Magnetic current sensing

Abstract

A magnetic field sensor architecture is disclosed that provides improved bandwidth and noise performance through the use of three distinct magnetic sensing elements: a spinning Hall- effect sensor for low-frequency and DC sensing, a non-spinning Hall-effect sensor for mid- frequency sensing, and a pickup coil for high-frequency sensing. The sensor combination includes a summing stage comprising frequency-selective filtering elements that process the outputs of the sensing elements to achieve a flat composite frequency response from DC to high frequencies. Two independently selectable crossover frequencies are used to decouple noise optimization from ripple suppression. In some embodiments, the pickup coil and non- spinning Hall-effect sensors are combined and processed through a shared path, with a simplified filter structure.

Description

[0001] Title: Magnetic current sensing

[0002] The present invention relates to a magnetic field sensor, an electrical current sensor comprising such a magnetic field sensor, an electric power converter comprising said electrical current sensor, a battery management system, an electric motor-generator, and an electric or a hybrid-electric vehicle comprising such electric power converter.

[0003] Magnetic field sensors are used in various applications, including automotive, consumer electronics, and industrial systems, where accurate measurement of magnetic fields across a wide frequency range is required. For example, the magnetic field sensor may be arranged at an electrical conductor, such as a current rail, to measure the magnetic field generated by an electric current in the current rail.

[0004] In conventional multipath magnetic field sensors, different pathways are dedicated to different frequency ranges. Typically, the high-frequency path incorporates a pickup coil, chosen for its differentiating characteristic, which significantly enhances the signal-to-noise ratio for high- frequency signals. Conversely, the low-frequency path employs a Hall-effect sensor, often in a spinning configuration, to mitigate sensor offset. Typically, the high-frequency path and the low-frequency path are combined in a summing stage to realize a wide-band magnetic field sensor. Both the pickup coil and the Hall-effect sensor may be integrated on-chip together with the read-out electronics in a Complementary Metal Oxide Semiconductor, CMOS, process.

[0005] To accurately process the high-frequency signal characterized by the pickup coil, the high- frequency path generally incorporates an integrator designed to flatten the output signal across its frequency range. However, the practical realization of an effective integrator presents a significant challenge. Real-world integrators are limited by their finite Direct Current, DC, gain, which means they essentially function as low-pass filters rather than true integrators. This limitation introduces several non-ideal characteristics, including parasitic poles that can cause a gain-flatness error over frequency. Additionally, the integrator may become saturated due to its own offset, particularly under conditions of high DC gain.

[0006] A second major limitation in conventional multipath architectures relates to the selection of the crossover frequency within the summing stage. The crossover frequency defines the point at which signal sensing responsibilities shift from the low-frequency path to the high-frequency path, playing an important role in minimizing the noise contribution of the sensor. In a typical design, the crossover frequency must also be sufficiently low to effectively filter out the ripple introduced by the spinning of the Hall-effect sensor in the low-frequency path. Balancing these requirements — optimizing for noise reduction while managing ripple — presents a substantial design challenge. Indeed, the optimal crossover frequency for minimizing noise might be considerably higher than what is required for effective ripple reduction, complicating the system’s overall design and limiting noise and ripple performance.

[0007] The present invention seeks to provide an improved magnetic field sensor.

[0008] According to an embodiment of the invention, there is provided a magnetic field sensor, comprising:

[0009] • a first sensing element comprising a pickup coil;

[0010] • a second sensing element comprising a low frequency magnetic sensor; and

[0011] • a summing stage configured to combine respective output signals of the first sensing element and the second sensing element, wherein the summing stage comprises a high-pass filter having a high-pass filter cutoff frequency and a low-pass filter comprising a low-pass filter cutoff frequency, the summing stage being configured to sum the output signal of the first sensing element filtered by the high-pass filter and the output signal of the second sensing element filtered by the low-pass filter,

[0012] • wherein the high-pass filter cutoff frequency is above the low-pass filter cutoff frequency,

[0013] • wherein the magnetic field sensor further comprises a third sensing element comprising a further magnetic sensor, and

[0014] • wherein the summing stage is configured to further combine an output signal of the third sensing element and to bandpass filter the output signal of the third sensing element between the low-pass filter cutoff frequency and the high-pass filter cutoff frequency.

[0015] Hybrid magnetic field sensors address the traditional tradeoff between resolution, limited by signal-to-noise ratio, and bandwidth by employing two types of CMOS-compatible sensing elements: Hall-effect sensors (also called Hall plates) and pickup coils. In such architectures, the Hall-plate is typically used to sense low-frequency magnetic field components, while the pickup coil is employed to sense high-frequency components. Optimizing the crossover frequency between these two sensing paths involves balancing conflicting performance constraints. From a noise optimization perspective, increasing the crossover frequency reduces the noise contribution of the pickup coil while increasing the noise contribution of the Hall plate. This tradeoff results in an optimal crossover frequency at which the total output noise is minimized. To achieve a flat overall response, the coil path output at the crossover frequency fx must match the Hall path output. Consequently, the coil path gain is defined as So / fx, where So is a constant determined by the system. Considering the equivalent noise bandwidth of a first-order low-pass filter, the total output noise power for the Hall path is directly proportional to the crossover frequency , and can be expressed as: ial!=2 / c7T?Hallx nfx where RHallis the output resistance of the Hall plate, k is Boltzmann’s constant, and T is the absolute temperature. Conversely, the coil path output noise power is inversely proportional to the crossover frequency fx, expressed as: where RCoilrepresents the coil's resistance. The total sensor output noise power results from the combined noise contributions of both the coil and Hall paths. If the crossover frequency is set too low, noise from the coil path dominates; if set too high, the noise contribution from the Hall path becomes dominant. Therefore, an optimal crossover frequency exists at which the noise contributions from both paths are equalized, achieving the minimum total output noise. This optimized crossover frequency is calculated as:

[0016] However, in most implementations, spinning techniques are applied to Hall plates. These techniques, which involve rotating the bias current and output terminals periodically, help cancel sensor offset by upmodulating it. A byproduct of spinning is the introduction of ripple tones at harmonics of the spinning frequency. Suppressing these ripple tones typically requires a very low crossover frequency, which contradicts the requirement for noise optimization.

[0017] Disclosed herein is a magnetic field sensor that includes three sensing elements, allowing the introduction of two separate crossover frequencies, thereby decoupling the tradeoffs between ripple suppression and noise performance. This magnetic field sensor comprises: a first sensing element comprising a pick-up coil for sensing high-frequency components, a second sensing element, such as a spinning Hall-effect sensor for sensing low-frequency and DC components; a third sensing element, such as a non-spinning Hall-effect sensor for sensing medium-frequency components.

[0018] The magnetic field sensor comprising three sensing elements enables the definition of two crossover frequencies: the low-pass filter cut off frequency may provide a crossover between the low-frequency and mid-frequency paths, which may be set low to attenuate ripple tones of the spinning Hall-effect sensor; the high-pass filter cut off frequency may provide a crossover between the mid-frequency and high-frequency paths, and which may be set independently to optimize for noise performance.

[0019] Noise and ripple suppression may be determined based on the two crossover frequencies, namely the low-pass filter cut off frequency and the high-pass filter cut off frequency, which may help enhance overall noise filtering. Furthermore, the three sensing elements and two crossover frequencies may improve suppression of ripple tones when using the spinning Halleffect sensor.

[0020] In an embodiment, the summing stage comprises an integrator having an integrator transfer function (1 / f) to integrate the output signal of the pickup coil. In the pickup coil path, an integrator may be used to compensate for the coil's differentiating behavior. This may be followed by the high-pass filter (HPF) to isolate the high-frequency content.

[0021] To read out the third sensing element, e.g. the non-spinning Hall plate, a band-pass filter (BPF) is employed with corner frequencies at the low-pass filter cutoff frequency and at the high- pass filter cutoff frequency to provide a pass band from the low-pass filter cut-off frequency to the high-pass filter cut-off frequency . The summing stage may accordingly comprise the bandpass filter. Notably, because spinning is not required in this path, offset ripple may not be present, and the BPF may effectively suppress any static offset without the need for spinning.

[0022] The summing stage may be configured to sum the output signal of the third sensing element filtered by the band pass filter to the output signal of the first sensing element filtered by the high-pass filter and the output signal of the second sensing element filtered by the low-pass filter. The summing stage may comprise a summation circuit configured to sum the output signal of the first sensing element filtered by the high-pass filter, the output signal of the second sensing element filtered by the low-pass filter and the output signal of the third sensing element filtered by the band pass filter. The summation circuit may be a multiple input analogue summing circuit, wherein the inputs are connected to the output signal of the first sensing element filtered by the high-pass filter, the output signal of the second sensing element filtered by the low-pass filter and the output signal of the third sensing element filtered by the band pass filter, respectively, and configured to sum the output signal of the first sensing element filtered by the high-pass filter, the output signal of the second sensing element filtered by the low-pass filter and the output signal of the third sensing element filtered by the band pass filter. As another example, the filters, or part of the filters, and the summation circuit may be integral as a multiple input filter, an example of which will be described further below.To read out the second sensing element, e.g. the spinning Hall-effect sensor, a low-pass filter (LPF) with a corner frequency at the low-pass filter cut-off frequency is used to isolate the low-frequency signal while attenuating the ripple tones at higher frequencies.

[0023] By combining the outputs of these three filtered paths, a flat and continuous frequency response is achieved across the full operating range — from DC to high frequencies.

[0024] The integrator and the high-pass filter may be combined to form a low-pass filter at the high- pass cut-off frequency.

[0025] For example, the integrator and high-pass filter in the high-frequency path may be combined into a single low-pass filter with a corner frequency at the low-pass filter cutoff frequency. Accordingly, the summing stage may comprise a combined low-pass filter at the high-pass cut-off frequency, and the integrator and the high-pass filter may be comprised in the combined low-pass filter at the high-pass cut-off frequency.

[0026] This configuration may simplify the design by eliminating the need for a standalone integrator. Implementing an ideal integrator may be inherently challenging, as practical integrators exhibit finite DC gain, resulting in a low-frequency pole. When used for the readout of a pickup coil, this non-ideal behavior may prevent the output signal from remaining flat over the required frequency range, which may introduce gain flatness errors. Moreover, the high DC gain of an integrator may amplify small input offsets, potentially driving the output into saturation. By combining the integrator and the high pass filter into a (combined) low-pass filter exhibiting limited DC gain, these issues are mitigated. The phrasing that the integrator and the high-pass filter are comprised in the combined low-pass filter may be understood in that the integrator transfer function of the integrator and the high-pass filter transfer function of the high-pass filter are comprised in a low-pass filter transfer function, i.e. result in a low-pass filter transfer function. The integrator and the high pass filter are accordingly implemented as the combined low-pass filter.

[0027] In an embodiment, the summing stage is configured to function as a (combined) band-pass filter for a combination of the output signals of the first and third sensing elements and as the low-pass filter for the output signal of the second sensing element. In other words, the summing stage may comprise a combined band-pass filter for a combination of the output signals of the first and third sensing elements. The combined band-pass filter may be configured to filter both the output signals of the first and third sensing elements.

[0028] For example, the outputs of the pickup coil and the third sensing element (e.g. a non-spinning Hall plate) are combined prior to signal conditioning. Instead of having separate filters for each element, the combined signal may be processed by a single combined band-pass filter, which may simplify the analog front-end. A pass band of the combined band-pass filter may extend from the low-pass cut-off frequency to the high-pass cut-off frequency. The physical combination may for example be implemented by connecting the pickup coil and non-spinning Hall plate in series, allowing their output voltages to be added directly. The resulting signal exhibits a flat frequency response in the low-frequency range, e.g. determined by the Hall plate, and may transition to a differentiating response at higher frequencies, where the inductive characteristics of the pickup coil may become dominant. This configuration may reduce circuit complexity by eliminating the need for separate filtering paths, enabling both signal components to be processed through a unified filter stage. The integrator and the high- pass filter may be comprised in the band-pass filter.

[0029] The summing stage may comprise the combined low-pass filter at the high-pass cutoff frequency for the combination of the output signals of the first and third sensing elements and a summing filter comprising a summing high-pass filter at the low-pass cut-off frequency for the low-pass filtered combination of the output signals of the first and third sensing elements and a summing low-pass filter at the low-pass cut-off frequency for the output signal of the second sensing element.

[0030] Instead of using a band-pass filter after combining the first sensing element (e.g. the pick-up coil) and the third sensing element (e.g. the non-spinning Hall plate), a low-pass filter with a corner frequency at the high-pass cut-off frequency is employed. The output of this low-pass and the output of the second sensing element, e.g. the spinning Hall plate, path are then combined in a shared summing filter. This shared summing filter simultaneously acts as a high-pass filter (HPF) with corner frequency at the low-pass cut-off frequency for the combined high- / mid-frequency path, and acts as a low-pass filter (LPF) with the same low-pass cutoff frequency for the low-frequency path. This shared architecture may simplify the overall system while potentially ensuring precise alignment of the crossover frequencies, since the same resistor and capacitor components define both the HPF and LPF characteristics.

[0031] The summing filter of the summing stage may comprise a second-order passive filter comprising two resistors and two capacitors.

[0032] The second-order passive filter may comprise two inputs for a low frequency path and a high frequency path, respectively. The second-order design may offer improved attenuation characteristics: the transfer function from the low-frequency path, LFP, input to the output may exhibit a second-order low-pass response, with two poles. Beyond the second pole, the response may roll off at -40 dB / decade, which may significantly improve the suppression of spinning-induced ripple tones compared to a first-order filter. Conversely, the transfer function from the high- / mid-frequency path, HFP, input to the output exhibits a high-pass behavior, with two poles and two zeroes. This response may complement the low-frequency path. The complementary characteristics of the HFP and LFP may ensure that the sum of their transfer functions equals unity (TFHFP + TFLFP = 1) across the frequency band of interest, thereby potentially preserving a flat overall system response. This technique may be further extended to implement higher-order crossover networks, such as third- or fourth-order filters, to achieve even sharper roll-off and enhanced selectivity.

[0033] For example, a spinning frequency of the spinning Hall-effect sensor may be at least 10 times larger, preferably at least 100 times larger than the low-pass filter cutoff frequency of the low- pass filter, thereby providing a high suppression of a ripple at the spinning frequency.

[0034] In an embodiment, the low-pass filter comprises a variable gain stage to match the sensitivities of the first and second sensing elements. Gain imbalances, due to e.g. component tolerances, may be taken into account thereby. The variable gain stage may further be configured to match the sensitivities of the first and second sensing elements to a sensitivity of the third sensing element. In an embodiment, the magnetic field sensor further comprises a final stage having an adjustable gain to adjust an absolute sensitivity of the magnetic field sensor.

[0035] According to a further aspect of the invention, there is provided an electrical current sensor for measuring electrical current in a current rail comprising the magnetic field sensor according to the invention, the magnetic field sensor configured to sense a magnetic field generated by the electrical current in the current rail. Current sensors based on sensing the magnetic field induced by current running through a conductor are also referred to as contactless or isolated current sensors.

[0036] According to a further aspect of the invention, there is provided an electric power converter comprising the electrical current sensor according to the invention.

[0037] According to a further aspect of the invention, there is provided a battery management system comprising the electric power converter according to the invention.

[0038] According to a further aspect of the invention, there is provided an electric motor-generator comprising the electric power converter according to the invention.

[0039] According to a further aspect of the invention, there is provided an electric or hybrid-electric vehicle comprising the electric power converter according to the invention.

[0040] With the electrical current sensor, the electric power converter, the battery management system, the elector motor-generator and the electric or hybrid-electric vehicle, the same or similar effects may be achieved as with the magnetic field sensor according to the invention. Also, the same or similar embodiments as described with reference to the magnetic field sensor may be provided for the electrical current sensor, the electric power converter, the battery management system, the elector motor-generator and the electric or hybrid-electric vehicle, which may achieve the same or similar effects as described with reference to the magnetic field sensor. The magnetic field sensor according to the invention may be described by the following numbered clauses which form part of the description:

[0041] 1 . A magnetic field sensor, comprising:

[0042] • a first sensing element comprising a pickup coil;

[0043] • a second sensing element comprising a low frequency magnetic sensor; and

[0044] • a summing stage configured to combine respective output signals of the first sensing element and the second sensing element, wherein the summing stage comprises high-pass filter having a high-pass filter cut-off frequency and a low- pass filter comprising a low-pass filter cut-off frequency, the summing stage being configured to sum the output signal of the first sensing element filtered by the high-pass filter and the output signal of the second sensing element filtered by the low-pass filter,

[0045] • wherein the high-pass filter cut-off frequency is above the low-pass filter cut-off frequency,

[0046] • wherein the magnetic field sensor further comprises a third sensing element comprising a further magnetic sensor, and

[0047] • wherein the summing stage is configured to further combine an output signal of the third sensing element and to band-pass filter the output signal of the third sensing element between the low-pass filter cut-off frequency and the high- pass filter cut-off frequency.

[0048] 2. The magnetic field sensor of clause 1 , wherein the third sensing element comprises a non-spinning Hall-effect sensor.

[0049] 3. The magnetic field sensor of clause 1 or 2, wherein the low frequency magnetic sensor comprises a spinning Hall-effect sensor.

[0050] 4. The magnetic field sensor of clause 3, wherein a spinning frequency of the spinning Hall-effect sensor is at least 10 times larger, preferably at least 100 times larger than the low-pass filter cut-off frequency of the low-pass filter.

[0051] 5. The magnetic field sensor of any one of the preceding clauses, wherein the summing stage comprises an integrator transfer function to integrate the output signal of the pickup coil and wherein the integrator and the high-pass filter are combined to form a low-pass filter at the high-pass cut-off frequency. 6. The magnetic field sensor of any one of the preceding clause, wherein the summing stage is configured to function as a band-pass filter for a combination of the output signals of the first and third sensing elements and as a low-pass filter for the output signal of the second sensing elements.

[0052] 7. The magnetic field sensor of clause 6, wherein the summing stage comprises a second-order passive filter comprising two resistors and two capacitors.

[0053] 8. The magnetic field sensor of any one of the preceding clauses, wherein the low-pass filter comprises a variable gain stage to match the sensitivities of the first and second sensing elements.

[0054] 9. The magnetic field sensor of any one of the preceding clauses, further comprising a final stage having an adjustable gain to adjust an absolute sensitivity of the magnetic field sensor.

[0055] 10. An electrical current sensor for measuring electrical current in a current rail comprising a magnetic field sensor as described in any one of the preceding clauses, the magnetic field sensor configured to sense a magnetic field generated by the electrical current in the current rail.

[0056] Further embodiments, features and effects of the invention will be explained with reference to the enclosed drawing, showing non-limiting embodiments of the invention, wherein:

[0057] Figure 1 illustrates a conventional hybrid magnetic field sensor architecture.

[0058] Figure 2 illustrates a hybrid magnetic field sensor architecture in accordance with an embodiment of the present invention.

[0059] Figure 3 illustrates a hybrid magnetic field sensor architecture in accordance with another embodiment of the present invention.

[0060] Figure 4 illustrates a further embodiment of a hybrid magnetic field sensor architecture in accordance with the present invention. Figure 5 provides a schematic diagram illustrating the combination of sensing elements employed in the embodiment of Figure 4.

[0061] Figure 6 illustrates yet another embodiment of a hybrid contactless current sensor architecture in accordance with the present invention.

[0062] Figure 7 provides a schematic diagram of a summing filter circuit utilized in the embodiment of Figure 6.

[0063] Figure 8 illustrates the frequency response of the transfer functions in the summing filter described with reference to Figure 7.

[0064] It is noted that throughout the figures, similar or the same reference numerals may refer to the same or similar items.

[0065] Figure 1 illustrates a conventional hybrid contactless current sensor architecture. The system includes two magnetic sensing elements, SE1 and SE2, which are positioned to sense the magnetic field. In case of a contactless current sensor these elements will be positioned close to a current rail to sense the magnetic field proportional to the current in the current rail. The outputs of these sensing elements are processed and combined within a summing stage to produce a unified output signal. The first sensing element, SE1 , is a pickup coil CL. Owing to its differentiating nature, the output of SE1 increases with frequency, making it suitable for detecting high-frequency components of the magnetic field. The second sensing element, SE2, is responsible for sensing the DC and low-frequency components. SE2 may be implemented as a spinning Hall-effect sensor SHS, which comprises of one or more Hallplates which may be sequentially read out in different orientations. This provides a flat frequency response in the low-frequency range, but may introduce ripple tones due to the spinning mechanism. The outputs of SE1 and SE2 are routed to a summing stage SST, which includes signal conditioning blocks for each path. The signal from SE1 is first processed by an integrator I NT to compensate for its differentiating behavior and recover a frequencyindependent signal. Following the integrator, a high-pass filter HPF with a corner frequency fx is applied to suppress residual low-frequency content and noise. Simultaneously, the output of SE2 is passed through a low-pass filter LPF with the same corner frequency fx, which serves to reject high-frequency components and spinning-induced ripple tones. By adding the outputs of the high-pass filter HPF and the low-pass filter LPF at summation circuit SC, the resulting output OUT exhibits a flat frequency response spanning from DC up to high frequencies. Figure 2 illustrates a hybrid magnetic field sensor architecture according to an embodiment of the present invention. Unlike the conventional design shown in Figure 1 , this embodiment includes three magnetic sensing elements, denoted as the first sensing element SE1 , the second sensing element SE2, and the third sensing element SE3. Each sensing element is configured to detect a distinct frequency band of the magnetic field, for example generated by a current in the nearby current rail. The second sensing element SE2, is implemented as a spinning Hall-effect sensor SHS and is responsible for sensing DC and low-frequency components of the magnetic field, specifically within the frequency range from DC up to a low- pass filter cut-off frequency, e.g. first crossover frequency fXi. The third sensing element SE3 is designed to sense the medium-frequency range, between fxi and a high-pass filter cut-off frequency, e.g. second crossover frequency fx2. In this embodiment, the third sensing element SE3 may be realized as a non-spinning Hall-effect sensor NHS, which eliminates spinning- induced ripple and provides a stable response in the mid-frequency band. The first sensing element SE1 is a pickup coil CL that detects high-frequency components, namely those above the high-pass filter cut-off frequency fx2. Due to its differentiating nature, the first sensing element SE1 produces a frequency-dependent output signal, which requires compensation to achieve a flat frequency response. The outputs of the first, second and third sensing elements, SE1 , SE2, and SE3 are each routed to a summing stage SST, which comprises the complete signal conditioning and combining circuitry. Within the summing stage, the output of SE2 is processed through a low-pass filter LPF with a low-pass filter cut-off frequency at fxi , isolating the low-frequency content. The output of SE3 is processed through a band-pass filter BPF centered between the low-pass filter cut-off frequency fxi and the high-pass filter cut-off frequency fx2, targeting the mid-frequency range. The output of the first sensing element SE1 is passed through an integrator I NT to flatten its differentiating behavior, followed by a high- pass filter HPF with a cut-off frequency at the high-pass filter cut-off frequency fx2, isolating the high-frequency components. These filtered and conditioned signals are then combined at summation circuit SC within the summing stage to form a unified output OUT. The introduction of two distinct crossover frequencies in the three-path architecture allows for enhanced design flexibility. The first crossover frequency fxi may be selected sufficiently low to attenuate ripple tones originating from the second sensing element SE2, such as the spinning Hall-effect plate. Similarly, the second crossover frequency fx2 may be optimized independently to achieve improved noise performance. Figure 3 depicts an alternative embodiment of a hybrid magnetic field sensor architecture, based on the configuration shown in Figure 2. Similar to Figure 2, this embodiment includes three magnetic sensing elements: Sensing element SE1 (e.g. a pickup coil CL) for high- frequency sensing, sensing element SE2 (e.g. a spinning Hall-effect plate SHS) for low- frequency and DC sensing, and sensing element SE3 (e.g. a non-spinning Hall-effect plate NHS) for mid-frequency sensing. Each sensing element is connected to a dedicated signal conditioning path within a common summing stage SST. As compared to the embodiment depicted in Figure 2, a difference in this embodiment lies in the signal processing applied to the output of the first sensing element SE1 , the pickup coil. Instead of using a separate integrator followed by a high-pass filter, the first sensing element SE1 path employs a single combined low-pass filter C-LPF with a corner frequency at the high-pass filter cut-off frequency fx2. This combined low-pass filter C-LPF is designed to simultaneously flatten the frequencydependent output of the coil and attenuate signal components below the high-pass filter cutoff frequency fx2, effectively combining the roles of the integrator and high-pass filter in a simplified structure. The outputs from all three signal paths are then summed by summing circuit SC within the summing stage to produce a unified output signal OUT exhibiting a flat frequency response from DC to high frequencies. In terms of system functionality, including ripple suppression and noise performance optimization, this embodiment offers similar benefits to the architecture shown in Figure 2. However, the present embodiment may achieve these benefits with a simplified implementation, substituting the integrator I NT and HPF combination with a single LPF in the first sensing element SE1 signal path.

[0066] Figure 4 depicts an alternative embodiment of a hybrid magnetic field sensor architecture, based on the configuration shown in Figure 3. As in previous embodiments, the sensor includes three magnetic sensing elements: the first sensing element SE1 (e.g. the pickup coil CL) for high-frequency sensing, the second sensing element SE2 (e.g. the spinning Hall-effect sensor SHS) for low-frequency and DC sensing, and the third sensing element SE3 (e.g. the non-spinning Hall-effect sensor NHS) for mid-frequency sensing. In this embodiment, the signal processing path for the second sensing element SE2 remains unchanged. The key difference lies in the combined processing of the first and third sensing elements SE1 and SE3 at the summing state SST. Instead of routing the outputs of the first and third sensing elements SE1 and SE3 through separate paths with distinct filters, their outputs are first combined, and the resulting signal is then passed through a combined band-pass filter (C-BPF) with corner frequencies at the high-pass cut-off frequency fxi and the low-pass cut-off frequency fx2. This combined band-pass filter C-BPF is configured to isolate the mid-to-high frequency range and inherently accommodates the combined characteristics of the pickup coil and non-spinning Hall plate. The filtered output from the first and third sensing element SE1-SE3 combination and the filtered output from the second sensing element SE2 are then summed by summing circuit SC within the summing stage to produce a unified output signal OUT. In terms of functional performance, including suppression of ripple tones and optimization of noise characteristics, this embodiment may provide benefits comparable to those achieved in the embodiment of Figure 3. However, it may achieve these benefits with a more simplified architecture by replacing the separate low-pass filter LPF for the first sensing element SE1 and the band-pass filter BPF for the third sensing element SE3 with a single band-pass filter C-BPF applied to the combined first and third sensing elements SE1 and SE3 outputs.

[0067] Figure 5 illustrates an example implementation of how the outputs of first and third sensing elements SE1 and SE3 can be combined, as used in the architecture shown in Figure 4. In this embodiment, a pickup coil CL (as an example of the first sensing element SE1) is placed in series with a non-spinning Hall-effect sensor NHS (as an example of the third sensing element SE3). This physical arrangement allows both sensing elements to respond to the same magnetic field while naturally summing their respective output signals. By connecting the sensing elements in series, the voltage contributions from the pickup coil and the nonspinning Hall-effect sensor (Hall plate) are electrically added at the analog voltage level. The resulting composite signal is then processed through a (combined) band-pass filter C-BPF, configured with corner frequencies at fxi and fx2, as described in Figure 4. The output of this band-pass filter C-BPF is subsequently combined with the output from the spinning Hall-effect sensor SHS (as an example for the second sensing element SE2), which is processed through a low-pass filter LPF with a corner frequency at fxi. The summation of these filtered signals yields a unified output which may exhibit a flat frequency response from DC through high frequencies. This embodiment demonstrates a potentially straightforward and / or efficient method for implementing the analog summation of the first and third sensing elements SE1 and SE3, possibly reducing circuit complexity while enabling to maintain the desired frequency-domain response characteristics.

[0068] Figure 6 depicts an alternative embodiment of a hybrid magnetic field sensor architecture, based on the configuration shown in Figure 4. As in that configuration, the outputs of sensing elements SE1 (e.g. the pickup coil CL) and SE3 (e.g. the non-spinning Hall-effect sensor NHS) are combined at the signal level, forming a single high-frequency path. The key difference in this embodiment lies in the signal processing that follows the combination of the first and third sensing elements SE1 and SE3 at the summing state SST. Instead of using a (combined) band-pass filter C-BPF, the combined signal is routed through a (combined) low-pass filter C- LPF with a corner frequency at fx2. This combined low-pass filter C-LPF serves to limit the bandwidth of the combined first and third sensing element SE1-SE3 signal to frequencies below fx2, effectively passing both mid- and high-frequency components while attenuating any undesired higher-frequency noise. In this architecture, the filtered output of the first and third sensing element SE1-SE3 path and the output of second sensing element SE2 (spinning Halleffect plate SHS, responsible for DC and low-frequency sensing) are then combined through a shared summing filter SF. For the second sensing element SE2 path, the summing filter functions as a summing low-pass filter SLP with a corner frequency at fXi, allowing only the low-frequency content to pass. For the first and third sensing element SE1-SE3 path, the same filter behaves as a summing high-pass filter SHP with the same corner frequency fXi, passing only the mid- and high-frequency content. This dual-mode filtering may enable efficient frequency-domain separation while reducing component duplication. Functionally, this embodiment may achieve comparable benefits to those of Figure 4, including ripple tones suppression and optimized noise performance. However, an advantage of this embodiment may lie in the use of a shared summing filter SF for both signal paths, i.e. the signal path of the first and third sensing element and the signal path of the second sensing element. By utilizing identical components to define both the high-pass and low-pass corner frequencies of the summing filter, the design may inherently minimize pole mismatch. Since mismatches between these poles may introduce gain flatness errors across the frequency spectrum, this shared-filter approach enhances gain flatness over frequency.

[0069] Figure 7 illustrates an example implementation of the summing stage SST filter used in the hybrid magnetic field sensor architecture shown in Figure 6. In this embodiment, the summing stage SST filter is realized as a second-order passive filter, comprising two resistors and two capacitors arranged to provide both summation and frequency-selective behavior. The filter functions as a high-pass filter for the first input, I N 1 , and acts as a low-pass filter for the second input, IN2. By sharing this filtering structure across both paths, the summing filter may enable efficient signal combination with minimal component overhead. Additionally, the second-order design may enhance the attenuation characteristics of the filter, which is particularly beneficial for suppressing ripple artifacts introduced by the spinning mechanism of the second sensing element SE2 when making use of a spinning Hall-effect sensor. The filter's order can be further increased, if desired, to improve the rejection of unwanted frequency components. A key benefit of employing a shared summing filter may lie in the fact that both the high-pass and low-pass corner frequencies of the summing filter are determined by the same set of resistors and capacitors. As a result, any component variations (e.g., due to temperature drift or manufacturing tolerances) may affect both poles in a correlated manner. This correlation may minimize mismatches between the high-pass and low-pass filter corners, thereby possibly reducing gain flatness errors across the frequency spectrum.

[0070] Figure 8 illustrates the frequency response of the transfer functions associated with the low- pass and high-pass paths in the summing filter described in Figure 7. The low-pass transfer function (TFLFP), defined as OUT / IN2, corresponds to a second-order low-pass filter characterized by two poles, located at frequencies p1 and p2. This path attenuates high- frequency components while allowing low-frequency signals to pass. The high-pass transfer function (TFHFP), defined as OUT / IN1 , also includes two poles at p1 and p2. Additionally, it features two zeros: One at DC, which defines the high-pass nature by blocking low-frequency content and the second one at p1+p2. The two transfer functions may be complementary, such that their sum is unity across all frequencies: TFHFP + TFLFP = 1. When these two transfer functions are combined at the output, the result may be a frequency response that is flat across the full spectrum, from DC to high frequencies.

[0071] The magnetic field sensor as described with reference to Figures 2 - 8 may be arranged proximate to a current rail to sense a magnetic field generated by an electric current in the current rail. A magnitude of the electric current in the current rail may be determined from a magnitude of the magnetic field. Accordingly, a current sensor may be provided configured to measure the electric current in the current rail. In the present document, the terms electric and electrical are to be understood so as to be the same.

[0072] The current sensor may be comprised in an electric power converter, such as a DC / DC converter, a DC / AC converter, an AC / DC converter, or an AC / AC converter. The current sensor and / or the electric power converter may for example be comprised in a battery management system, an electric motor-generator, and / or an electric or a hybrid-electric vehicle.

Claims

CLAIMS1 . A magnetic field sensor, comprising:• a first sensing element comprising a pickup coil;• a second sensing element comprising a low-frequency magnetic sensor; and• a summing stage configured to combine respective output signals of the first sensing element and the second sensing element, wherein the summing stage comprises a high-pass filter having a high-pass filter cutoff frequency and a low-pass filter comprising a low-pass filter cutoff frequency, the summing stage being configured to sum the output signal of the first sensing element filtered by the high-pass filter and the output signal of the second sensing element filtered by the low-pass filter,• wherein the high-pass filter cutoff frequency is above the low-pass filter cutoff frequency,• wherein the magnetic field sensor further comprises a third sensing element comprising a further magnetic sensor, and• wherein the summing stage is configured to further combine an output signal of the third sensing element and to bandpass filter the output signal of the third sensing element between the low-pass filter cutoff frequency and the high-pass filter cutoff frequency.

2. The magnetic field sensor of claim 1 , wherein the summing stage comprises an integrator having an integrator transfer function to integrate the output signal of the pickup coil.

3. The magnetic field sensor of claim 2, wherein the summing stage comprises a combined low-pass filter at the high-pass cutoff frequency, and wherein the integrator and the high-pass filter are comprised in the combined low-pass filter at the high-pass cut-off frequency.

4. The magnetic field sensor of any one of the preceding claims, wherein the summing stage comprises a band-pass filter for a combination of the output signals of the first and third sensing elements.

5. The magnetic field sensor according to claims 3 and 4, wherein the integrator and the high-pass filter are comprised in the band-pass filter.

6. The magnetic field sensor according to claim 4 or 5, wherein a pass band of the bandpass filter extends from the low-pass cut-off frequency to the high-pass cut-off frequency.

7. The magnetic field sensor according to any one of claims 4 - 6, wherein the first sensing element and the third sensing element are connected in series.

8. The magnetic field sensor according to any one of claims 3 - 7, wherein the summing stage comprises the combined low-pass filter at the high-pass cut-off frequency for the combination of the output signals of the first and third sensing elements and a summing filter comprising a summing high-pass filter at the low-pass cut-off frequency for the low-pass filtered combination of the output signals of the first and third sensing elements and a summing low-pass filter at the low-pass cut-off frequency for the output signal of the second sensing element.

9. The magnetic field sensor of claim 8, wherein the summing filter of the summing stage comprises a second-order passive filter comprising two resistors and two capacitors.

10. The magnetic field sensor of any one of the preceding claims, wherein the third sensing element comprises a non-spinning Hall-effect sensor.

11. The magnetic field sensor of any one of the preceding claims, wherein the low frequency magnetic sensor comprises a spinning Hall-effect sensor.

12. The magnetic field sensor of claim 11 , wherein a spinning frequency of the spinning Hall-effect sensor is at least 10 times larger, preferably at least 100 times larger than the low-pass filter cut-off frequency of the low-pass filter.

13. The magnetic field sensor of any one of the preceding claims, wherein the low-pass filter comprises a variable gain stage to match the sensitivities of the sensing elements.

14. The magnetic field sensor of any one of the preceding claims, further comprising a final stage having an adjustable gain to adjust an absolute sensitivity of the magnetic field sensor.

15. An electrical current sensor for measuring electrical current in a current rail comprising a magnetic field sensor of any one of the preceding claims, the magnetic field sensor configured to sense a magnetic field generated by the electrical current in the current rail.

16. An electric power converter comprising the electrical current sensor according to claim 15.

17. A battery management system comprising the electric power converter according to claim 16.

18. An electric motor-generator comprising the electric power converter according to claim 16.

19. An electric or hybrid-electric vehicle comprising the electric power converter according to claim 16.

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