JP4301114B2 - Induction heating device - Google Patents

Description

  The present invention relates to an induction heating apparatus such as a heating cooker used in general homes, restaurants, offices, factories, and the like.

A conventional induction heating apparatus will be described by taking an induction heating cooker as an example. There are those that detect the material of a pan or the like to be heated, switch the electrical parameters in the inverter circuit according to the material, and realize inverter operation suitable for the material (for example, Patent Documents 1 and 2). reference).
JP 2003-151747 A JP 2003-257610 A

However, the above conventional configuration obtains a desired induction heating output according to the material of the object to be heated when the inverter circuit is operating, and the electrical and thermal duties of the electrical components in the inverter circuit are appropriate. Therefore, the parameters are switched so that the influence of the magnetic flux applied from the outside when the inverter circuit is not operated is not taken into consideration. That is, when another induction heating cooker, induction heating rice cooker, induction motor device or the like is used on this induction heating cooker, the magnetic flux leaking from the upper device is induced in the lower conventional induction. A component of the inverter circuit is generated when an induction current or an induced electromotive force is generated in a current path in the inverter circuit where a high-frequency current necessary for induction heating should flow when the inverter circuit is operated. Excessive electrical stress is applied to the resonant capacitors and switching elements, resulting in deterioration of reliability. In the worst case, these components are destroyed, and the lower induction heating cooker may become unusable. Had the problem of occurring.

  In order to avoid this situation, there is a method of increasing the electrical tolerance of the components in the inverter circuit. However, tolerances that deviate from the general-purpose area of these components are required, which deteriorates the yield and costs of component production. It has the subject that it may become up or manufacture becomes impossible.

  Furthermore, it is not impossible to reduce the electrical stress applied to the component by increasing or decreasing the inductance of the heating coil and the capacitance of the resonant capacitor. It became a barrier when selecting parameters, and there was a problem that an increase in the burden of equipment design was a concern.

  The present invention solves the above-described problem. Even when the inverter circuit is not operating, it receives a magnetic flux from the outside of the device and affects the inverter circuit. A first object of the present invention is to provide an induction heating device that is relatively easy and reliable to prevent electrical stress from being applied to the electronic parts of the present invention, that is inexpensive, easy to use, and highly reliable. .

  A second object of the path opening means provided to solve the above problems is to reduce the size, reduce the cost, ensure durability, and ensure reliability.

In order to achieve the first object, an induction heating apparatus of the present invention includes a heating coil, a resonant capacitor, and switching means, and a high-frequency alternating current obtained by driving the switching means with a direct current obtained by rectifying and smoothing an alternating current power supply. converted to, and an inverter circuit for induction heating a heated body by generating a high-frequency current to the current path comprising the front Symbol said switching means and the heating coil and the resonant capacitor, when the inverter circuit is not operating, the A path opening means for disconnecting at least one of the one end of the heating coil, one end of the resonance capacitor or one end of the switching means from the current path and making it non-conductive, and an operation setting means for setting the operation of the inverter circuit are provided. When the operation setting means is set to stop, the inverter circuit is stopped and the second predetermined time Together with the path opening means is non-conductive the path after, while it is set to operate the inverter circuit by said operation setting means, said path opening means is obtained by a configuration that maintains the conduction .

  As a result, even when the inverter circuit is not operating, it receives magnetic flux from the outside of the device and affects the inverter circuit. The application of electrical stress can be suppressed or prevented.

  In addition, since the inverter circuit starts operating after the path opening means is surely turned on, the path opening means can be conducted with zero current switching operation, reducing the switching loss of the path opening means and ensuring the durability of the contacts. Becomes easier.

  In addition, when the inverter circuit is stopped as a protective action against momentary power failure of the AC power supply or abnormal operation of the inverter circuit, the conduction state of the path opening means can be maintained. Without interrupting the current, the same operation as when there is no path opening means is inherited, and the transient voltage and inflow current in each component of the inverter circuit are made the same as when there is no path opening means. At the same time, unnecessary conduction / non-conduction of the path opening means is prevented, and when the path opening means is a switching contact type, the number of opening / closing operations is suppressed, and the durability and reliability of the contact can be easily secured. Can do.

  The induction heating device according to the present invention has a relatively simple configuration in which a failure of a device due to an inadvertent application of electrical stress to its components when the inverter circuit is not in operation due to a leakage magnetic flux from an external device. Thus, it can be effectively mitigated or prevented.

The first invention includes a resonant capacitor and switching means and the heating coil, a direct current rectified and the smoothed AC power is converted into high-frequency AC by driving the switching means, the resonant capacitor to the previous SL heating coil An inverter circuit for inductively heating an object to be heated by generating a high-frequency current in a current path composed of the switching means, and when the inverter circuit is not operating , one end of the heating coil, one end of the resonant capacitor, or the a path opening means for at least one of one end of the switching means non-conductive disconnected from the current path, have a and operation setting means for setting the operation of the inverter circuit, when it is stopped set by the operation setting means Further, after the inverter circuit is stopped and the second predetermined time has elapsed, the path opening means makes the path non-conductive. Rutotomoni, while it is set to operate the inverter circuit by said operation setting means, said path opening means with the configuration to maintain the continuity, at the time the inverter circuit operation, close the path opening means, the A high-frequency current to be supplied to the heating coil is changed by securing a current path necessary for induction heating of the heating body, changing the conduction time or driving cycle or switching ratio of the switching means by the driving means, and changing the high-frequency current supplied to the heating coil. The induction heating of the heated object such as a pan can be controlled by the high frequency magnetic flux generated from the heating coil, and the induction heating output to the heated object can be controlled. When the inverter circuit is not operated, the path opening means is opened. Since this current path can be interrupted, the magnetic flux applied to the heating coil from the outside of the induction heating device, for example, the induction heating If this induction magnetic flux crosses the heating coil of the induction heating device of the present invention when another induction heating type device or induction motor device is placed and operated so as to face the heating coil of the device, this current path Is closed, it is possible to suppress or suppress the generation of the induced electromotive force or induced current, and the electrical stress applied to the switching means, resonant capacitor, heating coil, etc., which are the components of the inverter circuit. Can be reduced or eliminated.

  In addition, since the inverter circuit starts operating after the path opening means is surely turned on, the path opening means can be conducted with zero current switching operation, reducing the switching loss of the path opening means and ensuring the durability of the contacts. Becomes easier.

  In addition, when the inverter circuit is stopped as a protective action against momentary power failure of the AC power supply or abnormal operation of the inverter circuit, the conduction state of the path opening means can be maintained. Without interrupting the current, the same operation as when there is no path opening means is inherited, and the transient voltage and inflow current in each component of the inverter circuit are made the same as when there is no path opening means. At the same time, unnecessary conduction / non-conduction of the path opening means is prevented, and when the path opening means is a switching contact type, the number of opening / closing operations is suppressed, and the durability and reliability of the contact can be easily secured. Can do.

A second invention includes a heating coil, a resonance capacitor, and switching means, and converts a direct current obtained by rectifying and smoothing an AC power source into a high frequency alternating current by driving the switching means, and the heating coil, the resonance capacitor, An inverter circuit for inductively heating an object to be heated by generating a high-frequency current in a current path composed of switching means, and when the inverter circuit is not operating, one end of the heating coil, one end of the resonance capacitor, or the switching A path opening means for disconnecting at least one end of the means from the current path and making it non-conductive, and an operation setting means for setting the operation of the inverter circuit, and when the operation setting means is set to stop. The path opening means makes the path non-conductive after the inverter circuit is stopped and a second predetermined time has elapsed. Rutotomoni, while it is set to operate the inverter circuit by said operation setting means, by adopting a configuration that maintains the conduction path opening means, the protection operation against the abnormal operation of the momentary power failure or an inverter circuit of an AC power source When the inverter circuit is stopped, the conduction state of the path opening means can be maintained, and when the inverter circuit is stopped, the current that is flowing transiently is not interrupted, as is the case without the path opening means. Inheriting the above operation, the transient generated voltage and inflow current in each component of the inverter circuit are made the same as when there is no path opening means, and unnecessary conduction / non-conduction of the path opening means is prevented. When the path opening means is a switching contact type, the number of switching operations can be suppressed, and the durability and reliability of the contacts can be easily ensured.

In particular, the third invention has power failure detection means for detecting a power failure of the AC power supply of the first or second invention, and while the power failure detection means detects a power failure and stops the inverter circuit, By configuring the path opening means to maintain continuity, when the power failure detection means detects a power failure of the AC power supply, in order to avoid instability of the inverter circuit operation at the time of power failure recovery and electrical stress application, Stop. At this time, the conduction state of the path opening means can be maintained, and when the inverter circuit is stopped, the current that is flowing transiently is not interrupted, and the same operation as when there is no path opening means is inherited and the inverter circuit Transiently generated voltage and inflow current in each component of the inverter circuit is equivalent to when there is no path opening means, and transient generated voltage in each component of the inverter circuit due to the difference in timing when the path opening means becomes non-conductive In addition, the transitional operation when the inverter circuit is stopped is made constant by eliminating the change in current and inflow current, and unnecessary conduction / non-conduction of the path opening means is prevented, and the path opening means is a switching contact type. Can suppress the number of opening and closing operations, and can easily ensure the durability and reliability of the contacts.

The fourth invention has an abnormality detecting means for detecting an abnormal operation of the inverter circuit by detecting a current flowing through the inverter circuit or a voltage across the switching means , particularly in the first or second invention, when the abnormality detection unit detects the abnormal rise of the current or the voltage across the stops the operation of the inverter circuit, the path opening means with the configuration to maintain the conduction abnormality detection means, When an abnormal operation of the inverter circuit, for example, an abnormal increase in the voltage across the switching means or an inflow current is detected, the operation of the inverter circuit is stopped in order to avoid a permanent failure of the inverter circuit. At this time, the conduction state of the path opening means can be maintained, and when the inverter circuit is stopped, the current that is flowing transiently is not interrupted, and the same operation as when there is no path opening means is inherited and the inverter circuit Transiently generated voltage and inflow current in each component of the inverter circuit is equivalent to when there is no path opening means, and transient generated voltage in each component of the inverter circuit due to the difference in timing when the path opening means becomes non-conductive In addition, the transitional operation when the inverter circuit is stopped is made constant by eliminating the change in current and inflow current, and unnecessary conduction / non-conduction of the path opening means is prevented, and the path opening means is a switching contact type. Can suppress the number of opening and closing operations, and can easily ensure the durability and reliability of the contacts.

A fifth invention is, in particular, in the first or second aspect, the route opening means comprises a retractable contact, a contact abnormality detection means for detecting an abnormality of the contacts of the path opening means, the operation of the inverter circuit and a notifying means for notifying the setting state, the when the contact abnormality means detects an abnormality of the contacts to disable operation of said inverter circuit, abnormal said notification means of said contact of said path opening means or by adopting a configuration in which disablement of effect notification of the inverter circuit, the contact abnormality detection means, nonconductive if it is to be rendered conductive path opening means, or that conduct when it should have non-conductive, the contact states abnormal Can be detected. In addition, the notification means normally notifies the operation setting state of the inverter circuit, for example, the operation / non-operation of the inverter circuit, the induction heating output setting value to the heated object, etc. When the circuit is detected, by disabling the inverter circuit, when the path opening means should be conductive, the circuit remains open and the secondary circuit failure due to incomplete inverter circuit configuration is avoided. When the means should be non-conductive, electrical stress is applied to the components of the inverter circuit by applying the leakage magnetic flux from other induction heating type equipment to the heating coil of the induction heating device while remaining conductive. It is possible to notify the user that there is a possibility and prompt the user to take measures.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking an induction heating cooker as an example. In addition, this invention is not limited by this embodiment.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of the induction heating apparatus in the first embodiment of the present invention.

  In the induction heating cooker (induction heating apparatus) shown in FIG. 1, the rectifier circuit 2 is composed of a bridge-connected diode that rectifies the commercial power source (AC power source) 1, and the smoothing circuit 3 is composed of a choke coil 3a and a capacitor 3b. The inverter circuit (one voltage resonance type in the first embodiment) 4 includes switching means 4a and a resonance capacitor 4b, and the heating coil 5 is heated by a high-frequency current from the inverter circuit 4 to be heated such as a pot. A high frequency alternating magnetic field is applied to the body 6 to perform induction heating, and the control circuit 7 controls the operation of the inverter circuit 4 so that the switching means 4a is driven on and off, and the conduction time or drive cycle or conduction ratio of the switching means 4a. Drive means 8 for controlling the high-frequency current supplied to the heating coil 5 with variable power, the heating coil 5 and the resonance capacitor 4b, The heating coil 5 and the switching means 4a, or the path opening means 9 for switching at least one conduction / non-conduction of the current path comprising the heating coil 5, the resonance capacitor 4b and the switching means 4a, and the user to the object 6 to be heated The operation setting means 10 composed of a switch or the like for setting the operation state of the inverter circuit 4 to perform induction heating output setting, etc., and the contents set by the operation setting means 10 are displayed on the LED or LCD, or a buzzer or speaker. Informing means 11 for notifying, etc., power failure detecting means 12 for detecting a power failure of the commercial power source 1, abnormality detecting means 13 for detecting an operation abnormality of the inverter circuit 4, and contact abnormality detection for detecting abnormality of the path opening means 9 Means 14.

  In the first embodiment, first, the path opening means 9 is inserted on the high potential side of the switching means 4a, which is the current path between the heating coil 5 and the switching means 4a (when the path is opened, the switching means The case where 4a is on the low potential side will be described. Other cases will be described later.

  The notification means 11 informs the user of the setting of the induction heating output of the inverter circuit 4 performed by the user in the operation setting means 10, and based on this, the conduction time of the switching means 4a is varied by the driving means 8. The high-frequency current supplied to the heating coil 5 is changed, and the high-frequency magnetic flux generated from the heating coil 5 is used to induction-heat the heated body 6 such as a pan, and the induction heating output to the heated body 6 is also changed. Can be controlled.

At this time, until the user sets the operation start of the inverter circuit 4 by the operation setting means 10, the path opening means 9 is in a non-conductive state, interrupts the current path between the heating coil 5 and the switching means 4a, and induction heating is performed. Magnetic flux applied to the heating coil 5 from the outside of the cooker, for example, another induction heating type device or induction motor device instead of the heated body 6 such as a pan so as to face the heating coil 5 of the induction heating cooker. If the current path is closed, such as when the leakage flux of the other device is mixed with the heating coil 5 of the induction heating cooker after being energized and this current path is closed, The current path formed by the heating coil 5 and the resonant capacitor 4b suppresses the generation of the induced electromotive force or the induced current generated at both ends of the switching means 4a by cutting off the current path. No electrical stress applied to the switching means 4a, which is a component of the above, is generally composed of a semiconductor element, and is weaker against electrical stress than the heating coil 5 and the resonant capacitor 4b, or has high electrical stress resistance. It is possible to reduce the electrical stress of the switching means 4a that is difficult to achieve. In addition, in general, the high-frequency current value flowing through each component when the object to be heated 6 is inductively heated is determined by comparing the current of the heating coil 5 with the current of the switching means 4a. Since it becomes smaller (the smaller portion flows to the resonance capacitor 4b), if it is the insertion position of the present embodiment, the current capacity of the path opening means 9 can be reduced, and the path opening means 9 can be reduced in size and cost. Can be planned.

In the present embodiment, the path opening means 9 is an electromagnetic relay using an open / close contact. This is because, when the path opening means 9 is open, the electromotive force induced by the magnetic flux applied to the heating coil 5 from the outside of the induction heating cooker is generated at both open ends of the path opening means 9. When the path opening means 9 is constituted by a semiconductor switch in place of the switching contact, it is necessary to use a semiconductor switch having a high withstand voltage that can withstand this induced electromotive force. However, if the path opening means 9 is configured with an open / close contact, it is possible to achieve a high breakdown voltage with a relatively simple method of ensuring the distance between contacts when opening. Because it becomes.

  When the user sets the operation start of the inverter circuit 4 with the operation setting means 10, the path opening means 9 makes this current path conductive, and the inverter circuit 4 starts to operate approximately 2 seconds after the operation start is set. The time of about 2 seconds is a time with sufficient margin for the operation start setting and the timing at which the inverter circuit 4 starts to operate with respect to the operation time of the path opening means 9 and the time including the variation thereof, Therefore, the inverter circuit 4 starts to operate after the path opening means 9 is surely turned on, and before the current starts to flow to the inverter circuit 4 through the path opening means 9, the contact is made by zero current switching operation. It is closed to facilitate switching loss reduction of the path opening means 9 and ensuring the durability of the contacts.

  Next, when the user sets the operation stop of the inverter circuit 4 by the operation setting means 10, the drive means 8 stops the driving of the switching means 4a, whereby the inverter circuit 4 is stopped and the operation stop is set. After about 1 second, the path opening means 9 becomes non-conductive. The time of about 1 second is a time that has a sufficient margin with respect to the time when the path opening means 9 starts operating in the non-conductive state with respect to the time when the operation is set to stop and the inverter circuit 4 stops operating. Therefore, after the inverter circuit 4 is surely stopped, the path opening means 9 is brought into a non-conducting state, and after the path opening means 9 stops flowing in the inverter circuit 4, the contact is made by zero current switching operation. To reduce the switching loss of the path opening means 9 and to prevent arcing of the contacts, thereby ensuring durability.

If an instantaneous power failure occurs in the commercial power supply 1 while the inverter circuit 4 is operating, the operation of the inverter circuit 4 becomes unstable after the power failure is restored. In this embodiment, the power failure detection means 12 is provided to detect a power failure. Then, once the operation of the inverter circuit 4 is stopped and it is detected that the inverter circuit 4 has recovered from the power failure, the inverter circuit 4 is operated again. In general, when an instantaneous power failure occurs, the display circuit LED, etc., which is the load, etc. are used to reduce the current consumption of the control circuit so that the device can return to the state before the power failure as much as possible when the power failure is restored. The driving of the electromagnetic relay is stopped, but the driving of the electromagnetic relay ON of the path opening means 9 of the present embodiment is not stopped. This is because, when the inverter circuit 4 is stopped, the current flowing transiently to the path opening means 9 is not interrupted, and the same operation as in the case without the path opening means 9 is inherited and each component of the inverter circuit 4 is used. The transient generation voltage and inflow current of the inverter circuit 4 are the same as when the path opening means 9 is not provided, and the transient generation voltage and inflow in each component of the inverter circuit 4 due to the difference in timing when the path opening means 9 becomes non-conductive. The current change is eliminated, the transient operation when the inverter circuit 4 stops is always constant, and the power failure is usually recovered immediately. Therefore, the path opening means 9 is unnecessary from the start to the recovery of the power failure. When conduction / non-conduction is prevented and the path opening means 9 is a switching contact type, the number of switching operations is suppressed, and the durability and reliability of the contacts are easily ensured.

  Before starting operation or when power is not supplied to the electromagnetic relay for a long time (for example, when the power switch is turned off), the contact of the electromagnetic relay is open and the inverter circuit 4 is cut off. The influence of the magnetic flux can be suppressed.

Further, in this embodiment, the operation of the inverter circuit 4 becomes unstable, and when the abnormality detection means 13 that monitors the voltage across the switching means 4a detects an abnormal increase in the voltage across the switching means 4a, The operation is stopped and a permanent failure of the inverter circuit 4 is prevented. When the inverter circuit 4 stop, without interrupting the current flowing transiently in the path opening means 9, transients in each component of the inverter circuit 4 to inherit the same operation as no path opening means 9 The generated voltage and inflow current are equivalent to those when there is no path opening means 9, and the transient generated voltage and inflow current in each component of the inverter circuit 4 due to the difference in timing when the path opening means 9 becomes non-conductive. The transition operation when the inverter circuit 4 is stopped is always kept constant by eliminating the change, and the operation of the inverter circuit 4 is temporarily stopped to eliminate unstable factors in many cases. Instability of operation usually recovers immediately, so unnecessary conduction / non-conduction of the path opening means 9 is prevented from the start to the recovery of the instability. Action Achieving the number of suppression, to facilitate durability of the contact, to secure reliability.

  Furthermore, in the present embodiment, when the contact abnormality detection means 14 detects an abnormality in the contact state, such as non-conduction when the path opening means 9 should be conducted or conduction when it should be non-conduction, the inverter circuit 4 Is disabled when the path opening means 9 should be conductive, avoiding a secondary failure caused by an incomplete configuration of the inverter circuit 4, and the path opening means 9 Electrical stress on the components of the inverter circuit 4 due to leakage magnetic flux from other induction heating type appliances, etc. being applied to the heating coil 5 of the induction heating cooker while remaining conductive when it should be non-conductive The notification means 11 can notify the user that there is a possibility of application, and prompt the user to take measures.

  In this embodiment, the path opening means 9 is configured to make the high potential end of the switching means 4a conductive / non-conductive. However, the other end of the heating coil 5 is made conductive / nonconductive, The heating coil 5 itself that receives a leakage magnetic flux from a heating device or the like may be separated from the inverter circuit 4. In this case, it is possible to prevent an excessive electrical stress from being applied to all the components of the inverter circuit 4. . However, when the inverter circuit 4 is operating, the current of the heating coil 5 flows through the path opening means 9, so that the path is higher than when the high potential end of the switching means 4a is turned on / off. The opening means 9 needs to increase the allowable current capacity.

  Further, if the path opening means 9 is inserted at one end of the resonance capacitor 4b, the induced electromotive force due to the LC resonance generated in the current path between the heating coil 5 and the resonance capacitor 4b cannot be generated. Since the electromotive force is not applied and the application of electrical stress to the switching means 4a having relatively high resistance to electrical stress can be prevented, the effect of the present invention can be obtained.

  Furthermore, although the configuration of the inverter circuit 4 of the present embodiment has been described with the switching means 4a and the resonant capacitor 4b being each one voltage resonant inverter, the inverter having a configuration having a plurality of switching means 4a and resonant capacitors 4b, For example, a current path including the heating coil 5 is provided in any inverter configuration such as a half-bridge type single-end push-pull inverter as shown in FIG. 2, a full-bridge type inverter as shown in FIG. Needless to say, the effect is effective.

  In addition, although the abnormality detection means 13 is made to detect by the abnormal rise of the both-ends voltage of the switching means 4a, you may detect with physical quantities, such as the both-ends voltage and inflow current of the component of the other inverter circuit 4, The inverter circuit 4 may be protected from an abnormal increase of the power supply voltage by a physical quantity correlated with the size of the commercial power supply 1 such as the output voltage of the smoothing circuit 3.

  Note that the control of the induction heating output to the heated body 6 may change not only the conduction time of the switching means 4a but also the driving cycle and the driving time ratio according to the configuration of the inverter circuit 4 and the like.

The induction heating device of the present invention has already been put into practical use because it can mitigate or prevent inadvertent application of electrical stress to its components when the inverter circuit is not operating due to leakage magnetic flux from an external device or the like. It can be applied not only to induction heating cookers and induction heating rice cookers, but also to heating appliances such as electric water heaters, electric irons, dishwashers, and water heaters that can be used for induction heating. It can also be applied to other electrical equipment using a coil or a transformer, a microwave oven, a refrigerator, a washing machine, and the like.

The block diagram of the induction heating apparatus in Embodiment 1 of this invention Inverter circuit diagram of configuration example 1 of the induction heating apparatus in the first embodiment of the present invention The inverter circuit diagram of the structural example 2 of the induction heating apparatus in Embodiment 1 of this invention Inverter circuit diagram of configuration example 3 of the induction heating apparatus in the first embodiment of the present invention

Explanation of symbols

1 Commercial power supply (AC power supply)
4 Inverter circuit 4a Switching means 4b Resonance capacitor 5 Heating coil 6 Pan (Heating object)
9 Route opening means 10 Operation setting means 11 Notification means 12 Power failure detection means 13 Abnormality detection means 14 Contact abnormality detection means

Claims (5)

Wherein a resonant capacitor and switching means and the heating coil, a direct current rectified and the smoothed AC power is converted into high-frequency AC by driving the switching means, consisting of a pre-Symbol heating coil and the resonant capacitor the switching means current An inverter circuit for inductively heating an object to be heated by generating a high-frequency current in the path, and when the inverter circuit is not in operation, at least one end of the heating coil, one end of the resonance capacitor, or one end of the switching means a path opening means for non-conductive detach one from the current path, have a and operation setting means for setting the operation of the inverter circuit, when operatively set by the operation setting unit, the route opening means together with the inverter circuit starts operation but the first after a predetermined time conducting path, Serial while in operation setting means is set up to operate said inverter circuit, said path opening means induction heating device configured to maintain continuity. Wherein a resonant capacitor and switching means and the heating coil, a direct current rectified and the smoothed AC power is converted into high-frequency AC by driving the switching means, consisting of a pre-Symbol heating coil and the resonant capacitor the switching means current An inverter circuit for inductively heating an object to be heated by generating a high-frequency current in the path, and when the inverter circuit is not in operation, at least one end of the heating coil, one end of the resonance capacitor, or one end of the switching means Path opening means for disconnecting one from the current path and making it non-conductive, and operation setting means for setting the operation of the inverter circuit, and when the operation setting means is set to stop, the inverter circuit together with the path opening means in the second after a predetermined time to stop is non-conductive path, Serial while in operation setting means is set up to operate said inverter circuit, said path opening means induction heating device configured to maintain continuity. A power failure detecting means for detecting a power failure of the AC power supply, while the power failure detecting means is to stop the inverter circuit detects a power failure, the path opening means to claim 1 or 2 configured to maintain continuity The induction heating apparatus described. It has an abnormality detecting means for detecting an abnormal operation of the inverter circuit by detecting a current flowing through the inverter circuit or a voltage across the switching means, and the abnormality detecting means detects an abnormal increase in the current or the voltage across the both ends. 3. The induction heating apparatus according to claim 1, wherein when the operation is performed, the operation of the inverter circuit is stopped and the path opening means is maintained in conduction. The path opening means comprises a retractable contact has a contact abnormality detecting means for detecting an abnormality of the contacts of the path opening means, and informing means for informing the operation setting status of the inverter circuit, said contact abnormality means together when detecting an abnormality of the contacts to disable operation of the inverter circuit, according to claim 1 having the structure the notification means notifies the fact of the disablement of the abnormality or the inverter circuit of the contact of said path opening means Or the induction heating apparatus of 2.

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