Magnetic field sensor

Abstract

According to the magnetic field sensor provided by the invention, through an integrating circuit with a magnetic field sensing element and through inputting a matched periodic square wave signal (excitation signal), the characterization of the magnetic field intensity to be measured by a time constant of the integrating circuit is realized. Meanwhile, through an additional circuit part, the time constant is digitally output on the basis that an analog-to-digital converter does not need to be adopted. According to the magnetic field sensor provided by the invention, the to-be-measured magnetic field intensity is not represented by the output signal amplitude any more, but the digital time constant is used as a parameter for reflecting the to-be-measured magnetic field intensity. The magnetic field sensor provided by the invention has a certain anti-interference capability, and the influence of interference / crosstalk can be avoided when a sensing output signal of the magnetic field sensor is read; besides, the magnetic field sensor does not need to strictly limit the performance parameters of the magnetic field sensing element and the corresponding bias on the premise of considering the anti-interference capability and the measurement precision, and the arrangement of an application circuit is simplified.

Description

Technical Field

[0001] This application relates to the field of magnetic field measurement technology or magnetic field sensing technology, and in particular to a magnetic field sensor with good anti-interference ability, digital output signal and simple circuit. Background Technology

[0002] Magnetic sensors are devices that convert changes in the magnetic properties of a sensing element caused by a magnetic field into electrical signals to detect corresponding physical quantities. They are widely used in current detection, navigation, industrial control, electronic equipment, and other fields. Magnetic field sensors are mainly classified into Hall effect sensors, magnetoresistive sensors (such as AMR, GMR, and TMR), fluxgate sensors, and magnetoresistive sensors, based on their sensor type.

[0003] Among the many performance indicators for evaluating magnetic field sensors, measurement accuracy and anti-interference capability have always been key concerns. In addition to anti-interference capability and measurement accuracy, the ease of manufacturing magnetic field sensors often becomes another headache for the industry. For example, to balance anti-interference and measurement accuracy, existing magnetic field sensors often use multiple magnetic sensing elements to form a bridge circuit, ensuring that the parameters and sensing directions of the magnetic sensing elements on each bridge arm strictly meet certain relationships (otherwise, complex calibration algorithms are needed to correct the results). This is not easy to achieve due to the actual physical performance differences between different magnetic sensing elements caused by factors such as manufacturing processes. Furthermore, for magnetic field sensing elements that require bias settings (e.g., AMR magnetoresistive sensors), precise bias voltages must be provided to each magnetic field sensing element in the circuit. Summary of the Invention

[0004] In view of this, this application provides a magnetic field sensor with anti-interference capability and simple circuit setup. This magnetic field sensor incorporates the magnetic field sensing element within an integrating circuit, along with a corresponding square wave excitation signal and a numerical conversion circuit, to achieve a numerical representation of the strength of the measured magnetic field by the charging / discharging rate of the integrating circuit. This magnetic field sensor has a simple circuit setup and does not impose stringent limitations on the performance parameters and bias of the magnetic sensing element. It balances anti-interference capability and measurement accuracy without requiring precise setting of the magnetic field sensing element parameters and corresponding bias.

[0005] The magnetic field sensor provided in this application includes an integrating circuit with a magnetic field sensing unit and a digitization circuit. The excitation signal of the integrating circuit is a square wave signal, and the digitization circuit is used to detect and digitize the output of a digital quantity characterizing the charging or discharging speed of the integrating circuit to reflect the strength of the magnetic field (or component of the magnetic field) to be measured. The high level of the square wave signal... Positive voltage, low level is The duty cycle is 1:1 (i.e., the durations of high and low levels are equal). The frequency of the square wave signal is set so that the maximum voltage during charging of the integrator circuit's capacitor reaches [value missing]. The minimum voltage during discharge reaches .

[0006] Furthermore, the digital quantity refers to the voltage at which the charging and discharging capacitor of the integrating circuit is charged from... arrive The time taken; or, the digital quantity is the voltage from the discharge capacitor of the integrator circuit when it discharges. arrive The time taken; ,and Preferably, a is 10% and b is 90%.

[0007] Obviously, the digital quantity used to measure the charging or discharging speed of the capacitor in the integrator circuit can also be set as the time constant of the integrator circuit. , Where r is the resistance value of the magnetic field sensing unit in the integrating circuit, and c is the capacitance value of the integrating capacitor in the integrating circuit; or, the digital quantity can also be the voltage across the capacitor in the integrating circuit. There are no strict restrictions on the duration after midnight.

[0008] In some embodiments, the numericalization circuit includes two comparators, an RS latch, and a timer. The output signal of the integrator circuit is simultaneously connected to the positive inputs of both comparators. One comparator's negative input is connected to a first reference voltage, and its output is connected to the S terminal of the RS latch; the other comparator's negative input is connected to a second reference voltage, and its output is connected to the R terminal of the RS latch. The first reference voltage is set to... The second reference voltage is set to The output signal of the RS latch serves as the trigger signal for the timer. The timer is triggered by the rising edge of the trigger signal and stopped by the falling edge of the trigger signal. Its timing value is used as the digital quantity.

[0009] Further, the integrating circuit includes an amplifier U, a magnetic field sensing unit R, and a capacitor C; the positive input terminal of the amplifier U is grounded, the capacitor C is connected between the output terminal and the negative input terminal of the amplifier U, and one end of the magnetic field sensing unit R is connected to the square wave signal, and the other end is connected to the negative input terminal of the amplifier U. Preferably, the magnetic field sensor further includes a buffer, for example, a voltage follower. The input terminal of the buffer is connected to the output terminal of the integrating circuit, and its output terminal is connected to the input terminals of the two comparators.

[0010] Furthermore, the magnetic field sensing unit may be a circuit unit comprising a single magnetic field sensing element, several magnetic field sensing elements connected in series or parallel, or several magnetic field sensing elements connected in series or parallel. The magnetic field sensing element may be a magnetoresistive element or a Hall effect sensor, wherein the magnetoresistive element is an XMR magnetoresistive element, and the XMR element includes at least TMR, AMR, and GMR.

[0011] Corresponding to the aforementioned magnetic field sensor, this application also provides a magnetic field sensor system. The magnetic field sensor system includes the aforementioned magnetic field sensor and a data processing unit. The data processing unit obtains the corresponding magnetic field strength value by looking up a preset digital value-magnetic field strength lookup table based on the digital value output by the magnetic field sensor.

[0012] The magnetic field sensor provided by this invention is based on an integrating circuit (matched with a corresponding square wave excitation signal) and a numerical conversion circuit. It achieves the reflection of the strength of the measured magnetic field by the charging / discharging rate of the integrating circuit, without requiring a digital-to-analog converter. The magnetic field sensor does not output a signal amplitude to represent the strength of the measured magnetic field, thus balancing anti-interference capability and measurement accuracy. More importantly, its circuit setup is simple, and there are no stringent limitations on the performance parameters and bias of the magnetic sensing element. Attached Figure Description

[0013] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the overall structure of the magnetic field sensor provided by the present invention.

[0015] Figure 2 The circuit diagram of the integrating circuit in the magnetic field sensor provided by the present invention is shown in a portion of the embodiments. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] In this application, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0019] The technical solution provided by the present invention will be further described in detail below with reference to the accompanying drawings.

[0020] like Figure 1 As shown, in one embodiment, the magnetic field sensor provided in this application includes: an integrating circuit with a magnetic field sensing unit and a quantization circuit. The quantization circuit includes: two comparators, an RS latch, and a timer. Figure 1 As shown, in this embodiment, the magnetic field sensor further includes a buffer. The input terminal of the buffer is connected to the output terminal of the integrator circuit, and the output terminal is connected to the input terminals of the two comparators. Preferably, the buffer is a voltage follower.

[0021] exist Figure 1 In the illustrated embodiment, the details of the integrating circuit are as follows: Figure 2 As shown in the diagram, the integrating circuit includes an amplifier U, a magnetic field sensing unit R, and a capacitor C. The positive input terminal of amplifier U is grounded, and capacitor C is connected between its negative input terminal and output terminal. One end of the magnetic field sensing unit R is connected to the square wave signal, and the other end is connected to the negative input terminal of amplifier U.

[0022] In the above embodiments, the high level of the square wave signal Positive voltage, low level is The duty cycle is 1:1 (i.e., the ratio of the duration of high to low levels). The frequency of the square wave signal is set so that the maximum voltage during charging of the integrator circuit's charging and discharging capacitor reaches [value missing]. The minimum voltage during discharge reaches In this embodiment, the excitation signal for the integrator circuit is selected as a standard square wave signal.

[0023] Furthermore, the magnetic field sensing unit R can be a circuit unit comprising a single magnetic field sensing element, several magnetic field sensing elements connected in series or parallel, or several magnetic field sensing elements connected in series or parallel. The magnetic field sensing element can be a magnetoresistive element or a Hall effect sensor, wherein the magnetoresistive element is an XMR magnetoresistive element, and the XMR includes at least TMR, AMR, and GMR.

[0024] The integration time constant of an integrator circuit is τ = rc, where r is the resistance of the magnetic field sensing unit R in the integrator circuit, and c is the capacitance of the capacitor C in the integrator circuit. The integration principle of integrator circuits is used in electronic circuits to characterize the rate of charging and discharging. Therefore, given a fixed capacitance C, the rate of charging and discharging of the integrator circuit and its related parameters can also reflect the resistance r of the magnetic field sensing unit R, that is, the strength of the magnetic field being measured.

[0025] Furthermore, such as Figure 1 As shown, the output signal Vout of the integrator circuit is simultaneously connected to the positive input terminals of the two comparators. One comparator's negative input is connected to a first reference voltage, and its output is connected to the S terminal of the RS latch; the other comparator's negative input is connected to a second reference voltage, and its output is connected to the R terminal of the RS latch. The first reference voltage is set to... The second reference voltage is set to .

[0026] The timer is triggered by the rising edge of the trigger signal and stopped by the falling edge of the trigger signal. The reason for setting the reference levels of the negative inputs of the two comparators to [specific values ​​would be here] is... , This is so that the high-level duration of the pulse signal output by the latch can reflect the charging or discharging speed of the integrating circuit (i.e., the charging and discharging capacitor of the integrating circuit). Clearly, the timing value (digital quantity) of the timer can then represent the charging or discharging speed of the integrating circuit, reflecting the strength of the magnetic field (or component of the magnetic field) being measured. Obviously, the digital quantity can also be the voltage across the capacitor of the integrating circuit. Once the time has passed zero, the corresponding numerical circuit only needs simple modifications; no further restrictions are imposed here.

[0027] Of the two comparators, the output of one comparator is connected to the S terminal of the RS latch, and the output of the other comparator is connected to the R terminal of the RS latch; the output signal of the RS latch serves as the trigger signal for the timer. The timer can be a timer of an MCU or another type of digital time converter. Figure 1 As shown, when a is 10% and b is 90%, When the voltage is zero, the output waveform of the buffer in the magnetic field sensor is trapezoidal, and the output waveform of the RS latch is a periodic rectangular pulse signal.

[0028] The magnetic field sensor provided in this application uses a value representing the charging / discharging rate of the integrating circuit (rather than the amplitude of the traditional output signal) to reflect the strength of the magnetic field to be measured, which can effectively avoid errors caused by transient interference / crosstalk when reading the measurement results. Furthermore, to improve the accuracy of the measurement results, the average value of multiple digital outputs from the magnetic field sensor can be taken to obtain the corresponding magnetic field strength. This magnetic field sensor circuit is simple to set up, balances anti-interference capability and measurement accuracy, and does not impose strict limitations on the performance parameters and bias of the magnetic sensing element.

[0029] In accordance with the aforementioned magnetic field sensor, this application also provides a magnetic field sensor system. The magnetic field sensor system includes the aforementioned magnetic field sensor and a data processing unit. The data processing unit, based on the digital value output by the magnetic field sensor, looks up the corresponding magnetic field strength value in a preset digital value-magnetic field strength lookup table. That is, the digital value (timing value) output by the magnetic field sensor and its corresponding magnetic field strength can be pre-stored for later retrieval.

[0030] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A magnetic field sensor, characterized in that, The magnetic field sensor includes: an integrating circuit with a magnetic field sensing unit and a numerical conversion circuit. The excitation signal of the integrator circuit is a square wave signal, and the numerical circuit is used to detect and digitally output a digital quantity that characterizes the charging or discharging speed of the integrator circuit. The high level of the square wave signal Positive voltage, low level is The duty cycle is 1:1; the frequency of the square wave signal is set so that the maximum voltage during charging of the integrator circuit's charging and discharging capacitor reaches [value missing]. The minimum voltage during discharge reaches .

2. The magnetic field sensor as described in claim 1, characterized in that, The digital quantity refers to the voltage at which the capacitor of the integrator circuit is charged from the point where the voltage changes from... arrive The time taken; or, the digital quantity is the voltage from the discharge capacitor of the integrator circuit when it discharges. arrive The time taken; ,and .

3. The magnetic field sensor as described in claim 2, characterized in that, The numerical circuit includes: two comparators, an RS latch, and a timer; The output signal of the integrator circuit is simultaneously connected to the positive input terminals of the two comparators; the negative input terminal of one comparator is connected to the first reference voltage, and its output terminal is connected to the S terminal of the RS latch; the negative input terminal of the other comparator is connected to the second reference voltage, and its output terminal is connected to the R terminal of the RS latch. The first reference voltage is set to The second reference voltage is set to The output signal of the RS latch serves as the trigger signal for the timer. The timer is triggered by the rising edge of the trigger signal and stopped by the falling edge of the trigger signal. Its timing value is used as the digital quantity.

4. The magnetic field sensor as described in claim 3, characterized in that, a is 10%, and b is 90%.

5. The magnetic field sensor as described in claim 3, characterized in that, The integrating circuit includes an amplifier U, a magnetic field sensing unit R, and a capacitor C; the positive input terminal of the amplifier U is grounded, the capacitor C is connected between the output terminal and the negative input terminal of the amplifier U, and one end of the magnetic field sensing unit R is connected to the square wave signal, and the other end is connected to the negative input terminal of the amplifier U.

6. The magnetic field sensor as described in claim 5, characterized in that, The magnetic field sensor also includes a buffer; the input of the buffer is connected to the output of the integrator circuit, and its output is connected to the input of the two comparators.

7. The magnetic field sensor as described in claim 6, characterized in that, The buffer is a voltage follower.

8. The magnetic field sensor as described in claim 5, characterized in that, The magnetic field sensing unit is a circuit unit that includes a single magnetic field sensing element, several magnetic field sensing elements connected in series or in parallel, or several magnetic field sensing elements connected in series or in parallel.

9. The magnetic field sensor as described in claim 8, characterized in that, The magnetic field sensing element is a magnetoresistive or Hall effect sensor; the magnetoresistive element is an XMR magnetoresistive element, and the XMR includes at least TMR, AMR, and GMR.

10. A magnetic field sensor system, characterized in that, The magnetic field sensor system includes a magnetic field sensor and a data processing unit; the magnetic field sensor is the magnetic field sensor according to any one of claims 1-9, and the data processing unit obtains the corresponding magnetic field strength value by looking up a preset digital quantity-magnetic field strength lookup table based on the digital quantity output by the magnetic field sensor.

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