JP2004063550A - Choke coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a choke coil in which no signal deteriorates. <P>SOLUTION: Coils 11 divided into three are wound on a ferrite core 10. Then, a resistor R1 is coupled to a first divided coil 11a in parallel and a resistor R2 to a third 11c in the same way. Consequently, no notch property appears within a signal band, and deterioration of the signal can be prevented. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a choke coil for passing a power supply current, and is suitably applied to a CATV system.
[0002]
[Prior art]
2. Description of the Related Art In a CATV system or the like, a power source of a device that consumes power is installed in a remote place, and power is supplied to the device by using a signal line that transmits a CATV signal. In this case, a device located between the power consuming device and the power supply needs to pass the power supply current. Taking the branching device that passes the power supply current as an example, the circuit of the branching device is configured as shown in FIG. In such a branching device, the CATV signal input to the input terminal IN is output to the output terminal OUT via the DC cut capacitors C1 and C2 connected in series. Further, a branch signal is output from the branch terminal BR via the DC cut capacitors C1 and C3 connected in series. Then, a current passing circuit 100 is connected between the input terminal IN and the output terminal OUT to pass a power supply current from the input terminal IN to the output terminal OUT or from the output terminal OUT to the input terminal IN. The current passing circuit 100 is generally realized by a choke coil.
[0003]
[Problems to be solved by the invention]
In recent years, the choke coil used as the current passing circuit 100 has been required to allow a large current to pass therethrough. If the choke coil is used beyond its rating, hum modulation interference will occur. When the current flowing through the choke coil increases, heat is generated in proportion to the square of the current value. When the temperature of the ferrite core in the choke coil exceeds the Curie point due to heat generation, the choke coil does not function as a choke coil. For this reason, it is necessary to make the winding of the choke coil thick and use a thick ferrite core. However, in this case, the contact between the windings and the proximity area are increased, so that the stray capacitance component increases. As a result, the self-resonance frequency tends to appear in a low frequency range. When the self-resonant frequency appears in a low frequency range, the isolation to the high-frequency circuit is deteriorated, and the high-frequency signal is attenuated, thereby giving an adverse effect such as level fluctuation and signal error.
[0004]
FIG. 5 shows an example of the configuration of a conventional choke coil.
The choke coil 101 shown in FIG. 5 is configured by winding a coil part 111 divided into two parts on a ferrite core 110. In this case, when 10 turns are required as the number of turns, the first split coil 111a has 6 turns, and the second split coil 111b has 4 turns. FIG. 7 shows the frequency characteristics of the insertion loss of the branching device shown in FIG. 4 when such a choke coil 101 is used as the current passing circuit 100 shown in FIG. Referring to FIG. 7, notch characteristics in which insertion loss increases around 330 MHz and 1300 MHz appear. In this case, 330 MHz is within the band, and in a transmission channel of a frequency band including 330 MHz, a level difference occurs in the same channel, and there is a possibility that image / audio deterioration and a signal error may occur. Although 1300 MHz is out of the band, the insertion loss is extremely increased.
[0005]
FIG. 6 shows an example of a conventional choke coil which solves such a problem.
The choke coil 101 shown in FIG. 6 is configured by winding a coil part 111 divided into two parts on a ferrite core 110. In this case, when 10 turns are required as the number of turns, the first split coil 111a has 6 turns, and the second split coil 111b has 4 turns. The resistor R100 is connected in parallel to the first split coil 111a. FIG. 8 shows the frequency characteristics of the insertion loss of the branching device shown in FIG. 4 when such a choke coil 101 is used as the current passing circuit 100 shown in FIG. Referring to FIG. 8, a notch characteristic in which the insertion loss increases around 330 MHz and 1300 MHz appears to a lesser extent. Therefore, in a transmission channel of a frequency band including 330 MHz, a level difference occurs in the same channel, and there is a possibility that image / voice deterioration and a signal error may occur.
[0006]
Therefore, an object of the present invention is to provide a choke coil in which a signal is not deteriorated.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the choke coil of the present invention, the coil is divided into a plurality of pieces and wound on a ferrite core, and resistors are connected in parallel to the two split coils. Thereby, it is possible to prevent the notch characteristic from appearing in the band. Accordingly, since the signal does not deteriorate, when applied to a CATV system, image and voice deterioration and signal error do not occur.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a configuration example of an embodiment of a choke coil according to the present invention.
The choke coil 1 according to the present invention shown in FIG. 1 is configured by winding a coil part 11 divided into three parts on a ferrite core 10. In this case, when a number of turns of 9 turns is required, the number of turns of the first split coil 11a is 3 turns, the number of turns of the second split coil 11b is 2 turns, and the number of turns of the third split coil 11c is 4 turns. Have been. The resistor R1 is connected in parallel to the first split coil 11a, and the resistor R2 is connected in parallel to the third split coil 11c. The resistances R1 and R2 are, for example, 1 kΩ.
[0009]
FIG. 2 shows an equivalent circuit of the choke coil 1 shown in FIG. As shown in FIG. 2, the choke coil 1 includes a first split coil 11a (L1), a second split coil 11b (L2), and a third split coil 11c (one split terminal) between one terminal 12 and the other terminal 13. L3) are connected in series. The resistor R1 is connected in parallel to the first split coil 11a (L1), and the resistor R2 is connected in parallel to the third split coil 11c (L3). As a result, the impedance seen from one terminal 12 and the impedance seen from the other terminal in terms of high frequency are controlled by the resistors R1 and R2 because the impedance by L1 and L3 becomes extremely high. That is, by connecting the resistors R1 and R2 in parallel to the first split coil 11a and the third split coil 11c, the impedance of the one terminal 12 and the other terminal 13, which are the input terminal and the output terminal, is substantially the same as the impedance. can do. As a result, the frequency characteristics of a device in which the choke coil 1 according to the present invention is connected as a current passing circuit between the input terminal and the output terminal can be improved.
[0010]
Here, FIG. 3 shows the frequency characteristics of the insertion loss of the branching device shown in FIG. 4 when the choke coil 1 according to the present invention is used as the current passing circuit 100 shown in FIG. Referring to FIG. 3, a notch characteristic in which the insertion loss increases near 1250 MHz appears. However, 1250 MHz is out of the band, and the notch characteristic does not appear in the frequency band of the signal channel, so that it is possible to prevent image / voice deterioration and signal error from occurring.
[0011]
By the way, in the choke coil 1 according to the present invention, the winding of the coil portion 11 is made thicker and the thicker ferrite core 10 is used, so that the allowable current capacity is increased more than before. For this reason, the stray capacitance component increases because the contact between the windings and the proximity area increase, but the first split coil 11a (L1), the second split coil 11b (L2), and the third split coil 11b (L2). The coil is divided into three parts and wound around the divided coil 11c (L3). In addition, since the resistors R1 and R2 are connected in parallel to the two split coils 11a and 11c, the self-resonant frequency of the choke coil 1 is hardly generated in a low frequency range.
[0012]
Although the resistances R1 and R2 are set to 1 kΩ, the present invention is not limited to this, and can be selected according to the impedance of a device to which the choke coil 1 is applied. Further, the number of turns of the first divided coil 11a is 3 turns, the number of turns of the second divided coil 11b is 2 turns, and the number of turns of the third divided coil 11c is 4 turns. The number of turns of each split coil can be selected according to the transmission band.
[0013]
【The invention's effect】
As described above, according to the present invention, the coil is divided into a plurality of pieces and wound on a ferrite core, and resistors are connected in parallel to the two split coils. Thereby, it is possible to prevent the notch characteristic from appearing in the band. Accordingly, since the signal does not deteriorate, when applied to a CATV system, image and voice deterioration and signal error do not occur.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of an embodiment of a choke coil of the present invention.
FIG. 2 is a diagram showing an equivalent circuit of the choke coil according to the embodiment of the present invention.
FIG. 3 is a diagram illustrating frequency characteristics of insertion loss in a branching device to which the choke coil according to the embodiment of the present invention is applied;
FIG. 4 is a diagram illustrating a configuration example of a branch circuit.
FIG. 5 is a diagram showing a configuration of a conventional choke coil.
FIG. 6 is a diagram showing another configuration of a conventional choke coil.
FIG. 7 is a diagram showing frequency characteristics of insertion loss in a branching device to which the choke coil shown in FIG. 5 is applied.
8 is a diagram illustrating frequency characteristics of insertion loss in a branching device to which the choke coil illustrated in FIG. 6 is applied.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 choke coil, 10 ferrite core, 11 coil section, 11 a first split coil, 11 b second split coil, 11 c third split coil, 12 one terminal, 13 other terminal, 100 current passing circuit, 101 choke coil, 110 ferrite core, 111 coil part, first 111a split coil, 111b second split coil, BR branch terminal, C1, C2, C3 DC cut capacitor, IN input terminal, OUT output terminal, R1, R2 resistor, R100 resistor

Claims (3)

A choke coil in which a coil is divided into a plurality of pieces and wound on a ferrite core,
A first resistor connected in parallel to the split coil connected to one terminal;
A second resistor connected in parallel to the split coil connected to the other terminal;
A choke coil comprising: The choke coil according to claim 1, wherein the coil is divided into three parts and wound on the ferrite core. The number of turns of the first split coil to which the first resistor is connected in parallel is 3 turns, and the number of turns of the third split coil to which the second resistor is connected in parallel is 4 turns. The choke coil according to claim 2, wherein the number of turns of the second split coil located between the third split coils is two turns.

Images