be roughly divided into three types.

  The type (A) using electromagnetic induction is generally used in household appliances such as an electric shaver, but has a problem that it can be used only at a short distance of about several centimeters. The type (B) using radio waves can be used at a long distance, but has a problem that power is small. The type (C) using the resonance phenomenon is a relatively new technology, and is particularly expected from the fact that high power transmission efficiency can be realized even at a middle distance of about several meters. For example, a proposal has been studied in which a receiving coil is embedded in the lower part of an EV (Electric Vehicle) and electric power is sent in a non-contact manner from a power feeding coil in the ground. Hereinafter, the type (C) is referred to as “magnetic field resonance type”.

  The magnetic resonance type is based on a theory published by Massachusetts Institute of Technology in 2006 (see Patent Document 1). In Patent Document 1, four coils are prepared. These coils are called “exciting coil”, “power feeding coil”, “power receiving coil”, and “load coil” in order from the power feeding side. The exciting coil and the feeding coil face each other at a short distance and are electromagnetically coupled. Similarly, the power receiving coil and the load coil are also faced at a short distance and are electromagnetically coupled. Compared to these distances, the distance from the feeding coil to the receiving coil is a “medium distance”, which is relatively large. The purpose of this system is to wirelessly feed power from the feeding coil to the receiving coil.

  When AC power is supplied to the exciting coil, current also flows through the feeding coil due to the principle of electromagnetic induction. When the power feeding coil generates a magnetic field and the power feeding coil and the power receiving coil resonate magnetically, a large current flows through the power receiving coil. Due to the principle of electromagnetic induction, a current also flows through the load coil, and electric power is extracted from a load connected in series with the load coil. By using the magnetic field resonance phenomenon, high power transmission efficiency can be realized even if the distance from the power feeding coil to the power receiving coil is large.

US Publication No. 2008/0278264 JP 2006-230032 A International Publication No. 2006/022365 US Publication No. 2009/0072629

  In order to maximize the power transmission efficiency from the power feeding coil to the power receiving coil, it is necessary to generate an AC signal having a resonance frequency. For example, in Patent Document 2, a signal (rectangular wave) having a predetermined frequency is generated from an oscillator, and the frequency is further divided by 1 / n times by a frequency divider. Then, the drive bridge circuit (power feeding means) is driven by the divided signal. The inventor has conceived that the drive system of the feeding coil can be configured more simply by using the AC power itself.

  The present invention has been completed on the basis of the above recognition by the present inventor, and a main object of the present invention is to realize a drive system of a feeding coil with a simple configuration in a magnetic field resonance type wireless power feeding.

  A wireless power feeder according to the present invention is a device for wirelessly transmitting power from a power feeding coil to a power receiving coil at a resonance frequency of the power feeding coil and the power receiving coil. The apparatus includes a resonant circuit including a first coil and a capacitor connected in series, first and second switches for controlling supply of current from the first and second directions to the resonant circuit, And a power transmission control circuit that resonates the resonance circuit by alternately conducting the second switch and uses the first coil as a power supply coil to transmit AC power from the first coil to the power reception coil. The power transmission control circuit maintains the resonance state of the resonance circuit by performing feedback control of the first and second switches with AC power.

  This device can directly drive the feeding coil without using an exciting coil. Therefore, it is easy to reduce the manufacturing cost and make the configuration compact. Since the first and second switches are feedback-controlled using AC power generated by the apparatus, wireless power feeding can be easily maintained even when no other oscillation source is provided. As a result, the drive system of the power feeding system can be configured simply.

  The apparatus may further include a second coil that generates an induced current by a magnetic field generated by AC power. The power transmission control circuit may perform feedback control on the first and second switches with the induced current. Inductive current is generated in the second coil (detection coil) by the magnetic field generated by the AC power, and the first and second switches are feedback controlled using the induced current. Hard to take. For this reason, it becomes the structure which is easy to maintain a resonance state, suppressing the influence on the resonance characteristic of a feed coil.

  The power transmission control circuit may operate as an exciting coil instead of operating the coil of the resonance circuit as a power feeding coil, and supply power to a power feeding coil provided as another coil.

  The second coil may be wound around the toroidal core. Then, a coupling transformer may be formed by the first coil and the second coil by passing a part of the first coil through the toroidal core. Thus, by sharing the toroidal core between the first and second coils, an induced current can be suitably generated in the second coil.

  The apparatus may further include an effective signal generator that generates an effective signal. The power transmission control circuit may drive the first and second switches with AC power on condition that the effective signal is being generated. According to such an aspect, it becomes easy to adjust the magnitude of the AC power and the power supply period by controlling the length of the generation period of the effective signal.

  The power transmission control circuit may start driving one of the first and second switches, triggered by the generation of the valid signal. By using an effective signal as a start switch, the supply start timing of AC power can be controlled by the effective signal generator. Further, when the valid signal is stopped, the power supply may be forcibly stopped by turning off both the first and second switches.

  Another wireless power feeder according to the present invention is also a device for wirelessly transmitting power from the power feeding coil to the power receiving coil at the resonance frequency of the power feeding coil and the power receiving coil. The apparatus includes a power supply circuit including first and second current paths, a power supply coil, an exciting coil that is magnetically coupled to the power supply coil and supplies AC power supplied from the power supply circuit to the power supply coil, A power transmission control circuit is provided that supplies alternating power to the exciting coil by alternately conducting first and second switches connected in series to each of the second current paths at a resonance frequency. The power transmission control circuit maintains the supply of AC power to the exciting coil by performing feedback control of the first and second switches with AC power.

  Also in such an aspect, since the first and second switches are feedback-controlled using AC power generated by the apparatus, wireless power feeding can be easily maintained without having an oscillation source. As a result, the drive system of the power feeding system can be configured simply.

  The apparatus may further include a detection coil that generates an induced current by a magnetic field generated by AC power. The power transmission control circuit may feedback control the first and second switches with the induced current.

  The detection coil may generate an induced current by a magnetic field generated by an alternating current flowing through the feeding coil, or may generate an induced current by a magnetic field generated by an alternating current flowing through the exciting coil.

  The detection coil may be wound around a toroidal core. Then, a coupling transformer may be formed by one of the feeding coil and the exciting coil and the detection coil by passing a part of the feeding coil and the exciting coil through the toroidal core.

  The apparatus may further include an effective signal generator that generates an effective signal. The power transmission control circuit may drive the first and second switches on condition that the effective signal is being generated. Further, the power transmission control circuit may start driving either the first switch or the second switch in response to the generation of the valid signal.

  A wireless power transmission system according to the present invention includes the above-described various wireless power feeders, a power receiving coil, and a load coil that is magnetically coupled to the power receiving coil and is supplied with power received by the power receiving coil from the power feeding coil.

  It should be noted that any combination of the above-described constituent elements and a representation of the present invention converted between a method, an apparatus, a system, and the like are also effective as an aspect of the present invention.

  According to the present invention, in the magnetic field resonance type wireless power feeding technology, the drive system of the power feeding coil can be realized with a simple configuration.

1 is a system configuration diagram of a wireless power transmission system according to a first embodiment. It is an expanded block diagram of a detection coil and a feeding coil. It is a time chart which shows the change process of a voltage and an electric current. It is a time chart which shows the change process of the control potential before and behind the waveform amplifier. It is a timing chart which shows the relationship between an effective signal, a control signal, and the gate potential of each switching transistor. It is a system configuration figure as another example of the wireless power transmission system in a 1st embodiment. It is a system block diagram of the wireless power transmission system in 2nd Embodiment. It is a system configuration | structure figure of the wireless power transmission system in 3rd Embodiment. It is a system block diagram as another example of the wireless power transmission system in 3rd Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. First, a half-bridge type will be described as the first embodiment and the second embodiment. Next, a push-pull type will be described as a third embodiment. When the embodiments are not particularly distinguished, they are simply referred to as “this embodiment”.

[First embodiment: Half-bridge type]
FIG. 1 is a system configuration diagram of a wireless power transmission system 100 according to the first embodiment. The wireless power transmission system 100 includes a wireless power feeder 200, a power receiving coil circuit 130, and a load circuit 140. Wireless power supply apparatus 200 includes a feeding coil _{L 2} in a part thereof. There is a distance of about several meters between the feeding coil L ₂ and the receiving coil circuit 130. The main purpose of the wireless power transmission system 100 is to power the AC power at the wireless receiving coil circuit 130 from the feeding coil L _2. Wireless power transmission system according to the present embodiment is a system assumed to operate at 100MHz around the resonance frequency f _r. Therefore, the resonance frequency _{f r} of the feeding coil _{L 2} and the power receiving coil _{L 3} is set to 100 MHz. Note that the wireless power transmission system according to the present embodiment can be operated in a high frequency band such as an ISM (Industry-Science-Medical) frequency band.

Wireless power supply apparatus 200, without passing through the exciting coil, a circuit for directly supplying the half-bridge type AC power to the feeding coil L _2. As shown in FIG. 1, the wireless power feeder 200 is vertically symmetric. Current I _S flowing through the feeding coil L ₂ is an AC, and the direction indicated by arrow in FIG forward, the opposite direction a negative direction. The number of windings of the feeding coil _{L 2} in the present embodiment 7 times, the diameter of the wire 5 mm, the diameter of the feeding coil _{L 2} itself is 280 mm.

Receiving coil circuit 130 is a circuit in which a receiving coil L ₃ and capacitor C ₃ are connected in series. Feeding coil _{L 2} and the power receiving coil _{L 3} is face each other. Distance of the feeding coil _{L 2} and the power receiving coil _{L 3} is relatively long, about 0.2M～1m. Number of windings of the receiving coil _{L 3} in the present embodiment 7 times, the diameter of the wire 5 mm, the diameter of the power receiving coil _{L 3} itself is 280 mm. The resonance frequency _{f r} of the receiving coil circuit 130 as is the 100 MHz, The values of the receiving coil _{L 3} and capacitor _{C 3} are set. Thus, the feeding coil L ₂ and the power receiving coil L ₃ need not have the same shape. When the feeding coil L ₂ generates a magnetic field at the resonance frequency f _r, the feeding coil L ₂ and the power receiving coil L ₃ is magnetically resonate, even a large current flows through I ₃ in the receiving coil circuit 130. The direction indicated by the arrow in the figure is the positive direction, and the opposite direction is the negative direction. The flowing directions of the current I ₃ of the current I _S is reversed (reversed phase).

Load circuit 140 is a circuit for load R are connected in series with the load coil L _4. The load R in this embodiment is a light bulb. Receiving coil _{L 3} and loading coil _{L 4} are facing each other. The distance between the receiving coil _{L 3} and loading coil _{L 4} are follows relatively close 10 mm. Thus, the receiving coil L ₃ and loading coil L ₄ are electromagnetically strongly coupled to each other. The number of windings of the loading coil _{L 4} in this embodiment one, the diameter of the wire 3 mm, the diameter of the loading coil _{L 4} itself is 210 mm. When the current I ₃ flows in the power receiving coil L ₃ , an electromotive force is generated in the load circuit 140, and the current I ₄ flows in the load circuit 140. The direction indicated by the arrow in the figure is the positive direction, and the opposite direction is the negative direction. The direction of the current I _{3 and} the direction of the current I ₄ are opposite (reverse phase). That is, the current I ₄ is in phase with the current I _S. Thus, the AC power fed from the feeding coil L ₂ of the power supply circuit 200 is received by the receiving coil circuit 130 and loading circuit 140, it is taken out from the load R.

When the load R is connected in series to the power receiving coil circuit 130, the Q value of the power receiving coil circuit 130 is deteriorated. For this reason, the receiving coil circuit 130 for receiving power and the load circuit 140 for extracting power are separated. In order to increase the power transmission efficiency, it is preferable to align the center lines of the feeding coil L ₂ , the receiving coil L ₃ and the load coil L ₄ .

Next, the configuration of the wireless power supply apparatus 200 will be described. First, the drive circuit 162 is connected to the primary side of the gate drive transformer T1. Driving circuit 162 is a circuit for supplying an AC voltage operating frequency _{f o} in the transformer T1 primary coil _{L h} (driving signal DR). However, the drive circuit 162 is not an oscillator that independently generates an AC voltage. Driving circuit 162 supplies the AC voltage of the resonance frequency f _r is equal operating frequency f _o (the driving signal DR) by utilizing the AC power generated by the feeding coil L _2. Details will be described later.

The voltage waveform of the drive signal DR may be a sine wave, but will be described here as a rectangular wave. The driving signals DR, current flows alternately in both positive and negative directions in the transformer T1 primary coil L _h. Transformer T1 primary coil _{L h} and transformer T1 secondary coil _{L f,} the transformer T1 secondary coil _{L g} forms a gate-drive coupling transformer T1. By electromagnetic induction, alternating current flows in both positive and negative directions in the transformer T1 secondary coil L _f and transformer T1 secondary coil L _g. The drive circuit 162 and the gate drive transformer T1 control power transmission from the wireless power transmission system 100 to the power receiving coil circuit 130 and the like as a drive system of the wireless power transmission system 100.

One end of the transformer T1 secondary coil L _f is connected to the gate of the switching transistor Q _1, and the other end is connected to the source of a switching transistor Q _1. One end of the transformer T1 secondary coil L _g is connected to the other gate of the switching transistor Q _2, the other end is connected to the source of a switching transistor Q _2. When the driving circuit 162 generates a drive signal DR at the resonance frequency _{f r,} the respective gates of the switching transistors _{Q 1,} a switching transistor _{Q 2,} is applied alternately at voltage Vx (Vx> 0) is the resonance frequency _{f r} Is done. Therefore, the switching transistor Q _1, a switching transistor Q ₂ is turned on and off alternately at the resonance frequency f _r. While the switching transistor _{Q 1,} a switching transistor _{Q 2} is an enhancement-type MOSFET having the same characteristics (Metal Oxide Semiconductor Field Effect Transistor) , it may be other transistors such as a bipolar transistor. Other switches such as a relay switch may be used instead of the transistor.

The drain of the switching transistor _{Q 1} is, is connected to the positive pole of the power source _{V dd1.} The negative electrode of the power source _{V dd1} via the capacitor _{C 1} and the feeding coil _{L 2,} is connected to the source of the switching transistor _{Q 1.} The negative potential of the power supply V _dd1 is the ground potential. The source of the switching transistor _{Q 2} are connected to the negative pole of the power source _{V dd2.} The positive electrode of the power source _{V dd2} via a capacitor _{C 1} and the feeding coil _{L 2,} is connected to the drain of the switching transistor _{Q 2.} The potential of the positive electrode of the power supply V _dd2 is the ground potential.

The switching transistor to _{Q 1} source-drain voltage source-drain voltage _{V DS1} of, referred to as a switching transistor _Q source-drain voltage _{V DS2} a voltage between the source and drain of _2. Further, the switching transistor to Q ₁ source the current flowing between drain source drain current I _DS1, the switching transistor Q ₂ of the source-drain source-drain current the current flowing through the I _DS2. For the source / drain currents I _DS1 and I _DS2 , the direction indicated by the arrow in the figure is the positive direction, and the opposite direction is the negative direction.

Capacitor C ₁ and the feeding coil L ₂ is the value set to the current resonance at the resonance frequency f _r. In other words, the capacitor C ₁ and the feeding coil L ₂ forms a "resonance circuit" of the resonance frequency f _r. Further, due to the presence of the capacitor C ₁ and the feeding coil L ₂ , the current waveforms of the source / drain currents I _DS1 and I _DS2 are sinusoidal.

Capacitor C _Q1 between the source and drain of the switching transistor Q ₁ is connected in parallel between the source and drain of the switching transistor Q ₂ capacitor C _Q2 are connected in parallel. Capacitor C _Q1 and capacitor C _Q2 are capacitors having the same characteristics. Capacitor _{C Q1} will shape the voltage waveform of the source-drain voltage _{V DS1,} the capacitor _{C Q2} is inserted to shape the voltage waveform of the source-drain voltage _{V DS2.} Even if the capacitors C _Q1 and C _Q2 are omitted, wireless power feeding by the wireless power feeder 200 is possible. In particular, when the resonance frequency _fr is low, the influence of these capacitors is small.

When the switching transistor _{Q 1} is turned conductive (ON), the switching transistor _{Q 2} is turned non-conductive (OFF). The main current path (hereinafter referred to as “first current path 102”) at this time is a path for _returning from the power supply V _dd1 via the switching transistor Q ₁ , the feeding coil L ₂ , and the capacitor C ₁ . The switching transistor Q ₁ functions as a switch that controls conduction / non-conduction of the first current path 102.

When the switching transistor _{Q 2} is turned conductive (ON), the switching transistor _{Q 1} is turned non-conductive (OFF). The main current path (hereinafter referred to as “second current path 104”) at this time is a path for _returning from the power source V _dd2 via the capacitor C ₁ , the feeding coil L ₂ , and the switching transistor Q ₂ . The switching transistor Q ₂ functions as a switch that controls conduction / non-conduction of the second current path 104.

When the driving circuit 162 supplies a driving signal DR at the resonance frequency _{f r,} the first current path 102 and the second current path 104 is alternately turned on at the resonance frequency _{f r.} Since the capacitor C ₁ and the feeding coil L _2, which will be an alternating current of the resonance frequency f _r flows, capacitor C ₁ and the feeding coil L ₂ is a resonance state. The receiving coil circuit 130 is also a resonance circuit of the resonance frequency f _r, the feeding coil L ₂ and the power receiving coil L ₃ is magnetically resonate. At this time, the power transmission efficiency is maximized.

Near the feeding coil _{L 2,} the detection coil _{L SS} is installed. Detection coil _{L SS} is a coil which is wound _{N S} times the core 154 (toroidal core) having a penetration hole. For penetrating the core 154 also a part of the feeding coil _{L 2,} the feeding coil _{L 2} and the detection coil _{L SS} forms a coupling transformer. The AC magnetic field alternating current _{I S} of the resonance frequency _{f r} is to generate, in the detection coil _{L SS} flows induced current _{I SS} of the resonance frequency _{f r.} The current _IS and the induced current _ISS are in phase.

The resistance _{R 3} is connected to both ends of the detection coil _{L SS.} One end B of the resistor R ₃ is grounded, and the other end A is connected to the drive circuit 162 via the capacitor C ₅ and the waveform amplifier 160. Capacitor C ₅ is inserted in order to cut a DC component from the voltage waveform of the potential V _t0 of the connection point A. The potential after cutting is called a control potential V _t1 . The waveform amplifier 160 amplifies the control potential V _t1 having an analog waveform, binarizes it, and converts it into a control potential V _t2 having a digital waveform. The waveform amplifier 160 is an amplifier that outputs a saturation voltage of 5 (V) when the control potential V _t1 exceeds a predetermined threshold, for example, 0.1 (V). Therefore, even when the potential V _t1 has an analog waveform, the waveform potential 160 converts the control potential V _t1 into a digital waveform control potential V _t2 . Details will be described later with reference to FIG. The control potential V _t2 becomes an input signal to the drive circuit 162 as the control signal IN.

  The drive circuit 162 is a circuit that uses the control signal IN and the enable signal EN as input signals and the drive signal DR as an output signal. The valid signal EN is a binary signal supplied from the valid signal generator 164. The drive circuit 162 is a known circuit, and for example, an IC (Integrated Circuit) having a product number UCC37321 manufactured by Texas Instruments may be used.

When the valid signal EN changes from low level to high level, the drive signal DR changes from high level to low level. Therefore, instantaneous current flows in the direction of either the transformer T1 primary coil L _h. Since one of the switching transistors _{Q 1,} a switching transistor _{Q 2} is turned on, current flows _{I S} to either the first current path 102 or the second current path 104. Here, current _{I S} is the flow in the positive direction (the first current path 102). When the feeding coil _{L 2} flows forward current _{I S,} the induced current _{I SS} is generated in the detection coil _{L SS,} the control signal IN of high level is input to the drive circuit 162. The resonance of the resonant circuit (feeding coil _{L 2} and capacitor _{C 2),} eventually the direction of the current _{I S} is changed in the negative direction (second current path 104). At this time, a low-level control signal is input to the drive circuit 162. As a result, the control signal IN becomes a rectangular wave of the resonance frequency f _r. Further details will be described later in connection with FIG.

In a period in which the valid signal EN is maintained at a high level, the drive signal DR = the control signal IN. Since the driving signal DR is a rectangular wave, the switching transistor Q _1, a switching transistor Q ₂ are conducted alternately, the resonance state is maintained.

When the valid signal EN becomes low level, the drive signal DR is forcibly stopped. In this case, none of the switching transistor Q _1, a switching transistor Q ₂ turns off, the power supply is stopped.

When the operating frequency _{f o} of the wireless power supply apparatus 200 coincides with the resonance frequency _{f r,} the feeding coil _{L 2} AC current _{I S} flows at the resonance frequency _{f r,} in the receiving coil circuit 130 at the resonance frequency _{f r} AC current _{I 3} flows. A feeding coil _{L 2} and capacitor _{C 1,} the receiving coil _{L 3} and capacitor _{C 3} of the receiving coil circuit 130 to resonate at the same resonance frequency _{f r,} the power transmission from the power feeding coil _{L 2} to the power receiving coil _{L 3} Efficiency is maximized.

FIG. 2 is an enlarged configuration diagram of the detection coil L _SS and the feeding coil L ₂ . Figure 2 is a diagram showing a peripheral structure of the detection coil L _SS in detail. The shape of the core 154 is a cylindrical shape having a through hole, and the material thereof is a known material such as ferrite, a silicon steel plate, and permalloy. The number of turns _{N S} of the detection coil _{L SS} in this embodiment is 100 times. Some through holes of the core 154 of the feeding coil L ₂ extending therethrough. This means that the number of turns _{N P} of the feeding coil _{L 2} relative to the core 154 is one. With such a configuration, the detection coil L _SS and the feeding coil L ₂ form a coupling transformer.

Feeding coil L ₂ is the primary winding, the detection coil L _SS is the coupling transformer between them is formed by the secondary winding. The AC magnetic field alternating current _{I S} of the feeding coil _{L 2} is generating flows induced current _{I SS} of the same phase in the detection coil _{L SS.} According to the equal ampere-turn law, the magnitude of the induced current I _SS is I _S · (N _P / N _S ). Potential _{V t0} is a measurement target at one end A of the detection coil _{L SS.} Since the other end B of the detection coil L _SS is grounded, the potential V _t0 is equal to the voltage value applied to the resistor R ₃ .

FIG. 3 is a time chart showing a change process of voltage and current. A period from time t ₀ to time t ₁ (hereinafter referred to as “first period”) is a period in which the switching transistor Q ₁ is on and the switching transistor Q ₂ is off. A period from time t ₁ to time t ₂ (hereinafter referred to as “second period”) is a period in which the switching transistor Q ₁ is turned off and the switching transistor Q ₂ is turned on, and a period from time t ₂ to time t ₃ (hereinafter referred to as “second period”). , “Third period”) is a period in which the switching transistor Q ₁ is on and the switching transistor Q ₂ is off, and a period from time t ₃ to time t ₄ (hereinafter referred to as “fourth period”) is: the switching transistor Q ₁ is turned off, the switching transistor Q ₂ is a period in which an oN.

When the gate-source voltage _{V GS1} of the switching transistor _{Q 1} is greater than a predetermined threshold value _{V x,} the switching transistor _{Q 1} is a saturated state. Therefore, when the switching transistor Q ₁ is turned ON (conductive) at time t ₀ is the start timing of the first period, it starts flowing drain current I _DS1. In other words, the current _{I S} starts flowing in the positive direction (the first current path 102). The resonance circuit (feeding coil L ₂ and capacitor C ₁₎ is the current resonance, the current waveform in the first period of the current I _S does not become a rectangular wave, the rising and falling becomes gentle.

When the switching transistor Q ₁ is turned off (non-conductive) at time t ₁ which is the start timing of the second period, the source-drain current I _DS1 does not flow. Alternatively, the switching transistor _{Q 2} is turned on (conductive), the source-drain current _{I DS2} starts flowing. That is, the current _{I S} starts to flow in the negative direction (second current path 104).

The current _IS and the induced current I _SS are in phase, and the potential V _t1 is in phase with the induced current I _SS . Therefore, the voltage waveform of the current waveform and the potential V _t1 of the current I _S is synchronized. After the third period and the fourth period, the same waveform as that in the first period and the second period is repeated.

FIG. 4 is a time chart showing the changing process of the control potential V _t1 and the control potential V _t2 . In FIG. 4, it is assumed that the valid signal EN is fixed at a high level. If the instantaneous current flowing in the transformer T1 primary coil L _h, one of the switching transistors Q _1, a switching transistor Q ₂ is turned on, current I _S to one of the paths of the first current path 102 or the second current path 104 Flowing. Hereinafter, the current _{I S} flows through the first current path 102. Induced current _{I SS} is generated by the positive direction of the current _{I S} flowing in the feeding coil _{L 2.} As shown in FIG. 3, the control potential V _t1 increases in a sine wave shape. The waveform amplifier 160 amplifies the control potential V _t1 to the saturation voltage. Therefore, when the current I _S starts to flow in the positive direction (the first current path 102), the control signal IN of high level is input to the drive circuit 162.

The resonance of the resonant circuit (feeding coil _{L 2} and capacitor _{C 1),} the current _{I S} decreases gradually and tends to flow in the negative direction (second current path 104). At this time, the control potential V _t1 also gradually decreases, and the waveform amplifier 160 outputs the control potential V _t1 having the lowest potential (low level). Since the control signal IN having a low level is input to the drive circuit 162, the driving signal DR is generated at a low level, the switching transistor Q ₂ is turned on. The switching transistor _{Q 1} is turned off.

Thereafter are similar, the resonance of the resonant circuit (feeding coil L ₂ and capacitor C _1), the direction of current flow I _S changes at the resonance frequency f _r. Control potential V _t1 is changed every time the direction of flow of the current I _S changes, the switching transistor Q _1, a switching transistor Q ₂ is turned on alternately. Driving circuit 162, once after generating the resonance phenomenon, and feedback control of the switching transistor Q _1, a switching transistor Q ₂ by utilizing the resonance phenomenon. For this reason, the wireless power supply apparatus 200 can perform self-excited operation without having an oscillator.

FIG. 5 is a timing chart showing the relationship between the valid signal EN, the control signal IN, and the gate potential of each switching transistor. Enable signal EN during the period from time _{t 5} to _{t 6} is at a low level. Enable signal EN during the period from time t ₆ to t ₇ is at a high level. A period during which the valid signal EN is maintained at a low level is referred to as a “stop period”, and a period during which the valid signal EN is maintained at a high level is referred to as a “drive period”.

First, in the time t ₅ the stop period of t _6, the driving signal DR is fixed to a low level. Since no current flows in the transformer T1 primary coil L _h, none of the switching transistor Q _1, a switching transistor Q ₂ is turned off. Both the gate-source voltage _{V GS1, V GS2} is at a low level, since the resonant circuit current _{I S} does not flow, the control signal IN is also fixed at a low level.

When enabled signal EN at time t ₆ is changed from the low level to the high level, the drive signal DR is changed to the high level. Instantaneous current flows in the transformer T1 primary coil L _h, a current I _S starts to flow. When the current I _S flows, the resonant circuit starts a resonance, digital pulsed control signal IN changes at the resonance frequency f _r is produced. In the drive period, the drive signal DR changes in synchronization with the rise and fall of the control signal IN. Each time the drive signal DR changes, current flows through the transformer T1 primary coil L _h. The alternating current flowing through the transformer T1 primary coil L _h, a switching transistor Q _1, a switching transistor Q ₂ is turned on alternately. Therefore, in the driving period _{(t 7} from the time _{t 6),} I continue alternating current _{I S} of the resonance frequency _{f r} flows. Feeding coil L ₂ continues to feed the AC power of the resonance frequency f _r to the power receiving coil L _3.

When enabled signal EN at time t ₇ is changed to the low level, the drive signal DR is fixed to the low level, the current I _S does not flow. The power supply from the wireless power supply apparatus 200 is also stopped.

For wireless power supply apparatus 200, if the duty ratio is changed in the effective signal EN, it is possible to change the amount of AC power supplied from the feeding coil L _2. In the case of this embodiment, the brightness of the light bulb connected as the load R changes by changing the duty ratio of the effective signal EN.

Incidentally, instead of inductive current I _SS, when generating the control signal IN directly from the current I _S, takes a new load to the feeding coil L _2, the impedance Z of the resonance circuit to vary, Q value is degraded. It is to connect the drive circuit 162 or the like directly to the current path of the feeding coil L ₂ resonating is like measuring the vibration while touching the tuning fork. In the wireless power transmission system 100, by generating an induced current I _SS in the detection coil L _SS by using an alternating magnetic field feeding coil L ₂ is generating, it generates a control signal IN. The wireless power supply apparatus 200, in particular, since it is configured not to apply a load to the resonant circuit part, the switching transistor Q _1, a switching transistor Q ₂ may feedback control while suppressing the influence on the Q value.

Not only the feeding coil L _2, and the power receiving coil L ₃ and loading coil L ₄ forms a coupling transformer as a primary coil, may generate an induced current I _SS in the detection coil L _SS.

FIG. 6 is a system configuration diagram as another example of the wireless power transmission system 100 according to the first embodiment. The configurations denoted by the same reference numerals as those in FIG. 1 have the same or similar functions as the configurations described in FIG. In the system configuration of FIG. 1, the coupling transformer is configured by the feeding coil L ₂ and the detection coil L _SS sharing the core 154. In FIG. 6, the control potential V _t2 is extracted by the detection coil circuit 170. Detection coil circuit 170, because it does not share the core 154 such as the feeding coil L ₂ and the like, there is a merit that degree of freedom of installation is enhanced.

The detection coil circuit 170 is a circuit in which a detection coil L _SS and a resistor R ₃ are connected in series. Flux feeding coil L ₂ is generating is placed a detection coil circuit 170 so as to pass through the detection coil L _SS. As in FIG. 1, one end B of the resistor R ₃ is grounded, and the potential V _t0 is detected from the other end A. The AC magnetic field current _{I S} flowing in the feeding coil _{L 2} causes inductive current _{I SS} flows in the detection coil circuit 170. Generating a control signal IN from the potential _{V t0} generated by the induced current _{I SS.}

The purpose of installing the detection coil circuit 170 is not to be received from the power supply coil L _2, is to take out a control signal IN to be synchronized with the AC power transmitted from the feeding coil L _2. For this reason, the size of the detection coil L _SS can be made sufficiently smaller than that of the feeding coil L ₂ . The present invention is not limited to the feeding coil L _2, based on the alternating magnetic field current I ₄ flowing through the current I ₃ and loading coil L ₄ passing through the receiving coil L ₃ is to generate, to generate an induced current I _SS in the detection coil circuit 170 Thus, the control signal IN may be generated.

[Second Embodiment: Half Bridge Type]
FIG. 7 is a system configuration diagram of the wireless power transmission system 106 according to the second embodiment. In the wireless power transmission system 100 according to the first embodiment has been driven feeding coil L ₂ directly by the drive circuit 162, the wireless power transmission system 106 according to the second embodiment, the drive circuit 162 instead of the feeding coil L ₂ exciting coil to drive the L _1. The configuration of other parts of the wireless power transmission system 106 is the same as that shown in FIG. The configurations denoted by the same reference numerals as those in FIG. 1 have the same or similar functions as the configurations described in FIG.

Wireless power feeder 204 supplies AC power at the resonance frequency _{f r} in the exciting coil _{L 1.} Exciting coil _{L 1} and capacitor _{C 1} form a resonant circuit of the resonance frequency _{f r.} Feeding coil circuit 120 is a circuit in which a feeding coil L ₂ and capacitor C ₂ are connected in series. Exciting coil _{L 1} and the feeding coil _{L 2} are facing each other. Excite distance of the coil _{L 1} and the feeding coil _{L 2} are relatively close to about 10 mm. Thus, the exciting coil L ₁ and the feeding coil L ₂ are electromagnetically strongly coupled. When flow exciting coil _{L 1} to the current _{I S,} electromotive force is generated in the feeding coil circuit 120, a current flows _{I 2} in the feeding coil circuit 120. The direction indicated by the arrow in the figure is the positive direction, and the opposite direction is the negative direction. Direction and the current I ₂ direction of the current I _S is reversed (reversed phase). Current _{I 2} is much larger than the current _{I S.} The values of the feeding coil _{L 2} and capacitor _{C 2,} the resonance frequency _{f r} of the feeding coil circuit 120 may be set so as to 100kHz.

In the second embodiment, it sets up a detection coil L _SS on the side of the exciting coil L _1, to form a coupling transformer by the detection coil L _SS and the exciting coil L _1. By a magnetic field alternating current _{I S} is generated, the detection coil _{L SS} flows induced current _{I SS.} The induced current generates a control signal IN in the same manner as in the first embodiment based on the I _SS.

Also in the second embodiment, not only the exciting coil L ₁ but also a feeding transformer L ₂ , a receiving coil L ₃ , a load coil L _{4 and the} like are used as primary coils to form a coupling transformer, and an induction current I _SS is applied to the detection coil L _SS. It may be generated. The induced current I _SS may be generated by the detection coil circuit 170 described with reference to FIG.

[Third embodiment: push-pull type]
FIG. 8 is a system configuration diagram of the wireless power transmission system 108 according to the third embodiment. The wireless power transmission system 108 includes a wireless power feeder 206, a power receiving coil circuit 130, and a load circuit 140. The configuration of the wireless power feeder 206 can be broadly divided into a power supply control circuit 208, an exciting circuit 110, and a power feeding coil circuit 120. There is a distance of about several meters between the feeding coil circuit 120 and the receiving coil circuit 130. The main purpose of the wireless power transmission system 108 is to send power from the feeding coil circuit 120 to the receiving coil circuit 130. The configurations denoted by the same reference numerals as those in FIGS. 1, 6, and 7 have the same or similar functions as the configurations already described.

Exciting circuit 110 is a circuit in which an exciting coil _{L 1} and a transformer T2 secondary coil _{L i} are connected in series. Exciting circuit 110 receives AC power through the transformer T2 secondary coil L _i of the power control circuit 208 side. Transformer T2 secondary coil L _i forms a transformer T2 primary coil L _d and transformer T2 primary coil L _b with coupling transformer T2, it receives AC power by electromagnetic induction. The number of turns of the exciting coil L ₁ is 1, the diameter of the conducting wire is 3 mm, and the diameter of the exciting coil L ₁ itself is 210 mm. The current I ₁ flowing through the exciting circuit 110 is an alternating current, and the direction indicated by the arrow in the figure is the positive direction and the opposite direction is the negative direction.

The feeding coil circuit 120 is the same as the configuration of the feeding coil circuit 120 shown in the second embodiment, and is a circuit that resonates at a resonance frequency f _r = 100 kHz. The configurations of the receiving coil circuit 130 and the load circuit 140 are the same as the configurations shown in the first and second embodiments.

Power supply control circuit 208 is a circuit of a push-pull type operating at operating frequency f _o, a vertically symmetrical as shown in FIG. 13. Exciting circuit 110 receives AC power operating frequency _{f o} from the power control circuit 208. In this case, the exciting circuit 110, feeding coil circuit 120, receiving coil circuit 130 and loading circuit 140, the operating frequency _{f o} current _I 1 ~I ₄ of flows. When the operating frequency _{f o} and the resonance frequency _{f r} is matched, i.e., when the operating frequency _f o = 100kHz, the feeding coil circuit 120 and receiving coil circuit 130 for a magnetic field resonance, power transmission efficiency is maximized. The drive circuit 162 and the gate drive transformer T1 control power transmission from the wireless power feeder 206 to the power receiving coil circuit 130 as a drive system of the wireless power transmission system 108.

A drive circuit 162 is connected to the primary side of the gate drive transformer T1 included in the power supply control circuit 208. Driving circuit 162 generates an AC voltage of the resonance frequency _{f r} is equal operating frequency _{f o} (the drive signal DR). The driving signals DR, current flows alternately in both directions of positive and negative in the transformer T1 primary coil L _h. Transformer T1 primary coil _{L h} and transformer T1 secondary coil _{L f,} the transformer T1 secondary coil _{L g} forms a gate-drive coupling transformer T1. By electromagnetic induction, alternating current flows in both positive and negative directions in the transformer T1 secondary coil L _g and the transformer T1 primary coil L _h.

The secondary coil of the transformer T1 is grounded at the midpoint. That is, one ends of the transformer T1 secondary coil L _g of the transformer T1 secondary coil L _f are connected to each other and grounded as it is. The other end of the transformer T1 secondary coil L _f is connected to the gate of the switching transistor Q _1, the other end of the transformer T1 secondary coil L _g is connected to another gate of the switching transistor Q _2. The source of the switching transistor Q ₁ of the source and the switching transistor Q ₂ is also grounded. Therefore, the drive circuit 162 generates the AC voltage (driving signal DR) at the resonance frequency _{f r,} the respective gates of the switching transistors _{Q 1,} a switching transistor _{Q 2,} voltage Vx (Vx> 0) is the resonance frequency f _Applied alternately at _r . That is, the switching transistor _{Q 1,} a switching transistor _{Q 2} is turned on and off alternately at the resonance frequency _{f r.}

The drain of the switching transistor _{Q 1} is, connected in series with the transformer T2 primary coil _{L d.} Similarly, the drain of the switching transistor Q ₂ are connected transformer T2 primary coil L _b in series. The connection point of the transformer T2 primary coil _{L d} and transformer T2 primary coil _{L c,} the inductor _{L a} for smoothing is connected, further, the power supply _{V dd} is connected. Also, between the source and drain of the switching transistor Q ₁ capacitor C _Q1 are connected in parallel, between the source and drain of the switching transistor Q ₂ capacitor C _Q2 are connected in parallel.

Capacitor _{C Q1} will shape the voltage waveform of the source-drain voltage _{V DS1,} the capacitor _{C Q2} is inserted to shape the voltage waveform of the source-drain voltage _{V DS2.} Even if the capacitors C _Q1 and C _Q2 are omitted, wireless power feeding by the wireless power feeder 206 is possible. In particular, when the resonance frequency _fr is low, it is easy to maintain power transmission efficiency even if these capacitors are omitted.

The input impedance of the exciting circuit 110 is 50 (Ω). Further, the output impedance of the power supply control circuit 208 is set to the number of windings of the transformer T2 primary coil L _b and the transformer T2 primary coil L _d to be equal to the the input impedance 50 (Ω). When the output impedance of the power supply control circuit 208 matches the input impedance of the exciting circuit 110, the output of the wireless power feeder 206 is maximized.

When the switching transistor _{Q 1} is turned conductive (ON), the switching transistor _{Q 2} is turned non-conductive (OFF). The main current path at this time (hereinafter referred to as “first current path 112”) is from the power supply V _dd to the ground via the smoothing inductor L _a , the transformer T2 primary coil L _d , and the switching transistor Q ₁ . It becomes a route to reach. The switching transistor Q ₁ functions as a switch that controls conduction / non-conduction of the first current path 112.

When the switching transistor _{Q 2} is turned conductive (ON), the switching transistor _{Q 1} is turned non-conductive (OFF). The main current path of this time (hereinafter, referred to as "second current path 114") includes an inductor L _a a smoothing from the power supply V _dd, transformer T2 primary coil L _b, to ground via a switching transistor Q ₂ It becomes a route to reach. The switching transistor Q ₂ functions as a switch that controls conduction / non-conduction of the second current path 114.

In the third embodiment, the detection coil L _SS is installed on the side of the exciting circuit 110, and a coupling transformer is formed by a part of the exciting circuit 110 and the detection coil L _SS . The induced current I _SS flows through the detection coil L _SS by the magnetic field generated by the alternating current I ₁ . Based on this induced current I _SS , the control signal IN is generated by the same method as in the first embodiment or the second embodiment.

FIG. 9 is a system configuration diagram as another example of the wireless power transmission system 108 in the third embodiment. The configurations denoted by the same reference numerals as those in FIG. 8 have the same or similar functions as the configurations described in FIG. In the system configuration of FIG. 8, the exciting circuit 110 and the detection coil L _SS share the core 154 to form a coupling transformer. However, in the system configuration of FIG. 9, the feeding coil circuit 120 and the detection coil L _SS connect the core 154. A shared trans is formed by sharing.

Not only the exciting circuit 110 and the feeding coil circuit 120 but also a receiving transformer circuit 130, a load circuit 140, etc. may be formed on the primary coil side to form a coupling transformer, and the induction current I _SS may be generated in the detection coil L _SS . The induced current I _SS may be generated by the detection coil circuit 170 described with reference to FIG.

  The wireless power transmission systems 100, 106, and 108 have been described based on the embodiments. In this embodiment, the AC power is not controlled by an external oscillator, but a control signal IN is generated from the generated AC power, and the wireless power feeding apparatus is feedback-controlled by this control signal IN. For this reason, since AC power can be continuously supplied without installing an oscillator, the system configuration is simplified.

Feeding coil L _2, the power receiving coil L _3, the loading coil L _4, to resonate either at the same resonant frequency f _r, Q value when connecting any load to these coils will be sensitive. The same applies to the case of using the exciting coil L _1. In the present embodiment, AC power to be transmitted / received is not directly fed back to the drive circuit 162, but an induction current I _SS is generated in the detection coil L _SS by an AC magnetic field generated during power transmission / reception, and this induction current I _The drive circuit 162 is operated by _SS . For this reason, it becomes easy to suppress the influence with respect to the resonance characteristic (Q value) of feedback control.

Further, even if become oscillation stop for some reason, by varying the effective signal generator 164 is enabled signal EN from the low level to the high level, current can flow in the transformer T1 primary coil L _h. Enable signal generator 164 can control the valid signal EN at a low frequency that is much higher than the resonance frequency f _r.

Even when the power supplies V _dd1 , V _dd2 , and V _dd are constant power supplies, the magnitude of the AC power can be controlled by adjusting the duty ratio of the effective signal generator 164. Therefore, the cost of the entire system can be easily reduced.

  The present invention has been described based on the embodiments. The embodiments are exemplifications, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. .

100, 106, 108 Wireless power transmission system 102, 112 First current path 104, 114 Second current path 110 Excite circuit 120 Feed coil circuit 130 Receive coil circuit 140 Load circuit 154 Core 160 Waveform amplifier 162 Drive circuit 164 Effective signal generator 170 Detection coil circuit 200, 204, 206 Wireless power feeder 208 Power supply control circuit

Claims (8)

An apparatus for wirelessly transmitting power from the power supply coil to the power reception coil at a resonance frequency of the power supply coil and the power reception coil,
A resonant circuit including a first coil and a capacitor connected in series and resonating at the resonant frequency;
A first switch that controls the supply of current from the first direction to the resonant circuit;
A second switch for controlling supply of current from a second direction to the resonant circuit;
The resonance circuit is resonated by alternately conducting the first and second switches at the resonance frequency, and the first coil is used as the feeding coil, and AC power is supplied from the first coil to the receiving coil. A power transmission control circuit for transmitting power;
An effective signal generation circuit for generating an effective signal for setting a drive period in which the first and second switches can be driven and a stop period in which the first switch cannot be driven;
The duty ratio of the driving period and the stop period in the effective signal can be changed,
The wireless power feeding apparatus, wherein the power transmission control circuit maintains the resonance state of the resonance circuit by performing feedback control of the first and second switches with the AC power during the driving period. 2. The wireless power feeding apparatus according to claim 1 , wherein the power transmission control circuit starts driving one of the first and second switches in response to generation of the effective signal. A second coil for generating an induced current by a magnetic field generated by the AC power;
The power transmission control circuit, a wireless power supply apparatus according to claim 1 or 2, characterized in that feedback control of the first and the second switch by the induced current. The power transmission control circuit supplies the AC power from the power supply coil to the power reception coil by supplying the AC power from the first coil to the power supply coil that is a coil different from the first coil. wireless power feeder according to any one of claims 1 to 3, characterized in that the power transmission. An apparatus for wirelessly transmitting power from the power supply coil to the power reception coil at a resonance frequency of the power supply coil and the power reception coil,
A power supply circuit including first and second current paths;
The feeding coil;
An exciting coil that is magnetically coupled to the power supply coil and supplies AC power supplied from the power supply circuit to the power supply coil;
A power transmission control circuit that supplies the alternating current power to the exciting coil by alternately conducting first and second switches connected in series to the first and second current paths at the resonance frequency, and
An effective signal generation circuit for generating an effective signal for setting a drive period in which the first and second switches can be driven and a stop period in which the first switch cannot be driven;
The duty ratio of the driving period and the stop period in the effective signal can be changed,
The wireless power feeding apparatus, wherein the power transmission control circuit maintains the resonance state of the resonance circuit by performing feedback control of the first and second switches with the AC power during the driving period. The wireless power feeding apparatus according to claim 5 , wherein the power transmission control circuit starts driving one of the first switch and the second switch when the effective signal is generated. A detection coil that generates an induced current by a magnetic field generated by the AC power;
The wireless power feeding apparatus according to claim 5 , wherein the power transmission control circuit performs feedback control of the first and second switches by the induced current. The wireless power feeding apparatus according to claim 7 , wherein the detection coil is a coil that generates the induced current by a magnetic field generated by an alternating current flowing through the power feeding coil.

Images