JPH01307355A - Signal transmission circuit - Google Patents

Abstract

PURPOSE:To reduce the heat dissipation and to send a voltage signal from power supplies other than a station power supply as a signal by adopting the structure of applying voltage conversion by means of a DC-DC converter without employing any resistor and using a comparator circuit so as to control the DC-DC converter thereby obtaining an output voltage equal to that of a reference power supply. CONSTITUTION:A signal transmission circuit is provided with a converter section 2 converting a DC voltage of a station power supply 1 into a prescribed DC voltage, a voltage detection circuit 3 provided to an output side of the converter section 2 and a current detection circuit 4. The converter section 2 consists of a DC-DC converter 5 connecting to the output of the station power supply 1, a comparator circuit 6 controlling the output voltage of the DC-DC converter 5, a reference power supply 7 and an adder 8. Then the DC-DC converter 5 is in use to apply voltage conversion and the DC-DC converter 5 is controlled by the comparator circuit 6 so as to keep an output voltage equal to that of the reference power supply 7. Thus, the signal transmission circuit with less beat dissipation is obtained, which is able to send a voltage other than that of the station power supply 1 as a signal.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a signal transmission circuit, and in particular is used in a trunk circuit that interfaces between telephone exchanges or a subscriber circuit that interfaces between a telephone exchange and subscriber terminals. This invention relates to a signal sending circuit.

[Conventional technology]

Conventionally, this type of signal output path has a structure in which the voltage of the output signal is determined by connecting a resistor in series with a central office power supply, which is a DC power supply.

In other words, the power source of the central office was lowered to a predetermined voltage by the resistance of the resistor, and that voltage was set as the voltage of the output signal.

[Problem to be solved by the invention]

The conventional signal sending circuit described above uses a resistor connected in series with the station power supply as an internal resistance for determining the voltage of the output signal, and therefore has the following drawbacks.

A resistor as an internal resistance generates heat when current is conducted. The amount of heat generated is quite large because the resistor lowers the voltage of the station power supply to the required output signal voltage.

Particularly when a large number of signal sending circuits are installed in the same device, the total amount of heat generated from each circuit becomes significant. Therefore, it has been difficult to miniaturize a device equipped with a large number of conventional signal sending circuits due to the amount of heat generated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a signal sending circuit which generates extremely little heat and is capable of sending a signal using a voltage other than the station power supply.

[Means to solve the problem]

The signal sending circuit of the present invention includes a DC-DC converter that converts the DC voltage of a local power supply into a predetermined DC voltage and outputs the converted DC voltage; a voltage detection circuit that detects a signal voltage applied to the DC-DC converter; a current detection circuit that detects the output current of the DC-DC converter; and an adder that adds the signal voltage value of the voltage detection circuit and the voltage value applied to the current detection circuit. and a comparison circuit that has a reference power source and controls the DC-DC converter so that the voltage value of the reference power source and the added voltage value of the adder are equal.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a signal sending circuit according to an embodiment of the present invention.

The signal sending circuit includes a converter section 2 that converts the DC voltage of the station power supply 1 into a predetermined DC voltage, and a voltage detection circuit 3 and a current detection circuit 4 provided on the output side of the converter section 2.

The converter section 2 is connected to the output side of the station power supply 1.
It consists of a C-DC converter 5, a comparison circuit 6 that controls the output voltage of the DC-DC converter 5, a reference power source 7, and an adder 8. The DC-DC converter 5 is connected to the station power supply l.
converts the DC voltage of
It has a function to output between. The voltage of the reference power source 7 is output terminal A.

It is set to a voltage value expected as the output voltage between B and B. Further, the adder 8 has a function of adding the signal voltage value of the voltage detection circuit 3 and the voltage value applied to the current detection circuit 4 in an analog manner. Comparison circuit 6 is connected to each output side of reference power supply 7 and adder 8 . This comparator circuit 6 inputs the voltage information of the reference power supply 7 and the adder 8, and inputs the voltage information of the adder 8. D so that the added voltage value of D is equal to the voltage value of the reference power supply 7.
It has a function of controlling the C-DC converter 5.

The voltage detection circuit 3 generates a signal voltage E between output terminals C and B to be output to an external load 9. This is a circuit for detecting.

Therefore, this voltage detection circuit 3 is connected to the output lines a and b in parallel with the load 9. Also, voltage detection circuit 3
The output side of is connected to an adder 8.

The current detection circuit 4 is a circuit for detecting the current 11 output to the load 9. Therefore, this current detection circuit 4 is connected to the output line in series with the load 9. Also, like the voltage detection circuit 3, the output side of this current detection circuit 4 is connected to the adder 8.

Next, the operation of the signal sending circuit of this embodiment will be explained.

The DC voltage of the station power supply I is converted to a predetermined DC voltage by the DC-DC converter 5 and output as a voltage between terminals A and B. Of this output voltage, a signal voltage E0 to the load 9 is detected by the voltage detection circuit 3. Further, the current 11 flowing into the load 9 is detected by the current detection circuit 4. The signal voltage value detected by the voltage detection circuit 3 and the voltage value of the current detection circuit 4 are input to an adder 8 and are added in analog form.

This added voltage is equal to the output voltage between terminals A and B. Therefore, the comparator circuit 6 functions so that the value of the added voltage always has a constant voltage value. That is, the comparison circuit 6
, the reference power supply 7 having the voltage expected as the voltage between B
DC-
Controls the DC converter 5.

This relationship can be expressed by the following equation.

However, the voltage gain due to the input current 11 of the current detection circuit 40 is assumed to be, the voltage of the reference power source 7 is assumed to be r,t, and the resistance value of the load 9 is R.

From the result of equation 11 above, it can be seen that the internal resistance of the signal sending circuit is only K at most.

As described above, the signal sending circuit according to this embodiment has a DC-D
Since the C converter 5 is used to obtain a predetermined output voltage, the amount of heat generated from the circuit is extremely small. Also,
Since the DC-DC converter 5 is controlled by the comparator circuit 6 so as to maintain an output voltage equal to that of the reference power source 7, signals other than those from the station power source 1 can be sent out as output signals.

〔Effect of the invention〕

As explained above, since the signal sending circuit of the present invention has a structure in which voltage conversion is performed by a DC-DC converter without using a resistor, the amount of heat generated can be significantly reduced compared to the conventional signal sending circuit. There is.

In addition, in order to control the DC-DC converter by the comparison circuit so as to obtain an output voltage equal to that of the reference power source 7,
It is possible to send out voltages other than those from the central office power supply as signals.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a signal sending circuit according to an embodiment of the present invention. 1... Station power supply 2... Converter section 3... Voltage detection circuit 4... Current detection circuit 5... DC-DC converter 6...・Comparison circuit 7...Reference power supply 8...Adder 9...Load agent Yoshiyuki Iwasa, patent attorney

Claims (1)

[Claims] (1) A DC-DC converter that converts the DC voltage of the station power supply into a predetermined DC voltage and outputs it; and a DC-DC converter that is installed on the output side of this DC-DC converter and converts the signal voltage to be given to the external load from the output voltage. a voltage detection circuit for detecting; a current detection circuit for detecting the output current of the DC-DC converter; an adder for adding the signal voltage value of the voltage detection circuit and the voltage value applied to the current detection circuit; and a reference power supply. and a comparison circuit that controls the DC-DC converter so that the voltage value of the reference power supply and the added voltage value of the adder become equal.