JP5045143B2 - Induction heating device - Google Patents

Description

  The present invention relates to an induction heating apparatus having soft start means.

Conventionally, this type of induction heating device determines whether the object to be heated is appropriate or inappropriate during the soft start by the soft start means. If the object to be heated is inappropriate, the operation of the inverter circuit is stopped and the object is heated. When an object is appropriate, one that supplies power up to a set output is known (for example, see Patent Document 1). Also, when starting up the inverter circuit, it is determined whether the object to be heated is proper or inappropriate during operation with the low output setting fixed for a predetermined time. If the object to be heated is inappropriate, the operation of the inverter circuit is stopped. In the case where the object to be heated is appropriate, a low power output setting is canceled and a soft start is performed (for example, see Patent Document 2).
Japanese Patent No. 3399258 Japanese Patent No. 1744163

  However, in the above-described conventional configuration, during the start-up control of the inverter circuit, the efficiency of the inverter circuit is low during the soft start or during the operation with the low output setting fixed for a predetermined time. As the operation and the stop are repeated, the efficiency of the induction heating device is lowered.

  The present invention solves the above-described conventional problems, and an object thereof is to provide an induction heating apparatus that can increase the efficiency of an inverter circuit.

In order to solve the above-described conventional problems, an induction heating apparatus according to the present invention includes a heating coil that transmits energy by magnetic coupling with a load, a switching element that controls electric power supplied to the heating coil, and the switching element. An inverter circuit having a reverse conducting element connected in parallel with the heating coil and a resonant capacitor that forms a resonant circuit, a power supply for supplying power to the inverter circuit, and a drive control means for controlling conduction of the switching element And the drive control means has a soft start means for changing to a desired power value, and the power value at the start of the soft start means has a plurality of predetermined values.

  As a result, the power value at the start of the soft start means is changed according to the load itself or changes in the load characteristics, the state of the inverter circuit, the desired power value, etc., and the inverter circuit is operated with the optimal power value at the time of start Therefore, the efficiency of the inverter circuit can be increased.

  The induction heating device of the present invention can operate the inverter circuit with an optimum power value at the time of starting, and can increase the efficiency of the inverter circuit.

The first invention includes a heating coil that transmits energy by magnetic coupling with a load, a switching element that controls power supplied to the heating coil, a reverse conducting element connected in parallel with the switching element, An inverter circuit having a heating coil and a resonance capacitor that forms a resonance circuit; a power supply that supplies power to the inverter circuit; drive control means that controls conduction of the switching element; and improper load detection that detects an improper load and means, said drive control means have a soft start means for varying the output power at the time of starting up a desired power value, as well as chromatic plurality of predetermined value as a power value at the start of the soft-start means When the operation and stop of the inverter circuit are performed intermittently, the initial power value of the soft start means for the second and subsequent times is the first time. When the improper load detection means detects an improper load, the inverter circuit operation is stopped and the inverter circuit initial power value immediately after the inverter circuit operation is abnormally stopped is increased. Thus, the induction heating device is smaller than the power value of the inverter circuit immediately before the operation stops .

According to the present invention, the efficiency of the inverter circuit can be increased by confirming the safe operation and shortening the soft start period. In addition, abnormal operation such as heat generated by an improper load can be prevented, and damage to the inverter circuit caused by abnormal voltage applied to the components of the inverter circuit or abnormal current flowing can be prevented. can do. Furthermore, the inverter circuit can be started safely, and a period for discriminating an improper load can be provided by extending the soft start period.

A second invention is, in particular, in the first invention, the inappropriate load detecting means comprises a load monitoring means for monitoring the state of the load, in the operation of the inverter circuit of the second or later, the output of the load monitoring means If is not changed, the initial power value of the inverter circuit immediately after the operation of the inverter circuit is stopped, by the operation of the inverter circuit is an initial power value equivalent to said inverter circuit immediately before the stop, the inverter circuit However, the inverter circuit efficiency can be increased because the soft start is not performed at a low output setting at each start-up.

A third invention is, in particular, in the second invention, when detecting a change in the load state by the output of the load monitoring unit, by stopping the operation of the inverter circuit further when an abnormal condition occurs It is possible to improve safety by preventing heating.

  In the ninth invention, in particular, in any one of the first to eighth inventions, the initial power value of the inverter circuit immediately after the operation of the inverter circuit stops is the value of the inverter circuit immediately before the operation of the inverter circuit stops. By making it smaller than the power value, the inverter circuit can be started safely. In addition, it is possible to provide a period for determining an inappropriate load by extending the soft start period.

In a fourth aspect of the invention, in particular, in any one of the first to third aspects of the invention, the soft start means changes the output power at the time of startup to a desired power value with a time constant, and the operation of the inverter circuit. When the stop is performed intermittently, the time constant of the soft start means for the second and subsequent times is made smaller than the first time constant, thereby shortening the soft start period and increasing the efficiency of the inverter circuit. .

A fifth invention is, in particular, in the fourth invention, the time constant of said soft start means, by varying with the power value, to minimize the time constant at the level of load on the inverter circuit does not occur Therefore, the efficiency of the inverter circuit can be increased.

A sixth invention is particularly, in any one invention of the first to fifth, the soft-start means, if the desired power value is lower than a predetermined value, by which to not operate, less efficient extra It is possible to increase the efficiency of the inverter circuit by eliminating unnecessary operations.

In a seventh aspect of the invention, in particular, in any one of the first to sixth aspects of the invention, a relay for switching a path for transmitting electricity is provided, and a load to be heated by the relay is switched. Since it can heat with the same switching element, the number of parts which comprise an inverter circuit can be reduced and an inexpensive induction heating apparatus can be made.

An eighth invention is particularly, in any one invention of the first to seventh, power supplied to the load, by which is adapted to adjust to changing the driving frequency of the switching element, any power Can be supplied to the load.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
1 and 2 show an induction heating apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the induction heating device in the present embodiment includes a heating coil 11 that transmits energy by being magnetically coupled to a load, a switching element 12 that controls electric power supplied to the heating coil 11, and a switching element. The inverter circuit 15 having a reverse conducting element 13 connected in parallel to the circuit 12, a heating coil 11 and a resonant capacitor 14 forming a resonant circuit, a power supply 16 for supplying power to the inverter circuit 15, and the switching element 12 are conducted. Drive control means 17 for controlling.

  The drive control means 17 has a soft start means 18 that changes with a time constant up to a desired power value, and the power value when the soft start means 18 is activated has a plurality of predetermined values. This is, for example, the power values 1 and 2 at the time of startup in FIG. 2 and is increased to the desired power values 1 and 2, respectively. 2 indicates a path when the output power is raised to a desired power value 2 by the soft start means 18 having only one predetermined power value when the soft start means 18 is activated. ing.

  The induction heating apparatus in the present embodiment can control the output power by adjusting the conduction time of the switching element 12. Further, when the inverter circuit 15 transitions from the stopped state to the operating state, the inverter circuit 15 can be stably operated by using the soft start means 18 that gently changes the output power to a desired power value. .

In the induction heating device of the present invention, as shown in FIG. 2, the power value at the start of the soft start means 18 is a change in the load itself, a change in load characteristics, a change in the state of the inverter circuit 15, a desired power value. By using different predetermined values (in the embodiment, power value 1 or 2 at the time of startup in FIG. 2) due to differences or the like, the inverter circuit 15 can be started to operate at an optimal power value at the time of startup. Therefore, it is possible to suppress the operation at low output power at which the power conversion efficiency of the inverter circuit 15 is reduced, and to increase the power conversion efficiency of the inverter circuit 15.

  In addition, by increasing the power value at the start of the soft start means 18 as much as possible in accordance with the characteristics of the load and the state of the inverter circuit 15, the efficiency of the inverter circuit 15 is increased and the output power at the start is Since the soft start time is high, the efficiency of the inverter circuit 15 can be increased. Further, by soft-starting, it is possible to prevent the switching element 12 from being broken and improper heating due to an inappropriate load.

  If the soft start means 18 has a large power value at the time of start-up and a voltage surge or current surge is likely to cause a malfunction due to noise or the switching element 12 is likely to be destroyed, the soft start means 18 The power value at the time of starting can be reduced, and the components of the induction heating device can be prevented from being destroyed.

  In addition, the soft start means 18 changes optimally at start-up by changing with a time constant from a predetermined value (for example, power value 2 at start-up in FIG. 2) to a desired power value (the desired power value 2 in FIG. 2). When the operation of the inverter circuit 15 is started with the power value at that time, the power conversion efficiency of the inverter circuit 15 can be increased by shortening the soft start period during which the power conversion efficiency of the inverter circuit 15 decreases.

  In addition, the generation of noise is suppressed by gently changing the output power to a desired power value, and the unstable operation period of the inverter circuit 15 in which the output power is changing is shortened by shortening the soft start period. In addition, the switching element 12 can be prevented from being broken.

  In addition, by making the predetermined value of the soft start means 18 smaller than the desired power value, the output power does not exceed the desired power value, and the safety of the induction heating apparatus can be improved.

  In addition, since the predetermined value of the soft start means 18 varies with the desired power value, the inverter circuit 15 can be started to operate at an optimal power value at the time of startup. It is possible to increase the power conversion efficiency of the inverter circuit 15 by suppressing the operation at the low output power at which the inverter circuit 15 decreases.

(Embodiment 2)
FIG. 3 shows an induction heating device according to Embodiment 2 of the present invention.

  The difference from the first embodiment is that an inappropriate load detection means 19 for detecting an inappropriate load (for example, a spoon) is provided, and the operation of the inverter circuit 15 is performed when the inappropriate load detection means 19 detects an inappropriate load. Is to stop. Others are the same as in the first embodiment.

  Thereby, since abnormal operation | movement, such as heating an improper load accidentally, can be prevented, the safety | security of an induction heating apparatus can be improved.

  Further, it is possible to prevent the switching element 12 from being destroyed by heating the improper load so that an abnormal voltage is not applied to the switching element 12 or an abnormal current does not flow.

  Furthermore, by operating the improper load detection means 19 immediately after the inverter circuit 15 starts operating, it is possible to suppress the improper load from being heated as much as possible.

(Embodiment 3)
FIG. 4 shows the relationship of the output power with respect to time of the induction heating apparatus in Embodiment 3 of the present invention.

  The difference from the second embodiment is that when the operation and stop of the inverter circuit 15 are intermittently performed, the initial power value (second power value 2 at the time of start-up) of the soft start means 18 for the second and subsequent times is the first initial power. That is, it is made larger than the value (power value 1 at start-up). Others are the same as in the second embodiment.

  As a result, the initial power value of the soft start means 18 for the second and subsequent times can start the operation of the inverter circuit 15 with the optimal power value at the time of startup, so that the power conversion efficiency of the inverter circuit 15 is reduced with low output power. Thus, the power conversion efficiency of the inverter circuit 15 can be increased.

  In addition, since the operation can be stably performed even when the output power is raised to a desired power value by the operation of the inverter circuit 15 for the first time, if the initial power value is less than the desired power value after the second time, the switching element 12 can be operated safely without destruction.

  Further, in the second and subsequent operations, the output power is output to a desired power value in a short time, so that the response of the output power can be increased and the load can be heated quickly.

(Embodiment 4)
FIG. 5 shows an induction heating apparatus according to Embodiment 4 of the present invention.

  The difference from the third embodiment is that the improper load detecting means 19 includes a load monitoring means 20 for monitoring the load state, and the output of the load monitoring means 20 does not change in the second and subsequent operations of the inverter circuit 15. The initial power value of the inverter circuit 15 immediately after the operation of the inverter circuit 15 is stopped is the same value as the initial power value of the inverter circuit 15 immediately before the operation of the inverter circuit 15 is stopped. Others are the same as in the third embodiment.

  Thereby, when the state of the load does not change, the behavior of the current and voltage in the inverter circuit 15 does not change, so that the inverter circuit 15 can perform a constant operation, stabilize the operation of the inverter circuit 15, and The safety of the heating device can be improved.

  Further, since the inverter circuit 15 can continue to operate at a high initial power value without operating at a low output power every time it is started, an operation at a low output power that reduces the power conversion efficiency of the inverter circuit 15 is avoided. Thus, the power conversion efficiency of the inverter circuit 15 can be increased.

  Furthermore, when a change in the load state is detected by the output of the load monitoring means 20, the operation of the inverter circuit 15 is stopped to prevent the induction heating device from being continuously heated when an abnormal state occurs. Safety can be improved.

(Embodiment 5)
FIG. 6 shows the relationship of the output power with respect to time of the induction heating apparatus in Embodiment 5 of the present invention.

  The difference from the fourth embodiment is that the initial power value (power value 2 at startup) of the inverter circuit 15 immediately after the operation of the inverter circuit 15 is abnormally stopped is the inverter circuit 15 immediately before the operation of the inverter circuit 15 is stopped. It is made to make it smaller than the electric power value (power value 1 at the time of starting). Others are the same as in the fourth embodiment.

  As a result, when the load state is unstable, the inverter circuit 15 can be stably operated by gradually changing from a low output power to a desired power value.

  In addition, since the inappropriate load can be detected in the safe operation region where the output power is low, the switching element 12 can be prevented from being destroyed.

  Furthermore, since the power value at the time of starting of the inverter circuit 15 is low, in the case of an improper load, it is possible to suppress heating as much as possible before detecting the improper load.

(Embodiment 6)
FIG. 7 shows the relationship of the output power with respect to time of the induction heating apparatus in Embodiment 6 of the present invention.

  The difference from the fifth embodiment is that when the operation and stop of the inverter circuit 15 are performed intermittently, the time constant of the soft start means 18 for the second and subsequent times is set to be smaller than the time constant of the first time. The period was shortened. Others are the same as in the fifth embodiment.

  Thereby, after the stability of the load state can be confirmed by the first operation of the inverter circuit 15, the soft start period can be shortened and the efficiency of the inverter circuit 15 can be increased.

(Embodiment 7)
FIG. 8 shows the relationship of the output power with respect to time of the induction heating apparatus in Embodiment 7 of the present invention.

  The difference from the sixth embodiment is that the time constant of the soft start means 18 changes with the power value (desired power value 1 or 2). Others are the same as in the sixth embodiment.

  As a result, the time constant can be made as small as possible at a level that does not cause a burden on the inverter circuit 15, so that the efficiency of the inverter circuit 15 can be increased.

(Embodiment 8)
FIG. 9 shows the relationship of the output power with respect to time of the induction heating apparatus in the eighth embodiment of the present invention.

  The difference from the seventh embodiment is that the soft start means 18 does not operate when the desired power value is lower than a certain value. In the present embodiment, the soft start means 18 is not operated after the second time, but may not be operated even at the first time. The rest is the same as in the seventh embodiment.

  As a result, noise generated from the inverter circuit 15 is small, and soft start is not performed at low output power which is safe from the viewpoint of destruction of the switching element 12 and risk of erroneous heating. Therefore, the efficiency of the inverter circuit 15 can be increased.

(Embodiment 9)
FIG. 10 shows an induction heating apparatus according to Embodiment 9 of the present invention.

A difference from the eighth embodiment is that, in addition to the heating coil 11 and the resonance capacitor 14, a second heating coil 21, a second resonance capacitor 22, and a relay 23 that switches a path for transmitting electricity are provided. Thus, the heating coils 11 and 21 are switched to switch the heating load. The rest is the same as in the eighth embodiment.

  Thereby, since several load can be heated with the same switching element 12, the number of parts which comprise the inverter circuit 15 can be reduced, and an inexpensive induction heating apparatus can be made.

  Furthermore, the power supplied to the load can be adjusted by changing the drive frequency of the switching element 12 so that arbitrary power can be supplied to the load.

  As described above, the induction heating device according to the present invention can operate the inverter circuit with an optimal power value at the time of startup and increase the efficiency of the inverter circuit, and therefore can be applied to all inverter devices. This is particularly effective for a device that repeats the ON / OFF operation of the inverter. Therefore, it is applicable not only to household appliances such as IH cooking heaters but also to all induction heating devices including business supplies.

The circuit diagram which shows the induction heating apparatus in Embodiment 1 of this invention The figure which shows the relationship of the output electric power with respect to time in the induction heating apparatus The circuit diagram which shows the induction heating apparatus in Embodiment 2 of this invention The figure which shows the relationship of the output electric power with respect to the time of the induction heating apparatus in Embodiment 3 of this invention. The circuit diagram which shows the induction heating apparatus in Embodiment 4 of this invention The figure which shows the relationship of the output electric power with respect to time of the induction heating apparatus in Embodiment 5 of this invention. The figure which shows the relationship of the output electric power with respect to the time of the induction heating apparatus in Embodiment 6 of this invention. The figure which shows the relationship of the output electric power with respect to time of the induction heating apparatus in Embodiment 7 of this invention. The figure which shows the relationship of the output electric power with respect to the time of the induction heating apparatus in Embodiment 8 of this invention. The circuit diagram which shows the induction heating apparatus in Embodiment 9 of this invention

DESCRIPTION OF SYMBOLS 11 Heating coil 12 Switching element 13 Reverse conducting element 14 Resonance capacitor 15 Inverter circuit 16 Power supply 17 Drive control means 18 Soft start means 19 Improper load detection means 20 Load monitoring means 21 2nd heating coil 22 2nd resonance capacitor 23 Relay

Claims (8)

A heating coil that transmits energy by magnetic coupling with a load, a switching element that controls electric power supplied to the heating coil, a reverse conducting element connected in parallel with the switching element, the heating coil and a resonance circuit An inverter circuit having a resonance capacitor to be formed, a power supply for supplying power to the inverter circuit, drive control means for controlling conduction of the switching element, and improper load detection means for detecting improper load , drive control means have a soft start means for varying the output power at the time of starting up a desired power value, as well as chromatic plurality of predetermined value as a power value at the start of the soft-start means, the operation of the inverter circuit When the operation is stopped and stopped intermittently, the initial power value of the soft start means for the second and subsequent times is the first initial power value. When the improper load detection means detects an improper load, the operation of the inverter circuit is stopped and the initial power value of the inverter circuit immediately after the operation of the inverter circuit is abnormally stopped is stopped. An induction heating device that makes it smaller than the power value of the inverter circuit immediately before . The inappropriate load detecting means comprises a load monitoring means for monitoring the state of the load, in the operation of the inverter circuit of the second or subsequent, if the output of the load monitoring means does not change, just after the operation of the inverter circuit is stopped the initial power value of the inverter circuit, the induction heating device of claim 1 operation of the inverter circuit to an initial power value equivalent to said inverter circuit just before the stop. When detecting a change in the load state by the output of the load monitoring unit, the induction heating apparatus according to claim 2 for stopping the operation of the inverter circuit. It said soft-start means, the output power at start changing with the time constant to a desired power value, when performing intermittently the operation and stop of the inverter circuit, the time constant of said soft start means the second time or later, The induction heating device according to any one of claims 1 to 3 , wherein the induction heating device is smaller than a first time constant. The induction heating apparatus according to claim 4, wherein the time constant of the soft start means is changed with the power value. The induction heating apparatus according to any one of claims 1 to 5, wherein the soft start means does not operate when a desired power value is lower than a certain value . The induction heating apparatus according to any one of claims 1 to 6 , further comprising a relay that switches a path through which electricity is transmitted, wherein a load to be heated by the relay is switched. The induction heating apparatus according to any one of claims 1 to 7 , wherein electric power supplied to the load is adjusted by changing a driving frequency of the switching element.

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