JPS61126474A - Current value detecting device - Google Patents

Abstract

PURPOSE:To obtain tolerance to a noise and widen a measurement range by detecting a current value by a detection sensor, converting the value from a current to a voltage and further converting the level of the voltage into a frequency, and calculating the current value from the oscillation frequency. CONSTITUTION:This detecting device is provided with the detection sensor 3 which detects the current value relatively, a differential amplifier 4 as a current-voltage converter which outputs a high voltage value proportional the current value a frequency converter 5 which outputs the signal increasing the frequency corresponding to the voltage value, a CPU6 which counts the oscillation frequency of its output signal and oscillation intervals and calculates the current value on the basis of those counted values, etc. In this case, the CPU6 calculates the current value on the basis of the counted value when a current flowing through a line 2 is low or on the basis of the counted intervals when the current is large. Consequently, a current detector which is tolerant to a noise and has a wide measurement range and high precision is obtained.

Description

[Detailed description of the invention] Purpose of invention (Industrial application field) The present invention relates to a current value detection device.

(Prior Art) Conventionally, a current detection device detects the current flowing in a line using a current transformer, a magnetic detection sensor such as a Hall element, or the like. There is also a method that converts a detection signal of a current value relative to the current flowing through the line into a current-voltage, multiplies the voltage value by a certain coefficient, and directly detects the current flowing through the line.

In addition, the current value is directly detected by multiplying the detected current value relative to the current flowing through the line outputted from a current transformer, a Hall element, etc. by a magnetic detection sensor, etc. by a certain coefficient. There was something.

(Problems to be solved by the invention) This invention adopts a configuration different from conventional current detection.
It is an object of the present invention to provide a current detection device that is resistant to noise and can accurately measure current over a wide range.

Structure of the Invention (Means for Solving Problems) In order to achieve the above object, the present invention includes a detection sensor that relatively detects a current value, and a detection current of the detection sensor that increases as the current value increases. A current-voltage converter that outputs a relatively high voltage value; and a voltage-frequency converter that outputs an output signal whose frequency increases as the voltage value decreases in the output voltage from the current-voltage converter. , a counting means for counting the frequency of the output signal, a timekeeping means for counting the vibration interval of the output signal, and a clock means for counting the frequency of the vibration by the counter means within a predetermined time; determining the current value based on the vibration interval time measured by the clocking means when the frequency of vibration is not counted by the counter means within the predetermined time. The gist is a current value detection device.

(Function) The detection sensor detects the current flowing through the line, and the detected current is converted into a current-voltage converter so that the higher the current value, the lower the voltage value. and,
The output voltage from the current-voltage converter is subjected to voltage-frequency conversion by the voltage-frequency converter, which outputs an output signal whose frequency increases as the voltage value decreases.

Next, the counting means counts the frequency of the output signal, and the timekeeping means measures the vibration interval of the output signal by 8.
It's 1 o'clock. When the frequency is counted by the counter means within a predetermined time, the determining means determines the current value based on the frequency, and when the frequency is counted by the counter means within the predetermined time, When the current value is not counted, the current value is calculated based on the vibration interval time of the timer. (Embodiment) An embodiment embodying the present invention will be described below with reference to the drawings.

In FIG. 1, the cores are arranged in a circle surrounding the line 2, forming a magnetic circuit for a magnetic field generated based on the current flowing through the line 2. The magnetic sensing element 3 as a detection sensor is made of a Hall element, and is disposed between both ends of the core 1, and converts the strength of the magnetic field generated based on the current flowing through the line 2 into the magnitude of the current. Detect.

A differential amplifier 4 serving as a current-voltage converter performs current-voltage conversion and amplification of the detected current from the magnetic sensing element 3 so that the voltage value becomes higher in proportion to the higher the current value. A voltage-frequency converter (hereinafter referred to as a frequency converter) 5 receives the output voltage from the differential amplifier 4, and as shown in FIG. 2, the frequency F decreases as the output voltage value V increases. The output signal SG1 (amplitude is constant) is shaped into a pulse signal SG2, and the output signal is waveform-shaped and output as a pulse signal SG2. This waveform shaping is performed on the output signal S as shown in FIG.
This is done by a circuit (for example, a Schmitt circuit) that turns on when the level of G1 exceeds a predetermined reference value, and turns A off when it is below the reference value.

Therefore, when the voltage value V of the output voltage is small, that is, when the current value of the current flowing through the line 2 is small, the period T of the pulse signal SG2 is relatively short as shown in FIG. 4(a). On the contrary, when the voltage value V of the output voltage is large, that is, when the current value of the current flowing through the line 2 is large, the length becomes relatively long as shown in FIG. 4(b).

A central processing unit (hereinafter referred to as CPU) 6 as a counting means, a timekeeping means, and an indexing means operates based on a control program stored in a read-only memory (ROM) J: a program memory 7, and operates based on a control program stored in a read-only memory (ROM) J. The pulse signal SG2 output from the converter 5 is inputted. Then, the CPU 6 transmits the pulse signal SG2 to the CPU 6.
At the same time, a timer built in the CPU 6 measures the pulse interval Ts of the pulse signal SG2.

In the counting operation of the CPU 6, the number of pulse signals SG2 input during a preset reference time t1 is sequentially counted by a counter. Therefore, the period ill of pulse signal SG2
The shorter T, that is, the smaller the current value flowing through the line 2, the larger the count value becomes. On the contrary, the longer the period T of the pulse signal SG2, that is, the greater the value of the current flowing through the line 2, the smaller the count value becomes. At this time, it can be seen that when a relatively large current flows, the pulse period T becomes longer than the reference time t1, and the Callanmill value becomes "0".

On the other hand, in the timekeeping operation of the CPU, a timer sequentially measures the interval time Ts from the falling edge of the sequentially inputted pulse signal SG2 to the next rising edge. Therefore, the longer the period T of the pulse signal SG2, that is, the greater the value of the current flowing through the line 2, the longer the interval time Ts becomes. On the contrary, the shorter the period T of the pulse signal SG2 is, that is, the smaller the value of the current flowing through the line 2, the shorter the interval time TS. Note that in this embodiment, the interval time T
Although S is configured to measure the time from the falling edge to the rising edge of the pulse signal SG2, it may also be used to measure the time (period T) from the rising edge to the next rising edge.

The CPU 6 calculates the current value of the current flowing through the line 2 at that time by comparing the count value obtained in the processing operation and the interval time TS with the current value data stored in the program memory 7 together with the program data. Perform the processing operation to determine.

The current value data stored in the program memory 7 includes data of each current value for each count value and data of each current value for each interval time. Then, when the counter value is "1" or more at the reference time t1, the CPU 6 determines that the current is low, gives priority to the counter value, and reads out the current value data corresponding to the current value. The value of the current flowing through line 2 at that time is calculated. On the other hand, when the counter value is rOJ, the CPU 6 determines that the current is large, reads out the current value data corresponding to the timer interval time TS, and determines the value of the current flowing through the line 2 at that time. .

Therefore, when the current flowing through the line 2 is low, the CPU 6 determines the current value based on the counter value of the counter, and when the current is large, the CPU 6 determines the current value based on the timer interval Ts.

In this embodiment, the CPU 6 displays the determined current value on the display device 8, and outputs control signals to various circuit elements 9 for driving and controlling various devices based on the current value of the current flowing through the line 2. It is supposed to be done.

The working memory 10 is a readable and rewritable memory (RAM) in which calculation results calculated by the CPU 6 are temporarily stored.

Next, the operation of the current value detection device configured as described above will be explained.

Now, when a current is flowing through the line 2, the strength of the magnetic field formed by the core 1 is proportional to the current on the line 2.

Then, the magnetic sensing element 3 detects the strength of the magnetic field and outputs the detected current to the differential amplifier 4.

Therefore, the value of the detection current output to the differential amplifier 4 is proportional to the current of the line 2, and the detection current is converted to an output voltage of the differential amplifier 4, which increases in proportion to the current value. converted. This output voltage is converted by the next stage frequency converter 5 into a pulse signal SG2 whose period T becomes shorter as the voltage value V of the output voltage becomes larger.

Then, the CPU 6 counts the pulse signal SG2 input at the reference time t1, and simultaneously measures the pulse interval TS of the pulse signal SG2 using a timer. next,
CPU6 has a counter value of 11 at reference time 1-1.
” or more, if it is more than “1”, it is determined that the current is low and the value of that counter is given priority, and the data of the current value corresponding to that count value is read out and the low current flowing in line 2 at that time is determined. Figure out the value.

Then, the CPU 6 displays the current value on the display device 8 based on this current value, and controls the operation of various circuit elements 9 for driving and controlling various devices based on the current value.

On the other hand, when the counter value is rOJ, the CPU 6 determines that the current is large, reads out the current value data corresponding to the timer interval time Ts, and calculates the value of the large current flowing through the line 2 at that time. There is. Based on this current value, the CPU 6 displays the current value on the display device 8, and also controls the operation of various circuit elements 9 for driving and controlling various devices based on the current value.

In this embodiment, as the value of the current flowing through the line 2 increases in the frequency converter 5, the pulse signal S
The period T of G2 is made longer, and the CPU 6 determines whether the current flowing through the line 2 is a low current or a large current based on determining how many pulse signals SG2 are present within the reference time t1. However, when the current is low, the value of the current flowing through the line 2 is determined by the number of pulses of the pulse signal SG2, and when the current is large, the value of the current flowing through the line 2 is determined by the pulse interval TS of the pulse signal SG2, so it can be calculated over a very wide range and with high accuracy. Current detection can be performed.

Therefore, the circuit elements 10 that drive and control various devices are controlled by the CPU.
6 can be accurately and reliably controlled.

Moreover, in the case of low current, it is detected based on the number of pulses of the pulse signal SG2, so even if the line 2 is broken and no current flows, there is no need to provide a separate special detection circuit for detecting the break. Can be reliably detected.

Further, in this embodiment, since the detection current from the magnetic sensing element 3 is finally converted into the pulse signal SG2, the noise picked up by the magnetic sensing element 3 etc. can be suppressed to a very low level.

Note that the present invention is not limited to the above-described embodiment; for example, the frequency converter 5 of the above-mentioned embodiment may be replaced by the differential amplifier 4.
We shaped the output signal SG1 (amplitude is constant) in which the frequency F decreases as the output voltage value ■ increases, and then waveform-shaped the output signal to output it as a pulse signal SG2. Output signal SG before waveform shaping
Current detection may be performed based on I.

Effects of the Invention As detailed above, the present invention has an excellent effect of being resistant to noise and being able to accurately measure current over a wide range.

[Brief explanation of drawings]

FIG. 1 is an electrical block circuit diagram of a current detection device embodying the present invention, and FIG. 2 is a waveform diagram showing the relationship between the output voltage output from the differential amplifier and the output signal formed by the frequency converter. FIG. 3 is a waveform diagram showing waveform shaping from an output signal to a pulse signal, and FIGS. 4(a) and 4(b) are waveform diagrams for explaining the period of the pulse signal, respectively. -1'3- In the figure, 1 is a core, 2 is a line, 3 is a magnetic sensing element, 4 is a differential amplifier, 5 is a frequency converter, 6 is a CPU 17 is a program memory, 8 is a display device, and 9 is a circuit element. , 10 is a working memory. Patent Applicant Toyota Industries Corporation Toyota Industries Corporation Meidensha Representative Patent Attorney On1) Hironobu1), O-L Ku~Ku

Claims (1)

[Scope of Claims] 1. A detection sensor that relatively detects a current value, and a current-voltage converter that outputs a relatively high voltage value as the current value increases with respect to the detected current of the detection sensor; a voltage-frequency converter that outputs an output signal whose frequency increases as the voltage value decreases in the output voltage from the current-voltage converter; a counting means that counts the frequency of the output signal; and the output. a clock means for timing the vibration interval of the signal; and when the frequency of vibration is counted by the counting means within a predetermined time, the current value is determined based on the frequency; a current value detecting device comprising: determining means for determining the current value based on the vibration interval time measured by the time measuring means when the current value is not counted by the counter means. 2. The voltage-frequency converter is a converter that outputs a pulse signal whose pulse period becomes shorter as the voltage value of the output voltage from the current-voltage converter decreases, and the counter means outputs a pulse signal whose pulse period becomes shorter as the voltage value of the output voltage from the current-voltage converter decreases. 2. The current value detecting device according to claim 1, wherein the current value detecting device counts the number of pulses, and the time measuring means measures the pulse interval.