CN111665383B - Full-digital fluxgate type current sensor - Google Patents
Full-digital fluxgate type current sensor Download PDFInfo
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- CN111665383B CN111665383B CN202010443394.3A CN202010443394A CN111665383B CN 111665383 B CN111665383 B CN 111665383B CN 202010443394 A CN202010443394 A CN 202010443394A CN 111665383 B CN111665383 B CN 111665383B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
- G01R19/2506—Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values ; Details concerning sampling, digitizing or waveform capturing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0046—Arrangements for measuring currents or voltages or for indicating presence or sign thereof characterised by a specific application or detail not covered by any other subgroup of G01R19/00
- G01R19/0053—Noise discrimination; Analog sampling; Measuring transients
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
- G01R19/2506—Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values ; Details concerning sampling, digitizing or waveform capturing
- G01R19/2509—Details concerning sampling, digitizing or waveform capturing
Abstract
The invention discloses a full-digital fluxgate type current sensor, belongs to the field of sensors, and aims to solve the problem of inaccurate measurement result in the current detection of a current sensor by adopting an analog device. The digital processing circuit of the current sensor of the invention: the alternating current signal of the current to be measured is detected by the alternating current winding, and the detection signal output by the alternating current winding is processed by the integrating circuit to output an alternating current measurement value; the direct current signal of the current to be measured is detected by the exciting winding, the detection signal output by the exciting winding filters higher harmonic waves through the current filtering module, then the second harmonic wave component of the exciting current is extracted by the second harmonic wave extracting module, and the direct current measurement value is output after the second harmonic wave component is processed by the integrating circuit; and the alternating current measurement value and the direct current measurement value are subjected to integral summation by an integral circuit to obtain a final measured current value, the final measured current value is subjected to low-pass filtering again by a current filtering module to eliminate noise, and then the final measured current value is sent to an HOWLAND current source and is output by a feedback winding.
Description
Technical Field
The invention relates to a digital processing circuit of a current sensor, belonging to the field of sensors.
Background
The current sensor as a device for detecting current has wide application in the fields of motor drive control, inverter devices, switching power supplies, signal measurement, scientific instruments, photoetching machines, aerospace and the like. Among various principles of current sensor implementation, the current sensor implemented by using the fluxgate technology has the advantages of good linearity and high precision, and can convert a large current signal into a precise and accurate small current signal.
The excitation current signal of the current sensor is usually extracted by peak detection, and the required excitation current is obtained by using a diode, a capacitor, a resistor and an operational amplifier.
Disclosure of Invention
The invention aims to solve the problem that the current detection of a current sensor by adopting an analog device has inaccurate measuring result, and provides a full-digital fluxgate type current sensor.
The invention discloses a full digital fluxgate type current sensor, which comprises a sensor winding structure and a digital processing circuit; the sensor winding structure comprises a magnetic core, a double-winding excitation winding, an alternating current winding and a feedback winding;
the digital processing circuit comprises a digital processor and an HOWLAND current source, and a current filtering module, a second harmonic extraction module and an integrating circuit are built in the digital processor;
the alternating current signal of the current to be measured is detected by the alternating current winding, and the detection signal output by the alternating current winding is processed by the integrating circuit to output an alternating current measurement value;
the direct current signal of the current to be measured is detected by the exciting winding, the detection signal output by the exciting winding filters higher harmonic waves through the current filtering module, then the second harmonic wave component of the exciting current is extracted by the second harmonic wave extracting module, and the direct current measurement value is output after the second harmonic wave component is processed by the integrating circuit;
and the alternating current measurement value and the direct current measurement value are subjected to integral summation by an integral circuit to obtain a final measured current value, the final measured current value is subjected to low-pass filtering again by a current filtering module to eliminate noise, and then the final measured current value is sent to an HOWLAND current source and is output by a feedback winding.
Preferably, the excitation winding comprises a winding A and a winding B, and the two sets of windings have the same number of turns and are wound in opposite directions.
Preferably, a high-frequency square wave generating module is further built inside the digital processor, a high-frequency square wave signal output by the high-frequency square wave generating module is amplified by a power amplifier and then provides a driving signal for the exciting winding, and an exciting current output by the exciting winding forms an exciting magnetic field in the magnetic core.
Preferably, the high-frequency square wave generating module comprises a square wave generator and a PWM output unit, and the square wave output by the square wave generator is modulated by the PWM output unit to output a high-frequency square wave signal.
Preferably, the digital processor is further internally configured with an AD module and a DA module, the AD module is configured to convert an external signal received by the digital processor into a digital signal, and the DA module is configured to convert a signal output by the digital processor into an analog signal.
Preferably, a current compensation module is further built inside the digital processor, and the current compensation module is used for compensating noise interference and superposing the system intrinsic noise deviation on the input end of the HOWLAND current source in a feedforward mode.
Preferably, the current compensation module further comprises a bias elimination, which is compensated inside the digital processor.
Preferably, the digital processor is implemented using a PFGA or DSP.
Preferably, the current filtering module is implemented by a low-pass filter, and the second harmonic extraction module is implemented by a band-pass filter.
Preferably, the AD module and the DA module are 16-bit and above precision converters.
The invention has the advantages that: in order to eliminate the noise generated in the exciting current detection, the invention provides a full digital fluxgate type current sensor, which effectively extracts the second harmonic component and the fundamental component by the design method of a digital filter to realize the effective detection of the exciting current. The sensor of the invention can realize high precision and high linearity of the current sensor, has good advantages in the aspect of exciting current extraction, and is realized by a full digital control method, thereby reducing the inherent deviation of an analog device.
Drawings
FIG. 1 is a schematic diagram of the winding structure of an all-digital fluxgate-type current sensor in accordance with the present invention;
FIG. 2 is a functional block diagram of the all-digital fluxgate-type current sensor of the present invention;
FIG. 3 is a circuit diagram of the excitation winding drive signals.
Detailed Description
The first embodiment is as follows: the present embodiment is described below with reference to fig. 1 to 3, and the all-digital fluxgate current sensor according to the present embodiment includes a sensor winding structure and a digital processing circuit;
the sensor winding structure comprises a magnetic core, a double-winding excitation winding, an alternating current winding and a feedback winding; the excitation winding comprises a winding A and a winding B, the number of turns of the two windings is equal, the winding directions of the two windings are opposite, and the two windings are wound on the same magnetic core and used for generating magnetic fields with equal magnitude and opposite directions. The magnetic core is used for generating an excitation magnetic field and forming a magnetic field required by the fluxgate. The magnetic core is made of a winding type cobalt-based amorphous alloy material with high magnetic conductivity, low coercive force and low loss.
The inside of the digital processor is also constructed with a high-frequency square wave generating module, a high-frequency square wave signal output by the high-frequency square wave generating module is amplified by a power amplifier and then provides a driving signal for the exciting winding, and the exciting current output by the exciting winding forms an exciting magnetic field in the magnetic core. Because two sets of windings of the excitation winding use the same magnetic core, the number of turns is the same, but the winding directions are opposite, the magnetic field is zero under the condition of no current change.
The high-frequency square wave generation module comprises a square wave generator and a PWM output unit, and the square wave output by the square wave generator is modulated by the PWM output unit to output a high-frequency square wave signal. The high-frequency square wave signal directly drives the two excitation windings through the MOSFET power amplifier, so that enough current is ensured to drive the excitation windings, and the stability of an excitation magnetic field is ensured.
The digital processing circuit comprises a digital processor and an HOWLAND current source, and a current filtering module, a second harmonic extraction module and an integrating circuit are built in the digital processor; the holland current source is implemented using a linear power amplifier.
The alternating current signal of the current to be measured is detected by the alternating current winding, and the detection signal output by the alternating current winding is processed by the integrating circuit to output an alternating current measurement value;
the direct current signal of the current to be measured is detected by the exciting winding, the detection signal output by the exciting winding filters higher harmonic waves through the current filtering module, then the second harmonic wave component of the exciting current is extracted by the second harmonic wave extracting module, and the direct current measurement value is output after the second harmonic wave component is processed by the integrating circuit;
and the alternating current measurement value and the direct current measurement value are subjected to integral summation by an integral circuit to obtain a final measured current value, the final measured current value is subjected to low-pass filtering again by a current filtering module to eliminate noise, and then the final measured current value is sent to an HOWLAND current source and is output by a feedback winding.
The digital processor is further internally constructed with an AD module and a DA module, the AD module is used for converting the external signal received by the digital processor into a digital signal, and the DA module is used for converting the signal output by the digital processor into an analog signal.
And a current compensation module is further constructed in the digital processor, the current compensation module is used for compensating noise interference, and the inherent noise deviation of the system is superposed on the input end of the HOWLAND current source in a feedforward mode.
The current compensation module also includes bias cancellation for compensation within the digital processor.
The digital processor is implemented using a PFGA or DSP.
The current filtering module is realized by adopting a low-pass filter, and the second harmonic extraction module is realized by adopting a band-pass filter.
The AD module and the DA module are converters with the precision of 16 bits and above.
The detected current can be direct current or alternating current, and the all-digital processing circuit provided by the embodiment can detect direct current signals and alternating current signals, and the specific process is as follows:
the high-frequency square wave generating module sends out a 40kHz square wave signal with the duty ratio approximate to 50%, the square wave signal amplifies the signal into a power driving signal of 15v through a power tube MOSFET chip IRF640 and sends the power driving signal to an excitation winding, and therefore an excitation magnetic field is formed, and the excitation frequency is 40 kHz. Because the same magnetic core is used for the excitation winding, the number of turns is the same, but the winding direction is opposite, the magnetic field of the excitation winding is zero under the condition of no current change.
The detection process of the measured current as direct current quantity: when the external detected current changes, the excitation magnetic field changes due to the influence of magnetic core saturation and a rectangular magnetic hysteresis loop, and the generated current is output through the other end of the excitation winding; the current sends digital quantity to the inside of the digital chip by means of AD sampling.
And carrying out low-pass filtering on the collected excitation current, wherein the frequency of the low-pass filter is set to be 5 Hz. And simultaneously, the excitation current extracts second harmonic through a band-pass filter, and the band-pass frequency set by the band-pass filter is 2 times of the excitation frequency and is 80 kHz. Then, through an integration method, a current value is obtained inside the digital chip as a direct current measurement value.
The detection process of the measured current as the alternating current is as follows: the magnetic field will change in real time, in order to detect the magnetic field fast, detect the alternating current numerical value on the alternating current winding directly, then utilize AD module to change it into the digital quantity, obtain the corresponding current numerical value as the alternating current measured value through the method of the integral in the digital chip;
the current compensation module comprises a noise compensation unit and a bias magnetic elimination unit, wherein the current compensation module comprises a low-pass filter to eliminate noise, and the low-pass filter is used for filtering the excitation magnetic field and the processing circuit to eliminate the influence of noise. The HOWLAND current source adopts a linear power amplifier as a high-current linear power operational amplifier, the model is OPA541, and the chip can increase the output current under the condition of ensuring the linearity and precision. The noise compensation unit sends the detected noise to the linear power amplifier in a feedforward instruction mode so as to ensure that the noise is suppressed at the output end. The bias elimination unit compensates inside the digital unit. And after compensation, the compensation is sent to an external current source, and a final result is output through a feedback winding.
Claims (10)
1. A full digital fluxgate type current sensor is characterized by comprising a sensor winding structure and a digital processing circuit; the sensor winding structure comprises a magnetic core, a double-winding excitation winding, an alternating current winding and a feedback winding;
the digital processing circuit comprises a digital processor and an HOWLAND current source, and a current filtering module, a second harmonic extraction module and an integrating circuit are built in the digital processor;
the alternating current signal of the current to be measured is detected by the alternating current winding, and the detection signal output by the alternating current winding is processed by the integrating circuit to output an alternating current measurement value;
the direct current signal of the current to be measured is detected by the exciting winding, the detection signal output by the exciting winding filters higher harmonic waves through the current filtering module, then the second harmonic wave component of the exciting current is extracted by the second harmonic wave extracting module, and the direct current measurement value is output after the second harmonic wave component is processed by the integrating circuit;
and the alternating current measurement value and the direct current measurement value are subjected to integral summation by an integral circuit to obtain a final measured current value, the final measured current value is subjected to low-pass filtering again by a current filtering module to eliminate noise, and then the final measured current value is sent to an HOWLAND current source and is output by a feedback winding.
2. The all-digital fluxgate-type current sensor according to claim 1, wherein the excitation winding comprises a winding a and a winding B, and the two windings have the same number of turns and opposite winding directions.
3. The all-digital fluxgate-type current sensor according to claim 2, wherein the digital processor is further configured with a high-frequency square wave generating module therein, a high-frequency square wave signal output by the high-frequency square wave generating module is amplified by the power amplifier to provide a driving signal for the exciting winding, and the exciting current output by the exciting winding forms an exciting magnetic field in the magnetic core.
4. The all-digital fluxgate-type current sensor according to claim 3, wherein the high-frequency square wave generator comprises a square wave generator and a PWM output unit, and the square wave output by the square wave generator is modulated by the PWM output unit to output the high-frequency square wave signal.
5. The all-digital fluxgate-type current sensor as claimed in claim 1, wherein the digital processor is further internally constructed with an AD module for converting an external signal received by the digital processor into a digital signal and a DA module for converting a signal output from the digital processor into an analog signal.
6. The all-digital fluxgate-type current sensor according to claim 5, wherein the digital processor further comprises a current compensation module built therein, the current compensation module is for compensating noise interference, and the system intrinsic noise bias is superimposed on the input terminal of the HOWLAND current source in a form of feed forward.
7. An all-digital fluxgate-type current sensor according to claim 6, wherein the current compensation module further comprises a bias elimination for compensation within the digital processor.
8. An all-digital fluxgate-type current sensor according to claim 1, wherein the digital processor is implemented using PFGA or DSP.
9. The all-digital fluxgate-type current sensor according to claim 1, wherein the current filtering module is implemented by a low pass filter, and the second harmonic extraction module is implemented by a band pass filter.
10. The all-digital fluxgate-type current sensor according to claim 5, wherein the AD module and the DA module are converters with a precision of 16 bits or more.
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| CN202010443394.3A CN111665383B (en) | 2020-05-22 | 2020-05-22 | Full-digital fluxgate type current sensor |
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| CN202010443394.3A CN111665383B (en) | 2020-05-22 | 2020-05-22 | Full-digital fluxgate type current sensor |
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