JP5799656B2 - Power transmission system - Google Patents

Description

The present invention relates to power transmission system that transmits power through electric field coupling.

  As a typical system for transmitting power between two devices in close proximity to each other, there is a magnetic field coupling type power transmission system that uses a magnetic field to transmit power from a primary coil of a power transmission device to a secondary coil of a power reception device. Are known. However, when power is transmitted by magnetic field coupling, since the magnitude of magnetic flux passing through each coil greatly affects the electromotive force, high accuracy is required for the relative positional relationship between the primary coil and the secondary coil. In addition, since the coil is used, it is difficult to reduce the size of the apparatus.

  On the other hand, there is also an electric field coupling type wireless power transmission system that transmits electric power from a coupling electrode on the power transmission unit side to a coupling electrode on the load unit side using a quasi-electrostatic field as described in Patent Documents 1 to 3. Are known. In this system, power is transmitted from the coupling electrode of the power transmission apparatus to the coupling electrode of the power reception apparatus via an electric field. In this method, the relative positional accuracy of the coupling electrode is relatively loose, and the coupling electrode can be reduced in size and thickness.

  FIG. 10 is a diagram showing a basic configuration of the power transmission system of Patent Document 1. In FIG. This power transmission system includes a power transmission device and a power reception device. The power transmission device includes a power transmission circuit 1, a passive electrode 2, and an active electrode 3. The power receiving device includes a power receiving circuit 5, a passive electrode 7, and an active electrode 6. Then, when the active electrode 3 of the power transmission device and the active electrode 6 of the power reception device come close to each other through the high voltage electric field region 4, the two electrodes are subjected to electric field coupling.

Special table 2009-531009 JP 2009-296857 A JP 2009-089520 A

  In an electric field coupling type non-contact power transmission system, compared with a magnetic field coupling type non-contact power transmission system, a power transmission device and a power reception device are coupled with high impedance. A low-loss resonance circuit is used, and an overvoltage may be generated in the coupling electrode on the power receiving device side due to a coupling state or a variation in load impedance. Here, the overvoltage is an abnormal voltage, which is a voltage exceeding the rated voltage applied to the coupling electrode.

The present invention is to prevent the occurrence of an overvoltage in the contactless power transmission system of electric field coupling type, it is an object of the voltage applied to the coupling electrode to provide a power transmission system to be suppressed within a certain range.

(1) A power receiving device of the present invention receives power from a power transmission device including a power transmission device side coupling electrode composed of an active electrode and a passive electrode, and a high frequency high voltage generation circuit connected to the power transmission device side coupling electrode. A device that receives power,
A power receiving device side coupling electrode electrically coupled to the power transmission device side coupling electrode, and a load circuit connected to the power receiving device side coupling electrode;
The load circuit includes a step-down transformer connected to the power receiving device side coupling electrode, and a discharge-type overvoltage protection device connected between the power receiving device side coupling electrode and a primary coil of the step-down transformer. Features.

(2) The discharge-type overvoltage protection device includes: a cavity provided in an insulating ceramic body; first and second discharge electrodes exposed and opposed in the cavity; and the first and second discharge electrodes in the cavity. An ESD protection device comprising a discharge auxiliary electrode provided to electrically connect the two discharge electrodes,
The discharge auxiliary electrode preferably includes metal particles whose surfaces are coated with an inorganic oxide and semiconductor particles.

(3) The power transmission system of the present invention is configured to transmit power from a power transmission device including a power transmission device side coupling electrode composed of an active electrode and a passive electrode, and a high frequency high voltage generation circuit connected to the power transmission device side coupling electrode. A power receiving device for receiving the power, an active electrode and a passive electrode, a power receiving device side coupling electrode coupled to the power transmission device side coupling electrode, and a high frequency high voltage for applying a high frequency high voltage to the power transmission device side coupling electrode A power transmission device having a generation circuit,
The voltage of the power transmission device side coupling electrode or the input current of the high frequency high voltage generation circuit is measured, and the voltage of the power reception device side coupling electrode exceeds the threshold voltage of the discharge type overvoltage protection device, so that the discharge type overvoltage protection device It is characterized by comprising an overvoltage control means for detecting a discontinuous point of the voltage induced in the power transmission device side coupling electrode due to a sudden change in impedance of the coupling electrode due to discharge of the battery and performing overvoltage control.

(4) Preferably, the overvoltage control means lowers the output voltage of the high frequency high voltage generation circuit or stops voltage output.

  According to the present invention, when the voltage induced in the power receiving device side coupling electrode exceeds the threshold voltage, the discharge type overvoltage protection device is discharged and short-circuited. Generation of voltage can be prevented.

  In particular, a discharge-type overvoltage protection device includes a cavity provided in a glass ceramic body, first and second discharge electrodes exposed and opposed in the cavity, and the first and second discharge electrodes in the cavity. If it is composed of an ESD protection device composed of a discharge auxiliary electrode provided so as to be electrically connected, the electrostatic capacity is small and the stray capacitance of the coupling electrode on the power receiving device side is not increased. In addition, the power transmission efficiency can be increased.

FIG. 1 is an external perspective view of a power transmission system 401 according to the first embodiment. 2A is a front view of the jacketed terminal, and FIG. 2B is a side view of the power transmitting apparatus 101 with the jacketed terminal placed thereon. FIG. 3 is an equivalent circuit diagram of the power transmission system 401. FIG. 4 is another equivalent circuit diagram of the power transmission system 401. FIG. 5 is a block configuration diagram of the power transmission apparatus 101. FIG. 6 is a flowchart showing the processing contents of the overvoltage protection operation on the power transmission apparatus side by the operation of the ESD protection device 43 among the processing contents of the control circuit 52 shown in FIG. FIGS. 7A and 7B are waveform diagrams showing the operation of the power transmission system according to the embodiment of the present invention. FIGS. 8A and 8B show the power transmission system of the comparative example. It is a wave form diagram which shows operation | movement. FIGS. 8A and 8B are waveform diagrams showing the operation of the power transmission system of the comparative example. FIG. 9 is a schematic diagram showing an enlarged cross-sectional structure of the discharge portion. FIG. 10 is a diagram showing a basic configuration of the power transmission system of Patent Document 1. In FIG.

<< First Embodiment >>
FIG. 1 is an external perspective view of a power transmission system 401 according to the first embodiment. The power transmission system 401 includes a power transmission device 101 and a power reception device. In this example, the terminal 10 and the jacket 201 covered on the outer peripheral frame constitute a power receiving device. Then, the terminal 10 (hereinafter, referred to as “terminal with jacket”) in a state where the outer periphery frame is covered with the jacket 201 is placed on the power transmission apparatus 101. As will be described in detail later, a power receiving circuit is configured in the jacket 201, and the terminal 10 is connected to the power receiving circuit via a connector in the jacket 201.

  2A is a front view of the jacketed terminal, and FIG. 2B is a side view of the power transmitting apparatus 101 with the jacketed terminal placed thereon. As shown in FIG. 2A, the lower jacket 201B is slidably attached to the lower portion of the terminal 10, and the upper jacket 201T is slidably attached to the upper portion of the terminal 10. A connector plug 47 is provided inside the lower jacket. When the lower jacket 201B is mounted on the terminal 10, the plug 47 is connected to the receptacle 11 provided at the lower portion of the terminal 10.

  FIG. 3 is an equivalent circuit diagram of the power transmission system 401. In FIG. 3, the power transmission device 101 includes a power transmission circuit 39, a passive electrode 31, and an active electrode 32. The passive electrode 31 and the active electrode 32 are power transmission device side coupling electrodes. The power transmission circuit 39 includes a high-frequency voltage generation circuit 38, a step-up transformer TG, an inductor LG, and the like. The high frequency voltage generation circuit 38 generates a high frequency voltage of, for example, 100 kHz to several tens of MHz. The step-up circuit using the step-up transformer TG and the inductor LG steps up the voltage generated by the high-frequency voltage generation circuit 38 and applies it between the passive electrode 31 and the active electrode 32. The capacitor CG is a capacitance due to the passive electrode 31 and the active electrode 32. The booster circuit and the capacitor CG constitute a resonance circuit.

  The jacket 201 includes a power receiving circuit 49, a passive electrode 41, and an active electrode 42. The passive electrode 41 and the active electrode 42 are power receiving device side coupling electrodes. The power receiving circuit 49 includes a load circuit 48, an ESD protection device 43, a step-down circuit using a step-down transformer TL and an inductor LL, and the like. A step-down circuit using a step-down transformer TL and an inductor LL is connected between the passive electrode 41 and the active electrode 42. The capacitor CL is a capacitance due to the passive electrode 41 and the active electrode 42. The step-down circuit and the capacitor CL constitute a resonance circuit. A load circuit 48 is connected to the secondary side of the step-down transformer TL.

  For example, when the mounting position of the power receiving device with respect to the power transmitting device is greatly deviated, the resonance state of the power receiving device is greatly deviated from the steady state, and an overvoltage is applied between the power transmitting device side coupling electrodes 31 and 32. The voltage applied between the power receiving device side coupling electrodes 41 and 42 increases. When the voltage applied between the power receiving device side coupling electrodes 41 and 42 exceeds the threshold voltage (discharge start voltage) of the ESD protection device 43, the ESD protection device 43 is discharged inside the element. When the ESD protection device 43 is discharged, the impedance of the ESD protection device 43 becomes very small, so that an increase in the voltage applied to the load circuit 48 can be suppressed.

  FIG. 4 is another equivalent circuit diagram of the power transmission system 401. This circuit is also an experimental circuit diagram shown later. The coupling capacitance Cm shown in FIG. 3 is represented by a capacitor element in FIG. These capacitors CG, CL, and Cm are determined by capacitance components derived from the electric field distribution generated in the three-dimensional structure of the power transmitting device side passive electrode, the power transmitting device side active electrode, the power receiving device side passive electrode, and the power receiving device side active electrode. .

  The LC resonance circuit LC1 is configured by the inductor LG and the capacitor CG of the power transmission device 101. Further, an LC resonance circuit LC2 is configured by the primary side coil of the step-down transformer TL and the capacitor CL.

  Connected to the secondary side of the step-down transformer TL is a rectifying / smoothing circuit using a diode bridge DB and a capacitor Co and a load circuit composed of a load RL such as a secondary battery.

  FIG. 5 is a block configuration diagram of the power transmission apparatus 101. Here, the drive power supply circuit 51 is a power supply circuit that receives a commercial power supply and generates, for example, a constant DC voltage (for example, DC 5 V). The control circuit 52 controls each unit by inputting / outputting signals to / from each unit described below.

  The drive control circuit 55 switches the switch element of the switching circuit 56 according to the signal output from the control circuit 52. As will be described later, the switching circuit 56 alternately drives the input section of the booster circuit 37.

  The DCI detection circuit 53 detects a drive current flowing through the switching circuit 56 (that is, an amount of current supplied from the drive power supply circuit 51 to the booster circuit 37) I1. The control circuit 52 reads this detection signal V (I1). The ACV detection circuit 58 capacitively divides the voltage between the coupling electrodes 31 and 32, and generates a DC voltage obtained by rectifying the divided AC voltage as a detection signal V (V1). The control circuit 52 reads this detection signal V (V1).

  FIG. 6 is a flowchart showing the processing contents of the overvoltage protection operation on the power transmission apparatus side by the operation of the ESD protection device 43 among the processing contents of the control circuit 52 shown in FIG.

  First, the optimum frequency of the high frequency voltage to be generated is detected, and the frequency is determined so as to generate a high frequency voltage of that frequency (S11). Thereafter, the drive power supply circuit 51 starts feeding a constant voltage (S12). Subsequently, the detection value V1 of the ACV detection circuit 58 and the detection value I1 of the DCI detection circuit 53 are read (S13, S14).

  The detection value of the ACV detection circuit 58 is a voltage signal V (V1) corresponding to the applied voltage V1 of the power transmission device side coupling electrodes 31 and 32. It is determined whether or not the applied voltage V1 of the power transmission device side coupling electrodes 31 and 32 exceeds a predetermined threshold value V1th (S15). Further, it is determined whether or not the input current I1 exceeds a predetermined threshold value I1th. In this way, the voltage V2 between the power receiving device side coupling electrodes 41 and 42 exceeds the threshold voltage of the discharge type overvoltage protection device and the impedance of the power receiving device side coupling electrodes 41 and 42 is suddenly changed due to the discharge of the ESD protection device. The discontinuous point of the voltage induced to the power transmission apparatus side coupling electrodes 31 and 32 is detected.

  When the ESD protection device 43 is activated (discharged), the voltage V1 applied to the power transmission device side coupling electrodes 31 and 32 increases, and the drive current I1 flowing through the switching circuit 56 increases. If the conditions of V1> V1th and I1> I1th are satisfied, it is considered that the ESD protection device 43 has been activated (discharged), and overdrive control is performed by stopping driving of the drive control circuit 55 (S17).

  In addition to detecting that the ESD protection device 43 has been activated and stopping driving of the drive control circuit 55, the on-duty ratio of the switching circuit 56 by the drive control circuit 55 is reduced to reduce the power receiving device side coupling electrode 41. , 42 may suppress the voltage increase of the voltage V2.

  FIGS. 7A and 7B are waveform diagrams showing the operation of the power transmission system according to the embodiment of the present invention. FIGS. 8A and 8B show the power transmission system of the comparative example. It is a wave form diagram which shows operation | movement. The power transmission system of this comparative example is not provided with the ESD protection device. In each figure, the vertical axis represents an arbitrary unit voltage.

  FIGS. 7A and 8A are voltage waveform diagrams when the voltage V1 applied to the power transmission device side coupling electrodes 31 and 32 is gradually increased, and FIGS. 7B and 8B are obtained at that time. It is a wave form diagram of voltage V2 applied to the receiving device side coupling electrodes 41 and.

  FIG. 7B shows that the voltage V2 applied to the power receiving device side coupling electrodes 41 and 42 exceeds the threshold at time to. As shown in FIG. 7A, the voltage V1 applied to the power transmitting device side coupling electrodes 31 and 32 rapidly increases at time to. This is due to a change in impedance of the LC resonance circuit LC2 shown in FIG. That is, in the steady state, the impedance of the LC resonance circuit LC2 is high, but when the ESD protection device 43 is turned on, the impedance of the LC resonance circuit LC2 is lowered, and the resonance frequency is configured with a capacitance value that resonates equivalently with the inductor LG. Is close to the drive frequency, and as a result, the voltage V1 applied to the power transmission device side coupling electrodes 31, 32 changes discontinuously. In the example shown in FIG. 7A, the voltage V1 rapidly increases. However, if the resonance frequency changes away from the driving frequency, there is a condition that the voltage V1 changes discontinuously in the reverse direction. It can be.

  The ESD protection device (discharge overvoltage protection device) may be connected between the terminals of the secondary coil of the step-down transformer, but it is better to connect the ESD protection device between the power receiving device side coupling electrodes. It is preferable because the impedance change can be detected with high sensitivity on the power transmission device side. In addition, it is preferable that an ESD protection device is connected between the power receiving device side coupling electrodes, that is, where the circuit impedance is high, because the current that flows during the protection operation can be reduced, so that the current stress can be reduced. A current limiting resistor may be inserted in series with the ESD protection device 43.

  Since the voltage V2 applied to the power receiving device side coupling electrodes 41 and 42 is an AC voltage, after the ESD protection device 43 is turned on, the discharge is performed according to the instantaneous voltage of the applied AC voltage. Will be intermittent or continuous. Since FIGS. 7A and 7B are waveforms in the experimental state, the power transmission on the power transmission device side is maintained after time to, and the voltage V2 does not become 0 in FIG. The threshold voltage of the ESD protection device 43 is maintained substantially.

  On the other hand, when there is no ESD protection device, as shown in FIG. 8B, the voltage V2 applied to the power receiving device side coupling electrodes 41 and 42 becomes an overvoltage state at time t1. In the experiment, since the voltage V2 is gradually increased, the voltage V2 continues to be in an overvoltage state thereafter.

  8A and 8B, the voltage V2 applied to the power receiving device side coupling electrodes 41 and 42 is higher than the voltage V1 applied to the power transmission device side coupling electrodes 31 and 32. . This is because, in this example, the relationship of V1 <V2 is established due to the resonance action of the LC resonance circuit LC2 on the power receiving device side.

  Thus, since the voltage V2 does not exceed the threshold voltage of the ESD protection device 43, the IC chip in the load circuit 48 is protected from overvoltage.

  Here, the configuration of the ESD protection device 43 will be described. FIG. 9 is a schematic diagram showing a cross-sectional structure of the ESD protection device 43. First and second discharge electrodes 16 and 16 that are exposed and opposed to each other in a cavity 18 provided in an insulating ceramic layer 17 such as glass ceramic are provided. A discharge auxiliary electrode 19 is provided so as to electrically connect the first and second discharge electrodes 16 and 16.

  The discharge auxiliary electrode 19 includes a particulate metal material 19A whose surface is coated with an insulating film and a particulate semiconductor material 19B. Here, the metal material 19A is Cu particles, and the semiconductor material 19B is SiC particles. The insulating coating is an alumina coating.

  A glass-like substance 20 is formed so as to surround the discharge auxiliary electrodes 19A and 19B. The glass-like substance 20 is not formed artificially, but is formed by a reaction such as oxidation of a constituent material derived from a peripheral member such as the insulating ceramic layer 17.

  The manufacturing method of this ESD protection device 43 is as follows.

(1) Preparation of Ceramic Material As the ceramic material used as the material of the insulating ceramic layer 17, a material (BAS material) having a composition centered on Ba, Al, and Si is used. Each material is prepared and mixed to a predetermined composition and calcined at 800-1000 ° C. The obtained calcined powder is pulverized with a zirconia ball mill to obtain a ceramic powder. To this ceramic powder, an organic solvent such as toluene and echinene is added and mixed. Furthermore, a binder and a plasticizer are added and mixed to obtain a slurry. The slurry thus obtained is molded by a doctor blade method to obtain a ceramic green sheet having a thickness of 50 μm.

  In addition, an electrode paste for forming the discharge electrode is prepared. An electrode paste is obtained by adding a solvent to a binder resin composed of 80 wt% Cu powder having an average particle size of about 2 μm and ethyl cellulose, and stirring and mixing with a three-roll.

  A resin paste containing an organic solvent in an appropriate ratio with respect to PET is prepared as a resin paste for forming the cavity 18.

(2) Application of electrode and resin paste by screen printing The mixed paste for forming the discharge auxiliary electrode is made of Cu having an average particle diameter of about 3 μm formed by adhering Al2O3 powder having an average particle diameter of several nm to several tens of nm on the surface. Prepare powder. A SiC powder having an average particle shape of 1 μm is blended with the Cu powder at a predetermined ratio. A binder paste and a solvent are added to this blend, and a mixed paste is obtained by stirring and mixing with three rolls.

  First, the mixed paste is applied to the underlying green sheet. Thereafter, an electrode and a resin paste are applied.

(3) Lamination and pressure bonding A ceramic green sheet is stacked and pressure bonded to form a stacked body.

(4) Cut, application of end face electrode Next, the laminate is cut in the thickness direction and separated into each element body. Thereafter, an electrode paste (Cu paste) that becomes the external electrode 15 after firing is applied to the end face of the element body 14.

(5) Firing Next, firing is performed in an N ₂ atmosphere to obtain an ESD protection device.

(6) Plating Next, a Ni—Sn plating film is formed on the surface of the external electrode 15 by electrolytic Ni—Sn plating.

  In addition, the metal / ceramic mixed material for forming the discharge auxiliary electrode may be formed not only as a paste but also as a sheet.

  The auxiliary discharge electrode need not include all of the conductive particles, insulating particles, and semiconductor particles, and may include insulating particles or semiconductor particles together with the conductive particles.

CG, CL, Cm ... Capacitor Co ... Capacitor DB ... Diode bridge LC1, LC2 ... LC resonant circuit LG, LL ... Inductor RL ... Load TG ... Step-up transformer TL ... Step-down transformer 10 ... Terminal 11 ... Receptacle 14 ... Element body 15 ... External Electrode 16 ... Discharge electrode 17 ... Insulating ceramic layer 18 ... Cavity 19 ... Discharge auxiliary electrode 19A, 19B ... Discharge auxiliary electrode 20 ... Glass-like substance 31, 32 ... Power transmission device side coupling electrode 37 ... Boost circuit 38 ... High frequency voltage generation circuit 39 ... Power transmission circuit 41, 42 ... Power receiving device side coupling electrode 43 ... ESD protection device 47 ... Plug 48 ... Load circuit 49 ... Power receiving circuit 51 ... Drive power supply circuit 52 ... Control circuit 53 ... DCI detection circuit 55 ... Drive control circuit 56 ... Switching circuit 58... ACV detection circuit 101... Power transmission device 201. Packet 201T ... the upper jacket 401 ... power transmission system

Claims (6)

A power transmission device side coupling electrode composed of an active electrode and a passive electrode, and a power transmission device including a power transmission circuit connected to the power transmission device side coupling electrode and supplying a high-frequency voltage;
  A power receiving device comprising an active electrode and a passive electrode, and a power receiving device side coupling electrode coupled to the power transmission device side coupling electrode; and a power receiving device comprising a power receiving circuit connected to the power receiving device side coupling electrode;
In a power transmission system with
  The power receiving circuit includes a discharge type overvoltage protection device connected between the power receiving device side coupling electrodes,
  The voltage of the power transmission device side coupling electrode or the input current of the power transmission circuit is measured, and the voltage of the power reception device side coupling electrode exceeds the threshold voltage of the discharge type overvoltage protection device, and the discharge type overvoltage protection device is discharged. A power transmission system comprising overvoltage control means for detecting a discontinuity in voltage induced in the power transmission device side coupling electrode due to a sudden change in impedance of the power reception device side coupling electrode, and performing overvoltage control. The power transmission device includes a booster circuit,
The power transmission device side coupling electrode and the booster circuit constitute a resonance circuit.
The power transmission system according to claim 1. The power receiving device includes a step-down circuit,
The power receiving device side coupling electrode and the step-down circuit constitute a resonance circuit.
The power transmission system according to claim 2. The discharge overvoltage protection device includes: a cavity provided in an insulating ceramic body; first and second discharge electrodes exposed and opposed in the cavity; and the first and second discharge electrodes in the cavity. An ESD protection device comprising a discharge auxiliary electrode provided so as to be electrically connected,
4. The power transmission system according to claim 1 , wherein the discharge auxiliary electrode includes metal particles whose surfaces are coated with an inorganic oxide and semiconductor particles . 5. 5. The power transmission system according to claim 1, wherein the power reception circuit includes a resistance element in series with the discharge-type overvoltage protection device. The power transmission system according to any one of claims 1 to 5, wherein the overvoltage control unit lowers an output voltage of the power transmission circuit or stops voltage output.