RF energy emitting device

Abstract

An RF energy radiating apparatus includes a chamber for placing a heating object, an RF signal generating section, an RF amplifying section, a radiating element, a temperature sensor, and a control section. The RF signal generating section oscillates an RF signal. The RF amplifying section amplifies the RF signal and outputs RF energy. The radiating element radiates the RF energy into the chamber. The temperature sensor is disposed in the vicinity of the RF amplifying section. The control section controls the RF amplifying section to adjust the output of the RF energy in accordance with a detected temperature of the temperature sensor and a plurality of threshold levels. According to the present mode, the reliability of the apparatus can be improved.

Description

[0001] This application is a divisional application of the invention patent application entitled "RF Energy Emission Device", filed on September 5, 2019, with application number 201980048574.7 (international application number PCT / JP2019 / 034935). Technical Field

[0002] This disclosure relates to improving the reliability of RF energy radiating devices. Background Technology

[0003] Conventional RF (Radio Frequency) energy radiating devices, such as microwave ovens, detect reflected wave power and adjust output power accordingly, stopping output when the reflected wave power exceeds a predetermined value. Thus, existing RF energy radiating devices have their own protection mechanisms (see, for example, Patent Document 1). Patent Document 2 discloses a technology that, in addition to detecting reflected wave power, also detects high-frequency current, thereby improving the device's protective capabilities.

[0004] Figure 7 This refers to the existing RF energy emitting device described in Patent Document 1. For example... Figure 7 As shown, the existing RF energy emission device includes a magnetron 1, a control unit 6, and a detection unit 5.

[0005] Control unit 6 controls drive unit 7. When drive unit 7 supplies power to magnetron 1, magnetron 1 generates microwaves. Waveguide 2 transmits the microwaves to power supply unit 4. Power supply unit 4 radiates microwaves into cavity 3.

[0006] The detection unit 5 detects the power of the reflected wave returning from the chamber 3 to the waveguide 2 via the power supply unit 4. The control unit 6 controls the drive unit 7 based on the power of the reflected wave detected by the detection unit 5.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 4-245191

[0010] Patent Document 2: Japanese Patent Application Publication No. 2-087929 Summary of the Invention

[0011] In existing RF energy radiating devices, 30% to 50% of the consumed energy is released as heat, depending on the energy efficiency of the semiconductor amplifier. This energy efficiency varies depending on the load and ambient temperature, and the amount of heat released also varies. The relationship between heat generation and efficiency is a major issue in the use of semiconductor amplifiers. Terminators that receive reflected wave power absorb the reflected power and generate heat. Therefore, simply detecting reflected power and high-frequency current may not be sufficient to effectively protect the device.

[0012] The present invention is proposed to solve the aforementioned existing problems, and its purpose is to provide a highly reliable RF energy radiating device.

[0013] One aspect of the RF energy radiating device of the present invention includes a chamber for placing a heated object, an RF signal generating unit, an RF amplifying unit, a radiating element, a temperature sensor, and a control unit. The RF signal generating unit oscillates an RF signal. The RF amplifying unit amplifies the RF signal and outputs RF energy. The radiating element radiates RF energy into the chamber. The temperature sensor is disposed near the RF amplifying unit. The control unit controls the RF amplifying unit to adjust the RF energy output based on the temperature detected by the temperature sensor and multiple threshold levels.

[0014] This RF energy radiating device adjusts the RF energy by monitoring the temperature of the heating element, thereby efficiently radiating RF energy to the object being heated. Furthermore, by monitoring the temperature of the heating element, this RF energy radiating device can detect installation malfunctions and instantly stop the device. As a result, the reliability of the device is improved. Attached Figure Description

[0015] Figure 1 This is a block diagram illustrating the structure of an RF energy radiating device according to an embodiment of the present disclosure.

[0016] Figure 2 This is a block diagram illustrating the structure of the power amplifier in the embodiment.

[0017] Figure 3 This is a diagram showing the operating sequence of the RF energy radiating device in the embodiment.

[0018] Figure 4 It is a characteristic graph showing the two temperature rise lines of the object to be heated in the embodiment.

[0019] Figure 5 This is a cross-sectional view showing an installation configuration of the temperature sensor.

[0020] Figure 6 This is a cross-sectional view showing other mounting configurations of the temperature sensor.

[0021] Figure 7This is a block diagram representing the structure of an existing RF energy radiating device.

[0022] Label Explanation

[0023] 100RF: Energy emission device; 101a, 101b: Oscillators; 102a, 102b: Power amplifiers; 103a, 103b: Detectors; 104a, 104b: Circulators; 105a, 105b: Terminators; 106a, 106b, 106c, 106d: Temperature sensors; 107a, 107b: Emission elements; 108: Chamber; 109: Microprocessor; 110: Protection circuit; 201: Substrate; 202: Semiconductor element; 203: Base plate; 204: Through hole; 301: Variable attenuator; 302: Small signal amplifier; 303: Large signal amplifier. Detailed Implementation

[0024] The first aspect of the RF energy radiating device disclosed herein includes a chamber for placing a heated object, an RF signal generating unit, an RF amplifying unit, a radiating element, a temperature sensor, and a control unit. The RF signal generating unit oscillates an RF signal. The RF amplifying unit amplifies the RF signal and outputs RF energy. The radiating element radiates RF energy into the chamber. The temperature sensor is disposed near the RF amplifying unit. The control unit controls the RF amplifying unit to adjust the RF energy output based on the temperature detected by the temperature sensor and multiple threshold levels.

[0025] In the second aspect of the RF energy radiating device disclosed herein, based on the first aspect, if the temperature detected by the temperature sensor exceeds one of a plurality of threshold levels, the control unit controls the RF amplification unit to adjust the output value of the RF energy according to the temperature exceeding the threshold level.

[0026] In the third-party RF energy radiating device disclosed herein, based on the second approach, when the detected temperature by the temperature sensor exceeds another threshold level higher than the first threshold level, the control unit controls the RF amplification unit to reduce the output value of the RF energy.

[0027] In the fourth type of RF energy radiating device disclosed herein, based on the third type, the additional threshold level varies according to the rate of increase of the temperature detected by the temperature sensor.

[0028] In the fifth aspect of the RF energy radiating device disclosed herein, based on the second aspect, when the temperature detected by the temperature sensor exceeds another threshold level higher than the first threshold level, the control unit stops the RF signal generating unit.

[0029] In the sixth aspect of the RF energy emitting device disclosed herein, based on the first aspect, multiple threshold levels include a first threshold level, a second threshold level higher than the first threshold level, and a third threshold level higher than the second threshold level. When the temperature detected by the temperature sensor exceeds the first threshold level, the control unit controls the RF amplification unit to adjust the RF energy output according to the temperature exceeding the first threshold level. When the temperature detected by the temperature sensor exceeds the second threshold level, the control unit controls the RF amplification unit to reduce the RF energy output. When the temperature detected by the temperature sensor exceeds the third threshold level, the control unit stops the RF signal generation unit.

[0030] In the RF energy radiating device of the seventh aspect of this disclosure, based on the sixth aspect, the second threshold level varies according to the rate of increase of the temperature detected by the temperature sensor.

[0031] In the eighth aspect of the RF energy radiating device disclosed herein, based on the first aspect, a semiconductor element including an RF amplification section is disposed on a substrate such that the bottom of the semiconductor element contacts a base plate. A temperature sensor is disposed on the side of the substrate opposite to the side where the semiconductor element is disposed.

[0032] In the ninth aspect of the RF energy emitting device disclosed herein, based on the first aspect, a semiconductor element including an RF amplification section is disposed on a substrate such that the bottom of the semiconductor element contacts a base plate. A temperature sensor is disposed on the same side of the substrate as the side on which the semiconductor element is disposed.

[0033] Hereinafter, the RF energy emitting device 100 of the present disclosure will be described with reference to the accompanying drawings.

[0034] Figure 1 This is a block diagram showing the structure of the RF energy radiating device 100. Figure 2 This is a block diagram showing the structure of power amplifier 102a. Power amplifiers 102a and 102b have the same structure. Therefore, only power amplifier 102a will be described in detail, while the detailed description of power amplifier 102b will be omitted.

[0035] like Figure 1 As shown, the RF energy emitting device 100 includes oscillators 101a and 101b, power amplifiers 102a and 102b, detectors 103a and 103b, circulators 104a and 104b, terminators 105a and 105b, emitting elements 107a and 107b, and a chamber 108.

[0036] Oscillators 101a and 101b oscillate to generate RF signals. Power amplifiers 102a and 102b amplify the RF signals oscillated by oscillators 101a and 101b, respectively, to output RF power. Detectors 103a and 103b detect the RF power transmitted from the RF energy radiating device 100 to the radiating elements 107a and 107b, and the RF power transmitted from the radiating elements 107a and 107b to the RF energy radiating device 100.

[0037] Oscillators 101a and 101b are equivalent to RF signal generation units, power amplifiers 102a and 102b are equivalent to RF amplification units, and detectors 103a and 103b are equivalent to RF power detection units.

[0038] Hereinafter, the RF power transmitted from the RF energy radiating device 100 to the radiating elements 107a and 107b is called a traveling wave, and the RF power transmitted from the radiating elements 107a and 107b to the RF energy radiating device 100 is called a reflected wave.

[0039] Circulator 104a transmits the traveling wave from oscillator 101a to radiating element 107a, and transmits the reflected wave from radiating element 107a to terminal 105a. Similarly, circulator 104b transmits the traveling wave from oscillator 101b to radiating element 107b, and transmits the reflected wave from radiating element 107b to terminal 105b.

[0040] Terminators 105a and 105b have impedances that serve as loads for reflected waves from circulators 104a and 104b, respectively.

[0041] Circulators 104a and 104b, and terminators 105a and 105b protect oscillators 101a and 101b from reflected waves generated by load variations of the heated object (e.g., food) placed in chamber 108. Radiating elements 107a and 107b radiate RF energy into chamber 108.

[0042] The RF energy emitting device 100 also includes temperature sensors 106a, 106b, 106c, and 106d, a microprocessor 109, and a protection circuit 110.

[0043] Temperature sensors 106a to 106d are respectively disposed near power amplifiers 102a and 102b, and terminators 105a and 105b. Microprocessor 109 controls the control unit of the RF energy radiating device 100 based on the temperatures detected by temperature sensors 106a to 106d. Protection circuit 110 operates to protect the RF energy radiating device 100 if the detected temperatures by temperature sensors 106a to 106d exceed a predetermined value.

[0044] like Figure 2 As shown, the power amplifier 102a (102b) includes a variable attenuator 301, a small-signal amplifier 302, and a large-signal amplifier 303.

[0045] The variable attenuator 301 receives the RF signal from the oscillator 101a and adjusts the attenuation for the RF signal. The small-signal amplifier 302 amplifies the signal output from the variable attenuator 301 to a certain extent. The large-signal amplifier 303 amplifies the signal output from the small-signal amplifier 302 to the desired RF energy output value.

[0046] use Figure 3 , Figure 4 Explain the operation and function of the RF energy radiating device 100 constructed as described above. Figure 3 This is a diagram showing the sequence of operations in the RF energy radiating device 100. Figure 4 This is a characteristic graph representing the two temperature rise lines of the object to be heated in this embodiment.

[0047] Microprocessor 109 controls oscillators 101a and 101b to oscillate RF signals of arbitrary frequencies. Microprocessor 109 controls power amplifiers 102a and 102b to make the RF energy output reach the target value. The RF energy output is adjusted towards the initial target value by adjusting the attenuation of variable attenuator 301.

[0048] Regarding the traveling wave, the microprocessor 109 adjusts the attenuation of the variable attenuator 301 based on the power values ​​detected by the detectors 103a and 103b, so that the amount of RF energy remains stable even during operation.

[0049] Regarding the reflected wave, if at least one of the temperatures detected by temperature sensors 106a and 106b exceeds a first threshold level, in order to reduce the radiated heat from the heat-generating component equivalent to the temperature exceeding the first threshold level, the microprocessor 109 controls the power amplifiers 102a and 102b to reduce the output of RF energy.

[0050] If the power value detected by detectors 103a and 103b exceeds the allowable level, the protection circuit 110 will momentarily stop the RF energy radiating device 100 via hardware to protect the RF energy radiating device 100. The protection circuit 110 will report the stopping of the RF energy radiating device 100 to the microprocessor 109.

[0051] Terminals 105a and 105b are heat-generating components that receive reflected waves. The temperature rise in terminals 105a and 105b is significant.

[0052] Due to the change in load caused by the change in the physical properties of the object being heated during heating, and the rise in ambient temperature within the RF energy radiating device 100, the efficiency of the large signal amplifier 303 decreases. Consequently, the heat generated by the large signal amplifier 303 increases, and the detection temperature of the temperature sensors 106a and 106b rises.

[0053] Microprocessor 109 storage Figure 3 The first threshold level (e.g., 85°C), the second threshold level (e.g., 115°C), and the third threshold level (e.g., 120°C) are shown. Furthermore, because the small-signal amplifier 302 has low output power, the temperature rise due to heat generation is minimal. Therefore, the temperature rise of the power amplifiers 102a and 102b is mostly caused by the large-signal amplifier 303.

[0054] When at least one of the temperatures detected by temperature sensors 106a and 106b exceeds a first threshold level, in order to reduce the radiated heat from the heat-generating components equivalent to the exceeded temperature, the microprocessor 109 finely controls the attenuation amount D (dB) of the variable attenuator 301 via software control to reduce the output value of RF energy. For example, if a semiconductor thermal resistance is used as in equation (1), the attenuation amount D can be calculated. Thus, it is possible to prevent the temperature rise of the power amplifiers 102a and 102b.

[0055] D = 10 × log 10 P det -10×log 10 (P det -P down (1)

[0056] P det (W): Power value of the traveling wave

[0057] P down (W):(Detection temperature (°C) - 85 (°C)) × 1 / Z

[0058] Z (°C / W): Semiconductor thermal resistance between the junction and the housing

[0059] When the ambient temperature rises significantly and exceeds the second threshold level, the microprocessor 109 controls the variable attenuator 301 to significantly reduce the output value of RF energy in order to reduce the temperature significantly.

[0060] Figure 4 This indicates how the second threshold level changes based on the rate of temperature rise detected by temperature sensors 10⁶a to 10⁶d. For example... Figure 4 As shown, when the temperature rises rapidly, the temperature rise value in one cycle controlled by the software is large.

[0061] Therefore, when the temperature rises rapidly, the second threshold level is set lower compared to when the temperature rises slowly. This allows the RF energy output to be reduced before the temperature becomes too high within one cycle of software control.

[0062] Taking into account the rate of temperature rise detected by temperature sensors 106a to 106d and the response time (latency) when the output of RF energy is stopped by hardware, the second threshold level is automatically set to a level that can prevent the device from stopping due to hardware.

[0063] When poor installation, such as solder cracks, causes a rapid rise in temperature that exceeds the third threshold level, the protection circuit 110 uses hardware to instantly stop the RF energy radiating device 100 to protect it.

[0064] As described above, in this embodiment, temperature sensors 106a to 106d are respectively disposed near the power amplifiers 102a and 102b, and the terminators 105a and 105b. By monitoring the temperature of these heat-generating components and controlling the output value of RF energy, the temperature rise of the power amplifiers 102a and 102b, and the terminators 105a and 105b can be suppressed. As a result, the service life of the device can be extended.

[0065] Figure 5 This is a cross-sectional view showing an installation configuration of the temperature sensor 106a.

[0066] The mounting structure of temperature sensor 106a will be described here. The mounting structures of temperature sensors 106b to 106d are the same as those of temperature sensor 106a, so their descriptions are omitted.

[0067] like Figure 5 As shown, in this mounting configuration, the semiconductor element 202, which includes the large-signal amplifier 303, is disposed on the substrate 201 such that the bottom of the semiconductor element 202 contacts the base plate 203. The temperature sensor 106a is disposed on the side of the substrate 201 opposite to the side on which the semiconductor element 202 is disposed.

[0068] Temperature sensor 106a is disposed on the soldering surface of substrate 201 and contacts base plate 203 made of a material with high thermal conductivity, such as copper or aluminum. That is, temperature sensor 106a is disposed at a location with low thermal resistance between the heat-generating part (bottom) of semiconductor element 202 and the temperature sensor 106a.

[0069] This mounting configuration allows for the detection of temperatures close to the actual temperature of the heating element. Due to its low thermal resistance, temperature calibration is also easy. As a result, temperature can be detected with high accuracy and excellent responsiveness.

[0070] Figure 6 This is a cross-sectional view showing other mounting configurations of the temperature sensor 106a. (e.g.) Figure 6 As shown, in this installation configuration, with Figure 5 Similarly, in the mounting configuration, the semiconductor element 202, including the large-signal amplifier 303, is disposed on the substrate 201 such that the bottom of the semiconductor element 202 contacts the base plate 203. Figure 5 The mounting structure is different; the temperature sensor 106a is disposed on the same surface of the substrate 201 as the surface on which the semiconductor element 202 is disposed. A through hole 204 is provided near the semiconductor element 202 on the substrate 201.

[0071] According to this installation configuration, and Figure 5 Similarly, the installation structure allows for the detection of temperatures close to the actual temperature of the heating element. This enables high-precision control of the RF energy emission device 100.

[0072] Industrial availability

[0073] The RF energy radiating device disclosed herein can be applied to defrosting machines, heating and cooking machines, drying devices, etc.

Claims

1. An RF energy radiating device, comprising: A chamber, configured to hold an object to be heated; The RF signal generating unit is configured to oscillate and generate an RF signal. An RF amplifier section is configured to amplify the RF signal and output RF energy. A radiating element configured to radiate the RF energy into the cavity; A detector that detects the power transmitted from the RF amplifier to the radiating element; A temperature sensor is disposed near the RF amplifier section; as well as The control unit is configured to control the RF amplification unit to adjust the output value of the RF energy based on the power value detected by the detector, the temperature detected by the temperature sensor, and multiple threshold levels. When the detected temperature of the temperature sensor exceeds the lowest threshold level among the plurality of threshold levels, the control unit, through software control, adjusts the output value of the RF energy based on the power value detected by the detector and the detected temperature of the temperature sensor to reduce the output value of the RF energy. When the detected temperature of the temperature sensor exceeds the highest threshold level among the plurality of threshold levels, the control unit stops the output of the RF energy.

2. The RF energy radiating device according to claim 1, wherein, The RF energy radiating device also has a protection circuit. The RF amplification section has a variable attenuator. The control unit is configured to control the attenuation of the variable attenuator via software control, thereby adjusting the output value of the RF energy. The protection circuit is configured to stop the output of the RF energy via hardware.

3. The RF energy radiating device according to claim 1, wherein, The plurality of threshold levels includes a first threshold level, a second threshold level higher than the first threshold level, and a third threshold level higher than the second threshold level. When the detected temperature by the temperature sensor exceeds the first threshold level, the control unit controls the RF amplification unit to adjust the output value of the RF energy according to the temperature exceeding the first threshold level. When the detected temperature by the temperature sensor exceeds the second threshold level, the control unit controls the RF amplifier to reduce the output of the RF energy. When the detected temperature of the temperature sensor exceeds the third threshold level, the control unit stops the RF signal generation unit.

4. The RF energy radiating device according to claim 3, wherein, The second threshold level varies according to the rate of increase of the detected temperature by the temperature sensor.

5. The RF energy radiating device according to any one of claims 1 to 4, wherein, The semiconductor element including the RF amplification section is disposed on the substrate such that the bottom of the semiconductor element contacts the base plate, and the temperature sensor is disposed on the side of the substrate opposite to the side on which the semiconductor element is disposed.

6. The RF energy radiating device according to any one of claims 1 to 4, wherein, The semiconductor element including the RF amplification section is disposed on the substrate such that the bottom of the semiconductor element contacts the base plate, and the temperature sensor is disposed on the same side of the substrate as the side on which the semiconductor element is disposed.

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