Conditioning circuit based on fluxgate, chip and sensor

Abstract

The invention relates to a conditioning circuit based on a fluxgate, a chip and a sensor, the circuit comprises a power supply circuit, a power amplifier circuit, an excitation circuit, a conditioning circuit and a differential amplification circuit, the power amplifier circuit is used for carrying out demagnetization and current closed-loop compensation on an electrified sensor coil through symmetrical voltage and register configuration; the excitation circuit is used for generating self-excitation oscillation after the coils are switched on through a comparator H bridge and a D trigger, and driving the demagnetized coils with different sizes or turns; the conditioning circuit is used for conditioning a signal of a sensor coil through a plurality of operational amplifiers and a Trim circuit, and has a temperature compensation function; and the differential amplification circuit is used for carrying out differential amplification on the conditioned sensor signal. The whole system also has the functions of ERROR abnormity alarm and OCD overcurrent abnormity alarm. Through the integration of the amplifying circuit and the conditioning circuit, the precision and the integration level of the sensor are improved, and the temperature drift and the cost are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors and integrated chips, and in particular relates to a conditioning circuit, a chip and a sensor based on a fluxgate. Background Art

[0002] The development trend of current sensors is miniaturization, integration, and low cost. The traditional module type is mainly composed of magnetic rings, induction / feedback coils, PCBA, etc. The performance and cost of the sensor are mainly determined by the magnetic rings and PCBA. The area and cost of PCBA are composed of components of the signal detection circuit. With the development of application needs and technology, chip integration + magnetic ring module is a more suitable solution.

[0003] Fluxgate technology is a sensor technology that uses the nonlinear relationship between the magnetic induction intensity and the magnetic field intensity of a high permeability core under saturation excitation of an alternating magnetic field to measure weak magnetic fields.

[0004] The development of existing fluxgate and TMR products all use conditioning chips. Currently, products mainly use chips from TI, 3Peak, Nanochip and other companies for sensor control and signal acquisition. It is estimated that the annual usage of conditioning chips will exceed 1 million in 3-5 years. There is an urgent need for low-cost, highly integrated magnetic conditioning chips, which have huge cost and performance advantages for future mass applications. Summary of the invention

[0005] In order to improve the integration and accuracy of the conditioning chip, a conditioning circuit based on fluxgate is provided in the first aspect of the present invention, including: a power amplifier circuit, an excitation circuit, a conditioning circuit and a differential amplifier circuit, and a power supply circuit for powering the power amplifier circuit, the excitation circuit, the conditioning circuit and the differential amplifier circuit. The power amplifier circuit is used to demagnetize the sensor coil after power-on and perform closed-loop compensation of the current through symmetrical voltage and registers; the excitation circuit is used to drive coils of different sizes or numbers of turns through a comparator H bridge and a D trigger; the conditioning circuit is used to perform gain zero point conditioning on the sensor coil signal and abnormality detection by presetting the open drain output to a high level through multiple operational amplifiers and Trim circuits; the differential amplifier circuit is used to perform forward differential amplification, reverse differential amplification or forward and reverse simultaneous differential amplification on the conditioned sensor signal through an analog switch.

[0006] In some embodiments of the present invention, the output of the D flip-flop is electrically connected to the input of a comparator H-bridge, and the input and output of the comparator H-bridge are electrically connected to the output of the D flip-flop and the sensor coil, respectively.

[0007] Furthermore, the comparator H bridge includes at least four MOSs.

[0008] Furthermore, the excitation circuit sets the breakover voltage of the sensor coil by configuring the register to match coils of different sizes or numbers of turns.

[0009] In some embodiments of the present invention, the conditioning circuit includes: an operational amplifier circuit, configured to perform a first-stage adjustment on the zero-point gain of the sensor; and a Trim circuit, used to perform a second-stage adjustment on the zero-point gain of the sensor, wherein the maximum gain of the first-stage adjustment is greater than the maximum gain of the second-stage adjustment.

[0010] Furthermore, the operational amplifier circuit is also used for conditioning, amplifying or actively filtering the analog signal of the sensor.

[0011] A second aspect of the present invention provides a fluxgate-based conditioning chip, comprising the fluxgate-based conditioning circuit provided by the first aspect of the present invention.

[0012] A third aspect of the present invention provides a sensor, comprising the fluxgate-based conditioning chip provided in the second aspect of the present invention.

[0013] The beneficial effects of the present invention are: The present invention relates to a conditioning circuit, chip and sensor based on fluxgate, wherein the circuit includes: a power amplifier circuit, an excitation circuit, a conditioning circuit and a differential amplifier circuit, and a power supply circuit for the power amplifier circuit, the excitation circuit, the conditioning circuit and the differential amplifier circuit. The power amplifier circuit is used to demagnetize the sensor coil after power-on and perform closed-loop compensation of the current through symmetrical voltage and register; the excitation circuit is used to drive coils of different sizes or turns through a comparator H bridge and a D trigger; the conditioning circuit is used to perform gain zero point conditioning on the sensor coil signal and abnormality detection through a preset open drain output of a high level through multiple operational amplifiers and Trim circuits; the differential amplifier circuit is used to perform forward differential amplification, reverse differential amplification or forward and reverse simultaneous differential amplification on the conditioned sensor signal through an analog switch. It can be seen that the magnetic conditioning circuit or chip based on fluxgate technology of the present invention can be used for current sensor signal conditioning, and a complete fluxgate current sensor can be formed with very few peripheral devices. The current measurement range covers 0~±300A, with high precision, high integration, and low temperature drift. It is powered by a single 5V power supply, has an operating temperature range of -40~105℃, and is automotive grade and meets AEC-Q100. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a basic structural schematic diagram of a fluxgate-based conditioning circuit in some embodiments of the present invention; Figure 2 is a schematic circuit diagram of a power supply circuit in a fluxgate-based conditioning circuit in some embodiments of the present invention; Figure 3 is a circuit diagram of a power amplifier circuit in a fluxgate-based conditioning circuit in some embodiments of the present invention; Figure 4 A timing diagram of a register in a power amplifier circuit in a fluxgate-based conditioning circuit in some embodiments of the present invention; Figure 5 is a circuit diagram of an excitation circuit in a fluxgate-based conditioning circuit in some embodiments of the present invention; Figure 6 is a circuit diagram of an operational amplifier circuit in a fluxgate-based conditioning circuit in some embodiments of the present invention; Figure 7 is a circuit diagram of a trim circuit in a fluxgate-based conditioning circuit in some embodiments of the present invention; Figure 8 is a circuit diagram of a differential amplifier circuit in a fluxgate-based conditioning circuit in some embodiments of the present invention; Reference numerals 1. Conditioning circuit based on fluxgate; 11. Power amplifier circuit; 12. Excitation circuit; 13. Conditioning circuit; 14. Differential amplifier circuit; 15. Power supply circuit. DETAILED DESCRIPTION

[0015] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0016] refer to Figure 1 and Figure 2 In a first aspect of the present invention, a fluxgate-based conditioning circuit 1 is provided, comprising: a power amplifier circuit 11, an excitation circuit 12, a conditioning circuit 13 and a differential amplifier circuit 14, and a power supply circuit 15 for the power amplifier circuit 11, the excitation circuit 12, the conditioning circuit 13 and the differential amplifier circuit 14, wherein the power amplifier circuit 11 is used to demagnetize the sensor coil after power-on and perform closed-loop current compensation through symmetrical voltage and registers; the excitation circuit 12 is used to drive coils of different sizes or turns after demagnetization through a comparator H-bridge and a D-flip-flop; the conditioning circuit 13 is used to condition the signal of the sensor coil through multiple operational amplifiers and Trim circuits; the differential amplifier circuit 14 is used to differentially amplify the sensor signal through a sampling resistor.

[0017] It can be understood that fluxgate technology is a sensor technology that uses the nonlinear relationship between the magnetic induction intensity and the magnetic field intensity of a high permeability core under saturation excitation of an alternating magnetic field to measure weak magnetic fields. Without loss of generality, refer to Figure 2In some embodiments of the present invention, the power supply circuit 15 supplies power to the power amplifier circuit 11, the excitation circuit 12, the conditioning circuit 13 and the differential amplifier circuit 14. Specifically, the power supply is a single power supply with an input voltage range of 4.75V~5.25V. The power supply part has a built-in initial accuracy 1% output 3.3V LDO, a temperature drift coefficient of 60PPM / ℃, two 10ppm REF references are respectively REF external output, and the output current capacity is 10mA. Ref1 is the internal reference reference of the chip. Through the register configuration, the two REFs can generate 2.5V, 1.65V, 4.096V, 1 / 2VCC. The main function of LDO is to power the external MCU, the external TMR, HALL and other probes, and can also be used as an external pull-up voltage.

[0018] It can be understood that the demagnetization circuit is particularly important for the measurement accuracy and stability of the fluxgate sensor. It can be demagnetized regularly during operation to avoid excessive hysteresis caused by over-range current affecting the sensor's accuracy performance.

[0019] Specifically, the power amplifier circuit has a maximum driving capacity of 150mA, IN1 inputs an analog signal, Icomp1 and Icom2 linearly output a symmetrical voltage based on the median 1 / 2VCC, and compensate the coil current. It is mainly used in closed-loop Hall, closed-loop fluxgate and other application scenarios. Degauss is a function configured by the internal register. The Degauss timing is as follows: Figure 4 As shown in the figure, when this function is enabled, the corresponding register will be configured to 1, and the sensor will immediately perform the demagnetization function after power-on, mainly to eliminate the residual magnetism of magnetic materials and improve the measurement accuracy of the sensor.

[0020] refer to Figure 5 , in some embodiments of the present invention, the input terminal of the D flip-flop is electrically connected to the input terminal of the comparator H bridge; Specifically, the excitation circuit is mainly a fluxgate excitation circuit. As the core driver of the fluxgate sensor, it consists of four MOSs forming an H bridge with a driving current of 50mA. The coil is self-oscillated through the comparator and Q trigger, and hShunt is connected to the sampling resistor to the ground. IS2 and IS1 are connected to the magnetic ring coil, and ACMP+ is connected to hShunt. The fluxgate sensor's breakover voltage can be set by configuring the register to match coils of different sizes and numbers of turns. This module will be used in the application scenarios of open-loop fluxgate and closed-loop fluxgate.

[0021] refer to Figure 6 and Figure 7 , in some embodiments of the present invention, the conditioning circuit 13 includes: an operational amplifier circuit, configured to perform a first-stage adjustment on the zero-point gain of the sensor; Specifically, the independent op amp part consists of two op amps, which are flexible and can be configured as an independent op amp or an op amp with adjustable gain and zero point. The gain adjustment range is 1~3 times and the zero adjustment range is ±30mV. This module can be used as analog signal conditioning, integration circuit, amplifier circuit, active filter circuit, etc.

[0022] The Trim circuit is used to perform a second-stage adjustment on the zero-point gain of the sensor, wherein the gain of the second-stage adjustment is smaller than the gain of the first-stage adjustment.

[0023] Specifically, the main function of the trim circuit is to independently adjust the zero-point gain of the sensor. The temperature compensation function is also integrated into the module. The zero-point adjustment range is ±50mV, the gain adjustment range is 1~1.5 times, and the analog output port is Vout. This port reuses the OWI function. The ERROR pin is used for internal fault detection in the system. The pin is enabled by judging the internal oscillation frequency, compensation current and chip temperature. The default high level and open-drain output. The main application scenario of the Trim circuit is analog type sensors as signal conditioning output. For example, when the Hall sensor outputs 1V at 20A, the signal needs to be conditioned to 2.5V±2V output, and the open-loop Hall generally has temperature drift. Combined with temperature compensation, the measurement accuracy of the sensor in the entire temperature range can be improved.

[0024] refer to Figure 8 In some embodiments of the present invention, the differential amplifier circuit 14 is used to perform differential amplification on the conditioned sensor signal.

[0025] Specifically, the main function of the differential amplifier module is to perform differential amplification of the input signal by 4 times and output ±4 times. Through register configuration, hFlag, VCC, and GND pins can be selected. hFlag is a certain frequency signal to realize the PSD function. Refin is used as the reference input, which is generally connected to 2.5V. When the switch is configured to VCC, A and B1 are connected, and the output signal follows the input signal. When the switch is configured to Gnd, A and B2 are connected, and the output signal is opposite to the input signal.

[0026] Example 2 A second aspect of the present invention provides a fluxgate-based conditioning chip, comprising the fluxgate-based conditioning circuit provided by the first aspect of the present invention.

[0027] Specifically, the chip provided by the present invention includes 3.3V LDO, high-precision reference voltage 2.5V, 1.65V, 4.096V, 1 / 2VCC, which reduces the board area, reduces the cost and improves the performance for system applications. The chip includes a power amplifier circuit, a large current integrated drive, and provides compensation current in closed-loop applications. The chip includes a fluxgate core drive circuit, which is composed of a comparator H-bridge D trigger to generate self-oscillation. The chip includes two independent op amps, which can be configured to have a configurable gain zero point. The chip includes a Trim circuit, zero-point gain fine-tuning, independent adjustment, and a temperature compensation module. The chip includes a 4x fixed differential amplifier, and the output can be configured to be reversed, or a PSD function. The chip is packaged in QFN24 form. The chip includes fault diagnosis functions including overvoltage, overcurrent, overheating, and abnormal frequency. The chip also contains EEPROM. Through the configuration of registers, you can set Digauss function, temperature compensation parameters, OCD time, ERROR time, pulse oscillation and other functions. The chip is powered by a single power supply of 5V, with an operating temperature range of -40~105℃, and the automotive grade meets the AEC-Q100 standard.

[0028] A third aspect of the present invention provides a sensor, comprising the fluxgate-based conditioning chip provided in the second aspect of the present invention.

[0029] Specifically, the typical application scenarios of the chip include five categories: closed-loop Hall, closed-loop fluxgate, open-loop Hall, analog leakage current sensor, and digital leakage current sensor.

[0030] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present disclosure. In this regard, each box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should be noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fluxgate-based conditioning circuit, comprising: A power amplifier circuit, an excitation circuit, a conditioning circuit and a differential amplifier circuit, and a power supply circuit for supplying power to the power amplifier circuit, the excitation circuit, the conditioning circuit and the differential amplifier circuit, characterized in that: The power amplifier circuit is used to demagnetize the sensor coil after power-on and perform closed-loop compensation of the current through symmetrical voltage and register; The excitation circuit is used to drive coils of different sizes or numbers of turns through a comparator H bridge and a D flip-flop; The conditioning circuit is used to perform gain zero point conditioning on the signal of the sensor coil through multiple operational amplifiers and Trim circuits and perform abnormality detection by setting the open drain output to a high level; The differential amplifier circuit is used to perform forward differential amplification, reverse differential amplification, or forward and reverse differential amplification simultaneously on the conditioned sensor signal through an analog switch.

2. The fluxgate-based conditioning circuit according to claim 1, characterized in that: The output terminal of the D flip-flop is electrically connected to the input terminal of the comparator H bridge. The input end and the output end of the comparator H bridge are electrically connected to the output end of the D flip-flop and the sensor coil respectively.

3. The fluxgate-based conditioning circuit according to claim 2, characterized in that: The comparator H bridge includes at least four MOSs.

4. The fluxgate-based conditioning circuit according to claim 2, characterized in that: The excitation circuit sets the breakover voltage of the sensor coil by configuring the register to match coils of different sizes or numbers of turns.

5. The fluxgate-based conditioning circuit according to claim 1, characterized in that: The conditioning circuit comprises: an operational amplifier circuit configured to perform a first-order adjustment of the zero gain of the sensor; The Trim circuit is used to perform a second-stage adjustment on the zero-point gain of the sensor, wherein the maximum gain of the first-stage adjustment is greater than the maximum gain of the second-stage adjustment.

6. The fluxgate-based conditioning circuit according to claim 5, characterized in that: The operational amplifier circuit is also used for conditioning, amplifying or actively filtering the analog signal of the sensor.

7. A fluxgate-based conditioning chip, characterized in that: It includes the fluxgate-based conditioning circuit described in claims 1-6.

8. A sensor based on a fluxgate conditioning chip, characterized in that: Including the fluxgate-based conditioning chip as described in claim 7.

9. A sensor based on a fluxgate conditioning chip, characterized in that: Includes registers for configurable demagnetization function, temperature compensation parameters, overcurrent monitoring time, abnormality monitoring time and pulse oscillation signal.

10. A sensor according to claim 9, characterized in that The over-current monitoring port and the abnormality monitoring port are both open-drain outputs.

Images