JPH04371108A - Induction heating cooker pot detection device - Google Patents

Abstract

PURPOSE:To provide a pan detecting device for an induction heating cooking appliance which dispenses with a pan switch and a current transformer, and detects the existence of a pan and its material, and moreover is inexpensive, small-sized and nonregulatory. 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 circuit 9 to apply a resonance current to a heating coil 5. In this case, the current flowing through the reverse conducting diode 10 of a pan detecting circuit 12 connected to the switching element 8 in parallel differs greatly according to the existance of a pan mounted on the heating coil 5 and its material. Thus the output voltage of the pan detecting circuit 12 is compared with the reference voltage of a judging means 13 to judge the existence of the pan 4 and its material.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pot detection device for detecting the presence or absence of a pot being heated on an induction heating cooking device such as an electronic jar rice cooker using induction heating, and the material of the pot.

0002

[Prior Art] A pot presence/absence detection device for an induction heating rice cooker, which is one of the conventionally used induction heating cookers, is shown in FIG.
It is configured as shown in . 21 is the main body of the rice cooker, and the pot 4 is housed in the main body 21. 23
is a sliding part that moves up and down depending on the presence or absence of the pot 4. When the pot 4 is not set, the sliding section 23 is pushed upward by the spring 24, and when the pot 4 is stored in the main body 21 of the rice cooker, the pot 4
The sliding portion 23 is pushed down by the weight of the slider. Reference numeral 25 denotes a pot detection switch. When the sliding part 23 is pushed down, the pot detection switch 25 is turned on, and the pot detection switch 25 is sent to the judgment means 27 of the electronic circuit section through a connecting cable 26 with a connector etc. The presence or absence of a pot can be detected depending on the state of the switch 25.

[0003] Furthermore, the material of the pot heated on an induction heating cooker such as an electronic jar rice cooker using induction heating 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 was necessary to detect the material of the pot before starting heating, and to stop heating depending on the detection result.

Conventionally, this type of pot material detection device has a configuration as shown in FIG. That is, a rectifier circuit 2 converts alternating current supplied from an alternating current power source 1 into direct current, a filter 3 removes alternating current components from the output of the rectifier circuit 2, and a filter 3 connected to this filter 3 generates a high frequency magnetic field to heat a pot 4. A heating coil 5 to be heated, a resonant capacitor 7 forming a resonant circuit 6 together with the heating coil 5, a switching element 8 connected to the resonant circuit 6 for generating a resonant current, and an on/off control of the switching element 8. A control means 9 that controls the applied power by changing the time, and a Vce peak hold circuit 15 that converts the voltage between the collector and emitter of the switching element 8 to an easily handled voltage level of about 5V and holds the peak value. , AC power supply 1
and a rectifier circuit 2, the current detection means 1 consists of a current transformer or the like that outputs a voltage proportional to the flowing current.
6, Vce peak hold circuit 15 and current detection means 1
and a determining means 13 comprising an AD converter or the like, which determines the material of the pot based on each output voltage value of 6.

In the above configuration, when heating the pot 4 is started by passing a resonant current through the heating coil 5, Vce
An output voltage is generated in the peak hold circuit 15, and at this time,
The output voltage value varies greatly depending on the material of the pot 4. Based on the difference in output voltage, the determining means 13 determines the difference in pot material, particularly between aluminum and iron materials.

[0006]

[Problems to be Solved by the Invention] In the conventional configuration described above, the presence or absence of a pot is detected by installing a sliding part or a pot detection switch at the bottom of the pot inside the main body of the rice cooker. Since connectors and cables are used to connect to the electronic circuit section, there are problems in that it takes time to produce, it is difficult to automate the production, and the cost is high.

[0007] In addition, detection of the material of the pot was performed by determination means based on the relationship between the output voltage of the Vce peak hold circuit and the current detection means, and because it was necessary to use a current transformer with a large current capacity for the current detection means. However, there have been problems in that the cost is high and the size is large, so the printed circuit board is also large. Furthermore, there is a problem in that adjustment is required to accurately detect the flowing current, which increases the cost.

[0008] The present invention is an attempt to solve the various problems that such conventional configurations had, and detects the presence or absence of a pot and its material from the magnitude of the current flowing through the reverse conduction diode, and connects the connection cable. To provide a small-sized, low-cost pot detection device for an induction heating cooker that is easy to produce and does not require a current transformer.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the pot detection device of the present invention includes a rectifier circuit that converts alternating current supplied from an alternating current power source into direct current, and a high-frequency A heating coil that generates a magnetic field to heat the pot, a resonant condenser 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 control that controls on/off the switching element. a pot detection circuit connected in parallel to the switching element and comprising a series circuit of a reverse conduction diode and a pot detection resistor; and a determination device for determining the presence or absence of a pot and the material of the pot based on the output voltage of the pot detection circuit. The configuration has the following.

0010

[Function] According to the above configuration, when the control means starts on/off control of the switching element to detect a pot, a resonant current flows through the resonant circuit when the switching element is on.
When the switching element is off, a high voltage is generated between the collector and emitter of the switching element. When the switching element changes from off to on, the current flowing through the reverse conduction diode varies depending on the presence or absence of a pot and its material. This current is converted into voltage by the resistance of the pot detection means and compared with a predetermined reference voltage. By doing so, the determination means can determine the presence or absence of the pot and the material of the pot.

[0011]

Embodiments Hereinafter, embodiments will be described in detail with reference to FIGS. 1 to 3. FIG. 1 shows the circuit configuration of an induction heating electronic jar rice cooker according to an embodiment of the present invention. a filter 3 that removes alternating current components from the output of the filter 3; a heating coil 5 that is connected to the filter 3 and generates a high-frequency magnetic field to inductively heat the pot 4; and a resonant capacitor 7 that forms a resonant circuit 6 together with the heating coil 5.
, a switching element 8 connected to the resonant circuit 6 to generate a resonant current in the resonant circuit 6, a control means 9 for controlling on/off of the switching element 8, and a control means 9 connected in parallel to the switching element 8 to generate a resonant current in the resonant circuit 6; Conduction diode 1
A pot detection circuit 12 consisting of a series circuit of 0 and a pot detection resistor 11.
, a determining means 13 for determining the presence or absence of a pot and its material, and a holding means 14 for holding the pot detection 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. Detection of the presence of the pot 4 and its material is normally performed before starting rice cooking and when setting the rice cooking reservation timer. The reason for this is that the pot material of induction heating electronic jar rice cookers is usually made of iron. When the voltage is higher than that at the collector of the switching element 8,
This is because since it occurs between the emitters, there is a risk of destroying the switching element 8 and the like.

[0013] Therefore, before starting heating, it is necessary to detect the presence or absence of a pot and the material of the pot, and to stop heating if there is an irregular pot or no pot. Detection of the pot material is performed as follows. First, the control means 9 controls the switching element 8
When ON/OFF is controlled, a resonant current flows through the heating coil 5 and starts heating the pot 4.

FIG. 2 shows the voltage and current waveforms of the main parts when heating using a regular pot in an induction heating type electronic jar rice cooker. FIG. 2(a) shows a voltage waveform generated between the collector and emitter of the switching element 8,
FIG. 2(b) shows a current waveform flowing through the switching element 8. This current similarly flows to the heating coil 5 as a resonant current. Furthermore, FIGS. 2(c) and 2(d) respectively show the current flowing through the reverse conduction diode 10 and the voltage generated across the pot detection resistor 11 when a regular pot is heated. In this case, No current or voltage is generated.

FIG. 3 shows the voltage and current waveforms when heating is performed using an irregular pot made of aluminum or the like. A voltage waveform as shown in FIG. 3(a) is generated between the collector and emitter of the switching element 8. Also, Figure 3(b)
) flows through the switching element 8, and similarly a resonant current flows through the heating coil 5. Also, at this time, a current as shown in FIG. 3(c) flows through the reverse conduction diode 1.
3 (
A voltage proportional to the current is generated as shown in d). Even when heating without a pot, the waveform is similar to the waveform in Figure 3.

As described above, due to the presence or absence of the pot 4 and the difference in the material, when the switching element 8 changes from OFF to ON, the current flowing through the reverse conduction diode 10 is small when the pot is a regular pot 4, and when the pot is an irregular pot. It flows a lot at times. Therefore, the magnitude of this current is determined by the pot detection resistor 11 of the pot detection circuit 12.
The magnitude of the voltage is compared with the reference voltage of the determining means 13 to determine the presence or absence of a pot and the material of the pot.

The output voltage of the pot detecting circuit is compared with the reference voltage of the determining means 11, and when the output voltage of the pot detecting circuit 12>the reference voltage of the determining means 13, the pot 4 is made of a regular material. When the output voltage of the pot detection circuit 12<the reference voltage of the determining means 13, the pot 4 is made of an irregular material. The determination means 13 makes a determination, the holding circuit 14 holds the result, and outputs it to the control means 9. The control means 9 controls the switching element 8 according to the result. In other words, if the pot is a regular pot, the applied power is further increased to continue heating, and if the pot is an irregular pot, heating is stopped. In this way, due to differences in pot materials,
A large difference occurs in the output voltage of the pot detection circuit 12, and the material of the pot can be easily determined.

The determination by the determination means 13 is normally performed several times or more and is transmitted to the control means 9 to prevent detection errors due to noise or the like.

In the explanation of the embodiment, the output result of the determination means is held in a hold circuit and the control means looks at the result, but the output result of the determination means is directly read.
It may also be output to the interrupt input terminal of the control means.

As described above, according to this embodiment, the presence or absence of a pot can be detected without using a connector or cable for connection, and the material of the pot can be detected without using a current transformer. can be detected, no adjustment required, cost reduction,
It is possible to downsize the printed circuit board.

[0021]

As described above, according to the present invention, there is provided a rectifier circuit that converts alternating current supplied from an alternating current power source into direct current, and a heating coil that is connected to the rectifier circuit and generates a high-frequency magnetic field to heat a pot. a resonant capacitor constituting 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; connected in parallel to the switching element; By comparing the pot detection circuit consisting of a series circuit of a reverse conduction diode and a pot detection resistor and the output voltage of the pot detection circuit with a reference voltage, it is possible to determine the presence or absence of a pot placed on the heating coil and its material. The present invention is characterized in that it is equipped with a determination means for performing the determination, thereby making it possible to achieve miniaturization of the pot detection device, no adjustment required, and cost reduction.

[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 of voltage and current waveforms of main parts when heating using a regular pot in the same example.

FIG. 3 shows voltage and current waveforms of important parts when heating is performed using an irregular pot made of a material such as aluminum in the same example.

FIG. 4 is a configuration diagram of a conventional pot presence/absence detection device.

FIG. 5 is a circuit configuration diagram of a conventional pot material detection device.

[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... Reverse conduction diode, 11... Pot detection resistor,
12... Pot detection circuit, 13... Judgment means, 14
…Holding means.

Claims (1)

[Claims] [Claim 1] A rectifier circuit that converts alternating current supplied from an alternating current power source into direct current, a heating coil that is connected to the rectifier circuit and generates a high-frequency magnetic field to heat the pot, and together with the heating coil constitutes a resonant circuit. a resonant capacitor, a switching element connected to the resonant circuit to generate a resonant current, a control means for controlling on/off of the switching element, and a reverse conduction diode and a pot detection resistor connected in parallel to the switching element in series. A pot detection device for an induction heating cooker, comprising: a pot detection circuit consisting of a circuit; and determining means for determining the presence or absence of a pot and the material of the pot based on the output voltage of the pot detection circuit.