JP3568075B2 - Drive control circuit for brushless motor - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a brushless motor drive control circuit suitable for a spindle motor of a VTR or a polygon mirror or a spindle motor of a disk storage device or the like.
[0002]
[Prior art]
FIG. 1 is a sectional view of a brushless motor that directly drives the capstan shaft of a VTR to rotate, and FIG. 2 is a plan view of a stator portion of the brushless motor shown in FIG. The rotor 10 has a shaft 40, which is a capstan shaft, fixed at the center and is rotatably supported by bearing means 90, 100. A driving magnet 50 having eight sinusoidal driving magnetic poles on the surface facing the stator 20 is provided. Provided.
[0003]
The stator 20 has six air-core stator coils based on a stator substrate 70 (also serving as a wiring substrate) in which a copper foil is laminated on a soft magnetic steel plate via an insulating layer and a circuit pattern is formed by a method such as etching. 80 are arranged coaxially with the rotation center at intervals of 60 degrees and fixed. These stator coils 80 are opposed to the above-described drive magnetic poles in a plane, and two pairs, one set facing each other across the rotation center, are connected in series, and three sets constitute a star-connected three-phase stator coil. I have.
[0004]
At the center of these coils, two Hall elements 130 are arranged so as to output Hall signals U and V having a phase difference of 120 degrees according to the magnetic flux density of the portion for supplying the magnetic flux to the Hall elements of the driving magnetic poles described above. Have been.
[0005]
An MR type magnetic sensing element (not shown) is provided on the stator 20 and faces the FG magnetic pole on the outer periphery of the FG magnet 60 of the rotor 10 with a gap of about 0.1 mm. An FG signal of 360 cycles is output. The FG signal is converted into a speed control signal for controlling the motor to a target rotation speed, and is supplied to a drive circuit built in the IC 140 so as to control the drive current.
[0006]
The aforementioned hall signals U and V form a sum operation and inversion circuit and output a composite signal W. Each of these signals forms a three-phase position signal having a phase difference of 120 degrees and is supplied to a drive circuit. The drive circuit supplies a drive current of a magnitude corresponding to the above-described speed control signal to the three-phase stator coil 80. It acts so as to control and flow at a ratio according to the position signal. The driving current causes the stator coil 80 to generate a rotating magnetic field corresponding to the rotation of the rotor 10 and generate a rotational driving force by interaction with the magnetic field of the driving magnetic pole.
[0007]
[Problems to be solved by the invention]
In such a brushless motor, it is indispensable to suppress the rotation unevenness. For this purpose, the combined signal W obtained by performing a sum operation of the Hall signals U and V and forming an inversion circuit is as equal as possible to the Hall signals U and V signals. Is required, and it is necessary to reduce the deviation of the phase difference.
[0008]
When the Hall signals U and V are sine waves with a phase difference of 120 degrees and the same amplitude in the above-described inverting circuit, the composite signal W can also be a sine wave with a phase difference of 120 degrees. At this time, the waveforms of the hall signals U and V and the composite signal W are as shown in FIG. However, since the Hall elements always have variations in sensitivity, an amplitude shift naturally occurs between the Hall signals U and V. At this time, as shown in FIG. 21, the amplitude of the Hall signals U and V causes an amplitude shift, so that the phase of the synthesized signal W is shifted. This phase shift shifts the timing of the current flowing through the stator coil 80, and causes deterioration in rotation unevenness. Also, when the Hall signals U and V are not sinusoidal but trapezoidal signals due to an increase in torque, the composite signal W is similarly affected, and the composite signal W becomes a distorted triangular signal. At this time, the waveform of each signal is as shown in FIG. The above-described distorted triangular-wave composite signal W can be converted into a trapezoidal-wave converted signal W 'equivalent to the Hall signals U and V as shown in FIG. However, when the amplitude between the Hall signals U and V is shifted, distortion occurs as shown in FIG. 22 and the phase is also shifted. Therefore, as shown in FIG. 23, there is a problem that the larger the amplitude difference between the Hall signals U and V, the worse the rotation unevenness. SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object of the present invention is to provide an inexpensive brushless motor having good rotation unevenness.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, a brushless motor drive control circuit according to the present invention includes a rotor having a drive magnetic pole and rotatably held, a three-phase stator coil facing the drive magnetic pole, and a rotation of the rotor. Two Hall elements that are supplied with a magnetic flux according to the angle and output Hall signals U and V having a phase difference of 120 degrees in electrical angle, and combine the Hall signals U and V into the Hall signals U and V. On the other hand, a signal combining means for outputting a combined signal W having a phase difference of 120 degrees in electrical angle, and a drive current flowing through the stator coil according to the Hall signals U and V and the combined signal W. Composed of nonlinear circuit and limiter for A drive circuit, an amplitude control unit that outputs an amplitude difference signal corresponding to the amplitude difference between the Hall signals U and V, and an amplitude adjustment unit that adjusts the amplitude of the Hall signals U and V or both according to the amplitude difference signal Wherein the amplitude difference between the Hall signals U and V is reduced, and the amplitude adjusting means includes two differential amplifiers. The amplitude difference between the Hall signals Vu and Vv, which are the outputs of the two differential amplifiers, is reduced by adjusting the common current that is one of the current sources. Are equal to each other, the amplification factor of the differential amplifier for adjusting the common current is lower than the amplification factor of the other differential amplifier by 5% or more. The present invention has been made in order to solve the above problems.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The external configuration of the brushless motor according to one embodiment of the present invention is substantially the same as the conventional example described above with reference to FIGS. 1 and 2, and will be described with reference to FIGS. 1 and 2 again.
[0011]
In the brushless motor according to the present invention, a drive magnet 50 having trapezoidal drive magnetic poles including predetermined third and fifth harmonic components of eight poles is provided on the surface of the rotor 10. The stator 20 has a base on which a circuit pattern is formed in the same manner as in the prior art, and has six air-core coils arranged coaxially with the center of rotation at intervals of 60 degrees and fixed.
[0012]
These coils are opposed to the above-described drive magnetic poles in a plane, and a pair of two coils facing each other across the center of rotation are connected in series, and three sets constitute a star-connected three-phase stator coil 80. . At the center of these coils, two Hall elements 130 output Hall signals U and V having a phase difference of 120 degrees according to the magnetic flux density of the portion supplying magnetic flux to the Hall element of the driving magnetic pole described above. It is arranged.
[0013]
Further, similarly to the conventional example, an MR type magnetic sensing element is provided and outputs an FG signal. This FG signal is converted by a speed control means into a speed control signal for controlling the motor to a target rotation speed, and controls the drive current. As described above.
[0014]
(First embodiment)
FIG. 3 is a block diagram showing a first embodiment of the brushless motor drive control circuit according to the present invention, which will be specifically described with reference to FIG. First, the hall signals U and V are amplified by the amplifiers 1 and 2, respectively, and the output is input to the absolute value circuit 3. The output waveforms are like Uabs and Vabs in FIGS. 4A and 4B, and are applied to the comparator 4 to be converted into rectangular waves Vcmp as shown in FIGS. 5A and 5B. That is, the comparator 4 compares the magnitudes of the absolute values Uabs and Vabs output from the absolute value circuit 3 for each electrical angle, and converts the comparison result into binary values of “0” and “1”. A rectangular wave Vcmp as shown in (a) and (b) is obtained. At this time, if the amplitudes of the Hall signals U and V are the same as shown in FIG. 4A, the duty of the rectangular wave is 1: 1 (θ1 = θ2) (FIG. 5A), while FIG. As shown in (b), if the amplitude of the Hall signal U <the amplitude of the Hall signal V, the duty of Vcmp deviates (FIG. 5 (b)).
[0015]
Next, the output Vcmp of the comparator 4 is converted into a current, and smoothed by a capacitor C into a triangular waveform as shown in FIG. Here, the duty of the rectangular wave Vcmp is converted into a DC component of a triangular wave, and is input to the feedback amplifier 5 of the next stage, compared with the reference voltage 6, and amplified, so that the amplitude difference is reduced. The gain is adjusted, for example, by changing the common current. In other words, the adjustment is performed so that the duties of the rectangular waves shown in FIGS. 5A and 5B are equal (θ1 = θ2). As a result, as shown in FIG. 9, the output Vu of the amplifier 1 always outputs a signal having the same amplitude as the output Vv of the amplifier 2 due to these actions. By summing the amplitude-adjusted signals Vu and Vv and inverting them by an inverting means (addition circuit 7, nonlinear circuit 8, limiter 9), a constantly stable converted signal W 'with little waveform distortion and phase shift is output. You can do it. Then, the signals Vu and Vv from the amplifiers 1 and 2 and the conversion signal W ′ are supplied to the starter coil drive circuit 11 to drive the brushless motor in three phases.
[0016]
FIG. 7 is a circuit diagram showing a specific configuration of a drive control circuit to which a brushless motor according to one embodiment of the present invention is applied. HGU and HGV are Hall elements, respectively. The input terminals are connected in parallel, and a bias current is supplied by resistors R1 and R2. The output terminal of each of the Hall elements HGU and HGV is connected to the base terminal of a differential amplifier composed of transistors Q1 to Q4. The transistors Q1 to Q4 and Q78, the resistors R3 to R11, and the current source I1 constitute amplifiers 1 and 2, and the amplified Hall signals Vu and Vv are output to the respective collectors of the transistors Q1 to Q4.
[0017]
The amplified Hall signals Vu and Vv are connected to the base terminals of a differential amplifier composed of Q5 to Q8. The transistors Q5 to Q12, the resistors R12 to R17, the current sources I2 to I3, and the diode D1 constitute an addition circuit 7, and are output as currents to the collectors of the transistors Q13 and Q14. The output current is supplied to diodes D2 and D3 together with bias currents I4 and I5, and is converted into a voltage. Then, the respective anodes are connected to the bases of the transistors Q15 and Q18.
[0018]
The transistors Q15 to Q18, the resistors R18 to R19, and the current source I6 constitute a non-linear circuit 8, and are output as voltages to the collectors of the transistors Q16 and Q17, and are connected to the bases of the transistors Q19 and Q20. The transistors Q19 and Q20, the resistors R20 and R21, and the current source I7 constitute a limiter 9, and are output to the collectors of the transistors Q19 and Q20 as a conversion signal W '. The output converted signal W 'is connected to the bases of the transistors Q21 to Q26 as three-phase position signals together with the amplified hall signals Vu and Vv.
[0019]
The transistors Q21 to Q46, the resistors R23 to R29, the resistor R43, and the current sources I8 to I10 constitute a stator coil driving circuit 11, and store a current having a magnitude corresponding to a speed control signal input to the base of the transistor Q42. Control is performed at a ratio according to the signal so as to flow through the stator coil 80 represented by the inductances L1 to L3 connected to the collectors of the transistors Q44 to Q46.
[0020]
The above-mentioned Hall signals Vu and Vv are also connected to the base terminals of transistors Q47, Q48, Q57 and Q58, which are inputs of an absolute value circuit, for detecting the respective amplitude differences. Transistors Q47 to Q60, resistors R32 to R39, current sources I11 to I12, diodes D6 to D7, and voltage sources E1 and E2 constitute an absolute value circuit 3, and rectangular waves Uabs and Vabs are output to the collectors of transistors Q54 and Q60. You.
[0021]
The rectangular waves Uabs and Vabs are connected to the bases of the transistors Q65 and Q66, which are the inputs of the comparator 4. The transistors Q63 to Q66 and the current source I13 constitute the comparator 4 and are output to the collector of the transistor Q64. An amplitude control signal is output to the anode of D8. This signal is connected to the base of the transistor Q69, compared with the reference voltage 6 in the feedback amplifier 5 including the transistors Q69 to Q78, the resistors R41 and R42, the voltage source E3, and the current sources I16 and I17. Is output as current to the collector.
[0022]
This current becomes the above-mentioned common current of the amplifier 1, changes the common current according to the amplitude difference between the amplified Hall signals Vu and Vv, and finally controls the Hall signal Vu to have the same amplitude as the Hall signal Vv.
[0023]
The above-mentioned hall signals U and V are subjected to sum operation and inversion by a signal synthesizing means 7 to output a synthesized signal W. The hall signals U and V are trapezoidal signals as shown in FIG. 8, and the composite signal W is a distorted triangular signal. At this time, the synthesized signal W can be converted into a trapezoidal converted signal W 'equivalent to the Hall signals U and V by the nonlinear conversion circuit 8 as shown in FIG.
[0024]
Next, the driving magnetic poles of the rotor will be described. A magnetic pole waveform of a portion that supplies a magnetic flux to the Hall element according to the rotation angle of the rotor includes a third harmonic component and a fifth harmonic component in phase with a fundamental wave, and includes a third harmonic component. The difference between the content and the content of the fifth harmonic component is set to 16% or less. In recent years, there has been a demand for miniaturization and improved efficiency of devices, and it has been required to reduce the drive current and increase the torque even in such a brushless motor, and for this purpose, it is effective to increase the total magnetic flux amount. Therefore, I tried to make the driving magnetic pole from a sine wave to a trapezoidal wave.
[0025]
When the driving magnetic pole is changed from a sine wave to a trapezoidal wave, the maximum magnetic flux density determined by the characteristics of the magnet is constant. Therefore, as shown in FIG. It has also been found that this also increases the torque. That is, as shown in FIG. 11, for example, if the driving magnetic pole contains the third harmonic of 10%, the fundamental wave also increases by about 10%, and as a result, the torque also increases by 10%. However, the same applies to the portion that supplies the magnetic flux to the Hall element. The Hall signal also includes this third harmonic component, and when these are summed and inverted to generate a composite signal W, the waveform differs from the Hall signal waveform. When a waveform containing a large amount of distortion is generated and only the third harmonic component is increased, as shown in FIG. 12 (e), the slope of the triangular wave composite signal W near the zero cross becomes small, and even through the non-linear conversion means. A distorted trapezoidal wave output as shown in FIG. This resulted in a difference in the drive current between the stator coils of each phase, resulting in an uneven torque and an increase in the uneven rotation of the motor. In particular, when the content of the third harmonic exceeds 16%, the slope near the zero cross of the composite signal W is reversed as shown in FIG. 12 (g) and extremely distorted as shown in FIG. 12 (h). It becomes a conversion output, and becomes unusable for use, such as the generation of a reverse drive torque.
[0026]
As shown in FIG. 13, the rotation unevenness increases as the content of the third harmonic of the drive magnetic pole increases, and especially when the content exceeds 8%, the rotation unevenness exceeds 0.3%. Has a problem that they cannot endure the When the fifth harmonic is included in the driving magnetic pole in order to solve this problem, the synthesized signal W described above has a good slope near the zero cross as shown in FIG. 12 (i), and the distortion of the converted waveform W ′ is also reduced as shown in FIG. As shown in j), it is reduced, and excellent rotation unevenness characteristics are exhibited.
[0027]
For this reason, even if the content of the third harmonic exceeds 16%, if the difference obtained by subtracting the content of the fifth harmonic from the content of the third harmonic is 16% or less, the combined signal W Does not reverse, no driving torque is generated in the reverse direction, and if the difference in the content is 12% or less, good rotation unevenness characteristics are also exhibited.
[0028]
In addition, if the magnetic pole waveform of the portion that supplies the magnetic flux to the Hall element of the driving magnetic pole includes the third harmonic component and the fifth harmonic component as described above, the above-described problem is solved. Similar effects can be obtained even if the contents of the other parts of the magnetic pole are different.
[0029]
Next, the nonlinear conversion circuit will be described. As described above, the hall signals U and V are summed and inverted by the signal synthesizing means to output a synthesized signal W. Since the magnetic pole waveform of the portion for supplying the magnetic flux to the Hall element of the driving magnetic pole also has a trapezoidal waveform including the third harmonic component and the fifth harmonic component, the Hall signals U and V are also shown in FIGS. As shown in FIG. 12B, the signal becomes a trapezoidal wave, and the combined signal W is obtained as a distorted triangular wave signal as shown in FIG.
[0030]
The nonlinear conversion means has a high gain near the zero crossing of the input signal and an amplitude of the input signal so as to convert the input triangular-wave synthesized signal W into a trapezoidal-wave converted signal W ′ as shown in FIG. The circuit means has a characteristic in which the relationship between the input amplitude and the output amplitude has a triangular wave-trapezoidal wave conversion characteristic such that the gain decreases as the size increases and the output amplitude hardly increases even if the input amplitude eventually increases. .
[0031]
Specifically, in the case of the present embodiment, the input amplitude is raised to the power of 3/4, and then the triangular signal is converted into a trapezoidal signal by using the logarithmic conversion characteristic of the differential amplifier. In the experiment, necessary conversion characteristics were obtained between 1/2 power and 1/1 power, and particularly preferable triangular wave-trapezoidal wave conversion characteristics were obtained from 1/2 power to 5/6 power.
[0032]
Next, the arrangement of the Hall elements will be described. Even when the rotor drive magnet is manufactured with great care, surface runout remains on the surface facing the Hall element, and the magnetic flux density of the magnetic flux supplied to the Hall element changes due to the rotation of the rotor. This effect is so-called AM modulation of one cycle per rotation in which a portion where the amplitude of the Hall element output increases in rotation and a portion where the amplitude decreases in rotation are alternately repeated.
[0033]
As an inherent problem in the case where the signal synthesizing means is provided, if the arrangement of the two Hall elements is separated, when the amplitude of the output of one Hall element is large, the amplitude of the output of the other Hall element is small. And the waveforms of the combined signal W and the converted signal W ′ change, causing an increase in rotation unevenness.
[0034]
FIG. 14 shows the relationship between the interval between Hall elements expressed in mechanical angles and rotation unevenness when the surface deflection of the surface of the drive magnet facing the Hall element is large. The effect is reduced to a usable level of about 0.25%, and at 45 degrees or less, the effect of increased rotation unevenness is reduced to about 0.15%, which can be ignored. FIG. 15 shows that two Hall elements are arranged on a stator substrate so as to output Hall signals U and V having a phase difference of 120 degrees according to the above-mentioned drive magnetic poles at intervals of 30 degrees in mechanical angle. An example is shown.
[0035]
Next, the Hall element will be described. An inherent problem in the case where the above-described nonlinear conversion circuit is provided is that, when the sensitivity of the Hall element changes with temperature and the amplitude of the output of the Hall element changes, the output waveform of the nonlinear conversion means changes. This can lead to an increase and limits the temperature range that can be used.
[0036]
In order to solve this problem, there is a method of changing the conversion characteristic of the non-linear conversion means according to the temperature to compensate for the output waveform. However, another problem arises in that the circuit configuration becomes complicated. For this reason, by using a GaAs type Hall element having good temperature characteristics as the Hall element, the amplitude of the Hall element output is less likely to change due to a temperature change, and the output of the non-linear conversion means can be reduced without complicating the circuit configuration. The waveform does not change, stable rotation unevenness with respect to temperature is obtained, and the usable temperature range is expanded.
[0037]
In this embodiment, the amplitude difference between the Hall signals U and V is detected, the amplitude of the Hall signals U and V is adjusted according to the amplitude difference, and the signal after the amplitude difference is reduced is subjected to the sum operation and inversion. As a result, a stable converted signal W 'can be output, so that rotation unevenness can be greatly improved.
[0038]
The drive circuit shown in the circuit diagram of FIG. 16 generates a difference X between a signal corresponding to the Hall signal U and a signal corresponding to the Hall signal V, and generates a difference X according to the signal corresponding to the Hall signal V and the conversion signal W ′. A drive circuit is configured to generate a difference Y between the signal and the converted signal W ′, generate a difference Z between the signal corresponding to the converted signal W ′ and the signal corresponding to the Hall signal U, and control and drive a drive current to the stator coil. are doing.
[0039]
The drive circuit means acts to flow a current of a magnitude corresponding to the above-described speed control signal to the three-phase stator coil at a ratio corresponding to the magnitude of these signals, and thus acts as described above. When the hall signals U and V and the conversion signal W 'are trapezoidal waves, the change in the ratio of the current of the three-phase stator coil becomes steep, and there is a problem in that the amount of vibration, noise, and electromagnetic noise increases.
[0040]
A difference X between a signal corresponding to the Hall signal U and a signal corresponding to the Hall signal V is generated, a difference Y between a signal corresponding to the Hall signal V and a signal corresponding to the conversion signal W ′ is generated, and the conversion signal W is generated. When the difference Z between the signal corresponding to the 'and the signal corresponding to the Hall signal U is generated, the third harmonic signal cancels out the difference signal as shown in FIGS. 12 (k), (l) and (m). It has a substantially sinusoidal shape.
[0041]
By configuring the drive circuit so as to control and supply a drive current to the stator coil in accordance with the substantially sinusoidal signals X, Y and Z, the drive magnetic pole obtains an effect of increasing torque with a trapezoidal wave, and The change in the ratio of the currents of the three-phase stator coils becomes slow, the amount of vibration, noise, and electromagnetic noise is reduced, and the above-described problem is solved.
[0042]
(Second embodiment)
Next, a second embodiment will be described. The control current waveform by the feedback amplifier 5 has some ripples as shown in FIG. If the ratio of the ripple of the current to the DC component of the common current of the amplifier 1 becomes large, distortion occurs in the amplified waveform, and distortion occurs in the converted signal W ′. As a result, the rotation unevenness worsens. Would. For example, consider a case in which the common current of the amplifier that amplifies the Hall signal V is fixed and the common current of the amplifier that amplifies the Hall signal U is controlled. As shown in FIG. 6, when the amplitude of the Hall signal U> the amplitude of the Hall signal V, the DC component of the common current is reduced, and when the amplitude of the Hall signal U <the amplitude of the Hall signal V, the DC component is increased. However, the magnitude of the ripple does not change. Therefore, as shown in FIG. 17, the ratio of the ripple component to the DC component (hereinafter referred to as the ripple current ratio) increases as the amplitude of the Hall signal U> the amplitude of the Hall signal V, and the amplitude of the Hall signal U <the amplitude of the Hall signal V. It becomes smaller as the amplitude increases.
[0043]
Therefore, as shown in FIG. 18, if the amplitude difference between the Hall signals U and V is within the dynamic range の of the feedback amplifier, the more the common current of the amplifier for amplifying the Hall signal U is increased (that is, the amplitude of the Hall signal U < The more the amplitude of the Hall signal V becomes, the less the uneven rotation is.
[0044]
In this embodiment, attention is paid to this point, and as shown in FIG. 19, even when the amplitude difference between the Hall signals U and V is 0, the common current value of the amplifier on the controlling side is set to be 5 times smaller than the common current value of the other amplifier. (In other words, when the respective common current values are the same, the gain of the controlling amplifier is made 5% or more lower than the gain of the other amplifier) and the dynamic range of the feedback amplifier is also shifted to be constant. The average ripple current ratio within the range of the amplitude variation can be reduced, and the average rotation unevenness can also be reduced. Here, the reason why the difference in the common current value of the amplifier (the difference in the amplification factor of the amplifier) is 5% or more is that if the difference is less than 5%, the effect is small. If this ratio exceeds 20%, the dynamic range of the feedback amplifier becomes narrow, and the range in which the amplitude variation can be controlled may become narrow. Therefore, this ratio is preferably set to 20% or less.
[0045]
In the embodiments described so far, a so-called feedback type configuration is used. However, a so-called feed-forward type configuration may be used. In the embodiments, a so-called axial gap type brushless motor has been described. Even so, the present invention can be implemented and the same effect can be obtained. Further, the description has been given of the motor in which the drive magnetic poles are integrally provided on the same surface. However, a brushless motor in which a magnetic flux is supplied to the stator coil and a magnetic flux is supplied to the Hall element in a divided manner is also described. The present invention is not limited to the embodiments described herein, and various modifications are possible without departing from the invention.
[0046]
【The invention's effect】
According to the present invention, the amplitude difference between the Hall signals U and V is detected, the amplitude of the Hall signals U and V is adjusted according to the amplitude difference, and the amplitude difference is reduced. The signal is summed to produce a composite signal W, which is calculated by a non-linear circuit and a limiter. A stable conversion signal W 'can be output, so that rotational unevenness can be greatly improved. In addition, a three-phase motor can reduce the use of Hall elements to two, thereby providing an inexpensive and high-performance brushless motor. be able to. Also, when the value of the common current of the amplifier is the same, the ripple current ratio can be reduced by reducing the gain of the amplifier to be adjusted by 5% or more from the gain of the other amplifier, thereby reducing rotation unevenness. Can be.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a brushless motor that directly drives a capstan shaft of a VTR.
FIG. 2 is a plan view of a stator of the brushless motor shown in FIG.
FIG. 3 is a block diagram showing a brushless motor drive circuit according to one embodiment of the present invention.
FIG. 4 is a diagram showing an output waveform of an absolute value circuit.
FIG. 5 is a diagram showing an output waveform of a comparator.
FIG. 6 is a diagram showing a waveform smoothed by a capacitor.
FIG. 7 is a circuit diagram showing a specific configuration of a brushless motor drive circuit according to one embodiment of the present invention.
FIG. 8 is a diagram showing waveforms of a hall signal and a composite signal when the hall signal has a trapezoidal waveform.
FIG. 9 is a diagram showing the waveforms of the Hall signal and the converted signal when the synthesized signal is converted by a non-linear conversion circuit with the trapezoidal waveform of the Hall signal.
FIG. 10 is a diagram comparing a driving magnetic pole waveform including only a sine wave with a trapezoidal driving magnetic pole waveform including 15% of a third harmonic.
FIG. 11 is a diagram showing a torque increase rate depending on the content of the third harmonic.
FIG. 12 is a diagram showing waveforms of a hall signal, a composite signal, and a converted signal.
FIG. 13 is a diagram showing a ratio of rotation unevenness depending on a content rate of a third harmonic.
FIG. 14 is a diagram showing a ratio of rotation unevenness depending on an interval between Hall elements.
FIG. 15 is a plan view of another stator of the brushless motor used in the brushless motor drive control circuit according to one embodiment of the present invention.
FIG. 16 is another circuit diagram showing one embodiment of the present invention.
FIG. 17 is a diagram showing a ripple current ratio with respect to a DC current value.
FIG. 18 is a diagram showing a ratio of rotation unevenness depending on an amplitude ratio of U to V in the first embodiment of the present invention.
FIG. 19 is a diagram illustrating a ratio of rotation unevenness according to an amplitude ratio of U to V according to the second embodiment of the present invention.
FIG. 20 is a diagram showing waveforms of an ideal Hall signal and a composite signal.
FIG. 21 is a diagram showing waveforms of an actual hall signal and a composite signal.
FIG. 22 is a diagram showing waveforms of a Hall signal and a conversion signal when an amplitude shift occurs in the Hall signal.
FIG. 23 is a diagram showing a ratio of rotation unevenness based on an amplitude ratio of U to V when a conventional brushless motor drive control circuit is used.
[Explanation of symbols]
1,2 amplifier
3 Absolute value circuit
4 Comparator
5 Feedback amplifier
6 Reference voltage
7 Addition circuit
8 Nonlinear circuit
9 Limiter

Claims (1)

A rotor having a driving magnetic pole and rotatably held;
A three-phase stator coil facing the drive magnetic pole;
Two Hall elements that are supplied with a magnetic flux according to the rotation angle of the rotor and output Hall signals U and V having a phase difference of 120 degrees in electrical angle;
Signal combining means for combining the Hall signals U and V and outputting a combined signal W having a phase difference of 120 degrees in electrical angle with respect to the Hall signals U and V;
A drive circuit comprising a non-linear circuit for passing a drive current to the stator coil according to the Hall signals U and V and the composite signal W, and a limiter ;
Amplitude control means for outputting an amplitude difference signal corresponding to the amplitude difference between the Hall signals U and V;
Amplitude adjusting means for adjusting the amplitude of the Hall signals U, V or both according to the amplitude difference signal,
A brushless motor drive control circuit, wherein an amplitude difference between the hall signals U and V is reduced.

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