JP2007232571A - Effective value arithmetic circuit and measuring device of voltage or the like - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an arithmetic circuit of the effective value of voltage or the like that has high sampling clock speed, can response also to the case where the number of measuring channels increases, and employs an arithmetic element inexpensively and easily available as a general-purpose arithmetic circuit. <P>SOLUTION: The voltage effective value arithmetic circuit comprises an A/D conversion circuit 3 that is connected to an alternating voltage input and digitizing alternating voltage sampled at a clock of a certain period, a zero-cross detecting circuit 5 for detecting zero cross timing of the alternating current, and an arithmetic circuit 1 for sequentially accumulating the values of square of the voltage digital signals and outputting the voltage squared accumulation value every zero cross timing. A CPU (Central Processing Unit) 7 connected to the arithmetic circuit 1 has a function of dividing the voltage squared accumulation value by the number M of samplings, and a function of square-root calculating the division value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an arithmetic circuit for an effective value and an effective power value for an AC voltage, an alternating current input waveform, and further relates to a voltage / current power measuring device using the effective value arithmetic circuit.

  There is known a measuring apparatus that calculates an effective value from an input waveform such as a voltage and displays the effective value on a display or records it with a recorder. The effective value of the alternating current is calculated by the following formula.

式中のＵkはサンプリング個所における電圧値、Ｍはサンプリング回数である。

In the equation, Uk is the voltage value at the sampling location, and M is the number of samplings.

  Such calculation has been processed by a DSP (Digital Signal Processor) which is an independent integrated circuit or a high-speed CPU. That is, as shown in FIG. 3, the input waveform is sampled at M sampling clocks (20 times per cycle in the illustrated example) per AC cycle (or a plurality of cycles). The voltage value (analog data) at the sampling location is converted from analog to digital (A / D). The voltage value Uk is squared, added for each sampling clock, and divided by the number of times of sampling M, and then the value obtained by calculating the square root is the digital value of the voltage. Then, it is used for display and the like.

  A circuit configuration for calculating such an effective value is disclosed in Patent Document 1. In the disclosed circuit configuration, the DSP calculates a series of effective values such as voltages from the square of the S voltage value Uk to the addition for each sampling clock, the division by the sampling clock M, and the root mean square (rms). Arithmetic processing.

  However, if such a series of calculations is processed by the DSP, the sampling clock speed increases or the DSP calculation speed cannot be met when the number of measurement channels increases. In addition, if a series of effective value calculation processes from the square of the sampling voltage value Uk to the addition for each sampling, division by the number of samplings M, and square root calculation are implemented by a dedicated circuit, the circuit is not necessarily a general-purpose operation circuit, and therefore the cost is not high. I won't.

  On the other hand, circuit elements such as an FPGA (Field Programmable Gate Array) that is equipped with a multiplier and can perform a product-sum operation at low cost have recently become widespread, and a circuit that performs a product-sum operation at low cost and at high speed can be configured. However, when the square root calculation and the division calculation are configured by circuit elements, there is a problem that many gates are consumed and the cost is high.

Japanese Patent No. 3236710

  The present invention was made in order to eliminate the above-described defects in the processing method performed by the conventional DSP, and can cope with a case where the sampling clock speed is high and the number of measurement channels is increased. An object of the present invention is to provide an arithmetic circuit for an effective value of voltage / current / power using an arithmetic element that is inexpensive and easily available as an arithmetic circuit, and a voltage / current / power meter using the effective value arithmetic circuit.

  For the calculation of the effective voltage value, the above equation is broken down: 1. Square of the voltage value, 2. Addition every sampling, 3. Divide by the number of times of sampling M, 4. Calculate the square root, and divide into four arithmetic processing be able to. In this series of calculation processes, the processes that require multiple calculations during the calculation of one effective value are 1. and 2, and 3. and 4. are only once during the calculation of one effective value. It is processing of. Therefore, the processing of 1. and 2 uses dedicated circuit elements, and the processing of 3. and 4. is effective for the voltage even if it is distributed to some of the functions of a general-purpose CPU (Central Processing Unit). The calculation speed of is not substantially reduced as a whole. Based on such knowledge, the present invention described below has been completed.

  The voltage effective value arithmetic circuit according to claim 1 of the present invention made to achieve the above object is connected to an AC voltage input, and the AC voltage sampled with a clock having a constant period is converted into a digital signal. An analog / digital conversion circuit that performs this operation, a zero-cross detection circuit that detects the zero-cross timing of the alternating current, and an arithmetic circuit that sequentially accumulates and adds the squared value of the voltage digital signal and outputs this voltage-square accumulated addition value at each zero-cross timing. And a central processing circuit connected to the arithmetic circuit is provided with a function of dividing the voltage square cumulative addition value by the number of samplings M and a function of calculating the square root of the division value.

  A current effective value calculation circuit according to claim 2 of the invention, which is also made to achieve the above object, is connected to an alternating current input, and the alternating current sampled with a clock of a fixed period is a digital signal. The analog / digital conversion circuit to be converted, the zero cross detection circuit for detecting the zero cross timing of the alternating current, and the value obtained by squaring the current digital signal are cumulatively added in order, and this current square cumulative addition value is output at each zero cross timing. A central arithmetic processing circuit having a circuit and connected to the arithmetic circuit is provided with a function of dividing the current square cumulative addition value by the number of samplings M and a function of calculating the square root of the division value. .

  A power rms value arithmetic circuit according to claim 3 of the present invention, which is also made to achieve the above object, is connected to an AC voltage input, and the AC voltage sampled with a clock of a fixed period is a digital signal. The first analog / digital conversion circuit to be converted is connected to an alternating current input and connected to the second analog / digital conversion circuit, the alternating voltage input or the alternating current input that is converted into a digital signal from the alternating current sampled with a clock of a fixed period. A zero-cross detection circuit for detecting the zero-cross timing of the alternating current, and a power value obtained by multiplying the voltage digital signal from the first conversion circuit and the current digital signal from the second conversion circuit, in order, and cumulative addition An arithmetic circuit that outputs a value for each zero-cross timing signal, a central arithmetic processing circuit connected to the arithmetic circuit, The function of dividing the calculated power accumulated value by the sampling number M, characterized by comprising.

  Furthermore, in order to achieve the above object, the voltage measuring device according to claim 4 of the present invention has a voltage effective value arithmetic circuit according to claim 1 in the display means and / or the recording means. It is connected.

  In order to achieve the above object, the current measuring instrument according to claim 5 of the present invention is characterized in that the current effective value calculation circuit according to claim 2 is connected to the display means and / or the recording means. It is characterized by.

  In order to achieve the above object, a power measuring instrument according to claim 6 of the present invention is characterized in that the power effective value calculation circuit according to claim 3 is connected to display means and / or recording means. It is characterized by.

  The voltage / current / power meter of the invention according to claim 7, which has been made to achieve the above object, is connected to an AC voltage input, and the AC voltage sampled with a clock having a constant period is digitally converted. A first analog / digital conversion circuit to be converted into a signal, a first arithmetic circuit for sequentially accumulating the square value of the voltage digital signal, and outputting the voltage square accumulated value at each zero cross timing of the input AC, and an AC current input An analog / digital second conversion circuit that converts the alternating current sampled with a clock of a fixed period into a digital signal, and a square value of the current digital signal is cumulatively added in order, and this current square cumulative addition value is added to the zero cross timing. A second arithmetic circuit that outputs each time, a voltage digital signal from the first conversion circuit, and a current digital signal from the second conversion circuit. A third arithmetic circuit that sequentially accumulates and adds the power value multiplied by the power signal, and outputs the cumulative power addition value at each zero cross timing, and includes a first arithmetic circuit, a second arithmetic circuit, and a third arithmetic circuit. A voltage effective value arithmetic circuit comprising a central arithmetic processing circuit connected to the arithmetic circuit, a function of dividing the voltage square cumulative addition value output from the first arithmetic circuit by the number of sampling times M, and a function of calculating the square root of the divided value. The current effective value arithmetic circuit having the function of dividing the current square cumulative addition value output from the second arithmetic circuit by the number of sampling times M and the function of calculating the square root of the division value, and the third arithmetic circuit A power effective value calculation circuit having a function of dividing the accumulated power accumulated addition value by the sampling count M is connected to the display means and / or the recording means.

  The effective value arithmetic circuit for voltage or the like according to the present invention combines a dedicated arithmetic circuit that performs only product-sum operation and a central processing circuit (CPU) that receives the product-sum operation result for each zero cross and performs division and square root operation. An effective value arithmetic circuit can be realized at low cost. Since the calculation elements of the product-sum calculation circuit that is available at low cost can be used, the entire configuration of the effective value calculation circuit can be manufactured at low cost.

  This effective value calculation circuit can process a large number of repeated operations at a high speed with a dedicated calculation circuit while calculating one effective value, and assigns a single operation to a general-purpose CPU while calculating one effective value. There is no reduction in the speed of the effective value arithmetic circuit as a whole. The burden on the CPU does not increase so much. Furthermore, the effective value calculation circuit for voltage or the like according to the present invention can easily cope with an increase in the number of measurement channels even when the sampling clock speed is increased.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, preferred modes for carrying out the present invention will be described in detail with reference to the drawings, but the scope of the present invention is not limited to these embodiments.

  FIG. 1 is a schematic block diagram showing an embodiment of a voltage / current power measuring apparatus to which the present invention is applied. As shown in the figure, this voltage / current power measuring device includes analog / digital (A / D) conversion circuits 3 and 4 and a zero cross detector 5 with a product-sum operation circuit 1 as a center. The product-sum operation circuit 1 is connected to a central processing unit (CPU) 7. Analog / digital (A / D) conversion circuits 3 and 4 are connected to a clock circuit 6.

  The product-sum operation circuit 1 is an independent integrated circuit, and is composed of, for example, an FPGA (Field Programmable Gate Array). As shown in FIG. 2, the multiplication circuit 11 and the subsequent addition circuit 15, the multiplication circuit 12 and the subsequent addition circuit 16, the multiplication circuit 13 and the subsequent addition circuit 17 are included. 2, Uk is a digital voltage input and corresponds to the output Uk (see FIG. 1) of the analog / digital conversion circuit 3, and Ik is a digital current input and corresponds to the output Ik of the A / D conversion circuit 4. Therefore, the multiplier circuit 11 calculates (digital voltage Uk) × (digital voltage Uk), that is, the square of the voltage, the multiplier circuit 12 calculates the square of the current, and the multiplier circuit 13 calculates (digital voltage Uk) × (digital current Ik). ) That is, the power is calculated.

The adder circuit 15 is a circuit that sequentially adds the voltage squares that are the outputs of the multiplier circuit 11. The adder circuit 15 accepts the zero cross signal from the zero cross detector 5, transfers the addition result Σ (Uk) ² to the CPU 7, and then resets. And repeats the next addition. The adder circuit 16 is a circuit for adding the output current squares of the multiplier circuit 12 in order, transferring the addition result Σ (Ik) ² to the CPU 7 by a zero cross signal, and then repeating the addition. The adder circuit 17 is a circuit that adds the output voltages of the multiplier circuit 13 in order, transfers the addition result Σ (Uk · Ik) to the CPU 7 by a zero cross signal, and then repeats the addition.

The CPU 7 connected to the product-sum operation circuit 1 has a function of performing division and square root operation by software processing. The addition result Σ (Uk) ² from the addition circuit 15 is connected to the Urms area 21 that performs voltage division and square root calculation in the CPU 7. The addition result Σ (Ik) ² from the adder circuit 16 is connected to an Irms area 22 that performs current division and square root calculation. The addition result Σ (Uk · Ik) from the adder circuit 17 is connected to the P area 23 that performs power division in the CPU 7.

  Further, a printer 9 as recording means, a display 10 as display means, and a keyboard 2 are connected to the CPU 7 via a digital / analog (D / A) conversion circuit 8.

  The voltage / current power measuring device shown in FIGS. 1 and 2 operates as follows. First, the functional operation as a voltage measuring device will be described with reference to the time chart shown in FIG.

  The waveform of the AC voltage to be measured input from the AC voltage input is, for example, the waveform shown in FIG. This is sampled at an appropriate number of times. The sampling frequency M is set via the keyboard 2 by the clock circuit 6 according to the required accuracy of voltage measurement. In the illustrated example, M = 20 times are sampled for one period of the sine waveform of (A). However, the actual measurement target is not necessarily a sine wave, and one waveform period (from the zero cross point to the next zero cross point) is not necessarily sampled M times the set one clock. Since an error occurs when the fraction is obtained, the sampling number M is increased in order to reduce the error. That is, it is necessary to raise the clock.

When the clock circuit 6 is set and the clock pulse shown in FIG. 3B is generated, the analog value of the voltage is sampled at the sampling point shown in FIG. Digital conversion is performed at the timing shown. This voltage value Uk becomes two inputs of the multiplication circuit 11 by circuit processing and is squared at the timing shown in (D) by the multiplication circuit 11. The square value (Uk) ² is added by the adding circuit 15 (see (E)).

When the zero cross detector 5 detects the zero cross signal from the AC voltage as shown in (F) while this series of operations is repeated, the voltage square cumulative addition value Σ (Uk) ² as the addition result is added from the adding circuit 15 to the CPU 7. (See (G)). In the illustrated example, the next zero cross point is detected when the number of samplings M = 20, and the addition result is transferred.

The addition result sigma (Uk) ^2, divide the clock period M by software processing by CPU 7, the square root operation. That is, the central processing circuit (CPU) 7 performs arithmetic processing according to a program command stored in an external memory (not shown).

A program having the procedure shown in the flowchart of FIG. 4 is written in the external memory. A command is input with the keyboard 2, and this program is started with CPU7. As shown in step 101 of FIG. 4, if the voltage square cumulative addition value Σ (Uk) ² is transferred from the addition circuit 15 of the product-sum operation circuit 1 to the temporary storage area in the CPU 7, Σ (Uk) ² / M is executed (step 102). If not transferred, it waits until it is transferred, and then executes step 102. Next, when a square root operation of Σ (Uk) ² / M is executed (step 103), an effective voltage value is obtained.

  The voltage / current power measuring device shown in FIGS. 1 and 2 can also perform functional operations as a current measuring device and a power measuring device in addition to the functional operations as the voltage measuring device described above with reference to FIGS. 3 and 4. The functional operation as a current measuring device and a power measuring device is different in the input of alternating current to be measured, but the operation procedure and calculation contents are almost the same as those of the voltage measuring device.

  The current measuring device uses an alternating current input. Since the power meter uses an AC voltage input and an AC current input, and the multiplication circuit 13 calculates voltage × current (= power), the CPU 7 does not need the square root calculation (step 103).

1 is a schematic block diagram showing the entirety of an embodiment of a voltage / current power measuring device to which the present invention is applied.

The schematic block diagram which shows the principal part of one Example of the voltage current power measuring device to which this invention is applied.

The time chart figure in case the voltage current power measuring device to which this invention is applied functions as a voltage measuring device.

The flowchart figure which shows the operation | movement procedure of the central processing circuit in case the voltage current power measuring device to which this invention is applied functions as a voltage measuring device.

Explanation of symbols

  1 is a product-sum operation circuit, 2 is a keyboard, 3 and 4 are analog / digital (A / D) conversion circuits, 5 is a zero cross detector, 6 is a clock circuit, 7 is a central processing circuit, and 8 is digital / analog ( D / A) conversion circuit, 9 is a printer, 10 is a display, 11, 12 and 13 are multiplication circuits, 15, 16 and 17 are addition circuits, 21 is an area for voltage calculation Urms, 22 is an area for voltage calculation Irms, 23 Is an area of power calculation P.

Claims (7)

An analog / digital conversion circuit that converts the AC voltage sampled with a clock of a fixed period into a digital signal, a zero-cross detection circuit that detects the zero-cross timing of the AC, and a value obtained by squaring the voltage digital signal in order An arithmetic circuit that performs cumulative addition and outputs the voltage square cumulative addition value at each zero cross timing;
A voltage effective value arithmetic circuit characterized in that a central arithmetic processing circuit connected to the arithmetic circuit has a function of dividing the voltage square cumulative addition value by the number of times of sampling M and a function of calculating a square root of the division value. . An analog / digital conversion circuit that converts the alternating current sampled with a clock of a constant cycle into a digital signal, a zero-cross detection circuit that detects the zero-cross timing of the alternating current, and a value obtained by squaring the digital current signal in order An arithmetic circuit that performs cumulative addition and outputs the current square cumulative addition value at each zero-cross timing;
A current effective value arithmetic circuit characterized in that a central arithmetic processing circuit connected to the arithmetic circuit is provided with a function of dividing the current square cumulative addition value by the number of times of sampling M and a function of calculating the square root of the divided value. . An analog / digital first conversion circuit that converts the AC voltage sampled with a clock with a fixed period into a digital signal, connected to the AC voltage input, and converts the AC current sampled with a clock with a fixed period into a digital signal. Analog / digital second conversion circuit, zero-cross detection circuit connected to the AC voltage input or AC current input and detecting the zero-cross timing of the AC, voltage digital signal from the first conversion circuit and current from the second conversion circuit An arithmetic circuit that sequentially accumulates and adds the power value multiplied by the digital signal, and outputs the multiplied power accumulated addition value for each zero-cross timing signal,
A power effective value calculation circuit comprising a central processing circuit connected to the calculation circuit, and a function of dividing the cumulative power addition value by the number of sampling times M.   2. A voltage measuring instrument, wherein the voltage effective value calculation circuit according to claim 1 is connected to display means and / or recording means.   3. A current measuring instrument, wherein the current effective value calculation circuit according to claim 2 is connected to display means and / or recording means.   4. A power measuring instrument, wherein the power effective value calculation circuit according to claim 3 is connected to display means and / or recording means. An analog / digital first conversion circuit that converts the AC voltage sampled with a clock of a constant cycle into a digital signal and the square value of the voltage digital signal are cumulatively added in order, and this voltage square cumulative addition value is connected to the AC voltage input. A first arithmetic circuit that outputs each zero cross timing of the input AC;
An analog / digital second conversion circuit that is connected to an AC current input and converts the AC current sampled with a clock of a fixed period into a digital signal, and a square value of the current digital signal are sequentially accumulated and added. A second arithmetic circuit that outputs at each zero-cross timing;
A third arithmetic circuit that sequentially accumulates and adds power values obtained by multiplying the voltage digital signal from the first conversion circuit and the current digital signal from the second conversion circuit, and outputs the multiplied power cumulative addition value at each zero-cross timing. And
In the central arithmetic processing circuit connected to the first arithmetic circuit, the second arithmetic circuit, and the third arithmetic circuit,
A voltage effective value arithmetic circuit having a function of dividing the voltage square cumulative addition value output from the first arithmetic circuit by the number of times of sampling M and a function of calculating a square root of the divided value;
Current effective value arithmetic circuit having a function of dividing the current square cumulative addition value output from the second arithmetic circuit by the number of sampling times M and a function of calculating the square root of the divided value, and output from the third arithmetic circuit A power rms value arithmetic circuit having a function of dividing the cumulative power multiplication added value by the number of times of sampling M,
A voltage / current power measuring device connected to display means and / or recording means.

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