JPH0142324Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a transformer used in a double-tuned circuit such as a television tuner. The aim is to provide a transformer that can be easily adjusted.

Fig. 1 shows an intermediate frequency output circuit of a tuner employing a transformer according to the present invention, in which capacitors 2 and 6 are connected to the collector of a mixer transistor 1, a primary coil 3 is connected in series to the primary coil 3, and The connected coupling coil 5 forms a primary side tuned circuit tuned to the intermediate frequency, and the capacitors 7 and 1
0, 2 tuned to the intermediate frequency with the secondary coil 8
The primary side tuned circuit and the secondary side tuned circuit are inductively coupled to form a double tuned circuit. Note that 11 is an intermediate frequency output terminal.

Figure 2 shows the chassis 12 of the transformer according to the present invention.
FIG. 2 is a diagram showing a state in which the transformer is attached to a transformer according to the present invention, and the structure of the transformer according to the present invention will be described below based on FIG. 2.

In FIG. 2, the primary coil 3 is wound on the right end of the bobbin 13, the secondary coil 8 is wound on the left end of the bobbin 13 at an arbitrary distance from the primary coil 3, and the Between the coil 3 and the secondary coil 8,
Coupling coil 5 connected in series to primary coil 3
It is wrapped in The coupling coil 5 is an extension of one end of the primary coil 3, has an inner diameter slightly larger than the outer diameter of the bobbin 13, and is wound loosely around the bobbin 13 several times. It can move along the bobbin 13 between the primary coil 3 and the secondary coil 8. Inside the bobbin 13, a core 4 corresponding to the primary coil 3 and a core 9 corresponding to the secondary coil 8 are provided so as to be connected to the inner wall of the bobbin 13. As shown in FIG. 3, which is a side view of the cores 4 and 9 seen from the left side of the chassis 12, a groove 18 is provided at the end of the core 4 into which the tip of an adjustment tool can be inserted. is the groove 1 provided in the core 4
For example, a through hole 19 in the shape of a hexagonal column is provided.

In addition, in FIG. 2, 14 is a shield plate provided on the chassis 12, 15 is a terminal for connecting the secondary coil 9 and the capacitors 7 and 10, and 16 is a coupling terminal to which the capacitor 6 is connected. It is a terminal of the coil 5, and 17 is a terminal to which the transistor 1 and the capacitor 2 are connected.

Adjustment in this transformer is performed as follows. First, the adjusting tool is passed from the outside of the chassis 12 through the through hole 19 of the core 9 and inserted into the groove 18 of the core 4, and the core 4 is rotated and moved from side to side in FIG. , and tune the primary side tuning circuit to the intermediate frequency. Next, for example, by rotating the core 9 with a hexagonal wrench-shaped adjustment tool, the
Tunes the next-side tuning circuit to the intermediate frequency. Finally, the coupling coil 5 is moved left and right along the bobbin 13 using tweezers or the like to bring it closer to or away from the secondary coil 8, so that the primary side tuning circuit and the secondary side tuning circuit can achieve a predetermined bandwidth. Stop it at a position where you can obtain the desired bond.

Note that by moving the coupling coil 5, the tuning frequency of the primary side tuned circuit changes, but since the coupling coil 5 has a small number of turns and does not have a core, the primary side coil 3 The inductance is sufficiently small compared to the inductance, and fluctuations in the tuning frequency of the primary side tuning circuit are within a range that does not cause any practical problems. Further, the coupling coil 5 may be connected in series to the secondary coil 8 instead of the primary coil 3.

As mentioned above, the transformer according to the present invention has a simple structure in which the coupling coil 5 is provided between the primary coil 3 and the secondary coil 8. Since it is wound around the bobbin with an inner diameter larger than the diameter, it can be moved along the bobbin, and since it does not have a core, the inductance is small.

In other words, the transformer of the present invention can be manufactured at low cost, and the degree of coupling can be adjusted sufficiently without affecting the tuning frequency in practice.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram employing an embodiment of the present invention, FIG. 2 is a front view showing the embodiment of the present invention, and FIG. 3 is a side view of the same. 3... Primary side coil, 4, 9... Core, 5...
Coupling coil, 8...Secondary coil, 13...Bobbin, 18...Groove, 19...Through hole.

Claims (1)

[Claims for Utility Model Registration] A primary coil and a secondary coil are wound on one bobbin with a distance between them, and a core is provided for adjusting the inductance of the primary coil and the secondary coil. In a transformer configured to be provided inside the bobbin to correspond to both coils, the transformer is connected in series to either one of the primary coil and the secondary coil, and the primary coil and the secondary coil are connected in series. A transformer comprising a coupling coil movably wound around the bobbin with an inner diameter larger than an outer diameter of the bobbin in the middle of the coil, and having no core for adjusting inductance.