JP2010153168A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a microcomputer from erroneously detecting an output voltage of an input current detection circuit even in a circumstance of a high frequency electric field and operate it normally. <P>SOLUTION: An induction heating cooker includes: an inverter 4 which supplies a high frequency current to a heating coil 3 for heating a pan (cooking vessel) 1 and heats the pan (cooking vessel) 1 by electromagnetic induction; a current detector 7 which converts a current flowing through the heating coil 3 into a voltage; an input current detection circuit 5 which is composed of a first rectifier 8 for rectifying an output signal of the current detector 7 and a smoothing circuit 9 for smoothing an output signal of the first rectifier 8; and a control circuit 6 which receives an output signal of the input current detection circuit 5 and controls an input power of the inverter 4 to cause the output signal to be a predetermined output or lower, wherein a bypass capacitor 10 is connected parallel to the first rectifier 8 of the input current detection circuit 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an induction heating cooker provided with an inverter control circuit that operates normally without problems even in an environment of a high-frequency electric field.

Conventionally, in an induction heating cooker, the output voltage of the input current detection circuit in the inverter control circuit in the inverter current control circuit is normally operated without any problem by limiting the output voltage so that the output voltage is not more than a predetermined target value. What has such a function is known (for example, refer patent document 1).
Japanese Patent Laid-Open No. 02-072581

  However, in the configuration of the conventional induction heating cooker, when noise in a high frequency band enters the rectifier of the input current detection circuit in a strong electric field environment, the rectifier becomes an antenna, and the output voltage across the rectifier There is a problem that high-frequency noise is superimposed and the microcomputer erroneously detects the target value of the output voltage.

  The present invention solves the above-mentioned conventional problems, has a function of removing high frequency band noise, and the microcomputer operates normally without erroneously detecting the output voltage of the input current detection circuit even in an environment of a high frequency electric field. An object of the present invention is to provide an induction heating cooker.

  In order to solve the conventional problems, the induction heating cooker according to the present invention has a noise removal function when the high-frequency band noise enters the rectifier of the input current detection circuit in an environment of a strong electric field. In order to apply to the detection circuit, a bypass capacitor is inserted in parallel across the rectifier.

  As a result, when high-frequency noise passes through the rectifier, the noise can be removed by the bypass capacitor, and the microcomputer can operate the induction heating cooker normally without erroneously detecting the output voltage of the input current detection circuit. .

  When the induction heating cooker of the present invention operates in an external high frequency electric field, the high frequency noise superimposed on the output voltage of the input current detection circuit by the high frequency electric field can be reduced.

1st invention includes the heating coil which carries out induction heating of the to-be-heated material, converts the DC voltage which rectified commercial power into high frequency current, and supplies it to the heating coil, and the input of the commercial frequency which the inverter inputs A current detector for detecting current, a rectifier for rectifying the output signal of the current detector, a smoothing circuit for smoothing the output signal of the rectifier, and an output signal of the input current detection circuit And a control circuit for controlling the input power of the inverter below a predetermined output, and the input current detection circuit is connected to the rectifier in parallel so that the input current detection circuit is in an external high-frequency electric field. The induction heating cooker reduces the magnitude of high frequency noise superimposed on the output voltage of the input current detection circuit by the high frequency electric field when operated at It makes by the bypass capacitor has a function of reducing the magnitude of the high-frequency noise, it is possible to operate normally without malfunction even during high-frequency electric field.

  The second aspect of the invention is particularly the induction heating cooker of the first aspect of the invention, wherein the input current detection circuit is a first rectifier connected between one end of the output terminal of the current detector and a common potential, the first and second A series connection body in which two resistors are connected in series, a smoothing capacitor connected to both ends of the second resistor, and a bias circuit for setting the other end of the current detector to a predetermined potential, The voltage across the smoothing capacitor is output as an output voltage to the control circuit, and the capacitance of the bypass capacitor is different between the output voltage when the bypass capacitor is not connected and the output voltage when the bypass capacitor is connected. By making it as small as possible, it is possible to operate normally without problems even in a normal state where a strong electric field is not applied even in a high-frequency electric field.

  In the third aspect of the invention, particularly in the induction heating cooker of the second aspect of the present invention, the bypass condenser has a capacity that is 1/100 to 1/1000 times the capacity of the smoothing condenser. When operated in an external high frequency electric field, high frequency noise superimposed on the output voltage of the input current detection circuit can be reduced.

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

  In FIG. 1, a heating coil 3 for heating a pan (cooking vessel) 1, a top plate (top plate) 2 for placing the pan (cooking vessel) 1 on the heating coil 3, and a heating coil 3 An inverter 4 that supplies high-frequency current and heats the pan (cooking vessel) 1 by electromagnetic induction, a current detector 7 that converts the current flowing through the heating coil 3 into a voltage, and a first that rectifies the output signal of the current detector 7 An input current detection circuit 5 composed of a rectifier 8 and a smoothing circuit 9 for smoothing the output signal of the first rectifier 8, and an input signal of the input current detection circuit 5 is input to reduce the input power of the inverter 4 below a predetermined output. A control circuit (microcomputer) 6 for controlling is provided, and a bypass capacitor 10 is connected in parallel to the first rectifier 8 of the input current detection circuit 5 so that the induction heating cooker is operated normally in a high-frequency electric field without malfunction. It has a structure in which to operate.

  About the induction heating cooking appliance comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  In the induction heating cooker, for example, when heating is started by turning on a power switch (not shown) in an environment where a high frequency electric field is applied with a frequency of 1 MHz to 500 MHz, the first rectifier 8 is connected in parallel. For example, the magnitude of the high-frequency noise superimposed on the output voltage of the input current detection circuit by the high-frequency electric field can be reduced by the action of the bypass capacitor 10 having a capacitance of 500 pF to 5000 pF.

(Embodiment 2)
FIG. 2 shows the configuration of an induction heating cooker in the second embodiment of the present invention.

  FIG. 2 shows a bias circuit 14 connected to one end of the output terminal of the current detector 7 of the input current detection circuit 5 of the induction cooking device according to the first embodiment of the present invention, and the output terminal of the current detector 7. The current detector 7 and the smoothing circuit 9 connected to the other end of FIG. The current detector 7 has a configuration in which a signal supplied from the commercial AC power supply 22 detects an input current via the inverter 4, and the smoothing circuit 9 includes a first rectifier 8, first and second resistors 11. And 12 are connected in series, and the bias circuit 14 forms a third resistor 15, a second rectifier 16, and a fourth resistor 17 connected in series from the DC power supply 18.

  About the induction heating cooking appliance comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  In the induction heating cooker, when a power switch (not shown) is turned on in an environment where a high-frequency electric field is applied and heating is started, an input signal from the power supply outputs a voltage across the smoothing capacitor 13 of the input current detection circuit. In addition to being output as a voltage, the capacity of the bypass capacitor 10 is such that the user does not feel abnormal with respect to the setting output of the induction heating cooker when the bypass capacitor 10 is not connected and when the bypass capacitor 10 is connected. By suppressing the voltage to be equal to or lower than the voltage corresponding to the output reduction caused by the above, the bypass capacitor 10 can reduce the magnitude of the high frequency noise as in the first embodiment.

  As described above, the induction heating cooker according to the present invention can withstand high-frequency noise even in an environment of a high-frequency electric field, so that it is used in an area where a strong electric field is generated near a TV tower or the like. It can also be used for applications such as industrial or commercial induction heating cookers.

The block diagram of the induction heating cooking appliance in Embodiment 1 of this invention The block diagram of the input electric current detection circuit of the induction heating cooking appliance in Embodiment 2 of this invention

Explanation of symbols

1 Pot (to be heated)
3 Heating coil 4 Inverter 5 Input current detection circuit 6 Control circuit (microcomputer)
7 Current detector 8 First rectifier 9 Smoothing circuit 10 Bypass capacitor 11 First resistor 12 Second resistor 13 Smoothing capacitor 14 Bias circuit

Claims (3)

An inverter that includes a heating coil that induction-heats an object to be heated, converts a DC voltage rectified from a commercial power supply into a high-frequency current and supplies the high-frequency current to the heating coil, and current detection that detects an input current at a commercial frequency input to the inverter A first rectifier that rectifies the output signal of the current detector, a smoothing circuit that smoothes the output signal of the first rectifier, and an output signal of the input current detection circuit A control circuit for controlling the input power of the inverter below the output, and the input current detection circuit is connected to the first rectifier in parallel so that the input current detection circuit is in an external high-frequency electric field. An induction heating cooker that reduces the magnitude of high-frequency noise superimposed on the output voltage of the input current detection circuit by the high-frequency electric field when operated at. The input current detection circuit includes a first rectifier connected between one end of the output terminal of the current detector and a common potential, a series connection body in which the first and second resistors are connected in series, and the second resistor. A smoothing capacitor connected to both ends of the detector, and a bias circuit for setting the other end of the current detector to a predetermined potential, and outputs a voltage across the smoothing capacitor to the control circuit as an output voltage, and a bypass capacitor 2. The induction heating cooker according to claim 1, wherein the capacity of is reduced to such an extent that there is no difference between the output voltage when the bypass capacitor is not connected and the output voltage when the bypass capacitor is connected. The induction heating cooker according to claim 2, wherein the bypass capacitor has a capacity 1/100 to 1/1000 times the capacity of the smoothing capacitor.

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