JPH0864358A - Cooking device - Google Patents

Abstract

PURPOSE: To reduce the number of component items, reduce cost, and enhance reliability by detecting voltage applying to a switching element and driving the element with the detected voltage. CONSTITUTION: A commercial a.c. power source 1 is rectified and smoothed with a rectifying-smoothing circuit 2, the output of the circuit 2 is converted into high frequency with a switching element 4, and high frequency power is supplied to a magnetron 10 through a magnetron driving transformer 40. A microcomputer 31 has a cooking control function and an inverter circuit control function, and an inverter circuit input power variable interface is made unnecessary. A driving control means 51 controls a driving circuit 8, and drives the switching element 4 in specified pulse width. Voltage applied to the switching element 4 is detected with the driving control means 51 to drive the switching element 4. Since direct input power is variable, the interface is made unnecessary, and cost is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating cooker, and more particularly to a control for maintaining safety and stability of a switching element for generating a high frequency power source and operating it stably.

[0002]

2. Description of the Related Art As a conventional high-frequency heating device, Japanese Patent Publication No.
0-14585, JP-B-62-56755, JP-A-64-31390, JP-B-5-36795 and JP-A-62-140390. FIG. 28 is a circuit diagram showing the configuration of the high-frequency heating cooker. In the figure, 1 is a commercial AC power supply, 2 is a rectifying / smoothing circuit for rectifying and smoothing the AC of the commercial AC power supply 1,
A magnetron driving transformer 40 is connected to the output side of the rectifying / smoothing circuit 2, and the magnetron driving transformer 4 is connected.
The resonance capacitor 6 is connected in parallel to the primary winding 40a of 0 to form a resonance circuit, and the diode 5 is connected to the resonance circuit.
By connecting the switching element 4, an inverter circuit of the high-frequency heating cooker is configured.

A voltage doubler rectifying circuit 9 for driving the magnetron 10 is connected to the secondary winding 40c of the magnetron driving transformer 40 which constitutes an inverter circuit, and the tertiary winding is connected to the tertiary winding. The heater of the magnetron 10 is connected to the inverter circuit control Ic.
It is controlled by 216 so that an optimum output state is obtained. Further, the inverter circuit control Ic 216 is connected to an inverter circuit input power switching circuit 217 that varies the input power of the inverter circuit and the output of the magnetron, and cooking control that issues a switching command to the inverter circuit input power switching circuit 217. The microcomputer 218 for use is connected.

Next, the inverter circuit controlling Ic 216 will be described. The drive circuit 210 is the switching element 4
And is connected to the switching element 4. Reference numeral 211 denotes a collector voltage zero detection circuit for reducing the loss of the switching element 4. FIG. 29 shows a waveform at the time of its operation, and this operation will be described. 29A shows a collector voltage waveform of the switching element 4, and at the moment when the switching element 4 is turned off, LC resonance occurs due to the resonance capacitor 6 and the primary side winding 40a, and becomes a sine wave shape. And when the collector voltage becomes zero,
A collector voltage zero detection signal as shown in FIG. 29B is generated. After that, after the collector voltage zero detection signal is generated,
A pulse as shown in (C) of FIG. 29 is generated, and the switching element 4 is driven by the drive circuit 210. And
The collector current of the switching element 4 is (D) in FIG.
The sawtooth waveform as shown in (3) and the collector current and the collector voltage do not overlap, thus reducing the switching loss.

Further, 212 detects the voltage applied to the primary winding 40a, and the higher the instantaneous voltage applied, the higher the switching element 4
The switching element duty for improving the power factor of the inverter circuit by substantially equalizing the high frequency power supplied to the load in each T _ON and T _OFF cycle of the switching element 4 by controlling the T _ON time of This is a ratio variable circuit, and the waveform during its operation is shown in FIG. 30, and this operation will be described. FIG. 30A shows the primary winding 4
The instantaneous applied voltage is 0a, and as shown in FIG. 30B, T _{ON of the} switching element 4 becomes smaller as the instantaneous applied voltage to the primary winding 40a becomes higher.

Reference numeral 213 is an input current detection transformer 50.
The input current is detected by the input voltage, the input voltage is detected by the input voltage detection resistor 49, the input power of the inverter circuit is calculated from these information, and if it is lower than the input power, an instruction to increase the input power is issued and the input power is higher than the set input power. For example, a feedback circuit that issues a command to reduce the input power and performs control to always maintain the input power, 214 detects the anode current of the magnetron 10 by the current detection transformer 51, and when the inverter circuit is abnormal, the anode current of the magnetron 10 disappears and oscillation occurs. An abnormal operation detection circuit 215 that detects the stoppage and issues a command to stop the operation of the inverter circuit detects the anode current of the magnetron 10 by the current detection transformer 51, and a transient phenomenon from the power-on until the magnetron 10 oscillates. Detecting time, T of switching element 4 until oscillation
This is a soft start circuit that issues a command to turn _ON smaller than usual.

FIG. 31 is a circuit diagram showing another structure of a conventional high frequency heating cooker. In the figure, reference numeral 220 is an inverter circuit control Ic, and the inverter circuit control Ic 220 controls the magnetron 10 so as to be in an optimum output state. In addition, the Ic 220 for controlling the inverter circuit includes a microcomputer 22 for cooking control which issues start and stop commands for the inverter circuit.
2 is connected. Reference numeral 221 denotes a switching element circuit that drives the switching element 4, and the other configuration is shown in FIG.
This is similar to the conventional example.

Next, the inverter circuit controlling Ic 220 will be described. The instantaneous voltage stop detection circuit 216 detects the input voltage with the input voltage detection resistor 49 and stops the inverter circuit based on the input voltage. The operation of the other inverter circuit controlling Ic 220 is similar to that of the conventional inverter circuit controlling Ic 216 of FIG.

[0009]

In the conventional high-frequency heating apparatus as described above, the inverter circuit control Ic, the inverter circuit input power switching circuit and the cooking control microcomputer are indeterminate, and the inverter circuit is also indeterminate. Since the control Ic is not general-purpose, the custom Ic
There is also a problem that even if there is a problem with the internal circuit after the production, it cannot be corrected.
Also, when manufacturing an inverter circuit board for a high-frequency heating apparatus, an external resistor and a capacitor for adjusting the internal circuit of the inverter circuit control Ic and the inverter circuit control Ic are required, which is small, small in size and low in size. There was also the problem that the cost was difficult. Furthermore, there is no display of the input power at the time of inspecting the inverter power supply, so that there is a problem that the input setting cannot be confirmed without using a measuring instrument.

Further, in the conventional high frequency heating apparatus, FIG.
As shown in, there is a problem that the collector voltage zero detection of the collector voltage zero detection circuit 211 cannot be detected because the collector voltage becomes extremely small during the period when the instantaneous voltage applied to the primary winding 40a is low. As shown in (A) of FIG. 32, this is a pulsating current voltage that is rectified by the rectifying / smoothing circuit 2 by the instantaneous voltage applied to the primary winding 40a, and (B) of FIG.
This is because the collector voltage becomes smaller as the instantaneous voltage applied to the primary winding 40a becomes smaller as shown in FIG. 32. In the collector voltage undetectable period as shown in FIG. Since the collector voltage of (B) is small, the collector voltage zero detection circuit 211 cannot detect the collector voltage. Therefore, during the collector voltage undetectable period, the collector voltage and the collector current overlap with each other, resulting in an increase in switching loss.

Further, the duty factor of the switching element 4 is varied by the switching element duty ratio varying circuit 212 to improve the power factor of the inverter circuit. However, if the period for which the T _ON time of the switching element 4 is reduced is increased, the input power is increased. There was a problem that it would decrease. Further, there is a problem that the input power fluctuates greatly when the processing speed of the feedback circuit 213 is slow.

There is also a problem that the abnormal operation detection circuit 214 malfunctions due to power supply noise or the like and stops even when the inverter power supply is normal. Moreover, since the soft start circuit 215 has a long operating time in the soft start circuit 215, there is a problem that the set power is not reached in a long time, and the cooking time also becomes long. Further, the instantaneous voltage stop detection circuit 216 has a problem that the inverter circuit is stopped even if the commercial AC power supply is momentarily dropped or stopped for a few ms, and cooking cannot be performed. In addition, since a driving power source is always connected to the switching element drive circuit 221, a malfunction occurs due to power source noise or the like, and a voltage is applied to the switching element 4.

The present invention has been made to solve such a problem, and a microcomputer is provided with a function of controlling cooking and a function of controlling an inverter circuit, and the heating cooker is controlled by the microcomputer. This reduces the number of components, facilitates adjustment of the inverter circuit, change of control status, display of input power, etc., and more accurate control, which improves reliability of the heating cooker. Further, it is an object of the present invention to obtain a heating cooker in which the switching loss of the switching element can be reliably eliminated, the input power does not fluctuate, and malfunction does not occur.

[0014]

A heating cooker according to a first aspect of the present invention comprises a rectifying / smoothing circuit for rectifying and smoothing a commercial AC power source,
A switching element that converts the output of the rectifying and smoothing circuit into high frequency, supplies high frequency power to the magnetron through a transformer, or supplies high frequency power to the inductor, and detects the voltage applied to the switching element, and detects the detection signal. Based on the above, there is provided a control means having a drive control means for driving the switching element and a cooking control means for controlling cooking.

The heating cooker according to the second aspect of the present invention converts the output of the rectifying and smoothing circuit for rectifying and smoothing the commercial AC power source into a high frequency, and supplies high frequency power to the magnetron through a transformer, or Based on the switching element that supplies high frequency power to the inductor, the magnetic detection means that detects the magnetic flux of the transformer or the inductor and outputs the detection signal corresponding to the applied voltage of the switching element, and the detection signal from the magnetic detection means. , And a control means having a drive control means for driving the switching element and a cooking control means for controlling cooking.

In the heating cooker according to the third aspect of the present invention, the control means further determines that the voltage applied to the switching element becomes zero based on the voltage signal applied to the switching element or the detection signal from the magnetic detection means. And a voltage zero detecting means for outputting a control signal for driving the switching element to the drive control means. In the heating cooker according to the fourth aspect of the invention, the control means further detects an instantaneous voltage applied to the primary winding of the transformer or an instantaneous voltage applied to the inductor, and based on the instantaneous voltage. The duty ratio variable control means outputs a control signal for changing the duty ratio of the switching element to the drive control means.

In the heating cooker according to the fifth aspect of the present invention, the control means further detects the input voltage and the input current to the rectifying and smoothing circuit, and outputs a control signal for keeping the input power constant to the drive control means. It has a feedback control means for outputting to the drive control means. In the heating cooker according to the sixth aspect of the present invention, the control means further detects a current flowing through the magnetron or the inductor to detect an abnormal operation and stops the driving of the switching element, or an input to the rectifying / smoothing circuit. A control signal to lower the power,
It has an abnormal operation detection control means for outputting to the drive control means.

In the heating cooker according to the seventh aspect of the invention, the control means further detects the current flowing through the magnetron to detect an unstable period during a transient phenomenon until the magnetron oscillates, and the duty ratio of the switching element. It has a soft start control means for outputting to the drive control means a control signal for reducing the. In the heating cooker according to the eighth aspect of the present invention, the control means further directly changes the setting of the input power to the rectifying and smoothing circuit and outputs the value of the set input power to the feedback control means.

In the heating cooker according to the ninth aspect of the invention, the control means further detects a momentary drop or a momentary stop of the voltage of the commercial AC power supply, and outputs a control signal for stopping the driving of the switching element to the drive control means. It has an instantaneous voltage drop stop detection control means for outputting to. In the cooking device according to the tenth aspect of the invention, the instantaneous voltage drop stop detection control means further includes a return from the instantaneous voltage drop of the commercial AC power supply,
Alternatively, the control signal for detecting the return from the instantaneous stop and driving the switching element by the soft start control means is output to the drive control means.

In the heating cooker according to the eleventh invention,
The control means further has a display control means for detecting the input power to the rectifying and smoothing circuit and displaying the input power on the display means. In the heating cooker according to the twelfth invention, the control means further detects when the voltage applied to the switching element becomes zero, based on the voltage signal applied to the switching element or the detection signal from the magnetic detection means. And a voltage zero detection means for outputting a control signal for driving the switching element to the drive control means when the instantaneous voltage applied to the primary winding of the transformer or the instantaneous voltage applied to the inductor is equal to or higher than a predetermined voltage. Is to have.

In the heating cooker according to the thirteenth invention,
The control means further detects the instantaneous voltage applied to the primary winding of the transformer or the instantaneous voltage applied to the inductor, and the duty ratio of the switching element is small near the maximum value of the instantaneous voltage and is the minimum value. It has a duty ratio variable control means for outputting to the drive control means a control signal that is large in the vicinity and that changes stepwise between the maximum value and the minimum value. In the heating cooker according to the fourteenth aspect of the present invention, the control means further detects the input voltage and the input current to the rectifying / smoothing circuit at high speed, and outputs a control signal to the drive control means to keep the input power constant. It has a feedback control means for outputting to.

In the heating cooker according to the fifteenth invention,
The control means further detects a current flowing through the magnetron or the inductor to detect an abnormal operation, and outputs a control signal for stopping the driving of the switching element when the abnormal operation continues for a predetermined number of times or an input power to the rectifying / smoothing circuit. It has an abnormal operation detection control means for outputting a control signal for lowering it to the drive control means. In the heating cooker according to the sixteenth invention, the control means further detects the current flowing through the magnetron, detects an unstable period during a transient phenomenon until the magnetron oscillates, and reduces the duty ratio of the switching element. A soft start control means for outputting to the drive control means a control signal for gradually increasing the duty ratio for a predetermined period of time is provided.

In the heating cooker according to the seventeenth invention,
The control means further detects an instantaneous drop or an instantaneous stop of the voltage of the commercial AC power supply, and when the instantaneous drop or the instantaneous stop continues for a predetermined time, outputs a control signal for stopping the driving of the switching element to the drive control means. It has an instantaneous voltage drop stop detection control means. In the heating cooker according to the eighteenth invention, the control means further has a power supply means for supplying drive power for driving the switching element only when cooking is performed.

In the heating cooker according to the nineteenth invention, the control means is composed of a one-chip microcomputer. In the heating cooker according to the twentieth aspect of the present invention, the drive control means and the zero voltage detection means are configured by a hardware circuit including at least a flip-flop and a logic gate in the one-chip microcomputer.

[0025]

In the first aspect of the invention, the rectifying and smoothing circuit is used.
The commercial AC power supply is rectified and smoothed, the output of the rectification and smoothing circuit is converted to high frequency by the switching element, and the high frequency power is supplied to the magnetron through the transformer or the high frequency power is supplied to the inductor to perform control related to cooking. The drive control means of the control means detects the voltage applied to the switching element, and based on the detection signal,
The switching element is driven.

In the second aspect of the invention, the commercial AC power supply is rectified and smoothed by the rectifying and smoothing circuit, the output of the rectifying and smoothing circuit is converted into a high frequency by the switching element, and the high frequency power is supplied to the magnetron through the transformer. , Or high frequency power is supplied to the inductor, the magnetic flux of the transformer or the inductor is detected by the magnetic detection unit, and a detection signal corresponding to the voltage applied to the switching element is output, and the drive control unit of the control unit that performs control related to cooking Due to
The switching element is driven based on the detection signal from the magnetic detection means.

In the third invention, when the voltage zero detection means of the control means causes the voltage applied to the switching element to become zero based on the voltage signal applied to the switching element or the detection signal from the magnetic detection means. A control signal that is detected and drives the switching element is output to the drive control means. In the fourth invention, the duty ratio variable control means of the control means detects the instantaneous voltage applied to the primary winding of the transformer or the instantaneous voltage applied to the inductor, and based on the detected instantaneous voltage. A control signal for changing the duty ratio of the switching element is output to the drive control means.

In the fifth aspect of the invention, the feedback control means of the control means detects the input voltage and the input current to the rectifying and smoothing circuit, and the drive control means causes the drive control means to keep the input power constant. Is output to the means. In the sixth invention, the abnormal operation detection control means of the control means detects a current flowing through the magnetron or the inductor to detect an abnormal operation, and a control signal for stopping the driving of the switching element or an input to the rectifying / smoothing circuit. A control signal for reducing the power is output to the drive control means.

In the seventh aspect of the invention, the soft start control means of the control means detects the current flowing through the magnetron and detects an unstable period during a transient phenomenon until the magnetron oscillates, and the drive control means includes a switching element. A control signal for reducing the duty ratio of is output to the drive control means. In the eighth invention, the setting of the input power to the rectifying and smoothing circuit is directly changed by the control means, and the value of the set input power is output to the feedback control means. In the ninth invention, the instantaneous voltage drop stop detection control means of the control means detects an instantaneous drop or an instantaneous stop of the voltage of the commercial AC power supply, and a control signal for stopping the driving of the switching element is sent to the drive control means. Is output.

In the tenth aspect of the invention, the instantaneous voltage drop stop detection control means of the control means further detects the return of the commercial AC power supply voltage from the instantaneous drop or the return from the instantaneous stop, and the switching element A control signal for driving the soft start control means is output to the drive control means. In the eleventh aspect, the display control means of the control means detects the input power to the rectifying and smoothing circuit and displays the input power on the display means.

In the twelfth aspect of the invention, when the voltage zero detection means of the control means causes the voltage applied to the switching element to become zero on the basis of the voltage signal applied to the switching element or the detection signal from the magnetic detection means. The detected control signal for driving the switching element is output to the drive control means when the instantaneous voltage applied to the primary winding of the transformer or the instantaneous voltage applied to the inductor is equal to or higher than a predetermined voltage. In the thirteenth aspect, the duty ratio variable control means of the control means detects the instantaneous voltage applied to the primary winding of the transformer or the instantaneous voltage applied to the inductor to detect the duty ratio of the switching element. A control signal is output to the drive control means, which is small near the maximum value of the instantaneous voltage, large near the minimum value, and gradually changed between the maximum value and the minimum value.

In the fourteenth aspect of the invention, the feedback control means of the control means detects the input voltage and the input current to the rectifying and smoothing circuit at high speed, and the drive control means receives a control signal for keeping the input power constant. It is output at high speed. In the fifteenth aspect of the invention, the abnormal operation detection control means of the control means detects a current flowing through the magnetron or the inductor, detects the abnormal operation, and stops the driving of the switching element when the abnormal operation continues for a predetermined number of times. A signal or a control signal for reducing the input power to the rectifying and smoothing circuit is output to the drive control means.

In the sixteenth aspect of the present invention, the soft start control means of the control means detects the current flowing through the magnetron and detects the unstable period during the transient phenomenon until the magnetron oscillates, thereby changing the duty ratio of the switching element. A control signal that decreases the duty ratio and gradually increases the duty ratio for a predetermined time is output to the drive control unit. In the seventeenth aspect of the invention, the instantaneous voltage drop stop detection control means of the control means detects the instantaneous drop or instantaneous stop of the voltage of the commercial AC power supply, and drives the switching element when the instantaneous drop or instantaneous stop continues for a predetermined time. A control signal for stopping the drive is output to the drive control means.

In the eighteenth aspect, the power supply means of the control means supplies drive power for driving the switching element only when cooking is performed. In the nineteenth invention, the control means is composed of a one-chip microcomputer. In the twentieth aspect of the invention, the drive control means and the voltage zero detection means are constituted by a hardware circuit which is composed of at least a flip-flop and a logic gate in the one-chip microcomputer.

[0035]

【Example】

Example 1. FIG. 1 is a circuit diagram showing the configuration of a heating cooker according to an embodiment of the present invention. In the figure, the same components as those of the conventional example are designated by the same reference numerals, and the description of the duplicate components is omitted. Reference numeral 7 denotes a magnetic detecting means for detecting the magnetic flux of the magnetron driving transformer 40, and in this embodiment, the magnetic flux is detected by the quaternary winding 40d of the magnetron driving transformer 40. 8 is a drive circuit for driving the switching element, 31
Is a microcomputer that controls cooking, and the microcomputer 31 controls the switching element 4 and the like, and also controls the inverter circuit of the high-frequency heating cooker.

Further, the microcomputer 31 has both a function of controlling cooking of the high frequency heating device and a function of controlling an inverter circuit, and inside thereof, there is a drive control means 51, a collector voltage zero detection means 52, and a feedback control. The microcomputer 3 is provided with means 53, variable duty control means 54, instantaneous voltage drop stop detection means 55, abnormal operation detection control means 56, soft start control means 57, display control means 58 and cooking control means 59.
Since No. 1 has both a function of controlling cooking and a function of controlling an inverter circuit, it does not have an interface for varying the input power of the inverter circuit. Further, the drive control means 51
Controls the drive circuit 8 to drive the switching element 4 with a predetermined pulse width. This drive control means 5
1 may have the function of the drive control circuit 8. In that case, the drive control circuit 8 can be omitted and the switching element 4 can be driven directly from the drive control means 51 of the microcomputer 31.

The collector voltage zero detection control means 52 detects a voltage corresponding to the collector-emitter voltage of the switching element 4 from the quaternary winding 40d of the magnetron drive transformer 40, and based on this information, the collector-emitter voltage of 0V is detected. The feedback control means 53 has a function of detecting, and the signal obtained by rectifying the AC voltage of the input current detection transformer 50 by the rectifier circuit 41 and the signal obtained by rectifying the input voltage by the rectifier circuit 43 are input. It has the function of keeping the input power of the circuit constant. Also,
The duty ratio variable control means 54 has a function of varying the duty ratio of the switching element 4 according to the information from the pulse generating circuit 44 for detecting the frequency of the commercial AC power supply 1, and the instantaneous voltage drop stop detection control means 55 is Pulse generation circuit 44 for detecting the frequency of the commercial AC power supply 1
Based on the information from the above, it has a function of sending a command to the soft start control means 57 when the commercial AC power supply 1 is instantaneously dropped or stopped and the inverter circuit is stopped and when the commercial AC power supply 1 is restored.

Further, the abnormal operation detection control means 56 is inputted with a signal obtained by rectifying the AC voltage of the magnetron anode current detection transformer 51 by the rectifier circuit 45. Based on this information, the inverter circuit is stopped or the input power is supplied when the inverter circuit is abnormal. The soft start control means 57 has a function of lowering it, detects the transient time from power-on to oscillation of the magnetron 10 based on the information of the magnetron anode current detection transformer 51, and makes T _{ON of the} switching element 4 smaller than usual until oscillation. It has a function to do. Further, the display control means 58 has a function of performing control to display the input power on the display 60 in real time based on the input current and voltage information from the feedback control means 53, and the cooking control means 59 has the relay 70 and the sensor 71. It has the function of controlling cooking and controlling cooking. The power source of the microcomputer 31 is obtained from a power source smoothing circuit 42 that smoothes the commercial AC power source 1 with a transformer and a rectifying diode, and outputs a constant voltage with a capacitor and a zener diode.

Next, the operation of the microcomputer 31 of this embodiment will be described. 2 is a flow chart showing the operation of the collector voltage zero detection means 52, FIG. 3 is a waveform diagram for explaining the operation of the duty ratio variable control means 54, and FIG. 4 is a flow chart showing the operation of the duty ratio variable control means 54. 5 is a flow chart showing the operation of the feedback control means 53, FIG. 6 is a flow chart showing the operation of the abnormal operation detection control means 56, FIG. 7 is a flow chart showing the operation of the soft start control means 57, and FIG. 8 is an instantaneous voltage drop stop detection control. FIG. 9 is a waveform diagram for explaining the operation of the means 55, and FIG. 9 is an instantaneous voltage drop stop detection control means 55.
10 is a flowchart showing the operation of the display control means 5 shown in FIG.
8 is a flowchart showing the operation of FIG. 8, and FIG. 11 is a flowchart showing the operation of varying the input power.

Zero collector voltage detecting means 52 of this embodiment
Is the collector waveform shown in FIG.
The signal from d is taken in, the trailing edge of the collector waveform shown in FIG. 15 (A) is detected, and when the collector waveform becomes 0 [V], the collector voltage zero detection shown in FIG. 15 (B). After generating a signal and confirming the detection signal, (C) of FIG.
In order to generate the T _ON waveform shown in FIG.
The T _ON generation command is output to the
Will be described with reference to.

First, after the inverter circuit is started, a T _ON generation command is generated (S100) and the drive control means 51 is turned _{ON.
An ON} generation command is output (S101). Then, check if the collector waveform has been input. If it cannot be confirmed, S1
Returning to 00, T _ON is generated again (S102). S10
When the collector waveform is confirmed in 2, the loop is repeated until the collector waveform falls, that is, the collector voltage becomes 0 [V] (S103), and the collector voltage becomes 0 [V].
Then, a collector voltage zero detection signal is generated (S1
04). Then, it is confirmed whether or not the collector voltage zero detection signal is generated (S105). If the collector voltage zero detection signal cannot be confirmed in S105, the process returns to S104 and the collector voltage zero detection signal is generated again. If it is confirmed in S105, the process returns to S100 and T
Generates an _ON generation command. By such an operation of the collector voltage zero detection means 52 in the microcomputer 31, it is possible to reduce the loss of the switching element and improve the reliability.

In the duty ratio variable control means 54 of this embodiment, the commercial AC power supply shown in FIG. 3A is converted into the pulse waveform shown in FIG. 3B by the pulse generating circuit 44. 3C, the T _ON time of the switching element is set to the primary winding 40a as shown in FIG. 3C according to the rise and fall of the pulse waveform shown in FIG. 3B.
The T _ON generation command is output to the drive control means 51 so that it becomes smaller as the applied instantaneous voltage becomes higher. This operation will be described with reference to FIG.

First, after starting the inverter circuit, it is confirmed whether or not a pulse waveform is input (S110). If it is not confirmed in S110, it is confirmed again. If it is confirmed in S110, whether or not the rising edge of the pulse waveform is inputted. And repeat the loop until a rising edge can be detected (S1
11), drive control means 51 when detected in S111
A variable duty ratio command is output to (S112). Next, it is confirmed whether the trailing edge of the pulse waveform has been input, and the loop is repeated until the trailing edge can be detected (S11
3), the duty ratio variable command is output to the drive control means 51 at the time point detected in S113, and the process returns to S110 (S1).
14). The same control can be performed when the commercial frequency is 60 Hz. Such a microcomputer 31
By the operation of the duty ratio variable control means 54 inside, the high frequency power can be equalized, and the power factor of the high frequency heating device can be improved.

Further, the feedback control means 53 of this embodiment takes in a signal obtained by rectifying the voltage of the input current detection transformer 50 by the rectifier circuit 41 and a signal obtained by rectifying the input voltage by the rectifier circuit 43, and inputs the input power of the inverter circuit. If is smaller than the setting, a command to decrease T _ON is output to the drive control means 51, and if it is smaller than the setting, a command to increase T _ON is output. This operation will be described with reference to FIG.

First, after starting the inverter circuit, the input current is detected (S120) and the input voltage is detected (S12).
1), the power is calculated (S122). Then, it is determined whether the calculated value is equal to the set power (S123), and if the calculated value is equal to S123, a T _ON maintenance command is output to the drive control means 51, and the process returns to S120 (S124). If the calculated value and the set power are different in S123, it is determined whether or not the set power is larger than the set power (S125).
The T _ON small command is output to 1, and the process returns to S120 (S12
6) If it is not larger than the set power in S125, that is, if it is smaller than the set power, a T _ON large command is output to the drive control means 51, and the process returns to S120 (S127). By such an operation of the feedback control means 53 in the microcomputer 31, it is possible to make the high frequency power constant with a simple configuration.

Further, the abnormal operation detection control means 56 of this embodiment takes in a signal obtained by rectifying the voltage of the magnetron anode current detection transformer 51 by the rectification circuit 45, and when the inverter circuit is in an abnormal state, for example, the parts are broken, short-circuited or opened. When the magnetron is abnormal, it detects that the anode current becomes small or does not flow because the magnetron does not oscillate normally, and outputs an oscillation stop command or an input power reduction command. Refer to Fig. 6 for this operation. While explaining.

First, after starting the inverter circuit, the anode current is detected (S130), and it is determined whether the anode current is smaller than usual (S131). If it is not small in S131 and the anode current is normal and there is no abnormality, the process returns to S130, and if it is small in S131, an oscillation stop or input power reduction command is output to the drive control means 51 (S132). By such an operation of the abnormal operation detection control means 56 in the microcomputer 31, it becomes possible to make the high-frequency heating device safe without smoke or ignition.

Further, the soft start control means 57 of this embodiment takes in a signal obtained by rectifying the voltage of the magnetron anode current detecting transformer 51 by the rectifier circuit 45, and takes a transient phenomenon from the power-on of the inverter circuit to the oscillation of the magnetron. The instability period is detected by the anode current, and a command for making T _ON of the switching element smaller than usual is output until oscillation occurs. This operation will be described with reference to FIG. 7.

First, after starting the inverter circuit, a commercial AC power source is turned on (S140) to detect the anode current (S).
141). Then, it is determined whether the anode current is small, that is, whether oscillation has occurred (S142). If the anode current is small in S142, a command for performing soft start control is output to the drive control means 51, and the process returns to S141 (S143). S1
When the anode current becomes normal at 42, the magnetron determines that the oscillation is completed, and outputs a command for shifting to normal control to the drive control means 51 (S144). By such an operation of the soft start control means 57 in the microcomputer 31, the switching element can be protected and the reliability can be improved.

In the instantaneous voltage drop stop detection control means 55 of this embodiment, the commercial AC power supply shown in FIG. 3A is converted into the pulse waveform shown in FIG. 3B by the pulse generation circuit 44. When the commercial AC power supply is instantaneously dropped and stopped as shown in FIG. 8 (A), the frequency detection pulse waveform becomes smaller than usual as shown in FIG. 8 (B). When it disappears, the inverter circuit is stopped, and when the commercial AC power is restored, the pulse waveform is also restored as shown in FIG. 8B, so this is detected and a command is output to the soft start control means 57 to start the soft start. Then, the inverter circuit is started up. This operation will be described with reference to FIG.

First, after starting the inverter circuit, it is confirmed whether the frequency detection pulse waveform is input (S150).
If it cannot be confirmed, check again. If the pulse waveform is input in S150, it is determined whether the pulse waveform is normal (S151), and if normal, the process returns to S150 to repeat the inverter circuit operating loop. When the pulse waveform is abnormal in S151, that is, when the voltage drops or disappears due to the instantaneous voltage drop or stop, an inverter circuit stop command is output to the drive control means 51 (S152). Then, it is judged whether or not the pulse waveform has been restored (S153), and if it is not restored in SS153, the process returns to S152 to continue the inverter circuit stop command, and if it is restored in S153, the command is output to the soft start control means 57 and the software is started. At the start, the inverter circuit is started up, and the process returns to S150 (S154). By the operation of the instantaneous voltage drop stop detection control means 55 in the microcomputer 31 as described above, it is possible to protect the high frequency heating device when the commercial AC power supply is instantaneously dropped or is stopped, and the reliability can be improved. Become.

Further, the display control means 58 of this embodiment is
The input power information of the feedback control means 53 is detected,
The input power is displayed on the display 60 in real time, and this operation will be described with reference to FIG. First, after starting the inverter circuit, the input power is detected (S
160) Then, display information for the display 60 is created (S161), and a display command is output to the display 60 (S1).
62). By the operation of the display control means 58 in the microcomputer 31 as described above, it becomes possible to easily inspect the high frequency heating device and adjust the input power.

Further, in this embodiment, the microcomputer 31 has both the means for controlling the inverter circuit of the high-frequency heating apparatus as described above and the cooking control means for controlling cooking, so that the input power of the inverter circuit is It is possible to directly change the input power without using a variable interface. This operation will be described with reference to FIG. First, after starting the inverter circuit, the input power is set (S170), the set input power is output to the feedback control means 53, and feedback control is performed so that the input power becomes constant (S170).
171). Then, confirm whether to change the input power (S
172) If it is variable, the process returns to S170 and the input power is set again. If the input power is not varied in S172, the process returns to S171 to continue the feedback control. By such an operation of the microcomputer 31,
Since the input power can be directly changed by the microcomputer 31, the input power variable interface circuit can be omitted, the number of parts can be reduced, and the cost can be reduced.

In this embodiment, the magnetic detecting means 7
Is the fourth winding 40d of the magnetron drive transformer 40.
The voltage generated in the quaternary winding 40d is input to the microcomputer. However, the inductance element, the hall element, and the magnetoresistive element are arranged near the magnetron driving transformer 40, and the magnetic flux May be detected. In addition, in this embodiment, the voltage applied to the switching element 4 is indirectly detected by the magnetic detection means 7 and input to the microcomputer 31, but without using the magnetic detection means 7, The collector voltage of the switching element 4 may be directly input to the microcomputer 31.

Example 2. Further, in the first embodiment, the case of the high frequency heating device has been described, but as shown in FIG. 12, an induction heating device for controlling the coil 48 may be used, and the same effect as that of the first embodiment can be obtained. In this embodiment, the voltage applied to the switching element 4 is directly detected from the collector of the switching element 4 and input to the microcomputer 31, but as in the first embodiment, magnetic detection is performed near the coil 48. Arrange the means 7 and coil 48
It is also possible to detect the magnetic flux from the device and input the output signal of the magnetic detection means 7 to the microcomputer 31 to indirectly detect the voltage applied to the switching element 4.

Example 3. In this embodiment, the drive control means 51 and the collector voltage zero detection means 52 in the microcomputer 31 of the first embodiment are configured by a hardware circuit. FIG. 13 is a circuit diagram showing the configurations of the drive control means 51 and the collector voltage zero detection means 52 in the microcomputer 31. In the figure, the signal from the magnetic detection means 7 is input to the trigger edge selection unit multiplexer 200 as an external trigger input, and the trigger edge selection unit multiplexer 200 synchronizes with the input edge indicated by the register 201. Since an external trigger is performed, and in this embodiment, 0V of the collector-emitter voltage is detected, the external trigger is performed in synchronization with the fall of the external trigger input. Then, this input is input to the logic gate 202,
The signal is output from the logic gate 202 and becomes the collector voltage zero detection signal.

The output of the logic gate 202 is RS
RS is input to the set input of the flip-flop 203
The output Q of the flip-flop 203 is the logic gate 204.
Is output as an output of the drive control means 51, and drives the drive circuit 8. Further, signals from the microcomputer 31 are also input to the logic gate 202, the RS flip-flop 203, and the logic gate 204, and based on commands from each means in the microcomputer 31,
The output is controlled. As described above, in this embodiment, since the drive control means 51 and the collector voltage zero detection means 52 inside the microcomputer 31 are configured by hardware, the high speed is achieved in synchronization with the desired edge of the external trigger input. A signal for driving the switching element 4 can be output.

Example 4. FIG. 14 is a circuit diagram showing the configuration of a heating cooker according to another embodiment of the present invention. In the figure, 22 is a power supply circuit for supplying or stopping power to the switching element drive circuit 21, 31 is a microcomputer, and this microcomputer 31 controls the switching element 4 and the like, and a high frequency heating cooker The inverter circuit is also controlled.

The microcomputer 31 has a drive circuit control means 61 and a power supply control means 6 therein.
2, collector voltage zero detection means 63, feedback control means 64, duty ratio variable control means 65, instantaneous voltage drop stop detection control means 66, abnormal operation detection control means 67,
The soft start control means 68 is provided.

Zero collector voltage detecting means 63 of this embodiment
Is a voltage from the pulse generation circuit 44 for detecting the frequency of the commercial power source 1 by detecting the voltage corresponding to the collector-emitter voltage of the switching element 4 from the fourth winding 40d of the magnetron driving transformer 40. It has the function of detecting zero collector voltage and the function of stopping the detection of the collector voltage when the voltage applied instantaneously to the primary winding is small, that is, when the collector-emitter voltage is small and cannot be detected.

Next, the operation of the zero collector voltage detecting means 63 will be described. FIG. 15 is a waveform diagram for explaining the operation of the collector voltage zero detecting means 63 of this embodiment, and FIG.
Is a flow chart showing the operation of the collector voltage zero detecting means 63 of this embodiment. In the operation of the collector voltage zero detection function, first, the collector waveform shown in (A) of FIG. 29 is read from the signal from the fourth winding 40d, and the fall of the collector waveform shown in (A) of FIG. 29 is detected. When the collector waveform reaches 0 (V), the zero collector voltage detection signal shown in FIG.
In order to generate the T _ON waveform shown in (C), a T _ON generation command is output to the drive circuit control means 61.

Further, the operation of the stop function of the collector voltage zero detection function is as follows. First, when the commercial AC power supply shown in FIG. The voltage shown in (B) of 15 is applied. Since the pulse generation circuit 44 for detecting the frequency of the commercial AC power supply detects a period in which the voltage of the primary winding 40a of the transformer 40 is small, a pulse waveform is generated before the applied voltage of the commercial AC power supply becomes the minimum. Is adjusted by the resistance of the pulse generation circuit 44 so that the voltage rises.

In this embodiment, the commercial AC power source 50 (H
At z), the cycle is 20 (ms), 11 (ms) and 9 (m)
s). FIG. 15D shows a stop period of the collector voltage zero detection function. From the rising edge of the pulse waveform shown in FIG. 15C, 1 (ms) operation is stopped and then 9 (ms) operation is performed. The operation is continued, and after 9 (ms), the operation is stopped for 1 (ms). This operation is repeated. This operation will be described with reference to FIG.

First, after starting the inverter circuit, the frequency pulse signal is detected (S200). Then, it is confirmed whether the rising edge of the frequency pulse signal has been detected. If the rising edge of the frequency pulse signal cannot be recognized, the process returns to S200 and the rising edge is detected again (S201). If the rising edge of the frequency pulse signal is confirmed in S201, the counter operation is started (20
2). Then, the loop is repeated until 1 (ms) has elapsed from the start of the counter operation (S203), and after 1 (ms) has elapsed, a T _ON generation command is output to the drive circuit control means 61 (S204).

After the T _ON generation command is output, the collector voltage zero detection control is started (S205), the operation for 9 (ms) is continued (S206), and after 9 (ms) has elapsed, the drive circuit control means 61 is turned on. _{An ON} stop command is output (S207), and collector voltage zero detection control is stopped (S208). And
The loop is repeated until 1 (ms) has passed since the collector voltage zero detection control was stopped (S209), and after 1 (ms), it is confirmed whether 20 (ms) has passed from the start of the counter operation, and 20 (ms) has passed. If not, the process returns to S203 (S210).

Then, 20 (m
s) If it has passed, the counter time is cleared (S
211), and returns to S200 to repeat the operation. The same control can be performed when the commercial AC power source is 60 (Hz).

By the operation of the collector voltage zero detection control means 63 of the microcomputer 31 as described above, the loss of the switching element 4 can be reduced, and the loss of the switching element 4 can be reduced even in the collector voltage zero undetectable period.

Further, the duty ratio variable control means 65 of this embodiment has a function of varying the duty ratio of the switching element 4 according to the information from the pulse generating circuit 44 for detecting the frequency of the commercial AC power supply 1. There is.

Next, the operation of the duty ratio variable control means 65 will be described. FIG. 17 is a waveform diagram for explaining the operation of the duty ratio variable control means 65 of this embodiment, and FIG. 18 is a flow chart showing the operation of the duty ratio variable control means 65 of this embodiment. The operation of the function of the duty ratio variable control means is as follows. First, the commercial AC power supply shown in FIG.
The signal converted into the pulse waveform shown in FIG.
29B, the drive circuit is controlled so that the T _ON time of the switching element becomes smaller as the applied voltage of the primary winding 40a becomes higher, as shown in FIG. 29C, according to the rising and falling of the pulse waveform. A T _ON generation command is output to the means 61.

However, the conventional parabolic T shown in FIG.
Instead of changing the _ON time, as shown in (C) of FIG.
Was omitted period to reduce the T _ON time as possible, is to a variable stepwise T _ON time. This operation is shown in FIG.
Will be described with reference to.

First, after starting the inverter circuit, the frequency pulse signal is detected (S220). It is confirmed whether the rising edge of the frequency pulse signal is detected. If the rising edge of the frequency pulse signal is not detected, the processing returns to S220 and the rising edge is detected again (S2).
21). When the rising is detected in S221, a duty ratio variable command is output to the drive circuit control means 61 (222).

Then, it is confirmed whether or not the falling edge of the frequency pulse signal is detected, and the loop is repeated until the falling edge can be detected (S223). At the time when the falling edge of the frequency pulse signal is detected in S223, the drive circuit control is performed. A duty ratio variable command is output to the means 61, and the process returns to S220. The same control can be performed when the frequency of the commercial AC power supply 1 is 60 (Hz).

By the operation of the duty ratio variable control means 65 of the microcomputer 31 as described above, the high frequency power can be equalized, the power factor of the high frequency heating and cooking apparatus is improved, and the T _ON time of the switching element 4 is reduced. It is possible to prevent the input power from decreasing by reducing the period for which the power is supplied.

Further, the feedback control means 64 of this embodiment takes in the signal obtained by rectifying the voltage of the input current detecting transformer 50 by the rectifying circuit 41 and the signal obtained by rectifying the input voltage by the rectifying circuit 43, and inputs the input power of the inverter circuit. If it is larger than the setting, a command to decrease T _ON is output to the drive circuit control means 61, and if it is smaller than the setting, a command to increase T _ON is output to the drive circuit control means 61.
This processing speed is extremely high.

Further, in this operation, similarly to the operation shown in the flowchart of FIG. 5 of the first embodiment, the T _ON time is varied so that the calculated power becomes equal to the set power. Since the processing speed is very high in this embodiment, the fluctuation of the input power (W) with respect to the time (t) seen in the conventional feedback operation as shown in FIG. 19 (A). Since the time width is short as shown in FIG. 19B, the fluctuation of the input power is small. Such feedback control means 64 of the microcomputer 31
By this operation, the high frequency power can be kept constant with little fluctuation.

Further, the abnormal operation detection control means 67 of this embodiment takes in a signal obtained by rectifying the voltage of the magnetron anode current detection transformer 51 by the rectifying circuit 45, and when the inverter circuit is in an abnormal state, for example, parts break, short circuit, open, magnetron. When an abnormality occurs, the magnetron does not oscillate normally, so that it detects that the anode current becomes small or stops flowing, and outputs an oscillation stop command or an input power reduction command. Regarding the operation of the function of the abnormal operation detection control means 67, the abnormal operation detection control means malfunctions due to the power supply noise, etc., which has been conventionally observed, even when the inverter circuit is normal, so that the oscillation stop or the input power does not decrease. It is designed to operate only when abnormality detection is confirmed several times. This operation will be described with reference to FIG.

First, after starting the inverter circuit, the anode current is detected (S230), and it is determined whether the anode current is smaller than usual (S231). If it is determined in S231 that it is not small, and the anode current is not abnormal, , And returns to S230, and if the anode current is abnormal and is smaller than usual in S231, the number of times of abnormality is counted (S23).
2). Then, it is determined whether the count value in S232 is 5, that is, whether the anode current is smaller than usual for five consecutive times (S233).

If it is determined in S233 that the count value is not 5, the process returns to S231, and if it is determined in S233 that the count value is 5, an oscillation stop or input power reduction command is output to the drive circuit control means 61. Yes (S23
4). In this embodiment, the case where the anode current is less than normal for five consecutive times is determined to be abnormal, but the number may be set depending on the degree of malfunction. Such abnormal operation detection control means 67 of the microcomputer 31
The abnormal operation detection control means 67 does not malfunction due to the above operation, and it is possible to make the high-frequency heating device safe without smoke or ignition.

Further, the soft start control means 68 of this embodiment takes in a signal obtained by rectifying the voltage of the magnetron anode current detection transformer 51 by the rectifier circuit 45 and at the time of a transient phenomenon from power-on of the inverter circuit to oscillation of the magnetron. Of the instability of the switching element 4 is detected by the anode current of the magnetron and T _{ON of the} switching element 4 is oscillated.
It outputs a command to make the value smaller than usual. The operation of the function of the soft start control means 68 takes a long time until the soft start control ends because the switching element T _ON time is linearly increased in the conventional soft start control as shown in FIG. , FIG. 21
As shown in (B), the switching element T _ON time is gradually increased and a fixed T _ON time is provided to shorten the time until the end of the soft start control. This operation will be described with reference to FIG.

After the inverter circuit is started, the commercial AC power supply 1 is turned on (S240), and a soft start control command is output to the drive circuit control means 61 (S241). And
The anode current is detected (S242), and it is determined whether the anode current is normal, that is, whether it oscillates (S243).
Then, if it is smaller than usual in S243, it is determined that the transient phenomenon is in progress, and the process returns to S242. If the anode current becomes normal in S243, it is determined that the magnetron oscillation is completed,
A command for shifting to normal control is output to the drive circuit control means 61 (S244).

By the operation of the soft start control means 68 of the microcomputer 31 as described above, the cooking time can be shortened by protecting the switching element 4 and shortening the soft start control time.

The instantaneous voltage drop stop detection control means 66 of this embodiment detects the instantaneous voltage drop and stop of the commercial AC power supply based on the information from the pulse generating circuit 44 for detecting the frequency of the commercial AC power supply 1. Then, the operation of the inverter circuit is stopped. The operation of the function of the instantaneous voltage drop stop detection control means 66 is as shown in FIG. 23 when the commercial AC power supply shown in FIG.
It is detected that the pulse waveform disappears as shown in FIG. However, when the instantaneous voltage drop stop time is short as shown in FIG. 23 (C), the instantaneous voltage drop stop detection control means 66 is not operated and the instantaneous voltage drop / stop is performed as shown in FIG. 23 (D). Only when the time is long, the instantaneous voltage drop / stop detection control means is operated. This operation is shown in FIG.
Will be described with reference to.

First, after starting the inverter circuit, the frequency pulse signal is detected (S250), it is judged whether the frequency pulse signal is normal or not (S251), and if it is normal, that is, if there is no instantaneous voltage drop stop, S250 Back to
Repeat the loop while the inverter circuit is operating. In S251, the frequency pulse signal is abnormal, that is, when the instantaneous voltage drop stops,
When it becomes smaller or disappears, it is judged whether or not the width of the frequency pulse signal is 5 ms or more (S2).
52).

If it is 5 ms or less in S252, S250
Then, the frequency pulse signal is detected again in S250.
If it is 5 ms or more in S252, the drive circuit control means 61
A T _ON stop command is output to (S253). In this embodiment, when the instantaneous voltage drop stop of the commercial AC power supply is 5 ms or less, the instantaneous voltage drop stop detection control means 66 is not operated, but the time may be set arbitrarily. By the operation of the instantaneous voltage drop stop detection control means 66 of the microcomputer 31 as described above, the high frequency heating device is protected when the commercial AC power supply stops the instantaneous voltage drop, and the inverter circuit operates when the instantaneous voltage drop stops for a short time. Since it does not stop, it is possible to prevent the cooking from being interrupted.

Further, the power supply means 62 of this embodiment is
As shown in FIG. 25 (A), a cooking start / end command is detected, and as shown in FIG. 25 (B), a power supply command is output to the power supply circuit 22 in synchronization with cooking start / end. To do. After the power supply command is output, a T _ON generation command is output to the drive circuit control means 61 after a dead time of several ms. This operation will be described with reference to FIG.

First, the microcomputer 31 outputs a cooking start command output (S260), detects the cooking start command of S260, and outputs a power supply command to the power supply circuit 22 (S261). In S261, it is determined whether 1 ms has elapsed from the power supply command output (S262), and S26
When it is determined that 1 ms has not elapsed in step 2, the loop is repeated, and when it is determined that 1 ms has elapsed in S262, a T _ON generation command is output to the drive circuit control means 61 (S26
3).

After outputting the T _ON generation command in S263, it is determined whether or not 1 ms before the cooking end time (S264), and S2
If it is determined in 64 that the cooking end time is not 1 ms before, the loop is repeated, and in S264, the cooking end time is set to 1 ms.
When ms is determined as before, and outputs the T _ON stop command to the drive circuit control means 61 (S265), after T _ON Stop command output at S265, it is determined whether the 1ms has elapsed (S266),
If it is determined that 1 ms has not elapsed in S266, the loop is repeated, and if it is determined that 1 ms has elapsed in S266,
A cooking end command is output (S267).

Then, after the cooking end command is output in S267,
A power supply command stop is output to the power supply circuit 22 (S2
68). Incidentally. In this embodiment, the dead time from the power supply command output to the drive circuit control means 61 to the T _ON generation command output is set to 1 ms, but the time may be set arbitrarily. By the operation of the power supply means 62 of the microcomputer 31 as described above, power is not supplied to the switching drive circuit 21 except during cooking, so that a voltage is not applied to the switching element 4 due to power supply noise or the like, and a safe high frequency A heating device is possible.

Example 5. Further, although the case of the high-frequency heating device has been described in the fourth embodiment, an induction heating device that controls the coil 48 as shown in FIG. 27 may be used, and the same effect as that of the fourth embodiment can be obtained.

[0090]

As described above, according to the first aspect of the present invention, the drive control means of the control means having the cooking control means for controlling the cooking detects the voltage applied to the switching element, and the detection signal thereof. Since the switching element is driven based on, the number of components can be reduced,
It has an effect that the cost can be reduced and the reliability can be improved. According to the second invention, the magnetic detection means detects the magnetic flux of the transformer or the inductor, outputs the detection signal corresponding to the voltage applied to the switching element, and has the cooking control means for controlling the cooking. Since the drive control means drives the switching element based on the detection signal from the magnetic detection means, the number of constituent parts can be reduced, the number of heat generating parts can be reduced, the cost can be reduced, and the reliability can be improved. It has the effect of being able to.

According to the third invention, when the voltage zero detection means of the control means makes the voltage applied to the switching element zero based on the voltage signal applied to the switching element or the detection signal from the magnetic detection means. Is detected and the control signal for driving the switching element is output to the drive control means, so that the loss of the switching element can be reduced and the reliability can be further improved. According to the fourth invention, the variable duty ratio control means of the control means detects the instantaneous voltage applied to the primary winding of the transformer or the instantaneous voltage applied to the inductor, and based on the detected instantaneous voltage. Since the control signal for changing the duty ratio of the switching element is output to the drive control means, the high frequency power can be equalized, and the power factor of the cooking device can be improved.

According to the fifth aspect of the invention, the feedback control means of the control means detects the input voltage and the input current to the rectifying and smoothing circuit and drives the drive control means to drive the control signal for keeping the input power constant. Since it is output to the control means, there is an effect that the high frequency power can always be kept constant. According to the sixth aspect of the present invention, the abnormal operation detection control means of the control means detects a current flowing through the magnetron or the inductor to detect the abnormal operation, and stops the driving of the switching element, or a rectification smoothing circuit. Since the control signal for lowering the input power is output to the drive control means, there is an effect that it is possible to prevent the occurrence of smoke, ignition, etc. and to operate more safely.

According to the seventh aspect of the invention, the soft start control means of the control means detects the current flowing through the magnetron to detect an unstable period during a transient phenomenon until the magnetron oscillates, and switches to the drive control means. Since the control signal for reducing the duty ratio of the element is output to the drive control means, there is an effect that the switching element can be protected during the transient phenomenon and the reliability can be further improved. According to the eighth invention, the setting of the input power to the rectifying and smoothing circuit is directly changed by the control means, and the value of the set input power is output to the feedback control means. The interface circuit can be omitted, the input power can be changed directly, the number of parts can be reduced, and the cost can be reduced.

According to the ninth aspect of the invention, the instantaneous voltage drop stop detection control means of the control means detects an instantaneous drop or an instantaneous stop of the voltage of the commercial AC power supply, and outputs a control signal for stopping the driving of the switching element, Since the output is provided to the drive control means, it is possible to protect the cooker when the commercial AC power supply is momentarily dropped or stopped, and further it is possible to improve reliability. According to the tenth aspect of the invention, the instantaneous voltage drop stop detection control means of the control means further causes recovery from the instantaneous voltage drop of the commercial AC power supply,
Alternatively, a control signal for detecting the return from the instantaneous stop and driving the switching element by the soft start control means,
Since the signal is output to the drive control means, the cooking device can be protected when the commercial AC power supply is momentarily dropped or returned from the instantaneous stop, and further, the reliability can be improved.

According to the eleventh aspect of the invention, the display control means of the control means detects the input power to the rectifying and smoothing circuit and displays the input power on the display means. This has the effect that the power can be easily adjusted. According to the twelfth aspect, the voltage zero detection means of the control means detects when the voltage applied to the switching element becomes zero based on the voltage signal applied to the switching element or the detection signal from the magnetic detection means. Since the control signal for driving the switching element is output to the drive control means when the instantaneous voltage applied to the primary winding of the transformer or the instantaneous voltage applied to the inductor is equal to or higher than a predetermined voltage, The instantaneous voltage applied to the inductor is small, and malfunctions when detecting when the applied voltage to the switching element becomes zero can be eliminated, the loss of the switching element can be reliably reduced, and the reliability can be improved. It has the effect of being able to.

According to the thirteenth aspect of the present invention, the variable duty ratio control means of the control means detects the instantaneous voltage applied to the primary winding of the transformer or the instantaneous voltage applied to the inductor to detect the switching element. Since the duty ratio of is small near the maximum value of the instantaneous voltage, large near the minimum value, and changed stepwise between the maximum value and the minimum value, the control signal is output to the drive control means.
The high frequency power can be equalized, the power factor of the cooking device can be improved, the decrease of input power can be prevented, and further, the reliability can be improved. According to the fourteenth aspect, the feedback control means of the control means detects the input voltage and the input current to the rectifying / smoothing circuit at high speed and outputs a control signal for keeping the input power constant to the drive control means at high speed. Since the high-frequency power is output, the high-frequency power has a small variation, can be constantly kept constant, and further, the reliability can be improved.

According to the fifteenth aspect, the abnormal operation detection control means of the control means detects the abnormal operation by detecting the current flowing through the magnetron or the inductor, and drives the switching element when the abnormal operation continues for a predetermined number of times. Since the control signal for stopping the operation or the control signal for lowering the input power to the rectifying and smoothing circuit is output to the drive control means, it is possible to prevent smoke, ignition, etc., and to operate more safely. Therefore, it is possible to prevent an abnormal operation from being determined due to a malfunction and further improve reliability.

According to the sixteenth invention, the soft start control means of the control means detects the current flowing through the magnetron to detect the unstable period during the transient phenomenon until the magnetron oscillates, and the duty ratio of the switching element is detected. Is output to the drive control means so as to increase stepwise while fixing the duty ratio for a predetermined time, so that the switching element can be protected during a transient phenomenon and the soft start control can be controlled. This has the effect that the time can be shortened and the reliability can be improved. According to the seventeenth aspect, the instantaneous voltage drop stop detection control means of the control means detects the instantaneous drop or the instantaneous stop of the voltage of the commercial AC power supply, and when the instantaneous drop or the instantaneous stop continues for a predetermined time, the switching element Since the control signal to stop the drive is output to the drive control means, the cooker can be protected when the commercial AC power supply is momentarily dropped or returned from the instantaneous stop, and the voltage of the commercial AC power supply for a short time can be protected. With the instantaneous descent or the instantaneous stop, cooking is not interrupted, and further, the reliability can be improved.

According to the eighteenth invention, the power supply means of the control means supplies the driving power for driving the switching element only when cooking, so that the voltage is applied to the switching element due to power source noise or the like. There is an effect that a safe high-frequency heating device can be obtained without being applied and the reliability can be improved. According to the nineteenth invention, since the control means is configured by the one-chip microcomputer, there is an effect that the number of components can be reduced and the device can be downsized. According to the twentieth aspect of the invention, the drive control means and the voltage zero detection means are constituted by a hardware circuit including at least a flip-flop and a logic gate in the one-chip microcomputer, so that the switching element is driven at high speed. It has the effect of being able to.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a heating cooker according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the collector voltage zero detection means 52 of the first embodiment.

FIG. 3 is a waveform diagram for explaining the operation of the duty ratio variable control means 54 of the first embodiment.

FIG. 4 is a flowchart showing the operation of the duty ratio variable control means 54 of the first embodiment.

FIG. 5 is a flowchart showing the operation of the feedback control means 53 of the first embodiment.

FIG. 6 is a flowchart showing an operation of the abnormal operation detection control means 56 according to the first embodiment.

FIG. 7 is a flowchart showing the operation of the soft start control means 57 of the first embodiment.

FIG. 8 is an instantaneous voltage drop stop detection control means 5 of the first embodiment.
5 is a waveform chart for explaining the operation of FIG.

FIG. 9 is an instantaneous voltage drop stop detection control means 5 of the first embodiment.
6 is a flowchart showing the operation of FIG.

FIG. 10 is a flowchart showing the operation of the display control means 58 in the first embodiment.

FIG. 11 is a flowchart showing an operation of varying the input power according to the first embodiment.

FIG. 12 is a circuit diagram showing a configuration of a heating cooker according to a second embodiment.

FIG. 13 is a circuit diagram showing the configurations of drive control means 51 and collector voltage zero detection means 52 in the microcomputer 31 of the third embodiment.

FIG. 14 is a circuit diagram showing a configuration of a heating cooker according to another embodiment of the present invention.

FIG. 15 is a waveform diagram for explaining the operation of the collector voltage zero detection means 63 of the fourth embodiment.

FIG. 16 is a flowchart showing the operation of the collector voltage zero detection means 63 of the fourth embodiment.

FIG. 17 is a duty ratio variable control means 65 according to the fourth embodiment.
6 is a waveform diagram for explaining the operation of FIG.

FIG. 18 is a duty ratio variable control means 65 according to the fourth embodiment.
3 is a flowchart showing the operation of FIG.

FIG. 19 is a waveform diagram for explaining the operation of the feedback control means 64 according to the fourth embodiment.

FIG. 20 is a flowchart showing an operation of the abnormal operation detecting means 67 according to the fourth embodiment.

FIG. 21 is a waveform diagram for explaining the operation of the soft start control means 68 according to the fourth embodiment.

FIG. 22 is a flowchart showing the operation of the soft start control means 68 in the fourth embodiment.

FIG. 23 is a waveform diagram for explaining the operation of the instantaneous voltage drop / stop detection control means 66 according to the fourth embodiment.

FIG. 24 is a flowchart showing the operation of the instantaneous voltage drop / stop detection control means 66 in the fourth embodiment.

FIG. 25 is a waveform diagram for explaining the operation of the power supply control means 62 according to the fourth embodiment.

FIG. 26 is a flowchart showing the operation of the power supply control means 62 of the fourth embodiment.

FIG. 27 is a circuit diagram showing a configuration of a heating cooker according to a fifth embodiment.

FIG. 28 is a circuit diagram showing a configuration of a conventional heating cooker.

FIG. 29 is a waveform diagram showing operation waveforms of a conventional collector voltage zero detection circuit.

FIG. 30 is a waveform diagram showing operation waveforms of a conventional switching element duty ratio variable circuit.

FIG. 31 is a circuit diagram showing a configuration of a conventional cooking device.

FIG. 32 is an explanatory diagram for explaining a problem of the conventional collector voltage zero detection circuit.

[Explanation of symbols]

1 commercial AC power supply, 2 rectification smoothing circuit, 4 switching element, 7 magnetic detection means, 8 drive circuit, 21 switching element drive circuit, 22 power supply circuit, 31 microcomputer (control means), 40 magnetron drive transformer (transformer) ), 48 coil (inductor), 51 drive control means, 52 collector voltage zero detection means, 53 feedback control means, 54 duty ratio variable control means, 55 instantaneous voltage drop stop detection control means, 56 abnormal operation detection control means, 57 software Start control means, 58 Display control means, 59 Cooking control means, 60 Display, 61 Drive circuit control means, 62 Power supply control means, 63 Collector voltage zero detection means, 64
Feedback control means, 65 Duty ratio variable control means, 66 Instantaneous voltage drop stop detection control means, 67
Abnormal operation detection means, 68 soft start control means.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Koji Hishiyama 1728 Omaeda, Omaeda, Hanazono-cho, Oza-gun, Saitama 1 Mitsubishi Electric Home Equipment Co., Ltd.

Claims (20)

[Claims] 1. A rectifying / smoothing circuit for rectifying and smoothing a commercial AC power supply, converting the output of the rectifying / smoothing circuit to a high frequency, and supplying high frequency power to a magnetron through a transformer or supplying high frequency power to an inductor. A switching element; and a control means having a drive control means for detecting a voltage applied to the switching element and driving the switching element based on the detection signal, and a cooking control means for controlling cooking. Cooker characterized by. 2. A rectifying / smoothing circuit for rectifying and smoothing a commercial AC power source, converting the output of the rectifying / smoothing circuit to a high frequency, supplying the magnetron with high frequency power via a transformer, or supplying high frequency power to an inductor. A switching element, a magnetic detection unit that detects the magnetic flux of the transformer or the inductor, and outputs a detection signal corresponding to the voltage applied to the switching element; and the switching element based on the detection signal from the magnetic detection unit. A heating cooker, comprising: a drive control unit that drives the motor and a control unit that has a cooking control unit that controls the cooking. 3. The control means further detects when the voltage applied to the switching element becomes zero, based on a voltage signal applied to the switching element or a detection signal from the magnetic detection means, The heating cooker according to claim 1 or 2, further comprising: a voltage zero detection unit that outputs a control signal for driving the switching element to the drive control unit. 4. The control means further comprises one of the transformers.
An instantaneous voltage applied to the next winding or an instantaneous voltage applied to the inductor is detected, and a control signal for changing the duty ratio of the switching element based on the instantaneous voltage is output to the drive control means. 4. A variable duty ratio control means is provided.
The cooker described. 5. The feedback control means, which detects the input voltage and the input current to the rectifying and smoothing circuit and outputs a control signal for making the input power always constant, to the drive control means. It has, The heating cooker of Claim 1, 2, 3 or 4 characterized by the above-mentioned. 6. The control means further detects a control signal for detecting a current flowing through the magnetron or the inductor to detect an abnormal operation and stopping driving of a switching element, or an input power to the rectifying / smoothing circuit. 6. An abnormal operation detection control means for outputting a control signal for lowering the drive control means to the drive control means.
Or the heating cooker according to 5. 7. The control signal, which further detects a current flowing through the magnetron to detect an unstable period during a transient phenomenon until the magnetron oscillates to reduce a duty ratio of the switching element. 7. The soft start control means for outputting to the drive control means is included.
The cooker described. 8. The control means further directly changes the setting of the input power to the rectifying and smoothing circuit and outputs the value of the set input power to the feedback control means. The cooking device according to claim 5, 6 or 7. 9. The control unit further detects a momentary drop or a momentary stop of the voltage of the commercial AC power supply, and outputs a control signal for stopping the driving of the switching element to the drive control unit. A descent stop detection control means is provided, Claims 1, 2, 3, 4, 5, 6,
The heating cooker according to 7 or 8. 10. The instantaneous voltage drop stop detection control means further detects the return from the instantaneous drop or the return from the instantaneous stop of the voltage of the commercial AC power source, and controls the drive of the switching element by the soft start. The heating cooker according to claim 9, wherein the control signal output by the means is output to the drive control means. 11. The control means further comprises a display control means for detecting an input power to the rectifying and smoothing circuit and displaying the input power on a display means. The heating cooker according to 4, 5, 6, 7, 8, 9 or 10. 12. The control means further detects when the voltage applied to the switching element becomes zero based on a voltage signal applied to the switching element or a detection signal from the magnetic detection means, Zero voltage detection for outputting a control signal for driving the switching element to the drive control means when the instantaneous voltage applied to the primary winding of the transformer or the instantaneous voltage applied to the inductor is equal to or higher than a predetermined voltage. 3. A method according to claim 1, further comprising means.
The cooker described. 13. The control means further detects an instantaneous voltage applied to the primary winding of the transformer or an instantaneous voltage applied to the inductor to determine the duty ratio of the switching element by the instantaneous voltage. A variable duty ratio control means for outputting to the drive control means a control signal that is small near the maximum value of the voltage, large near the minimum value, and that changes stepwise between the maximum value and the minimum value. The heating cooker according to claim 1, 2 or 12. 14. The control means further rapidly detects an input voltage and an input current to the rectifying and smoothing circuit, and outputs a control signal for keeping the input power always constant to the drive control means at high speed. The heating cooker according to claim 1, 2, 12, or 13, further comprising feedback control means. 15. The control means further detects a current flowing through the magnetron or the inductor to detect an abnormal operation, and stops the driving of the switching element when the abnormal operation continues for a predetermined number of times. 15. An abnormal operation detection control means for outputting to the drive control means a control signal for lowering the input power to the rectifying / smoothing circuit.
The cooker described. 16. The control means further detects a current flowing through the magnetron to detect an unstable period during a transient phenomenon until the magnetron oscillates to reduce a duty ratio of the switching element to a predetermined value. 13. A soft start control means for outputting to the drive control means a control signal for gradually increasing the duty ratio while fixing the duty ratio for a period of time.
The heating cooker according to 13, 14 or 15. 17. The control means further detects an instantaneous drop or an instantaneous stop of the voltage of the commercial AC power supply, and stops the drive of the switching element when the instantaneous drop or the instantaneous stop continues for a predetermined time. 3. An instantaneous voltage drop stop detection control means for outputting a signal to the drive control means is provided.
The heating cooker according to 5 or 16. 18. The control means further comprises a power supply means for supplying a drive power source for driving the switching element only when cooking is performed. , 15, 16 or 17 cooker. 19. The control means comprises a one-chip microcomputer.
3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1
The heating cooker according to 3, 14, 15, 16, 17 or 18. 20. The cooked food according to claim 19, wherein the drive control means and the zero voltage detection means are constituted by a hardware circuit, which is composed of at least a flip-flop and a logic gate, in the one-chip microcomputer. vessel.