JPS61100663A - Smoothing circuit - Google Patents

Abstract

PURPOSE:To make it possible to miniaturize a smoothing circuit and to enhance the economical efficiency thereof by reducing the electrostatic capacity of the condenser for constituting an integrating circuit, by comparing the output of the integrating circuit with a predetermined threshold value by a comparing circuit. CONSTITUTION:When the input signal vl inputted to an input terminal 1 is 0 volt, the output voltage v2 outputted from a gate 2 is held to +5 volt and, because a condenser 4 is charged through a resistor 3, a comparing circuit 7outputs a logical value 1. When a call-out signal arrives the input terminal in this state, the condenser 4 repeats charging and discharging at every half cycle of 16 Hz. At this time, by setting the resistance value of the resistor 3 and the electrostatic capacity value of the condenser 4 so that outlet voltage v3 does not exceed threshold value voltage Vt, an output signal v4 comes to a logical value 0 and it can be succeedingly displayed that the call-out signal arrived the input terminal 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in smoothing circuits in circuits for detecting alternating current signals.

For example, in automatic switchboards, it is often necessary to detect alternating current signals (eg, 16 Hertz) used for telephone ringing signals.

[Conventional technology]

FIG. 3 is a diagram showing an example of a conventional smoothing circuit in this type of calling signal detection circuit, and FIG. 4 is a diagram showing an example of signal waveforms at various parts in FIG. In FIG. 3, the input terminal l is connected via the gate 2 to an integrating circuit 5 composed of a resistor 3 and a capacitor 4, and the integrating circuit 5 is connected to an output terminal 6.

In FIGS. 3 and 4, when the input signal v1 input to the input terminal 1 is 0 volts, the output voltage v2 output from the gate 2 is maintained at a predetermined voltage 0 (for example, +5 volts). . In the bending state, capacitor 4
is charged via the resistor 3, and sets the output voltage v3 outputted to the output terminal 6 to +5 volts.

In this state, when a call signal arrives at the input terminal 1 at time tQ and the input signal v1 oscillates between 0 and +5 volts at 16 hertz, the output voltage v2 output from the gate 2 will change when the input signal v1 is 0 to +2.゜When indicating 5 volts (time t
Q to t1, t2 to t3, t4 to t5, . . . ) is set to +5 volts, and the output voltage v2 shows +2.5 to +5 volts (times tl to t2, t3 to t4, . . . ). ) is set to O volts. Output voltage v2
At a time tl, etc., when V is set to O volts, the capacitor 4 is immediately discharged via the gate 2, setting the output voltage v3 to 0 volts. In addition, when the output voltage v2 is set to +5 volts, the capacitor 4 is charged via the resistor 3 at a time point t2, etc., and the output voltage V2 becomes a time constant determined by the resistance value of the resistor 3 and the capacitance value of the capacitor 4. increase gradually based on However, the half period of 16 Hz (i.e. 31
．． At a time point t3 (25 milliseconds) has elapsed, the output voltage (2) becomes O volts again, so the capacitor 4 is discharged again, and the output voltage v3 is set to O volts again.

For example, if the resistor 3 is set to 1.2 kilohms and the capacitor 4 is set to about 150 microfarads, the output voltage v3 will not exceed 0.8 volts even at time t3.
For example, O volts to 0.8 volts are logical values 0, +2.4
When a T T L logic circuit that determines a logic value of 1 to +5 volts is connected to the output terminal 6, the logic circuit is connected to the output terminal 6.
1 and thereafter, it is determined that the output voltage (3) is continuously set to the logical value O, and it is determined that the calling signal has arrived.

[Problem that the invention seeks to solve]

As is clear from the above explanation, in a conventional smoothing circuit, the output voltage v3 of the integrating circuit 5 is directly outputted in order to continuously display that the call signal has arrived at the input terminal 1, so the capacitor 4 It is necessary to set a large capacitance value, which hinders miniaturization and economicalization of the smoothing circuit.

[Means for solving problems]

The above problem is solved by connecting an integrating circuit consisting of a resistor and a capacitor to the output terminal of the gate circuit, and maintaining the output of the integrating circuit within a predetermined voltage range when an AC signal of a predetermined frequency is input to the gate circuit. In the circuit, the output of the integrating circuit is inputted to one input terminal of a comparison circuit, and a predetermined threshold voltage is inputted to the other terminal of the comparison circuit,
The problem is solved by the present invention, characterized in that when the alternating current signal is input to the gate circuit, the output of the comparator circuit is maintained at a predetermined potential.

[Effect]

That is, according to the present invention, since the output of the integrating circuit is compared with a predetermined threshold voltage by the comparing circuit, by setting the threshold voltage sufficiently high, it is possible to set the time constant of the integrating circuit to be small. The smoothing circuit can be made smaller and more economical.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a smoothing circuit according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of signal waveforms at various parts in FIG. 1. Note that the same reference numerals indicate the same objects throughout the figures.

In FIG. 1, an output voltage v3 of an integrating circuit 5 composed of a resistor 3 and a capacitor 4 is input to one input terminal (+) of a comparator circuit 7, and the other input terminal (- ) is inputted with the threshold voltage Vt. Comparison circuit 7
compares the output voltage v3 and the threshold voltage Vt, and calculates the output voltage v
3 exceeds the threshold voltage Vt, the output signal v4 becomes a logical value 1.
, and if the output voltage v3 is less than or equal to the threshold voltage Vt, the output signal v4 is set to a logical value of 0. Note that the threshold voltage {circle around (2)} is set to a sufficiently high voltage (for example, +4 volts) in consideration of the time constant of the integrating circuit 5. Furthermore, the output signal v4 of the comparison circuit 7 is outputted to the output terminal 6.

In FIGS. 1 and 2, when the input signal vl input to the input terminal 1 is 0 volts, the output voltage v2 output from the gate 2 is a predetermined voltage V as in FIG.
(e.g. +5 volts). In this state, the capacitor 4 is charged via the resistor 3, setting the output voltage 3 to +5 volts. The comparator circuit 7 compares the output voltage V3 and the threshold voltage Vt, and when it identifies that the output voltage v3 is higher than the threshold voltage Vt, sets the output signal v4 outputted to the output terminal 6 to a logic value of 1.

In this state, when a call signal arrives at the input terminal 1 at the time to, the output voltage 2 output from the gate 2 changes from the time to to tiStz to t3, t as in FIG.
4 to t5, . . . and set to +5 volts at times tl to t2, t3 to t4, .
Set in Porto.

As a result, capacitor 4 is immediately discharged via gate 2 at time tl, etc., and resistor 3 at time t2, etc.
The output voltage v3 gradually increases based on a time constant determined by the resistance value of the resistor 3 and the capacitance value of the capacitor 4.

However, at a time point t3, etc., after a half period of 16 Hz (i.e. 31.25 milliseconds), the output voltage v2 is again set to 0 volts, the capacitor 4 is discharged again, and the output voltage v
3 is again set to 0 port.

If we now set the resistance value of resistor 3 to 1.2 kilohms and the capacitance value of capacitor 4 to approximately 17 microfarads, the output voltage v3 will be the threshold voltage Vt (=4
volts), the comparator circuit 7 continuously sets the output signal v4 to the logical value O after time t1.

As is clear from the above description, according to this embodiment, the output voltage v3 of the integrating circuit 5 is determined by the comparator circuit 7 to be the threshold voltage Vt.
Therefore, the threshold voltage Vt is set to a sufficiently high voltage (+4 volts in the previous example). It becomes possible to maintain the value at 0, and the capacitance value of the capacitor 4 can be set small.

Note that FIGS. 1 and 2 are only one embodiment of the present invention, and for example, the frequency of the input signal v1, the voltage values of the voltage VO and the threshold voltage Vt, the resistance value of the resistor 3, and the electrostatic capacitor 4 The capacitance value is not limited to what is shown in the drawings, and many other modifications may be considered, but the effects of the present invention will not change in any case. Further, the waveforms of the input signal v1, output voltages v2 and v3, and output signal v4 are not limited to those shown in the drawings, and many other modifications may be considered, but the effects of the present invention will not be affected in any case. It doesn't change.

〔Effect of the invention〕

As described above, according to the present invention, the capacitance of the capacitor constituting the integrating circuit 5 is reduced, and the smoothing circuit can be made smaller and more economical.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a smoothing circuit according to an embodiment of the present invention;
2 is a diagram showing an example of the signal waveform of each part in FIG. 1, FIG. 3 is a diagram showing an example of a conventional smoothing circuit in this kind of ringing signal detection circuit, and FIG. 4 is a diagram showing an example of the signal waveform of each part in FIG. 3. FIG. 3 is a diagram showing an example of a signal waveform. In the figure, 1 is an input terminal, 2 is a gate, 3 is a resistor, and 4
is a capacitor, 5 is an integrating circuit, 6 is an output terminal, 7 is a comparison circuit, tQ to t5 are time points, VO is a voltage, vl is an input signal, v2 is the output voltage of the gate, v3 is the output voltage of the integrating circuit 5, v4 is the output signal, and vt is the threshold voltage. Figure 1 Figure 2

Claims (1)

[Claims] In the circuit that connects an integrating circuit composed of a resistor and a capacitor to an output terminal of a gate circuit, and maintains the output of the integrating circuit within a predetermined voltage range when an alternating current signal of a predetermined frequency is input to the gate circuit. The output of the integrating circuit is input to one input terminal of the comparator circuit, a predetermined threshold voltage is input to the other terminal of the comparator circuit, and the output of the comparator circuit is determined when the alternating current signal is input to the gate circuit. A smoothing circuit that maintains a predetermined potential.