JP5974965B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to a high-frequency heating cooker that is applied to a microwave oven or the like and that heats an object to be cooked, which is a load, using a magnetron.

  Conventionally, temperature detection using an infrared sensor has been performed to determine whether or not there is a load in the microwave oven. However, it took a long time to detect, causing electric field concentration and increasing the temperature of the magnetron.

  With respect to such a problem, in Patent Document 1, focusing on the fact that the anode current of the magnetron increases as the load becomes light or no load, and increases as the output is set higher, the anode current detection unit detects the magnetron current. By detecting the anode current and providing a threshold value according to the set output individually, a high frequency for determining the load state based on the comparison between the anode current detection value detected by the anode current detection unit and the threshold value during the operation of the magnetron A cooking device has been proposed.

Japanese Patent No. 5094054

    In the above-mentioned Patent Document 1, it is possible to detect in a short time by adopting a method of determining the load state by detecting the anode current of the magnetron. However, the high-frequency heating cooker shipped as a product also has a magnetron and an inverter unit that supplies high-frequency output power to the magnetron vary from product to product. Therefore, the load state cannot be correctly determined by simply changing the threshold value according to the set output.

  An object of this invention is to provide the high frequency heating cooker which can determine a load state correctly in consideration of the dispersion | variation factor for every product in view of the said problem.

  In the first aspect of the invention, when the maximum input current is passed through the inverter unit, the input current reference value, the input voltage reference value, and the anode current reference value are stored in the control unit in advance before shipment. When the magnetron is actually operated in advance, a threshold value serving as a reference for determining the load state is set based on the anode current reference value that differs for each product. This threshold value is set by taking into account the inverter unit and magnetron that vary from product to product, so if the anode current detection value detected by the anode current detection unit is compared with the threshold value when the magnetron is operated, the product It is possible to accurately determine the load state in consideration of each variation factor.

  In the invention of claim 2, when the operation time of the magnetron becomes longer, the temperature of the magnetron rises and the anode current detection value becomes higher. Therefore, if the threshold value is changed according to the operation time of the magnetron, It is possible to suppress erroneous determination of the load state during long-time operation.

  In the invention of claim 3, when it is determined that the load state is not normal, the inverter unit is controlled to reduce the input power to the inverter unit, or to stop the inverter unit, so that the electric field concentration and magnetron Temperature rise can be suppressed.

  In the invention of claim 4, when the output set by the output setting unit becomes small, the anode current detection value also becomes small. Therefore, by accurately changing the threshold value accordingly, the load state can be accurately determined according to the set output. Is possible.

  In the invention of claim 5, since the anode current detection value changes depending on the power supply voltage applied to the product, the load state can be accurately determined according to the power supply voltage by changing the threshold value according to the power supply voltage. It becomes possible.

  According to the first aspect of the present invention, it is possible to provide a high-frequency cooking device capable of accurately determining the load state in consideration of the variation factor for each product.

  According to the invention of claim 2, it is possible to suppress erroneous determination of the load state during long-time operation of the magnetron.

  According to the invention of claim 3, when it is determined that the load state is not normal, electric field concentration and temperature increase of the magnetron can be suppressed.

  According to the invention of claim 4, it is possible to accurately determine the load state according to the set output.

  According to the invention of claim 5, it is possible to accurately determine the load state according to the power supply voltage.

It is a whole circuit diagram of the microwave oven in one embodiment of the present invention. FIG. 3 is an input current detection circuit and its peripheral circuit diagram. FIG. 3 is an anode current detection circuit and its peripheral circuit diagram. It is a graph which shows an anode current detection value and threshold value when operating a microwave oven for a predetermined period of time as above. It is a graph which shows the relationship of the anode current detection value with respect to a different setting output when a microwave oven is made to operate | move for a predetermined time same as the above. It is a graph which shows the threshold value with respect to a different setting output as above. It is a graph which shows the anode current detection value with respect to different power supply voltages same as the above. It is a graph which shows the relationship between a power supply voltage and a threshold value same as the above.

  Hereinafter, an embodiment of a preferred high-frequency cooking device of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a circuit configuration of a microwave oven as a high-frequency heating cooker in the present embodiment. In the figure, 1 is a plug to be inserted into an outlet (not shown), 2 is a power transformer formed by connecting a primary winding 2A between both ends of a power line, and the power transformer 2 is a primary winding from the outlet through the power line. When a power supply voltage (primary AC voltage) is applied to the line 2A, a secondary AC voltage corresponding to the turn ratio of the primary winding 2A and the secondary winding 2B is supplied from the secondary winding 2B to the power circuit in the subsequent stage. 3 is supplied. The power supply circuit 3 corresponds to an AC / DC converter that converts the secondary AC voltage from the transformer 2 into one or a plurality of DC operating voltages. In FIG. The structure which supplies is shown.

  Reference numeral 5 denotes a rectifying / smoothing circuit connected to the power supply voltage line. Reference numeral 6 denotes an inverter circuit connected to the rectifying / smoothing circuit 5. Here, the power supply voltage is rectified and smoothed by the rectifying / smoothing circuit 5 to become a DC voltage. It is applied to the circuit 6. As is well known, the inverter circuit 6 includes one or a plurality of switching elements 7 and receives a pulse drive signal from the control circuit 21 so that the switching element 7 is switched on and off at a high speed, thereby rectifying and smoothing the circuit. 5 is provided as a DC / AC converter that converts the DC voltage from 5 into a high-frequency AC voltage. Here, as the switching element 7, for example, a semiconductor switch element with a control terminal such as a bipolar transistor, a MOS type FET, or an IGBT is used, and the aforementioned pulse drive signal is given to the control terminal of the switching element 7.

  Reference numeral 11 denotes a high-frequency transformer that boosts high-frequency power from the inverter circuit 6. The high-frequency transformer 11 has a primary winding 11 A connected to the output side of the inverter circuit 6, a secondary winding 11 B connected to the input side of the voltage doubler rectifier circuit 12, and a heater winding 11 C connected to the cathode of the magnetron 14. Connected. The voltage doubler rectifier circuit 12 double voltage rectifies the AC voltage induced in the secondary winding 11B of the high frequency transformer 11 and supplies a high DC voltage between the anode and cathode of the magnetron 14. When the high voltage DC voltage from the voltage doubler rectifier circuit 12 is applied to the magnetron 14 with the cathode of the magnetron 14 preheated by the AC voltage from the heater winding 11C of the transformer 11, the magnetron 14 oscillates at a high frequency and the microwave is generated. It has the structure which heat-cooks the to-be-heated material which generate | occur | produces and was put in the inside of the cooking chamber which is not illustrated.

  21 is a control for appropriately controlling the switching operation of the switching element 7 by varying the duty ratio and frequency of the pulse drive signal applied to the inverter circuit 6 in order to cook the object to be heated with a desired output from the magnetron 14. Circuit. The control circuit 21 includes, for example, a one-chip microcomputer 23 (microcomputer) in which a storage unit 22 and the like are incorporated in addition to a CPU, an input / output interface, and a timer unit (not shown). Further, an input current detection circuit 24, an input voltage detection circuit 25, an anode current detection circuit 26, and an output setting unit 27 are connected to the input port of the control circuit 21, respectively. The control terminal of the switching element 7 is connected.

  The input current detection circuit 24 detects a current flowing through a microwave oven as a product as an input current of the inverter circuit 6, which includes a current transformer 31 as a current detector and 4. The rectifier 36 is formed by bridge-connecting the diodes 32, 33, 34, 35, resistors 37, 38, 39, a clamp diode 40, and a capacitor 41.

  The current transformer 31 is provided by being inserted into one power supply line connected between the plug 1 and the rectifying / smoothing circuit 5, and the input terminal of the rectifier 36 is connected between the output windings of the current transformer 31. In addition, a current-voltage conversion resistor 37 is connected to the output terminal of the rectifier 36. Another series circuit of resistors 38 and 39 is connected between one end of the resistor 37 and the input port CT of the microcomputer 23, and a DC 5 V operation connected to the connection point of the resistors 38 and 39 and the power supply circuit 3. A clamp diode 40 is connected between the voltage lines. These resistors 38 and 39 and the clamp diode 40 are all provided as elements for protecting the input port CT of the microcomputer 23. One end of a capacitor 41 constituting a low-pass filter is connected to the connection point of the resistors 38 and 39, and the other end of the capacitor 41 is grounded together with the other end of the resistor 37.

  Therefore, in the input current detection circuit 24 shown in FIG. 2, the current of the power supply line flowing through the entire product is read by the current transformer 31, is full-wave rectified by the rectifier 36, and is converted into a voltage value by the resistor 37. . The voltage converted by the resistor 37 is applied to the input port CT of the microcomputer 23 as a value proportional to the input current of the inverter circuit 6. Note that the input current detection circuit 24 shown in FIG. 2 is merely an example, and may be replaced with another circuit configuration having an equivalent function. For example, the current detector is not limited to the current transformer 31, and a shunt resistor or the like can be substituted.

  The input voltage detection circuit 25 generates a primary voltage applied to the primary winding 2 </ b> A of the power transformer 2 from the secondary voltage induced in the secondary winding 2 </ b> B of the power transformer 2, and thus an input voltage to the inverter circuit 6. For example, it includes a plurality of voltage dividing resistors (not shown) connected between the secondary windings 2B. The voltage generated across the voltage dividing resistor is applied to the input port of the microcomputer 23 as a value proportional to the input voltage of the inverter circuit 6. Note that the input voltage detection circuit 25 may be replaced with another circuit configuration other than the voltage dividing resistor as long as it has an equivalent function.

  The anode current detection circuit 26 is connected between the voltage doubler rectifier circuit 12 and the magnetron 14 and detects the anode current of the magnetron 14. FIG. 3 shows a secondary side circuit of the high-frequency transformer 11 including the anode current detection circuit 26. The voltage doubler rectifier circuit 12 here includes capacitors 44 and 45 and diodes 46 and 47. 11 is formed as a full-wave voltage doubler rectifier circuit in which a series circuit of a capacitor 44 and a diode 46 and a series circuit of a capacitor 45 and a diode 47 are connected to the 11 secondary windings 11B. Further, a resistor 48 for current-voltage conversion is connected between the output terminals of the voltage doubler rectifier circuit 12, and a high voltage generated between both ends of the resistor 48 is connected to the magnetron 14 via the anode current detection circuit 26. Applied between the anode and the cathode. The voltage doubler rectifier circuit 12 may be configured, for example, as a half-wave voltage doubler rectifier circuit, or may be a rectifier circuit that does not include a capacitor.

  The anode current detection circuit 26 shown in FIG. 3 includes resistors 51, 52, 53, 54, and 55 and a clamp diode 56. A parallel circuit of resistors 51 and 52 corresponding to a current detector is inserted and connected to an output line between the voltage doubler rectifier circuit 12 and the anode of the magnetron 14, one end of the resistors 51 and 52, and an input port Ib of the microcomputer 23. In between, another series circuit of resistors 53 and 54 is connected, and a clamp diode 56 is connected between the connection point of the resistors 53 and 54 and the operating voltage line of DC 5V connected to the power supply circuit 3. Is done. These resistors 53 and 54 and the clamp diode 56 are all provided as elements for protecting the input port 56 of the microcomputer 23. Further, a resistor 55 as a shunt is connected between the other end of the resistors 51 and 52 and a connection point of the resistors 53 and 54.

  Therefore, in the anode current detection circuit 26 shown in FIG. 3, when the microwave oven and thus the magnetron 14 is operated, the anode current of the magnetron 14 flowing to the secondary side of the high-frequency transformer 11 is a voltage value by the resistors 51, 52 and 55. Is converted to The voltage converted by the resistors 51, 52, and 55 is applied to the input port Ib of the microcomputer 23 as a value proportional to the anode current of the magnetron 14.

  Returning to FIG. 1 again, reference numeral 27 denotes an output setting unit that receives an operation input from the user and sends an output operation signal corresponding to the output set by the user to the control circuit 21. The output setting unit 27 is provided, for example, on the front surface of a housing (not shown) of a microwave oven, and includes a rotary switch, an operation key, and the like that select and set any one cooking item.

  The microwave oven according to the present embodiment is configured so that when the maximum input current is passed through the inverter circuit 6 before being shipped to the user as a product, that is, when the output of the magnetron 14 is maximized, the input current detection circuit 24 The detected input current reference value, the input voltage reference value detected by the input voltage detection circuit 25, and the anode current reference value detected by the anode current detection unit 26 are stored in the storage means 22 of the control circuit 21, respectively. The The storage means 22 is composed of a non-volatile memory, and these reference values are stored and held even when no power is supplied.

  Thereafter, when the user operates the microwave oven at the shipping destination, the control circuit 21 specifies the output (set output) set by the user based on the output operation signal from the output setting unit 27, while the input current detection circuit 24. The input power value to the inverter circuit 6 is calculated by the product of the input current detection value detected by the input voltage detection value and the input voltage detection value detected by the input voltage detection circuit 25, and this input power value is stored in the storage means 22. Appropriate for the switching element 7 of the inverter circuit 6 so that the output value at the time of operation of the magnetron 14 calculated from the stored input current reference value and input voltage reference value becomes the set output by the output setting unit 27 described above. It has a function to send a simple pulse drive signal.

  Furthermore, the control circuit 21 of the present embodiment also has a function as a determination unit that determines the state of the heated object heated by the magnetron 14, that is, the presence or absence of the heated object. This determination unit is determined in advance as a constant based on the input voltage detection value detected by the input voltage detection circuit 25 and the anode current reference value stored in the storage means 22 when the user operates the microwave oven at the shipping destination. The anode current detection value detected by the anode current detection circuit 26 is compared with the threshold value, and if the anode current detection value exceeds the threshold value, it is determined that there is no load, and the input power to the inverter circuit 6 is A pulse driving signal to be lowered is sent to the inverter circuit 6 to control the switching element 7 of the inverter circuit 6. On the other hand, if the detected anode current value is less than the threshold value, the output value of the magnetron 14 is as described above. The switching element 7 of the inverter circuit 6 is controlled so that the output is set by the output setting unit 27.

  Next, the operation of the microwave oven having the above configuration will be described in detail with reference to the graphs of FIGS.

  In the microwave oven of this embodiment, the reference value is written to the storage means 22 of the control circuit 21 on the line before shipment as a product. In this writing operation, in order to make the operating conditions common to each product, for example, a water load of 275 cc is placed in the cooking chamber, and a stable AC 100 V outlet voltage is applied from the plug 1 as the primary side voltage, and the actual electronic The range is operated, and the maximum current value flowing through the product is stored in the storage unit 22 as the input current reference value from the input current detection circuit 24. At that time, in the control circuit 21, the current flowing through the anode of the magnetron 14, that is, the current flowing through the secondary side of the high-frequency transformer 11 is detected by the anode current detection circuit 26, and this detected value is stored as the anode current reference value in the storage means 22. The secondary outlet voltage of the power transformer 2 is also detected by the input voltage detection circuit 25 and the detected value is stored in the storage means 22 as the input voltage reference value. Remember.

  As a result of the above writing operation, each product to be shipped includes an input current corresponding to the maximum input current of the inverter circuit 6 when the magnetron 14 is operated at the maximum output when the outlet voltage is 100 V as a reference. The reference value, the input voltage reference value corresponding to the input voltage of the inverter circuit 6, and the anode current reference value corresponding to the anode current of the magnetron 14 are written in the storage means 22 of the control circuit 21. These reference values differ from product to product due to variations in characteristics of the magnetron 14 and the inverter circuit 6 and the like.

  When the product is shipped and the user operates the microwave oven at the shipping destination, the control circuit 21 reads the output operation signal from the output setting unit 27 and outputs a setting output indicating how much the output of the magnetron 14 should be. In particular, the operation of the switching element 7 of the inverter circuit 6 and thus the operation of the magnetron 14 is controlled so that the output value at the time of operation of the magnetron 14 becomes the set output. At this time, the control circuit 21 reads the input current detection value detected by the input current detection circuit 24 and the input voltage detection value detected by the input voltage detection circuit 25, respectively, and these input current detection value and input voltage detection value are read. The input power value of the inverter circuit 6 that can be calculated by the product of is calculated. Then, for example, the duty ratio or the frequency of the pulse drive signal supplied to the inverter circuit 6 is changed so that the input power value becomes a value commensurate with the set output.

  For example, in a microwave oven, if the set output is 1000 W, the magnetron 14 is controlled so that the input power value is 1400 W, and if the set output is 600 W, the magnetron 14 is controlled so that the input power value is 1050 W. . The correlation between the output of the magnetron 14 and the input power of the inverter circuit 6 is determined for each product based on the input current reference value and the input voltage reference value written in the storage means 22 before shipment. Since the product of the input current reference value and the input voltage reference value corresponds to the input power value when the magnetron 14 is operated at the maximum output, the correlation between the input power value at this time and the maximum output value of the magnetron. Is applied as it is after shipment, the magnetron 14 can be operated with the set output while monitoring the input current detection value and the input voltage detection value for each product.

  In the case where the storage unit 22 can store the setting output by the output setting unit 27, when the setting output is changed by the output setting unit 27, the changed setting output is written in the storage unit 22 and the microwave oven is changed. When operating, the control circuit 21 may control the switching element 7 of the inverter circuit 6 so that the output value at the time of operation of the magnetron 14 becomes the set output stored in the storage means 22.

  Further, the determination unit incorporated in the control circuit 21 sets a threshold value to be compared with the anode current detection value detected by the anode current detection circuit 26 in order to determine whether or not there is an object to be heated in the cooking chamber. Set. This threshold value is a product-specific anode current reference value stored in advance in the storage means 22 before shipment, an operation duration time of the magnetron 14, a setting output by the output setting unit 27, and an input detected by the input voltage detection circuit 25. For each voltage detection value, a predetermined value is adjusted and set. Therefore, the threshold value here is set to a different value for each product in consideration of the variation in characteristics of the magnetron 14 and the inverter circuit 6 described above.

  The determination unit compares the set threshold value with the anode current detection value, and determines that there is no load in the cooking chamber when the anode current detection value is equal to or greater than the threshold value, and inputs to the inverter circuit 6. For example, a pulse drive signal is sent to the inverter circuit 6 to lower the power from 1400 W corresponding to the set output to 1000 W, which is lower than that, or a pulse drive signal is sent to stop the operation of the inverter circuit 6. By interrupting and controlling the switching element 7 of the inverter circuit 6, the electric field concentration and the temperature rise of the magnetron 14 are suppressed. On the other hand, if the anode current detection value is less than the threshold value, the switching element 7 of the inverter circuit 6 is controlled so that the output value of the magnetron 14 becomes the set output as described above, and the load in the cooking chamber is set to a desired value. Heat with set output.

  As an example, FIG. 4 shows an anode current detection value Ib and a threshold value when the microwave oven is continuously operated for 20 minutes in a state where the set output is 600 W and a water load of 2000 cc is put in the cooking chamber. The magnetron 14 increases in temperature as its operating time increases, and the anode current detection value Ib also increases. In this case, regardless of the operation time of the magnetron 14, if the threshold value is set to a constant value, there is no difference between the anode current detection value Ib and the threshold value, and the presence or absence of the load cannot be determined correctly. Therefore, the determination unit of the present embodiment is configured to change the threshold according to the operation time of the magnetron 14 and to set the threshold to a higher value stepwise as the operation time of the magnetron 14 becomes longer. In this way, as shown in FIG. 4, even if the operation time of the magnetron 14 becomes longer and the anode current detection value Ib increases, there is no possibility that the determination unit erroneously determines that there is no load in the cooking chamber. it can.

  FIG. 5 shows anode current detection values Ib when the set outputs are 1000 W, 600 W, and 500 W, respectively. Since the control circuit 21 controls the output of the magnetron 14, the anode current detection value Ib detected by the anode current detection circuit 26 decreases as the set output decreases. Therefore, the determination unit according to the present embodiment is configured to change the threshold value according to the setting output, and to set the threshold value to a higher value stepwise as the setting output becomes larger. In this way, the determination unit can correctly determine the presence or absence of a load regardless of the set output.

  FIG. 6 shows threshold values when the microwave oven is continuously operated for 10 minutes when the set output is set to 1000 W, 600 W, and 500 W. As described above, as the operation time of the magnetron 14 becomes longer and the set output becomes larger, the threshold value is set in a stepwise higher value, thereby making it possible to more reliably determine whether there is a load by the determination unit. Can be avoided.

  FIG. 7 shows the anode current detection value Ib when the power supply voltage applied to the microwave oven is 110V, 100V, 95V, and 90V, respectively. Since the anode current detection value Ib changes according to the power supply voltage, the determination unit is configured to change the threshold value according to the power supply voltage and to set the threshold value to a lower value step by step as the power supply voltage decreases. If comprised, it will become possible for a determination part to determine the presence or absence of a load correctly irrespective of a power supply voltage.

  FIG. 8 shows the relationship between the power supply voltage and the threshold when the microwave oven is operated with a set output of 600 W. As also shown in this figure, the determination unit sets the threshold value to a lower value stepwise as the power supply voltage decreases. Note that the input voltage detection circuit 25 of the present embodiment detects the secondary side voltage generated in the secondary winding 2B of the power transformer 2 to detect the primary side voltage applied to the primary winding 2A of the power transformer 2. As a result, the power supply voltage applied to the microwave oven can be detected. The control circuit 21 can read the input voltage detection value from the input voltage detection circuit 25 as the value of the power supply voltage applied to the microwave oven.

  As described above, in this embodiment, in the high-frequency heating cooker that feeds high-frequency output power from the inverter circuit 6 that is the inverter unit to the magnetron 14 and heats the cooking object that is the load, the input to the inverter circuit 6 is performed. The value detected by the input current detection circuit 24 that is an input current detection unit and the input voltage to the inverter circuit 6 that is applied to the high-frequency cooking device are detected by the input voltage detection circuit 25 that is the input voltage detection unit. The value and the value detected by the anode current detection circuit 26 that is an anode current detection unit are input to the control circuit 21 that is a control unit, and the inverter circuit 6 is controlled. In particular, the control circuit 21 is detected by the input current detection circuit 24 when the maximum input current flows through the inverter circuit 6 in common with each product. The input current reference value that is detected, the input voltage reference value that is detected by the input voltage detection face path 25, and the anode current reference value that is detected by the anode current detection circuit 26 are stored in advance, and the input current reference value and input The correlation between the integrated value with the voltage reference value and the maximum output of the magnetron 14 is calculated, and a threshold value is set according to the anode current reference value, which is detected by the input current detection circuit 24 during operation of the magnetron 14 after shipment. Based on the integrated value of the input current detection value and the input voltage detection value detected by the input voltage detection face 25, the inverter circuit 6 is controlled so that the magnetron 14 operates at a desired output using the correlation. In addition, the load state is determined by comparing the threshold value with an anode current detection value detected by the anode current detection circuit 26 when the magnetron 14 is operated. To have.

  In this case, when the maximum input current is supplied to the inverter circuit 6, the input current reference value, the input voltage reference value, and the anode current reference value are stored in the control circuit 21 in advance before shipment. When the magnetron 14 is actually operated, a threshold value serving as a reference for determining the load state is set based on the anode current reference value that differs for each product. Since this threshold value is set in consideration of the inverter circuit 6 and the magnetron 14 which vary from product to product, when the magnetron 14 is operated, the anode current detection value detected by the anode current detection circuit 26 is compared with the threshold value. Then, it becomes possible to accurately determine the load state in consideration of the variation factor for each product.

  Further, when the magnetron 14 is actually operated using the correlation between the integrated value of the input current reference value and the input voltage reference value stored in advance in the control circuit 21 and the maximum output of the magnetron 14, Based on the integrated value of the input current detection value detected by the input current detection circuit 24 and the input voltage detection value detected by the input voltage detection circuit 25, the output control of the magnetron 14 is performed in consideration of a variation factor for each product. It becomes possible to carry out accurately.

  Further, the control circuit 21 in the present embodiment has a configuration in which the threshold value is changed stepwise, for example, according to the operation time of the magnetron 14.

  In this case, when the operation time of the magnetron 14 becomes longer, the temperature of the magnetron 14 rises and the anode current detection value detected by the anode current detection circuit 26 becomes higher. Therefore, the threshold value is set according to the operation time of the magnetron 14. If it is made to change, the erroneous determination of the load state at the time of long-time operation of the magnetron 14 can be suppressed.

  In addition, when it is determined that the load state is not normal, the control circuit 21 in the present embodiment controls the inverter circuit 6 so that the input power to the inverter circuit 6 is reduced or the inverter circuit 6 is stopped. It has the composition to do.

  In this case, when it is determined that the load state is not normal, by controlling the inverter circuit 6 and reducing the input power to the inverter circuit 6, electric field concentration and the temperature rise of the magnetron 14 can be suppressed.

  In this embodiment, in addition to the above configuration, an output setting unit 27 is provided, and the control circuit 21 is configured so that the threshold value varies depending on the output set by the output setting unit 27.

  In this case, when the output set by the output setting unit 27 becomes small, the anode current detection value also becomes small. Accordingly, by changing the threshold value accordingly, it is possible to accurately determine the load state according to the set output. Become.

  Furthermore, in the present embodiment, the control circuit 21 is configured so that the power supply voltage applied to the high-frequency heating cooker is detected by the input voltage detection circuit 25 during operation of the magnetron 14, and the threshold value varies depending on the power supply voltage. .

  In this case, since the anode current detection value changes depending on the power supply voltage applied to the microwave oven as a product, the load state can be accurately determined according to the power supply voltage by changing the threshold value according to the power supply voltage. It becomes possible.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, when the anode current detection value detected by the anode current detection circuit 26 is equal to or greater than the threshold value, the control circuit 21 according to the present embodiment determines that there is no load and the load state is not normal, but the magnetron 14 is adversely affected. It is good also as a structure which can determine that a load state is not normal including the state of the light load which may affect.

6 Inverter circuit (inverter part)
14 Magnetron 21 Control circuit (control unit)
24 Input current detection circuit (input current detection unit)
25 Input voltage detection circuit (input voltage detector)
26 Anode current detection circuit (anode current detection unit)
27 Output setting section

Claims (5)

In a high-frequency heating cooker that feeds high-frequency output power from the inverter unit to the magnetron,
The input current to the inverter unit is detected by the input current detection unit, the input voltage to the inverter unit is detected by the input voltage detection unit, and each value detected by the anode current detection unit by the anode current of the magnetron, It is set as the structure which inputs into a control part and controls the said inverter part,
The control unit includes an input current reference value detected by the input current detection unit, an input voltage reference value detected by the input voltage detection unit, and the anode when a maximum input current is passed through the inverter unit. An anode current reference value detected by the current detection unit is stored, a threshold value is set by the anode current reference value, and the threshold value and an anode current detection value detected by the anode current detection unit when the magnetron operates The high-frequency heating cooker characterized by determining a load state by comparison.   The high-frequency cooking device according to claim 1, wherein the control unit is configured to change the threshold value according to an operation time of the magnetron.   When the control unit determines that the load state is not normal, the control unit controls the inverter unit so as to reduce input power to the inverter unit or stop the inverter unit. The high-frequency heating cooker according to claim 1 or 2. With an output setting section,
The high-frequency cooking device according to any one of claims 1 to 3, wherein the control unit is configured such that the threshold value varies depending on an output set by the output setting unit.   5. The control unit according to claim 1, wherein a power supply voltage during operation of the magnetron is detected by the input voltage detection unit, and the control unit is configured so that the threshold value varies depending on the power supply voltage. The high-frequency heating cooker described in 1.

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