Control method of high-frequency power supply device and high-frequency power supply device

Abstract

In the frequency range, the output command value is suppressed to not exceed the upper limit of the output command allowable for the high-frequency amplifier. The control method of the high-frequency power supply device of the present application and the high-frequency power supply device perform frequency control in the frequency range of the variable frequency, and in the frequency range of the variable frequency, the upper limit of the output command value for controlling the output of the high-frequency amplifier is limited by the output limit value, thereby preventing damage to the high-frequency amplifier caused by excessive command.

Description

Technical Field

[0001] The present invention relates to a control method for a high-frequency power supply device that supplies high-frequency power to a load, and to the high-frequency power supply device itself. Background Technology

[0002] To efficiently supply high-frequency power from a high-frequency power supply to a load, impedance matching techniques are known to reduce reflected wave power by adapting to load impedance variations. For example, in the case of a plasma load, besides the transition from an unignited to an ignited state, the load impedance varies due to changes in the chamber environment, such as gas and pressure conditions. When impedance mismatch occurs due to these load impedance variations, the reflected wave power returning from the load to the high-frequency power supply increases, reducing the load power effectively supplied to the load. Furthermore, the load power, obtained by subtracting the reflected wave power returning from the load from the traveling wave power supplied by the high-frequency power supply to the load, represents the power effectively supplied to the load.

[0003] As an impedance matching technique, the following techniques are known: detecting the reflected wave power returning from the load side to the high-frequency power supply side, and increasing the traveling wave power supplied from the high-frequency power supply to the load side based on the detected reflected wave power, thereby compensating for the reduction in load power caused by the reflected wave power.

[0004] Patent Document 1 illustrates impedance matching based on frequency control. When compensating for the reduction in load power by adding power equivalent to the reflected wave power to the traveling wave power, the traveling wave power may be excessive if the reflected wave power is high, potentially leading to an excessively high output. Patent Document 1 discloses a technique that, in order to reduce excessive output, controls the frequency to reduce the reflected wave power, and then controls the output by adding power equivalent to the reflected wave power to the traveling wave power (Patent Document 1).

[0005] Patent Document 2 discloses a technique for limiting the frequency range of a variable frequency in frequency-controlled impedance matching, changing the oscillation frequency in a manner that minimizes the absolute value of the reflection coefficient within a predetermined frequency range including the reference frequency. When changing the oscillation frequency, even with a narrow range of frequency variation, the load impedance can fluctuate significantly. If the load impedance fluctuates significantly, the voltage applied to the load decreases, sometimes making it difficult to maintain a discharge state. Therefore, Patent Document 2 limits the frequency range of frequency control to suppress the decrease in supplied power (Patent Document 2).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2013-197080

[0009] Patent Document 2: Japanese Patent Application Publication No. 2006-310245 (Paragraph 0073) Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] As mentioned above, frequency control is a control method that changes the oscillation frequency. In this control method, in order to suppress the large impedance changes caused by the change in oscillation frequency, the frequency range of the variable frequency of frequency control is limited.

[0012] Regarding frequency control, Patent Document 2 cites the reduction in supplied power caused by variations in load impedance. In Patent Document 2, the reduction in supplied power is suppressed by limiting the frequency range of the variable frequency. In this case, the variable frequency for frequency control is limited to a specific frequency range, and frequencies outside this range are excluded from frequency control.

[0013] Therefore, under load conditions with larger impedance variations, there is a problem that frequency control within a limited frequency range cannot be adequately controlled, and a wider frequency range is desired.

[0014] In frequency control, to compensate for the output reduction caused by the limitations of the high-frequency amplifier's output characteristics, the output of the high-frequency amplifier in the high-frequency power supply device is increased. However, with an expanded frequency range, the output increase of the high-frequency amplifier becomes even greater, potentially causing the voltage and current applied to capacitors and coils—components of circuits such as high-frequency filters—to exceed their rated values.

[0015] The output rise of this high-frequency amplifier is due to the unevenness of its open-loop characteristic relative to the load impedance. Depending on the load, the output rise relative to the output command value is insufficient. Frequency control aims to address this insufficient output rise, allowing the command value for the high-frequency amplifier to increase further.

[0016] Figure 23 This is a graph used to illustrate the relationship between the open-loop characteristics and output control of a high-frequency amplifier. Additionally, Figure 23 The open-loop characteristics shown are a rough representation of the actual characteristics. The horizontal axis represents frequency, and the vertical axis represents the output of the high-frequency amplifier. The solid line represents the open-loop characteristics of the high-frequency amplifier, the dashed line represents a flat open-loop characteristic, and the single-dot dashed line represents the upper limit of the output of the high-frequency amplifier.

[0017] High-frequency amplifiers exhibit frequency-dependent open-loop characteristics. Therefore, if an output command value Pcommand1 with a predetermined flat output characteristic is used, the output value Pout will be smaller than Pcommand1 due to the open-loop characteristic. Consequently, to increase the output value Pout, the high-frequency amplifier generates an output command value Pcommand2 that is larger than Pcommand1 through output control. In this case, there is a possibility that the output command value Pcommand2 exceeds the upper limit of the high-frequency amplifier's output, Plimit.

[0018] Output command values ​​exceeding the upper limit of a high-frequency amplifier's output may damage the circuit components of the high-frequency amplifier and filter. Therefore, to protect the circuit components, it is required that the output command value for the high-frequency amplifier not exceed the upper limit.

[0019] The purpose of this invention is to solve the above-mentioned problems by supplying the set load power (LOAD power) or traveling wave power (FWD power) to the load within the frequency range of the variable frequency controlled by the frequency, and suppressing the output command value to not exceed the upper limit of the output command allowed by the high-frequency amplifier.

[0020] Methods for solving problems

[0021] The present invention includes a control method for a high-frequency power supply device and various modes of the high-frequency power supply device, which performs frequency control within a variable frequency range, and limits the upper limit of the output command value of the high-frequency amplifier to the output limit value within the variable frequency range, thereby preventing damage to the high-frequency amplifier caused by excessive output command and reducing reflected wave power.

[0022] (Control method for high-frequency power supply device)

[0023] The control method for the high-frequency power supply device of the present invention comprises:

[0024] (1) Output control, controlling the output of the high-frequency amplifier based on output commands; and

[0025] (2) Impedance matching control: The impedance between the high-frequency amplifier that outputs high-frequency power through DC-AC conversion and the load is matched, and output control and impedance matching control are performed independently. The load object supplied with power by the control of this invention is, for example, a plasma load with impedance fluctuations.

[0026] Impedance matching control features:

[0027] (A) Frequency control, based on the feedback signal from the high-frequency amplifier, uses frequency variation to achieve impedance matching; and

[0028] (B) Frequency limit control, determining the frequency limit values ​​used to define the frequency range of said frequency control.

[0029] (C) Frequency control: The frequency of the high-frequency amplifier is controlled within the frequency range of the frequency limit value determined by the frequency limit value control.

[0030] Impedance matching control limits the frequency range of the variable frequency controlled by frequency control, thereby suppressing the output command value so as not to exceed the upper limit of the output command allowed by the high-frequency amplifier.

[0031] The output control also includes: (D) output limit control, which determines the output limit value used to limit the output within the frequency range.

[0032] (E) The output of the high-frequency amplifier is controlled by setting the output limit value determined by the output limit value control to the upper limit of the output command value.

[0033] (F) Output control and impedance matching control are performed independently.

[0034] In the impedance matching control of the present invention, in the frequency control for impedance matching, the upper limit of the output command value is suppressed by the output limit value determined by the output limit value control, thereby suppressing the output command value to no more than the upper limit of the output command allowed by the high-frequency amplifier.

[0035] (High-frequency power supply device)

[0036] The high-frequency power supply device of the present invention is a high-frequency power supply device that supplies high-frequency power to a load, and the high-frequency power supply device comprises:

[0037] A high-frequency amplifier that outputs high-frequency power;

[0038] The output control unit controls the output of the high-frequency amplifier; and

[0039] The impedance matching control unit controls the frequency of the high-frequency amplifier output to match the impedance with the load.

[0040] The impedance matching control unit includes:

[0041] (a) A frequency control unit that performs impedance matching by varying the control frequency through frequency control based on a feedback signal from a high-frequency amplifier; and

[0042] (b) A frequency limit control unit that determines the frequency limit values ​​used to specify the frequency range for frequency control.

[0043] The frequency control unit performs the following control:

[0044] (c) The frequency of the high-frequency amplifier is controlled within the frequency range of the frequency limit value determined by the frequency limit control unit.

[0045] In frequency control for impedance matching, the control unit uses the output limit value determined by the output limit value control to suppress the upper limit of the output command value, thereby suppressing the output command value to no more than the upper limit of the output command allowed by the high-frequency amplifier.

[0046] The output control unit also has:

[0047] (d) Output limit control, which determines the output limit value used to limit the output control value of the output control unit within the frequency range.

[0048] (e) The output of the high-frequency amplifier is controlled by setting the output limit value determined by the output limit value control to the upper limit of the output command value.

[0049] The output control unit and the impedance matching control unit are controlled independently by (f).

[0050] (Limit control: frequency limit control and output limit control)

[0051] Frequency control is a control method that changes the control frequency based on the impedance matching state between the high-frequency power supply device and the load. In frequency control, when the frequency for impedance matching is set as the reference frequency, the greater the deviation of the control frequency from the reference frequency, the greater the difference between the output command value and the output feedback signal. Therefore, the goal is to eliminate this difference and increase the output command value.

[0052] In impedance matching, the output limit value at the frequency end of a variable frequency range is lower than the output limit value at the center of the frequency range. This invention applies limit control to frequency control of impedance matching with frequency characteristics, providing both frequency limit control and output limit control for impedance matching frequency control.

[0053] Frequency limit control controls the frequency range of a variable frequency. Output limit control suppresses the output command value by ensuring that the increased output command value does not exceed the allowable range of the high-frequency amplifier. The output limit value is determined and used as the upper limit to restrict the output command value.

[0054] In limit control, the output command value for the control frequency obtained during the frequency control process is limited by limiting the frequency range based on the frequency limit value control and limiting the output command value based on the output limit value control, so that the output command value does not exceed the upper limit of the output command allowed by the high-frequency amplifier.

[0055] (Frequency limit control)

[0056] In impedance matching control, which uses frequency control for impedance matching, a frequency limit value is determined for the control frequency, and the control frequency can be made variable within the frequency range specified by the frequency limit value.

[0057] (Output limit control)

[0058] Output limit control is a control method that limits the output command value to the output limit value within the variable frequency range. When the output command value exceeds the output limit value, the output command value is limited to the output limit value so as not to output the output command value exceeding the output limit value to the high frequency amplifier.

[0059] The output limit value has a frequency characteristic. Besides a frequency characteristic where the output limit value is a fixed value within a frequency range, it can also be a frequency characteristic where the output limit value varies within the frequency range. For example, a frequency characteristic where, within a variable frequency range, the output limit value at the frequency endpoints is set to a lower value than the output limit value at the center of the frequency range.

[0060] In output limit control, the output increases as the output command value increases. To prevent damage to circuit components such as high-frequency amplifiers from excessive output voltage, the upper limit of the output command value is set to the output limit value, suppressing the output command value from exceeding the output limit value. The frequency characteristic of the output command value depends on the frequency characteristic of the load impedance. Generally, the output command value increases as the control frequency deviates from the reference frequency. Therefore, the frequency characteristics of the output command value at frequencies higher than the reference frequency are roughly symmetrical to those at frequencies lower than the reference frequency.

[0061] In this way, if the frequency characteristics of the output command values ​​are considered to be equally symmetrical relative to the high-frequency and low-frequency sides of the reference frequency, the frequency characteristics of the output limit value can be symmetrically set relative to the reference frequency within the variable frequency range, with respect to the frequency characteristics of the high-frequency side and the low-frequency side.

[0062] Furthermore, within the variable frequency range, there are cases where the frequency characteristics of the output command value at a control frequency higher than the reference frequency differ from those at a control frequency lower than the reference frequency. For example, the open-loop characteristics of a high-frequency amplifier significantly influence the frequency characteristics of the output limit, resulting in different frequency characteristics on the high-frequency and low-frequency sides of the control frequency relative to the reference frequency. In such cases, the frequency characteristic is asymmetrical relative to the reference frequency, thus allowing the frequency characteristic of the output limit to be set asymmetrical relative to the reference frequency within the variable frequency range.

[0063] The output limit value can be set in multiple types according to the output mode of the high-frequency power supply device, and is determined for the output command corresponding to the multiple feedback signals used for frequency control.

[0064] (Feedback signal)

[0065] In frequency control and limit control, the feedback signal of the high-frequency power supply device uses the signal obtained from the high-frequency amplifier at the output side of the high-frequency power supply device. This feedback signal includes traveling wave power (FWD power), reflected wave power (REF voltage), load power (LOAD power), and output voltage. On the other hand, the DC power supply signal at the input side of the high-frequency power supply device includes DC voltage and DC current. Additionally, as a signal generated during the power supply of the high-frequency power supply device, there is power loss. Load power can be obtained by subtracting reflected wave power from traveling wave power.

[0066] The feedback signals for traveling wave power, reflected wave power, load power, and output voltage change according to variations in load impedance. Frequency control is based on these feedback signals to control the output frequency of the high-frequency amplifier. Additionally, the feedback signals for DC voltage and DC current indicate the output state of the DC power supply providing drive power to the high-frequency amplifier, and similarly affect the variation in the power supplied to the load as changes in load impedance.

[0067] Frequency control, based on these feedback signals, controls the output frequency of the high-frequency amplifier for impedance matching. This corresponds to variations in load impedance and the output state of the DC power supply, matching the impedance between the high-frequency power supply and the load to reduce reflected wave power. Furthermore, output control and frequency control are performed independently, controlling the power supply to achieve the target power. The target power can be set as, for example, traveling wave power or load power, and controlled so that the output of the high-frequency power supply becomes the traveling wave power command value or the load voltage command value.

[0068] The output limit values ​​corresponding to the feedback signals for traveling wave power, reflected wave power, and output voltage are the traveling wave power limit value, reflected wave power limit value, and output voltage limit value, respectively. Additionally, the output limit values ​​corresponding to the feedback signals for the DC voltage and DC current of the DC power supply are the DC voltage limit value and DC current limit value, respectively.

[0069] The power loss limit corresponding to the feedback signal of the power loss is the output limit corresponding to the power loss generated in the power supply from the high-frequency power supply device to the load. Here, the power loss is the amount of loss generated in the power supply of the high-frequency power supply device, which is equivalent to the power obtained by subtracting the effective power from the supplied power, and is calculated by subtracting the traveling wave power and the reflected wave power from the amount of power supplied from the high-frequency power supply device.

[0070] It is possible to determine the output limit value for at least one of these multiple feedback signals, and the output limit value for multiple feedback signals can also be determined by any combination.

[0071] Invention Effects

[0072] As explained above, according to the present invention, within the frequency range of the variable frequency controlled by the frequency, the set load power (LOAD power) or traveling wave power (FWD power) is supplied to the load, and the output command value is suppressed to not exceed the upper limit of the output command allowed by the high-frequency amplifier. Attached Figure Description

[0073] Figure 1 This is a diagram illustrating the general structure of the high-frequency power supply device of the present invention.

[0074] Figure 2 It is a flowchart used to illustrate the transition from output control to frequency control when the output voltage rises.

[0075] Figure 3 It is a waveform diagram used to illustrate the power change state as output control transitions to frequency control when the output voltage rises.

[0076] Figure 4 This is a diagram illustrating the general structure of the high-frequency power supply device of the present invention.

[0077] Figure 5 This is a flowchart of impedance matching control based on frequency control and frequency limit control.

[0078] Figure 6 This is the output frequency response diagram of frequency control.

[0079] Figure 7 This is a diagram used to illustrate S2 for reflecting power control.

[0080] Figure 8 This is a diagram used to illustrate frequency limit control.

[0081] Figure 9 It is a diagram used to illustrate the action state of FWD limit value control.

[0082] Figure 10 It is a diagram used to illustrate the action state of FWD limit value control.

[0083] Figure 11 It is a flowchart of frequency limit control and limit value control.

[0084] Figure 12 This is an explanation Figure 10 The flowchart shows the frequency response of each process.

[0085] Figure 13 This diagram shows the switching between FWD limit control and REF limit control.

[0086] Figure 14 This is a diagram used to illustrate the switching of load power (P1→P2).

[0087] Figure 15 This is a power change diagram used to illustrate the switching of load power (P1→P2).

[0088] Figure 16 This is a flowchart illustrating the switching of load power (P1→P2).

[0089] Figure 17 This is a diagram used to illustrate the switching of load power (P2→P1).

[0090] Figure 18 It is used to explain and Figure 17 A diagram showing the switching of load power (LOAD power) at different start frequencies (P2→P1).

[0091] Figure 19 This is a diagram illustrating an example of the structure of the high-frequency power supply device of the present invention.

[0092] Figure 20 This is a diagram illustrating an example of the frequency characteristics of the FWD limit.

[0093] Figure 21 This is a diagram illustrating an example of the frequency characteristics of the FWD limit.

[0094] Figure 22 This is a diagram illustrating an example of the frequency characteristics of the FWD limit.

[0095] Figure 23 This is a diagram used to illustrate the relationship between the open-loop characteristics and output control of a high-frequency amplifier. Detailed Implementation

[0096] The following uses Figures 1-5 A summary of the high-frequency power supply device and control method of the present invention will be described, using... Figures 6 to 18 This section explains frequency control and limit control, and demonstrates their application. Figure 19 The structure of a high-frequency power supply device will be described using an example. Figures 20-22 An example illustrating the frequency characteristics of the traveling wave power limit will be given. Furthermore, frequency control and limit control will be explained using the case where the output command is used as a load power command (LOAD power command) as an example.

[0097] Figure 1 This includes the control method for the high-frequency power supply device and a schematic diagram of the high-frequency power supply device. Figure 2 , 3 It is a flowchart used to illustrate the transition from output control to frequency control when the output voltage rises, and a waveform diagram to represent the power change state.

[0098] Figure 4 This is a diagram illustrating the general structure of the high-frequency power supply device of the present invention. Figure 5 This is a flowchart of impedance matching control based on frequency control and frequency limit control.

[0099] Figures 6 to 18 The frequency control and limit control described herein are control examples when the load power command is used as the output command. Figure 6 It is the output frequency response diagram of frequency control. Figure 7 This is a diagram used to illustrate the tuning of reflected power control. Figure 8 This is a diagram used to illustrate frequency limit control. Figure 9 , 10 This is a diagram used to illustrate the operating state of output limit control (FWD (Traveling Wave Power Limit Control)). Figure 11 , 12 It includes flowcharts for frequency limit control and output limit control, as well as frequency response diagrams. Figure 13 This diagram shows the switching between output limit control (FWD limit control (traveling wave power limit control value control)) and REF limit control (reflected wave power limit control value control).

[0100] Figures 14-18 This is a diagram used to illustrate the switching of the load power command (LOAD power command). Figure 14 , Figure 15 as well as Figure 16 It includes a graph illustrating the frequency-power characteristics when switching the load power command from P1 to P2, a graph illustrating the time variation of power, and a flowchart illustrating the switching process. Figure 17 , 18 This is a graph illustrating the frequency-power characteristics when switching the load power command from P2 to P1. Additionally, it is... Figure 17 The start frequency and Figure 18 Examples of different starting frequencies. Figure 19 This is a diagram illustrating an example of the structure of the high-frequency power supply device of the present invention. Figure 20 This is an example of the frequency response that represents the power limit of a traveling wave. Figure 21 , Figure 22 This is another example of the frequency characteristics representing the power limit of a traveling wave.

[0101] The following uses Figure 1 The control method of the high-frequency power supply device of the present invention and the general structure of the high-frequency power supply device are described.

[0102] (Overview structure, overview control)

[0103] (Output control and impedance matching control)

[0104] The control of the high-frequency power supply device of the present invention includes output control that controls the output of the high-frequency power supply device to a set output, and impedance matching control that matches the impedance between the high-frequency power supply device and the load. Figure 1 This section outlines the control of the high-frequency power supply device of the present invention.

[0105] exist Figure 1 In this process, output control controls the power supplied from the high-frequency power supply to the load to a predetermined power according to a command value. Output control can employ either traveling wave power control (FWD control), which controls the traveling wave power (FWD power) sent from the high-frequency power supply to the load, or load power control (LOAD control), which controls the load power (LOAD power) supplied to the load. Furthermore, the load power (LOAD power) is the power obtained by subtracting the reflected wave power (REF power) returning from the load to the high-frequency power supply from the traveling wave power (FWD power) sent from the high-frequency power supply to the load (LOAD power = FWD power - REF power). Hereinafter, load power (LOAD power) control as output control will be explained. Load power (LOAD power) control controls the load power obtained by subtracting the reflected wave feedback value (REF-FB) from the traveling wave power feedback value (FWD-FB) towards the load power command value (LOAD-CO).

[0106] Impedance matching control is the control that matches the impedance between the high-frequency power supply and the load. By performing impedance matching, the reflected power (REF power) returning from the load to the high-frequency power supply is reduced, thus suppressing the reduction of the load power (LOAD power) supplied from the high-frequency power supply to the load.

[0107] Impedance matching control controls the operating frequency of a high-frequency amplifier through frequency control, thereby achieving impedance matching. In impedance matching control, the frequency range for frequency control is determined by frequency limit value control (FLV control). Frequency limit value control calculates the frequency limit based on the traveling wave power value (FWD power value). The frequency limit value defines the upper and lower frequency limits of the frequency control range. Frequency control performs impedance matching within the frequency range determined by the frequency limit value calculated through frequency limit value control. The control method of the high-frequency power supply device of the present invention continuously calculates the frequency limit value determined by the traveling wave power value (FWD power value) and reflects the frequency range based on the calculated frequency limit value into the frequency control.

[0108] On the other hand, in output control, output limit control is performed to bring the power supplied to the load within the allowable power range. Output limit control suppresses the supplied power within the output limit value. Output control can apply traveling wave power control based on traveling wave power command or load power control based on load power command.

[0109] The traveling wave power control uses the traveling wave power feedback value (FWD-FB) as the traveling wave power command value (FWD-CO) to control the output command value of the high-frequency amplifier. The load power control uses the load power (LOAD power) obtained by subtracting the reflected wave power feedback value (REF-FB) from the traveling wave power feedback value (FWD-FB) as the load power command value (LOAD-CO) to control the output command value of the high-frequency amplifier.

[0110] Output limit control suppresses the supplied power within the output limit value by suppressing the upper limit of the output command value to the output limit value. The output limit value is the FWD limit value or the LOAD limit value obtained through output limit control.

[0111] When FWD control is applied in the output control, the upper limit of the traveling wave power is suppressed by using the FWD limit value obtained through FWD limit value control. Similarly, when LOAD control is applied in the output control, the upper limit of the load power is suppressed by using the LOAD limit value obtained through LOAD limit value control.

[0112] When traveling wave power control is performed as output control, the FWD limit value obtained through FWD limit value control is used as the output limit value. The FWD control of the output control suppresses the upper limit of the traveling wave power by using the FWD limit value obtained from the FWD limit value control.

[0113] In addition, when load power control is performed as output control, the LOAD limit value obtained by LOAD limit value control is used as the output limit value. In addition to suppressing the load power command value to below the LOAD limit value, the traveling wave power command value obtained by adding reflected wave power feedback (FER-FB) to the LOAD command value is also suppressed to below the FWD limit value.

[0114] By controlling the output limit value, the upper limit of the output command value is suppressed to the output limit value, thereby suppressing the supplied power within the output limit value.

[0115] (The shift from output control to frequency control)

[0116] use Figure 2 , 3 The flowcharts and waveforms illustrate the output control and variable frequency control of the high-frequency power supply device. Figure 3 An example of a power waveform.

[0117] This invention supplies load power (LOAD power) or traveling wave power (FWD power) to the load through output control, and minimizes reflected wave power through frequency control. In output control, impedance mismatches arise due to increases in output power, changes in load conditions, etc., sometimes requiring an increase in the output command value to achieve the set load power (LOAD power) or traveling wave power (FWD power). This invention sets an output limit value to restrict the output command value. If the output command value increases beyond the output limit value through output control, the system switches to output limit control to restrict further increases in the output command value.

[0118] By limiting the output command value, the supply of load power (LOAD power) or traveling wave power (FWD power) to the load is restricted, resulting in insufficient power supply to the load and difficulty in increasing the output power. To avoid this situation, when the output limit control is reached, variable frequency control is used to escape the output limit state. In the non-limit state of the output, after escaping the output limit state, minimum reflected wave power is minimized through minimum reflected power control, and the set power is supplied to the load for stable output control. In stable output control, if the output command value exceeds the output limit value due to impedance mismatch caused by load variations, etc., it switches back to output limit control, and frequency control for impedance matching control and output control are performed separately. Furthermore, here, variable frequency control represents the frequency control for escaping the limit state, and frequency control represents the frequency control for impedance matching control.

[0119] Figure 2The output control shown on the left indicates the state of reaching the output limit. The output is controlled by the output control to set the output (A1). If the output reaches the set output (A2) and becomes the output limit state (A3, A5), the variable frequency control is used to control the output to get out of the output limit state.

[0120] Figure 2 The variable frequency control shown on the right represents the state of breaking free from the output limit state.

[0121] After escaping the output limit state through variable frequency control and minimizing the reflected wave power through minimum reflected power control, the power supply is controlled by output control and impedance matching control in stable output control.

[0122] As an output limit state, there are, for example, a reflected wave power limit state where the reflected wave power exceeds the limit value, or a power loss limit state where the power loss exceeds the limit value. In this output limit state, the setpoint frequency (B1) of the control frequency is changed to perform variable frequency control that changes the control frequency. Furthermore, the setpoint frequency is an arbitrarily set frequency for starting variable frequency control (B2). Through variable frequency control, the feedback value of traveling wave power (FWD-FB) decreases (B3), and by becoming below the traveling wave power limit value (FWD-Limit), it escapes from the output limit state (B4). In the state of escaping the output limit state, the reflected wave power is minimized by minimum reflected wave power control, thereby increasing the power supply to the load (B5). By minimizing the reflected wave power, after the power supply to the load reaches the set output (B6), it switches to stable output control, and the power supply control of the set power is performed through output control and impedance matching control.

[0123] Figure 3 This indicates the transition state from output control (A) to variable frequency control (B). Figure 3 Images (a), (b), and (c) show the variations in load power (LOAD power), traveling wave power feedback (FWD-FB), and reflected wave power feedback (REF-FB), respectively. Figure 3 (d) shows the control frequency ω for frequency control. Additionally, in Figure 3 In (a), the dashed line represents the load power command value (LOAD-CO), the solid line represents the load power feedback value (LOAD-FB) with limit control enabled, and the dashed line represents the load power feedback value (LOAD-FB) without limit control enabled. Additionally, in Figure 3In (b), the long dashed line represents the traveling wave power limit (FWD-Limit), the solid line represents the feedback value of the traveling wave power (FWD-FB) under limit control, and the short dashed line represents the output value (traveling wave power value) without limit control.

[0124] The interval from t0 to t1 represents the state of output control (A). Through output control, the traveling wave power feedback value (FWD-FB) increases, and the reflected wave power feedback value (REF-FB) also increases. The load power (LOAD power) becomes the value obtained by subtracting the reflected wave power feedback value (REF-FB) from the traveling wave power feedback value (FWD-FB).

[0125] When the traveling wave power feedback value (FWD-FB) exceeds the traveling wave power limit (FWD-Limit), reaching the output limit state (t1), the control switches from output control (A) to variable frequency control (B), switching to the setpoint frequency (B1), making the control frequency variable (B2). In variable frequency control (B), the traveling wave power (FWD) is limited by the traveling wave power limit (FWD-Limit) and decreases towards the traveling wave power limit (FWD-Limit). Figure 3 In (b), without limit control, the output value exceeds the traveling wave power limit (FWD-Limit) voltage and increases, as shown by the short dashed line. However, with limit control, the output value decreases towards the traveling wave power limit (FWD-Limit), as shown by the solid line. In this state, the traveling wave power (FWD) exceeding the traveling wave power limit (FWD-Limit) is output to the load, but the period of output power increase is a relatively short time width that the high-frequency amplifier can tolerate. After reaching the set output (B6), it switches to stable output control and performs control. When the traveling wave power (FWD) is below the traveling wave power limit (FWD-Limit), it becomes a state where output limit control is not required, thus escaping the limit state (B4). Subsequently, the reflected wave power is minimized by minimum reflected power control (B5), causing the LOAD power supplied to the load to increase towards the LOAD power command value as the set output (B6).

[0126] According to the control of the high-frequency power supply device of the present invention, output control and impedance matching control are performed separately, and impedance matching control is performed within the frequency range obtained by frequency limit control. Output control uses the output limit value obtained by output limit control to suppress the upper limit power.

[0127] According to the control of the high-frequency power supply device of the present invention, droop control that causes the traveling wave power (FWD power) or load power (LOAD power) to droop is not performed as output control, so output control and impedance matching control can be performed without reducing the output supplied to the load.

[0128] (Overview Structure)

[0129] use Figure 4 The general structure of the high-frequency power supply device of the present invention will be described. Figure 4 In the process, the high-frequency power supply device 1 includes a power supply source, a high-frequency amplifier 3, a high-frequency sensor 4, a matching device 5, and a controller 10, which outputs high-frequency output to the load 6. Figure 4 In the example shown, the output control performed by the controller 10 includes load power control (LOAD control) or traveling wave power control (FWD control).

[0130] The power supply source of high-frequency power supply device 1 is in Figure 4 The example shown represents a DC power supply 2, but it is not limited to a DC power supply; an AC power supply can also be used.

[0131] The high-frequency amplifier 3 converts the DC power from the DC power supply 2 into high-frequency AC power, thereby generating high-frequency AC power. In a structure that uses an AC power supply as a power source, the AC signal frequency of the AC power supply is converted into a high-frequency signal to generate high-frequency AC power.

[0132] High-frequency sensor 4 detects the traveling wave power FWD output from high-frequency power supply 1 to load 6 and the reflected wave power REF returned from load 6 to high-frequency power supply 1, and feeds back the detected traveling wave power FWD feedback value FWD-FB and reflected wave power REF feedback value REF-FB to controller 10. For example, the traveling wave power FWD and reflected wave power REF are detected separately via a directional coupler (not shown).

[0133] Matching circuit 5 is a circuit that matches the impedance between high-frequency power supply unit 1 and load 6. For example, by setting the values ​​of its circuit elements, matching the impedance of high-frequency power supply unit 1 during stable operation with the impedance of load 6, the matching circuit minimizes the reflected wave power returning from load 6 to high-frequency power supply unit 1 when maximum power is supplied, and maximizes the traveling wave power from high-frequency amplifier 3 to load 6. Typically, matching circuit 5 is constructed using a fixed matching circuit with a fixed coil and a fixed capacitor. While a variable matching circuit using a variable capacitance and a variable coil can be used, constructing a variable matching circuit increases the cost of the control circuit, drive mechanism such as the motor, in addition to the matching circuit itself.

[0134] Matching unit 5 performs impedance matching when the impedance is stable. However, if the impedance matching state changes from the stable state to an impedance mismatch state due to load changes, the impedance mismatch is eliminated by frequency control of the high-frequency amplifier.

[0135] The controller 10 performs output control (FWD control or LOAD control) and impedance matching control on the high-frequency amplifier 3.

[0136] Output control generates an output command value that brings the output to the target value and controls the high-frequency amplifier 3. Traveling wave power control (FWD control) generates an output command value that controls the traveling wave power FWD towards the target traveling wave power value. Load power control (LOAD control) generates an output command value that controls the traveling wave power FWD by using the load power obtained by subtracting the reflected wave power feedback from the traveling wave power feedback value as the set power.

[0137] Impedance matching control achieves impedance matching by controlling the output frequency when the impedance matching state deviates from the steady state. Furthermore, the steady state is the state where the impedance between the high-frequency power source and the load is matched. In the matching circuit 5, which consists of a fixed matching circuit, impedance matching is achieved by determining the values ​​of a fixed coil and a fixed capacitor.

[0138] When impedance mismatch occurs, the controller 10 changes the output control frequency ω through frequency control to achieve impedance matching and reduce reflected wave power, and generates an output command value to control the output value of the high-frequency amplifier 3 through output control.

[0139] The controller 10 generates a control frequency ω through the frequency control unit 10Ba based on the feedback values ​​of traveling wave power FWD and reflected wave power REF detected by the high-frequency sensor 4, the feedback value of output voltage Vpp-FB detected at the output terminal of the high-frequency power supply device 1, and the feedback values ​​of DC voltage Vdc and DC current Idc supplied to the high-frequency amplifier 3 from the DC power supply 2, the feedback values ​​of DC voltage Vdc and DC current Idc, and the feedback values ​​of DC voltage Vdc and DC current Idc. The controller 10 generates an output command value through the output control unit (FWD control unit or LOAD control unit).

[0140] The controller 10 includes an output control unit 10A, an impedance matching control unit 10B, and a drive control unit 10C, which independently perform frequency control and output control for impedance matching control.

[0141] (Output Control Unit 10A)

[0142] When output control is performed via traveling wave power control (FWD control), the output control unit 10Aa includes an FWD control unit, and the output limit control unit 10Ab includes an FWD limit control unit. When output control is performed via load power control (LOAD control), the output control unit 10Aa includes a LOAD control unit, and the output limit control unit 10Ab includes a LOAD limit control unit.

[0143] The output control unit 10Aa generates an output command value based on the feedback value FWD-FB of the traveling wave power FWD detected by the high-frequency sensor 4, the feedback value REF-FB of the reflected wave power REF, and the output target value.

[0144] The output control unit 10Aa suppresses the upper limit of the output command value based on the output limit value generated by the output limit value control unit 10Ab.

[0145] The output limit control unit 10Ab has an output limit value that determines the upper limit of the output command value for each frequency within a variable frequency range including the reference frequency. When the output command value exceeds the output limit value, the output command value is replaced with the output limit value to limit the upper limit of the output command value. When the control frequency obtained through frequency control is within this frequency range, the output limit value is read out as the value corresponding to the control frequency at this time.

[0146] When output control is performed via traveling wave power control (FWD control), the output limit control unit 10Ab has a traveling wave power limit value for each frequency within a variable frequency range including the reference frequency, which determines the upper limit of the traveling wave power command value. When the traveling wave power command value exceeds the traveling wave power limit value, the traveling wave power command value is replaced with the traveling wave power limit value, thereby limiting the upper limit of the traveling wave power command value.

[0147] When output control is performed via load power control (LOAD control), the output limit control unit 10Ab has a traveling wave power limit value for each frequency within a variable frequency range including the reference frequency, which determines the upper limit of the traveling wave power command value. Assuming there is no reflected wave power, the load power command value is processed as the traveling wave power command value. If the load power command value exceeds the traveling wave power limit value, the load power command value is replaced with the traveling wave power limit value, thereby limiting the upper limit of the load power command value.

[0148] (Impedance matching control unit 10B)

[0149] The impedance matching control unit 10B includes a frequency control unit 10Ba and a frequency limit control unit 10Bb.

[0150] The frequency control unit 10Ba calculates the control frequency ω of the high-frequency amplifier 3 based on feedback signals such as the feedback value FWD-FB of the traveling wave power FWD and the feedback value REF-FB of the reflected wave power REF detected by the high-frequency sensor 4. Subsequently, during repeated frequency control, the control frequency obtained in the previous frequency control is set as the reference frequency ωo, and the control frequency ω of the matching impedance is calculated by changing the frequency from this reference frequency ωo.

[0151] The frequency limit control unit 10Bb controls the frequency limit values ​​and determines the upper and lower limits of the frequency range that determine the control frequency when the frequency control unit 10Ba performs impedance matching. The frequency limit control unit 10Bb limits the upper limit of the output command value generated by the output limit control unit 10Ab to the output limit value, thereby controlling the damage to the circuit elements of the high-frequency amplifier 3 caused by excessively large output command values.

[0152] (Drive Control Unit 10C)

[0153] The drive control unit 10C uses the output command value obtained by the output control unit 10Aa of the output control unit 10A and the control frequency ω obtained by the frequency control unit 10Ba of the impedance matching control unit 10B as the output command value to control the amplification of the high-frequency amplifier 3.

[0154] Furthermore, the output control unit 10A, impedance matching control unit 10B, and drive control unit 10C are not necessarily limited to a structure composed of individual circuits; each control unit may also be composed of a DSP. Moreover, each control unit of 10A, 10B, and 10C represents a component used to explain various control functions such as output control (FWD control, LOAD control), output limit control, frequency control, and frequency limit control. Output limit control and frequency limit control are not necessarily limited to a structure performed in the output control unit 10A and impedance matching control unit 10B; for example, it may be a structure in which output limit control and frequency limit control are performed together with the frequency control of the impedance matching control unit 10B.

[0155] (Frequency control and frequency limit control)

[0156] use Figure 5 Flowchart and Figures 6-10 The frequency characteristics of each control are used to illustrate frequency control and frequency limit control.

[0157] In the following flowchart, the feedback values ​​related to the output of the high-frequency power supply device, including traveling wave power FWD, reflected wave power REF, and output voltage Vpp, as well as the feedback values ​​of voltage and current related to the power output of the high-frequency power supply device, are collectively referred to as output values ​​for explanation.

[0158] exist Figure 5 In the flowchart, frequency control (S1, S2) and frequency limit value control (FLV (Frequency Limit Value) control) (S11 to S19) are performed through parallel processing.

[0159] The following sections will explain frequency control, frequency limit value control (FLV (Frequency Limit Value) control), and output limit value control in sequence. Additionally, Figure 6 , Figure 7 This is a diagram used to illustrate the reflected power control (S2) in frequency control. Figure 8 This is a diagram used to illustrate Frequency Limit Value (FLV) control. Figure 9 , 10 This is a diagram used to illustrate output limit control.

[0160] (Frequency control)

[0161] Frequency control is impedance matching control that matches the impedance changes of the load by changing the output frequency of the high-frequency power supply device, thereby reducing the reflected wave power returning from the load to the high-frequency power supply device and controlling the power supply from the high-frequency power supply device to the load.

[0162] A matching circuit is installed between the high-frequency power supply and the load to match the impedance between them under steady-state conditions. Additionally, the high-frequency amplifier performs impedance matching to accommodate impedance variations in the load by varying its operating frequency. The power supply's output impedance is set to Z... O Set the characteristic impedance of the matching circuit, which includes the load impedance, to Z. L The input impedance on the load side, as observed from the high-frequency power supply device, is set to Z. in When, the reflection coefficient Γ is given by Γ=(Z L -Z O ) / (Z L +Z O ) indicates that each impedance Z L Z O Z in And Γ is a function of frequency ω. In response to changes in load impedance, the high-frequency output ω of the high-frequency power supply is made variable, thereby making each impedance variable and controlling the frequency of the reflection coefficient Γ to a minimum value.

[0163] Frequency control, in setting the output high-frequency ω to a variable impedance matching, involves two control steps: a phase control step at the start (S1) and a reflection power control step after the start (S2). These steps aim to output a high-frequency frequency that minimizes the reflected wave power. While maintaining this frequency control, the reflection coefficient Γ and / or reflection amount Wr are stored as minimum values.

[0164] Furthermore, by repeatedly performing the phase control process and the reflection power control process, the reflected wave power is maintained at a minimum. The phase control process S1 and the reflection power control process S2 perform the following controls respectively.

[0165] (Phase control process S1)

[0166] In the phase control process, at the start of control, the scanning direction of the frequency that increases or decreases the frequency that causes the frequency change is determined based on the phase state of the high-frequency power supply device.

[0167] The frequency scanning direction is the direction in which the frequency that reduces the reflection coefficient and / or reflection amount decreases during frequency control. In the phase control process, the frequency control scanning direction is determined at the start of control, thereby shortening the processing time for frequency control that reduces reflected wave power.

[0168] In the phase control process, the scanning direction of the frequency is determined by whether the phase φ of the reflection coefficient Γ is positive or negative. A positive phase is equivalent to a delay load, and a negative phase is equivalent to a lead load.

[0169] In the phase control process, the phase state is detected (S1a) based on the phase difference between the voltage and current at the output terminal of the high-frequency power supply device or the phase difference between the phase of the reflected wave and the traveling wave at the output terminal of the high-frequency power supply device, and it is determined whether the detected phase state is a positive phase or a negative phase (S1b).

[0170] When the phase state is positive, it is determined to be a delayed load, and a frequency scan is performed to increase the frequency ω. The frequency ω is increased relative to the initial frequency ω(0), and the frequency ω(1) is determined (S1c). When the phase state is negative, it is determined to be a leading load, and a frequency scan is performed to decrease the frequency ω. The frequency ω is decreased relative to the initial frequency ω(0), and the frequency ω(1) is determined (S1d).

[0171] Based on the scanning direction of the frequency determined in the phase control process, the frequency is increased or decreased to control the reflected power (S2). Additionally, in Figure 5 In the reflection power control process shown, the reflection coefficient Γ(k) at frequency ω(k) is shown.

[0172] In phase control S1, depending on the load condition, there may be a situation where the relationship between the aforementioned phase state and the scanning direction of the frequency becomes opposite. In such cases, the scanning direction is reversed in the steps S1e to S1h.

[0173] In step S1c or step S1d, the frequency is changed in the scanning direction, and the reflection coefficient Γ or reflection amount Wr is detected (S1e). The increase or decrease of the reflection coefficient Γ or reflection amount Wr is determined (S1f). If the reflection coefficient Γ or reflection amount Wr increases, it is determined that the scanning direction is reversed, and reverse control is performed to reverse the scanning direction of frequency ω (S1g). On the other hand, if the reflection coefficient Γ or reflection amount Wr decreases, it is determined that the scanning direction is correct, and control is performed while maintaining the scanning direction of frequency ω (S1h).

[0174] (Reflection power control process S2)

[0175] The goal of frequency control is to minimize the absolute value |Γ| of the reflection coefficient Γ. However, the absolute value |Γ| of the reflection coefficient Γ may not be minimized when the phase φ is 0°. Therefore, after the phase φ of the reflection coefficient Γ is oriented towards 0° to begin frequency scanning through phase control, the frequency is controlled by reflection power control to minimize the absolute value |Γ| of the reflection coefficient.

[0176] In the reflection power control step S2, after frequency change begins in the scanning direction determined in the phase control step S1, the reflection coefficient value and / or reflection amount of the high-frequency power supply device are used as control completion conditions to control the continuation / stopping of frequency change. Here, as the control completion condition, the case where the reflection coefficient value and / or reflection amount of the high-frequency power supply device becomes extremely small through frequency change control is used to determine whether the reflection coefficient Γ and / or reflection amount is extremely small.

[0177] When the starting point of frequency control is in positive phase, after shifting the frequency control that increases the frequency towards 0° phase through the phase control process, the frequency at which the reflection coefficient Γ or the reflection amount becomes minimal is determined through reflection power control. Conversely, when the starting point of frequency control is in negative phase, after shifting the frequency control that decreases the frequency towards 0° phase through the phase control process, the frequency at which the reflection coefficient Γ or the reflection amount becomes minimal is determined through reflection power control.

[0178] In the reflection power control (S2) following the phase control process (S1), frequency scanning is performed while changing the frequency ω(k) at the timing (sampling) k (S2a), and the reflection coefficient Γ(k) is calculated at the frequency ω(k) of each sampling timing k (S2b).

[0179] Compare the reflection coefficient Γ(k-1) obtained at time (k-1) with the reflection coefficient Γ(k) obtained at time (k) (S2c). If the Γ(k) obtained in subsequent sampling (k) is smaller than the Γ(k-1) obtained through sampling (k-1) one sampling point earlier (Γ(k-1)≥Γ(k)), it is determined that a smaller reflection coefficient Γ is obtained by continuously performing frequency scanning, and the S2a and S2b processes are repeated.

[0180] On the other hand, if the Γ(k) obtained in the subsequent sample (k) exceeds the Γ(k-1) obtained in the sample (k-1) one sample before (Γ(k-1) < Γ(k)), it is determined that if the frequency scan continues, the reflection coefficient Γ will increase, and in the next sample (k+1), it is set to Γ(k+1) = Γ(k-1) to complete the control (S2d).

[0181] (Re-control process)

[0182] Maintain the frequency determined in the phase control process and the reflection power control process, and provide the output to the load.

[0183] Subsequently, when changes occur on the load side, the impedance matching will deviate from the appropriate state.

[0184] In this situation, the phase control step S1 and the reflection power control step S2 are repeatedly performed through the re-control process to determine the appropriate frequency ω again and perform impedance matching. In the re-control process, the reflection coefficient and reflection amount at the frequency obtained in the phase control step and the reflection power control step are stored as minimum values. If the reflection coefficient and reflection amount obtained later exceed the threshold, re-control is performed.

[0185] based on Figure 6 One example of frequency characteristic change is the shift in the control frequency of n in the reflection power control process S2. Here, the case where the output command value is set to the load power command is used as an example. Furthermore, Figure 6 The frequency response changes shown are schematic and do not represent the actual characteristics.

[0186] (a) Control frequency ωo:

[0187] Figure 6(a) represents the impedance-matched state. In the impedance-matched state, the high-frequency amplifier outputs high-frequency power at the reference frequency ωo, where the reflection coefficient Γ is small. Because the reflection coefficient Γ is small in the impedance-matched state, the feedback value of the reflected power REF-FB becomes smaller, the traveling wave power command value FWD-CO becomes approximately equal to the load power command value LOAD-CO, and the feedback value of the traveling wave power FWD-BF becomes close to the load power command value LOAD-CO (traveling wave power command value FWD-CO). Hereinafter, FWD-BF represents the traveling wave power and the traveling wave power feedback value, and REF-BF represents the reflected wave power and the reflected wave power feedback value. The power obtained by subtracting the reflected wave power REF-BF from the traveling wave power FWD-BF (FWD-BF﹣REF-BF) is the load power, which is the effective power supplied to the load.

[0188] (b) Control frequency ωo:

[0189] Figure 6 (b) represents the state where the impedance transitions from a matched state to a mismatched state when the reference frequency ωo is set as the control frequency. Due to load variations, the impedance deviates from the matched state, and if it becomes an impedance mismatched state, the frequency characteristics of the reflection coefficient Γ change, and the frequency at which the reflection coefficient Γ deviates to its minimum from the reference frequency ωo. Figure 6 In (b), the characteristic curve of the reflection coefficient Γ is shown as it shifts towards the lower frequency side. When the reflection coefficient Γ at the reference frequency ωo increases due to the shift in the reflection coefficient Γ, the reflected wave power REF-FB increases. As the reflected wave power REF-FB increases, the traveling wave power feedback value FWD-FB increases. At this point, the traveling wave power feedback value FWD-FB exceeds the traveling wave power threshold, and the reflected wave power feedback value REF-FB exceeds the reflected wave power threshold.

[0190] (c) Control frequency ω1:

[0191] Through frequency control, the control frequency changes from the reference frequency ωo to the control frequency ω1. Figure 6 (c) represents the frequency control state at control frequency ω1. The reflection coefficient Γ of control frequency ω1 is smaller than the reflection coefficient Γ of reference frequency ωo, and the reflected wave power REF-FB is reduced.

[0192] As the reflected wave power REF-FB decreases, the traveling wave power feedback value FWD-FB also decreases.

[0193] Figure 6 The state shown in (c) is still the state where the traveling wave power feedback value FWD-FB exceeds the traveling wave power threshold and the reflected wave power feedback value REF-FB exceeds the reflected wave power threshold.

[0194] (d) Control frequency ω2:

[0195] Through frequency control, the control frequency changes from the reference frequency ω1 to the control frequency ω2. Figure 6 (d) represents the frequency control state at control frequency ω2. The reflection coefficient Γ at control frequency ω2 is smaller than the reflection coefficient Γ at reference frequency ω1, and the reflected wave power feedback value REF-FB also decreases. As the reflected wave power feedback value REF-FB decreases, the traveling wave power feedback value FWD-FB also decreases further. Figure 6 In the state shown in (d), the reflected wave power feedback value REF-FB is at its minimum.

[0196] Figure 7 The steps S2a to S2d in the reflection power control (S2) are schematically shown.

[0197] In the S2c process, the reflection coefficient Γ(k-1) obtained by different sampling timings is compared with the reflection coefficient Γ(k). If the Γ(k) obtained in a subsequent sampling (k) exceeds the Γ(k-1) obtained in the sampling (k-1) one sampling earlier (Γ(k-1) < Γ(k)), it is determined that if frequency scanning continues, the reflection coefficient Γ will increase. In the S2d process, in the next sampling (k+1), control is completed as Γ(k+1) = Γ(k-1). Figure 7 The frequency return position near the adjustment frequency indicates the process of S2d.

[0198] (Frequency limit control)

[0199] Next, frequency limit value control (FLV control) will be explained. The following is based on... Figure 5 Flowcharts and Figure 8 The diagram below provides an explanation.

[0200] In output control, it is determined whether the output is in an output limit state that restricts the upper limit of the output command value. Furthermore, when output control is performed using traveling wave power control, the determination of whether it is a traveling wave power limit state (FWD limit state) is based on a comparison between the traveling wave power feedback value (FWD-FB) and the traveling wave power limit value (FWD-Limit). Conversely, when output control is performed using load power control, the determination of whether it is a load power limit state (LOAD limit state) is based on a comparison between the load power feedback value (LOAD-FB) obtained by subtracting the reflected wave power feedback value (REF-FB) from the traveling wave power feedback value (FWD-FB) and the load power limit value (LOAD-Limit) (S11).

[0201] When the output limit state is reached, in order to update and perform frequency limit control, the control frequency ω is shifted toward the reference frequency ωo (S12), the output limit state is released and the system is set to a reset state, and the control frequency at this time is stored as ωs (S13). The control frequency ±ωs is set as the frequency limit value ±ωLimit (S14).

[0202] On the other hand, when not in the output limit state, the frequency limit value ωLimit is set according to the output state (S15~S19). In the output limit state, the output value is obtained from the high-frequency power supply. As the output value, a feedback value selected from the following can be used (S15): the feedback value of traveling wave power FWD-FB, the feedback value of reflected wave power REF-FB, the feedback value of output voltage Vpp-FB, the output voltage of the DC power supply, the feedback values ​​of output current Vdc-FB, Idc-FB, and the load power feedback value (LOAD-FB).

[0203] The obtained output value is compared with the output value obtained in the previous frequency limit control, and the output change Δ of the difference is calculated (S16), and compared with a predetermined threshold. The threshold is a value set to determine whether the output value has changed, and can be determined based on the expected hysteresis under impedance matching conditions (S17).

[0204] In the process of comparing the output change Δ with the threshold, if the output change Δ does not exceed the threshold, the control frequency is maintained without setting a frequency limit. On the other hand, if the output change Δ is above the threshold, a frequency limit is set for the control frequency ω. The frequency limit is set by restoring the frequency limit ωLimit to the preset default value ωmax (S18), and the frequency limit ±ωLimit is set using ωmax (S19). Furthermore, in the process of comparing the output change Δ with the threshold in S17, if the output change Δ is equal to the threshold, either setting a frequency limit or not can be performed.

[0205] Figure 8 This is a diagram used to illustrate frequency limit control. Figure 8 (a) represents the case where the traveling wave power is in the limit state in S11. Figure 8 (b) indicates the case where the traveling wave power limit is not in S11.

[0206] When under the traveling wave power limit:

[0207] exist Figure 8In (a), the frequency range marked with slashes indicates the region where the traveling wave power limit is reached. When the traveling wave power limit is reached, the output frequency ω is shifted inward (S12), the traveling wave power limit is released, and the frequency ωs at this time is set as the frequency limit value ωLimit (S13, S14).

[0208] Not under the traveling wave power limit state:

[0209] exist Figure 8 In (b), the frequency range marked with slashes indicates the region that is not in the traveling wave power limit state. When not in the traveling wave power limit state, the frequency limit value ωLimit is restored to the preset maximum frequency ωmax (S18), and the frequency ωmax is set as the frequency limit value ωLimit (S19).

[0210] In frequency control, the frequency ω for reflecting power control is within the frequency range of the frequency limit value ± ωLimit set by the frequency limit value.

[0211] On the other hand, the output control (FWD control, LOAD control) performed differently from frequency control is carried out within the limits of the output limit values ​​(FWD limit value, LOAD limit value) set in the output limit value control (FWD limit value control, LOAD limit value control) (S20).

[0212] [Frequency limit control, output limit control, and examples of output control actions]

[0213] based on Figure 9 , Figure 10 An example of frequency characteristic variation is given, illustrating the operation of frequency limit control, output limit control, and output control. Here, the output command value is set to the load power command value, and the traveling wave power value is set to the output value for output control. The frequency limit control and output limit control in this case are shown. Furthermore, Figure 9 , 10 The frequency response changes shown are schematic and do not represent actual frequency response changes.

[0214] Figure 9 (A) and (B) represent the case where the impedance is in a matched state at the reference frequency ωo. Figure 10 (A) and (B) represent the case where the impedance is mismatched at the reference frequency ωo. Furthermore, here, in... Figure 9 , Figure 10 In the diagram, “×” represents the traveling wave power feedback value FWD-FB, “○” represents the reflected wave power feedback value REF-FB, “△” represents the control value, and a dashed line represents the traveling wave power limit value FWD-Limit.

[0215] • Impedance matching:

[0216] Indicating impedance matching state Figure 9 In (A) and (B), Figure 9 (A) indicates the case where the output value is greater than the traveling wave power limit. Figure 9 (B) indicates the case where the output value is less than the traveling wave power limit. Additionally, Figure 9 The frequency characteristics of the traveling wave power limit shown in (A) and (B) represent examples where the traveling wave power limit FWD-Limit is set to an equal value within the frequency range [ω-, ω+] determined by the frequency limit. The traveling wave power limit FWD-Limit shown by the dashed line is the same value throughout the entire frequency range [ω-, ω+].

[0217] (A) Traveling wave power value > Traveling wave power limit value:

[0218] (A1) indicates a state where the traveling wave power value, which is the output value, exceeds the traveling wave power limit. When the traveling wave power FWD-FB is greater than the traveling wave power limit FWD-Limit, the output (traveling wave power (FWD)) limit control uses the traveling wave power limit FWD-Limit as the control value to impose a limit on the control value.

[0219] (A2) indicates the state where the control value is limited to the traveling wave power limit FWD-Limit. The control value is limited to the traveling wave power limit FWD-Limit shown by the dashed line throughout the frequency range [ω-, ω+].

[0220] (A3) indicates the state of output control (traveling wave power control) based on the control value that is limited to the traveling wave power limit FWD-Limit.

[0221] Output control is performed based on the control value obtained through traveling wave power (FWD) limit control, thereby suppressing the reflected wave power feedback value REF-FB to below the reflected wave power threshold.

[0222] The illustrated traveling wave power feedback value FWD-FB and reflected wave power feedback value REF-FB show an example of output control based on the control values ​​of the frequency limit controlled by the frequency limit and the traveling wave power limit controlled by the traveling wave power limit.

[0223] (B) Traveling wave power ≤ Traveling wave power limit:

[0224] (B1) indicates a state where the traveling wave power value, as the output value, is below the traveling wave power limit. Furthermore, similar to (A), the traveling wave power limit value FWD-Limit shown by the dashed line in (B) is set to the same value across the entire frequency range [ω-, ω+] determined by the frequency limit value.

[0225] (B2) indicates a control state based on a control value without imposing a traveling wave power limit. When the traveling wave power FWD-FB is less than the traveling wave power limit FWD-Limit, output (traveling wave power (FWD)) limit control does not require imposing a limit on the control value. The control value is determined based on the load power command value LOAD-CO.

[0226] (B3) indicates the state of output control (traveling wave power control) based on the control value. Since the control value based on the load power command value LOAD-CO is less than the traveling wave power limit value FWD-Limit, the output control is performed based on the control value, thereby suppressing the reflected wave power feedback value REF-FB to below the reflected wave power threshold.

[0227] The illustrated traveling wave power feedback value FWD-FB and reflected wave power feedback value REF-FB show an example of output control based on the control value. Furthermore, in the comparison of the traveling wave power value and the traveling wave power limit value described above, the choice when the two values ​​are equal can be made by either (A) or (B).

[0228] • Impedance mismatch:

[0229] Indicates impedance mismatch state Figure 10 Both (A) and (B) represent cases where the traveling wave power value is greater than the traveling wave power limit. Figure 10 (A) shows an example of a flat frequency response where the traveling wave power limit is set to the same value across the frequency range. Figure 10 The frequency response example of (B) is compared to Figure 10 (A) has a wide frequency range and exhibits a tilting characteristic that allows the traveling wave power limit to be set to different values.

[0230] in addition, Figure 10 The frequency characteristics of the traveling wave power and the reflected wave power illustrate an example of frequency characteristics that tilt from high frequencies to low frequencies by not minimizing the reference frequency ωo through impedance mismatch.

[0231] Under impedance mismatch conditions, the reflection coefficient Γ deviates from the impedance matching state, and the minimum value of the reflection coefficient Γ deviates from the reference frequency ωo when impedance is matched. Therefore, the reflected wave power feedback value REF-FB becomes a value exceeding the reflected wave power threshold.

[0232] (A) Traveling wave power value > Traveling wave power limit value:

[0233] The dashed line represents a frequency characteristic where the traveling wave power limit FWDlimit is the same across the entire frequency range [ω-, ω+] within the set traveling wave power limit value.

[0234] (A1) indicates a state where the traveling wave power value, which is the output value, exceeds the traveling wave power limit. When the traveling wave power FWD-FB is greater than the traveling wave power limit FWD-Limit, the output (traveling wave power (FWD)) limit control uses the traveling wave power limit FWD-Limit as the control value to impose a limit on the control value.

[0235] (A2) indicates the state where the control value is limited to the traveling wave power limit FWD-Limit. The control value is limited to the traveling wave power limit FWD-Limit shown by the dashed line throughout the frequency range [ω-, ω+].

[0236] (A3) indicates the state of output control (traveling wave power control) based on a control value limited to the traveling wave power limit (FWD-Limit). Output control is performed based on the control value obtained in the traveling wave power (FWD) limit control, causing the reflected wave power feedback value REF-FB to decrease in the direction below the reflected wave power threshold, thus suppressing it below the reflected wave power threshold. The illustrated traveling wave power feedback value FWD-FB and reflected wave power feedback value REF-FB represent an example of output control based on the control values ​​of the frequency limit controlled by the frequency limit control and the traveling wave power limit controlled by the traveling wave power limit control.

[0237] (B) Power limit of traveling waves with non-flat frequency characteristics:

[0238] To control the output limit value over a wider frequency range, the traveling wave power limit value is set to a larger value for frequencies near the reference frequency ωo, and a smaller value for frequencies that deviate significantly from the reference frequency ωo, thus creating a non-flat frequency characteristic. Example of a non-flat frequency characteristic in (B) is a frequency characteristic example with a tilted characteristic where the traveling wave power limit value is set to different values ​​over a wider frequency range than in (A). The traveling wave power limit value shown by the dashed line is a value that is the same near the reference frequency ωo within the frequency range [ω-, ω+], decreasing towards ω- and ω+.

[0239] (B1) indicates a state where the traveling wave power value, which is the output value, exceeds the traveling wave power limit. When the traveling wave power FWD-FB is greater than the traveling wave power limit FWD-Limit, the output (traveling wave power (FWD)) limit control uses the traveling wave power limit FWD-Limit as the control value to impose a limit on the control value.

[0240] In the frequency characteristics shown in (B1), due to the wide frequency range, the reflected wave power REF-FB sometimes exceeds the reflected wave power threshold (indicated by the dashed line), resulting in excess reflected wave power. In (B1), the reflected wave power REF-FB exceeds the reflected wave power threshold in the high-frequency band.

[0241] (B2) indicates the state where the control value is limited to the traveling wave power limit (FWD-Limit). The control value is limited to the traveling wave power limit (FWD-Limit) shown by the dashed line throughout the frequency range [ω-, ω+]. In (B2), the control value is limited to the traveling wave power limit (FWD-Limit) shown by the dashed line throughout the frequency range [ω-, ω+]. Within the frequency range [ω-, ω+], the traveling wave power limit (FWD-Limit) at the frequency ends is set lower than the traveling wave power limit (FWD-Limit) near the reference frequency ωo at the frequency center. In the example shown in (B2), the value of the traveling wave power limit (FWD-Limit) is set to a fixed value near the reference frequency ωo, and is set to gradually decrease towards the frequency ends.

[0242] The traveling wave power limit (FWD-Limit) is set to a smaller value at the frequency ends of the frequency range and a larger value at the frequency center of the frequency range. The FWD-Limit set at the frequency center can be an example of a FWD-Limit with a flat frequency response as shown in (A). The maximum value of the FWD-Limit can be obtained, for example, by adding a predetermined margin to the rating of the high-frequency power supply device. This margin can be arbitrarily set, for example, based on the operating conditions of the high-frequency power supply device, such as the allowable value for handling excessive power supply over a short period of time.

[0243] (B3) indicates the state of output control (traveling wave power control) based on the control value that is limited to the traveling wave power limit FWD-Limit.

[0244] The control value for frequency control is based on the control value that is limited to the traveling wave power limit (FWD-Limit) through frequency limit control and traveling wave power limit control (FWD limit control). Frequency control is performed based on the control value obtained by frequency limit control and traveling wave power limit control (FWD limit control), thereby reducing the reflected wave power feedback value REF-FB towards a direction below the reflected wave power threshold.

[0245] In frequency control, the traveling wave power limit is set to a non-flat frequency response, thus limiting the control value at the frequency ends to be larger than that at the center of the frequency. By setting a larger limit on the traveling wave power at the frequency ends, the control value at the control frequency that deviates significantly from the reference frequency can be significantly limited, thereby reducing the control value, suppressing the reflected wave power feedback value REF-FB, and expanding the frequency range of the limit control.

[0246] By setting a larger limit on the traveling wave power limit at the frequency end and suppressing the traveling wave power control amount to a lower level, even when the frequency range of (B) is set wider than the frequency range shown in (A), the reflected wave power feedback value REF-FB can be suppressed to be less than the reflected wave power threshold.

[0247] [Example of frequency limit control]

[0248] Next, as a frequency limit control, it is used Figure 11 Flowcharts and Figure 12 The power state diagram of traveling wave power limit control is used to illustrate control where the output command is the load power command. Here, the output control of traveling wave power control based on the load power command value is used as an example for explanation. Figure 11 S31 to S39 in the flowchart represent frequency limit control, corresponding to Figure 5 The flowchart shown illustrates frequency limit control in steps S11 to S20. Additionally, Figure 11 S41 to S45 in the flowchart represent FWD limit value control, corresponding to Figure 5 The flowchart shown illustrates the frequency limit control of S20.

[0249] In output limit control where the load power command is used as the output command, it is determined whether the FWD limit state of the traveling wave power limit value is set for the control value. In addition, since the load power is the power obtained by subtracting the reflected wave power from the traveling wave power, when the traveling wave power command value is set, a command value based on the load power command value obtained by subtracting the reflected wave power from the traveling wave power can be obtained (S31).

[0250] (FWD Limit State)

[0251] When the FWD (Flying Wave Power Limit) state is in a state where the traveling wave power limit is set, the frequency in the FWD state is shifted towards the reference frequency ωo within the frequency range until the setting of the traveling wave power limit is deviated (S32), the traveling wave power limit state is eliminated, and the frequency ωs in the operation is stored (S33). Figure 12 (a) S32, S33). The stored frequency ωs is set to the frequency limit value ωLimit. Therefore, the frequency range [-ωLimit, +ωLimit] is set (S34, Figure 12 (a) of S34). After that, it returns to FWD control after frequency control and FWD limit value control.

[0252] (FWD non-limit state)

[0253] If it is determined in process S31 that the operation is not in the FWD limit state, the frequency limit value ωLimit is set through processes S35 to S39.

[0254] The output data for frequency control is obtained. Here, monitoring values ​​FWDmonitor(t1) and REFmonitor(t1) are obtained from the feedback value of traveling wave power FWD-FB and the feedback value of reflected wave power REF-FB detected by the high-frequency sensor. In addition, each monitoring value is set to the value at the detection time (t1) (S35). Based on the difference ΔFWD (=FWDmonitor(t1)﹣FWDmonitor(t0)) between the obtained traveling wave power monitoring value FWDmonitor(t1) and the traveling wave power monitoring value FWDmonitor(t0) obtained at the previous detection time (t0), the change in traveling wave power is calculated (S36). Figure 12 (d) of S36).

[0255] The change in the traveling wave power monitoring value FWDmonitor obtained in S36 is determined, i.e., the variation state of the differential ΔFWD. The variation state can be determined by comparing the differential ΔFWD with a threshold ΔFWDset. The threshold ΔFWDset can be determined, for example, based on the hysteresis of the differential ΔFWD (S37). Figure 12 (d) of S37).

[0256] In the determination in S37, if the differential ΔFWD is above the threshold ΔFWDset, there is a change in hysteresis exceeding the traveling wave power feedback value FWD-FB. This is determined to be a change in the impedance matching state, causing the frequency limit ωLimit to return to the preset default value ωmax (S38). Based on ωmax, the frequency limit ±ωLimit is set (S39). After that, through frequency control and FWD limit control, it returns to FWD control.

[0257] On the other hand, in the determination of S37, if the difference ΔFWD is less than the threshold ΔFWDset, even if the traveling wave power feedback value FWD-FB does not change or the traveling wave power feedback value FWD-FB changes, it is determined that the change is less than the hysteresis. Then, the same change determination is made for the reflected wave power REF.

[0258] The difference ΔREF (=REFmonitor(t1)﹣REFmonitor(t0)) between the obtained reflected wave power monitoring value REFmonitor(t1) and the reflected wave power monitoring value REFmonitor(t0) obtained at the previous detection time (t0) is calculated (S37a). Figure 12 (d) of S37).

[0259] The change in the time variation of the reflected wave power monitoring value REFmonitor, obtained in S37a, is determined, i.e., the variation state of the differential ΔREF. This determination can be made by comparing the differential ΔREF with a threshold ΔREFset. The threshold ΔREFset can be determined, for example, based on the hysteresis of the differential ΔREF (S37b, ...). Figure 12 (d) of S37).

[0260] In the determination in S37b, if the differential ΔREF is above the threshold ΔREFset, there is a change in hysteresis exceeding the reflected wave power REF-FB, which is determined to be a change in the impedance matching state. In the subsequent steps in S38, the frequency limit value ωLimit is set.

[0261] In the determination in S37b, if the differential ΔREF is less than the threshold ΔREFset, even if the reflected wave power REF-FB does not change or changes, it is determined that the change is less than the hysteresis, and it is determined that traveling wave power limit control is not required. After that, it returns to FWD control after frequency control and FWD limit control (S37c).

[0262] (Output Limit Control (FWD))

[0263] Output limit control (FWD limit (traveling wave power limit)) is performed via S41 to S45. The control frequency is shifted from the frequency range's frequency end ± ωLimit. The shift of the control frequency can be selected as either a shift from the high-frequency end of the frequency range +ωLimit towards the low-frequency side, or a shift from the low-frequency end of the frequency range -ωLimit towards the high-frequency side (S41, S45). Figure 12(b) and (e) of S41). During the displacement with controlled frequency, the traveling wave power limit value FWD-limit set for the frequency ωs at the displacement is read out (S42, Figure 12 (b) of S42).

[0264] The output command value is compared with the traveling wave power limit value FWD-Limit read in step S42 (S43). In the comparison step of S43, if the output command value is less than the traveling wave power limit value FWD-Limit, the limitation based on the traveling wave power limit value is not required, so the output command value is set as the control value (S44). Figure 12 (b) of S44). On the other hand, when the output command value is above the traveling wave power limit FWD-limit, in order to limit the output command value based on the traveling wave power limit, the traveling wave power limit FWD-Limit is used as a control value to limit the upper limit of the output command value (S45). Figure 12 (b) and (e) of S45).

[0265] (Frequency control)

[0266] Figure 12 (b), (c) and Figure 12 (e) and (f) show frequency control and limit control in the case of FWD limit state and in the case of not being in FWD limit state.

[0267] Furthermore, under the FWD limiting state, Figure 12 (b) represents the case where the output value is greater than or equal to the traveling wave power limit (FWD-Limit). Figure 12 (c) indicates the case where the output value is less than the traveling wave power limit (FWD-Limit). Additionally, when not in the FWD-Limit state, Figure 12 (e) indicates the case where the output value is greater than or equal to the traveling wave power limit (FWD-Limit). Figure 12 (f) indicates the case where the output value is less than the traveling wave power limit FWD-Limit.

[0268] • The situation under the FWD limit:

[0269] Figure 12 (b) represents the FWD limit state, an example of frequency control when the output value is greater than or equal to the traveling wave power limit value FWD-Limit. Frequency control is performed based on the frequency limit value ωs obtained in S34. Since the output value at this frequency ωs exceeds the traveling wave power limit value FWD-Limit (S43), the traveling wave power limit value FWD-Limit is used as the limit value for output control (S45).

[0270] Figure 12 (c) represents the FWD limit state, an example of frequency control when the output value is less than the traveling wave power limit FWD-Limit. In the FWD limit state, frequency control is performed based on the frequency limit value ωs obtained in S34. Since the output value at this frequency ωs does not exceed the traveling wave power limit FWD-Limit (S43), output control is performed without imposing the traveling wave power limit FWD-Limit (S44).

[0271] • In cases where the FWD limit is not reached:

[0272] Figure 12 (e) represents the case where the output value is not in the FWD limit state, indicating an example of frequency control when the output value is greater than or equal to the traveling wave power limit value FWD-Limit. Frequency control is performed based on the frequency limit value ωmax obtained in S39. Since the output value obtained through this frequency control exceeds the traveling wave power limit value FWD-Limit (S43), the traveling wave power limit value FWD-Limit is used as the limit value for output control (S45).

[0273] Figure 12 (f) represents the case where the output value is less than the traveling wave power limit (FWD-Limit), an example of frequency control. Frequency control is performed based on the frequency limit value ωs obtained in S39. Since the output value obtained by this frequency control does not exceed the traveling wave power limit (FWD-Limit) (S43), output control is performed without imposing a restriction based on the traveling wave power limit (FWD-Limit) (S44).

[0274] [Switching between FWD limit control and REF limit control]

[0275] Next, use Figure 13 The switching between FWD limit control and REF limit control is explained.

[0276] When the output value is greater than the traveling wave power limit FWD-Limit, the traveling wave power limit FWD-Limit is used as the control value for output control through FWD limit control.

[0277] Even when the traveling wave power limit FWD-Limit is set as the control value through FWD limit control, if the reflected wave power is greater than the reflected wave power limit REF-Limit, REF limit control is used instead of FWD-Limit for output control. By switching from FWD limit control to REF limit control, damage to circuit components can be suppressed by the excess reflected wave power.

[0278] Figure 13 (a) and (b) represent the frequency characteristics and flowcharts of the switching state between FWD limit control and REF limit control.

[0279] exist Figure 13 In (a), within a frequency range lower than the frequency shown by the dashed line, the reflected wave power REF-FB does not exceed the reflected wave power limit REF-Limit; therefore, a control value limited to the traveling wave power limit is used for output limit control. On the other hand, within a frequency range higher than the frequency shown by the dashed line, the reflected wave power REF-FB exceeds the reflected wave power limit REF-Limit; therefore, a control value limited to the reflected wave power limit is used for reflected wave limit control.

[0280] In step S41, the frequency is shifted from ±ωLimit. In step S42, after reading the traveling wave power limit value of frequency ωs, the load power command value LOAD-CO and the load power limit value LOAD-Limit are compared (S51).

[0281] In step S51, if the load power command value LOAD-CO is less than the load power limit value LOAD-Limit, the control value is set through steps S43 and later. In step S51, if the load power command value LOAD-CO is greater than the load power limit value LOAD-Limit, the reflected wave power feedback value REF-FB and the reflected wave power limit value REF-Limit are compared (S52).

[0282] In step S52, if the reflected wave power feedback value REF-FB is less than the reflected wave power limit value REF-Limit, a control value is set in step S43 or later. In step S52, if the reflected wave power feedback value REF-FB is less than the reflected wave power limit value REF-Limit, the reflected wave power limit value REF-Limit is set as the control value (S53).

[0283] [Switching Load Power Command Values]

[0284] Next, use Figures 14-18 Control examples for cases where the load power command value is switched are explained. Three switching examples are shown below. Switching example 1 is an example of switching the load power from low power to high power, and switching examples 2 and 3 are examples of switching the load power from high power to low power. Switching examples 2 and 3 represent examples where the starting control frequency is different. Furthermore, here, the terms "high power" and "low power" are used to compare the magnitude of the power, and the absolute value of the power is not specified. Here, an example is shown where the low power is set to 200W and the high power is set to 600W. Additionally, in... Figure 14 , 17 In 18, the %Freq shown on the horizontal axis represents the degree of deviation from the reference frequency. Setting the reference frequency to 0%Freq will display the frequency components that deviate from the reference frequency as a percentage relative to the reference frequency.

[0285] exist Figures 14-18 In the diagram, P1 represents the output characteristic with a load power of 200W, and P2 represents the output characteristic with a load power of 600W. In the diagram, FWD(P1) represents the traveling wave power characteristic of output characteristic P1, FWD(P2) represents the traveling wave power characteristic of output characteristic P2, REF(P1) represents the reflected wave power characteristic of output characteristic P1, REF(P2) represents the reflected wave power characteristic of output characteristic P2, FWDLimit represents the traveling wave power limit, and REFLimit represents the reflected wave power limit.

[0286] (Switch to Example 1)

[0287] Figures 14 to 16 This represents switching example 1. Switching example 1 is an example of switching from load recipe P1 to load recipe P2. Figure 14 In the process, load formula P1 is controlled in the order of circle word 1 to circle word 3, and the switch from load formula P1 to load formula P2 is carried out in circle word 4. Load formula P2 is controlled in the order of circle word 5 to circle word 7.

[0288] exist Figure 16 In the flowchart, frequency control begins with load formula P1 based on a load power of 200W (S100). Through frequency control, the frequency changes in the direction of decreasing reflected wave power (S101).

[0289] Determine whether the reflected wave power has reached the minimum (S102). If the reflected wave power has reached the minimum, end the frequency control of load formula P1 (S104). If the traveling wave power FWD reaches the traveling wave power limit FWD-Limit before the reflected wave power reaches the minimum (S103), also end the frequency control of load formula P1 (S104).

[0290] After the frequency control of load formula P1 is terminated, if the load formula is changed (S105), load formula P1 is changed to load formula P2 (S106).

[0291] In load formulation P2, the frequency is changed in the direction of reducing the power of the reflected wave through frequency control (S107).

[0292] Determine whether the reflected wave power has reached the minimum (S108). If the reflected wave power has reached the minimum, end the frequency control of load formula P2 (S110). If the traveling wave power FWD reaches the traveling wave power limit FWD-Limit before the reflected wave power reaches the minimum (S109), also end the frequency control of load formula P1 (S110).

[0293] Figure 15 (a), (b), (c), and (d) represent the load power (LOAD power), traveling wave power feedback value (FWD-FB), reflected wave power feedback value (REF-FB), and the time variation of frequency ω, respectively. Figure 14 and Figure 15 The circled words 1 through 7 represent the same output state.

[0294] Based on the frequency control of load formula P1, frequency control ends when the traveling wave power feedback value FWD-FB changes to a frequency exceeding the traveling wave power limit value FWD-Limit, and switching to load formula P2 begins. Switching to load formula P2 starts from the frequency at which the traveling wave power feedback value FWD-FB of load formula P2 becomes below the traveling wave power limit value FWD-Limit.

[0295] (Switch to Example 2)

[0296] Figure 17 This represents switching example 2. In switching example 2, the switch is from load recipe P2 to load recipe P1. Load recipe P2 is controlled in the order of circle 1 to circle 2, and the switch from load recipe P2 to load recipe P1 occurs between circle 2 and circle 3. Load recipe P1 is controlled in the order of circle 3 to circle 5. Furthermore, the starting control frequency in switching example 2 is the same as the starting frequency in switching example 1.

[0297] (Switch to Example 3)

[0298] Figure 18This represents switching example 3. Similar to switching example 2, switching example 3 is an example of switching from load recipe P2 to load recipe P1, but the starting control frequency is different. In switching example 2, load recipe P2 is controlled in the order of circle words 1 to 4, and the switching from load recipe P2 to load recipe P1 occurs between circle words 4 and 5. Load recipe P1 is controlled in the order of circle words 5 to 7.

[0299] In switching example 3, since the traveling wave power feedback value FWD-FB at the start of control of circle word 1 exceeds the traveling wave power limit value FWD-Limit, frequency control starts from circle word 2, where the characteristics of traveling wave power feedback value FWD-FB and traveling wave power limit value FWD-Limit intersect.

[0300] [Detailed structural example]

[0301] based on Figure 19 A detailed structural example of the high-frequency power supply device of the present invention is described below. The high-frequency power supply device 1 includes a DC power supply 2, a high-frequency amplifier 3, a transformer 7, a high-frequency filter 8, a high-frequency sensor 4, a matching circuit 5, and a controller 10, and provides the output to the load 6.

[0302] DC power supply 2 is the power source that supplies DC power to high-frequency amplifier 3. High-frequency amplifier 3 converts the DC power supplied from DC power supply 2 into high frequency and amplifies and controls the frequency and output based on the control value of controller 10. Transformer 7 transforms the high-frequency voltage value of high-frequency amplifier 3 into a voltage corresponding to load 6. High-frequency filter 8 filters the high-frequency output of transformer 7, outputting the frequency components required by load 6.

[0303] The high-frequency sensor 4 detects the traveling wave power FWD from the high-frequency power supply 1 toward the load 6 and the reflected wave power REF reflected back to the high-frequency power supply 1 from the load 6, and feeds back the feedback values ​​of the detected traveling wave power FWD-FB and the reflected wave power REF-FB to the controller 10. In the high-frequency sensor 4, the separation of the traveling wave power FWD and the reflected wave power REF can be achieved, for example, using a directional coupler (not shown).

[0304] Matching unit 5 matches the impedance between high-frequency power supply unit 1 and load 6. The impedance matching of matching unit 5 matches the impedance of high-frequency power supply unit 1 at its rated output with the impedance of load 6 under steady-state conditions. The output voltage Vpp of high-frequency power supply unit 1 is detected by the output voltage at the output terminal of matching unit 5, and the detected feedback value Vpp-FB is fed back to controller 10. Furthermore, the output voltage Vpp is the peak-to-peak voltage between the positive and negative peak values ​​of the output voltage.

[0305] The controller 10 includes an output control unit 10AA, a limit control unit 10AB, and a drive control unit 10C. Furthermore, the output control unit 10AA includes... Figure 4 The structural diagram shows the structure of the output control unit 10Aa and the frequency control unit 10Ba. Additionally, the limit control unit 10AB includes... Figure 4 The structural diagram shows the structure of the output limit control unit 10Ab and the frequency limit control unit 10Bb. The drive control unit 10C receives control values ​​related to output control from the output control unit 10Aa and control values ​​related to frequency control from the frequency control unit 10Ba as output command values ​​to control the high-frequency amplifier 3. The controller 10 performs output control (FWD control) and frequency control respectively.

[0306] In controller 10, the control section corresponding to frequency control unit 10Ba performs frequency control based on the output command value (traveling wave power command value 10a) and each feedback signal (traveling wave power feedback value FWD-FB and reflected wave power feedback value REF-FB) to determine the control frequency for impedance matching between high-frequency power supply device 1 and load 6. The control section corresponding to output control unit 10Aa performs output control based on the output command value (traveling wave power command value 10a) and each feedback signal (traveling wave power feedback value FWD-FB and reflected wave power feedback value REF-FB) for either FWD control or LOAD control. In this output control, the control frequency obtained by impedance matching control unit 10B is used, and the output is suppressed to power limits using an output limit value determined within the frequency range of the control frequency. In the case of output control using traveling wave power, the FWD limit value determined within the frequency range determined in frequency limit value control is used.

[0307] Furthermore, in the output control unit 10AA, the traveling wave power control based on the traveling wave power command value 10a and the load power control based on the load power command value (LOAD power command value) 10b can be switched via the switch 10Aa-2. The load power control uses the value obtained by subtracting the reflected wave power feedback value REF-FB from the traveling wave power feedback value FWD-FB by the calculation unit 10Aa-1 as the load power feedback value LOAD-FB.

[0308] The limit control unit 10AB limits the frequency range of the control frequency by using frequency limit value control, and limits the upper limit of the output command value at the control frequency to the traveling wave power limit value (FWD limit value) by using traveling wave power limit value control (FWD limit value control).

[0309] The limit control unit 10AB has various limit values, including a traveling wave power limit value 10d that limits the traveling wave power command value, a reflected wave power limit value 10e that limits the reflected wave power command value, an output voltage limit value 10c that limits the output voltage Vpp, a DC voltage limit value 10f that limits the DC power supply voltage, a DC current limit value 10g that limits the DC power supply current, and a loss power limit value 10h that limits the power loss. Additionally, the output control unit 10AA has a traveling wave power command value 10a that corresponds to a target value of the traveling wave power output by the high-frequency power supply device, and a load power command value (LOAD power command value) 10b that corresponds to a target value of the load power.

[0310] Each limit value can be stored in the memory of the limit control unit 10AB, or it can be pre-stored in an external device (not shown) and input from that external device.

[0311] The limit control unit 10AB includes an arithmetic unit 10Ab-c that calculates the difference between the feedback value Vpp-FB of the output voltage and the output voltage limit value 10c (Vpp-limit), an arithmetic unit 10Ab-d that calculates the difference between the feedback value FWD-FB of the traveling wave power and the traveling wave power limit value 10d, and arithmetic units 10Ab-e to 10Ab-h that output output command values ​​based on the comparison between the feedback value of each output and each limit value.

[0312] The arithmetic unit 10Ab-c compares the feedback value Vpp-FB of the output voltage with the output voltage limit value 10c (Vpp-limit). If the feedback value Vpp-FB of the output voltage is less than the output voltage limit value 10c (Vpp-limit), the output voltage command value Vpp-CO is directly output. If the feedback value Vpp-FB of the output voltage exceeds the output voltage limit value 10c (Vpp-limit), the output voltage limit value 10c (Vpp-limit) is used as the output voltage command value Vpp-CO instead of the output voltage command value Vpp-CO.

[0313] The arithmetic unit 10Ab-d calculates the difference between the travel wave power feedback value FWD-FB and the travel wave power limit value 10d, and the frequency control unit 10Ba performs frequency control based on this difference.

[0314] When the feedback value of the output is less than each limit value, the arithmetic units 10Ab-e to 10Ab-h directly output the output instruction value. When the feedback value of the output exceeds each limit value, the limit value is used as the output instruction value instead of the output instruction value.

[0315] The arithmetic unit 10Ab-d compares the feedback value of traveling wave power FWD-FB with the traveling wave power limit value 10d (FWD-limit). If the feedback value of traveling wave power FWD-FB is less than the traveling wave power limit value 10d (FWD-limit), the traveling wave power command value FWD-CO is directly output. If the feedback value of traveling wave power FWD-FB exceeds the traveling wave power limit value 10d (FWD-limit), the traveling wave power limit value 10d (FWD-limit) is output instead of the traveling wave power command value FWD-CO.

[0316] The arithmetic unit 10Ab-e compares the feedback value REF-FB of the reflected wave power with the reflection wave power limit value 10e (REF-limit). If the feedback value REF-FB of the reflected wave power is less than the reflection wave power limit value 10e (REF-limit), the reflected wave power command value REF-CO is directly output. If the feedback value REF-FB of the reflected wave power exceeds the reflection wave power limit value 10e (REF-limit), the reflection wave power limit value 10e (REF-limit) is replaced by the reflection wave power command value REF-CO and output as the reflection wave power command value REF-CO.

[0317] The arithmetic unit 10Ab-f compares the feedback value Vdc-FB of the DC power supply voltage with the DC voltage limit value 10f (Vdc-limit). If the feedback value Vdc-FB of the DC voltage is less than the DC voltage limit value 10f (Vdc-limit), the DC voltage command value Vdc-CO is directly output. If the feedback value Vdc-FB of the DC voltage exceeds the DC voltage limit value 10f (Vdc-limit), the DC voltage limit value 10f (Vdc-limit) is replaced by the DC voltage command value Vdc-CO and output as the DC voltage command value Vdc-CO.

[0318] The arithmetic unit 10Ab-g compares the feedback value Idc-FB of the DC power supply current with the DC current limit value 10g (Idc-limit). If the feedback value Idc-FB of the DC power supply current is less than the DC current limit value 10g (Idc-limit), the DC current command value Idc-CO is directly output. If the feedback value Idc-FB of the DC power supply current exceeds the DC current limit value 10g (Idc-limit), the DC current limit value 10g (Idc-limit) is replaced by the DC current command value Idc-CO and output as the DC current command value Idc-CO.

[0319] The arithmetic unit 10Ab-h compares the feedback value of power loss Loss-FB with the power loss limit value 10h (Loss-limit). If the feedback value of power loss Loss-FB is less than the power loss limit value 10h (Loss-limit), the power loss command value Loss-CO is directly output. If the feedback value of power loss Loss-FB exceeds the power loss limit value 10h (Loss-limit), the power loss limit value 10h (Loss-limit) is replaced by the power loss command value Loss-CO and output as the power loss command value Loss-CO.

[0320] The loss power limit value Loss-limit, corresponding to the feedback signal Loss-FB, is the limit value corresponding to the power loss generated in the power supply from the high-frequency power supply device to the load. The power loss is the amount of loss generated in the power supply from the high-frequency power supply device, equivalent to the power obtained by subtracting the effective power from the supplied power, and is calculated by subtracting the traveling wave power and reflected wave power from the power supplied from the high-frequency power supply device. The calculation unit 10Ab-2 calculates the feedback value Pdc-FB of the DC power supply by multiplying the feedback value Vdc-FB of the DC power supply voltage by the feedback value Idc-FB of the DC power supply current. The calculation unit 10Ab-3 calculates the loss power Loss by subtracting the feedback value FWD-FB of the traveling wave power from the feedback value Pdc-FB of the DC power supply and adding the feedback value REF-FB of the reflected wave power.

[0321] The controller 10 effectively controls the damage to the circuit elements of the high-frequency amplifier 3 caused by excessively large output command values ​​when the upper limit of the output limit value is limited by the limit control unit 10AB.

[0322] The drive control unit 10C includes: a holding circuit 10Ca that holds a control value obtained in the previous control cycle; a control value error amplifier circuit 10Cb that calculates the difference between the control value held by the holding circuit 10Ca in the previous control cycle and the control value in the current control cycle, and amplifies the error; and a drive circuit 10Cc that generates a drive signal for driving the high-frequency amplifier 3 based on the signal amplified by the control value error amplifier circuit 10Cb. Figure 4 The control frequency obtained and the output command value whose upper limit is limited by the limit control unit 10AB are used as control values ​​to control the amplification of the high-frequency amplifier 3.

[0323] [Example of traveling wave power limit]

[0324] The following uses Figures 20-22An example of output limit values ​​is provided. The output limit values ​​are set within a frequency range that includes the reference frequency, and the frequency characteristics can be set symmetrically or asymmetrically relative to the reference frequency within the frequency range.

[0325] Figure 20 This illustrates an example of an output limit. Here, the frequency range is defined as [-20% to +20%]. The frequency response of the output limit depends on the standing wave ratio (VSWR). A reflection coefficient of "0" is equivalent to a VSWR of "1". The frequency response of one output limit is represented by the thick solid line in the figure. At 0% of the frequency, the limit decreases linearly towards the end of the frequency range, with the traveling wave power limit (FWD-Limit) as the apex.

[0326] The dashed and dotted lines in the figure represent the frequency characteristics of the output limit values ​​for VSWRs of 1.1, 2, 3, 5, and 10, respectively. A higher VSWR results in a lower output limit value, thus reducing the impact of reflected wave power. Additionally, the horizontal axis shows %Freq and... Figure 13 , 16 The same as shown in 17, with the percentage indicating the degree of deviation from the reference frequency.

[0327] (An example of symmetrical frequency characteristics)

[0328] When the frequency characteristics of the output command values ​​on the high-frequency side and the low-frequency side are regarded as the same as the reference frequency, the frequency characteristics can be set to be symmetrical with respect to the reference frequency in the frequency range.

[0329] Figure 21 Examples of symmetrical frequency characteristics are those in which a frequency range with equal frequency width on both the high-frequency and low-frequency sides is centered at a reference frequency ωo, and thus exhibits symmetrical frequency characteristics.

[0330] In example (a), within the frequency range, the range of output limit values ​​with fixed values ​​on both sides of the reference frequency ωo decreases with a fixed slope towards the frequency ends ω- and ω+. The output limit values ​​near the reference frequency ωo can be determined based on the rated output. For example, a value obtained by adding a predetermined margin to the rated value of the high-frequency power supply can be used. The margin can be arbitrarily set, for example, according to the operating conditions of the high-frequency power supply, such as the allowable value for withstanding excessive power supply for a short period of time.

[0331] In example (b), the output limit value decreases at a fixed angle from the reference frequency ωo towards the frequency ends ω- and ω+. The output limit value at the reference frequency ωo can be determined based on the rated output. For example, it can be a value obtained by adding a predetermined margin to the rated value of the high-frequency power supply. The margin in example (b) can be set to be larger than the margin in example (a). Figure 19 Examples of frequency response representations (a) and (b).

[0332] In examples (c), (d), and (e), within the frequency range, the range of output limit values ​​with fixed values ​​on both sides of the reference frequency ωo decreases towards the frequency ends ω- and ω+ with a predetermined curve.

[0333] Similar to example (a), the output limit near the reference frequency ωo can be determined based on the rated output. The reduction curve can be, for example, the reduction characteristic corresponding to the open-loop characteristic of the high-frequency amplifier. Examples (c) and (d) are examples of a concave reduction curve towards the frequency end, with a larger reduction rate at the reference frequency ωo side and a smaller reduction rate at the frequency ends ω- and ω+. Example (c) represents an example of a slow reduction characteristic, and example (d) represents an example of a steep reduction characteristic.

[0334] (e) is an example of a decrease that occurs in a convex curve toward the frequency end.

[0335] In example (f), there is a frequency range with equal frequency width on the high-frequency side and the low-frequency side centered on the reference frequency ωo, and a fixed output limit value is available within this frequency range.

[0336] (Example of asymmetric frequency characteristics)

[0337] There are cases where the frequency characteristics of an output command value with a control frequency higher than the reference frequency differ from those with a control frequency lower than the reference frequency. When the frequency characteristic of the output command value is asymmetrical relative to the reference frequency, the frequency characteristic of the output limit value can be set asymmetrically relative to the reference frequency within the frequency range.

[0338] For example, the open-loop characteristics of a high-frequency amplifier have a significant impact on its frequency characteristics. When the frequency characteristics of the control frequency differ between the high-frequency and low-frequency sides relative to the reference frequency, the frequency characteristics of the open-loop amplifier will be asymmetrically set relative to the reference frequency within the frequency range.

[0339] exist Figure 22 In the following examples (a) to (d), the open-loop characteristics of the high-frequency amplifier and the corresponding output limit values ​​are given.

[0340] Figure 22The open-loop characteristic of the high-frequency amplifier in (a) is a linear traveling wave power decrease from the cutoff frequency toward the high-frequency side. The output limit of (a) becomes a fixed value at the low-frequency side from the reference frequency ωo, and decreases at the high-frequency side from the reference frequency ωo toward the frequency end ω+ with a fixed slope.

[0341] Figure 22 The open-loop characteristics of the high-frequency amplifiers in (b) and (c) exhibit a concave traveling wave power reduction from the cutoff frequency toward the high-frequency side. The output limit values ​​of (b) and (c) are fixed at the low-frequency side from the reference frequency ωo, and decrease at the high-frequency side from the reference frequency ωo toward the frequency ω+ in a concave curve. Example (b) illustrates a slow reduction characteristic, while example (c) illustrates a steep reduction characteristic.

[0342] Figure 22 The open-loop characteristic of the high-frequency amplifier (d) shows a convex curve with decreasing traveling wave power from the cutoff frequency toward the high-frequency side. The output limit of (d) becomes a fixed value at the low-frequency side from the reference frequency ωo, and decreases at the high-frequency side from the reference frequency ωo toward the frequency end ω+ with a convex curve.

[0343] Furthermore, the above-described embodiments and variations are examples of the high-frequency power supply of the present invention. The present invention is not limited to each embodiment, and various modifications can be made based on the spirit of the present invention without excluding them from the scope of the present invention.

[0344] Industrial utilization potential

[0345] In addition to supplying power to plasma generating devices, the high-frequency power supply device of the present invention can also be used as a power supply device for supplying pulse output to loads such as pulsed laser excitation and electrical discharge machining.

[0346] Symbol Explanation

[0347] 1. High-frequency power supply device

[0348] 2 DC power supply

[0349] 3. High-frequency amplifier

[0350] 4. High-frequency sensor

[0351] 5 Matcher

[0352] 6. Load

[0353] 7 Transformers

[0354] 8. High-frequency filter

[0355] 10 Controllers

[0356] 10A Output Control Unit

[0357] 10B Impedance Matching Control Section

[0358] 10C Drive Control Unit

[0359] 10AA Output Control Unit

[0360] 10AB Limit Control Department

[0361] 10Aa Output Control Unit

[0362] 10Ab Output Limit Control Unit

[0363] 10Ba Frequency Control Unit

[0364] 10Bb Frequency Limit Control Unit

[0365] 10Ca holding circuit

[0366] 10Cb control value error amplifier circuit

[0367] 10Cc drive circuit

[0368] 10Ab-c~10Ab-h Arithmetic Unit

[0369] 10Ab-2~10Ab-3 Arithmetic Unit

[0370] 10a Traveling wave power command value

[0371] 10b Load power command value

[0372] 10c Output (Vpp) Voltage Limit

[0373] 10d traveling wave power limit

[0374] 10e Reflected wave power limit

[0375] 10f DC voltage limit

[0376] 10g DC current limit

[0377] 10h power loss limit

[0378] FWD traveling wave power

[0379] FWD-CO Traveling Wave Power Command Value

[0380] FWD-BF Traveling Wave Power Feedback Value

[0381] FWD-limit Traveling Wave Power Limit

[0382] FWDmonitor Traveling Wave Power Monitoring Value

[0383] Idc-CO DC current command value

[0384] Idc-FB DC current feedback value

[0385] Loss-limit: Power loss limit

[0386] Loss-CO Load Power Command Value

[0387] Loss power

[0388] Pcommand1 outputs the command value.

[0389] Pcommand2 outputs command value

[0390] Feedback value of Pdc-FB DC power supply

[0391] Plimit (maximum value)

[0392] Pout output

[0393] REF reflected wave power

[0394] REF-CO reflected wave power command value

[0395] REF-BF reflected wave power feedback value

[0396] REFmonitor reflected wave power monitoring value

[0397] Vdc-CO DC voltage command value

[0398] Vdc-FB DC voltage feedback value

[0399] Vpp output voltage

[0400] Vpp-CO output voltage command value

[0401] Vpp-FB output voltage feedback value

[0402] Γ Reflection coefficient

[0403] Δ difference

[0404] Δhigh (Predetermined frequency bandwidth)

[0405] Δlow Pre-defined frequency bandwidth

[0406] ΔFWD differential

[0407] ΔFWDset threshold

[0408] ΔREF difference

[0409] ΔREFset threshold

[0410] ω controls the frequency

[0411] ωo is the reference frequency.

Claims

1. A control method for a high-frequency power supply device, wherein the high-frequency power supply device supplies high-frequency power to a load, characterized in that, The control method includes: output control, which controls the output of a high-frequency amplifier based on an output command, wherein the high-frequency amplifier outputs high-frequency power through a DC-AC converter. The output control controls the high-frequency amplifier so that the power feedback value of the effective load power supplied to the load, i.e., the LOAD power, or the traveling wave power supplied from the high-frequency power supply to the load, becomes the power command value. (α) When the output command value increases through output control and exceeds the output limit value, the system transitions to an output limit state that suppresses the output command value to the output limit value, thereby limiting the increase of the output command value. The output limiting state is either the reflection power limit state where the reflected power exceeds the limit value, or the loss power limit state where the loss power exceeds the limit value. (β) If the output reaches the set output and becomes the output limit state, switch to variable frequency control to control the output away from the output limit state by reducing the traveling wave feedback value. Furthermore, the control method includes: impedance matching control, which matches the impedance between the high-frequency amplifier and the load. The impedance matching control includes: (A) Frequency control, using a control frequency variation based on the feedback signal from the high-frequency amplifier to perform impedance matching; and (B) Frequency limit control: In output control, it is determined whether the output is in an output limit state that restricts the upper limit of the output command value, and a frequency limit value is set to determine the frequency limit value used to define the frequency range of the frequency control. (C) The frequency control controls the frequency of the high-frequency amplifier within the frequency range determined by the frequency limit value control. The output control includes: (D) Output limit control, determining the output limit value used to limit the output within the frequency range. (E) The output of the high-frequency amplifier is controlled by setting the output limit value determined by the output limit control to the upper limit of the output command value. (F) The output control and the impedance matching control are independent controls.

2. The control method for the high-frequency power supply device according to claim 1, characterized in that, During continuous control, the output control freely switches the instruction value of the output command at multiple stages.

3. The control method for the high-frequency power supply device according to claim 1, characterized in that, In the output limit control, when the output command value of the high-frequency amplifier exceeds the output limit value, the output command value is replaced with the output limit value to limit the output command value.

4. The control method for the high-frequency power supply device according to claim 1, characterized in that, The feedback signal is at least one of the following signals from the high-frequency amplifier: traveling wave power, reflected wave power, output voltage, DC voltage, and DC current. The output limit values ​​are respectively set corresponding to the traveling wave power limit value, reflected wave power limit value, output voltage limit value, DC voltage limit value, DC current limit value, and / or power loss limit value for each of the feedback signals. At each control frequency, when the output command value exceeds the output command limit value, the output command value is limited to the output limit value, and the output of the high-frequency amplifier is controlled according to the limited output command value.

5. The control method for the high-frequency power supply device according to claim 1, characterized in that, The frequency characteristics of the output limit value are symmetrical with respect to the reference frequency within the frequency range.

6. The control method for the high-frequency power supply device according to claim 1, characterized in that, The frequency response of the output limit value is asymmetric with respect to the reference frequency within the frequency range. The asymmetry refers to the frequency characteristics corresponding to the amplification frequency characteristics of the high-frequency amplifier and the frequency characteristics of the load impedance.

7. A high-frequency power supply device that supplies high-frequency power to a load, characterized in that, The high-frequency power supply device includes: A high-frequency amplifier that outputs the aforementioned high-frequency power; The output control unit controls the output from the high-frequency amplifier based on output commands. The high-frequency amplifier outputs high-frequency power through DC-AC conversion. The output control unit controls the output from the high-frequency amplifier based on the output command value, such that the power feedback value of the effective load power supplied to the load, i.e., the LOAD power, or the traveling wave power supplied from the high-frequency power supply to the load, becomes the power command value. (α) When the output command value increases through output control and exceeds the output limit value, the system transitions to an output limit state that suppresses the output command value to the output limit value, thereby limiting the increase of the output command value. The output limiting state is either the reflection power limit state where the reflected power exceeds the limit value, or the loss power limit state where the loss power exceeds the limit value. (β) If the output reaches the set output and becomes the output limit state, switch to variable frequency control to control the output away from the output limit state by reducing the traveling wave feedback value; and The impedance matching control unit matches the impedance of the high-frequency amplifier to that of the load. The impedance matching control unit includes: (a) A frequency control unit that performs impedance matching by varying the control frequency based on the feedback signal from the high-frequency amplifier; and (b) A frequency limit control unit, which, in output control, determines whether the output is in an output limit state that limits the upper limit of the output command value and sets a frequency limit value, and determines a frequency limit value used to define the frequency range of the frequency control. The frequency control unit performs the following control: (c) The frequency of the high-frequency amplifier is controlled within the frequency range of the frequency limit value determined by the frequency limit control unit. The output control unit includes: (d) Output limit control, which determines the output limit value used to limit the output control value of the output control unit within the frequency range. (e) The output of the high-frequency amplifier is controlled by setting the output limit value determined by the output limit control to the upper limit of the output command value. (f) The output control unit and the impedance matching control unit are controlled independently.

Images