Chopping system and method

Abstract

Embodiments of the present application relate to chopping systems and methods. Systems and methods are provided herein, wherein a chopping modulator and a chopping demodulator are described, and a chopping device (11) having a variable chopping frequency is provided. A feedback path (16) is provided for reducing ripple and / or residual offset caused by the variable chopping frequency.

Description

Technical Field

[0001] The present application relates to systems and corresponding methods that employ chopping (sometimes referred to as "Zerhacken" in German). Background Art

[0002] Chopping is a technique in which the input and output signals of a device are modulated using a chopping signal having a chopping frequency. The device may be, for example, an analog-to-digital converter or an amplifier and is generally referred to as a chopping device within the scope of this application. For example, the chopping signal having the chopping frequency may alternately take on values of +1 and -1, and the input and output signals of the chopping device are multiplied by this signal for modulation.

[0003] This chopping eliminates or at least reduces the DC voltage offset of the chopping device. However, chopping causes ripples at the chopping frequency. To eliminate these ripples, conventional methods require low-pass filters or notch filters, which can mean additional implementation costs, additional delay times, and undesirable transient or overshoot characteristics. In addition, using such filters, interfering signals may also appear at frequencies that are several times the chopping frequency. This can occur in the event of undesirable interference coupling at the output of the chopping component and lead to undesirable demodulation effects, which can distort the useful signal in the DC component or in the useful frequency range, especially in systems with high-frequency interference from the system environment.

[0004] In some methods, the chopping frequency is varied randomly or pseudo-randomly in order to reduce such interference signals at frequencies that are multiples of the chopping frequency. However, this has the disadvantage that the offset component cannot be fully modulated up to the fixed chopping frequency and then filtered out in a targeted manner. Instead, mixed frequencies result in a downward folding (downmodulation), which can be perceived as increased noise in the useful signal. These mixed frequencies are generated by the continuously varying chopping frequency. Summary of the Invention

[0005] A system and method according to the present application are provided.

[0006] In one embodiment, a system is provided, comprising: a chopping apparatus having a chopping modulator at an input and a chopping demodulator at an output;

[0007] means for providing a chopping signal having a variable chopping frequency to said chopping modulator and said demodulator; and

[0008] A feedback path is provided from the output of the chopping demodulator to a chopping arrangement arranged to reduce ripple and / or offset caused by the variable chopping frequency.

[0009] In another embodiment, a method is provided, comprising:

[0010] providing a chopping signal having a variable chopping frequency to the chopping component, and

[0011] Feedback is provided from the output of the chopping assembly to the chopping device to compensate for ripple or offset caused by the variable chopping frequency.

[0012] The above summary provides only a brief overview of some embodiments and should not be construed as limiting, as other embodiments may have features that differ from those discussed above. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a block diagram of a system according to one embodiment.

[0014] Figure 2 is a flowchart for explaining a method according to some embodiments.

[0015] Figure 3 by Figures 3A to 3D FIG. 1 shows an apparatus according to an embodiment in four different operating phases.

[0016] Figure 4A and Figure 4B A graph illustrating the variable chopping frequency is shown.

[0017] Figure 5A is a block diagram used to illustrate the operation of some embodiments.

[0018] Figure 5B It is the use of Figure 5A Examples of signals generated by the device.

[0019] Figure 6 is a circuit diagram of a device for generating a chopping signal having a pseudo-random chopping frequency.

[0020] Figure 7 is a diagram of an implementation example of a feedback path.

[0021] Figures 8 to 10 are graphs for explaining the effects of some embodiments compared with conventional systems. DETAILED DESCRIPTION

[0022] Different embodiments are explained in detail below. These embodiments are for illustrative purposes only and should not be construed as restrictive. Although specific implementation details are described in some embodiments, in other embodiments, other implementations with other features (e.g., components, processes, elements, etc.) may be used.

[0023] The features of the different embodiments can be combined with each other unless otherwise stated. Variations and modifications described for one of the embodiments can also be applied to the other embodiments and will not be explained again. In addition to the features explicitly shown and described, other features can be provided, such as those used in conventional systems with chopping devices.

[0024] The connections and couplings described herein are electrical connections or electrical couplings, unless otherwise specified. Such connections or couplings may be modified as long as the basic working mode of the connection or coupling remains substantially unchanged.

[0025] Figure 1 A system according to one embodiment is shown.

[0026] Figure 1 The system includes a signal source 10. The signal source 10 may have, for example, a sensor for detecting a physical variable and, if necessary, other components for processing the signal output by the sensor, such as a filter and an amplifier. Other types of signal sources, such as an audio signal source, may also be used.

[0027] The signal from the signal source 10 is supplied to a chopping device 11. The chopping device 11 has a chopping modulator 13 at its input and a chopping demodulator 14 at its output. The chopping device 11 can be any type of device that conventionally uses chopping, such as an analog-to-digital converter for converting an analog signal output from the signal source 10 into a digital signal, or an amplifier for amplifying the signal provided by the signal source 10. The output signal of the chopping device 11 is supplied to a signal receiver 12 after being demodulated by the chopping demodulator 14.

[0028] In the case of a signal source 10 comprising a sensor, the sensor signal can be further processed in the signal receiver 12, for example, and other devices can be controlled, for example, depending on the sensor signal. Other types of signal receivers that process the signal from the signal source can also be used.

[0029] also, Figure 1The system has a device 15 for generating a chopping signal c with a variable chopping frequency fchop. The signal c can, for example, have alternating values of +1 and -1, which are multiplied with the signal of the signal source 10 in the chopping modulator 13 or with the signal of the chopping device 11 in the chopping demodulator 14. Other signal sequences used in conventional choppers can also be used. The chopping signal c has a variable chopping frequency, that is to say, for example, the switching from +1 to -1 (or other signal values of the chopping signal c) does not take place at a fixed frequency, but varies around a certain frequency. This variation can be carried out according to a predetermined scheme (i.e. a predetermined frequency sequence), randomly, or pseudo-randomly. Possible implementations of this pseudo-random generation of a variable chopping frequency will be described later with reference to Figures 4 to 5. Figure 6 By using such a variable chopping frequency, interference signals at high frequencies can be reduced, for example, distributed over a larger frequency range and thus having a lower intensity. However, without further measures, ripple or offset in the output signal supplied to the signal receiver 12 may remain or be increased by the variable chopping frequency.

[0030] In order to suppress or reduce this effect, Figure 1 The system further provides a feedback path 16 from the output of the chopping demodulator 14 to the chopping device 11. The offset of the chopping device 11 is adjusted via the feedback path 16. Many chopping devices, such as analog-to-digital converters or amplifiers, offer the ability to adjust the offset. In an analog-to-digital converter, this can be achieved by adding or subtracting a settable digital value from the output; in the case of an amplifier, this can be achieved, for example, by setting the amplifier's bias voltage. In other embodiments, the input signal of the chopping device 11 can also be modified using the signal from the feedback path.

[0031] The feedback path can be analog, digital, or a mixture of the two, and by processing the signal output by the chopping demodulator 14, a compensation signal can be generated, with which the ripple and residual offset caused by the variable chopping frequency can be eliminated or at least reduced. To this end, the feedback path can have an integrator. The feedback path can have a filter function that completely or partially suppresses the effective signal of the system (i.e., the effective signal from the signal source 10 and processed by the chopping device 11) and allows the ripple and / or offset generated by the variable chopping frequency to pass, so that the chopping device 11 can be controlled inversely based on these ripples and / or offsets to then suppress these ripples and / or offsets at the output end of the system.

[0032] For example, if the chopping device 11 is an amplifier with an open-loop gain of G, the feedback function H at the amplifier causes an inverse function G / (1+GH) at the amplifier output. If the gain G is large enough, this results in a characteristic that is approximately proportional to 1 / H. When the feedback signal now represents ripple and / or offset, these ripples and / or offsets are suppressed. On the other hand, since the effective signal in the feedback path is suppressed, the effective signal at the output of the amplifier is rarely affected by the feedback.

[0033] By means of this combination of a variable chopping frequency and a feedback path, it is possible to take advantage of the advantages of the variable chopping frequency, in particular to reduce interference when the frequency is several times the fixed chopping frequency, and at the same time significantly reduce the ripple and offset to zero or close to zero. In addition, the modulation effect in subsequent systems such as the signal receiver 12 can be reduced, and the filtering of effective signals near the chopping frequency can be reduced. However, without the feedback path 16, the use of a variable chopping frequency would bring about the disadvantages described at the beginning. No low-pass filter or notch filter is required at the output of the chopper 14, and the disadvantages associated therewith do not occur. In addition, the sensitivity to high-frequency interference signals can be reduced. The increase in noise in the effective signal range, which is associated with the variable chopping frequency in conventional solutions, can also be reduced or avoided by the feedback path 16.

[0034] As described above, feedback path 16 causes effective filtering of the output signal. In some embodiments, the filter frequency of this filtering through the feedback path (e.g., the boundary frequency of the low-pass filter used to filter out the useful signal, as described above) is at most half the repetition frequency of the variable chopping frequency. The repetition frequency describes how quickly the frequency sequence repeats in a pseudo-random sequence or a predetermined order. In some implementations, this can increase the stability of the system, in particular by allowing the signal output from feedback path 16 to be better aligned to a stable value. In particular, this prevents the feedback path from following the changing chopping frequency. This can have the additional effect of less suppressing useful signals near the chopping frequency.

[0035] Additionally or alternatively, the filtering frequency may be at most half the minimum chopping frequency of the variable chopping frequency.

[0036] In some embodiments, the frequency range over which the variable chopping frequency of the chopping signal c varies is above the effective signal range, i.e., above the frequency range of the signal output by the signal source 10. This can prevent the ripple energy in the effective signal range from increasing. In some embodiments, a relatively wide frequency range is used above the effective signal range so as to distribute the energy as widely as possible when the frequency is several times the chopping frequency. For example, the effective frequency range can reach 200kHz, with an average chopping frequency of 300kHz, where the variable chopping frequency varies between 200kHz and 400kHz. In this case, the feedback path can then have a filtering frequency of less than 100kHz. However, these numerical examples are for illustrative purposes only, and other values are possible depending on the implementation.

[0037] Figure 2 A flow chart illustrating a method according to some embodiments is shown. For example, Figure 2 The method can be Figure 1 is implemented in the system and to avoid duplication refer to Figure 1 However, Figure 2 The method can also be implemented in other systems, such as the system described below, and is therefore not limited to any particular device. Figure 2 The method has two parts, but the described processes can be performed substantially simultaneously, as Figure 1 The same situation in .

[0038] In step 20, a chopping signal having a variable chopping frequency, such as Figure 1 The chopped signal c is provided to the chopping components, such as the chopping modulator 13 and the chopping demodulator 14. At 21, feedback is provided from the output to the chopping device, for example, so as to Figure 1 The feedback path 16 is described as setting the offset of the chopping device.

[0039] Figure 3, by Figures 3A to 3D Composition, showing a system according to another embodiment, wherein reference Figure 1 and Figure 2 The discussed technique is applied to the specific case of processing signals from a Hall sensor operating using the spinning current technique. In this technique, the terminals of the Hall sensor to which the bias current is delivered and the terminals to which the Hall voltage is tapped are cyclically exchanged, which can be used to compensate for the offset of the Hall sensor. Figures 3A to 3D , shows the application of a four-stage spinning current technique, where Figures 3A to 3D Each of the figures shows a stage denoted by PH1 to PH4 in the figure. Figure 3A Describe the device. Figures 3B to 3D Only the same devices are shown for the other stages.

[0040] The arrangement of Figure 3 has a Hall sensor 30, which is represented by a circuit of four resistors 31 to 34. The nodes between the resistors are labeled hnw, hne, hse and hsw.

[0041] When a bias current is applied between two opposing nodes, the Hall voltage can be tapped between two other nodes. Figure 3A In the case of , the bias current applied from node hnw to node hse. Figure 3A In the case of a Hall voltage, a Hall voltage is tapped between nodes hne and hsw and supplied to a chopper modulator 35. The output of the first chopper 35 is connected to a differential amplifier 37 via a DC voltage coupling 36, which transmits the DC component of the output signal of the chopper modulator 35. The differential amplifier 37 is an example of a chopper device.

[0042] The output signal of the differential amplifier 37 is supplied to the chopper demodulator 38. The output signal of the chopper demodulator 38 is buffered in the operational amplifier 39 and output. On the other hand, the output signal is supplied to a feedback path including an analog demodulator 310, an analog-to-digital converter 311, a feedback control device 312, and a digital-to-analog converter 313. The output signal of the digital-to-analog converter 313 changes the offset of the differential amplifier 37.

[0043] In operation, a chopping signal having a non-constant chopping frequency fchop (indicated by "fchop≠constant") is applied to the chopping modulator 35 and the chopping demodulator 38. In synchronization therewith, the spinning current method also operates at a non-constant frequency fspin, which may be an integer multiple of fchop (e.g., 2*fchop).

[0044] exist Figure 3AIn phase 1, as already explained, a bias current is applied between terminals hnw and hse, and a Hall voltage is tapped between terminals hne and hsw. This generates a voltage of +Vs+Voh-Vnl1, where Vs is the voltage actually measured due to the magnetic field, Voh is the offset of Hall sensor 30, and Vnl1 is the voltage generated by resistors 31 to 34, which in this case is caused by resistor 32, due to the fact that resistors 31 to 34 do not exhibit identical characteristics. This voltage is amplified by differential amplifier 37, with its offset Voa additionally added. The resulting voltage at the output of chopper 38 is +Vs+Voh+Voa-Vnl1. The output signal is demodulated again in demodulator 310 using the chopping frequency, and the offset of differential amplifier 37 is then set based on this modulated signal via feedback control 312. This feedback path can operate essentially as described above with respect to feedback path 16, with the useful signal being suppressed via feedback control 312 and differential amplifier 37 then controlled based on ripple and / or offset.

[0045] The lines in the chopper modulator 35 show an example of the connection between the Hall sensor 30 and the differential amplifier 37 in each phase PH1 to PH4. In the illustrated embodiment, this is essentially achieved by making Voh (Hall bridge offset) and Voa (amplifier offset) run synchronously, while in contrast, the sign of the signal Vs changes, so that the two can be separated and the offset can be suppressed, as described below. The lines in the chopper demodulator 38 show the connection from the differential amplifier 37 to the output terminal of the system (the positive output terminal, respectively, if a differential output is implemented).

[0046] exist Figure 3B In phase 2, a bias current is applied between terminals hsw and hne, i.e., with Figure 3A In the phase 1, the opposite direction is applied, and the output signal corresponds to -Vs-Voh-Vnl1. +Vs+Voh+Voa+Vnl1 is obtained as the output signal of the differential amplifier 37, and +Vs+Voh+Voa+Vnl1 is obtained as the output signal of the chopper demodulator 38. Figure 3C and Figure 3D In the phase of , the bias current 314 is then applied between the terminals hne and hsw with different polarities and the Hall voltage is tapped between the terminals hnw and hse. Figure 3C In the case of generating output voltage +Vs-Voh-Voa+Vnl2, and Figure 3D When these four output signals are added, the Voh and Voa components compensate for each other and the value of 4Vs is retained.

[0047] The above description primarily applies to (DC) signals that remain constant over time. In this case, the AC component (AC) is already maintained at a high modulated chopping frequency. For example, the Voa component disappears over time, but it appears at the output as an AC voltage signal with +Voa and -Voa. The frequency of the alternation between +Voa / -Voa is equal to the chopping frequency.

[0048] Feedback paths 310 to 313 now operate as negative feedback of this AC voltage signal in differential amplifier 37 , so that after a transient oscillation of the feedback path (corresponding to its filter frequency), the AC component disappears at the output of the sensor.

[0049] Furthermore, by combining variable chopping frequency with feedback, it is possible to achieve interference signals at higher frequencies while suppressing offset or ripple caused by the variable chopping frequency.

[0050] Figure 4A and Figure 4B An example of a variable chopping frequency over time is shown, wherein the chopping frequency is plotted against time. Figure 4A In FIG, eleven periods of chopping signals 1 to 11 are plotted over time, wherein the frequency is between 300 and 180 kHz. Such a frequency can be generated, for example, using a pseudo-random number generator. Figure 4B Another example of variable frequency is shown in . Here, the pattern of frequencies is repeated after a certain time, where Figure 4B Two repetitions are shown in . Therefore, the repetition has the repetition frequency explained above.

[0051] A possible approach for generating a variable chopping frequency will now be explained.

[0052] Figure 5A A device is shown, which includes an oscillator section 50 supplied by a supply voltage VDDA and a section 51 supplied by a supply voltage VDDD and including frequency dividers 52 to 55 and pseudo-random generators 56 and 57. One possible approach to generating a chopping signal with a variable chopping frequency is to feed a random sequence from pseudo-random generator 57 to a dither register of the oscillator section, thereby varying the frequency of the chopping signal. This can be done, for example, by selecting a binary-weighted current source corresponding to the dither register for the integrator current of the relaxation oscillator. In the case of a digitally controlled oscillator (DCO), the dither register can be part of the control word, and thus the frequency can also be varied. Otherwise, the frequency is set by the Trim_OSC signal. Oscillator section 50 can, for example, output a signal with a frequency of approximately 6 MHz, which can be varied as necessary by controlling the dither register.

[0053] In addition or as an alternative to the variations made via the dither register, the output signal of the pseudo-random generator 56 can control a variable frequency divider 52 which variably divides the frequency of its input signal by a factor between 5 and 8 (5, 6, 7, 8 in the example shown) and thereby generates a variable frequency. Figure 5A In the exemplary embodiment, fixed frequency dividers 53 and 54 are further connected downstream of the variable frequency divider to divide the frequency by two to generate the chopping signal Clk_chop, which can have a frequency of 250 kHz, 187.5 kHz, 214.28 kHz, or 300 kHz in the numerical example. Furthermore, a signal Clk_spin is branched off between frequency dividers 53 and 54, which can serve as a clock signal for the spinning current method and has twice the frequency of signal Clk_chop. Furthermore, the oscillator signal is fed directly to frequency divider 55, which divides the signal by two to generate signal Clk_adc, which can be used, for example, as a clock signal for an analog-to-digital converter.

[0054] Figure 5A All numbers in the examples are for illustration only, and other values, other numbers of dividers, or other division ratios may also be used. In addition, the dither register and variable divider 52 of the oscillator section 50 may be used together, but may also be used independently of each other to generate a variable chopping frequency.

[0055] Figure 5B It is shown that a 1000W CMOS process can be used without a dither register but with a variable divider 52. Figure 5A An example of a device to generate a signal. Figure 5B The curve 58 in FIG. 5 shows an example of a chopping signal Clk_chop, wherein the frequency division ratio of the variable frequency divider 52 is shown above. In addition, the phases of the spinning current technique are described based on the signal Clk_spin running at twice the frequency. This also serves only as an illustrative example.

[0056] Figure 6 An example of a pseudo-random generator is shown, which is implemented using a shift register chain and controls a programmable frequency divider 60, which may correspond to Figure 5A A variable frequency divider 52 is provided to generate a signal having a variable chopping frequency fchop from the oscillator signal fosc. Other implementations of the pseudo-random number generator may also be used.

[0057] Figure 7 An example implementation of a feedback path is shown, such as may be used in the embodiment of FIG. 3 .

[0058] Figure 7The feedback path receives the output signal rm from the chopping device after the chopping demodulator (and if necessary after gain as by the operational amplifier 39 of FIG. 3 ) at the demodulator 70, the function of which corresponds to Figure 3C The output signal of the demodulator 70 is fed to an analog-to-digital converter 71. In the example shown, the analog-to-digital converter is a 1-bit analog-to-digital converter, i.e. an analog-to-digital converter that outputs a 1-bit signal. Figure 7 In FIG. 4 , the output signal is denoted comprr_o. An example of this signal for multiple phases of the spinning current method is shown (twice as PH1 to PH4).

[0059] The signal comprr_o is provided to an integrator 72 , which may be implemented as a simple up / down counter and counts up or down depending on the value of the signal comprr_o.

[0060] To illustrate the function of the integrator, the amplitude 78 of the example signal shows, for example, the offset signal of the amplifier Voa in the phases PH1 to PH4. The amplitude 79 shows the useful signal in the phases PH1 to PH4. Since the useful signal is sometimes positive and sometimes negative for the same component, the useful signal is averaged in the integrator 72 and thus suppressed, while the Voa component (offset) according to the amplitude 78 is always further integrated.

[0061] When the undesired components in the output signal disappear through the negative feedback caused by the feedback path, the integral is then Figure 7 In the case of , the operation of the amplifier 77) through the feedback path is completed. Then the system is set.

[0062] The signal output from integrator 72 can be, for example, a 12-bit signal. The output signal of integrator 72 is fed to a digital-to-analog converter, in the example shown, a 13-bit ODAC (target digital-to-analog converter). The signal generated in this way is then superimposed via resistor 76 on the input of amplifier 77, which is an example of a chopping device. Here, the signal of the feedback signal is thus fed into the input of amplifier 77, which effectively changes the offset of amplifier 77. The signal "ripple measurement" is then tapped off at the amplifier as an input signal for the feedback path. This can also be done at the output of amplifier 77 or after the chopping demodulator as explained above.

[0063] Figure 7 Only one possible implementation of the feedback path is shown, and other implementations are contemplated, for example implementations similarly used in systems with a constant chopping frequency.

[0064] Now refer to Figures 8 to 10The exact course of the curves shown depends on the respective implementation, so that the curves shown are to be understood only as examples. Figure 8 The signal curves of the output signal of a system such as the system of FIG. 3 are shown for a fixed chopping frequency in curve 81 and for a variable chopping frequency in curve 80. As can be seen, with a fixed chopping frequency fchop, the signal is very strongly suppressed (visible by a pronounced downward peak). With a variable chopping frequency that varies around fchop, the signal is less suppressed near fchop (visible by a smaller, downwardly distributed peak). Consequently, this less suppression results in each chopping frequency occurring only for a short period of time.

[0065] So external Figure 9 As can be seen from the curves 90 , in particular the sensitivity to high-frequency interference is significantly more pronounced in the curve 90 with a constant chopping frequency than in the curve 91 with a random chopping frequency.

[0066] also, Figure 10 Curve 1002 in FIG. 1 shows the noise density, and curve 1001 shows the cumulative noise density. In particular, at high frequencies, significantly smaller peaks occur than with conventional methods, and in particular, there is no frequency overhang. Curve 1001 shows that due to the remaining ripple, there is no sudden increase near the chopping frequency, but rather, it only increases by 10 dB / dec, corresponding to the bandwidth, as theoretically predicted. If only a variable chopping frequency were used without feedback, the ripple at high frequencies would be undesirably noticeable, and the overall cumulative noise would be amplified. Therefore, feedback also significantly reduces the residual ripple formed by chopping at a variable chopping frequency.

[0067] Some embodiments are defined by the following examples:

[0068] Example 1. A system comprising:

[0069] a chopping device having a chopping modulator at an input and a chopping demodulator at an output;

[0070] means for providing a chopping signal having a variable chopping frequency to said chopping modulator and said chopping demodulator; and

[0071] A feedback path is provided from the output of the chopping demodulator to the chopping means, which is arranged to reduce ripple or offset caused by the variable chopping frequency.

[0072] Example 2. The system of example 1, wherein the output signal of the feedback path is configured to set an offset of the chopping device.

[0073] Example 3. The system of example 1 or 2, wherein the variable chopping frequency has a repetition frequency, the chopping frequency repeats at the repetition frequency, and

[0074] The feedback path has a filtering frequency that is at most half of the repetition frequency.

[0075] Example 4. The system of any of Examples 1 to 3, wherein the variable chopping frequency is in a frequency range above an effective frequency range of the chopping device.

[0076] Example 5. The system of any one of Examples 1 to 4, wherein the feedback path has a filtering frequency that is at most half of a minimum chopping frequency of the variable chopping frequency.

[0077] Example 6. The system of any one of Examples 1 to 5, wherein the feedback path comprises a demodulator and an integrator, the demodulator being configured to operate based on the chopped signal.

[0078] Example 7. The system of any one of Examples 1 to 6 further includes a rotating current Hall sensor, wherein an output of the rotating current Hall sensor is coupled to an input of the chopping modulator, wherein the rotating current Hall sensor is configured to operate at a variable rotating frequency that is an integer multiple of the variable chopping frequency.

[0079] Example 8. A method comprising:

[0080] providing a chopping signal having a variable chopping frequency to the chopping component, and

[0081] Feedback is provided from the output of the chopping assembly to the chopping device to compensate for ripple or offset caused by the variable chopping frequency.

[0082] Example 9. The method of Example 8, wherein the feedback is configured to set an offset of the chopping device.

[0083] Example 10. The method of example 8 or 9, wherein the variable chopping frequency has a repetition frequency, the chopping frequency repeats at the repetition frequency, and

[0084] The feedback has a filtering frequency that is at most half of the repetition frequency.

[0085] Example 11. The method of any one of Examples 8 to 10, wherein the variable chopping frequency is in a frequency range above an effective frequency range of a chopping device associated with the chopping component.

[0086] Example 12. The method of any one of Examples 8 to 11, wherein the feedback has a filtering frequency that is at most half of a minimum chopping frequency of the variable chopping frequency.

[0087] Example 13. The method of any one of Examples 8 to 12, wherein providing the feedback comprises demodulating an output signal of the chopping component based on the chopping signal and integrating the demodulated output signal.

[0088] Example 14. The method of any one of Examples 8 to 13 further includes operating a Hall sensor using a spinning current technique, wherein the output of the Hall sensor is coupled to the input of the chopping component, wherein the spinning current technique is operated at a variable spinning frequency that is an integer multiple of the variable chopping frequency.

[0089] Although specific embodiments have been shown and described in this specification, those skilled in the art will recognize that various alternative and / or equivalent implementations may be selected to replace the specific embodiments shown and described in this specification without departing from the scope of the invention as shown. This application is intended to cover all adaptations or variations of the specific embodiments discussed herein.

Claims

1. A chopping system comprising: A chopping device is connected to a chopping modulator (13; 35) at the input and to a chopping demodulator (14; 38)； means (15) for providing a chopping signal (c) having a variable chopping frequency to the chopping modulator (13; 35) and the chopping demodulator (14; 38); and A feedback path (16) from the output of the chopping demodulator (14; 38) to the chopping device (11) is provided, wherein the chopping device is configured to reduce ripple or offset caused by the variable chopping frequency, wherein the chopping frequency varies randomly or pseudo-randomly according to a predetermined frequency sequence.

2. A chopping system according to claim 1, wherein the output signal of the feedback path (16) is arranged to set an offset of the chopping device (11).

3. The chopping system according to claim 1 or 2, wherein the variable chopping frequency has a repetition frequency, the chopping frequency repeats at the repetition frequency, and The feedback path (16) has a filtering frequency that is at most half the repetition frequency.

4. The chopping system according to claim 1 or 2, wherein the variable chopping frequency is in a frequency range above 200 kHz.

5. The chopping system according to claim 1 or 2, wherein the feedback path has a filtering frequency that is at most half of a minimum chopping frequency of the variable chopping frequency.

6. The chopping system according to claim 1 or 2, wherein the feedback path (16) comprises an analog demodulator (310; 70) and an integrator (72), the analog demodulator being arranged to operate based on the chopping signal (c).

7. The chopping system according to claim 1 or 2, further comprising a rotating current Hall sensor (30), wherein an output of the rotating current Hall sensor (30) is coupled to an input of the chopping modulator (13; 35), wherein the rotating current Hall sensor (30) is arranged to operate at a variable rotation frequency, wherein the variable rotation frequency is An integer multiple of the variable chopping frequency.

8. A method for chopping, comprising: providing a chopping signal (c) having a variable chopping frequency to a chopping component comprising a chopping modulator and a chopping demodulator, and providing feedback from the output of the chopping demodulator to a chopping device (11; 37) to compensate for ripple or offset caused by the variable chopping frequency, The chopping frequency is varied according to a predetermined frequency sequence, randomly, or pseudo-randomly.

9. A method according to claim 8, wherein the feedback is arranged to set an offset of the chopping means (11).

10. The method according to claim 8 or 9, wherein the variable chopping frequency has a repetition frequency, the chopping frequency repeating at the repetition frequency, and The feedback has a filtering frequency that is at most half the repetition frequency.

11. The method according to claim 8 or 9, wherein the variable chopping frequency is in a frequency range above 200 kHz.

12. A method according to claim 8 or 9, wherein the feedback has a filtering frequency which is at most half the minimum chopping frequency of the variable chopping frequency.

13. The method of claim 8 or 9, wherein providing the feedback comprises: An output signal of the chopping demodulator is demodulated based on the chopping signal (c), and the demodulated output signal is integrated.

14. The method according to claim 8 or 9, further comprising operating a Hall sensor (30) using a spinning current technique, wherein the output of the Hall sensor (30) is coupled to the input of the chopping modulator, wherein the spinning current technique is operated at a variable spinning frequency, which is an integer multiple of the variable chopping frequency.

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