RF energy radiating device

Abstract

In an RF energy irradiation apparatus, a control section controls an oscillator and a power amplifier in accordance with a reflected wave power returned from an irradiation element and detected by a detector, and sets an operation mode to a first control mode or a second control mode. In the first control mode, the oscillator oscillates a pulsed RF signal having a first pulse width and a first pulse period. In the first control mode, a protection circuit does not cut off a traveling wave power. In the second control mode, the oscillator oscillates a pulsed RF signal having a second pulse width different from the first pulse width and a second pulse period different from the first pulse period. Alternatively, the oscillator continuously oscillates an RF signal. In the second control mode, the protection circuit cuts off the traveling wave power when the reflected wave power exceeds a prescribed threshold value.

Description

Technical Field

[0001] This invention relates to improving the reliability of RF energy radiation devices. Background Technology

[0002] Conventional RF (radio frequency) energy radiating devices detect reflected wave power and suppress output power based on the level of reflected wave power. Conventional RF energy radiating devices supply output signals as burst pulse waves in a manner that ensures the reflected wave power does not exceed an allowable value. Supplying output power as burst pulse waves means radiating RF energy while alternately setting the on time of continuous output power and the off time of stopping output power (for example, see Patent Document 1).

[0003] Patent document 2 describes an RF energy radiation device for high-precision protection of the device through hardware control and software control based on the detection value of reflected wave power and the temperature detection value of the RF power element.

[0004] The RF energy radiation device described in Patent Document 2 includes a chamber for housing an object to be heated, an RF signal generation unit, an RF amplification unit, a radiation element, a temperature sensor, and a control unit. The RF power element includes, for example, a transistor included in an RF power amplifier that amplifies the RF signal, and an RF power connector constituting the power supply unit. In the case where the RF energy radiation device includes a circulator, the RF power element also includes a terminator for consuming reflected waves.

[0005] Conventional RF power radiating devices continuously heat the device when the load impedance between the device and the object being heated reaches a certain level of matching. Therefore, to protect the RF power components from reflected waves, the output power is reduced or the heating operation is stopped when specified conditions are met. As a result, depending on the object being heated, sometimes insufficient heating is not achieved. These specified conditions refer to situations such as detecting a specified amount of reflected wave power or the ambient temperature of the RF power components rising above a specified value.

[0006] Furthermore, when supplying RF power as a burst pulse wave, the turn-on time is set in a way that the level of the reflected wave power converges within the allowable range of the RF power element. In operations such as plasma ignition, the load impedance sometimes becomes a state that causes total reflection of RF energy at the start of the operation.

[0007] Therefore, an external matching device is used, or the output level is lowered at the start of operation and then gradually raised to a specified value. When a matching device is configured, the space required for the matching device and its cost become obstacles to development.

[0008] Under controlled conditions where the output level is gradually increased to a specified value, sufficient energy cannot be obtained to generate plasma by radiating RF energy to the dielectric surface. If the RF output power level is increased to obtain sufficient RF energy to generate plasma, it becomes difficult to protect the device.

[0009] Heating can be achieved by changing the on-time without altering the peak power, while simultaneously supplying output power as a burst pulse wave. Alternatively, output power can be continuously supplied as a burst pulse wave when RF power is insufficient. Even under these conditions, it is difficult to protect the device.

[0010] RF power components refer to, for example, the transistors contained in an RF power amplifier used to amplify RF signals, and the RF power connectors that constitute the power supply section. In the case of an RF energy radiating device that includes a circulator, a terminator used to absorb reflected waves is also considered an RF power component.

[0011] The matching device includes not only the device for adjusting the distribution constant and lumped constant of the load impedance, but also the unit for changing the angle and rotation angle of the radiating part used to radiate microwaves.

[0012] Existing technical documents

[0013] Patent documents

[0014] Patent Document 1: Japanese Patent Application Publication No. 2018-142452

[0015] Patent Document 2: Japanese Patent Application Publication No. 2018-167408 Summary of the Invention

[0016] The purpose of this invention is to provide an RF energy radiation device with high reliability relative to the heated object as a load.

[0017] The RF energy radiating device according to one aspect of this disclosure includes an oscillator, a power amplifier, a radiating element, a detector, a control unit, and a protection circuit.

[0018] An oscillator oscillates an RF signal with variable pulse width and variable pulse period. A power amplifier amplifies the RF signal and outputs traveling wave power. A radiating element radiates the traveling wave power. A detector detects the reflected wave power returning from the radiating element. A control unit controls the oscillator and the power amplifier based on the reflected wave power, setting the operating mode to a first control mode or a second control mode.

[0019] In the first control mode, the control unit performs pulse width control, intermittently outputting traveling wave power by setting the pulse width and pulse period to a first pulse width and a first pulse period, respectively. The control unit causes the oscillator to oscillate a pulsed RF signal with the first pulse width and the first pulse period. In the first control mode, the protection circuit does not shut down the power amplifier.

[0020] In the second control mode, the control unit performs pulse width control, setting the pulse width and pulse period to a second pulse width and a second pulse period, respectively, to intermittently output traveling wave power. The second pulse width and the second pulse period are different from the first pulse width and the first pulse period, respectively. The control unit causes the oscillator to oscillate a pulsed RF signal with the second pulse width and the second pulse period, or causes the oscillator to oscillate the RF signal continuously.

[0021] In the second control mode, when the reflected wave power exceeds the specified threshold, the protection circuit will cut off the power amplifier.

[0022] In this disclosure, pulse width control is performed in a first control mode at the start of operation to prevent damage to the oscillator. The RF energy radiating device continues its operation until the load impedance of the heated object stabilizes. In the pulse width control, the pulse duration is adjusted according to the oscillator temperature to avoid damaging the oscillator. According to this disclosure, the reliability of the RF energy radiating device can be improved. Attached Figure Description

[0023] Figure 1 This is a schematic structural diagram of the RF radiation energy device according to Embodiment 1 of this disclosure.

[0024] Figure 2 This is a block diagram showing the protection circuit and its surrounding components in the RF radiation energy device of Embodiment 1.

[0025] Figure 3 This is a diagram showing the operating sequence of the RF radiation energy device in Embodiment 1.

[0026] Figure 4 This is a diagram showing the operating sequence of the RF radiation energy device in Embodiment 1.

[0027] Figure 5 This is a diagram showing the operating sequence of the RF radiation energy device in Embodiment 1.

[0028] Figure 6 This is a flowchart illustrating the operation of the RF radiation energy device in Embodiment 1.

[0029] Figure 7 This is a diagram showing the operating sequence of the RF radiation energy device according to Embodiment 2 of this disclosure.

[0030] Figure 8 This is a flowchart of the operation of the RF radiation energy device in Implementation Method 2.

[0031] Figure 9 This is a graph showing the frequency characteristics of the reflectivity obtained by frequency scanning of the RF radiation energy device of Embodiment 2. Detailed Implementation

[0032] The RF energy radiating device of the first aspect of this disclosure includes an oscillator, a power amplifier, a radiating element, a detector, a control unit, and a protection circuit.

[0033] An oscillator oscillates an RF signal with variable pulse width and variable pulse period. A power amplifier amplifies the RF signal and outputs traveling wave power. A radiating element radiates the traveling wave power. A detector detects the reflected wave power returning from the radiating element. A control unit controls the oscillator and the power amplifier based on the reflected wave power, setting the operating mode to a first control mode or a second control mode.

[0034] In the first control mode, the control unit performs pulse width control, intermittently outputting traveling wave power by setting the pulse width and pulse period to a first pulse width and a first pulse period, respectively. The control unit causes the oscillator to oscillate a pulsed RF signal with the first pulse width and the first pulse period. In the first control mode, the protection circuit does not shut down the power amplifier.

[0035] In the second control mode, the control unit performs pulse width control, setting the pulse width and pulse period to a second pulse width and a second pulse period, respectively, to intermittently output traveling wave power. The second pulse width and the second pulse period are different from the first pulse width and the first pulse period, respectively. The control unit causes the oscillator to oscillate a pulsed RF signal with the second pulse width and the second pulse period, or causes the oscillator to oscillate an RF signal continuously.

[0036] In the second control mode, when the reflected wave power exceeds the specified threshold, the protection circuit will cut off the power amplifier.

[0037] This method of RF energy radiating device allows it to continue operating even when the traveling wave power is almost completely reflected at the start of operation. This improves the reliability of the RF energy radiating device.

[0038] The second aspect of the RF energy radiating device disclosed herein, based on the first aspect, in a first control mode, involves a control unit that causes an oscillator to oscillate a pulsed RF signal having a first pulse velocity. The control unit also causes a power amplifier to output a pulsed traveling wave power having the first pulse velocity.

[0039] In the second control mode, the control unit causes the oscillator to oscillate a pulsed RF signal with a second pulse velocity lower than the first pulse velocity. Alternatively, the control unit causes the oscillator to continuously oscillate an RF signal. The control unit causes the power amplifier to output a pulsed traveling wave power with a second pulse velocity or a continuous traveling wave power.

[0040] The protection circuit includes a switching section and a gate control section. The switching section cuts off the pulsed reflected wave power with a first pulse velocity, but does not cut off the pulsed reflected wave power with a second pulse velocity or the reflected wave power of a continuous wave. The gate control section cuts off the traveling wave power based on the output signal from the switching section.

[0041] According to this method, in the first control mode, the traveling wave power is not cut off even if the reflected wave power exceeds a specified threshold. That is, in the first control mode, the protection circuit does not function regardless of the reflected wave power. In the second control mode, the protection circuit functions according to the reflected wave power.

[0042] Based on the first approach, the third-party RF energy radiating device disclosed herein, in the first control mode, after a predetermined period has elapsed since the load condition stabilizes, the control unit switches the operating mode from the first control mode to the second control mode. After switching the operating mode from the first control mode to the second control mode, the control unit switches the operating mode from the second control mode back to the first control mode according to the load condition.

[0043] According to this method, when the load condition becomes unstable after it has stabilized, the action mode can be set back to the first control mode.

[0044] The fourth aspect of the RF energy radiating device disclosed herein, based on the first aspect, involves a control unit determining the stability of the load state based on the reflected wave power, and causing the oscillator to change the pulse width and pulse period of the RF signal. The control unit then adjusts the threshold voltage used to determine the stability of the load state based on the pulse width and pulse period.

[0045] The conversion unit determines the stability of the load state based on the reflected wave power. The permissible range of reflected wave power for the RF power element varies depending on the pulse width and pulse period of the traveling wave power controlled by the pulse width, as well as the ambient temperature of the RF power element. According to this method, the threshold voltage can be changed based on these conditions.

[0046] When the pulse duration of the pulsed reflected wave power is shorter than the response time of the processor's A / D converter, the conversion unit converts the pulsed reflected wave power into voltage. This allows the determination of the stability of the load condition.

[0047] The fifth aspect of the RF energy radiating device disclosed herein, based on the first aspect, further includes a memory that pre-stores the unstable time and stable time of the load state as a lookup table. The control unit, based on the lookup table and the elapsed operating time, changes the pulse width or pulse period of the pulsed RF signal oscillated by the oscillator.

[0048] Specifically, the memory, acting as a lookup table that uses various data obtained through experiments as pre-defined conditions, is capable of processing both stable and unstable load states under both the first and second control modes. This allows RF energy radiation to cease without determining the stability of the load state.

[0049] When the pulse time of the reflected wave power is shorter than the response time of the processor's A / D converter, it is difficult to determine the stability of the load state. Therefore, this method is effective as a control method in this situation. Below are examples of various data stored in memory as lookup tables.

[0050] For the first control mode, the following settings are stored in the lookup table based on the ambient temperature of the RF power element: 1. Output power, 2. Frequency, 3. Frequency scan interval, 4. Action time, 5. Pulse time, 6. Pulse period, 7. Pulse duty cycle.

[0051] For the second control mode, the following settings are stored in a lookup table based on the ambient temperature of the RF power element: 1. Output power, 2. Frequency, 3. Activation time, 4. Pulse duration, 5. Pulse period, 6. Pulse duty cycle, and 7. Threshold for load stability determination. Furthermore, the pulse duration in the second control mode is longer than that in the first control mode. Moreover, in addition to pulse width control for supplying pulsed traveling wave power, the second control mode also includes control for supplying continuous traveling wave power.

[0052] The RF energy radiating device according to the sixth aspect of this disclosure, based on the first aspect, further includes a memory that pre-stores the frequency of the RF signal capable of stabilizing the load state as a lookup table.

[0053] The oscillator can change the frequency of the oscillating RF signal. The control unit changes the oscillator frequency based on a lookup table and the elapsed operating time. This method can promote the stabilization of the load condition.

[0054] The seventh aspect of the RF energy radiating device disclosed herein, based on the first aspect, allows the oscillator to change the frequency of the oscillating RF signal. The control unit determines the stability of the load state based on the output signal from the detector. The control unit causes the oscillator to change the frequency of the RF signal as the operating time elapses. According to this aspect, by performing frequency scanning, load state stabilization can be promoted.

[0055] The eighth aspect of the RF energy radiating device disclosed herein, based on the first aspect, further includes: a terminator for terminating reflected wave power; and a temperature sensor for detecting the temperature of the power amplifier and the terminator. The oscillator is capable of changing the frequency of the oscillated RF signal.

[0056] In the first control mode, the control unit adjusts the pulse width or pulse period of the oscillator based on the temperature of the power amplifier and the terminator. This provides a safe operating range where the power amplifier and the terminator are not damaged by reflected wave power. This method improves the reliability of the RF energy radiating device.

[0057] The RF energy radiating device of the ninth aspect of the present invention, based on the first aspect, wherein the control unit causes the power amplifier to set the traveling wave power during the on-time to a first power level and the traveling wave power during the off-time to a second power level in pulse width control. The second power level is not zero, but a power level lower than the first power level.

[0058] According to this method, the off-time in pulse width control allows a certain amount of reactive current to continuously flow in the output circuit supplying power to power amplifier 2a. This, in turn, stabilizes the output voltage supplying power to the power amplifier.

[0059] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0060] (Implementation Method 1)

[0061] Figure 1 This is a schematic structural diagram of the RF energy radiation device 100 according to Embodiment 1 of the present invention.

[0062] like Figure 1 As shown, the RF energy radiation device 100 includes an oscillator 1, a power amplifier 2, a detector 3, a circulator 4, a terminator 5, a temperature sensor 6, a radiation element 7, a processor 9, a protection circuit 20, and a memory 30.

[0063] Oscillator 1 includes two oscillators (1a, 1b). Power amplifier 2 includes two power amplifiers (2a, 2b). Detector 3 includes two detectors (3a, 3b). Circulator 4 includes two circulators (4a, 4b).

[0064] Terminator 5 includes two terminators (5a, 5b). Temperature sensor 6 includes four temperature sensors (6a, 6b, 6c, 6d). Radiation element 7 includes two radiation elements (7a, 7b).

[0065] Oscillators 1a and 1b oscillate and output RF signals respectively. Power amplifiers 2a and 2b amplify the RF signals oscillated by oscillators 1a and 1b respectively, and output them as traveling wave power. Detectors 3a and 3b both detect the traveling wave power and the reflected wave power.

[0066] Traveling wave power refers to the RF energy from power amplifiers 2a and 2b, respectively, via circulators 4a and 4b, directed toward radiating elements 7a and 7b. Reflected wave power refers to the RF energy from radiating elements 7a and 7b returning to circulators 4a and 4b, respectively, within the traveling wave power.

[0067] Circulators 4a and 4b are positioned in the path of traveling wave power and the path of reflected wave power, respectively. Circulators 4a and 4b protect power amplifiers 2a and 2b from the influence of reflected wave power that varies according to the load of the heated object. Terminators 5a and 5b each have a specific impedance relative to the reflected wave power from circulators 4a and 4b, which becomes the load.

[0068] Radiation element 7a radiates the RF energy transmitted from power amplifier 2a via circulator 4a into chamber 8. Radiation element 7b radiates the RF energy transmitted from power amplifier 2b via circulator 4b into chamber 8. The object to be heated, placed inside chamber 8, is heated using the RF energy.

[0069] Temperature sensors 6a and 6b are respectively positioned near power amplifiers 2a and 2b to detect the temperature of power amplifiers 2a and 2b. Temperature sensors 6c and 6d are respectively positioned near terminators 5a and 5b to detect the temperature of terminators 5a and 5b.

[0070] Memory 30 is, for example, a semiconductor memory that stores the software and data used by processor 9. The data stored in memory 30 includes lookup tables prepared in advance to set RF energy suitable for the temperatures detected by temperature sensors 6a-6d.

[0071] Processor 9 is a general-purpose microprocessor that functions as a control unit for controlling the RF energy radiation device 100. Processor 9 controls oscillators 1a and 1b and power amplifiers 2a and 2b based on the temperatures detected by temperature sensors 6a to 6d.

[0072] Specifically, processor 9 causes oscillators 1a and 1b to oscillate RF signals with arbitrary frequencies within a specified frequency band. Furthermore, processor 9 performs pulse width control by causing oscillators 1a and 1b to oscillate RF signals with variable pulse widths and variable pulse periods. Pulse width control, pulse width, and pulse period will be explained later.

[0073] In this embodiment, the processor 9 can refer to, for example, the temperatures detected by temperature sensors 6a to 6d at a frequency of 50 times per second. The processor 9 can, for example, output instructions to oscillators 1a and 1b and power amplifiers 2a and 2b based on these temperatures detected 50 times per second. That is, the software control cycle (hereinafter referred to as the control cycle) in the processor 9 is 20 ms.

[0074] The protection circuit 20 functions to protect the circuitry within the device based on the traveling wave power and reflected wave power detected by detectors 3a and 3b, and the temperatures of temperature sensors 6a to 6d.

[0075] As described above, the reflected wave power, which fluctuates due to load variations, reaches the terminator 5 via the circulator 4 and is consumed by the terminator 5. This mitigates the impact of the reflected wave power on the power amplifier 2 and reduces the characteristic changes in the power amplifier 2 caused by load variations. Thus, the circulator 4 protects the power amplifier 2.

[0076] However, as the reflected wave power is consumed, heat is generated in the terminator 5, which limits the operation of the RF energy radiating device 100. Considering the lifespan of the terminator 5, it is used in a manner that keeps the temperature rise caused by heat within a safe range in the operating environment. Therefore, continuous use of the RF energy radiating device 100 is always limited when the reflected wave power level is high.

[0077] like Figure 1 As shown, the RF energy radiating device 100 includes two RF energy radiating devices with identical structures. One of the two systems is located on the radiating element 7a side, and the other is located on the radiating element 7b side. The processor 9, protection circuit 20, and memory 30 are common to both RF energy radiating devices.

[0078] The following description will only focus on the RF energy radiating device 100a of the system on the radiating element 7a side, and will omit the description of the RF energy radiating device 100b of the system on the radiating element 7b side.

[0079] Figure 2 This is a block diagram showing the details of the protection circuit 20 of the RF energy radiation device 100a of this embodiment and the constituent elements of the protection circuit 20.

[0080] like Figure 2 As shown, the RF energy radiating device 100a includes an oscillator 1a, a power amplifier 2a, a detector 3a, a circulator 4a, a terminator 5a, a radiating element 7a, a reflected wave power feedback 24, a traveling wave power feedback 25, a second FV converter 26, a first directional coupler 27, and a second directional coupler 28. The detector 3a includes a first detector 3a1 and a second detector 3a2.

[0081] A first directional coupler 27 is disposed between power amplifier 2a and circulator 4a. The first directional coupler 27 sends a portion of the traveling ripple power from power amplifier 2a toward circulator 4a to a first detector 3a1. The first detector 3a1 detects the portion of the traveling ripple power and sends the detected signal to traveling ripple power feedback 25. The traveling ripple power feedback 25 receives the signal from the first detector 3a1 and detects the level of the traveling ripple power based on this signal.

[0082] The second directional coupler 28 is disposed between the circulator 4a and the terminator 5a. The second directional coupler 28 sends a portion of the reflected wave power from the circulator 4a toward the terminator 5a to the second detector 3a2. The second detector 3a2 detects a portion of the reflected wave power and sends the detected signal to the second FV converter 26.

[0083] The second FV converter 26 is a low-pass filter that receives the signal from the second detector 3a2 and outputs a smoothed signal. That is, the second FV converter 26 converts a portion of the reflected wave power detected by the second detector 3a2 into a voltage level corresponding to the level of the reflected wave power. The reflected wave power feedback 24 detects the level of the reflected wave power based on the voltage level from the second FV converter 26.

[0084] The RF energy radiating device 100a also includes a processor 9, a protection circuit 20, and a memory 30, which are common components to the RF energy radiating device 100b. The protection circuit 20 includes a first FV conversion unit 21, a reflected wave power cutoff feedback 22, and a gate control unit 23.

[0085] Like the second FV converter 26, the first FV converter 21 is a low-pass filter that receives the signal from the second detector 3a2 and outputs a smoothed signal. That is, the first FV converter 21 converts a portion of the reflected wave power detected by the second detector 3a2 into a voltage level corresponding to the level of the reflected wave power.

[0086] The circuit constant of the first FV converter 21 is set to prevent the pulsed reflected wave power with the first pulse velocity (described later) under the first control mode from passing through. The circuit constant of the first FV converter 21 is set to allow the pulsed reflected wave power with the second pulse velocity (described later) under the second control mode and the reflected wave power of the continuous wave to pass through. Therefore, in the first control mode, the output power level from the first FV converter 21 is always zero. On the other hand, in the second control mode, the first FV converter 21 outputs a voltage level corresponding to the reflected wave power (see reference). Figure 3 The waveform (c)).

[0087] That is, in the first control mode, the reflected wave power cutoff feedback 22 does not cut off the power amplifier 2a, and the traveling wave power is not cut off. In the second control mode, the reflected wave power cutoff feedback 22 cuts off the power amplifier 2a according to the voltage level from the first FV converter 21, thus cutting off the traveling wave power.

[0088] use Figures 3-5 The operation and function of the RF energy radiation device 100 configured as described above will be explained.

[0089] Figure 3 This illustrates an example of the sequence of actions when transitioning from a first control mode to a second control mode. For example... Figure 3 As shown, at time T31, the processor 9 sets the operation mode to the first control mode and starts the operation of the RF energy radiation device 100a.

[0090] The processor 9 causes the oscillator 1a to oscillate an RF signal at a desired frequency and alternately switches the power supply to the oscillator 1a on and off. Thus, the oscillator 1a oscillates the RF signal while alternately setting the on-time for continuous oscillation and the off-time for stopping the oscillation. The processor 9 amplifies the RF signal by the power amplifier 2a in a manner that makes the RF energy the desired output value.

[0091] As a result, in the first control mode, pulsed microwaves are supplied to chamber 8 as traveling wave power.

[0092] Furthermore, supplying pulsed microwaves (traveling wave power) means that the power amplifier 2a outputs microwaves (traveling wave power) while alternately setting the on and off times. The on time refers to the duration during which the power amplifier 2a continuously outputs traveling wave power. The off time refers to the duration during which the power amplifier 2a stops outputting traveling wave power.

[0093] In this embodiment, the control of supplying pulsed microwaves (traveling wave power) while simultaneously adjusting the amplification of the RF signal, the on-time, and the off-time is called pulse width control. In pulse width control, the pulse width (pulse time) is the length of the on-time, and the pulse period is the sum of the on-time and off-time.

[0094] In other words, pulse width control refers to outputting pulsed microwaves (traveling wave power), that is, outputting microwaves (traveling wave power) intermittently.

[0095] On the other hand, continuously supplying microwaves (traveling wave power) without pulse width control is called supplying continuous waves with microwaves (traveling wave power).

[0096] Processor 9 is based on temperature sensor 6c (reference) Figure 1 The pulse width and pulse period are calculated based on the measured temperature of the terminator 5a and its temperature-dependent safe operating range. The temperature-dependent safe operating range of the terminator 5a is pre-stored in memory 30.

[0097] In the absence of a circulator 4a in the RF energy radiating device 100a, the safe operating area of ​​the power amplifier 2a is considered as a condition for setting the pulse width and pulse period. That is, in the first control mode, the pulse width and pulse period can be controlled based on the temperature of the power amplifier 2a and the terminator 5a, in a way that provides a safe area where the power amplifier 2a and the terminator 5a will not be damaged by the reflected wave power.

[0098] like Figure 3 As shown in waveform (a), in the first control mode, RF energy is output as a pulsed microwave (traveling wave power) with a specified pulse width and a specified pulse period, or one of them.

[0099] Figure 3 Waveform (b) is the output signal of the second detector 3a2, representing the voltage corresponding to the reflected wave power detected by the second detector 3a2. Figure 3 The waveform (c) is the output signal of the first FV converter 21, representing the voltage corresponding to the power of the reflected wave that has passed through the first FV converter 21. Figure 3 The waveform (d) is the output signal of the reflected wave power feedback 24. This signal is a voltage representing the level of the reflected wave power detected by the reflected wave power feedback 24, and is input to the A / D (analog-to-digital) converter of the processor 9.

[0100] Typically, a second FV converter 26 is configured before the reflected wave power feedback 24. The second FV converter 26 functions as a low-pass filter (LPF) for removing noise such as power supply ripple. Figure 3 The waveform (d) is the differential waveform after passing through the LPF.

[0101] The pulse width and pulse period in the pulse width control can be adjusted. For example, the pulse period can be set to any value within the range of 10μs to 2ms, depending on the ambient temperature and load condition of the terminator 5a. The threshold voltage used to determine the stability of the load condition can be changed by either the pulse width or the pulse period. The load response characteristics of the power supply to the oscillator 1a also need to be considered; sometimes, the period of the capacitor best suited to the power supply wire is selected.

[0102] After starting in the first control mode, such as Figure 3 As shown in waveform (b), if the pulsed traveling wave power is reflected almost by total internal reflection, then a pulsed reflected wave power is generated.

[0103] According to its circuit constant, the first FV converter 21 does not transmit the pulsed reflected wave power in the first control mode. In the second control mode, the first FV converter 21 transmits the pulsed reflected wave power with a pulse velocity lower than that in the first control mode, as well as the reflected wave power of a continuous wave.

[0104] In this embodiment, pulse velocity refers to the reciprocal of the pulse period in microwave pulse width control. The pulse velocity in the first control mode is called the first pulse velocity, and the pulse velocity in the second control mode is called the second pulse velocity. The second pulse velocity is lower than the first pulse velocity.

[0105] In the second control mode, the processor 9 causes the oscillator 1a to oscillate a pulsed RF signal with a second pulse velocity lower than the first pulse velocity of the first control mode, or to continuously oscillate an RF signal. As a result, in the second control mode, the radiating element 7a radiates a pulsed traveling wave power or a continuous traveling wave power with a second pulse velocity lower than the first pulse velocity of the first control mode.

[0106] Furthermore, the pulse width and pulse period in the first control mode are referred to as the first pulse width and the first pulse period, respectively. The pulse width and pulse period in the second control mode are referred to as the second pulse width and the second pulse period, respectively. The first pulse width and the first pulse period are different from the second pulse width and the second pulse period.

[0107] The first FV conversion unit 21 is a filter circuit that uses passive components (resistors, capacitors, inductors). The first FV conversion unit 21 can be an active filter that appropriately changes the time constant through passive components, operational amplifiers, and digital potentiometers.

[0108] In the first control mode, the first FV converter 21 does not transmit a voltage equivalent to the protection threshold for the reflected wave power to the reflected wave power cutoff feedback 22. As a result, even under a load condition of total reflection, the processor 9 does not cut off the oscillator 1a. That is, in the first control mode, even if the level of the reflected wave power detected by the second detector 3a2 exceeds the predetermined threshold, the oscillator 1a does not cut off the RF energy.

[0109] Therefore, even under unstable load conditions, the RF energy radiating device 100a can continue to operate without stopping.

[0110] In the first control mode, when Figure 3 When the output signal of the reflected wave power feedback 24, as shown in waveform (d), is below the first threshold, the processor 9 determines that the load state is stable (time T32). The first threshold is a specified threshold used to determine the load state via software. Software-based load state determination refers to... Figure 3 The stability of the output signal of the reflected wave power feedback 24, as shown in waveform (d), is determined based on the load state of the processor 9.

[0111] When the load condition stabilizes, the processor 9 switches the operating mode from a first control mode that radiates pulsed microwaves to a second control mode that radiates traveling wave power of a continuous wave. In the second control mode, either pulsed traveling wave power or continuous traveling wave power is output. The pulse width and pulse period of the pulsed microwaves in the second control mode differ from those in the first control mode, and the pulse velocity is lower than that in the first control mode.

[0112] In the case of continuous wave microwaves, the reflected wave power detected by the second detector 3a2 is transmitted to the reflected wave power cutoff feedback 22 via the first FV conversion unit 21.

[0113] In the second control mode, the load condition sometimes becomes unstable, causing the reflected wave power to increase. Therefore, the reflected wave power cutoff feedback 22 determines whether the level of the reflected wave power exceeds a threshold set by hardware. If the reflected wave power exceeds this threshold (see reference...), Figure 3 The waveform (c) indicates that the gate control unit 23 will cut off the power amplifier 2a (see waveform (c)). Figure 3 The waveform (a)).

[0114] In this way, protection circuit 20 operates, protecting the RF power components from the influence of reflected wave power. Afterwards, no further determination is made regarding the operation of protection circuit 20.

[0115] In the first control mode, in order to maintain the stability of the load state, the operation mode can be switched from the first control mode to the second control mode after a specified period of time after the load state has been stabilized in the first control mode.

[0116] In the second control mode, the first FV converter 21 directly outputs the input reflected wave power. When the reflected wave power cutoff feedback 22 detects that the level of the reflected wave power exceeds a predetermined threshold, the gate control unit 23 cuts off the power amplifier 2a (at time T33). As a result, the radiation of RF energy stops, protecting the terminator 5a from the effects of excessive reflected wave power.

[0117] An example of the hardware structure for the reflected wave power cutoff feedback 22 is a comparator. The safe operating range of the terminator 5a varies depending on the ambient temperature. Therefore, the processor 9 changes the threshold voltage of the comparator via a D / A (digital-to-analog) converter.

[0118] If the reflected wave power increases after the operation mode is switched to the second control mode, the processor 9 can make the operation mode return from the second control mode to the first control mode. Figure 4 This indicates the sequence of actions in this situation. Figure 4 The waveforms (a) to (d) are respectively with Figure 3 The signals corresponding to waveforms (a) to (d). Figure 4 The vertical and horizontal axes of waveforms (a) to (d) are respectively perpendicular to... Figure 3 The waveforms (a) to (d) are the same.

[0119] exist Figure 4 In the middle, from time T41 to the time immediately preceding T43 Figure 4 The waveforms (a) to (d) show the signal characteristics and Figure 3 The waveforms (a) to (d) are the same. Therefore, the explanation will focus on time T43 and later.

[0120] like Figure 4 As shown in waveform (d), at time T43, the reflected wave power feedback 24 determines that the output signal of the first FV converter 21 exceeds the second threshold. The second threshold is a predetermined threshold higher than the first threshold used to determine the load state by software. In this case, the operating mode switches from the second control mode to the first control mode.

[0121] Processor 9 continues operation in the first control mode until the load stabilizes through pulse width control that enables terminator 5a to operate within its safe operating range. As mentioned above, load stabilization means... Figure 4 The output signal of the reflected wave power feedback 24, as shown in waveform (d), becomes below the first threshold.

[0122] At time T44, if Figure 4 If the output signal of the reflected wave power feedback 24, as shown in waveform (d), is below the first threshold, then the processor 9 determines that the load state is stable. When the load state is stable, the processor 9 again switches the operating mode from the first control mode to the second control mode.

[0123] In the first control mode, by shortening the pulse period, the RF power element can continue operating within the safe operating range for reflected wave power. Due to the load response characteristics of the power supply, the current increases sharply as the traveling wave power rises in pulse width control. Consequently, the output voltage supplying power to power amplifier 2a is sometimes transiently suppressed. In this case, the traveling wave power is disconnected if the traveling wave power does not reach the desired value.

[0124] Figure 5 This represents an example of the action sequence of pulse width control used to solve this problem. Figure 5 The waveforms (a) to (d) are respectively with Figure 3 The signals corresponding to waveforms (a) to (d). Figure 5 The vertical and horizontal axes of waveforms (a) to (d) are respectively perpendicular to... Figure 3 The waveforms (a) to (d) are the same.

[0125] like Figure 5 As shown, during times T51 to T52, the level of the traveling wave power during the on-time in the pulse width control is set to the same as... Figure 3 The first power level is the same as the first power level. On the other hand, the traveling wave power during the disconnection time is set to a second power level that is non-zero and smaller than the first power level. The second power level is a power level that does not affect the degree to which the object being heated is heated.

[0126] In this way, the off-time in pulse width control allows a certain amount of current to continuously flow in the output circuit that supplies power to power amplifier 2a. This, in turn, stabilizes the output voltage supplying power to power amplifier 2a.

[0127] exist Figure 5 In the middle, after the action mode is switched to the second control mode, it is in harmony with... Figure 3 The same applies. When the reflected wave power cutoff feedback 22 detects that the level of the reflected wave power exceeds a predetermined threshold, the gate control unit 23 cuts off the power amplifier 2a (time T53).

[0128] exist Figure 5In the example shown, the on / off ratio, i.e., the ratio of the first power level to the second power level of the traveling wave power, can be adjusted within the range of 20dB to 30dB. Therefore, with a traveling wave power of 250W, the output traveling wave power is 0.25W to 2.5W during the off-time. This on / off ratio is appropriately set according to the level of the traveling wave power.

[0129] exist Figure 5 In the example shown, detector 3a includes a logarithmic amplifier with an input range of 20 dB, which can be converted into a voltage range of approximately 20 dB relative to the input power.

[0130] Even if 0.25W to 2.5W of traveling wave power is totally reflected and input to the second detector 3a2 as reflected wave power, the output voltage of the second detector 3a2 will not affect the first control mode.

[0131] Temperature sensor 6c (reference) Figure 1 The processor 9 monitors the temperature of the terminator 5a. When the temperature outside the safe operating range of the terminator 5a is detected under unstable load conditions, the processor 9 stops the operation of the RF energy radiating device 100a.

[0132] Figure 6 This is an example of a flowchart illustrating the operation of the RF energy radiating device 100a according to this embodiment.

[0133] When the RF energy radiating device 100a starts operating, in step S61, the processor 9 sets the operating mode to the first control mode. The processor 9 causes the oscillator 1a to oscillate an RF signal with the desired frequency. At the same time, the processor 9 causes the power amplifier 2a to amplify the RF signal in a manner that outputs RF energy at the desired output level.

[0134] In the first control mode, processor 9 outputs RF energy via pulse width control. The duty cycle in the pulse width control is set to 50%. The duty cycle is the ratio of the on-time to the sum of the on-time for continuous RF energy output and the off-time for stopping RF energy output.

[0135] In the first control mode, when the processor 9 determines that the load state is stable based on the output signal of the reflected wave power feedback 24 (the determination in step S62 is "stable"), the operation mode is switched to the second control mode. In the second control mode, the processor 9 controls the oscillator 1a and the power amplifier 2a in a manner that radiates the traveling wave power of a continuous wave. The processor 9 starts counting the timer for the operation time to perform the operation of the second control mode (step S63).

[0136] In the first control mode, if the load state is not confirmed to be stable based on the software (the determination in step S62 is "unstable"), the processor 9 refers to the temperature of the terminator 5a (step S64). When a temperature outside the safe operating area of ​​the terminator 5a is detected (the determination in step S64 is "above the specified value"), the processor 9 stops the operation of the RF energy radiation device 100a (step S65).

[0137] As described above, in step S63, when the second control mode is activated, the reflected wave power cutoff feedback 22 monitors the output voltage of the first FV converter 21 (step S66). When the level of the output signal of the first FV converter 21 exceeds a predetermined threshold (determined as "unstable" in step S66), the processor 9 treats this state as a sudden load change and monitors the temperature of the terminator 5a (step S68). When a temperature outside the safe operating area of ​​the terminator 5a is detected (determined as "above the predetermined value" in step S68), the processor 9 stops the operation of the RF energy radiation device 100a (step S69).

[0138] Additionally, when the timer count for the action time in the second control mode becomes zero (the determination in step S66 is "count is zero"), the processor 9 stops the operation of the RF energy radiation device 100a (step S67).

[0139] In step S64, when the temperature within the safe operating area of ​​the terminator 5a is detected (the determination in step S64 is "less than the specified value"), the processor 9 returns the process to step S61. Similarly, in step S68, when the temperature within the safe operating area of ​​the terminator 5a is detected (the determination in step S68 is "less than the specified value"), the processor 9 returns the process to step S61.

[0140] The memory 30 can also pre-store the unstable time of the load state and the stable time in relation to the action time as a lookup table. The processor 9 can, based on the lookup table and the elapsed action time, cause the oscillator 1a to change the pulse width or pulse period of the pulsed RF signal.

[0141] The instability time of the load state is the length of the period during which the load state is unstable, and it is determined in advance through experiments. The settling time of the load state is the length of the period during which the load state is stable, and it is determined in advance through experiments. That is, processor 9 can switch operating modes through feedforward control based on lookup tables, rather than feedback control based on reflected wave power.

[0142] The RF energy radiating device 100a executes the first control mode and the second control mode through hardware and software.

[0143] Pulse width control is performed in the first control mode. In pulse width control, the pulse duration is set such that the reflected wave power is within the allowable range of the RF power element when the traveling wave power is totally reflected. In this embodiment, the RF power element includes an oscillator 1a, a power amplifier 2a, and a terminator 5a. Furthermore, the pulse duration is set such that the temperature rise of the RF power element when the RF energy radiating device 100a is activated is within the safe operating range of the RF power element.

[0144] The RF energy radiating device 100a includes components for stopping the protection circuit 20, which protects the RF power element from reflected wave power in a first control mode. These components include a first FV conversion unit 21 and a second FV conversion unit 26.

[0145] In the second control mode, pulsed traveling wave power or continuous traveling wave power with a pulse velocity lower than that in the first control mode is radiated. This protects the RF energy radiating device 100a from the effects of reflected wave power levels and temperature rise from the temperature sensor.

[0146] As a result, in the first control mode, for a heated object with load characteristics that cause total reflection, it can continue to operate until the load impedance becomes stable.

[0147] After the load impedance stabilizes, the operating mode switches to the second control mode. In the second control mode, the duration required for continuous RF energy radiation can be determined. The safe operating range of the RF power element can also be appropriately adjusted based on the ambient temperature of the RF power element. Furthermore, load impedance stabilization refers to the load impedance being in a region close to the output impedance of the RF energy radiating device 100a.

[0148] (Implementation Method 2)

[0149] Hereinafter, the RF energy radiating device 100a according to Embodiment 2 of the present invention will be described. The RF energy radiating device 100a of this embodiment has the same structure as that of Embodiment 1. The difference between this embodiment and Embodiment 1 is that when the RF energy radiating device 100a starts to operate, the processor 9 first performs a frequency scan.

[0150] Figure 7 This indicates the operating sequence of the RF energy radiating device 100a according to Embodiment 2 of the present invention. For example... Figure 7 As shown in waveform (a), when the RF energy radiating device 100a starts to operate, in the first control mode, the processor 9 performs a frequency scan (time T71).

[0151] During frequency scanning, the processor 9 causes the oscillator 1a to oscillate an RF signal while changing the frequency sequentially at predetermined frequency intervals within a specified frequency band (e.g., 2.4 GHz to 2.5 GHz).

[0152] Specifically, such as Figure 7 As shown in waveform (a), firstly, oscillator 1a oscillates at frequency F1 for a predetermined on-time, and then stops operating after that time. After a predetermined off-time, oscillator 1a oscillates at frequency F2 for a predetermined on-time, and then stops operating after that time. In this way, oscillator 1a oscillates sequentially with predetermined pulse widths and pulse periods to generate RF signals with frequencies F1 to F8 (times T71 to T72).

[0153] Furthermore, if n is set to a natural number greater than 1 and less than 7, then frequency Fn+1 is greater than frequency Fn, and the frequency interval between frequency Fn+1 and frequency Fn is constant.

[0154] Oscillator 1a can be composed of a VCO (voltage-controlled oscillator) and a PLL (phase-locked loop), or it can be composed of a DDS (direct digital synthesizer) with a fast frequency shift time. The choice of which depends on the pulse period of the pulse width control used. Furthermore, the period of frequency changes during frequency scanning depends on the control cycle of processor 9.

[0155] The second detector 3a2 detects the level of the reflected wave power relative to any one of frequencies F1 to F8 during the control cycle. This information is input to the A / D (analog-to-digital) converter of the processor 9 via the reflected wave power feedback 24.

[0156] Processor 9 selects the frequency that produces the minimum reflected wave power from the reflected wave power measured during the frequency scan, or a frequency near that frequency, as the frequency to be used (time T72). Processor 9 uses microwaves with the selected frequency to perform pulse width control in the first control mode. Figure 7 In waveform (a), frequency F5 is selected as the frequency to be used.

[0157] When the load condition stabilizes and the reflected wave power falls below a predetermined threshold used for software-based determination, processor 9 switches the operating mode from the first control mode to the second control mode (time T73). As mentioned above, a stable load condition means... Figure 7 The waveform (d) shows that the output signal of the reflected wave power feedback 24 is below the first threshold.

[0158] By variably controlling the frequency to facilitate load stabilization, the operating mode can be transitioned more quickly from the first control mode to the second control mode. This improves the reliability of load stabilization. Consequently, during RF energy radiation such as plasma ignition, the frequency that is most likely to ignite can be searched more quickly from a state of total internal reflection, increasing the ignition probability.

[0159] In this embodiment, compared with embodiment 1 (refer to embodiment 1) Figure 4 Similarly, when the load condition becomes unstable after switching to the second control mode, the processor 9 switches the operating mode back to the first control mode and performs a frequency scan again. This allows it to search again for a frequency that can stabilize the load condition.

[0160] Figure 8 This is a flowchart of the operation of the RF energy radiation device 100a in this embodiment.

[0161] When the RF energy radiating device 100a starts operating, in step S81, the processor 9 sets the operating mode to the first control mode, causing the oscillator 1a to oscillate and generate an RF signal for frequency scanning. Simultaneously, the processor 9 causes the power amplifier 2a to amplify the RF signal and output RF energy at the desired output level.

[0162] In this embodiment, in the first control mode, the pulse width in the pulse width control is set to half the pulse period. That is, the duty cycle in the pulse width control is set to 50%.

[0163] In step S82, processor 9 selects the frequency to be used by frequency scanning. Processor 9 then uses microwaves with the selected frequency to continue pulse width control.

[0164] In the first control mode, when the processor 9 determines that the load state is stable based on the output signal of the reflected wave power feedback 24 (the determination in step S83 is "stable"), the operation mode is switched to the second control mode. In the second control mode, the processor 9 controls the oscillator 1a and the power amplifier 2a in a manner that radiates the traveling wave power of a continuous wave. The processor 9 starts counting the timer for the operation time to perform the operation of the second control mode (step S84).

[0165] In the first control mode, if the load state is not confirmed to be stable based on the software (the determination in step S83 is "unstable"), the processor 9 refers to the temperature of the terminator 5a (step S85). When a temperature outside the safe operating area of ​​the terminator 5a is detected (the determination in step S85 is "above the specified value"), the processor 9 stops the operation of the RF energy radiation device 100a (step S86).

[0166] As described above, when the second control mode is operated in step S84, the reflected wave power cutoff feedback 22 monitors the output voltage of the first FV converter 21 (step S87). If the level of the output signal of the first FV converter 21 does not exceed the predetermined threshold (the determination in step S87 is "stable"), the processor 9 returns the processing to step S84.

[0167] When the level of the output signal of the first FV converter 21 exceeds a predetermined threshold (determined as "unstable" in step S87), the processor 9 treats this state as a sudden load change and monitors the temperature of the terminator 5a (step S89). If a temperature outside the safe operating area of ​​the terminator 5a is detected (determined as "above the predetermined value" in step S89), the processor 9 stops the operation of the RF energy radiation device 100a (step S90).

[0168] In addition, when the timer count for the action time in the second control mode becomes zero (the determination in step S87 is "count is zero"), the processor 9 stops the operation of the RF energy radiation device 100a (step S88).

[0169] In step S85, when the temperature within the safe operating area of ​​the terminator 5 is detected (the determination in step S85 is "less than a specified value"), the processor 9 returns the process to step S81. Similarly, in step S89, when the temperature within the safe operating area of ​​the terminator 5 is detected (the determination in step S89 is "less than a specified value"), the processor 9 returns the process to step S81.

[0170] Alternatively, processor 9 can perform a frequency scan again to select the frequency to be used and repeat the same operation.

[0171] In this embodiment, such as Figure 7 As shown, processor 9 performs a frequency scan and selects frequency F5 as the frequency to be used. However, this disclosure is not limited thereto. Processor 9 may select the frequency to be used based on the reflectivity obtained during the frequency scan.

[0172] Figure 9 This represents the frequency characteristics of reflectivity obtained through frequency scanning. Figure 9 In the graph, the horizontal axis represents the frequency of the traveling wave power, and the vertical axis represents reflectivity. Reflectivity is the ratio of reflected wave power (Pr) to traveling wave power (Pf), serving as an indicator of load stability. For example... Figure 9 As shown, processor 9, for example, selects a frequency near 2.42 GHz that brings the minimum reflectivity as the frequency to be used.

[0173] The memory 30 can pre-store the pulse width control operation conditions (pulse width, frequency, operation time, etc.) in the first control mode as a menu corresponding to the type of heated object.

[0174] The memory 30 can pre-store a lookup table that establishes a correlation between the frequency that enables load stabilization and the elapsed operating time. The processor 9 can change the frequency of the oscillator 1a based on the elapsed operating time and the lookup table.

[0175] The processor 9 can acquire the signal from the detector 3a, determine the frequency that can stabilize the load state, and cause the oscillator 1a to change the frequency according to the elapsed operating time.

[0176] Industrial utilization potential

[0177] As described above, the RF energy radiating device disclosed herein can be applied to heating devices that require high precision in the output control of RF energy, such as commercial heating devices.

[0178] Explanation of reference numerals in the attached figures

[0179] 1, 1a, 1b: Oscillator; 2, a, 2b: Power amplifier; 3, 3a, 3b: Detector; 3a1: First detector; 3a2: Second detector; 4, 4a, 4b: Circulator; 5, 5a, 5b: Terminator; 6, 6a, 6b, 6c, 6d: Temperature sensor; 7, 7a, 7b: Radiation element; 8: Chamber; 9: Processor (control unit); 20: Protection circuit; 21: First FV converter; 22: Reflected wave power cutoff feedback; 23: Gate control unit; 24: Reflected wave power feedback; 25: Traveling wave power feedback; 26: Second FV converter; 27: First directional coupler; 28: Second directional coupler; 30: Memory; 100, 100a, 100b: RF energy radiation device.

Claims

1. An RF energy radiating device, wherein, The RF energy radiating device includes: An oscillator is configured to oscillate an RF signal with a variable pulse width and a variable pulse period. A power amplifier configured to amplify the RF signal and output traveling wave power; A radiating element configured to radiate the traveling wave power; A detector configured to detect the power of the reflected wave returning from the radiating element; and The control unit is configured to control the oscillator and the power amplifier based on the reflected wave power. The control unit is configured to set the operation mode to a first control mode or a second control mode. The first control mode includes performing pulse width control by outputting the traveling wave power by setting either a predetermined pulse width or a predetermined pulse period. The second control mode includes performing pulse width control as described below: outputting the traveling wave power by performing one or both of setting the pulse width to a pulse width different from that of the first control mode and setting the pulse period to a pulse period different from that of the first control mode. In the first control mode, the traveling wave power is not cut off; in the second control mode, the traveling wave power is cut off when the reflected wave power exceeds a predetermined threshold.

2. The RF energy radiating device according to claim 1, wherein, The RF energy radiation device also has a protection circuit. In the first control mode, the control unit is configured to perform pulse width control, which intermittently outputs the traveling wave power by setting the pulse width and the pulse period to a first pulse width and a first pulse period, respectively. The control unit is configured to cause the oscillator to oscillate and generate a pulse-shaped RF signal having the first pulse width and the first pulse period. In the first control mode, the protection circuit is configured to not cut off the traveling wave power. In the second control mode, the control unit is configured to perform pulse width control, which intermittently outputs the traveling wave power by setting the pulse width and the pulse period to a second pulse width and a second pulse period, respectively, wherein the second pulse width is different from the first pulse width, and the second pulse period is different from the first pulse period. The control unit is configured to either cause the oscillator to oscillate a pulsed RF signal having the second pulse width and the second pulse period, or to cause the oscillator to continuously oscillate the RF signal. In the second control mode, the protection circuit is configured to cut off the traveling wave power when the reflected wave power exceeds a predetermined threshold.

3. The RF energy radiating device according to claim 2, wherein, In the first control mode, the control unit is configured to: cause the oscillator to oscillate a pulse-shaped RF signal having a first pulse velocity; and the control unit is configured to: cause the power amplifier to output a pulse-shaped traveling wave power having the first pulse velocity. In the second control mode, the control unit is configured to either cause the oscillator to oscillate a pulse-shaped RF signal having a second pulse velocity lower than the first pulse velocity, or cause the oscillator to continuously oscillate the RF signal. The control unit is also configured to cause the power amplifier to output a pulse-shaped traveling wave power having the second pulse velocity or a continuous traveling wave power. The protection circuit includes a switching section and a gate control section. The conversion unit is configured to cut off the pulsed reflected wave power having the first pulse velocity, but not to cut off the pulsed reflected wave power having the second pulse velocity or the reflected wave power of the continuous wave. The gate control unit is configured to cut off the traveling wave power based on the output signal from the conversion unit.

4. The RF energy radiating device according to claim 1, wherein, After a predetermined period has elapsed since the load condition stabilizes in the first control mode, the control unit switches the operation mode to the second control mode. The control unit is configured to, after switching the operation mode from the first control mode to the second control mode, switch the operation mode from the second control mode to the first control mode according to the load state.

5. The RF energy radiating device according to claim 1, wherein, The control unit is configured to: determine the stability of the load state based on the reflected wave power, and cause the oscillator to change the pulse width and pulse period of the RF signal. The control unit is configured to change the threshold voltage used to determine the stability of the load state based on the pulse width and the pulse period.

6. The RF energy radiating device according to claim 2, wherein, The RF energy radiating device also includes a memory that stores in advance, as a lookup table, the unstable time of the load state and the elapsed stable time and operating time. The control unit is configured to change the pulse width or pulse period of the pulse-shaped RF signal oscillated by the oscillator based on the lookup table and the elapsed action time.

7. The RF energy radiating device according to claim 1, wherein, The RF energy radiating device also includes a memory that stores the frequency of the RF signal, which enables load stabilization, in advance as a lookup table, correlated with the elapsed operating time. The oscillator can change the frequency of the oscillated RF signal. The control unit is configured to change the frequency of the oscillator based on the lookup table and the elapsed action time.

8. The RF energy radiating device according to claim 1, wherein, The oscillator can change the frequency of the oscillated RF signal. The control unit determines the stability of the load state based on the output signal from the detector. The control unit is configured to change the frequency of the RF signal by the oscillator as the operation time elapses.

9. The RF energy radiating device according to claim 1, wherein, The RF energy radiating device also features: Terminator, configured to terminate the reflected wave power; and A temperature sensor configured to detect the temperature of the power amplifier and the terminator. The oscillator can change the frequency of the oscillated RF signal. The control unit is configured such that, in the first control mode, based on the temperature of the power amplifier and the terminator, the oscillator changes the pulse width or the pulse period in a manner that provides a safe region where the power amplifier and the terminator are not damaged by the reflected wave power.

10. The RF energy radiating device according to claim 1, wherein, The control unit is configured such that, in the pulse width control, the power amplifier sets the traveling wave power during the on-time to a first power level, and sets the traveling wave power during the off-time to a non-zero second power level that is smaller than the first power level.

Images