JPS6030079A - Electromagnetic cooking device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to an electromagnetic cooker.

Conventionally, an electromagnetic cooker rectifies an AC power source 1 with a rectifier circuit 2 as shown in FIG. The output of the input detection circuit 19 comprising the DC conversion circuit 10 and the output of the output setting circuit 13 are compared and amplified by the differential amplifier circuit 14, and the inverter circuit 18 is controlled by the output via the output control circuit 16. there were. 6 is the choke coil.

4.6 is a capacitor, 7 is a diode, 8 is a switching element, 15 is an oscillation circuit, and 17 is a driver circuit. Specifically, the above control method converts the current into voltage using the current transformer 9, compares it with the reference voltage of the output setting circuit 1, and increases the heating output if it is smaller than the reference voltage. If it is large, inverter circuit 1 should be used to reduce the heating power.
The pulse width control is performed by controlling the conduction pulse width of the switching element 8 of 8 to keep the heat output of the force 11 constant and the heating of the cooking container constant.

In the case of such a configuration, only iron was specified as the material for the second cooking vessel. If other materials such as non-magnetic stainless steel are used, the switching element 8 will be thermally destroyed. That is, as shown in FIG. 2, during the period when the switching element 8 of the inverter circuit 18 is conductive, comparing the case of using non-magnetic stainless steel and the case of using magnetic iron, the input current is kept constant. Since it is a control method, the conduction period of the switching element 8 is longer when made of non-magnetic stainless steel than when made of iron, and the frequency of the inverter circuit 18 is 26 K when made of iron and 28 K when made of stainless steel. Therefore, in the case of non-magnetic stainless steel, the switching loss of the switching element 8 increases due to the higher frequency, which increases the temperature of the case of the switching element and prevents thermal damage. Iron can be used as a material, but stainless steel cannot be used.

Similarly, even with the same lunar quality, the equivalent impedance differs depending on the shape, and the switching element 8 may be destroyed due to the above-mentioned tendency. This has resulted in a drawback that the range of usable cooking vessels that can be used is narrowed.

The present invention eliminates the above drawbacks and improves the material of the cooking container.

The aim was to obtain an electromagnetic cooker that could operate stably and heat even if its shape changed, and for this purpose an inverter circuit current detection circuit was connected to the inverter circuit, and its output was input to a differential amplifier. 0 A detailed explanation of one embodiment of the present invention will be given below according to the drawings. FIG. 6 shows a block diagram of an electric circuit of an electromagnetic cooker according to the present invention. The difference from Figure 1 is that the inverter circuit 1
8, an inverter circuit current detection circuit (4) consisting of a current transformer 11 and a DC conversion circuit 12 for detecting the high frequency current switched by the switching element 8 is connected between the emitter of the switching element 8 and one pole of the rectifier 2. , its output is connected to the differential amplifier circuit 14 together with the output of the DC conversion circuit 10.

Next, the operation will be explained in detail with reference to the main operation waveforms of each part in FIG. 4 when using a cooking vessel made of stainless steel and iron.

In FIG. 4, (a) shows a current waveform flowing between one pole of the rectifier 2 and the emitter of the switching element 8 in FIG. The solid line indicates the case where the cooking vessel is made of iron, and the broken line indicates the case where the cooking vessel is made of stainless steel. It will appear in the same way below. In this current waveform, the repetition period differs between iron and stainless steel due to the difference in equivalent impedance. The current value detected by the current transformer 11 and compared is (
b) Diagram. The output voltage is as shown in the diagram (C), and the output voltage (2) in the case of stainless steel is greater than the output voltage (2) in the case of iron. This is switching element 8 when made of stainless steel.
This is due to the fact that the area where the peak value of the current flowing through is converted into voltage is larger than that of iron. This is combined with the output of the input detection circuit 19 (shown in Figure (d). There is almost no difference in the voltages Vr and v2 since it is converted to a commercial frequency) and input to the differential amplifier circuit 14. Here, as described above, it is compared and amplified with the output of the output setting circuit 13 and input to the output control circuit 16. Here, the output V3 of the oscillation circuit 15 is combined as shown in figure (e), and the width of the 0N48 wire added to the base of the switching element 8 as shown in figure (f) is compared in the case of stainless steel and in the case of iron. and make it narrower. This makes it possible to control the heating output and provide a stable output. Further, the peak value of the current flowing through the switching element 8 can be controlled to be below a certain value, and it is possible to prevent the switching element 8 from being destroyed by the feathers of the cooking container as described above.

Moreover, the same effect can be obtained not only by the quality of the cooking container but also by its shape.

As described above, according to the present invention, an inverter circuit current detection circuit is simply added to a conventional circuit.

It is possible to instantly detect and control the current flowing through the switching element in response to changes in the cooking container, allowing the use of cooking containers made of materials other than iron, and also detecting and controlling changes in the current at the input terminal at the same time. In such cases, it is possible to stabilize changes in the heating output for heating the cooking container.

[Brief explanation of drawings]

Figure 1 is a block diagram of the electrical circuit of a conventional induction cooker, Figure 2
The figure is a current waveform diagram of the same switching element. FIG. 3 is a block diagram of one electric circuit of an electromagnetic cooker according to an embodiment of the present invention, and FIG. 4 is a diagram of main waveforms of the same operation. 1... AC power supply, 2... rectifier circuit. 5... Heating coil, 13... Output setting circuit. 14. Differential amplifier circuit, 16. Output control circuit. 18... I/verter circuit, 19... Input detection circuit. Applicant: Hitachi Thermal Appliances Co., Ltd. Figure 2 Figure 3 Figure 4 - → Fat opening

Claims (1)

[Claims] An AC power source (1) is rectified by a rectifier circuit (2), and its output is applied to a heating coil (5) via an inverter circuit α. Furthermore, the output of the input detection circuit OI connected to the AC power supply (1) and the output of the output setting circuit θ4 are compared and amplified by the differential amplifier circuit 0→, and the output is connected to the inverter circuit O via the output control circuit (G). In an electromagnetic cooker that controls the
An electromagnetic cooking device characterized in that an inverter circuit current detection circuit is connected to an inverter circuit, and its output is input to a differential amplifier circuit α along with two outputs of an input detection circuit.