Regeneration circulator, high-frequency power supply device, and high-frequency power regeneration method

An excessive voltage rise of load voltage, caused by an impedance mismatching on a transmission path, is prevented, and high-frequency power is regenerated. A parallel impedance is connected to the transmission path during the voltage rise, thereby regenerating voltage caused by a standing wave and preventing excessive load voltage, together with enhancing energy usage efficiency. Establishing the parallel impedance for the load impedance, on the transmission path between the high-frequency amplifier circuit of the high-frequency power supply device and the high-frequency load, reduces impedance at the connecting position to prevent generation of excessive voltage on the transmission path, and high-frequency power is regenerated from the transmission path by the parallel impedance.

TECHNICAL FIELD

The present invention relates to a supply of power, for feeding high-frequency power into a load device where plasma is a load, such as liquid crystal panel manufacturing equipment, semiconductor manufacturing equipment, and laser oscillator. More particularly, it relates to a regeneration circulator configured to regenerate power from a transmission path for transmitting high-frequency power, a high-frequency power supply device provided with the regeneration circulator, and a method of regenerating high-frequency power.

BACKGROUND ART

Ask a high-frequency power supply (RF generator) that feeds high-frequency power into a high-frequency load such as a plasma load (plasma source), a class-D high-frequency power supply device is known, for instance. Since the class-D high-frequency power supply device operates in a switch mode according to switching of high-frequency power amplifying elements, internal resistance Rinin the class-D high-frequency power supply device is determined by an ON-resistance value Ronin a saturated region of the high-frequency power amplifying elements. In general, the ON-resistance value Ronhas resistance which is lower than characteristic impedance Z0for transmitting output power.

The class-D high-frequency power supply device feeds the output power into the load device via a transmission path having the characteristic impedance Z0. Therefore, the impedance Zg0viewed from the output end of the generator is designed in such a manner that it becomes equal to the characteristic impedance Z0(Zg0=Z0) in a steady state, thereby maximizing the supplying of power.

The high-frequency power supply device outputs high-frequency waves generated in a high-frequency amplifier circuit internally provided, into the transmission path via an output circuit such as a power combining circuit and a matching circuit, and feeds the high-frequency waves into the load. In general, the impedance Zampviewed from the high-frequency amplifier circuit is represented by the impedance that is obtained by impedance transformation of the impedance Zg0at the output end of the high-frequency power supply device in a steady state, through the output circuit within the high-frequency power supply device.

FIG. 15schematically illustrates a circuit of the class-D high-frequency power supply device. InFIG. 15A, the class-D high-frequency power supply device101allows the high-frequency amplifier circuit112to make direct current from the DC power source111higher in frequency, passes thus obtained high-frequency wave through the output circuit113, and thereafter, feeds the high-frequency wave from the output end of the generator into the load102, via the transmission path104.

The high-frequency amplifier circuit112may include, for example, a bridge circuit112aof the high-frequency power amplifying elements and a transformer112b. The output circuit113may include, for example, a matching circuit113afor matching impedance to the impedance Z0of the transmission path104, and a filter circuit113bfor removing a noise component. The impedance Zampviewed from the high-frequency amplifier circuit112is obtained by impedance transformation of the impedance Zg0at the output end of the class-D high-frequency power supply device101by using the impedance of the output circuit113.

FIG. 15Bbriefly illustrates the impedance Zamp, showing a configuration that a circuit of AC voltage source Vinand internal resistance Rinsubstitutes for the DC power source111and the high-frequency amplifier circuit112including the bridge circuit112aand the transformer112b. The output power of this circuit is maximized when the relationship of Zamp=Rin=2RonN2is established. However, in fact, there are restrictions by design of the high-frequency power amplifying elements and the DC power source part, and further, the impedance Zampis required to be defined as a lagging load. Therefore, it is not necessarily defined as Zamp=Rinfor maximizing power.

In the high-frequency power supply device, in order to prevent damage on the high-frequency source and unstable operations, caused by reflected waves due to an impedance mismatch on the transmission path, a configuration is suggested where the class-D high-frequency power supply device incorporates a 3-dB coupler to reduce the reflected waves by using an internal dummy load.

There is also known another configuration that prevents reflected waves from returning to the high-frequency source by placing a circulator on the transmission path, and converts the reflected waves into heat by a dummy load (see the part of “Background Art” of the Patent Document 1). In here, the circulator is a passive element having a function to output high-frequency signals inputted in a certain port among plural ports, to the next port only, preventing reflected waves from returning to the high-frequency source, whereby it is possible to avoid damage and unstable operations of the high-frequency source.

In the configuration where the 3-dB coupler is employed, however, a main body of the 3-dB coupler and the internal dummy load have to be implemented within the high-frequency power supply device, thus causing a problem that the configuration of the high-frequency power supply device may become large in size. Further in the configuration employing the 3-dB coupler, there is a problem that the required number of high-frequency amplifier circuits is a multiple of 2 of the number of the 3-dB couplers, and there is another problem that when a reflected wave is generated, reflected current passing through the high-frequency amplifier circuit may cause unbalance of over 200% at a maximum.

Therefore, in the configuration where the dummy load is employed, reflected waves are thermally converted by the dummy load that is connected to a port, causing a problem that energy usage efficiency is low. As a configuration for solving the problems above, there is suggested a power regeneration technique that extracts reflected harmonics from the transmission path, and converting the reflected harmonics being extracted into direct current, thereby regenerating high-frequency power (Patent Document 1).

PRIOR ART DOCUMENT

Patent Document

Patent Document 1

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

In the circuit configuration ofFIG. 15B, if the matching circuit, the filter circuit, and the transmission path are lossless, the power fed into the load is expressed by Vin, Rin, and Zampwhich are used as parameters. Among those three parameters defining the supply of power, Zampis a value obtained by impedance transformation of the impedance Zg0at the output end of the high-frequency power supply device. This value corresponds to the impedance viewed from the internal high-frequency amplifier circuit, and variations of the load impedance are reflected thereon.

The load state varies according to an impedance mismatch. By way of example, a plasma load is known as a dynamic load that fluctuates according to various conditions such as pressure, gas flow volume, and arching within a plasma chamber. The impedance Zampvaries in association with the fluctuation of the load impedance. On the other hand, among the three parameters described above, when high-frequency power is being applied, Rinindicates a fixed constant determined by characteristics of the power amplifier elements and Vinindicates voltage VDDof the DC power source.

FIG. 16illustrates one example of output power variation in association with fluctuation of the impedance Zamp. This example here indicates power that is supplied to the load, where Vin=52 V and Rin=2Ω, the impedance Zampin a steady state is 50Ω, and the impedance Zampvaries from 1Ω to 100Ω, in the circuit configuration ofFIG. 15B. According toFIG. 16, for example, an impedance mismatch occurs due to load variation starting from the state of rated operation (Zamp=50Ω, output power=50 W), and the impedance Zampvaries from 50Ω to 2Ω. In this case, the supply of power into the load varies from 50 W to 340 W, resulting in approximately seven-times change.

Since constant-voltage control on Vincan be performed, against the fluctuation in supplying power caused by abrupt change of the impedance Zamp, it is possible to maintain the output power to be a set value, as long as the varying velocity of the impedance Zampfalls within a range of response speed for performing the constant-voltage control on Vin. However, if the impedance Zampchanges abruptly while high-frequency power is applied, exceeding the response speed of the constant-power control on Vin, it becomes difficult to prevent the fluctuation in supplying power into the plasma load, just by the constant-voltage control of Vin.

Such abrupt change in supplying power into the plasma load may cause abrupt increase of load voltage, including electrode voltage Vpp. Excessively large electrode voltage Vpp, even for a moment, may become a factor of arching generation due to dielectric breakdown, resulting in a failure of a semiconductor or liquid crystal panel in process.

An object of the present invention is to solve the conventional problems as described above, and it is directed to preventing an excessive rise of load voltage caused by the impedance mismatch on the transmission path, and to regeneration of high-frequency power.

Means for Solving the Problems

The present invention puts focus on that a voltage rise due to an impedance mismatch on a transmission path is likely to become excessive, by a standing wave caused by a reflected wave which is generated by the impedance mismatch, and the present invention is directed to a configuration that a parallel impedance is connected to the transmission path during the voltage rise time, thereby regenerating voltage that is based on the standing wave, further reducing the excessive voltage on the load, as well as enhancing energy usage efficiency.

(Electrical Length and Voltage Variation Due to Standing Wave)

There will now be described an electrical length of the transmission path and voltage variation due to the standing wave. It is known that voltage on the load side varies according to the electrical length of the transmission path connecting between the high-frequency power supply device and the load.

FIG. 17illustrates a circuit example where a plasma impedance and a matching circuit substitute for the load as shown inFIG. 15. In the circuit example ofFIG. 17, the matching circuit performs matching in such a manner that the load impedance ZLbecomes 50Ω when an active component RLin the plasma impedance is 100Ω. It should be noted that the description here shows an example that an operation runs at an operating frequency of 13.56 MHz.

As an operation example of the high-frequency power supply device, in terms of the active component RLof the plasma load impedance ZL, a resistance component at a steady time is assumed as 100Ω. If the resistance component at the open time when plasma is extinguished, is assumed as 100 kΩ,FIG. 18AandFIG. 18Billustrate respectively, electrode voltage Vppbeing the load voltage, and an absolute value |Zamp| of the impedance Zamp, when the electrical length l of the transmission path varies from 0 degree angle to 180 degree angle. InFIG. 18C, the load impedance ZLand the impedance Zampof the high-frequency amplifier circuit are shown in the Smith chart.

As shown inFIG. 18AandFIG. 18B, the electrode voltage Vppwhich is proportional to the load voltage VLbecomes the local maximal value when an absolute value |Zamp| of the impedance Zampis the local minimal value. Therefore, it is possible to know an increase of the load voltage VLincreases according to the relationship between the absolute value |Zamp| of Zampand the electrical length l.

In general, the load impedance ZLis determined by the impedance Zg0and current Ig0at the output end of the high-frequency power supply device, the characteristic impedance Z0of the transmission path, and a length of the transmission path. If there is an impedance match between the impedance Zg0at the output end of the high-frequency power supply device, and the impedance Zampviewed from the high-frequency amplifier circuit within the high-frequency power supply device, the impedance Zampviewed from the high-frequency amplifier circuit corresponds to the impedance Zg0at the output end.

Therefore, if the electrical length within the high-frequency power supply device is already known, the load impedance ZLis used instead of the impedance Zamp, thereby obtaining the electrical length l of the transmission path that maximizes the load voltage VL. Furthermore, since the magnitude of the electrode voltage Vppis proportional to the load voltage VL, it is possible to obtain the electrical length l of the transmission path that maximizes the electrode voltage Vpp.

In the Smith chart ofFIG. 18C, m1 (Γ=0.998 ∠32.352 degree angle) indicates a voltage reflection coefficient Γ in association with the load impedance ZLwhen plasma is extinguished, and m2 indicates the voltage reflection coefficient Γ when the impedance Zampis short-circuited and its phase angle is 180 degree angle. In addition, m3 indicates the voltage reflection coefficient Γ when the impedance is ∞. The example illustrates that the electrical length l of the transmission path between the load impedance ZLand the impedance Zampof the high-frequency amplifier circuit is 106 degree angle (=180 degree angle +32 degree angle/2).

FIG. 18Aillustrates the electrode voltage VPPat the position of the electrical length l of the transmission path, with respect to m1. The electrode voltage VPPat the steady time indicates a constant value 200 V irrespective of the electrical length l of the transmission path. On the other hand, the electrode voltage Vpp, when plasma is extinguished, significantly varies depending on the electrical length l of the transmission path, indicating that when the electrical length l is at the angle of 106 degree angle (at the position indicated by m2), the electrode voltage Vppbecomes approximately 5×104V at the maximum, which is around 25 times larger than the voltage at the steady time.

Typically, a vacuum chamber is not designed in a manner as having resistance to such high voltage being 25 times higher than the voltage at the steady time, and therefore generation of this excessive electrode voltage Vppmay cause arching.

FIG. 18Billustrates the absolute value |Zamp| of the impedance Zampat the position of the electrical length l of the transmission path, with respect to m1. The absolute value |Zamp| of the impedance Zampvaries depending on the electrical length l of the transmission path, indicating that the absolute value |Zamp| is locally minimized when the electrical length l corresponds to the position of 106 degree angle (the position indicated by m2). Therefore, m2 corresponds to the position where the absolute value |Zamp| of the impedance Zampviewed from the high-frequency amplifier circuit is locally minimized.

InFIG. 18AandFIG. 18B, the position where the electrical length of the transmission path corresponds to 0 degree angle indicates the position where the load impedance ZLis open and the voltage reflection coefficient Γ is m1, and the position where the electrical length of the transmission path is 106 degree angle indicates the position where the impedance Zampis short-circuited and voltage reflection coefficient Γ is m2.

According to the aforementioned relationship between the electrical length of the transmission path and voltage, by configuring the electrical length l of the transmission path in such a manner as preventing the impedance Zampfrom being short-circuited, it is possible to assume that the electrode voltage Vppis avoided to approach an excessive voltage. However, the electrical length l of the transmission path may vary depending on the length of the transmission path, fluctuations of a distributed constant, and the like. Therefore, it is difficult to match the length of a cable actually installed, to the electrical length l being provided. And further, as the fluctuations of the distribution constant may change the electrical length, it is also difficult to avoid stably that the electrode voltage Vppapproaches excessive voltage.

It is known that a standing wave is generated by a reflected wave due to an impedance mismatch, and when amplitude of the standing wave has the local maximal value, the voltage raised by the impedance mismatch becomes more readily approach an excessive voltage.

FIG. 19is a schematic view illustrating the state of the standing wave at the time of matching and mismatching;FIG. 19Aillustrates the state of matching,FIG. 19Billustrates the state of mismatching where the load is short-circuited and the reflection coefficient of the load impedance ZLis −1, andFIG. 19Cillustrates the mismatching state where the load is open and the reflection coefficient of the load impedance ZLis 1. As for the voltage and current inFIG. 19A,FIG. 19B, andFIG. 19C, the voltage is shown by a solid line and the current is shown by a broken line, when the ends of the transmission path are short-circuited.

At the time of matching, no standing wave is generated, and at the time of mismatching, a standing wave is generated. As for the standing wave generated in the short-circuited load and the standing wave generated in the open state, nodes and antinodes of one standing wave are positioned in such a manner as opposed to the node and antinode of the other standing wave.

When the characteristic impedance Z0of the transmission path is 50Ω, if the load is terminated with 50Ω, voltage and current to the transmission path are constant irrespective of the electrical length. Therefore, any standing wave is not generated. On the other hand, if the load is short-circuited, voltage becomes zero and current is locally maximized at the end of the load side of the transmission path, forming a node of the standing wave. If the load is open, current becomes zero and voltage is locally maximized at the end of the load side of the transmission path, forming an antinode of the standing wave.

As described above, the load voltage VLin the load impedance ZLrises according to the impedance mismatching of the transmission path, and when a position on the transmission path corresponds to the antinode of the standing wave, a voltage rise may become much more excessive.

(Configuration of the Present Invention)

The present invention has a configuration that a parallel impedance is provided for the load impedance, on the transmission path between the high-frequency amplifier circuit of the high-frequency power supply device and the high-frequency load, thereby reducing impedance at a connecting position and preventing generation of excessive voltage on the transmission path, and further regenerating high-frequency power from the transmission path by the parallel impedance, thereby enhancing energy efficiency.

As a function usually provided in a circulator, there is known a configuration that separates a forward wave from a reflected wave, and provides directionality in the conduction direction respectively of the forward wave and the reflected wave. On the other hand, the function provided in the circulator of the present invention does not relate to the forward wave nor the reflective wave of a general circulator, but the function of the present invention may cause branching of current from the transmission path, making the branched current thus conduct with a directionality. In the present invention, the term of “circulator” is used from a viewpoint of the function that brings current with directionality into conduction.

The present invention includes aspects of a regeneration circulator, a high-frequency power supply device, and a method of regenerating high-frequency power, and any of those aspects are provided with common technical items relating to the regeneration circulator. Each of the aspects of the present invention is commonly provided with technical items relating to the regeneration circulator which changes the impedance state at a predetermined position on the transmission path, thereby reducing a rise of a voltage standing wave ratio by changing the voltage state of the standing wave, as well as regenerating power from the transmission path.

(Aspect of the Regeneration Circulator)

The regeneration circulator of the present invention is provided with a regenerating function, having a configuration to change the state of impedance at a predetermined position on a transmission path, thereby preventing a rise of a voltage standing wave ratio, by changing the voltage state of the standing wave, together with regenerating power from the transmission path.

The regeneration circulator of the present invention is to regenerate high-frequency power from the transmission path between the high-frequency amplifier circuit of the high-frequency power supply device and the high-frequency load, where an input end of the regeneration circulator is connected to the transmission path, configuring a parallel impedance for the transmission path, on the basis of a comparison between the voltage at the input end of the regeneration circulator and set voltage. The parallel impedance incorporates high-frequency power in one direction from the connecting position on the transmission path, and then regenerates the power.

The regeneration circulator returns power that is regenerated from the transmission path to the high-frequency power supply device, and in addition, it is further possible to supply power to other device including a power generator, and to store electricity in an electrical storage device.

Functions of Parallel Impedance in the Regeneration Circulator:

Parallel impedance in the regeneration circulator will be described. On the transmission path, in the state of impedance matching, voltage at the input end of the regeneration circulator is in the state of steady voltage, and therefore the voltage is lower, relative to the set voltage. In this voltage state, current is not conducted from the transmission path to the regeneration circulator side, and the regeneration circulator does not constitute parallel impedance for the transmission path.

On the other hand, on the transmission path, generation of the standing wave raises the voltage at the input end of the regeneration circulator, and the voltage may become higher, relative to the set voltage. In the state where the voltage is raised, the current is conducted from the transmission path to the regeneration circulator side, and the regeneration circulator configures the parallel impedance for the transmission path. Impedance mismatching may be a factor for generating the standing wave, but even when impedance is in the state of mismatching, there is a possibility that the voltage at the input end of the regeneration circulator does not rise depending on the load impedance and an electrical length of a transmission line.

The parallel impedance connected to the transmission path may change the state of the impedance state, caused by the standing wave on the transmission path, and lower a voltage standing wave ratio (VSWR), thereby preventing a rise of voltage.

In addition, the parallel impedance is able to regenerate power by incorporating current from the transmission path.

Modes of Connecting Position of the Regeneration Circulator:

The regeneration circulator has plural configuration modes as to a position for connecting its input end on the transmission path.

First Mode:

The first mode of position to which the input end of the regeneration circulator is connected corresponds to a position of one of antinode parts of a standing wave that is generated by an impedance mismatching on the transmission path. On the transmission path, when the standing wave is generated due to the impedance mismatching, voltage becomes high at the antinode parts, whereas it becomes low at node parts.

On the transmission path, by connecting the input end of the regeneration circulator to the antinode part where high voltage is generated, the regeneration circulator incorporates current from the high voltage part on the transmission path, and when the voltage being incorporated exceeds the set voltage, parallel impedance may be established for the transmission path.

The second mode of position to which the input end of the regeneration circulator is connected corresponds to a position indicating an odd multiple of the electrical length being one-fourth wavelength (λ/4) of the high-frequency wavelength (λ) that is outputted by the high-frequency power source on the transmission path, the length starting from the output of the high-frequency amplifier circuit.

On the transmission path, the input end of the regeneration circulator is connected to the position of the electrical length where high voltage is generated, whereby the regeneration circulator incorporates current from the high voltage part on the transmission path, and then, the parallel impedance can be established for the transmission path, when the voltage being incorporated exceeds the set voltage.

The regeneration circulator of the present invention is provided with a directional coupler configured to incorporate high-frequency power in one direction from the transmission path. The directional coupler incorporates high-frequency power from the transmission path, on the basis of a comparison between the voltage at the input end of the regeneration circulator and the set voltage, and configures an upper limit of the voltage at the input end of the regeneration circulator, as the set voltage during the regenerative operation.

A first mode of the directional coupler according to the present invention is provided with a transformer. A turn ratio of the transformer is a value that is based on a voltage ratio of the set voltage and the voltage at the output end of the regeneration circulator. Therefore, the set voltage is determined by the turn ratio of the transformer, and the voltage at the output end of the regeneration circulator.

When the turn ratio of the transformer is 1:1 (=primary turns:secondary turns), the set voltage is determined according to the voltage at the output end of the regeneration circulator.

A second mode of the directional coupler has a configuration that is provided with a rectifier configured to convert AC into DC, in addition to the transformer of the first mode. The rectifier converts the AC output from the transformer into DC, and regenerates the DC thus converted. In the first mode and the second mode, it is further possible to configure such that a capacitor is provided on the secondary side of the transformer, a DC reactor is provided on a subsequent stage of the rectifier, or the capacitor is provided on the secondary side of the transformer together with the DC reactor in the subsequent stage of the rectifier. The capacitor provided on the secondary side of the transformer or the DC reactor provided in the subsequent stage of the rectifier may remove a noise component. It is possible to install the capacitor on a diode bridge that constitutes the rectifier.

(Aspect of the High-Frequency Power Supply Device)

The high-frequency power supply device of the present invention is provided with a high-frequency power source configured to feed high-frequency power into a high-frequency load, and a regeneration circulator configured to incorporate high-frequency power in one direction from a transmission path between a high-frequency amplifier circuit provided in a high-frequency power supply device and the high-frequency load, for regenerating power. The regeneration circulator of the present invention is provided in the high-frequency power supply device, and an input end of the regeneration circulator is connected to the transmission path, and on the basis of comparison between the voltage at the input end of the regeneration circulator and the set voltage, the circulator establishes a parallel impedance for the transmission path. Then, the parallel impedance incorporates high-frequency power from the connecting position and regenerates the power.

The regeneration circulator provided in the high-frequency power supply device of the present invention may have the same aspect as the regeneration circulator that is described above.

The method of regenerating high-frequency power of the present invention is to regenerate high-frequency power by a regeneration circulator from a transmission path between a high-frequency amplifier circuit of a high-frequency power supply device and a high-frequency load, and in the method, an input end of the regeneration circulator is connected to the transmission path, configuring a parallel impedance for the transmission path, on the basis of comparison between voltage at the input end of the regeneration circulator and the set voltage, and the parallel impedance incorporates high-frequency power from the connecting position and regenerates the power.

In the high-frequency power regeneration method of the present invention, the regeneration circulator may have the same aspect as the regeneration circulator that is described above.

In the first mode of the high-frequency power regeneration method, the input end of the regeneration circulator is connected to a position of one of antinode parts of a standing wave that is caused by an impedance mismatching on the transmission path, and a parallel impedance is established for the transmission path on the basis of comparison between the voltage at the input end of the regeneration circulator and the set voltage, incorporating high-frequency power from the connecting position and regenerating the power according to the parallel impedance.

In the second mode of the high-frequency power regeneration method of the present invention, the input end of the regeneration circulator is connected to a position on the transmission path, indicating an odd multiple of an electrical length being one-fourth (λ/4) of the high-frequency waveform (λ) of high-frequency power outputted from the high-frequency power source on the transmission path, the length starting from the output end of the amplifier circuit, a parallel impedance is established for the transmission path on the basis of comparison between voltage at the input end of the regeneration circulator and the set voltage, and high-frequency power is incorporated by the parallel impedance in one direction from the connecting position and the power is regenerated.

In the first and the second modes, high-frequency power is incorporated from the transmission path by the parallel impedance, on the basis of the comparison between the voltage at the input end of the regenerative circular and the set voltage, and an upper limit of the voltage at the input end of the regeneration circulator is configured as the set voltage during the regenerative operation. In addition, the AC output of the high-frequency power is converted into DC, and thereafter the power is regenerated.

Advantages of the Invention

As described above, according to the present invention, it is possible to prevent an excessive rise of load voltage, which is caused by the impedance mismatching on the transmission path. It is also possible to regenerate high-frequency power.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference toFIGS. 1 to 4, there will be described a regeneration circulator and a high-frequency power supply device incorporating the regeneration circulator, according to the present invention.

(Configuration of the Present Invention)

FIG. 1is a schematic view illustrating a configuration of the regeneration circulator and the high-frequency power supply device of the present invention.

The high-frequency power supply device1is provided with a high-frequency power source10and a regeneration circulator20, and the regeneration circulator20being connected to a transmission path3of the high-frequency power source10, establishes a parallel impedance for the transmission path3, and incorporates power from the transmission path3for regenerating power. Regeneration by the regeneration circulator20may be executed by returning the incorporated power to the high-frequency power source10, and in addition, by feeding power into a device not illustrated, or by storing electric power in a storing device not illustrated.

By way of example, a DC power source11and a high-frequency amplifier circuit12may constitute the high-frequency power source10. The high-frequency amplifier circuit12performs DC/RF conversion to convert direct current from the DC power source11into a high-frequency wave, and raises voltage to output a high-frequency output. The high-frequency output is supplied to a high-frequency load2via the transmission path3.

The transmission path3is a transmission line for supplying power from the output end of the high-frequency amplifier circuit12to the input end of the high-frequency load2, and it may be formed of a power cable disposed between the high-frequency power source10and the high-frequency load2, and wiring and a circuit configuration in the high-frequency power source10.

On the transmission path3, if there is a matching between a characteristic impedance of the transmission path and the impedance of the high-frequency load2, a forward wave outputted from the high-frequency amplifier circuit12may be supplied to the high-frequency load2without being reflected. On the other hand, if the impedance of the high-frequency load2varies, causing a mismatching between the characteristic impedance of the transmission path and the impedance of the high-frequency load2, a part or all of the forward wave outputted from the high-frequency amplifier circuit12may be reflected, and the forward wave and the reflected wave may form a standing wave.

The regeneration circulator20has a function to establish conduction of current that branches from the transmission path3, only in one direction; i.e., only in the direction toward the regeneration circulator20. The circulator within the regeneration circulator represents a function for conducting current with a directionality.

The regeneration circulator20is provided with a regenerating function, in addition to the aforementioned circulator function. The regenerating function of the regeneration circulator20may vary the impedance state at a predetermined position on the transmission path3, between the high-frequency amplifier circuit12of the high-frequency power source10and the high-frequency load2, thereby changing the voltage state of the standing wave, and preventing a rise of a voltage standing wave ratio, together with regenerating high-frequency power from the transmission path. The input end of the regeneration circulator20is connected onto the transmission path3, and establishes parallel impedance for the transmission path3, on the basis of the comparison between the voltage at the input end of the regeneration circulator20and preset voltage. The parallel impedance incorporates high-frequency power in one direction from the connecting position on the transmission path3, and regenerates the high-frequency power.

During an impedance matching on the transmission path3, since the voltage at the input end of the regeneration circulator20is steady voltage, the voltage is lower relative to the set voltage. In the state of steady voltage, current is not conducted from the transmission path3toward the regeneration circulator20side, and therefore, the regeneration circulator20does not establish the parallel impedance for the transmission path3.

When a standing wave is generated on the transmission path3, the voltage at the input end of the regeneration circulator rises, and it may become higher relative to the set voltage. The standing wave is generated when an impedance mismatching occurs. The voltage at the input end of the regeneration circulator does not necessarily rise every time when the impedance mismatching occurs. There is a possibility that the voltage at the input end of the regeneration circulator is not raised even during the impedance mismatching, depending on the load impedance or an electrical length of the transmission line.

In the state where the voltage at the input end of the regeneration circulator is higher relative to the set voltage, current is conducted from the transmission path3to the regeneration circulator20side, and the regeneration circulator20establishes parallel impedance for the transmission path3. The parallel impedance connected to the transmission path3may change the impedance state of the transmission path3, so as to lower the voltage standing wave ratio (VSWR), to prevent a voltage rise, and to incorporates current from the transmission path3, thereby regenerating power to the DC power source11. It is to be noted that the power may be regenerated not only into the DC power source11, but also into other DC power source or storage device.

The first embodiment and the second embodiment will now be described as to the example how the regeneration circulator is connected to the transmission path3. A configuration example of the second embodiment corresponds to that of the first embodiment.

First Embodiment

FIG. 1shows the first embodiment of a connection between the regeneration circulator and the transmission path. In the first embodiment, the input end of the regeneration circulator20is connected to a position corresponding to one of antinode parts of the standing wave that is generated by an impedance mismatching on the transmission path3. When the standing wave is generated by the impedance mismatching on the transmission path3, voltage becomes high at the antinode parts, whereas voltage becomes low at node parts.FIG. 1shows a configuration example where the input end of the regeneration circulator20is connected to the antinode parts of the standing wave on the transmission path3.

By connecting the input end of the regeneration circulator20to the antinode parts where high voltage is generated on the transmission path3, the regeneration circulator20incorporates current from the antinode part on the transmission path3, and when thus incorporated voltage exceeds the set voltage, parallel impedance is established for the transmission path3.

Second Embodiment

FIG. 2is a schematic view describing the second embodiment of the connection between the regeneration circulator and the transmission path, andFIG. 2shows an example where the input end of the regeneration circulator is connected to a position indicating a predetermined electrical length from the output end of the high-frequency amplifier circuit. InFIG. 2, the connecting position of the input end of the regeneration circulator20is represented by P, and the impedance at the position P is represented by ZP.

InFIG. 2, in a high-frequency power source10the transmission line4with the characteristic impedance Z0connects the high-frequency power source10with the high-frequency load2, and the high-frequency amplifier circuit12is connected to an output circuit13, provided with an impedance matching at Z0. With this impedance matching at Z0in the output circuit13, the impedance Zampwhen viewing the load side from the high-frequency amplifier circuit12, matches the impedance Zg0at the output end of the high-frequency power source10.

When the high-frequency load is in a short-circuited state or in the open state, an impedance mismatching occurs on the transmission path, causing a reflected wave, and accordingly, a standing wave is formed. The second embodiment shows the state where the high-frequency load is short-circuited state.

The second embodiment is directed to reducing the standing wave that is generated when the end of the transmission path is in a short-circuited state, and the input end of the regeneration circulator20is connected to a position indicating an odd multiple of an electrical length being one-fourth wavelength (λ/4) of the high-frequency wavelength (λ) on the transmission path3, the length starting from the output end (the position of impedance Zamp) of the high-frequency amplifier circuit12, and the high-frequency wave being outputted from the high-frequency power source10.

FIG. 3illustrates the case where the input end of the regeneration circulator20is connected to the position indicating an odd multiple of an electrical length being one-fourth wavelength (λ/4) of the high-frequency wavelength (λ), from the output end of the high-frequency amplifier circuit12on the transmission path3. The connecting position is represented by (2n−1)λ/4, where n is integer.

FIG. 3Aillustrates the state where the regeneration circulator establishes a parallel impedance, when the impedance ZLof the high-frequency load is in a short-circuited state,FIG. 3Billustrates a standing wave that is generated when the impedance ZLof the high-frequency load is in a short-circuited state, andFIG. 3Cshows a standing wave caused by the parallel impedance during the regenerative operation.

When the end of the transmission path is in a short-circuited state, an impedance mismatching occurs and a standing wave is generated. In this case, the position indicating an odd multiple of an electrical length being one-fourth wavelength (λ/4) of the high-frequency wavelength (λ) outputted from the high-frequency power source on the transmission path, corresponds to an antinode part of the standing wave, and therefore voltage is high. In here, the electrical length starts from the output end of the high-frequency amplifier circuit being the end point. As for the voltage and current shown inFIG. 3BandFIG. 3C, the voltage is indicated by a solid line and the current is indicated by a broken line when the end of the transmission path is short-circuited.FIG. 3Bshows the state before regeneration, andFIG. 3Cshows the state after regeneration.

The input end of the regeneration circulator is connected to the position indicating an electrical length where high voltage is generated on the transmission path, then the regeneration circulator incorporates current from the high voltage part on the transmission path, and establishes parallel impedance for the transmission path, when the incorporated voltage exceeds preset voltage.FIG. 3shows an example where voltage being k-times larger than the voltage VLon the high-frequency load is assumed as the preset voltage. It is to be noted that the standing wave voltage is zero at the end being in a short-circuited. In this example, it is assumed that on the load side, the voltage at the position corresponding to the antinode part of the standing wave indicates voltage VLon the high-frequency load side.

The regeneration circulator being connected establishes the parallel impedance ZR, and with this impedance, the peak value of the standing wave is reduced, and then the voltage VLon the high-frequency load side is also reduced.

FIG. 4illustrates the regenerative operation according to the parallel impedance. In this example, the voltage being k-times larger than the load voltage VLis used as the set voltage for performing the regenerative operation. InFIG. 4A, the voltage VPat the connecting position P of the regeneration circulator corresponds to the steady voltage that is determined on the basis of the matched impedance, during the state of impedance matching, whereas during the mismatching state, the impedance Zampat the output end of the high-frequency amplifier circuit is reduced from Z0, resulting in a rise of voltage. When the voltage VPexceeds the set voltage k·VL, the regenerative operation of the regeneration circulator is started, and then current passes into the circulator from the transmission path (FIG. 4B).

The regeneration circulator operates as the parallel impedance ZRaccording to the regenerative operation (FIG. 4C). When the parallel impedance ZRis connected to the impedance Zg0at the output end of the high-frequency power supply device, impedance is increased, and then, the impedance Zamphaving been reduced at the output end of the high-frequency amplifier circuit is enabled to prevent a voltage rise of the voltage VP(FIG. 4D). It is to be noted that the impedance Zampduring the regenerative operation does not exceed the value that is obtained under normal operating conditions.

Configuration Example

With reference toFIGS. 5 to 8, a configuration example of the second embodiment will now be described, as to the regeneration circulator and the high-frequency power supply device.

FIG. 5illustrates a configuration example where the input end of the regeneration circulator20is connected at the position indicating the electrical length of (2n−1)λ/4 from the output end of the high-frequency amplifier circuit12. In the high-frequency power supply device1, a bridge circuit12aof semiconductor switching elements and a transformer12bconstitute the high-frequency amplifier circuit12. The output circuit13comprises a series connection circuit between a matching circuit13athat performs impedance matching with the characteristic impedance Z0of the transmission line4and an LPF (low-pass filter)13bfor removing a noise component. An LC circuit, for instance, may constitute the matching circuit13a. The LC circuit and the LPF (low-pass filter circuit)13bare designed in such a manner that the electrical length becomes equal to (2n−1)λ/4.

When AC voltage at the input end of the regeneration circulator20exceeds a certain level, current starts to pass into the circuit of the regeneration circulator. Therefore, the load (impedance) is seemingly connected to the circuit of the regeneration circulator20in parallel, and accordingly, this leads to an operation to prevent the connecting position of the regeneration circulator from becoming high impedance. At the same time, this operation similarly indicates that the impedance Zampat the point of the electrical length (2n−1)λ/4 from the regenerative circuit is prevented from becoming low impedance.

The regeneration circulator20is a circuit to start regenerating regeneration circulator power, and as shown inFIG. 1andFIG. 2, it is provided with a directional coupler21for incorporating high-frequency power in one direction from the transmission path and a rectifier circuit22. The directional coupler21incorporates high-frequency power from the transmission path, on the basis of comparison between the voltage at the input end of the regeneration circulator20and the set voltage, and during the regenerative operation, the upper limit of the voltage at the input end of the regeneration circulator is configured as the set voltage. The rectifier circuit22converts AC to DC, and regenerates the DC into a DC power source11, and the like.

FIG. 6shows that the high-frequency amplifier circuit including the transformer12bwith the turn ratio of 1:2 as shown inFIG. 5, is connected to a circuit of the output circuit13, and assuming the case where plasma is extinguished with an active component of the load impedance ZLbeing 100 kΩ (≈Open), two situations are illustrated; one is when the regeneration circulator is provided, and the other is when it is not provided for the electrode voltage Vpp, where the electrical length l of the transmission path varies from 0 degree angle to 180 degree angle. The electrode voltage VppinFIG. 6indicates that the regenerative operation is performed within the range of the electrical length from approximately 85 degree angle to 125 degree angle, so as to reduce the electrode voltage Vpp.

FIG. 7andFIG. 8show circuit configurations of the regeneration circulator. In the circuit example as shown inFIG. 7, the regeneration circulator20is provided with a transformer20aon the input side, and a rectifier20bcomprising a diode bridge circuit on the output side. The transformer20ais associated with the directional coupler21, and the rectifier20bis associated with the rectifier circuit22. By way of example, the output side is connected to a DC voltage source of the DC power source11, thereby regenerating the DC power into the DC voltage source. It is to be noted that the DC power may be regenerated not only into the DC voltage source of the high-frequency power supply device, but also into other DC voltage source.

FIG. 8shows modified circuit examples of the regeneration circulator. The circuit example as shown inFIG. 8Aconnects a capacitor20cto the secondary side of the transformer constituting the transformer20a, thereby compensating for voltage-waveform distortion on the secondary side of the transformer, caused by a commutation overlap angle due to leaked current (leakage) passing through the transformer.

In the circuit examples as shown inFIG. 8BandFIG. 8C, inductances20dand20eare connected on the output side of the diode bridge, thereby reducing an AC component directed to the DC power source (VDD) being a destination of regeneration. Another example may be possible where the capacitor inFIG. 8Aand the inductance as shown inFIG. 8BorFIG. 8Care combined.

Operation Example

With reference toFIGS. 9 to 13, operation examples of the regeneration circulator of the present invention will now be described.

FIG. 9is a circuit example of the high-frequency power supply device and the regeneration circulator. In the circuit example ofFIG. 9, there are shown parameters as the following; in the steady state where plasma is ignited, and in the abnormal state where plasma is extinguished for the cases where the regeneration circulator is provided and not provided. It is to be noted that the load impedance ZLis 50Ω and the active component RLis 100Ω, when plasma is ignited.

DC power source voltage VDD: 290 V

Forward wave: 4,000 W (measured value at the output end of high-frequency power supply device)

Reflected wave: 0 W (measured value at the output end of high-frequency power supply device)

In the circuit example ofFIG. 9, when the regeneration circulator is not provided, parameters in the abnormal state where plasma is extinguished are as the following. It is to be noted that the active component RLof the load impedance is 100 kΩ when plasma is extinguished.

DC power source voltage VDD: 290 V

Forward wave: 49,000 W (Measured value at the output end of high-frequency power supply device)

Reflected wave: 49,000 W (Measured value at the output end of high-frequency power supply device)

FIG. 10shows waveforms within a time domain, respectively of the output-end voltage Vg0of the high-frequency power supply device, the electrode voltage Vpp, the output current Idcfrom the DC power source, and the input voltage Iinvinto the high-frequency amplifier circuit.FIG. 10illustrates data when plasma is extinguished at t=12 us.

In the case where the regeneration circulator is not provided, output power of 49 kW is outputted to 4-kW rated power source, and there is a possibility that power amplifier element is broken due to over voltage or excessive loss. In addition, the electrode voltage Vppat the steady time is 1,794 V, whereas at the abnormal time, high voltage of 12,530 V is applied to the electrodes within the vacuum device, and there is a problem that this high voltage may be a factor of arching generation due to an electrode fracture or dielectric breakdown.

In the circuit example as shown inFIG. 9, when the regeneration circulator is provided, parameters in the abnormal state where plasma is extinguished are as the following. When plasma is extinguished, the active component RLof the load impedance is assumed as 100 kΩ.

DC power source voltage VDD: 290 V

Forward wave: 4,000 W (measured value at the output end of high-frequency power supply device)

Reflected wave: 4,000 W (measured value at the output end of high-frequency power supply device)

FIG. 11shows waveforms within the time domain, respectively of the output-end voltage Vg0of the high-frequency power supply device, the electrode voltage Vpp, the output current Idcof the DC power source, and the input voltage Iinvinto the high-frequency amplifier circuit.FIG. 11illustrates data when plasma extinguished at t=12 us.

FIG. 12illustrates on the Smith chart, an impedance locus of the output end impedance Zampwith respect to the electrical length of the transmission line.FIG. 12Ashows variation of the output end impedance Zampwhen plasma is extinguished, without the regeneration circulator.FIG. 12Bshows variation of the output end impedance Zampwhen plasma is extinguished, with the regeneration circulator being provided.

InFIG. 12A, the reference symbols A, B, and C correspond to the impedance, respectively when the electrical length is 0, λ/4, and λ/2, and in accordance with the variation of the electrical length from 0 to λ/2, the impedance varies in the order of A, B, and C.

Since there is a relationship of λ/4 in electrical length, between the antinode part and the node part of the standing wave, the load-end voltage is maximized when the load end is located at the position corresponding to the antinode part of the standing wave. In this situation, the impedance Zampviewed from the high-frequency amplifier circuit, in association with the node part of the standing wave is low impedance, which corresponds to the impedance in the short-circuited state. Since the load end voltage is proportional to the electrode voltage, when the electrode voltage is maximized, the impedance Zampbecomes low.

InFIG. 12A, when the load end voltage (electrode voltage) is maximized, the impedance at the load end is located at the electrical length A, and the impedance Zampviewed from the high-frequency amplifier circuit is located at the electrical length B, moved only by λ/4 from the position A. The impedance of the electrical length B is zero, and this corresponds to the short-circuited state.

Therefore, observing the impedance Zampviewed from the high-frequency amplifier circuit, when the impedance Zampis located at the electrical length B where the impedance is zero, the impedance at the load end is located at the electrical length A, where the impedance corresponds to co, and the load end voltage (electrode voltage) increases.

InFIG. 12B, the reference symbols A and C correspond to the impedance, respectively when the electrical length is zero 0 and λ/2, D corresponds to the impedance when the electrical length is between 0 and λ/4, E corresponds to the impedance when the electrical length is between λ/4 and λ/2, and the impedance varies in the order of A, D, E, and C, along with the variation of the electrical length from 0 to λ/2.

In the configuration where the regeneration circulator is provided, when the impedance Zampis coming into the short-circuited state, between 0 and λ/4, the parallel impedance becomes connected to the transmission path at the electrical length D. Then, another active component may be generated, in addition to those provided in the load impedance, and the impedance may vary along with the impedance locus that avoids the low impedance point at the electrical length B.

When the impedance Zampreturns from the short-circuited state to the open state, between λ/4 and λ/2, the parallel impedance is disconnected from the transmission path, and the active component being generated disappears at the electrical length E, and the impedance varies toward the high impedance point at the electrical length C.

Therefore, with the regeneration circulator, it is possible to allow the output end impedance Zampof the high-frequency amplifier circuit to be away from the low impedance of the short-circuited state.

Since the parallel impedance according to the regeneration circulator allows the impedance Zampto be away from becoming low impedance, it is possible to prevent the load voltage VLand the electrode voltage Vppfrom boosting up to be a value several ten folds larger than a value in the steady state.

The active component caused by the parallel impedance is generated by resuming power in the DC power source voltage VDDvia the regeneration circulator, and it is not generated by adding a loss component such as an internal dummy load. Therefore, it is possible to avoid a loss of energy being regenerated, thereby enhancing the regenerative efficiency.

In addition, the output power at the time of total reflection time is limited to 4,000 W, and as a result, the upper limit of the electrode voltage Vppis also restricted.

By setting the upper limit of the output power and voltage, it is possible to prevent a fracture of the power amplifier element, electrode breakage of the vacuum device, a fracture of a semiconductor element due to arching, and the like.

(Condition for Starting the Regenerative Operation)

As described above, the impedance state where the impedance Zampviewed from the output end of the high-frequency amplifier circuit becomes low, is associated with a rise of the load end voltage caused by a standing wave. There will now be described an operating condition that prevents the impedance Zampfrom becoming low according to the regenerative operation.

The class-D high-frequency power supply device generates a square wave by an inverter. In the circuit example ofFIG. 13, the internal resistance Rinis expressed by the following formula, where an effective value voltage of a basic wave component of the square wave voltage is Vin, on-resistance of the inverter is Ron, and the transformer turn ratio is N:
Rin=2RonN2(1)

In this case, a relationship between an effective value voltage Vg0and an effective value current ig0of high-frequency output is expressed as:
vamp=vg0=vin−Riniamp=vin−Rinig0
iamp=ig0
Zamp=vamp/iamp=Vg0/ig0=Zg0(2)

Following formulas are established, where the effective value voltage on the load side at the coaxial cable length l is VL, the effective value current is iL, the transmission path length is 1=λ/4 and βl=π/2, VLsubstitutes for VL(λ/4), assuming VL(λ/4)=VL-setwhere VL(λ/4)is set as a reference vector:
vL-set=vP-set
iL-set=iP-set
ZL=ZP(3)
Vg0(λ/4)=j(VP-setZ0)/ZP
ig0(λ/4)=jvP-set/Z0
Zg0(λ/4)=Vg0(λ/4)/ig0(λ/4)=Z02/ZP(4)
[Allowable Voltage Ratio k and ZampDuring the Regenerative Operation]

In the formula 4, the subscript at the time of impedance matching where ZL=Z0is represented as “Z0”, the subscript during the regenerative operation is represented as “regen”, and when the allowable voltage ratio k of the load voltage VLis defined, assuming that the regenerative operation starts when the load voltage VLbecomes k times larger than the load voltage VL-Z0at the time of impedance matching, the impedance Zamp(λ/4)-regenviewed from the high-frequency amplifier circuit at the time of regeneration, and the impedance ZP(λ/4)-regenat the connecting position P of the regeneration circulator are expressed respectively as the following:
Zamp(λ/4)-regen={Z0−(k−1)Rin}/k
ZP(λ/4)-regen=kZ02/{Z0−(k−1)Rin}  (5)

When the electrical length between the connecting position P of the regeneration circulator and the load end has an integral multiple relation in terms of the wavelength λ, this leads to a relation of VL=VP. Therefore, the allowable voltage ratio k can be set by the voltage VPat the connecting position P, instead of the load voltage VL, and the allowable voltage ratio k may be configured in such a manner that the regenerative operation starts when the regenerative-operation starting voltage VP-regenbecomes k times larger than the voltage VP-Z0at the time of impedance matching.FIG. 14shows a relation between the regenerative-operation starting voltage VP-regenand the voltage VP-Z0, where the allowable voltage ratio k is 2.

Under the following condition for maximizing the load voltage vL, as a calculation example,
ZL=∞
Rin=8Ω
Z0=50Ω, and

Electrical length of the transmission line l=λ/4; there will now be described an example for reducing the load voltage VL, where k=2 with the use of the regeneration circulator.

In the state where the impedance ZPon the load side relative to the connecting position P of the regeneration circulator is open (ZP=∞) on the load side, the impedance ZPbecomes ZP=ZRaccording to image impedance, when the parallel impedance ZRis connected by the regeneration circulator.

Here, Zampand ZPare obtained by using the formula 5 as the following:
Zamp={Z0−(k−1)Rin}/k={50−(2−1)×8}/2=21[Ω]
ZP=ZR=kZ02/{Z0−(k−1)Rin}=2×502/{50−(2−1)×8}≈119[Ω]

This indicates that ZR(approximately 119Ω) is connected in parallel with the infinite load impedance at the point P, then preventing Zampfrom becoming low impedance (short-circuited).

In the formula 5, even when the load is in the open state (ZL=∞), the allowable voltage ratio k is set to 1, thereby establishing Zamp=ZP=50Ω and leading to the state of impedance matching.

The allowable voltage ratio k=1 indicates that the load voltage VLfor starting the regenerative operation is set to be the load voltage VL−Z0of impedance matching, and by performing the regenerative operation even during the normal state, it is possible to maintain the load voltage VLto be the load voltage VL−Z0of impedance matching, against abnormality caused by an impedance mismatching.

[Relation Between VL-regenDuring Regenerative Operation and DC Power Source Voltage VDD]

When the load voltage VLbecomes k times larger than the effective value voltage VL−Z0of impedance matching, the regenerative operation is started to perform regeneration of DC power into the DC power source voltage VDD. Simultaneously, the upper-limit of the load voltage VLis restricted to the load voltage VL-regenfor the regenerative operation.

In the case where the regeneration is performed by using the transformer, the DC power source voltage VDDbeing a regenerating destination may be defined by an average value (2√2vP-regen/π) of VP-regen(VL-regen), and the turn ratio N of the transformer.

When ZLis equal to Z0, if the DC power source voltage VDDapplied to the inverter of the high-frequency amplifier circuit and the regenerative-operation starting voltage VP-z0(VL-z0) are already known, the turn ratio N of the transformer may be expressed by the following formula 6, using the allowable voltage ratio k:
N×VDD=2√2×VL-regen/π=(2√2×k×vL-z0))/π
N=(2√2×k×VL-Z0)/(π×VDD)≈(0.9×k×vL-Z0)/((π×VDD)  (6)

The descriptions of the above embodiments and modifications are intended to illustrate the DC generator and the method of controlling the DC generator as an example relating to the present invention, and the present invention is not limited to those embodiments. More specifically, it is intended that the invention embrace all modifications and variations of the exemplary embodiments described herein that fall within the spirit and scope of the invention.

INDUSTRIAL APPLICABILITY

The regeneration circulator, the high-frequency power supply device, and the regeneration method according to the present invention are applicable to a power supply unit and a power supply method for supplying high-frequency power to a load device being a plasma load, such as liquid-crystal panel manufacturing equipment, semiconductor producing equipment, and laser oscillator.

DESCRIPTION OF SYMBOLS