JPH0577987B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a voltage change detection device that detects voltage rise and fall changes.

Prior Art Conventionally, in order to detect a change in voltage, the voltage value is measured and then the state of change is observed, and the circuit configuration for this purpose has become complicated. In addition, in some systems, it is not necessary to know the magnitude of the input voltage as part of its control content, but it is necessary to detect whether the input voltage is changing at a faster rate than expected. In some cases, it is sufficient.

Purpose The present invention was made in consideration of the above points, and
The present invention provides a voltage change detection device having a simple configuration and capable of detecting only a state in which the voltage increases or decreases faster than a preset speed among changes in input voltage.

Configuration An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an example of the configuration of a voltage change detection device according to the present invention when detecting a state of voltage increase faster than a preset speed among changes in input voltage. a first operational amplifier OP1 that amplifies the input voltage Vin, a second operational amplifier OP2 that amplifies the input voltage Vin, and a voltage comparator CMP that compares the respective amplified output voltages V1 and V2.
It is composed of: In addition, each resistor R1~
In R7, the same numbers indicate those having the same resistance value.

In the configuration shown in the figure, the voltage obtained by dividing the reference voltage +Vs by resistor R5 and resistors R6 and R7 is applied to the common-mode input terminal (+) side of operational amplifier OP1.
4, and the voltage obtained by dividing the reference voltage +Vs by resistors R5, R6 and resistor R7 is applied to the in-phase input terminal (+) side of operational amplifier OP2.
4, and each operational amplifier OP1,
The output of OP2 is set to have a predetermined operating point voltage, and the output voltage V1 of operational amplifier OP1 is set to be slightly higher than the output voltage V2 of operational amplifier OP2.

The negative phase input circuit and return circuit on the input terminal (-) side of each operational amplifier OP1, OP2 have equivalent circuit configurations in terms of direct current. Therefore, the input/output static characteristics of each operational amplifier OP1 and OP2 are almost the same as shown in Figure 2 (the output voltage of operational amplifier OP1 is slightly higher due to the difference in common-mode input voltage), and the static characteristics are linear. It's summery. Therefore, for a DC voltage that does not change, the output voltage V1 of operational amplifier OP1 is higher than that of operational amplifier OP1, regardless of its level.
The value is slightly higher than the output voltage V2 of OP2.

In addition, the negative phase input circuit and feedback circuit on the input terminal (-) side of each operational amplifier OP1, OP2 are as follows:
In terms of AC, they have different circuit configurations.
That is, the operational amplifier OP2 functions as a simple amplifier, but since the operational amplifier OP1 has the capacitor C in its anti-phase input circuit,
If the resistance value is selected so that R1>>R3, it will operate as a differential amplifier from the time constant determined by capacitor C and resistor R1 to the time constant determined by capacitor C and resistor R3. . Therefore, the gain-frequency characteristics of each operational amplifier OP1 and OP2 are as shown in FIG.
When the frequency of the input voltage Vin exceeds a predetermined value, the output voltage V1 of the operational amplifier OP1 is higher than that of the operational amplifier OP2.
output voltage V2.

The operation of the voltage change detection device according to the present invention configured as described above will be explained with reference to an example of the change state of the voltage waveform of each part shown in FIG. In addition, Fig. 4a is a characteristic diagram when looking at the temporal change of the input voltage Vin, Fig. 4b is a characteristic diagram when looking at the temporal change of the output voltage V1 of the operational amplifier OP1, and Fig. 4c is a characteristic diagram when looking at the temporal change of the output voltage V1 of the operational amplifier OP1. The characteristic diagram when looking at the temporal change of the output voltage V2, d of the same figure is the voltage comparator CMP.
FIG. 3 is a characteristic diagram when looking at temporal changes in the output voltage Vout.

Now, when the input voltage Vin as shown in Fig. 4a is sent, each operational amplifier OP1 and OP2 acts as a simple amplifier during periods A, C, and E where the voltage does not change. At this time, as described above, the output voltage V1 of the operational amplifier OP1 is slightly higher than the output voltage V2 of the operational amplifier OP2, so the output voltage Vout of the voltage comparator CMP becomes a low level "L".

In addition, during period B when the input voltage Vin increases, if the rate of voltage increase is larger than a predetermined time constant, the operational amplifier OP1 acts as a differential amplifier as described above, and the amplification degree is calculated as follows. The amplification degree is larger than that of amplifier OP2, and as shown in Fig. b,
As shown in Fig. c, the output voltage V1 of the operational amplifier OP1 becomes smaller than the output voltage V2 of the operational amplifier OP2, and therefore the output voltage Vout of the voltage comparator CMP becomes high level "H" as shown in Fig. d.

Furthermore, during the period D in which the input voltage Vin decreases, if the rate of voltage decrease is greater than a predetermined time constant, the operational amplifier OP1 acts as a differential amplifier as described above, so that the amplification degree is the same as that of the operational amplifier. The amplification degree is larger than that of OP2, and the figure b,
As shown in d of the figure, the output voltage V1 of the operational amplifier OP1 becomes larger than the output voltage V2 of the operational amplifier OP2, and therefore the output voltage Vout of the voltage comparator CMP becomes low level "L" as shown in d of the same figure.

Therefore, from the voltage comparator CMP, the input voltage
The output voltage Vout at a high level "H" is obtained only during a period in which Vin gradually increases at a voltage increase rate greater than a predetermined time constant. At that time, if the voltage increase rate of the input voltage Vin changes slowly so that it becomes smaller than the predetermined time constant,
Since the operational amplifier OP1 acts only as an amplifier, the output voltage Vout of the voltage comparator CMP is at a low level "L" even during the voltage rising period.

In this way, the voltage change detection device according to the present invention can detect only the state in which the input voltage Vin increases at a faster rate than the time constant set in advance for the operational amplifier OP1. become.

Further, FIG. 5 shows a configuration example of a voltage change detection device according to the present invention in the case of detecting a state of voltage drop faster than a preset rate among changes in input voltage.

In this case, the operational amplifier OP1 in FIG.
I'm trying to swap the relationships in OP2 with each other.
In other words, the operational amplifier OP1', which acts as a simple amplifier when the input voltage Vin is constant, and the
It acts as a simple amplifier when Vin is constant and changes at a rate of change smaller than the time constant set in the negative phase input circuit, and acts as a differential amplifier when the input voltage Vin changes at a rate of change greater than the time constant. The output voltage of each operational amplifier OP1 and OP2 is compared with the operational amplifier OP2' which is set to produce a higher output voltage than the operational amplifier OP1' when the input voltage Vin is constant. The voltage comparator CMP' generates a high level output while the voltage Vin gradually decreases at a rate of change greater than the time constant.

Figure 6 shows the input/output static characteristics of each operational amplifier OP1 and OP2 in this case, and its gain -
The frequency characteristics are shown in FIG. 7. Further, FIG. 8 shows an example of changes in voltage waveforms at various parts. In this case, in particular, the output voltage V1' of the operational amplifier OP1' is increased only during the period D in which the input voltage Vin decreases at a rate of voltage decrease equal to or greater than a predetermined time constant.
becomes smaller than the output voltage V2' of the operational amplifier OP2', and the output voltage Vout' of the voltage comparator CMP' becomes high level. Even in this case, if the voltage drop rate of the input voltage Vin changes slowly so that it becomes smaller than the predetermined time constant, the operational amplifier
Since OP2' acts only as a simple amplifier, the output voltage Vout' of voltage comparator CMP' is at a low level even during the voltage drop period.

In this manner, the voltage change detection device according to the present invention can detect only the state in which the input voltage Vin decreases at a faster rate than the time constant set in advance for the operational amplifier OP2'. It becomes like this.

FIG. 9 shows a voltage fluctuation detection device according to the present invention,
For example, an example of a system configuration when actually used in an object detection system that detects obstacles while driving a car is shown. This consists of an oscillator 1 that generates a constant frequency signal, a network 2 consisting of a resistor divider circuit provided on the output side of the oscillator 1, a sensor S consisting of an electrode plate connected to the dividing point, and the network 2. A bandpass filter amplifier 3 performs noise removal and amplification processing on the high-frequency output voltage from the workpiece 2, a detector 4 detects the amplified output signal, and a sensor S detects the falling state of the detected voltage signal. The voltage change detection device 5 detects the approach of the object O to the voltage change detection device 5 and sends an alarm command to the driver 6 via an alarm device 7 if the voltage decreases due to a rate of change exceeding a preset time constant. . However, in such a structure, as the object O approaches the sensor S, the stray capacitance between the two increases.
As Cd increases, the output frequency signal of the network 2 attenuates, and the voltage change detection device 5 detects a falling state of the output voltage of the detector 4 in accordance with the attenuation, and the alarm 7 is activated as necessary. It is operated to notify that the object O is approaching at a speed higher than a preset speed.

Effects As described above, the voltage fluctuation detection device according to the present invention can detect whether the input voltage is increasing or decreasing at a rate of change faster than a preset rate with a simple configuration. It has the excellent advantage of being easy to perform.

[Brief explanation of drawings]

FIG. 1 is an electrical connection diagram showing an embodiment of the voltage change detection device according to the present invention, FIG. 2 is a diagram showing the input/output static characteristics of each operational amplifier in the same embodiment, and FIG.
Figure 4 also shows the gain-frequency characteristics.
The figure is a time chart showing an example of changes in voltage waveforms at various parts in the same embodiment, FIG. 5 is an electrical wiring diagram showing another embodiment of the present invention, and FIG. 6 is an input diagram of each operational amplifier in the same embodiment. Diagram showing output static characteristics,
FIG. 7 is a diagram showing the gain-frequency characteristics,
FIG. 8 is a time chart showing an example of changes in voltage waveforms at various parts in the same embodiment, and FIG. 9 is a block diagram showing an example of the configuration of a system actually using the voltage change detection device according to the present invention. OP1, OP2, OP1', OP2'... operational amplifier,
CMP…Comparator.

Claims (1)

[Claims] 1. Acts as a simple amplifier when the input voltage is constant and when it changes at a rate of change smaller than the time constant set in the negative phase input circuit, and when the input voltage changes at a rate of change greater than the time constant. a first operational amplifier that acts as a differential amplifier when the input voltage varies; and a second operational amplifier that acts as a simple amplifier configured to produce a lower output voltage than the first operational amplifier when the input voltage is constant; , and a voltage comparator that compares the output voltages of the operational amplifiers and generates a detection output while the input voltage gradually increases at a rate of change greater than the time constant. 2. The first operational amplifier acts as a simple amplifier when the input voltage is constant, and the first operational amplifier acts as a simple amplifier when the input voltage is constant and changes at a rate of change smaller than the time constant set in the negative phase input circuit. and a second operational amplifier configured to act as a differential amplifier when the input voltage changes at a rate of change greater than the time constant, and to produce an output voltage lower than that of the first operational amplifier when the input voltage is constant. Voltage change detection configured by an amplifier and a voltage comparator that compares the output voltages of each operational amplifier and produces a detection output while the input voltage gradually decreases at a rate of change greater than the above-mentioned time constant. Device.