JPS63293475A - Measurement system for duty ratio - Google Patents

Abstract

PURPOSE:To realize simple circuit constitution and to take an accurate measurement by converting a signal to be measured into an in-phase signal and an opposite-phase signal, converting them into DC signals individually, and measuring their duty ratio from their potential difference. CONSTITUTION:A coupling circuit 1 which is supplied with the signal f0 to be measured divides a voltage VBB to the same level by resistances R1 and R2, and the AC component of a signal f0 is superposed upon a bias voltage obtained through the resistance R1 to supply a signal phi1 to a differential amplifier 2. Further, a reference voltage Vref is obtained through the resistance R2. The amplifier 2 obtain the in-phase signal phi0 and opposite-phase signal phi0' from the input signal phii and supplies them to a trailing-stage smoothing and differential measuring circuit 3. The circuit 3 generates a measurement voltage V0 corresponding to the duty ratio of the signals phi0 and phi0'. Thus, the signals f0 is converted into the signals phi0 and phi0' having their center at the reference voltage Vref and both signals are converted into the DC signals individually to measure the duty ratio from their potential difference, so the measurement is performed by the simple circuit constitution. Further, the signals phi0 and phi0' are converted into DC signals to reduce an error at the time of high-frequency signal measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a measurement circuit for measuring the duty ratio of a pulse signal, and particularly to a measurement method that is effective when measuring the duty ratio of a high frequency pulse signal. .

[Conventional technology]

During C0DEC-LSI or digital code transmission, Ilo (Input
t/0output) A design with a margin is required so that the boat retains its identification ability. For this reason, the duty ratio of the original waveform must be managed to maintain a constant duty ratio at °C, and duty ratio measurement is required.

Regarding the measurement of duty ratio, please refer to the "Electrical Measurement Handbook" (
Published in August 1978, published by Ohmsha, Chapter 3). The outline of this method is to measure the If period T and pulse width TH (time when the pulse is at high level) of the signal under test, and perform TH/T calculation.The calculation is performed by measuring the pulse width ratio using a frequency counter. That is.

The present inventors conducted studies to perform the above duty ratio measurement with high efficiency and accuracy.

Although the following is not a publicly known technique, it is a technique studied by the present inventors, and its outline is as follows.

That is, when the resolution of the frequency counter is ±Ins, the frequency that can be measured with an accuracy of 1% or less is IOMH2. It was also necessary to perform two 1-hour measurements.

[Problem that the invention seeks to solve]

As described above, in duty ratio measurement using a frequency counter, the measurement accuracy is determined by the accuracy of the time measure of the measuring instrument, in other words, the resolution of the counting clock or the resolution of the heterodyne-converted clock. The normally available locking resolution is on the order of ±ins, and there is a limit to high frequency duty ratio measurements.

Therefore, the inventors of the present invention have conducted repeated studies in order to easily and accurately measure the duty ratio even for high-frequency pulse signals in addition to being easy to measure. As a result, I found that if the signal under test was converted to DC, it would be possible to measure everything related to frequency.
With this in mind, we have come to propose the present invention.

An object of the present invention is to provide a duty ratio measuring method that can easily measure the duty ratio regardless of whether the frequency is high or low.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

That is, a pulse signal, which is a signal to be measured, is supplied to a differential amplifier to obtain a normal phase signal and a negative phase signal that are opposite in phase to each other.

A smoothing circuit according to the present invention is provided at the next stage of the differential amplifier, and smoothes (converts) the normal phase signal and the negative phase signal individually, and measures the duty ratio based on the voltage difference between the two. It is.

[Effect]

According to the above-mentioned means, when the reference levels of the positive-phase signal and the negative-phase signal match, the smoothed voltage level becomes a value relative to the duty ratio, and the duty ratio is measured by the voltage difference between the two. be able to. Since the normal phase signal and the negative phase signal are converted to direct current, the object of the present invention, which is to measure the duty ratio regardless of the frequency, can be achieved.

[Example 1] Hereinafter, a first example of a method for measuring a duty ratio to which the present invention is applied will be described with reference to FIGS. 1 to 3. In addition, the first
The figure is a block diagram showing the circuit configuration of the entire measuring circuit, FIG. 2 is a waveform diagram for explaining the circuit operation, and FIG. 3 is a circuit diagram showing a specific example.

The coupling circuit 1 is supplied with a signal under test f0 as shown in FIG. As shown in FIG. 3, the coupling circuit 1 is composed of a capacitor C% for cutting DC, and resistors R1 and R for dividing the voltage VflB to obtain a bias voltage and a reference voltage.

The resistors R, ,R, divide the voltage VBB to the same level, and apply the measured signal f, to the bias voltage obtained via the resistor RL.
The alternating current components of are superimposed and supplied to the differential amplifier 2 as the input signal φi.

Further, the °C reference voltage Vref is obtained via the resistor R2, and the reference voltage Vref and the input signal φi are set as shown in FIG. 2 (5).

The differential amplifier 2 converts the input signal φi into a normal-phase signal φ0° and a negative-phase signal φ, which have opposite phases to each other as shown in FIG. 2 (Q).

This is what you get. The accuracy of this measurement circuit is based on the above positive phase signal φ. , the delay time between the negative phase signal φ0, and the voltage level difference between high level and low level, etc. are determined. For this reason, the differential amplifier 2 has a circuit configuration that emphasizes symmetry, and the positive-phase signal φ0. Reverse phase signal φ. It is designed so that it can be calibrated. Also, the signal under test f
If 0 is a high frequency signal, E CL t GAA8
It is constructed of circuit elements capable of high-speed response, such as elements, and is designed to expand the measurement range.

The next stage smoothing differential measuring circuit 3 is basically a smoothing circuit (integrating circuit) consisting of resistors R, , R4 and capacitor C8+04 as shown in FIG.

The smooth differential measurement circuit 3 includes resistors R, , as shown in FIG.
It is made into a time constant circuit consisting of R4, capacitors C8 and C4,
Positive phase signal φ. , a measurement voltage vo corresponding to the duty ratio of the negative phase signal φ0 is obtained.

Here, the positive phase signal φ0. Reverse phase signal φ. Assuming that is symmetrical, the voltage Vφ smoothed by resistor R3 and capacitor C1 is V1=Vt, +(Tu/T) (Vl(-VI,)
++t+m (1) The voltage Vφ that has been smoothed by resistor R4 and capacitor C4 is as follows: Vφ=VL+C(T-TH)/T) (VH-VL
)-(2). Note that (1) above (
In equation 2), VH and vL are positive phase signals φ1. Is the reverse phase signal φ, Ga No 1 Repel and Hero Level Tearto? ! f)
'FL pressure L/S#, TH is the time when it is at high level, and T is the time of one cycle.

The measurement voltage v0 is obtained from the voltage difference between the voltages Vφ and Vφ, so Vo=Vφ−V1=2 (TH/T I/2) (V
H-VL),', TH/'r=v,/2 (VHVL
) + 1/2 --- (Determined by 31. By the way,
The duty ratio becomes 50% when the measurement voltage V,=O, and the duty ratio is measured in the range of VH-Vr, based on this voltage level.

In this example, the time constants for obtaining the voltages ■φ and Vφ are 1/f o < Rs = Cs, 1/
f.

<　R4,'　Set to C4.

The measurement circuit shown in this embodiment has the following effects.

(1) The signal under test f0 is a normal phase signal φ having opposite phases to each other with a predetermined reference voltage Vref as the center. and the reverse phase signal φ. K conversion and the above positive phase signal φ. and the reverse phase signal φ.

Since the structure is configured such that the duty ratio can be measured by converting the voltages into direct currents and the voltage difference between the two, it is possible to measure the duty ratio with a simple circuit configuration.

(2) Positive phase signal φ0. Reverse phase signal φ. Since it converts to DC,
This has the effect of reducing errors when measuring high frequency signals.

(3) According to (1) and (2) above, low-cost and accurate duty ratio measurement can be performed.

[Embodiment 2] Next, a second embodiment of the present invention will be described with reference to FIG.

Note that the same reference numerals are given to parts that perform the same circuit operations as in the first embodiment to avoid duplication of explanation.

The difference between this embodiment and the first embodiment is that the differential amplifier 2
The configuration is such that the bias voltage supplied to the positive phase signal φ4. This is because the configuration is such that the reverse phase signal φ1 is amplified twice.

That is, a bias voltage is supplied to one input terminal of the differential amplifier 2 via the variable resistor VR. As a result, the asymmetry of the differential amplifier 2 is corrected.

Further, the smoothed voltages ■φ and ■φ are amplified by resistors R, to R1 and an amplifier 4. Voltage V
, , vφ is amplified by the amplifier 4, and the voltage difference of the measurement voltage v0, V , ) =
2 K (TH/T-1/2) (VH-ML).

Therefore, the measurement circuit shown in this example has the above-mentioned (1) to (3)
), the following effects are also achieved.

(4) By varying the bias voltage of the differential amplifier, the asymmetry of the differential amplifier 2 is corrected and measurement accuracy is improved.

(5) By amplifying the smoothed voltage difference, it is possible to obtain the effect that the duty ratio can be easily measured.

[Embodiment 3] Next, a third embodiment of the present invention will be described with reference to FIG.

In this embodiment, the signal under test f0. This shows a circuit configuration when the symmetry of f0 has been confirmed.

In this case, the above coupling circuit 1° differential amplifier 2, etc. for obtaining symmetry can be omitted.

That is, the signal under test f0. f, smooth differential measurement circuit 3
supplied directly to The operation of the smooth differential measurement circuit 3 in this case is performed in the same manner as in the first embodiment, and a measurement voltage vo is obtained.

The measurement circuit shown in this embodiment is based on the above-mentioned No. 1. The circuit configuration is extremely simple compared to the measurement circuit shown in the second embodiment.

Above, the invention made by the present inventors has been specifically explained based on each example, but the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Needless to say.

For example, the amplifier 4 described in the second embodiment may be applied to the smooth differential measurement circuit 3 described in the third embodiment.

Also, the measurement voltage ■. If it is confirmed that the measuring device has a predetermined capacitance value, it is also possible to reduce the capacitor C8,C.

In the above explanation, the invention made by the present inventors and others was mainly applied to a pulse signal duty ratio measuring circuit, which is the field of application that formed the background of the invention, but the invention is not limited to this and is not limited to this. It can also be used to obtain a corresponding control signal.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

In other words, the signal under test for which the duty ratio is to be measured is converted into a normal phase signal and a negative phase signal that are opposite in phase to each other, and these are individually converted to direct current to measure the duty ratio based on the voltage difference. In addition to being simple, accurate measurements can be made regardless of the frequency.

[Brief explanation of the drawing]

1 to 3 show a first embodiment of the present invention. FIG. 1 is a block diagram showing the circuit configuration of the entire measurement circuit, and FIG. 2 is a waveform diagram illustrating the circuit operation. , FIG. 3 is a circuit diagram showing a specific example of a measuring circuit, FIG. 4 is a circuit diagram of a measuring circuit showing a second embodiment of the present invention, and FIG. 5 is a circuit diagram of a measuring circuit showing a third embodiment of the present invention. It is a circuit diagram. 1... Coupling circuit, 2... Differential amplifier, 3... Smoothing differential measurement circuit, 4... Amplifier, RI""' R?・・・
・Resistance, C1゜C2... Capacitor, fo... Signal under test, φ. , φ0... Positive phase and negative phase signal, Vφ,
Vφ...DC voltage, vo...Measurement voltage. °No Figure 1 Figure 2 Figure 0 (v)

Claims (1)

[Claims] 1. A duty ratio measurement method characterized by individually smoothing a plurality of signals under test that change in a pulse-like manner with mutually opposite phases, and measuring the duty ratio of the signals under test based on the voltage difference between the smoothed components.