Microwave generating device and microwave generating method

Abstract

To provide a microwave generation device capable of starting an oscillation operation without flowing an excessive current to an oscillation circuit portion.SOLUTION: A microwave generation device 10 includes an oscillation circuit portion 20, an oscillation state detection portion 40, and a control portion 30. The oscillation circuit portion 20 outputs high frequency waves used to generate microwaves. The oscillation state detection portion 40 detects whether the oscillation circuit portion 20 is in an oscillation state. The control portion 30 inputs a bias voltage to the oscillation circuit portion 20. The control portion 30 checks the detection result by the oscillation state detection portion 40. The control portion 30 increases a bias voltage when it is detected that the oscillation circuit portion 20 is not in an oscillation state. The control portion 30 stops increasing the bias voltage when it is detected that the oscillation circuit portion 20 is in an oscillation state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a microwave generator and a microwave generation method. [Background technology]

[0002] In the self-oscillating device described in Patent Document 1, the gate voltage applied to the semiconductor element is first boosted up to a threshold value to initiate self-oscillation of the semiconductor element, and then the gate voltage is lowered to a target value lower than the threshold value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-103921 Summary of the Invention [Problem to be solved by the invention]

[0004] The gate voltage at which self-oscillation of a semiconductor element begins can vary depending on individual differences in the semiconductor element, temperature, etc. In the self-oscillation device described in Patent Document 1, the threshold value of the gate voltage needs to be set to a high value in order to ensure that the semiconductor element self-oscillates reliably under any conditions.

[0005] However, when the gate voltage at which self-oscillation begins is lower than a set threshold, boosting the gate voltage to the threshold results in an excessively high gate voltage. When the gate voltage is excessively high, an excessive current flows through the circuit containing the semiconductor element, resulting in increased power consumption. Therefore, the circuit containing the semiconductor element must be designed to handle excessive current and power consumption, which results in an increased circuit size.

[0006] In view of the above problems, an object of the present invention is to provide a microwave generator and a microwave generating method that can start an oscillation operation without causing an excessive current to flow in an oscillation circuit section. [Means for solving the problem]

[0007] The microwave generator according to the present invention comprises an oscillation circuit unit, an oscillation state detection unit, and a control unit. The oscillation circuit unit outputs a high frequency wave used to generate microwaves. The oscillation state detection unit detects whether the oscillation circuit unit is in an oscillation state. The control unit inputs a bias voltage to the oscillation circuit unit. The control unit checks the detection result by the oscillation state detection unit. If the control unit detects that the oscillation circuit unit is not in an oscillation state, it increases the bias voltage. If the control unit detects that the oscillation circuit unit is in an oscillation state, it stops increasing the bias voltage.

[0008] In the microwave generation method according to the present invention, a bias voltage is input to an oscillator circuit that outputs a high frequency wave used to generate microwaves. It is also detected whether the oscillator circuit is in an oscillating state. If it is detected that the oscillator circuit is not in an oscillating state, the bias voltage is increased. If it is detected that the oscillator circuit is in an oscillating state, the increase in the bias voltage is stopped. [Effects of the Invention]

[0009] According to the microwave generator and microwave generation method of the present invention, the bias voltage is increased or stopped depending on whether the oscillation circuit is in an oscillating state. Therefore, regardless of the individual differences of the circuit elements included in the oscillation circuit and conditions such as temperature, the minimum bias voltage required to start oscillation is input to the oscillation circuit. The bias voltage does not increase beyond the minimum value. Therefore, an excessive current is not passed through the oscillation circuit, and oscillation of the oscillation circuit is reliably started. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a diagram schematically illustrating a configuration of a microwave generation device according to an example of an embodiment. [Figure 2] 10 is a graph showing an example of a bias voltage and a change in an output state detection signal over time. [Figure 3] FIG. 4 is a flow chart showing an example of the operation of the microwave generating device. [Figure 4] 10 is a graph showing temporal changes in bias voltage and output state detection signal in another example of operation of the microwave generator. [Figure 5] FIG. 10 is a flow chart showing another example of the operation of the microwave generating device. [Figure 6] 1 is a diagram schematically illustrating a configuration of a microwave generator including an oscillation state detection unit configured to detect a current input to an oscillation circuit unit. [Figure 7] 10 is a graph showing yet another example of temporal changes in bias voltage and output state detection signal. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and description thereof will not be repeated.

[0012] First, the configuration of a microwave generator 10 according to one example of an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram schematically showing the configuration of a microwave generator 10 according to one example of an embodiment.

[0013] The microwave generator 10 outputs a high frequency wave used to generate microwaves. The high frequency wave output by the microwave generator 10 is used, for example, to generate microwaves for heating an object to be heated in a microwave oven. As shown in FIG. 1 , the microwave generator 10 includes a DC power supply 12, an oscillation circuit unit 20, a control unit 30, and an oscillation state detection unit 40.

[0014] The DC power supply 12 is a device that supplies power at a constant DC voltage (for example, 50 V) and is connected to the control unit 30 .

[0015] The oscillation circuit section 20 includes a bias voltage terminal 14, a power supply terminal 16, an output terminal 18, a switching element 21, an input matching circuit section 22, a bias resistor 22a, a grounded capacitor 22b, an output matching circuit section 23, a grounded capacitor 23a, an output capacitor 23b, and a feedback circuit section 24. The oscillation circuit section 20 outputs a high frequency wave used to generate microwaves.

[0016] The bias voltage terminal 14 is a terminal connected to the control unit 30. The bias voltage terminal 14 is connected to a bias resistor 22a and a ground capacitor 22b. A bias voltage is input to the bias voltage terminal 14 from the control unit 30. The bias voltage input to the bias voltage terminal 14 is applied to a terminal (e.g., a gate) of the switching element 21 via the bias resistor 22a and the input matching circuit unit 22.

[0017] The power supply terminal 16 is a terminal connected to the control unit 30. A power supply voltage is input to the power supply terminal 16 from the control unit 30. The power supply voltage input from the power supply terminal 16 is applied to the output matching circuit unit .

[0018] The output terminal 18 is a terminal that outputs the high frequency wave oscillated in the oscillation circuit section 20 to another device. The output terminal 18 is connected to, for example, the magnetron of a microwave oven.

[0019] The switching element 21 is an element that generates high-frequency oscillation by alternately repeating conduction and interruption between its terminals (switching operation). The switching element 21 in FIG. 1 has three terminals, two of which are connected to the input matching circuit section 22 and the output matching circuit section 23, respectively, and the remaining terminal is grounded. The switching element 21 is, for example, a field effect transistor (FET). The switching element 21 may be, for example, a bipolar transistor, a thyristor, or a vacuum tube, other than a FET. In the following description, the switching element 21 will be described as a FET, and the three terminals of the switching element 21 will be referred to as the gate, drain, and source, respectively. In FIG. 1, the terminal connected to the input matching circuit section 22 (to which a bias voltage is applied) is the gate, the terminal connected to the output matching circuit section 23 is the drain, and the terminal connected to the ground is the source. A power supply voltage from the power supply terminal 16 is applied to the drain via the output matching circuit section 23. The switching operation is performed by switching between conduction and cutoff between the drain and source depending on the voltage applied to the gate (input from the bias voltage terminal 14 and the feedback circuit section 24). In the following, the switching element 21 will be described as a depletion-type FET in which the drain and source are cut off when the gate voltage is −5V.

[0020] The input matching circuit section 22 is connected to the switching element 21 and the feedback circuit section 24. A bias resistor 22a and a grounded capacitor 22b are connected in series to the input matching circuit section 22. The terminal of the grounded capacitor 22b opposite to the bias resistor 22a is grounded. A bias voltage terminal 14 is connected between the bias resistor 22a and the grounded capacitor 22b. The input matching circuit section 22 is a circuit including, for example, a coil and a capacitor. The input matching circuit section 22, together with the bias resistor 22a and the grounded capacitor 22b, performs impedance matching between the switching element 21 and the feedback circuit section 24.

[0021] The output matching circuit section 23 is connected to the power supply terminal 16, the switching element 21, and the feedback circuit section 24. The output matching circuit section 23 is also connected to a grounded capacitor 23a and an output capacitor 23b. The terminal of the grounded capacitor 23a opposite to the output matching circuit section 23 is grounded. The terminal of the output capacitor 23b opposite to the output matching circuit section 23 is connected to the output terminal 18. The power supply terminal 16 is connected between the output matching circuit section 23 and the grounded capacitor 23a. The output matching circuit section 23 is a circuit including, for example, a coil and a capacitor. The output matching circuit section 23, together with the grounded capacitor 23a and the output capacitor 23b, performs impedance matching between the switching element 21 and a device (e.g., an applicator) connected to the output terminal 18. The output capacitor 23b removes (filters) a DC component from the high frequency signal output to the output terminal 18.

[0022] The feedback circuit section 24 is connected to the input matching circuit section 22 and the output matching circuit section 23. The feedback circuit section 24 feeds back the output from the drain (output) of the switching element 21 to the gate (input). The feedback circuit section 24 includes a resonator such as a coil-capacitor resonator (LC circuit) or a dielectric resonator. The output from the drain is fed back to the gate via the feedback circuit section 24 including the resonator, causing the switching element 21 to oscillate.

[0023] The control unit 30 includes an oscillation management unit 32, a bias voltage setting unit 34, and a power supply unit 36. The control unit 30 inputs a bias voltage to the oscillation circuit unit 20 via a bias voltage terminal 14. The control unit 30 inputs a power supply voltage to the oscillation circuit unit 20 via a power supply terminal 16.

[0024] The oscillation management unit 32 is connected to the bias voltage setting unit 34, the power supply unit 36, and the oscillation state detection unit 40. The oscillation management unit 32 is a processor such as a CPU (Central Processing Unit). While checking the signal from the oscillation state detection unit 40, the oscillation management unit 32 instructs the bias voltage setting unit 34 on the value of the bias voltage to be input to the oscillation circuit unit 20. When the entire microwave generator 10 is started up, the oscillation management unit 32 instructs the power supply unit 36 ​​to input the power supply voltage to the oscillation circuit unit 20.

[0025] The bias voltage setting unit 34 is connected to the oscillation management unit 32 and the bias voltage terminal 14. The bias voltage setting unit 34 is a unit that can set and output a voltage of a specified value. The bias voltage setting unit 34 is configured, for example, by a digital-to-analog converter. The bias voltage setting unit 34 sets a bias voltage in accordance with instructions from the oscillation management unit 32 and inputs the set bias voltage to the bias voltage terminal 14.

[0026] The power supply unit 36 ​​is connected to the DC power supply 12, the oscillation management unit 32, and the power supply terminal 16. The power supply unit 36 ​​is a unit that can adjust DC power. The power supply unit 36 ​​adjusts the voltage and current of the DC power supply 12, for example, using resistors, coils, capacitors, semiconductor elements, etc. In accordance with instructions from the oscillation management unit 32, the power supply unit 36 ​​adjusts the power of the DC power supply 12 to a quality appropriate for operation of the oscillation circuit unit 20 (for example, adjusting to the rated voltage and rated current of the oscillation circuit unit 20), and inputs the power to the power supply terminal 16.

[0027] The oscillation state detection unit 40 is connected to the oscillation management unit 32. The oscillation state detection unit 40 is configured by, for example, a power detection circuit or a current detection circuit. The oscillation state detection unit 40 detects whether the oscillation circuit unit 20 is in an oscillating state. The oscillation state detection unit 40 transmits a signal indicating the detection result (output state detection signal) to the oscillation management unit 32.

[0028] More specifically, the oscillation state detection unit 40 is, for example, a power detection circuit that detects the power output by the oscillation circuit unit 20, or a current detection circuit that detects the current input to the oscillation circuit unit 20. In FIG. 1, the oscillation state detection unit 40 monitors the wiring between the output capacitor 23b and the output terminal 18, i.e., the output of the oscillation circuit unit 20, and detects whether the oscillation circuit unit 20 is in an oscillating state based on the current flowing through the wiring or the power consumed via the wiring. Because a high frequency wave is output to the output terminal 18, if the oscillation state detection unit 40 in FIG. 1 is a power detection circuit, the power detection circuit is capable of detecting high frequency power. The power detection circuit may be directly connected to the wiring, or may be a circuit that can detect power without being directly connected to the wiring (such as a clamp meter).

[0029] When the oscillator circuit unit 20 is in an oscillating state, power consumption is greater than when it is not in an oscillating state. Therefore, the oscillation state detection unit 40 can determine whether the oscillator circuit unit 20 is in an oscillating state by checking whether the power value detected by the power detection circuit exceeds a threshold (a specific wattage value) without checking the output waveform of the oscillator circuit unit 20. For example, if the oscillation state detection unit 40 is a power detection circuit, the power value detected by the power detection circuit is converted into a digital signal via an analog-to-digital converter or the like. A power value exceeding the threshold is converted into an H (High) signal, and a power value not exceeding the threshold is converted into an L (Low) signal. Therefore, when the oscillator circuit unit 20 is in an oscillating state, an H signal (e.g., a voltage of 5 V) indicating that the oscillator circuit unit 20 is in an oscillating state is sent to the oscillation management unit 32. When the oscillator circuit unit 20 is not in an oscillating state, an L signal (e.g., a voltage of 0 V) ​​indicating that the oscillator circuit unit 20 is not in an oscillating state is sent to the oscillation management unit 32.

[0030] Next, the operation of the microwave generator 10 will be described with reference to Figures 1 and 2. Figure 2 is a graph showing an example of temporal changes in the bias voltage and the output state detection signal.

[0031] While the microwave generator 10 is operating, the oscillation management unit 32 of the control unit 30 checks the detection result by the oscillation state detection unit 40. If the oscillation state detection unit 40 detects that the oscillation circuit unit 20 is not in an oscillating state, the oscillation management unit 32 of the control unit 30 increases the bias voltage input to the bias voltage terminal 14 of the oscillation circuit unit 20 via the bias voltage setting unit 34. If the oscillation circuit unit 20 is detected to be in an oscillating state, the oscillation management unit 32 of the control unit 30 stops increasing the bias voltage input to the bias voltage terminal 14 of the oscillation circuit unit 20.

[0032] As shown in Fig. 2, at operation start time t0 when application of the bias voltage and power supply voltage begins, the bias voltage is increased by a voltage difference ΔV (e.g., 0.1 V). Then, periodically, for example, every time a time difference Δt (e.g., 100 nanoseconds) elapses, the output state detection signal is checked. If the output state detection signal is an L signal (if the oscillator circuit unit 20 is not oscillating), the bias voltage is increased by the voltage difference ΔV. In Fig. 2, because the output state detection signal is an L signal at time t0+Δt, the bias voltage is increased from ΔV to ΔV+ΔV.

[0033] If the output state detection signal is an H signal (if the oscillation circuit unit 20 is oscillating), the increase in the bias voltage is stopped. In FIG. 2, the output state detection signal becomes an H signal at the oscillation start time tx (for example, 2 microseconds after the start of operation). After the oscillation start time tx, the bias voltage is increased from the oscillation start time t X The oscillation start voltage Vx (for example, -3 V) is not increased.

[0034] The flow of operation of the microwave generator 10 will be described with reference to Figs. 1, 2, and 3. Fig. 3 is a flow diagram showing an example of the operation of the microwave generator 10. In Fig. 1, the operation of the microwave generator 10 includes steps S11 to S13. At operation start time t0 of the microwave generator 10, application of the bias voltage and the power supply voltage begins (START). It is assumed that the bias voltage is -5V before operation start time t0.

[0035] When the application of the bias voltage and the power supply voltage starts, in step S11, the control unit 30 increases the bias voltage. Specifically, the oscillation management unit 32 instructs the bias voltage setting unit 34 to set the bias voltage to a value that is increased by the voltage difference ΔV from the current value (the value of ΔV at the operation start time t0). The bias voltage setting unit 34 inputs the voltage of the value instructed by the oscillation management unit 32 to the bias voltage terminal 14 of the oscillation circuit unit 20. The bias voltage input to the bias voltage terminal 14 is applied to the gate of the switching element 21 via the bias resistor 22a and the input matching circuit unit 22.

[0036] After the operation start time t0, the control unit 30 periodically (for example, every time the time difference Δt elapses), executes step S12. In step S12, the control unit 30 (the oscillation management unit 32) checks the detection result by the oscillation state detection unit 40. If the oscillation state detection unit 40 detects that the oscillation circuit unit 20 is not in an oscillation state (NO in step S12), the control unit 30 returns to step S11 and further increases the bias voltage.

[0037] If it is detected that the oscillation circuit unit 20 is in an oscillating state (YES in step S12), the control unit 30 proceeds to step S13 and stops increasing the bias voltage. X After the increase in the bias voltage is stopped at the oscillation start time t X When the oscillation of the oscillation circuit section 20 is stopped due to the operation of the microwave generator 10 being stopped, the application of the bias voltage and the power supply voltage is stopped.

[0038] In the microwave generator 10 of FIGS. 1, 2, and 3, the control unit 30 gradually increases (raises) the bias voltage while checking whether the oscillation circuit unit 20 is in an oscillating state. Then, once it is confirmed that the oscillation circuit unit 20 is in an oscillating state, the control unit 30 stops increasing the bias voltage. Therefore, regardless of the individual differences of the circuit elements (particularly the switching element 21) included in the oscillation circuit unit 20 and conditions such as temperature, the control unit 30 can reliably input the minimum bias voltage required to start oscillation to the oscillation circuit unit 20. Furthermore, although it is difficult to predict in advance the fluctuations in the oscillation start voltage Vx due to the individual differences of the circuit elements, the control unit 30 can reliably input the minimum bias voltage required to start oscillation to the oscillation circuit unit 20, regardless of any individual differences that may occur.

[0039] Furthermore, because the bias voltage input to the oscillation circuit unit 20 is kept at a minimum value, the bias voltage does not become excessively high. Therefore, an excessive current does not flow in the oscillation circuit unit 20, and power consumption does not become excessively large. Therefore, there is no need to increase the size of the oscillation circuit unit 20 to accommodate excessive current and power consumption, and the oscillation circuit unit 20 can be made smaller.

[0040] Next, another example of the operation of the microwave generator 10 will be described with reference to Figures 1, 2, 4, and 5. Figure 4 is a graph showing temporal changes in the bias voltage and the output state detection signal in another example of the operation of the microwave generator 10. Figure 5 is a flow chart showing another example of the operation of the microwave generator 10.

[0041] In FIG. 4, at the operation start time t0, the bias voltage is increased to an initial value V0. Then, the oscillation circuit unit 20 operates until it is detected that it is in an oscillating state (when the bias voltage reaches the oscillation start voltage V X The bias voltage is increased in increments of the voltage difference ΔV from the initial value V0.

[0042] In addition, the bias voltage at the time when it is detected that the oscillation circuit unit 20 is in an oscillating state, that is, the oscillation start voltage V Xis stored as the next initial value V0. The control unit 30 is provided with a storage device (not shown), and the initial value V0 is stored in the storage device of the control unit 30. The storage device of the control unit 30 is preferably a non-volatile memory. The flow of operations of the microwave generator 10 when the initial value V0 is stored will be described with reference to the flow diagram of FIG. 5. In FIG. 5, the operation of the microwave generator 10 includes steps S21 to S26.

[0043] At operation start time t0 of the microwave generator 10, application of the bias voltage and application of the power supply voltage begin (START). When application of the bias voltage and application of the power supply voltage begin, in step S21, the control unit 30 sets the bias voltage to an initial value V0. Note that the initial value V0 is set in advance even before storage.

[0044] The initial value V0 before storage is set to a voltage value that is certain to prevent oscillation. For example, the voltage value that is certain to prevent oscillation is -5V. If it is known by taking statistics on various types of oscillation circuit units 20 that a voltage value other than -5V that is certain to prevent oscillation may be set to a value other than -5V (for example, -4V) as the initial value V0 before storage. The higher the initial value V0 before storage is, the more likely it is that the bias voltage will reach the oscillation start voltage V X Therefore, it is preferable that the initial value V0 is as high as possible.

[0045] After setting the bias voltage to the initial value V0, the control unit 30 waits until the operation of the oscillation circuit unit 20 stabilizes (in FIGS. 4 and 5, after the time difference Δt has elapsed since the operation start time t0), and then executes step S22. In step S22, the control unit 30 (oscillation management unit 32) checks the detection result by the oscillation state detection unit 40. If the oscillation state detection unit 40 detects that the oscillation circuit unit 20 is in an oscillating state (YES in step S22), the control unit 30 keeps the bias voltage at the initial value V0 until the oscillation of the oscillation circuit unit 20 stops (until END).

[0046] If the oscillation state detection unit 40 detects that the oscillation circuit unit 20 is not in an oscillation state (NO in step S22), the control unit 30 proceeds to step S23 to increase the bias voltage. Specifically, the oscillation management unit 32 instructs the bias voltage setting unit 34 to set the bias voltage to a value increased by the voltage difference ΔV from the current value (the value of V0+ΔV at time t0+Δt).

[0047] After increasing the bias voltage, the control unit 30 periodically (for example, every time the time difference Δt has elapsed) executes step S24. In step S24, the control unit 30 checks the detection result by the oscillation state detection unit 40. If it is detected that the oscillation circuit unit 20 is not in an oscillation state (NO in step S24), the control unit 30 returns to step S23 and further increases the bias voltage.

[0048] Oscillation start time t X If it is detected that the oscillation circuit unit 20 is in an oscillating state (YES in step S24), the control unit 30 proceeds to step S25 to stop increasing the bias voltage. Then, the control unit 30 proceeds to step S26 to determine the oscillation start time t X The bias voltage at the oscillation start voltage V X is stored as the initial value V0.

[0049] After the increase in the bias voltage is stopped in step S25 and the initial value V0 is stored in step S26, the bias voltage is maintained at the oscillation start voltage Vx until the oscillation of the oscillation circuit unit 20 is stopped (until END). When the oscillation of the oscillation circuit unit 20 is stopped due to a shutdown of the microwave generator 10 or the like, the application of the bias voltage and the power supply voltage is stopped, but the initial value V0 remains stored in the storage device.

[0050] After the oscillation of the oscillation circuit unit 20 has stopped (after END), when the next oscillation is performed in the oscillation circuit unit 20 (processing is performed again from START), in step S21, the control unit 30 sets the bias value to the stored initial value V0.

[0051] As described above, in the operations of FIGS. 4 and 5, the control unit 30 detects that the oscillation circuit unit 20 is in an oscillating state (oscillation start time t X ) is stored as an initial value V0, and the next time the oscillation circuit unit 20 oscillates after the oscillation of the oscillation circuit unit 20 has stopped, the bias voltage is set to the initial value V0. Furthermore, if the oscillation circuit unit 20 is not detected to be in an oscillating state when the bias voltage is set to the initial value V0, the control unit 30 increases the bias voltage from the initial value V0.

[0052] The storage device of the control unit 30 stores the oscillation start voltage V X is stored as the initial value V0 of the bias voltage. Therefore, in the next and subsequent operations of the microwave generator 10, oscillation of the oscillation circuit section 20 is attempted from the optimal initial value V0 according to conditions such as individual differences of the circuit elements included in the oscillation circuit section 20. Therefore, the time until oscillation of the oscillation circuit section 20 starts is shortened.

[0053] Furthermore, if oscillation does not occur at the stored initial value V0 due to differences in conditions such as temperature, the bias voltage is further increased from the initial value V0, and the increase in the bias voltage is stopped when oscillation starts. Therefore, even if oscillation does not occur at the initial value V0, the control unit 30 can reliably input the minimum bias voltage required to start oscillation to the oscillation circuit unit 20. Furthermore, if the stored initial value V0 is a value greater than −5V, the time until oscillation of the oscillation circuit unit 20 starts is shorter than when the initial value V0 is −5V.

[0054] FIG. 6 is a diagram schematically illustrating the configuration of a microwave generator 10, as another example of an embodiment, that includes an oscillation state detection unit 40 configured to detect a current input to the oscillation circuit unit 20. In FIG. 6, the oscillation state detection unit 40 is connected to the oscillation management unit 32 of the control unit 30, and detects whether the oscillation circuit unit 20 is in an oscillating state based on a current flowing through the wiring between the power supply unit 36 ​​and the power supply terminal 16. Since DC power is input to the power supply terminal 16 of the oscillation circuit unit 20, the current detection circuit serving as the oscillation state detection unit 40 in FIG. 6 is capable of detecting DC current. Note that the current detection circuit may be one that detects a current flowing through the wiring between the DC power supply 12 and the power supply unit 36. The current detection circuit may be one that is directly connected to the wiring, or one that can detect current without being directly connected to the wiring (such as a clamp meter).

[0055] When the oscillation circuit unit 20 is in an oscillating state, the required current value is larger than when it is not in an oscillating state. Therefore, the oscillation state detection unit 40 can determine whether the oscillation circuit unit 20 is in an oscillating state by determining whether the current value detected by the current detection circuit exceeds a threshold value (a specific ampere value) without examining the output waveform of the oscillation circuit unit 20. When the oscillation state detection unit 40 is a current detection circuit, the current value detected by the current detection circuit is converted into a digital signal via an analog-to-digital converter or the like. A current value exceeding the threshold value is converted into an H (High) signal, and a current value not exceeding the threshold value is converted into an L (Low) signal. Therefore, when the oscillation circuit unit 20 is in an oscillating state, an H signal (e.g., a voltage of 5 V) indicating that the oscillation circuit unit 20 is in an oscillating state is sent to the oscillation management unit 32. When the oscillation circuit unit 20 is not in an oscillating state, an L signal (e.g., a voltage of 0 V) ​​indicating that the oscillation circuit unit 20 is not in an oscillating state is sent to the oscillation management unit 32.

[0056] 7 is a graph showing another example of the change over time of the bias voltage and the output state detection signal. In FIG. 7, the intervals at which the control unit 30 checks the oscillation state of the oscillation circuit unit 20 are not constant (time difference Δt), but are gradually extended. That is, after the operation start time t0, there are times t1, t2, t3, t4, t5, and t6, and the oscillation start time t7. X If an oscillation state is confirmed at time t1, the interval from time t1 to time t2 is longer than the interval from operation start time t0 to time t1. Similarly, at time t3, time t4, time t5, and the oscillation start time t X As the time progresses, the intervals between timings at which the control unit 30 checks the oscillation state of the oscillation circuit unit 20 become longer. Note that in Fig. 7, the increase in the bias voltage at operation start time t0, time t1, time t2, time t3, time t4, and time t5, when the oscillation circuit unit 20 is not oscillating, is a constant voltage difference ΔV.

[0057] It takes some time for the oscillation to stabilize after the oscillation conditions of the oscillator circuit unit 20 are satisfied. The higher the bias voltage, the higher the possibility that oscillation will start. Therefore, by extending the interval between timing checks for the oscillation state as the bias voltage increases over time, the oscillation state can be checked only after it has stabilized.

[0058] After the oscillation has stabilized, the oscillation start voltage V X Since oscillation may continue even if the bias voltage is slightly lowered, the control unit 30 may stop increasing the bias voltage and then decrease the bias voltage slightly.

[0059] Although the above description has been given assuming that the switching element 21 is a depletion-type FET, an enhancement-type FET may also be used as the switching element 21. In an enhancement-type FET, the drain and source are disconnected when the gate voltage is 0 V. When the switching element 21 is an enhancement-type FET, the value of the bias voltage before the operation start time t0 should be 0 V.

[0060] The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments and can be embodied in various forms without departing from the spirit and scope of the present invention. The drawings mainly show each component in a schematic manner for ease of understanding, and the thickness, length, number, spacing, etc. of each component shown in the drawings may differ from the actual ones due to the convenience of creating the drawings. Furthermore, the materials, shapes, dimensions, etc. of each component shown in the above embodiments are merely examples and are not particularly limited, and various modifications are possible within a scope that does not substantially deviate from the configuration of the present invention. [Industrial Applicability]

[0061] The present invention provides a microwave generating device and a microwave generating method, and has industrial applicability. [Explanation of symbols]

[0062] 10 Microwave generator 12 DC power supply 14 Bias voltage terminal 16 Power terminal 18 Output terminal 20 Oscillator circuit section 21 Switching element 22 Input matching circuit section 22a Bias resistor 22b Ground capacitor 23 Output matching circuit section 22a ground capacitor 22b Output Capacitor 24 Feedback circuit section 30 Control Unit 32 Oscillation control unit 34 Bias voltage setting section 36 Power supply section 40 Oscillation state detection unit

Claims

1. an oscillator circuit unit that outputs a high frequency wave used to generate microwaves; an oscillation state detection unit that detects whether the oscillation circuit unit is in an oscillation state; a control unit that inputs a bias voltage to the oscillation circuit unit, The control unit checks the detection result by the oscillation state detection unit, and if it is detected that the oscillation circuit unit is not in an oscillation state, increases the bias voltage, and if it is detected that the oscillation circuit unit is in an oscillation state, stops increasing the bias voltage.

2. 2. The microwave generator according to claim 1, wherein the oscillation state detection unit is a power detection circuit that detects the power output from the oscillation circuit unit, or a current detection circuit that detects the current input to the oscillation circuit unit.

3. 2. The microwave generator according to claim 1, wherein the control unit stores the value of the bias voltage at the time when it is detected that the oscillation circuit unit is in an oscillating state as an initial value, and when the oscillation circuit unit oscillates next time after oscillation of the oscillation circuit unit has stopped, the bias voltage is set to the initial value.

4. 4. The microwave generation device according to claim 3, wherein when the bias voltage is set to the initial value and the oscillation circuit unit is not detected to be in an oscillating state, the control unit increases the bias voltage from the initial value.

5. Bias power is input to an oscillator circuit that outputs a high frequency wave used to generate microwaves, It is detected whether the oscillation circuit unit is in an oscillating state, When it is detected that the oscillation circuit unit is not in an oscillating state, a bias voltage input to the oscillation circuit unit is increased, and when it is detected that the oscillation circuit unit is in an oscillating state, the increase in the bias voltage is stopped.

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