JPH04258106A - Power supply transformer device - Google Patents

Abstract

PURPOSE:To provide for a power supply transformer device which can be produced easily, at a low cost, and with an improved noise-elimination effect. CONSTITUTION:In a power supply transformer device where a primary coil winding NP and a secondary coil winding N2 are wound around a core 2, a bifilar coil winding 3 is provided between layers of the primary coil winding NP and the secondary coil winding N2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transformer device, and more particularly to a power transformer device having excellent noise blocking characteristics.

0002

2. Description of the Related Art Generally, DC voltage is switched by switching elements such as transistors, stepped up and down by a power transformer, and rectified again to convert it into DC voltage, which is then used as a power source for circuits in electronic equipment. Most of the power transformer devices used in this type of power supply device are constructed by winding a primary coil through a bobbin around a ferrite core called an EI or EE core, and then winding a secondary coil and a control coil. Conventionally, as a method of reducing noise that enters from the primary side to the secondary side, a shield plate (foil plate) is inserted between the layers of the primary winding and secondary winding of a power transformer, and Faraday shielding is performed. A method called shielding is used.

0003

[Problems to be Solved by the Invention] In the conventional electrostatic shield using the shield plate described above, it is difficult to wrap the thin shield plate between layers and solder the lead wires, which makes it difficult to manufacture the transformer. There was a problem that the number of man-hours increased and the cost increased. Therefore, in order to solve the above problem, a coil winding was used instead of a shield plate, and 1
Next, a method of reducing costs by winding the secondary winding between layers is considered, but there remains the problem that it may not be effective depending on the winding specifications.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a power transformer device that is easy to manufacture, can be obtained at low cost, and has a good noise removal effect. It is said that

[0005]

[Means for Solving the Problems and Effects] A power transformer device of the present invention includes a primary winding and a secondary winding wound around a core, wherein the primary winding and the secondary winding A bifilar winding is provided between the layers. In this power transformer device, the electrostatic shield is a wire-wound shield, so it is easy to manufacture, and the shield winding is a bifilar winding, so the voltage generated in each coil is reversed and leaks current through the line capacitance. By canceling out the flowing noise components, excellent noise blocking characteristics are achieved.

[0006]

[Examples] The present invention will be explained in more detail with reference to Examples below. FIG. 1 is a connection diagram of a power transformer device showing one embodiment of the present invention. This power transformer device 1 includes primary windings NP, NP' and secondary windings N2, N3.
A control winding NB is wound around a ferrite core 2, and a bifilar winding, which is a feature of the present invention, is installed between the primary windings NP and NP' and the secondary windings N2 and N3. A winding shield 3 is provided.

The structure of this power transformer device 1 is as shown in FIG. ,
N3, the primary winding NP', and the control winding NB are wound in this order. Note that the primary windings NP and NP' are 2
It has a sandwich winding structure with the next windings N2 and N3 sandwiched therebetween. Also, between the primary winding NP and the secondary winding N2, 2
A bifilar shield winding 3 is wound between the secondary winding N3 and the primary winding NP'.

As shown in FIG. 3, the bifilar shield winding 3 is triple-layered by winding a polyester tape 5a around the primary winding NP, winding the bifilar windings 3a and 3b, and then winding polyester tapes 5b and 5c. The insulation of the primary and secondary windings is strengthened by wrapping them with polyester tape. One end A1 of bifilar windings 3a and 3b
, B1 are connected to a portion of the power transformer where the voltage does not change on the primary side as shown in FIG. 5, and the other ends A2 and B2 are each left open.

Switching noise generated in the primary winding NP (NP') flows into the line capacitance CS with the bifilar shield winding 3 as a leakage current. At this time, since the bifilar windings 3a and 3b are grounded,
Noise leakage to the secondary winding N2 (N3) is reduced. Further, at this time, a voltage proportional to the number of turns is induced at the open ends A2 and B2, but since the voltages are the same and opposite in each winding, they cancel each other out and have no effect on the secondary winding.

Next, FIGS. 6 to 11 show a comparison of the noise terminal voltages of the power transformer device of the above embodiment, a power transformer having a conventional configuration, and a power transformer device provided with a Faraday shield. Figure 6 shows the 0 to 2 MHz characteristics of the above embodiment, that is, when the bifilar shield winding 3 shown in Figure 3 is used, and Figure 7 shows the 0 to 30 MHz characteristics in the same case.
z characteristics, Figure 8 shows the 0 to 2 MHz characteristics with just a polyester tape wrapped between the primary and secondary windings, Figure 9 shows the 0 to 30 MHz characteristics in the same case, and Figure 10 shows the Faraday shield using a thin metal plate. Characteristics from 0 to 2 MHz when
1 is a characteristic of 0 to 30 MHz.

[0011] As is clear from these characteristic diagrams, the power transformer according to the embodiment of the present invention can attenuate the noise level between 100 KHz and 15 MHz compared to the conventional power transformer, and the Faraday shield by the thin metal plate has been removed. Results similar to Kotata transformer can be obtained.

0012

According to the present invention, common mode noise can be attenuated and blocked without using a line bypass capacitor, and the primary and secondary circuits can be completely insulated, so there is no risk of electric shock. In addition, unlike the Faraday shield, there is no increase in cost due to the increase in man-hours during transformer manufacturing, and since it can be done with normal transformer manufacturing man-hours, the effect of noise reduction can be obtained with almost no increase in cost.

[Brief explanation of the drawing]

FIG. 1 is a winding connection diagram of a power transformer device according to an embodiment of the present invention.

FIG. 2 is a partial structural sectional view of the power transformer device of the same embodiment.

FIG. 3 is an explanatory diagram of a bifilar shield winding of the power transformer device of the same embodiment.

FIG. 4 is a circuit diagram for explaining the noise removal operation of the power transformer of the same embodiment.

FIG. 5 is a connection diagram of the bifilar shield winding of the power transformer of the same embodiment.

FIG. 6 is a diagram showing the noise voltage characteristics of the power transformer device of the same embodiment at 0 to 2 MHz.

FIG. 7 is a diagram showing the noise voltage characteristics of the power transformer device of the same embodiment in the frequency range of 0 to 30 MHz.

FIG. 8 is a diagram showing noise voltage characteristics of a conventional power transformer from 0 to 2 MHz.

FIG. 9 is a diagram showing the noise voltage characteristics of the same power transformer from 0 to 30 MHz.

[Figure 10] Zero of power transformer with Faraday shield
It is a figure which shows the noise voltage characteristic of -2MHz.

FIG. 11 is a diagram showing the noise voltage characteristics of the same power transformer from 0 to 30 MHz.

[Explanation of symbols]

NP/NP’ Primary winding N2/N3 Secondary winding 2 Core 3 Bifilar shield winding

Claims (1)

[Claims] 1. A power transformer device comprising a primary winding and a secondary winding wound around a core, wherein a bifilar winding is provided between the layers of the primary winding and the secondary winding. Characteristic power transformer device.