JPH0418273Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to an AC/DC separation circuit that separates AC and DC from a signal in which AC is superimposed on DC.
Concerning simplification, compactness, and weight reduction of circuit configuration.

[Conventional technology]

Signals used for telephone calls, intercom circuits, etc. are composite signals in which a direct current signal for driving functional parts such as telephones, circuits, and interphonic circuits is superimposed with an alternating current signal consisting of voice and the like. In this case, on the transmitting side, it is necessary to superimpose the AC signal on the DC signal with as little loss as possible, and on the receiving side, such as a telephone or intercom, it is necessary to separate the DC signal and AC signal from the composite signal. AC/DC separation circuits are required.

As shown in FIG. 2, such an AC/DC separation circuit includes a rectifier circuit 2 installed at the signal input section, a capacitor 4 for blocking the DC signal, and an inductor for blocking the AC signal at the output section of the rectifier circuit 2. 6 is installed, and a capacitor 8 and a Zener diode 10 are installed on the output side of the inductor 6. In this case, the rectifier circuit 2 is constituted by a diode bridge rectifier circuit consisting of four diodes 12.

Therefore, when a composite signal of AC and DC is applied to the input terminals 14a and 14b from a telephone line or the like, this composite signal is full-wave rectified by the rectifier circuit 2. The DC component of this rectified output is removed via the capacitor 4, and an AC signal is taken out from the output terminal 16a.The AC component is removed by a filter circuit consisting of the inductor 6 and the capacitor 8, and the DC signal is output from the output terminal 16b. A signal is extracted.

Also, instead of such an AC/DC separation circuit, a third
An AC/DC separation circuit as shown in the figure is used.
As is clear from a comparison with the AC/DC separation circuit shown in FIG. 2, this has a constant voltage circuit 18 installed in place of the filter circuit consisting of the inductor 6 and capacitor 8 on the DC output side. This constant voltage circuit 18 includes a transistor 20, a Zener diode 22, a resistor 24, a capacitor 8,
It consists of 25. Therefore, even when such a constant voltage circuit 18 is installed, the AC component in the rectified output can be removed, and only the DC signal can be taken out from the output terminal 16b.

[Problem that the invention attempts to solve]

By the way, in the AC/DC separation circuit shown in FIG. 2, in order to reliably remove the AC component from the DC output side, it is necessary to make the inductance of the inductor 6 considerably large and to make the DC resistance sufficiently small. Therefore, it is necessary for the inductor 6 to use a relatively thick conducting wire in order to reduce DC resistance, and to increase the number of turns in order to increase the inductance. Such an inductor 6 has a large volume and weight, and is also expensive.In a one-piece telephone in which the receiver and the telephone body are integrated, the weight causes fatigue to the user. There were flaws.

Further, in the AC/DC separation circuit shown in FIG. 3, since the inductor 6 is removed, the inconvenience caused by the inductor is eliminated, but since the AC impedance on the input side of the constant voltage circuit 18 is low, the output terminal 16
There was a drawback that the signal from the main body of the telephone connected to the terminal a was absorbed by the constant voltage circuit 18 side, which affected the call signal. For this reason, in conventional telephones, the second
AC/DC separation circuits using filter circuits as shown in the figure have been widely used.

Therefore, the object of this invention is to provide an AC/DC separation circuit which is lightweight and compact by omitting the inductor, and which prevents AC impedance and avoids influence on the AC signal system.

[Means for solving problems]

The AC/DC separation circuit of this invention is an AC/DC separation circuit comprising a rectifier circuit 2 that rectifies a signal obtained by superimposing alternating current on direct current, and a stabilizing circuit 26 with a high input impedance that stabilizes the rectified output of this rectifier circuit. A first output terminal 16a for taking out the AC output via the first capacitor 4 is formed at one output part of the rectifying circuit, and the stabilizing circuit includes a transistor 28,
30, a series circuit of a first resistor 32 and a second capacitor 8 is connected, and a series circuit of a first resistor 32 and a second capacitor 8 is connected through a
6. Connect a series circuit consisting of a third capacitor 40 and a first Zener diode 33, connect the base of the transistor to the connection point of the second resistor and the third capacitor, and connect the base of the transistor to the connection point of the second resistor and the third capacitor; A second Zener diode 34 is connected in parallel to the , a third resistor 38 is connected in parallel to the third capacitor, and a DC output is provided at the connection point between the first resistor and the second capacitor. take out the second
It is characterized in that an output terminal 16b is formed.

[Effect]

The AC/DC separation circuit of this invention blocks the AC component in the rectified output using a stabilizing circuit with high input impedance without using an inductor, and can accurately separate and extract the DC output and AC output.

〔Example〕

Hereinafter, embodiments of this invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the AC/DC separation circuit of this invention.

As shown in FIG. 1, a first output terminal 16a for extracting an alternating current signal via a first capacitor 4 is formed on the rectifier output side of a rectifier circuit 2 composed of four diodes 12. Along with being there,
A stabilizing circuit 26 with a high input impedance is installed in order to cut off the AC component in the rectified output and extract the DC signal.

The stabilizing circuit 26 has transistors 28 and 30 connected in Darlington, the emitter of the transistor 30 is connected to the output point of the rectifier circuit 2, and a first resistor 32 is connected to the emitter of the transistor 28 and the collector of the transistor 30 which are connected in common. An output terminal 16b is formed through the terminal. Further, on the base side of the transistor 28, there is a bias circuit including a first Zener diode 33, a second Zener diode 34 for instant start, second and third resistors 36, 38, and a third capacitor 40. is set up.

A second capacitor 8 for removing the AC component is installed between the DC output point where the second output terminal 16b is formed and the AC/DC common point of the rectifier circuit 2.

From the above configuration, in this AC/DC separation circuit, when a composite signal consisting of DC and AC is applied to the input terminals 14a and 14b, the composite signal is
The rectifier circuit 2 rectifies the signal, and the rectified output AC signal is taken out from the output terminal 16a.

In addition, the rectified output of the rectifier circuit 2 is connected to the stabilizing circuit 26.
In addition, the transistor 28 is turned off instantaneously due to the conduction of the Zener diode 34, and at the same time, the transistor 30 is also turned on.

Then, the capacitor 40 is charged by the rectified output via the resistor 36, and the charging voltage is charged to a constant voltage determined by the resistors 36, 38 and the Zener diode 33. Base voltage is set. Due to such a stabilized bias input, a constant current flows through the transistors 28 and 30, and the current value is limited by the resistor 32 before being applied to the capacitor 8. As a result, a DC output is obtained from the capacitor 8, and the DC output is taken out from the output terminal 16b.

Therefore, in this AC/DC separation circuit, the input impedance of the stabilizing circuit 26 is high, and the rectifying circuit 2
Since it exhibits high AC impedance to
Separated from the AC signal system on the AC output side, for example,
There is no absorption of audio signals from the telephone main circuit connected to the output terminal 16a, and the influence on the audio signal system can be prevented.

In addition, in such an AC/DC separation circuit, when obtaining an AC impedance equivalent to that of the AC/DC separation circuit shown in FIG. 2, the circuit configuration is 1/10 to It can be realized with a volume of about 1/20, and along with the size reduction, the price can also be reduced to about 1/10, and the weight can be significantly reduced as no inductor is used.

When such an AC/DC separation circuit is applied to a telephone circuit, its characteristics can be easily measured and implemented using commercially available return loss and DC current measuring instruments.

[Effect of idea]

As explained above, according to this invention, the AC signal is separated using a stabilizing circuit without using an inductor, so the DC output and AC output can be accurately separated, and it is possible to separate the AC signal from the DC output without using an inductor. It is lighter, more compact, and lower in price compared to conventional products that use constant voltage circuits.Also, compared to conventional products that use constant voltage circuits, AC impedance can be set higher, and adverse effects on the AC signal system are avoided. I can,
In addition to highly stabilizing the DC output, it is possible to prevent the influence of high frequency noise, and improve the reliability of AC/DC separation.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the AC/DC separation circuit of this invention, and FIGS. 2 and 3 are circuit diagrams showing conventional AC/DC separation circuits. 2... Rectifier circuit, 4... First capacitor, 8
...Second capacitor, 16a...First output terminal, 16b...Second output terminal, 26...Stabilization circuit, 28, 30...Transistor, 32...First resistor, 33... first zener diode,
34... Second Zener diode, 36... Second resistor, 38... Third resistor, 40... Third capacitor.

Claims (1)

[Scope of Claim for Utility Model Registration] An AC/DC separation circuit comprising a rectifying circuit that rectifies a signal obtained by superimposing alternating current on direct current, and a stabilizing circuit with high input impedance that stabilizes the rectified output of this rectifying circuit, A first output terminal for taking out an AC output via a first capacitor is formed at one output part of the rectifier circuit, and a first output terminal is formed between the outputs of the rectifier circuit via a transistor. connecting a series circuit of a resistor and a second capacitor; and connecting a series circuit of a second resistor, a third capacitor, and a first Zener diode;
The base of the transistor is connected to the connection point between the second resistor and the third capacitor, and the second
A second Zener diode is connected in parallel to the resistor, a third resistor is connected in parallel to the third capacitor, and a DC output is provided at the connection point between the first resistor and the second capacitor. An AC/DC separation circuit characterized in that a second output terminal is formed to take out the AC/DC separation circuit.