JPS63186410A - Power transformer - Google Patents

Abstract

PURPOSE:To make it possible to control the ON-OFF switching of high pressure output independent of a low pressure output by controlling a primary input by a method wherein a core, which forms two sets of closed magnetic circuits in which a leg part becomes magnetic circuit, is provided and the reluctance of the core part constituting one closed magnetic circuit of the two sets of closed magnetic circuits to be formed on the core is made smaller in size than that of the closed magnetic circuit. CONSTITUTION:A core 5 has two sets of closed magnetic circuits, namely, a closed magnetic circuit Ma of low reluctance having the center leg part 5b as a common magnetic circuit and containing one external leg part 5a, and another closed magnetic circuit Mc of high reluctance having the center leg part 5b as a common magnetic circuit and containing other external leg part 5c. When only the control switching means 2 on the low voltage side is turned ON, low voltage output only is generated, and when the control switch means 3 on the high voltage side is turned ON, high voltage output is generated. Accordingly, the high voltage output can be ON-OFF controlled independent of the low voltage output by performing an ON-OFF switching of the control switch means 3 on the primary input side of the transformer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a power transformer that is mainly installed in a power supply device of a plain paper copying machine (RPC) and generates a low voltage output and a high voltage output.

<Prior Art> The power supply device in the copying machine described above supplies high voltage output to the photosensitive drum and low voltage output to other sequence circuits, and the high voltage output is turned on independently of the low voltage output. - Can be controlled to turn off. This is because if high pressure is continuously applied to the photosensitive drum, the photosensitive drum deteriorates, so high pressure is applied only when necessary to prevent this deterioration.

<Problems to be Solved by the Invention> By the way, in the above power supply device, in order to control the high voltage output on the output side, a switch means that can withstand use at high voltage is required. It is difficult to control the high voltage output at the input end, and it is actually desirable to control the high voltage output at the input end.

Therefore, in conventional power supplies, dedicated transformers are prepared for low voltage and high voltage, and the primary input to each transformer is controlled so that low voltage output and high voltage output are generated in the required order. was.

However, according to such a configuration, the power supply device has two
Since it has a transformer and two circuits, the configuration is complicated.
It had the disadvantage of high cost.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to simplify the circuit configuration of a power supply device and reduce its cost.

The inventor of the present invention believes that the reason why the conventional power supply device has no choice but to adopt the above configuration is that all the secondary terminals are connected simultaneously to the input to the primary side. We believe that there is a problem with the configuration of the transformer itself where the output appears, and by making improvements to the configuration of the transformer itself, by controlling the primary input in a single transformer, low voltage output and high voltage can be generated in the required order on the secondary side. The above objective was achieved by generating an output.

That is, in order to achieve the above object, the present invention provides a power transformer having at least three legs,
A core is provided that forms two sets of closed magnetic paths in which at least one of the legs forms a common magnetic path, and one of the two sets of closed magnetic paths formed in the core is formed. The magnetic resistance of the core portion is made smaller than that of the other, and the magnetic resistance of the core portion on the other closed magnetic path side is made larger than the one. The primary coil and the secondary coil are respectively a low-voltage primary coil and a low-voltage secondary coil for extracting low-voltage output, and a high-voltage primary coil and a high-voltage secondary coil for extracting high-voltage output, respectively. configure,
A core that forms a closed magnetic path with high magnetic resistance by winding a low voltage side primary coil and a low voltage side secondary coil around a portion of the core portion that forms the closed magnetic path with low magnetic resistance that is not the common magnetic path. A high voltage side primary coil and a high voltage side secondary coil are wound around a portion of the portion that is not the common magnetic path.

<Operation> According to the above configuration, when the low voltage side primary coil is energized,
Magnetic flux is generated along a closed magnetic path with low magnetic resistance, and an electromotive force is induced in the low-voltage side secondary coil.

At this time, since almost no magnetic flux passes through the coil portion wound around the closed magnetic path with high magnetic resistance, almost no electromotive force is induced in the high-voltage side secondary coil on this closed magnetic path.

Next, when the high-voltage side primary coil is energized, magnetic flux is generated along the closed magnetic path with high magnetic resistance, which causes the high-voltage side
Next, an electromotive force is induced in the coil.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 is a block diagram of a power supply device equipped with a power transformer according to the present invention, and this power supply device consists of a single 1! The power transformer 1 includes a source transformer 1, two control switch means 2.3 corresponding to a low voltage output and a high voltage output, and a switching circuit 4.

The core 5 of the transformer 1 is made of a magnetic material such as ferrite, and has three legs 5 a, 5 b, and 5 c,
They are integrally formed with each other by connecting portions 5 d and 5 e. That is, the core 5 is formed by, for example, a pair of E-shaped cores butted against each other.

Among the leg portions 5 a, 5 b, and 5 c, a thin spacer (not shown) is interposed between the abutting surfaces of the E-shaped cores to form gaps 6 a, 5 b in the leg portions 5 a, 5 b.
6b is formed. Further, the remaining leg portion 5c is provided with the leg portion 5a.

A gap 6 larger than the gaps 6a and 6b is formed by interposing a spacer (not shown) that is thicker than the spacer 5b.
c is formed.

With this configuration, the core 5 has the central leg 5b as a common magnetic path, and a closed magnetic path Ma with low magnetic resistance including one of the outer legs 5a and the central leg 5b as a common magnetic path. It has two sets of closed magnetic circuits, including a closed magnetic circuit Mc having a large magnetic resistance and including the other outer leg portion 5c.

On the other hand, the primary coil of the power transformer 1 consists of a low voltage side primary coil 712 and a high voltage side primary coil 7h, and the low voltage side primary coil 7a forms a closed magnetic path with low magnetic resistance of the core 5. The high-voltage side primary coil 7h is wound around the outer leg 5C of the core 5, which forms a closed magnetic path with high magnetic resistance of the core 5. . The low-voltage side primary coil 7g and the high-voltage side primary coil 7h are connected to the DC power source 8 via the control switch means 2.3 so that they are connected in parallel to each other when the switching circuit 4 is on. , and both primary coils 7Q, 7h are wound so that the magnetic fluxes generated thereby and passing through the central leg portion 5b are in the same direction. Further, a low voltage side secondary coil 912 is wound around the leg portion 5a around which the low voltage side primary coil 7Q of the core 5 is wound, and a low voltage side secondary coil 912 is wound around the leg portion 5c around which the high voltage side primary coil 7h is wound.
A high voltage side secondary coil 9h is wound.

The switching circuit 4 consists of a switching transistor IO whose emitter is connected to ground potential, a damper diode 11 and a resonant capacitor 12 connected between its collector and emitter, and a pulse wave of a predetermined frequency is applied to the base of the switching transistor 10. It is supposed to be done.

In the above configuration, when the switching circuit 4 is operating and the control switch means 2 is turned on, an intermittent current flows through the low voltage side primary coil 7Q, and this current causes the coil 7Q to be wound. Magnetic flux is generated in the leg portion 5a. This magnetic flux hardly passes through the leg portion 5c, which forms a closed magnetic path Mc with a large magnetic resistance, but passes through the central leg portion 5b, which forms a part of a closed magnetic path Ma with a small magnetic resistance.

As a result, an electromotive force is induced in the low voltage side secondary coil 9Q, and a low voltage output is generated.

Next, when the control switch means 3 is turned on, the high voltage side 1
An intermittent current flows through the next coil 7h, and magnetic flux is generated in the leg portion 5C. This magnetic flux does not pass much through the leg portion 5a located away from the leg portion 5c, and instead passes through the closed magnetic path M with high magnetic resistance.
through the central leg 5b forming part of c. As a result, an electromotive force is also induced in the high voltage side secondary coil 9h, and a high voltage output is generated.

In this way, when only the low voltage side control switch means 2 is turned on, only a low voltage output is generated, and when the high voltage side control switch means 3 is turned on, a high voltage output is generated. Therefore, by switching the control switch means 3 on/off on the primary input side of the transformer I,
The high pressure output can be controlled on and off independently of the low pressure output.

Note that in the above embodiment, gaps 6 a, 6 b,
Although we have shown the case where the magnetic resistance is set by changing the size of 6 c, it is also possible to adjust the magnetic resistance by configuring a part of the core 5 with a material that has a different magnetic permeability from the other parts. However, the means for adjusting the magnetic resistance is not limited to those in the embodiment.

In addition, the primary coils 7 Q, 7 h and the secondary coil 9 Q
, 9h means the core leg 5a as shown in FIG.
, 5c may be stacked inside and outside and wound.
As shown in the figure, the core legs 5 a and 5 c may be wound in parallel in the longitudinal direction.

Furthermore, the core 5 has E as shown in FIGS. 1 and 2.
In addition to the shape of the core, as shown in FIG. 3, an E-shaped core 5E and a single-shaped core 5■ may be combined, or a shape with two central legs 5b may be used. In short, the core 5 has at least three legs 5a,
Any shape having 5 b and 5 c may be used.

<Effects of the Invention> As described above, according to the present invention, by controlling the primary input, it is possible to turn on and off the high voltage output independently of the low voltage output, and by controlling the input side, the copying machine It is possible to supply the required low voltage output and high voltage output to power consuming parts such as the main body.

Therefore, a single transformer is required for the power supply, and the power supply can have one transformer and one circuit configuration, which simplifies the circuit configuration and significantly reduces costs compared to conventional power supplies. reduction is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a power supply device using a power transformer according to one embodiment of the present invention, and FIGS. 2 and 3 are block diagrams showing other embodiments of the power transformer. l...Power transformer, 2.3...Control switch means, 5...Core, 5a, 5b, 5c...
Legs, 7Q...low voltage side primary coil, 7h...high voltage side primary coil, 9Q...low voltage side secondary coil, 9h...
High voltage side secondary coil, Ma, Mc...closed magnetic circuit.

Claims (1)

[Claims] (1) A power transformer that generates low voltage output and high voltage output, and has at least three legs, at least one of which
It is equipped with a core that forms two sets of closed magnetic paths in which the legs of the book serve as a common magnetic path, and the magnetic resistance of the core part that forms one of the two sets of closed magnetic paths formed in the core is The magnetic resistance of the core portion on the other closed magnetic path side is made smaller than the other, and the magnetic resistance of the core portion on the other closed magnetic path side is made larger than that of the one, and the primary coil is composed of a low voltage side primary coil and a high voltage side primary coil that can be energized separately. , the secondary coil is composed of a low-voltage side secondary coil and a high-voltage side secondary coil, and the low-voltage side primary coil and the low-voltage side are arranged in a part of the core part forming the closed magnetic path with low magnetic resistance that is not the common magnetic path. A high-voltage side primary coil and a high-voltage side secondary coil are wound around a portion of the core that forms the closed magnetic path with high magnetic resistance that is not the common magnetic path. A transformer for power supply.