JPH02270289A - Induction heat cooling appliance - Google Patents

Abstract

PURPOSE:To lower voltage of a noise terminal having a controlling a circuit as a noise source by installing >=2 of GND leads connecting an inverter circuit and the controlling circuit. CONSTITUTION:Additionally to a conventional first GND lead 12 led from the periphery of an emitter of a switching device of an inverter circuit, a second GND lead 13 is led from a spot having the same voltage of the emitter of the switching device and except a part of a loop in which a high frequency current flows. The second GND lead 13 works to stabilize the voltage of a controlling circuit 11 against ground and weakens the function of the controlling circuit as a noise source. Consequently, voltage increase of a noise terminal is suppressed even when a part of a controlling circuit 11 such as a power setting and displaying unit of a built-in type induction heat cooking appliance is separated from a controlling circuit main body and connected with the main body by a long lead wire.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an induction heating cooker.

2. Description of the Related Art Conventionally, this type of induction heating cooker has a structure as shown in FIG.

In other words, the inverter circuit and control circuit 207 consisting of the smoothing capacitor 203, heating coil 204, resonance capacitor 206, and switching element 206 are connected to one GND wire 2.
09, and the GND line 209 was taken from point 2 near the emitter of the switching element 206 in order to stably drive the switching element 206. In addition.

201 is a commercial AC power supply, 202 is a rectifier circuit, and 208 is a q drive circuit in the control circuit 207.

Problems to be Solved by the Invention However, with such a configuration, there is a problem in that the control circuit 207 becomes a noise source and the noise terminal voltage increases. In particular, 1. Although not shown in the figure, a part of the control circuit is located away from the control circuit body and is connected with a long lead wire, such as the power setting/display unit of a built-in induction heating cooker. , the problem of increased noise terminal voltage was noticeable.

In other words, in loop 2 of the inverter circuit of the induction heating cooker, a high frequency current flows through which the heating coil 204 generates a high frequency magnetic field, so the GND of the control circuit 207 is determined by the resistance and actance of the wiring of loop 2. Point 2 has a potential that moves at a high frequency with respect to the earth (earth),
The control circuit 207, which operates with these two points connected to GND, becomes a noise source, especially in the built-in induction heating cooker.
Connecting a part of the control circuit, such as a setting/display unit, away from the control circuit body using long lead wires will increase the noise source, and as a result, the noise terminal voltage will increase. there were.

Therefore, one object of the present invention is to reduce the noise terminal voltage caused by the control circuit as a noise source.

A means to solve problems And in order to achieve the above object, the present invention.

Two or more GND wires are installed to connect the inverter circuit and the control circuit.

Function: The induction heating cooker of the present invention uses the first grain GN taken from the vicinity of the emitter of the switching element of the conventional inverter circuit.
In addition to the D line, by taking the second GND line from a point other than the loop through which the high-frequency current of the inverter circuit flows and from a point that has the same potential as the emitter of the switching element, the second GND line acts to stabilize the potential of the control circuit with respect to ground, thereby weakening the effect of the control circuit as a noise source. As a result, the increase in noise terminal voltage can be suppressed even when a part of the control circuit is separated from the control circuit body and connected with a long lead wire, such as in the power setting/display unit of a built-in induction heating cooker. It is something that can be done.

Example An embodiment of the present invention will be described below with reference to FIG.

In Fig. 1, 1 is a commercial AC power supply, 2 is a rectifier circuit that rectifies the commercial AC power supply 1, 3 is a smoothing capacitor that smoothes the output of the rectifier circuit 2, 4 is a heating coil, 6 is a resonant capacitor, is a bipolar transistor which is a switching element, and the smoothing capacitor 3, heating coil 4, resonance capacitor 6, and bipolar transistor 6 constitute an inverter circuit. Further, 11 is a control circuit that controls the inverter circuit, 7 is a main body part of the control circuit 11, 9 is a drive circuit included in the control circuit main body 7,
8 is a control circuit main body other than the drive circuit 9, and 10 is a power setting/display circuit that is a part of the control circuit located away from the control circuit main body 7. Also, the thick solid line in Figure 1 is GND, which is the GND of the inverter circuit.
A line connecting GND of the control circuit 11 and a point near the emitter of the bipolar transistor e and the drive circuit 90
and the GND line 12 that connects the GND points.

Point C other than loop 1 through which high-frequency current flows in the inverter circuit, drive circuit 9 in control circuit 11, and drive circuit 9
A GND line 130 is connected to point d on the GND line connecting other control circuit main bodies 8 by two GND lines.

Next, the operation of the configuration of this embodiment will be explained. When the induction heating cooker operates, a high frequency current flows through loop 1 of the inverter circuit, and the GND point a on this loop 1
has a potential that moves at a high frequency with respect to the ground, and the control circuit 11 that operates with this GNDO point a as a reference tends to become a noise source.

However, the GNDO point C on the inverter circuit side, which has a stable potential with respect to the ground, is the control circuit 11! l111 GN
Since it is connected to the point d of D by the C1ND wire 13 of the second grain, the GND of the control circuit main body 8 other than the drive circuit 9 and the power setting/display circuit has a stable potential with respect to the ground.

As a result, most parts of the control circuit 11 except for the drive circuit 9 cannot serve as noise sources, and the noise terminal voltage does not increase as in the conventional case.

Effects of the Invention As described above, the present invention reduces the number of GND wires connecting the inverter circuit and the control circuit to two (and if necessary, increases the number of GND wires to two or more), and one wire to stably drive the switching elements of the inverter circuit. The other wire is connected to stabilize the GND potential of the control circuit, so it can be used as a part of the control circuit, such as the power setting/display unit of a built-in induction heating cooker. Even when the control circuit is used away from the main body of the control circuit, an increase in the noise terminal voltage can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a schematic circuit diagram of an induction heating cooker according to an embodiment of the present invention, and FIG. 2 is a schematic circuit diagram of a conventional induction heating cooker. 4...Heating coil, 11...Control circuit, 12゜13...GND wire. Name of agent: Patent attorney Shigetaka Awano and 1 other person 1st
Figure 4. -77°, 4. . 1F - Old plaster

Claims (1)

[Claims] an inverter circuit including a heating coil; and a control circuit for controlling the inverter circuit;
An induction heating cooker in which an ND and a GND of the control circuit are connected at two or more places.