阅读说明：本技术 连接到有刷直流电机的检测电路和电机旋转信息检测方法 (Detection circuit connected to brush DC motor and motor rotation information detection method ) 是由 村田勉 于 2019-07-09 设计创作，主要内容包括：本发明涉及一种连接到有刷直流电机的检测电路和一种用于检测有刷直流电机的旋转信息的方法。本技术的各种实施方案可以检测换向器的切换,并且利用指示切换的信号来确定电机的转速和/或旋转信息。在一个实施方案中,装置包括彼此串联连接的ADC、差值电路、绝对值电路和比较器。(The present invention relates to a detection circuit connected to a brushed dc motor and a method for detecting rotation information of a brushed dc motor. Various embodiments of the present technology may detect a switch of the commutator and utilize the signal indicative of the switch to determine the rotational speed and/or rotational information of the motor. In one embodiment, an apparatus includes an ADC, a difference circuit, an absolute value circuit, and a comparator connected in series with each other.)

1. A detection circuit connected to a brushed dc motor, the detection circuit comprising:

a differential amplifier configured to detect a current of the brushed DC motor and generate an analog signal proportional to the current;

an analog-to-digital converter (ADC) connected to the differential amplifier and configured to convert the analog signal to a first digital signal; and

a digital circuit connected to the ADC and comprising:

a difference circuit configured to:

receiving the first digital signal; and

calculating a second digital signal, wherein the second digital signal is a difference of the first digital signal and a previous first digital signal;

an absolute value circuit connected to the difference circuit and configured to calculate an absolute value of the second digital signal; and

a comparator circuit connected to the absolute value circuit and configured to:

comparing the calculated absolute value with a predetermined threshold; and

a comparator output is generated based on the comparison.

2. The detection circuit of claim 1, further characterized in that the detection circuit comprises a reference voltage generator circuit connected to the non-inverting terminal of the differential amplifier and configured to generate a reference voltage.

3. The detection circuit of claim 1, wherein the difference circuit further comprises a delay register configured to store the previous first digital signal.

4. The detection circuit of claim 1, wherein the digital circuit further comprises a register coupled to the comparator and configured to store the predetermined threshold.

5. The detection circuit of claim 1, further characterized in that the detection circuit comprises a sense resistor comprising a first end and a second end; and wherein:

the first end is connected to the brushed DC motor and the inverting terminal of the differential amplifier; and is

The second end is connected to the non-inverting terminal of the differential amplifier and ground.

6. The detection circuit of claim 1, wherein:

the comparator circuit generates a HIGH comparator output if the calculated absolute value is greater than the predetermined threshold;

the comparator circuit generates a LOW comparator output if the calculated absolute value is less than the predetermined threshold; and is

The HIGH comparator output represents the switching contact of the brush from one commutator to a different commutator.

7. The detection circuit of claim 1, wherein the predetermined threshold is selected based on a signal level indicative of switching of the brushed dc motor.

8. A method for detecting rotational information of a brushed dc motor, the method comprising:

detecting a current of the brushed direct current motor, wherein the brushed direct current motor comprises a plurality of commutators;

generating an analog signal proportional to the detected current;

converting the analog signal to a first digital signal;

calculating a second digital signal, wherein the second digital signal is a difference of the first digital signal and a previous first digital signal;

calculating an absolute value of the second digital signal;

comparing the calculated absolute value with a predetermined threshold; and is

Generating an output based on the comparison, wherein the output indicates a switch from one commutator to a different commutator of the brushed DC motor.

9. The method of claim 8, further characterized by comprising analyzing the output to determine a rotational speed of the brushed dc motor.

10. The method of claim 8, further characterized by comprising analyzing the output to determine a total number of revolutions of the brushed dc motor over a period of time.

Technical Field

The present invention relates to a detection circuit connected to a brushed dc motor and a method for detecting rotation information of a brushed dc motor.

Background

Brushed dc motors are used in a variety of applications, such as in automobiles. In automotive applications, brushed dc motors may be used to control the position of the side view mirrors, up/down position and control of the windows, position of the seats, optical axis of the headlights, etc. Accordingly, it is desirable to detect rotational information of a motor to improve the performance of the motor and/or to provide improved motor control.

Disclosure of Invention

The present invention relates to a detection circuit connected to a brushed dc motor and a method for detecting rotation information of a brushed dc motor.

The invention solves the technical problem that the conventional detection circuit for detecting the rotation information of the brushed direct current motor realizes a technology called ripple detection. However, this technique produces results that are affected by noise, which can affect the accuracy of the detected rotation information.

Various embodiments of the present technology may detect a switch of the commutator and utilize the signal indicative of the switch to determine the rotational speed and/or rotational information of the motor. In one embodiment, the detection circuit includes an ADC, a difference circuit, an absolute value circuit, and a comparator connected in series with each other.

According to one aspect, a detection circuit connected to a brushed dc motor includes: a differential amplifier configured to detect a current of the brushed dc motor and generate an analog signal proportional to the current; an analog-to-digital converter (ADC) connected to the differential amplifier and configured to convert the analog signal to a first digital signal; and a digital circuit connected to the ADC and including: a difference circuit configured to: receiving a first digital signal; and calculating a second digital signal, wherein the second digital signal is a difference of the first digital signal and a previous first digital signal; an absolute value circuit connected to the difference circuit and configured to calculate an absolute value of the second digital signal; and a comparator circuit connected to the absolute value circuit and configured to: comparing the calculated absolute value with a predetermined threshold; and generating a comparator output based on the comparison.

In one embodiment, the detection circuit further comprises a reference voltage generator circuit connected to the non-inverting terminal of the differential amplifier and configured to generate a reference voltage.

In one embodiment, the difference circuit further comprises a delay register configured to store the previous first digital signal.

In one embodiment, the digital circuit further comprises a register coupled to the comparator and configured to store the predetermined threshold.

In one embodiment, the detection circuit further comprises a sense resistor comprising a first end and a second end; and wherein: the first end is connected to the brush direct current motor and the inverting terminal of the differential amplifier; and a second end is connected to the non-inverting terminal of the differential amplifier and ground.

In one embodiment, the comparator circuit generates a HIGH comparator output if the calculated absolute value is greater than a predetermined threshold; if the calculated absolute value is less than a predetermined threshold, the comparator circuit generates a LOW comparator output; and the HIGH comparator output indicates the switching contact of the brush from one commutator to the other.

In one embodiment, the predetermined threshold is selected based on a signal level indicative of switching of the brushed dc motor.

According to another aspect, a method for detecting rotation information of a brushed dc motor includes: detecting a current of a brushed direct current motor, wherein the brushed direct current motor comprises a plurality of commutators; generating an analog signal proportional to the detected current; converting the analog signal into a first digital signal; calculating a second digital signal, wherein the second digital signal is a difference of the first digital signal and a previous first digital signal; calculating an absolute value of the second digital signal; comparing the calculated absolute value with a predetermined threshold; and generating an output based on the comparison, wherein the output indicates a switch from one commutator to a different commutator of the brushed dc motor.

In one operation, the method further includes analyzing the output to determine a rotational speed of the brushed dc motor.

In one operation, the method further includes analyzing the output to determine a total number of revolutions of the brushed dc motor over a period of time.

A technical effect achieved by the present invention is to provide a detection circuit that detects rotation information of a brushed dc motor based on a comparator output that responds to changes in motor current, which improves the accuracy of the detected rotation information and the overall performance and control of the motor.

Drawings

The present technology may be more fully understood with reference to the detailed description when considered in conjunction with the following exemplary figures. In the following drawings, like elements and steps in the various figures are referred to by like reference numerals throughout.

FIG. 1 is a block diagram of a brushed DC motor system in accordance with an exemplary embodiment of the present technique;

FIG. 2A is a motor current waveform in accordance with an exemplary embodiment of the present technique;

FIG. 2B is an output waveform of a differential amplifier in accordance with an exemplary embodiment of the present technique;

FIG. 2C is an output waveform of a comparator in accordance with an exemplary embodiment of the present technique; and is

Fig. 3 representatively illustrates a brushed dc motor in accordance with an exemplary embodiment of the present technique.

Detailed Description

The present techniques may be described in terms of functional block components and various processing steps. Such functional blocks may be realized by any number of components configured to perform the specified functions and achieve the various results. For example, the present techniques may employ various motors, microcontrollers, drive circuits, amplifiers, signal converters, comparators, and the like, which may perform various functions. Further, the present techniques may be implemented in connection with any number of systems, such as automation, robotics, Computer Numerical Control (CNC) machines, etc., and the systems described are merely exemplary applications for the techniques.

Methods and apparatus for rotation detection of a brushed dc motor according to various aspects of the present technique may operate with any suitable system, such as an automotive system. Referring to fig. 1, an exemplary brushed dc motor system 100 may be incorporated into an automotive system where a high level of accuracy and versatility is desired. For example, in an exemplary embodiment, the brushed dc motor system 100 may include the drive circuit 105, the motor 110, the detection circuit 170, and the microcontroller 172 that operate together to detect rotational information of the motor 110.

The driving circuit 105 is configured to be dependent on the applied voltage and/or the supply voltage V_DDTo drive and/or control the motor 110. For example, the drive circuit 105 may be connected to the microcontroller 172 and configured to receive feedback signals therefrom, such as signals related to the rotational position of the motor 110 and/or the rotational direction of the motor 110. The drive circuit 105 may control the rotational speed of the motor 110 and/or change the rotational direction of the motor 110 in response to a feedback signal from the microcontroller 172. For example, at least one terminal of the motor 110 may be connected to the drive circuit 105. Drive circuit 105 may include any circuit suitable for driving the operation of motor 110. In an exemplary embodiment, the drive circuit 105 may include a plurality of transistors connected in series, each transistor responsive to an applied voltage and/or a supply voltage V_DDWherein one terminal of the motor 110 is connected to the drive circuit 105.

In an alternative embodiment, the drive circuit 105 may be connected to both terminals of the motor 110. In the present case, the driving circuit 105 may include a plurality of series-connected transistors, wherein the plurality of series-connected transistors are connected in parallel with each other.

The motor 110 is responsive to the drive circuit 105 and can change its rotational position in accordance with the drive circuit 105. In an exemplary embodiment, and referring to fig. 3, the motor 110 comprises a brushed dc motor. For example, the motor 110 includes: a plurality of stator magnets 320, 325; a rotor 300 comprising a plurality of poles 305, 310, 315 and a plurality of commutator segments 330, 335, 340 (collectively referred to as commutators); and a plurality of brushes 360, 370. The plurality of poles 305, 310, 315 are connected to a shaft 350 configured to rotate. Commutator segments 330, 335, 340 are circumferentially disposed at equal intervals on the outer surface of shaft 350. The brushes 360, 370 are positioned on either side of the shaft 350 and opposite each other. Each of the brushes 360, 370 is further positioned to contact one of the commutator segments. As the rotor 300 rotates, the contact positions between the brushes 360, 370 and the segments 330, 335, 340 are sequentially changed.

Referring back to fig. 1, the detection circuit 170 detects the current I through the motor 110_MAnd according to the motor current I_MRotation information of the motor 110 is generated. For example, the detection circuit 170 may be connected to the motor 110 and configured to measure and/or detect various operating specifications (such as current, voltage, etc.) of the motor 110. The detection circuit 170 may generate a final output signal C representing rotation information of the motor 110_OUTAnd will finally output signal C_OUTTo the microcontroller 172. The detection circuit 170 may include various systems and/or circuits that operate together to generate rotation information. For example, the detection circuit 170 may include a differential amplifier 120, a reference voltage generator circuit 125, an analog-to-digital circuit (ADC)130, and a digital circuit 140.

The differential amplifier 120 generates a differential output DA representing an amplified difference of two inputs_OUT. For example, the differential amplifier 120 includes an inverting terminal (-) configured to receive a first input and a non-inverting terminal (+) configured to receive a second input. Thus, the differential output DA_OUTIs the difference of the first and second inputs at the inverting and non-inverting terminals, respectively. According to an exemplary embodiment, a differential amplifier 120 is connected to the motor 110 and operates in conjunction with the sense resistor 115 to measure the motor current I_M. For example, the input terminals of the differential amplifier 120 are connected to the first and second ends of the sense resistor 115 to detect a voltage drop across the sense resistor 115, wherein the voltage drop across the sense resistor 115 is related to the motor current I_MAnd (4) in proportion. Thus, the differential output DA_OUTAnd the motor current I_MAnd (4) in proportion.

According to an exemplary embodiment, the sense resistor 115 is also connected to the motor 110 at a first end and to a reference potential (such as ground potential) at a second end.

Reference voltage generator circuit 125 generates reference voltage V_REF. Reference voltage generator circuit 125 may be configured to generate reference voltage V_REFTo the differential amplifier 120. For example, the reference voltage generator circuit 125 may be connected to the non-inverting terminal (+) of the differential amplifier 120. Reference voltage generator circuit 125 may include any circuit suitable for generating a reference voltage. In an exemplary embodiment of the present invention,the reference voltage generator circuit 125 may include a plurality of resistors 190, 195 connected in series and an operational amplifier 185 connected to the series-connected resistors 190, 195. The reference voltage generator circuit 125 may also be connected to a supply voltage V_DDAnd a ground.

ADC130 converts the analog signal to a digital signal and generates an ADC output S_N(where N is the sample number). In an exemplary embodiment, the ADC130 is connected to the output terminals of the differential amplifier 120 and is configured to receive the differential output DA_OUT. The ADC130 outputs the differential DA_OUTConverted into a digital signal. ADC130 may include any suitable signal converter, and the particular ADC architecture may be selected according to a particular application or desired output. ADC130 may output S from the ADC_NTo digital circuitry 140 for further processing.

Digital circuit 140 performs various calculations on the input signal and generates a digital output signal. For example, the digital circuit 140 may be connected to an output terminal of the ADC130 and receive the ADC output S_NAs inputs and perform difference calculations, absolute value calculations, comparisons, etc. According to an example embodiment, the digital circuit 140 may include a difference circuit 145, an absolute value circuit 150, and a comparator circuit 155 connected in series with one another. The digital output signal of the detection circuit 140 may correspond to the final output signal C_OUTIn which the digital output signal (e.g. the final output signal C)_OUT) Is transmitted to the microcontroller 172.

The difference circuit 145 is configured to calculate a difference of the two input values. For example, difference circuit 145 may be connected to ADC130 and receive ADC output S_N. According to an example embodiment, the difference circuit 145 may be configured to calculate the current ADC output (e.g., S)_N) With previous ADC output (e.g. S)_N-1) The difference of (a). For example, the difference circuit 145 may include an arithmetic circuit 175, such as a circuit for performing addition/subtraction, configured to output S from the current ADC_NAdding/subtracting previous ADC outputs S_N-1And generates a difference signal D based on the addition/subtraction. According to an exemplary embodiment, the difference circuit 145 may further include a delay register 180 coupled toTo the operational circuit 175 and configured to store the previous ADC output S_N-1And outputs S from the previous ADC_N-1To the arithmetic circuit 175. The difference circuit 145 may be configured to transmit the difference signal D to the absolute value circuit 150.

Absolute value circuit 150 is configured to receive an input value and generate an output representative of the absolute value of the input value. For example, the absolute value circuit 150 may be connected to an output terminal of the difference circuit 145 and configured to receive the difference signal D, calculate an absolute value (| D |) of the difference signal D, and output the absolute value ABS (i.e., | D |). Absolute value circuitry 150 may include any suitable device or circuitry for performing absolute value calculations.

Comparator 155 compares two input values and generates an output based on the comparison. For example, the comparator 155 may include a first input terminal connected to the absolute value circuit 150 and configured to receive the absolute value ABS, and a second input terminal connected to a register 160 configured to store a predetermined threshold value. The predetermined threshold may be selected based on the particular specifications of motor 110, such as a known signal level indicating switching from one commutator segment to a different commutator segment. The comparator 155 may compare the absolute value ABS with a predetermined threshold and generate an output signal (i.e., C) according to whether the predetermined threshold is less than or greater than the absolute value ABS_OUT). For example, if the absolute value ABS is greater than a predetermined threshold, the comparator 155 outputs a HIGH signal (e.g., a digital 1 or a voltage greater than 0); and if the absolute value ABS is less than the predetermined threshold, the comparator 155 outputs a LOW signal (e.g., digital 0 or a voltage equal to 0). Therefore, in the output waveform of the comparator 155, the HIGH signal is represented as a pulse. Comparator 155 may include any circuit element and/or logic device suitable for performing a comparison of two signals. Output signal C of comparator 155_OUTCorresponds to the rotation information and may also correspond to the final output signal of the detection circuit 170.

The microcontroller 172 receives various input signals (such as rotation information) and makes decisions based on the various input signals. For example, the microcontroller 172 may receive the final output signal C from the detection circuit 170_OUT. According to an exemplary embodiment, the microcontroller 172 may beIs configured to receive the final output signal C_OUTAnd determines the rotation speed of the motor 110, the number of rotations of the motor 110, and the like using the signal. For example, the microcontroller 172 may be configured to measure the final output signal C_OUTTo determine the rotational speed of the motor 110, and to count the final output signal C_OUTTo determine the number of revolutions of the motor 110. The longer the duration between each pulse, the slower the motor 110 and vice versa. In addition, the number of revolutions and the number of pulses are related to the total number of commutators. For example, in an exemplary embodiment where the motor 110 includes three (3) commutators, 7 pulses (or 6 time slots between pulses) correspond to one full rotation of the motor 110.

According to an exemplary embodiment, the microcontroller 172 is also connected to the drive circuit 105, wherein the microcontroller 172 transmits various control signals (such as feedback signals) to the drive circuit 105 to control the rotational speed and/or rotational direction of the motor 110. The particular feedback signal may be selected based on desired operation, motor specifications, particular motor applications, and the like.

In operation, and with reference to fig. 1-3, as the motor 110 rotates, each brush 360, 370 sequentially contacts one commutator at a time. However, when each brush 360, 370 switches from one commutator to the next, a discontinuity may be observed in the motor current waveform (fig. 2A) due to the gap between each commutator. The discontinuity may be detected with a differential amplifier 120 and appears as a spike coincident with the discontinuity (fig. 2B). Then the difference is output DA_OUTAfter conversion to digital values and processing of the digital values with difference circuit 145 and absolute value circuit 150, the comparator outputs a waveform (fig. 2C) that is also precisely related to the motor current I_MThe discontinuities in (1) coincide. Accordingly, since a discontinuity in the motor current waveform indicates a switch of the commutator, the microcontroller 172 may utilize the comparator output waveform to determine the rotational speed of the motor 110 and/or the number of revolutions of the motor 110 over a particular period of time. For example, the microcontroller 172 may count the time elapsed between each pulse in the comparator output waveform (fig. 2C) and/or count the number of pulses within a predetermined time period. The microcontroller 172 may analyze the pulse and timing relationships to determine the rotational speed and/or number of revolutions of the motor 110.

Depending on the automotive application, the rotational speed and/or rotational information of the motor 110 may be related to the distance the motor 110 moves the seat, the length of time it takes for the motor 110 to move the side view mirror, and the like.

In the foregoing description, the technology has been described with reference to specific exemplary embodiments. The particular embodiments shown and described are illustrative of the technology and its best mode and are not intended to otherwise limit the scope of the technology in any way. Indeed, for the sake of brevity, conventional manufacturing, connecting, fabrication, and other functional aspects of the methods and systems may not be described in detail. Furthermore, the connecting lines shown in the various figures are intended to represent example functional relationships and/or steps between the various elements. There may be many alternative or additional functional relationships or physical connections in a practical system.

The described techniques have been described with reference to specific exemplary embodiments. However, various modifications and changes may be made without departing from the scope of the present technology. The specification and figures are to be regarded in an illustrative rather than a restrictive manner, and all such modifications are intended to be included within the scope of present technology. Accordingly, the scope of the described technology should be determined by the general embodiments described and their legal equivalents, rather than by merely the specific examples described above. For example, the steps recited in any method or process embodiment may be performed in any order, unless explicitly stated otherwise, and are not limited to the exact order provided in the specific examples. Additionally, the components and/or elements recited in any apparatus embodiment may be assembled or otherwise operationally configured in a variety of permutations to produce substantially the same result as the present technique and are therefore not limited to the specific configuration set forth in the specific example.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, any benefit, advantage, solution to problem or any element that may cause any particular benefit, advantage, or solution to occur or to become more pronounced are not to be construed as a critical, required, or essential feature or element.

The terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, composition, or apparatus that comprises a list of elements does not include only those elements recited, but may include other elements not expressly listed or inherent to such process, method, article, composition, or apparatus. Other combinations and/or modifications of the above-described structures, arrangements, applications, proportions, elements, materials or components used in the practice of the present technology, in addition to those not specifically recited, may be varied or otherwise particularly adapted to specific environments, manufacturing specifications, design parameters or other operating requirements without departing from the general principles thereof.

The present technology has been described above in connection with exemplary embodiments. However, changes and modifications may be made to the exemplary embodiments without departing from the scope of the present techniques. These and other changes or modifications are intended to be included within the scope of the present technology, as set forth in the following claims.

According to one aspect, a detection circuit connected to a brushed dc motor includes: a differential amplifier configured to detect a current of the brushed dc motor and generate an analog signal proportional to the current; an analog-to-digital converter (ADC) connected to the differential amplifier and configured to convert the analog signal to a first digital signal; and a digital circuit connected to the ADC and including: a difference circuit configured to: receiving a first digital signal; and calculating a second digital signal, wherein the second digital signal is a difference of the first digital signal and a previous first digital signal; an absolute value circuit connected to the difference circuit and configured to calculate an absolute value of the second digital signal; and a comparator circuit connected to the absolute value circuit and configured to: comparing the calculated absolute value with a predetermined threshold; and generating a comparator output based on the comparison.

In one embodiment, the detection circuit further comprises a reference voltage generator circuit connected to the non-inverting terminal of the differential amplifier and configured to generate a reference voltage.

In one embodiment, a reference voltage generator circuit includes: a first resistor connected in series with a second resistor; and an operational amplifier connected to the first resistor and the second resistor.

In one embodiment, the difference circuit further comprises a delay register configured to store the previous first digital signal.

In one embodiment, the digital circuit further comprises a register coupled to the comparator and configured to store the predetermined threshold.

In one embodiment, the detection circuit further comprises a sense resistor comprising a first end and a second end; and wherein: the first end is connected to the brush direct current motor and the inverting terminal of the differential amplifier; and a second end is connected to the non-inverting terminal of the differential amplifier and ground.

In one embodiment, the comparator circuit generates a HIGH comparator output if the calculated absolute value is greater than a predetermined threshold.

In one embodiment, the comparator circuit generates a LOW comparator output if the calculated absolute value is less than a predetermined threshold.

In one embodiment, the HIGH comparator output represents the switching contact of the brush from one commutator to another.

In one embodiment, the predetermined threshold is selected based on a signal level indicative of switching of the brushed dc motor.

According to another aspect, a method for detecting rotation information of a brushed dc motor having a plurality of commutators includes: detecting the current of the brushed direct current motor; generating an analog signal proportional to the detected current; converting the analog signal into a first digital signal; calculating a second digital signal, wherein the second digital signal is a difference of the first digital signal and a previous first digital signal; calculating an absolute value of the second digital signal; comparing the calculated absolute value with a predetermined threshold; and generating an output based on the comparison, wherein the output indicates a switch from one commutator to a different commutator of the brushed dc motor.

In one operation, the method further includes analyzing the output to determine a rotational speed of the brushed dc motor.

In one operation, the method further includes analyzing the output to determine a total number of revolutions of the brushed dc motor over a period of time.

According to yet another aspect, a brushed dc motor system includes: a drive circuit; a brushed DC motor connected to and controlled by the drive circuit, wherein the brushed DC motor includes a plurality of commutators; a detection circuit connected to the brushed DC motor and including: a differential amplifier configured to detect a current of the brushed dc motor and generate an analog signal proportional to the current; an analog-to-digital converter (ADC) connected to the differential amplifier and configured to convert the analog signal to a first digital signal; a difference circuit, the difference circuit comprising: an arithmetic circuit configured to: receiving a first digital signal; and calculating a second digital signal, wherein the second digital signal is a difference of the first digital signal and a previous first digital signal; a register connected to the arithmetic circuit and configured to store a previous digital signal; an absolute value circuit connected to the difference circuit and configured to calculate an absolute value of the second digital signal; and a comparator circuit connected at a first terminal to the absolute value circuit and configured to: comparing the calculated absolute value with a predetermined threshold; and generating a comparator output based on the comparison; and a microcontroller connected to the detection circuit and configured to analyze the comparator output to determine at least one of: the rotating speed of the brushed direct current motor; and the total number of revolutions of the brushed dc motor over a period of time.

In one embodiment, the comparator circuit generates a HIGH comparator output if the calculated absolute value is greater than a predetermined threshold.

In one embodiment, the comparator circuit generates a LOW comparator output if the calculated absolute value is less than a predetermined threshold.

In one embodiment, the HIGH comparator output represents a switching contact of a brush from a first commutator of the plurality of commutators to a second commutator of the plurality of commutators.

In one embodiment, the brushed dc motor system further includes a reference voltage generator circuit connected to the non-inverting terminal of the differential amplifier and including: a first resistor connected in series with a second resistor; and an operational amplifier connected to the first resistor and the second resistor.

In one embodiment, the predetermined threshold is selected based on a signal level indicative of switching of the brushed dc motor.

In one embodiment, the microcontroller is further coupled to the drive circuit and configured to provide a feedback signal to the drive circuit, wherein the feedback signal controls at least one of a rotational speed and a rotational direction of the brushed dc motor.