JP2897343B2 - Motor drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a motor, and more particularly, to a reduction in a switching pulse when a current-carrying phase is switched.

2. Description of the Related Art In recent years, small DC motors have been recognized for their good controllability not only in the acoustic field but also in the information industry field, and their applications are expanding at an extremely rapid pace. Among them, a brushless motor has no contact portion such as a brush and a commutator and has an advantage of a long life, and therefore its use as an industrial motor in which reliability is particularly important is expanding.

Under these circumstances, small axial fans using brushless motors are increasing in number.

The axial fan is required to house the drive circuit in a limited space and to be low in cost. In order to realize these, a two-phase half-wave driving system which can be driven by one magnetic detecting element and has simple wiring is widely adopted. Moreover, in order to simplify the circuit and increase the efficiency, a method of performing a switching operation of the output circuit and absorbing a generated switching pulse by a capacitor, a Zener diode, or the like has been generally used.

FIG. 4 shows a conventional example using a capacitor. In the figure, 30 is a Hall IC, 31 and 32 are two-phase stator windings of a motor, 33
And 34 are capacitors for absorbing switching pulses.

According to this method, the magnitude of the switching pulse generated at the time of phase switching can be reduced by appropriately selecting the capacitance of the capacitors 33 and 34, but a satisfactory result is not obtained. That is, if the capacitance is small, the effect is small, and if the capacitance is large, a time delay occurs to hinder the switching timing, or the resonance energy with the stator winding increases and the current flows back to the power supply. Therefore, the actual situation is a compromise of about several μF.

Problems to be Solved by the Invention As described above, since the axial fan motor has a limited space, it is difficult to mount two capacitors of several μF, which are relatively large components, in terms of space.
Although there is a method using a Zener diode instead of a capacitor, the space is small and it is possible to implement an IC, but there is a disadvantage that switching noise generated at the time of phase switching is rather large.

Means for Solving the Problems The present invention detects a rotational position of a rotor and outputs a two-phase signal; a position signal amplifying means for amplifying a position signal output by the position detecting means; Automatic gain control means for receiving the signal from the position signal amplifying means and correcting the variation of the output signal of the position signal amplifying means, threshold setting means, switching means, and the output of the switching means. Output means for supplying a current to the motor winding in response to the two-phase half-wave driven brushless motor, wherein the switching means comprises two mirror-connected two-phase windings. , A transistor receiving the output of the threshold circuit, a current source commonly connected to the emitters of these three transistors via diodes, and receiving the output of the threshold circuit A mirror circuit for amplifying the collector current of the transistor, and a mirror circuit connected to the current source. The corrected two-phase signal and the output of the threshold circuit are input to the bases of the three transistors. Of the inputs, only the highest level input is selectively amplified and output.

Function The output of the two-phase position signal amplifier whose AC amplitude is stabilized by the AGC circuit and the output of the threshold circuit stabilized by the constant current circuit are compared by a three-differential switching circuit, and phase switching is performed. While the current flowing into the motor stator winding at the time of switching is suppressed, the sensitivity of the three-differential switching circuit becomes non-linearly dull as the sensitivity approaches at the time of switching, and the gradient of the current flowing into the motor stator winding at the time of phase switching is reduced. This reduces the magnitude of the switching pulse due to L di / dt.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration thereof. Reference numeral 1 denotes a magnetic detection circuit including a magnetic detection element 10, which outputs a position signal of a motor rotor. Reference numeral 2 denotes a position signal amplifying circuit for amplifying an output signal of the magnetic detection circuit. Reference numeral 3 denotes an AGC circuit, a reference voltage applied to the base of the transistor 11 and a detection diode.
The output of the position signal amplifier circuit 2 is stabilized using the detection outputs of 12 and 13 as a comparison input. Reference numeral 4 denotes a threshold circuit which is stabilized in the same manner as the position signal amplifier circuit 2. Reference numeral 5 denotes a three-differential switching circuit which receives as input the two-phase signal output from the position signal amplifier circuit 2 and the threshold signal output from the threshold circuit 4, and the input having the highest level among the three inputs. Only one is selectively amplified and output. Reference numeral 6 denotes an output circuit for supplying a current to two-phase stator windings 28 (A phase) and 29 (B phase) of the motor. 14, 15 and 16 are constant current power supplies. Although the numeral 7 surrounding the entire circuit represents an integrated circuit, a magnetic detection circuit can be incorporated in the integrated circuit 7 if necessary.

FIG. 2 is a diagram in which the circuit of FIG. 1 is divided into blocks for each circuit.

Regarding the operation of the present invention configured as described above,
This will be described with reference to FIGS.

(A) is a rotation signal of the rotor detected by the magnetic detection circuit 1. (B) and (c) are the two-phase output, the A-phase signal, and the B-phase signal of the position signal amplifier circuit 2. The broken line in the figure indicates the threshold level output from the threshold circuit 4. (D), (e), (f)
Are transistors 17, 18, and 19, respectively, constituting a three differential switching circuit.
3 shows an output current waveform of the first embodiment.

In the case of the two-phase half-wave drive, since no induced voltage is generated at the time of phase switching, the current flowing into the stator winding increases, and a switching pulse represented by L di / dt is generated. To suppress this switching pulse, it is only necessary to limit the magnitude of the current and reduce the slope of the current change.However, if it is too slow, the range of the torque dead center near the switching point will be widened, covering that part. The reluctance torque must be increased, and the vibration noise of the motor may increase. In order to solve such a problem, in this embodiment, diodes are added to the emitters of the transistors constituting the three differential switching circuit 5, respectively. That is, the diodes 20, 21 and 22 are connected to the emitters of the transistors 17, 18 and 19, respectively, and the collector of the transistor 23 forming a current mirror circuit is connected to the diodes 20 and 2.
Connected to 1 and 22 common cathodes. In this way, as the output current of the transistor 17 receiving the output signal of the threshold circuit 4 increases, the collector current of the transistor 23 constituting the current mirror circuit increases and flows into the constant current source 16. As a result, the current flowing through the three differential switching circuit 5 decreases accordingly. As the current decreases, the impedance of the diodes 20, 21 and 22 increases, and the switching sensitivity of the three-differential switching circuit decreases. These series of operations are continued up to the switching point, and after that, the operation is reversed, and the switching is performed smoothly.

Therefore, by appropriately selecting the ratio of the resistors 24 and 25 and determining the current ratio of the current mirror circuit, the current gradient at the time of phase switching can be arbitrarily determined. As a result, the above-mentioned problem that the reluctance torque must be increased is solved, and the switching pulse can be almost eliminated. By the way, conventionally, a method of reducing a switching noise at the time of phase switching by flowing a trapezoidal waveform driving current through a motor coil has been proposed, but a trapezoidal waveform forming circuit or the like is required at a signal processing stage, and the circuit configuration is complicated. In addition, the switching noise cannot be effectively reduced unless the slope of the trapezoidal drive current is considerably laid and the overlap with the drive current of the next phase is made large. In addition, if the slope of the drive current is considerably laid down and the overlap is increased, the reactive current increases, and the period during which the output transistor connected to the coil operates in the active region becomes longer, which undesirably increases the heat generation of the output transistor.

In this embodiment, the output transistor is grounded to the collector in order to reduce the impedance of the output circuit. However, a normal grounded emitter does not pose a problem.

It is needless to say that the three-phase half-wave driving method can be applied.

According to the present invention, a switching pulse can be prevented without using a large external component, and a highly efficient drive circuit having no switching noise and a small reactive current at the time of switching can be provided. It is. Therefore, the effects of reducing the number of parts, securing a sufficient space, and the like are great.

Further, in particular, the switching means in the present invention connects the output of the position signal amplifying means to the respective paces of the transistors corresponding to the number of coil phases, and connects the output of the threshold setting means to the base of another transistor. A differential transistor pair in which the transistors for the number of coil phases and the emitters of the another transistor are connected to one current source via diodes, respectively, and a current path proportional to the current flowing in the another transistor is provided. With the configuration connected to the current source, when switching the motor coil phase, the switching sensitivity of the switching means can be reduced, and a steep phase switching can be avoided. Further, by selecting, for example, the resistance ratio of the resistors 24 and 25 in FIG. 1, the current ratio of the current mirror circuit can be determined, and the current gradient at the time of phase switching can be determined to a desired state. As a result, switching noise generated at the time of phase switching can be removed or reduced.

As apparent from the above, the present invention is a motor driving device having the above-mentioned various excellent advantages, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of one embodiment according to the present invention, FIG. 2 is a block diagram of one embodiment according to the present invention, and FIGS.
(F) is a timing chart of one embodiment according to the present invention,
FIG. 4 is a circuit diagram of a conventional example. 1 position detecting means (magnetic detection circuit), 2 position signal amplifying means (position signal amplifying circuit), 3 automatic gain control means (AGC circuit), 4 threshold setting means (threshold) Switching circuit (3 differential switching circuits), 6 ... output means (output circuit), 28, 29 ... stator windings of the motor.

Claims (1)

(57) [Claims] 1. A position detecting means for detecting a rotational position of a rotor and outputting a two-phase signal, a position signal amplifying means for amplifying a position signal output by the position detecting means, and a position signal amplifying means for the position signal Automatic gain control means for receiving the signal from the position signal amplifying means and correcting the variation of the output signal of the position signal amplifying means, a threshold setting means, a switching means, and a motor winding according to the output of the switching means. A driving means for a two-phase half-wave driven brushless motor, comprising: an output means for supplying a current to the two-phase winding, wherein the switching means includes two transistors mirror-connected to a two-phase winding; A transistor receiving the output of the threshold circuit, a current source commonly connected to the emitters of these three transistors via a diode, and a collector of the transistor receiving the output of the threshold circuit. And a mirror circuit connected to the current source. The corrected two-phase signal and the output of the threshold circuit are input to the bases of the three transistors. A two-phase half-wave driven brushless motor drive device characterized in that only the highest level input is selectively amplified and output.