JP2015079572A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to gain an intended heating output in a simple configuration even when connected to a plurality of different commercial power supplies.SOLUTION: An induction heating cooker comprises: a control part 20 including a commercial power supply voltage determination part 16 for determining a magnitude of a commercial power supply voltage; and a reference value setting part 13 which changes when a voltage value detected by the commercial power supply voltage determination part 16 becomes high, a Ton reference value Ton1 and an input current reference value Iin1 which are set by the reference value setting part 13 to be smaller. As a result, the induction heating cooker can gain an intended heating output in a simple configuration.

Description

  The present invention relates to an induction heating cooker such as a rice cooker configured so that a positional relationship between a pan and a heating coil for induction heating the pan is constant.

  Conventionally, in this type of induction heating cooker, the control unit includes an input current detection unit that measures an input current value of the inverter circuit, and is input when the input current value is a reference input current value Iin1 that is a setting target. A reference input detection output value m1 that is a value output by the current detection unit and a reference conduction time Ton1 that is a conduction time of a switching element set in advance to obtain a reference input current value Iin1 are stored. The time and the conduction time of the switching element are set to the reference conduction time Ton1, the operation is performed, and an error (m1−) between the input detection output value m2 that is a value output by the input current detection unit and the reference input detection output value m1 at that time. m2) is calculated and stored. Thereafter, the control unit monitors the input detection output value m of the input current detection unit, and performs control to set the conduction time of the switching element so as to be a value obtained by subtracting the error from the input detection output value m. (For example, refer to Patent Document 1).

  FIG. 3 shows a circuit block diagram of a conventional induction heating cooker described in Patent Document 1. As shown in FIG. As shown in FIG. 3, the pot 31, the DC power supply 33 having the diode bridge 33 a connected to the commercial power supply 34 and the smoothing capacitor 33 b connected to the output terminal of the diode bridge 33 a, and the pot 31 are induction-heated. The inverter circuit 38 includes the heating coil 32 and the control unit 46 that controls the inverter 38. The inverter circuit 38 includes a heating coil 32, a resonance capacitor 36 that forms a resonance circuit with the heating coil 32, a collector connected to the connection part of the resonance capacitor 36 and the heating coil 32, and an emitter connected to the negative terminal of the diode bridge 33. A conductive switching element 37 is provided.

  The control unit 46 includes a timer unit 39, a trigger unit 40, an input current detection unit 47 that detects an input current value of the inverter circuit 38, a Ton setting unit 42, a reference value setting unit 43, a calculation unit 44, and a correction unit 45.

  The timer unit 39 outputs a pulse having a width of the set time Ton, and makes the switching element 37 conductive for the set time Ton. The trigger unit 40 detects the voltage across the heating coil 32 and determines the start timing of the set time Ton output from the timer unit 39.

  When the heating operation is started, the control unit 50 performs the induction heating operation for a short time, for example, about 1 second. At that time, the reference value setting unit 43 outputs the Ton reference value Ton1 to the Ton setting unit 42 and simultaneously outputs the reference input detection output value m1 to the calculation unit 44. The Ton setting unit 42 performs the heating operation by setting the set time Ton to the Ton reference value Ton1, and at this time, an input current value Iin2 different from the reference input current value Iin1, for example, 12.5 A (input detection output value m2) is obtained. Suppose that

  The calculation unit 44 calculates an error Dm (= m1−m2) that is a value obtained by subtracting the input detection output value m2 that is the detection output of the input current detection unit 41 from the reference input detection output value m1. Next, the correction unit 45 outputs a value (m−Dm) obtained by subtracting the error Dm from the input detection output value m detected by the input current detection unit 41 to the Ton setting unit 12.

  Thereafter, the correction unit 15 controls the Ton setting unit 42 so that... Becomes a value (m−Dm) obtained by subtracting the error Dm from the input detection output value m detected by the input current detection unit 11. Make it. Thereby, the influence of various variations in heating power can be reduced.

JP 2012-245299 A

  However, in the conventional configuration, when a commercial power supply having a different voltage level is connected, a predetermined input current value or a predetermined heating power cannot be obtained, and a different reference value setting unit is provided for each commercial power supply to be used. There was a problem that had to be taken.

  The present invention solves the above-described conventional problems, and induction heating cooking that can be controlled so as to obtain a predetermined power supply current or a predetermined heating power with a simple configuration even when connected to commercial power supplies of different voltages. The purpose is to provide a vessel.

  In order to solve the above-mentioned conventional problems, the induction heating cooker of the present invention has a commercial power supply voltage determination unit in which the control unit determines the voltage of the commercial power supply, and the reference value setting unit has a commercial power supply voltage determination unit. When the detected voltage value is increased, the Ton reference value Ton1 and the input current reference value Iin1 set at the start of heating are changed to be small so that a predetermined heating power can be obtained with a simple configuration. is there.

  The induction cooking device of the present invention has a simple circuit configuration and can obtain a predetermined heating power even when connected to a commercial power supply having a different voltage.

The circuit block diagram of the induction heating cooking appliance in Embodiment 1 of this invention The figure which shows the collector current and gate voltage waveform of a switching element at the time of operation | movement of the induction heating cooking appliance Circuit block diagram of a conventional induction heating cooker

  1st invention forms the pan which heats cooking by putting a foodstuff, DC power supply which inputs a commercial power supply and outputs DC voltage, The heating coil which induction-heats the said pan, The said heating coil and a resonance circuit are formed A resonance capacitor and a switching element that generates resonance current in the resonance circuit that repeats conduction and interruption, and an inverter circuit that inputs a DC power source and generates high-frequency current in the heating coil; and controls conduction and interruption of the switching element A control unit that monitors the voltage generated in the heating coil after the switching element is shut off, and the timer unit A trigger unit that starts counting the set time Ton; an input current detection unit that detects an input current value Iin of the inverter circuit; A reference value setting unit that outputs an input current reference value Iin1 and a Ton reference value Ton1, and when the set time Ton is set to the Ton reference value Ton1 at the start of heating and is operated from the input current reference value Iin1 A calculation unit that calculates a correction value that is a value obtained by subtracting the input current value Iin detected by the input current detection unit; and the input current detected by the input current detection unit after the calculation unit calculates the correction value. A correction unit that outputs a value obtained by subtracting the correction value from the value Iin; and a Ton setting unit that sets the set time Ton so as to change the output value of the correction unit. The power supply voltage determination unit further determines a power supply voltage, and the reference value setting unit sets the reference value setting unit when the voltage value detected by the commercial power supply voltage determination unit is high. By changing the on reference value Ton1 and the input current reference value Iin1 to a small value, the reference value Ton1, which is the conduction time of the switching element set at the start of heating, is changed according to the commercial power source to be used. The difference between the reference value Iin1 that is the detection current of the input current detection unit and the current value Iin detected by the input current detection unit when the input current value is the input current value is measured. In addition, since the set time Ton can be corrected, variations in the obtained input current value 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 a block diagram of a rice cooker that is an induction heating cooker according to Embodiment 1 of the present invention, and FIG. 2 shows voltage / current waveforms applied to the switching element 7 during induction heating. . In FIG. 1, the induction heating cooker in Embodiment 1 of this invention is the pan 1 which puts a food and heat-cooks, the DC power supply 3 containing the diode bridge 3a and the smoothing capacitor 3b, the inverter circuit 8, And a control unit 20 that controls conduction and interruption of the switching element 7 of the inverter circuit 8. The inverter circuit 8 includes a heating coil 2 that induction-heats the pan 1, a resonance capacitor 6 that forms a resonance circuit with the heating coil 2, and a switching element 7 that repeats conduction and interruption to generate a resonance current in the resonance circuit.

  The control unit 20 includes a timer unit 9, a trigger unit 10, an input current detection unit 11, a Ton setting unit 12, a reference value setting unit 13, a calculation unit 14, and a correction unit 15.

  The timer unit 9 makes the switching element 7 conductive for the set time Ton. The trigger unit 10 monitors the voltage generated in the heating coil 2 after the switching element 7 is cut off, and causes the timer unit 9 to start measuring the set time Ton. The input current detector 11 detects the input current value Iin of the inverter circuit 8. The reference value setting unit 13 outputs an input current reference value Iin1 and a Ton reference value Ton1. The calculation unit 14 is a value obtained by subtracting the input current value Iin detected by the input current detection unit 11 from the input current reference value Iin1 when the set time Ton is set to the Ton reference value Ton1 at the start of heating. Calculate the correction value. After the calculation unit 14 calculates the correction value, the correction unit 15 outputs a value obtained by subtracting the correction value from the input current value Iin detected by the input current detection unit 11 to the Ton setting unit 12. The Ton setting unit 12 sets the set time Ton so that the value input from the correction unit 15 becomes the input current reference value Iin1.

  The control unit 20 further includes a commercial power supply voltage determination unit 16 that determines the voltage of the commercial power supply 4, and when the voltage value detected by the commercial power supply voltage determination unit 16 becomes high, the Ton reference value set by the reference value setting unit 13 Ton1 and input current reference value Iin1 are changed small.

  The operation and action of the induction heating cooker configured as described above will be described below.

  The heating coil 2 generates a high frequency magnetic field when a high frequency current flows, and the high frequency magnetic field induction heats the pan 1. The diode bridge 3a of the DC power supply 3 rectifies the AC current input from the commercial power supply 4 and supplies a unidirectional power supply to the smoothing capacitor 3b. The voltage across the smoothing capacitor 3 b of the DC power supply 3 is supplied to an inverter circuit 8 including a resonance capacitor 6 and a switching element 7. When the switching element 7 becomes conductive, the inverter circuit 8 flows into the heating coil 2 from the smoothing capacitor 3b, and when the current is flowing into the heating coil 2, the switching element 7 is cut off and resonates with the heating coil 2. High frequency current is generated in the heating coil 2 by the resonance of the capacitor 6.

  When the timer unit 9 stops outputting pulses to the gate of the switching element 7 and the switching element 7 is cut off, a resonance voltage is generated in the heating coil 2 as shown in FIG. When a resonance voltage is generated in the heating coil 2, the collector-emitter voltage Vce of the switching element 7 has a resonance voltage waveform as shown in FIG. The trigger unit 10 detects the collector-emitter voltage Vce (the voltage of the heating coil 2) of the switching element 7, and after the collector-emitter voltage Vce becomes zero, the reverse current flows through the switching element 7. In addition, the timer unit 9 turns on the switching element 7 and starts measuring the set time Ton. The trigger unit 10 significantly reduces loss during switching of the switching element 7 by turning on the switching element 7 while the collector-emitter voltage Vce is substantially zero.

  Further, when the set time Ton is increased, the heating output is increased, and when the set time Ton is decreased, the heating output is decreased. Therefore, the heating output can be controlled by changing the set time Ton. Moreover, since the input current detection part 11 which detects an input current value is provided, the heating output which heats the pan 1 is controlled by changing the setting time Ton and controlling the input current value to be a predetermined current value. can do.

  When the input current value is larger than a predetermined current value based on the output from the correction unit 15 that corrects the output of the input current detection unit 11, the Ton setting unit 12 decreases the input current value by decreasing Ton. On the contrary, when the input current value is smaller than the predetermined current value, the control is performed so as to obtain a target input current value having a predetermined magnitude by increasing Ton and increasing the input current value.

  When the heating operation is started, the control unit 20 performs induction heating for a short time, for example, about 1 second. At that time, the reference value setting unit 13 outputs to the Ton setting unit 12 a reference value Ton1 corresponding to the input current value to be set. The Ton setting unit 12 sets the set time Ton to the Ton reference value Ton1 to perform control, and outputs the reference current value Iin1 to the calculation unit 14.

  The Ton reference value Ton1 is set so that the input current value Iin detected by the input current detector 11 becomes the reference current value Iin1 when the timer unit 9 outputs the Ton reference value Ton1. However, in a mass-produced product, the detection current value of the input current detection unit 11 deviates from Iin1 due to constant variations of the circuit components of the inverter circuit 8 or the control unit 20 and machine variations such as the distance between the pan 1 and the heating coil 2. There is a case. The calculation unit 14 calculates a correction value DIin = Iin1-Iin, which is a value obtained by subtracting the input current value Iin detected by the input current detection unit 11 from the reference current value Iin1.

  In the subsequent heating control, the Ton setting unit 12 changes the output of the correction unit 15, that is, the value obtained by subtracting the correction value DIin from the input current value Iin detected by the input current detection unit 11 (Iin−DIin). The Ton setting unit 12 performs control. This reduces the influence of various variations that affect the correlation between the input current value (heating power) and the Ton reference value Ton1.

  In addition, the commercial power supply voltage determination unit 16 determines the voltage of the commercial power supply 4 before setting the set time Ton to the Ton reference value Ton1 and performing the heating operation in order to calculate the correction value DIin. Based on the determination result of the commercial power supply voltage determination unit 16, the reference value setting unit 13 selects the reference values Ton1 and Iin1 as optimum values from a plurality of different reference values provided for each commercial power supply voltage. When the voltage value detected by the commercial power supply voltage determination unit 16 increases, the reference value setting unit 13 changes the Ton reference value Ton1 and the input current reference value Iin1 set by the reference value setting unit 13 to be small.

  When operating at the same set time Ton, the input current value and the heating output increase when connected to a second commercial power source having a voltage higher than that of the first commercial power source. Since the value Ton1 and the input current reference value Iin1 are changed smaller than when connected to the first commercial power supply, the same input power can be obtained even if the power supply voltage is changed. Thus, for example, even when operated using a plurality of commercial power sources having different voltages, such as a 100 V household power source in Japan and a 120 V household power source in the United States, a predetermined heating power can be obtained with a simple circuit configuration. be able to.

  The present invention can be controlled with a simple circuit configuration so that predetermined heating power can be obtained even when connected to a plurality of different commercial power sources, and in addition to the rice cooker, the positional relationship between the pan and the heating coil is fixed. It can also be applied to induction heating cookers.

DESCRIPTION OF SYMBOLS 1 Pan 2 Heating coil 3 DC power supply 3a Diode bridge 3b Smoothing capacitor 4 Commercial power supply 6 Resonance capacitor 7 Switching element 8 Inverter circuit 9 Timer part 10 Trigger part 11 Input current detection part 12 Ton setting part 13 Reference value setting part 14 Calculation part 15 Correction unit 16 Commercial power supply voltage determination unit 20 Control unit

Claims (1)

DC power supply that inputs commercial power and outputs DC voltage;
A pan for cooking and cooking,
A heating coil for inductively heating the pan, a resonance capacitor that forms a resonance circuit with the heating coil, and a switching element that generates a resonance current in the resonance circuit by repeatedly conducting and interrupting, and the DC power supply is input to the heating coil An inverter circuit that generates a high-frequency current;
A control unit for controlling conduction and interruption of the switching element,
The control unit is a timer unit for conducting the switching element for a set time Ton;
A trigger unit for monitoring a voltage generated in the heating coil after the switching element is cut off, and for causing the timer unit to start counting the set time Ton;
An input current detector for detecting an input current value Iin of the inverter circuit;
A reference value setting unit that outputs an input current reference value Iin1 and a Ton reference value Ton1,
Correction that is a value obtained by subtracting the input current value Iin detected by the input current detection unit from the input current reference value Iin1 when the set time Ton is set to the Ton reference value Ton1 at the start of heating. A calculation unit for calculating a value;
A correction unit that outputs a value obtained by subtracting the correction value from the input current value Iin detected by the input current detection unit after the calculation unit calculates the correction value;
A Ton setting unit that sets the set time Ton so as to change the output value of the correction unit,
The control unit further includes a commercial power supply voltage determination unit that determines a voltage of the commercial power supply,
The reference value setting unit is configured to change the Ton reference value Ton1 and the input current reference value Iin1 set by the reference value setting unit to be small when the voltage value detected by the commercial power supply voltage determination unit is high. Induction heating cooker.

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