JPH0745451A - Switching transformer - Google Patents

Abstract

PURPOSE:To reduce noise significantly by disposing electrostatic shield layers constituted of single layer of independent windings, connected respectively with live and nonlive parts, between the main constitutional parts of the primary and secondary windings constituting the live part and the nonlive part, respectively. CONSTITUTION:The high frequency switching transformer is constituted of the main constitutional parts 3, 4 of primary and secondary windings isolated from each other. Independent single layer electrostatic shield layers 5, 6, constituted of first and second windings, are interposed between the main constitutional parts 3, 4. The electrostatic shield layer 5 has one end 13 connected with the DC potential 7 on the primary of a power supply and the other open end 9. The second electrostatic shield layer 6 has one end 8 connected with a ground point 12 on the secondary of power supply and the other open end 10. Consequently, DC potential difference between the shield layers 5, 6 of winding is stabilized constantly to form an electrostatic shield between the primary and secondary windings 3, 4. This structure reduces asymmetrical component in the undesired radiation of power supply significantly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire wound type switching transformer with an electrostatic shield.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional example relating to the present invention is an electrostatic shield type switching transformer using a copper foil. Further, as described in JP-A-59-129571, noise is reduced by generating anti-phase noise voltages in a circuit and superposing them on each other. However, the circuit configuration is complicated.

[0003]

The problems of the prior art will be described by taking an electrostatic shield type switching transformer using copper foil as an example. A shield 1 made of copper foil connected to stable potential terminals on the primary side and the secondary side, respectively, is connected between the primary side and secondary side windings of the power source.

The electrical connection between the stable potential terminal and the copper foil is
It is soldering or electric welding 2. Therefore, the assembly of the transformer is a two-step process, and since work such as manual soldering is added, complete automation cannot be achieved. Therefore, the switching transformer with the electrostatic shield is expensive.

An object of the present invention is to provide an inexpensive switching transformer with an electrostatic shield which eliminates the above-mentioned drawbacks and does not provide a transformer structure which can be automatically assembled.

[0006]

In order to achieve the above-mentioned object, in the present invention, in a switching transformer which constitutes a switching element of a switching power supply circuit, a main component of a primary winding which constitutes a live part and a non-element Between the main constituent part of the secondary winding which constitutes the live part, an electrostatic shield formed by an independent single layer winding connected to the live part and the non-active part, respectively.
The rudder layer is provided.

[0007]

According to the present invention, the noise generated by the switching power supply, especially the asymmetrical noise component in the unnecessary radiation of the power supply, can be greatly reduced. As a result, the number of line filters used in the power supply filter circuit can be reduced. Further, since the electrostatic shield is composed of the winding wire, the transformer can be completely assembled automatically, and the electrostatic shield is composed of the winding wire, so that the transformer can be automatically assembled. -It is possible to reduce the cost of the switching transformer with a resistor.

[0008]

1 is a diagram showing the structure of a switching transformer as an embodiment of the present invention, and FIG. 2 is a waveform diagram showing the operation waveforms of the main parts in FIG.

In FIG. 1, the winding configuration of the present high frequency switching transformer has two configurations, a main configuration section 3 of a primary winding and a secondary side winding main configuration section 4, which are mutually separated. . In addition, between the main constituent part 3 of the primary winding and the main constituent part 4 of the secondary winding, an independent one-layer electrostatic shield composed of the first and second windings, respectively. Layers 5 and 6 are arranged respectively.

One end 13 of the first electrostatic shield layer 5 is connected to the DC potential 7 on the primary side of the power supply, and the other end 9 is open. Similarly, one end 8 of the second electrostatic shield layer 6 is also connected to the ground point 12 on the secondary side of the power supply, and the other end 10 is opened. Further, the high frequency induced voltages a and b generated at the open terminals 9 and 10 of the first and second electrostatic shields 5 and 6 composed of the windings are the reference values on the power source primary side or the power source secondary side. The connection polarity has a common-mode voltage with respect to the potential 12 (ground point). At this time, the number of turns n of the first and second electrostatic shields formed by the windings is the same, and the number of turns n is at least the number of turns n2 of the secondary winding. Further, the winding width 11 of the electrostatic shield is the same as the winding width of either the primary winding 3 or the secondary winding 4 of the power source, whichever has the larger winding width.

As a result, the electrostatic shields 5 and 6 are formed between the primary winding 5 and the secondary winding 4 by the windings. A high frequency voltage proportional to the number of turns is generated at the open terminals 9 and 10 of the electrostatic shield winding. As shown in Fig. 2, ground point 1
2, the induced voltages a and b of the open terminals 9 and 10 are
It is a rectangular wave voltage that is in phase and has the same peak value. As a result, the potential difference c between the winding shields 5 and 6 always maintains the DC stable potential, and the electrostatic shield between the primary winding 3 and the secondary winding 4 is maintained.
Forming a fold. Therefore, it is possible to significantly reduce the asymmetric component in the power source unnecessary radiation. This makes it possible to eliminate the line filter in the power supply filter circuit. In addition, since the electrostatic shield is composed of windings, the transformer can be fully assembled automatically, and the transformer with electrostatic shield can be assembled completely automatically. The cost of the transformer with electrostatic shield is low. Can be realized.

[0012]

According to the present invention, it is possible to provide a switching transformer with an electrostatic shield formed by windings only. Further, the transformer can be assembled only by a single winding work, and the automatic assembling can be performed, so that a low-cost switching transformer with an electrostatic shield can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is an operation waveform diagram of a main part in FIG.

FIG. 3 is a diagram showing an example of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrostatic shield by copper foil, 2 ... Soldering or electric welding point, 3 ... Main constituent part of primary winding, 4 ... Main constituent part of secondary winding, 5 ... 1st electrostatic shield -Shield part, 6 ... Second electrostatic shield part, 7 ... DC potential on primary side of power supply, 8 ... Second electrostatic shield
One end of the shield layer 6, 9 ... the other end of the first electrostatic shield layer 5,
10 ... One end of the second electrostatic shield layer 6, 11 ... Electrostatic shield
Winding layer width, 12 ... ground point (stable potential), 13 ... first
, One end of the electrostatic shield layer 5, n ... Number of turns, a ... Voltage of the open terminal 9 of the first electrostatic shield layer 5, a '... Voltage across both ends of the first electrostatic shield layer 5. , B ... voltage of the development terminal 10 of the second electrostatic shield layer 6, c ... potential difference between the first and second winding shields 5 and 6.

Claims (1)

[Claims] 1. In a switching power supply circuit which is mounted on a device, converts a commercial power supply into a stabilized DC power supply, and supplies electric power to a load, noise generated by a switching element which supplies electric power from the commercial power supply to the load is reduced. In addition to the winding for exchanging electric power, an electrostatic shield composed of only the winding is added to the switching transformer forming the switching element, in addition to the winding for transmitting and receiving electric power. Switching transformer.