JPH04371109A - Induction heating cooking appliance - Google Patents

Abstract

PURPOSE:To provide an induction heating cooking appliance which dispenses with a current transformer, and can freely control output electric power according to power source voltage, and is inexpensive and small-sized. CONSTITUTION:An alternating current in a power source is converted into a direct current through a rectifying circuit 2, and the on-off control of a switching element 8 is carried out through a control means 9 to apply a resonance current to a heating coil 5, which generates a high-frequency magnetic field to heat a pan 4. In this case, a Vce peak-hold means 11 level-converts voltage occurring between the collector and emitter of the switching element 8 to hold a peak value. On the other hand, a power source voltage measuring means 12 measures power source voltage, and a criterion converting means 13 gives reference voltage according to the level-converted voltage. A judging means 14 compares peak-hold voltage with the reference voltage, and the control means 9 controls the switching element 8 so that the peak-hold voltage may converge to the reference voltage on the result of the above judgment.

Description

[Detailed description of the invention]

0001

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

0002

2. Description of the Related Art Induction heating cooking devices such as electronic jar rice cookers using induction heating control output power in accordance with changes in power supply voltage. This is due to the following reason.

If the output power is not controlled according to changes in the power supply voltage, as the power supply voltage increases, the voltage between the collector and emitter of the switching element will increase, exceeding the maximum voltage rating of the switching element, and the switching There is a risk that the element may be destroyed. Conversely, when the power supply voltage decreases, more current flows to try to output the same power as at the rated voltage, causing higher heat generation in parts such as switching elements and filters, and lowering the heat resistance grade of the parts. You will need to raise the temperature or improve cooling. Therefore, it is necessary to determine the output power control curve according to the power supply voltage that is optimal for the product.

[0004] Conventionally, an output power control device for this type of induction heating electronic jar rice cooker has generally had a configuration as shown in FIG. The configuration will be described below with reference to FIGS. 4 and 5.

As shown in FIG. 4, the conventional example includes a rectifier circuit 2 that converts alternating current supplied from an alternating current power source 1 into direct current;
A filter 3 that removes alternating current components from the output of the rectifier circuit 2, a heating coil 5 that is connected to the filter 3 and generates a high-frequency magnetic field to heat the pot 4, and a resonant capacitor 7 that forms a resonant circuit 6 together with the heating coil 5. and the resonant circuit 6
a switching element 8 connected to the switching element 8 for generating a resonant current; a control means 9 for controlling the switching element 8 on and off and controlling the output power by changing the length of on-time; Vce peak hold means 11 for converting the voltage into an easily handled voltage level of about 5V and holding the peak value;
A Vce voltage measuring means 16 that measures the output voltage, a current detecting means 15 connected between the AC power supply 1 and the rectifier circuit 2, and consisting of a current transformer or the like that outputs a voltage proportional to the flowing current, and holding the output voltage. The measurement results of the Iin peak hold means 17 that measures the output voltage, the Iin voltage measurement means 18 that measures the output voltage, the Vce voltage measurement means 16, and the Iin voltage measurement means 18 are compared with each internal reference voltage, and one of the microprocessor means 10 for controlling the switching element 8 by the control means 9 so as to converge to the other reference voltage within a range that does not exceed the reference voltage of the other reference voltage, and controlling the output power according to the power supply voltage; It consists of

FIG. 5 shows the change in output power when the power supply voltage changes. In this figure, when the power supply voltage is below 100V, the emitter is applied by the current Iin flowing through the circuit, and when it is above 100V, the emitter of the switching element 8 is applied. A limiter is applied by the collector-emitter voltage Vce, and the output power changes.

[0007]

However, in such a conventional configuration, the Vce peak hold means 11 and the I
Since the control means 9 adjusts the output power depending on the magnitude of the output voltage of the in-peak hold means 17, it is necessary to use a current transformer with a large current capacity for the current detection means 15, which increases the cost. , and the shape becomes larger, and the printed circuit board also becomes larger. Furthermore, there is a problem in that adjustment is required to accurately detect the flowing current, which increases the cost.

Therefore, the present invention aims to solve the problems of the conventional configuration, and provides a small, low-cost output power control device without using a current transformer. An object of the present invention is to provide an induction heating cooker equipped with the following.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the induction heating cooker of the present invention includes a rectifier circuit that converts alternating current supplied from an alternating current power source into direct current, and an alternating current component from the output of the rectifier circuit. a heating coil connected to the filter for generating a high-frequency magnetic field to heat the pot; a resonant capacitor forming a resonant circuit together with the heating coil; and a resonant capacitor connected to the resonant circuit for generating a resonant current. A switching element, a control means for controlling on/off of the switching element, and a collector of the switching element.
Vce peak hold means for level converting the voltage between the emitters and holding the peak value; power supply voltage measuring 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. , determination means for comparing the reference voltage and the output voltage of the Vce peak hold means and outputting the result, and the control means:
Based on the determination result of the determination means, the switching element is controlled so that the output voltage of the Vce peak hold means converges to the reference voltage of the determination reference conversion means.

0010

[Operation] According to the above structure, when the control means starts on/off control of the switching element, a resonant current flows through the resonant circuit, a high voltage is generated between the collector and emitter of the switching element, and the voltage is held at the Vce peak hold. The level is converted by means and the peak value is maintained. on the other hand,
According to the voltage level-converted and measured by the power supply voltage measurement means, the determination reference conversion means outputs a reference voltage corresponding to the power supply voltage. Therefore, while the voltage held by the Vce peak hold means is compared with the reference voltage, the control means controls the switching elements so as to converge to the reference voltage.

[0011]

Embodiments Hereinafter, embodiments will be described in detail with reference to the drawings. FIG. 1 shows the circuit configuration of an electronic jar rice cooker using an induction heating method according to an embodiment of the present invention. a filter 3 that removes alternating current components from the output of the circuit 2; a heating coil 5 that is connected to the filter 3 and generates a high-frequency magnetic field to inductively heat the pot 4;
A resonant capacitor 7 constituting a resonant circuit 6 together with the heating coil 5, a switching element 8 connected to the resonant circuit 6 and for generating a resonant current in the resonant circuit 6, and a switching element 8 which is controlled to turn on and off. A microprocessor means 10 having a control means 9 for generating an oscillating current in the resonant circuit 6 and a voltage between the collector and emitter of the switching element 8, which generates a voltage of several hundred V, are reduced to an easy-to-handle voltage level of 5 V or less. Vce peak hold means 1 for converting and holding the peak value of the voltage
1, 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 the power supply voltage;
a determination reference conversion means 13 built in the microprocessor means 10 that outputs a reference voltage according to the measured voltage;
It is comprised of a determination means 14 that compares the voltage held by the ce peak hold means 11 and a reference voltage determined by the determination reference conversion means 13 and outputs the result.

Next, the operation of this embodiment will be explained. AC1
AC supplied from a 00V commercial AC power supply 1 is converted into DC by a rectifier circuit 2 and a filter 3, and is supplied to a heating coil 5. When the control means 9 turns on the switching element 8, a resonant current flows through the heating coil 5, and when the switching element 8 is turned off, a high voltage is generated between the collector and emitter of the switching element 8. This voltage is Vce
The peak hold means 11 converts the voltage into a voltage of about 5V, which is easy to handle, and holds the peak value. On the other hand, rectifier circuit 2
The power supply voltage measuring means 12 measures the output voltage of the determination means 14, and the determination reference conversion means 13 in the microprocessor means 10 determines the reference voltage of the determination means 14 according to the measurement result.

FIG. 2 is a judgment criterion conversion table created in the memory of the microprocessor means 10, which is one of the judgment 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 3.188V, the power supply voltage is between 96V and 98V. The reference voltage of the determination means at this time is 3.43V in the determination reference conversion table. While comparing this reference voltage with the voltage held by the Vce peak hold means 11, the control means 9 controls the on-time of the switching element 8 so that the output voltage of the Vce peak hold means 11 converges to the reference voltage. As a result, the output voltage control curve when controlled based on the criterion conversion table is as shown in FIG. 3.

That is, the output power can be freely controlled by simply converting the reference voltage using the determination reference conversion table in accordance with the power supply voltage.

[0015] The output power control curve can be easily changed by simply changing the data in the criterion conversion table.

The resolution of this power supply voltage is 2V, but by reducing this resolution, the control curve of the output power can be changed from a stepwise shape to a linear shape.

[0017] Here, the explanation has been made using a judgment standard conversion table as the judgment standard conversion means, but instead of this judgment standard conversion table, a relational expression between the judgment standard and the power supply voltage is created, and based on the calculation result, , a reference voltage for determination may be determined.

As described above, according to this embodiment, the output power can be controlled simply by changing the voltage of the criterion without using a current transformer, eliminating the need for adjustment, reducing costs, and reducing the cost of printed circuit boards. It is also possible to make the shape smaller.

[0019]

As described above, according to the present invention, there is provided a rectifier circuit that converts alternating current supplied from an alternating current power supply into direct current, a filter that removes alternating current components from the 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 pot, a resonant capacitor that forms a resonant circuit together with the heating coil, a switching element that is connected to the resonant circuit and generates a resonant current, and an on/off control for this switching element. a control means for level-converting the voltage between the collector and emitter of the switching element and holding the peak value thereof; a power supply voltage measuring means for measuring the voltage of the AC power supply; and a determination means for comparing the reference voltage and the output voltage of the Vce peak hold means and outputting the result,
The control means is configured to control 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 to the reference voltage of the judgment reference conversion means, it is possible to easily control the output power according to the power supply voltage, and the current Since no transformer is used, miniaturization, no adjustment, and cost reduction can be achieved.

[Brief explanation of drawings]

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

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

FIG. 3 is a diagram showing an output power control curve with respect to changes 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 a conventional output power control curve.

[Explanation of symbols]

1...AC power supply, 2...rectifier circuit, 3...filter,
4... Pot, 5... Heating coil, 6... Resonance circuit, 7...
Resonant capacitor, 8... Switching element, 9...
Control means, 10...Microprocessor means, 1
1... Vce peak hold means, 12... Power supply voltage measuring means, 13... Judgment reference conversion means, 14... Judgment means.

Claims (1)

[Claims] Claim 1: A rectifier circuit that converts alternating current supplied from an alternating current power source into direct current, a filter that removes alternating current components from the output of the rectifier circuit, and a heating device connected to the filter that generates a high-frequency magnetic field to heat a pot. a coil, a resonant capacitor forming a resonant circuit together with the heating coil, a switching element connected to the resonant circuit for generating a resonant current, a control means for controlling on/off the switching element, and a collector-emitter of the switching element. Vce peak hold means for converting the level of the voltage between and holding the peak value; power supply voltage measuring means for measuring the voltage of the AC power supply; and measurement standard converting means for outputting a reference voltage based on the power supply voltage measurement result. , determination means for comparing the reference voltage and the output voltage of the Vce peak hold means and outputting the result, and the control means determines the output voltage of the Vce peak hold means based on the determination result of the determination means. 1. An induction heating cooker characterized in that the switching element is controlled so that the voltage is converged to the reference voltage of the determination reference conversion means.