JPS61204569A - Transducer for straight line effective value - Google Patents

Abstract

PURPOSE:To improve an input/output straight line characteristic even when the order of an input signal is small by correcting the amplification degree by an amplification degree correcting means provided with an arithmetic circuit only by the value reduced by the characteristic of a rectifying circuit beforehand. CONSTITUTION:A feedback impedance is composed of diodes D11 and D12 and a feedback resistance R12, and an operation amplifier M1 is composed of this and an input resistance R11 for an inverting amplifying device. At diodes D11 and D12, the element of the characteristic is respectively selected in which the forward direction voltage drop value is coincident to the forward direction voltage. When a since wave alternating current voltage is inputted to an input terminal 11, the voltage is inputted to an inverting amplifying device, the output voltage of the inverting amplifying device is half-wave-rectified by the diode D2, and the voltage drop value of the diodes D11 and D12 is canceled by the forward direction voltage value of the diode D2. The rectifying output of the diode D2 is smoothed by a resistance R1 and a capacitor C1, and integrated by an integrating circuit composed of a resistance R1 and a capacitor C2. Thus, the alternating current part included in the output signal is sufficiently removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a linear effective value transducer that outputs a direct current proportional to the effective value of an input voltage or current.

[Conventional technology]

Generally, when measuring distorted alternating voltage or alternating current, an effective value response indication i+5 such as a moving iron #F instrument or a thermoelectric instrument is used. However, these meters often have drawbacks such as the fact that the scale distribution is not uniform and that printed scale plates cannot be used due to variations in the scale distribution during manufacturing.

In addition, recent measurement equipment uses V
Alternatively, since calculations are often performed using measured values, a transducer with effective value response with good linearity is required. Figure 7 shows, for example, Jitsugan Sho No. 56-1866.
This is a circuit diagram of a linear effective value voltage transducer disclosed in Publication No. 02, which was designed to realize a transducer with effective linearity and effective value response as described above.

In FIG. 7, 11 and 12 are input terminals of this linear effective IT voltage transformer, and the input terminal 11 is connected to a resistor R.
1 is connected. D2 is a half-wave rectifying diode that half-wave rectifies the AC signal input from the input terminals 11 and 12, and is connected in series with the resistor R1. R3 is a resistor connected in parallel to the resistor R1, and linearity correction diodes D++ and D+2 are connected in series to this resistor R5, respectively, for correcting input/output direct expansion. 02
R2 is connected in parallel to the half-wave rectifying diode D2, and is used to smooth the signal waveform half-wave rectified by the diode D2. #Jl This is a resistor for taking out the output voltage from the effective value voltage transducer. The resistance Rj mentioned above.

The element values of R2 and R5 are R2(R1+R3)/
R+・Rs = (3,5~4,5), R3=2R
t is selected.

Note that 21 and 22 are output terminals of the linear effective value voltage transducer.

A conventional effective value voltage transducer is constructed as described above. For example, when an AC voltage is applied between input terminals 11 and 12, the AC voltage is divided by a series body of resistors R1 and R3 and diodes D++ and D+2. Of this divided voltage, the voltage applied across the series body of resistor R5 and diodes D++ and D+2 is half-wave rectified by diode D2. Then, the voltage half-wave rectified by the diode D2 is smoothed by the capacitor C, and the voltage is smoothed by the resistor R2.
Therefore, the AC component is removed from both ends of resistor R2, and even if there is some distortion in the input voltage, a DC voltage proportional to the effective value with little error is applied as the output voltage. . In addition, in the above-mentioned effective value voltage transducer, the influence of waveform distortion of the input voltage is small and output with relatively good linearity can be obtained because of the connection between the above-mentioned resistors R1, R2゜R5. R2(R+ +Rs
) /R+・Rs=(3,5-4.5) and R3:2
This is a case where the relational expression R1 holds true.

[Problem that the invention seeks to solve]

By the way, in the conventional linear effective value voltage transducer as described above, diodes 011. A series body of D12 and resistor R3 is inserted, and the values of resistors R+, Rz, and R3 are selected so that the above-mentioned relational expression is established between resistor R5 and resistors R1, R2.

However, although this linearity correction is effective when the input voltage is on the order of several tens of volts or more, when the input voltage is on the order of several volts or around the forward voltage of the rectifying diode D2, the input voltage signal is There was a problem in that the linearity correction effect was significantly reduced and the input/output linearity became extremely poor.

This invention was made to solve this problem, and even when a voltage signal of a very low order of, for example, several volts to several tens of mV is input, the input/output linearity is good.
Another object of the present invention is to obtain a linear effective value transducer capable of keeping an error between an effective value of an input signal and an output signal within a small range even when there is some distortion in the input voltage.

[Means for solving problems]

The linear effective value transducer according to the present invention includes an operational amplifier circuit in which an amplification correction value for correcting the amplification determined by a feedback resistor and an input resistor is connected to the feedback resistor, and a signal amplified by the operational amplifier circuit. A rectifier circuit that performs rectification and removes a correction value in the increment 111, a smoothing circuit that smoothes the signal output from the rectifier circuit, and a resistor and capacitor element that integrates and outputs the signal output from the smoothing circuit. It has an integrating circuit made up of.

[For production]

In this invention, the order of the input signal given to the operational amplifier circuit is adjusted by correcting the amplification degree in advance by the amplification degree correction value provided in the operational amplifier circuit by a value that is attenuated by the characteristics of the rectifier circuit. Input/output linearity can be improved even when the amplitude is small. In addition, the value of the resistance element constituting the smoothing circuit, the value of the resistance element constituting the next-stage integrating circuit, and the value of the resistance element connected in parallel to the output terminal of this linear effective value transducer for taking out the output signal. By selecting each element so that the values have a certain relationship, a DC signal with a small error proportional to the effective value of the input signal can be obtained even if the input signal is somewhat distorted. Furthermore, the output signal from the smoothing circuit is integrated in an integrating circuit composed of a resistor and a cap element to sufficiently remove the alternating current component contained in the output signal.

〔Example〕

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

FIG. 1 is a circuit diagram showing one embodiment of the present invention.
is an input terminal of the linear effective value transducer, and input resistor R+1 is connected to the input terminal 11. Ml is an operational amplifier (hereinafter referred to as "op-amp") constituting an operational amplifier circuit, and its non-inverting input terminal is grounded via a resistor R+3. The input resistor R11 and the feedback resistor R12 are connected to the inverting input terminal of the operational amplifier M1. Dll is a diode connected in series with the feedback resistor R+2 to stabilize the operation of the operational amplifier M1 without opening the feedback loop of the operational amplifier M1, and D12 is connected in parallel with the diode D11 to the feedback resistor R+2. diode. These diodes D++, D1z and feedback resistor R+2 constitute a feedback impedance, and this feedback impedance and the input resistor R++ constitute the operational amplifier M1 as an inverting amplifier.

For the diodes D++ and D+2 described above, elements having characteristics whose one-way voltage drop value matches the forward voltage of the rectifying diode D2, which will be described later, are selected. D2 is connected to the output terminal of the operational amplifier M1.
This is a luxury circuit, ie, a rectifying diode, that performs full-half-wave rectification of the signal output from the . This rectifier diode D2 receives the output signal + of the output signal generated by the diodes D++ and D+2.
Elements are used that have forward voltage characteristics that eliminate unidirectional voltage drop values.

R1 is a resistor connected to the rectifying diode D2, and a capacitor C1 is connected in parallel with this resistor R1.
At the same time, by smoothing the signal waveform rectified by the rectifying diode D2, a smoothing circuit is constructed that reduces the influence of waveform distortion of the input voltage to the linear effective voltage transducer. R21 is a resistor connected to the output side of this smoothing circuit, and a capacitor C2 is connected to this resistor R2+, and the resistor Rz+ and capacitor C2 form an integrating circuit that integrates the output signal from the smoothing circuit. are doing. In one embodiment of the present invention, the value of the resistor R1 constituting the smoothing circuit, the value of the resistor R21 constituting the integrating circuit, and the resistor R22 connected in parallel to the output terminal 21 side of the transducer are provided. The relationship with the value of is (Rz+ 1 R22)/R+ = (3,5~
4.5) Each element is selected to have a value that satisfies the following. As described above, the resistor R21 and the capacitor C2 constitute an integrating circuit, and by integrating the signal output from the smoothing circuit, the alternating current component contained in this signal is sufficiently removed. R22 is a resistor connected in parallel to the output terminal 21 of the transducer, and is used to take out an output signal from this transducer.

In the linear effective value transducer shown in FIG. ), the output of the inverting amplifier is -(Rz-
・e-)-vD).

(VD is a value representing the forward voltage drop of the diodes D++ and D+2.) The output voltage of the inverting amplifier is half-wave rectified by the rectifying diode D2, and then the output voltage of the diodes Dll and D12 is
The forward voltage drop value -vD of is canceled by the forward voltage value VD of this diode D2. Therefore, the voltage waveform on the cathode side of the rectifier diode D2, indicated by reference numeral 51, is the waveform e' shown in FIG.
Since the relational expression of et=-fat/e holds true, the voltage waveform at the 51 points is a faithful half-wave rectified voltage of the input voltage. After half-wave rectification with rectifier diode D2, diodes D1+, D+z
The voltage e' from which the forward voltage drop value -vD is removed is smoothed by a smoothing circuit composed of a resistor R1 and a capacitor C1, and the voltage waveform EC shown in FIG. It will take a while.

The signal waveform thus amplified in the inverting amplifier and then half-wave rectified by the rectifying diode D2 is smoothed by the resistor R1 and the capacitor C1.
Direct+11 of the above-mentioned circuit configuration according to an embodiment of the present invention
How the input/output linearity of the effective value transducer has been improved compared to the conventional one will be analyzed using mathematical formulas and with reference to FIGS. 2 to 5 below.

Here, the section on the horizontal axis in FIG. 2 [φ1. φ2] is the charging section to the capacitor C1, and the section [φ2. (2π+φ1)] is the discharge section from this capacitor C1. By the way, if the charging charge to the capacitor C1 in the charging section is Qa, and the discharging charge from the capacitor C1 in the discharging section is Qb, then Qa.

Qb can be expressed by equations (1) and (2) shown below, respectively.

When the operation of the circuit shown in FIG. 1 shifts from a transient state to a steady state, Qa = Qb, and therefore the first-order equation (3) is established.

Here, for simplicity, the input resistance R++ and the feedback resistance R
+2 is set to R++=R+2, and the half-wave rectified voltage C' represents the positive half cycle of the input voltage e.

Next, if a capacitor element is selected for the capacitor C1 so that the ripple contained in the voltage Ec is negligibly small, the waveform containing the minute ripple shown in Fig. 2 is shown in Fig. 3. Then, it can be expressed as a substantially flat straight line, so in equation (3) above, approximately φ1=
It is possible to set φ, φ22 (π−φ). Therefore, by substituting φ1=φ and φ2=(π−φ) into equation (3), the following equation (4) can be obtained.

Since the input voltage e is a sinusoidal AC, s'=Il'TE
Substituting sin θ into equation (4).

Also, since e'4inθ, EO= 'r”r E s inφ 19162
100010900910100006. (5) I holds true.

Generally, when an input signal waveform is distorted, it often becomes a waveform that can be approximated to a rectangular wave or a triangular wave. Therefore, if the voltage EO applied to both ends of the capacitor C1 is determined for a sine wave, a rectangular wave, and a triangular wave with the same effective value of the input voltage C, and a constant is determined by determining the conditions under which these are all equal, the distorted waveform This will reduce errors.

Below, we will calculate the voltage hie when the input voltage waveform is a rectangular wave and when the input voltage waveform is a triangular wave, and then find the conditions under which these EOs are equal.

[1] When the input voltage waveform is a rectangular wave (waveform ratio 1) When the input voltage waveform is a rectangular wave, the rectifying diode D
Voltage C' half-wave rectified by 2 and capacitor C1
The voltage EO applied across both ends is as shown in FIG.

Therefore, in equation (4), I = E.

Substitute φ=Q (because the rising edge of the square wave on the horizontal axis is θ=0, and the falling edge is 0=π).

EO:=−−−−1−・E, π 2πR1+πR2 1□・E ・・・・・・・・・・・・・・・・・・
+6)2R++Rz, and the above formula (6) is obtained.

[2] When the input voltage waveform is a triangular wave <tEL shape ratio 1,1
55) When the input voltage waveform is a triangular wave, the voltage e' passed by half mu by the rectifying diode D2 and the voltage Eo applied across the capacitor C1 are as shown in FIG. Therefore, when the triangular wave shown in FIG. 5 is used in a mathematical formula, the following formula (7) is obtained.

By substituting φ=φ' in equation (4) and substituting the above equation (7) for e', the above equation (8) is obtained.

Also, when θ=φ', e'=E□=child・−E・φ′ ・・・・・・・・・
... (9) π holds true.

Next, finding φ' from equations [8] and (9), we get 4R2φ”−4π(
ft2+2R+)φ'1π2R2==0.

As a result, the above formula 00 is obtained.

Substituting the above R1 formula into IIJ formula (8), = 6(
(2R1+Rz)-2 transfer, ,,000. (lυ
Thus, the above formula (Il) is obtained.

Therefore, the conditions under which the voltage IO applied to both ends of the capacitor C1 becomes equal when the input voltage waveform is a rectangular wave and when the input voltage waveform is a triangular wave are found to be equal when equation (6) and equation R9 become equal.

So, if we rearrange the above equation regarding R2.

(2-JT)Rz'+2(3-2ff)R+Rz+2(
3-2/T) Rt' = 0 konin and zff-3<l171
-2j-12B-3)0. R+)0゜1Lt)0 It comes out now, so now 4.275R1...River, River...
・You can get aa.

Therefore, if the relationship between the resistor R+, which together with the capacitor Ct constitutes the smoothing circuit, and the input resistor R1 of the # operational amplifier M2 is selected as shown in Equation 3, it will be possible to determine whether the input voltage waveform is a rectangular wave or a triangular wave. The capacitor C1
1 pressure E applied to both ends of.

You can match Jin.

Therefore (substituting formula 03 into formula 61 to find the above voltage go, ÷ 〇, 681E... river... old...
・River・ (You can get +3.

Next, the voltage EC when the input voltage waveform is a sine wave is determined.

Substituting formula (121) into formula (5), the above formula and the above f51' (Eo = ("E E s in
φ) is obtained, and solving the above equation in the range of 0〈φ〈d, we get
φ→0.5075 (+29.08°).

- Substitute this into equation 51 to find the voltage EO.

Eo = (”'r E sin (29,08°)+
0,687 E・・・・・・・・・・・・
......I Comparing the above-mentioned α country type and the above-mentioned 04 type, there are differences.

As described above, according to the linear effective value transducer shown in FIG. 1, it is possible to obtain a DC output voltage proportional to the effective value of the input AC voltage (or current).

Furthermore, as a result of an experiment using the transducer shown in Fig. 1, when the constants were determined to satisfy the above conditions, the error was 1% even when 15 third harmonics were included.
I was able to keep it within the following range. Furthermore, the relationship between resistors R+, R2+ and R22 is expressed as (R21+R2
2) It was confirmed that even when /R+ =' (3.5 to 4.5) was selected, it could be sufficiently put to practical use.

In addition, in FIG. 1, the connection direction of the rectifier diode D2 is determined so that the voltage at point 51 becomes a positive voltage.
Naturally, as shown in FIG. 7, the same operation is performed even if the connection direction of the diode D2 is reversed, only that the polarity of the output voltage is reversed between FIG. 1 and FIG. 6. It is. Note that in FIG. 6, only the portions necessary for explanation are reproduced from FIG. 1.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a first operational amplifier circuit in which the gain correction means for correcting the gain to 1 determined by the feedback resistor and the input resistance is connected to the feedback resistor; It consists of a rectifier circuit that rectifies the signal amplified by and removes the amplification correction value, a smoothing circuit that smoothes the signal output from the rectifier circuit, a resistor, and a capacitive element, and is output from the smoothing circuit. Since it has an integrating circuit that integrates the signal, even when a very low order signal is input, input/output linearity is good, and even when there is some distortion in the input voltage, this distortion causes the output to be This has the effect of providing a linear effective value transducer in which the error occurring in the signal can be kept within a small range.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a DC output voltage transducer showing an embodiment of the present invention, and FIGS. 2 and 3. 4 and 5 are voltage waveform diagrams of various parts used to explain the operation of the circuit of the present invention, and FIG. 6 is a partial diagram of a circuit of a linear effective value voltage transducer showing another embodiment of the present invention. FIG. 7 is a circuit diagram showing a conventional linear effective value voltage transducer. In the equation, Rat is the input resistance, R12 is the feedback resistance, and D
+1 is a diode, D12 is a diode, M+ is an operational amplifier, D2 is a rectifier diode bR + rs resistor, C1
is a capacitor, R21 is a resistor, and C2 is a capacitor. Note that the same reference numerals in each figure indicate the same or corresponding parts. Patent applicant: Mitsubishi Electric Corporation (2 others) “Figure 1 Figure 7

Claims (1)

[Claims] an operational amplifier circuit in which a feedback resistor is connected to an amplification correction means for correcting the amplification determined by the feedback resistor and the input resistance; a rectifier circuit that removes the amplification degree correction value corrected by the correction means from;
a smoothing circuit that smoothes the output signal from this rectifier circuit;
A linear effective value transducer comprising a resistor and a capacitive element, and an integrating circuit that integrates and outputs a signal output from the smoothing circuit.