JP2016161276A - Current sensor circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of necessity of adding an extra process to acquire correction data if a sensor sensitivity and an offset have to be corrected for dealing with environmental temperature change based on existing correction data stored.SOLUTION: Conducting the usual inspection by an inspection device inspecting an output of a current sensor corresponding to environmental temperature change alone allows the sensitivity and offset setting data corresponding to the environmental temperature to be automatically stored, and the current sensor can supply a stable output based on the corrected setting data if it is subject to the environmental temperature change.SELECTED DRAWING: Figure 1

Description

The present invention automatically acquires and stores the sensitivity and offset setting value related to the output of the current sensor circuit with respect to the environmental temperature without changing the existing inspection equipment, and can automatically set the sensitivity setting and offset setting for the environmental temperature. The present invention relates to a current sensor circuit capable of providing a sensor.

A conventional method for correcting output fluctuations due to environmental temperature changes in a sensor circuit including a current sensor is based on correction data recorded in an EEPROM, as seen in the embodiment of a pressure sensor disclosed in Japanese Patent Laid-Open No. 2000-214029. The sensor output is corrected due to temperature changes.

JP2000-214029

In the above invention, sensor sensitivity and offset correction are performed using the data recorded in the EEPROM with sensor circuit output fluctuations accompanying environmental temperature changes. However, the controller circuit configured by the CPU in the above invention obtains correction data. Since the control circuit does not have a function for obtaining the timing, the control circuit cannot read the output from the sensor itself, obtain correction data, and record it in the EEPROM. Therefore, it is necessary to add an inspection device and a process for reading the output from the sensor at each environmental temperature, obtaining a correction value from the read value and recording it in the EEPROM, and a practical problem that an increase in manufacturing cost is inevitable. was there.

In order to solve the above-mentioned problems, a current sensor circuit according to a first aspect of the present invention includes a hall sensor that detects a magnetic flux generated by a measurement current, an amplifier circuit that amplifies the hall sensor output, and a hall sensor that drives the hall sensor. A constant current circuit for determining sensitivity, an offset setting D / A circuit for determining an offset of an amplifier circuit output, a sensitivity setting D / A circuit for setting the current value of the constant current circuit and setting the sensitivity of the current sensor, and the environment A temperature sensing circuit for detecting the temperature, an offset setting D / A circuit for setting an offset of the amplifier circuit output, and a CPU for outputting setting data to the sensitivity setting D / A circuit for setting the sensitivity of the current sensor, When the CPU determines that an A / D converter is connected to the outside, the environmental temperature data is acquired, and the current sensor output and the offset output are predetermined values with respect to the environmental temperature. While reading the output data of the externally attached A / D converter, the sensitivity determination D / A circuit and offset setting D / A circuit are controlled to automatically calibrate the sensitivity and offset of the current sensor. Inspection function to obtain the current temperature sensitivity and offset temperature characteristics by passing the existing measurement current, because it has a setting data acquisition function that records the environmental temperature data, sensitivity setting data, and offset setting data to the EEPROM inside the CPU. Sensitivity setting data and offset setting data for the environmental temperature can be automatically acquired, stored, and inspected using equipment and inspection processes, and variations in environmental temperature characteristics of individual parts can be corrected to avoid an increase in manufacturing costs and man-hours. It is possible to supply a highly accurate current sensor that enables

According to a second aspect of the present invention, there is provided a current sensor circuit that detects a magnetic flux generated by a measurement current, an amplifier circuit that amplifies the Hall sensor output, a constant current circuit that drives the Hall sensor and determines the sensitivity of the Hall sensor, An offset setting D / A circuit for determining the offset of the amplifier circuit output, a sensitivity setting D / A circuit for setting the current value of the constant current circuit and setting the sensitivity of the current sensor, and a temperature sensing circuit for detecting the environmental temperature. And an offset setting D / A circuit for setting the offset of the amplifier circuit output, and a CPU for outputting setting data to the sensitivity setting D / A circuit for setting the sensitivity of the current sensor. The CPU is externally provided with an A / D converter. If it is determined that the sensor is connected, the sensitivity setting data and offset setting data acquisition function is executed, and whether or not the current sensor is flowing current from the inspection device The CPU automatically reads the output of the A / D converter and automatically determines whether it is the timing to acquire sensitivity setting data that is a constant current value to be passed through the Hall sensor related to sensitivity or the timing to acquire offset setting data. In particular, it is not necessary to exchange signals with the existing inspection apparatus, and the existing equipment can be used.

According to the present invention, it is possible to supply a highly accurate current sensor using existing inspection equipment and processes.

Circuit diagram of current sensor Processing flowchart of CPU in current sensor

Embodiments of the present invention will be described below.

The current sensor in the present invention is a magnetic proportional current sensor that detects and amplifies a magnetic flux generated by a measurement current with a Hall sensor that is a magnetic detection element, and outputs a voltage proportional to the measurement current.

FIG. 1 is a diagram showing a current sensor circuit of the present invention. The sensitivity of the Hall sensor 1 varies depending on the current flowing through the Hall sensor 1, and the sensitivity of the current sensor is determined by the current value flowing through the Hall sensor 1. The sensitivity of Hall sensor 1 has a maximum sensitivity change of -600 ppm with respect to environmental temperature changes. To increase the accuracy of the current sensor, the sensitivity of the current flowing through Hall sensor 1 to the environmental temperature is set to the sensitivity corresponding to the environmental temperature. It is necessary to control with the output voltage of D / A and keep the sensitivity of the current sensor constant with respect to the environmental temperature change.
When the voltage supplied to the current sensor is 5V, the output voltage of the amplifier circuit 2 is set to 2.5V with the output voltage of the offset setting D / A4 when the measurement current is 0A. This voltage is defined as an offset voltage in the present invention. Since the output voltage of the hall sensor 1 and the amplifier circuit 2 fluctuates with respect to the environmental temperature change, the offset voltage fluctuates with the environmental temperature change at a fixed offset setting. Therefore, it is necessary to control with the output voltage of the offset setting D / A4 corresponding to the environmental temperature, and to keep the output voltage when the measured current is 0 at 2.5 V even when the environmental temperature changes.

In FIG. 1, a CPU and a temperature detection circuit 6, an offset setting D / A4, a sensitivity setting D / A5, and an A / D8 connected to a current sensor circuit are connected by a serial interface, and are individually identified by an address.

First, in order to obtain sensitivity setting data and offset setting data, the current sensor is set in an existing inspection apparatus capable of inspecting the temperature characteristics of the current sensor output. In the case of the existing current sensor, only the connection for reading the power supply to the current sensor and the output of the current sensor is used. In the present invention, the current sensor output is additionally connected to the input of the A / D converter 8. The internal CPU 7 and serial A / D converter 8 are additionally connected through a serial interface.

The operation of the CPU 7 will be described below based on the flowchart of FIG. Turn on the power to the current sensor set in the inspection device. Immediately after the power is turned on, the CPU 7 checks whether the A / D converter 8 is connected outside the current sensor. For example, the CPU 7 sends A / D conversion condition setting data to the A / D converter 8, and if the A / D conversion condition setting data is returned from the A / D converter 8, the A / D converter 8 It is determined that it is connected, and the setting data acquisition mode is entered.
The setting data acquisition mode will be described with reference to the flowchart of FIG. 2 by taking as an example a case where the current sensor specification is measured current ± 300 A, the output voltage at 0 A is 2.5 V, and the output voltage at +300 A is 4.5 V.

When the setting data acquisition mode is entered, the CPU 7 continues to read the output voltage of the amplifier circuit 2 via the A / D converter 8. When the CPU 7 confirms that the output voltage has changed significantly, it is determined in the determination 14 that the measurement current 300A has flowed from the inspection device, and the CPU 7 executes the sensitivity data acquisition process 15. The sensitivity data acquisition process 15 reads the output voltage of the amplifier circuit 2 via the A / D converter 8 while changing the output data to the sensitivity setting D / A converter 5, and the output voltage from the amplifier circuit 2 is 4.5V most. Repeat until the voltage is close.

When this process is completed, the process waits until the output voltage of the amplifier circuit 2 is greatly reduced from 4.5V to around 2.5V while reading the output voltage of the amplifier circuit 2 through the A / D 7 in decision 16. When the output voltage of the amplifier circuit 2 greatly decreases, the inspection apparatus determines that the measurement current has been reduced from 300 A to 0 A, and executes the offset setting data acquisition process 17.

The offset setting data acquisition process 17 performs a process equivalent to the sensitivity setting data acquisition process, and changes the output data to the offset D / A converter 4 so that the output voltage of the amplifier circuit 2 is closest to 2.5V.

When the offset data acquisition process 17 ends, an environmental temperature data acquisition process 18 for reading the environmental temperature data from the temperature detection circuit 6 is executed.

After acquiring the environmental temperature data, the output data and offset to the sensitivity setting D / A converter 5 when the output voltage of the amplification circuit 2 obtained in the environmental temperature data and sensitivity data acquisition process 15 is closest to 4.5V. The output data to the offset setting D / A converter 4 when the output voltage of the amplifier circuit 2 obtained in the setting data acquisition process 18 is closest to 2.5 V is stored in the EEPROM built in the CPU.

The inspection device causes the measurement current to flow 300A when the temperature reaches a preset environmental temperature, for example, −40 ° C., −20 ° C., 0 ° C., 20 ° C., 40 ° C., 60 ° C., 80 ° C. After the CPU 7 waits for a sufficient time for acquiring sensitivity setting data, if the inspection apparatus sets the measured current to 0 A, the current sensor automatically acquires and stores sensitivity setting data and offset setting data for the environmental temperature. When the CPU 7 determines that the setting data acquisition at the set environmental temperature has been completed, the CPU 7 shifts to the current measurement mode.

When the current measurement mode is entered, the CPU 7 acquires environmental temperature data in the process 11. In the process 12, the acquired environmental temperature data is obtained by judging which temperature of -40 ° C, -20 ° C, 0 ° C, 20 ° C, 40 ° C, 60 ° C, 80 ° C stored in the EEPROM. The sensitivity setting data and offset setting data at the ambient temperature are calculated and obtained. If the acquired environmental temperature data is 50 ° C., the sensitivity setting D / A converter data acquired and stored at 40 ° C. is VH40, the offset setting D / A converter data is V040, and the sensitivity setting D / A acquired and stored at 60 ° C. When the A converter data is VH60 and the offset setting D / A data is V060,
ΔVH = (VH60−VH40) / (60−40) ―――― (1)
ΔV0 = (V060−V040) / (60−40) ―――― (2)
Sensitivity setting D / A data at 50 ° C is VH50. VH50 = VH40 + ΔVH × (50-40) ―――― (3)
If the offset setting D / A data at 50 ° C. is V050, V050 = V040 + ΔV0 × (50-40) ―――― (4)
(1) Calculate the sensitivity setting D / A converter data VH50 and the offset setting D / A converter data V050 at 50 ° C. from the equations (2), (3), and (4).

The CPU 7 outputs the VH50 and V050 obtained in the process 12 in the process 13 to the sensitivity setting D / A converter 5 and the offset setting D / A converter 4. The CPU 7 continues to repeat the processes 11, 12, and 13 until the power supplied to the current sensor is cut off.

When the current sensor of the present invention determines that the A / D converter 8 is not connected at the time of power supply, it enters the current measurement mode and repeats the processes 11, 12, and 13, and as a result, there is little characteristic variation with respect to the environmental temperature change. It becomes a highly accurate current sensor.

According to the present invention, it is possible to supply a high-accuracy current sensor that eliminates fluctuations in current sensor characteristics due to environmental temperature changes in the range of −40 ° C. to 80 ° C. without requiring any special manufacturing process. become.

1 Hall sensor
2 Amplifying circuit 3 Constant current circuit 4 Offset setting D / A converter 5 Sensitivity setting D / A converter 6 Environmental temperature detection circuit 7 CPU
8. A / D converter that performs A / D conversion on the output of the amplifier circuit 2 and sends the converted data to the CPU.
11 Environmental temperature measurement processing 12 Processing for obtaining sensitivity setting D / A data and offset setting D / A data with respect to the environmental temperature read from data stored in the EEPROM.
13 Output sensitivity setting D / A data and offset setting D / A data obtained in process 12 to each D / A converter.
14 Process for determining whether measurement current has flowed 15 Process for obtaining the value of a sensitivity setting D / A converter that is set sensitivity for the measurement current.
16 Processing for determining whether the measured current has become zero.
17 Processing for obtaining the value of the offset setting D / A converter in which the offset voltage becomes the setting voltage.
18 Processing for measuring environmental temperature data 19 Processing for writing each data obtained in processing 15, 16, 17, 18 to the EEPROM.
20 Judgment processing of whether or not sensitivity setting data and offset setting data for the set environmental temperature have been acquired.

Claims (2)

Hall sensor that detects the magnetic flux generated by the measurement current, an amplifier circuit that amplifies the Hall sensor output, a constant current circuit that drives the Hall sensor and determines the sensitivity of the Hall sensor, and an offset setting D that determines the offset of the amplifier circuit output A sensitivity setting D / A conversion circuit for setting the current value of the A / A conversion circuit, the constant current circuit and setting the sensitivity of the current sensor, and a temperature sensing circuit for detecting the ambient temperature, and setting the offset of the amplification circuit output An offset setting D / A circuit and a CPU that outputs setting data to a sensitivity setting D / A circuit that sets the sensitivity of the current sensor are provided. The CPU acquires environmental temperature data, and the sensitivity of the current sensor with respect to the environmental temperature and The sensitivity setting D / A conversion circuit and the offset setting D / A conversion circuit for setting the offset are controlled so that the offset output becomes a predetermined value. The sensor sensitivity and offset are automatically measured, and the obtained environmental temperature data, sensitivity setting data, and offset setting data are recorded in the EEPROM inside the CPU, and the sensitivity setting for the environmental temperature is detected while detecting the environmental temperature. Data and offset setting data are output to each D / A circuit. When the power is turned on, the CPU detects whether the A / D converter is connected to the outside of the current sensor, and selects either of the two functions. A current sensor circuit that determines whether to execute. Hall sensor that detects the magnetic flux generated by the measurement current, an amplifier circuit that amplifies the Hall sensor output, a constant current circuit that drives the Hall sensor and determines the sensitivity of the Hall sensor, and an offset setting D that determines the offset of the amplifier circuit output A sensitivity setting D / A conversion circuit for setting the current value of the A / A conversion circuit, the constant current circuit and setting the sensitivity of the current sensor, and a temperature sensing circuit for detecting the ambient temperature, and setting the offset of the amplification circuit output An offset setting D / A circuit and a CPU that outputs setting data to a sensitivity setting D / A circuit that sets the sensitivity of the current sensor are provided. The CPU acquires environmental temperature data, and the sensitivity of the current sensor with respect to the environmental temperature and Sensitivity setting D / A converter circuit to set the offset output to a predetermined value, offset setting D / A converter circuit is controlled, current sensor sensitivity is turned off A setting data acquisition function that records the ambient temperature data, sensitivity setting data, and offset setting data obtained in the EEPROM inside the CPU, and sensitivity setting data and offset for the ambient temperature while detecting the ambient temperature. The current sensor has a function to output the setting data to each D / A circuit, and when the setting data acquisition function is selected, the CPU is used to determine whether to acquire sensitivity setting data or offset setting data. A current sensor circuit that performs depending on whether the measurement current is flowing or not.

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