JPS6041793A - 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 Technical Field The present invention relates to an electromagnetic cooker having a load detection circuit for detecting small objects such as knives and knives placed on the top plate of the electromagnetic cooker.

<Prior Art> The diagram below shows the configuration of a conventional electromagnetic cooker, in which a heating coil 2, a capacitor 3, and an inverter 4 are connected in series in this order between both terminals of a DC power source 1. A drive circuit 5 that turns on and off the inverter 4 is connected, and further includes a start signal generation circuit 8 and a load detection circuit 9.
, a stop signal generating circuit 11 which receives the output of the current transformer 10 as an input is connected to the drive circuit 5 in item 1.

In addition, the output signal of the inverter 4 (dl drive circuit 5 is applied to the transistor ψ1'16) and the tampering transistor 6 is connected in the opposite direction between the collector and emitter terminals of the switch transistor 6. It is composed of a diode 7 and a diode 7.

By the way, depending on the size of the load placed on the top plate 1 of the electromagnetic cooker, the switching transistor 6
V. 1. Conventionally, the output voltage on the collector side of the switching transistor 6 was directly introduced into the load detection circuit 9. In this case, the voltage of the switching transistor 6 changes. 1. - The voltage on the next side becomes the signal for the load detection circuit 9 on the secondary side, and there is a safety problem in that the next side and the secondary side are not electrically isolated. A simple circuit configuration was desired in terms of product reliability and safety measures.

<Purpose> The present invention has been made in view of two points, and an object thereof is to electrically separate the load detection circuit and the inverter circuit.

<Configuration> In order to achieve the two objectives of the present invention, the input signal of the load detection circuit that detects the size of the load is connected to the heating coil.
The present invention is characterized in that the inverter circuit on the primary side and the load detection circuit on the secondary side of the current transformer for detecting the 1-A current are separated.

<Example> An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a configuration diagram of an electromagnetic cooker showing an embodiment of the present invention.

In the figure, the same reference numerals are given to the parts having the same functions as in the conventional dual example, and detailed explanations are omitted. 9' is the output terminal 1 a of the current transformer IO,
This is a load detection circuit connected to a' and includes the load detection circuit shown in FIG. In the figure, 12
．． 12' are the output terminals a, a of the current transformer IO.
'[This is the input terminal of the load detection circuit to be connected, and the grounding force is applied via diode 13, I/l, which is connected in the opposite direction. 5. Resistance 4 plate L16 and tie auto 17
, a series circuit consisting of a resistor I8 is connected in parallel, and a connection point 1 between the tie 17 and the resistor 187 is connected in parallel.
961 is connected to the −(V input terminal of the comparator 20. 21 is the reference voltage connected to the 10-pole input terminal of the ratio amplifier 20. 2 2 (l:i) The output terminal of the comparator 7'7 connected to the drive circuit 5 shown in FIG.
There is -c.

Next, the operation of the load detection circuit shown in FIG. 3 will be explained. At the input terminals 12 and 12' (d, a current corresponding to the current flowing through the heating coil 2 IC shown in Figure 4 is connected to the heating coil 7).
1 - Input via lance 10. Here, the solid line 23-
Large load, broken line 24V"Current waveform for small load 7
j, and when the load is heavy (L-J/J・sashis
Sometimes, the damping coefficient becomes large because the specific resistance is large, and in the negative direction of the coil current, the current level for large loads is smaller than for small loads.Now, when input to input terminal 12.12' The coil current flows to the ground side via the positive terminal side diodes 15 and the resistor 16, and on the other hand,
− pole side is grounded Vζ via diode 14 and resistor 18
Current flows.

Therefore, the electric ratio generated across the resistor 18 is applied to the one-pole input terminal of the comparator 20, and the reference voltage 21 corresponds to the preset voltage across the resistor 18, that is, the voltage level in the case of a small load. If the load is small, it is determined whether the load is small or small by comparing it with 4 is stopped, electricity is cut off to the heating coil 2, and heating is stopped. In this way, it is possible to determine whether the load is large or small by detecting the coil current detected by the current transformer IOK. The circuits can be electrically separated from each other.

<Effects> As explained above, the present invention includes a load detection circuit connected to the output terminal of the current transformer that detects the current of the heating coil. By comparing the load level with a predetermined level and determining whether the load is small or small, it is possible to prevent small objects such as knives and forks from being accidentally placed on the plate.
It is possible to stop the energization of the heating coil ＼ when the heating coil is turned off, and by indirectly detecting the current flowing through the heating coil via a current transformer, the electric circuit system of the heating coil and the load detection circuit can be The system can be completely electrically isolated, which is extremely useful for safety measures.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional electromagnetic cooker, FIG. 2 is a block diagram of an electromagnetic cooker showing an embodiment of the present invention, and FIG. 3 is an embodiment of the load detection circuit in FIG. FIG. 4 is a diagram of the current waveform of the heating coil that changes depending on the magnitude of the load. 2... Heating coil, 4... Inverter, 5 Drive circuit, 9'... Load detection circuit, 10... Current transformer. Figure 1 Figure #2 Shino 3ri: J Arm 4 Figure

Claims (1)

[Claims] 1. An electromagnetic cooker characterized by a load detection circuit connected to the output terminal of a current transformer for detecting the current of a heating coil.