Negative resistance oscillator with multi-parameter programmable characteristics and inductance sensor system

Abstract

This invention provides a negative resistance oscillator and inductor sensor system with multi-parameter programmable characteristics, relating to the field of electronics and electrical engineering. It includes an amplification unit, a resonant circuit, and a feedback network. The resonant circuit is connected between the non-inverting input terminal and a reference potential. The feedback network consists of first, second, and positive feedback units connected between the inverting input terminal, the output terminal, and the non-inverting input terminal. The equivalent parameter values ​​of the feedback units are configured through programming to collaboratively determine the equivalent negative resistance, matching it with the equivalent loss of the resonant circuit. The beneficial effects are that programmable parameter configuration achieves precise matching of the equivalent negative resistance with resonant circuits of different specifications, solving the problems of poor adaptability and rigid settings in traditional oscillators. Furthermore, active compensation for temperature characteristics is achieved through multi-parameter collaborative adjustment, significantly improving the system's versatility, flexibility, and stability under different hardware environments and temperature scenarios.

Description

Technical Field

[0001] This invention relates to the field of electronic and electrical technology, and in particular to a negative resistance oscillator and inductive sensor system with multi-parameter programmable characteristics. Background Technology

[0002] In the design of oscillating sensors (such as inductive proximity sensors), the oscillator is the core unit. Traditional negative resistance oscillators typically use feedback networks with fixed parameters, which results in a lack of versatility and flexibility when dealing with resonant circuits of different specifications (such as coils with different inductances or LC circuits with different quality factors).

[0003] Specifically, existing oscillators often struggle to precisely match the equivalent losses of specific resonant circuits, resulting in inflexible settings for oscillation start-up and shutdown conditions. Furthermore, the drift characteristics of the oscillation system with temperature variations are often fixed by hardware parameters, making reverse compensation or fine-tuning difficult for different application scenarios. Therefore, there is an urgent need for a technical solution that can programmatically configure multiple feedback parameters to collaboratively determine the equivalent negative resistance, enabling matching with various resonant circuits and allowing for free setting of oscillation start-up, shutdown conditions, and temperature characteristics. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a negative resistance oscillator with multi-parameter programmable characteristics, including an amplification unit, a resonant circuit, and a feedback network. The feedback network includes a first feedback unit, a second feedback unit, and a positive feedback unit. The amplification unit has a non-inverting input terminal, an inverting input terminal, and an output terminal. The resonant circuit is connected between the non-inverting input terminal and a reference potential. The first feedback unit is connected between the inverting input terminal and the reference potential. The second feedback unit is connected between the output terminal and the inverting input terminal. The positive feedback unit is connected between the output terminal and the non-inverting input terminal. The equivalent parameter values ​​of at least one of the first feedback unit, the second feedback unit, and the positive feedback unit are configured in a programmable manner. By coordinating the configuration of multiple parameters of the first feedback unit, the second feedback unit, and the positive feedback unit, different equivalent negative resistance conditions are generated under different oscillation state boundaries, thereby simultaneously defining the oscillation initiation condition and the oscillation disappearance condition.

[0005] The equivalent negative resistance of the negative resistance oscillator is generated in a coordinated manner, so that the equivalent negative resistance matches the equivalent loss impedance of the resonant circuit with different parameter specifications.

[0006] Preferably, the first feedback unit and / or the second feedback unit are composed of at least two resistive elements with different temperature coefficients. By programming and configuring the proportional relationship between the equivalent parameter values ​​of the first feedback unit and the second feedback unit, the equivalent temperature coefficient of the negative resistance oscillator can be adjusted between the positive and negative directions to compensate for the temperature drift of the equivalent loss impedance of the resonant circuit with different parameter specifications.

[0007] Preferably, the positive feedback unit includes a fixed feedback resistor, a first incremental resistor, and a second incremental resistor in the same positive feedback loop; Based on the current oscillation state of the oscillator, the connection relationship between the first incremental resistor and the second incremental resistor in the positive feedback loop is dynamically adjusted to adjust the equivalent parameter value of the positive feedback unit, so as to form a hysteresis interval between the oscillation start-up condition and the oscillation disappearance condition. The oscillation state is determined by whether the amplitude of the oscillator output signal meets the preset oscillation judgment condition.

[0008] Preferably, the adjustment method for the connection relationship of the fixed feedback resistor, the first incremental resistor, and the second incremental resistor includes: When the negative resistance oscillator switches from the oscillation state to the non-oscillation state, the first incremental resistor is connected to the positive feedback loop where the fixed feedback resistor is located through an analog switch to increase the equivalent parameter value of the positive feedback unit. When the negative resistance oscillator switches from a non-oscillating state to an oscillating state, the second incremental resistor is moved out of the positive feedback loop where the fixed feedback resistor is located or the resistance value of the second incremental resistor is reduced by an analog switch, so as to reduce the equivalent parameter value of the positive feedback unit.

[0009] Preferably, the values ​​of the first incremental resistor and the second incremental resistor can be independently programmed and configured, and the two values ​​are not equal, so as to form an asymmetrical hysteresis characteristic.

[0010] Preferably, it also includes a configuration component, which includes a shift register; The configuration component receives external instructions through a digital interface and configures the first incremental resistor and the second incremental resistor and their temperature coefficients online through the shift register.

[0011] Preferably, the configuration component further includes a non-volatile memory connected to the shift register; The non-volatile memory stores pre-configured configuration parameters, and the shift register reads the configuration parameters to configure the first incremental resistor and the second incremental resistor and their temperature coefficients.

[0012] Preferably, the digital interface supports IO-Link, I²C, or SPI communication protocols.

[0013] The present invention also provides an inductive sensor system, including the negative resistance oscillator as described above, wherein the negative resistance oscillator is used to sense changes in the electromagnetic parameters of the resonant circuit caused by an external target; Also includes: A buffer amplifier is connected to the output terminal of the negative resistance oscillator; A peak detector is used to extract the amplitude information of the output signal of the buffer amplifier; The comparator compares the amplitude information with a preset threshold and outputs a switching signal.

[0014] Preferably, the switching signal output by the comparator is connected as a feedback control signal to the feedback network of the negative resistance oscillator, and is used to control the analog switch in real time to adjust the equivalent parameter value of the positive feedback unit according to the feedback control signal.

[0015] The above technical solution has the following advantages or beneficial effects: The present invention achieves precise matching of equivalent negative resistance and resonant circuits of different specifications through programmable configuration of feedback network parameters. It not only solves the problems of poor adaptability and rigid start / stop settings of traditional oscillators, but also achieves active compensation of equivalent temperature characteristics through multi-parameter coordinated adjustment, which significantly improves the versatility, flexibility and stability of oscillators in different hardware environments and temperature scenarios. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a negative resistance oscillator with multi-parameter programmable characteristics in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of an inductive sensor system in Embodiment 7 of the present invention. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment; other embodiments that conform to the spirit of the present invention may also fall within the scope of the present invention.

[0018] In a preferred embodiment of the present invention, based on the above-mentioned problems existing in the prior art, a negative resistance oscillator with multi-parameter programmable characteristics is provided.

[0019] Example 1: like Figure 1 As shown, the negative resistance oscillator provided in this embodiment has a core structure including an amplification unit 1, a resonant circuit 2, and a feedback network 3 composed of a first, a second, and a positive feedback unit.

[0020] The connection relationship between them is as follows: the non-inverting input terminal of the amplifier unit 1 is connected to the resonant circuit 2 (LC parallel circuit), the inverting input terminal is connected to the reference potential (GND) through the first feedback unit R1, the output terminal is connected to the second feedback unit R2 (forming closed-loop gain control), and the output terminal is connected to the non-inverting input terminal (providing positive feedback current).

[0021] In this embodiment, the negative resistance oscillator programs the equivalent parameter values ​​(such as resistance values) of the first, second, or positive feedback units via a digital interface. The equivalent parameter values ​​of at least one of the first feedback unit R1, the second feedback unit R2, and the positive feedback unit 31 are configured programmably. By coordinating the configuration of multiple parameters of the first feedback unit, the second feedback unit, and the positive feedback unit, different equivalent negative resistance conditions are generated under different oscillation state boundaries, thereby simultaneously defining the oscillation initiation condition and the oscillation disappearance condition.

[0022] Through the coordinated configuration of these three units, the magnitude of the equivalent negative resistance is no longer determined by a single resistor. Technicians can programmatically configure multiple parameters to generate different equivalent negative resistance conditions, thereby simultaneously and precisely setting the critical points for oscillation initiation and cessation—that is, simultaneously defining the oscillation initiation and oscillation termination conditions. This multi-parameter coordinated design allows the same circuit to be adapted to various inductors ranging from microhenries to millihenries, greatly improving the circuit's versatility.

[0023] Specifically, the amplification unit 1 (an operational amplifier OC in this embodiment) and the first feedback unit Second feedback unit and Together they form an active circuit, which exhibits negative resistance at the resonant circuit connection point (non-inverting input).

[0024] By adjusting the resistance ratio of the first feedback unit (R1) and the second feedback unit (R2) through digital programming, the reference amplitude of the negative resistance can be coarsely adjusted; by adjusting the positive feedback unit... The resistance value can be finely adjusted to finely control the negative resistance strength injected into the resonant circuit. This dual-layer adjustment mechanism allows the system to precisely match the equivalent loss resistance of the resonant circuit over a very wide range.

[0025] This invention provides a negative resistance oscillator with multi-parameter programmable characteristics, achieving the following technical effects: Extremely high versatility and adaptability: By programmably configuring the equivalent parameter values ​​of at least one of the first feedback unit R1, the second feedback unit R2, and the positive feedback unit 3, the limitation of fixed parameters in traditional feedback networks is broken. This allows the same circuit to adjust the negative resistance intensity online through software programming, thereby precisely matching inductors or LC resonant circuits with different inductance values ​​and quality factors (Q values), solving the problem of lack of versatility in existing technologies when dealing with resonant circuits of different specifications.

[0026] Flexible setting of oscillation start-up and shutdown conditions: By programming and configuring the equivalent parameter values ​​to match the equivalent loss of the resonant circuit, the oscillator's start-up and shutdown critical points can be set freely and accurately according to application requirements. This not only improves the sensor's sensitivity control capability at different detection distances but also solves the pain point of inflexible threshold setting in existing technologies.

[0027] Programmable temperature characteristic compensation: By configuring the parameters of the feedback unit through programming, the system characteristics of the equivalent negative resistance can be artificially set so that its temperature change trend matches the resonant circuit loss change trend. This multi-parameter collaborative determination mechanism realizes the active adjustment of the equivalent temperature characteristics, solving the technical defects of traditional solutions where temperature drift characteristics are fixed by hardware and it is difficult to perform reverse compensation for complex scenarios.

[0028] Example 2: In this embodiment, based on embodiment 1, the first feedback unit R1 and / or the second feedback unit R2 are composed of at least two resistive elements with different temperature coefficients. By programming and configuring the proportional relationship between the equivalent parameter values ​​of the first feedback unit R1 and the second feedback unit R2, the temperature coefficient of the equivalent negative resistance can be adjusted between the positive and negative directions to compensate for the temperature drift of the equivalent loss impedance of the resonant circuit with different parameter specifications.

[0029] Specifically, in this embodiment, the composition of the first and second feedback units is refined. The first feedback unit R1 and the second feedback unit R2 are respectively composed of components with positive temperature coefficients (such as nWell resistors) and negative temperature coefficients (such as polysilicon resistors).

[0030] By programming the equivalent impedance ratio of R1 and R2, the temperature drift slope of the entire feedback network can be artificially adjusted. The equivalent temperature coefficients of the first feedback unit R1 and the second feedback unit R2 are defined respectively. and .

[0031] Under the first-order approximation, the resistance of the feedback unit as a function of temperature can be expressed as: .in, The resistance value at the reference temperature. The temperature coefficient of resistance, This is the change in temperature. Because... , therefore The temperature coefficient of one is approximately equal to the difference between the temperature coefficients of the other two.

[0032] Taking a certain integrated circuit manufacturing process as an example, the temperature coefficient of polysilicon resistors is approximately The temperature coefficient of the well region resistance is approximately By programming to select different resistor chain ratios, it is possible to... The equivalent temperature coefficient is programmable between positive and negative values, and its adjustable range is limited by the temperature coefficient difference mentioned above.

[0033] The internal switching matrix is ​​controlled by a shift register to change the weights of resistive components with different temperature coefficients within the cells, thereby adjusting... and The difference determines the slope of the equivalent negative resistance as a function of temperature, enabling it to accurately track and offset the loss drift curve of the inductor coil as it changes with temperature, thus ensuring the consistency of the sensor's detection distance at different temperatures.

[0034] Furthermore, by adjusting the temperature drift slope through the first feedback unit R1 and the second feedback unit R2, and further combining the configuration of the fixed feedback unit RF, the variation amplitude of the equivalent negative resistance with temperature can be refined, so that it matches the temperature variation trend of the resonant circuit loss parameters.

[0035] When the resonant circuit 2 (including inductor L and capacitor C) loses more power as the temperature rises, the equivalent negative resistance can be increased by configuration, thereby canceling the temperature characteristics and making the temperature drift of the entire sensor system approach 0, which significantly improves the sensing accuracy in high-temperature environments.

[0036] Example 3: In this embodiment, a hysteresis control module 4 is introduced into the feedback network 3. This module dynamically adjusts the equivalent parameter values ​​of the positive feedback unit according to the current oscillation state of the oscillator, so as to form a hysteresis interval between the oscillation start-up condition and the oscillation disappearance condition.

[0037] Specifically, the positive feedback unit 31 includes a fixed feedback resistor RF, a first incremental resistor ΔRF1, and a second incremental resistor ΔRF2 in the same positive feedback loop; When the system is on the verge of vibration, the feedback strength is changed by dynamically fine-tuning the equivalent parameter values ​​of the positive feedback unit. This establishes a physical interval between the vibration initiation and shutdown conditions. Its function is to prevent the sensor from experiencing frequent jitter or signal jumps when the target object is at the critical detection distance, significantly enhancing the system's anti-interference capability under critical conditions.

[0038] Example 4: In this embodiment, the hysteresis control module 4 includes analog switches connected to the first incremental resistor ΔRF1 and the second incremental resistor ΔRF2. When the negative resistance oscillator switches from the oscillation state to the non-oscillation state, the first incremental resistor is superimposed on the equivalent parameter value of the positive feedback unit through an analog switch; when the negative resistance oscillator switches from the non-oscillation state to the oscillation state, the second incremental resistor is removed or reduced through an analog switch. The oscillation state is determined by whether the amplitude of the oscillator output signal meets the preset oscillation judgment condition.

[0039] Specifically, this embodiment further refines the implementation logic of the hysteresis control module based on embodiment 3. The module incorporates a first incremental resistor ΔRF1 and a second incremental resistor ΔRF2. When the oscillation disappears, ΔRF1 is connected to reduce the positive feedback; when the oscillation starts, ΔRF2 is removed to enhance the positive feedback. Furthermore, the values ​​of ΔRF1 and ΔRF2 can be independently configured to be unequal.

[0040] The asymmetric hysteresis characteristic allows engineers to set different sensitivities for entering and leaving the sensing zone, depending on the actual noise level in the industrial environment. For example, a larger departure hysteresis can be set to ensure that the signal is released only after the target has completely moved away, thus providing a higher level of protection against false alarms.

[0041] By adjusting the first incremental resistor ΔRF1 and the second incremental resistor ΔRF2 in the positive feedback parameters, the hysteresis formed between the oscillation start-up condition and the oscillation disappearance condition is aimed at preventing the sensor from generating jitter in the output signal near the critical detection distance.

[0042] Specifically, in order to improve the stability of the negative resistance oscillator near the critical oscillation condition, this invention introduces a hysteresis control mechanism controlled by the sensor output state in the positive feedback unit.

[0043] When the oscillator switches from an oscillating state to a non-oscillating state, the first incremental resistor ΔRF1 is connected to the positive feedback loop according to the current oscillating state, changing the positive feedback resistance from RF to RF+ΔRF1, thereby reducing the positive feedback current. When the oscillator switches from a non-oscillating state to an oscillating state, the second incremental resistor ΔRF2 is removed from the positive feedback loop or reduced equivalently according to the current oscillating state, reducing the positive feedback resistance and thus increasing the positive feedback current. This creates a hysteresis interval between the oscillation start-up condition and the oscillation disappearance condition, the magnitude of which is determined by the numerical relationship between ΔRF1 and ΔRF2. The resistance values ​​and temperature coefficients of ΔRF1 and ΔRF2 can be configured by a shift register, which can be set via an external control interface or the chip's internal non-volatile memory.

[0044] Furthermore, the determination of the oscillation state is based on whether the amplitude of the oscillator output signal meets the preset oscillation determination conditions. In a specific implementation, the amplitude of the oscillation signal can be monitored in real time through a built-in amplitude detection circuit (such as a peak detector) and a threshold comparator. When the amplitude is higher than the set threshold, it is determined to be in an oscillation state; otherwise, it is determined to be in a non-oscillation state. This determination mechanism is implemented entirely within the oscillator, without relying on an external MCU or digital processor, thereby ensuring the real-time performance and determinism of hysteresis control and avoiding misjudgments of the state caused by external system delays or interference.

[0045] Example 5: This embodiment adds a configuration component 5 and a standardized interface. Configuration component 5 integrates a shift register SR and non-volatile memory (OTP / EEPROM), and supports IO-Link, I²C, or SPI protocols. This enables the oscillator to be calibrated after packaging. After the sensor assembly is complete, configuration parameters (such as compensation parameters and hysteresis values) can be written online via the IO-Link interface without disassembling the casing. The shift register SR receives the configuration parameters online and configures the first incremental resistor and the second incremental resistor, along with their temperature coefficients. Furthermore, in the aforementioned embodiment, the parameters of the first feedback unit R1, the second feedback unit R2, and the fixed feedback resistor RF are all programmed and configured by the shift register SR based on the received configuration parameters. In particular, the support for IO-Link allows the oscillator to be directly connected to Industry 4.0 smart production lines, enabling real-time parameter monitoring and cloud configuration.

[0046] The use of non-volatile memory (OTP / EEPROM) enables the sensor to retain power-off characteristics. This means that after a power outage and restart in the field, the configuration component can automatically load preset configuration parameters (such as compensation parameters and hysteresis values) without reconfiguration. The shift register SR directly reads from the non-volatile memory and configures the first and second incremental resistors and their temperature coefficients. Similarly, in the aforementioned embodiment, the parameters of the first feedback unit R1, the second feedback unit R2, and the fixed feedback resistor RF are all programmed and configured by the shift register SR based on the received configuration parameters. Furthermore, the overall structure of the solution provided in this embodiment is suitable for integrated circuit implementation, facilitating automatic calibration in mass production.

[0047] The resistance values ​​and temperature coefficients of all the above feedback parameters can be set online through industrial data interfaces (including but not limited to SPI, I²C, IO-Link or other serial communication interfaces) after the sensor is packaged, so that the negative resistance oscillator of the present invention can be used as a general programmable oscillation platform in various inductive sensors.

[0048] Example 6: In this embodiment, the negative resistance oscillator also has a self-detection function. Since the equivalent parameter values ​​of the first feedback unit R1, the second feedback unit R2, and the positive feedback unit RF can all be configured programmably, the system can manually adjust the feedback network parameters via a digital interface to make the generated equivalent negative resistance less than the equivalent loss of the resonant circuit, thereby forcing the oscillator to enter a stop-oscillation state, or increasing the negative resistance to force the system into an oscillation state. By monitoring whether the comparator output signal flips accordingly with the parameter configuration, online self-diagnosis of the chip's internal amplification unit and signal processing link can be achieved.

[0049] The working principle of the negative resistance oscillator technology will be explained in general, based on the content of Examples 1-5 above: The main task of the negative resistance oscillator in this invention is to generate a controlled negative resistance to compensate for the loss of the resonant circuit, thereby maintaining or stopping the oscillation.

[0050] 1.Reference Figure 1 The circuit diagram of the negative resistance oscillator in the diagram illustrates its negative resistance generation logic: In a resonant circuit (LC parallel circuit), the oscillation will decay due to losses such as resistance in the inductor coil without external energy replenishment. This solution utilizes an amplifier unit and a feedback network to construct a negative resistance generator.

[0051] First Feedback Unit ( ) and the second feedback unit ( These terminals are connected to the inverting input of the op-amp's open-circuit (OC) circuit and determine the closed-loop gain of the OC circuit. This can be changed through programming. The ratio of [value] can be used to directly adjust the negative resistance amplitude generated by the circuit.

[0052] Positive feedback unit ( It is connected to the output terminal and the non-inverting terminal (resonant circuit) of amplifier unit 1, and it determines how much negative resistance energy is injected into the resonant circuit.

[0053] The circuit oscillates when the generated equivalent negative resistance is sufficient to offset the equivalent parallel resistance loss of the resonant circuit. This is achieved through programming. This allows the same circuit to be adapted to coils with different quality factors (Q values).

[0054] 2. Temperature compensation principle of the negative resistance oscillator of the present invention Since the loss of the inductor increases with temperature, if the negative resistance is fixed, the oscillator may stop oscillating at high temperatures.

[0055] use and The characteristics of materials with different temperature coefficients (such as polycrystalline silicon and well region resistors). By adjusting the ratio of these two components through programming, the desired effect can be achieved. The resulting gain also changes with temperature, and its trend is exactly opposite to that of the coil loss, thus achieving stability across the entire temperature range.

[0056] 3. Hysteresis control principle of the negative resistance oscillator of the present invention At the edge of vibration initiation and shutdown, the system is prone to false triggering due to noise.

[0057] When the system is determined to be in an oscillation state, the impedance of the positive feedback unit RF is changed by connecting or disconnecting the first / second incremental resistor (ΔRF1 / ΔRF2) through a control switch. This dynamic adjustment creates a difference between the energy required to start oscillation and the energy required to maintain oscillation, thus forming a physical hysteresis range.

[0058] Example 7: like Figure 2 As shown, this embodiment provides an inductive sensor system, including the aforementioned negative resistance oscillator, which is used to sense changes in the electromagnetic parameters of the resonant circuit caused by an external target; Also includes: Buffer amplifier 6 is connected to the output of the negative resistance oscillator; Peak detector 7 is used to extract amplitude information of the output signal of the buffer amplifier; Comparator 8 compares the amplitude information with a preset threshold and outputs a switching signal.

[0059] The switching signal output by comparator 8 is connected to the feedback network of the negative resistance oscillator as a feedback control signal, which is used to trigger the hysteresis control module to adjust the equivalent parameter value in real time.

[0060] Specifically, in this embodiment, the inductor sensor system realizes the complete process from energy compensation to logic output by converting the physical changes of the oscillator into digital switching signals. The logical sequence is as follows: 1. Establishment of the core energy field (initiation phase) The system operates starting from the stable electromagnetic field generated by the negative resistance oscillator.

[0061] Because resonant circuit 2 (LC circuit) has inherent losses, the system configures the first feedback unit (by programming) ), second feedback unit ( The gain is determined by the ratio of the given information and is determined by the fixed feedback unit ( ). Energy is injected into the circuit.

[0062] When the negative resistance generated by the injected energy exactly cancels out the equivalent loss resistance of the resonant circuit, the circuit begins to oscillate, establishing a high-frequency sinusoidal oscillation signal. This is a prerequisite for sensing physical quantities.

[0063] 2. Real-time sensing of physical quantities (physical interaction stage) Resonant circuit 2 consists of an LC resonant circuit composed of sensing inductor L and capacitor C. The inductance parameters of sensing inductor L change as the measured metal target approaches (e.g., due to eddy current effects), thereby causing changes in the equivalent impedance and equivalent loss of the LC resonant circuit.

[0064] By configuring the first feedback unit R1, the second feedback unit R2, and the fixed feedback resistor RF, respectively, the first feedback parameters, the second feedback parameters, and the positive feedback parameters are configured to form a preset equivalent negative resistance injection condition: when there is no target being measured or the target is far away, the equivalent negative resistance is greater than the equivalent loss of the resonant circuit, and the oscillator is in an oscillating state; when the target being measured approaches and causes a change in the sensor inductance parameters, resulting in an increase in equivalent loss, and the equivalent negative resistance is less than the equivalent loss, the oscillator oscillation disappears or the oscillation amplitude decreases significantly. After the oscillation is established, the sensor enters the detection state for external targets.

[0065] Eddy current effect: When a metal object approaches the inductor coil of a resonant circuit, eddy currents are generated on the metal surface.

[0066] When the energy balance is disrupted, eddy currents absorb energy from the oscillating circuit, causing a sharp increase in the equivalent loss of the resonant circuit. Since the negative resistance generated at this time is predetermined and cannot fully compensate for the increased loss, the amplitude of the oscillation signal will decrease accordingly, or even stop oscillating completely.

[0067] This step converts changes in external physical distance into changes in the amplitude of the oscillation waveform.

[0068] 3. Precise signal processing and conversion (conversion stage) The weakened oscillation signal needs to undergo a series of processing steps before it can be converted into a signal that the controller can recognize.

[0069] Isolation and driving are achieved through buffer amplifier 6: The oscillation signal first passes through the buffer amplifier, which isolates the precision oscillation source from the subsequent circuit and prevents changes in the load of the subsequent stage from interfering with the frequency and stability of the oscillator.

[0070] Peak detector 7 converts the high-frequency sinusoidal signal into a smooth DC voltage signal. The magnitude of this voltage directly reflects the distance between the target object and the sensing surface.

[0071] Comparator 8 compares the DC voltage with a preset reference threshold. Once the voltage falls below the threshold (indicating that the object is approaching the critical point), the comparator outputs a flip signal (changing from high to low).

[0072] 4. Dynamic Adaptation and Hysteresis Closed Loop (Feedback Stabilization Phase) This is the key difference between this solution and traditional solutions: by using feedback to apply the results back to the source.

[0073] The switching signal output by the comparator is not only sent to the industrial interface as the final result, but is also fed back to the feedback network of the negative resistance oscillator in real time.

[0074] When it is determined that an object is leaving or entering, the feedback signal will trigger the hysteresis control module to dynamically adjust the equivalent parameter value in the positive feedback path (connect ΔRF1 or remove ΔRF2).

[0075] This feedback alters the energy threshold for the next oscillation start or stop. This ensures that when the target object is at the sensing critical point, the sensor's output signal will not frequently switch between on and off due to minor vibrations or noise.

[0076] 5. Digital configuration interface (system adaptation layer) All parameters in the above steps (negative resistance, temperature compensation slope, hysteresis range) are set online by the configuration component (SR / EEPROM) via IO-Link or I²C interface. This allows the system to be calibrated after packaging for different metal materials or different coil specifications.

[0077] Meanwhile, by utilizing the programmable nature of multiple parameters, this system can perform online correction of the sensitivity coefficient for targets of different materials (such as iron, aluminum, copper and other metals). By configuring different equivalent negative resistance parameter mapping tables, it ensures that there is a consistent action distance for targets of different materials.

[0078] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present invention.

Claims

1. A negative resistance oscillator with multi-parameter programmable characteristics, characterized in that, The system includes an amplification unit, a resonant circuit, and a feedback network. The feedback network includes a first feedback unit, a second feedback unit, and a positive feedback unit. The amplification unit has a non-inverting input terminal, an inverting input terminal, and an output terminal. The resonant circuit is connected between the non-inverting input terminal and a reference potential. The first feedback unit is connected between the inverting input terminal and the reference potential. The second feedback unit is connected between the output terminal and the inverting input terminal. The positive feedback unit is connected between the output terminal and the non-inverting input terminal. The equivalent parameter values ​​of at least one of the first feedback unit, the second feedback unit, and the positive feedback unit are configured in a programmable manner. By coordinating the configuration of multiple parameters of the first feedback unit, the second feedback unit, and the positive feedback unit, different equivalent negative resistance conditions are generated under different oscillation state boundaries, thereby simultaneously defining the oscillation initiation condition and the oscillation disappearance condition.

2. The negative resistance oscillator according to claim 1, characterized in that, The first feedback unit and / or the second feedback unit are composed of at least two resistive elements with different temperature coefficients. By programming and configuring the proportional relationship between the equivalent parameter values ​​of the first feedback unit and the second feedback unit, the equivalent temperature coefficient of the negative resistance oscillator can be adjusted between the positive and negative directions to compensate for the temperature drift of the equivalent loss impedance of the resonant circuit with different parameter specifications.

3. The negative resistance oscillator according to claim 1, characterized in that, The positive feedback unit includes a fixed feedback resistor, a first incremental resistor, and a second incremental resistor in the same positive feedback loop; Based on the current oscillation state of the oscillator, the connection relationship between the first incremental resistor and the second incremental resistor in the positive feedback loop is dynamically adjusted to adjust the equivalent parameter value of the positive feedback unit, so as to form a hysteresis interval between the oscillation start-up condition and the oscillation disappearance condition. The oscillation state is determined by whether the amplitude of the oscillator output signal meets the preset oscillation judgment condition.

4. The negative resistance oscillator according to claim 3, characterized in that, The adjustment methods for the connection relationship of the fixed feedback resistor, the first incremental resistor, and the second incremental resistor include: When the negative resistance oscillator switches from the oscillation state to the non-oscillation state, the first incremental resistor is connected to the positive feedback loop where the fixed feedback resistor is located through an analog switch to increase the equivalent parameter value of the positive feedback unit. When the negative resistance oscillator switches from a non-oscillating state to an oscillating state, the second incremental resistor is moved out of the positive feedback loop where the fixed feedback resistor is located or the resistance value of the second incremental resistor is reduced by an analog switch, so as to reduce the equivalent parameter value of the positive feedback unit.

5. The negative resistance oscillator according to claim 4, characterized in that, The values ​​of the first incremental resistor and the second incremental resistor can be independently programmed and configured, and the two values ​​are not equal to form an asymmetrical hysteresis characteristic.

6. The negative resistance oscillator according to claim 5, characterized in that, It also includes a configuration component, which includes a shift register; The configuration component receives external instructions through a digital interface and configures the first incremental resistor and the second incremental resistor and their temperature coefficients online through the shift register according to the external instructions.

7. The negative resistance oscillator according to claim 6, characterized in that, The configuration component also includes a non-volatile memory connected to the shift register; The non-volatile memory stores pre-configured configuration parameters, and the shift register reads the configuration parameters to configure the first incremental resistor and the second incremental resistor and their temperature coefficients.

8. The negative resistance oscillator according to claim 6, characterized in that, The digital interface supports IO-Link, I²C, or SPI communication protocols.

9. An inductive sensor system, characterized in that, Includes the negative resistance oscillator as described in any one of claims 1 to 8, the negative resistance oscillator being used to sense changes in the electromagnetic parameters of the resonant circuit caused by an external target; Also includes: A buffer amplifier is connected to the output terminal of the negative resistance oscillator; A peak detector is used to extract the amplitude information of the output signal of the buffer amplifier; The comparator compares the amplitude information with a preset threshold and outputs a switching signal.

10. The inductive sensor system according to claim 9, characterized in that, The switching signal output by the comparator is connected to the feedback network of the negative resistance oscillator as a feedback control signal, and is used to control the analog switch to adjust the equivalent parameter value of the positive feedback unit in real time according to the feedback control signal.

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