RF Energy Radiation Devices

Abstract

An RF energy radiation device according to the present disclosure comprises: an oscillator; a power amplifier; a radiation element; a detector; and a control unit. The oscillator generates oscillating RF signals. The power amplifier amplifies the RF signals, and outputs RF power. The radiation element radiates the RF power. The detector detects traveling wave power. The control unit performs output control of the RF power through closed loop control for setting an output setting value of the RF power by a closed loop and through open loop control for setting the output setting value of the RF power by an open loop. The control unit switches the output control of the RF power from the closed loop control to the open loop control when a prescribed switching condition is satisfied during output is stopped for the RF power in a burst operation in which switching is performed alternately between a period for outputting the RF power and a period for stopping the RF power.

Description

[Technical Field]

[0001] TECHNICAL FIELD This disclosure relates to RF (radio frequency) energy emitting devices. [Background technology]

[0002] For example, Patent Document 1 discloses a conventional RF energy radiating device that radiates RF energy by burst operation. Burst operation refers to radiating RF energy to an object to be heated by alternating periods during which RF power (radio frequency power) is output and periods during which the RF power is stopped.

[0003] Patent Document 2 discloses that in this type of RF energy radiating device, closed-loop control and open-loop control are used to stabilize the output level of RF power.

[0004] In closed-loop control, forward power is detected and the output level of RF power is determined according to the error between the detected forward power and the target output level, whereas in open-loop control, the output level of RF power is determined using a table prepared in advance based on the frequency of the RF power to be output, element temperature information, etc.

[0005] 10 is a schematic diagram showing the configuration of the RF energy radiating device described in Patent Document 2. As shown in FIG. 10, the conventional RF energy radiating device includes a control unit 201, an oscillator 202, a power amplifier 203, a power source 204, and a detector 220.

[0006] Oscillator 202 oscillates and outputs an RF signal. Power amplifier 203 amplifies the RF signal from oscillator 202 and outputs it as RF power. The RF power is supplied into cavity 207, and microwave-heats object 208 placed in cavity 207. Object 208 is, for example, food.

[0007] The detector 220 detects the RF signal. The control unit 201 includes a processor 205 and a memory 206. The control unit 201 receives information from the detector 220 and controls the oscillator 202 and the power amplifier 203. The power supply 204 supplies power to the control unit 201, the oscillator 202, and the power amplifier 203. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2018-142452 [Patent Document 2] Special Publication No. 2019-509587 Summary of the Invention

[0009] Fig. 11 is a diagram showing the change over time in the RF power output by power amplifier 203 and the temperature of power amplifier 203 during burst operation of the RF energy radiating device shown in Fig. 10. During burst operation, when power amplifier 203 resumes outputting RF power from a state in which its temperature has dropped, a phenomenon similar to an overshoot occurs in the output RF power.

[0010] This phenomenon occurs due to a sudden change in the junction temperature of the transistors that make up power amplifier 203. Power amplifier 203 typically has temperature characteristics in which the RF power it outputs fluctuates depending on the temperature. As a result, the RF power decreases as the temperature of power amplifier 203 rises. As a result, an overshoot appears in the RF power as shown in FIG.

[0011] In microwave heating processes where RF power output is precisely controlled, the above phenomenon affects the heating quality of the object. Therefore, when using burst operation, precision in RF power output control is important. Conventionally, when using burst operation, RF power output control is switched from closed-loop control to open-loop control. However, this method is incomplete when dealing with phenomena similar to RF power overshoot.

[0012] The present disclosure aims to improve the accuracy of RF power output control in an RF energy radiating device.

[0013] The RF energy radiating device of the present disclosure includes an oscillator, a power amplifier, a radiating element, a detector, and a control unit. The oscillator oscillates an RF signal (radio frequency signal). The power amplifier amplifies the RF signal and outputs RF power (radio frequency power). The radiating element radiates the RF power. The detector detects traveling wave power, which is the RF power directed toward the radiating element.

[0014] The control unit performs output control of RF power by closed-loop control, which sets an output set value of RF power by a closed loop, and open-loop control, which sets an output set value of RF power by an open loop.

[0015] The control unit switches the RF power output control from closed-loop control to open-loop control when a predetermined switching condition is satisfied while the RF power output is stopped during burst operation that alternates between periods when RF power is output and periods when RF power is stopped.

[0016] The RF energy radiating device of the present disclosure can control the output of RF power without being affected by the temperature rise of the heat generating element during burst operation, and can suppress RF power overshoot, thereby improving the accuracy of the RF power output control. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of an RF energy radiating device according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram illustrating a configuration of a power amplifier according to an embodiment. [Figure 3] FIG. 3 is a schematic diagram showing the arrangement of a temperature sensor, a large signal amplifier, and a terminator according to an embodiment. [Figure 4]FIG. 4 is a graph showing the change over time in the temperature rise value D(t) for different reflected wave powers. [Figure 5] FIG. 5 is a graph showing the change over time in temperature difference X(t) for different forward wave powers. [Figure 6] FIG. 6 is a diagram showing an example of a switching condition for switching the RF power output control during burst operation from closed-loop control to open-loop control. [Figure 7] FIG. 7 is a diagram showing another example of the switching conditions for switching the RF power output control during burst operation from closed-loop control to open-loop control. [Figure 8] FIG. 8 is a diagram showing temporal changes in the output setting value of RF power during a transition period after the output of RF power is resumed during burst operation. [Figure 9] FIG. 9 is a graph showing the changes over time in RF power and fan rotation speed during a transitional period after the RF power output is resumed during burst operation. [Figure 10] FIG. 10 is a schematic diagram showing the configuration of a conventional RF energy radiating device. [Figure 11] FIG. 11 is a diagram showing changes over time in RF power and temperature of the power amplifier during burst operation in the conventional RF energy radiating device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] A RF energy radiating device according to a first aspect of the present disclosure includes an oscillator, a power amplifier, a radiating element, a detector, and a control unit. The oscillator oscillates an RF signal. The power amplifier amplifies the RF signal and outputs RF power. The radiating element radiates the RF power. The detector detects forward power, which is RF power directed toward the radiating element.

[0019] The control unit performs output control of RF power by closed-loop control, which sets an output set value of RF power by a closed loop, and open-loop control, which sets an output set value of RF power by an open loop.

[0020] The control unit switches the RF power output control from closed-loop control to open-loop control when a predetermined switching condition is satisfied while the RF power output is stopped during burst operation that alternates between periods when RF power is output and periods when RF power is stopped.

[0021] This allows the output of RF power to be controlled without being affected by the temperature rise of the heating element during burst operation, and makes it possible to suppress overshoot of RF power.

[0022] In the RF energy radiating device according to the second aspect of the present disclosure, in addition to the first aspect, the predetermined switching condition is that the time during which the output of RF power is stopped exceeds a predetermined time.

[0023] According to a third aspect of the present disclosure, in addition to the first aspect, the RF energy radiating device further includes a temperature sensor configured to detect a temperature of the power amplifier, wherein the predetermined switching condition is that a change in the temperature of the power amplifier while the RF power output is stopped exceeds a predetermined value.

[0024] In the RF energy radiating device according to the fourth aspect of the present disclosure, in addition to the first aspect, the control unit applies at least one transient coefficient to the output target value of RF power determined by closed-loop control or open-loop control, thereby gradually increasing the output setting value to the output target value.

[0025] According to a fifth aspect of the present disclosure, in addition to the first aspect, the RF energy radiating device further includes a memory for storing a prepared table, and the control unit sets an output setting value of the RF power using the table in open-loop control.

[0026] In an RF energy radiating device according to a sixth aspect of the present disclosure, in addition to the first aspect, the control unit does not switch the RF power output control from closed-loop control to open-loop control even if a predetermined switching condition is satisfied, in order to generate an overshoot in the RF power during burst operation.

[0027] A seventh aspect of the present disclosure provides an RF energy radiating device according to the first aspect, further comprising: a temperature sensor for detecting the temperature of a power amplifier; and a terminator for terminating reflected power, which is RF power returning from the radiating element among forward power. The power amplifier includes a large-signal amplifier. The control unit calculates an approximation of the case temperature of the large-signal amplifier from the temperature detected by the temperature sensor based on heat generation of the terminator.

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Fig. 1 is a schematic diagram showing the configuration of an RF energy radiating device 100 according to the present embodiment.

[0029] As shown in FIG. 1, the RF energy radiating device 100 includes an oscillator 1, a power amplifier 2, a detector 3, a circulator 4, a terminator 5, a temperature sensor 6, a radiating element 7, a processor 9, and a memory 10.

[0030] Oscillator 1 includes two oscillators (oscillator 1a and oscillator 1b). Power amplifier 2 includes two power amplifiers (power amplifier 2a and power amplifier 2b). Detector 3 includes two detectors (detector 3a and detector 3b). Circulator 4 includes two circulators (circulator 4a and circulator 4b).

[0031] The terminator 5 includes two terminators (terminator 5a and terminator 5b). The temperature sensor 6 includes four temperature sensors (temperature sensor 6a, temperature sensor 6b, temperature sensor 6c, and temperature sensor 6d). The radiating element 7 includes two radiating elements (radiating element 7a and radiating element 7b).

[0032] Each of the oscillators 1a and 1b oscillates and outputs an RF signal. Each of the power amplifiers 2a and 2b amplifies the RF signals output by the oscillators 1a and 1b and outputs the amplified signals as forward power. Each of the detectors 3a and 3b detects the forward power and the reflected power.

[0033] The forward power refers to the RF power traveling from the power amplifiers 2a and 2b to the radiating elements 7a and 7b via the circulators 4a and 4b, respectively. The reflected power refers to the RF power of the forward power that returns from the radiating elements 7a and 7b to the circulators 4a and 4b, respectively.

[0034] The circulators 4a and 4b fix the paths of the forward and reflected power, protecting the power amplifiers 2a and 2b from reflected power that fluctuates depending on the load fluctuation of the object being heated. The terminators 5a and 5b each have a specific impedance that acts as a load for the reflected power from the circulators 4a and 4b.

[0035] Radiating element 7a radiates RF energy transmitted from power amplifier 2a via circulator 4a into cavity 8. Radiating element 7b radiates RF energy transmitted from power amplifier 2b via circulator 4b into cavity 8.

[0036] Temperature sensors 6a and 6b are arranged near power amplifiers 2a and 2b, respectively, to detect the temperatures of power amplifiers 2a and 2b. Temperature sensors 6c and 6d are arranged near terminators 5a and 5b, respectively, to detect the temperatures of terminators 5a and 5b.

[0037] The memory 10 is, for example, a semiconductor memory that stores software and data for controlling the RF energy radiating device 100. The data stored in the memory 10 includes a look-up table that is prepared in advance to set RF power appropriate for the temperatures detected by the temperature sensors 6a to 6d.

[0038] The processor 9 is a general-purpose microprocessor that functions as a control unit for controlling the RF energy radiating device 100. The processor 9 controls the oscillators 1a and 1b and the power amplifiers 2a and 2b by software in accordance with the temperatures detected by the temperature sensors 6a to 6d.

[0039] In this embodiment, processor 9 can refer to the temperatures detected by each of temperature sensors 6a-6d, for example, 50 times per second. Processor 9 can output instructions to oscillators 1a, 1b and power amplifiers 2a, 2b in accordance with those temperatures, for example, 50 times per second. That is, the software control period (hereinafter referred to as the control period) in processor 9 is 20 ms.

[0040] FIG. 2 is a schematic diagram showing the configuration of each of the power amplifiers 2a and 2b. The power amplifiers 2a and 2b have the same configuration. Therefore, only the power amplifier 2a will be described. As shown in FIG. 2, the power amplifier 2a includes a variable attenuator 41, a small-signal amplifier 42, and a large-signal amplifier 43.

[0041] Variable attenuator 41 receives the RF signal from oscillator 1a and adjusts the amount of attenuation for the RF signal. Small signal amplifier 42 amplifies the signal output by variable attenuator 41 to a certain extent. Large signal amplifier 43 amplifies the signal output by small signal amplifier 42 to an output level of the desired RF power.

[0042] The processor 9 controls the oscillators 1a and 1b to generate RF signals having any frequency within a predetermined frequency band, and controls the power amplifiers 2a and 2b to amplify the RF signals from the oscillators 1a and 1b, respectively, so that the output level of the RF power reaches the target output value.

[0043] When controlling the output of RF power by open-loop control, the processor 9 calculates the target output value of RF power based on a look-up table prepared in advance and taking into account the temperature conditions at that time.

[0044] The power amplifiers 2a and 2b are heat generating elements. The values ​​of RF power (traveling wave power) and Efficiency due to load fluctuationsThe heat generation of the power amplifiers 2a and 2b fluctuates in response to changes in the temperature. The processor 9 controls the RF power output using closed-loop control or open-loop control. This output control is performed based on temperature information detected by the temperature sensors 6a and 6b, and the forward and reflected power detected by the detectors 3a and 3b.

[0045] Temperature sensors 6a and 6b are arranged to detect the case temperatures of large signal amplifiers 43 in power amplifiers 2a and 2b, respectively, for the following reason: the case temperature means the surface temperature of a semiconductor device.

[0046] A thermal resistance occurs between temperature sensor 6 and large signal amplifier 43. The magnitude of the thermal resistance is related to the value of the output RF power, the cooling air for power amplifiers 2a and 2b, and whether RF power is being output or not. This thermal resistance affects whether the temperature detected by temperature sensor 6 is close to the case temperature of large signal amplifier 43.

[0047] Therefore, in order to minimize errors in the detected temperature due to thermal resistance, it is desirable that the temperature sensors 6a and 6b be located near the power amplifiers 2a and 2b, respectively.

[0048] When RF power is supplied into the cavity 8 by the radiating elements 7a and 7b and radiated to the object to be heated, the state of the object to be heated changes, and the reflected wave power fluctuates according to the heating state.

[0049] Terminators 5a and 5b are connected to the detectors 3a and 3b. The terminators 5a and 5b convert the reflected wave power into heat. That is, the RF energy radiating device 100 has the terminators 5a and 5b as heat generating elements in addition to the large signal amplifier 43.

[0050] The reflected power affects the calculated value of the case temperature of the large signal amplifier 43 calculated by the processor 9. The processor 9 calculates the effect of the amount of heat generated in the terminators 5a and 5b according to the value of the reflected power. This allows the processor 9 to accurately approximate the case temperature from the temperatures detected by the temperature sensors 6a and 6b.

[0051] 3 is a schematic diagram showing the arrangement of temperature sensors 6a and 6b, large signal amplifier 43, and terminators 5a and 5b on substrate 31. As shown in FIG. 3, for example, assume that temperature sensor 6a or 6b, large signal amplifier 43 of power amplifier 2a or 2b, and terminator 5a or 5b are arranged in the positional relationship shown in FIG. 3. Substrate 31 has holes 32 penetrating base plate 33. Temperature sensors 6a and 6b are arranged in holes 32.

[0052] Here, let X(t) be the temperature difference between the actual case temperature of large signal amplifier 43 and the temperature K detected by temperature sensors 6a and 6b during the transient period. Let D(t) be the temperature rise of large signal amplifier 43 due to the heat generated by terminators 5a and 5b during the transient period when the reflected power is high. The transient period is the period after the RF power output resumes during burst operation, during which the heat flow between the positions of temperature sensors 6a and 6b and the position of large signal amplifier 43 reaches a steady state.

[0053] Fig. 4 is a graph showing the change over time in temperature rise D(t) for different reflected wave powers. As shown in Fig. 4, the greater the reflected wave power, the greater the temperature rise D(t). Fig. 5 is a graph showing the change over time in temperature difference X(t) for different RF powers (forward wave powers). As shown in Fig. 5, the greater the RF power (forward wave power), the greater the temperature difference X(t).

[0054] The processor 9 calculates an approximate value of the case temperature of the large signal amplifier 43 based on the approximate formula for the temperature difference X(t) shown in FIG. 5, the approximate formula for the temperature rise value D(t) shown in FIG. 4, and the temperatures detected by the temperature sensors 6a and 6b, as follows:

[0055] Approximate case temperature ≒ X(t) + K (when reflected wave power is small) Approximate case temperature = X(t) + D(t) + K (when reflected power is large) The processor 9 may correct the temperatures detected by the temperature sensors 6a and 6b, respectively, taking into account the temperatures detected by the temperature sensors 6c and 6d located near the terminators 5a and 5b. By improving the accuracy of the approximation of the case temperature, the accuracy of the output control of the RF power output during the closed loop is improved.

[0056] That is, processor 9 considers the effect of heat generation from terminators 5a and 5b on the temperatures detected by temperature sensors 6a and 6b during both the transient and steady states of RF power output operation, and thereby calculates an approximation of the case temperature of large signal amplifier 43 from the temperatures detected by temperature sensors 6a and 6b.

[0057] Hereinafter, when simply referred to as temperature, the temperature refers to an approximation of the case temperature of large signal amplifier 43. Therefore, a temperature change refers to a change in the approximation of the case temperature.

[0058] In burst operation, processor 9 optimally switches the RF power output control between closed-loop control and open-loop control, thereby suppressing overshoot of the output RF power and improving the accuracy of RF power output control in burst operation.

[0059] Fig. 6 is a diagram showing an example of a switching condition for switching the RF power output control during burst operation from closed-loop control to open-loop control. As shown in Fig. 6, the processor 9 sets the RF power output control to either closed-loop control or open-loop control based on a comparison between the temperature To when the RF power output is stopped and the temperature Tr when the RF power output is resumed.

[0060] Specifically, if the temperature change (Tr-To) during the halt of RF power output in burst operation exceeds a predetermined threshold, the processor 9 switches the RF power output control from closed-loop control to open-loop control and resumes the burst operation.

[0061] If the temperature change (Tr-To) is equal to or less than a predetermined threshold, the processor 9 continues the closed-loop control and resumes the burst operation. That is, the predetermined switching condition in this case is that the temperature change during the period when the RF power output is stopped exceeds a predetermined temperature range.

[0062] When the temperature change (Tr-To) exceeds a predetermined threshold, the processor 9 sets the RF power output using a lookup table as an initial setting when the burst operation is resumed. From the second control cycle onward after the RF power output is resumed, the processor 9 switches the RF power output control from open-loop control to closed-loop control as appropriate.

[0063] 7 is a diagram showing another example of a switching condition for switching the RF power output control during burst operation from closed-loop control to open-loop control. As shown in FIG. 7, the processor 9 may switch the RF power output control from closed-loop control to open-loop control according to the output stop time. The output stop time is the time from when the RF power output is stopped to when the output is resumed, that is, the time during which the RF power output is stopped during burst operation.

[0064] It is not appropriate to use the RF power output target value obtained by closed-loop control during the transition period after the RF power output is resumed, because if large signal amplifier 43 is stopped for a certain period of time, the temperature of large signal amplifier 43 will drop significantly (see FIG. 11).

[0065] Therefore, when the output stop time exceeds a predetermined time width, the processor 9 switches the RF power output control from closed-loop control to open-loop control using a look-up table stored in the memory 10 before restarting the RF power output. This makes it possible to suppress the RF power overshoot shown in FIG.

[0066] From the second control cycle onward after the RF power output is resumed, the processor 9 switches the RF power output control from open-loop control to closed-loop control as appropriate. That is, the predetermined switching condition in this case is that the output stop time exceeds a predetermined time width.

[0067] In this way, in order to suppress overshoot, the processor 9 switches between closed-loop control and open-loop control. In addition, in this embodiment, the processor 9 operates the power amplifiers 2a and 2b as follows during the transition period after the RF power output is resumed.

[0068] FIG. 8 is a diagram showing temporal changes in the output setting value of RF power during a transition period after the output of RF power is resumed during burst operation.

[0069] 8, first, processor 9 determines the output target value of RF power. Processor 9 subtracts a transient coefficient from the output target value to set the output setting value of RF power to a value smaller than the output target value of RF power.

[0070] Thereafter, the processor 9 increases the output setting value of the RF power stepwise at predetermined intervals up to the output target value, until the output setting value of the RF power finally reaches the output target value. 8 As shown in FIG. 1, the predetermined period is, for example, a control cycle in software control of the processor 9.

[0071] As an example, as shown below, the processor 9 applies at least one transient coefficient to the output target value of the RF power to set the output setting value after the output of the RF signal is resumed.

[0072] Set value Bu(tn) = Target value T(tn) - Transient coefficient C(tn) Here, tn is the nth control cycle. The set value Bu(tn) is the RF power output set value for the control cycle tn. The target value T(tn) is the RF power output target value for the control cycle tn, calculated by closed-loop control or open-loop control.

[0073] The transient coefficient C(tn) is a value for setting the set value Bu(tn) to a value lower than the target value T(tn) during a transient period. The set value Bu(tn), the target value T(tn), and the transient coefficient C(tn) are dimensionless values ​​set within the processor 9.

[0074] In this way, processor 9 applies at least one transient coefficient to the target value of RF power output, thereby causing the set value of RF power output to reach the target value of RF power output in stages after a predetermined period of time has elapsed.

[0075] By gradually increasing the RF power output setting, the overshoot that occurs during the transient period after RF power output is resumed during burst operation is suppressed. This improves the accuracy of RF power output control for not only the average power during burst operation but also the peak power. As a result, optimal heating of the heating target can be achieved.

[0076] As described above, improving the approximation accuracy of the case temperature improves the accuracy of RF power output control by closed-loop control. Furthermore, by combining this with the method for setting the RF power output setting value shown in Figure 8, RF power overshoot can be suppressed, further improving the accuracy of RF power output control during burst operation.

[0077] The above-described RF power output control can suppress RF power overshoot. Conversely, if burst operation is performed without using the above-described output control, overshoot occurs in the output RF power.

[0078] That is, the processor 9 can adjust the magnitude of the overshoot of the RF power during burst operation by controlling the timing at which the output control of the RF power is switched between closed-loop control and open-loop control.

[0079] Figure 9 is a graph showing the changes over time in RF power and fan rotation speed during the transient period after the RF power output is resumed during burst operation. The junction temperature of large signal amplifier 43 rises rapidly after the operation of large signal amplifier 43 is resumed. As a result, an overshoot occurs in the output RF power, as shown in Figure 9. By utilizing this overshoot, it is possible to generate a peak output level for the RF power for a very short period of time.

[0080] That is, processor 9 does not intentionally perform control to suppress overshoot that occurs during the transient period of burst operation. Instead, processor 9 controls the peak output level of RF power to utilize the overshoot as an effect on heating.

[0081] Such short burst operation is particularly effective when microwave heating is not performed on the object to be heated. In other words, by emitting RF energy that does not affect the state of the object to be heated, the state of the object to be heated can be detected in real time. In this case, it is necessary to radiate a certain amount of RF energy with shorter pulses.

[0082] As described above, the junction temperature of large signal amplifier 43 rises rapidly when large signal amplifier 43 resumes operation. Accordingly, the temperature difference X(t) rises rapidly, as shown in Figure 5. The approximate curve shown in Figure 5 depends on the heat dissipation design of large signal amplifier 43, including the airflow rate of the fan. Depending on the selected device and heat dissipation design, it is possible to obtain a curve that shows the change in junction temperature over time, and to find its approximate formula.

[0083] As described above, large signal amplifier 43 has temperature characteristics in which the output RF power fluctuates depending on the temperature. By relating the approximate equation for the temperature rise during the transient period to the output RF power, it is possible to generate an overshoot in the output RF power during the transient period after large signal amplifier 43 resumes operation.

[0084] The processor 9 may control the airflow rate of the blower fan in accordance with the RF power output time, the RF power output level, and the temperature of the device, taking into consideration the safety and efficiency of the entire system. In this case, the processor 9 can estimate the instantaneous peak output level of the RF power by, for example, taking into consideration factors related to the airflow rate of the blower fan in an approximation equation for various conditions obtained from actual data.

[0085] 9, the processor 9 controls the blower fan to increase the airflow rate when RF power is stopped and to decrease the airflow rate when RF power is output, thereby enabling the RF power to momentarily generate a high peak output level.

[0086] When using hardware such as ASICs (application-specific integrated circuits) and FPGAs (field-programmable gate arrays), RF power output control can be performed at a shorter control period than software control. However, in this case, the cost of the hardware circuitry accounts for a larger proportion of the total material cost. Furthermore, high development costs are also required. Therefore, it is difficult to use hardware-controlled RF energy radiating devices in, for example, consumer heating devices and consumer medical devices.

[0087] When burst operation is performed by software control using a general-purpose processor rather than dedicated hardware, the control period depends on the processor's performance. The control period corresponds to the period during which the RF power output setting can be changed.

[0088] For example, for a 32-bit processor with an operating frequency of about 200 MHz, the control period is approximately 20 ms. This is a reference value for a complex heating algorithm. As shown in Figure 8, by deliberately generating an overshoot in the output RF power, it is possible to generate RF power with a peak output level for a period shorter than the control period.

[0089] White goods often use 8-bit microcomputers, which means the control cycle becomes even longer. However, by utilizing the overshoot that occurs in the output RF power, it is possible to output RF power with a shorter peak time. In addition, by detecting the heating state of the object to be heated in real time, it is possible to maintain the same heating state. [Industrial Applicability]

[0090] As described above, the RF energy radiating device according to the present disclosure is applicable to commercial heating devices that require high accuracy in controlling the output of RF power. [Explanation of symbols]

[0091] 1, 1a, 1b oscillators 2, 2a, 2b power amplifier 3, 3a, 3b detector 4, 4a, 4b Circulator 5, 5a, 5b terminator 6, 6a, 6b, 6c, 6d Temperature Sensors 7, 7a, 7b Radiating elements 8 cavities 9 processors 10. Memory 31 PCB 32 holes 33 Base Plate 41 Variable Attenuator 42 Small Signal Amplifier 43 Large Signal Amplifier 100 RF energy radiating devices 201 Control Unit 202 Oscillator 203 Power Amplifier 204 Power supply 205 processors 206 memory 207 Cavity 208 Heating object 220 detector

Claims

1. an oscillator configured to generate an RF signal; a power amplifier configured to amplify the RF signal to output RF power; a radiating element configured to radiate the RF power; a detector configured to detect forward power, the RF power being directed toward the radiating element; a control unit configured to perform output control of the RF power by closed-loop control that sets an output setting value of the RF power in accordance with an error between the forward wave power detected by the detector and an output target value, and open-loop control that sets the output setting value of the RF power by an open loop; the control unit switches the output control of the RF power from the closed-loop control to the open-loop control when a predetermined switching condition is satisfied while the output of the RF power is stopped during burst operation in which a period in which the RF power is output and a period in which the RF power is stopped are alternately switched.

2. 2. The RF energy emitting device of claim 1, wherein the predetermined switching condition is that the time during which the RF power output is stopped exceeds a predetermined time.

3. a temperature sensor configured to detect a temperature of the power amplifier; 2. The RF energy emitting device of claim 1, wherein the predetermined switching condition is that a change in the temperature during the period when the RF power output is stopped exceeds a predetermined value.

4. The control unit setting the power setting value set by the closed-loop control or the open-loop control to a value less than the predetermined power target value of the RF power by subtracting at least one transient coefficient from the predetermined power target value; 2. The RF energy emitting device of claim 1, wherein the power setting of the RF power is increased in steps until the power setting matches the target power value.

5. further comprising a memory for storing a table prepared in advance; 2. The RF energy radiating device according to claim 1, wherein the control unit uses the table in the open-loop control to set the output setting value of the RF power.

6. 2. The RF energy radiating device of claim 1, wherein the control unit does not switch the output control of the RF power from the closed-loop control to the open-loop control even if the predetermined switching condition is satisfied in order to generate an overshoot in the RF power in the burst operation.

7. a temperature sensor configured to detect a temperature of the power amplifier; a terminator configured to terminate reflected power, which is the RF power returning from the radiating element, of the forward power; the power amplifier includes a large signal amplifier; 2. The RF energy radiation device according to claim 1, wherein the control unit calculates an approximation of the case temperature of the large signal amplifier from the temperature detected by the temperature sensor based on heat generation in the terminator.

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