JPS636770A - Induction heating cooker - 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 Field of Industrial Application The present invention relates to an induction heating cooker applying the principle of electromagnetic induction heating.

Prior Art FIG. 3 shows a circuit diagram of this type of induction heating cooker in the prior art as found in the inventor's previous application.

In the figure, 1 is a DC power supply, 2 is a current limiting coil for reducing current ripple, and both constitute a power supply circuit 3. One end of the power supply circuit 3 is connected to the midpoint terminal of the heating coil 4, and a capacitor 5 is connected to both ends of the heating coil 4.
Further, switching elements 6 and 7 made of transistors, for example, are connected to both ends of the heating coil 4, and the switching elements 6 and 7 are controlled to be turned on and off by a control circuit 8. 9 in the figure is a pot serving as a load.

Next, the operation of the conventional technique will be explained with reference to FIG. FIG. 4 shows the terminal voltage ma1. of the switching element 6 of the induction heating cooker shown in FIG. It is a waveform diagram of current 11 and terminal voltage v2 of switching element 7+current 12. 0≦t (At tl, switching element d is off and switching element a is on. During this period, resonance between the heating coil 4 and the capacitor 6 generates 7 in the switching element 6, and when 1 = 1., vl- ○, the capacitor voltage v0=0. When 1=1, the control circuit 8 turns on the switching cable 6 and turns off the switching element 7.

Then, a voltage v2 is generated under the switching element due to the resonance between the heating coil 4 and the capacitor 5, and t=t2.
Then, 72=o and vc=o. At t=t2, the control circuit 8 turns the switching element 6 off and turns on the switching cable 7. Similarly, the control circuit 8 switches the switching cable 6 and the switching element 7 on and off when vc=0, supplies high frequency current to the heating coil, and heats the pot 9 by induction. .

Problems to be Solved by the Invention In such a conventional configuration, it is necessary to provide a midpoint terminal on the heating coil, which makes the structure of the heating coil complicated.
In addition, there was a problem in that it took time and effort to assemble.

In view of the above-mentioned problems, the present invention simplifies the structure of the heating coil by eliminating the midpoint terminal of the heating coil, and also reduces the number of man-hours during assembly, thereby providing a low-cost induction heating cooker. This is what we provide.

Means for solving the problem In order to solve this object, the induction heating cooker of the present invention has the following features:
A power supply circuit configured by connecting a DC power supply and a current limiting coil in series, a heating coil having one terminal connected to one terminal of the power supply circuit, a capacitor connected between both terminals of the heating coil, and the heating The coil has a configuration including switching elements connected from both ends of the coil to the other terminal of the power supply circuit, and a control circuit.

Function: With this configuration, the induction heating cooker of the present invention can eliminate the center terminal of the heating coil. Therefore, the structure of the heating coil becomes simple, and the number of man-hours during assembly can be reduced, making it possible to provide a low-cost induction heating cooker.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of an induction heating cooker according to an embodiment of the present invention. In the figure, 11 is a DC power supply, 12
is a current limiting coil for reducing current ripple, and both constitute the power supply circuit 13. One end of this power supply circuit 13 is connected to one end of a heating coil 14. A capacitor 15 is connected to both ends of the heating coil 14 in parallel with the heating coil 14.
Reverse conduction type switching elements 16 and 17 each constituted of a transistor and a diode, for example, are placed at both ends of 4.
are connected. The switching element 16 and the switching element 17 are controlled to be turned on or off by a control circuit 18. 19 in the figure is a pot.

Next, the operation of one embodiment of the present invention will be explained with reference to FIG. 2, 'riThe terminal voltage v1. of the switching element 16 of the induction heating cooker shown in FIG. Current ±
1 is a waveform diagram of terminal voltage v2+current i2 of switching element 17 and switching element 17. FIG. O≦1 (At 11, the switching element 16 is off and the switching element 17 is on.

During this period, a voltage v1 is applied across the switching element 16 due to resonance between the heating coil 14 and the capacitor 16.
occurs, and at t=t1, vl=○, and the voltage of the capacitor 15 becomes C=Q. When 70=Q, the reverse conduction diode of the switching element 16 turns on, and becomes 1l(o).

The control circuit 18 turns off the switching cable 17 at tl after Δta has passed from tl. Then, a voltage v2 due to resonance between the heating coil 14 and the capacitor 16 is generated across the switching element 170, and at t5, v2=○, and after Δtb has elapsed, the control circuit 18c, t
4, the switching element 1e is turned off.

By repeating the above operations, the heating coil 14
A high frequency current is supplied to inductively heat the pot 19. Δta
During the period Δtb, both the switching cable 16 and the switching element 17 are in a conductive state. Δt4 and Δt
When b becomes longer, the current flowing out from the DC power supply 11 increases, and the heating power increases.

Therefore, in the induction heating cooker of this embodiment, the heating power can be controlled by eliminating the midpoint terminal from the heating coil and by changing the operating frequency below the resonance frequency of the heating coil and the capacitor.

Effects of the Invention As is clear from the above embodiments, the induction heating cooker of the present invention is particularly constructed by connecting a DC power supply and a current limiting coil in series, and has an FC power supply circuit and one terminal connected to one of the power supply circuits. A heating coil connected to a terminal of the heating coil, a capacitor connected between both terminals of the heating coil, a switching element connected from both ends of the heating coil to the other terminal of the power supply circuit, and a control circuit. As a result, the center terminal of the heating coil can be eliminated. Therefore, the structure of the heating coil becomes simple, and the number of man-hours during assembly can be reduced, making it possible to provide a low-cost induction heating cooker.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an induction heating cooker according to an embodiment of the present invention;
Figure 2 is an operational waveform diagram of the induction heating cooker shown in Figure 1.
Figure 3 is a circuit diagram of a conventional induction heating cooker;
FIG. 4 is an operational waveform diagram of the induction heating cooker shown in FIG. 3. 11... DC power supply, 12... Current limiting coil, 13... Power supply circuit, 14... Heating coil, 15... Capacitor, 16...
- Switching element, 17... Switching element, 18... Control circuit. Name of agent: Patent attorney Toshio Nakao and one other person U-
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4 Figure

Claims (2)

[Claims] (1) A power supply circuit configured by connecting a DC power supply and a current limiting coil in series, a heating coil whose one terminal is connected to one terminal of the power supply circuit, and a capacitor connected between both terminals of the heating coil. , an induction heating cooker comprising switching elements connected from both ends of the heating coil to the other terminal of the power supply circuit, and a control circuit. (2) The induction heating cooker according to claim 1, wherein the switching element is a reverse conduction type switching element, and the control circuit drives the switching element at a frequency lower than the resonance frequency of the heating coil and the capacitor.