JPH0915276A - Phase measuring device - Google Patents

Abstract

PURPOSE: To make it possible to measure phase difference with high resolution and high accuracy. CONSTITUTION: A waveform shaping circuit 2a shapes the waveform of a signal to be measured. A phase shifter 3 makes the phase of a reference signal variable according to the control voltage. This reference signal is inputted to another waveform shaping circuit 2b via the phase shifter 3. This waveform shaping circuit 2b shapes the waveform of this reference signal. A phase comparator 4 outputs and output signal conformed to the phase difference between those of output signals of both the waveform shaping circuits 2a and 2b. An amplifier 5 gives an output signal conformed to the output signal of the phase comparator 4 to the phase shifter 3 as the control voltage. Another amplifier 6 converts the output signal of the amplifier 5 into a specified standard voltage or standard current. The phase shifter 3, having a variable time constant circuit, alters time constant of this variable time constant circuit, thereby altering the phase of the reference signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase measuring device for measuring a phase angle (phase difference between voltage and current).

[0002]

2. Description of the Related Art Conventionally, a phase angle is measured by comparing the phase of a reference signal and the phase of a signal under measurement and detecting the phase difference. FIG. 5 shows a schematic configuration of a conventional phase measuring device. FIG. 6 shows the state of the signal before and after waveform shaping. FIG. 7 shows the waveform at each node of the device of FIG.

The signal under measurement is applied to the input terminal 11a, and the reference signal is applied to the input terminal 11b. The waveform shaping circuit 12a is composed of a comparator, a diode clamp, etc., and shapes the waveform of the signal under measurement and outputs it as a pulse signal a. Similarly, the waveform shaping circuit 12b
Is composed of a comparator, a diode clamp, etc., and waveform-shapes the reference signal and outputs it as a pulse signal b.

The phase difference detection circuit 13 includes a waveform shaping circuit 12
pulse signal a output from a and waveform shaping circuit 12b
Detects a phase difference from the pulse signal b output from, and outputs a pulse signal c corresponding to the phase difference.

On the other hand, the reference voltage generating circuit 14 generates a constant voltage and is connected to an integrating circuit 16 via a gate 15 composed of an analog switch or the like.
The integrating circuit 16 is connected to the output terminal 17.

The pulse signal c output from the phase difference detection circuit 13 is input to the gate 15 and the gate 15
It controls the on / off of. That is, by controlling the on / off of the gate 15, the phase difference between the pulse signal a output from the waveform shaping circuit 12a and the pulse signal b output from the waveform shaping circuit 12b is output from the output terminal 17. The corresponding voltage is obtained.

[0007]

In the above-described phase measuring device, the voltage generated by the reference voltage generating circuit cannot be increased infinitely, so that the resolution (minimum value that can detect a change in the phase difference) and the phase measuring There is a drawback that the accuracy cannot be improved so much.

Further, since the pulse width of the pulse signal output from the phase difference detecting circuit changes in proportion to the frequency of the signal under measurement, the phase difference cannot be measured for the signal under measurement having a too high frequency.

The present invention has been made to solve the above-mentioned drawbacks, and an object thereof is to ensure high resolution without being restricted by the characteristics of the elements constituting the phase measuring apparatus.

[0010]

In order to achieve the above object, the phase measuring apparatus of the present invention is provided with a signal to be measured,
A first waveform shaping circuit for shaping the waveform of the signal under measurement;
A phase shifter capable of changing the phase of a reference signal according to a control voltage, a second waveform shaping circuit for shaping the waveform of the reference signal by inputting the reference signal through the phase shifter, and the first waveform shaping The phase of the output signal of the circuit and the second
A phase comparator that outputs an output signal corresponding to the phase difference between the phases of the output signals of the waveform shaping circuits, an amplifier that gives an output signal corresponding to the output signal of the phase comparator to the phase shifter as the control voltage, and Means for extracting the output signal of the amplifier to the outside in order to measure the phase difference between the signal under measurement and the reference signal.

The phase shifter has a variable time constant circuit, and changes the phase of the reference signal by changing the time constant of the variable time constant circuit. The means converts the output signal of the amplifier into a predetermined standard voltage or standard current and then takes it out.

[0012]

According to the above construction, the phase difference between the signal under measurement and the reference signal is measured by detecting the output signal of the amplifier which is proportional to the phase difference between the signal under measurement and the reference signal. Therefore, the characteristics of the phase measuring device are not affected by the pulse width of the output signal of the first waveform shaping circuit. Also, if an amplifier with a large amplification degree such as an operational amplifier is used,
High-resolution and high-accuracy phase difference measurement is possible without using special parts.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The phase measuring apparatus of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a phase measuring device according to an embodiment of the present invention. The signal under measurement is applied to the input terminal 1a. The waveform shaping circuit 2a is
It is composed of a comparator, diode clamp, etc.,
The signal under measurement is waveform-shaped and output as a pulse signal a.

The reference signal is applied to the input terminal 1b.
The reference signal is input to the phase shifter 3. Phase shifter 3
Shifts the phase of the reference signal by a predetermined amount. The phase shifter 3 is connected between the amplifier A1, the input terminal 1b and one input terminal of the amplifier A1, and is connected to the MOS transistor Q1 to which a control voltage is applied to the gate and one input terminal of the amplifier A1. A capacitor C1 connected between the points, a resistor R1 connected between the input terminal 1b and the other input end of the amplifier A1, and a resistor R2 connected between the output end of the amplifier A1 and the other input end. It consists of and.

The resistance value R between the source and the drain of the MOS transistor Q1 changes according to the value of the control voltage (gate voltage). The time constant τ is set by the resistance value R of the MOS transistor Q1 and the capacitance of the capacitor C1.

The waveform shaping circuit 2b is composed of a comparator, a diode clamp, etc., and shapes the output signal of the phase shifter 3 into a pulse signal b. The phase comparator 4 compares the phase of the pulse signal a output from the waveform shaping circuit 2a with the phase of the pulse signal b output from the waveform shaping circuit 2b, and outputs an output signal c according to the phase difference. To do.

The amplifier 5 amplifies the output signal c of the phase comparator 4 and also the MOS transistor Q1 of the phase shifter 3.
A control voltage is supplied to the gate. The amplifier 6 is the amplifier 5
Output signal is converted into a predetermined voltage conforming to the standard and guided to the output terminal 7.

Next, the operation of the phase measuring device of FIG. 1 will be described. 2 shows the waveforms of the nodes of the apparatus of FIG. 1 in the initial state, FIG. 3 shows the waveforms of the nodes of the apparatus of FIG. 1 during the phase shift, and FIG. 2 shows the waveforms of the nodes of the device of FIG. 1 after the end of the phase shift.

First, the signal under measurement is waveform-shaped by the waveform shaping circuit 2a and input to the phase comparator 4. on the other hand,
The reference signal is input to the waveform shaping circuit 2a via the phase shifter, shaped in the waveform shaping circuit 2a, and then input to the phase comparator 4.

The phase comparator 4 outputs an output signal c corresponding to the phase difference between the pulse signal a output from the waveform shaping circuit 2a and the pulse signal b output from the waveform shaping circuit 2b. The output signal c is applied to the gate of the MOS transistor Q1 of the phase shifter 3 via the amplifier 5.

Since the resistance value R between the source and the drain of the MOS transistor Q1 changes according to its gate voltage, the time constant τ determined by the resistance value R and the capacitance of the capacitor C1 also changes.

As a result, the phase of the reference signal is shifted by the phase shifter 3 by a predetermined amount in the direction in which the phase of the signal under measurement matches the phase of the reference signal. That is, the amplifier 5
The output signal of 1 corresponds to a value necessary to match the phase of the signal under measurement with the phase of the reference signal, that is, the phase difference between the signal under measurement and the reference signal. Therefore, an output signal corresponding to the phase difference between the signal under measurement and the reference signal is output from the output terminal 7.

According to the phase measuring device having the above-mentioned configuration, the output signal of the amplifier necessary for matching the measured signal and the reference signal is used instead of detecting the pulse width of the pulse signal indicating the phase difference. The phase difference between the measurement signal and the reference signal is detected.

Therefore, the characteristics of the phase measuring device are not affected by the pulse width of the pulse signal indicating the phase difference,
Further, if an amplifier having a large amplification degree such as an operational amplifier is used as the amplifier, it is possible to measure the phase difference with high resolution and high accuracy without using special parts.

Although the time constant τ of the phase shifter 3 is changed by fixing the capacitance C and changing the resistance R in the above embodiment, a variable capacitance diode or the like is used. Therefore, the resistance R may be fixed and the capacitance C may be changed to change. Further, the present invention can also be applied as a detection circuit for power factor measurement by using two inputs as a voltage input or a current input, respectively.

[0026]

As described above, the phase measuring device of the present invention has the following effects. In the conventional measurement method, a pulse having a phase difference is generated, and the phase difference is detected by a combination of the pulse width itself and a DC reference voltage. Therefore, the resolution and accuracy of the conventional phase measuring device depend on the pulse width and the reference voltage and are limited.

On the other hand, in the measuring method of the present invention, instead of detecting the pulse width of the pulse signal indicating the phase difference,
The phase difference between the signal under measurement and the reference signal is detected by the output signal of the amplifier required to match the signal under measurement with the reference signal. Therefore, the characteristics of the phase measuring device are not affected by the pulse width of the pulse signal indicating the phase difference, and if an amplifier having a large amplification degree such as an operational amplifier is used, a special component is used. Without this, it is possible to measure the phase difference with high resolution and high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a phase measuring device according to an embodiment of the present invention.

2 is a diagram showing waveforms of respective nodes of the apparatus of FIG. 1 in an initial state.

3 is a diagram showing the waveforms of the nodes of the device of FIG. 1 in a phase-shifted state.

FIG. 4 is a diagram showing waveforms of respective nodes of the apparatus of FIG. 1 after completion of phase shift.

FIG. 5 is a diagram showing a conventional phase measuring device.

FIG. 6 is a diagram showing a state of an input signal before and after waveform shaping.

FIG. 7 is a diagram showing the waveform of each node of the apparatus of FIG.

[Explanation of symbols]

1a, 1b, 11a, 11b ... Input terminal, 2a, 2b, 12a, 12b ... Waveform shaping circuit, 3 ... Phase shifter, 4 ... Phase comparator, 5, 6, A1 ... Amplifier, 7, 17 ... Output terminal, 13 ... phase difference detection circuit, 14 ... reference voltage generation circuit, 15 ... gate, 16 ... integration circuit, Q1 ... MOS transistor, C1 ... capacitor, R1, R2 ... resistance.

Claims (3)

[Claims] 1. A first waveform shaping circuit which receives a signal under measurement and shapes the waveform of the signal under measurement, a phase shifter which can change the phase of the reference signal according to a control voltage, and the reference signal A second waveform shaping circuit that is input through a phase shifter and shapes the waveform of the reference signal, and a phase difference between the phase of the output signal of the first waveform shaping circuit and the phase of the output signal of the second waveform shaping circuit. A phase comparator that outputs a corresponding output signal, and an amplifier that gives an output signal corresponding to the output signal of the phase comparator to the phase shifter as the control voltage,
A phase measuring device comprising: means for extracting the output signal of the amplifier to the outside in order to measure the phase difference between the signal under measurement and the reference signal. 2. The phase measurement according to claim 1, wherein the phase shifter has a variable time constant circuit, and changes the phase of the reference signal by changing the time constant of the variable time constant circuit. apparatus. 3. The phase measuring device according to claim 1, wherein the means converts the output signal of the amplifier into a predetermined standard voltage or standard current and then extracts the signal to the outside.