Current sensor device

Abstract

To provide a current sensor device preventing an AC component having large amplitude from being detected as a DC current by mistake.SOLUTION: A current sensor device 10 comprises: a self-excited oscillation circuit 20; a duty ratio calculation section 42; a clock introduction section 44; a re-sampling section 46; and a low-pass filter 48. The self-excited oscillation circuit 20 has an annular magnetic core 22. A primary conductor 70 is passed to the inside of the magnetic core 22. The self-excited oscillation circuit 20 generates a pulse signal and operates on the basis of the pulse signal according to current flowing through the primary conductor 70. The duty ratio calculation section 42 calculates a duty ratio of the pulse signal and outputs a duty ratio signal. The clock introduction section 44 generates a clock signal having a fixed frequency. The re-sampling section 46 re-samples the duty ratio signal on the basis of the clock signal. The low-pass filter 48 integrates a re-sampling signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a current sensor device. [Background technology]

[0002] Patent Document 1 discloses an example of a self-oscillation type current sensor device.

[0003] The current sensor device disclosed in Patent Document 1 has an annular magnetic core, a secondary conductor wound around the magnetic core, and a primary conductor passing through the magnetic core.

[0004] In the current sensor device of Patent Document 1, a current flows through the secondary conductor during detection. The direction of the current flowing through the secondary conductor is switched based on a pulse signal. When no current flows through the primary conductor, the duty ratio of the pulse signal is 0.5.

[0005] In the current sensor device of Patent Document 1, changes in the current flowing in the primary conductor affect the current flowing in the secondary conductor. The current flowing in the secondary conductor is converted into a voltage, which is used to detect the current flowing in the primary conductor and also to generate a pulse signal for switching the current flowing in the secondary conductor. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2023-146957 Summary of the Invention [Problem to be solved by the invention]

[0007] In the current sensor device of Patent Document 1, if the current flowing through the primary conductor contains a large-amplitude AC component, the magnetic core becomes magnetically saturated, and as a result, the current sensor device of Patent Document 1 may detect the large-amplitude AC component as a DC current.

[0008] An object of the present invention is to provide a current sensor device that does not erroneously detect AC components with large amplitude as DC current. [Means for solving the problem]

[0009] The present invention provides a self-oscillating current sensor device as a first current sensor for detecting a current flowing through a primary conductor, The current sensor device includes a self-oscillating circuit, a duty ratio calculation unit, a clock introduction unit, a resampling unit, and a low-pass filter; the self-oscillating circuit has an annular magnetic core, The primary conductor is passed through the magnetic core, the self-oscillating circuit generates a pulse signal in response to a current flowing through the primary conductor and operates based on the pulse signal; the duty ratio calculation unit calculates a duty ratio of the pulse signal and outputs a duty ratio signal; the clock introduction unit generates a clock signal having a constant frequency; the resampling unit receives the duty ratio signal and the clock signal, and resamples the duty ratio signal based on the clock signal to generate a resampled signal; The low-pass filter integrates the resampled signal. A current sensor device is provided.

[0010] The present invention also provides a first current sensor device as a second current sensor, the duty ratio calculation unit includes a counter and a duty conversion unit, the clock introduction unit has a base clock generation unit and a frequency divider, the basic clock generating unit generates a basic clock signal; the counter counts the on-periods and the off-periods for each cycle of the pulse signal based on the basic clock signal, the duty conversion unit calculates a duty ratio for each cycle of the pulse signal from the count result of the counter, and generates a duty ratio signal representing the duty ratio; The frequency divider divides the basic clock signal from the basic clock generating unit and outputs the divided signal as the clock signal. A current sensor device is provided.

[0011] Furthermore, the present invention provides a third current sensor as the first current sensor device, The current sensor device further includes a comparator that receives an output of the low-pass filter and compares the output of the low-pass filter with the predetermined threshold value. A current sensor device is provided.

[0012] Furthermore, the present invention provides a fourth current sensor, which is the first current sensor device, the self-oscillating circuit includes a drive circuit, a detection resistor, and a pulse signal generating circuit; the drive circuit includes a drive unit and a load; the load is a secondary conductor wound around the magnetic core, the detection resistor is connected in series with the drive circuit, converts the current flowing through the secondary conductor into a voltage, and generates a detection voltage at one end of the detection resistor; the pulse signal generating circuit generates the pulse signal in response to the detected voltage; the driving unit switches the direction of a current flowing through the secondary conductor based on the pulse signal, The pulse signal generating circuit monitors the detection voltage generated at the one end of the detection resistor and inverts the on and off of the pulse signal. A current sensor device is provided.

[0013] Furthermore, the present invention provides a fifth current sensor, which is the fourth current sensor device, The driver is an H-bridge circuit with four switches. A current sensor device is provided.

[0014] Furthermore, the present invention provides a sixth current sensor, which is the first current sensor device, the self-oscillation circuit has a drive circuit control unit, the drive circuit control unit generates a demagnetization pulse signal for AC demagnetizing the magnetic core by frequency-modulating the pulse signal for a predetermined period after the power is turned on, the demagnetization pulse signal having a duty ratio of 51.5±1%; The self-oscillating circuit operates based on the degaussing pulse signal during the predetermined period. A current sensor device is provided.

[0015] Furthermore, the present invention provides a seventh current sensor, which is the sixth current sensor device, the self-oscillating circuit includes a drive circuit and a detection resistor; the detection resistor is connected in series with the drive circuit; the detection resistor switches its resistance value between a first resistance value and a second resistance value greater than the first resistance value in response to a switching signal; The drive circuit control unit generates the switching signal to select the first resistance value during the predetermined period and the second resistance value after the predetermined period has elapsed, thereby controlling the current flowing through the drive circuit. A current sensor device is provided.

[0016] Furthermore, the present invention provides an eighth current sensor, which is the sixth current sensor device, the self-oscillating circuit includes a drive circuit; the drive circuit includes a drive unit and a load; the load is a secondary conductor wound around the magnetic core, The drive section of the drive circuit switches the direction of the current flowing through the secondary conductor based on the degaussing pulse signal instead of the pulse signal during the predetermined period. A current sensor device is provided. [Effects of the Invention]

[0017] According to one aspect of the present invention, a current sensor device resamples a duty ratio signal representing the duty ratio of a pulse signal generated by a self-oscillating circuit based on a clock signal having a constant frequency. The resampled signal is not affected by the oscillation frequency of the self-oscillating circuit or the period of the pulse signal. As a result, even if the current flowing through the primary conductor contains a large-amplitude AC component, part of the AC component is not erroneously detected as a DC component. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a circuit block diagram showing a current sensor device according to an embodiment of the present invention. [Figure 2] 2 is a diagram for explaining the relationship between a magnetic core, a primary conductor, and a secondary conductor included in the current sensor device of FIG. 1. FIG. [Figure 3] 2 is a graph showing waveforms of an AC current flowing through a primary conductor and a detection signal of a current sensor device configured by removing a resampling unit from the current sensor device of FIG. 1. [Figure 4] 2 is a graph showing waveforms of an AC current flowing through a primary conductor of the current sensor device of FIG. 1 and a detection signal. DETAILED DESCRIPTION OF THE INVENTION

[0019] 1, a current sensor device 10 according to an embodiment of the present invention includes a self-oscillating circuit 20, a detection unit 40, and an overcurrent detection unit 60. The current sensor device 10 of this embodiment is a self-oscillating current sensor device that detects a current (primary current) flowing through a primary conductor 70, which will be described later.

[0020] As shown in FIG. 1, the current sensor device 10 of this embodiment further includes a self-diagnosis unit 34. The self-diagnosis unit 34 has an additional conductor 341 and a self-test drive circuit (current supply unit) 343. The additional conductor 341 is at least partially passed inside the magnetic core 22. The additional conductor 341 may be wound around the magnetic core 22. The self-test drive circuit 343 supplies current to the additional conductor 341 during testing. A detailed description of the self-diagnosis unit 34 will be omitted here.

[0021] As shown in FIG. 1, the self-oscillating circuit 20 includes a magnetic core 22, a drive circuit 24, a detection resistor 26, a pulse signal generating circuit 28, and a drive circuit control unit 32.

[0022] 2, the magnetic core 22 has an annular shape. The magnetic core 22 is associated with a primary conductor 70 and a secondary conductor (load) 243. More specifically, the primary conductor 70 is passed through the inside of the magnetic core 22, and the secondary conductor 243 is wound around the magnetic core 22.

[0023] 1, the drive circuit 24 has a drive unit 241 and a load 243. In this embodiment, the drive unit 241 is an H-bridge circuit having four switches SW1, SW2, SW3, and SW4. In this embodiment, the load 243 is the above-mentioned secondary conductor 243. The drive unit 241 is connected to a power supply and is a circuit that switches the direction of a current (secondary current) flowing through the load 243.

[0024] As shown in FIG. 1, the detection resistor 26 is connected in series with the drive circuit 24. The detection resistor 26 converts the current flowing through the secondary conductor 243, which is a load, into a voltage and generates a detection voltage VRs at one end of the detection resistor 26. As will be described later, in this embodiment, the detection resistor 26 is configured to be able to select either a first resistance value Rs1 or a second resistance value Rs2 (>Rs1). The detection resistor 26 functions as a resistor having either the first resistance value Rs1 or the second resistance value Rs2 in response to a switching signal (Select) input from the outside.

[0025] As shown in FIG. 1 , the pulse signal generation circuit 28 includes a comparator 281, a T flip-flop 283, and an inverter 285. The comparator 281 compares the detection voltage VRs with a predetermined threshold voltage Vth and outputs an output voltage VC that is on when the detection voltage exceeds the threshold voltage Vth and off when the detection voltage falls below the threshold voltage Vth. The T flip-flop 283 detects the rising edge of the output voltage VC and inverts its output signal, a pulse signal VP, between on and off each time it detects a rising edge. The inverter 285 outputs an inverted pulse signal VPi, which is the inverted version of the pulse signal VP. In this way, the pulse signal generation circuit 28 monitors the detection voltage VRs generated at one end of the detection resistor 26 and generates the pulse signal VP by inverting the on and off state of the pulse signal VP in response to the detection voltage VRs. Hereinafter, both the pulse signal VP and the inverted pulse signal VPi may be referred to simply as pulse signals.

[0026] 1, the drive circuit control unit 32 receives pulse signals (pulse signal VP and inverted pulse signal VPi) from the pulse signal generation circuit 28. The drive circuit control unit 32 generates drive signals VH (first drive signal VH1 and second drive signal VH2) based on the pulse signals from the pulse signal generation circuit 28. The drive circuit control unit 32 also generates a switching signal Select.

[0027] As shown in FIG. 1, drive signals VH (first drive signal VH1 and second drive signal VH2) from drive circuit control unit 32 are supplied to drive unit 241. The first drive signal VH1 and second drive signal VH2 are used to control the on / off of switches SW1 to SW4. Drive unit 241 switches the direction of current flowing through secondary conductor 243 in accordance with the first drive signal VH1 and second drive signal VH2. Because the first drive signal VH1 and second drive signal VH2 are both based on pulse signal VP, it can be said that drive unit 241 switches the direction of current flowing through secondary conductor 243 based on pulse signal VP.

[0028] Here, assume that in an ideal current sensor device 10, no current flows through the primary conductor 70. In this case, the self-excited oscillator circuit 20 operates so that the duty ratio of the pulse signal VP is 50%. In other words, in an ideal current sensor device 10, when no current flows through the primary conductor 70, the self-excited oscillator circuit 20 operates so that the off-period and on-period of the pulse signal VP are equal to each other.

[0029] Next, assume that a current flows through the primary conductor 70 in the current sensor device 10. In this case, a change in the current flowing through the primary conductor 70 causes a change in the current flowing through the secondary conductor 243. The change in the current flowing through the secondary conductor 243 changes the detection voltage VRs. As a result, the duty ratio of the pulse signals (pulse signal VP and inverted pulse signal VRi) generated by the pulse signal generating circuit 28 also changes.

[0030] 1, the drive circuit control unit 32 outputs the pulse signal VP as the first drive signal VH1 and outputs the inverted pulse signal VRi as the second drive signal VH2 during normal operation. Furthermore, the drive circuit control unit 32 outputs a switching signal for selectively switching the second resistance value Rs2 (>Rs1) during normal operation. The first drive signal VH1 and the second drive signal VH2 output from the drive circuit control unit 32 are used to control the switches SW1 to SW4 in the drive unit 241.

[0031] As described above, the self-oscillating circuit 20 generates pulse signals (pulse signal VP and inverted pulse signal VRi) in accordance with the current flowing through the primary conductor 70, and operates based on the pulse signals.

[0032] 1, the detection unit 40 includes a duty ratio calculation unit 42, a clock introduction unit 44, a resampling unit 46, and a low-pass filter 48. In this embodiment, the detection unit 40 further includes a temperature correction unit 52 and a comparator 54, although these are not essential.

[0033] As shown in FIG. 1, duty ratio calculation unit 42 includes counter 421 and duty conversion unit 423. Clock introduction unit 44 includes base clock generation unit 441 and 1 / n divider 443. Base clock generation unit 441 generates a base clock signal Clk having a predetermined frequency. Base clock signal Clk is supplied to 1 / n divider 443 and also to counter 421 of duty ratio calculation unit 42. 1 / n divider 443 divides the base clock signal Clk by 1 / n to generate clock signal Clk-d having a constant frequency, i.e., a frequency 1 / n of the predetermined frequency. As described above, in this embodiment, clock introduction unit 44 generates base clock signal Clk and also generates clock signal Clk-d.

[0034] As can be seen from FIG. 1, the counter 421 of the duty ratio calculation unit 42 receives the inverted pulse signal VPi (pulse signal) from the inverter 285 and the basic clock signal Clk from the basic clock generation unit 441. The counter 421 counts the on-period and off-period for each cycle of the inverted pulse signal VPi based on the basic clock signal Clk. The duty conversion unit 423 calculates the duty ratio for each cycle of the inverted pulse signal VPi from the count result of the counter 421 and generates a duty ratio signal representing the calculated duty ratio. In this way, the duty ratio calculation unit 42 calculates the duty ratio of the pulse signal (inverted pulse signal VPi) and outputs the duty ratio signal.

[0035] As shown in FIG. 1, the resampling unit 46 receives the duty ratio signal from the duty ratio calculation unit 42 and also receives the clock signal Clk-d from the 1 / n divider 443. The resampling unit 46 resamples the duty ratio signal based on the clock signal Clk-d to generate a resampling signal. This resampling signal is not affected by the oscillation frequency (period of the pulse signal) of the self-excited oscillation circuit 20. Note that the resampling unit 46 can be configured using, for example, a multi-bit D-flip-flop (D-FF). In this case, the D-FF has a number of bits equal to the number of bits of the duty ratio signal.

[0036] 1, the temperature correction unit 52 includes a temperature sensor 521 and a temperature correction circuit 523. The temperature sensor 521 detects the ambient temperature and generates a temperature detection signal. The temperature correction circuit 523 performs temperature correction on the resampling signal from the resampling unit 46 based on the temperature detection signal, and generates a temperature-corrected resampling signal.

[0037] 1, the low-pass filter 48 integrates the temperature-compensated resampled signal to remove high-frequency components, and the resampled signal from which the high-frequency components have been removed is output to the comparator 54.

[0038] The comparator 54 receives the output of the low-pass filter 48 and compares the output of the low-pass filter 48 with a predetermined threshold. The comparator 54 outputs a detection signal (Digital out) based on the result of comparing the output of the low-pass filter 48 with the predetermined threshold. Note that thresholds for DC current and AC current can be prepared as the predetermined threshold. When the comparator 54 corresponds to thresholds for DC current and AC current, it outputs detection signals for DC current and AC current to corresponding output terminals (not shown).

[0039] As shown in FIG. 1, the overcurrent detection unit 60 includes an overcurrent comparator 601, a frequency comparator 603, and an OR (logical sum) circuit 605.

[0040] The overcurrent comparator 601 compares the current value indicated by the duty ratio signal from the temperature correction circuit 523 with a preset overcurrent threshold value. When the current value indicated by the duty ratio signal exceeds the overcurrent threshold value, the overcurrent comparator 601 outputs an overcurrent detection signal.

[0041] A preset frequency threshold value Fth is input to the frequency comparator 603. The frequency comparator 603 obtains the frequency of the pulse signal (inverted pulse signal VRi) from the count value of the counter 421 and compares it with the frequency threshold value Fth. When the frequency of the pulse signal exceeds the frequency Fth, the frequency comparator 603 outputs an overcurrent detection signal.

[0042] The overcurrent detection signal from the overcurrent comparator 601 and the overcurrent detection signal from the frequency comparator 603 are both input to an OR circuit 605. The OR circuit 605 outputs either of the overcurrent detection signals to the outside as an overcurrent flag indicating an overcurrent.

[0043] As described above, the current sensor device 10 according to this embodiment can detect the current flowing through the primary conductor 70 based on changes in the duty ratio of the pulse signal by utilizing the magnetic core 22. Furthermore, by providing the overcurrent detection unit 60, the current sensor device 10 can detect when a current significantly exceeding expectations flows through the primary conductor 70 and cannot be accurately detected by the detection unit 40.

[0044] Next, consider the case where the current flowing through the primary conductor 70 contains a large-amplitude AC component. When a current containing such a large-amplitude AC component flows through the primary conductor 70, the magnetic core 22 may become magnetically saturated. When the magnetic core 22 becomes magnetically saturated, the oscillation frequency of the self-excited oscillator circuit 20 increases rapidly. Meanwhile, the duty ratio calculation unit 42 calculates the duty ratio for each period of the pulse signal, regardless of the oscillation frequency of the self-excited oscillator circuit 20. This means that as the oscillation frequency of the self-excited oscillator circuit 20 increases, the frequency at which the duty ratio is calculated increases. In other words, the sampling frequency of the duty ratio increases. When a duty ratio signal with such a high sampling frequency is supplied to the low-pass filter 48, the low-pass filter 48 operates as a low-pass filter with a bandwidth wider than its intended passband. As a result, the current sensor device 10 erroneously detects part of the AC component as DC, as shown in FIG. 3 .

[0045] FIG. 3 shows the waveform of an AC current with no or zero DC component flowing through the primary conductor 70 when the current sensor device 10 does not include the resampling unit 46, and the detection signal from the comparator 54. On the waveform of the AC current (5 Arms) flowing through the primary conductor 70, dots indicate the timing at which the duty ratio signal is output from the duty ratio calculation unit 42. As can be seen from FIG. 3, when the duty ratio signal is output frequently, the detection signal also changes in accordance with changes in the AC current. In other words, even though the AC current has no or zero DC component, some of it is erroneously detected as a DC current (detection signal "1").

[0046] On the other hand, in the current sensor device 10 according to this embodiment, the duty ratio signal from the duty ratio calculation unit 42 is resampled by the resampling unit 46 and then supplied to the low-pass filter 48. As described above, the resampling unit 46 performs resampling using the clock signal Clk-d. The clock signal Clk-d is obtained by dividing the master clock Clk generated by the master clock generation unit 441 and is independent of the oscillation frequency of the self-oscillation circuit 20. Therefore, the resampled signal is not affected by the oscillation frequency of the self-oscillation circuit 20. In other words, the low-pass filter 48 always operates as a low-pass filter having a constant band (designed passband). As a result, even if the primary conductor 70 contains a large-amplitude AC component, the current sensor device 10 will not erroneously detect part of it as a DC current, as shown in FIG. 4 .

[0047] FIG. 4 shows the waveform of an AC current (5 Arms) with no or zero DC component flowing through the primary conductor 70 of the current sensor device 10 according to this embodiment, and the detection signal from the comparator 54. On the waveform of the AC current flowing through the primary conductor 70, dots indicate the timing at which the duty ratio signal is output from the duty ratio calculation unit 42. As is clear from a comparison with FIG. 3, the frequency at which the duty ratio signal is output (resampling frequency) is significantly lower than the case of FIG. 3 (sampling frequency). As a result, the current sensor device 10 according to this embodiment is not affected by the presence of AC current, and the detection signal indicates "0." This means that the current sensor device 10 according to this embodiment will not erroneously detect a portion of the current flowing through the primary conductor 70 as DC, even if the current contains a large-amplitude AC signal.

[0048] As described above, when the current flowing through the primary conductor 70 contains a large-amplitude AC signal, the self-oscillating current sensor device outputs different detection signals depending on whether or not resampling has been performed on the duty ratio signal. From this, if the current flowing through the primary conductor 70 contains a large-amplitude AC signal and part of it is erroneously detected as DC, it can be assumed that resampling has not been performed. Conversely, when the current flowing through the primary conductor 70 contains a large-amplitude AC signal and part of it is not erroneously detected as DC, it can be assumed that resampling has been performed on the duty ratio signal at a constant frequency.

[0049] Incidentally, the magnetic core 22 of the current sensor device 10 according to this embodiment is magnetized as the current sensor device 10 is used. Therefore, the output characteristics of the current sensor device 10 change depending on the magnetization state of the magnetic core 22. Therefore, in the current sensor device 10 according to this embodiment, the magnetic core 22 is demagnetized every time the device is started (every time the power is turned on) to suppress changes in the output characteristics. This control is performed by the drive circuit control unit 32.

[0050] 1, the drive circuit control unit 32 outputs a switching signal for selecting the resistance value of the detection resistor 26. The detection resistor 26 has a first resistance value Rs1 and a second resistance value Rs2 that is greater than the first resistance value Rs1. The detection resistor 26 switches its resistance value between the first resistance value Rs1 and the second resistance value Rs2 in response to the switching signal from the drive circuit control unit 32.

[0051] The drive circuit control unit 32 generates a switching signal that selects the first resistance value Rs1 for a predetermined period after the power is turned on. After the predetermined period has elapsed, the drive circuit control unit 32 generates a switching signal that selects the second resistance value Rs2 as described above. In this way, the drive circuit control unit 32 controls the current flowing through the drive circuit 24.

[0052] Additionally, the drive circuit control unit 32 outputs a demagnetizing pulse signal as the drive signal VH (first drive signal VH1 and second drive signal VH2) for a predetermined period after the power is turned on. The demagnetizing pulse signal is a frequency-modulated pulse signal having a predetermined duty ratio. Specifically, the drive circuit control unit 32 frequency-modulates a pulse signal having a duty ratio of 51.5±1% and outputs the resulting demagnetizing pulse signal. This frequency modulation is performed so that the frequency increases over time. The self-excited oscillator circuit 20 operates based on the demagnetizing pulse signal for a predetermined period after the power is turned on. Thus, during the predetermined period, the drive unit 241 of the drive circuit 24 switches the direction of the current flowing through the secondary conductor 243 based on the demagnetizing pulse signal instead of the pulse signal. As a result, the magnetic core 22 is demagnetized every time the current sensor device 10 is activated, thereby limiting changes in its output characteristics within an acceptable range.

[0053] The reason for using a frequency-modulated pulse signal as the demagnetizing pulse signal in this embodiment is based on the results of experiments conducted by the inventors. The inventors conducted experiments on demagnetizing the magnetic core 22 using a frequency-modulated pulse signal and an amplitude-modulated pulse signal, and found that using a frequency-modulated pulse signal resulted in more efficient demagnetization than using an amplitude-modulated pulse signal. Furthermore, the inventors conducted demagnetization experiments with various duty ratios of the amplitude-modulated pulse signal and found that a duty ratio of 51.5% achieved the maximum demagnetization effect. Furthermore, they confirmed that a duty ratio of 51.5±1% achieved a demagnetization effect approximately twice as effective as a duty ratio of 50%. The frequency modulation can be performed, for example, by increasing the frequency by +11% per step from 70 Hz to 25 kHz. The time required for demagnetization, for example, is approximately 150 ms under the above frequency conditions, for example, but is not limited to this.

[0054] The present invention has been described above by presenting an embodiment thereof, but the present invention is not limited to the above-described embodiment, and various modifications and changes are possible within the scope of the gist of the present invention.

[0055] For example, in the above embodiment, clock signal Clk-d is generated using basic clock generating unit 441 and 1 / n divider 443, but the method of generating clock signal Clk-d is not particularly limited as long as it has a constant frequency independent of the magnitude of the current flowing through primary conductor 70. For example, clock signal Clk-d may be generated using an oscillator circuit (clock generating unit) separate from basic clock generating unit 441. Furthermore, the frequency may be determined taking into consideration the specifications of low-pass filter 48 and the oscillation frequency of self-oscillating circuit 20 during proper operation, and does not necessarily have to be lower than the frequency of the self-oscillating circuit.

[0056] Furthermore, in the present invention, the self-oscillating circuit 20 may include a chopper circuit between the driving section 241 and the secondary conductor 243, similar to the current sensor device described in Patent Document 1. [Explanation of symbols]

[0057] 10 Current sensor device 20 Self-oscillating circuit 22 Magnetic core 24 Drive circuit 241 Drive unit 243 Secondary conductor (load) 26 Detector resistor 28 Pulse signal generation circuit 281 Comparator 283 T Flip-Flop 285 inverter 32 Drive circuit control section 34 Self-diagnosis section 341 Additional Conductors 343 Self-Test Drive Circuit 40 Detector 42 Duty ratio calculation section 421 Counter 423 Duty conversion unit 44 Clock Introduction 441 Basic clock generation unit 443 1 / n frequency divider 46 Resampling section 48 Low-pass filter 52 Temperature correction section 521 Temperature Sensor 523 Temperature compensation circuit 54 Comparator 60 Overcurrent detection section 601 Overcurrent comparator 603 Frequency Comparator 605 OR circuit (logical sum circuit) 70 Primary Conductor

Claims

1. A self-oscillating current sensor device that detects a current flowing through a primary conductor, The current sensor device includes a self-oscillating circuit, a duty ratio calculation unit, a clock introduction unit, a resampling unit, and a low-pass filter; the self-oscillating circuit has an annular magnetic core, The primary conductor is passed through the magnetic core, the self-oscillating circuit generates a pulse signal in response to a current flowing through the primary conductor and operates based on the pulse signal; the duty ratio calculation unit calculates a duty ratio of the pulse signal and outputs a duty ratio signal; the clock introduction unit generates a clock signal having a constant frequency; the resampling unit receives the duty ratio signal and the clock signal, and resamples the duty ratio signal based on the clock signal to generate a resampled signal; The low-pass filter integrates the resampled signal. Current sensor device.

2. 2. The current sensor device according to claim 1, the duty ratio calculation unit includes a counter and a duty conversion unit, the clock introduction unit has a base clock generation unit and a frequency divider, the basic clock generating unit generates a basic clock signal; the counter counts the on-periods and the off-periods for each cycle of the pulse signal based on the basic clock signal, the duty conversion unit calculates a duty ratio for each cycle of the pulse signal from the count result of the counter, and generates a duty ratio signal representing the duty ratio; The frequency divider divides the basic clock signal from the basic clock generating unit and outputs the divided signal as the clock signal. Current sensor device.

3. 2. The current sensor device according to claim 1, The current sensor device further includes a comparator that receives an output of the low-pass filter and compares the output of the low-pass filter with the predetermined threshold value. Current sensor device.

4. 2. The current sensor device according to claim 1, the self-oscillating circuit includes a drive circuit, a detection resistor, and a pulse signal generating circuit; the drive circuit includes a drive unit and a load; the load is a secondary conductor wound around the magnetic core, the detection resistor is connected in series with the drive circuit, converts the current flowing through the secondary conductor into a voltage, and generates a detection voltage at one end of the detection resistor; the pulse signal generating circuit generates the pulse signal in response to the detected voltage; the driving unit switches the direction of a current flowing through the secondary conductor based on the pulse signal, The pulse signal generating circuit monitors the detection voltage generated at the one end of the detection resistor and inverts the on and off of the pulse signal. Current sensor device.

5. 5. The current sensor device according to claim 4, The driver is an H-bridge circuit with four switches. Current sensor device.

6. 2. The current sensor device according to claim 1, the self-oscillation circuit has a drive circuit control unit, the drive circuit control unit generates a demagnetization pulse signal for AC demagnetizing the magnetic core by frequency-modulating the pulse signal for a predetermined period after the power is turned on, the demagnetization pulse signal having a duty ratio of 51.5±1%; The self-oscillating circuit operates based on the degaussing pulse signal during the predetermined period. Current sensor device.

7. 7. The current sensor device according to claim 6, the self-oscillating circuit includes a drive circuit and a detection resistor; the detection resistor is connected in series with the drive circuit; the detection resistor switches its resistance value between a first resistance value and a second resistance value greater than the first resistance value in response to a switching signal; The drive circuit control unit generates the switching signal to select the first resistance value during the predetermined period and the second resistance value after the predetermined period has elapsed, thereby controlling the current flowing through the drive circuit. Current sensor device.

8. 7. The current sensor device according to claim 6, the self-oscillating circuit includes a drive circuit; the drive circuit includes a drive unit and a load; the load is a secondary conductor wound around the magnetic core, The drive section of the drive circuit switches the direction of the current flowing through the secondary conductor based on the degaussing pulse signal instead of the pulse signal during the predetermined period. Current sensor device.

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