An optimized signal conditioning circuit for inductive encoders

Abstract

The utility model relates to the technical field of signal conditioning circuit of inductive encoder, especially to an optimized signal conditioning circuit for inductive encoder, which comprises signal input unit, gain amplification module, RC filter module, voltage follower module and signal output unit connected in sequence, and further comprises reference voltage unit for providing bias for gain amplification module, analog power supply for supplying power for gain amplification module and voltage follower module, and ADC module of MCU connected with signal output unit. In the utility model, through the signal input, gain amplification, RC filter, voltage follower and signal output unit connected in sequence, the reference voltage unit and the analog power supply are matched, and each of the four differential signals is matched with an independent conditioning module; based on the principle of gain amplification precision amplitude modulation, RC filter high-frequency noise filtering and voltage follower driving enhancement, the ADC module of the MCU is adapted, and the sampling precision, anti-interference performance and system reliability are improved.

Description

Technical Field

[0001] This utility model relates to the field of signal conditioning circuit technology for inductive encoders, and in particular to an optimized signal conditioning circuit for inductive encoders. Background Technology

[0002] Inductive encoders, due to their adaptability to complex environments, are widely used in various scenarios requiring precise position and speed detection. Signal transmission, as a crucial link between the sensor and the signal processing unit, directly determines the overall performance of the detection system. The raw signal output by the sensor is a weak analog signal, while real-world applications often encounter adverse factors such as electromagnetic interference. The signal is easily distorted during transmission due to external influences. Therefore, a reasonable signal transmission scheme is needed to ensure signal stability and processability, providing a reliable foundation for subsequent ADC sampling and data processing. The core of its technical design revolves around the faithful transmission and adaptation of the signal.

[0003] Most existing inductive encoder signal transmission solutions lack specific conditioning design for the weak analog signals output by the sensors. These solutions lack precise gain adjustment capabilities, failing to adapt to subsequent processing requirements based on signal characteristics; they lack targeted noise filtering mechanisms, making it difficult to effectively suppress noise introduced by environmental interference; and they lack signal buffering and driving stages, resulting in limited sensor driving capabilities. These design flaws directly lead to weak signal anti-interference capabilities, mismatch with the input level of the MCU's ADC module, and insufficient sensor driving capability. This, in turn, causes reduced ADC sampling accuracy, signal saturation distortion, or wasted quantization precision, ultimately resulting in slow system response and significantly limited overall operational reliability. Summary of the Invention

[0004] To overcome the problems of existing inductive encoder signal transmission schemes, which lack precise gain adjustment, targeted noise filtering, and signal buffering design when conditioning the weak analog signal output by the sensor, resulting in weak signal anti-interference ability, mismatch with the input level of the MCU's ADC module, insufficient sensor driving capability, and consequently low ADC sampling accuracy, easy signal saturation distortion or waste of quantization accuracy, slow system response, and limited reliability.

[0005] The technical solution of this utility model is as follows: an optimized signal conditioning circuit for an inductive encoder, comprising a signal input unit, a gain amplification module, an RC filter module, a voltage follower module, and a signal output unit connected in sequence; it also includes a reference voltage unit providing bias for the gain amplification module, an analog power supply for powering the gain amplification module and the voltage follower module, and an ADC module of an MCU connected to the signal output unit; the input terminal of the signal input unit is connected to the differential signal output terminal of the inductive encoder sensor, and the output terminal is connected to the input terminal of the gain amplification module; the input terminal of the signal output unit is connected to the output terminal of the voltage follower module, and the output terminal is connected to the input terminal of the ADC module of the MCU; the gain amplification module includes an operational amplifier U and resistive-capacitive components, receives the differential signal from the signal input unit and biases it through the reference voltage unit; the RC filter module includes resistors and capacitors, connecting the gain amplification module and the voltage follower module; the voltage follower module includes an operational amplifier U and a capacitor, and its output terminal is connected to the signal output unit.

[0006] Preferably, the gain amplification module includes resistors R1-R4 and capacitors C1-C3; the non-inverting terminal of U1 is connected to the non-inverting signal terminal of the signal input unit via R1, the inverting terminal is connected to the inverting signal terminal via R2, the reference voltage unit is connected to the non-inverting terminal of U1 via R3 and C1, the inverting terminal of U1 is connected to the output terminal via R4 and C2, and C3 is connected between the power supply pin of U1 and ground.

[0007] Preferably, the RC filter module includes a resistor R5 and a capacitor C4; one end of R5 is connected to the output terminal of the gain amplifier module, and the other end is connected to C4 and the input terminal of the voltage follower module, and the other end of C4 is grounded.

[0008] Preferably, in the voltage follower module, the non-inverting terminal of U2 is connected to the output terminal of the RC filter module, the inverting terminal is shorted to the output terminal, and the capacitor C5 is connected between the power supply pin of U2 and ground.

[0009] Preferably, the operational amplifiers U1 and U2 are both TP2302-VR; the reference voltage unit outputs 1.5V, and the analog power supply outputs 3.3V.

[0010] Preferably, the output signal amplitude of the gain amplification module is 80%-90% of the input range of the MCU's ADC module; the cutoff frequency of the RC filter module is 20-50kHz.

[0011] Preferably, the differential signal output terminals of the inductive encoder sensor include Sin+, Sin-, Cos+, and Cos-, and each channel is equipped with an independent gain amplification module, RC filter module, and voltage follower module.

[0012] The beneficial effects of this utility model are: 1. The differential signal from the inductive encoder sensor is received through the signal input unit. The differential input design, in which the non-inverting input of the operational amplifier U1 in the gain amplification module is connected to the non-inverting signal input of the signal input unit through R1 and the inverting input through R2, together with R3 and C1, introduces the 1.5V bias signal of the reference voltage unit into the non-inverting input of U1. Then, through R4 and C2, a negative feedback loop of U1 is formed to accurately adjust the signal amplitude to 80%-90% of the input range of the MCU's ADC module. This fully utilizes the dynamic resolution of the ADC, avoids the waste of quantization accuracy due to the signal being too small or the saturation distortion due to the signal being too large, and completely solves the signal level mismatch problem. 2. By connecting one end of resistor R5 in the RC filter module to the output terminal of U1 in the gain amplifier module and the other end to capacitor C4 and the input terminal of the voltage follower module, with the other end of C4 grounded, high-frequency interference above 20-50kHz in the signal is accurately filtered out. At the same time, capacitor C3 in the gain amplifier module is connected in parallel between the power supply pin of U1 and ground, and capacitor C5 in the voltage follower module is connected in parallel between the power supply pin of U2 and ground, which effectively suppresses the influence of power supply noise on the operational amplifier, significantly improves the signal-to-noise ratio, enhances the circuit's anti-electromagnetic interference capability, and solves the problem of noise contamination of the signal during transmission. 3. By connecting the output signal of the RC filter module to the non-inverting input of the operational amplifier U2 in the voltage follower module and directly shorting the inverting input to its own output, a high input impedance characteristic is formed, which avoids damage to the filtering characteristics of the preceding RC filter module. At the same time, its low output impedance characteristic can quickly drive the sampling capacitor of the MCU's ADC module, ensuring that the signal is quickly and stably established in high sampling rate or multi-channel sampling scenarios, solving the problems of signal distortion and slow system response speed caused by insufficient sensor driving capability. Attached Figure Description

[0013] Figure 1 The diagram shown is a schematic representation of the overall process structure of this utility model. Figure 2 The diagram shown is a schematic diagram of the circuit principle structure of this utility model.

[0014] In the attached diagram, the following are the reference numerals: 1. Signal input unit; 2. Gain amplification module; 3. RC filter module; 4. Voltage follower module; 5. Signal output unit; 6. Reference voltage unit; 7. Analog power supply; 8. Inductive encoder sensor; 9. MCU's ADC module. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] refer to Figure 1-2The structure shown represents an optimized signal conditioning circuit for an inductive encoder, comprising a signal input unit 1, a gain amplification module 2, an RC filter module 3, a voltage follower module 4, and a signal output unit 5, which are connected in sequence. It also includes a reference voltage unit 6 providing bias to the gain amplification module 2, an analog power supply 7 supplying power to the gain amplification module 2 and the voltage follower module 4, and an ADC module 9 of the MCU connected to the signal output unit 5. The input terminal of the signal input unit 1 is connected to the differential signal output terminal of the inductive encoder sensor 8, and its output terminal is connected to the input terminal of the gain amplification module 2. The input terminal of the signal output unit 5 is connected to the output terminal of the voltage follower module 4, and its output terminal is connected to the input terminal of the ADC module 9 of the MCU. The gain amplification module 2 includes an operational amplifier U1 and resistive-capacitive components, receives the differential signal from the signal input unit 1, and biases it through the reference voltage unit 6. The RC filter module 3 includes resistors and capacitors, connecting the gain amplification module 2 and the voltage follower module 4. The voltage follower module 4 includes an operational amplifier U2 and a capacitor, and its output terminal is connected to the signal output unit 5.

[0017] The Sin+, Sin-, Cos+, and Cos- differential signals output by the inductive encoder sensor 8 are transmitted to the gain amplification module 2 via the signal input unit 1. This module, through a specific connection between operational amplifier U1 and resistors R1-R4 and capacitors C1-C3, and with a stable 1.5V bias output from the reference voltage unit 6, precisely adjusts the signal amplitude to 80%-90% of the input range of the MCU's ADC module 9, thus solving the core problem of mismatch between the sensor's original signal and the ADC input level. The adjusted signal then enters the RC filter module 3, where a low-pass filter circuit composed of resistor R5 and capacitor C4 filters out 20-5... High-frequency noise above 0kHz significantly improves the signal-to-noise ratio, overcoming the challenges of electromagnetic noise and power supply noise interference during transmission. Subsequently, the signal flows into the voltage follower module 4, where the inverting input and output of the operational amplifier U2 are directly shorted, creating a high input impedance characteristic to avoid affecting the load of the preceding filter circuit. At the same time, the low output impedance enhances the signal driving capability, solving the problem of slow charging of the ADC sampling capacitor and long signal establishment time caused by insufficient sensor driving capability. Finally, the signal is transmitted to the ADC module 9 of the MCU via the signal output unit 5, achieving high-quality signal sampling and comprehensively improving the system's position detection accuracy, anti-interference, and reliability.

[0018] To address the issues of load interference between different functional modules and power supply noise conduction interference during single-channel signal conditioning, as well as channel crosstalk, poor signal consistency, insufficient operational amplifier stability, and the difficulty in balancing filtering performance and signal integrity during simultaneous conditioning of multiple differential signals, this paper refers to... Figures 1-2 The structure shown is as follows: Furthermore, the gain amplification module 2 includes resistors R1-R4 and capacitors C1-C3; the non-inverting terminal of U1 is connected to the non-inverting signal terminal of the signal input unit 1 via R1, the inverting terminal is connected to the inverting signal terminal via R2, the reference voltage unit 6 is connected to the non-inverting terminal of U1 via R3 and C1, the inverting terminal of U1 is connected to the output terminal via R4 and C2, and C3 is connected between the power supply pin of U1 and ground.

[0019] Specifically, resistor R1 establishes the signal transmission path between the non-inverting signal terminal of signal input unit 1 and the non-inverting signal terminal of U1, while resistor R2 establishes the connection channel between the inverting signal terminal of signal input unit 1 and the inverting signal terminal of U1, enabling U1 to accurately receive differential signals. R3 and C1 are connected in series to the reference voltage unit 6, smoothly transmitting the 1.5V bias signal to the non-inverting terminal of U1, avoiding the influence of bias voltage fluctuations on signal amplification accuracy. R4 and C2 form a negative feedback loop for U1, stabilizing the amplification gain and preventing distortion during signal amplification. Capacitor C3 is connected in parallel between the power supply pin of U1 and ground to filter out high-frequency noise in the 3.3V power supply output from analog power supply 7, ensuring stable operating voltage of U1 and further improving the consistency of signal amplification.

[0020] Furthermore, the RC filter module 3 includes a resistor R5 and a capacitor C4; one end of R5 is connected to the output terminal of the gain amplifier module 2, and the other end is connected to C4 and the input terminal of the voltage follower module 4, and the other end of C4 is grounded.

[0021] In this circuit, resistor R5 is connected in series between the output terminal of U1 of gain amplifier module 2 and the non-inverting terminal of U2 of voltage follower module 4 to limit the transmission rate of high-frequency signals. One end of capacitor C4 is connected to the connection point of R5 and the non-inverting terminal of U2, and the other end is grounded to form a high-frequency signal discharge circuit to ground. The two work together to set the cutoff frequency at 20-50kHz, accurately filtering out the high-frequency noise and electromagnetic interference remaining in the signal after gain amplification, while not affecting the amplitude and phase of the useful signal, thus ensuring signal integrity.

[0022] Furthermore, in voltage follower module 4, the non-inverting terminal of U2 is connected to the output terminal of RC filter module 3, the inverting terminal is shorted to the output terminal, and capacitor C5 is connected between the power supply pin of U2 and ground.

[0023] Specifically, the non-inverting input of U2 is directly connected to the output of R5 of the RC filter module 3 to ensure that the filtered signal is completely input. The inverting input of U2 is shorted to the output to form a voltage follower feedback structure, so that the output signal of U2 is consistent with the input signal without amplitude attenuation or phase shift. The capacitor C5 is connected in parallel between the power supply pin of U2 and ground to filter out noise in the analog power supply 7 and stabilize the operating voltage of U2. At the same time, the high input impedance of U2 avoids the impact on the load of the RC filter module 3, and the low output impedance enhances the driving capability of the sampling capacitor of the ADC module 9 of the MCU and shortens the signal settling time.

[0024] Furthermore, operational amplifiers U1 and U2 are both TP2302-VR; reference voltage unit 6 outputs 1.5V, and analog power supply 7 outputs 3.3V.

[0025] The TP2302-VR operational amplifiers are selected for U1 and U2. Their low noise and low offset voltage characteristics ensure the accuracy of signal amplification and tracking, avoiding signal distortion caused by the characteristics of the device itself. A stable 1.5V bias voltage is provided by the reference voltage unit 6, providing a precise reference potential for the differential amplification of U1, so that the DC bias after signal amplification meets the input requirements of the MCU's ADC module 9. A stable 3.3V voltage is output by the analog power supply 7 to provide operating power for U1 and U2, ensuring the stable operation of the two operational amplifiers and providing a basic guarantee for the performance of the entire conditioning circuit.

[0026] Furthermore, the output signal amplitude of the gain amplification module 2 is 80%-90% of the input range of the ADC module 9 of the MCU; the cutoff frequency of the RC filter module 3 is 20-50kHz.

[0027] Specifically, by limiting the output signal amplitude of the gain amplification module 2 to 80%-90% of the input range of the ADC module 9 of the MCU, a safety margin is reserved for the signal peak to avoid overload saturation, while maximizing the utilization of the ADC's dynamic range and improving the quantization accuracy of the signal. By setting the cutoff frequency of the RC filter module 3 to 20-50kHz, the effective frequency range of the output signal of the inductive encoder sensor 8 is precisely matched. This effectively filters out high-frequency noise and aliasing interference without losing key information of the useful signal, ensuring the accuracy of subsequent ADC sampling.

[0028] Furthermore, the differential signal output terminals of the inductive encoder sensor 8 include Sin+, Sin-, Cos+, and Cos-, each of which is equipped with an independent gain amplification module 2, an RC filter module 3, and a voltage follower module 4.

[0029] Specifically, by configuring independent gain amplification module 2, RC filter module 3, and voltage follower module 4 for the four differential signals Sin+, Sin-, Cos+, and Cos- respectively, channel crosstalk caused by multiple signals sharing the same conditioning module is avoided, ensuring that the conditioning process of each signal does not affect each other. The independent module configuration enables each signal to obtain consistent amplification factor, filtering effect, and driving capability, improving the consistency of the four signals. This provides an accurate signal basis for the MCU's ADC module 9 to perform position calculation after synchronous sampling, further improving the position detection accuracy of the system.

[0030] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. An optimized signal conditioning circuit for an inductive encoder, characterized in that: It includes a signal input unit (1), a gain amplifier module (2), an RC filter module (3), a voltage follower module (4), and a signal output unit (5) connected in sequence; it also includes a reference voltage unit (6) that provides bias to the gain amplifier module (2), an analog power supply (7) that powers the gain amplifier module (2) and the voltage follower module (4), and an ADC module (9) of the MCU connected to the signal output unit (5); The input terminal of the signal input unit (1) is connected to the differential signal output terminal of the inductive encoder sensor (8), and the output terminal is connected to the input terminal of the gain amplifier module (2); the input terminal of the signal output unit (5) is connected to the output terminal of the voltage follower module (4), and the output terminal is connected to the input terminal of the ADC module (9) of the MCU. The gain amplification module (2) includes an operational amplifier U1 and resistor-capacitor components, receives the differential signal from the signal input unit (1) and is biased by the reference voltage unit (6); the RC filter module (3) includes resistors and capacitors, and connects the gain amplification module (2) and the voltage follower module (4); the voltage follower module (4) includes an operational amplifier U2 and capacitors, and its output terminal is connected to the signal output unit (5).

2. The optimized signal conditioning circuit for an inductive encoder according to claim 1, characterized in that: The gain amplification module (2) includes resistors R1-R4 and capacitors C1-C3; the non-inverting terminal of U1 is connected to the non-inverting signal terminal of the signal input unit (1) via R1, the inverting terminal is connected to the inverting signal terminal via R2, the reference voltage unit (6) is connected to the non-inverting terminal of U1 via R3 and C1, the inverting terminal of U1 is connected to the output terminal via R4 and C2, and C3 is connected between the power supply pin of U1 and ground.

3. The optimized signal conditioning circuit for an inductive encoder according to claim 1, characterized in that: The RC filter module (3) includes a resistor R5 and a capacitor C4; one end of R5 is connected to the output terminal of the gain amplifier module (2), and the other end is connected to C4 and the input terminal of the voltage follower module (4), and the other end of C4 is grounded.

4. An optimized signal conditioning circuit for an inductive encoder according to claim 1, characterized in that: In the voltage follower module (4), the non-inverting terminal of U2 is connected to the output terminal of the RC filter module (3), the inverting terminal is shorted to the output terminal, and the capacitor C5 is connected between the power supply pin of U2 and ground.

5. An optimized signal conditioning circuit for an inductive encoder according to claim 1, characterized in that: The operational amplifiers U1 and U2 are both TP2302-VR; the reference voltage unit (6) outputs 1.5V and the analog power supply (7) outputs 3.3V.

6. An optimized signal conditioning circuit for an inductive encoder according to claim 1, characterized in that: The output signal amplitude of the gain amplification module (2) is 80%-90% of the input range of the ADC module (9) of the MCU; the cutoff frequency of the RC filter module (3) is 20-50kHz.

7. An optimized signal conditioning circuit for an inductive encoder according to claim 1, characterized in that: The differential signal output terminals of the inductive encoder sensor (8) include Sin+, Sin-, Cos+, and Cos-, each of which is equipped with an independent gain amplification module (2), RC filter module (3), and voltage follower module (4).

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