JP2696278B2 - Induction heating cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker such as an induction heating type electronic jar rice cooker.

[0002]

2. Description of the Related Art An induction heating cooker such as an electronic jar rice cooker of an induction heating system controls output power in accordance with a change in power supply voltage. It is for the following reasons.

If output power is not controlled in response to a change in power supply voltage, if the power supply voltage increases, the voltage between the collector and the emitter of the switching element increases, exceeding the maximum voltage rating of the switching element. The element may be destroyed. Conversely, when the power supply voltage decreases, a large amount of current flows in order to output the same power as that at the time of the rated voltage, and the heat generation of components such as switching elements and filters increases. You need to raise it or cool it down. For this purpose, it is necessary to determine an output power control curve according to the power supply voltage that is optimal for the product.

Conventionally, an output power control device of this type of induction heating type electronic jar rice cooker generally has a configuration as shown in FIG. Hereinafter, the configuration will be described with reference to FIGS.

As shown in FIG. 4, in the conventional example, a rectifier circuit 2 for converting AC supplied from an AC power supply 1 to DC,
Filter 3 for removing AC components from the output of rectifier circuit 2
A heating coil 5 connected to the filter 3 for generating a high-frequency magnetic field to heat the pan 4; a resonance capacitor 7 forming a resonance circuit 6 together with the heating coil 5; A switching element 8 for generating the switching element, a control means 9 for controlling the switching element 8 to be turned on and off and controlling the output power by changing the length of the on time, and a voltage between the collector and the emitter of the switching element 8 of about 5 V. Vce peak hold means 11 for converting to a voltage level which is easy to handle and holding the peak value;
Vce voltage measuring means 16 for measuring the output voltage, current detecting means 15 connected between the AC power supply 1 and the rectifier circuit 2 and comprising a current transformer for outputting a voltage proportional to the flowing current, and holding the output voltage Iin peak hold means 17 and Iin voltage measurement means 18 for measuring its output voltage
And each of the measurement results of the Vce voltage measuring means 16 and the Iin voltage measuring means 18 is compared with each of the internal reference voltages so that one of the reference voltages does not exceed the other. And a microprocessor means 10 for controlling the switching element 8 by the control means 9 and controlling the output power according to the power supply voltage.

FIG. 5 shows a change in output power when the power supply voltage changes. In this figure, when the output power is 100 V or less, the emitter is applied by the current Iin flowing through the circuit, and
At 0 V or more, a limiter is applied by the voltage Vce between the collector and the emitter of the switching element 8, so that the output power changes.

[0007]

However, in such a conventional configuration, the Vce peak hold means 11 and Iin
Since the control means 9 adjusts the output power according to the magnitude of the output voltage of the peak hold means 17, it is necessary to use a current transformer having a large current capacity for the current detection means 15, and thus the cost is high. And the shape becomes big,
There is also a problem that the printed circuit board becomes large. In addition, adjustment is required to accurately detect the flowing current,
There was also a problem that the cost was high.

Accordingly, the present invention is to solve such a problem of the conventional configuration, and to provide a small and low-cost output power control device without using a current transformer. It is an object of the present invention to provide an induction heating cooker provided.

[0009]

To achieve the above object, an induction heating cooker according to the present invention comprises a rectifier circuit for converting an alternating current supplied from an alternating current power supply into a direct current, and an AC component from the output of the rectifier circuit. A filter to be removed, a heating coil connected to the filter to generate a high-frequency magnetic field to heat the pan, a resonance capacitor forming a resonance circuit together with the heating coil, and a resonance coil connected to the resonance circuit to generate a resonance current. A switching element, control means for controlling on / off of the switching element, Vce peak hold means for converting a voltage between a collector and an emitter of the switching element and holding a peak value thereof, and a power supply voltage for measuring a voltage of an AC power supply A measuring means and a measuring reference converting means for outputting a reference voltage based on the measurement result of the power supply voltage; Comparing the output voltage of the field unit,
Determining means for outputting the result, wherein the control means controls the switching element based on the determination result of the determining means so that the output voltage of the Vce peak hold means converges on the reference voltage of the determination reference conversion means. The configuration is such that:

[0010]

According to the above construction, when the control means starts the on / off control of the switching element, a resonance current flows through the resonance circuit, and a high voltage is generated between the collector and the emitter of the switching element. The level is converted by the means, and the peak value is held. on the other hand,
The criterion conversion means outputs a reference voltage corresponding to the power supply voltage according to the voltage measured by the level conversion by the power supply voltage measurement means. Therefore, the voltage held by the Vce peak hold means acts to control the switching element by the control means so as to converge on the reference voltage while being compared with the reference voltage.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments will be described below in detail with reference to the drawings. FIG. 1 shows a circuit configuration of an electronic jar rice cooker using an induction heating method according to an embodiment of the present invention. The rectifier circuit 2 includes a diode for rectifying AC supplied from an AC power supply 1 and a rectifier. A filter 3 for removing an AC component from the output of the circuit 2, a heating coil 5 connected to the filter 3 for generating a high-frequency magnetic field and inductively heating the pan 4;
A resonance capacitor 7 which forms a resonance circuit 6 together with the heating coil 5, a switching element 8 connected to the resonance circuit 6 for generating a resonance current in the resonance circuit 6, and an on / off control of the switching element 8 A microprocessor means 10 having a control means 9 for generating an oscillating current in the resonance circuit 6; Vce peak hold means 11 for converting and holding the peak value of the voltage
And a power supply voltage measuring means 12 connected to the output of the rectifier circuit 2 and comprising an AD converter or the like for measuring a power supply voltage, and a judgment reference conversion built in a microprocessor means 10 for outputting a reference voltage in accordance with the measured voltage. The determination means 14 compares the voltage held by the Vce peak hold means 11 with the reference voltage determined by the determination reference conversion means 13 and outputs the result.

Next, the operation of this embodiment will be described. AC10
AC supplied from a commercial AC power supply 1 of 0 V is converted into DC by a rectifier circuit 2 and a filter 3 and supplied to a heating coil 5. When the control means 9 turns on the switching element 8, a resonance current flows through the heating coil 5, and when the switching element 8 is off, the collector of the switching element 8
A high voltage is generated between the emitters. This voltage is converted to a voltage of about 5 V which is easily handled by the Vce peak hold means 11, and the peak value is held. On the other hand, the output voltage of the rectifier circuit 2 is measured by the power supply voltage measuring means 12, and the criterion converting means 13 in the microprocessor means 10 determines the reference voltage of the deciding means 14 according to the measurement result.

FIG. 2 shows a criterion conversion table created in the memory of the microprocessor means 10, which is one of the criterion conversion means. That is, the reference voltage is determined based on the result measured by the power supply voltage measuring means 12. For example, if the value measured by the power supply voltage measuring means 12 is 3.188 V, the power supply voltage is between 96 V and 98 V.
At this time, the reference voltage of the judging means is set in the judgment reference conversion table.
3.43V. While comparing this reference voltage with the voltage held by the Vce peak hold means 11, the output voltage of the Vce peak hold means 11 converges to the reference voltage.
The control means 9 controls the on time of the switching element 8. As a result, an output voltage control curve obtained when the control is performed based on the determination reference conversion table is as shown in FIG.

That is, it is possible to freely control the output power simply by converting the reference voltage in accordance with the power supply voltage using the determination reference conversion table.

The output power control curve can be easily changed only by changing the data in the criterion conversion table.

Although the resolution of the power supply voltage is 2 V, the control curve of the output power can be changed from a step shape to a straight shape by reducing the resolution.

Here, a description has been given using a criterion conversion table as the criterion conversion means. Instead of this criterion conversion table, a relational expression between the criterion and the power supply voltage is created, and based on the calculation results. Alternatively, a reference voltage for determination may be determined.

As described above, according to the present embodiment, the output power can be controlled only by changing the reference voltage without using a current transformer, and no adjustment, cost reduction, and printed circuit board Can be made smaller.

[0019]

As described above, according to the present invention, a rectifier circuit for converting AC supplied from an AC power supply to DC, a filter for removing an AC component from an output of the rectifier circuit, and a filter connected to the filter, A heating coil that generates a high-frequency magnetic field to heat the pan, a resonance capacitor that forms a resonance circuit together with the heating coil, a switching element that is connected to the resonance circuit, and that generates a resonance current; Control means, a Vce peak hold means for converting the voltage between the collector and the emitter of the switching element to hold the peak value, a power supply voltage measuring means for measuring the voltage of the AC power supply, and a power supply voltage measurement result. And a reference voltage conversion means for outputting a reference voltage, and comparing the reference voltage with the output voltage of the Vce peak hold means. And a judging means for outputting a result,
The control means controls Vce based on the determination result of the determination means.
Since the switching element is controlled so that the output voltage of the peak hold means converges with the reference voltage of the judgment reference conversion means, the output power can be easily controlled according to the power supply voltage, and the current Since no transformer is used, downsizing, no adjustment, and cost reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an electronic jar rice cooker using an induction heating method according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a criterion conversion table in the embodiment.

FIG. 3 is a diagram illustrating an output power control curve with respect to a change in power supply voltage when control is performed based on the conversion table of FIG. 2;

FIG. 4 is a circuit configuration diagram of a conventional example.

FIG. 5 is a diagram showing an output power control curve of a conventional example.

[Explanation of symbols]

1: AC power supply, 2: Rectifier circuit, 3: Filter, 4:
Pan, 5 heating coil, 6 resonance circuit, 7 resonance capacitor, 8 switching element, 9 control means,
10: microprocessor means, 11: Vce peak hold means, 12: power supply voltage measurement means, 13: judgment reference conversion means, 14: judgment means.

Claims (1)

(57) [Claims] 1. A rectifier circuit for converting AC supplied from an AC power supply to DC, a filter for removing an AC component from an output of the rectifier circuit, and a heating device connected to the filter for generating a high-frequency magnetic field to heat the pan. A coil, a resonance capacitor forming a resonance circuit together with the heating coil, a switching element connected to the resonance circuit for generating a resonance current, control means for controlling on / off of the switching element, and a collector-emitter of the switching element Vce peak hold means for converting the voltage between the two, and holding the peak value, power supply voltage measurement means for measuring the voltage of the AC power supply, and measurement reference conversion means for outputting a reference voltage based on the power supply voltage measurement result. Determining means for comparing the reference voltage with the output voltage of the Vce peak hold means and outputting the result. Wherein the control means controls the switching element based on the determination result of the determination means such that the output voltage of the Vce peak hold means converges on the reference voltage of the determination reference conversion means. Cooking cooker.