JPS6133616Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a balanced unbalanced conversion transformer having at least two or more transformers.

As shown in FIG. 1, a conventional balanced-unbalanced transformer 100 includes a two-line type transformer 2 in which paired wires 22 are wound around a magnetic core 1 at a ratio of 1:1, a primary winding 3 and a secondary winding. The wires 4 are each composed of an insulated transformer 6 wound around a magnetic core 5, and the double line transformer 2 is connected to a balanced load side 7, and the insulated transformer 6 is connected to an unbalanced load side 8. are doing. In order to obtain good transmission characteristics in such a balanced unbalanced conversion transformer 100, the characteristic impedance of the double line type transformer 2 is
It is necessary that the value of Wb (Ω) be sufficiently close to the value of the balanced load 7. However, when the impedance of the balanced load 7 is high, for example 300Ω, it is very difficult to realize a double line transformer 2 having a Wb of 300Ω, and the transmission characteristics are significantly deteriorated.

The object of the present invention is to provide a balanced-unbalanced conversion transformer which eliminates the above-mentioned drawbacks.

Next, the present invention will be explained in detail with reference to the drawings.
FIG. 2 is a circuit diagram showing an embodiment of the present invention.
In the figure, the transformer of the present invention has a first winding 9 and a second winding 9.
A two-line transformer 11 having a turns ratio of 1:1 with the winding 10, a primary winding 12, and a secondary winding 13.
and an isolated transformer 15 having an electrostatic shield 14, and the isolated transformer 15 has a balanced load 16.
The two-line transformer 11 is connected to an unbalanced load 17, and the electrostatic shield 14 is connected to the end 18 of the second winding 10, and the beginning 19 of the second winding 10 is grounded.

Next, the operation of the transformer having such a configuration will be explained.
Generally, the impedance of unbalanced load 17 is 50Ω
Or since it is 75Ω, the double line type transformer 1 in this case
The characteristic impedance Wb of 1 may be 50Ω or 75Ω. This characteristic impedance is obtained by bifilar winding the first and second windings and 9, 10 using commercially available wires around a toroidal magnetic core.

Next, the amount of longitudinal current attenuation (20logE ₁ /E ₂ ) will be explained. In Fig. 2, the longitudinal current flowing from the midpoint 20 of the balanced load flows through the secondary winding 13 and the electrostatic shield 1.
It is printed on the end winding 18 of the second winding ₁₀ via a capacitance C 2S of 4. From this, the equivalent circuit for the longitudinal current in FIG. 2 can be written as shown in FIG. 3. Third
In the figure, i ₁ and i ₂ are the currents in each loop when a closed loop is taken as shown in the figure. Here, the first winding 9 and the second winding 10 are tightly coupled, that is, the inductance L of the first and second windings 9 and 10 is
Assuming that the mutual inductance M between the first and second windings 9 and 10 is equal, the voltages V _R and V ₂₃ generated in the load 17 and the resistor 23 due to i ₂ have the same magnitude and opposite directions. have. On the other hand, since the double line type transformer 9 has the property of outputting the input voltage as it is, the voltage across the resistor 23 is
V ₂₃ is output to the load 17 as is. Therefore,
Since the load 17 is applied with the voltage V _R and the voltage V ₂₃ with a different polarity from this, the combined voltage is zero. That is, the current i ₂ flowing through the load 17 becomes zero, and its longitudinal current attenuation becomes infinite. but,
Actually, since the stray capacitance and the coupling coefficient (M/L) are not 1, they are finite values.

Figure 4 shows a comparison of the characteristics of the transformer of the present invention and that of a conventional one, taking as an example a transformer with an impedance ratio of 75Ω (characteristic impedance of transformer 11):300Ω (impedance of balanced load 16). As shown in Fig. B, the mismatch attenuation is greatly improved in the transformer of the present invention. Also,
The longitudinal current decay is also improved as shown in curve A.

Here, the characteristics of each element of the transformer will be explained. The characteristic impedance Wb of the double line type transformer 11 is 75
Ω, and can be easily realized. Transformer 15
In this case, the balanced load impedance of the winding 13 is 300Ω, so the winding specifications are determined to be close to 300Ω. Similarly, the winding specifications for the winding 12 are set so that the characteristic impedance approaches 75Ω.

As described above, in the transformer of the present invention, a double line type transformer is installed on the unbalanced side, an insulation type transformer with electrostatic shielding is installed on the balanced side, and the longitudinal current is
Since it is configured to be applied to the grounded winding side of the strip line type transformer, both mismatch attenuation and longitudinal current attenuation are improved.

Note that the present invention is not limited to the above-described embodiments, and the turns ratio and magnetic core shape of the insulation type transformer can be changed arbitrarily, and as shown in FIG. A configuration may also be adopted in which a double line type transformer 21 is further connected between them.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional balanced/unbalanced conversion transformer, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
Figure 3 shows the special price circuit for the longitudinal current in Figure 2, and Figure 4.
The figure shows a comparison of characteristics between the transformer of the present invention and a conventional one, and FIG. 5 is a circuit diagram showing another embodiment of the present invention. In Figs. 1 to 5, 1, 5...Magnetic core, 2,9,21...Double line type transformer, 3,12...Primary winding, 4,13...Secondary winding, 6 , 15...Insulated transformer, 7, 16...
...Balanced load, 8,17...Unbalanced flat load, 9...
1st winding, 10...2nd winding, 14...static shielding, 18...end of winding, 19...beginning of winding, 20...
Midpoint.

Claims (1)

[Scope of utility model registration request] A balanced-unbalanced conversion transformer in which a two-line type transformer is provided on the unbalanced side and an insulating type transformer that is not magnetically coupled to this transformer is provided on the balanced side, the second line of the two-line type transformer being The beginning of the first winding is connected to an unbalanced load, the beginning of the second winding of the two-line transformer is grounded, and the end of the first winding is connected to the primary winding of the isolated transformer. and connecting the end of the second winding to the other end of the primary winding to provide electrostatic shielding between the primary and secondary windings of the isolated transformer; A balanced/unbalanced conversion transformer, characterized in that the electrostatic shielding means is connected to the end of the second winding.