JPH02121292A - Magnetron driving apparatus - Google Patents

Abstract

PURPOSE:To enable obtaining a large output from the title apparatus without enlarging the cross-sectional area of each core by winding a primary coil round a magnetism leaking means in such a manner as packaging the magnetism leaking means therein and yet winding secondary coils in lots round positions facing each other with this primary coil in between. CONSTITUTION:A step-up transformer 55 has a pair of E-shaped cores 31, 32 formed of a ferrite core, etc., between which a gap AG forming a magnetism leaking means is provided. A primary winding portion for winding a primary coil 55a with this gap AG as the center of the primary coil is set up, while secondary winding portions for winding secondary coil 55b in lots across to the respective cores 31, 32 with the primary coil 55a between are provided. Accordingly, the density of magnetic flux in the respective cores 31, 32 is set up on almost equal terms with each other. Thus, high output can be obtained from the title apparatus without enlarging the cross-sectional area of each of the cores.

Description

Detailed Description of the Invention [Objective of the Invention 1 (Field of Industrial Application) The present invention relates to a magnetron drive device for high-frequency heating devices such as microwave ovens, and particularly to a magnetron drive device for reducing the size and weight of the magnetron drive device. This invention relates to a magnetro drive device that achieves high output.

(Prior Art) In recent years, various microwave ovens have been proposed that drive a magnetron and heat an object by irradiating the object with microwaves emitted from the magnetron. .

FIG. 4 is an overall configuration diagram of a conventional microwave oven.

A commercial power source 1 is connected to a rectifier stack 2.

This rectifier stack 2 is composed of four bridge-connected diodes, and when the commercial power supply 1 is input, full-wave rectification η is performed. The rectifier stack 2 is connected to a smoothing circuit 4A. This smoothing circuit 4A is composed of a choke coil 3 and a smoothing capacitor 4, and smoothes the pulsating current that has been full-wave rectified by the rectifier stack 2. Smoothing circuit 4A
The positive side of is connected to one end of the primary winding 55a of the step-up transformer 55, and the other end of the primary winding 655a is connected to the negative side of the smoothing circuit 4A via the resonance capacitor 6. This primary winding 55a and the resonance capacitor 6 constitute a series resonance circuit.

A freewheeling diode 7 and a transistor 8 are connected in parallel to this resonance capacitor 6. The base of the transistor 8 is connected to the l11wJ circuit 9, and the transistor 8 repeatedly turns on and off based on the pulse signal from the control circuit 9. These series resonant circuits and the freewheeling diode 7 , transistor 8, and control circuit 9 constitute a quasi-E class inverter circuit.

The secondary winding 55b of the step-up transformer 55 is the voltage doubler rectifier circuit 1
Connected to 1A. This double voltage! The I-stream four circuit 1A is composed of a rectifier diode 10 and a charging capacitor 11. The positive output of this voltage doubler rectifier circuit 11A is connected to the anode AD of the magnetron 12, and
The negative side is connected to the filament F of the magnetron 12. Further, the filament F of the magnetron 12 is connected to the heater winding 55c of the step-up transformer 55, and a predetermined heating voltage is input thereto.

Next, the operation of the magnetron driven IJI device shown in FIG. 4 will be explained. First, the commercial power source 1 is full-wave rectified by the rectifier stack 2, smoothed by the smoothing circuit 4A, converted into a predetermined DC power source, and output to the primary winding 55a. Further, when the transistor 8 repeats on and off operations based on the pulse signal from the control circuit 9, the primary winding 55a
A high frequency current flows through the primary winding 1!558, and a high frequency magnetic field is generated in the primary winding 1!558. A high frequency electromotive force is induced in the secondary winding 55b by this high frequency magnetic field, and is boosted to, for example, a DC voltage of '100 OV by the voltage doubler rectifier circuit 11A.

This boosted DC voltage is applied to the anode AD of the magnetron 12. Further, the filament F of the magnetron 12 is supplied with a predetermined heating voltage, for example 4V, from a heater winding 55c. When the heating voltage is supplied to the filament F in this manner, thermoelectrons are emitted from the filament F toward the anode AD. At this time, these thermionic electrons perform a swirling motion in a static magnetic field created by a magnet (not shown), resonate, and output microwaves. In this manner, the object to be heated is heated by irradiating the object with high frequency waves, that is, microwaves, emitted from the magnetron 12.

FIG. 5 is a sectional view of the step-up transformer 55 shown in FIG. 4.

As shown in FIG. 5, the step-up transformer 55 has a pair of cores 13
1 and 133. The core 133 has a bobbin 14
3, a primary winding 55a is wound therebetween. Further, a secondary winding 55b and a heater winding 55c are wound around the core 131 via a bobbin 141. Furthermore, a pair of cores 13
A gap AG is interposed between 1 and 133.

Therefore, the magnetic flux generated in the primary winding 55a is transferred to the secondary winding 55b.
and heater winding JI! 55c, and induces a high frequency electromotive force in each winding according to the number of windings.

By the way, in the example shown in FIG. 5, since the secondary winding 55b and the heater winding 55c are wound around one core 131, the joint between the secondary winding 55b and the heater winding 55c is set tightly. Ru. Furthermore, since the gap AG is interposed between the pair of cores 131 and 133, magnetic flux leaks in this gap AG. As a result, the primary volume a55a
The magnetic flux density in the core 133 around which is wound becomes high.

When the magnetic flux density in the core 133 reaches the saturation magnetic flux density, the inductance of the primary winding 55a decreases rapidly.
A large current flows to this primary winding 1155a, and the transistor 8
Tai! ! There was a fear that this would happen.

In order to prevent saturation of the magnetic flux in the core 133 around which the primary winding 55a is wound, it is conceivable to set the cross-sectional area of the core 133 to be large.

However, if the cross-sectional area of the core 133 is set to be large, the step-up transformer 55 becomes large, resulting in an increase in the size of the bundled microwave oven.

Then, as shown in FIG. 6, the primary winding 55a is wound around the gap AG to set a large magnetic resistance.
A device that prevents magnetic flux saturation has been proposed.

That is, the primary winding 55a is wound around the gap AG provided between the pair of E-type cores 135 and 137. In addition, the core 135 has a long winding portion 135a for winding each winding, and the winding portion 135a is long.
A secondary winding 55b and a heater winding 55c are wound around the bobbin 145.

(Problem to be Solved by the Invention) However, in the example shown in FIG.
5 and 137 become asymmetrical, making it necessary to use two types of cores with different shapes.

For this reason, two types of molds must be provided when manufacturing the cores 135 and 137, and the length of the core legs becomes long, resulting in poor manufacturing yields and increased costs.

Further, the magnetic flux generated from the primary winding 55a generates a back electromotive force in the primary winding 55b, and the magnetic flux generated by this back electromotive force acts so as not to cancel the magnetic flux from the primary winding 55a. However, since there is a gap AG between the pair of cores 135 and 137, core 137
In this case, it is difficult to be affected by the magnetic flux in the opposite direction from the secondary winding 55b described above. Therefore, whether or not the magnetic flux in the step-up transformer 55 is saturated is determined by the core 137.

The present invention has been made in view of the above, and is a transformer that prevents the saturation of magnetic flux in the core of a step-up transformer and can obtain a large output without increasing the shape of the step-up transformer, that is, the cross-sectional area of the step-up transformer. The purpose of the present invention is to provide a magnetron drive device using a magnetron drive device.

[Structure of the Invention] (Means for Solving the Problems) The means provided by the present invention to achieve the above object is to input high frequency power converted and outputted by a frequency converter to the primary winding of a transformer, and to convert the high frequency power into the primary winding of the transformer. In a magnetron drive device that rectifies high-voltage power output from a secondary winding of a transformer and supplies it to an anode of a magnetron, a magnetic path C is formed by the primary winding and secondary winding of the transformer. A leakage means for increasing the leakage flux of the magnetic path is provided, and the primary winding is wound so as to incorporate this leakage means, and the secondary winding is placed at a position facing the primary winding. It was constructed by dividing and winding.

(Function) The present invention inputs the high frequency power converted and outputted by the frequency converter into the primary winding of the transformer, rectifies the high voltage power output from the secondary winding of the transformer, and supplies it to the anode of the magnetron. supply Further, a magnetic leakage means for increasing leakage magnetic flux of the magnetic path is provided in the magnetic path formed by the primary winding and the secondary winding of the transformer. In addition, the primary winding is wound so as to incorporate this magnetic leakage means, and the secondary winding is divided and wound at opposite positions sandwiching the primary winding, so that the magnetic flux density in each core is reduced. set almost evenly.

(Example) Hereinafter, an example according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a four-voltage transformer used in a magnetron drive device. The magnetron drive device using the 4-voltage transformer 55 shown in FIG. 1 is the same as that shown in FIG. 4, and detailed explanation will be omitted.

The ascending transformer 55 is an E formed from a ferrite core or the like.
It has a pair of cores 31 and 32 of the mold. The pair of cores 31 and 32 are formed in symmetrical shapes. Further, a gap AG is provided between the pair of cores 31 and 32 as a leakage means. This gap AG is maintained at a constant distance between the cores 31 and 32 by interposing a spacer or the like between the pair of cores 31 and 32, for example.

A primary winding portion is set for winding the primary winding 55a around this gap AG. 1, that is, the primary winding 55a through the bobbin 42 so as to include the gap AG.
is rolled around.

In addition, each core 3 is
A secondary winding section is provided for winding the secondary winding 55b around the windings 1 and 32 in minutes vlL. To be more specific, a secondary winding 55b is connected to the back of the core 31 via a bobbin 41.
is wound, and a secondary winding 55b is wound symmetrically to the inner part of the core 32 via a bobbin 43. Further, the bobbin 41 is provided with a partition wall 41a, and the portion insulated by the partition wall 41a, that is, the bobbin 41
A heater winding 55c is wound around the upper part of the heater.

As described above, the secondary winding 55b is divided and wound around both cores 31 and 32, and the secondary winding 55b of each divided core is connected in series.

Further, a partition wall 41a is provided on the bobbin 41 provided in the core 31, and a secondary winding 55h and a heater winding 55C are respectively wound thereon. The coupling coefficient is set to be large.

Next, the action will be explained.

Based on the pulse signal from the control circuit 9, the transistor 8
When the on/off operation is repeated, a magnetic flux is generated by the high frequency current flowing through the primary winding 55a. This primary winding 5
The magnetic flux generated from 5a passes through the core 31 to the secondary winding 55.
b and the heater winding 55C. At the same time, the magnetic flux generated from the primary winding 55a passes through the core 32 and intersects with the secondary winding 55b.

At this time, since the primary winding 55a is wound around the center of both cores so as to include the gap AG provided between the cores 31 and 32, the magnetic flux density due to the magnetic flux generated from the secondary winding 55a is The cores 31 and 32 are set almost uniformly.

In addition, in the secondary winding 55b and the heater winding 1155c wound around the core 31, a back electromotive force is generated depending on the number of windings in each due to the magnetic flux from the primary winding 55a, and this back electromotive force causes a current to flow. As a result, magnetic flux is generated in a direction that cancels the magnetic flux from the primary winding 1m55a described above.

Similarly, in the secondary winding 55t) wound around the core 32, magnetic flux is generated in a direction that cancels the magnetic flux from the primary winding 55a described above.

Therefore, the magnetic flux passing through the core 31 is the value obtained by subtracting the magnetic flux generated by the secondary winding 55b and the heater winding 55C from the magnetic flux caused by the primary winding 55a.Similarly, the magnetic flux passing through the core 32 is the value obtained by subtracting the magnetic flux generated by the secondary winding 55b and the heater winding 55C from the magnetic flux caused by the primary winding 1m55a. Secondary winding 55b
This is the value obtained by subtracting the magnetic flux in the opposite direction generated by .

Further, the power output from the heater winding 55c is transferred to the secondary winding 5.
Since it is about 1/20 of the electric power output from the heater winding 55b, the influence of the magnetic flux caused by the heater winding 55c is slight.

Therefore, since the magnetic flux densities in each of the cores 31 and 32 are set to be equal, a large current can be passed through the primary winding 11A55a without the magnetic flux becoming saturated.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the example shown in FIG. 2, C4 cores 34 and 35 are used.
It is characterized by having completed M.

A gap AG is provided between the pair of cores 34 and 35, and the primary winding 55a is wound around the bobbin 45 so as to include this gap AG. Further, the core 34 is connected to the secondary winding 551) and the heater winding 5 via the bobbin 44.
It is wrapped around 5c.

A secondary winding 5 is connected to the other core 35 via a bobbin 46.
5b is wound around.

Next, a further embodiment of the present invention will be described with reference to FIG.

The example shown in FIG. 3 is characterized in that the secondary winding 551) and the heater winding 55c are wound separately around both of the pair of cores 37 and 38, respectively.

The primary winding 55a is wound so as to include a gap AG set between the pair of cores 37 and 38. Also"
A secondary winding 55b and a heater winding 55c are wound around the coil 737 via the bobbin 47, respectively. Similarly, a secondary winding 55b and a heater winding 55c are wound around the core 38 via a bobbin 49.

In the secondary winding 55a and the heater winding 55c, which are thus divided and wound around the cores 37 and 38, the windings of the respective cores are connected in series.

As described above, the secondary winding 55b and the heater winding 55C are symmetrically divided and wound around the pair of cores 37 and 38,
The magnetic flux densities in cores 37 and 38 can further be set to be equal to 2.

In the embodiment described above, the divided secondary windings are connected in series, but they may be connected in parallel.

Note that the transformer used in the tc example mentioned above is the 7
The present invention is not limited to the gnotron drive device, but can be applied to any appropriate device.

[Effects of the Invention] As explained above, according to the present invention, since the magnetic flux densities in each of the pair of cores are set uniformly, a large current can be passed through the primary winding. , a correspondingly large output can be obtained from the secondary winding.

Furthermore, since high output can be obtained without increasing the cross-sectional area of the core, the transformer can be made smaller and lighter, and the cost of the magnetron drive device can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an embodiment of the present invention, Fig. 2 is a cross-sectional view showing an embodiment of the messenger according to the present invention, and Fig. 3 is a cross-sectional view showing an embodiment of the messenger according to the present invention. 4 is a general configuration diagram of a magnetron drive device, FIG. 5 is a sectional view showing a conventional example, and FIG. 6 is a sectional view showing another conventional example. 55a...Primary winding 55b...Secondary winding 31
．． 32, 34.35.37.38...Core AG...
gap

Claims (1)

[Claims] High-frequency power converted and output by a frequency converter is input to the primary winding of a transformer, and high-voltage power output from the secondary winding of the transformer is rectified and supplied to the anode of the magnetron. In the magnetron drive device, a magnetic leakage means for increasing leakage magnetic flux of the magnetic path is provided in the magnetic path formed by the primary winding and the secondary winding of the transformer, and the magnetic leakage means is installed internally. A magnetron drive device characterized in that the primary winding is wound in such a manner that the secondary winding is divided and wound at opposing positions sandwiching the primary winding.