JPH1168498A - Impedance transformation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impedance transformation circuit with reduced heat generation by connecting to supply a larger amount of current to a braided wire of a coaxial cable of its winding. SOLUTION: In an impedance transformation circuit, transformers T10, T20, T30 are used of impedance transformation to constitute coils at a primary side and a secondary side of a core wire and the braided wire respectively. Coils L12, L21, L32 at a side to which larger amount of the current is supplied are constituted by the braided wire of the coaxial cable, while coils L11, L22, L31 at the side to which smaller amount of the current is supplied are constituted by the core wire of the coaxial cable respectively. Thus larger amount of the current is supplied to the braided wire with larger current capacity and heat generation is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impedance conversion circuit using an impedance conversion transformer that forms a primary coil and a secondary coil with a core wire and a braided wire of a coaxial cable.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional impedance conversion circuit for this type of high-frequency power, and is a connection diagram for explaining in principle the method of connecting an impedance conversion transformer in the impedance conversion circuit. This impedance conversion circuit includes transformers T1, T2, and T3 for converting 12.5Ω to 50Ω. The transformer T1 includes a primary coil L11 and a secondary coil L12, the transformer T2 includes a primary coil L21 and a secondary coil L22, and the transformer T3 includes a primary coil L31. Secondary coil L3
And 2. Since 250 volts is applied to the 12.5Ω side of this impedance conversion circuit, the coils L11, L12, L21, L22, L3
1, L32 have currents of 1.97 A and 2.59, respectively.
A, 2.59A, 2.27A, 1.97A, 2.27A
Only flows.

FIG. 3 shows a conventional example in which the impedance conversion circuit of FIG. 2 is assembled with an actual transformer. Here, the transformers T1, T2, T3 in FIG. 2 are replaced by transformers T11, T21, T
31, respectively. The coaxial cable has a structure in which a core wire as a circular inner conductor and a braided wire as an outer conductor are concentrically insulated and arranged. In the transformer T11, the primary coil L11 is formed of a core wire of a coaxial cable, and the secondary coil L12 is formed of a braided wire. In the transformer T21, the primary coil L21 is formed of a core wire, and the secondary coil L22 is formed of a braided wire. In the transformer T31,
The primary coil L31 is composed of a core wire, and the secondary coil L31
32 is configured with a braided wire.

[0004]

In the above-described method of connecting the impedance conversion transformer in the conventional impedance conversion circuit, when the coil winding uses a coaxial cable as shown in FIG. Although the braided wire of the cable has a larger current capacity (cross-sectional area) than the core wire, this is not carefully considered for the current flowing through each coil.

For example, in the transformer T21 shown in FIG.
2.59A flows through the primary coil L21, 2.27A flows through the secondary coil L22, and the primary coil L2
Although the current flowing through 1 is larger than that of the secondary coil L22, the core side is used for the primary coil L21, and the braided wire side is used for the secondary coil L22. As a result, the conventional impedance conversion circuit easily generates heat, and causes problems such as dielectric breakdown.

In order to solve the above problems, the present invention solves the above problems by providing a primary side and a secondary side of a transformer in an impedance converter.
The purpose is to provide an impedance conversion circuit that generates less heat from the transformer by carefully considering the current flowing in the secondary coil and connecting it so that more current flows to the braided wire of the coaxial cable used for the transformer winding. And

[0007]

According to a first aspect of the present invention, a primary coil and a secondary coil are formed by a first conductive wire and a second conductive wire having different current capacities. In the impedance conversion circuit using the impedance conversion transformers respectively constituting the first and second coils, of the primary side coil and the secondary side coil of the impedance conversion transformer, the coil on the side where more current flows flows through the first side coil and the first side coil.
The conductive wire and the second conductive wire described above are characterized in that the coil having the larger current capacity and the coil having the smaller current capacity are formed by the coil having the smaller current capacity.

[0008] A second invention is an impedance conversion circuit using an impedance conversion transformer that forms a primary coil and a secondary coil with a core wire and a braided wire of a coaxial cable, respectively. Of the primary and secondary coils of the transformer,
The coil on the side where more current flows is constituted by the braided wire of the coaxial cable, and the coil on the side where less current flows is constituted by the core wire of the coaxial cable.

Further, according to a third aspect of the present invention, the primary coil and the secondary coil of the impedance transforming transformer are formed of a core wire or a braided wire of the coaxial cable depending on the magnitude of current flowing therethrough. , At least in transformers for impedance conversion which are considered to generate heat to an undesirable extent.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of an impedance conversion circuit according to the present invention. The impedance conversion circuit is realized using three transformers in which each coil is a core wire or a braided wire of a coaxial cable. The structure of the first, second, and third transformers used in the impedance conversion circuit of FIG. 1 is substantially the same as the structure of the three transformers used in the impedance conversion circuit of FIG. , 1st, 2nd, 3rd
The currents flowing through the primary and secondary coils of each of the three transformers are the same as those shown in FIG.

Referring to FIG. 1, a first transformer T10
, The primary coil L11 is formed of a core wire of a coaxial cable, one end is connected to an input terminal IN, the secondary coil L12 is formed of a braided wire of a coaxial cable, and one end is connected to ground. . In the second transformer T20, the primary coil L21 is formed of a braided wire of a coaxial cable, and one end is connected to the input terminal IN and the other end is connected to the other end of the secondary coil L12 of the first transformer T10. Each is connected, and the secondary coil L12 is formed of a core wire of a coaxial cable, and one end is connected to the ground.
Further, in the third transformer T30, the primary coil L31 is formed of a core wire of a coaxial cable, and one end is connected to the other end of the primary coil L11 of the first transformer T10, and the other end is connected to the output terminal OUT. The secondary coil L32 is formed of a braided wire of a coaxial cable, and has one end connected to the other end of the secondary coil of the second transformer T20 and the other end connected to the ground.

Therefore, in the primary side coil L11 and the secondary side coil L12 of the first transformer T10, more current (2.59A from FIG. 2) flows through the secondary side coil L12, so that the primary side coil L12 The core wire of the coaxial cable is used for L11, and the braided wire of the coaxial cable is suitably used for the secondary coil L12. Similarly, in the primary coil L21 and the secondary coil L22 of the second transformer T20, more current (2.59
Since A) flows, a braided wire of a coaxial cable is used for the primary coil L21 and a core wire of the coaxial cable is used for the secondary coil L22 (as opposed to the conventional example of FIG. 3). Primary coils L31 and L31 of the third transformer T30
With the secondary side coil L32, more current (2.27A) flows through the secondary side coil L32.
31 is a core wire of a coaxial cable, and the secondary coil L
32, a braided coaxial cable is used.

As described above, the first, second, and third transformers T1 used in the impedance conversion circuit of FIG.
Regarding the primary coil and the secondary coil of 0, T20, and T30, it is checked which coil passes more current, and the coil of the coaxial cable which is a winding is connected to the side where more current flows. The braided wire side with large current capacity is used. Therefore, these transformers T1
In the coils 0, T20 and T30, the generation of heat by the flowing current is kept to a minimum.

In the above example, the currents flowing through the primary coil and the secondary coil are both small.
The above considerations may not be necessary for transformers that cannot generate heat using either side of the core wire. Further, in the above-described example, the winding constituting the transformer is a coaxial cable. However, the present invention is not limited to this. The windings of the primary coil and the secondary coil of the transformer have different current capacities. It goes without saying that the above-described principle is also applied to a case where two kinds of wires are used.

[0015]

As described in detail above, the impedance conversion circuit according to the first aspect of the present invention has the first
The primary coil and the second conductive wire,
In an impedance conversion circuit using an impedance conversion transformer constituting each of the secondary coils, the primary coil and the secondary coil of the impedance conversion transformer are connected to the coil on the side where more current flows through the second coil. Of the first conductive wire and the second conductive wire, a coil having a larger current capacity and a coil having a smaller current capacity are formed on the side having a smaller current capacity, so that the coil of the transformer can be formed. The generation of heat by the flowing current is kept to a minimum, and there is an effect that the adverse effect of the generated heat can be prevented.

Further, the second invention is a typical case in which the first and second conductive wires are each constituted by a core wire and a braided wire of a coaxial cable, and is similar to the first invention. It works. Further, the third aspect of the present invention has an effect that the contents of the second aspect of the present invention are always implemented only in necessary transformers, and the other transformers are appropriately implemented in accordance with actual conditions, so that the implementation is easy.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing an embodiment of an impedance conversion circuit according to the present invention using three transformers in which the winding of each coil is a core wire or a braided wire of a coaxial cable.

FIG. 2 is a connection diagram for describing in principle the method of connecting an impedance conversion transformer in the impedance conversion circuit.

FIG. 3 is a connection diagram showing a conventional example in which the impedance conversion circuit of FIG. 2 is assembled with an actual transformer.

[Explanation of symbols]

 T10, T20, T30 Transformers L11, L21, L31 Primary coil L12, L22, L32 Secondary coil IN input terminal OUT output terminal

Claims (3)

[Claims] A first conductive wire and a second conductive wire having different current capacities;
An impedance conversion circuit using an impedance conversion transformer that forms a primary side coil and a secondary side coil with the conductive wires described above, wherein the primary side coil and the secondary side coil of the impedance conversion transformer are connected to each other.
Of the secondary coil, the coil on the side where the current flows more is the coil on the side with the larger current capacity between the first conductive wire and the second conductive wire and the coil on the side where the current flows less. An impedance conversion circuit comprising a circuit having the smaller current capacity. 2. A coaxial cable comprising a core wire and a braided wire.
In an impedance conversion circuit using an impedance conversion transformer constituting a secondary coil and a secondary coil, respectively, a primary coil and a secondary coil of the impedance conversion transformer are connected.
An impedance conversion circuit characterized in that, of the secondary coil, the coil on the side through which more current flows is constituted by the braided wire of the coaxial cable, and the coil on the side on which less current flows is constituted by the core wire of the coaxial cable. 3. The transformer for impedance conversion according to claim 1, wherein:
Whether the secondary coil and the secondary coil are constituted by the core wire or the braided wire of the coaxial cable according to the magnitude of the current flowing therethrough is at least implemented in an impedance conversion transformer which is considered to generate heat to an undesirable extent. 3. The impedance conversion circuit according to claim 2, wherein: