CIRCUIT, CIRCUIT ASSEMBLY AND METHOD

Abstract

This document describes a circuit for use with an inductive sensor. The inductive sensor comprises a transmitting coil and two series-coupled receiving coils for receiving signals induced by a magnetic field generated by the transmitting coil when it is excited; and a movable conductive target for influencing the magnetic field. In particular, the circuit is configured to generate a sequence of pulses for discontinuous excitation of the transmitting coil.

Description

Technical field

[0001] The present disclosure relates generally to techniques relating to contactless switches, and in particular to techniques relating to contactless switches based on inductive position sensing. background

[0002] Inductive position sensing (IPS) is a well-known technology used in various applications to measure the position or proximity of metallic objects. For example, conventional devices such as inductive resolvers use a set of inductive coils to determine the position of a metallic target placed in front of them. Similarly, Hall-effect switches are commonly used to detect magnetic fields for position sensing purposes.

[0003] In one possible implementation of the conventional inductive proximity switch, the sensor typically has a transmitter coil (TX coil) and a receiver coil (RX coil). The receiver coil is often designed with two symmetrical segments that have opposite orientations and are coupled or connected in series, as in Fig. Figure 1 (which is described in more detail below) illustrates this. An oscillator excites the resonant circuit, formed by the transmitter coil and a parallel capacitor, at its resonant frequency. Generally speaking, this configuration generates a high current in the transmitter coil while requiring a relatively low drive current.

[0004] However, conventional IPS-based switch implementations can have certain limitations. For example, the LC tank formed by the TX coil and capacitor would have a very low Q factor (too many energy losses), and the power requirements for the rest of the circuit would increase drastically as the oscillation frequency increases.

[0005] Therefore, there is a need for an improved design for the IPS-based contactless switch that can overcome some or all of the problems associated with conventional techniques, and in particular one that allows miniaturization of the sensor coils (preferably to integrate them into the silicon chip), i.e., to be able to operate with extremely low inductance of the TX / RX coils. Summary

[0006] In view of some or all of the above technical problems, the present disclosure generally provides a circuit, a circuit assembly and a corresponding method having the features of the respective independent claims.

[0007] According to one aspect of the disclosure, a circuit (sometimes referred to herein as a circuit design, assembly, implementation, or the like) is provided. Such a circuit (e.g., an application-specific integrated circuit (ASIC) or the like) can be used with an inductive sensor (e.g., an inductive position sensing (IPS) sensor). The inductive sensor and the circuit can be suitably coupled to each other, for example, for joint operation.

[0008] In particular, the inductive sensor can have a transmitter coil (TX coil) and two series-coupled receiver coils (RX coils). The two receiver coils can be identical, but need not be. The receiver coils can be configured to receive signals induced by a magnetic field generated by the transmitter coil when it is excited (e.g., by a trigger or excitation signal). The inductive sensor can further include a movable conductive target for influencing the magnetic field. For example, the target can be made of any suitable metallic material, such as copper or the like.

[0009] In particular, the circuit can be configured to generate a sequence of pulses (pulse signals) for discontinuous excitation of the transmitter coil. The pulse can be in any suitable shape, such as square, rectangular, or the like.

[0010] Thus, the present disclosure generally proposes a circuit design (ASIC) that enables miniaturization of the sensor coils (preferably for integration into the silicon chip), i.e., to operate with extremely low inductance of the TX / RX coils. In particular, considering short pulses as the TX signal (e.g., ~30 ns or the like), the efficiency of the transformer (sensor) could still be sufficiently high even with much smaller coil inductances. This drastically increases energy efficiency and greatly simplifies the design of the TX driver. Furthermore, the glitch-like TX signal (e.g., a short rectangular pulse) typically exhibits a fairly wide spectral bandwidth, which generally increases the efficiency of power transfer between the TX and RX coils of the sensor transformer, even when the latter is miniaturized and the coil inductance is low.This is particularly true thanks to the high-frequency components in the TX signal. Furthermore, the sensor's power consumption could be significantly reduced, as there would be no continuous power supply to the coils. Additionally, a rectifier would be unnecessary, since both the currents supplied to the coils and the induced currents are already in a form suitable for further processing. Finally, the pulse-driven approach also enables the implementation of randomized TX pulse phases, offering several positive effects in terms of electromagnetic compatibility (EMC) and noise reduction that were not applicable to conventional techniques. For example, the electromagnetic radiation that the transmitter coil can generate for nearby circuits can be reduced.

[0011] In some embodiments, the generation of the pulse sequence can involve a randomized clock scheme, so that the generated pulse sequence has a variable duration between two consecutive pulses. For example, this can be achieved by using an analog random number generator or any other suitable means. This can significantly reduce EMC interference that the TX coil can cause for adjacent circuits.

[0012] In some embodiments, the circuit may include a comparator stage configured to generate an output signal indicating the target's position relative to the receiver coils, based on a differential output signal generated by the receiver coils. In some possible examples, the comparator stage may be implemented as simply as a conventional comparator. Of course, depending on various circumstances and / or requirements, any other suitable implementation may be adopted.

[0013] In some embodiments, the comparator stage may include a compensation stage coupled to the receiver coils to apply asymmetric attenuation or amplification to a differential output signal generated by the receiver coils.

[0014] In some embodiments, the compensation stage can be configured to zero (balance) the differential output signal, allowing the target's position relative to the receiver coils to be derived from information indicating the applied attenuation or gain. This enables a more precise determination (with a certain resolution) of the target's position relative to the receiver coils compared to conventional techniques, where it is usually only possible to determine whether the target is closer to one or the other of the two receiver coils. Zeroing the differential output signal or balancing the P-channel and N-channel signals can be achieved by respective trimmer amplifiers or attenuators placed in their respective signal paths.For example, if the target is relatively closer to the N-channel coil (or has a greater overlap with the N-channel coil), the N-channel signal will be smaller in magnitude than the P-channel signal. In this case, the P-channel signal may require attenuation (or more attenuation) to zero out the differential output signal. Consequently, the fact that more attenuation is applied to the P-channel signal than to the N-channel signal can indicate that the target is relatively closer to the N-channel coil (or has a greater overlap with the N-channel coil), and vice versa.

[0015] In some embodiments, the compensation stage can have two attenuators or amplifiers configured to individually attenuate or amplify respective outputs of the receiver coils. This allows for asymmetrical attenuation or amplification of the differential output signal.

[0016] In some embodiments, the attenuators or amplifiers can have variable (e.g., adjustable) gains to generate an output signal that indicates the position of the target relative to the receiver coils.

[0017] In some embodiments, the comparator stage can include a superregenerative receiver (SRR) concept-based stage capable of self-erasing, so that in the event of a fault, the output of the SRR concept-based stage can gradually be restored to a safe state. In other words, the output is enabled to be restored to a neutral state after a certain period of time if the input signal disappears for any reason.

[0018] In some embodiments, the circuit may further include an integrator stage configured to be charged or discharged based on an output of the comparator stage. In some possible examples, the integrator stage can be implemented as simply as a (conventional) integrator. Of course, depending on various circumstances and / or requirements, any other suitable implementation may be adopted.

[0019] In some embodiments, the circuit may further include a control stage coupled to the integrator stage for controlling at least one integration constant (or coefficient, e.g., a step, a slope, or the like) that indicates how quickly an output of the integrator stage changes for each successive integration cycle. In some possible examples, the control stage may include current sources configured to control the charging / discharging of the integrator stage. Of course, depending on various circumstances and / or requirements, any other suitable implementation may be adopted.

[0020] In some embodiments, the control stage can be configured such that when the comparator stage output indicates a change in position, the comparator stage output is integrated with a smaller step in the integrator stage than when the comparator stage output does not indicate a change in position. This can be achieved, for example, by carefully controlling the integrator's charge / discharge steps (or slopes) or by any other suitable means. Furthermore, it may be worth noting that one of the considerations behind such asymmetric integration can actually be understood as providing so-called probability hysteresis, which generally improves the plausibility of the switch activation, for example, when operating in a highly noisy environment.

[0021] In some embodiments, the circuit may include both a compensation stage coupled to the receiver coils for attenuating or amplifying a differential output signal generated by the receiver coils, and a superregenerative receiver (SRR) concept-based stage coupled to the compensation stage, which is capable of self-quenching. In some other possible examples, either one or even both of the compensation stage and the SRR concept-based stage could be replaced by a comparator, for example, to reduce cost and complexity.

[0022] In some embodiments, the circuit can be powered synchronously with the sequence of pulses. This could significantly reduce the power consumption of the overall system, as there would be no continuous power supply.

[0023] In some implementations, the comparator stage can receive and process signals from the receiver coils synchronously with the sequence of pulses. In other words, the entire signal path is only activated during the TX pulses. For example, in the case of a simple (conventional) comparator-based implementation, the comparator can remain in "reset" mode during TX pauses and start the decision-making process synchronously with the TX pulse generation. On the other hand, if an SRR stage is used, it can also be driven in alignment with the TX pulse generation, thus enabling so-called "synchronous clearing," since otherwise the SRR would be blocked for the Rx signal due to natural noise.Furthermore, the integrator stage can also be configured to perform a single integration step for each TX pulse, while remaining in a "quiet" state during pauses, in which the current integrated value is kept unchanged.

[0024] In some embodiments, the circuit can be configured to determine a short or long distance, a one-way or two-way movement of the target, and / or to detect a linear position or rotation angle of the target. Of course, as those skilled in the art will understand, depending on various circumstances and / or requirements, any other suitable operating mode and / or application scenario may also be applicable.

[0025] Accordingly, according to another aspect of the present disclosure, a circuit assembly is also provided which includes both the circuit according to the preceding aspect and the inductive sensor, which are coupled in series.

[0026] Furthermore, according to another aspect of the present disclosure, a method for operating a circuit for use with an inductive sensor is provided. The inductive sensor may be analogous to or similar to the one described above. For example, the inductive sensor may comprise a transmitting coil and two series-coupled receiving coils for receiving signals induced by a magnetic field generated by the transmitting coil when it is excited. The inductive sensor may further comprise a movable conductive (e.g., copper) target for influencing the magnetic field.

[0027] In particular, the method can include generating a sequence of pulses for discontinuous excitation of the transmitter coil.

[0028] As proposed, the present disclosure generally attempts to suggest techniques that can enable miniaturization of the sensor coils (preferably for integration into the silicon chip), i.e., to be able to operate with extremely low inductance of the TX / RX coils. In particular, considering short pulses as the TX signal (e.g., ~30 ns or the like), the efficiency of the transformer (sensor) could still be sufficiently high even with much smaller coil inductances. Along with this, energy efficiency is drastically increased, and the design of the TX driver is greatly simplified. Furthermore, the glitch-like TX signal (e.g.,A short rectangular pulse typically covers a fairly wide spectrum bandwidth, which generally increases the efficiency of energy transfer between the TX and RX coils of the sensor transformer, even if the latter is miniaturized and the coils have low inductance. This is especially true thanks to the high-frequency components in the TX signal. Furthermore, the sensor's power consumption could be significantly reduced, as there would be no continuous power supply to the coils. Additionally, a rectifier would not be required, since both the currents supplied to the coils and the induced currents are already in a form suitable for further processing. Finally, the pulse-driven approach also enables the implementation of randomized TX pulse phases, with several positive effects in terms of electromagnetic compatibility (EMC) and noise reduction that were not applicable to conventional techniques.For example, the electromagnetic radiation that the transmitter coil can generate for neighboring circuits can be reduced.

[0029] Details of the disclosed method can be implemented as systems (e.g., in the form of a circuit) designed to perform some or all of the steps of the method, and vice versa, as the person skilled in the art will recognize. In particular, it is understood that methods according to the disclosure refer to methods for operating the systems (or the circuit) according to the embodiments and variations thereof described above, and that any statements relating to the systems (or the circuit) apply equally to the corresponding methods and vice versa.

[0030] It is also understood that the term "coupled" or "coupled" in the present disclosure refers to elements that are in electrical communication with one another, whether they are connected directly, e.g., via wires, or in some other way (e.g., indirectly). In particular, an example of being coupled is being connected. Brief description of the drawings

[0031] Exemplary embodiments of the disclosure are explained below with reference to the accompanying drawings, wherein identical reference numerals denote identical or similar elements, and wherein Fig. Figure 1 schematically illustrates an example of a possible implementation of a conventional sensor based on inductive position sensing (IPS). Fig. Figure 2 schematically illustrates an example of a possible conventional implementation, which includes both the inductive sensor of Fig. 1 as well as an application-specific integrated circuit (ASIC) that can be used with the switch, Fig. 3A and Fig. Figure 3B schematically illustrates examples of possible arrangements of the inductive sensor in relation to the ASIC. Fig. Figure 4 schematically illustrates an example of a possible implementation of coils for the inductive sensor. Fig. Figure 5 schematically illustrates another example of a possible implementation of an inductive sensor, Fig. Figure 6 schematically shows an example of a possible output and possible behavior of the inductive sensor of Fig. 5 illustrates, Fig. Figure 7 schematically illustrates an example of a possible implementation of a circuit assembly which includes both the TX part of the inductive sensor and the ASIC according to embodiments of the present disclosure, Fig. Figure 8 schematically illustrates another example of a possible implementation of a circuit assembly that includes both the inductive sensor and the ASIC according to embodiments of the present disclosure, Fig. 9A and Fig. Figure 9B schematically illustrates examples of a possible implementation of determining the digitized position of the sensor's target according to embodiments of the present disclosure. Fig. 10A to Fig. 10E schematically illustrates examples of possible implementations of application scenarios of the circuit assembly according to embodiments of the present disclosure and Fig. 11 is a flowchart which schematically illustrates an example of a method for operating a circuit for use with an inductive sensor according to embodiments of the present disclosure. Detailed description

[0032] As stated above, identical or the same reference numerals in this disclosure, unless otherwise indicated, may denote identical or the same elements, so that repeated descriptions thereof may be omitted for the sake of brevity. Furthermore, it should also be noted that the symbols used in the figures, unless otherwise indicated, serve only for illustrative purposes and should therefore not be understood as a limitation of any kind.

[0033] As briefly mentioned above, this disclosure relates generally to the technical field of contactless switches and in particular to techniques relating to contactless switches based on inductive position sensing (IPS) techniques.

[0034] For example, in Fig. As illustrated in Figure 1, a typical sensor circuit 100 typically comprises a transmitter coil 101 and a receiver coil 102. The receiver coil 102 can often be designed with two symmetrical segments 103 and 104, which have opposite orientations and are connected in series. An oscillator excites the resonant circuit, formed by the transmitter coil 101 and a parallel capacitor 105, at its resonant frequency.

[0035] An alternating current (AC) in the transmitter coil 101 generates an alternating magnetic field, which in turn induces voltages in the receiver coil segments 103 and 104. Sometimes these receiver coil segments can be viewed or implemented as (separate) receiver coils. In the absence of a target 106, the induced voltages in the two symmetrical receiver coil segments 103 and 104 would be equal in magnitude but opposite in sign, resulting in a voltage of zero.

[0036] As a conductive target 106 approaches the sensor, eddy currents would be induced within the target material. These eddy currents generate an opposing magnetic field that reduces the total magnetic flux in both the transmitter and receiver coils 101 and 102 below the target 106. Consequently, the induced voltage is reduced in the region of the receiver coil 102 closest to the target 106. If the target 106 does not cover identical regions of the two receiver coil segments 103 and 104, a net voltage Vrec can be measured at the receiver coil terminals. The sign (polarity) of this voltage corresponds to the segment with less (smaller) target coverage, as shown in the lower part of Fig. 1 is shown as an illustration.

[0037] From the sign of the output voltage, it is possible to determine whether the target is more in line with segment 103 or segment 104. Fig. 2 overlaps. In the broadest sense, this allows for the implementation of a 2-state switch / sensor (in this case, left or right).

[0038] In some possible implementations, the output voltage Vrec can be provided by an application-specific integrated circuit (ASIC) 210, as in Fig. Figure 2 illustrates this. As stated above, identical or equivalent reference symbols in Fig. 2 identical or equal elements in Fig. 1, so that repeated descriptions of it can be omitted for reasons of brevity. In particular, the ASIC 210 in the example of Fig. Figure 2 schematically shows an electromagnetic interference (EMI) filter 211, a rectifier 212, a low-pass filter 213, an amplifier 214, and a comparator 245. This is, of course, merely one possible example for illustrative purposes and should not be understood as a limitation of any kind. As those skilled in the art will understand, depending on various implementations and / or circumstances, any other suitable design for the ASIC can be assumed.

[0039] One of the most important practical limitations of such conventional inductive sensor techniques can be understood as lying in the LC tank formed by the TX coil and the capacitor, which could have a very low Q-factor (too many energy losses), and as a result, the power requirements for the rest of the circuit would be drastically increased as the oscillation frequency increases.

[0040] Therefore, one of the primary technical goals of the present disclosure, in a broad sense, is to find a low-power ASIC architecture that enables miniaturization of the sensor coils (preferably for integration into the silicon chip), i.e., to be able to operate with extremely low inductance of the TX / RX coils. Any other applicable goal and / or any other applicable advantages of the present disclosure would also become apparent from the detailed description below.

[0041] As mentioned above, the present disclosure generally relates to an ASIC capable of processing the differential output of an induction-based sensor coupled to its input. Depending on various implementations, the sensor can be separate from the ASIC (as in Fig. 3A as illustrated) or be integrated (as in Fig. 3B is shown illustratively).

[0042] Regarding the sensor component, a simple implementation example was already given above with reference to Fig. 1. Illustrative description.

[0043] Now, the focus will shift to... Fig. 4. Reference is made to the schematically illustrated possible arrangements of the sensor coils. Another example (with a conductive target included) from two different perspectives (cross-sectional view in the upper part and top view in the lower part) is shown in Fig. Figure 5 also illustrates this. Similar to the above, identical or the same reference symbols can be used in Fig. 4 or Fig. 5, unless otherwise specified, as identical or equal elements in Fig. 1 can be considered significant, so repeated descriptions of it can be omitted for reasons of brevity.

[0044] In particular, as in Fig. As shown in Figure 4, the dashed line 401 ("transmitting coil 401") designates the transmitting coil (in Fig. 5, designated as the "Tx coil"), the dotted line 403 ("Rx1 403") designates the first receiving coil (in Fig. 5, designated as "Rx1") and the solid line 404 ("Rx2 404") designates the second receiving coil (in Fig. 5, referred to as "Rx2"). The line, which has both dots and dashes 410, 510, is used to illustrate the axis of symmetry for Rx1 and Rx2.

[0045] As from Fig. 4 and Fig. As can be seen in Figure 5, the transmitting coil 401 completely surrounds the two receiving coils 403 and 404. Since Rx1 403 and Rx2 404 are positioned identically and symmetrically, in the absence of any other elements (such as a conductive element), the magnetic flux generated by the transmitting coil 401, which penetrates Rx1 403, is equal to the magnetic flux penetrating Rx2 404. Under such conditions, the induced current in Rx1 and Rx2 would completely cancel each other out.

[0046] The sensor may also include a conductive element (in Fig. 5 referred to as the “Cu target”). In one possible implementation, the conductive element could be a solid copper plate.

[0047] The conductive element can take on various shapes. In one possible implementation, the conductive element can be shaped such that it is symmetrical, with a symmetry axis 520 that is parallel to the symmetry axis indicated by the lines 510 of Rx1 and Rx2.

[0048] When the sensor is in use, the conductive element is positioned so that it faces the two receiving coils Rx1 and Rx2. The conductive element is also penetrated by the field generated by the transmitting coil Tx. The AC field component induces eddy currents on the conductive plate, resulting in a reduction of the overall magnetic flux in the covered areas.

[0049] If the target symmetry axis 520 does not coincide with the 510 (Δx) axis of the coils, an asymmetry in the flux distribution would be generated, resulting in a non-zero electromotive force (ξ) in the receiving section (Rx1 + Rx2). In other words, the described system can be considered a known differential transformer. Generally speaking, the value of the induced signal (ξ) depends on the displacement (Δx), but also on the target quantity and shape, which could be used to adjust the mechanical threshold and hysteresis of the switch.

[0050] Therefore, the polarity of the induced signal (ξ) allows us to determine whether the conductive element, i.e., the Cu target, is currently located closer to Rx1 or closer to Rx2. An illustrative diagram showing the possible output and behavior of the sensor is shown in Fig. Figure 6 is given. In this figure, the dotted line 610 (labeled "differential sensor signal") generally represents the differential output of the sensor as the copper target moves across the receiving coils Rx1 and Rx2. The thick line 620 generally represents the output of the ASIC, as explained in more detail below.

[0051] With reference to the ASIC part, which is generally considered one of the main aspects of the present disclosure, in order to keep the pin count of the final product as low as possible, the transmitter coil can first be coupled (connected) in series with an ASIC supply (as also shown in Fig. 3A and Fig. 3B is illustrated) and is stimulated by a sequence of (short) impulses, as shown in Fig. 7. It should also be noted that Fig. Figure 7, for the sake of brevity, only illustrates the TX part of the sensor, but not the RX coils or the connections, as a person skilled in the art can also understand. In some possible implementations, the pulses can be converted into a sequence of square (or rectangular) pulses. Of course, as a person skilled in the art will understand, any other suitable pulse conversion can also be assumed. This is a first major difference compared to conventional techniques, where, as illustrated above, the coils are typically supplied by AC currents.

[0052] More precisely, while in conventional sensor implementations (such as those used in Fig. 1 and Fig. (as shown in Figure 2) where the coils are supplied with an AC current from an oscillator, the ASIC in the present disclosure can supply (e.g., quadratic) pulses to the transmitter coil to excite the transmitter coil discontinuously. In particular, exciting the transmitter coil with short (discontinuous) pulses can be considered to have at least the following effects.

[0053] First, a glitch-like TX signal (e.g., a short rectangular pulse) typically exhibits a fairly wide spectral bandwidth. This can increase the efficiency of power transfer between the TX and RX coils of the sensor transformer, even if the latter is miniaturized and the coils have low inductance. This is especially true due to the high-frequency components in the TX signal.

[0054] Furthermore, the sensor's power consumption can be significantly reduced, as there would be no continuous power supply to the coils, which is necessary compared to conventional AC-based techniques. Accordingly, the ASIC can also be powered synchronously with the sequence of pulses.

[0055] Furthermore, a rectifier would not be required, since both the currents supplied to the coils and the induced currents are already in a form suitable for further processing.

[0056] However, the electromagnetic (EM) radiation that the transmitter coil can generate for neighboring circuits could also be reduced.

[0057] Finally, the design of the TX excitation generator can also be greatly simplified.

[0058] In some possible implementations, the clock scheme for generating the pulses can be randomized (e.g., by using an analog random number generator). This can significantly reduce the electromagnetic compatibility (EMC) interference that the TX coil can cause for adjacent circuits. In other words, using the randomized clock scheme can eliminate any possible correlation with, for example, external interference signals, thus positively increasing immunity to electromagnetic interference.

[0059] In some other possible cases, the transmitter coil can be considered an antenna when exposed to an external electromagnetic field. In such cases, for improved EMC performance of the system, the transmitter coil could be divided into two identical halves and coupled sequentially (similar to the receiver coil segments).

[0060] Now, the focus will shift to... Fig. Reference is made to Figure 8, which schematically illustrates a possible circuit implementation of the ASIC 820 according to embodiments of the present disclosure. The ASIC 820 is coupled to the inductive sensor 810 and can be used together with it.

[0061] In particular, when receiving the differential output signal (in Fig. 8 designated as “InP” and “InN”) from sensor 810, a first stage in the receive path may be designated as a compensation stage (or sometimes also as an attenuator stage or the like) 821. In particular, the compensation stage may be configured to apply asymmetric attenuation (or gain) to the differential output signal generated by the receiver coils.

[0062] In some possible examples, this compensation stage can be implemented as simply as by incorporating attenuators. It should be noted that, as will become apparent from the description below, although the term "attenuator" is used here, such attenuators (or more generally, the compensation / attenuator stage) are capable of providing a gain that is not only less than 1 (unit gain) but also greater than (or sometimes equal to) 1. In this sense, it is understood that the "attenuator" can, in some cases, also behave like an amplifier. Likewise, it may also be possible to implement this compensation stage by using amplifiers (or a combination of amplifier(s) and attenuator(s)) that are also capable of providing a gain less than 1.Of course, as the expert understands and will understand, any other suitable implementation can also be assumed.

[0063] In some possible implementations, the relative position of the target can be used to define the asymmetric attenuation (or gain) of the signals in both receiver coils. That is, if the target is closer to Rx1, the flux at Rx1 can be attenuated more than the flux passing through Rx2, which would then result in a non-zero differential output from the sensor.

[0064] The use of the compensation stage (which, as illustrated above, can be implemented as attenuators and / or amplifiers) at the input stage can produce at least the following technical effect(s).

[0065] By individually and differently attenuating / amplifying the output of each coil, it is possible to shift the transition threshold at which the switch / sensor changes state (ON / OFF, left / right, etc.). In other words, one effect of the attenuators is the ability to (artificially / virtually) mechanically "move" the switching threshold point across the sensor's active range, which in turn allows for the introduction of mechanical hysteresis into the system. This effect is specifically illustrated in the figures and referred to as "dynamic control of the electrical AFE asymmetry."

[0066] Furthermore, in some possible examples, the attenuators / amplifiers can be implemented to provide variable gain. In such cases, it may also be possible to determine the actual position of the target (with higher resolution), instead of merely estimating whether the target is closer to one or the other of the two receiver coils.

[0067] More precisely, in some possible implementations, this asymmetric attenuation of the signals in both receiver coils can be compensated for or increased by the respective attenuators (or amplifiers). Once the respective attenuator / amplifier gain that compensates for the asymmetric attenuation is determined, it is then possible to determine the exact (at least to some extent) position of the target relative to the receiver coils. In other words, the compensation stage can be configured to zero out (compensate for) the differential output signal (e.g., by using a suitable trimmer amplifier (or attenuators) together with any suitable search algorithm / search strategy), so that a position of the target relative to the receiver coils can be derived from information indicating the applied attenuation or gain.

[0068] An illustrative, non-restrictive example for deducing the position of the target relative to the receiver coils is as follows. If the system (i.e., the compensation stage) must apply more attenuation to the P-channel than to the N-channel of the differential output signal to compensate for these signals (i.e., to zero out the differential output signal), it can be inferred that the target is relatively closer to the N-channel coil. The rationale is that a target that is relatively closer to the N-channel coil implies a smaller N-channel signal, which then requires that the P-channel signal be attenuated relative to the N-channel signal to zero out the differential output signal. Conversely, if more attenuation must be applied to the N-channel signal, it can be inferred that the target is relatively closer to the P-channel coil.As the person skilled in the art will understand, attenuation factors for balancing the P-channel and N-channel signals, which can be applied by suitable amplifiers, can be found by a variety of search strategies or algorithms, such as successive approximation algorithms or the like, as will be discussed in detail later. Importantly, however, the person skilled in the art will understand that suitable attenuation factors for balancing the P-channel and N-channel signals can be found and that these attenuation factors allow the derivation of the target's position relative to the P-channel and N-channel coils. It is also understood that the aforementioned attenuation factors (or, analogously, gain factors) can be relative to reference attenuation factors (or gain factors) that zero out the differential output signal for a symmetrical arrangement of the target.

[0069] In some possible implementations, finding the correct settings for the compensation stage may involve the application of a suitable search algorithm. For example, in some cases, a successive approximation algorithm can be implemented using hardware (HW) control logic or software (SW) in the microcontroller unit (MCU), which may be configured to monitor the output of the switch / sensor for toggling at each iteration step. Of course, as the expert will understand, depending on the specific implementation and / or circumstances, any other suitable algorithms may be used.

[0070] The output value from the search routine can indeed be viewed as a digitized representation of the target's relative position with respect to the sensor's axis of symmetry. Illustrative examples are provided in Fig. 9A and Fig. Figure 9B shows a schematic illustration of how to determine the P-channel attenuation and the N-channel attenuation at the input stage of the ASIC. Fig. 8 can be used to determine the digitized position of the target.

[0071] In other words, the relative position of the target affects the relative signal strengths of the signals from the receiver coils (i.e., P-channel and N-channel signals) and therefore the attenuation factors (attenuation values) required to compensate for the signals from the receiver coils. Depending on the target position, the required attenuation factors are generally asymmetric, i.e., different for P-channel and N-channel signals. As the target moves along the receiver coils, the (asymmetric) attenuation factors can be dynamically adjusted using front-end compensation settings (e.g., using trim amplifiers or the like). This adjustment can be achieved by a suitable search algorithm or search strategy for the attenuation factors. The search algorithm (e.g.,(An algorithm of successive approximation) can be used to determine the correct asymmetry compensation settings for each position, for example by iteratively checking the switch output (in . Fig. 9A specified by “differential sensor signal”) and adjusting the respective damping settings (in Fig. 9A, specified by "P-channel attenuation" or "N-channel attenuation," for example, until the switch toggles, indicating that the required attenuation setting has been found (and, by extension, the current position of the target has been detected). This is shown in the "switch output" diagram of Fig. Figure 9A illustrates this. The values ​​of the asymmetric attenuation (P-channel attenuation and N-channel attenuation) can be adjusted (e.g., iteratively) to compensate for the differential output signal detected by the receiver coils until the differential output signal reaches or crosses a predetermined threshold, such as the "background noise" level, as shown in Fig. Figure 9A illustrates this. While the target is moving, whenever the switching output indicates that an adjustment of the damping factors is necessary, the existing damping factors can be used as a starting point for the search algorithm, so that for continuous linear movement of the target, the damping factor for one of the channels is gradually reduced (e.g., P-channel attenuation in Figure 9A). Fig. 9A), while the damping factor for the other of the channels is gradually increased (e.g., N-channel attenuation in Fig. 9A). A similar example is shown in the diagram of Fig. Figure 9B illustrates where new combinations of P-channel and N-channel attenuation values ​​are determined at each zero-crossing point of the differential output signal as the target moves from the P-channel coil to the N-channel coil. Specifically, in this example, the N-channel attenuation value is held constant, while at each zero-crossing point of the differential output signal (i.e., when the P-channel signal reaches the N-channel signal), the P-channel attenuation value is adjusted (i.e., increased) by a certain amount, as indicated by decreasing slopes of signals Rx_P.

[0072] The “digitalized position”, as in the example of Fig. As illustrated in Figure 9A, the target position can be derived from the difference between the P-channel and N-channel attenuation values ​​and can be representative of the target position relative to the sensor system's axis of symmetry. In the preceding section, the granularity of the available attenuation values ​​determines the granularity of the digitized target position.

[0073] It can be noted that this approach is applicable to both types of target displacement, namely linear or angular (if the accuracy requirements are not too high), and is particularly advantageous for its energy and cost efficiency. Generally speaking, the resolution of the measurement can be considered limited by the resolution of the asymmetry compensation attenuators / amplifiers.

[0074] It should also be noted that the introduction of the compensation stage is indeed a significant improvement over conventional sensor techniques, which can only indicate whether the target is closer to one or the other receiver coil (in other words, a two-state switch). In particular, the introduction of the compensation stage, as proposed in the present disclosure, generally allows the determination of how close the target is to one or the other coil (resulting in a multi-state switch, or in other words, a position sensor).

[0075] Furthermore, returning to Fig. In Figure 8, a second stage 822 of the receive path is implemented based on a modified superregenerative receiver (SRR) concept. The SRR concept itself can be considered generally known to those skilled in the art. In fact, in some possible cases, it may not be essential for the function of the overall system that this stage be implemented as an SRR. For example, in some possible examples, it could also be implemented as simply as a (conventional) comparator, where, if the differential output is positive (for example, in the case where the current generated at Rx1 is greater than the current generated at Rx2), the output of the stage becomes almost immediately a high (positive) potential (e.g., Vdd), whereas otherwise it becomes a low (negative) potential (e.g., Vss). In such cases, the switch would still generally function.However, as the expert understands, the output would remain stuck on the positive or negative voltage rail of the comparator. This lacks an advantageous feature offered by the SRR concept, namely the ability to return to a safe state in the event of a fault.

[0076] In the broadest sense, this SRR-based stage relies on positive feedback from its output, which is fed to an LC oscillator coupled to its input. This oscillator amplifies the input signal until it reaches the magnitude of the supply voltage. In this sense, the output can be similar to that of a comparator, but with SRR, this value would be reached gradually (until saturation). For the SRR to function as intended, the supply current driving the transmitter coil would be in pulses, as illustrated above.

[0077] Additionally, in some possible implementations, there may also be an integrator stage 823 that follows the SRR stage 822 and could be appropriately loaded or discharged based on the output of the SRR 822 (for example, via the current sources of the control stage 824 or the like). That is, the integrator stage 823 can be configured to perform an integration of the multiple decisions subsequently made by the comparator. In this sense, the integrator stage 823 can be understood as being able to filter out the noise and make the correct decision as to whether the target has been placed at the position (e.g., for an on-state or an off-state) when it accumulates a certain number of correct decisions provided by the comparator. In some possible examples, this integrator stage 823 may be configured to perform integration in both directions.This means it doesn't simply count a certain number of positive output signals from the comparator, but is also able to subtract from the accumulated value in the event of an incorrect decision (for example, due to noise, external interference, or the like). Furthermore, the rate (step / slope) at which it increases or decreases its output can vary in some implementations, which in turn ensures a certain degree of hysteresis in the system, thus providing a certain level of noise immunity.

[0078] In some possible cases, the current sources of the control stage 824 can be configured to appropriately control the magnitude of the output of the integrator stage 823, thereby producing an electrical hysteresis effect on the switch / sensor. That is, in some possible examples, the control stage 824 can be coupled to the integrator stage and configured to control at least one integration constant (or coefficient / parameter, e.g., a step, a slope, or the like) that indicates how quickly an output of the integrator stage changes for each successive integration cycle (as its input (e.g., the comparator or SRR output) changes).Furthermore, in some possible examples, the control stage 824 can be configured such that if the output of the SRR stage 822 (or, in the case of a simple comparator-based implementation, the output of this comparator) indicates a change in the target's position, the output is integrated with a smaller step (slope) in the integrator stage 823 than in the case where the output of the SRR or the comparator does not indicate a change in position. It may be worth noting that one of the considerations behind such asymmetric integration can indeed be understood as providing so-called probability hysteresis, which generally improves the plausibility of the switch activation, for example, when operating in a highly noisy environment.Of course, as the expert can understand, the control stage 824, implemented using current sources, is provided merely as one possible example for illustrative purposes and should not be interpreted as a limitation of any kind. Depending on various circumstances, any other suitable implementation for the control stage 824 could be adopted. In particular, by passing the output of the SRR stage 822 to the integrator stage 823, the EMC robustness of the signal could be improved, and any noise that may be present could be reduced. It further improves the stability of the switch output, as it provides hysteresis to the output.

[0079] Unlike a simple comparator-based implementation, the SRR stage 822, particularly in the event of a fault, can benefit from a so-called self-clearing action, which generally ensures that the output of this stage 822 will gradually return to a safe state. In other words, the output is released to allow it to return to a neutral state after a certain period of time if the input signal disappears for any reason. This, in turn, makes the switch / sensor suitable for higher vehicle safety integrity levels (ASILs) as defined by ISO 26262.

[0080] A major difference between a simple comparator-based implementation and the SRR concept-based technique proposed here is the presence of an additional state (sometimes considered or referred to as a "safe state") at the output of the SRR stage, which it settles to after a certain period of time in the event of a fault, such as a missing clock signal or the like. While the latched comparator would retain the latest result from the decision-making process (e.g., "1" or "0") at its output, the SRR stage generally does not remain in this state for long, and neither an "I" nor a "0" signal would reach the integrator stage. As a result, the comparator-based switch may trigger incorrectly in the event of a fault, since it is generally not possible to ensure that the latest latching results at its output would reflect the actual position of the target (e.g.,(due to noise or electromagnetic interference, etc.). Conversely, the SRR-concept-based IPS switch would retain the latest valid state simply because the aforementioned additional safe state of the SRR stage output can be used to completely disable the charging / discharging current sources in the integrator stage. Furthermore, depending on application requirements, the integrator stage could be designed to slowly self-discharge when such an event occurs, ensuring a predefined safe state of the switch (e.g., "On," "Off," or the like) to which the switch would automatically return, regardless of the target position and the latest valid state of the switch before the fault occurs. Thus, the SRR-concept-based technique, as proposed here, has a distinct advantage over a comparator, at least in terms of safety.

[0081] As mentioned above, the ASIC 820 can, in some cases, be powered synchronously with the pulse sequence, resulting in certain power consumption advantages. Additionally, in some possible implementations, the entire signal path can be activated only during the TX pulses. For example, in a simple (conventional) comparator-based implementation, the comparator can remain in "reset" mode during TX pauses and initiate the decision-making process synchronously with the TX pulse generation. On the other hand, if an SRR stage 822 is used, it can also be driven in alignment with the TX pulse generation, enabling so-called "synchronous clearing," since otherwise the SRR would be blocked for the RX signal due to natural noise.In addition, the integrator stage 823 can also be configured to perform a single integration step for each TX pulse, while remaining in a "quiet" state during pauses, in which the current integrated value is kept unchanged.

[0082] It may also be worth mentioning that in some possible examples, either one or even both of the two stages mentioned above—namely, the compensation stage 821 and the SRR concept-based stage 822—could be replaced by a single comparator, for example, to reduce cost and complexity. In such cases, the control stage can be configured to ensure that, for a given position, a comparator output indicating a change in position has a smaller output magnitude than a comparator output indicating no change in position. This can be achieved, for example, by carefully controlling the integrator's charge / discharge gradients or by any other suitable means.

[0083] The rest of the circuit follows known receiver path topologies and is therefore not discussed in detail due to brevity.

[0084] Nevertheless, it may be worth mentioning that, although the basic sensor configuration and principle may have been largely reused here, there are still some important aspects to consider for its design when used in the pulse-driven system as proposed in the present disclosure. For example, the parasitic capacitance can be minimized. Furthermore, unlike conventional techniques, the Q-factor of all resonances can be kept sufficiently low, which normally requires the introduction of additional ohmic losses into the circuit. However, it would also be possible to utilize the intrinsic resistance of the copper material for the coils on the sensor printed circuit board (PCB). To avoid the so-called "long-wire" effect in the circuit, the overall length of the wires forming the coils can be shortened (e.g., by 1 / 3 of a wire).The frequency components of the TX signal relevant for switch operation must be more than 10 times shorter, which can be defined by the cutoff frequency of the low-pass filter in the circuit. Furthermore, for improved performance of the proposed switch architecture, the sensor parameters may also need to be tuned to ensure aperiodic transition processes around the TX pulse edges without significant signal ringing.

[0085] By using techniques proposed in the present disclosure, the system can be applicable to various operating modes and application scenarios, some of which are in Fig. 10A to Fig. 10E illustrates this. In short, the proposed techniques are not limited to linear inductive position sensors, as shown in Fig. 1 shown, applicable, but to a wide variety of target and coil configurations, a few non-restrictive illustrative examples of which are briefly described below.

[0086] In particular, illustrates Fig. Figure 10A schematically illustrates an application scenario for detecting short-distance, two-way (linear or angular) movement of the target. Specifically, in this case, the target is smaller than the sensor coils and never leaves their active area. The switch state upon activation is fully defined. This can be used to detect any type of local movement where the mechanical displacement is smaller than the sensor dimensions.

[0087] Fig. Figure 10B schematically illustrates an application scenario for detecting long-distance, one-way target movement. In this case, the target is larger than the sensor coils and can completely cover and exit the active area. Switching occurs when one of the target edges passes through the sensor's active area. At the switching points, the front-end asymmetry setting is reversed, enabling the detection of the target's leading / trailing edge. Accurate response can be achieved after a single initialization cycle following power-up (target on and off). This is particularly suitable for industrial production lines or unidirectional large-object motion detection.

[0088] Fig. Figure 10C schematically illustrates an application scenario for detecting a long distance and a two-way movement of the target without it passing through the sensor. Specifically, in this case, the target is larger than the sensor coils and can completely cover and exit the active area. Switching occurs when the leading edge of the target passes through the sensor's active area. This contrasts with the previous case in Fig. 10B requires the correct operation of adding a static asymmetry to the front-end signal path. This causes the settings at the switching point to toggle, but their sign remains unchanged; that is, the signal from one of the receiver coils is always more attenuated than the other. Accurate response is obtained after a single initialization cycle following power-up (target on and off). In particular, this can be considered well-suited for all types of end-point switches widely used in industrial plants.

[0089] Fig. Figure 10D schematically illustrates an application scenario for detecting a long distance, a two-way movement of the target crossing the sensor. This can be seen as an improvement on the operating mode in Fig. 10B can be viewed, thereby eliminating the restriction for unidirectional movement. In particular, in this case, switching occurs when one of the target edges passes through the sensor's active area in any direction. The front-end asymmetry settings toggle continuously, allowing the simultaneous operation of two sensors of this type. Fig. The 10B sensors, which operate in opposite directions, are aligned. At the switching points, the switching phase is reversed, virtually swapping the two sensors and preventing an undefined switch state. A precise response is achieved after a single initialization cycle upon power-up (target on and off). In particular, this operating mode emulates so-called "presence detection" while still ensuring stable and accurate switching positions compared to conventional techniques.

[0090] Finally, illustrates Fig. Figure 10E schematically shows an application scenario for an incremental binary application interface encoder (ABI encoder) with a multi-strip target. Specifically, there can be two possible realizations of such a system, which can use two copies of the sensor coils from the previous embodiments, but with a multi-strip target: • aligned pairs of receiver coils, combined with two rows of strips in the target, offset from each other by a quarter period (illustrated above); or • a single raw multi-strip target in combination with shifted pairs of receiver coils, again with quarter period.

[0091] The denser the stripes, the higher the resolution of the displacement detection could be achieved, but the sensitivity of the system could be reduced. An accurate response is available immediately after power-up, meaning no initialization cycles are necessary.

[0092] As stated above, the above are merely examples of possible application scenarios for illustrative purposes. As a person skilled in the art will understand, depending on various circumstances and / or requirements, any other suitable operating mode and / or application scenario may also be applicable.

[0093] Finally, in Fig.Figure 11 schematically shows a flowchart illustrating an example of a method 1100 for operating a circuit for use with an inductive sensor. The circuit and the inductive sensor can be implemented according to the possible embodiment described above with reference to the figures, or the like. For example, the inductive sensor can have a transmitting coil and two series-coupled receiving coils for receiving signals induced by a magnetic field generated by the transmitting coil when it is excited. The inductive sensor can further have a movable conductive (e.g., copper) target for influencing the magnetic field.

[0094] In particular, the method 1100 can feature, at step S1110, the generation of a sequence of pulses for discontinuous excitation of the transmitter coil.

[0095] As proposed, the present disclosure generally attempts to suggest techniques that can enable miniaturization of the sensor coils (preferably for integration into the silicon chip), i.e., to be able to operate with extremely low inductance of the TX / RX coils. In particular, considering short pulses as the TX signal (e.g., -30 ns or the like), the efficiency of the transformer (sensor) could still be sufficiently high even with much smaller coil inductances. Along with this, energy efficiency is drastically increased, and the design of the TX driver is greatly simplified. Furthermore, the glitch-like TX signal (e.g.,A short rectangular pulse typically exhibits a fairly wide spectrum bandwidth, which generally increases the efficiency of energy transfer between the TX and RX coils of the sensor transformer, even if the latter is miniaturized and the coils have low inductance. This is especially true thanks to the high-frequency components in the TX signal. Furthermore, the sensor's power consumption could be significantly reduced, as there would be no continuous power supply to the coils. Additionally, a rectifier would not be required, since both the currents supplied to the coils and the induced currents are already in a form suitable for further processing. Finally, the pulse-driven approach also allows for the implementation of randomized TX pulse phases (e.g.,(through the use of an analog random number generator or similar) with several positive effects from the perspective of electromagnetic compatibility (EMC) and noise reduction that were not applicable to conventional techniques. For example, the electromagnetic radiation that the transmitter coil can generate for neighboring circuits can be reduced.

[0096] To summarize the foregoing, the present disclosure generally focuses on and describes in detail the following elements. First, there is an inductive sensor, which may be similar to those conventionally used. Second, an ASIC is also described, which is coupled to the transmitter coil and the receiver coils, such that it controls the current supplied to the transmitter coil and processes the current output by the receiver coils. The ASIC itself may, among other things, include an SRR-concept-based input amplification stage, which enables operation with very low RX signals. This is one of the side effects of sensor miniaturization, but this comes without significant complexity on the amplifier, simply because it is reused many times to amplify the same input signal (i.e., the SRR concept).It should be noted that even if the function of this block can be considered to some extent identical to a classical comparator, the design of the latter would be quite challenging, considering the low input signals and the short pulses used to drive the transformer. Furthermore, using the SRR also allows the sensor to be triggered with pulses, which in turn enables the technical goals / effects discussed above. Considering short pulses as the TX signal (e.g., ~30 ns), the efficiency of the transformer (sensor) would still be sufficiently high even with much smaller coil inductances. Along with this, energy efficiency is drastically increased, and the design of the TX driver is greatly simplified. Moreover, the pulse-driven approach also allows for the implementation of a randomized TX pulse phase (e.g.,...(through the use of an analog random number generator) with many positive effects from the perspective of EMC and noise reduction. Additionally, the addition of asymmetry compensation attenuators / amplifiers at the input generally allows for precise mechanical adjustment of the system's switching point (sensor + ASIC) and the implementation of mechanical hysteresis, which can be considered advantageous for attenuating unwanted switching due to vibrations.

[0097] Techniques proposed in the present disclosure also bring several further advantages, including (but certainly not limited to): an analog-based design that is of low complexity and allows for relatively simple implementation; no need for digital control logic for basic switching functionality; the possibility of mounting the sensor coils inside the IC package or even integrating them into the ASIC chip; automatic safe state entry by design when the SRR stage is present; high EMC robustness; low power consumption; low cost of goods sold (COGS); and a minimized bill of materials (BOM) of external components.

[0098] It should be noted that the exemplary implementations using transmitter and receiver coils, which appear to have a specific winding, arrangement, or placement as shown in the figures, are provided for possible illustrative purposes only and are certainly not to be understood as a limitation of any kind. As the person skilled in the art can understand, any other suitable arrangement, implementation, and / or application may be assumed.

[0099] It should be noted that, for reasons of brevity, the device / equipment features described above correspond to respective process features, which, however, cannot be explicitly described. It is understood that the disclosure of this document also extends to such process features. In particular, it is understood that this disclosure also relates to methods for manufacturing and / or operating the circuits described above and / or to providing and / or arranging respective elements of these circuits.

[0100] It should also be noted that examples of embodiments of the disclosure are applicable to various applications or system configurations, depending on the underlying technical fields. In other words, the examples shown in the figures described above (such as the power tools), which serve as the basis for the examples discussed above, are merely illustrative and do not limit the present disclosure in any way. That is to say, additional existing and proposed new functionalities available in a suitable operating environment can be used in conjunction with examples of embodiments of the present disclosure based on the defined principles.

[0101] It should also be noted that the disclosed exemplary embodiments can be implemented in many ways using hardware and / or software configurations. For example, the disclosed embodiments can be implemented using dedicated hardware, dedicated software, and / or hardware in conjunction with software executable thereon. The components and / or elements in the figures are only examples and do not limit the scope of use or functionality of hardware, software in combination with hardware, firmware, embedded logic components, or a combination of two or more such components that implement certain embodiments of the present disclosure.

[0102] Finally, it should be noted that the description and drawings merely illustrate the principles of the proposed circuits and methods. A person skilled in the art will be able to implement various arrangements which, although not explicitly described or shown here, embody the principles of the invention and are included in its meaning and scope. Furthermore, all examples and embodiments set forth in this document are expressly intended to serve only as illustrations to aid the reader in understanding the principles of the proposed method. Moreover, all statements herein that provide principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to include equivalents thereof.

Claims

[1] Circuit for use with an inductive sensor, wherein the inductive sensor comprises: a transmitter coil and two series-coupled receiver coils for receiving signals induced by a magnetic field generated by the transmitter coil when it is excited; and a movable conductive target for influencing the magnetic field, wherein the circuit is configured to generate a sequence of pulses for discontinuous excitation of the transmitter coil. [2] Circuit according to claim 1, wherein the generation of the sequence of pulses involves a randomized clock scheme such that the generated sequence of pulses has a variable duration between two successive pulses. [3] Circuit according to claim 1, wherein the circuit has a comparator stage configured to generate an output signal indicating a position of the target relative to the receiver coils based on a differential output signal generated by the receiver coils. [4] Circuit according to claim 3, wherein the comparator stage comprises a compensation stage coupled to the receiver coils for applying asymmetric attenuation or amplification to a differential output signal generated by the receiver coils. [5] Circuit according to claim 4, wherein the compensation stage is configured to zero the differential output signal so that a position of the target relative to the receiver coils can be derived from information indicating the applied attenuation or gain. [6] Circuit according to claim 4, wherein the compensation stage comprises two dampers or amplifiers configured to individually dampen or amplify respective outputs of the receiver coils. [7] Circuit according to claim 6, wherein the dampers or amplifiers have variable gains for generating an output signal that indicates a position of the target relative to the receiver coils. [8] Circuit according to claim 3, wherein the comparator stage comprises a superregenerative receiver (SRR) concept-based stage capable of self-erasing, so that in the event of a fault, an output of the SRR concept-based stage can be gradually restored to a safe state. [9] Circuit according to claim 3, wherein the circuit remote has an integrator stage configured to be loaded or discharged based on an output of the comparator stage. [10] Circuit according to claim 9, wherein the circuit further comprises a control stage coupled to the integrator stage for controlling at least one integration constant indicating how quickly an output of the integrator stage changes for each successive integration cycle. [11] Circuit according to claim 10, wherein the control stage is configured such that when the output of the comparator stage indicates a change in position, the output of the comparator stage is integrated in the integrator stage with a smaller step than in the case where the output of the comparator stage does not indicate a change in position. [12] Circuit according to claim 1, wherein the circuit comprises both a compensation stage coupled to the receiver coils for attenuating or amplifying a differential output signal generated by the receiver coils and a superregenerative receiver (SRR) concept-based stage coupled to the compensation stage which is capable of self-quenching. [13] Circuit according to claim 1, wherein the circuit is supplied with energy synchronously with the sequence of pulses. [14] Circuit according to claim 3, wherein the comparator stage receives and processes signals from the receiver coils synchronously with the sequence of pulses. [15] Circuit according to claim 1, wherein the circuit is configured to determine a short or long distance, a one-way or two-way movement of the target and / or is configured to detect a linear position or rotation angle of the target. [16] Circuit according to claim 1, wherein the circuit and the inductive sensor are coupled in series. [17] Method for operating a circuit for use with an inductive sensor, wherein the inductive sensor comprises: a transmitter coil and two series-coupled receiver coils for receiving signals induced by a magnetic field generated by the transmitter coil when it is excited; and a movable conductive target for influencing the magnetic field, the procedure has the following features: Generating a sequence of pulses to discontinuously excite the transmitter coil.

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