JPS5820939Y2 - Potential fluctuation detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a potential fluctuation detection circuit for detecting the rise and fall of an incoming signal whose potential varies stepwise.

Conventionally, in a circuit that detects fluctuations in the potential in an incoming signal, or in other words, the rise and fall of the signal, counts the number of times the potential rises and falls, and performs a predetermined process, the potential fluctuation is shown in Figure 1. It was detected by the means shown.

That is, in the conventional potential fluctuation detection circuit, a signal whose potential fluctuates is applied from the input terminal 1, and this signal is supplied to the capacitors 2 and 3, respectively.

Resistors 5 and 6 are connected to each of the capacitors 2 and 3, forming differentiating circuits 6 and 7, respectively.

The output of the differentiating circuit 6 is connected to the connection point of diodes 8 and 9 connected in series between the power supply terminal and the reference potential, and a pulse obtained by differentiating the rise of the potential is generated at this connection point. A pulse corresponding to the number of rises is supplied to the counting circuit.

In addition, a diode 11 connected to the output point of the differentiating circuit 7
At the connection point 12, a pulse is obtained by differentiating the falling edge of the signal, and this pulse is counted by the falling edge counting circuit 13.

However, in the conventional potential fluctuation detection circuit with such a configuration, the threshold value of the pulse supplied to the rising counting circuit 10 or the falling counting circuit 13 is lower than the potential fluctuation level of the input signal, and the counting circuit is sufficiently controlled. There are many cases where the counting operation that can be driven is not performed normally, and to deal with this, it is necessary to provide a pulse amplifier at the front stage of the counting circuit.

Furthermore, when the input impedance of the counting circuit is low, it is necessary to increase the capacitance of capacitors 2 and 3 to obtain the necessary pulse width, and for this reason, the signal source is affected by the differentiating circuits 6 and 7 during charging and discharging. .

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned difficulties and provide a potential fluctuation detection circuit that reliably generates a pulse in response to fluctuations in the power supply of an input signal.

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

FIG. 2 is a circuit diagram showing a typical embodiment of the present invention, and an input terminal 20 to which a signal whose potential fluctuates (having a rising part and a falling part) is applied with a resistor R1,
One end of resistor R2 is connected, the other end of resistor R1 is connected to the base of transistor Q1, and the other end of resistor R2 is connected to the base of transistor Q2.

Between the emitter of Ql of the transistor and the reference potential, there is a capacitor C which together with the resistor R1 forms a differential circuit.
1 is connected, and the collector of transistor Q1 and power supply ■1
A resistor R3 is connected between them.

A diode D1 whose anode is connected to the emitter side is connected between the base and emitter of the transistor Q1.

Further, a diode D2 is connected between the other end of the resistor R2 and the emitter of the transistor Q2, a capacitor C2 is connected between the emitter and a reference potential, and a resistor R4 is connected between the collector and the reference potential. has been done.

The collector of this transistor Q2 is connected to the power supply V2 via a diode D3, and is also connected to the human power of a falling pulse counting circuit 30 that detects the fall of the potential fluctuation of the human power signal.

The collector of the transistor Q1 is connected to the input terminal of a rising pulse counting circuit 40 that detects the rising edge of the potential fluctuation of the input signal, and the input terminal is connected to the power supply V
A diode D4.2 is connected in series between D4.2 and the reference potential. It is connected to the connection point of resistor R5.

Note that the rise counting circuit 40 is connected to a power source v2.

An embodiment of the present invention having the above circuit configuration will be described. First, the transistor Q1 operates at the rising edge of the input signal, and the transistor Q2 operates at the rising edge of the input signal.

Now, let us consider the case where an input signal arrives with potential fluctuations in the rising portion 51 twice and the falling portion 52 twice as shown in FIG.

Here, for convenience, looking at the counting operation in the falling part, the diode D2 becomes conductive in the rising part 51 at time to, and charges the capacitor C2 to the potential of vl via the resistor R2 and the diode D2.

At time t1, the input signal falls, diode D2 cuts off, transistor Q2 becomes conductive, and capacitor C
The charges charged in the transistor Q2 are transferred to the transistor Q2 through the emitter and collector current path of the transistor Q2 and the resistor R4.
It is discharged so that the voltage level of the emitter of 2 becomes 2.

At this time, since the capacitor C2 and the resistor R4 form a differentiating circuit, a differentiated waveform 53 is generated at time t1.

This differential waveform 53 is supplied to a falling pulse counting circuit 30, and the number of falling pulses is counted.

Next, the detection operation of the rising portion 51 will be described with reference to FIG. 3. At time t1, the diode D1 is cut off, and at this time, the transistor Q1 is conductive, and the capacitor C1 is charged to a voltage whose level is approximately 1. be done.

Next, from time t1 to t2, the diode D1 becomes conductive, and the charge charged at the voltage 1 is discharged through the resistor R1, so that the voltage across the capacitor C1 becomes the voltage level v2.

Then, when the voltage level rises from ■2 to ■3 at time t2, the transistor Q1 becomes conductive at the same time, generating a differential waveform 54 by the resistor R3 and the capacitor C1, and a pulse corresponding to the rising edge of the input signal is applied to the capacitor. It is supplied to the rising pulse counting circuit 40 via C3.

In this way, the rising edge 51 and the falling edge 52 of the input signal are detected, but the rising pulse and falling pulse to be detected are the transistor Q1. Q2 is used, so there is no pulse threshold fluctuation and the counting circuit 3
0.40 malfunction can be suppressed.

Furthermore, unlike the conventional art, when determining the capacitance of a capacitor for charging and discharging, it is not restricted by the input impedance of the rising and falling pulse counting circuit.

As is clear from the above description, according to the present invention, it is possible to provide a potential fluctuation detection circuit that reliably generates a pulse in accordance with potential fluctuations of an input signal.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional potential fluctuation detection circuit, FIG. 2 is a circuit diagram showing an embodiment of the potential fluctuation detection circuit according to the present invention, and FIG. 3 explains the operation of the circuit shown in FIG. 2. FIG. 20... Input terminal, DI, D2... Switching means, C1, C2... Capacitor,
R1, R2...First resistor, R3, R4...
...Second resistance.

Claims (1)

[Claims for Utility Model Registration] An input terminal to which an input signal whose potential changes from a first voltage level to a second voltage level is applied; a first resistor having one end connected to the input terminal; a switching means having one end connected to the other end of the first resistor and the other end connected to a capacitor for charging and discharging the capacitor by switching according to voltage level fluctuations of the input signal; It includes a transistor whose base side is connected to one end and whose collector and emitter current paths are connected between the other end of the switching means and a ground potential, and a second resistor which is connected to the collector and emitter current paths of this transistor. and detecting a change in the voltage level of the input signal.