JPH04370692A - Deep pan material sensing device for induction heating cooking apparatus - Google Patents

Abstract

PURPOSE:To construct a non-adjust type deep pan sensing deice for an induction heating cooking apparatus at a low cost and in small size, and therewith sense which sort of material the deep pan is made of without use of any current transformer. CONSTITUTION:AC current from commercial power supply is converted into DC current by a rectifier circuit 2, and resonant current is allowed to flow through a heater coil 5 through on/off control of a switching element 8 made by a control means 9, and a deep pan 4 is heated with a high frequency magnetic field generated by this heater coil 5. In the On time of switching element 8 determined previously, the output voltage of a Vce peak hold circuit 10 differs greatly depending upon which sort of material the pan 4 is made from. When peak appears in the supply voltage which is sensed by a power supply peak sensing means 12, comparison is made with the reference voltage generated by a reference voltage generating means 11, and a judging means 13 judges the material of the pan 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting the material of a pot heated by, for example, an induction heating electronic jar rice cooker or an induction heating cooker.

0002

2. Description of the Related Art The material of a pot for a cooker employing an induction heating method is normally required to be iron-based. When an irregular pot made of aluminum or other material is placed on top of a heating coil and the pot is heated by the high-frequency magnetic field generated by the heating coil, a higher voltage is generated than when using an iron pot, causing the switching element to There is a risk that it may be destroyed. Therefore, it is necessary to detect the material of the pot before starting heating, and to stop heating if the detection result indicates that an unauthorized pot is being used.

Conventionally, a pot material detection device for this type of induction heating electronic jar rice cooker has a configuration as shown in FIG. 12. The conventional example will be explained below.

As shown in FIG. 12, this conventional example includes a rectifier circuit 2 that rectifies and converts AC from a commercial AC power source 1 into DC, and a filter 3 that removes AC components from the output of the rectifier circuit 2.
A heating coil 5 is connected to the filter 3 and heats the pot 4 by generating a high-frequency magnetic field; a resonant capacitor 7 is connected to the resonant circuit 6 and forms a resonant circuit 6 together with the heating coil 5; A switching element 8 for generating current, a control means 9 for controlling the switching element 8 on and off and controlling applied power by changing the on time, and a voltage between the collector and emitter of the switching element 8 of about 5V. A current detection means consisting of a Vce peak hold circuit 10 that converts the voltage level to an easily handled voltage level and holds the peak value, and a current transformer connected between the AC power supply 1 and the rectifier circuit 2 and outputting a voltage proportional to the flowing current. 16, and a determining means 13 comprising an AD converter or the like that determines the material of the pot based on the output voltages of the Vce peak hold circuit 10 and the current detecting means 16.

In the above configuration, when heating the pot 4 is started by passing a resonant current through the heating coil 5, Vce
Output voltages are generated in the peak hold circuit 10 and the current detection means 16, respectively. At this time, each output voltage value varies greatly depending on the material of the pot 4. Based on the relationship between the output voltages, the determining means 13 determines the difference between the materials of the pan, especially the materials of aluminum and iron.

[0006]

[Problems to be Solved by the Invention] In such a conventional pot material detection device, the determination means 13 detects the pot material based on the relationship between the output voltages of the Vce peak hold circuit 10 and the current detection means 16. Therefore, it is necessary to use a current transformer with a large current capacity as the current detecting means 16, which results in problems such as high cost, large size, and large printed circuit board. There is also the problem that adjustment is required to accurately detect the flowing current, which increases cost.

[0007] Therefore, the present invention aims to solve the problems that such conventional configurations had.
The primary purpose of this invention is to provide a small, low-cost pot material detection device for an induction heating cooker without using a current transformer.

In addition to the first object, a second object is to provide a pot material detection device for an induction heating cooker that reduces errors in determining the pot material due to voltage fluctuations of an AC power source.

A third object of the present invention is to provide a means for realizing the second object with a simpler structure.

[0010] A fourth object is to realize the second object by other means.

Furthermore, a fifth object is to realize the first to fourth objects by simpler means.

0012

[Means for Solving the Problems] A first pot material detection device of the present invention for achieving the first object includes a rectifier circuit that rectifies alternating current of an alternating current power source and converts it into direct current; A heating coil that is connected to generate 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 that generates a resonant current, and a switching element that turns the switching element on and off. a control means that outputs a predetermined power at a predetermined applied voltage; a Vce peak hold circuit that converts the level of the voltage between the collector and emitter of the switching element and holds the peak value; and a pot material. a reference voltage generating means for generating a reference voltage that is a criterion for the determination of the voltage, a power supply peak detecting means for detecting the peak timing of the AC power supply and outputting a detection pulse, and a predetermined on-time for on/off control of the switching element. The output voltage of the Vce peak hold circuit is controlled to be a certain period of time, and when the peak detection pulse of the power supply peak detection means is generated, the output voltage of the Vce peak hold circuit is compared with the reference voltage of the reference voltage generation means. The apparatus is configured to include a determining means for determining the material of the pot to be heated.

[0013] In order to achieve the second object, the second pot material detection device of the present invention converts the output voltage of the rectifier circuit into a level instead of the reference voltage generating means of the first pot material detection device. , and a power level converting means for maintaining the peak value thereof.

A third pot material detection device of the present invention for achieving the third object eliminates the power peak detection means of the second pot material detection device, and has a power level control system constructed of an integrating circuit. The configuration is such that the integration time constant of the conversion means and the integration time constant of the Vce peak hold circuit are the same.

[0015] A fourth pot material detection device of the present invention for achieving the fourth object has the same configuration as the first pot material detection device, and further includes power supply voltage measuring means for measuring the voltage of an AC power source. , the control means controls the switching element to have a predetermined constant on time according to the voltage measured by the power supply voltage measuring means, and a Vce peak hold circuit when a detection pulse of the power supply peak detection means is generated. By comparing the output voltage of the with the reference voltage of the reference voltage generating means,
The structure is such that the material of the pot placed on the heating coil and heated is determined.

A fifth pot material detection device of the present invention for achieving the fifth object eliminates the power peak detection means of the first pot material detection device and has a predetermined on-time. When the control means controls the switching element, the output voltage of the Vce peak hold circuit is compared with the reference voltage of the reference voltage generation means, and the determination means outputs the result to the interrupt terminal of the control circuit. The heating stop control is performed only when an abnormality is detected in the pot material placed on the coil and being heated.

[0017]

[Operation] The first pot material detection device of the present invention operates as follows. When the control means starts on/off control of the switching element to detect the pot, a resonant current flows through the resonant circuit, and a high voltage is generated between the collector and emitter of the switching element. When the control means controls the ON time of the switching element to a certain predetermined time, this generated voltage will differ depending on the material of the pot, and will be higher if the material is aluminum than if it is iron. become. By comparing this generated voltage with a predetermined reference voltage,
A determining means determines the material of the pot.

In the second pan material detection device of the present invention, the voltage generated between the collector and the emitter of the switching element is proportional to the output voltage of the AC power source, but it is possible to misjudge the material of the pan due to a change in the voltage of the AC power source. In order to reduce
As a criterion, the output voltage of the AC power supply is level-converted,
In addition, by using the output of the power level converter that changes in proportion to the power supply voltage, the voltage generated between the collector and emitter of the switching element and the reference voltage for judgment change in proportion to the power supply voltage. , which acts so that the determination result of the pot material is independent of the power source.

The third pot material detection device of the present invention operates as follows. By making the integration time constant of the power supply level conversion means composed of an integrating circuit and the integration time constant of the Vce peak hold circuit the same, each output voltage value of the power supply level conversion means and the Vce peak hold circuit can be changed whenever necessary. The material of the pot can be determined by comparing the

In the fourth pot material detection device of the present invention, the voltage generated between the collector and emitter of the switching element is proportional to the output voltage of the AC power source, but the misjudgment of the pot material may occur due to changes in the voltage of the AC power source. In order to reduce
The power supply voltage is measured by the power supply voltage measurement means, and the control means controls the switching element so that the ON time is a predetermined one according to the measurement result, and each output voltage of the Vce peak hold circuit and the reference voltage generation means is adjusted. Since the comparison is made, the result of determining the pot material is independent of the power source.

In the fifth pan material detection device of the present invention, by inputting the determination result of the material of the pan to the interrupt terminal of the control means, the determination result of the determination means notifies the control means when the pan is not the specified pan. It works like this.

[0022]

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, which is a first embodiment of the present invention. The first embodiment includes a rectifier circuit 2 consisting of a diode or the like that rectifies an alternating current supplied from an alternating current power source 1, a filter 3 that removes an alternating current component from the output of the rectifying circuit 2, and a filter connected to the filter 3, A heating coil 5 that heats the pot 4 by generating an eddy current, a resonant capacitor 7 that forms a resonant circuit 6 together with the heating coil 5, and a resonant capacitor 7 that is connected to the resonant circuit 6 and generates a resonant current in the resonant circuit 6. switching element 8 for
A control means 9 generates an oscillating current in the resonant circuit 6 by on/off control, and sets the output power to a predetermined output power of 1200 W at a predetermined applied voltage of 100 V AC, and a voltage of several hundred V. There is a Vce peak hold circuit 10 that level-converts the voltage between the collector and emitter of the switching element 8 where the voltage is generated to an easily handled voltage of 5V or less and holds the peak value of the voltage, and an on-time of the switching element 8. Generates a reference voltage set in advance so that at a certain time, the voltage is higher than the output voltage of the Vce peak hold circuit 10 when the pot is made of iron, which is a regular pot material, and lower than when it is made of aluminum, which is an irregular pot material. a reference voltage generating means 11 that detects the peak timing of the AC power supply 1 and outputs a detection pulse; and a power supply peak detection means 12 that detects the peak timing of the AC power supply 1 and outputs a detection pulse; The material of the pot is determined by comparing each output of the generating means 11,
The judgment means 13 outputs the result to the control means 9.

Next, the operation of this embodiment will be explained. AC1
AC from a commercial AC power supply 1 of 00V is converted into DC by a rectifier circuit 2 and a filter 3, and is supplied to a heating coil 4. Detection of the pot material is normally performed before starting rice cooking and when setting the rice cooking reservation timer. The pot material of induction heating electronic jar rice cookers is usually iron-based, and the heating coil 5
This is because, if heated, a higher voltage than in the case of an iron-based pot will be generated between the collector and emitter of the switching element 8, which may destroy the switching element 8 and the like. Therefore, it is necessary to detect the material of the pot before starting heating, and to stop heating if the pot is an irregular one.

The material of the pot is detected as follows. First, when the control means 9 starts on/off control of the switching element 8, a resonant current starts to flow through the heating coil 5, and the pot 4 starts to be heated. In order to further increase the power applied to the heating coil 5, the ON time of the switching element 8 is gradually increased. Control continues until a certain on-time for detecting the pot material determined in advance is reached. In this state, the output voltage of each Vce peak hold circuit and the reference voltage of the reference voltage generating means 11 are as shown in FIG. 2 when the material of the pot 4 is aluminum or iron. In FIG. 2, the power peak detection means 12
When the detection pulse of Vce peak hold circuit 1 is output,
The output voltage of 0 is compared with the reference voltage of the reference voltage generation means 11, and when the output voltage of the Vce peak hold circuit 10<the reference voltage of the reference voltage generation means 11, the pot 4 is made of a regular material. When the output voltage of the Vce peak hold circuit 10>the reference voltage of the reference voltage generating means 11, the pot 4 is made of an irregular material. The determination means 13 makes a determination, and outputs the result to the control means 9.

The control means 9 controls the switching element 8 according to the result. That is, if the pot is a regular pot, the applied voltage is further increased to continue heating, and if the pot is an irregular pot, heating is stopped. When the on-time of the switching element 8 is controlled to be the same for an aluminum pot and an iron pot, there will be a large difference in the output voltage of the Vce peak hold circuit 10 depending on the material of the pot, so it is easy to determine the material of the pot. can be done.

Note that the determination by the determination means 13 is normally performed several times or more to prevent detection errors due to noise or the like. In addition, the Vce peak hold circuit 10
Although the determination means 13 for determining the output voltage of the output voltage has been described as a comparator for comparing both voltages, it is also possible to configure the reference voltage of the reference voltage generation means using the ROM etc. in the control means 9 using an AD comparator. Good too.

The reference voltage generating means 11 can be constructed using resistance division in the simplest manner, but it may also be constructed using a Zener diode or other reference voltage generating IC.

Further, the power supply peak detection means 12 normally consists of a zero volt detection circuit for detecting the zero volt timing of the AC power supply 1 and a timer (for example, at 60 Hz, the timer time is 8.33 msec). After that, a timer is generally operated in accordance with the frequency of the AC power source, and the peak of the AC power source is determined after the timer time has elapsed, but other peak detection circuits may be used.

As described above, according to the first embodiment,
The material of the pot can be detected without using a current transformer, eliminating the need for adjustment, reducing costs, and reducing the size of the printed circuit board.

Next, FIG. 3 shows a second embodiment of the present invention.
~Explained based on FIG. 5. In the following embodiments, the same parts as those in the first embodiment are denoted by the same reference numerals, and the explanation thereof will be omitted.

In the second embodiment, a rectifier circuit 2 is used instead of the reference voltage generating means 11 in the first embodiment.
changes in proportion to the magnitude of the power supply voltage, and
Connect a power level converter 14 that converts the level to an easy-to-handle voltage of 5 V or less, and use its output as a reference voltage.
The information is input to the determination means 10. This power level conversion means 14
When detecting the peak timing of the AC power supply 1, the output voltage of the Vce peak hold circuit 10 is higher than the output voltage of the Vce peak hold circuit 10 when using an iron pot, which is a regular pot material, and lower than that of a pot made of an irregular pot material, such as aluminum. The voltage is preset. Further, the output of the power supply peak detection means 12 which detects the timing of the peak of the AC power supply 1 and outputs a detection pulse is also connected to the input of the determination means 13, and when the detection pulse is output, the determination means 13 determines the material of the pot. It has become.

The operation of the second embodiment will be explained below. In order to detect the pot material, on/off control of the switching element 8 is started, and the control is continued until a certain predetermined on-time for detecting the pot material is reached, and when that state is reached, the power level converting means 14 output voltage and Vce peak hold circuit 10 when the pot material is aluminum or iron.
The output voltage of is as shown in FIG. In FIG. 4, when a detection pulse is output from the power supply peak detection means 12, the output voltage of the Vce peak hold circuit 10 is compared with the output voltage of the power supply level conversion means 14, and the output voltage of the Vce peak hold circuit 10<the power supply level conversion means. At an output voltage of 14, the pot is of regular material. When the output voltage of the Vce peak hold circuit 10>the output voltage of the power level converting means 14, the pot is made of an irregular material. The determining means 13 determines that.

When the voltage of the AC power supply 1 is changed, the output voltage of the Vce peak hold circuit 10 changes proportionally as shown in FIG. Since this is difficult to perform, the reference voltage for determination also needs to be changed in proportion to the voltage of the AC power supply 1.

As described above, in comparison with the reference voltage of the reference voltage generating means used in the first embodiment, it may be difficult to determine the material of the pot due to the high dependence on the power supply. According to the second embodiment, the output voltage of the power supply level conversion means 14 follows the fluctuation of the power supply voltage in proportion, and therefore,
Since the judgment criteria also change, errors in judgment due to fluctuations in the AC power supply are eliminated. In addition, the material of the pot can be detected without using a current transformer, making it possible to downsize and reduce costs.

In the second embodiment, the reference voltage was created by converting the level of the power supply voltage, but the power supply voltage is measured by an AD converter, etc., and the switching elements are controlled using a microcomputer or the like according to the measurement result. The collector-emitter voltage may be calculated and used as a criterion for determining the pot material.

Next, regarding the third embodiment, FIGS. 6 and 7
The explanation will be based on. The power supply peak detection means 12 in the second embodiment is abolished, and the Vce peak hold circuit 10
and the power supply level converting means 14 are constructed by integrating circuits, and the time constants of the integrating circuits are made the same.

The operation of the third embodiment will be explained below. In order to detect the pot material, on/off control of the switching element 8 is started, and the control is continued until a certain predetermined on-time for detecting the pot material is reached, and when this state is maintained, the power level converting means 14 The output voltage of the Vce peak hold circuit 10 when the pot material is aluminum and when the pot material is iron are as shown in FIG. 7, respectively. Since the power level converting means 14 and the Vce peak hold circuit 10 are composed of integral circuits having the same time constant, the power level converting means 14 and the Vce peak hold circuit 10 when the pan material is aluminum or iron The respective output voltages do not cross as shown in FIG. 4, and the same result can be obtained no matter when the pot material is determined.

The output voltage of the Vce peak hold circuit 10 is compared with the output voltage of the power supply level converting means 14, and the Vce
When the output voltage of the peak hold circuit 10<the output voltage of the power level converting means 14, the pot is made of a regular material. When the output voltage of the Vce peak hold circuit 10>the output voltage of the power level converting means 14, the pot is made of an irregular material. The determination means 13 makes a determination.

As described above, in the second embodiment, the pot material detection is determined only at the peak of the power supply, but in the third embodiment, the determination can be made at any time. Furthermore, the power peak detection means required in the second embodiment can be eliminated, and costs can be reduced. Furthermore, the material of the pot can be detected without using a current transformer, making it possible to downsize and reduce costs.

Next, FIG. 8 shows a fourth embodiment of the present invention.
, will be explained based on FIG. The configuration of the first embodiment is further provided with a power supply voltage measuring means 15 for measuring the AC power supply voltage, the measurement result is immediately transmitted to the control means 9, and the ON time of the switching element is controlled according to the measurement result. It is supposed to be done.

The operation of the fourth embodiment will be explained below. In order to detect the pot material, first, the power supply voltage measuring means 15
Measure the voltage of AC power supply 1, and according to the measurement result,
On/off control of the switching element 8 is started so that a predetermined constant on time is reached, and the control is continued until a predetermined constant on time for pot material detection is reached, and that state is maintained. In the example of FIG. 9, it is determined whether the voltage is above or below 100V, and when the voltage is above 100V, TonU is set to 100V.
The on-time of the switching element is controlled by the control means 9 so that TonD occurs when the voltage is below Vce, and when a detection pulse is output from the power supply peak detection means 12, the output voltage of the Vce peak hold circuit 10 is changed to the output voltage of the reference voltage generation means 11. Compare with reference voltage. When the output voltage of the Vce peak hold circuit 10 is smaller than the output voltage of the reference voltage generating means 11, the pot is made of a regular material. When the output voltage of the Vce peak hold circuit 10>the output voltage of the reference voltage generating means 11, the pot is made of an irregular material. The determining means 13 determines that.

As shown in FIG. 5, when the voltage of the AC power supply 1 is changed, the output voltage of the Vce peak hold circuit 10 changes proportionally. Since it is difficult to perform this, the reference voltage for determination also needs to be changed in proportion to the voltage of the AC power supply 1.

Therefore, as in the first embodiment, it was often difficult to determine the material of the pot due to the high dependence on the power supply by mere comparison with a constant reference voltage. According to the above, the output voltage of the Vce peak hold circuit 10 is changed by controlling the ON time of the switching element according to the magnitude of the power supply voltage, thereby eliminating errors in determination due to changes in the AC power supply. In addition, the material of the pot can be detected without using a current transformer, making it possible to downsize and reduce costs.

In this example, the on-time of the switching element depending on the power supply voltage is explained as having two levels, but the levels may be increased further, or it may be made proportional to the power supply voltage.

Next, a fifth embodiment will be explained based on FIGS. 10 and 11. The power peak detection means 12 in the first embodiment is omitted, and the output of the determination means 13 is input to the interrupt terminal of the control means 9.

The operation of the fifth embodiment will be explained below. In order to detect the pot material, on/off control of the switching element 8 is started, and the control is continued until a certain predetermined on-time for detecting the pot material is reached, and while maintaining this state, the Vce peak hold circuit is activated. 10 is compared with the output voltage of the reference voltage generating means 11, and when the output voltage of the Vce peak hold circuit 10<the output voltage of the reference voltage generating means 11, the pot is made of the correct material. When the output voltage of the Vce peak hold circuit 10>the output voltage of the reference voltage generating means 11, the pot is made of an irregular material. The determining means 13 determines that.

That is, when the pot material is aluminum, the output voltage of the Vce peak hold circuit 10 is equal to the reference voltage generating means 1.
1, the determination means 13 determines that the reference voltage of FIG.
An output as shown in (b) is output and input to the interrupt terminal of the control means 9. The control means 9 is designed to process the signal input from the interrupt terminal with the highest priority, so if an interrupt occurs while the pot is being detected, it will determine that the pot is an unauthorized pot and will stop heating the pot. Stop. If the pot is a regular pot, no output will be generated from the determination means, and the control means will continue heating without interruption.

As described above, in the first embodiment, the pot material detection is determined only during peak power hours;
In the fourth embodiment, treatment can be carried out only when an abnormality is found in the material of the pot. Furthermore, the power peak detection means required in the first embodiment can be eliminated, resulting in cost reduction. In addition, the material of the pot can be detected without using a current transformer, making it possible to downsize and reduce costs.

In the fifth embodiment, the reference voltage generating means 11
has been described using the configuration shown in the first embodiment, but the power level converting means 14 or the like shown in the second embodiment may also be used.

Furthermore, in the fifth embodiment, the control means 9 includes:
Although it has been explained that the heating is stopped immediately when an interrupt occurs, the heating may be stopped when an interrupt occurs several times in succession to prevent malfunctions due to noise.

[0051]

As described above, according to the first configuration of the present invention, there is a rectifier circuit that rectifies AC power supply current and converts it into DC, and a rectifier circuit that is connected to the rectifier circuit and generates a high frequency magnetic field to heat the pot. A heating coil that heats, 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, a control means that controls on/off the switching element, and a collector of the switching element. A Vce peak hold circuit that level converts the voltage between the emitters and holds the peak value, a reference voltage generation means that generates a reference voltage that is a criterion for determining the material of the pot, and a detection pulse that detects the peak timing of the AC power supply. The output voltage of the Vce peak hold circuit when the detection pulse of the power supply peak detection means is generated is determined by the reference voltage generation means. It consists of a determination means that determines the material of the pot placed on the heating coil and heated by comparing it with the reference voltage, so it is possible to reduce the size, no adjustment, and low cost without using a current transformer. It is possible to realize cost reduction.

According to the second configuration of the present invention, a power supply level converting means for level converting the voltage of the rectifier circuit is provided in place of the reference voltage generating means of the first configuration, and the pot is less dependent on the power source. The material can be detected.

According to the third configuration of the present invention, the power peak detection means in the second configuration is deleted, and the integration time constant and Vc of the power level conversion means constituted by an integrating circuit are changed.
Since the integration time constant of the e-peak hold circuit is made the same, the pot material can be detected whenever necessary.

According to the fourth configuration of the present invention, the first configuration is further provided with a power supply voltage measuring means for measuring the power supply voltage, and the on-time of the switching element is determined according to the power supply voltage. Since the control means is used to control the pot material such that the pot material is less dependent on the power source, the pot material can be detected with less dependence on the power source.

According to the fifth configuration of the present invention, the power peak detection means in the first configuration is deleted, and the Vce peak is controlled so that the on-time of the on-off control of the switching element is a certain fixed time. The determination means compares the output voltage of the hold circuit with the reference voltage of the reference voltage generation means,
Since the results are input to the interrupt terminal of the control circuit, heating can be stopped only when there is an abnormality in the material of the pot.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of a pot material detection device for a rice cooker using an induction heating method according to a first embodiment of the present invention.

FIG. 2 is a voltage waveform diagram of each part of the circuit in the first embodiment.

FIG. 3 is a circuit configuration diagram of a second embodiment of the present invention.

FIG. 4 is a voltage waveform diagram of each part of the circuit in the second embodiment.

FIG. 5 is a diagram showing changes in the output voltages of the Vce peak hold circuit and power level converting means due to changes in the AC power supply voltage in the second embodiment.

FIG. 6 is a circuit configuration of a third embodiment of the present invention.

FIG. 7 is a voltage waveform diagram of each part of the circuit in the third embodiment.

FIG. 8 is a circuit configuration of a fourth embodiment of the present invention.

FIG. 9 shows the collector-emitter voltage Vc of the switching element when the power supply voltage changes in the fourth embodiment;
FIG. 3 is a diagram showing changes in the on-time required to keep e constant.

FIG. 10 is a circuit configuration diagram of a fifth embodiment of the present invention.

FIG. 11 is a voltage waveform diagram of each part of the circuit in the fifth embodiment.

FIG. 12 is a circuit diagram of a conventional induction heating pot material detection device for a rice cooker.

[Explanation of symbols]

1... AC power supply, 2... Rectifier circuit, 4... Pot, 5
...Heating coil, 6. Resonance circuit, 7. Resonance capacitor, 8. Switching element, 9. Control means,
10...Vce peak hold circuit, 11...Reference voltage generation means, 12...Power supply peak detection means, 1
3... Determination means, 14... Power level conversion means, 1
5...Power supply voltage measuring means.

Claims (5)

[Claims] Claim 1: A rectifier circuit that converts alternating current of an alternating current power source into direct current; a heating coil connected to the rectifier circuit that generates a high-frequency magnetic field to heat a pot; and a resonant capacitor that forms a resonant circuit together with the heating coil. , a switching element connected to the resonant circuit to generate a resonant current, a control means for controlling on/off of the switching element so that a predetermined power is output at a predetermined applied voltage, and a collector of the switching element. A Vce peak hold circuit that level converts the voltage between the emitters and holds the peak value, a reference voltage generation means that generates a reference voltage that is a criterion for determining the material of the pot, and detects and detects the peak timing of the AC power source. The power supply peak detection means outputs a pulse, and the ON/OFF control of the switching element is controlled so that the on-time is a predetermined constant time, and when the detection pulse of the power supply peak detection means is generated, the Vce peak hold circuit is activated. A pot for an induction heating cooker, characterized in that it is equipped with a determining means for determining the material of the pot placed on a heating coil and being heated by comparing the output voltage with the reference voltage of the reference voltage generating means. Material detection device. 2. The pot material detection device according to claim 1, further comprising power supply level converting means for level converting the output voltage of the rectifying circuit and maintaining its peak value instead of the reference voltage generating means. Features a pot material detection device for induction heating cookers. 3. In the pot material detection device according to claim 2, the power peak detection means is omitted, and the integral time constant of the power level conversion means constituted by an integrating circuit and the integral time constant of the Vce peak hold circuit are changed. A pot material detection device for an induction heating cooker characterized by having the same material. 4. The pot material detection device according to claim 1, further comprising power supply voltage measuring means for measuring the voltage of the AC power supply, and in accordance with the measured voltage measured by the power supply voltage measuring means.
The control means controls the switching element so as to have a predetermined constant on time, and compares the output voltage of the Vce peak hold circuit when the detection pulse of the power supply peak detection means is generated with the reference voltage of the reference voltage generation means. A pan material detection device for an induction heating cooker, characterized in that the material of the pan placed on a heating coil and heated is determined by: 5. The pot material detection device according to claim 1, wherein the power supply peak detection means is omitted and the Vce peak hold circuit is provided when the control means controls the switching element so that a predetermined on-time is reached. The output voltage of the heating coil is compared with the reference voltage of the reference voltage generating means, and the determination means outputs the result to the interrupt terminal of the control means. A pot material detection device for an induction heating cooker, characterized in that it controls heating stop only when the heating is stopped.