JP2584047Y2 - Brushless motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a brushless motor driving circuit for driving a brushless motor having three-phase coils and capable of rotating forward and reverse.

[Prior Art] JP-A-62-71485 has a three-phase coil.
A section drive circuit for driving a brushless motor capable of rotating forward and backward is disclosed.

In this circuit, the slope waveform of the edge part is extracted from the HG signal output by the Hall element corresponding to the rotation position of the rotor, and a trapezoidal drive signal is generated, and the coil is driven according to the drive signal I am trying to do it.

As described above, when the driving is performed by the driving current having the inclination, the switching of the driving current is gradually performed, and the noise due to the switching can be reduced. Also, unlike the case of the linear drive system using a sinusoidal drive current,
A decrease in motor efficiency can be prevented. Japanese Patent Application Laid-Open No. 62-293986 discloses that the HG signal is clamped at a predetermined level to compensate for torque ripple.

[Problem to be Solved by the Invention] However, since the circuit described in the first publication uses a trapezoidal drive signal, the circuit has a higher torque than a drive method (switching method) using a rectangular wave drive signal. There is a problem that the ripple is slightly increased. In addition, the motor described in the second publication has a problem that the torque ripple cannot be smoothly compensated because the modulation current 14 is conducted only during the period A shown in FIG. 7 in addition to the inappropriate clamp level. There is. The present invention has been made in view of such a situation, and aims to smoothly compensate for torque ripple.

[Means for Solving the Problems] A brushless motor drive circuit according to the present invention is a brushless motor drive circuit for driving a forward / reversely rotatable brushless motor having a three-phase drive coil. A matrix circuit for calculating a difference between two predetermined phase signals and outputting a difference signal from which a harmonic component is removed; and outputting each difference signal of the matrix circuit to a peak value of √3 / 2 level, a clamp circuit for generating a three-phase trapezoidal drive signal whose level is flat during the clamp period, and a drive current obtained by converting each of the three-phase drive signals into a current. And a drive circuit for flowing the air through the motor.

[Operation] In the brushless motor drive circuit having the above configuration, the trapezoidal drive signal is generated by clamping at a level of (3 ^1/2 ) / 2 of the peak value so as to generate a smooth ripple. Therefore, torque ripple can be smoothly compensated by the ripple of the drive current.

FIG. 1 is a block diagram showing the principle of a brushless motor drive circuit according to the present invention.

Three-phase HG signals U, V, and W output by a Hall element (not shown) corresponding to the rotational position of the rotor are amplified by the amplifier 1 and input to the matrix circuit 2 as HU, HV, and HW signals. The matrix circuit 2 receives the input three-phase signals HU, H
The difference between the two-phase signals (HU-HV, HV-HW, HW-HU) among V and HW is calculated. The output of the matrix circuit 2 is amplified by the amplifier 3 and then input to the level clamp circuits 5 and 6. The amplitude control circuit 4 controls the amplitude in the amplifier 3.

The level clamp circuits 5 and 6 clamp an input signal at a predetermined clamp level and output the signal to a drive circuit 8 having a current converter 7. The driving circuit 8 has three driving currents of three phases.
Drive the phase coils 9U, 9V, 9W respectively.

 Next, the operation will be described with reference to FIG.

The three-phase HG signals HU, HV, HW output from the amplifier 1 have a phase difference of 2π / 3 from each other (FIG. 2A). This signal is input to the matrix circuit 2, and the difference signals HU-HV, HV-HW, HW
-HU (FIG. 2B). The difference signal is amplified by the amplifier 3 to the amplitude specified by the amplitude control circuit 4 and then input to the level clamp circuits 5 and 6.

In the level clamp circuit 5, the voltage at the center of the difference signal is Vc,
When the peak voltage from the voltage Vc is Vp, the input signal is clamped at two levels: the clamp level Vc + 0.25 Vp and the clamp level Vc + 0.7 Vp. On the other hand, the level clamp circuit 6 clamps the input signal at two levels, the clamp level Vc−0.25 Vp and the clamp level Vc−0.7 Vp (FIG. 2C). In this way, a trapezoidal drive signal is generated.

These drive signals are input to the current converter 7 of the drive circuit 8 and converted into drive currents to drive the coils 9U, 9V, 9W (FIG. 2D).

The above values 0.25Vp and 0.7Vp are respectively sin (π / 12)
And sin (3π / 12). That is, in the case of this embodiment, these values correspond to the levels at the positions π / 12 and 3π / 12 which are shifted by ± π / 12 from the position where the signals of the two phases intersect.

When the clamp level is set in this manner, a ripple occurs in the total current supplied to the coil 9 (FIG. 2E). The drive current ripple is maximum at the point where the signals of the two phases intersect, where the torque ripple (FIG. 2F) is at a minimum. Therefore, when the torque decreases, the driving current increases, so that the torque reduction is eventually compensated to some extent. However, the compensation is still inadequate.

FIG. 3 shows the configuration of an embodiment of the brushless motor drive circuit according to the present invention, and portions corresponding to those in FIG. 1 are denoted by the same reference numerals.

In the case of this embodiment, only one level clamp circuit 11 is provided, and its clamp level is 0 and Vc ± (3
^1/2 ) It is set to Vp / 2. Other configurations are the same as those in FIG.

Also in this embodiment, as shown in FIGS. 4A to 4C,
A difference signal is generated from the HG signal, and the difference signal is clamped at a clamp level to generate a trapezoidal drive current.

The values 0 and (3 ^1/2 ) Vp / 2 are sin0 and sin, respectively.
(2π / 6). That is, in the case of this embodiment, these values are shifted to the levels at the positions of 0 (π / 6−π / 6) and 2π / 6 shifted by ± π / 6 from the position where the signals of the two phases intersect. Yes, it is.

Therefore, the current ripple shown in FIG. 4E is generated with respect to the torque ripple shown in FIG. 4D, so that the torque ripple can be compensated in the same manner as in the embodiment.

If the range of the clamp level in which the torque ripple can be compensated is defined by the corresponding electric angle, the range from the intersection of the two difference signals is ± α [rad] (0 <α ≦ π / 6). Also, the amount of torque ripple compensation (correction amount)
Can be adjusted by adjusting α.

In the case of the principle of FIG. 1, α = π / 12, and in the case of the embodiment of FIG. 3, α = π / 6.

When the HG signal is a sine wave, assuming that the minimum value of the current ripple is 100%, as shown in FIGS.
As shown in the following equation, the ratio of the ripple from the minimum value to the maximum value is 7.6 in the case of the principle of FIG. 1 (FIG. 5A).
%, In the case of the embodiment of FIG. 3 (FIG. 5 (b)), 15.47%
Becomes

7.6 = 100 2 [sin (π / 6)-sin (π / 12)] / [sin (π / 4)-sin (π / 12)]-100 15.47 = 100 2 sin (π-6) / sin (π / 3)｝ − 100 Compared to E and F in FIG. 2 and D and E in FIG. 4, it is clear that the clamp level is set as in the embodiment of FIG. However, since the current ripple changes more smoothly, the torque ripple can be compensated more smoothly.

[Effect of the Invention] As described above, according to the brushless motor drive circuit of the present invention, a trapezoidal waveform is obtained by clamping at a level of (3 ^1/2 ) / 2 of the peak value so as to generate a smooth ripple. Since the drive current is generated, torque ripple can be smoothly compensated by the ripple of the drive current.

That is, by generating the drive signal and supplying the drive signal to the drive coil, a current ripple having a phase opposite to that of the torque ripple of the total current is generated in the drive signal, and the torque ripple can be substantially canceled and reduced.

Further, even if the sensitivity of the Hall element included in the brushless motor varies, the above-described effect can be obtained without adjusting the sensitivity, and a high torque can be obtained even when the driving magnetic pole of the rotor has a substantially rectangular wave. This has the effect of improving the efficiency. Furthermore, by supplying a drive signal to the motor drive coil, torque ripple is stably reduced without being affected by back electromotive force, power supply voltage, coil resistance, motor rotation speed, etc. generated in the motor drive coil. There is an effect that can be.

[Brief description of the drawings]

1 is a block diagram showing the principle of the brushless motor drive circuit of the present invention, FIG. 2 is a timing chart for explaining the operation of the embodiment of FIG. 1, and FIG. 3 is another brushless motor drive circuit of the present invention. FIG. 4 is a block diagram showing the configuration of the embodiment, FIG. 4 is a timing chart for explaining the operation of the embodiment in FIG. 3, and FIGS. 5 (a) and 5 (b) are waveform diagrams of ripples. 1,3 ... amplifier, 2 ... matrix circuit, 4 ... amplitude control circuit, 5,6,11 ... level clamp circuit, 7 ... current converter, 8 ... drive circuit, 9,9U, 9V, 9W …… Coil.

Claims (1)

(57) [Scope of request for utility model registration] 1. A brushless motor drive circuit for driving a forward / reverse rotatable brushless motor having a three-phase drive coil, wherein a difference between predetermined two-phase signals among three-phase signals corresponding to a rotational position of a rotor is provided. And a matrix circuit that outputs a difference signal from which harmonic components have been removed, and clamps each output of each difference signal of the matrix circuit at a level of √3 / 2 of a peak value, and the clamp period is a level. A driving circuit for generating a driving signal in the form of a three-phase trapezoidal wave having a flat surface, and a driving circuit for supplying a driving current obtained by converting the driving signal of the three phases into a current to the driving coil. Brushless motor drive circuit.