JP2008135321A - Induction heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating device capable of stably preventing rush current into a power supply switch with a simple constitution. <P>SOLUTION: This is equipped with the power supply switch 22 to turn on/off the power supply from a commercial alternate current power supply 21, a heating coil 27 to heat a load 26, an inverter 23 to supply high frequency power to the heating coil 27, a relay 30 connected in series between the power supply switch 22 and the inverter 23, a thermistor 28 connected in parallel with the relay 30, an input current detecting means 29, and a control means to control the relay 30. The control means 32 turns on the relay 30 when a current flowing in the power supply switch 22 becomes equal or less than a prescribed current. By this, since the rush current flowing into the power supply switch is suppressed low by the thermistor 28 and the relay 30 is turned on with the current of a prescribed level or less, the inverter 23 can be energized via the relay 30 when an equipment is used. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an induction heating apparatus such as an induction heating cooker provided with inrush current prevention means.

Conventionally, the initial power supply in this type of induction heating apparatus is charged to a capacitor as a smoothing means via a rectifying means when the power switch is closed. The inrush current flowing through the power switch at that time increases as the capacity of the capacitor increases, and exceeds the rating of the power switch. Therefore, the capacity of the capacitor is set so as not to exceed the rating of the power switch. If there is a risk of exceeding, a current is limited by inserting a resistor from the power switch to the capacitor (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-191639

  However, in the conventional configuration, in the induction heating apparatus that can also heat aluminum and copper in recent years, the stability of the power source is required, and therefore the capacity of the capacitor that is a smoothing means tends to be increased. The size is increased, and there is a problem in incorporation into equipment.

  The present invention solves the above-described conventional problems, and an object thereof is to provide an induction heating device that can stably prevent an inrush current to a power switch with a simple configuration.

  In order to solve the above-described conventional problems, an induction heating apparatus according to the present invention includes a power switch for turning on / off a power supply from a commercial AC power source to a device, a heating coil for heating a load by a magnetic field, a rectifier, and a smoothing unit. An inverter that rectifies commercial AC power by means and supplies high frequency power to the heating coil, a relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, and a current flowing through the power switch is detected. Provided with an input current detection means and a control means for controlling the relay by a signal from the input current detection means, and the control means turns on the relay when the current flowing through the power switch becomes a predetermined current or less. It is.

  As a result, the inrush current that flows to the power switch by the thermistor is kept low by the resistance value of the thermistor, and the relay is turned on when the inrush current disappears because the capacitor of the smoothing means is sufficiently charged below the predetermined current. In this case, the inverter can be energized via a relay instead of a thermistor.

  In the induction heating apparatus of the present invention, the control means for controlling the relay by a signal from the input current detection means turns on the relay after a predetermined time has elapsed since the current flowing through the power switch becomes equal to or higher than the predetermined current. Is.

  As a result, the inrush current flowing to the power switch by the thermistor is kept low by the resistance value of the thermistor, and after a predetermined time has elapsed since the current flowing to the power switch becomes the predetermined current, that is, the capacitor of the smoothing means is sufficiently charged and the inrush current is reduced. Since the relay is turned on when it disappears, the inverter can be energized via the relay instead of the thermistor when the device is used.

  In addition, the induction heating apparatus of the present invention includes a resistance measurement circuit that measures the resistance value of the thermistor, and the control means turns on the relay when the resistance value of the thermistor becomes less than a predetermined resistance value by the resistance measurement circuit. It is a thing.

  As a result, the inrush current flowing to the power switch by the thermistor is kept low by the resistance value of the thermistor, and the relay is turned on when the thermistor generates heat by the inrush current and falls below the predetermined resistance value. The inverter can be energized via a relay instead of a thermistor.

  The induction heating device of the present invention includes a temperature detection circuit for the thermistor, and the control means turns on the relay when the temperature of the thermistor exceeds a predetermined temperature, and further contacts the relay when the temperature of the thermistor rises. An abnormality is detected.

  As a result, the inrush current flowing to the power switch by the thermistor is kept low by the resistance value of the thermistor, and when the thermistor generates heat due to the inrush current and exceeds the specified temperature, the relay is turned on. Instead, the inverter can be energized through a relay. Also, when the temperature of the thermistor rises, it is possible to detect a relay contact abnormality and respond quickly.

  The induction heating device of the present invention can stably prevent inrush current to the power switch with a simple configuration.

  The first invention is a power switch for turning on / off a power supply from a commercial AC power source to a device, a heating coil for heating a load by a magnetic field, a rectifying unit and a smoothing unit for rectifying the commercial AC power source and applying a high frequency to the heating coil. An inverter for supplying power, a relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, an input current detecting means for detecting a current flowing through the power switch, and an input current detecting means And a control means for controlling the relay by a signal. The control means is an induction heating device configured to turn on the relay when the current flowing through the power switch becomes a predetermined current or less. As a result, the inrush current that flows to the power switch by the thermistor is kept low by the resistance value of the thermistor, and the relay is turned on when the inrush current disappears because the capacitor of the smoothing means is sufficiently charged below the predetermined current. In this case, the inverter can be energized via a relay instead of a thermistor.

  According to a second aspect of the present invention, a power switch for turning on / off power supply from a commercial AC power source to a device, a heating coil for heating a load by a magnetic field, a rectifying unit and a smoothing unit rectify the commercial AC power source, An inverter for supplying power, a relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, an input current detecting means for detecting a current flowing through the power switch, and an input current detecting means And a control means for controlling the relay by a signal, wherein the control means is an induction heating device configured to turn on the relay after a predetermined time has elapsed since the current flowing through the power switch becomes equal to or higher than a predetermined current. As a result, the inrush current flowing to the power switch by the thermistor is kept low by the resistance value of the thermistor, and after a predetermined time has elapsed since the current flowing to the power switch becomes the predetermined current, that is, the capacitor of the smoothing means is sufficiently charged and the inrush current is reduced. Since the relay is turned on when it disappears, the inverter can be energized via the relay instead of the thermistor when the device is used.

  According to a third aspect of the invention, in particular, in the first or second aspect of the invention, when the power switch is turned off, the control means turns off the relay when the voltage of the smoothing means becomes less than a predetermined voltage. Thus, the relay can be reliably turned off to prepare for the next time.

  According to a fourth aspect of the present invention, there is provided a power switch for turning on / off a power supply from a commercial AC power source to a device, a heating coil for heating a load by a magnetic field, a rectifying unit and a smoothing unit for rectifying the commercial AC power source, An inverter that supplies power, a relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, a resistance measurement circuit that measures the resistance value of the thermistor, and a relay based on a signal from the resistance measurement circuit The control means is an induction heating device configured to turn on the relay when the resistance measurement circuit causes the thermistor to have a resistance value lower than a predetermined resistance value. As a result, the inrush current flowing to the power switch by the thermistor is kept low by the resistance value of the thermistor, and the relay is turned on when the thermistor generates heat by the inrush current and falls below the predetermined resistance value. The inverter can be energized via a relay instead of a thermistor.

  According to a fifth aspect of the invention, in particular, in the fourth aspect of the invention, when the power switch is turned off, the control means turns off the relay when the resistance value of the thermistor exceeds a predetermined resistance value. The relay can be reliably turned off to prepare for the next time.

  According to a sixth aspect of the present invention, there is provided a power switch for turning on / off a power supply from a commercial AC power source to a device, a heating coil for heating a load by a magnetic field, a rectifying unit and a smoothing unit for rectifying the commercial AC power source, An inverter that supplies power, a relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, a temperature detection circuit of the thermistor, and a control means for controlling the relay by a signal from the temperature detection circuit And the control means is an induction heating device that turns on the relay when the temperature of the thermistor exceeds a predetermined temperature, and further detects that the relay contact is abnormal when the temperature of the thermistor rises. It is. As a result, the inrush current flowing to the power switch by the thermistor is kept low by the resistance value of the thermistor, and when the thermistor generates heat due to the inrush current and exceeds the specified temperature, the relay is turned on. Instead, the inverter can be energized through a relay. Also, when the temperature of the thermistor rises, it is possible to detect a relay contact abnormality and respond quickly.

  According to a seventh aspect of the invention, in particular, in the sixth aspect of the invention, when the control means detects a relay contact abnormality, the seventh invention is provided with a display means for displaying an abnormal state so that the relay contact abnormality can be visually confirmed. It can correspond to.

  In an eighth aspect of the invention, in particular, in the sixth or seventh aspect of the invention, when the control means detects a contact abnormality of the relay, a notification means for notifying an abnormal state is provided. Check your hearing and respond quickly.

  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 illustrate an induction heating cooker as an induction heating apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the induction heating apparatus in the present embodiment includes a power switch 22 that turns on / off power supply from a commercial AC power supply 21 to a device, and a heating coil 27 that heats a load 26 such as a pan with a magnetic field. An inverter 23 that rectifies the commercial AC power supply 21 and supplies high-frequency power to the heating coil 27; a relay 30 connected in series between the power switch 22 and the inverter 23; and a thermistor 28 connected in parallel thereto; Input current detection means 29 for detecting the current flowing through the switch 22 and control means 32 for controlling the relay 30 by a signal from the input current detection means 29 are provided. The induction heating apparatus also includes a power switch detection circuit 31 that detects the on / off of the power switch 22 and an input voltage detection means 33 that measures the voltage of the capacitor 25.

  The inverter 23 includes a rectifying unit 24, a capacitor 25 that is a smoothing unit, and a semiconductor switching element 34 having a driving unit 35.

  The control means 32 controls the relay 30 to be turned on when the current flowing through the power switch 22 by the input current detection means 29 becomes a predetermined current or less.

  In the induction heating apparatus described above, an inrush current flows into the capacitor 25 when the power switch 22 is turned on. The thermistor 28 for preventing the inrush current has a high resistance value at the beginning, and suppresses the inrush current. However, when the current flows and self-heats, the resistance value decreases. If, for example, an induction heating device is used as it is, the consumption current of the inverter 23 flows into the thermistor 28 and the temperature rises and the thermistor 28 is destroyed. Therefore, the input current detection means 29 that detects the current flowing through the power switch 22 is used. Thus, when the current flowing through the power switch 22 becomes a predetermined current or less, the control means 32 turns on the relay 30 so that the current does not flow into the thermistor 28.

  At this time, ON / OFF of the power switch 22 is detected by the power switch detection circuit 31. The control means 32 controls this movement and instructs the relay 30 to turn on / off.

  FIG. 2 shows this timing. The capacitor 25 is charged by the current suppressed via the thermistor 28, and the relay 30 is turned on when the peak of the inrush current has passed and the power switch 22 has been turned on to become a predetermined current value I or less. .

  Thus, in this embodiment, the inrush current flowing to the power switch by the thermistor is kept low by the resistance value of the thermistor, and the relay is turned on when the inrush current disappears because the capacitor of the smoothing means is sufficiently charged below the predetermined current, that is, the smoothing means. Therefore, when using the device, the inverter can be energized via a relay instead of a thermistor. That is, it is possible to stably prevent inrush current to the power switch with a simple configuration.

(Embodiment 2)
FIG. 3 shows the relay ON / OFF timing of the induction heating apparatus according to Embodiment 2 of the present invention. Since the circuit configuration is the same as that of the first embodiment, the description thereof is omitted.

  In this embodiment, the control means 32 controls the relay 30 to be turned on after a lapse of a predetermined time after the current flowing through the power switch 22 exceeds a predetermined current by the input current detection means 29. The rest is the same as in the first embodiment.

  As shown in FIG. 3, the power switch 22 is turned on, and the capacitor 25 is charged by the current suppressed via the thermistor 28. After a predetermined time H from the power switch 22 being turned on, the relay 30 is turned on and the current is turned on. This prevents the thermistor 28 from flowing.

  As described above, in this embodiment, the inrush current flowing to the power switch by the thermistor is suppressed by the resistance value of the thermistor, and the current flowing to the power switch becomes a predetermined current after a predetermined time has elapsed, that is, to the capacitor of the smoothing means. Since the relay is turned on when the inrush current disappears when the battery is sufficiently charged, the inverter can be energized via the relay instead of the thermistor when the device is used. That is, similarly to the first embodiment, the inrush current can be stably prevented with a simple configuration.

  In the first and second embodiments, when the power switch 22 is turned off and the voltage of the capacitor 25 decreases, the relay is detected when the voltage detected by the input voltage detection means 33 becomes less than a predetermined voltage. 30 is off. As a result, the relay can be reliably turned off to prepare for the next time.

(Embodiment 3)
4 and 5 show an induction heating apparatus according to Embodiment 3 of the present invention. The same elements as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 4, the present embodiment includes a resistance measurement circuit 36 that measures the resistance value of the thermistor 28 for preventing inrush current. Then, the control means 32 controls the relay 30 with a signal from the resistance measurement circuit 36. Other configurations are the same as those of the first embodiment.

  In the induction heating apparatus described above, the power switch 22 is turned on, and the capacitor 25 is charged with the current suppressed via the thermistor 28. Then, when the temperature of the thermistor 28 increases due to self-heating due to the inrush current and the resistance value decreases, it is determined that the inrush current has decreased, and the relay 30 is turned on.

  The timing at that time is shown in FIG. When the capacitor 25 is charged by the current suppressed via the thermistor 28 and the temperature of the thermistor 28 rises to a predetermined resistance value R due to the charging current, it is determined that the peak of the inrush current has passed, and the relay 30 To turn on.

  In this way, in this embodiment, the inrush current flowing to the power switch by the thermistor is kept low by the resistance value of the thermistor, and the relay is turned on when the thermistor generates heat by the inrush current and falls below the predetermined resistance value. In use, the inverter can be energized via a relay instead of a thermistor. That is, similarly to the first embodiment, the inrush current can be stably prevented with a simple configuration.

  In the present embodiment, when the power switch 22 is turned off, the relay 30 is turned off when the resistance value of the thermistor 28 exceeds a predetermined resistance value. As a result, the relay can be reliably turned off to prepare for the next time.

(Embodiment 4)
6 and 7 show an induction heating apparatus according to Embodiment 4 of the present invention. The same elements as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 6, in the present embodiment, the relay 30 is turned on when the temperature of the thermistor 28 becomes equal to or higher than a predetermined temperature T, and when the temperature of the thermistor 28 rises, the contact abnormality of the relay 30 and the control means are controlled. 32 is to be detected. In addition, when the control unit 32 detects a contact abnormality of the relay 30, a display unit 38 that visually displays the abnormal state with light, characters, symbols, or the like, and a notification unit 39 that provides an auditory notification of the abnormal state with a buzzer, voice, or the like. It is what it has. The rest is the same as in the first embodiment.

  In the above-described induction heating device, when the power switch 22 is turned on, the capacitor 25 is charged by the current suppressed via the thermistor 28, and the temperature of the thermistor 28 becomes equal to or higher than a predetermined temperature T due to self-heating due to the inrush current. Is determined that the inrush current has decreased, and the relay 30 is turned on. The timing at that time is shown in FIG.

  When the thermistor 28 further rises in temperature, it is determined that the relay 30 has not been turned on, and the control means 32 detects that the relay 30 has a contact abnormality. When the control unit 32 detects the contact abnormality of the relay 30, the display unit 38 displays the abnormal state, so that the contact abnormality of the relay 30 can be visually confirmed and dealt with promptly. In addition, by notifying the abnormality state display on the display means 38 or individually by the notification means 39, it is possible to aurally check the contact abnormality of the relay 30 and respond quickly.

  In this way, in this embodiment, the inrush current flowing to the power switch by the thermistor is kept low by the resistance value of the thermistor, and the relay is turned on when the thermistor generates heat by the inrush current and exceeds a predetermined temperature. In use, the inverter can be energized via a relay instead of a thermistor. Also, when the temperature of the thermistor rises, it is possible to detect a relay contact abnormality and respond quickly.

  As described above, the induction heating device according to the present invention has a simple configuration and can stably prevent inrush current to the power switch. Applicable in general.

The block diagram which shows the circuit of the induction heating apparatus in Embodiment 1, 2 of this invention The timing chart which shows the operation | movement at the time of power-on of the induction heating apparatus in Embodiment 1 of this invention Timing chart showing operation at power-on of induction heating device in embodiment 2 of the present invention The block diagram which shows the circuit of the induction heating apparatus in Embodiment 3 of this invention. Timing chart showing the operation of the induction heating device when the power is turned on The block diagram which shows the circuit of the induction heating apparatus in Embodiment 4 of this invention. Timing chart showing the operation of the induction heating device when the power is turned on

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Commercial alternating current power supply 22 Power switch 23 Inverter 24 Rectification means 25 Capacitor 26 Load 27 Heating coil 28 Thermistor 29 Input current detection means 30 Relay 31 Power switch detection circuit 32 Control means 33 Input voltage detection means 34 Semiconductor switching element

Claims (8)

A power switch for turning on / off the power supply from the commercial AC power source to the device, a heating coil for heating the load by a magnetic field, an inverter for rectifying the commercial AC power source by the rectifying means and the smoothing means and supplying high-frequency power to the heating coil; The relay is controlled by a relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, an input current detecting means for detecting a current flowing through the power switch, and a signal from the input current detecting means And an induction heating device configured to turn on the relay when the current flowing through the power switch becomes a predetermined current or less. A power switch for turning on / off the power supply from the commercial AC power source to the device, a heating coil for heating the load by a magnetic field, an inverter for rectifying the commercial AC power source by the rectifying means and the smoothing means and supplying high-frequency power to the heating coil; The relay is controlled by a relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, an input current detecting means for detecting a current flowing through the power switch, and a signal from the input current detecting means And an induction heating device configured to turn on the relay after a lapse of a predetermined time after the current flowing through the power switch becomes equal to or greater than a predetermined current. The induction heating apparatus according to claim 1 or 2, wherein the control means turns off the relay when the voltage of the smoothing means becomes less than a predetermined voltage when the power switch is turned off. A power switch for turning on / off the power supply from the commercial AC power source to the device, a heating coil for heating the load by a magnetic field, an inverter for rectifying the commercial AC power source by the rectifying means and the smoothing means and supplying high-frequency power to the heating coil; A relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, a resistance measurement circuit for measuring the resistance value of the thermistor, and a control means for controlling the relay by a signal from the resistance measurement circuit; And the control means turns on a relay when the resistance value of the thermistor becomes less than a predetermined resistance value by a resistance measurement circuit. The induction heating apparatus according to claim 4, wherein when the power switch is turned off, the control means turns off the relay when the resistance value of the thermistor exceeds a predetermined resistance value. A power switch for turning on / off the power supply from the commercial AC power source to the device, a heating coil for heating the load by a magnetic field, an inverter for rectifying the commercial AC power source by the rectifying means and the smoothing means and supplying high-frequency power to the heating coil; A relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, a temperature detection circuit of the thermistor, and a control means for controlling the relay by a signal from the temperature detection circuit, the control The means is an induction heating device that turns on the relay when the temperature of the thermistor becomes equal to or higher than a predetermined temperature, and detects that the relay contact is abnormal when the temperature of the thermistor rises. The induction heating apparatus according to claim 6, further comprising display means for displaying an abnormal state when the control means detects a contact abnormality of the relay. The induction heating apparatus according to claim 6 or 7, further comprising notification means for notifying an abnormal state when the control means detects a contact abnormality of the relay.

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