JP2674107B2 - High voltage transformer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a high voltage transformer for converting high frequency power obtained by an inverter circuit into high voltage. In particular, the present invention relates to a core in which a gap is provided to reduce the coupling between the primary winding and the secondary winding.

2. Description of the Related Art A conventional high-voltage transformer of this type is devised to reduce the distributed capacitance between lines and the loss due to high frequencies by dividing the secondary winding. As an example thereof, FIG. 5 shows an example of a high voltage transformer for driving a magnetron. As shown in FIG. 5, the primary winding 2 is wound around the primary bobbin 1,
The secondary winding 4 and the tertiary winding 5 are wound around the secondary bobbin 3, and the gaps 8, 9 are formed in the magnetic path formed by the cores 6, 7.
Is provided. The secondary winding 4 has a divided structure and is wound by dividing the winding wire in each of the divided grooves to reduce the loss and secure the withstand voltage as described above. That is, the voltage generated in the secondary winding 4 is divided for each division groove. The gap 9 is provided to reduce the coupling coefficient between the primary winding 2 and the secondary winding 4 in order to reduce the influence of load fluctuations on the secondary side. It is provided between.

However, in the configuration in which the split windings are almost evenly formed as in the conventional example, there is a problem that the characteristics of the split windings 4a, 4b, 4c, 4d, 4e are different. That is, the gap 9
Since the magnetic permeability of the divided winding 4a closer to the magnetic field is reduced, the inductance is smaller than that of the divided winding 4e separated from the gap 9. Therefore, the inductance of each divided winding is different, and the voltage generated in each is also different. For this reason, the reliability of the split winding 4e, which generates the highest voltage, is reduced. Furthermore, in order to ensure the reliability as a whole, an excessive breakdown voltage structure has to be taken.

Means for Solving the Problems In order to solve the above problems, the high-voltage transformer of the present invention is
The secondary winding has a split structure, and each split winding has a configuration in which the number of windings increases as the gap of the core becomes closer.

Effect The present invention prevents the inductance of each of the divided secondary windings from changing due to the positional relationship with the core gap. Therefore, since the voltage induced in each winding can be made substantially equal, insulation measures for the winding can be made uniform and easy, and a partial decrease in reliability can be prevented.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a high voltage transformer for driving a magnetron. In FIG. 1, the same components as those in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, the secondary winding 120 is divided and wound around the secondary bobbin 3. As for the divided winding (divided winding), the winding 10a is closest to the gap 9 of the core.
The windings are farthest in the order of b, 10c, and 10d, and the winding 10e is farthest. The number of turns of each of the divided windings 10a, 10b, 10c, 10d, and 10e is na,
If nb, nc, nd, and ne, the size relationship is na>nb> nc
It is set to have the relationship of ＞ nd ＞ ne ＞. That is, the number of turns is increased as the divided winding is closer to the gap 9. Since FIG. 1 shows a case where the divided windings have the same winding width, the number of windings is increased as the divided winding is closer to the gap 9. Since FIG. 1 shows the case where the winding widths of the respective divided windings are the same, the number of windings increases as the distance to the gap 9 increases, so that the winding height increases. This is such that the inductances of the respective divided windings are substantially the same, and the windings are increased until the inductance of the windings close to the gap 9 decreases due to the lowering of the magnetic susceptibility. As a result, the voltages induced in the respective divided windings become substantially equal, and the withstand voltage design of each winding can be performed on the same basis, which facilitates the design and improves the reliability.

FIG. 2 shows an embodiment of the drive circuit for the high voltage transformer shown in FIG. In FIG. 2, the power of the commercial power supply 11 is rectified by the diode bridge 12 to form a unidirectional power supply. Reference numeral 13 is an inductor, and 14 is a capacitor, which serves as a filter for high-frequency switching operation.

The inverter circuit 15 is a resonance capacitor 16 and a step-up transformer.
It includes a transistor 17, a transistor 18, a diode 19, and a drive circuit 20. The transistor 18 performs a switching operation with a predetermined cycle and duty (that is, on / off time ratio) by the base current supplied from the drive circuit 20.
As a result, the current Ic / Id as shown in FIG. 3A, that is, the collector current Ic of the transistor 18 and the current Id of the diode 19 are obtained.
Flows. On the other hand, when the transistor 18 is off, the resonance of the capacitor 16 and the primary winding 2 causes a voltage Vce as shown in FIG. Therefore, a current as shown in FIG. 3 (c) flows through the primary winding 2,
High frequency power is generated at both ends of the primary winding 2. Therefore,
High frequency power and high frequency low voltage power are generated in the secondary winding 10 and the tertiary winding 5, respectively. This high frequency high voltage power is a capacitor
It is rectified by the diode 21 and the diode 22, and is supplied between the anode and cathode of the magnetron 23, while high-frequency low-voltage power is supplied to the cathode and the heater. Therefore, the magnetron 23 oscillates.

FIG. 4 shows another embodiment of the high voltage transformer of the present invention.
4, the same components as those in FIG. 1 are designated by the same reference numerals. The primary winding 2 and the secondary winding 10 have a core gap 8,
As the structure is wound on top of 9, the winding positions are separated and the coupling is lowered by the gap. In the secondary winding 10, the split winding 10a close to the gap 9
The number of windings is larger than that of the divided windings 10b and 10c farther from, so that the inductances of the secondary divided windings are substantially the same. As a result, the voltage induced in each split winding is made substantially the same, and the reliability is improved.

Effects of the Invention As described above, according to the high voltage transformer of the present invention, the following effects are obtained.

(1) Since the secondary winding is divided into windings and the number of windings of each divided winding is increased as it approaches the gap of the core, the voltage induced in each divided winding is made uniform and reliability is improved. improves.

(2) Since the voltage of each split winding can be made substantially the same, the breakdown voltage design can be made the same for each secondary split winding, and the design can be easily optimized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a high voltage transformer according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of a magnetron power feeding device using the high voltage transformer of the present invention, and FIG. 3 is an operation waveform of the circuit of FIG. FIG. 4 is a sectional view of a high voltage transformer of another embodiment of the present invention, and FIG. 5 is a sectional view of a conventional high voltage transformer. 2 ... Primary winding, 6,7 ... Core, 8,9 ... Gap, 10 ...
… Secondary winding, 10a, 10b, 10c, 10d, 10e …… Split winding, 15…
… Inverter circuit, 17 …… High voltage transformer.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuho Sakamoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Takashi Niwa 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Haruo Suenaga 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References: Kaihei 2-2817 (JP, U)

Claims (1)

(57) [Claims] 1. A secondary winding comprising: a primary winding; a secondary winding; and a core having a gap in a magnetic path for reducing a coupling coefficient between the primary winding and the secondary winding. A high-voltage transformer in which the wire has a split winding structure, and the number of split windings of the split winding structure is larger as the split winding is closer to the core gap.