JPH0927388A - High frequency heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency heating device for constantly controlling input current without using a current transformer by ON/OFF-controlling a semiconductor element so as to constantly control the output value of ripple voltage detecting means by a control part. SOLUTION: Ripple voltage detecting means 17 receives the output of a unidirectional power source part 20 composed of a diode bridge 9 for converting a commercial power source 2 to a unidirectional voltage and a smoothing capacitor 11, and detects the ripple voltage superposed on the output voltage of the power source part 20. A control part 16 ON/OFF-controls the semiconductor element 15 of an inverter part 1 so as to constantly control the output value of the means 17 to a desired value. According to this constitution, the control part 16 works to realize a power control substantially equal to the constant control of input current, enabling the regular emission of a constant electromagnetic wave energy from a magnetron 7 in the heating of a food. Thus, an inexpensive high frequency heating device capable of realizing a power control close to the input current constant control without using a current transformer can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency heating device for heating foods, fluids and the like, and more particularly to a high frequency heating device using a semiconductor power converter for generating high frequency power in its power supply device. Is.

[0002]

27 is a circuit diagram of the high-frequency heating device. Fig. 2 shows the power circuit of a high-frequency heating device for home use.
A configuration in which the frequency is increased by an inverter as shown in FIG. 7 is often used. The commercial power supply 2, the diode bridge 9, the inductor 10 for limiting the current, and the filter circuit including the smoothing capacitor 11 for smoothing the voltage constitute the unidirectional power supply unit 20 for converting the AC voltage into the DC voltage, and the resonance capacitor 12 The step-up transformer 3, the transistor 15, and the commutation diode 14 constitute the inverter unit 1. The transistor 15 is 40
A switching control signal of ˜50 KHz is given to perform switching operation. Therefore, the primary winding 13 of the step-up transformer 3
Generates a high-frequency voltage. A high-voltage rectifier circuit 18 is composed of a capacitor 5 and a diode 6. The voltage generated in the secondary winding 4 of the step-up transformer 3 is rectified by half-wave voltage, and the cathode is indirectly heated by the heater winding 8 for emission. When a high voltage DC voltage is applied to the magnetron 7 in this state, electromagnetic wave energy starts to be generated. In summary, the unidirectional power supply unit 20 converts a commercial power supply into a unidirectional voltage, the inverter unit 1 converts the commercial power supply into a high-frequency voltage, the booster transformer 3 boosts the voltage, and the high-voltage rectifier circuit 18 again rectifies the voltage. Then, it is configured to drive the magnetron 7 by converting it into a high voltage DC voltage. A signal proportional to the input current supplied from the commercial power supply 2 is sent to the control unit 16 by the current transformer 19. The control unit 16 is configured to constantly control the electromagnetic wave output of the magnetron 7 by so-called pulse width control, which controls the conduction time and the non-conduction time of the transistor 15 so that the input current has a predetermined value.

[0003]

However, in this configuration, a current transformer for detecting the input current is indispensable in order to control the input current at a constant level, resulting in a very high cost. Controlling the input current to a constant value means that a constant amount of electromagnetic wave energy is constantly radiated while the food is being heated by the high-frequency heating device, which means that there is no large variation in cooking time regardless of the time of cooking. Is very easy to use. For example, control for making the circuit current on the secondary side of the step-up transformer constant is also proposed and put to practical use. In the circuit of FIG. 27, the current detected by the current transformer 21 (the anode current and the dynamic characteristics are almost the same) is controlled to be constant, but in this case, the anode voltage accompanying the temperature rise of the magnetron during food heating. The electromagnetic wave output also decreases in proportion to the decrease in the. Therefore, there is a problem that the time required to finish the product to the desired warmth varies depending on the temperature condition of the device during use, even if the same amount of food is heated. From such an example as well, the method of controlling the input current at a constant level is very advantageous to the user.

On the other hand, sparks or arc discharges generated in the high voltage circuit on the secondary side of the step-up transformer are ignited due to insulation deterioration due to external factors (contact between terminals due to insects such as cockroaches, dew condensation, dust accumulation, etc.). There is a possibility that it may cause a fatal unsafe accident for equipment such as smoke generation, and detect abnormalities in the high voltage circuit such as sparks and arc discharge and stop the circuit operation promptly or insulate the accident so that the accident does not occur. It is an indispensable function as a device to design with sufficient consideration.

Therefore, it is a first object of the present invention to provide a high-frequency heating device that controls input current constant without using a current transformer.

Further, while realizing constant input current control without using a current transformer for detecting the input current, the insulation between the terminals on the secondary side of the step-up transformer 3 may be due to some external factor (between terminals due to insects such as cockroaches). When there is a spark or arc discharge due to deterioration due to contact, dew condensation, dust accumulation, etc.), it has the function of detecting an abnormality and stopping the circuit operation promptly to improve the safety of the equipment. It has a secondary purpose.

A third object is to achieve the second object without using a current transformer for detecting the secondary current.

[0008]

In order to achieve the first object, the present invention comprises a diode bridge for converting an AC power supply into a unidirectional voltage, an inductor for limiting current, and a smoothing capacitor for smoothing voltage. A unidirectional power supply unit, an inverter unit that has at least one semiconductor element, converts the power from the unidirectional power supply unit into high frequency power by turning the semiconductor element on and off at high frequencies, and an output voltage of the inverter unit. Step-up transformer for step-up, high-voltage rectifier composed of at least one capacitor and diode for double-voltage rectifying output voltage of step-up transformer, magnetron for radiating output of high-voltage rectifier as electromagnetic wave, output of unidirectional power source A ripple voltage detecting means for detecting a ripple voltage superimposed on the voltage and a control section for controlling the semiconductor element are provided.

In order to achieve the second object, the present invention has at least a unidirectional power supply section comprising a diode bridge for converting an AC power supply into a unidirectional voltage, an inductor for current limitation, and a smoothing capacitor for voltage smoothing. An inverter unit that has one semiconductor element, converts the power from the unidirectional power supply unit into high-frequency power by turning the semiconductor element ON / OFF at a high frequency, and a step-up transformer that boosts the output voltage of the inverter unit. A high-voltage rectifier composed of one or more capacitors and diodes that double-rectifies the output voltage of the step-up transformer, a magnetron that radiates the output of the high-voltage rectifier as electromagnetic waves, and a ripple voltage that is superimposed on the output voltage of the unidirectional power supply. Ripple voltage detecting means for detecting and secondary side current for detecting current flowing in a branch connected to the anode of the magnetron An output circuit, an abnormality detection circuit that outputs an abnormality detection signal when the output of the ripple voltage detection unit and the output of the secondary side current detection unit deviate from a desired relative relationship, and a control unit that controls the semiconductor element Is.

Further, the semiconductor device includes a unidirectional power supply unit including a diode bridge for converting an AC power supply into a unidirectional voltage, an inductor for limiting current, and a smoothing capacitor for smoothing voltage, and at least one semiconductor element. ON /
An inverter that converts the power from the unidirectional power supply to high-frequency power by turning it off, a step-up transformer that steps up the output voltage of the inverter, and at least one capacitor and a diode that double the output voltage of the step-up transformer. A high-voltage rectifier for voltage rectification, a magnetron for radiating the output of the high-voltage rectifier as electromagnetic waves, a secondary-side current detector for detecting the current value flowing in a branch connected to the anode of the magnetron, and a secondary-side current detector. A multiplying circuit for detecting the product of the output of the means and the ON / OFF duty ratio of the semiconductor element, a control section for controlling the semiconductor element so as to constantly control the output of the multiplying circuit to a desired value, and an output of the secondary side current detecting means. And an abnormality detection circuit that outputs an abnormality detection signal when the output of the multiplication circuit deviates from the desired relative relationship.

Further, the semiconductor device includes a unidirectional power supply unit composed of a diode bridge for converting an AC power supply into a unidirectional voltage, an inductor for limiting current, and a smoothing capacitor for smoothing voltage, and at least one semiconductor element. ON at high frequency
The output voltage of the step-up transformer is composed of an inverter part that converts the power from the unidirectional power supply part to high frequency power by turning on / off, a step-up transformer that steps up the output voltage of the inverter part, and at least one capacitor and a diode. A high-voltage rectifier that doubles the voltage, a magnetron that radiates the output of the high-voltage rectifier as electromagnetic waves, a secondary-side current detector that detects the value of the current that flows in a branch that is connected to the anode of the magnetron, and a semiconductor device ON / OFF with
Switching rate detecting means for detecting the duty ratio of, the output of the secondary side current detecting means and the ON / OFF of the semiconductor element.
A multiplication circuit that detects the product of the OFF duty ratios, a control unit that controls the semiconductor element so as to constantly control the output of the multiplication circuit to a desired value, and the outputs of the multiplication circuit and the switching rate detection means deviate from the desired relative relationship. An abnormality detection circuit that outputs an abnormality detection signal when the above is performed is provided.

In order to achieve the third object, the present invention provides a unidirectional power source section comprising a diode bridge for converting an AC power source into a unidirectional voltage, an inductor for limiting current, and a smoothing capacitor for smoothing voltage. An inverter unit that has at least one semiconductor element, converts the power from the unidirectional power supply unit into high-frequency power by turning the semiconductor element ON / OFF at a high frequency, and a step-up transformer that boosts the output voltage of the inverter unit, A high-voltage rectifier that consists of at least one capacitor and a diode that rectifies the output voltage of the step-up transformer by double voltage, a magnetron that radiates the output of the high-voltage rectifier as electromagnetic waves, and a ripple voltage that is superimposed on the output voltage of the unidirectional power supply. Voltage detecting means for detecting the ON / OFF duty ratio of the semiconductor device Abnormality when the output of the switching rate detection means and the output of the ripple voltage detection means deviates from the desired relative relationship, and the detection means, the control section for controlling the semiconductor element so as to constantly control the output of the ripple voltage detection means to a desired value. An abnormality detection circuit that outputs a detection signal is provided.

Further, the semiconductor device includes a unidirectional power supply unit including a diode bridge for converting an AC power supply into a unidirectional voltage, a current limiting inductor, and a smoothing capacitor for voltage smoothing, and at least one semiconductor element. ON at high frequency
The output voltage of the step-up transformer is composed of an inverter part that converts the power from the unidirectional power supply part to high frequency power by turning on / off, a step-up transformer that steps up the output voltage of the inverter part, and at least one capacitor and a diode. A high-voltage rectifier that doubles the voltage, a magnetron that radiates the output of the high-voltage rectifier as electromagnetic waves, a ripple voltage detector that detects the ripple voltage that is superimposed on the output voltage of the unidirectional power supply, and a reference voltage that determines the high-frequency power. The high-frequency output setting means to be set, the control section for controlling the semiconductor element so as to constantly control the output value of the ripple voltage detecting means to a desired value, and the desired relative relationship between the output of the high-frequency output setting means and the output of the ripple voltage detecting means. And an abnormality detection circuit that outputs an abnormality detection signal when the deviation from

[0014]

The present invention has the following functions due to the above structure.

That is, the high-frequency heating apparatus of the present invention is substantially equivalent to the control unit controlling ON / OFF of the semiconductor element and constant control of the input current in order to control the output value of the ripple voltage detecting means to a desired value. It is intended to realize the power control of.

Further, the control unit turns on / off the semiconductor element so that the output value of the ripple voltage detecting means is constantly controlled to a desired value.
It realizes the electric power control which is almost equivalent to the F control to control the input current constant, and the abnormality detection circuit detects that an abnormality has occurred in the high voltage circuit on the secondary side of the step-up transformer by the ripple voltage detection means and the secondary side. An abnormality detection signal is output by detecting from a change in the relative relationship of the output of the current means. Further, the control unit detects the abnormality detection signal to turn off the semiconductor element or once the semiconductor element is turned off.
After that, it acts to restart.

Further, the control section realizes power control which is almost equal to the ON / OFF control of the semiconductor element so as to control the output value of the multiplication circuit to a desired value, and the input current is controlled to be constant, and the abnormality is detected. The circuit detects that an abnormality has occurred in the high voltage circuit on the secondary side of the step-up transformer from the change in the relative relationship between the outputs of the multiplication circuit and the secondary side current means, and outputs an abnormality detection signal. Further, the control unit detects the abnormality detection signal and turns off the semiconductor element or once turns it off and then restarts it.

Further, the control section realizes power control which is almost equal to ON / OFF control of the semiconductor element so as to constantly control the output value of the integrating circuit to a desired value, and controls the input current to be constant, and also detects an abnormality. The circuit detects that an abnormality has occurred in the high voltage circuit on the secondary side of the step-up transformer based on the change in the relative relationship between the multiplication circuit and the output of the switching rate detecting means, and outputs an abnormality detection signal. Further, the control unit detects the abnormality detection signal and turns off the semiconductor element or once turns it off and then restarts it.

Further, the control unit turns on / off the semiconductor element so that the output value of the ripple voltage detecting means is constantly controlled to a desired value.
It realizes the electric power control which is almost equivalent to the F control to control the input current constant, and the abnormality detection circuit detects the abnormality in the high voltage circuit on the secondary side of the step-up transformer by detecting the ripple voltage and the switching rate. The abnormality detection signal is output by detecting the change in the relative relationship of the output of the means. Further, the control unit detects the abnormality detection signal and turns off the semiconductor element or once turns it off and then restarts it.

Further, the control unit turns ON / OF the semiconductor element so that the output value of the ripple voltage detecting means is constantly controlled to a desired value.
It realizes the power control which is almost equivalent to the F control and the input current is controlled to be constant, and the abnormality detection circuit sets the ripple voltage detection means and the high frequency output to indicate that an abnormality has occurred in the high voltage circuit on the secondary side of the step-up transformer. The abnormality detection signal is output by detecting the change in the relative relationship of the output of the means. Further, the control unit detects the abnormality detection signal to turn off the semiconductor device or once
It works so as to restart after FF.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A high frequency heating apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of essential parts of a high frequency heating apparatus according to the present invention. Those having the same reference numerals as those in FIG. 27 have the same functions and will not be described.

The high voltage rectifier circuit 18 includes a high voltage diode 24,
25 is a double-wave voltage doubler circuit including a high voltage condenser 26 and a high voltage condenser 26.

The ripple voltage detecting means 17 receives the output of the unidirectional power supply section 20, filters and extracts the ripple voltage superimposed on the signal during the operation of the high frequency heating device by a high pass filter, and detects the peak value by a peak hold circuit. Convert to DC voltage.

FIG. 2 is a circuit diagram of the ripple voltage detecting means 17, and FIG. 3 is a waveform of each part. The output of the unidirectional power supply unit 20 is divided by the resistors 28 and 29, and a stepped-down signal is generated across the resistor 29.

As shown in FIG. 3 (a), the voltage waveform generated at point (a) is a waveform obtained by full-wave rectifying the commercial power supply 2 (the cycle is 1 / 2f when the commercial power supply frequency is f). The ripple voltage of the part is superimposed. In the ripple voltage, when the transistor 15 and the commutation diode in the inverter unit 1 are conducting, a regenerative current flows through the smoothing capacitor 11 to discharge the charge from the smoothing capacitor 11 to lower the voltage, and the transistor 15 and the commutation. When the diode is non-conducting, the smoothing capacitor 11 is charged by the current flowing through the inductor 10 and the voltage rises, and the voltage fluctuates as one cycle, and the frequency is equal to the switching frequency (40 to 50 KHz) of the transistor 15. On the other hand, the envelope waveform has a period of 1/2 f and a frequency of 100 to 120 Hz, so both frequencies have 50 dB.
It can be seen that there is a clear difference in degree. For the voltage generated across the resistor 29, the cutoff frequency is set to a little less than 40 KHz by the high-pass filter including the capacitor 30 and the resistor 31, and the ripple voltage is extracted. The diode 32 clamps the voltage swing to the negative side. Therefore, the voltage waveform at point (b) after passing through the filter is as shown in Fig. 3 (b).

The diode 33 and the capacitor 3
4, detected by a peak hold circuit composed of a resistor 35 and converted into a DC voltage. Since the discharge time constants of the capacitor 34 and the resistor 35 are set to values sufficiently larger than the cycle of the envelope waveform, the waveform at point (c) is almost a DC voltage as shown in FIG. 3 (c). This voltage is applied to the operational amplifier 38 resistor 36, 3
The non-inverting amplifier composed of 7 is level-shifted to the optimum voltage level for control.

Therefore, the input current and ripple voltage detecting means 1
The output 7 has a linear relationship as shown in FIG. 4, and if the output voltage of the ripple voltage detecting means 17 is controlled to Vrp / DC, the input current can be constantly controlled to Iin.

The control unit 16 has a circuit configuration as shown in FIG. 5, and the error signal between the output of the ripple voltage detecting means 17 and the signal of the high frequency output setting means 42 is a negative feedback amplifier circuit including resistors 39 and 40 and an operational amplifier 41. It is configured to be amplified by and sent to the pulse width control circuit 43. Therefore,
The conduction time of the transistor 15 is controlled by the pulse width control circuit 40 so that the output of the ripple voltage detecting means 17 becomes substantially constant by well-known pulse width control. Here, the output signal of the high frequency output setting means 42 can change the voltage level through a control unit that controls the entire device, and thereby the high frequency output can be varied.

FIG. 6 shows the time transition of the waveform of each part of the inverter unit 1. The pulse width control circuit 40 generates a GATE signal for driving the transistor 15 as shown in FIG.

When the GATE signal is turned off at the point (a), a resonance voltage is generated between the collector and the emitter of the transistor 15 as shown in the figure (b), and the voltage is applied in the forward direction of the commutation diode 14 from the point (b). Then, the current flows as shown in Figure (d). During this time, a minute voltage corresponding to the forward voltage of the commutation diode 14 is applied between the collector and the emitter of the transistor 15, and at this point (C), the GATE signal turns ON as shown in FIG. . This operation is called a zero volt switching operation (ZVS operation) which is extremely popular in the field of switching power supplies. After that, the GATE signal continues to be turned on up to the point (d), and the current shown in FIG. By controlling this ON period by the pulse width control circuit 40, the output of the ripple voltage detecting means 17 operates substantially constant, that is, the input current operates substantially constant. This cycle is the switching frequency (40 ~
It will be 50 KHz).

Further, the high-frequency heating apparatus of the present invention will be described with reference to the circuit diagram of the main part of FIG. However, description of elements having the same functions and configurations as those of FIG. 1 will be omitted. Reference numeral 21 is a current transformer for detecting a current flowing in a branch connected to the anode of the magnetron. However, the position of the current transformer 21 is not limited to this. The signal detected by the current transformer 21 is waveform-shaped by the secondary-side current detection means 22 into a shape suitable for control.

FIG. 8 is a circuit diagram of the secondary side current detecting means 22. The current transformer 21 is converted into an AC voltage by the load resistance 44 and full-wave rectified by the diode bridge 45. Only the DC component of the signal is filtered and extracted by a low-pass filter consisting of a resistor 46 and a capacitor 47.
It is level-shifted to a voltage level suitable for control by a non-inverting amplifier composed of 9, 50 and operational amplifier 48 and output to the control unit 16.

FIG. 9 shows the abnormality detection circuit 63 of the control unit 16.
2 is an example of a circuit diagram of FIG. The control unit 16 turns on / off the transistor 15 so that the output of the ripple voltage detection means 17 is controlled to be constant by power control similar to the circuit shown in FIG.
The FF signal is controlled and output to the AND gate 63.

On the other hand, the outputs of the ripple voltage detecting means 17 and the secondary side current detecting means 22 are input to the abnormality detecting circuit 63. The output of the ripple voltage detecting means 17 is converted into low impedance by the buffer circuit 51. Circuit power supply voltage Vc
Current flows from the c to the diodes 52 to 56 through the resistors 52 and 57, and the output of the buffer circuit 51 is the diode 5
Applied to the junction of 4 and 55. Therefore, the potential of (a) becomes the potential of the output voltage of the buffer circuit 51 + 2VF (VF is the forward voltage of the diode). On the other hand, the potential of (b) becomes the output voltage of the buffer circuit 51, which is −2VF. These (a) and (b) signals and the output signal of the secondary side current detecting means 22 are input to the window comparator 66 including comparators 58 and 59.

This operation will be described with reference to FIG. When the input current is plotted on the horizontal axis and the voltage is plotted on the vertical axis, it is obvious that the output of the ripple voltage detection means 17 and the output of the secondary side current detection means 22 are substantially proportional to the input current in this circuit. Are set in a relative relationship so that they almost match. This can be achieved by setting the resistors 36 and 37 of FIG. 2 and the values of the resistors 49 and 50 of FIG. 8 to optimize the gain of the non-inverting amplifier. Both signals are (a) and
When it is in the shaded area defined by (b), the comparator 5
Both 8 and 59 are High output, and the output of the window comparator 66 is also High. However, even if insulation or spark discharge occurs due to dielectric breakdown in the high-voltage rectifier circuit 18 due to some external factor, the output of the ripple voltage detection means 17 indicated by the solid line is constantly controlled, so that normal feedback control functions. Although it does not change so much as far as possible, it is known that the secondary side current and the output of the secondary side current detecting means 22 corresponding to it indicated by the dotted line are affected by the influence and have a value far from the normal state. . As a result, the relative relationship between the two changes and the output of the secondary side current detection means 17 deviates from the shaded area, and either comparator becomes Low, and the output of the window comparator 66 turns to Low. That is, the output of the window comparator 66 is High when normal and Low when abnormal.
The output of the window comparator 66 is output to the start / stop circuit 62.

The start / stop circuit 62 comprises an RS flip-flop 60 and a start command circuit 61. Window
The output of the comparator 66 is the RS flip-flop 60.
When it is input to the S port of the and is High (normal time), the Q port becomes High. However, at the time of Low (at the time of abnormality), the S port is set and the Q port becomes Low. Therefore, the AND gate 63 that receives the output of the Q port is High.
The operation of the inverter unit 1 is stopped by opening the gate at the time of (normal time) and allowing the gate signal to be sent to the transistor 15, and closing it at the time of Low (at the time of abnormal) and prohibiting it. When operating again, start command circuit 6
The reset signal enters from 1 to the R port of the RS flip-flop 60 to release the prohibited state.

FIG. 11 shows a time transition of the input waveform of the window comparator 66 in the case where dielectric breakdown occurs at both ends of the high voltage diode 25 of the high voltage rectifier circuit 18 and an arc discharge state occurs. (a) is the signal of the secondary side current detection means 17, (b)
Is the signal of the ripple voltage detection means 17. After the occurrence of an abnormality, the insulation between the terminals is lowered due to arc discharge, a short-circuit closed loop is formed through the current transformer 21, the secondary side current is increased, and the signal of the secondary side current detection means 17 is increased accordingly. Eventually, the upper threshold (a) of the window comparator 66 is exceeded and an abnormality is detected. Of course, receiving this, the circuit operation is stopped and the spread damage of combustion is prevented.

Further, the high-frequency heating apparatus of the present invention will be described with reference to the circuit diagram of the main part of FIG. Descriptions of components having the same functions and configurations as those of FIG. 7 are omitted.

In the multiplication circuit 67, the secondary side current detection means 2
The secondary side current signal detected through 2 and the transistor 15
Then, the product of the duty ratios (switching rates) of the ON / OFF signals output from the control unit 16 that drives is calculated and the result is output. The control unit 16 and the abnormality detection circuit 63 have the same configurations as in FIG. However, the input signal is different and the output of the multiplication circuit 67 is input to the input A. The input A is the output of the secondary side current detection means 22 as in FIG.

The secondary side current detecting means 22 adopts either the method of taking the average value of FIG. 8 or the method of taking the peak value shown in FIG. In the operation of FIG. 13, a voltage corresponding to the AC component of the secondary side current is generated across the load resistor 72 of the current transformer 21. This is detected by the diode 73 and held by the tank circuit of the resistor 74 and the capacitor 75. This is resistance 7
It is converted into a signal level suitable for control by a non-inverting amplifier composed of 9, 80 and an operational amplifier 81.

Next, the operation of the multiplication circuit 67 will be described with reference to FIG. Here, the open collector output type comparator 6 is pulled up by the resistors 67 and 68 and the resistor 70.
9 forms a comparator, which shapes the switching signal of the transistor 15 into a rectangular wave pulse train with low impedance and regularity. Furthermore, pull-up resistor 7
Since 0 is coupled to the output signal of the secondary side current detection means, the peak value of the pulse train is approximately the value of that output signal.
However, at that time, the magnitude relationship between the resistor 71 and the resistor 70 is
>> It is necessary to make resistance 70. The charging / discharging path to the capacitor 72 in the low-pass filter including the resistor 71 and the capacitor 72 includes a charging path through the resistors 70 and 71 and a discharging path through the resistor 71 and a transistor whose emitter is grounded in the comparator 69. The low-pass filter circuit removes high-frequency components and filters only DC components, that is, average values. Finally, this signal is converted into a signal level suitable for control by a non-inverting amplifier composed of resistors 76 and 77 and an operational amplifier 71.

Information contained in this output signal will be described with reference to FIG. The switching signal shown here has an amplitude which is the output of the secondary side current detection means 22, and a frequency which is an ON / OFF control signal for the transistor 15. Multiplication circuit 6
Output signal VOUT filtered by 7 low pass filter circuit
Is the DC term when this input signal is expanded in the Fourier series. This signal VOUT corresponds to the average value, and when expressed by the formula, Vout = A. (Ton / T) = A.τ, which is exactly the multiplication operation of the output A of the secondary side current detection means 22 and the switching rate τ of the transistor 15. It becomes the value which did.

Returning to the control unit 16, the power control is a control for keeping the output of the multiplication circuit 67 constant. According to this control law, it is possible to realize control close to a constant input current.

In the abnormality detection circuit 63, the multiplication circuit 67 is used.
This is an abnormality detection method in which the output of the above is compared with the output of the secondary side current detection means 22, and this operation will be described with reference to FIG. The output of the secondary side current detection means 22 is resistance 49, 50 in FIG. 8 in the case of the average value method, and resistance 7 in the case of the peak method.
Select 9, 80 and adjust to the level indicated by the dotted line. It is normal when the output of the multiplication circuit 67 and the output of the secondary side current detection means 22 are in a relative relationship within the shaded line, and abnormal when they deviate from this.

Therefore, FIG. 11 shows the time transition of the input waveform of the window comparator 66 when dielectric breakdown occurs in both ends of the high voltage diode 25 of the high voltage rectifier circuit 18 and an arc discharge state is reached. (a) is an output signal of the secondary side current detection means 17, and (b) is an output signal of the multiplication circuit 67. After the occurrence of an abnormality, the insulation between the terminals is lowered due to arc discharge, a short-circuit closed loop is formed through the current transformer 21, the secondary side current is increased, and the signal of the secondary side current detection means 17 is increased accordingly. However, when the normal feedback control is functioning, the switching rate is controlled and the output of the multiplication circuit 67 is controlled to be constant. Eventually, when the signal of the secondary side current detection means 17 exceeds the upper threshold (a) of the window comparator 66, an abnormality is detected. Of course, receiving this, the circuit operation is stopped and the spread damage of combustion is prevented. Although the dielectric breakdown of a specific portion is taken as an example here, the abnormality of the output of the multiplying circuit 67 and the output of the secondary side current detecting means 22 can be similarly detected in other places of the high voltage rectifier circuit 18 as well.

Finally, the feature of controlling the output of the multiplication circuit 67 to be constant will be described. FIG. 17 shows the transition of the input current when the controlled object during the heating operation is changed, and is a graph in which the initial value is normalized to 1.
(a) is a control in a circuit configuration in which an input current is fed back by a current transformer, that is, a case of constant input current control. (b) is a control in a circuit configuration in which the secondary side current is fed back by a current transformer, that is, a case of constant secondary side current control. (C) is the case of constant multiplication signal control in which the multiplication signal obtained by multiplying the ratio of the average current of the high-voltage rectifier circuit and the switching rate of the transistor is subjected to constant control. (d) shows the transition of the input current in the case of the constant multiplication signal control in which the multiplication signal obtained by multiplying the ratio of the peak current of the high-voltage rectifier circuit to the switching rate of the transistor is constantly controlled.

In (a), even though the input current constant control is performed, 2
After 0 minutes, it changed about 1% from the initial value, which is considered to be due to the temperature characteristic of the feedback system. From the same viewpoint, in the case of the secondary current constant control (b), a temperature drift of nearly 9% is confirmed, whereas in the case of the multiplication signal constant control (c), the temperature drift is 3% (b ) Compared to 1
The temperature drift is reduced to about / 3. Further, it can be seen that in the case of the multiplication signal constant control (d), it is about 2%, which is closer to the input current constant control (a) than the average current (c).

As described above, according to the constant multiplication signal control, the power control close to the constant input current control can be performed although the secondary side current of the step-up transformer is the control target.

Further, the high-frequency heating device of the present invention will be described with reference to the circuit diagram of the main part of FIG. However, description of elements having the same functions and configurations as those of FIG. 12 will be omitted. The power control for constant control of the output of the multiplication circuit 67 is the same as the example of the invention shown in FIG.

FIG. 19 shows the switching rate detecting means 23.
FIG. ON / OF to transistor 15
The F command signal is fed back to this circuit and impedance-converted by a buffer composed of an operational amplifier 82, and then a resistor 83,
Only a DC component is filtered and extracted by a low-pass filter circuit composed of a capacitor 84, and further level-shifted to a voltage level suitable for control by a non-inverting amplifier composed of resistors 85 and 86 and an operational amplifier 87, and converted into a signal corresponding to a switching rate. It

The circuit configurations of the abnormality detection circuit 63 and the control unit 16 are exactly the same as those in FIG. 9, and the signal A as an input signal is the output of the multiplication circuit 67, and the input B is the output of the switching rate detection means 23. This operation will be described with reference to FIG. 20 showing the input relationship of the window comparator 66. This figure shows the relative relationship of each signal when the horizontal axis represents the input current. The output of the multiplication circuit 67 and the output of the switching rate detection means 23 are set by adjusting the amplification degree of the non-inverting amplifier circuit provided in the output stage of each input signal so that they are located on substantially the same line. Here, the output of the multiplication circuit 67 does not move from this solid line even when an abnormality occurs due to a control rule (multiplication circuit output constant control) that is very similar to the constant input current control. Absent. On the other hand, the output of the switching rate detecting means 23 shown by the dotted line changes simultaneously with the output of the switching rate detecting means 23 when the output of the secondary side current detecting means 22 changes at the time of abnormality in order to establish this control law. When the output signal of the switching rate detecting means 23 deviates from the thresholds (a) and (b) of the window comparator, an abnormality detection signal is output and the operation of the inverter section 1 is stopped.

Therefore, FIG. 21 shows a time transition of the input waveform of the window comparator 66 when dielectric breakdown occurs at both ends of the high-voltage diode 25 of the high-voltage rectifier circuit 18 and an arc discharge state occurs. (c) is the output signal of the switching rate detecting means 23, and (b) is the output signal of the multiplication circuit 67. After the occurrence of an abnormality, the insulation between the terminals is lowered due to arc discharge, a short-circuit closed loop is formed through the current transformer 21, the secondary side current is increased, and the signal of the secondary side current detection means 17 is increased accordingly. However, when the normal feedback control is functioning, the output of the multiplying circuit 67 is controlled to be constant, so that the output signal of the switching rate detecting means 23 decreases conversely by the increase in the signal of the secondary side current detecting means 17. If the threshold value (b) of the lower side of the window / comparator 66 is reached, an abnormality is detected. Of course, receiving this, the circuit operation is stopped and the spread damage of combustion is prevented. Here, the dielectric breakdown of a specific portion is taken as an example, but the abnormality can be detected at other portions of the high-voltage rectifier circuit 18 as well by the change in the relative relationship between the output of the multiplication circuit 67 and the output of the switching rate detection means 23.

Further, the high-frequency heating device of the present invention will be described with reference to the circuit diagram of the main part of FIG. However, description of elements having the same functions and configurations as those of FIG. 1 will be omitted. The power control for constant control of the output of the ripple voltage detection means 17 is the same as the example of the invention shown in FIG.

The circuit configurations of the abnormality detection circuit 63 and the control unit 16 are exactly the same as those of FIG. 9, and as input signals, the input A is the output of the ripple voltage detecting means 17, and the input B is the output of the switching rate detecting means 23. There is. This operation will be described with reference to FIG. This figure shows the relative relationship of each signal when the horizontal axis represents the input current. The amplification degree of the non-inverting amplifier circuit provided at the output stage of each input signal is adjusted so that the output of the ripple voltage detecting means 17 (solid line) and the output of the switching rate detecting means 23 (dotted line) are located substantially on the same line. Is set by. Here, as long as the feedback control functions even when an abnormality occurs in the output of the ripple voltage detecting means 17 according to a control rule (constant output control of the ripple voltage detecting means 17) that is very similar to the constant input current control, on this line. Never move. On the other hand, in the output of the switching rate detecting means 23, when the output of the secondary side current changes at the time of abnormality, the switching rate of the transistor 15 also changes at the same time. This is detected by the switching rate detecting means 23, and when the output signal deviates from the threshold values (a) and (b) of the window comparator, an abnormality detection signal is output and the operation of the inverter section 1 is stopped.

Therefore, FIG. 11 shows the time transition of the input waveform of the window comparator 66 when dielectric breakdown occurs in both ends of the high voltage diode 25 of the high voltage rectifier circuit 18 and an arc discharge state occurs. (a) is an output signal of the switching rate detecting means 23, and (b) is an output signal of the ripple voltage detecting means 17. When an insulation discharge between terminals progresses due to arc discharge after the occurrence of an abnormality and a short circuit closed loop is formed, the power supply to the magnetron 7 is finally cut off and the input current, that is, the output of the ripple voltage detection means 17 decreases. In response to this, the power control system controls the output of the ripple voltage detecting means 17 to be constant, so that the power transistor 15 is turned on.
Increase the time to encourage an increase in input current. As a result, the output signal of the switching rate detecting means 23 rises, exceeds the upper threshold (a) of the window comparator 66, and an abnormality is detected. Of course, receiving this, the circuit operation is stopped and the spread damage of combustion is prevented. Here, the dielectric breakdown of a specific portion is taken as an example, but the abnormality can be detected at other portions of the high-voltage rectifier circuit 18 as well by the change in the relative relationship between the output of the ripple voltage detecting means 17 and the output of the switching rate detecting means 23.

Further, the high-frequency heating apparatus of the present invention will be described with reference to the circuit diagram of the main part of FIG. However, description of elements having the same functions and configurations as those of FIG. 1 will be omitted. The power control for constant control of the output of the ripple voltage detection means 17 is the same as the example of the invention shown in FIG.

The circuit configurations of the abnormality detection circuit 63 and the control unit 16 are shown in FIG. The signal input to the buffer 51 is a signal obtained by level-shifting the output of the high frequency output setting means 42 by resistors 88 and 89. The comparison signal (input B in FIG. 9) to the window comparator 66 is the output of the ripple voltage detecting means 17 of the input A, and other configurations are the same as those in FIG.

This operation is performed by the window comparator 66.
It demonstrates using FIG. 26 which showed the input relationship of. This figure shows the relative relationship of each signal when the horizontal axis represents the input current. The output of the ripple voltage detecting means 17 (dotted line) and the output of the high-frequency output setting means 42 (solid line) are set by the level shifter provided at the output stage of each input signal so as to be located on substantially the same line. Here, it is self-evident that the output of the high-frequency output setting means 42 has no causal relationship that causes a change when an abnormality occurs in the high-voltage rectifier circuit 18, and there is no movement from the solid line during an abnormality. On the other hand, the output of the ripple voltage detecting means 17 is on a dotted line as long as the feedback control functions even when an abnormality occurs, by the control law (the constant output control of the ripple voltage detecting means 17) which is very similar to the constant input current control. However, when an abnormality occurs that deviates from the controllable range of the feedback control, the non-inverting amplifier composed of the resistors 39 and 40 and the operational amplifier 41 cannot maintain the virtual short-circuit state, and the ripple voltage detection is performed. It is quite possible that the output of the means 17 deviates from the dotted line. At this time, the output signal of the ripple voltage detection means 17 deviates from the threshold values (a) and (b) of the window comparator, and an abnormality detection signal is output to stop the operation of the inverter unit 1.

Therefore, FIG. 21 shows a time transition of the input waveform of the window comparator 66 when dielectric breakdown occurs in both ends of the high voltage diode 25 of the high voltage rectifier circuit 18 and an arc discharge state occurs. (b) is an output signal of the high frequency output setting means 42, and (c) is an output signal of the ripple voltage detecting means 17. When an insulation discharge between terminals progresses due to arc discharge after the occurrence of an abnormality and a short circuit closed loop is formed, the power supply to the magnetron 7 is finally cut off and the input current, that is, the output of the ripple voltage detection means 17 decreases. In response to this, the power control system controls the output of the ripple voltage detecting means 17 to be constant, so that the ON time of the power transistor 15 is increased to prompt the increase of the input current. However, if the feedback control deviates from the controllable range, it becomes impossible to control the output of the ripple voltage detection means 17 at a constant level, and the signal becomes
It decreases as shown in (c). As a result, the output signal of the ripple voltage detection means 17 exceeds the lower threshold (b) of the window comparator 66, and an abnormality is detected. Of course, receiving this, the circuit operation is stopped and the spread damage of combustion is prevented. Here, the dielectric breakdown of a specific portion is taken as an example, but also at other portions of the high voltage rectifier circuit 18, an abnormality can be similarly detected by a change in the relative relationship between the output of the high frequency output setting means 42 of the ripple voltage detecting means 17 and the output. .

[0061]

As described above, the following effects can be obtained in the high-frequency heating apparatus of the present invention.

(1) Since the input current is controlled to be constant, a constant electromagnetic wave energy is always radiated during the heating of the food by the high-frequency heating device, which causes a large variation in cooking time regardless of the time of cooking. It is very convenient for users in that it does not exist. Provide a low-cost high-frequency heating device that realizes power control close to constant input current control, which is extremely advantageous for this user, without using any current detection means (current transformer) that detects the input current and secondary side current. can do.

(2) External power factors (contact between terminals due to insects such as cockroaches, condensation, dust accumulation, etc.) in power control with a constant input current obtained by controlling the output of the ripple voltage detection means at a constant level. Spark or arc discharge generated in the high voltage circuit on the secondary side of the step-up transformer due to insulation deterioration due to is detected from the change in the relative relationship between the output of the ripple voltage detection means and the secondary side current detection means, and the circuit operation is stopped immediately. As a result, it is possible to provide a high-safety high-frequency heating device that prevents a fatal unsafe accident such as ignition / smoke.

(3) In the power control of the constant input current control, which is obtained by controlling the output of the multiplication circuit constant, due to external factors (contact between terminals due to insects such as cockroaches, dew condensation, dust accumulation, etc.) Spark or arc discharge generated in the high voltage circuit on the secondary side of the step-up transformer due to insulation deterioration is detected from the change in the relative relationship between the output of the multiplication circuit and the secondary side current detection means, and the circuit operation is quickly stopped, It is possible to provide a highly safe high-frequency heating device that prevents a fatal unsafe accident for equipment such as ignition and smoking.

(4) In the power control of constant input current control obtained by controlling the output of the multiplication circuit constant, due to external factors (contact between terminals due to insects such as cockroaches, condensation, dust accumulation, etc.) Spark or arc discharge generated in the high voltage circuit on the secondary side of the step-up transformer due to insulation deterioration is detected from the change in the relative relationship between the output of the multiplication circuit and the switching rate detection means, and the circuit operation is stopped promptly to ignite. It is possible to provide a high-safety high-frequency heating device that prevents a fatal unsafe accident caused by smoking.

(5) In the power control with a constant input current obtained by controlling the output of the ripple voltage detecting means at a constant level, external factors (contact between terminals due to insects such as cockroaches, condensation, dust accumulation, etc.) The circuit operation is promptly stopped by detecting the spark or arc discharge generated in the high voltage circuit on the secondary side of the step-up transformer due to the insulation deterioration due to the change in the relative relationship between the outputs of the ripple voltage detection means and the switching rate detection means. It is possible to provide a highly safe high-frequency heating device that prevents a fatal unsafe accident for equipment such as ignition and smoke generation, and it is extremely low cost because it does not use the secondary current detection means that requires a current transformer. The above safety can be realized with.

(6) External power factors (contact between terminals due to insects such as cockroaches, dew condensation, dust accumulation, etc.) in power control with a constant input current obtained by controlling the output of the ripple voltage detecting means at a constant level. The circuit operation is promptly stopped by detecting the spark or arc discharge generated in the high voltage circuit on the secondary side of the step-up transformer due to the insulation deterioration due to the change in the relative relationship between the output of the ripple voltage detection means and the high frequency output setting means, It is possible to provide a highly safe high-frequency heating device that prevents a fatal unsafe accident for equipment such as ignition and smoking, and further reduce the cost because it does not use the secondary side current detection means that requires a current transformer. The above safety can be realized with.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a main part of a high-frequency heating device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a ripple voltage detecting means of the high frequency heating device.

FIG. 3 is a voltage waveform diagram of each part of the ripple voltage detection means.

FIG. 4 is an input current characteristic diagram of the output of the ripple voltage detection means.

FIG. 5 is a circuit diagram of a control unit of the high-frequency heating device.

FIG. 6 is a view showing a time transition of current-voltage waveforms of respective parts of the high-frequency heating device.

FIG. 7 is a circuit diagram of a main part of a high-frequency heating device according to another embodiment of the present invention.

FIG. 8 is a circuit diagram of a secondary side current detection means of the same high frequency heating device.

FIG. 9 is a circuit diagram of a control unit and an abnormality detection circuit of the same high-frequency heating device.

FIG. 10 is an input current characteristic diagram of an input signal of a window comparator in the abnormality detection circuit.

FIG. 11 is a diagram showing a time transition of the input signal of the window comparator when the high-voltage rectifier circuit is abnormal.

FIG. 12 is a circuit diagram of essential parts of a high-frequency heating device according to another embodiment of the present invention.

FIG. 13 is a circuit diagram of a secondary-side current detection unit of the same high-frequency heating device.

FIG. 14 is a circuit diagram of a multiplication circuit of the high-frequency heating device.

FIG. 15 is a principle diagram showing a multiplication operation of the multiplication circuit.

FIG. 16 is a diagram showing a time transition of the input signal of the window comparator when the high-voltage rectifier circuit is abnormal.

FIG. 17 is a diagram showing a heating time transition of an input current normalized value in each power control method.

FIG. 18 is a circuit diagram of a main part of a high-frequency heating device according to another embodiment of the present invention.

FIG. 19 is a circuit diagram of a switching rate detecting means of the high-frequency heating device.

FIG. 20 is an input current characteristic diagram of an input signal of a window comparator in the abnormality detection circuit.

FIG. 21 is a diagram showing a time transition of the input signal of the window comparator when the high-voltage rectifier circuit is abnormal.

FIG. 22 is a circuit diagram of a main part of a high-frequency heating device according to another embodiment of the present invention.

FIG. 23 is an input current characteristic diagram of an input signal of a window comparator in the abnormality detection circuit.

FIG. 24 is a circuit diagram of a main part of a high-frequency heating device according to another embodiment of the present invention.

FIG. 25 is a circuit diagram of a control unit and an abnormality detection circuit of the high frequency heating device.

FIG. 26 is an input current characteristic diagram of an input signal of a window comparator in the abnormality detection circuit.

FIG. 27 is a circuit diagram of a main part of a conventional high-frequency heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter section 2 Commercial power supply 3 Booster transformer 7 Magnetron 9 Diode bridge 10 Inductor 11 Smoothing capacitor 15 Transistor (semiconductor element) 16 Control section 17 Ripple voltage detecting means 18 High-voltage rectifying circuit 20 Unidirectional power supply section 22 Secondary side current detecting means 23 Switching rate detecting means 42 High frequency output detecting means 63 Abnormality detecting circuit 67 Multiplier circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Sakai 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A unidirectional power supply unit comprising a diode bridge for converting an AC power supply into a unidirectional voltage, an inductor for limiting current, and a smoothing capacitor for voltage smoothing, and at least one semiconductor element. ON at high frequency
An inverter unit that converts power from the unidirectional power supply unit into high frequency power by turning it off, a step-up transformer that steps up the output voltage of the inverter unit, and an output of the step-up transformer that includes at least one capacitor and a diode. A high-voltage rectifier that doubles the voltage, a magnetron that radiates the output of the high-voltage rectifier as an electromagnetic wave, a ripple voltage detector that detects a ripple voltage that is superimposed on the output voltage of the unidirectional power supply, and the semiconductor element A high-frequency heating apparatus configured to control ON / OFF of the semiconductor element so that the output value of the ripple voltage detection means is constantly controlled to a desired value. 2. A unidirectional power supply unit comprising a diode bridge for converting an AC power supply into a unidirectional voltage, a current limiting inductor, and a smoothing capacitor for voltage smoothing, and at least one semiconductor element. ON at high frequency
An inverter unit that converts power from the unidirectional power supply unit into high frequency power by turning it off, a step-up transformer that steps up the output voltage of the inverter unit, and an output of the step-up transformer that includes at least one capacitor and a diode. A high-voltage rectifying unit that doubles the voltage, a magnetron that radiates the output of the high-voltage rectifying unit as an electromagnetic wave, a ripple voltage detection unit that detects a ripple voltage that is superimposed on the output voltage of the unidirectional power supply unit, and a magnetron of the magnetron. Secondary side current detection means for detecting a current flowing in a branch connected to the anode, and ON / OF of the semiconductor element for constant control of the output value of the ripple voltage detection means to a desired value.
The control unit includes an F-control unit and an abnormality detection circuit that outputs an abnormality detection signal when the output of the ripple voltage detection unit and the output of the secondary side current detection unit deviate from a desired relative relationship. A high-frequency heating device configured to turn off or once turn off the semiconductor element and then restart when the abnormality detection circuit outputs an abnormality detection signal. 3. A unidirectional power supply unit comprising a diode bridge for converting an AC power supply into a unidirectional voltage for unidirectional conversion, an inductor for current limitation, and a smoothing capacitor for voltage smoothing, and at least one semiconductor element. Then, an inverter unit that converts the power from the unidirectional power supply unit into high-frequency power by turning on / off the semiconductor element at a high frequency, a step-up transformer that boosts the output voltage of the inverter unit, and at least one or more A high-voltage rectification unit that is composed of a capacitor and a diode that double-rectifies the output voltage of the step-up transformer, a magnetron that radiates the output of the high-voltage rectification unit as an electromagnetic wave, and a current value that flows in a branch connected to the anode of the magnetron. Secondary side current detecting means for detecting, output of the secondary side current detecting means and ON / OFF duty of the semiconductor element. A multiplication circuit for detecting the product of the output ratio, a control unit for controlling the semiconductor element so as to constantly control the output of the multiplication circuit to a desired value, an output of the multiplication circuit and an output of the secondary side current detection means. And an abnormality detection circuit that outputs an abnormality detection signal when a deviation from a desired relative relationship occurs, and the control unit turns off the semiconductor element once or once after turning it off when the abnormality detection circuit outputs the abnormality detection signal. High-frequency heating device configured to start. 4. A unidirectional power supply section comprising a diode bridge for converting an AC power supply into a unidirectional voltage, an inductor for limiting current, and a smoothing capacitor for voltage smoothing, and at least one semiconductor element. ON at high frequency
An inverter unit that converts power from the unidirectional power supply unit into high frequency power by turning it off, a step-up transformer that steps up the output voltage of the inverter unit, and an output of the step-up transformer that includes at least one capacitor and a diode. A high-voltage rectifier that doubles the voltage, a magnetron that radiates the output of the high-voltage rectifier as an electromagnetic wave, a switching rate detector that detects the ON / OFF duty ratio of the semiconductor element at a high frequency, and an anode of the magnetron. A secondary side current detecting means for detecting a value of a current flowing in a branch connected to the multiplying circuit; a multiplication circuit for detecting a product of an output of the secondary side current detecting means and an ON / OFF duty ratio of the semiconductor element; A control unit for controlling the semiconductor element so as to constantly control the output of the multiplication circuit to a desired value; An abnormality detection circuit that outputs an abnormality detection signal when the output and the output of the switching rate detection means deviate from a desired relative relationship, and the control unit is configured to output the abnormality detection signal when the abnormality detection circuit outputs the abnormality detection signal. A high-frequency heating device having a structure in which a semiconductor element is turned off or is turned off and then restarted. 5. A unidirectional power supply unit comprising a diode bridge for converting an AC power supply into a unidirectional voltage, an inductor for current limitation, and a smoothing capacitor for voltage smoothing, and at least one semiconductor element, wherein the semiconductor element is provided. ON at high frequency
An inverter unit that converts power from the unidirectional power supply unit into high frequency power by turning it off, a step-up transformer that steps up the output voltage of the inverter unit, and an output of the step-up transformer that includes at least one capacitor and a diode. A high-voltage rectifying unit that doubles the voltage, a magnetron that radiates the output of the high-voltage rectifying unit as an electromagnetic wave, a ripple voltage detection unit that detects a ripple voltage that is superimposed on the output voltage of the unidirectional power supply unit, and a magnetron of the magnetron. A secondary side current detecting means for detecting a current value flowing in a branch connected to the anode, a switching rate detecting means for detecting an ON / OFF duty ratio of the semiconductor element, and an output of the ripple voltage detecting means to a desired value. And a ripple voltage control unit for controlling ON / OFF of the semiconductor device for constant control. An abnormality detection circuit that outputs an abnormality detection signal when the output of the output unit and the output of the switching rate detection unit deviate from a desired relative relationship, and the control unit outputs the abnormality detection signal by the abnormality detection circuit. In this case, the semiconductor device is turned off, or a high-frequency heating device is configured to be turned off and then restarted. 6. A unidirectional power supply section comprising a diode bridge for converting an AC power supply into a unidirectional voltage, an inductor for limiting current, and a smoothing capacitor for voltage smoothing, and at least one semiconductor element. ON at high frequency
An inverter unit that converts power from the unidirectional power supply unit into high frequency power by turning it off, a step-up transformer that steps up the output voltage of the inverter unit, and an output of the step-up transformer that includes at least one capacitor and a diode. A high-voltage rectifier that doubles the voltage, a magnetron that radiates the output of the high-voltage rectifier as an electromagnetic wave, a ripple voltage detection unit that detects a ripple voltage that is superimposed on the output voltage of the unidirectional power supply unit, and a high-frequency power. A high frequency output setting means for setting a reference voltage to be determined, a control section for controlling the semiconductor element so as to constantly control the output value of the ripple voltage detecting means to a desired value, an output value of the ripple voltage detecting means and a high frequency output setting An abnormality detection circuit that outputs an abnormality detection signal when the output of the means deviates from a desired relative relationship, Serial high-frequency heating device controller when the abnormality detecting circuit has output the abnormality detection signal which is configured to restart after OFF or temporarily OFF the semiconductor device.