JP3080157B2 - Subscriber circuit with earth detection function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a subscriber circuit and, more particularly, to a subscriber circuit for detecting the ground of a subscriber line.

[0002]

2. Description of the Related Art As a conventional subscriber circuit with a ground detection function, the one disclosed in Japanese Patent Application Laid-Open No. 61-144193 is well known. The subscriber circuit with the earth detection function has a configuration including a current-voltage conversion circuit, a filter for earth detection, and a comparator.

[0003]

In the above-mentioned conventional subscriber's circuit with a ground detection function, a filter for detecting the ground is indispensable. However, since the components constituting the filter need to have a high withstand voltage, they are composed of large components, so that high-density mounting is difficult, and miniaturization of the subscriber circuit is difficult.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to enable integration of a ground detection circuit without using a filter for ground detection, to reduce the size of a subscriber circuit, and to implement high-density mounting. It is an object of the present invention to provide a subscriber circuit with a ground detection function that can be implemented.

[0005]

According to the present invention, there is provided a power supply circuit for supplying a direct current to a telephone and a subscriber line including a subscriber line connected to the telephone, and a power supply circuit for the subscriber line and the power supply circuit. A first switch group for connection and disconnection, and a current for outputting a voltage proportional to a current flowing between the subscriber line and the power supply
A voltage conversion circuit , a second switch for connecting and disconnecting the subscriber line and the current-voltage conversion circuit, a reference voltage generation circuit for outputting an arbitrary reference voltage, an output voltage of the current-voltage conversion circuit, and the reference Comparing the voltage value, a comparator that outputs a high-level or low-level logical value, a counter that performs up-counting or down-counting according to the output level of the comparator, and detects the count value of the counter, A comparator for determining whether or not the count value is greater than an initial value, and outputting a ground detection display or a ground non-detection display in accordance with the determination result;
The output voltage of the current-voltage conversion circuit is higher than the reference voltage.
Output a low level signal when the
When the low level signal is received from the comparator,
Continue counting down from the value, and the earth detection display circuit
If the count value is smaller than the initial value,
As a result, a subscriber circuit with a ground detection function characterized by performing a ground detection display as detected is obtained.

[0006]

Further, according to the present invention, the comparator includes:
When the output voltage of the current-voltage conversion circuit is smaller than the reference voltage, a high-level signal is output, and the counter includes:
When receiving a high level signal from the comparator, continue counting up from the initial value, the ground detection display circuit,
When the count value is larger than the initial value, it is determined that the ground is not detected, and a ground non-detection display is performed, thereby providing a subscriber circuit with a ground detection function.

Further, according to the present invention, the output voltage of the current-to-voltage conversion circuit is V _DET , the potential of the subscriber line is V _L , the power supply voltage of the power supply is V _BB , Is R, the current-voltage conversion coefficient is α
, The output voltage V of the current-voltage conversion circuit
A subscriber circuit with a ground detection function is obtained, wherein _DET is determined by α × (V _BB −V _L ) / R.

Further, according to the present invention, a power supply circuit connected to the telephone and supplying a direct current to a subscriber line including a subscriber line in which AC induction is introduced, and the subscriber line and the power supply. A first group of switches for connecting and disconnecting circuits , a current-to-voltage conversion circuit for outputting a voltage proportional to a current flowing between a subscriber line and a power supply, and a connection and disconnection between the subscriber line and the current-to-voltage conversion circuit And a reference voltage generation circuit that outputs an arbitrary reference voltage, and compares the output voltage of the current-voltage conversion circuit with the value of the reference voltage,
A comparator that outputs high-level and low-level logic values, a counter that performs up-counting and down-counting based on the output level of the comparator, and detects a count value of the counter to determine whether the count value is greater than an initial value. Determine whether or not, comprising a ground detection display circuit that outputs a ground detection display or a ground non-detection display according to the determination result,
The comparator outputs the current-voltage conversion circuit during one cycle.
Where the output voltage is smaller than the output voltage of the reference voltage generator
The output voltage of the current-voltage conversion circuit
The section that is larger than the output voltage of the generator is longer
In such a case, the high-level signal and the
Outputs a low-level signal with a longer output time than the high-level signal
And the counter outputs the low level signal.
While the counter is down, the high level signal is output.
While the power is being applied, the counter counts up and the earth detection table is displayed.
Indicating circuit, when the count value is smaller than the initial value,
There is provided a subscriber circuit with a ground detection function, characterized in that a ground detection is displayed on the assumption that the ground is detected .

[0010]

Further, according to the present invention, the comparator includes:
During a period, an interval in which the output voltage of the current-voltage conversion circuit is lower than the output voltage of the reference voltage generation circuit is longer than an interval in which the output voltage of the current-voltage conversion circuit is higher than the output voltage of the reference voltage generation circuit. If it is longer, the counter outputs a low-level signal and a high-level signal whose output time is longer than the low-level signal in one cycle, and the counter counts down while the low-level signal is being output. Upcounting is performed while the high level signal is being output, and the ground detection display circuit performs ground nondetection display as not detecting ground when the count value is larger than the initial value. A characteristic subscriber circuit with a ground detection function is obtained.

Further, according to the present invention, the output voltage of the current-to-voltage converter is V _DET , the potential of the subscriber line is V _L , the power supply voltage of the power supply is V _BB , and the AC induced voltage is V _{When AC} is used, R is the internal resistance of the current-voltage conversion circuit, and α is the current-voltage conversion coefficient, the output voltage V _DET of the current-voltage conversion circuit is α × (V _BB − (V _L +
_V.sub.AC )) / R is obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described in detail with reference to FIG. As shown in FIG. 1, the subscriber circuit with the earth detection function includes a power supply circuit 3, a first switch group 4, a current-voltage conversion circuit 6, and a second switch 5.
, A reference voltage generating circuit 8, a comparator 9, a counter 10
And an earth detection display circuit 11.

The power supply circuit 3 supplies a direct current as a speech current to a subscriber line including the telephone 1 and the subscriber line 2 connected to the telephone 1. The first switch group 4 includes the power supply circuit 3
And connection with the subscriber line 2 and release. The second switch 5 connects and disconnects the subscriber line 2 and the current-voltage conversion circuit 6. The current-voltage conversion circuit 6 outputs a voltage proportional to the current flowing between the subscriber line 2 and the power supply 7. The reference voltage generation circuit 8 outputs a predetermined reference voltage. The comparator 9 compares the output voltage of the current-voltage conversion circuit 7 with the output voltage of the reference voltage generation circuit 7. The counter 10 counts up or down according to the output level (high level or low level) output from the comparator 9. The ground detection display circuit 11 reads the count value of the counter 10 and outputs a ground detection display.

Next, the operation of the subscriber circuit having the above-described configuration with a ground detection function will be described in detail with reference to FIG. When the ground of the subscriber line 2 is detected, the power supply circuit 3 and the subscriber line 2 are cut off by the first switch group 4. afterwards,
The connection between the current-voltage conversion circuit 6 and the subscriber line 2 is performed by the second switch 5. The current-voltage conversion circuit 6 is connected to the subscriber line 2
And a voltage proportional to the current flowing between the power supply 7. Assuming that the potential of the subscriber line 2 is V _L , the power supply voltage of the power supply 7 is V _BB , the internal resistance of the current-voltage conversion circuit 6 is R, and the current-voltage conversion coefficient is α, the output voltage V of the current-voltage conversion circuit 6
_DET is obtained by the following mathematical formula (1).

[0016]

(Equation 1) The comparator 9 compares the output voltage V _DET of the current-voltage conversion circuit 6 with the output voltage V _ref of the reference voltage generation circuit 7. Here, when the ground is supplied to the subscriber line 2, the output voltage V _DET of the current-voltage conversion circuit 6 is obtained by the product of α and V _BB / R, and the output voltage V _DET of the current-voltage conversion circuit 6 is obtained. Becomes higher than the output voltage _Vref of the reference voltage generation circuit 7, and the comparator 9 outputs a low level (L level) signal having a logical value 0. Since the low level signal is output from the comparator 9, the counter 10 continues counting down from the initial value. The ground detection display circuit 11 reads the count value of the counter 10 and detects whether or not the read count value is larger than the initial value. Is detected and the earth detection display is performed. When the earth is supplied to the subscriber line 2, the counter 10 counts down from the initial value, so that the count value becomes smaller than the initial value, and the earth detection is detected by the earth detection display circuit 11. Is displayed.

On the other hand, when the ground is not supplied to the subscriber line 2, that is, when the subscriber line 2 is in the open state, no current flows through the current-voltage conversion circuit 6. Since the voltage V _DET becomes zero (0) and the output voltage V _DET of the current-voltage conversion circuit 6 becomes lower than the output voltage V _ref of the reference voltage generation circuit 7, the comparator 9 outputs a high level (H level) of the logical value 1 ) A signal is output. Since the high level signal is output from the comparator 9, the counter 10 continues counting up from the initial value. The ground detection display circuit 11 reads the count value of the counter 10 and detects whether the read count value is larger than the initial value. If the read count value is larger than the initial value, the ground Is not detected, and a non-detection display is performed. When the earth is not supplied to the subscriber line 2, the counter 10 is counted up from the initial value, and the count value becomes larger than the initial value.
From the ground detection display circuit 11, a ground non-detection display indicating that the ground is not detected is made.

Next, a case where an AC induction is guided to the subscriber line 2 will be described. In the embodiment shown in FIG.
When the AC induction is induced in the subscriber line 2, the AC induction is superimposed on the output voltage V _DET of the current-voltage conversion circuit 6 when the subscriber line 2 is connected. If the AC induction voltage is V _AC, the output voltage V _DET of the current-voltage conversion circuit 6 is obtained by the equation shown in the equation (2) below.

[0019]

(Equation 2) Here, when the output voltage V _DET of the current-voltage conversion circuit 6 is higher than the output voltage V _ref of the reference voltage generation circuit 7, a low level (L level) signal having a logical value 0 is output from the comparator 9, When the output voltage V _DET of the current-voltage conversion circuit 6 is smaller than the output voltage V _ref of the reference voltage generation circuit 7, a high level (H level) signal having a logical value of 1 is output. The counter 10 continues to count down while the comparator 9 outputs a low-level signal, and counts up while the comparator 9 outputs a high-level signal.

When the earth is supplied to the subscriber line 2, the output voltage V _DET of the current-voltage conversion circuit 6 is α and (V _BB
−V _AC ) / R. In this case, in the output of the comparator 9, the output voltage V _DET of the current-to-voltage conversion circuit 6 is smaller than the output voltage V _ref of the reference-voltage generation circuit 7 during one cycle.
_{The section where DET} is larger than the output voltage _Vref of the reference voltage generating circuit 7 is longer. For this reason, the section where the low level signal is output is longer than the section where the high level signal is output during one cycle.

Accordingly, the comparator 9 outputs a low level and a high level rectangular wave in one cycle. The counter 10 counts down while the comparator 9 outputs a low-level signal, and counts up while the comparator 9 outputs a high-level signal. Therefore, the count value of the counter 10 is smaller than the initial value because the time for performing down counting is longer than the time for performing up counting in one cycle.
The ground detection display circuit 11 reads the count value of the counter 10 at a cycle that is an arbitrary integral multiple of the cycle of the AC induction.
In this case, the ground detection display circuit 11 detects a count value smaller than the initial value. The ground detection display circuit 11 which has detected the count value displays a ground detection indicating that the ground is detected.

On the other hand, when the earth is not supplied to the subscriber line 2, that is, when the subscriber line 2 is in the open state, the output voltage V _DET of the current-voltage conversion circuit 6 is α and (−V _AC ) /
It is obtained by the product of R. In this case, in the output of the comparator 9, the output voltage V _DET
There towards the reference voltage generating circuit 7 outputs a voltage V _ref from the larger output voltage V _DET of the current-voltage conversion circuit 6 from the section is less than the output voltage V _ref of the reference voltage generating circuit 7 interval becomes long. For this reason, the section where the high-level signal is output is longer than the section where the low-level signal is output during one cycle.

Accordingly, the comparator 9 outputs a low level and a high level rectangular wave in one cycle. The counter 10 counts down while the comparator 9 outputs a low-level signal, and counts up while the comparator 9 outputs a high-level signal. Therefore, the count value of the counter 10 is larger than the initial value because the time for performing the up-count is longer than the time for performing the down-count in one cycle.
The ground detection display circuit 11 reads the count value of the counter 10 at a cycle that is an arbitrary integral multiple of the cycle of the AC induction.
In this case, the ground detection display circuit 11 detects a count value larger than the initial value. From the earth detection display circuit 11 which has detected the count value, an earth air non-detection display indicating that earth is not detected is made.

[0024]

As described above, according to the present invention, it is possible to detect the ground of a subscriber line without using a filter for detecting the ground.

Further, according to the present invention, since a filter for detecting the ground air is not required, a large component is not required. Therefore, integration of the earth detection circuit becomes possible, and miniaturization of the subscriber circuit and high-density mounting can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a subscriber circuit with a ground detection function of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 telephone 2 subscriber line 3 power supply circuit 4 first switch group 5 second switch 6 current-voltage conversion circuit 7 power supply 8 reference voltage generation circuit 9 comparator 10 counter 11 ground detection display circuit

Claims (6)

(57) [Claims] 1. A power supply circuit for supplying a direct current to a telephone and a subscriber line including a subscriber line connected to the telephone, and a first switch group for connecting and disconnecting the subscriber line and the power supply circuit. A current-voltage conversion circuit that outputs a voltage proportional to the current flowing between the subscriber line and the power supply, a second switch that connects and disconnects the subscriber line and the current-voltage conversion circuit, and an arbitrary reference voltage. A reference voltage generating circuit for outputting,
A comparator that compares the output voltage of the current-voltage conversion circuit and the value of the reference voltage and outputs a high-level or low-level logical value, and a counter that performs up-counting or down-counting based on the output level of the comparator. A ground detection display circuit that detects a count value of the counter, determines whether the count value is greater than an initial value, and outputs a ground detection display or a ground non-detection display according to the determination result. The comparator outputs the output voltage of the current / voltage conversion circuit.
If the voltage is higher than the reference voltage, a low level signal is output.
The counter outputs a low level signal from the comparator.
If you receive a
In the geo-mechanical detection display circuit, the count value is smaller than the initial value.
In this case, it indicates that the earth has been detected.
Earthed detection function subscriber circuit and performs. 2. The comparator outputs a high-level signal when an output voltage of the current-voltage conversion circuit is smaller than the reference voltage. The counter initializes when a high-level signal is received from the comparator. 2. The earth detection display circuit continues up counting from a value, and when the count value is larger than an initial value, performs earth air non-detection display on the assumption that earth air is not detected. Subscriber circuit with earth detection function. 3. An output voltage of the current-voltage conversion circuit is V
_DET , the potential of the subscriber line is _VL , the power supply voltage of the power supply is _VBB , the internal resistance of the current-voltage conversion circuit is R, and the current-voltage conversion coefficient is α. The output voltage V _{DET of the} circuit is α × (V _BB
-V L) _/ earthed detection function subscriber circuit according to claim 1 or 2, wherein the sought R. 4. A power supply circuit for supplying a direct current to a telephone and a subscriber line connected to the telephone and including a subscriber line in which AC induction is introduced, and connecting and disconnecting the subscriber line and the power supply circuit. A first switch group to be performed, and a current-voltage conversion circuit for outputting a voltage proportional to a current flowing between the subscriber line and the power supply.
Path , a second switch for connecting and disconnecting the subscriber line and the current-to-voltage conversion circuit, a reference voltage generation circuit for outputting an arbitrary reference voltage, and an output voltage of the current-to-voltage conversion circuit and the reference voltage. A comparator that compares the values and outputs high-level and low-level logic values; a counter that performs up-counting and down-counting based on the output level of the comparator; and a counter that detects a count value of the counter, Is determined whether or not is larger than the initial value, and a ground detection display circuit that outputs a ground detection display or a ground non-detection display according to the determination result, and the comparator has one cycle.
The output voltage of the current-voltage conversion circuit
From the section where the output voltage is smaller than the output voltage of the
The output voltage of the circuit is higher than the output voltage of the reference voltage generation circuit.
If the larger section is longer, the size of one cycle
When a high-level signal and output from the high-level signal
Output a long low level signal between
Count down while the low level signal is being output.
And while the high-level signal is being output,
Performs the counting, and the earth detection display circuit performs the counting.
If the value is smaller than the initial value, it indicates that the earth has been detected.
A subscriber circuit with a ground detection function characterized by performing a ground detection display . 5. The comparator according to claim 1, wherein the output voltage of the current-to-voltage conversion circuit is greater than the output voltage of the reference-voltage generation circuit during one cycle. If the section in which the output voltage is smaller than the output voltage is longer, a low-level signal and a high-level signal whose output time is longer than the low-level signal are output in one cycle, and the counter outputs the low-level signal. Performs down counting while being output, performs up counting while the high level signal is output,
5. The subscriber with a ground detection function according to claim 4, wherein the ground detection display circuit performs the ground non-detection display on the assumption that the ground is not detected when the count value is larger than the initial value. circuit. 6. An output voltage of the current-voltage conversion circuit is V
And _DET, the potential of the subscriber line and _{V L,} the power supply voltage of the power source was _{V BB,} an AC induced voltage and _{V AC,}
When the internal resistance of the current-voltage conversion circuit is R and the current-voltage conversion coefficient is α, the output voltage V _DET of the current-voltage conversion circuit is α × ( _VBB− (V _L + V _AC )) / R
6. A subscriber circuit with a ground detection function according to claim 4 or 5, wherein