JPH02312211A - Power source device for magnetron - Google Patents

Abstract

PURPOSE:To contrive prevention of thermal deformation of a cathode material by a method wherein a winding, which interlinks only with a part of the magnetic flux flowing to a yoke passing through the hole or the notch provided on the yoke, is provided and the output voltage of this winding is applied to the cathode of a magnetron. CONSTITUTION:A notch 1AA is provided on the yoke end part which comes in contact with the non-magnetic part crossing the magnetic circuit of a yoke 1A, and a cathode-heating wiring 4 is wound around the above-mentioned notch 1AA. Accordingly, if the distance (x) between the notch 1AA and the outside surface of the yoke is reduced, the winding 4 also becomes small, its area can be reduced, and by properly selecting the area, optical heating voltage can be supplied to the cathode of a magnetron 12. As a result, the heating temperature of the cathode of the magnetron 12 is brought to an appropriate one, the life of electron emission is prolonged, the thermal deformation of the cathode is suppressed, and the generation of characteristic fluctuation can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply device for a magnetron that is capable of applying an appropriate voltage to the cathode of a magnetron.

[Conventional technology] After rectifying power from a commercial AC power source, it is converted to a frequency higher than the commercial frequency by a switching circuit and input to the primary winding of a transformer, and the high voltage obtained from the secondary line is rectified. The so-called inverter-type magnetron power supply device, which applies voltage to the anode of the magnetron, has a high frequency, so the transformer can be made small and lightweight, and it is relatively easy to output over a wide range.
In recent years, it has begun to be widely used in household microwave ovens, etc., as it can be used for various purposes (Japanese Unexamined Patent Publication No. 60-250588).
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Figure 2 shows an example of this type of power supply device.In Figure 1, 1 is a transformer, 2 is a primary winding of the transformer, 3 is a booster secondary winding that serves as the magnetron's anode power source, and 4 is a magnetron's secondary winding. A low-voltage secondary winding serving as a cathode power supply, 5 a switching circuit, 6 a rectifier circuit, 7 a commercial AC power supply, 9 a capacitor forming a voltage doubler rectifier circuit for supplying DC high voltage to the anode of the magnetron; 10 is a rectifier diode of the voltage doubler rectifier circuit.

11 is a diode that smooths the voltage waveform applied to the magnetron and reduces charging and discharging of a capacitor of a noise prevention filter built into the magnetron to prevent overheating; 12 is a magnetron; The AC input from the commercial power supply g7 is once rectified at the rectifier port g6 and converted into a pulsating current, and then converted into AC at a frequency of about 20 to 100 kHz by the switching circuit 5, and then sent to the primary winding 2 of the transformer 1. is input. The output of the boosting secondary winding 3 of the transformer is applied as a high voltage pulsating current to the anode of the magnetron 12 by a capacitor 9 and a diode 10 forming a voltage doubler rectifier circuit, thereby driving the magnetron.

FIG. 3 is a diagram showing the main parts of the transformer 1, LA.

Each IB is a so-called EI type yoke made of soft ferrite, and constitutes a magnetic circuit. IC is York LA, I
A nonmagnetic insulating spacer sandwiched between the two yokes prevents magnetic saturation of the yokes by providing a nonmagnetic space between the two yokes.The sixth winding 2 is wound around the center leg of the yoke IA. A secondary winding 3 is wound on top of this winding. The cathode heating winding 4 is merely wound one turn around the right leg of the yoke IA. With this conventional structure, the frequency of the inverter system is hundreds of times higher than that of the commercial power supply, so
Both the amount of magnetic flux flowing through the yoke and the number of turns are significantly reduced.
- The number of turns of the next winding 2 is usually a little over 10 turns, and the voltage induced in the 9 windings 4 is actually the cathode heating voltage required by the cathode of the magnetron 12, for example 3
-4V, the cathode temperature became too high, causing major reliability problems such as thermal deformation of the cathode material.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems that conventionally occurred in inverter-type power supplies for magnetrons, and provides an inverter-type magnetron power supply device that can generate a voltage just suitable for j3Fm heating. The purpose is to provide.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, a through hole or notch is provided in the yoke through which the magnetic flux of the transformer of an inverter type power source for a magnetron flows. A winding was installed that passed through the gap and interlinked with only a portion of the magnetic flux flowing to the yoke, and the output voltage of this winding was applied to the cathode of the magnetron.

[Function] Assuming that the magnetic flux density in the yoke is 84, the area of the magnetic flux passing part in the winding is N, the number of turns of the A2 winding is N, and the electromotive force in M is e, as is well known, e = -N = -NA - raw sword - dt
dt becomes 0 In the present invention, since N is already 1 and cannot be reduced any further, it was decided to reduce the area A of the magnetic flux passing portion within one winding. If a hole or notch is placed at an appropriate position on the yoke, and one turn of winding is installed by passing the winding wire through this, depending on the position of the hole or notch,
The amount of magnetic flux interlinking with this winding can be adjusted arbitrarily.

[Embodiment FIG. 1(a) shows the main parts of a transformer according to an embodiment of the present invention.
A notch IAA is provided at the end of the yoke that is in contact with a non-magnetic portion that crosses the magnetic circuit of the yoke IA, and the cathode heating winding 4 is wound around this notch IAA. By reducing the distance X of the notch IAA from the outer surface of the yoke, the winding 4 will also become smaller, and the area A can be reduced. By appropriately selecting this area, the optimum heating voltage for the magnetron cathode can be achieved. can be supplied.

FIG. 1(b) shows the main parts of the transformer of the second embodiment.

In this embodiment, a notch for the cathode heating winding 4 is provided in the central leg of the E-shaped yoke IA. It is clear that any voltage can be induced.

FIG. 1(c) shows the main parts of the transformer of the third embodiment.

In this case, hole I drilled in the ferrite of E-type yoke IA.
A cathode heated masterpiece AlX4 is inserted into the AA. The winding is securely fixed, and even if mechanical force is applied, the winding will not be deformed and the output will not fluctuate.

FIG. 1(d) shows the main parts of the transformer of the fourth embodiment.

In this embodiment, a through hole IBA is provided in the ■-shaped yoke IB,
The cathode heating winding 4 is inserted through it.

This may be more convenient than the third embodiment due to reasons such as the location of the terminals.

[Effects of the Invention] As explained above, according to the present invention, the heating temperature of the magnetron cathode becomes appropriate, and the electron emission life becomes longer.
Effects such as thermal deformation of the cathode being suppressed and characteristic fluctuations no longer occurring can be obtained.

[Brief explanation of the drawing]

Figure 1 (a), (b), (c), (d)
are diagrams showing main parts of transformers of different embodiments of the present invention,
Figure 2 shows an overview of an inverter type magnetron power supply.
1 and 3 are diagrams showing essential parts of a transformer of a conventional inverter-type magnetron power supply device. 1... Transformer, 2... Primary winding of transformer, 3
... Secondary winding for boosting, 4... Secondary winding for low voltage,
5... Switching circuit, 6... Rectifier circuit,
7... Commercial AC power supply, 12... Magnetron, IA... E-type yoke, IB... Shaped yoke, IC... Spacer, IAA... Hole or notch drilled in E-type yoke . IBA...A hole drilled in the shaped yoke. Figure 1 + d)

Claims (1)

[Claims] 1. After rectifying the power from the commercial AC power supply, the switching circuit converts it to a higher frequency than the commercial frequency and inputs it to the primary winding of the transformer.The high voltage output from the secondary winding is then rectified and sent to the anode of the magnetron. In a magnetron power supply device that applies voltage to the yoke, a through hole or notch is provided in the yoke through which the magnetic flux of the transformer flows, and only a part of the magnetic flux flowing in the yoke passes through the hole or notch. A power supply device for a magnetron, characterized in that intersecting windings are installed and the output of the windings is used to heat a cathode of the magnetron.