JP2017093175A - High frequency power supply device and non-contact power transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency power supply device capable of suppressing damage on a high frequency inverter due to reflection wave power, even during a period when the load side impedance is matched to the power supply side impedance by an impedance matching device with reference to the output end of the high frequency power supply device, and to provide a non-contact power transmission system including the high frequency power supply device.SOLUTION: A high frequency power supply device outputting high frequency waves to a load via an impedance matching device includes a high frequency inverter 113 having a level switching unit 113a outputting any one of a plurality of DC voltages of different levels, and a RF conversion unit 113b for converting a DC voltage outputted from the level switching unit 113a into high frequency waves, an impedance detector 114 for detecting the output side impedance of the high frequency inverter 113, and a control unit 14 for switching the level of the DC voltage outputted from the level switching unit 113a, based on said impedance.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a high-frequency power supply device that converts DC power into high-frequency AC power and supplies it to a load, and a non-contact power transmission system including the high-frequency power supply device.

  Conventionally, a non-contact power transmission system that uses two magnetically coupled coils (a power transmission coil and a power reception coil) to transmit power from a power transmission device to a power reception device in a non-contact manner and supplies the power transmitted to the power reception device to a load. Exists. In this non-contact power transmission system, high-frequency AC power is used when power is transmitted from the power transmitting device to the power receiving device. Therefore, the power transmission device is provided with a high-frequency power supply device as a source of high-frequency AC power. For example, a high frequency power supply device switches a switching element of a high frequency inverter between an on state and an off state at high speed to generate high frequency AC power. In such a non-contact power transmission system, the impedance when the load side is viewed from the output end of the high-frequency power supply device (hereinafter referred to as “load-side impedance”) is opposite to the load side from the output end of the high-frequency power supply device (that is, the power supply). When the impedance is different from the impedance (hereinafter referred to as “power supply side impedance”), the high frequency AC power output from the high frequency power supply device is reflected on the load side and returns to the high frequency power supply device as reflected wave power. (Entered). Due to this reflected wave power, the transmission efficiency of power from the power transmitting device to the power receiving device is deteriorated, so the conventional non-contact power transmission system includes an impedance matching unit that changes the load side impedance and matches the power source side impedance, The reflected wave power is suppressed (Patent Document 1). For example, when the load side impedance is matched to the power supply side impedance and the positional relationship between the power transmission coil and the power reception coil changes, the load side impedance changes and deviates from the power supply side impedance. Is done.

  Similarly, a plasma processing system for forming a thin film on a semiconductor wafer, etching, or the like includes a high frequency power supply device as a source of high frequency AC power. Also in the plasma processing system, the load-side impedance changes depending on the plasma state. In particular, when the high frequency output starts, the load side impedance changes abruptly. As a result, reflected wave power is generated, which causes the plasma state to become unstable. Therefore, the conventional plasma processing system also includes an impedance matching unit that matches the load side impedance to the power source side impedance, and suppresses reflected wave power (Patent Document 2).

JP 2011-142559 A JP 2006-166212 A

  As described above, in a non-contact power transmission system and a plasma processing system equipped with an impedance matching device, even if the load side impedance changes due to load fluctuations, the load side impedance is changed by impedance matching. To match. However, it takes time to match the load side impedance to the power source side impedance by impedance matching. Therefore, until the impedance matching is completed, the load-side impedance changes every moment and the reflected wave power is generated. If a large reflected wave power is input to the high-frequency inverter during impedance matching, the high-frequency inverter (particularly, the switching element) may be damaged.

  Therefore, the present invention has been created in view of the above problems, and its purpose is to wait until the load-side impedance is matched to the power-side impedance by the impedance matching device with reference to the output end of the high-frequency power device. Even so, an object of the present invention is to provide a high-frequency power supply device that can suppress damage to the high-frequency inverter due to reflected wave power, and a non-contact power transmission system including the high-frequency power supply device.

  The high frequency power supply device provided by the first aspect of the present invention is a high frequency power supply device that outputs a high frequency to a load via an impedance matching device, and converts DC power into high frequency power by a switching operation of a switching element. The high frequency generation means for generating a high frequency, the detection means for detecting the characteristic value on the output side of the high frequency generation means, and the switch unit disposed on the input side of the high frequency generation means, the detection means Switching means for switching a DC voltage input to the high-frequency generating means to any one of a plurality of DC voltages having different levels by switching the switch unit based on the detected characteristic value. .

  In a preferred embodiment of the high frequency power supply device, the characteristic value is a load side impedance which is an impedance when the load side is viewed from an output end of the high frequency generating means, and the detecting means detects the load side impedance. The switching unit calculates an impedance difference that is a difference between the load side impedance and a power source side impedance that is an impedance viewed from the output end opposite to the load side, and the impedance difference is equal to or greater than a first threshold value. If the impedance difference is less than the first threshold value, the highest level of the plurality of DC voltages is output. The switch unit is switched so as to output a DC voltage.

  In another preferred embodiment of the high-frequency power supply device, the characteristic value is a load-side impedance that is an impedance when the load side is viewed from an output end of the high-frequency generating means, and the detection means is the load-side impedance. And the switching means calculates an impedance difference that is a difference between the load side impedance and a power source side impedance that is an impedance when the opposite side of the load side is viewed from the output end, and the impedance difference is a first impedance difference. When the threshold voltage is equal to or higher than the threshold value, the DC voltage of the lowest level among the plurality of DC voltages is output, and when the impedance difference is equal to or smaller than the second threshold value which is smaller than the first threshold value, The switch unit is switched so as to output the highest level DC voltage among the voltages.

  In another preferred embodiment of the high-frequency power supply device, the characteristic value is reflected wave power reflected from the load side, the detection means detects a value of the reflected wave power, and the switching means When the value of the reflected wave power is greater than or equal to a first threshold value, a DC voltage of the lowest level among the plurality of DC voltages is output, and the value of the reflected wave power is smaller than the first threshold value. When the threshold value is 2 or less, the switch unit is switched so as to output the highest level DC voltage among the plurality of DC voltages.

  In a preferred embodiment of the high-frequency power supply device, the high-frequency power supply device further includes a determination unit that determines the start of the high-frequency output from the high-frequency conversion unit, and the switching unit is configured to output the plurality of DC voltages at the start of the high-frequency output. The switch unit is switched to output the lowest level DC voltage and output the highest level DC voltage among the plurality of DC voltages after the impedance matching by the impedance matching unit is completed. .

  In a preferred embodiment of the high-frequency power supply device, the switching means receives a DC voltage from a DC voltage source, and the highest level is the same level as the DC voltage input from the DC voltage source to the switching means. is there.

  In a preferred embodiment of the high-frequency power supply device, the switching means includes a plurality of capacitors arranged in front of the switch unit in order to divide the input DC voltage, and the switch unit includes the plurality of capacitors. The number of switches is the same as the number of switches, and one terminal of each switch is connected to a high potential side terminal of each of the capacitors, and the other terminal of each switch is Are connected to each other and connected to a high potential side terminal on the input side of the high frequency conversion means.

  In a preferred embodiment of the high frequency power supply device, the high frequency generating means is connected in series between the switching element that performs a switching operation based on an input high frequency control signal, and the switching means and the switching element. And an inductor.

  In another preferred embodiment of the high-frequency power supply device, the high-frequency generating means is connected in series between the switching element that performs a switching operation based on an input high-frequency control signal, and between the switching means and the switching element. And a resonance circuit that is connected in parallel to the switching element and has an impedance of zero at a frequency twice the frequency of the high-frequency control signal.

  In another preferred embodiment of the high-frequency power supply device, the high-frequency generating means includes a plurality of the switching elements that are half-bridge connected or full-bridge connected between the switching means and the impedance matching unit. Composed.

  In another preferred embodiment of the high-frequency power supply device, the high-frequency generating means is connected in series between the switching element that performs a switching operation based on an input high-frequency control signal, and between the switching means and the switching element. The length of the transmission line is approximately one-fourth the length of the transmission wavelength in the transmission line of the frequency of the high-frequency control signal.

  In another preferred embodiment of the high-frequency power supply device, the high-frequency generating means is connected in series between the switching element that performs a switching operation based on an input high-frequency control signal, and between the switching means and the switching element. An inductor connected to the first transmission line, one terminal connected to a connection point between the inductor and the switching element, and the other terminal opened, and one terminal connected to the inductor and the switching element. The second transmission line is connected to the connection point, and the other terminal is short-circuited, and the length of the first transmission line and the length of the second transmission line are respectively The frequency of the high-frequency control signal is approximately one-eighth of the transmission wavelength in each transmission line.

  A contactless power transmission system provided by the second aspect of the present invention is a contactless power transmission system that supplies power from a power transmission device to a power reception device in a contactless manner, and the power transmission device is the first aspect of the present invention. The high-frequency power supply device provided by the above-mentioned side is provided.

  According to the present invention, the switching means switches the switching unit based on the characteristic value on the output side of the high-frequency generating means, so that the DC voltage input to the high-frequency generating means is any one of a plurality of DC voltages having different levels. I switched to DC voltage. As a result, even if the load-side impedance is matched with the impedance viewed from the output end of the high-frequency generating means to the opposite side of the load side by the impedance matching device, the high-frequency power supply device is based on the above characteristic value. Since the level of the input reflected wave power can be switched, it is possible to prevent large reflected wave power from being input to the high frequency power supply device. Therefore, it is possible to suppress damage to the high frequency power supply device.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a figure showing the whole non-contact electric power transmission system composition concerning a 1st embodiment. It is a figure which shows a detailed structure about a part of non-contact electric power transmission system which concerns on 1st Embodiment. It is a figure which shows the time chart of level switching control (when one threshold value is provided) which concerns on 1st Embodiment. It is a figure which shows the time chart of level switching control (when two threshold values are provided) which concerns on the modification of 1st Embodiment. It is a figure which shows the modification of the level switching part which concerns on 1st Embodiment. It is a figure which shows the level switching part which concerns on 2nd Embodiment. It is a figure which shows the time chart of the level switching control which concerns on 2nd Embodiment. It is a figure which shows the whole structure of the non-contact electric power transmission system which concerns on 3rd Embodiment. It is a figure which shows the time chart of the level switching control which concerns on 3rd Embodiment. It is a figure which shows the 1st modification of RF conversion part. It is a figure which shows the 2nd modification of RF conversion part. It is a figure which shows the 3rd modification of RF conversion part. It is a figure which shows the 4th modification of RF conversion part. It is a figure which shows the whole structure of the plasma processing system which concerns on 4th Embodiment.

  A high frequency power supply device according to the present invention and a non-contact power transmission system including the high frequency power supply device will be described with reference to the drawings.

  FIG. 1 is a diagram showing an overall configuration of a non-contact power transmission system A according to the first embodiment of the present invention. FIG. 2 shows a part of the non-contact power transmission system A (a high-frequency inverter 113, an impedance detector 114). FIG. 4 is a diagram illustrating a detailed configuration in a control unit 14). The non-contact power transmission system A according to the present embodiment transmits power supplied from a commercial power source P from the power transmission device 1 to the power reception device 2 in a non-contact manner and charges the battery 3. The commercial power input from the commercial power source P to the power transmission device 1 is converted into high frequency AC power by the power transmission device 1, and the converted high frequency AC power is transmitted to the power receiving device 2 in a contactless manner. Then, the high-frequency AC power transmitted to the power receiving device 2 is converted into power suitable for the battery 3 and supplied to the battery 3. For example, the non-contact power transmission system A is applied as a charging system that charges a battery of an electric vehicle in which the power transmission device 1 is embedded in the ground such as a parking space and the power receiving device 2 is mounted on the electric vehicle or the like.

  The non-contact power transmission system A is non-contact from the power transmission device 1 to the power reception device 2 by using two coils (power transmission coil L13 and power reception coil L21, which will be described later) that are magnetically coupled with high frequency AC power of several MHz to several hundred MHz. Transmit with. The non-contact power transmission system A uses a magnetic resonance method. In the present embodiment, a case where 13.56 MHz AC power is used as high-frequency AC power will be described as an example.

  Then, each component of the non-contact electric power transmission system A which concerns on 1st Embodiment comprised in this way is demonstrated.

  The power transmission device 1 converts commercial AC power input from the commercial power source P into high-frequency AC power, and transmits the power to the power receiving device 2 in a contactless manner. The power transmission device 1 includes a high-frequency power circuit 11, an impedance matching device 12, a power transmission unit 13, and a control unit 14.

The high-frequency power circuit 11 performs full-wave rectification on commercial AC power input from the commercial power source P and converts it to DC power. Then, the converted DC power is converted into high-frequency AC power and output. At this time, the high frequency power supply circuit 11 detects an impedance Z _{A when the} load side is viewed from the output end of the high frequency power supply circuit 11 (hereinafter referred to as “load side impedance Z _A ”), and based on the load side impedance Z _A. , Two types of high-frequency AC power of different sizes are output. The high-frequency power circuit 11 has the same impedance Z _B (hereinafter referred to as “power-side impedance Z _B ”) when viewed from the output end of the high-frequency power circuit 11 on the opposite side of the load side, that is, the commercial power supply P side. Output high frequency AC power with optimal transmission efficiency. The high frequency power supply circuit 11 includes a rectifier circuit 111, a smoothing circuit 112, a high frequency inverter 113, and an impedance detector 114. The high-frequency power supply circuit 11 and the control unit 14 correspond to a “high-frequency power supply device” recited in the claims.

  The rectifier circuit 111 is, for example, a rectifier circuit in which six rectifier diodes are bridge-connected, and full-wave rectifies a commercial AC voltage (three-phase AC voltage) input from the commercial power supply P to generate a DC voltage. In the present embodiment, since a three-phase AC voltage is input from the commercial power supply P, six rectifier diodes are bridge-connected. However, when a single-phase AC voltage is input from the commercial power supply P, rectification is performed. What is necessary is just to comprise 4 diodes in a bridge connection. Note that the configuration of the rectifier circuit 111 is not limited to this, and any configuration that converts a commercial AC voltage into a DC voltage may be used.

  The smoothing circuit 112 smoothes the DC voltage input from the rectifier circuit 111. The smoothing circuit 112 is configured by connecting an inductor and a capacitor in an L shape, for example.

  The high frequency inverter 113 converts a DC input input from the smoothing circuit 112 into a high frequency output. The high frequency inverter 113 is controlled by various control signals input from the control unit 14. As shown in FIG. 2, the high-frequency inverter 113 includes a level switching unit 113a and an RF conversion unit 113b.

  As shown in FIG. 2, the level switching unit 113a includes two capacitors C1 and C2 and two switches Q1 and Q2.

  One end of the capacitor C1 is connected to the output terminal on the high potential side of the smoothing circuit 112, and the other end is connected to one end of the capacitor C2. The other end of the capacitor C2 is connected to the output terminal on the low potential side of the smoothing circuit 112. That is, the two capacitors C1 and C2 are connected in series.

  The switches Q1 and Q2 are configured, for example, by connecting two MOSFETs in anti-series. A diode is connected in antiparallel to each of the two MOSFETs. The two MOSFETs constituting the switch Q1 have source terminals connected to each other, a drain terminal of one MOSFET connected to a connection point between one end of the capacitor C1 and an output terminal on the high potential side, and a drain of the other MOSFET. The terminal is connected to one input terminal (upper input terminal in FIG. 2) of the RF conversion unit 113b. The switching control signal S1 is input from the control unit 14 to both gate terminals. The two MOSFETs constituting the switch Q2 have source terminals connected to each other, the drain terminal of one MOSFET is connected to the connection point between the capacitor C1 and the capacitor C2, and the drain terminal of the other MOSFET is connected to the RF converter. 113b is connected to the input terminal. The switching control signal S2 is input from the control unit 14 to both gate terminals. The switches Q1 and Q2 perform a switching operation for switching between an on state and an off state in accordance with the switching control signals S1 and S2. When one of the switches Q1 and Q2 is in an on state, switching control signals S1 and S2 are input from the control unit 14 so that the other is in an off state.

The level switching unit 113a configured as described above converts the DC voltage input from the smoothing circuit 112 into two types of DC voltages having different levels based on the control signals (switching control signals S1 and S2) from the control unit 14. Switch to output. Of the two types of DC voltages having different levels, a DC voltage level having a high level is expressed as a high level, and a DC voltage level having a low level is expressed as a low level. The level switching unit 113a outputs a high-level DC voltage when the switch Q1 is on and the switch Q2 is off. On the other hand, the level switching unit 113a is low when the switch Q1 is off and the switch Q2 is on. Output level DC voltage. Specifically, when the DC voltage input from the smoothing circuit 112 is Vin [V], and the capacitances of the two capacitors C1 and C2 are c1 [F] and c2 [F], the voltage V1 between the terminals of the capacitors C1 and C2 is V1. [V] and V2 [V] are represented by the following formulas (1) and (2), respectively.
V1 = (c2 / (c1 + c2)) · Vin (1)
V2 = (c1 / (c1 + c2)) · Vin (2)

  When the switch Q1 is on and the switch Q2 is off, the output voltage Vout of the level switching unit 113a is V1 + V2 [V], that is, Vin [V]. This means that the DC voltage input from the smoothing circuit 112 is output as it is. On the other hand, when the switch Q1 is off and the switch Q2 is on, the output voltage Vout of the level switching unit 113a is V2 [V], that is, (c1 / (c1 + c2)) · Vin [V]. This is because the DC voltage input from the smoothing circuit 112 is divided by the capacitors C1 and C2 (voltage drop), so that the level of the DC voltage input from the smoothing circuit 112 is reduced and output.

  From the above, the level switching unit 113a can switch the DC voltages having two different levels (high level and low level) by the switching operation of the switches Q1 and Q2 and output them to the RF conversion unit 113b. In this embodiment, a mode in which the level of the DC voltage output to the RF conversion unit 113b is switched using the MOSFET switches Q1 and Q2 will be described as an example. However, other various switches (for example, mechanical switches) As long as two types of DC voltages having different levels can be switched using the, the present invention is not limited to this.

  The RF conversion unit 113b generates a high frequency based on the DC voltage input from the level switching unit 113a. The RF conversion unit 113b is disposed between the level switching unit 113a and the impedance detector 114.

  The RF conversion unit 113b includes an inductor L3, a switching element Qs, a capacitor C4, and an LC series resonance circuit LC1 in which an inductor L5 and a capacitor C5 are connected in series. In the present embodiment, as shown in FIG. 2, the switching element Qs is constituted by a MOSFET, and a diode is connected in antiparallel to the MOSFET. The inductor L3 has one terminal connected to the output terminal on the high potential side of the level switching unit 113a and the other terminal connected to the drain terminal of the switching element Qs. Therefore, the inductor L3 and the switching element Qs are connected in series. The source terminal of the switching element Qs is connected to the output terminal on the low potential side of the level switching unit 113a, and the gate terminal of the switching element Qs is connected to the control unit 14. The RF conversion unit 113b is configured by a so-called class E inverter (class E amplifier). Further, in the RF converter 113b, the capacitor C4 is connected in parallel with the switching element Qs so that a current flows continuously in order to suppress a rapid voltage increase when the switching element Qs changes from the on state to the off state. It is connected to the. In addition, an LC series resonance circuit LC1 that functions as a filter that passes a high-frequency current of a predetermined frequency is connected to a connection point between the inductor L3 and the switching element Qs.

  The RF conversion unit 113b receives the high frequency control signal SW from the control unit 14 at the gate terminal of the switching element Qs, and switches the switching element Qs between the on state and the off state, thereby converting the direct current flowing through the inductor L3 into the high frequency alternating current. Convert to The high-frequency control signal SW is a pulse signal that repeats a high level and a low level at 13.56 MHz, for example, and when the high-frequency control signal SW input to the gate terminal of the switching element Qs is at a high level, the switching element Qs Is turned on and current flows. On the other hand, at low level, the switching element Qs is turned off and no current flows. Thereby, the RF conversion unit 113b converts the direct current flowing through the inductor L3 into a high frequency output (high frequency alternating current) of 13.56 MHz. In the RF conversion unit 113b, a direct current flows through the inductor L3 due to the direct current voltage input from the level switching unit 113a. The direct current is converted into a high-frequency alternating current by the switching operation of the switching element Qs. Therefore, the RF conversion unit 113b can be regarded as converting the DC voltage input from the level switching unit 113a into a high-frequency AC current by the switching operation of the switching element Qs.

The impedance detector 114 detects the load side impedance Z _A. The impedance detector 114 includes a current / voltage sensor 114a and a calculation unit 114b.

  The current / voltage sensor 114a is provided between the high frequency inverter 113 and the impedance matching unit 12, and detects a current corresponding to the high frequency current flowing in the power supply line and a voltage corresponding to the high frequency voltage generated in the power supply line. The current / voltage sensor 114a outputs the detected current signal i and voltage signal v to the computing unit 114b.

Computing unit 114b, on the basis of the current signal i and the voltage signal v inputted from the current-voltage sensor 114a, is for calculating the load impedance Z _A. The calculation unit 114b calculates the current effective value I, the voltage effective value V, and the phase difference θ between the current signal i and the voltage signal v from the input current signal i and voltage signal v. Then, using these parameters, the impedance is calculated. The calculation unit 114b outputs the calculated impedance to the control unit 14 as the load side impedance Z _A. Note that the method for detecting the load side impedance Z _A performed by the impedance detector 114 is not limited to the above.

Impedance matching device 12, in order to suppress the amount of traveling wave output from the high-frequency power supply circuit 11 is reflected at the input side of the impedance matching device 12 (reflected power Pr), and adjusts the load impedance Z _A is there. For example, the impedance matching unit 12 is configured by a π-type circuit in which two capacitors and an inductor are connected to the π side (illustration is omitted). Impedance matching box 12, by two respective capacitances and inductor inductor chest of the capacitor is adjusted by the control unit 14 to adjust the load impedance Z _A, to match the power source side impedance Z _B (match) . The impedance matching unit 12 may be configured by an L-type circuit, an inverted L-type circuit, a T-type circuit, or the like in addition to the π-type circuit. The impedance matching device 12, using a transformer comprising a ferrite core and a primary winding and a secondary winding, by changing the turns ratio may be one to change the load impedance Z _A.

The power transmission unit 13 transmits the high-frequency AC power input from the impedance matching unit 12 to the power reception unit 21 of the power reception device 2 in a non-contact manner. The power transmission unit 13 includes a series resonance circuit including a power transmission coil L13 formed of a circular coil having a plurality of turns and a capacitor C13 connected in series to the power transmission coil L13. The power transmission coil L13 is not limited to a circular coil, and may be a coil wound in a square or a long and thin shape. In the power transmission unit 13, the series resonance frequency f _O (= 1 / [2π · √ (L · C)]) (L: self-inductance of the power transmission coil L13, C: capacitance of the capacitor C13) of the series resonance circuit is the high frequency power supply circuit. 11 is adjusted to the frequency (hereinafter referred to as “power supply frequency”) f _g [MHz] (13.56 MHz in the present embodiment) of the high-frequency AC power output from 11.

The control part 14 controls the whole power transmission apparatus 1, and is comprised by the microcomputer provided with ROM, RAM, CPU, etc., for example. In FIG. 2, only a part of the functional configuration of the control unit 14 (functional configuration according to the present invention) is shown. The control unit 14 controls the impedance matching unit 12 so that the load side impedance Z _A input from the impedance detector 114 becomes the power source side impedance Z _B. For example, the control unit 14 changes the capacitances of the two capacitors included in the impedance matching unit 12 and the inductance of the inductor to match the load side impedance Z _A with the power source side impedance Z _B.

  Further, the control unit 14 inputs the high frequency control signal SW to the switching element Qs of the RF conversion unit 113b, and controls the switching operation of the switching element Qs. Therefore, the control unit 14 includes a control signal generation unit 141 as illustrated in FIG. The control signal generation unit 141 and the RF conversion unit 113b correspond to “high-frequency generation means” described in the claims.

  The control signal generation unit 141 inputs the high frequency control signal SW to the switching element Qs of the RF conversion unit 113b. The control signal generation unit 141 generates a high frequency control signal SW that is a pulse signal that repeats a high level and a low level at 13.56 MHz, and inputs the high frequency control signal SW to the gate terminal of the switching element Qs.

Further, the control unit 14 performs level switching control for switching the level of the DC voltage output from the level switching unit 113a based on the load side impedance Z _A input from the impedance detector 114. Therefore, the control unit 14 includes a determination unit 142 and a switching command unit 143 as illustrated in FIG. The determination unit 142, the switching command unit 143, and the level switching unit 113a correspond to the “switching unit” described in the claims.

The determination unit 142 calculates an absolute value ΔZ (hereinafter, referred to as “impedance difference ΔZ”) of the difference between the load side impedance Z _A and the power source side impedance Z _B input from the impedance detector 114 and calculates the impedance. The difference ΔZ is compared with a preset threshold value. This threshold value is preset in the determination unit 142, and is a threshold value Z1 for switching the DC voltage output from the level switching unit 113a to a low level. The determination unit 142 subtracts the magnitude | Z _B | of the power supply side impedance Z _B from the magnitude | Z _A | of the input load side impedance Z _A and calculates the absolute value as the impedance difference ΔZ. Then, the determination unit 142 determines whether or not the impedance difference ΔZ is greater than or equal to the threshold value Z1, and outputs the determination result to the switching command unit 143.

  The switching command unit 143 generates switching control signals S1 and S2 to be input to the switches Q1 and Q2 of the level switching unit 113a based on the determination result of the determining unit 142, and inputs the switching control signals S1 and S2 to the switches Q1 and Q2. To do. Specifically, when the determination unit 142 determines that the impedance difference ΔZ is equal to or greater than the threshold value Z1, the switching command unit 143 sets the switch Q1 so that a low-level DC voltage is output from the level switching unit 113a. Switching control signals S1 and S2 for turning the switch Q2 on and the switch Q2 on are generated and input to the switches Q1 and Q2, respectively. When the determination unit 142 determines that the impedance difference ΔZ is not equal to or greater than the threshold value Z1 (that is, less than the threshold value Z1), the switch Q1 is turned on so that a high-level DC voltage is output from the level switching unit 113a. The switch control signals S1 and S2 for turning off the switch Q2 are generated and input to the switches Q1 and Q2, respectively. As described above, the switching command unit 143 inputs the switching control signals S1 and S2 to the switches Q1 and Q2 of the level switching unit 113a, thereby changing the output voltage Vout of the level switching unit 113a between the high level and the low level. You can switch to either.

The threshold value Z1 may be set as appropriate based on the durability performance of the switching element Qs of the high-frequency inverter 113. Specifically, the reflected wave power Pr increases as the impedance difference ΔZ increases, that is, as the load-side impedance Z _A is further away from the power supply-side impedance Z _B. Therefore, the reflected wave power Pr input to the switching element Qs increases. Considering this, it is necessary to set the threshold value Z1 smaller as the durability performance of the switching element Qs is lower.

  The power receiving device 2 receives high-frequency AC power transmitted from the power transmitting device 1 in a contactless manner and charges the battery 3. The power receiving device 2 includes a power receiving unit 21, a rectifying / smoothing circuit 22, and a charging circuit 23.

The power reception unit 21 receives high-frequency AC power from the power transmission unit 13 in a contactless manner. The power receiving unit 21 has the same configuration as that of the power transmission unit 13 and is composed of a circular coil having a plurality of turns. The power receiving coil L21 is magnetically coupled to the power transmitting coil L13, and the capacitor C21 is connected in series to the power receiving coil L21. The series resonance circuit. The power receiving coil L21 is not limited to a circular coil, and may be a coil wound in a square or a long and thin shape. The power receiving unit 21 also has a resonance frequency f _O ′ (= 1 / [2π · √ (L ′ · C ′)]) of the series resonance circuit (L ′: self-inductance of the power receiving coil L21, C ′: capacitance of the capacitor C21). Is adjusted to the power supply frequency f _g [MHz].

  The rectifying / smoothing circuit 22 rectifies and smoothes the high-frequency AC power input from the power receiving unit 21. The rectifying / smoothing circuit 22 is configured by, for example, four Schottky barrier diodes connected in a bridge, and is configured using a rectifying circuit unit that rectifies high-frequency AC power and a capacitor, and the DC power rectified by the rectifying circuit unit. A smoothing circuit portion for smoothing is provided.

  The charging circuit 23 supplies the DC power input from the rectifying / smoothing circuit 22 to the battery 3 for charging. The charging circuit 23 executes various charging controls in accordance with the charging characteristics of the battery 3. For example, constant current constant voltage control including a constant current charging process for supplying a constant charging current to the battery 3 and constant voltage charging for controlling the charging current so that the battery voltage of the battery 3 becomes constant after constant current charging. Execute. In this case, the charging circuit 23 includes an ammeter that detects the charging current and a voltmeter that detects the battery voltage. The charging circuit 23 may be configured to output constant current and constant voltage control by outputting a charging current and a battery voltage to a control unit (not shown) and the control unit controlling the charging circuit 23.

  The battery 3 is a secondary battery that accumulates electric power, and is composed of, for example, a lithium ion battery or a nickel metal hydride battery. When the battery 3 is a lithium ion battery, it is charged by constant current and constant voltage control by the charging circuit 23. Further, the battery 3 may be a livestock appliance such as a capacitor.

Next, the operation of the non-contact power transmission system A configured as described above will be described with reference to FIG. Figure 3 shows a time chart of the level switching control contactless power transmission system A is carried out, FIG. 3 (a) changes in the load impedance Z _A, FIG. 3 (b) changes in the impedance difference [Delta] Z, FIG. 3 (c) shows a change in the reflected wave power Pr, and FIG. 3 (d) shows a change in the output voltage Vout of the level switching unit 113a. In FIG. 3, since it is drawn in a simplified manner, there may actually be some fluctuation.

The period from time T0 to time T1 is a state where the load side impedance Z _A is matched with the power source side impedance Z _B by the impedance matching of the impedance matching device 12. Therefore, the impedance difference ΔZ is zero. At this time, the reflected wave power Pr is zero because it is not generated, and the high-level DC voltage Vout is output from the level switching unit 113a.

Time T1 indicates a time when a load change occurs. For example, in the non-contact power transmission system A, a load fluctuation occurs due to a shift in the positional relationship between the power transmission coil L13 of the power transmission device 1 and the power reception coil L21 of the power reception device 2. Due to this load fluctuation, the load-side impedance Z _A changes. In the following description, the case where load impedance Z _A is increased by load fluctuation in the Examples.

Period from the time T2 from the time T1, the load fluctuation generated at time T1, shows the process of load impedance Z _A is varied (increased). At this time, the load side impedance Z _A rises, so that the load side impedance Z _A deviates from the power source side impedance Z _B. Thereby, the reflected wave power Pr is generated. The reflected wave power Pr increases as the load side impedance Z _A increases.

Time T2 is load impedance Z _A is increased by load fluctuation, which indicates when the impedance difference ΔZ becomes the threshold Z1 or more. At this time, the control unit 14 determines that the impedance difference ΔZ is equal to or greater than the threshold value Z1, and switches the output voltage Vout of the level switching unit 113a from a high level to a low level as shown in FIG. Thereby, since the high frequency alternating current power output from the high frequency inverter 113 becomes small, as shown in FIG.3 (c), the reflected wave electric power Pr becomes small. Therefore, the reflected wave power Pr input to the high frequency inverter 113 is also reduced, and damage to the high frequency inverter 113 can be suppressed.

The period from time T2 to time T3 shows a process in which the load side impedance Z _A is still rising due to load fluctuation. Reflected power Pr is a time T2, becomes temporarily smaller by switching the output voltage Vout of the level switching part 113a, with the increase of the load impedance Z _A, increases.

Time T3, the load-side impedance Z _A indicates the time and which has been fully raised by the load variation. At this time, the load side impedance Z _A becomes maximum, and thereafter decreases due to impedance matching. Further, the impedance difference ΔZ becomes maximum and thereafter decreases, and the reflected wave power Pr does not increase at the timing when the load side impedance Z _A becomes maximum, and thereafter decreases.

The period from time T3 to time T4 shows a process in which the load side impedance Z _A is lowered by impedance matching and matched with the power source side impedance Z _B. At this time, the impedance difference ΔZ decreases due to impedance matching, and the reflected wave power Pr also decreases.

Time T4, the load-side impedance Z _A is lowered by the impedance matching, which indicates when the impedance difference ΔZ is less than the threshold value Z1. At this time, the control unit 14 determines that the impedance difference ΔZ is less than the threshold value Z1, and switches the output voltage Vout of the level switching unit 113a from the low level to the high level as shown in FIG. As a result, the high-frequency AC power output from the high-frequency inverter 113 is increased, and the reflected wave power Pr is once increased, as shown in FIG. However, since the impedance difference ΔZ is reduced by impedance matching, the reflected wave power Pr is reduced to the extent that the high-frequency inverter 113 is not damaged.

In the period from time T4 to time T5, since the load side impedance Z _A is not yet matched with the power source side impedance Z _B , the impedance matching is continuously performed. The reflected wave power Pr once increases due to switching of the output voltage Vout of the level switching unit 113a at time T4, but decreases due to impedance matching being performed.

Time T5 indicates a time when the load side impedance Z _A matches the power source side impedance Z _B and the impedance matching is completed. At this time, since the load side impedance Z _A matches the power source side impedance Z _B , the impedance difference ΔZ becomes zero and the reflected wave power Pr also becomes zero. Thereafter, the state where the load side impedance Z _A is matched with the power source side impedance Z _B is maintained.

In the time chart shown in FIG. 3, the case where the load side impedance Z _A is increased due to the load variation has been described as an example, but conversely, even when the load side impedance Z _A is decreased due to the load variation, Since the impedance difference ΔZ varies, the level of the output voltage Vout of the level switching unit 113a can be switched according to the impedance difference ΔZ.

From the above, the non-contact power transmission system A according to a first embodiment of the present invention, due to the influence of load fluctuation, load impedance Z _A of the load side is viewed from the output terminals of the high frequency power supply circuit 11 is changed, When the difference from the power supply side impedance Z _B (impedance difference ΔZ) becomes equal to or greater than a preset threshold value Z1, the output voltage Vout of the level switching unit 113a is switched from a high level to a low level. After that, when the impedance difference ΔZ is less than the threshold value Z1 by impedance matching of the impedance matching unit 12, the output voltage Vout of the level switching unit 113a is switched from the low level to the high level. Thus, even when the load matching impedance Z _A is matched with the power supply impedance Z _B by the impedance matching device 12, the high frequency output from the high frequency inverter 113 according to the fluctuation of the load impedance Z _A. Since the level of the AC voltage can be switched, large reflected wave power can be prevented from being input to the high-frequency inverter 113. Therefore, it is possible to suppress damage to the high-frequency inverter 113.

  In the first embodiment, the control unit 14 determines whether or not the impedance difference ΔZ is greater than or equal to one threshold value Z1, and the output voltage Vout of the level switching unit 113a is set to a high level or a low level according to the determination result. Although the case of switching to any of the levels has been described, the present invention is not limited to this. For example, in addition to the threshold value Z1 (which is expressed as “first threshold value Z1”), a second threshold value Z2 (Z2 <Z1) is provided. The output voltage Vout of the level switching unit 113a is switched from the low level to the high level when the impedance difference ΔZ becomes less than the second threshold value Z2, not when the impedance difference ΔZ becomes less than the first threshold value Z1. Also good. This case will be described below.

FIG. 4 shows a time chart of level switching control when two thresholds are provided. 4A shows a change in the load side impedance Z _A , FIG. 4B shows a change in the impedance difference ΔZ, FIG. 4C shows a change in the reflected wave power Pr, and FIG. 4D shows a level switching unit. The change of the output voltage Vout of 113a is shown. As shown in FIG. 4 (a), load impedance Z _A is assumed to have varied in the same manner as in FIG. 3 (a). The time chart shown in FIG. 4 differs from the time chart shown in FIG. 3 in the timing (time T4) at which the output voltage Vout of the level switching unit 113a is switched from the low level to the high level.

As shown in FIG. 4, the output voltage Vout of the level switching unit 113a is decreased when the impedance difference ΔZ is not less than the first threshold value Z1 but not more than the second threshold value Z2 (time T4). Switching from level to high level. Therefore, the switching timing is delayed compared to the time chart shown in FIG. Therefore, the impedance difference ΔZ is smaller, that is, the load side impedance Z _A can be switched at a timing closer to the power source side impedance Z _B. Therefore, the reflected wave power Pr when the output voltage Vout of the level switching unit 113a is switched from the low level to the high level is lower than that in the case of FIG. Thereby, when the output voltage Vout of the level switching unit 113a is switched from the low level to the high level, the possibility that a large reflected wave power Pr is input to the high-frequency inverter 113 is reduced.

Further, the load impedance Z _A to be detected by the impedance detector 114, due to the effects of detection errors, sometimes slight change. Therefore, there is a possibility that the impedance difference ΔZ may be equal to or greater than the first threshold Z1 or less than the first threshold Z1 in the vicinity of the first threshold Z1. As a result, the output voltage Vout is frequently switched. Therefore, by providing two threshold values, it is possible to prevent frequent switching of the output voltage Vout due to this minute fluctuation.

  In the first embodiment, the switches Q1 and Q2 of the level switching unit 113a have been described by taking an example of a configuration in which two MOSFETs are connected in anti-series as shown in FIG. As shown in FIG. 5, it may be constituted by one MOSFET. Even in this case, similarly to the first embodiment, two types of DC voltages having different levels can be switched by the switching control signals S1 and S2 input to the switches Q1 and Q2.

  In the first embodiment, the level switching unit 113a has been described as an example in which two types of DC voltages having different levels can be switched. However, three or more types of DC voltages having different levels are used. It may be configured to be switched. For example, by configuring the level switching unit 113a as shown in FIG. 6, it is possible to switch three types of DC voltages having different levels. Of the three types of DC voltages having different levels, the highest level is expressed as a high level, the lowest level is expressed as a low level, and the level between the high level and the low level is expressed as a medium level. In this case, a high level DC voltage is output when only the switch Q1 is on, a medium level DC voltage is output when only the switch Q2 is on, and a low level when only the switch Q3 is on. DC voltage is output. Similarly, by adding and connecting a capacitor and a switching element, it is possible to switch a plurality of levels of DC voltage.

  For example, a case where three types of DC voltages having different levels are switched using the level switching unit 113a 'illustrated in FIG. 6 will be described below as a second embodiment. The non-contact power transmission system B according to the second embodiment is different from the non-contact power transmission system A according to the first embodiment in that the level switching unit 113a is replaced with a level switching unit 113a '. Since the other configuration is the same or similar, the same reference numerals are given and description thereof is omitted.

The voltage output from the smoothing circuit 112 arranged in the previous stage of the level switching unit 113a ′ is Vin [V], and the capacitances of the three capacitors C1, C2, and C3 are c1 [F], c2 [F], and c3 [F]. Then, the inter-terminal voltages V1 [V], V2 [V], and V3 [V] of the capacitors C1, C2, and C3 are expressed by the following equations (3), (4), and (5), respectively.
V1 = (c2 · c3 / (c1 · c2 + c2 · c3 + c3 · c1)) · Vin (3)
V2 = (c3 · c1 / (c1 · c2 + c2 · c3 + c3 · c1)) · Vin (4)
V3 = (c1 · c2 / (c1 · c2 + c2 · c3 + c3 · c1)) · Vin (5)

  When only the switch Q1 is in the on state, the output voltage Vout of the level switching unit 113a 'is V1 + V2 + V3 [V], that is, Vin [V]. This means that the DC voltage input from the smoothing circuit 112 is output as it is. When only the switch Q2 is on, the output voltage Vout of the level switching unit 113a ′ is V2 + V3 [V], that is, ((c3 · c1 + c1 · c2) / (c1 · c2 + c2 · c3 + c3 · c1)). Vin [V]. When only the switch Q3 is in the on state, the output voltage Vout of the level switching unit 113a ′ is V3 [V], that is, ((c1 · c2) / (c1 · c2 + c2 · c3 + c3 · c1)) · Vin [ V]. Therefore, as described above, when only the switch Q1 is in the ON state, a high level DC voltage is output, and when only the switch Q2 is in the ON state, a medium level DC voltage is output, and only the switch Q3 is in the ON state. When a low-level DC voltage is output.

  From the above, the level switching unit 113a 'can switch the DC voltage of three magnitudes and output it to the RF conversion unit 113b by the switching operation of the switches Q1, Q2, and Q3.

  As described above, when the level switching unit 113a ′ configured to be able to switch the DC voltage of the three types of high level, medium level, and low level is used, the determination unit 142 determines the impedance difference ΔZ between two levels. Compare with threshold. Note that these two threshold values are a first threshold value Z1 and a second threshold value Z2 ', and Z1> Z2'. Then, the switching command unit 143 determines the level switching unit based on the determination result from the determination unit 142, specifically, the determination result of whether ΔZ ≦ Z2 ′, Z2 ′ <ΔZ <Z1, Z1 ≦ ΔZ is satisfied. Switching control signals S1, S2, S3 to be input to the switches Q1, Q2, Q3 of 113a ′ are generated. When the impedance difference ΔZ satisfies Z1 ≦ ΔZ based on the determination result of the determination unit 142, the switching command unit 143 turns on only the switch Q3 in order to set the output voltage Vout of the level switching unit 113a ′ to a low level. The switching control signals S1, S2 and S3 to be generated are generated. When the impedance difference ΔZ satisfies Z2 ′ <ΔZ <Z1, the switching command unit 143 switches the switching control signal S1, which turns on only the switch Q2 in order to set the output voltage Vout of the level switching unit 113a ′ to an intermediate level. S2 and S3 are generated. When the impedance difference ΔZ satisfies ΔZ ≦ Z2 ′, the switching command unit 143 switches the switching control signal S1, which turns on only the switch Q1 in order to set the output voltage Vout of the level switching unit 113a ′ to a high level. S2 and S3 are generated. Therefore, the control unit 14 performs level switching control for switching the output voltage Vout of the level switching unit 113a 'to any one of a high level, a medium level, and a low level DC voltage.

FIG. 7 shows a time chart of level switching control performed by the non-contact power transmission system B using the level switching unit 113a ′ according to the second embodiment. 7 (a) is the change in load impedance Z _A, FIG. 7 (b) changes in the impedance difference [Delta] Z, FIG. 7 (c) change in the reflected power Pr, and FIG. 7 (d) level switching unit The change of the output voltage Vout of 113a 'is shown. Incidentally, as shown in FIG. 7 (a), load impedance Z _A is assumed to vary in the same manner as in FIG. 3 (a). Also in FIG. 7, there may actually be some fluctuation.

Since the impedance difference ΔZ becomes larger than the second threshold value Z2 ′ at time T2, the control unit 14 switches the output voltage Vout of the level switching unit 113a ′ from the high level to the middle level. Thereby, the reflected wave power Pr becomes small. Since then, he continued to load impedance Z _A rose further by load variation, at time T3, when the impedance difference ΔZ becomes equal to or larger than the first threshold Z1, in turn, control unit 14, the output voltage level switching section 113a ' Vout is switched from medium level to low level. Thereby, the reflected wave power Pr becomes small. Then, the load-side impedance Z _A continues to increase due to the load fluctuation, and the load-side impedance Z _A stops increasing at time T4 and thereafter starts to decrease due to impedance matching. Along with this, the increase in the impedance difference ΔZ and the reflected wave power Pr ends, and thereafter, the impedance difference ΔZ and the reflected wave power Pr begin to decrease.

Thereafter, the medium in time T5, the reduced load impedance Z _A is the impedance matching, the impedance difference ΔZ is less than the first threshold value Z1, the control unit 14, the output voltage Vout of the level switching part 113a 'from the low-level Switch to level. By switching the output voltage Vout of the level switching unit 113a ′, the reflected wave power Pr increases as in the first embodiment, but the amount of increase at this time is smaller than that in the first embodiment. At time T6, when the impedance difference ΔZ becomes equal to or smaller than the second threshold value Z2 ′, the output voltage Vout of the level switching unit 113a ′ is switched from the medium level to the high level. At time T7, the load side impedance Z _A matches the power source side impedance Z _B , and the impedance matching is completed. Thereby, the reflected wave power Pr becomes zero.

In the time chart shown in FIG. 7 described above, the case where the load side impedance Z _A is increased due to the load variation has been described as an example. Conversely, even when the load side impedance Z _A is decreased due to the load variation, Since the impedance difference ΔZ varies, the level of the output voltage Vout of the level switching unit 113a can be switched according to the impedance difference ΔZ.

From the above, in the second embodiment, even in the non-contact power transmission system B equipped with the level switching section 113a ', the similar to the first embodiment, the power load impedance Z _A is than the impedance matching device 12 Even during the period until matching with the side impedance Z _B , the level of the high-frequency AC voltage output from the high-frequency inverter 113 can be switched according to the fluctuation of the load-side impedance Z _A. As a result, large reflected wave power can be prevented from being input to the high-frequency inverter 113. Accordingly, it is possible to suppress damage to the high-frequency inverter 113.

  Further, since the output voltage Vout of the level switching unit 113a ′ can be switched at three levels, the level of the high-frequency AC voltage (high-frequency AC power) output from the high-frequency inverter 113 can be increased stepwise. . Therefore, when compared with the first embodiment (see FIG. 3), when the output voltage Vout of the level switching unit 113a ′ is switched to a DC voltage one level higher (low level to medium level, medium level to high level). The amount of increase in the reflected wave power Pr can be reduced. That is, it is possible to mitigate a rapid increase in the reflected wave power Pr.

In the first embodiment and the second embodiment, the control unit 14 compares the impedance difference ΔZ with a predetermined threshold value, and performs level switching control of the level switching unit 113a (113a ′) according to the result. Although the embodiment has been described, it is determined whether or not the magnitude of the load side impedance Z _A detected by the impedance detector 114 is within a predetermined range including the power source side impedance Z _B , and the level switching is performed according to the result. The level switching control of the unit 113a (113a ′) may be performed. For example, in the first embodiment, the control unit 14 determines that the input load-side impedance Z _A includes a predetermined range including the power-side impedance Z _B (Z _B −Z _m ≦ Z _A ≦ Z _B −Z _n , m ≦ n; Z _m and Z _n are within a predetermined range), and if not within the predetermined range, the output voltage Vout is switched to a low level, and if within the predetermined range, the output voltage Switch Vout to high level. As described above, the level switching control of the level switching unit 113a (113a ′) may be performed based on the magnitude of the load side impedance Z _A instead of the impedance difference ΔZ.

  Moreover, in the said 1st Embodiment and the said 2nd Embodiment, although the aspect which performs level switching control of the level switching part 113a (113a ') based on impedance difference (DELTA) Z was demonstrated, the value of the reflected wave electric power Pr by the side of a load is demonstrated. The level switching control of the level switching unit 113a (113a ′) may be performed based on the above. This case will be described below as a third embodiment.

  FIG. 8 is a diagram for explaining the overall configuration of the non-contact power transmission system C according to the third embodiment. The non-contact power transmission system C according to the third embodiment is different from the non-contact power transmission system A according to the first embodiment in that a power detector 115 is provided instead of the impedance detector 114. In addition, about the structure same or similar to the non-contact electric power transmission system A which concerns on the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  The power detector 115 detects the traveling wave power Pf and the reflected wave power Pr of the high frequency AC power output from the high frequency inverter 113. The power detector 115 is, for example, a bidirectional coupler and a converter that converts a traveling wave detection signal and a reflected wave detection signal output from the bidirectional coupler into traveling wave power Pf and reflected wave power Pr, respectively. It consists of. The traveling wave power Pf and the reflected wave power Pr detected by the power detector 115 are input to the control unit 14.

  Compared with the control unit 14 of the first embodiment, the control unit 14 ′ switches the level of the DC voltage output from the level switching unit 113a based on the reflected wave power Pr input from the power detector 115. It differs in that it performs. Therefore, as shown in FIG. 8, the control unit 14 ′ has a determination unit 142 ′ and a switching command unit 143 ′ instead of the determination unit 142 and the switching command unit 143.

  The determination unit 142 ′ compares the value of the reflected wave power Pr input from the power detector 115 with a preset threshold value. The determination unit 142 ′ has the value of the reflected wave power Pr input from the power detector 115 equal to or higher than the first threshold value Pr1 (Pr1 ≦ Pr) or equal to or lower than the second threshold value Pr2 (Pr ≦ Pr2). Or between them (Pr2 <Pr <Pr1). Then, the determination unit 142 'outputs the determination result to the switching command unit 143'.

  As a result of determination by the determination unit 142 ′, the switching command unit 143 ′ switches the switch so that a low-level DC voltage is output from the level switching unit 113a when the reflected wave power Pr is greater than or equal to the first threshold value Pr1. Switching control signals S1 and S2 for turning Q1 off and switch Q2 on are generated and input to switches Q1 and Q2, respectively. As a result of determination by the determination unit 142 ′, when the reflected wave power Pr is equal to or less than the second threshold value Pr2, the switch Q1 is turned on so that a high-level DC voltage is output from the level switching unit 113a. Switching control signals S1 and S2 for turning off Q2 are generated and input to switches Q1 and Q2, respectively. Note that the switching command unit 143 ′ determines that the switches Q1 and Q2 are turned on when the reflected wave power Pr is less than the first threshold value Pr1 and greater than the second threshold value Pr2 as a determination result of the determination unit 142 ′. Maintain state and off state as is. As described above, the switching command unit 143 ′ inputs the switching control signals S1 and S2 to the switches Q1 and Q2 of the level switching unit 113a, thereby changing the output voltage Vout of the level switching unit 113a between the high level and the low level. You can switch to either.

  The first threshold value Pr1 may be set to be equal to or lower than the durability performance of the switching element Qs based on the durability performance of the switching element Qs of the high-frequency inverter 113. Specifically, the higher the endurance performance of the switching element Qs, the higher the reflected wave power Pr can be withstood. Therefore, it is necessary to reduce the first threshold value Pr1 as the durability performance is lower. Further, the second threshold value Pr2 may be appropriately set based on the output difference between the low level and the high level of the output voltage Vout of the level switching unit 113a. Specifically, if the difference between the first threshold value Pr1 and the second threshold value Pr2 is small, the reflected wave power Pr becomes greater than or equal to the first threshold value Pr1 when the output voltage Vout is switched from a low level to a high level. There is a possibility. In this case, the output voltage Vout is immediately switched from the high level to the low level, and the switching between the high level and the low level is repeated. In order to avoid this, based on the output difference between the high level and the low level, the reflected wave power Pr that rises when the output voltage Vout is switched from the low level to the high level does not exceed the first threshold value Pr1. The second threshold value Pr2 is set.

Next, the operation of the non-contact power transmission system C configured as described above will be described with reference to FIG. 9 shows a time chart of the level switching control performed by the non-contact power transmission system C. FIG. 9A shows the change in the reflected wave power Pr, and FIG. 9B shows the output voltage Vout of the level switching unit 113a. Shows changes. Although not shown, the load side impedance Z _A is assumed to vary as in FIG 3 (a). In addition, in FIG. 9A, there is actually some fluctuation.

As shown in the figure, during the period from time T0 to time T1, the reflected wave power Pr is zero because the load side impedance Z _A matches the power source side impedance Z _B due to the impedance matching of the impedance matching device 12. In such a situation, when a load change occurs at time T1 and the load side impedance Z _A increases (or decreases), the reflected wave power Pr starts to be generated. When the rising reflected wave power Pr becomes equal to or higher than the first threshold value Pr1 at time T2, the control unit 14 determines that the reflected wave power Pr input from the power detector 115 is equal to or higher than the first threshold value. Then, as shown in FIG. 9B, the output voltage Vout of the level switching unit 113a is switched from the high level to the low level. As a result, the high-frequency AC power output from the high-frequency inverter 113 is reduced, and the reflected wave power Pr is also reduced, as shown in FIG. Therefore, since the reflected wave power Pr input to the high frequency inverter 113 is reduced, damage to the high frequency inverter 113 can be suppressed.

Thereafter, the reflected wave power Pr is lowered by matching the load side impedance Z _A to the power source side impedance Z _B by impedance matching while the output voltage Vout of the level switching unit 113a is still switched to a low level. I will do it. When the reflected wave power Pr that decreases decreases at the time T3, the control unit 14 determines that the reflected wave power Pr input from the power detector 115 is equal to or less than the second threshold. As shown in FIG. 9B, the output voltage Vout of the level switching unit 113a is switched from the low level to the high level.

Thereafter, at time T4, when the load side impedance Z _A matches the power source side impedance Z _B and the impedance matching is completed, the reflected wave power Pr becomes zero.

From the above, the non-contact power transmission system C according to the third embodiment of the present invention reduces the output voltage Vout of the level switching unit 113 from a high level to a low level when the reflected wave power Pr becomes equal to or higher than the first threshold value Pr1. Switch to. Thereafter, when the reflected wave power Pr becomes equal to or lower than the second threshold value Pr2 by impedance matching of the impedance matching unit 12, the output voltage Vout of the level switching unit 113a is switched from the low level to the high level. Thus, even when the load matching impedance Z _A is matched with the power supply impedance Z _B by the impedance matching device 12, the high frequency alternating current output from the high frequency inverter 113 according to the fluctuation of the reflected wave power Pr. Since the voltage level can be switched, large reflected wave power can be prevented from being input to the high-frequency inverter 113. Accordingly, it is possible to suppress damage to the high-frequency inverter 113.

  In the first to third embodiments, the case where the RF conversion unit 113b of the high-frequency inverter 113 is configured by an E-class inverter has been described as an example, but the present invention is not limited to this. Another configuration example of the RF conversion unit 113b will be described below with reference to the drawings.

  FIG. 10 is a diagram illustrating an RF conversion unit 113c which is a first modification of the RF conversion unit 113b. As shown in the drawing, the RF conversion unit 113c includes an inductor L3, a switching element Qs, a capacitor C4, an LC series resonance circuit LC1, and a resonance circuit LC2 in which an inductor L6 and a capacitor C6 are connected in series. The Therefore, the RF conversion unit 113c is configured by adding the resonance circuit LC2 to the RF conversion unit 113b in the first embodiment. The resonance circuit LC2 is connected in parallel to the switching element Qs. The resonance frequency of the resonance circuit LC2 is set to twice the frequency of the high frequency control signal SW. In the present embodiment, since the frequency of the high frequency control signal SW is 13.56 MHz, the resonance frequency of the resonance circuit LC2 is set to 27.12 MHz. In the RF conversion unit 113c configured as described above, a current flows through the inductor L3 by the DC voltage input from the level switching unit 113a. Then, the current flowing through the inductor L3 is converted into a high-frequency alternating current by the switching operation of the switching element Qs, and is output from the RF conversion unit 113c.

  FIG. 11 is a diagram illustrating an RF conversion unit 113d which is a second modification of the RF conversion unit 113b. As shown in the drawing, the RF conversion unit 113d includes two switching elements Qs and an LC series resonance circuit LC1. The two switching elements Qs are bridge-connected, and the drain terminal of one (upper side in FIG. 11) is connected to the output terminal on the high potential side of the level switching unit 113a, and the other (lower side in FIG. 11). The source terminal of the switching element Qs is connected to the output terminal on the low potential side of the level switching unit 113a. The gate terminals of the two switching elements Qs are connected to the control unit 14 and perform a switching operation according to the high frequency control signal SW input from the control unit 14. The high frequency control signal SW is input so that when one of the two switching elements Qs is on, the other is off. An LC series resonance circuit LC1 that functions as a filter is connected to a connection point between the two switching elements Qs that are bridge-connected. The RF conversion unit 113d is configured by a so-called class D inverter (class D amplifier). In addition, in FIG. 11, although it is a half-bridge structure which bridge-connected two switching elements Qs, full-bridge connection may be sufficient. The RF conversion unit 113d converts the DC voltage input from the level switching unit 113a into a high-frequency AC voltage by the switching operation of the two switching elements Qs, and outputs it.

FIG. 12 is a diagram illustrating an RF conversion unit 113e which is a third modification of the RF conversion unit 113b. As shown in the drawing, the RF conversion unit 113e includes a transmission line K1, a switching element Qs, a capacitor C4, and an LC series resonance circuit LC1. Therefore, the RF conversion unit 113e is configured by using the transmission line K1 instead of the inductor L3 of the RF conversion unit 113b in the first embodiment. The transmission line K1 is a line for transmitting power, and for example, a coaxial cable, a coaxial tube, or the like is used. Further, the transmission line K1 uses a length of about ¼ of the transmission wavelength in the transmission line K1 of the frequency of the high-frequency output (frequency of the high-frequency control signal SW) output from the RF converter 113e. . If the velocity of the radio wave in the transmission line K1 is ν and the frequency is f, the transmission wavelength λ in the transmission line K1 is represented by λ [m] = ν [m / s] / f [Hz]. For example, when a coaxial cable (made of polyethylene) is used as the transmission line K1, the velocity ν of the radio wave in the transmission line K1 is the velocity c (= 3.0 × 10 ⁸ [m / s]) of the radio wave in vacuum. Since the frequency f is the switching frequency (frequency of the high-frequency control signal SW) f _SW of the switching element Qs, the transmission wavelength λ in the transmission line K1 is λ = (c · (66/100)). / F _SW = (3.0 × 10 ⁸ ) × (66/100) / (13.56 × 10 ⁶ ) ≈14.60 [m]. Since the length of the transmission line K1 is approximately 1/4 of the transmission wavelength λ, 14.60 × (1/4) ≈3.7 [m]. Note that the radio wave velocity ν on the coaxial cable is approximately 66% of the radio wave velocity in vacuum, but the radio wave velocity on the coaxial cable depends on the wavelength reduction rate of the coaxial cable used (more specifically, the coaxial cable). Depending on the insulation material). Therefore, the length of the transmission line K1 may be appropriately changed according to the type of the coaxial cable used. In the RF conversion unit 113e configured as described above, a current flows through the transmission line K1 by the DC voltage input from the level switching unit 113a. Then, the current flowing through the transmission line K1 is converted into a high-frequency alternating current by the switching operation of the switching element Qs, and is output from the RF conversion unit 113e.

FIG. 13 is a diagram illustrating an RF conversion unit 113f which is a fourth modification of the RF conversion unit 113b. As illustrated, the RF conversion unit 113f includes an inductor L3, a switching element Qs, a capacitor C4, an LC series resonance circuit LC1, and two transmission lines K2 and K3. Therefore, the RF conversion unit 113f is configured by adding two transmission lines K2 and K3 to the RF conversion unit 113b in the first embodiment. One end of each of the transmission line K2 and the transmission line K3 is connected to a connection point between the inductor L3 and the switching element Qs, the other end of the transmission line K2 is opened, and the other end of the transmission line K3 is short-circuited. Further, the transmission line K2 (K3) has a length of about 1/8 of the transmission wavelength λ in the transmission line K2 (K3), which is the frequency of the high-frequency output output from the RF converter 113f. Specifically, when a coaxial cable (made of polyethylene) is used similarly to the transmission line K1, the transmission wavelength λ in the transmission line K2 (K3) is λ = (3.0 × 10 ⁸ ) × (66/100 ) / (13.56 × 10 ⁶ ) ≈14.60 [m]. Since the length of the transmission line K2 (K3) is about 1/8 of the transmission wavelength λ, 14.60 × (1/8) ≈1.8 [m]. In the RF conversion unit 113f configured as described above, a current flows through the inductor L3 by the DC voltage input from the level switching unit 113a. Then, the current flowing through the inductor L3 is converted into a high-frequency alternating current by the switching operation of the switching element Qs, and is output from the RF conversion unit 113f.

  Even when the RF converters 113c to 113f configured as described above are replaced with the RF converter 113b of the high-frequency inverter 113 according to the first to third embodiments, a large reflected wave power is input. Since there is a possibility that the high-frequency inverter 113 (switching element Qs) may be damaged, the same effects as those of the first to third embodiments can be obtained.

  In the first to third embodiments, the case where the high-frequency power supply device according to the present invention is applied to a non-contact power transmission system has been described as an example. However, the present invention is not limited to this. You may apply to the high frequency power supply device of another use. For example, you may apply to the plasma processing system D which performs the thin film formation and etching process of a semiconductor wafer as shown in FIG. This case will be described below as a fourth embodiment. In addition, the same code | symbol is attached | subjected about the same or similar structure as the said 1st Embodiment thru | or 3rd Embodiment, and the description is abbreviate | omitted.

  FIG. 14 is a diagram showing the entire plasma processing system D. As shown in FIG. The plasma processing system D converts commercial AC power input from the commercial power source P into high frequency AC power by the high frequency power supply circuit 11 and supplies it to the plasma processing apparatus 15.

  The plasma processing apparatus 15 includes a work processing unit, and is a device for processing (etching, CVD, etc.) a work such as a semiconductor wafer or a liquid crystal substrate carried into the work processing unit. In order to process the workpiece, the plasma processing apparatus 15 introduces a plasma discharge gas into the workpiece processing portion, and applies high-frequency AC power (voltage) supplied from the high-frequency power supply circuit 11 to the plasma discharge gas. Thus, the plasma discharge gas is discharged to change from the non-plasma state to the plasma state. And the workpiece | work is processed using the gas which became the plasma state.

In such a plasma processing system D, the internal impedance of the plasma processing apparatus 15 varies depending on the state of plasma discharge. For this reason, the load side impedance Z _{A when the} load side is viewed from the input end of the impedance matching device 12 (the output end of the high frequency inverter 113) varies. Therefore, as in the first embodiment, the control unit 14 controls the level switching of the output voltage Vout of the level switching unit 113a based on the impedance difference ΔZ, so that a large reflected wave power is input to the high-frequency inverter 113. Can be prevented. Accordingly, it is possible to suppress damage to the high-frequency inverter 113. In the plasma processing system D, the DC voltage level output from the level switching unit 113a may be switched based on the reflected wave power Pr instead of the impedance difference ΔZ. Furthermore, you may comprise using RF conversion part 113c-113f shown in FIGS.

In the non-contact power transmission systems A, B, C and the plasma processing system D described above, when the output of the high-frequency AC power from the high-frequency inverter 113 is started, there is a high possibility that the impedance is not matched. Therefore, the output start of the high-frequency AC power is determined, and immediately after the start, the low-level DC voltage is output from the level switching unit 113a. After the impedance matching is completed by the impedance matching unit 12, the level switching unit 113a May output a high level DC voltage. The determination of the output start can be made by operating a power switch (output start switch) (not shown) provided in each system, detecting the output power by a power detector, or the like. After that, as in the first to fourth embodiments, the level switching unit 113a (level switching unit 113a ′) is switched based on the value of the load side impedance Z _A or the reflected wave power Pr.

  As described above, the high-frequency power supply device and the non-contact power transmission system according to the present invention have been described. However, the present invention is not limited to the above-described embodiment. Various design changes can be made in various ways.

A, B, C Non-contact power transmission system P Commercial power supply 1 Power transmission device 11 High frequency power supply circuit 111 Rectifier circuit 112 Smoothing circuit 113 High frequency inverter 113a, 113a ′ Level switching unit 113b to 113f RF conversion unit Q1, Q2, Q3 switch C1, C2, C3, C4, C5, C6 Capacitor Qs Switching element L3, L5, L6 Inductor LC1 LC series resonant circuit LC2 resonant circuit K1, K2, K3 Transmission line 114 Impedance detector 114a Current / voltage sensor 114b Calculation unit 115 Power detector DESCRIPTION OF SYMBOLS 12 Impedance matching device 13 Power transmission unit C13 Capacitor L13 Power transmission coil 14,14 'Control part 141 Control signal generation part 142,142' Judgment part 143,143 'Switching command part 2 Power receiving apparatus 21 Power receiving unit C21 Condensate Sa L21 power receiving coil 22 rectifying and smoothing circuit 23 the charging circuit 3 Battery D plasma processing system 15 a plasma processing apparatus

Claims (13)

A high frequency power supply device that outputs a high frequency to a load via an impedance matching unit,
High-frequency generating means for generating a high frequency by converting DC power into high-frequency power by switching operation of the switching element;
Detecting means for detecting a characteristic value on the output side of the high-frequency generating means;
A switching unit disposed on an input side of the high-frequency generation unit; and by switching the switch unit based on the characteristic value detected by the detection unit, a DC voltage input to the high-frequency generation unit is Switching means for switching to any one of a plurality of different DC voltages;
A high frequency power supply device comprising: The characteristic value is a load-side impedance that is an impedance viewed from the output end of the high-frequency generating means,
The detection means detects the load side impedance,
The switching unit calculates an impedance difference that is a difference between the load side impedance and a power source side impedance that is an impedance when the opposite side of the load side is viewed from the output end, and the impedance difference is equal to or greater than a first threshold value. In some cases, the DC voltage at the lowest level among the plurality of DC voltages is output, and the DC voltage at the highest level among the plurality of DC voltages is output when the impedance difference is less than the first threshold. Switching the switch unit to output a voltage;
The high frequency power supply device according to claim 1. The characteristic value is a load-side impedance that is an impedance viewed from the output end of the high-frequency generating means,
The detection means detects the load side impedance,
The switching unit calculates an impedance difference that is a difference between the load side impedance and a power source side impedance that is an impedance when the opposite side of the load side is viewed from the output end, and the impedance difference is equal to or greater than a first threshold value. In some cases, the DC voltage of the lowest level among the plurality of DC voltages is output, and when the impedance difference is equal to or smaller than a second threshold value that is smaller than the first threshold value, Switching the switch unit to output the highest level DC voltage;
The high frequency power supply device according to claim 1. The characteristic value is reflected wave power reflected from the load side,
The detection means detects the value of the reflected wave power,
When the value of the reflected wave power is greater than or equal to a first threshold, the switching unit outputs a DC voltage of the lowest level among the plurality of DC voltages, and the value of the reflected wave power is the first value. When the second threshold value is less than or equal to a second threshold value, the switch unit is switched to output the highest level DC voltage among the plurality of DC voltages.
The high frequency power supply device according to claim 1. A judgment means for judging the start of output of the high frequency from the high frequency conversion means;
The switching means outputs the lowest level DC voltage among the plurality of DC voltages at the start of the high frequency output, and after the impedance matching by the impedance matching unit is completed, Switching the switch unit to output the highest level DC voltage;
The high frequency power supply device according to any one of claims 1 to 4. The switching means receives a DC voltage from a DC voltage source,
The highest level is the same level as the DC voltage input from the DC voltage source to the switching means.
The high frequency power supply device according to any one of claims 2 to 5. The switching means has a plurality of capacitors arranged in front of the switch unit in order to divide the input DC voltage,
The switch unit is configured by the same number of switches as the plurality of capacitors,
One terminal of each switch is connected to a high potential side terminal of each of the capacitors, which is different from each other,
The other terminal of each switch is connected to each other and connected to a high potential side terminal on the input side of the high frequency conversion means.
The high frequency power supply device according to any one of claims 1 to 6. The high frequency generation means includes the switching element that performs a switching operation based on an input high frequency control signal, and an inductor that is connected in series between the switching means and the switching element. The
The high frequency power supply device according to any one of claims 1 to 7. The high-frequency generating means includes the switching element for performing a switching operation based on an input high-frequency control signal, an inductor connected in series between the switching means and the switching element, and in parallel with the switching element. A resonance circuit that is connected and has an impedance of zero at a frequency that is twice the frequency of the high-frequency control signal.
The high frequency power supply device according to any one of claims 1 to 7. The high-frequency generation means includes a plurality of switching elements that are half-bridge connected or full-bridge connected between the switching means and the impedance matching unit.
The high frequency power supply device according to any one of claims 1 to 7. The high frequency generation means includes the switching element that performs a switching operation based on an input high frequency control signal, and a transmission line that is connected in series between the switching means and the switching element. And
The length of the transmission line is approximately one-fourth the length of the transmission wavelength in the transmission line of the frequency of the high-frequency control signal.
The high frequency power supply device according to any one of claims 1 to 7. The high frequency generation means includes the switching element for performing a switching operation based on an input high frequency control signal, an inductor connected in series between the switching means and the switching element, and one terminal of the inductor Is connected to the connection point of the switching element, the other terminal is opened, one terminal is connected to the connection point of the inductor and the switching element, the other terminal is short-circuited A second transmission line, and
The length of the first transmission line and the length of the second transmission line are each approximately one-eighth of the transmission wavelength in each transmission line of the frequency of the high-frequency control signal.
The high frequency power supply device according to any one of claims 1 to 7. A non-contact power transmission system that supplies power from a power transmission device to a power reception device in a non-contact manner,
The power transmission device is:
A high-frequency power supply device according to any one of claims 1 to 12 is provided.
Non-contact power transmission system.

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