JPH0357190A - High frequency heating device - Google Patents

Abstract

PURPOSE:To prevent saturation of a core, and to downsize the core by providing gaps on a lower core of a primary winding. CONSTITUTION:A pressure rise transformer is formed out of a core 3 made of ferrite, etc., a primary winding 4, a secondary winding 5, and gaps 1, 2. The primary winding 4 is wound in a line, while on a lower core 3 of the primary winding 4, gaps 1 are provided. On the core on the side winding is not wound, a gap 2 is provided. To the lower core of the primary winding 4, a magnetic flux is focused and the core is easy to saturate. By providing the gaps 1 on the lower core of the primary winding 4, magnetic flux generated by each wire of the primary winding 4 is equally regulated, and the saturation thereof can thus be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-frequency heating device equipped with a so-called inverter circuit. BACKGROUND OF THE INVENTION A step-up transformer of a conventional high-frequency heating device I will be explained below with reference to the drawings. Figure 2 is a sectional view showing the structure of a conventional step-up transformer. In the same figure, the step-up transformer is in the middle 7'l, 2,
Core 3 made of magnetic material, primary winding wire 4, secondary winding wire 5
The gap l is to prevent magnetic saturation of the core 3,
One is provided below the primary winding 4. Further, the other gap 2 is provided on the core on the side where the winding is not wound. For the primary winding &iI4, Linz wire is used to reduce high frequency loss. First roll! The number of turns of 114 is 2 o turns or more, and it is wound in about 5 layers. A voltage of approximately 500V at the peak value is applied to the primary winding 4. Therefore, a maximum potential difference of about 170V occurs between adjacent wires. FIG. 3 is a circuit diagram showing the circuit configuration of a conventional high-frequency heating device. In the same figure, the commercial power 'a9 is connected to the rectifier lO
The current is converted into direct current by the converter 11, and is applied to an inverter circuit consisting of a resonant circuit of a capacitor 11 and an inductor l2, a transistor l3, and a control circuit 14 that controls the transistor l3. The inverter circuit converts direct current into alternating current at a resonant frequency determined by the resonant circuit by switching the transistor l3, and outputs the alternating current. The output of the inverter circuit is boosted by a step-up transformer 15 to generate a high voltage. The high voltage is converted into a DC high voltage by a half-wave voltage doubler rectifier circuit consisting of a capacitor 16 and a diode 17, and then the magnetron 1
Applied to 8. The magnetron 18 generates microwaves, which are guided to an oven of a high-frequency heating device, and are irradiated onto food in the oven to heat and cook the food. The inductor l2 of the resonant circuit is shared with the primary winding 4 of the step-up transformer 15. Therefore, the resonant frequency of the resonant circuit is determined by the inductance of the primary winding ls4 of the step-up transformer 15 and the capacitance of the capacitor 1l. Problems to be Solved by the Invention The step-up transformers of conventional high-frequency heating devices have been large and expensive. For this reason, it was necessary to make the step-up transformer smaller and cheaper. In order to downsize a step-up transformer, it is necessary to reduce the inductance of the resonant circuit, that is, the inductance of the primary winding of the step-up transformer, and the capacitance of the capacitor to increase the resonant frequency.

Reducing the inductance of the primary winding of the step-up transformer reduces the number of turns of the primary winding, and when wires are wound in layers, the potential difference that occurs between the overlapping wires becomes extremely large, causing corona and damaging the wire's insulation coating. This will significantly shorten the lifespan. For this reason, when winding the wires in the primary winding in a single row instead of overlapping them, the conventional method of creating a gap below the primary winding would not allow each wire in the primary winding to There was a tJIM in which it was impossible to reduce the cross-sectional area of the core, making it impossible to make the step-up transformer smaller and lighter, because the generated magnetic flux could not be evenly restricted and the core would easily become saturated. ! ! Means for Solving Fl The present invention has been made in consideration of this problem, and the step-up transformer of the present invention comprises a plurality of windings and a core made of a magnetic material such as ferrite, and The windings are wound on the core, and a plurality of gaps are provided in the core below the primary winding among the plurality of windings. Furthermore, the sizes of the plurality of gaps provided in the core below the primary winding are made to differ depending on the degree of aggregation of magnetic flux in the core. According to the present invention, in order to downsize the step-up transformer, the number of turns of wire in the primary winding is reduced, the inductance is reduced, and the potential difference generated between adjacent wires in the primary winding is reduced. Even if the wire is wound in a row, by providing a plurality of gaps in the core below the primary winding, saturation of the core can be prevented, the core can be made smaller and lighter, and the wire can have corona. This has the effect of making it possible to realize a highly reliable, low-cost step-up transformer that does not occur. EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing the structure of a step-up transformer that is an embodiment of the present invention. In the same figure, the step-up transformer is
A core 3 made of ferrite or the like, a primary winding 4, a secondary winding 5, and a gap l2 are arranged, and the primary winding 4 is wound in a row, and the core 3 below the primary winding 4 has
Multiple gaps l are provided. Furthermore, a gaff 2 is also provided on the core on the side where no wire is wound.

The circuit width of the high-frequency heating device of the present invention is the same as the circuit width of the conventional high-frequency heating device in FIG. 3, so its explanation will be omitted here. Invention tries to solve! !
As mentioned in the title, in order to downsize the step-up transformer, it is sufficient to reduce the inductance of the primary winding 4. To do this, the number of turns of the primary winding 4 can be reduced and the resonant frequency of the resonant circuit can be increased. Bye. For example, if the resonance frequency is 100 kHz or more, the number of turns of the primary winding 4 will be about 9 turns.

The primary winding 4 generates magnetic flux, and this magnetic flux interlinks with the secondary winding 5, thereby transmitting energy. The magnetic flux generated by the primary winding 4 is divided into magnetic flux 6 that passes through the core 3 and interlinks with the secondary winding 5, and magnetic flux 6 that does not pass through the core 3 but connects the secondary winding 5.
It consists of a magnetic flux 7 that interlinks with the secondary winding vA5, and a magnetic flux 8 that does not interlink with the secondary winding vA5. Magnetic flux concentrates in the core below the primary winding vA4, making it easy for the core to become saturated. For this reason,
By providing the gap 1 in the core below the primary winding 14, the magnetic flux passing through the core can be restricted and saturation can be prevented.

However, the gap 1 in the core below the primary winding 14
If there is only one location, the magnetic flux generated by the primary winding 4 near the gap can be restricted, but the magnetic flux generated by the primary winding 4 far from the gap cannot be restricted. In particular, when the primary winding 4 is wound in a row, the winding becomes long in the vertical direction, and the primary winding 8
! If there is only one gap in the lower core of the primary winding 4, the magnetic flux generated by each wire of the primary winding 4 cannot be restricted.

Therefore, by providing a plurality of gaps l in the lower core of the primary winding 4 as shown in Fig. 1 (in the figure, gaps 1 are provided at three locations), each wire of the primary winding 4 is The generated magnetic flux can be equally limited. Furthermore, since the magnetic flux tends to concentrate near the center of the primary winding 4 wound in a row in the vertical direction, as shown in FIG. By making the gamb larger than the primary winding 4
The magnetic flux created by each wire can be more evenly restricted.

In this way, by providing a plurality of gambles l in the lower core of the primary winding 4, the primary winding 4 is wound in a row < t*
However, saturation of core 3 can be prevented, core 3 can be made smaller, and a low-cost step-up transformer can be realized. Effects of the invention (1) The step-up transformer directly connected to high-frequency heating equipment of the present invention has the following features:
It consists of a plurality of windings and a core made of a magnetic material such as ferrite, and the plurality of windings are wound on the core, and among the plurality of windings, a core below the primary winding is wound. By creating multiple gaps,
Since the magnetic flux created by each wire of the primary winding can be equally restricted, saturation of the core can be prevented, the core can be made smaller and lighter, and the method of winding the tvA of the primary winding in a single row can be Because it can reduce the potential difference that occurs between adjacent wires of the primary winding, corona does not occur in tvA, and it has the effect of realizing a highly reliable, compact, and low-cost step-up transformer. It is. (2) By making the multiple gaps provided in the lower core of one winding different in size, the magnetic flux created by each wire in the winding can be more evenly restricted, and the core Saturation can be more effectively prevented.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a step-up transformer that is an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the configuration of a conventional step-up transformer, and FIG. This is a circuit diagram.

Claims (2)

[Claims] (1) A DC power source obtained by rectifying a battery or commercial power source, a series resonant circuit consisting of a semiconductor switching element such as a transistor, a capacitor, and an inductor that converts the DC power source into a high-frequency power source, and the semiconductor switching element. and a step-up transformer that steps up the output of the inverter circuit, the step-up transformer comprising a plurality of windings and a core made of a magnetic material such as ferrite, The plurality of windings are wound on the core, and a plurality of gaps are provided in the core below one winding among the plurality of windings. (2) The high-frequency heating device according to claim 1, wherein the plurality of gaps provided in the lower core of one winding have different sizes.