JP6609166B2 - High frequency power supply device and contactless power transmission system - Google Patents

Description

  The present invention relates to a high-frequency power supply device that converts a direct current into a high-frequency current and outputs the same, and a non-contact power transmission system including the high-frequency power supply device.

  In recent years, non-contact power transmission technology for transmitting power from a power supply device to a multi-function mobile phone (smart phone) or an electric vehicle without using a metal contact or connector has been attracting attention. However, high frequency power of several MHz to several hundred MHz is used. In such a high-frequency power supply device that generates high-frequency power, a half-bridge inverter circuit using two switching elements and a full-bridge inverter circuit using four switching elements are generally used. . The drive circuit that drives these inverter circuits needs to have a dead time in order to reduce switching loss, and the circuit configuration becomes complicated.

  Therefore, an inverter circuit, a so-called class E amplifier, in which the configuration of the drive circuit is simplified by replacing the switching element on the high potential side of the half-bridge type or full-bridge type inverter circuit with an inductor is known. For example, Patent Document 1 describes a non-contact power transmission device using such a high-frequency power supply device.

JP2013-115908A

  However, it is known that in a conventional high-frequency power supply device, the voltage generated in the switching element becomes large and becomes three times or more of the DC voltage input to the inverter circuit. Therefore, the switching element to be used must have a high breakdown voltage.

  Therefore, the present invention has been created in view of the above problems, and a purpose thereof is a high-frequency power supply device capable of suppressing a voltage generated in a switching element and a non-contact power transmission system including the high-frequency power supply device. Is to provide.

  The high-frequency power supply device provided by the first aspect of the present invention is a high-frequency power supply device that converts a direct current into a high-frequency current and outputs the high-frequency power supply. And a switching element that switches between a non-conducting state and at least a circuit component having an impedance of zero at a frequency that is twice the frequency of the high-frequency drive signal, and that converts the direct current into the high-frequency current. Conversion means; and impedance matching means that is arranged at the output end of the high-frequency conversion means and automatically adjusts the impedance when the load side is viewed from the output end to the impedance when the DC power supply side is viewed from the output end. .

  In a preferred embodiment of the present invention, the high-frequency conversion means includes an inductor connected in series to an output terminal on the high potential side of the DC power supply, and a first connected in series to the inductor on the output side of the inductor. The switching element is connected in series to the inductor on the output side of the inductor, and the circuit component is connected in parallel to the switching element on the output side of the inductor. The second resonance circuit is set so that the impedance becomes zero at a frequency twice the frequency of the high-frequency drive signal.

  In a preferred embodiment of the present invention, the second resonance circuit is a series resonance circuit in which an inductor and a capacitor are connected in series.

  In another preferred embodiment of the present invention, the circuit component is a transmission line connected in series to an output terminal on the high potential side of the DC power supply, and the switching element is on the output side of the transmission line. The transmission line is connected in series, and the high-frequency conversion means further includes a first resonance circuit connected in series to the transmission line on the output side of the transmission line, and the length of the transmission line is The high frequency output from the high frequency conversion means is approximately one quarter of the transmission wavelength in the transmission line.

  In another preferred embodiment of the present invention, the high-frequency conversion means is connected in series to an output terminal on the high potential side of the DC power supply, and is connected in series to the inductor on the output side of the inductor. A first resonant circuit, wherein the switching element is connected in series to the inductor on the output side of the inductor, and the circuit component has one terminal at the inductor and the switching element. A first transmission line that is connected to the connection point of the first transmission line, the other terminal being open, and a second transmission in which one terminal is connected to the connection point of the inductor and the switching element, 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 high-frequency output from the high-frequency conversion means. Approximately 8 minutes 1 transmission wavelength in each said transmission line is long.

  In a preferred embodiment of the present invention, the transmission line is a coaxial cable.

  In a preferred embodiment of the present invention, the frequency of the high frequency drive signal is 6.78 MHz or more.

  In a preferred embodiment of the present invention, the switching element is composed of an FET.

  In a preferred embodiment of the present invention, the apparatus further comprises detection means for detecting impedance viewed from the load side or reflected wave power at the output terminal of the high-frequency conversion means, and the impedance matching means comprises two variable capacitors and 1 Each of the two variable capacitors is driven by driving a motor attached to each of the variable capacitors based on a detection value of the detection means. The impedance is automatically adjusted to the impedance seen from the DC power supply side.

  In a preferred embodiment of the present invention, the apparatus further comprises control means for generating the high-frequency drive signal and inputting the high-frequency drive signal to the switching element, wherein the control means is an average of electric power output from the high-frequency conversion means within a predetermined period. The ratio of the period during which high-frequency power is output from the high-frequency conversion means and the period during which it is not output is changed so that the value becomes the target output power.

  The contactless power transmission system provided by the second aspect of the present invention includes the high frequency power supply device provided by the first aspect, a power transmission coil and a power reception coil magnetically coupled to each other, and the high frequency power supply device A power transmission unit that transmits high-frequency power output from the power transmission coil to the power reception coil in a contactless manner.

  According to the present invention, at least the second harmonic is attenuated by the circuit component whose impedance is zero at least twice the frequency of the high frequency drive signal, and is generated in the switching element by the second harmonic component. Voltage can be suppressed. Therefore, the voltage generated in the switching element of the high-frequency conversion means can be suppressed lower than that of the high-frequency power supply device using the class E amplifier for the high-frequency conversion means (inverter circuit). Furthermore, impedance matching means is provided inside the high-frequency power supply device, and the impedance matching means automatically adjusts the impedance seen from the output end of the high-frequency conversion means to the impedance seen from the output end to the DC power supply side. I tried to do it. Thereby, even when the impedance seen from the load side changes, the impedance seen from the load side is automatically matched to the impedance seen from the DC power supply side, so that the reflected wave power can be suppressed. Therefore, since it is possible to suppress large reflected wave power from being input to the switching element, it is possible to suppress a voltage generated in the switching element due to the reflected wave power.

  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 the circuit structure of the high frequency conversion part which concerns on 1st Embodiment. It is a figure which shows the circuit structure (modification) of the high frequency conversion part which concerns on 1st Embodiment. It is a figure which shows the structural example of an impedance matching part. It is a figure which shows the structural example (modification) of an impedance matching part. It is a figure which shows the waveform of the drain voltage of the switching element when it simulates using the high frequency power supply device which concerns on 1st Embodiment, and the conventional inverter circuit. It is a figure which shows the circuit structure of the high frequency conversion part which concerns on 2nd Embodiment. It is a figure which shows the circuit structure (modification) of the high frequency conversion part which concerns on 2nd Embodiment. It is a figure which shows the waveform of the drain voltage of the switching element when it simulates using the high frequency power supply device which concerns on 2nd Embodiment, and the conventional inverter circuit. It is a figure which shows the circuit structure of the high frequency conversion part which concerns on 3rd Embodiment. It is a figure which shows the frequency characteristic of the magnitude | size of the impedance of the transmission line part which concerns on 3rd Embodiment. It is a figure which shows the circuit structure (modification) of the high frequency conversion part which concerns on 3rd Embodiment. It is a figure for demonstrating the PDM control of the high frequency electric power in a modification.

  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 shows the overall configuration of a non-contact power transmission system A according to the first embodiment of the present invention. A contactless power transmission system A according to the present embodiment includes a high frequency power supply device 1 that generates high frequency power, a power transmission unit 2 that transmits the high frequency power generated by the high frequency power supply device 1 in a contactless manner, and power transmission from the power transmission unit 2. The power receiving unit 3 that receives the received high frequency power and the charging device 4 that charges the battery 5 using the high frequency power received by the power receiving unit 3 are configured. That is, the aspect which applied the non-contact electric power transmission system A which concerns on 1st Embodiment to the charging system is demonstrated.

  In the non-contact power transmission system A, when power is transmitted from the power transmission unit 2 to the power reception unit 3, high frequency power of several MHz to several hundred MHz is used. The power transmission coil L2 of the power transmission unit 2 and the power reception coil L3 of the power reception unit 3 are magnetically coupled to each other. The high frequency current flowing in the power transmission coil L2 changes the magnetic flux generated in the power transmission coil L2, and the change in the magnetic flux A high frequency current flows through the receiving coil L3. Note that the inductance of the power transmission coil L2 (L3) and the capacitance of the capacitor C2 (C3) are adjusted to values that resonate with the frequency output by the high-frequency power supply device 1. Thereby, in the non-contact power transmission system A, power is transmitted from the power transmission unit 2 to the power reception unit 3 in a non-contact manner. In the present embodiment, a case where the magnetic resonance method is used as the non-contact power transmission method will be described as an example, but other transmission methods may be used.

  Each component of the non-contact power transmission system A according to the first embodiment will be described in detail.

  The high frequency power supply device 1 generates high frequency power by converting commercial power (alternating current) input from a commercial power source (not shown) into high frequency power (alternating current). The high frequency power supply device 1 includes a DC power supply unit 11, a high frequency conversion unit 12, a power detection unit 13, an impedance matching unit 14, and a power supply control unit 15.

  The DC power supply unit 11 generates a DC current and outputs it to the high-frequency conversion unit 12. The DC power supply unit 11 rectifies an AC voltage (for example, a commercial voltage 200 [V]) input from a commercial power supply (not shown) by a rectifier circuit (not shown) and smoothes it by a smoothing circuit (not shown), thereby converting it into a DC voltage. To do. Then, it is converted into a DC voltage of a predetermined level (set voltage value) by a DC-DC converter (not shown). The DC power supply unit 11 converts the DC voltage after rectification and smoothing into a DC voltage of a predetermined level by controlling the conversion operation of the DC-DC converter by the drive signal S1 input from the power supply control unit 15.

  The high frequency converter 12 converts a direct current input from the direct current power supply unit 11 into a high frequency current. The high frequency conversion unit 12 generates a high frequency current by switching the switching element Q with the high frequency drive signal S2 input from the power supply control unit 15. FIG. 2 is a diagram illustrating a circuit configuration of the high-frequency converter 12. As shown in the figure, the high frequency converter 12 includes a first capacitor Cf, an inductor Lf, a switching element Q such as a bipolar transistor or a field effect transistor (FET), a diode D, a second capacitor Cs, and an inductor. And a first resonance circuit LCf in which a capacitor is connected in series, and a second resonance circuit LCs in which an inductor and a capacitor are connected in series. In the present embodiment, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is used as the switching element Q.

  In the high frequency converter 12, the first capacitor Cf is connected to the DC power supply unit 11 in parallel. One end (input side terminal) of the inductor Lf is connected to the output terminal on the high potential side of the DC power supply unit 11 and connected in series. The drain terminal of the switching element Q is connected to the other end (terminal on the output side) of the inductor Lf, and the source terminal is connected to the output terminal on the low potential side of the DC power supply unit 11. The gate terminal of the switching element Q is connected to the power supply control unit 15. The diode D is connected in antiparallel to the switching element Q, and the second capacitor Cs is connected in parallel to the switching element Q. The first resonance circuit LCf is connected in series to the output-side terminal of the inductor Lf. The second resonance circuit LCs is connected in parallel to the DC power supply unit 11, one end of which is connected to the connection point between the output side terminal of the inductor Lf and the drain terminal of the switching element Q, and the other end is connected to the DC power supply unit. 11 is connected to the output terminal on the low potential side.

  In the high-frequency conversion unit 12 configured as described above, the high-frequency drive signal S2 is input from the power supply control unit 15 to the gate terminal of the switching element Q, and the switching element Q is turned on / off. The high frequency drive signal S2 is a pulse signal that repeats an on voltage and an off voltage at a predetermined frequency f (for example, 13.56 MHz), as will be described later. The switching element Q is in a conductive state (on) when the high-frequency drive signal S2 is on-voltage, and is in a non-conduction state (off) when the high-frequency drive signal S2 is off-voltage. Therefore, a current flows through the switching element Q when the switching element Q is on, and a current flows through the second capacitor Cs when the switching element Q is off. The resonance frequency of the first resonance circuit LCf is set to the output frequency f (13.56 MHz in the present embodiment) of the high-frequency conversion unit 12, and the high-frequency conversion unit 12 Therefore, a sinusoidal alternating current corresponding to the resonance frequency is generated. As a result, the sinusoidal alternating current is output from the high frequency converter 12.

  The first capacitor Cf smoothes the DC voltage output from the DC power supply unit 11, and the inductor Lf supplies a constant voltage to the high-frequency conversion unit 12 based on the DC voltage smoothed by the first capacitor Cf. It operates as a direct current source for supplying current. Further, the diode D is a so-called flywheel diode, and prevents a high reverse voltage due to the counter electromotive force generated by switching the switching element Q from being applied to the switching element Q. When the switching element Q has a function of operating as a diode inside, the diode D may not be provided. The second resonance circuit LCs is set so that the impedance becomes zero at a frequency twice the frequency f (switching frequency f) of the high-frequency drive signal S2. Thereby, the current of the frequency component (second harmonic) twice the switching frequency f can be short-circuited. Therefore, the second harmonic voltage of the switching frequency f generated in the switching element Q can be attenuated.

  As shown in FIG. 3, the high-frequency converter 12 is a push-pull circuit that connects two circuits of the high-frequency converter 12 shown in FIG. 2 symmetrically and amplifies only one polarity signal. It may be configured. Also in this case, since the second harmonic current of the switching frequency f is short-circuited by each second resonance circuit LCs, the voltage generated by the second harmonic in the switching element Q can be attenuated.

  The power detection unit 13 is for monitoring the traveling wave power Pf output from the high frequency conversion unit 12. The power detection unit 13 includes a directional coupler, and detects a traveling wave voltage Vf and a reflected wave voltage Vr included in the high frequency voltage from the directional coupler. The power detection unit 13 converts the traveling wave voltage Vf into traveling wave power Pf and outputs it to the power supply control unit 15. Further, the reflected wave voltage Vr may be converted into the reflected wave power Pr and output to the power supply control unit 15. The traveling wave power Pf and the reflected wave power Pr may be detected by a detector 141 described later.

  The impedance matching unit 14 is connected to the load side (battery 5 side) from the output end of the high frequency conversion unit 12 in order to suppress the amount of reflected wave output from the high frequency conversion unit 12 (reflected wave power Pr). ) Impedance (hereinafter referred to as “load-side impedance”) viewed from the output terminal of the high-frequency converter 12 to the DC power supply 11 side (hereinafter referred to as “power-side impedance”) (for example, 50Ω) Impedance matching is performed to match. FIG. 4 is a diagram illustrating an example of a circuit configuration of the impedance matching unit 14. As illustrated, the impedance matching unit 14 includes a detector 141, two variable capacitors 142 and 143, one inductor 144, and two motors 145 and 146. A circuit in which the variable capacitor 142 and the inductor 144 are connected in series and the variable capacitor 143 are connected in an inverted L shape.

  The detector 141 detects load side impedance, and includes a current / voltage sensor and a calculation unit. The current / voltage sensor detects a high-frequency current and a high-frequency voltage on the output side of the high-frequency conversion unit 12, and outputs the detected current signal and voltage signal to the calculation unit. The computing unit computes the current effective value, the voltage effective value, and the phase difference between the current signal and the voltage signal from the current signal and the voltage signal input from the current / voltage sensor. Then, the load side impedance is detected using these parameters. The load side impedance detected by the detector 141 is output to the power supply control unit 15. The detector 141 may be provided inside the high frequency power supply device 1 and at a position where the load side impedance can be detected, and need not be inside the impedance matching unit 14. The detector 141 further performs a predetermined calculation using the detected value to obtain the traveling wave power Pf and the reflected wave power Pr output from the high frequency converter 12 and outputs them to the power supply controller 15. You may do it. In this case, the high-frequency power supply device 1 may not include the power detection unit 13.

  The variable capacitors 142 and 143 are capacitors that can change the capacitance. In the present embodiment, the variable capacitors 142 and 143 are constituted by variable capacitors of a type in which one of a pair of electrodes facing each other is configured by a movable electrode and the electrode facing area is changed by rotating the movable electrode. doing. Note that the present invention is not limited to this as long as the capacitance can be changed.

  Motors 145 and 146 for rotating the movable electrode are attached to the variable capacitors 142 and 143, respectively. The motor drive signals S3 and S4 (drive voltage) are input to the motors 145 and 146 from the power supply control unit 15, respectively, and the motors 145 and 146 are driven according to the motor drive signals S3 and S4, whereby the variable capacitors 142 and 143 are obtained. The movable electrode is rotated. Thereby, the capacitances of the variable capacitors 142 and 143 are controlled to arbitrary capacitances, respectively. Each of the variable capacitors 142 and 143 is provided with a position detection sensor (not shown) for detecting the rotational position of the movable electrode so that the power supply control unit 15 monitors the rotational position of the movable electrode. A detection signal from the detection sensor is input to the power supply control unit 15. Further, the inductance of the inductor 144 is set to a predetermined value.

  From the above, the impedance matching unit 14 performs impedance matching by adjusting the capacitances of the variable capacitors 142 and 143 by the motor drive signals S3 and S4 input from the power supply control unit 15.

  The impedance matching unit 14 is not limited to the configuration shown in FIG. 4 as long as the load side impedance can be automatically matched to the power source side impedance. For example, as shown in FIG. 5, an impedance matching unit 14 ′ in which two variable capacitors 142 and 143 and an inductor 144 are connected in a π type may be used.

  The power supply control unit 15 controls the entire high-frequency power supply device 1 and is composed of, for example, a microcomputer or FPGA including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The The power supply control unit 15 controls the DC power supply unit 11 by inputting the drive signal S1, the high frequency conversion unit 12 to the high frequency drive signal S2, and the impedance matching unit 14 by inputting the motor drive signals S3 and S4. .

  The power supply control unit 15 changes the level of the high-frequency voltage output from the high-frequency conversion unit 12 by changing the level of the DC voltage generated by the DC power supply unit 11 by feedback control. When the level of the high frequency voltage changes, the traveling wave power Pf output from the high frequency power supply device 1 changes, so the power supply control unit 15 monitors the power difference ΔPf between the traveling wave power Pf and the target output power Pfs, and the power The output voltage of the DC power supply unit 11 is adjusted so that the difference ΔPf becomes zero. Specifically, the power supply control unit 15 generates the drive signal S <b> 1 based on the traveling wave power Pf input from the power detection unit 13 and outputs the drive signal S <b> 1 to the DC power supply unit 11. The drive signal S1 is a signal for controlling the output voltage of the DC power supply unit 11 so that the output power (traveling wave power Pf) of the high-frequency power supply device 1 becomes the target output power Pfs. The target output power Pfs may be manually input by operating an input device (not shown), or may be automatically input by a preset program. The power supply control unit 15 calculates a power difference ΔPf (= Pfs−Pf) between the detected value of the traveling wave power Pf input from the power detection unit 13 and the target output power Pfs, and sets the power difference ΔPf to zero. The control pulse signal is generated. Then, the control pulse signal is amplified to a level at which the DC-DC converter can be driven by a drive circuit (not shown), and is output to the DC power supply unit 11 as the drive signal S1.

  Moreover, the power supply control part 15 performs the high frequency conversion control which converts a direct current into a high frequency current by inputting the high frequency drive signal S2 into the high frequency conversion part 12. The power supply control unit 15 generates a pulse signal (which may be a sine wave signal or the like) having an on-voltage and an off-voltage having a predetermined frequency f based on the reference clock, and a drive circuit (not shown) Is amplified to a level at which the switching element Q can be driven, and is output to the high-frequency converter 12 as a high-frequency drive signal S2. In the present embodiment, since the power supply control unit 15 outputs a 13.56 MHz pulse signal as the high frequency drive signal S2 to the high frequency conversion unit 12, the frequency of the high frequency voltage output from the high frequency conversion unit 12 is 13.56 MHz. It becomes.

  Furthermore, the power supply control unit 15 controls the impedance matching unit 14 to perform impedance matching for matching the load side impedance to the power supply side impedance. Specifically, the power supply control unit 15 inputs motor drive signals S3 and S4 to the motors 145 and 146, respectively, so that the load-side impedance detected by the detector 141 matches the power-supply-side impedance. , 146 is controlled. At this time, the power supply control unit 15 controls driving of the motors 145 and 146 while monitoring the rotational position of the movable electrode based on a detection signal from a position detection sensor attached to each of the variable capacitors 142 and 143. Then, the driving of the motors 145 and 146 is controlled, and the capacitances of the variable capacitors 142 and 143 are adjusted. Thereby, impedance matching is performed. The power supply control unit 15 may perform impedance matching using the reflected wave power Pr detected by the power detection unit 13 instead of the load side impedance so that the reflected wave power Pr becomes zero. In this case, the power detection unit 14 corresponds to “detection means” described in the claims. In addition, when impedance matching is performed using the reflected wave power Pr, the impedance matching unit 14 may not include the detector 141.

  The power transmission unit 2 transmits the high frequency power input from the high frequency power supply device 1 to the power receiving unit 3 in a contactless manner. The power transmission unit 2 includes a series resonance circuit including a power transmission coil L2 formed of a circular coil having a plurality of turns and a capacitor C2 connected in series to the power transmission coil L2. In the power transmission unit 2, the resonance frequency of the series resonance circuit is adjusted to the frequency of the high frequency power output from the high frequency power supply device 1 (the output frequency f of the high frequency converter 12).

  The power receiving unit 3 receives the high-frequency power transmitted from the power transmission unit 2 in a contactless manner. The power reception unit 3 has the same configuration as that of the power transmission unit 2 and is configured by a series resonance circuit including a power reception coil L3 formed of a multi-turn circular coil and a capacitor C3 connected in series to the power reception coil L3. In the power receiving unit 3 as well, the resonance frequency of the series resonance circuit is adjusted to the frequency of the high frequency power output from the high frequency power supply device 1 (the output frequency f of the high frequency converter 12).

  Note that the power transmission unit 2 and the power reception unit 3 are not limited to the above configuration as long as they can transmit high-frequency power from the power transmission unit 2 to the power reception unit 3 in a contactless manner. For example, in the power transmission unit 2 (power reception unit 3), the power transmission coil L2 and the capacitor C2 (power reception coil L3 and capacitor C3) may be configured by a parallel resonance circuit connected in parallel. In the present embodiment, as described above, the case where the power transmission unit 2 and the power reception unit 3 have the same configuration has been described as an example. However, the configurations of the resonance circuits on the power transmission side and the power reception side are different. Also good. For example, the power transmission unit 2 may be configured by a series resonance circuit of a power transmission coil L2 and a capacitor C2, and the power reception unit 3 may be configured by a parallel resonance circuit of a power reception coil L3 and a capacitor C3 (and vice versa). Further, the power transmission coil L2 and the power reception coil L3 may have different sizes.

  The charging device 4 charges the battery 5 by converting the high frequency power received by the power receiving unit 3 into power suitable for charging the battery 5 and supplying the power to the battery 5. The charging device 4 rectifies and smoothes the high-frequency power input from the power receiving unit 3 and converts it to DC power, and then converts it into power suitable for charging the battery 5. For example, the charging device 4 converts the rectified and smoothed DC power into power suitable for constant current and constant voltage charging control, and supplies the power to the battery 5.

  The battery 5 is a secondary battery that stores electric power, and is composed of, for example, a lithium ion battery or a nickel metal hydride battery. When the battery 5 is a lithium ion battery, it is charged by constant current and constant voltage control by the charging device 4. Further, the battery 5 may be a livestock appliance such as a capacitor.

  The operation of the non-contact power transmission system A configured as described above will be described with reference to FIG.

  6 shows the waveform of the drain voltage of the switching element Q of the high-frequency converter 12 (see FIG. 6A) and the waveform of the drain voltage of the switching element of the conventional inverter circuit (class E amplifier) in the simulation. b)). In the simulation, the DC voltage input to the high frequency converter 12 is 200 V, the frequency f (switching frequency f) of the high frequency drive signal S2 is 13.56 MHz, and a 50Ω load is connected to the high frequency power supply device 1. The same conditions are used in the conventional inverter circuit. In FIG. 6A and FIG. 6B, the input voltage from the DC power supply unit 11 is also indicated by a broken line.

  In the case of the conventional inverter circuit (when the second resonance circuit LCs is not provided), as shown in FIG. 6B, the DC input voltage is 200 V, whereas the drain voltage when the switching element is OFF. Is about 700 V (at maximum), which is about 3.5 times the DC input voltage. On the other hand, when the second resonance circuit LCs is provided, as shown in FIG. 6A, the DC input voltage of the high-frequency converter 12 is 200 V, whereas the switching element Q is off. The drain voltage at that time is about 450 V (maximum), which is about 2.2 times the DC input voltage. As described above, it was confirmed that the voltage generated in the switching element Q was suppressed by providing the second resonance circuit LCs.

  From the above, according to the high frequency power supply device 1 according to the first embodiment of the present invention, since the second resonant circuit LCs is connected to the drain terminal of the switching element Q, the high frequency output from the high frequency converter 12 is high. The second harmonic current flows through the second resonance circuit LCs. Thereby, the voltage generated by the second harmonic current between the drain and source of the switching element Q can be suppressed.

  Further, when the distance between the power transmission coil L2 and the power reception coil L3 changes, the impedance when the load side is viewed from the output end of the high frequency converter 12 changes. Even in such a situation, the high frequency power supply device 1 can suppress the reflected wave power because impedance matching is automatically performed by the impedance matching unit 14 and the power supply control unit 15. Therefore, since the high frequency power supply device 1 suppresses large reflected wave power from being input to the switching element Q, the voltage generated in the switching element Q due to the reflected wave power can also be suppressed. In addition, the power loss of the switching element Q due to impedance mismatch can be suppressed.

  In the present embodiment, since the impedance matching unit 14 is provided inside the high frequency power supply device 1, it is possible to continue to supply high frequency power efficiently regardless of the device (load) connected to the high frequency power supply device 1. It is.

  Next, a non-contact power transmission system B according to the second embodiment of the present invention will be described. The overall configuration of the non-contact power transmission system B according to the second embodiment is substantially the same as the non-contact power transmission system A (see FIG. 1) according to the first embodiment, and the high-frequency conversion unit 12 is replaced with the high-frequency conversion unit 16. It is different in that it is replaced by. 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 high frequency converter 16 converts a direct current input from the direct current power supply unit 11 into a high frequency current. FIG. 7 is a diagram illustrating a circuit configuration of the high-frequency conversion unit 16. As shown in the figure, the high frequency converter 16 includes a first capacitor Cf, a transmission line K1, a switching element Q, a diode D, a second capacitor Cs, an inductor and a capacitor connected in series. Resonance circuit LCf. Therefore, the high frequency converter 16 has a circuit configuration different from that of the high frequency converter 12 according to the first embodiment, and uses the transmission line K1 instead of the inductor Lf and the second resonance circuit LCs.

  The transmission line K1 attenuates a frequency component (even harmonics) that is an even multiple of the fundamental wave of the high frequency from the high frequency generated by the high frequency converter 16. One end of the transmission line K1 is connected to the output terminal on the high potential side of the DC power supply unit 11, and the other end is connected to the drain terminal of the switching element Q and one end of the first resonance circuit LCf. In the present embodiment, the transmission line K1 is a coaxial cable. The transmission line K1 is not limited to a coaxial cable, and may be, for example, a coaxial pipe, a line formed on a substrate, or the like.

The length of the transmission line K1 is set to approximately one quarter of the transmission wavelength of the high-frequency fundamental wave output from the high-frequency converter 16 in the transmission line K1. Specifically, the high-frequency wavelength λ output from the high-frequency converter 16 is λ [m] = ν [m / s] / f [, where f is the frequency and ν is the velocity of the radio wave in the transmission line K1. Hz]. The velocity ν of radio waves on the coaxial cable (made of polyethylene) is about 66% of the velocity of radio waves in vacuum (3.0 × 10 ⁸ [m / s]), and the frequency f is 13.56 [MHz]. Therefore, the wavelength λ of the high frequency output from the high frequency converter 16 is λ = (3.0 × 10 ⁸ ) × (66/100) / (13.56 × 10 ⁶ ) ≈14.60 [m]. Since the length of the transmission line K1 is approximately ¼ of the wavelength λ, 14.60 × (1/4) ≈3.65 [m]. The radio wave velocity ν on the coaxial cable is about 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 (specifically, the coaxial cable It depends on the insulating material. Therefore, the length of the transmission line K1 may be appropriately changed according to the type of the coaxial cable used. As can be seen from the above calculation formula, the lower the frequency of the high frequency output from the high frequency converter 16, the longer the wavelength λ. Therefore, when the frequency is low, it is necessary to use a long transmission line K1. In order to accommodate the transmission line K1 in the housing of the high-frequency power supply device 1, the size of the high-frequency power supply device 1 must be increased. Therefore, the high frequency output from the high frequency converter 16 is preferably 6.78 MHz or more.

  As described above, the length of the transmission line K1 is set to a length of approximately one quarter of the transmission wavelength in the transmission line K1 of the high frequency output from the high frequency converter 16, so that the high frequency fundamental wave (frequency is 13.56 MHz) and frequency components that are odd multiples of the fundamental wave (odd order harmonics), the impedance is infinite, and frequency components that are even multiples of the fundamental wave (even harmonics), the impedance is zero. Become. Therefore, the harmonics generated in the switching element Q due to the current of even harmonics (second harmonics, fourth harmonics, etc.) of the high frequency output from the high frequency converter 16 flowing in the transmission line K1. Attenuate the component voltage.

  As shown in FIG. 8, the high frequency converter 16 is a push-pull circuit that connects two circuits of the high frequency converter 16 shown in FIG. 7 symmetrically and amplifies only one polarity signal. It may be configured. Also in this case, the voltage of the even harmonic component generated in the switching element Q can be attenuated by each transmission line K1, so that the voltage generated in the switching element Q can be suppressed.

  The operation of the non-contact power transmission system B configured as described above will be described with reference to FIG.

  9 shows the waveform of the drain voltage of the switching element Q of the high-frequency converter 16 (see FIG. 9A) and the waveform of the drain voltage of the switching element of the conventional inverter circuit (class E amplifier) in the simulation (see FIG. 9). b)). In the simulation, the DC voltage input to the high frequency converter 16 is 200 V, the frequency (switching frequency) of the high frequency drive signal S2 is 13.56 MHz, and a 50Ω load is connected to the high frequency power supply device 1. Note that FIG. 9B shows the same waveform as that shown in FIG. Also in FIG. 9A, the input voltage from the DC power supply unit 11 is indicated by a broken line.

  When the transmission line K1 is provided, as shown in FIG. 9A, the DC input voltage of the high-frequency converter 16 is 200 V, whereas the drain voltage when the switching element Q is OFF is The voltage is 400 V (maximum), which is about 2.0 times the DC input voltage. As described above, it was confirmed that the voltage generated in the switching element Q was suppressed by providing the transmission line K1.

  From the above, according to the high frequency power supply device 1 according to the second embodiment of the present invention, the transmission line K1 short-circuits the even-numbered higher harmonic current of the high frequency output from the high frequency converter 16. As a result, among the components included in the voltage generated in the switching element Q, the even harmonic components are reduced, so that the voltage can be suppressed. Further, when the transmission line K1 is provided, compared to the case where the second resonance circuit LCs of the high-frequency conversion unit 12 of the first embodiment is provided, not only the second harmonic but also the fourth order, the sixth order, and the like. Since even-order harmonics can also be attenuated, the drain voltage can be further suppressed than in the first embodiment (see FIGS. 6A and 9A).

  Also in the high frequency power supply device 1 according to the second embodiment, the impedance matching unit 14 and the power supply control unit 15 automatically perform impedance matching in the same manner as in the first embodiment. The voltage generated in Q and the power loss generated in the switching element Q can be suppressed. Furthermore, by providing the impedance matching device 14 inside the high frequency power supply device 1, it is possible to continue to supply high frequency power efficiently regardless of the device (load) connected to the high frequency power supply device 1.

  Next, a non-contact power transmission system C according to the third embodiment of the present invention will be described. The overall configuration of the non-contact power transmission system C according to the third embodiment is substantially the same as the non-contact power transmission system A (see FIG. 1) according to the first embodiment, and the high-frequency conversion unit 12 is replaced with the high-frequency conversion unit 17. It is different in that it is replaced by. In addition, about the structure same or similar to the said 1st Embodiment and 2nd Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  FIG. 10 shows a circuit configuration of the high-frequency conversion unit 17. As shown in the drawing, the high-frequency conversion unit 17 includes a first capacitor Cf, an inductor Lf, a switching element Q, a diode D, a second capacitor Cs, a transmission line unit K2, and a first resonance circuit LCf. It is comprised including. Therefore, the high frequency conversion unit 17 has a circuit configuration different from that of the high frequency conversion unit 12 according to the first embodiment, and uses a transmission line unit K2 instead of the second resonance circuit LCs.

  The transmission line part K2 attenuates the harmonics of a predetermined order from the high frequency generated by the high frequency converter 17. The transmission line unit K2 includes a transmission line K21 and a transmission line K22. The transmission line K21 is a transmission line in which one end is connected between the output-side terminal of the inductor Lf and the input-side terminal of the first resonance circuit LCf, and the other end is opened. The transmission line K22 is a transmission line having one end connected between the output-side terminal of the inductor Lf and the input-side terminal of the first resonance circuit LCf1, and the other end short-circuited. In the present embodiment, the transmission lines K21 and K22 are coaxial cables. The transmission lines K21 and K22 are not limited to coaxial cables, and may be, for example, coaxial pipes, lines formed on a substrate, or the like.

The lengths of the transmission lines K21 and K22 are approximately one-eighth the length of the transmission wavelength in the transmission lines K21 and K22 of the high frequency output from the high frequency converter 17. Specifically, when the same coaxial cable (made of polyethylene) as the transmission line K1 according to the second embodiment is used, the high-frequency wavelength λ output from the high-frequency conversion unit 17 is λ = (3 0.0 × 10 ⁸ ) × (66/100) / (13.56 × 10 ⁶ ) ≈14.60 [m], the lengths of the transmission lines K21 and K22 are approximately 1 / wavelength λ. 8, 14.60 × (1/8) ≈1.8 [m]. As in the second embodiment, the lower the frequency of the high frequency output from the high frequency converter 17, the longer the transmission lines K21 and K22. Therefore, in order to accommodate the transmission lines K21 and K22 in the housing of the high-frequency power supply device 1, the high-frequency frequency output from the high-frequency conversion unit 17 is desirably 6.78 MHz or more.

  FIG. 11 is a diagram illustrating a frequency characteristic of the magnitude of impedance when the transmission line portion K2 is viewed from the drain terminal side of the switching element Q. The horizontal axis indicates the frequency, and the vertical axis indicates the magnitude of the impedance. As shown in the figure, the impedance is infinite at a frequency f (= 13.56 MHz) and an odd multiple of the frequency f, and the impedance is zero at an even multiple of the frequency f. Therefore, the high-frequency fundamental wave and odd-order harmonics (third harmonic, fifth harmonic, etc.) output from the high-frequency converter 17 do not flow through the transmission line unit K2, and even harmonics ( (Second harmonic, fourth harmonic, etc.) current flows, and the voltage of even harmonic components generated in the switching element Q is attenuated.

  The high-frequency conversion unit 17 configured as described above is provided with the transmission line unit K2, so that the even-order harmonics generated in the switching element Q (like the high-frequency conversion unit 16 according to the second embodiment described above) ( Second harmonic, fourth harmonic, etc.) component voltage is attenuated. That is, even when the transmission line portion K2 is provided, the same effects as those of the high-frequency power supply device 1 according to the second embodiment can be obtained. Therefore, the drain voltage of the switching element Q becomes a waveform equivalent to the waveform shown in FIG. 9A, and the voltage generated in the switching element Q can be suppressed.

  As shown in FIG. 12, the high-frequency converter 17 is a push-pull circuit that amplifies only a signal of one polarity by connecting two circuits of the high-frequency converter 17 shown in FIG. 10 symmetrically. It may be configured. Also in this case, the voltage of the even harmonic component generated in the switching element Q can be attenuated by each transmission line portion K2, so that the voltage generated in the switching element Q can be suppressed.

  In the first to third embodiments, the DC power supply unit 11 includes a DC-DC converter, and the level of the DC voltage output from the DC power supply unit 11 is changed, so that the DC power supply unit 11 outputs the DC voltage. Although the aspect (pulse amplitude modulation (PAM) control) which controls high frequency electric power to target output electric power was demonstrated, it is not limited to this. For example, pulse density modulation (PDM) control for controlling the high frequency power output from the high frequency power supply device 1 to the target output power is performed by changing the ratio between the period during which the high frequency power is output and the period during which the high frequency power is not output. Also good. Specifically, the power supply control unit 15 controls the high frequency conversion unit 12 (16, 17) so that the average value of the high frequency power output from the high frequency power supply device 1 within a predetermined period becomes the target output power. This is realized by outputting a high-frequency drive signal S2 ′ having a period for outputting a pulse signal and a period for not outputting a pulse signal.

  The generation of the high frequency drive signal S2 'will be described with reference to FIG. The power supply control unit 15 calculates a power difference ΔPf (= Pfs−Pf) between the traveling wave power Pf input from the power detection unit 13 and the target output power Pfs. The traveling wave power Pf at this time is an average value for a predetermined period (for example, one cycle of a carrier signal Sc described later). The power difference ΔPf is multiplied by a predetermined feedback gain, and the power difference ΔPf ′ multiplied by the feedback gain is compared with a carrier signal Sc (sawtooth wave or triangular wave) having a predetermined frequency (for example, 400 Hz). As a result, when the power difference ΔPf ′ is greater than the carrier signal Sc (period T1), a 13.56 MHz pulse signal is generated, and when the power difference ΔPf ′ is less than or equal to the carrier signal Sc (period T2), 13. A 56 MHz pulse signal is not generated. Thereby, the high frequency drive signal S2 'having a period during which the pulse signal is output and a period during which the pulse signal is not output can be generated.

  Here, when the target output power Pfs is increased, the power difference ΔPf ′ increases, so that the power difference ΔPf ′ moves upward in FIG. Therefore, the period T1 in which the power difference ΔPf ′ is larger than the carrier signal Sc becomes longer, and the period in which the pulse signal is output in the high-frequency drive signal S2 ′ becomes longer. On the other hand, when the target output power Pfs is decreased, the power difference ΔPf ′ is decreased, so that the power difference ΔPf ′ moves downward in FIG. Therefore, the period T1 in which the power difference ΔPf ′ is larger than the carrier signal Sc is shortened, and the period for outputting the pulse signal in the high-frequency drive signal S2 ′ is shortened. From the above, the ratio between the period during which the pulse signal is output and the period during which the pulse signal is not output changes in the high-frequency drive signal S2 'due to the power difference ΔPf between the traveling wave power Pf and the target output power Pfs.

  Then, the power supply control unit 15 inputs the generated high-frequency drive signal S2 ′ to the high-frequency conversion unit 12 (16, 17) so that the high-frequency power is output from the high-frequency conversion unit 12 (16, 17) and the output. There will be a period that is not done. At this time, if the period during which the high-frequency power is output is long, the average value of the high-frequency power becomes large. Therefore, the power supply control unit 15 controls the average value of the output power of the high-frequency conversion unit 12 (16, 17) within a predetermined period (for example, one cycle of the carrier signal) to the target output power Pfs by PDM control. be able to. Therefore, it is not necessary to provide a power control device such as a DC-DC converter in the high frequency power supply device 1, and the configuration of the high frequency power supply device 1 can be simplified.

  In the said 1st Embodiment thru | or 3rd Embodiment, although the aspect which applied the high frequency power supply device which concerns on this invention to the non-contact electric power transmission system (charging system) was demonstrated to an example, it is not restricted to this. The high frequency power supply device according to the present invention can be applied to any system using high frequency power. For example, it may be used as a power source for a plasma processing system or a power source for an induction heating apparatus. Moreover, you may apply to the non-contact electric power transmission system of other uses (other than a charging system).

  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, and the specific configuration of each part is within the scope of the claims of the present invention. The design can be changed in various ways.

A, B, C Non-contact power transmission system 1 High frequency power supply device 11 DC power supply unit 12, 16, 17 High frequency conversion unit Cf First capacitor Lf Inductor Q Switching element Cs Second capacitor LCf First resonance circuit LCs Second Resonant circuit K1 Transmission line K2 Transmission line part K21, K22 Transmission line 13 Power detection part 14, 14 'Impedance matching part 141 Detector 142, 143 Variable capacitor 144 Inductor 145, 146 Motor 15 Power supply control part 2 Power transmission unit L2 Power transmission coil C2 capacitor 3 power receiving unit L3 power receiving coil C3 capacitor 4 charging device 5 battery

Claims (6)

A high-frequency power supply device that converts a direct current into a high-frequency current and outputs it,
A direct current power source for generating the direct current;
A switching element that switches between a conducting state and a non-conducting state in accordance with a high-frequency drive signal, and a circuit component that has at least a zero impedance at a frequency that is twice the frequency of the high-frequency drive signal. High-frequency conversion means for converting to high-frequency current;
Impedance matching means arranged at the output end of the high-frequency conversion means, and automatically adjusting the impedance when the load side is viewed from the output end to the impedance when the DC power supply side is viewed from the output end;
Equipped with a,
The circuit component is a transmission line connected in series to the output terminal on the high potential side of the DC power supply,
The switching element is connected in series to the transmission line on the output side of the transmission line,
The high-frequency conversion means further includes a first resonance circuit connected in series to the transmission line on the output side of the transmission line,
The length of the transmission line is approximately a quarter of the transmission wavelength of the high frequency output from the high frequency conversion means in the transmission line,
The transmission line is a coaxial cable.
High frequency power supply. A high-frequency power supply device that converts a direct current into a high-frequency current and outputs it,
A direct current power source for generating the direct current;
A switching element that switches between a conducting state and a non-conducting state in accordance with a high-frequency drive signal, and a circuit component that has at least a zero impedance at a frequency that is twice the frequency of the high-frequency drive signal. High-frequency conversion means for converting to high-frequency current;
Impedance matching means arranged at the output end of the high-frequency conversion means, and automatically adjusting the impedance when the load side is viewed from the output end to the impedance when the DC power supply side is viewed from the output end;
With
The high-frequency conversion means includes
An inductor connected in series to the output terminal on the high potential side of the DC power supply;
A first resonant circuit connected in series with the inductor on the output side of the inductor,
The switching element is connected in series to the inductor on the output side of the inductor,
In the circuit component, one terminal is connected to a connection point between the inductor and the switching element, the other terminal is open, and one terminal is a connection between the inductor and the switching element. A second transmission line connected to the point and having the other terminal short-circuited.
The length of the first transmission line and the length of the second transmission line are each approximately one-eighth of the transmission wavelength of each high-frequency wave output from the high-frequency conversion means. Yes ,
High-frequency power supply. The transmission line is a coaxial cable.
The high frequency power supply device according to claim 2 . A high-frequency power supply device that converts a direct current into a high-frequency current and outputs it,
A direct current power source for generating the direct current;
A switching element that switches between a conducting state and a non-conducting state in accordance with a high-frequency drive signal, and a circuit component that has at least a zero impedance at a frequency that is twice the frequency of the high-frequency drive signal. High-frequency conversion means for converting to high-frequency current;
Impedance matching means arranged at the output end of the high-frequency conversion means, and automatically adjusting the impedance when the load side is viewed from the output end to the impedance when the DC power supply side is viewed from the output end;
With
Further comprising a detecting means for detecting an impedance viewed from the load side or a reflected wave power at an output end of the high-frequency converting means,
The impedance matching means has two variable capacitors and one inductor, and drives the motors attached to the variable capacitors on the basis of the detection value of the detection means. each varying the capacitance of the capacitor, the impedance viewed the load side, you automatically adjusted to the impedance viewed the DC power supply side,
High-frequency power supply. Control means for generating the high-frequency drive signal and inputting it to the switching element,
The control means changes a ratio between a period during which high-frequency power is output from the high-frequency conversion means and a period during which the high-frequency power is not output so that an average value of power output from the high-frequency conversion means within a predetermined period becomes a target output power. Let
The high frequency power supply device according to any one of claims 1 to 4 . The high frequency power supply device according to any one of claims 1 to 5 ,
A power transmission unit having a power transmission coil and a power reception coil magnetically coupled to each other, and transmitting high-frequency power output from the high-frequency power supply device from the power transmission coil to the power reception coil in a contactless manner;
A non-contact power transmission system comprising: