JP3985362B2 - Motor rotation pulse generation circuit for DC motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor rotation pulse generation circuit that uses a DC motor having a brush and generates an accurate pulse that changes in accordance with the rotation of the DC motor.
[0002]
[Prior art]
2. Description of the Related Art In recent years, DC motor rotation detection devices have been used in various fields for performing motor position control using a DC motor. For example, in a vehicle, the position of a seat is controlled in a memory seat, and in a window regulator, a sunroof or the like, it is used for an apparatus for detecting pinching.
[0003]
In addition, when control is performed using the motor current of a DC motor, when the DC motor rotates, the number of coils connected when a plurality of segments of the commutator pass through the brush changes with rotation. The number of connected coils changes, the resistance value changes, and the current flowing through the coils changes. For this reason, if the control based on the current flowing in the motor coil is performed, a ripple will appear in the current waveform, and if control such as pinching is performed based on the current with the ripple in this way, the motor will rotate. The exact control corresponding to it becomes impossible.
[0004]
Therefore, the present inventors have proposed as follows in Japanese Patent Laid-Open No. 10-109534. In the device disclosed in this publication, a voltage proportional to the current flowing through the DC motor is input to the control device, and the A / D input capture timing is configured by a filter circuit, first and second differentiating circuits, and a voltage comparison circuit. It is determined by the output from the input timing circuit, and A / D input is performed at the timing of the signal obtained from the input timing circuit to detect pinching.
[0005]
[Problems to be solved by the present invention]
In general, the motor current that flows when a DC motor is driven is composed of a DC current proportional to the motor torque, a ripple component proportional to the rotational speed, and a noise component. However, in the method shown in the above publication, the noise component is attenuated by the filter circuit, but the cutoff frequency of the filter is set to the maximum motor rotation speed in order to correspond to the changing motor rotation speed.
[0006]
On the other hand, it is known that the motor rotation slows down when driving at low voltage or at low temperatures. When the motor rotation speed slows down, it is abnormal due to noise due to the influence of noise components near the cutoff frequency that cannot be sufficiently attenuated by the filter circuit A pulse (for example, a pulse is generated at a place where no pulse is generated) may be generated. As a result of experiments, it has been found that the amount of change in current cannot be accurately detected due to abnormal pulses generated by noise, and that the noise component that cannot be attenuated by the filter becomes prominent when the motor rotation speed becomes slow. did.
[0007]
Therefore, Japanese Patent Application No. 10-180981 proposed a circuit for generating a ripple pulse by using an analog circuit composed of a low-pass filter, a differential circuit, an amplifier, a comparator and the like for a ripple component included in a motor current. The noise is removed by a low-pass filter LPF including a low-frequency filter and a high-frequency filter, the output of the low-pass filter is differentiated by the first differentiation circuit to attenuate the DC component, and the output of the first differentiation circuit is obtained by the first amplifier. The second differential circuit differentiates the output of the first amplifier and shifts the phase, and the comparator compares the output of the second differential circuit and the output of the first amplifier, and the low frequency filter and the high frequency filter are By switching, the cut-off frequency of the low-pass filter is switched.
[0008]
In this way, in a fixed constant circuit that switches the filter constants of the low-frequency and high-frequency filters in the low-pass filter with a switch, it is necessary to switch the filter constant in several steps based on the signal from the motor, and to perform accurate pulse shaping that does not affect noise There is. However, if a motor with a large noise component is used, the filter attenuation factor must be increased to eliminate noise, and the motor rotation speed detection range will be narrowed if the filter attenuation factor is increased. By changing the filter in multiple stages and changing the cut-off frequency of the filter in multiple stages, the filter constant must be switched. Therefore, switching control by software or hardware becomes difficult.
[0009]
Therefore, the present invention has been made in view of the above problems, and provides a circuit that can obtain a pulse output that accurately follows the rotation of a motor without stepwise switching the cutoff frequency of the filter. Is a technical issue.
[0010]
[Means for Solving the Problems]
The technical measures taken to solve the above problems are a filter that removes noise from the input signal from the DC motor, a pulse shaping circuit that generates a ripple pulse from the filter output, and a filter cutoff based on the ripple pulse. Based on the output of the pulse generator and pulse generator that outputs a pulse that changes the frequency linearly, it corrects ripple pulses including abnormal pulses that decrease and increase pulses, and generates corrected ripple pulses that are synchronized with the rotation of the DC motor. A pulse correction circuit is provided.
[0011]
With the above configuration, based on the ripple pulse obtained from the pulse shaping circuit, the ripple pulse is corrected by the pulse correction circuit with the pulse from the pulse generation circuit that linearly changes the cutoff frequency of the filter, and synchronized accurately with the rotation of the DC motor. Pulse output (correction ripple pulse) is generated.
[0012]
This is because even if an abnormal pulse is generated in the ripple pulse (a pulse increase where the pulse cannot be generated or a pulse decrease where the pulse skips), the pulse correction circuit generates a ripple based on the output from the pulse generation circuit. Since the correction is performed on the pulse, it is possible to generate an accurate pulse based on the motor rotation. In this case, the cutoff frequency of the filter is changed linearly by feedback of the ripple pulse, and the cutoff frequency is changed. Therefore, the cutoff frequency becomes a linear change, and there is no need to switch the filter cutoff frequency step by step. Output is obtained. In addition, the switching can be handled by hardware.
[0013]
If the filter is a switched capacitor filter, and a pulse with a ripple pulse frequency as the cutoff frequency is input to the clock input of the switched capacitor filter, then the filter cutoff frequency is switched by the switched capacitor filter. Can be changed following the ripple pulse.
[0014]
In addition, the pulse correction circuit includes an integration circuit that integrates the output from the pulse generation circuit, a comparison circuit that compares the output of the integration circuit with a predetermined threshold, and an edge detection circuit that detects the edge of the ripple pulse. When the edge of the ripple pulse is detected, the output (integrated value) from the pulse generation circuit is compared with a predetermined threshold value, and the ripple pulse can be corrected based on the result.
[0015]
Further, when the integration value is smaller than the first threshold value, the integration circuit does not clear the integration value when the edge of the ripple pulse is detected, and becomes larger than the second threshold value (> first threshold value). If the integral value is cleared at the same time, even if an abnormal pulse occurs in the ripple pulse, it is possible to correct the pulse increase by comparing the integral value with the first threshold value. By comparing with the threshold value, it is possible to correct the pulse decrease.
[0016]
If a pulse is output at a timing when the integral value falls within the range of the first threshold value and the second threshold value, and a correction ripple pulse is generated by this pulse and the ripple pulse, a simple comparison circuit and logic circuit Thus, a correction pulse can be generated.
[0017]
If the threshold value is variable depending on the rotation state of the DC motor, even if a sudden change (motor lock, etc.) occurs in the motor rotation state, the threshold value follows that and an accurate pulse is generated. It becomes.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 shows a motor rotation pulse generation circuit 30 that outputs a pulse according to the number of rotations of the DC motor 11. The circuit 30 includes a filter (switched capacitor filter) 3a, a ripple pulse shaping circuit (pulse shaping circuit) 3b, a pulse generation circuit, and a pulse correction circuit 7. The pulse generation circuit includes a PLL (Phase Locked Loop) 3c, a frequency dividing circuit 3d, a low-pass filter (LPF) 3e, and an addition / subtraction circuit 3f.
[0020]
Therefore, each circuit block will be described in detail. The switched capacitor filter 3a is basically a circuit composed of an analog switch and a capacitor (switched capacitor circuit) as shown in FIG. ) Applied to the filter. As shown in the operation explanatory diagram of FIG. 2, it is basically composed of two switches and a capacitor. When the switches S1 and S2 are alternately turned on / off with a period T, the current i becomes i = V / (1 / FC), the switched capacitor can be regarded as equivalent to a resistor. In the case of a CR filter composed of a resistor and a capacitor to which this is applied (see (b)), the cutoff frequency fc of the circuit is the frequency at which two switches are turned on / off (in the case of a switched capacitor filter, the clock frequency). The cutoff frequency fc is expressed as shown in (b). Here, a commercially available IC (MF6-50) is used as the switched capacitor filter 3a for removing noise, and the cutoff frequency fc of this IC is fc = fCLK (clock input frequency) / N (constant). For example, constant: 50).
[0021]
The ripple pulse shaping circuit 3b has a circuit configuration shown in FIG. The circuit 3b includes a high frequency active filter FL2, first and second differentiating circuits DC1 and DC2, an amplifier AP1, and a comparator (voltage comparator) CM.
[0022]
In the high-frequency active filter FL2, resistors R3 and R4 are input to the non-inverting input terminal of the operational amplifier OP1, and a capacitor C2 connected to the connection point of the resistors R3 and R4 is further connected to the inverting input terminal. A capacitor C3 is connected to a connection point between the inverting input terminal and the resistors R3 and R4, and feedback is applied to the output. This filter FL2 removes high frequency components. For example, a noise component higher than the maximum rotation speed (for example, 6000 rpm) of the motor 11 can be reliably removed by increasing the attenuation amount. It functions as a low-pass filter LPF that can remove noise on the motor rotation signal (ripple frequency).
[0023]
The first differentiation circuit DC1 is connected to the output (b) of the low-pass filter LPF, and differentiates the input signal to attenuate the DC component. In the first differentiating circuit DC1, a resistor R7 and a coupling capacitor C5 are connected in series to the inverting input terminal of the operational amplifier OP2. On the other hand, a voltage divided by resistors R5 and R6 is applied to the non-inverting input terminal, and a bypass capacitor C4 is connected to the voltage dividing point. A resistor R8 and a capacitor C6 are connected in parallel between the inverting input terminal and the output of the operational amplifier OP2.
[0024]
The amplifier AP1 amplifies the output (c) of the first differentiating circuit DC1, resistors R9 and R10 are connected in series to the non-inverting input terminal of the operational amplifier OP3, and a capacitor C9 is connected to the non-inverting input terminal. Has been. In addition, a capacitor C7 is connected to a connection point between the inverting input terminal and the resistors R9 and R10 via a resistor R11, and a capacitor C8 and a resistor R12 are connected in parallel between the output of the operational amplifier OP3. Has been.
[0025]
The second differentiation circuit DC2 differentiates the output (d) of the amplifier AP1 and shifts the phase by 90 °. The output (d) of the amplifier AP1 is connected to the resistor R14 and the capacitor C11 at the non-inverting input terminal of the operational amplifier OP4. Connected through a filter. On the other hand, a resistor R13 and a capacitor C10 are connected in series to the inverting input terminal, and a resistor R15 and a capacitor C12 are connected in parallel between the output (e) of the operational amplifier OP4 and the non-inverting input terminal.
[0026]
The comparator CM compares the output (e) of the second differentiating circuit DC2 and the output (d) of the amplifier circuit AP1, and the output (d) of the amplifier circuit AP1 is connected to the inverting input of the operational amplifier OP5 via the resistor R17. ) Is connected, the output (e) of the second differentiation circuit DC2 is connected to the non-inverting input terminal via the resistor R16, and the resistor R18 is further connected to the output (f) of the operational amplifier OP5. , A rectangular pulse (ripple pulse) matching the ripple frequency is output from the output (f).
[0027]
FIG. 4 shows output waveforms at each part of the pulse shaping circuit 3b described above. The current flowing through the motor 11 shown in FIG. 1 is converted into a voltage signal (motor rotation signal) proportional to the current, and a ripple peculiar to the DC motor is added to this voltage signal along with noise (a waveform). Ripple is generated when the DC motor 11 is used, and the cause thereof is that coils connected in parallel because the number of coils connected when a plurality of segments of the commutator pass through the brush changes with rotation. This occurs when the current flowing through the coil changes due to the change in resistance value during motor rotation.
[0028]
Ripple noise is removed by passing the rippled signal through the switched capacitor filter 3a, but noise on the clock input (clock frequency fCLK) of the switched capacitor filter 3a appears at the output. Thereafter, by passing through a low-pass filter LPF, it is smoothed and noise components are removed as in the b waveform. Next, when the signal (b waveform) that has passed through the low-pass filter LPF is passed through the first differentiating circuit DC1, the signal is differentiated to attenuate the DC component and become a c waveform with only a ripple component. Furthermore, when the amplifier AP1 is passed through the c waveform, the amplitude of the c waveform is amplified to become a waveform d, and then when the second differentiation circuit DC2 is passed through, the phase is delayed by 90 ° with respect to the c waveform. The waveform after the differentiation circuit DC2 becomes an e waveform. Next, a ripple pulse (f waveform) is obtained by comparing the output of the amplifier AP1 (d waveform) with the output of the second differentiating circuit (e waveform) by the comparator CM.
[0029]
The pulse generation circuits 3c to 3f generate a pulse to be given to the clock input of the switched capacitor filter 3a by converting the frequency fp of the ripple pulse by an integral multiple based on the ripple pulse. In this embodiment, the ripple pulse waveform is fed back so that the ripple pulse frequency fp becomes the cutoff frequency fc of the switched capacitor filter 3a. That is, based on the constant N (= 50) of the relational expression (fc = fCLK / N) of the cutoff frequency of the output of the switched capacitor filter 3a with respect to the frequency fp of the ripple pulse (f waveform) input to the PLL 3c. The PLL 3c outputs a frequency (frequency 50 times fp: 50 fp). Therefore, the PLL 3c has a frequency conversion function. The output of the PLL 3c (frequency: 50 fp) is divided by 50 with respect to the input frequency 50 fp to the frequency dividing circuit 3d, and the frequency fp is output to the PLL 3c. In this pulse generation circuit, the oscillation is controlled so as to coincide with the frequency fp of the ripple pulse input to the PLL 3c, and the phase of the output signal of the frequency dividing circuit 3d is controlled. Therefore, the cutoff frequency fc of the switched capacitor filter 3a changes linearly based on the state of the ripple pulse.
[0030]
Further, an LPF 3e and an addition / subtraction circuit 3f are added to the PLL 3c in order to stabilize the output from the PLL 3c when the pulse generation circuit is activated. By applying the voltage Vb for driving the motor 11 as an external signal to the adder / subtractor circuit 3f at the time of starting the pulse generating circuit, the oscillation of the PLL 3c is maintained at a constant voltage level in the initial state. It has a configuration that oscillates depending on the input ripple pulse.
[0031]
The waveforms at these positions (output waveform j of frequency dividing circuit 3d, output waveform g from PLL 3c to LPF 3e, output waveform h from LPF, and pulse output waveform f) are as shown in FIG. Here, (a) in FIG. 5 shows a waveform at startup, and (b) shows a waveform at steady state. In this case, the signal (g waveform) of the PLL 3c to the LPF 3e appears as a signal proportional to the phase difference between the ripple pulse (f waveform) and the signal (j waveform) from the frequency divider 3d, and the ripple pulse f is output from the frequency divider 3d. The phase control is performed so as to match the outputs.
[0032]
FIG. 6 shows a case where the filter constant of the low-pass filter LPF is switched to switch the cutoff frequency of the filter, and a case where the cutoff frequency of the switched capacitor filter 3a is changed based on the ripple pulse. A conventional method for switching the filter cut-off frequency (for example, specifically, in the low pass filter LPF in FIG. 3, a switch having a resistor interposed between the resistors R3 and R4 so that the filter constant is changed is provided in parallel. In the method of switching the filter constant with a switch), the ripple pulse has a pulse decrease (pulse skip) or an abnormal pulse increase. For this reason, since it becomes impossible to obtain a signal that is accurately synchronized with the rotation of the motor, a pulse correction circuit 7 that corrects the ripple pulse is provided so that such an abnormal pulse is not reliably generated.
[0033]
The pulse correction circuit 7 integrates the output (frequency: 50 fp) from the PLL 3c with an integration circuit 7a that integrates the output (integration value) of the integration circuit 7a with a predetermined threshold value (threshold value 1, threshold value 1). Comparison circuits 7e and 7f for comparison with a larger threshold value 2), AND1 circuit 7g for outputting the logical sum of the outputs of the comparison circuits 7e and 7f, AND2 circuit 7h for outputting the logical sum of the output of the AND1 circuit 7g and the ripple pulse An edge detection circuit 7c for detecting an edge from a ripple pulse, an amplification circuit 7j for amplifying a motor current signal from the motor 11, a current change detection circuit 7i for detecting a current change of the motor 11 from the amplified signal, and a current change detection circuit 7 based on the output of the comparator 7, and an adder circuit 7b for changing the threshold value 2 of the comparator circuit 5f. The integral value of 7a and a AND3 circuit 7d to clear (reset).
[0034]
FIG. 7 shows the operation of such a pulse correction circuit 7. In this figure, a clock input pulse (pre-correction pulse) having a frequency fp is output from the pulse shaping circuit 3b. The following description will be given on the assumption that an abnormal pulse such as a pulse increase or a pulse decrease is added to the pre-correction pulse. The pre-correction pulse (frequency: fp) is input to the pulse generation circuit, and a tracking delay occurs from the pulse generation circuit with respect to the input of the ripple pulse, and an output (frequency: 50f) smoothed by the LPF 3e is generated. The output (50 fp) is input to the output integration circuit 7a and integrated, and the output (integration value) of the integration circuit 7a is input to both the comparison circuits 7e and 7f. The comparison circuit 7e switches the output when the voltage level of the threshold value 1 (first threshold value) is exceeded, and the comparison circuit 7f basically has a threshold value 2 (> threshold value). The output is switched when the voltage level of value 1) is exceeded. The threshold values 1 and 2 are set to values having a predetermined margin (for example, ± 25 fp) above and below, taking into account variations in motor rotation, based on the duty ratio of the pulse before correction being 50:50. .
[0035]
In this case, the integration value of the integration circuit 7a is added within the edge, but if there is no clear condition for the integration value, the integration value is the threshold value 1 at the place where the pulse increase occurs when an abnormal pulse occurs. Do not exceed. On the other hand, since the threshold value 2 is exceeded at the place where the pulse decrease occurs, if the integral value is smaller than the threshold value 1, the integral value is not cleared when the ripple pulse edge is detected. The addition is continued until an edge is input and then cleared, and when the integrated value becomes larger than the threshold value 2, the integrated value is cleared when the threshold value 2 is exceeded. The pulses are switched at the timing when the integrated value obtained in this way deviates from the range of the threshold value 1 to the threshold value 2 (output of the AND1 circuit), and the pulse is based on the output of the AND1 circuit 7g and the ripple pulse before correction. Output is made.
[0036]
Since the threshold value 2 for changing the output of the comparison circuit 7f is added and changed by the addition circuit 7b depending on the rotation state of the motor 11, a sudden change in the motor current (for example, motor lock or the like) occurs. However, the ripple pulse can be optimally corrected.
[0037]
Therefore, the ripple pulse is fed back, the cutoff frequency fc of the switched capacitor filter 3a is linearly changed to generate a ripple pulse, and the ripple pulse is corrected based on the signal from the pulse generation circuit. It is possible to switch accurately to a current waveform with no error component, and to obtain a stable waveform (see FIG. 6) without an error component. That is, the pulse output after the pulse correction circuit is synchronized with the movement of the commutator of the motor 11, and the CPU switches at the timing of switching the pulse based on the accurate pulse synchronized with the motor rotation obtained in this way. If it is taken in, accurate control by motor current becomes possible. In this case, since the motor rotation state is known by the motor current, a sensor for detecting the motor rotation state is not necessary.
[0038]
【effect】
According to the present invention, a filter that removes noise from an input signal from a DC motor, a pulse shaping circuit that generates a ripple pulse from a filter output, and a pulse that linearly changes the cutoff frequency of the filter based on the ripple pulse. A ripple correction circuit that corrects the ripple pulse based on the output of the pulse generation circuit and the pulse generation circuit and generates a correction ripple pulse synchronized with the rotation of the DC motor is provided. In addition, a ripple pulse is corrected by a pulse correction circuit with a pulse from a pulse generation circuit that linearly changes the cutoff frequency of the filter, and an accurate pulse output (correction ripple pulse) synchronized with the rotation of the DC motor is generated.
[0039]
In this case, the cutoff frequency of the filter is changed linearly by feedback of the ripple pulse, and the cutoff frequency is changed. Therefore, the cutoff frequency becomes a linear change, and there is no need to switch the filter cutoff frequency step by step. Output is obtained. Moreover, it can be handled with hardware.
[0040]
If the filter is a switched capacitor filter, and a pulse with a ripple pulse frequency as the cutoff frequency is input to the clock input of the switched capacitor filter, then the filter cutoff frequency is switched by the switched capacitor filter. Can be changed following the ripple pulse.
[0041]
In addition, the pulse correction circuit includes an integration circuit that integrates the output from the pulse generation circuit, a comparison circuit that compares the output of the integration circuit with a predetermined threshold, and an edge detection circuit that detects the edge of the ripple pulse. When the edge of the ripple pulse is detected, the output (integrated value) from the pulse generation circuit is compared with a predetermined threshold value, and the ripple pulse can be corrected based on the result.
[0042]
Further, when the integration value is smaller than the first threshold value, the integration circuit does not clear the integration value when the edge of the ripple pulse is detected, and becomes larger than the second threshold value (> first threshold value). If the integral value is cleared at the same time, even if an abnormal pulse occurs in the ripple pulse, it is possible to correct the pulse increase by comparing the integral value with the first threshold value. Pulse reduction can be corrected by comparing with the threshold value.
[0043]
If a pulse is output at a timing when the integral value falls within the range of the first threshold value and the second threshold value, and a correction ripple pulse is generated by this pulse and the ripple pulse, a simple comparison circuit and logic circuit Thus, a correction pulse can be generated.
[0044]
If the threshold value is variable depending on the rotation state of the DC motor, even if a sudden change (motor lock, etc.) occurs in the motor rotation state, the threshold value follows that and an accurate pulse is generated. It becomes.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram of a motor rotation pulse generation circuit according to an embodiment of the present invention.
FIG. 2 is an operation explanatory diagram of a switched capacitor filter of a motor rotation pulse generation circuit according to an embodiment of the present invention.
FIG. 3 is an electric circuit diagram of the ripple pulse shaping circuit shown in FIG. 1;
4 is a timing chart showing waveforms at each point of the pulse shaping circuit shown in FIG. 3;
5 is a timing chart of the pulse generation circuit shown in FIG. 1, where (a) shows a waveform at startup and (b) shows a waveform at steady state.
FIG. 6 is a comparison diagram showing pulse outputs when the filter is switched and the cutoff frequency of the filter is switched, and when the cutoff frequency is switched by a switched capacitor filter.
7 is a timing chart showing output waveforms at each point of the pulse correction circuit shown in FIG. 1;
[Explanation of symbols]
3a switched capacitor filter 3b ripple pulse shaping circuit 3c PLL (pulse generation circuit)
3d frequency divider (pulse generator)
3e LPF (pulse generation circuit)
3f Addition / subtraction circuit (pulse generation circuit)
7 Pulse correction circuit 11 DC motor (motor)
30 Motor rotation pulse generation circuit fCLK Clock input frequency

Claims (6)

A filter that removes noise from the input signal from the DC motor,
A pulse shaping circuit for generating a ripple pulse for the filter output;
A pulse generation circuit that outputs a pulse that linearly changes the cutoff frequency of the filter based on the ripple pulse;
A pulse correction circuit is provided that corrects the ripple pulse including abnormal pulses of pulse decrease and pulse increase based on the output of the pulse generation circuit and generates a correction ripple pulse synchronized with the rotation of the DC motor. A motor rotation pulse generation circuit for a DC motor. The motor rotation pulse of a DC motor according to claim 1, wherein the filter is a switched capacitor filter, and a pulse whose frequency is the cutoff frequency is input to a clock input of the switched capacitor filter. Generation circuit. The pulse correction circuit includes:
An integrating circuit for integrating the output from the pulse generating circuit;
A comparison circuit for comparing the output of the integration circuit with a predetermined threshold value;
An edge detection circuit for detecting an edge of the ripple pulse;
A pulse decrease of the ripple pulse is corrected based on a comparison result by the comparison circuit, and a pulse increase of the ripple pulse is corrected based on a comparison result by the comparison circuit at the time of edge detection by the edge detection circuit. The motor rotation pulse generation circuit of the DC motor according to claim 1 or 2 . The integration circuit does not clear the integration value when the edge of the ripple pulse is detected when the integration value is smaller than the first threshold value, and clears the integration value when the integration value becomes larger than the second threshold value. Item 4. A motor rotation pulse generation circuit for a DC motor according to Item 3. 5. The motor rotation of a DC motor according to claim 4, wherein a pulse is output at a timing at which the integrated value falls within a range between the first threshold value and the second threshold value, and a correction ripple pulse is generated by the pulse and the ripple pulse. Pulse generation circuit. 4. The motor rotation pulse generation circuit for a DC motor according to claim 3, wherein the threshold value is variable depending on a rotation state of the DC motor.

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