JP2019039680A - Electronic circuit for measurement device, measurement device, and measurement method - Google Patents

Abstract

To provide an electronic circuit for a measurement device which has simple construction and low electric power consumption, and to provide the measurement device and a measurement method.SOLUTION: An electronic circuit for a measurement device comprises a current-output type sensing element, a power storage section, a resistor for measurement, and at least one constant-voltage element. The power storage section is connected at one terminal to a ground and one output terminal of the sensing element and is connected at the other terminal to the other output terminal of the sensing element. The resistor is connected at one terminal to the ground. The constant-voltage element is connected between the other terminal of the power storage section and the other terminal of the resistor so as to be in a forward direction with respect to a voltage between the terminals of the power storage section. When a charging voltage of the power storage section exceeds a threshold value voltage of the constant-voltage element, a current from the sensing element flows to the resistor and a voltage proportional to magnitude of the current is output between the terminals of the resistor while the charging voltage of the power storage section maintained in a range of an operating voltage of a measurement processing section by the constant-voltage element is supplied to the measurement processing section which measures the voltage between the terminals of the resistor.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electronic circuit, a measuring device, and a measuring method for a measuring device.

  In recent years, technological development of sensors used in IoT (Internet of Things) has been actively promoted. In IoT, for example, many different sensors that measure physical quantities such as the position, speed, acceleration, pressure, weight, temperature, humidity, light, magnetic field, voltage, current, and power of the measurement target can be used. In addition, many of these sensors can be used in various indoor and outdoor locations, such as homes, commercial facilities, factories, etc., depending on the application.

  Therefore, when a large number of sensors are used in various environments in IoT, it is important whether a power source for driving these sensors can be secured. In particular, when the sensor is used outdoors, it is often difficult to secure a commercial power supply as compared to when the sensor is used indoors. Even when a commercial power supply is used indoors (for example, in a factory), the number of commercial power supply ports (so-called outlets) is usually limited. Can be complex. On the other hand, when driving a sensor using a battery, there is a problem that it takes much time and cost if the batteries of many sensors are replaced.

  In relation to this, in Patent Document 1 below, when the input current of the current transformer is measured using a microcomputer, the output current of the current transformer is stored in a capacitor and used as the driving power of the microcomputer. A measuring device to be used is disclosed. According to the measurement apparatus of Patent Document 1, since the electric charge stored in the capacitor is used as driving power for a microcomputer (hereinafter referred to as “microcomputer”), an external power source such as a commercial power source and a battery are not required.

  However, the measuring device disclosed in Patent Document 1 generates an output voltage to the microcomputer (output of the terminal ADC4 in FIG. 6) by the storage circuit, and then switches the circuit to the measurement circuit by the relay circuit (storage / measurement control unit). Since the measurement is performed by the (measurement unit), there is a problem that the configuration is complicated and large, and the measurement frequency is low. As a result, there is a possibility that the measuring device of Patent Document 1 cannot sufficiently cope with the downsizing and power saving required by IoT.

JP 2014-85241 A

  The present invention has been made in view of the above problems. Accordingly, an object of the present invention is to provide an electronic circuit, a measuring device, and a measuring method for a measuring device that have a simple configuration and low power consumption.

  The above object of the present invention is achieved by the following.

  An electronic circuit for a measuring device includes a current output type sensing element, a power storage unit, a measuring resistor, and at least one constant voltage element. The power storage unit has one terminal connected to the ground and one output terminal of the current output type sensing element, and the other terminal connected to the other output terminal of the current output type sensing element. One terminal of the measuring resistor is connected to the ground. At least one constant voltage element is connected between the other terminal of the power storage unit and the other terminal of the measuring resistor so as to be in a forward direction with respect to the voltage between the terminals of the power storage unit. Yes. When the charging voltage of the power storage unit exceeds the threshold voltage of the constant voltage element, the current from the current output type sensing element flows through the measuring resistor, and the voltage proportional to the magnitude of the current is measured. Output between the terminals of the resistor for measurement, and to the measurement processing unit for measuring the voltage between the terminals of the measurement resistor, the constant voltage element is maintained within the operating voltage range of the measurement processing unit The charging voltage of the power storage unit is supplied.

  In addition, the measuring method uses a measuring device having an electronic circuit for the measuring device and a measurement processing unit that measures a voltage between terminals of the measuring resistor, and from the current output type sensing element. A measurement method for measuring current, the step of charging the power storage unit with the current, and the charging voltage of the power storage unit maintained within the operating voltage range of the measurement processing unit by the constant voltage element Supplying to the processing unit, measuring a voltage drop generated in the measuring resistor by the current when a charging voltage of the power storage unit exceeds a threshold voltage of the constant voltage element, and measuring Measuring a current from the current output type sensing element based on the voltage drop in the resistor.

  ADVANTAGE OF THE INVENTION According to this invention, the voltage for operating a measurement process part can be ensured using the threshold voltage of a constant voltage element simultaneously with converting the electric current from a current output type sensing element into a voltage with a resistor. Therefore, the relay circuit and control circuit which switch an electrical storage circuit and a measurement circuit unlike the past are unnecessary. In addition, the voltage supplied to the measurement processing unit is quickly secured by the constant voltage element, maintained within the operating voltage range of the measurement processing unit, and a voltage proportional to the current from the current output type sensing element is used for measurement. Is output across the resistor terminals. Thereby, an electronic circuit for a measuring apparatus having a simple configuration and low power consumption can be realized.

It is a schematic block diagram which illustrates the composition of the measuring device of one embodiment. FIG. 2 is a circuit diagram illustrating a configuration of a rectifying unit illustrated in FIG. 1. FIG. 2 is a circuit diagram illustrating a configuration of a power storage unit illustrated in FIG. 1. FIG. 2 is a circuit diagram illustrating the configuration of a booster and an output generator shown in FIG. 1. FIG. 2 is a circuit diagram illustrating a configuration of a measurement control unit illustrated in FIG. 1. It is a simulation model which illustrates the circuit which acquires a voltage with the output current of a current transformer. It is a graph which shows the result of having performed simulation by LTspice about the simulation model of Drawing 6A. It is a simulation model which illustrates the composition which restricts the charge voltage of a capacitor. It is a graph which shows the result of having performed simulation by LTspice about the simulation model of Drawing 7A. 8B is a graph illustrating the relationship between the output current of the current transformer and the voltage at the output terminal OUT in the case illustrated in FIGS. 7A and 7B. It is a simulation model which illustrates the composition which acquires the voltage for measurement with a resistor. It is a graph which shows the result of having performed simulation by LTspice about the simulation model of FIG. It is a flowchart which illustrates about the measuring method of the input current of a current transformer. It is a circuit diagram which shows the modification of the output generation part of this embodiment. It is a circuit diagram which shows the other modification of the output generation part of this embodiment. It is a circuit diagram which shows the other modification of the output generation part of this embodiment. It is a circuit diagram which shows the other modification of the output generation part of this embodiment.

  Embodiments of an electronic circuit, a measuring device, and a measuring method for a measuring device according to the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals are used for the same members. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  With reference to FIGS. 1-5, the measuring apparatus of one Embodiment is demonstrated. FIG. 1 is a schematic block diagram illustrating the configuration of a measurement apparatus according to an embodiment, and FIG. 2 is a circuit diagram illustrating the configuration of a rectifying unit illustrated in FIG. 3 is a circuit diagram illustrating the configuration of the power storage unit illustrated in FIG. 1, FIG. 4 is a circuit diagram illustrating the configuration of the boosting unit and the output generation unit illustrated in FIG. 1, and FIG. It is a circuit diagram which illustrates the composition of the measurement control part shown.

<Measurement device 100>
As illustrated in FIG. 1, the measurement apparatus 100 includes a current transformer 110, a rectification unit 120, a power storage unit 130, a boosting unit 141, an output generation unit 142, a measurement control unit 150, and a measurement processing unit 160. The measurement apparatus 100 is a non-powered measurement apparatus that stores electric charges with current from a current output type sensing element and secures an operating voltage of a measurement processing unit without receiving power from a power source such as a commercial power source or a battery. It is. In the present embodiment, the measuring apparatus 100 measures the input current of the current transformer 110 by the microcomputer while accumulating electric charge by the current from the current transformer 110 as a current output type sensing element to secure the operating voltage of the microcomputer.

  In the following, the current transformer 110 is described as an example of the current output type sensing element, but the current output type sensing element is not limited to the current transformer 110. The current output type sensing element may be, for example, a solar cell, a thermocouple, a vibration power generation element, a radio wave antenna, or the like.

<Current transformer 110>
The current transformer 110 generates and outputs an output current having a magnitude proportional to an input current (for example, an AC current of 50 [Hz]) flowing through the electric wire w. The current transformer 110 is, for example, a clamp-type current transformer having a mechanism for clamping the electric wire w, and two output terminals are respectively connected to two input terminals of the rectifying unit 120.

Assuming that the number of turns of the current transformer 110 is N, the input current is i _in , and the output current is i _out , the output current i _out can be expressed as the following formula (1).

Note that the magnitudes of the input current i _in and the output current i _out are not particularly limited. However, practically, the number of turns N is preferably set according to the expected maximum value of the input current i _in so that the maximum value of the output current i _out is, for example, about 20 to 50 [mA]. . The current transformer 110 is not limited to a clamp-type current transformer, and may be a split-type, wound-type, or through-type current transformer.

<Rectifying unit 120>
The rectifying unit 120 rectifies the output current i _out output from the current transformer 110 and converts it into a direct current _ID . As illustrated in FIG. 2, the rectifying unit 120 includes a full-wave rectifier including, for example, four Schottky barrier diodes D _{01 to} D ₀₄ . The two input terminals T ₀₁ and T ₀₂ of the full-wave rectifier are connected to two output terminals of the current transformer 110, respectively, and the two output terminals of the rectifier 120 are connected to the power supply line VCC and the ground GND, respectively.

  The rectifying unit 120 can also be configured using a half-wave rectifier instead of the full-wave rectifier.

<Power storage unit 130>
As shown in FIG. 3, the power storage unit 130 includes a capacitor C <b> ₁₁ and is charged with a direct current _ID output from the rectifying unit 120. Capacitor _{C 11} can be, for example, an electrolytic capacitor.

One terminal (negative electrode) of the capacitor _{C 11} is connected to one output terminal of the rectification section 120 (ground GND), the other terminal of the capacitor _{C 11} (positive electrode), the other output terminal of the rectification section 120 (power source Line VCC).

  Power storage unit 130 may include a plurality of capacitors connected in parallel. The power storage unit 130 may include a small secondary battery instead of the capacitor.

<Boosting Unit 141 and Output Generation Unit 142>
The booster 141 secures a voltage for operating the measurement processor 160 using the forward voltage (threshold voltage) of the diode (constant voltage element). The output generator 142 outputs a voltage proportional to the magnitude of the direct current _ID from the rectifier 120.

As shown in FIG. 4, the boosting unit 141 has a light-emitting diode _{D 21.} The output generation unit 142 includes a voltage generation unit and a filter unit. Voltage generator includes a resistor (a resistor for measurement) R _21. One terminal of the resistor _{R 21} is connected to the ground GND, the other terminal of the resistor _{R 21} is connected to one terminal of the light emitting diode _{D 21} of the boosting unit 141 (the cathode). Resistor R ₂₁ outputs a voltage of a magnitude proportional to the magnitude of the DC current I _D to the other terminal.

The other terminal of the light emitting diode _{D 21} (anode) is connected to the power supply line VCC. Accordingly, the light emitting diode D ₂₁ is connected in a forward direction with respect to the inter-terminal voltage of the storage unit 130 between the other terminal of power storage unit 130 and the other terminal of the resistor R _21.

Emitting diode D _21, when the power storage unit 130 is charged, to limit the voltage across the terminals of the power storage unit 130 rises above the forward voltage of the light emitting diode D _21. If the inter-terminal voltage of the storage unit 130 has reached the forward voltage of the light-emitting diodes _{D 21,} flowing through all the DC current _{I D} flowing from the rectifier unit 120 is a light emitting diode _{D 21} and a resistor _{R 21.} Details of the role of the light emitting diode D ₂₁ and the resistor R ₂₁ will be described later.

Filter unit includes a resistor _{R 22} and capacitor _{C 21.} One terminal of the resistor R _{22 is connected to} the other terminal of the resistor R ₂₁ and one terminal (cathode) of the light emitting diode D ₂₁ , and the other terminal of the resistor R ₂₂ is connected to the output generator 142. output terminal T ₂₁ of and are connected to one terminal of the capacitor C _21. The output terminal T ₂₁ is connected to the measurement processing unit 160.

The other terminal of the capacitor _{C 21} is connected to the ground GND. Resistor R ₂₂ and capacitor C ₂₁ operate as a low-pass filter for the voltage signal output from the other terminal of resistor R ₂₁ .

<Measurement control unit 150>
The measurement control unit 150 controls activation and termination of the measurement processing unit 160. As shown in FIG. 5, the measurement control unit 150 includes a voltage detection circuit 151, resistors R ₃₁ and R ₃₂ , and FETs Q ₃₁ and Q ₃₂ .

The voltage detection circuit 151 has an input terminal V _in , a ground terminal Gd, and an output terminal V _out . Input terminal _{V in} the voltage detection circuit 151 is connected to a power supply line VCC, a ground terminal Gd is connected to the drain terminal D of the FETs Q _32, the output terminal _{V out} is connected to the gate terminal G of the FETs Q _31.

Voltage detection circuit 151, when the voltage at the input terminal _{V in} is less than the threshold voltage TH, then a non-conductive state between the input terminal _{V in} and the output terminal _{V out,} between the ground terminal Gd and the output terminal _{V out} Make it conductive. On the other hand, the voltage detecting circuit 151, when the voltage of the power supply line VCC is equal to or higher than the threshold voltage TH, and the conduction state between the input terminal _{V in} and the output terminal _{V out,} the ground terminal Gd and the output terminal _{V out} Make the connection non-conductive.

One terminal of the resistor _{R 31} is connected to the power supply line VCC, the other terminal of the resistor _{R 31} is connected to the gate terminal G of the output terminal _{V out} and FETs Q ₃₁ of the voltage detection circuit 151. One terminal of the resistor _{R 32} is connected to the power supply line VCC, the other terminal of the resistor _{R 32} is connected to the gate terminal G of the output terminal _{T 31} and FETs Q ₃₂ of the measurement control unit 150.

The FETs Q ₃₁ and Q ₃₂ are n-type FETs and operate as switches. The gate terminal G of the FET Q ₃₁ is connected to the output terminal V _out of the voltage detection circuit 151 and the other terminal of the resistor R ₃₁ , the source terminal S is connected to the ground GND, and the drain terminal D is the output terminal of the measurement control unit 150. It is connected to the T _32. The gate terminal G of the FET Q ₃₁ is connected to the other terminal of the resistor R ₃₂ , the source terminal S is connected to the ground GND, and the drain terminal D is connected to the ground terminal Gd of the voltage detection circuit 151. The output terminals T ₃₂ and T ₃₂ are connected to the measurement processing unit 160.

<Measurement processing unit 160>
Measurement processing unit 160 is driven by the voltage between the power supply line VCC and ground GND, and on the basis of the voltage across the resistor R ₂₁ of the output generation unit 142, measures the input current of the current transformer 110.

  The measurement processing unit 160 includes a small and low power consumption one-chip microcomputer in which components such as an arithmetic processing unit, a memory unit, a communication unit, and an AD converter (all not shown) are integrated.

  The memory unit has a RAM (Randam Access Memory) and a flash memory.

The communication unit includes a wireless communication module, a PWM (Pulse Width Modulation) module, a UART (Universal Asynchronous Receiver / Transmitter) module, an SPI (Serial Peripheral Interface) module, and an I ² C (Inter-Integrated C module). An antenna (not shown) is connected to the wireless communication module.

Input terminal of the AD converter is connected to the output terminal T ₂₁ of the output generation unit 142, AD converter, a voltage signal output from the other terminal of the resistor R ₂₁ is converted into a digital signal, as the measurement data Store in RAM.

The arithmetic processing unit calculates a direct current _ID using the measurement data. The arithmetic processing section calculates the input current i _in on the basis of the number of turns N of the current transformer 110, further, on the basis of the input current i _in calculated, to calculate the power (apparent power) due to the input current i _in You can also. More specifically, the arithmetic processing unit acquires a voltage applied to the load of the electric device through which the measured input current i _in flows, and calculates a product of this voltage and the input current i _in .

<Operation Principle of Measuring Device 100>
Hereinafter, the operation principle of the measuring apparatus 100 will be described in detail with reference to FIGS. 6A to 10.

1. Acquisition of Operating Voltage of Microcomputer FIG. 6A is a simulation model illustrating a circuit that acquires a voltage by the output current of a current transformer. FIG. 6B is a graph showing a result of simulation performed on the simulation model of FIG. 6A by LTspice, a Spice electronic circuit simulator manufactured by Linear Technology. In FIG. 6B, the horizontal axis represents the elapsed time [s] from the start of the simulation, and the vertical axis represents the voltage [V] at the output terminal OUT.

  As shown in FIG. 6A, in the simulation model, the current transformer is represented as a current source I1 of 50 [Hz] and 1 [mA]. The output current of the current transformer is rectified by a full-wave rectifier including Schottky barrier diodes D3 to D6 to generate a direct current I, and then charged to the capacitor C1 (220 [μF]). The charging voltage of the capacitor C1 (hereinafter simply referred to as “charging voltage”) can be obtained from the output terminal OUT.

  As shown in FIG. 6B, when the capacitor C1 was charged for 3 seconds, the voltage at the output terminal OUT increased linearly over time for 3 seconds from the start to the end of the simulation. From this result, it is possible to obtain a voltage exceeding the lower limit (for example, 2 [V]) of the operating voltage required to drive the microcomputer or the like by charging the capacitor C1 for about 1 second.

2. Restriction of Charging Voltage FIG. 7A is a simulation model illustrating a configuration for restricting the charging voltage of the capacitor C1, and FIG. 7B is a graph showing a result of executing simulation by LTspice for the simulation model of FIG. 7A. In FIG. 7B, the horizontal axis represents the elapsed time [s] from the start of the simulation, and the vertical axis represents the voltage [V] at the output terminal OUT.

  As described above, in the simulation model of FIG. 6A, the charging voltage increases linearly with time. Therefore, as shown in FIG. 6B, when the charging of the capacitor C1 by the direct current I continues for 1.3 [s] or more, the charging voltage exceeds the upper limit (eg, 3.6 [V]) of the microcomputer operating voltage. End up.

  Therefore, a diode is further inserted between the output terminal OUT and the ground GND, and the charging voltage is limited by the forward voltage of the diode. In the example shown in FIG. 7A, a Schottky barrier diode D1 and a light emitting diode D2 are inserted in series between the output terminal OUT and the ground GND. The charging voltage is limited at most by the sum of the forward voltage VF1 of the Schottky barrier diode D1 and the forward voltage VF2 of the light emitting diode D2.

  In general, the forward voltage of a diode varies depending on the type of the diode. Therefore, by using a combination of a plurality of diodes having different forward voltages, the charging voltage can be set to a different value as required. For example, the forward voltage of the PN junction diode is about 1.2 [V], the forward voltage of the Schottky barrier diode is about 0.6 [V], and the forward voltage of the red light emitting diode is about 1.8 [V]. The forward voltage of the blue light emitting diode is about 3 [V].

  For example, if a voltage of 3.6 [V] is required to drive the microcomputer, 0.6 [V] +3 [V] = 3.6 is obtained by connecting a Schottky barrier diode and a blue light emitting diode in series. The voltage of [V] can be acquired.

  In the example shown in FIG. 7A, the current transformer is a current source I1 of 50 [Hz] and 100 [μA]. Therefore, since the current flowing through the Schottky barrier diode D1 and the light emitting diode D2 is extremely small, the charging voltage is limited to a voltage lower than the sum of the forward voltages described above.

  As shown in FIG. 7B, the voltage at the output terminal OUT increases linearly at a rate of about 0.3 [V / s] until about 8 seconds from the start of the simulation. The constant value of about 2.3 [V] is maintained from 11 seconds to 20 seconds when the simulation ends. From this result, the voltage of the output terminal OUT does not exceed the upper limit (eg, 3.6 [V]) of the operating voltage of the microcomputer even if the capacitor C1 is charged for a long time. Even when the current source I1 is a weak current of 100 [μA], a voltage necessary for driving the microcomputer can be secured.

3. Correlation between DC Current I and Charging Voltage FIG. 8 is a graph illustrating the relationship between the output current of the current transformer and the voltage at the output terminal OUT in the case shown in FIGS. 7A and 7B. In the example shown in FIGS. 7A and 7B, the capacitor C1 is charged by the direct current I until the charging voltage reaches the sum of the forward voltage of the Schottky barrier diode D1 and the forward voltage of the light emitting diode D2.

  The charging voltage is about 2. after about 11 seconds after the charging of the capacitor C1 by the direct current I proceeds and the charging voltage reaches the sum of the forward voltage VF1 of the Schottky barrier diode D1 and the forward voltage VF2 of the light emitting diode D2. 3 [V] is constant. Thereafter, the direct current I does not flow to the capacitor C1, but flows to the Schottky barrier diode D1 and the light emitting diode D2, and is converted into light in the light emitting diode D2. That is, the Schottky barrier diode D1 and the light emitting diode D2 are turned on, and the direct current I all flows through the Schottky barrier diode D1 and the light emitting diode D2.

  When the Schottky barrier diode D1 and the light emitting diode D2 are in the “on” state, the charging voltage of the capacitor C1 depends on the DC current I, that is, the output current of the current source I1, according to the voltage / current characteristics of both the diodes D1 and D2. It becomes the size.

  As shown in FIG. 8, the output current of the current transformer is changed from 100 [μA] to 20 [mA], and the change in the voltage at the output terminal OUT is examined. As a result, the range in which the microcomputer can operate at all currents (For example, 2.0 to 3.6 [V]). Therefore, when the output current of the current transformer is in the range of 100 [μA] to 20 [mA], the capacitor C1, the Schottky barrier diode D1, and the light emitting diode D2 are used as a power supply circuit that generates a microcomputer drive voltage from the direct current I. Playing a role. The light emitting diode D2 also plays a role of consuming excess DC current I by converting it to light after the charging voltage reaches the operating voltage of the microcomputer.

  The voltage at the output terminal OUT changes in a logarithmic function with respect to the output current of the current transformer. That is, the output current of the current transformer changes exponentially with respect to the voltage at the output terminal OUT. This corresponds to the voltage / current characteristics of the Schottky barrier diode D1 and the light emitting diode D2. Therefore, by inputting the voltage at the output terminal OUT to the microcomputer as the measurement voltage, the microcomputer determines the voltage at the output terminal OUT based on the correspondence between the voltage at the output terminal OUT and the output current of the current transformer in FIG. It can be converted to the output current of the current transformer.

4). Improvement of Measurement Accuracy FIG. 9 is a simulation model illustrating a configuration for acquiring a measurement voltage using a resistor, and FIG. 10 is a graph showing a result of simulation performed by LTspice on the simulation model of FIG. In FIG. 10, the horizontal axis represents the output current [mA] of the current transformer, and the vertical axis represents the voltage [V] at the output terminals PowerSupply and DataOutput.

  In the example shown in FIG. 7A, the voltage at the output terminal OUT is affected by the temperature dependence of the Schottky barrier diode D1 and the light emitting diode D2. Further, there is an exponential / logarithmic function relationship corresponding to the voltage / current characteristics of the diode between the voltage at the output terminal OUT and the output current of the current transformer. Thereby, when the output current of the current transformer is measured, if the output current is large, the measurement error of the output current can be enlarged even if the measurement error of the voltage at the output terminal OUT is small.

  On the other hand, in the example shown in FIG. 9, the light emitting diode D2 and the resistor R1 are connected in series between the output terminal OUT and the ground GND, and the voltage between the terminals of the resistor R1 is acquired as the measurement voltage. After the charging voltage reaches the forward voltage of the light emitting diode D2, all the direct current I flows through the light emitting diode D2 and the resistor R1. The voltage across the resistor R1 is input to the microcomputer and converted to a direct current I.

  Since the output current of the current transformer is the current source I1, and the resistor R1 has a very small temperature dependency compared to the diode, a current corresponding to the current source I1 flows through the resistor R1. Therefore, the voltage across the resistor R1 is hardly affected by temperature. In addition, since the resistor R1 is a linear element, even if the output current is large, the measurement error of the output current is not expanded due to the error of the voltage between the terminals of the resistor R1. Therefore, a measurement voltage with a small error can be provided to the microcomputer.

  When an AC current of 50 [Hz] is supplied from the current source I1, a ripple of 50 [Hz] that cannot be removed by the full-wave rectifier can be an error. This error can be sufficiently reduced by increasing the capacitance of the capacitor C1 so that the ripples are averaged. Further, by averaging the acquired measurement voltage by microcomputer software processing, it is possible to reduce ripple errors.

  As shown in FIG. 10, the output current of the current transformer was changed from 1 to 100 [mA], and the voltages at the output terminal PowerSupply and the output terminal DataOutput were examined. As a result, it was confirmed that a voltage necessary for the operation of the microcomputer can be acquired from the output terminal PowerSupply, and a linear measurement voltage can be acquired from the output terminal DataOutput. In the example shown in FIG. 10, when the operating voltage range of the microcomputer is 2 to 3.6 [V], it is possible to measure the direct current I of approximately 6 to 77 [mA].

  In practice, a diode and a resistor are selected so that the operating voltage range of the microcomputer matches the measurement range of the direct current I, and the circuit is designed. More specifically, the intercept and slope of the voltage (power supply voltage) at the PowerSupply terminal are adjusted so that the range of the operating voltage of the microcomputer is satisfied in the DC current measurement range. The intercept of the power supply voltage is adjusted by the forward voltage of the light emitting diode D2. Further, since the slope of the power supply voltage is the same as the slope of the measurement voltage, it is adjusted by the value of the resistor R1. In practice, it is preferable to add a low-pass filter between the output terminal DataOutput and the input terminal of the microcomputer.

<Measurement method of current transformer input current>
Next, a method for measuring the input current of the current transformer of this embodiment will be described with reference to FIG. FIG. 11 is a flowchart illustrating a method for measuring the input current of the current transformer.

First, the power storage unit 130 is charged (step S101). When the input current i _in flows through the electric wire w, the current transformer 110 generates and outputs an output current i _out proportional to the input current i _in . The rectifying unit 120 rectifies the output current i _out output from the current transformer 110 and converts it into a direct current _ID . The power storage unit 130 is charged with the direct current _ID output from the rectification unit 120.

When the power supply line VCC becomes equal to or higher than the threshold voltage TH, the measurement control unit 150 drops the ground terminal of the microcomputer of the measurement processing unit 160 to the ground level and starts the microcomputer. Power storage unit 130 supplies the charging voltage is maintained within the range of the operating voltage of the microcomputer by a light emitting diode D ₂₁ to the microcomputer (step S102).

Then, it outputs a voltage drop across resistor _{R 21} (step S103). The output generator 142 outputs a voltage drop generated in the resistor R ₂₁ by the DC signal _ID after the charging voltage of the capacitor C ₁₁ reaches the forward voltage of the light emitting diode D ₂₁ .

Next, the input current i _in of the current transformer 110 is measured (step S104). Measurement processing unit 160, based on the voltage drop across resistor _{R 21,} measures the input current _{i in} of the current transformer 110.

Next, power by the input current i _in is calculated (step S105). Measurement processing unit 160, based on the input current _{i in} which is measured to calculate the power from the input current _{i in.} And a communication part transmits a measurement result.

As described above, the current _ID from the current transformer 110 is converted into a voltage by the resistor R _21, and at the same time, the measurement processing unit 160 is operated using the forward voltage of the light emitting diode D ₂₁ that is a constant voltage element. Can be secured. Therefore, there is no need for a relay circuit and a control circuit for switching between the storage circuit and the measurement circuit as in the prior art. This is because the present invention utilizes the properties of light-emitting diodes D _21, from the storage operation for operating the measurement processing portion 160, seamlessly transition to operation of measuring the input current, in order to perform without control is there. When the charging voltage of the storage unit 130 exceeds the forward voltage of the light-emitting diodes _{D 21,} the current _{I D} from the current transformer 110 light-emitting diodes _{D 21} is turned on flows through the resistor _{R 21.} Therefore, the charging voltage supplied to the measurement processing unit 160 is rapidly ensured by a light emitting diode D _21, while being maintained within the range of the operating voltage of the measurement processing unit 160, a current resistor output from the current transformer 110 It is consumed in the R _21. The voltage proportional to the current from the current transformer 110 is outputted between the terminals of the resistor R _21. Thereby, an electronic circuit for a measuring apparatus having a simple configuration and low power consumption can be realized.

<Modification>
FIG. 12 is a circuit diagram showing a modification of the booster 141 and the output generator 142 of the present embodiment, and FIGS. 13 to 15 show other modifications of the booster 141 and the output generator 142 of the present embodiment. FIG.

As shown in FIG. 12, the step-up unit 141 includes a diode _{D 42} in series to the light emitting diode _{D 41.} Because the current transformer 110 is a current source, even if the diode D ₄₂ is inserted in series with resistor R ₄₁ and the light emitting diode D _41, the DC current I _D is not affected. Therefore, it is possible to measure the DC current I _D with respect to the resistor R ₄₁ and the light emitting diode D ₄₁ by connecting at least one diode in series. Further, the DC current _ID can be measured even if another resistor is inserted in series with the resistor R ₄₁ and the light emitting diode D ₄₁ .

Thus, in the present embodiment, at least one diode between the power supply line VCC and the resistor R _41. By addition to the light-emitting diodes D ₄₁ to insert the other diodes, can set the charging voltage of the capacitor C ₁₁ in the voltage of the sum of the forward voltage and the forward voltage of the other diode of the light emitting diode D _41. Therefore, the setting range of the charging voltage can be expanded by combining a plurality of diodes.

As illustrated in FIG. 13, the boosting unit 141 includes a light emitting diode D ₅₂ and a light emitting diode D ₅₃ that are connected in parallel to the light emitting diode D ₅₁ and in a forward direction with respect to the voltage across the power storage unit 130.

The output generation unit 142 includes a resistor R ₅₂ and a resistor R ₅₃ having one terminal connected to the ground GND and the other terminal connected to the light emitting diode D ₅₂ and the light emitting diode D ₅₃ , respectively. The number of light emitting diodes and resistors connected in parallel with the light emitting diode D ₅₁ is not limited to two, and may be three or more.

As described above, by providing at least one light emitting diode connected in parallel with the light emitting diode D ₅₁ , when the output current _ID of the current transformer 110 is large, the direct current _ID is distributed to a plurality of light emitting diodes. Can be consumed. Therefore, the measuring apparatus 100 can handle even when the output current of the current transformer 110 is large.

As shown in FIG. 14, even if a diode-connected transistor Q ₆₁ is inserted in series with respect to the light emitting diode D ₆₁ so as to be forward with respect to the voltage across the power storage unit 130, the direct current I _D can be measured. In this specification, the diode connection means a state in which a base and a collector of a transistor are short-circuited, for example.

As shown in FIG. 15, even if the shunt regulator IC ₇₁ is inserted in series with the light emitting diode D _{71 in} a forward direction with respect to the voltage across the power storage unit 130, the direct current _ID is measured. Is possible.

  As described above, in the embodiment, the electronic circuit, the measuring device, and the measuring method for the measuring device of the present invention have been described. However, it goes without saying that the present invention can be appropriately added, modified, and omitted by those skilled in the art within the scope of the technical idea.

  For example, in the above-described embodiment, the light emitting diode sets the charging voltage and plays a role of converting the current from the current transformer into light and consuming it. However, the present invention is not limited to this case, and at least one diode and a lamp are provided instead of the light emitting diode, and at least one diode plays a role of setting a charging voltage, and the lamp converts the current from the current transformer into light. It may be configured to play a role of consumption.

100 measuring device,
110 Current transformer,
120 rectifier,
130 power storage unit,
141 booster,
142 output generator,
141 voltage generator,
150 measurement control unit,
151 voltage detection circuit,
160 Measurement processing unit.

The electronic circuit for the measuring device includes a current output type sensing element, a power storage unit, a measuring resistor, at least one constant voltage element, and a measurement control unit . The power storage unit has one terminal connected to the ground and one output terminal of the current output type sensing element, and the other terminal connected to the other output terminal of the current output type sensing element. One terminal of the measuring resistor is connected to the ground. At least one constant voltage element is connected between the other terminal of the power storage unit and the other terminal of the measuring resistor so as to be in a forward direction with respect to the voltage between the terminals of the power storage unit. Yes. The measurement control unit controls activation and termination of the measurement processing unit that measures the voltage across the terminals of the measurement resistor. The electronic circuit for the measuring device supplies the charging voltage of the power storage unit maintained within the operating voltage range of the measurement processing unit by the constant voltage element to the measurement processing unit, and activates the measurement processing unit In addition, when the charging voltage of the power storage unit exceeds the threshold voltage of the constant voltage element, the current from the current output type sensing element flows through the measurement resistor, and a voltage proportional to the magnitude of the current is obtained. Output between the terminals of the measuring resistor .

Further, the measurement method includes an electronic circuit for the measurement device, a measurement processing unit that measures a voltage between terminals of the measurement resistor, and a measurement control unit that controls activation and termination of the measurement processing unit. A measurement method for measuring a current from the current output type sensing element using a measuring device having a step of charging the power storage unit with the current, and an operating voltage of the measurement processing unit with the constant voltage element Supplying the charging voltage of the power storage unit maintained within the range to the measurement processing unit and starting the measurement control unit, and the charging voltage of the power storage unit exceeds a threshold voltage of the constant voltage element And measuring a voltage drop generated in the measurement resistor by the current, and measuring a current from the current output type sensing element based on the voltage drop in the measurement resistor. With the method comprising the steps of, a.

Claims (7)

A current output type sensing element;
A power storage unit having one terminal connected to the ground and one output terminal of the current output sensing element, and the other terminal connected to the other output terminal of the current output sensing element;
A measuring resistor with one terminal connected to the ground; and
At least one constant voltage element connected between the other terminal of the power storage unit and the other terminal of the measurement resistor so as to be in a forward direction with respect to the voltage between the terminals of the power storage unit; Have
When the charging voltage of the power storage unit exceeds the threshold voltage of the constant voltage element, the current from the current output type sensing element flows through the measuring resistor, and the voltage proportional to the magnitude of the current is measured. And output between the resistor terminals,
For a measuring device, which supplies a charging voltage of the power storage unit maintained within a range of operating voltage of the measurement processing unit by the constant voltage element to a measurement processing unit that measures a voltage between terminals of the measurement resistor Electronic circuit.   The electronic circuit for a measuring apparatus according to claim 1, further comprising at least one resistor having one terminal connected to the ground and the other terminal connected to the at least one constant voltage element.   3. The electronic circuit for a measurement device according to claim 1, wherein the at least one constant voltage element includes at least one of at least one diode, a light emitting diode, a diode-connected transistor, and a shunt regulator.   The electronic circuit for a measuring apparatus according to claim 1, wherein the current output type sensing element includes any of a current transformer, a solar cell, a thermocouple, a vibration power generation element, and a radio wave antenna. An electronic circuit for a measuring device according to any one of claims 1 to 4,
The measurement processing unit,
The current output type sensing element is a current transformer that generates an output current proportional to an input current,
The measurement processing unit uses a voltage between terminals of the power storage unit of the electronic circuit as a power supply voltage, and measures an input current of the current transformer based on a voltage between terminals of the measurement resistor. apparatus. The measurement processing unit
The measuring apparatus according to claim 5, further calculating power based on the input current based on the measured voltage applied to a load through which the input current flows and the input current. A current output type sensing element;
A power storage unit having one terminal connected to the ground and one output terminal of the current output sensing element, and the other terminal connected to the other output terminal of the current output sensing element;
A measuring resistor with one terminal connected to the ground; and
At least one constant voltage element connected between the other terminal of the power storage unit and the other terminal of the measurement resistor so as to be in a forward direction with respect to the voltage between the terminals of the power storage unit; A measurement method for measuring a current from the current output type sensing element using a measurement device having a measurement processing unit for measuring a voltage between terminals of the measurement resistor,
Charging the power storage unit with the current;
Supplying a charging voltage of the power storage unit maintained by the constant voltage element within a range of an operating voltage of the measurement processing unit to the measurement processing unit;
Measuring a voltage drop generated in the measuring resistor by the current when a charging voltage of the power storage unit exceeds a threshold voltage of the constant voltage element;
Measuring a current from the current output type sensing element based on the voltage drop in the measuring resistor.