JPH06103998B2 - Brushless motor drive circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drive circuit for a brushless motor.

[Conventional technology]

Conventionally, motor drive circuits are roughly classified into a current drive system and a voltage drive system. The former current drive method has a current feedback function and always drives the motor with a constant current when the motor control signal is constant. With this function, particularly in the case of a brushless motor, even if there is an interphase imbalance of the drive circuit, it is possible to substantially suppress the torque fluctuation of the motor due to the interphase imbalance. However, as a fate when driving a motor with a constant current, about 14% of the total torque is generated per revolution of the motor, which is the least common multiple of the number of stator drive coil poles and the number of rotor magnet magnetic poles. To do.

Therefore, as a motor drive circuit for correcting the torque ripple, those shown in FIGS. 12 to 15 have been disclosed in Japanese Utility Model Publication No. 56-34551, Japanese Patent Application Publication No. 58-192490, and Japanese Patent Application Publication No.
It is known from JP-A-9-35585 and JP-A-59-76192.

In the structure shown in FIG. 12, the rotation speed of the motor 11 is detected by the rotation speed detector 12, and the rotor rotation position of the motor 11 is detected by the rotor rotation position detection means 13 including a Hall element. The reference voltage is compared with the output signal of the rotation speed detector 12 in the comparison circuit 15 via the superimposing circuit 14, and the error signal causes the control circuit 16 to respond to the output signal of the rotor rotation position detecting means 13 in each winding 17 of the motor 11. To switch on and energize. Further, the rotation speed fluctuation amount detection circuit 18 detects a high frequency component in the rotation speed fluctuation amount of the motor 11 from the output signal of the rotor rotation position detection means 13, and the detection signal is used as a superposition circuit 14
The torque ripple of the motor 11 is corrected by being superimposed on the reference voltage at.

In the one shown in FIG. 13, the coil 20 in the motor having the field means 19 and the coil 20 is energized by the power supply means 21, and the power supply means 21 outputs the output signal according to the input signal by the control means 22. The output signal of the control means 22 causes the drive transistor 23 to drive the coil 20 and
Is detected by the coil current detection means 24, and the output signal of the current detection means 24 is negatively fed back to the control means 22.
The similar current generating means 25 generates a similar current according to the command signal, and this similar current is modulated by the modulating signal by the modulating means 26, and the command signal is output from the modulating means 26 by the synthesizing means 27 via the similar current generating means 25. By superimposing the signal and inputting it to the control means 22, the torque ripple of the motor is corrected.

In the structure shown in FIG. 14, field means 28 and coils 29 of multiple phases are used.
The position of the coil 29 in the motor having the
Switches the plurality of phase coils 29 in accordance with the position detecting means 30 based on the output signal of the modulating means 32 to energize. Further, the power supply means 31 generates a modulation signal, and the command signal is a modulation means.
The torque ripple of the motor is corrected by being modulated by the modulation signal from the power supply means 31 at 32.
In this case, the position detecting means 30 is configured so that the switching timing of the coils 29 of multiple phases and the timing when the output signal of the power supply means 31 becomes zero, and the modulating means 32
Is configured such that the output signal of the modulation means 32 is temporally symmetrical with respect to the timing when the output signal of the position detection means 30 becomes zero.

In the motor shown in FIG. 15, the coil 34 in the motor having the field means 33 and the coil 34 is supplied with current by the current supply means 35, and the current supply means 35 is means for changing the supplied current.
36, a coil current detecting means 37 and a synthesizing means 38. The means 36 supplies a current to the coil 34 in response to the command signal from the command signal generation means 39, the current of the coil 34 is detected by the coil current detection means 37, and the detection signal of the coil current detection means 37 is combined means. Negative feedback is made to the means 36 via 38. Further, the command current generation means 40 generates a current signal according to the command signal from the command signal generation means 39, and the modulation signal generation means 41 generates a modulation signal according to the movement of the motor movable portion 42. Then, the current signal from the command current generation means 40 is modulated by the modulation means 43 by the modulation signal from the modulation signal generation means 41 and combined by the combining means 38 with the detection signal from the coil current detection means 37 to the above means 36. By
The torque ripple of the motor is corrected.

However, although the drive circuit of the motor is formed as an IC, the number of internal elements of the IC increases due to the addition of the circuit for correcting the torque ripple, which complicates the IC circuit and considerably increases the IC price. Further, since the hall element is used as the position detecting means for detecting the position of the rotor and the output signal of the hall element is used to generate the torque ripple correction signal, the torque ripple correction signal causes variations in the output signal waveform of the hall element, distortion, It is easily affected by temperature characteristics, etc., and the torque ripple correction effect depends on the accuracy of the Hall element.

As a drive circuit for a brushless motor that has improved these drawbacks, there is one described in Japanese Patent Application No. 1-172547. FIG. 10 shows an example described in Japanese Patent Application No. 1-172547.

The position detecting means consisting of Hall elements Hu, Hv, Hw is supplied with current from the power supply through resistors R1 and R2, detects the rotational position of the rotor consisting of the rotor magnet magnetized to the 2n pole, and detects this rotor. And a three-phase sine-wave-like output having a phase difference of 120 ° from each other as shown in FIG. 11 (a) according to the relative positional relationship between the stator having three-phase drive coils Lu, Lv, and Lw. Signal V
yields u, Vv, Vw. Assuming that the three-phase output signals Vu, Vv, Vw are sine waves for convenience, Vu = 0.2sin θ Vv = 0.2sin (θ−120 °) Vw = 0.2sin (θ−240 °).

Transistors Q1 to Q6, current sources CS1 to CS that generate current I ₀
3, the resistors R3 to R5 having the resistance value R ₀ and the diodes D1 and D2 constitute the Hall amplifier circuit and the signal combining circuit 44, and the Hall element H
The output signals Vu, Vv, Vw of u, Hv, Hw are amplified and logarithmically compressed to
A three-phase soft switching signal is formed while the waveform is shaped like a rectangular wave pulse with an inflection point blunted as shown in FIG.
Combined into Vu ′, Vv ′ and Vw ′. That is, Hall element Hu, H
The output signals Vu, Vv, Vw of v, Hw are amplified by the transistors Q1 to Q6, and the collector outputs of the transistors Q1, Q4 are combined into a soft switching signal Vu ', which is the transistor Q1.
The collector outputs of 3, Q6 are combined into a soft switching signal Vv ', and the collector outputs of the transistors Q2, Q5 are combined into a soft switching signal Vw'. These soft switching signals Vu ′, Vv ′, Vw ′ are Becomes Here, e is the base of the natural logarithm, K is the Boltzmann constant [J / ° K], T is the absolute temperature [° K], and q is the electron charge (c).

Transistors Q7 to Q12, variable current source C generating current I _CTL
S4 constitutes the first signal circuit 45, and the transistors Q7 to Q9 are variable current sources CS4 by the three-phase soft switching signals Vu ', Vv', Vw 'from the Hall amplifier circuit and the signal combining circuit 44.
The currents Iu ′, Iv ′, Iw ′ proportional to the current I _{CTL of} are output from the collectors through the transistors Q10 to Q12. In addition, transistors Q13 to Q18, variable current source CS that generates current I _CTL
5, the diodes D3 to D5 and the resistor R6 constitute the second signal circuit 46, and the transistors Q16 to Q18 are the three-phase soft switching signals V from the Hall amplification circuit and the signal synthesis circuit 44.
u ', Vv', current is proportional to the current I _CTL of the variable current source CS5 by Vw 'Iu, Iv, via the transistor Q13~Q15 from the collector and Iw outputted. These currents Iu ′, Iv ′, Iw ′, Iu, Iv, I
w is Becomes

The three sets of Darlington-connected transistors Q19 to Q24 form a first transistor group, amplify the output currents Iu ′, Iv ′, Iw ′ of the first signal circuit 45 by α times and drive coils of three phases. Source current flows into Lu, Lv, and Lw. The three sets of Darlington-connected transistors Q25 to Q30 form a second transistor group, and output currents Iu, Iv, Iw of the second signal circuit 46.
Is amplified by α times and a sink current is caused to flow out to the three-phase drive coils Lu, Lv, Lw.

The current detection resistor Rs detects the current flowing through the three-phase drive coils Lu, Lv, Lw and converts it into a voltage. This voltage is compared with the motor speed control signal V _{CTL by the} current feedback amplifier Ai, and its error Variable current sources CS4 and CS5 are changed by the voltage and variable current source C
The current I _CTL of S4 and CS5 is controlled. Motor speed control signal V
_{When CTL} maintains a constant value, the current I _CTL is controlled so that the current flowing through the current detection resistor Rs becomes constant, and a constant current is supplied to the drive coils Lu, Lv, Lw.

The hall amplifier circuit and signal combining circuit 44 are hall elements Hu, Hv,
The output signals Vu, Vv, and Vw of Hw are amplified, logarithmically compressed, and shaped like a rectangular wave pulse with blunted inflection points as shown in FIG. 11 (b) and a three-phase soft switching signal V.
When combining u ′, Vv ′ and Vw ′ If the amplitude setting of the soft switching signals Vu ′, Vv ′ and Vw ′ is made small, the source current and sink current of the drive coils Lu, Lv and Lw in phase are generated simultaneously. There will be a timing to do. For example, as shown in FIG. 8, the source current αI of the U-phase drive coil Lu
Timing T _{0 when} u ′ and sink current αIu occur simultaneously
Exists. This timing T ₀ corresponds to a section in which no current flows in the U-phase drive coil Lu as shown in FIG. 7 in another conventional brushless motor drive circuit. Further, as shown in FIG. 8, before and after the center point of the timing T ₀ , αIu ′
≉αIu, and almost no current flows through the U-phase drive coil Lu, and current flows from the power supply _cc to the current detection resistor Rs via the transistors Q20 and Q26. This means that a relatively large amount of reactive current that does not contribute to torque generation of the motor is generated. Moreover, since the feedback is applied so that a constant current flows through the current detection resistor Rs regardless of the presence or absence of the reactive current, the current flowing through the current detection resistor Rs remains constant. Therefore, in the section of the timing T ₀ , the total torque of the motor decreases by the amount of the reactive current. This phenomenon is the same for the V phase and the W phase, and occurs at a rate of once every 60 °, and as can be seen from FIG. 8, it is synchronized with the cycle of the peak of the combined torque. Therefore, the reduction of the torque due to the reactive current suppresses the peak of the combined torque, and the torque ripple is reduced. As shown in FIG. 8, some reactive current also flows in the section a in which the drive coils Lu, Lv, Lw should be energized.

The characteristic curve A in FIG. 5 shows the ratio of the torque ripple to the amplitude of the soft switching signals Vu ', Vv', Vw 'from the Hall amplifier circuit and signal combining circuit 44. When the current values of the current sources CS1 to CS3 or the values of the resistors R3 to R5 in the Hall amplifier circuit and the signal combining circuit 44 are changed to change the amplitudes of the soft switching signals Vu ', Vv', Vw ', the torque ripple becomes the fifth value. It changes as shown in the figure. Therefore, it becomes possible to greatly improve the torque ripple by varying the current value of the current sources CS1 to CS3 or the value of the resistors R3 to R5.

Further, in this example, it is not necessary to add a new circuit to correct the torque ripple. Moreover, since the Hall amplifier circuit is used in the saturation region, the Hall element has nothing to do with the torque ripple correction function and is not affected by variations in the Hall element or output accuracy.

Also, in this example, the drive coil L of the brushless motor is
There is also an example in which a counter electromotive voltage including the fifth harmonic is generated in u, Lv, and Lw.

[Problems to be Solved by the Invention]

In the brushless motor drive circuit described in Japanese Patent Application No. 1-172547, the combined torque of the brushless motor becomes small as shown in FIG. 8, and the brushless motor drive circuit of another conventional brushless motor as shown in FIG. It decreases compared with the synthetic torque of the motor. Further, there is a drawback that the torque ripple is apt to be deteriorated when an imbalance between phases occurs due to variations in constituent elements. Further, as shown by the characteristic curve A in FIG. 5, the torque ripple correction effect is at most 30% at maximum.

The present invention improves the above-mentioned drawbacks, minimizes the reduction of the combined torque, prevents the torque ripple from being deteriorated due to the variation of the constituent elements, and can enhance the torque ripple correction effect. It is an object of the present invention to provide a driving circuit of the.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the invention of claim 1 has a stator having an m-phase drive coil, a rotor having magnetic poles that are rotationally biased by the stator, and a relative position between the rotor and the stator. A position detecting means for obtaining an m-phase sine wave-like output signal according to the positional relationship, and an output signal of the position detecting means are logarithmically compressed to form a rectangular wave pulse having an inflection point blunted and m Signal synthesizing circuit for synthesizing a soft switching signal of a phase, a plurality of transistor groups for switching energization to the m-phase driving coil by an output signal of the signal synthesizing circuit, and the m-phase driving coil by the plurality of transistor groups Current control means for controlling each energization amount to be energized, a current detection resistor connected so as to detect a current flowing through the drive coil and apply negative feedback to the current control means, and the m-phase In the energization period which should be each non-energization period to the moving coil, the transistors of the same phase among the plurality of transistor groups are simultaneously turned on to cause a reactive current to flow into the current detection resistor at the same time. The drive coil of the brushless motor according to claim 1, wherein the drive coil is provided with a reactive current interruption means for interrupting a reactive current in an energized section where the drive coil should be energized. The fifth harmonic wave is superimposed on the counter electromotive voltage.

[Action]

According to the first aspect of the invention, the rotor is rotationally biased by the stator, and the position detecting means obtains an m-phase sinusoidal output signal according to the relative positional relationship between the rotor and the stator. The signal synthesizing circuit logarithmically compresses the output signal of the position detecting means to shape it like a rectangular wave pulse with blunted inflection points and synthesizes it into an m-phase soft switching signal. The transistor group switches the energization of the m-phase drive coil. The amount of electricity supplied to the m-phase drive coil is controlled by the current control means by the plurality of transistor groups, and the current flowing in the drive coil is negatively fed back to the current control means by the current detection resistor. In the energization period which should be each non-energization period to the m-phase drive coil, the transistors of the same phase among the plurality of transistor groups are simultaneously turned on by the simultaneous on-section generating means, and a reactive current flows through the current detection resistor, so that the m-phase In the energization section in which the drive coil should be energized, the reactive current interrupting means interrupts the reactive current.

In the invention of claim 2, a counter electromotive voltage in which the fifth harmonic is superimposed is generated in the drive coil.

〔Example〕

FIG. 1 shows an embodiment of the present invention, and the same parts as those in the example of FIG. 10 are designated by the same reference numerals.

In the Hall amplification circuit and signal synthesis circuit 44, current sources CS1 to CS3
Variable current sources CS6 to CS8 are used instead of. The variable current source CS6~CS8 the current corresponding to the input voltage from the adjustment terminal T ₁
I ₀ is generated and the voltage of the adjustment terminal T ₁ is varied to change the variable current source CS
The current I _{0 of 6} to CS8 can be arbitrarily set and adjusted.

The soft switching signals Vu ', Vv', Vw 'from the Hall amplifier circuit and signal combining circuit 44 pass through resistors R7-R12, respectively, and are PNP type transistors Q31-Q33, NPN type transistor Q34.
.About.36 and variable current sources CS9 and CS10 are converted into currents and amplified by three differential amplifiers. The output currents Iu ″, Iv ″, Iw ″ and Iu, Iv, Iw from the three differential amplifiers are output to the pre-driver PD via a mirror circuit composed of transistors Q37 to Q42 and resistors Q43 to Q48.

Further, for example, in the U phase, the soft switching signal Vu 'from the Hall amplifier circuit and the signal combining circuit 44 is converted into a current by the transistors Q31 and Q34 through the resistors R7 and R10 and amplified, and the output current from the collector of the transistor Q31. Is fed back to the base (point) of the transistor Q34 by the mirror circuit composed of the transistors Q43 and Q52 and the resistors R17 and R20. The collector current of the transistor Q34 is the base of the transistor Q31 due to the mirror circuit consisting of the transistors Q37 and Q49 and the resistors R13 and R16. Be fed back to. At this time, transistor Q34,
The feedback current fed back to the base of Q31 is assumed to be considerably smaller than the current I ₀ of the variable current sources CS6, CS7, CS8.

Similarly for the V phase and the W phase, the soft switching signals Vv 'and Vw' from the Hall amplifier circuit and the signal synthesizing circuit 44 respectively pass through the resistors R8, R11, R9 and R12 and the transistors Q32 and Q3.
5, converted to current by Q33, Q36 and amplified, the output current from the collector of transistors Q32, Q33 is
The mirror circuit consisting of Q44, Q53, Q45, Q54 and resistors R18, R19, R20 makes the bases (points,
Feedback). Also, transistor Q35,
The collector current of Q36 is the base of transistors Q32, Q33 by the mirror circuit consisting of transistors Q38, Q50, Q39, Q51 and resistors R14, R15, R16. Be fed back to. Also at this time, the transistor Q3
It is assumed that the feedback current fed back to the bases of 2, Q33, Q35, Q36 is considerably smaller than the current I ₀ of the variable current sources CS6, CS7, CS8.

Thereby, the cathode side of the diode D2 and the above,
, Voltage between points V _su , V _sv , V _sw and diode D2
On the cathode side and above The voltages V _su ′, V _sv ′ and V _sw ′ between and are as shown in FIG. The diodes D6, D9, D7, D10, D8 and D11 are
_It works as an amplitude limiter that limits the amplitudes of _su , V _sv , V _sw , V _su ′, V _sv ′, and V _sw ′.

The transistor group consisting of the transistors Q55, Q56, Q57 is a three-phase drive coil Lu, Lv, depending on the output signal of the pre-driver PD.
Source currents αIu ″, αIv ″, αIw ″ flow into Lw, and the transistor group consisting of transistors Q58, Q59, Q60 causes three-phase drive coils Lu, Lv, Lw by the output signal of the pre-driver PD.
The sink currents αIu, αIv, and αIw are caused to flow out.
This source current αIu ″, αIv ″, αIw ″ is the pre-driver
The PD input currents Iu ″, Iv ″, Iw ″ are the currents amplified α times by the pre-driver PD and the transistor groups Q55, Q56, Q57, and the sink currents αIu, αIv, αIw are the input currents Iu of the pre-driver PD. , Iv, Iw are currents amplified by α times by the pre-driver PD and the transistor groups Q58, Q59, Q60.

The current detection resistor Rs detects the current flowing through the three-phase drive coils Lu, Lv, Lw and converts it into a voltage. This voltage is compared with the motor speed control signal V _{CTL by the} current feedback amplifier Ai, and its error Variable current sources CS9 and CS10 are variable by voltage
The current I _CTL of CS9 and CS10 is controlled. Motor speed control signal
When V _CTL maintains a constant value, the current I _CTL is controlled so that the current flowing through the current detection resistor Rs becomes constant, and a constant current is supplied to the drive coils Lu, Lv, Lw.

Fig. 9 shows the source current αIu "and the sink current αIu of the U-phase drive coil Lu obtained by the simulation in this embodiment. As can be seen from this figure, the source current αIu" and the sink current αIu drive the U-phase. During the energization period T ₀ , which should be a non-energization period for the coil Lu, the U-phase transistors Q55 and Q58 are turned on at the same time to flow as a reactive current in the current detection resistor Rs, and the U-phase drive coil Lu is energized. It does not occur at exactly the same time in the energized section a.
The same applies to the V phase and the W phase. Drive coil Lu, Lv,
The torque ripple obtained by simulation based on the drive current of Lw is about 6.0%, which is improved by about 38% compared to the torque ripple of about 9.7% in the example of FIG.
The combined torque is also increased compared to the example shown in FIG.

The characteristic curve B in FIG. 5 shows the amplitude of the soft switching signals Vu ', Vv', Vw 'in this embodiment from 20 mV _pp to 600 mV.
Shows the torque ripple obtained by simulation while varying up to _pp . From this figure, it can be seen that the torque ripple of this embodiment is dramatically improved over the torque ripple of the example of FIG. 10 shown by the characteristic curve A of FIG.

Fig. 6 shows the torque ripple obtained by simulation by changing the fifth harmonic contained in the back electromotive voltage of the drive coil from -15% to + 15%. The characteristic curve A shows the torque ripple of the conventional circuit. The characteristic curve B shows the torque ripple of the example of FIG. 10, and the characteristic curve C shows the torque ripple of the present embodiment. As can be seen from this figure, in this embodiment, the torque ripple can be minimized with the smallest fifth harmonic component.

In order to include the fifth harmonic in the counter electromotive voltage of the drive coil, there is known a method of superimposing the fifth harmonic by magnetizing the drive magnet with different polarities, non-magnetizing, or the like. .

In this embodiment, by setting the current I ₀ of the variable current sources CS6 to CS8 to a certain small value, the transistor groups Q55, Q56, Q57, Q58, Q59, Q60 are set as shown in FIGS. 8 and 9.
Among them, a simultaneous ON section in which transistors in the same phase are simultaneously turned ON occurs, and in this simultaneous ON section, a reactive current flows through the current detection resistor Rs. The simultaneous ON section generating means for generating this simultaneous ON section is composed of variable current sources CS6 to CS8, Hall amplifying circuit transistors Q1 to Q6, resistors R3 to R5,3 differential amplifying transistors Q31 to Q33, Q34 to Q36. ing. Further, as shown in FIG. 9, the reactive current is eliminated in the energizing section a, but the reactive current interruption means for eliminating the reactive current in the energizing section a is resistors R7 to R12, diodes D6 to D11, transistors.
It is composed of Q49 to Q54 and resistors 20 and R16. Also, 3
The current control means for controlling the amount of each current supplied to the phase drive coils Lu, Lv, Lw are the current detection resistor Rs and the current feedback amplifier A.
i, composed of variable current sources CS9 and CS10.

The in-phase simultaneous transistor on-state current in the section a in FIG. 8 is an ineffective current that does not contribute to the motor drive because it is inversely proportional to the amplitudes of the soft switching signals Vu ', Vv', Vw '. If the reactive current interferes with the torque ripple correction effect, and if the reactive current has a variation between phases, the torque ripple is deteriorated. In this embodiment, the following effects can be obtained by eliminating the reactive current in the section a as described above. That is, the reduction of the combined torque can be suppressed to a minimum, and even if the amplitude of the soft switching signals Vu ′, Vv ′, Vw ′ is reduced, the reactive current does not flow in the conduction section a, so the soft switching signal Vu ′ , V
The torque ripple can be further improved by reducing the amplitudes of v ′ and Vw ′. Moreover, soft switching signal
Reducing the amplitudes of Vu ', Vv', and Vw 'is also effective in reducing motor noise. Torque ripple is less likely to deteriorate due to phase-to-phase variations in drive circuit components. The torque ripple correction effect is improved as shown in FIG. Further, as shown in FIG. 6, since the torque ripple can be reduced even if the harmonic components in FIG. 5 are small, it is not necessary to perform unreasonable correction magnetization on the rotor magnet.

The resistors R13 to R20 may be omitted in the above embodiment.

FIG. 3 shows a part of another embodiment of the present invention.

In this embodiment, the Hall elements Hu, Hv, Hw are the same as in the above embodiment.
Is the current supplied from the power supply and detects the rotational position of the rotor consisting of the rotor magnet magnetized to the 2n pole and detects the relative position of this rotor and the stator with the three-phase drive coils Lu, Lv, Lw. Three-phase sine wave-like means signals having a phase difference of 120 ° from each other according to the positional relationship are output from both output terminals.

Transistors Q61 to Q84 and current sources CS1 to CS3 form a Hall amplifier circuit and a signal combining circuit, which amplify the output signals of Hall elements Hu, Hv, and Hw respectively, logarithmically compress them, and square the inflection point. The waveform is shaped into a pulse line and combined into a three-phase soft switching signal.

The resistors R20 to R25 and the diodes D12 to D18 form a current-voltage converter, which converts each output signal of the Hall amplifier circuit and the signal combining circuit into a voltage to output a signal as shown in FIG.
▼, ▲ ▼, ▲ ▼, Vsu, Vsv, Vsw. Where ▲ ▼, ▲ ▼, ▲
▼ is a waveform which is upside down from the Vsu ′, Vsv ′ and Vsw ′ waveforms shown in FIG. This signal is converted into currents Iu ″, Iv ″, Iw ″, Iu, Iv, Iw by the voltage-current converter composed of the transistors Q85 to Q90 and the variable current sources CS9 to CS10, and sent to the pre-driver PD to be changed. The current sources CS9 to CS10 are controlled by the output signal of the current feedback amplifier Ai and their current value I _CTL
Is variable. The steps after the pre-driver PD are the same as those in the above embodiment.

FIG. 4 shows a part of another embodiment of the present invention.

In this embodiment, the transistors Q91 to Q102, the current sources CS11 to CS16, the resistors R26 to R31 and the diodes D19 to D26 form a Hall amplifier circuit, a signal synthesizing circuit, and a current-voltage converter as compared with the embodiment shown in FIG. , The output signals of the Hall elements Hu, Hv, Hw are respectively amplified and logarithmically compressed to form a rectangular wave pulse with an inflection point blunted, and the three-phase soft switching signal The soft switching signal is converted into voltage and the signal Vs as shown in Fig. 2 is obtained.
u ', Vsv', Vsw ', Vsu, Vsv, Vsw. This signal is supplied to the currents Iu ″, Iv ″, Iw ″, Iu by the voltage-current converter composed of the transistors Q103 to Q108 and the variable current sources CS9 to CS10.
, Iv, Iw are converted and sent to the pre-driver PD, and the variable current sources CS9 to CS10 are controlled by the output signal of the current feedback amplifier Ai to change the current value I _CTL . The steps after the pre-driver PD are the same as those in the above embodiment.

〔The invention's effect〕

As described above, according to the first aspect of the present invention, the stator having the m-phase drive coil, the rotor having the magnetic poles that are rotationally biased by the stator, and the relative position of the rotor and the stator. A position detecting means for obtaining an m-phase sine wave-like output signal according to the relationship, and an output signal of the position detecting means is logarithmically compressed to form a rectangular wave pulse having an inflection point blunted and the m-phase Of the soft switching signal, a plurality of transistor groups for switching the energization to the m-phase drive coil by the output signal of the signal synthesis circuit, and the m-phase drive coil by the plurality of transistor groups. Current control means for controlling each energization amount to be energized,
A current detection resistor connected to detect the current flowing through the drive coil and apply negative feedback to the current control means,
Simultaneous on-section generating means for simultaneously turning on the transistors of the same phase among the plurality of transistor groups during an energization period that should be each non-energization period to the m-phase drive coil to flow a reactive current to the current detection resistor, Since the m-phase drive coil is provided with a reactive current interruption means for interrupting a reactive current in an energization section in which it should be energized, it is possible to suppress the decrease of the combined torque to a minimum and to suppress the torque against the variation of the constituent elements. The ripple is less likely to deteriorate, and the torque ripple correction effect can be increased.

According to a second aspect of the present invention, in the brushless motor drive circuit according to the first aspect, the fifth harmonic is superimposed on the counter electromotive voltage generated in the drive coil.
The torque ripple can be reduced even if the fifth harmonic is small.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing a signal waveform of the same embodiment, and FIGS. 3 and 4 show a part of other embodiments of the present invention. FIG. 5 is a characteristic diagram showing torque ripple characteristics of the embodiment and the conventional circuit. FIG. 6 is a characteristic diagram showing relationship between fifth ripple and torque ripple of the embodiment and the conventional circuit. 7 and 8 are waveform diagrams showing the drive coil current and combined torque of the conventional circuit, and FIG.
FIG. 10 is a waveform diagram showing the drive coil current and combined torque of the above embodiment, FIG. 10 is a circuit diagram showing an example of a conventional circuit, FIG. 11 is a waveform diagram showing signal waveforms of the circuit, and FIGS. The figure is a block diagram showing another conventional circuit. Hu, Hv, Hw …… Hall element, Q1 to Q108 …… Transistor,
D1 to D26 …… Diode, CS1 to CS16 …… Current source, R1 to R3
1 …… Resistance, Lu, Lv, Lw …… Drive coil, Ai …… Current feedback amplifier.

Claims (2)

[Claims] 1. A stator having an m-phase drive coil, a rotor having a magnetic pole that is rotationally biased by the stator, and an m-phase rotor having a relative positional relationship between the rotor and the stator. A position detecting means for obtaining a sine wave-like output signal, and an output signal of the position detecting means are logarithmically compressed to form a rectangular wave pulse having an inflection point blunted and are combined into an m-phase soft switching signal. A signal synthesizing circuit, a plurality of transistor groups that switch energization to the m-phase drive coil by an output signal of the signal synthesizing circuit, and respective energization amounts that are energized to the m-phase drive coil by the plurality of transistor groups. A current control unit for controlling, a current detection resistor connected to detect the current flowing in the drive coil and apply negative feedback to the current control unit, and a non-energization period for the m-phase drive coil. Simultaneous on-section generating means for simultaneously turning on in-phase transistors of the plurality of transistor groups in a desired energization period to supply a reactive current to the current detection resistor, and energization section for energizing the m-phase drive coil. A drive circuit for a brushless motor, comprising: 2. The brushless motor drive circuit according to claim 1, wherein the counter electromotive voltage generated in the drive coil is a fifth
A drive circuit for a brushless motor, characterized in that harmonics are superimposed.