JPH0238414Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an improvement of a current-controlled variable inductor used in an electronic tuning circuit such as a circuitr.

[Prior art and its problems]

FIG. 4 is an explanatory diagram of a current-controlled variable inductor to which the present invention is applied.
It has already been filed as No. 59-14822.

A control coil 2 is wound around the first core 1, and a second core 5 around which a tuning coil 4 is wound is inserted into a hollow portion 3 provided in the winding portion. Furthermore, the first core 1 is covered with a pot-shaped third core 6. 7 is a base on which the first core 1 and the second core 5 are placed and the third core 6 is fitted, and 8 is a terminal pin. Further, 14 is a tuning capacitor fixed to the base 7. The magnetic path by the control coil 2 mainly extends from the first core 1 to the third core 6 as represented by the dotted line 9,
Further, the magnetic path by the tuned coil 4 mainly extends from the second core 5 to the first core 1 as indicated by the dotted line 10, but both the magnetic paths 9 and 10 extend from the winding of the second core 5. The line portion 11 overlaps the most. and control coil 2
By changing the magnetic flux density, the effective magnetic permeability of the second core 5 can be controlled and the inductance of the tuned coil 4 can be changed.

In this current-controlled variable inductor, the magnetic path is not a completely closed magnetic path, but between the third core 6 and the lower flange 12 of the first core 1, and the lower flange 13 of the first core 1 and the second core 5. Since there is space between the two, variations in characteristics can be reduced.

Fig. 5 shows an equivalent circuit diagram of a current-controlled variable inductor surrounded by a dotted line together with a circuit for passing current through the control coil 2. It will be done.

Figure 1 shows the current I of the control coil 2 and the tuning coil 4.
This is an example of a characteristic diagram showing the relationship between the inductance L and the characteristic curve changes with temperature mainly due to the characteristics of the core. For example, if you are trying to get 150μH, 20mA at 25℃, 24mA at -20℃, and 24mA at 70℃
Then, if the current I changes to 16mA and you want to obtain 700μH, then at 25℃ it is 10mA, at -20℃ it is 12mA,
At 70℃, it changes to 8mA.

Although it is possible to reduce the variation in characteristics due to the structure, it is practically inconvenient to have to change the current I depending on the temperature in this way.

[Purpose of invention]

The purpose of the present invention is to automatically change the current flowing through the control coil in order to obtain a fixed inductance of the tuning coil by utilizing temperature changes in the resistance value of the control coil.

[Means for solving problems]

In the present invention, a hollow part is provided in the winding part of the first core, and the second core is inserted into the hollow part so that the winding part of the first core is provided with a hollow part.
The first core is inserted so that it is parallel to the winding part of the third core, and the first core is inserted into the pot-shaped third core so that its winding part is perpendicular to the bottom surface of the third core. A current-controlled variable type that is inserted, and the magnetic paths of the control coil wound on one of the first and second cores and the tuning coil wound on the other overlap at the winding part of the second core. The inductor is characterized in that the resistance of the control coil and the absolute value of the temperature change rate of the current flowing through the control coil are approximately the same in order to obtain a predetermined inductance of the tuning coil.

[Example of idea]

The following description will be given mainly with reference to FIGS. 2 and 3, which are characteristic diagrams of the current controlled variable inductor of the present invention. FIG. 2 shows the temperature change in the current I flowing through the control coil when the inductance L of the tuning coil is set to 150 μH and 700 μH, respectively, and FIG. 3 shows the temperature change in the resistance R of the control coil.

Figure 2 is a characteristic diagram obtained from Figure 1,
At 150μH, the temperature is -20℃ from 70℃ centering on the temperature of 25℃.
The current I changes from 16mA to 24mA in the range of °C. Also, at 700μH, 8mA to 16mA in the same temperature range
changes up to. The current I at 25℃ is 150μH.
In the case of 20mA and 700μH, it is 10mA. The temperature change rate ΔI/I of the current I is the same for 150 μH and 700 μH, and is expressed by equations (1) and (2), respectively.

△I/I=(16-24/20)/(70+20) =-0.0044...(1) △I/I=(8-12/10)/(70+20) =-0.0044...(2) The resistance R changes from 94Ω to 63Ω in the range from 70°C to -20°C with the temperature centered at 25°C. At 25℃ it is 78Ω. The temperature change rate ΔR/R of the resistance R is expressed by equation (3).

△R/R=(94-63/78)/(70+20) =0.0044...(3) The current-controlled variable inductor of the present invention has the temperature change rate △I/I of the current I of the control coil in the usage range. The absolute values of the temperature change rate ΔR/R of the resistor R and the temperature change rate ΔR/R are made almost equal.

In this state, if a constant voltage of 1.5V is applied to the connection point P in Figure 5, the inductance L will be 150μH.
When the temperature changes, the current I flows automatically according to the temperature change. Also, if the voltage is set to a constant voltage of 0.75V, the current I when the inductance L is set to 700μH can be automatically passed. There is no need to adjust the current I by changing the voltage at the connection point P. In order to increase the temperature change rate △R/R of the resistance, the wire diameter and number of turns of the control coil are adjusted.In addition to normal copper, nickel, iron, or Alloys thereof may also be used.

[Effect of idea]

As described above, the current-controlled variable inductor of the present invention automatically changes the current even when the ambient temperature changes by selecting the temperature change rate of the resistance of the control coil, so that the tuned coil always maintains a constant inductance. It is extremely practical as it can be obtained from

[Brief explanation of the drawing]

Figures 1, 2, and 3 are characteristic diagrams of the current-controlled variable inductor of the present invention, Figure 4 is an explanatory diagram of the current-controlled variable inductor that is the object of the present invention, and Figure 5
The figure shows an equivalent circuit diagram of FIG. 4 and a circuit diagram for passing a current through the control coil. 1...First core, 2...Control coil, 3...
Hollow part, 4... Tuning coil, 5... Second core,
6... Third core, 9, 10... Magnetic path, E... Power supply, P... Connection point.

Claims (1)

[Scope of utility model registration request] A hollow part is provided in the winding part of the first core, and a second core is inserted into the hollow part so that the winding part of the second core is parallel to the winding part of the first core, Further, the first core is inserted into the pot-shaped third core such that its winding portion is perpendicular to the bottom surface of the third core, and the first core is wound around one of the first core and the second core. In a current-controlled variable inductor in which the magnetic paths of a control coil that is turned and a tuning coil that is wound on the other side overlap at the winding part of the second core, in order to obtain a predetermined inductance for the resistance of the control coil and the tuning coil. 1. A current controlled variable inductor characterized in that the absolute values of the temperature change rates of the current flowing through the control coil are approximately the same.