JP2005322560A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a rush current at the time of switching on of a power supply switch by using a thermistor. <P>SOLUTION: A thermistor 6 and a relay 7 in parallel with the thermistor are provided in the passage of a rush current, and the thermistor 6 is short-circuited by the relay 7 after a prescribed time from switching on of power supply. When the voltage of a smoothing capacitor is a prescribed value or more, the thermistor 6 is short-circuited by the relay 7. By detecting the temperature rise or the resistance value drop of the thermistor, the thermistor 6 is short-circuited by the relay 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an induction heating cooker provided with inrush current preventing means.

  The structure of the conventional general induction heating cooking appliance is shown in FIG. 6 and FIG. Conventionally, this type of induction heating cooker supplies power to an inverter 3 by closing a power switch 2 of a commercial AC power supply 1 as shown in FIG. As shown in FIG. 7, the inverter 3 includes a rectifier 4, a capacitor 5 as a smoothing means, and a switching element 14 that performs high-frequency switching. The high-frequency power source produced by the inverter 3 is supplied to a heating coil 12 that is induction heating means, and a load metal pan 13 is heated by a magnetic field generated from the heating coil 12.

At this time, the initial power supply is charged to the capacitor 5 via the rectifier 4 when the power switch 2 is closed as shown in FIG. FIG. 8 shows changes in the inrush current flowing from the power switch 2 to the capacitor 5 via the rectifier 4 at that time. As indicated by the dotted line in FIG. 8, the inrush current increases as the capacity of the capacitor 5 increases, and exceeds the rating of the power switch 2. Therefore, the capacity of the capacitor 5 is set so as not to exceed it. If there is a risk of exceeding, there is a precedent in which a current is limited by inserting a resistor from the power switch 5 to the capacitor 5 (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-191639

  In recent induction heating cookers that can also heat aluminum and copper, since the stability of the power source is required, there has been a tendency to increase the capacity of the capacitor 5 as a smoothing means. However, in the configuration of the conventional induction heating cooker shown in FIG. 6, in this state, the rating of the power switch 2 will be exceeded, and in order not to exceed it, there is a further problem that is problematic for incorporation in equipment. It had the problem of having to be a switch.

  This invention solves the said subject, and it aims at providing the induction heating cooking appliance which can prevent the inrush current to a power switch stably with a simple structure.

  In order to solve the above problems, an induction heating cooker according to the present invention includes a power switch for turning on / off the supply of commercial AC power to an apparatus, induction heating means for heating a load by a magnetic field, and commercial heating to the induction heating means. An inverter provided with a rectifying means and a smoothing means for supplying a high-frequency power converted from an AC power supply, a relay connected in series between the inverter from the power switch, a thermistor connected in parallel to the relay, and the power supply A power switch detection circuit for detecting whether the switch is turned on or off is provided, and the relay is turned on after a predetermined time has elapsed since the power switch detection circuit detects that the power switch is turned on. is there.

  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 after a predetermined time. The inverter can be energized.

  In addition, the induction heating cooker of the present invention is a power switch for turning on / off the supply of commercial AC power to the device, induction heating means for heating a load by a magnetic field, and conversion from commercial AC power to the induction heating means. An inverter including a rectifying unit and a smoothing unit that supplies high-frequency power, a relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, and a voltage of the smoothing unit are detected. A VIN detection circuit that turns on the relay when the voltage of the smoothing means exceeds a predetermined voltage by the VIN detection circuit.

  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 inrush current disappears because the capacitor of the smoothing means is sufficiently charged. In this case, the inverter can be energized through a relay instead of a thermistor.

  In addition, the induction heating cooker of the present invention is a power switch for turning on / off the supply of commercial AC power to the device, induction heating means for heating a load by a magnetic field, and conversion from commercial AC power to the induction heating means. An inverter including a rectifying unit and a smoothing unit that supplies high-frequency power, a relay connected in series between the inverter from the power switch, a thermistor connected in parallel to the relay, and a temperature detection circuit of the thermistor The relay is turned on by the temperature detection circuit when the temperature of the thermistor exceeds a predetermined temperature.

  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. Can energize the inverter via a relay instead of a thermistor.

  As described above, according to the configuration of the present invention, inrush current is suppressed with a simple configuration using a thermistor, and when an induction heating cooker is used, the relay connected in parallel to the thermistor is energized. By doing so, it is possible to prevent a failure of the power switch with a simple configuration.

  An induction heating cooker according to a first aspect of the present invention is a power switch that turns on / off power supply from a commercial AC power source to a device, a heating coil that heats a load by a magnetic field, a rectifying unit, and a smoothing unit. An inverter that rectifies and supplies high-frequency power to the heating coil by induction heating means, a relay connected in series between the power switch and the inverter, a thermistor connected in parallel to the relay, and the power switch is ON or A power switch detection circuit for detecting that the power switch is turned off; and a control means for controlling the relay, wherein the control means detects that the power switch is turned on by the power switch detection circuit and a predetermined time has elapsed. The relay is turned on.

  An induction heating cooker according to a second aspect of the present invention is a power switch that turns on / off power supply from a commercial AC power source to a device, a heating coil that heats a load by a magnetic field, a rectifying unit, and a smoothing unit. An inverter that rectifies and supplies high-frequency power to the heating coil by induction heating means, a relay connected in series between the inverter from the power switch, a thermistor connected in parallel to the relay, and a voltage of the smoothing means A VIN detection circuit for detecting and a control means for controlling the relay are provided, and the control means turns on the relay when the voltage of the smoothing means exceeds a predetermined voltage by the VIN detection circuit. It is what.

  Further, when the power switch is turned off, the relay is turned off when the voltage of the smoothing means becomes less than a predetermined voltage.

  An induction heating cooker according to a third aspect of the present invention is a power switch that turns on / off power supply from a commercial AC power source to a device, a heating coil that heats a load by a magnetic field, a rectifying unit, and a smoothing unit. An inverter that rectifies and supplies high-frequency power to the heating coil by induction heating means, a relay connected in series between the inverter from the power switch, a thermistor connected in parallel to the relay, and a temperature detection circuit of the thermistor And a control means for controlling the relay, wherein the control means is configured to turn on the relay when the temperature of the thermistor exceeds a predetermined temperature by the temperature detection circuit.

  Further, when the power switch is turned off, the relay is turned off when the temperature of the thermistor becomes lower than a predetermined temperature.

  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, and a rectifying unit and a smoothing unit for rectifying the commercial AC power source for induction heating unit. An inverter for supplying high-frequency power to the heating coil, a relay connected in series between the inverter from the power switch, a thermistor connected in parallel to the relay, and a resistance measurement circuit for measuring a resistance value of the thermistor And a control means for controlling the relay, wherein 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.

  When the power switch is turned off, the relay is turned off when the resistance value of the thermistor exceeds a predetermined resistance value.

  Hereinafter, the embodiment will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows the configuration of an induction heating cooker according to the first embodiment of the present invention.

  As shown in FIG. 1, the main part equivalent to the conventional example of the induction heating cooker of the present invention is constituted by a power switch 2 for turning on / off the commercial power source 1 and an inverter 3 for producing a high frequency power source from the commercial AC power source 1. doing. Further, the inverter 3 is provided with a rectifier 4 and a capacitor 5, and the pan 13 is subjected to high-frequency induction heating via a heating coil 12 by induction heating means. When the power switch 2 is turned on, an inrush current flows into the capacitor 5. The thermistor 6 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 cooker is used as it is, the current consumed by the inverter 3 flows to the thermistor and the temperature rises and the thermistor 6 is destroyed. Therefore, the relay 7 is turned on for a predetermined time after the power switch 2 is turned on. Thus, current is prevented from flowing to the thermistor 6.

  At this time, ON / OFF of the power switch 2 is detected by the power switch detection circuit 8 shown in FIG. The control means 15 controls this movement and instructs ON / OFF of the relay 7.

  FIG. 2 shows this timing chart. When the capacitor 5 is charged by the current suppressed through the thermistor 6 and the peak of the inrush current has passed, the relay 7 is turned on.

(Embodiment 2)
According to the second embodiment of the present invention, the voltage of the capacitor 5 is measured by the VIN detection circuit 9 as shown in FIG.

  When the power switch 2 is turned on and the capacitor 5 is charged by the current suppressed via the thermistor 6 and the voltage of the capacitor 5 exceeds a predetermined voltage, it is determined that the inrush current has decreased, and the relay 7 Is turned on. The timing at that time is shown in FIG. When the capacitor 5 is charged by the current suppressed via the thermistor 6 and the voltage of the capacitor 5 rises and the peak of the inrush current has passed, the relay 7 is turned on.

  Further, when the power switch 2 is turned off and the voltage of the capacitor 5 decreases, the relay 7 is opened to prevent an inrush current when the power switch 2 is turned on next time.

(Embodiment 3)
According to the third embodiment of the present invention, as shown in FIG. 1, the temperature detection circuit 10 measures the temperature of the thermistor 6 for preventing inrush current.

  When the power switch 2 is turned on, the capacitor 5 is charged by the current suppressed via the thermistor 6, and when the temperature of the thermistor 6 increases due to self-heating due to the inrush current, it is determined that the inrush current has decreased, 7 is ON. The timing at that time is shown in FIG. When the capacitor 5 is charged by the current suppressed via the thermistor 6 and the temperature of the thermistor 6 rises due to the charging current, it is determined that the peak of the inrush current has passed, and the relay 7 is turned on. .

  When the power switch 2 is turned off and the temperature of the thermistor 6 decreases, the relay is opened to prevent an inrush current when the power switch 2 is turned on next time.

(Embodiment 4)
According to the fourth embodiment of the present invention, as shown in FIG. 1, the resistance measurement circuit 11 measures the resistance value of the thermistor 6 for preventing inrush current.

  When the power switch 2 is turned on, the capacitor 5 is charged by the current suppressed via the thermistor 6, and when the temperature of the thermistor 6 rises due to self-heating due to the inrush current and the resistance value decreases, the inrush current is It is determined that the voltage has decreased, and the relay 7 is ON. The timing at that time is shown in FIG. When the capacitor 5 is charged by the current suppressed via the thermistor 6 and the temperature of the thermistor 6 increases and the resistance value decreases due to the charging current, it is determined that the peak of the inrush current has passed, and the relay 7 is turned on. It is turned on.

  Further, when the power switch 2 is turned off and the temperature of the thermistor 6 decreases and the resistance value increases, the relay is opened to prevent an inrush current when the power switch 2 is turned on next time.

  The operation | movement of the memory | storage means of this invention can be diverted to general induction heating cooking appliances in a general household.

The block diagram which shows the structure of the power supply part of the induction heating cooking appliance in Embodiment 1-4 of this invention. The timing chart which shows the operation | movement at the time of power ON of the induction heating cooking appliance of Embodiment 1 of this invention The timing chart which shows the operation | movement at the time of power ON of the induction heating cooking appliance of Embodiment 2 of this invention The timing chart which shows the operation | movement at the time of power ON of the induction heating cooking appliance of Embodiment 3 of this invention The timing chart which shows the operation | movement at the time of power ON of the induction heating cooking appliance of Embodiment 4 of this invention The block diagram which shows the structure of the power supply part of the induction heating cooking appliance of a prior art example The block diagram which shows the whole structure of the induction heating cooking appliance of a prior art example Timing chart showing the operation of the conventional induction heating cooker when the power is turned on

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial AC power supply 2 Power switch 3 Inverter 4 Rectifier 5 Capacitor 6 Thermistor 7 Relay 8 Power switch detection means 9 VIN detection means 10 Temperature detection circuit 11 Resistance measurement circuit 12 Heating coil 13 Load pan 14 Switching element 15 Control means

Claims (7)

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, and rectifying the commercial AC power source by the rectifying means and the smoothing means, and applying high frequency to the heating coil by the induction heating means An inverter for supplying electric power; a relay connected in series between the inverter from the power switch; a thermistor connected in parallel to the relay; and a power switch detection circuit for detecting whether the power switch is turned on or off. And the control means for controlling the relay, the control means is configured to turn on the relay after a predetermined time has elapsed since the power switch detection circuit detects that the power switch is turned on. vessel. 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, and rectifying the commercial AC power source by the rectifying means and the smoothing means, and applying high frequency to the heating coil by the induction heating means An inverter for supplying electric power, a relay connected in series between the inverter from the power switch, a thermistor connected in parallel to the relay, a VIN detection circuit for detecting the voltage of the smoothing means, and controlling the relay An induction heating cooker configured to turn on the relay when the voltage of the smoothing unit becomes equal to or higher than a predetermined voltage by the VIN detection circuit. The induction heating cooker according to claim 2, wherein 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. 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, and rectifying the commercial AC power source by the rectifying means and the smoothing means, and applying high frequency to the heating coil by the induction heating means An inverter for supplying electric power; a relay connected in series between the inverter from the power switch; a thermistor connected in parallel to the relay; a temperature detection circuit for the thermistor; and a control means for controlling the relay. And the control means is an induction heating cooker configured to turn on the relay when the temperature of the thermistor exceeds a predetermined temperature by the temperature detection circuit. The induction heating cooker according to claim 4, wherein the control means turns off the relay when the temperature of the thermistor becomes lower than a predetermined temperature 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, and rectifying the commercial AC power source by the rectifying means and the smoothing means, and applying high frequency to the heating coil by the induction heating means An inverter that supplies power, a relay connected in series between the inverter from the power switch, a thermistor connected in parallel to the relay, a resistance measurement circuit that measures a resistance value of the thermistor, and the relay An induction heating cooker configured to turn on the relay when the resistance measurement circuit causes a resistance value of the thermistor to be less than a predetermined resistance value. The induction heating cooker according to claim 6, wherein the control means turns off the relay when the resistance value of the thermistor exceeds a predetermined resistance value when the power switch is turned off.

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