A magnetic field sensing circuit

Abstract

The utility model provides a kind of magnetic field sensing circuit, it is based on 555 timer chip and contains magnetic resistance's capacitor charging-discharging circuit to build self-excitation oscillation circuit, realize the output frequency of the output end OUT of 555 timer chip with the resistance value transformation square wave signal of magnetic resistance.This utility model provides above-mentioned magnetic field sensing circuit (can realize digital transmission magnetic field intensity sensed by magnetic resistance with cooperation counter) compared with prior art scheme with voltage amplitude to characterize magnetic field intensity, greatly improve the anti-interference ability of magnetic field sensing signal.The connection relationship of above-mentioned magnetic field sensing circuit is simple, low in cost, and digital sensing signal is suitable for electromagnetic interference signal transmission processing.

Description

Technical Field

[0001] This application relates to the field of magnetic field detection circuit design, specifically to a magnetic field sensing circuit that transmits magnetic field sensing signals digitally. Background Technology

[0002] Magnetoresistive sensors are a primary physical component for measuring magnetic field strength. Magnetoresistive sensors offer advantages such as fast response, low power consumption, and small size, and are widely used in mobile phones, computers, automobiles, aviation, aerospace, and other equipment for measuring related physical quantities. They are also core components in various magnetic shaft buttons. The development of magnetoresistive sensors primarily focuses on designing magnetic sensor structures that meet the requirements of various application scenarios.

[0003] Currently, the anti-interference capability is a core indicator most frequently considered in the design of magnetoresistive sensors, while anti-saturation capability is another important core indicator. However, the focus is usually on how to eliminate the measurement influence caused by the interfering magnetic field in the magnetic field sensed by the magnetoresistive sensor itself (for example, using a circuit composed of multiple magnetic sensing units to cancel the influence of the interfering magnetic field), while often neglecting the interference of temperature and electromagnetic signals on the sensed signal during transmission. In fact, the magnetic field sensing signal of existing magnetic field detection circuits is usually an analog voltage signal, which is easily affected by temperature and electromagnetic signals during transmission, resulting in a non-negligible error in the subsequent calculation of magnetic field strength. Utility Model Content

[0004] To address the problem that existing magnetic field sensors, which use analog voltage signals as the sensing signal, are easily affected by environmental interference during transmission, this invention provides a magnetic field sensing circuit. This circuit utilizes low-cost electronic components to construct a self-excited oscillation circuit whose output square wave signal frequency is modulated by the resistance value of a magnetoresistor, ensuring good anti-interference capability of the sensing signal during transmission. The receiving end then acquires the digital quantity reflecting the magnetic field strength through pulse counting.

[0005] The magnetic field sensing circuit provided by this utility model includes: a 555 timer chip and a capacitor charging / discharging branch containing a magnetoresistor R1. The 555 timer chip and the capacitor charging / discharging branch constitute (electrically connected) a self-excited oscillation circuit. The output terminal OUT (pin OUT) of the 555 timer chip serves as the signal output terminal of the self-excited oscillation circuit, used to output a square wave signal whose frequency varies with the resistance value of the magnetoresistor R1. The 555 timer chip integrates a comparator and a trigger; by connecting the corresponding capacitor charging / discharging branch and the magnetoresistor R1 to the corresponding pins to form positive feedback, the oscillation start-up conditions for self-excited oscillation are met.

[0006] Furthermore, the capacitor charging / discharging branch includes a magnetoresistive resistor R1, diodes D1 and D2, resistors R2 and R3, and a discharge capacitor C. The anode of diode D1 and the cathode of diode D2 are both connected to the first terminal of magnetoresistive resistor R1 and the discharge pin DIS. The second terminal of magnetoresistive resistor R1 is connected to the power supply terminal VDD. One end of resistor R2 is connected to the cathode of diode D1, and one end of resistor R3 is connected to the anode of diode D2. The other ends of resistors R2 and R3 are both connected to the first terminal of the charging / discharging capacitor C, and the second terminal of the charging / discharging capacitor C is grounded.

[0007] Furthermore, the second terminal of the magnetoresistor R1 is connected to the reset pin RST of the 555 timer chip, the first terminal is connected to the discharge pin DIS of the 555 timer chip, and the power supply terminal VDD is connected to the power supply pin VCC of the 555 timer chip. The first terminal of the charging / discharging capacitor C is connected to the threshold pin THR and the trigger pin TRI of the 555 timer chip, and the second terminal of the charging / discharging capacitor C serves as the ground terminal of the charging / discharging branch of the capacitor.

[0008] Furthermore, the magnetoresistive R1 is composed of several magnetoresistive units connected in series, in parallel, or in series and in parallel. The magnetoresistive unit is an XMR magnetoresistive unit, and the XMR includes GMR, TMR, and AMR.

[0009] In addition, in order to further eliminate electric field interference, reduce loop inductance, and ensure that high-frequency noise is guided to the ground terminal in a timely manner, the control terminal CON / CTR of the 555 timer chip is grounded through decoupling capacitor C1.

[0010] The magnetic field sensing circuit provided by this invention generates digital magnetic field sensing signals with simple connection relationships and low cost (the corresponding magnetic field strength can be calculated by the number of pulses per unit time). Compared with the existing magnetic field sensing scheme that uses voltage amplitude to characterize magnetic field strength, it greatly improves the anti-interference capability of the magnetic field sensing signal itself. Attached Figure Description

[0011] To more clearly illustrate the specific embodiments of this utility model 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 this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0012] Figure 1 The circuit diagram of the magnetic field sensing circuit provided by this utility model in one embodiment. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0014] 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.

[0015] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0016] The present invention will now be described in further detail with reference to the accompanying drawings.

[0017] like Figure 1 As shown, in one embodiment, the magnetic field sensing circuit provided by this utility model includes diodes D1 and D2, a magnetoresistive resistor R1, resistors R2 and R3, capacitors C and C1, and a 555 timer chip; wherein, capacitor C is a charging and discharging capacitor. Diodes D1 and D2, resistors R2 and R3, magnetoresistive resistor R1, and discharging capacitor C constitute a capacitor charging and discharging branch.

[0018] The anode of diode D1 and the cathode of diode D2 are both connected to the first terminal of magnetoresistive R1 and the discharge pin DIS. The second terminal of magnetoresistive R1 is connected to the power supply terminal VDD. One end of resistor R2 is connected to the cathode of diode D1, and one end of resistor R3 is connected to the anode of diode D2. The other ends of resistors R2 and R3 are both connected to the first terminal of charging / discharging capacitor C, and the second terminal of charging / discharging capacitor C is grounded. Pin DIS is a dedicated discharge pin for the 555 timer chip.

[0019] The 555 timer chip and the capacitor charging / discharging branch constitute a self-excited oscillation circuit. The output terminal OUT (pin OUT) of the 555 timer chip serves as the signal output terminal of the self-excited oscillation circuit, used to output a square wave signal whose frequency varies with the resistance value of the magnetoresistive R1.

[0020] Specifically, such as Figure 1As shown, the second end of the magnetoresistor R1 is connected to the power supply terminal VDD and the reset pin RST of the 555 timer chip, and the first end is connected to the discharge pin DIS of the 555 timer chip. The power supply terminal VDD is connected to the power supply pin VCC of the 555 timer chip. The first end of the charging / discharging capacitor C is connected to the threshold pin THR and the trigger pin TRI of the 555 timer chip, and the second end of the charging / discharging capacitor C serves as the ground terminal for the charging / discharging branch of the capacitor.

[0021] The 555 timer chip integrates a comparator and a flip-flop. By connecting the corresponding capacitor charging / discharging branch and the magnetoresistor R1 to the corresponding pins, positive feedback is formed, satisfying the oscillation start-up condition for self-excited oscillation. The comparator and flip-flop are cascaded, with the threshold pin THR used to connect to the threshold voltage of the comparator, and the trigger pin TRI serving as the signal input pin for the flip-flop.

[0022] Furthermore, in order to further eliminate electric field interference, reduce loop inductance, and ensure that high-frequency noise is guided to the ground terminal in a timely manner, the control terminal CON / CTR of the 555 timer chip is grounded through decoupling capacitor C1.

[0023] Of course, the magnetoresistive R1 is composed of several magnetoresistive units connected in series, parallel, or series-parallel. The magnetoresistive unit is an XMR magnetoresistive unit, and XMR includes GMR, TMR, and AMR. The magnetoresistive R1 can be in the form of discrete magnetoresistive units electrically connected, or it can be in the form of a chip package.

[0024] The internal logic of the 555 timer chip and Figure 1 As shown in the circuit, the frequency f of the square wave output from the OUT terminal of the 555 timer chip is related to the charging and discharging constant of the capacitor charging and discharging branch. Negative correlation. Among them, ; Let R1 be the resistance value presented by the magnetoresistor. This is the capacitance value of the charging / discharging capacitor C.

[0025] In one embodiment, the magnetoresistive R1 is selected from Jiangsu Multidimensional Technology Co., Ltd.'s TMR9082BP, whose resistance value varies within a certain range. to The charging / discharging capacitor C is fixed at 1nF. When the resistance of the magnetoresistive resistor R1 is... When the output terminal OUT of the 555 timer comparator chip has a square wave frequency of 34.232kHz, the output terminal OUT of the 555 timer comparator chip has a square wave frequency of 26.59kHz when the resistance of the magnetoresistor R1 is 8kΩ.

[0026] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A magnetic field sensing circuit, characterized by, The magnetic field sensing circuit includes: a 555 timer chip and a capacitor charging and discharging branch containing a magnetoresistor R1; the 555 timer chip and the capacitor charging and discharging branch constitute a self-excited oscillation circuit, and its output terminal OUT serves as the magnetic field sensing signal output terminal; the magnetic field sensing signal output terminal is used to output a square wave signal whose frequency varies with the resistance value of the magnetoresistor R1.

2. The magnetic field sensing circuit of claim 1, wherein, The capacitor charging / discharging branch includes: a magnetoresistor R1, diodes D1 and D2, resistors R2 and R3, and a discharge capacitor C; the anode of diode D1 and the cathode of diode D2 are both connected to the first end of magnetoresistor R1 and the discharge pin DIS of the 555 timer chip, and the second end of magnetoresistor R1 is connected to the power supply terminal VDD; one end of resistor R2 is connected to the cathode of diode D1, one end of resistor R3 is connected to the anode of diode D2, and the other ends of resistors R2 and R3 are both connected to the first end of the charging / discharging capacitor C, and the second end of the charging / discharging capacitor C is grounded.

3. The magnetic field sensing circuit of claim 2, wherein, The second end of the magnetor R1 is connected to the reset pin RST of the 555 timer chip, the first end is connected to the discharge pin DIS of the 555 timer chip, and the power supply terminal VDD is connected to the power supply pin VCC of the 555 timer chip; the first end of the charging and discharging capacitor C is connected to the threshold pin THR and the trigger pin TRI of the 555 timer chip, and the second end of the charging and discharging capacitor C serves as the ground terminal of the charging and discharging branch of the capacitor.

4. The magnetic field sensing circuit of claim 3, wherein, The control terminal CON / CTR of the 555 timer chip is grounded through decoupling capacitor C1.

5. The magnetic field sensing circuit of claim 1, wherein, The magnetoresistive R1 is composed of several magnetoresistive units connected in series, in parallel, or in a series-parallel configuration.

6. The magnetic field sensing circuit of claim 5, wherein, The magnetoresistive unit is an XMR magnetoresistive unit, and XMR includes GMR, TMR, and AMR.

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