JPH0356096A - Rotation control method for pulse motor - Google Patents

Abstract

PURPOSE:To eliminate a load resistor in a driving voltage line and prevent generation of heat by lengthening the high level duration of one of two detection pulses with a pulse duration modulation circuit and rotating a motor with low speed. CONSTITUTION:A Hall element 10 detects rotation of a rotor 12 and outputs detection pulses (A), (B). A wave shape (A) inputted from a terminal 10a is fed to a pulse duration conversion circuit 20 and integrated through a capacitor (C1) and a resultant wave shape is obtain at point (C'). Since a control signal 22 is at an H level during high speed rotation, a transistor Tr4 is in OFF-state and a comparator 21 is not operated. Therefore, the pulse width conversion circuit is not operated and the rotor rotates as before. Since the control signal 22 is at an L level during low speed rotation, the comparator 21 is operated. Since the output of the comparator 21 is at the H level when the signal at the point (C') is smaller than a reference signal at point (D'), the duration in which a transistor Tr2 is in ON-state is shortened and a motor rotates at the low speed.

Description

[Detailed Description of the Invention] (Summary) Regarding a pulse motor rotation control method that switches the rotation speed of the pulse motor between high and low speeds and controls ijj, there is no heat generation in the load resistor during low speed rotation and no noise is generated in the drive voltage line. For this purpose, the magnetic poles of the rotor's magnets are detected by a Hall element f to generate first and second detection pulses with mutually different polarities, and the stator's magnetic poles are adjusted to each other in accordance with the first and second pulses. Switches the current flowing through two sets of coils whose magnetic fluxes are perpendicular to each other.
In a rotation control system for a pulse motor that rotates the rotor by rotating the rotor, the pulse width conversion circuit includes a pulse width conversion circuit that extends a high level period of one of the first and second detection pulses by a predetermined period. The pulse width conversion circuit is configured to extend the high-level bright period of one of the detection pulses so that the energization time of each of the two sets of coils overlaps, thereby reducing the rotational speed of the rotor.

[Industrial application field]

The present invention relates to a pulse motor rotation control method, and more particularly to a pulse motor rotation υIII1 method for controlling the rotation speed of a pulse motor by switching between high and low speeds.

BACKGROUND ART Conventionally, pulse motor-driven cooling fans have been widely used to reduce heat generation in electronic devices and the like.

Recent electronic equipment has strict demands for low noise, and the sound generated by this cooling fan has been widely cited as noise, and since it generates a particularly loud noise when rotating at high speed, the rotation is set to two speeds, high and low, and the cooling fan is kept at room temperature. In this case, it is used at low speed rotation.

(Conventional technology) Figure 4 (A). (B) shows a structural diagram of a pulse motor.

When the Hall element 10 detects the N pole of the magnet 12 of the rotor 11 in the state shown in FIG.
A current is passed through. As a result, the core parts A and C of the stator 13
is magnetized to N pole, and other core parts B, D, a, b, c, d
is magnetized to the S pole, the magnet 12 of the rotor 11 is attracted, and the rotor 11 and the blades 14 provided thereon rotate.

When the rotor 11 is rotated by 90 degrees as shown in FIG. 2B, the Hall element 10 detects the S pole of the magnet 12 of the rotor 11, and the coil L2 . Apply current to L4. by this,
Core parts B and D are N poles, and the other 17 parts A, (:,, a, b
, c, and d are magnetized to S poles, and the rotor 11 rotates.

This repetition causes the rotor 11 to rotate continuously.

A conventional rotation control circuit is shown in FIGS. 5(A) and 5(B). In both figures, transistors "r1 and Tr2 are made conductive by the output of the Hall element 10, and a current is caused to flow through either coil L+.L3 or coil L2.L4 whose magnetic fluxes are orthogonal to each other.

In FIG. 5(A), the control signal causes the switch 2o to
The magnet 12, that is, the rotor 11, is rotated at high speed while the load resistor 21 is bypassed by conducting the switch 20.
is cut off, the voltage is dropped across the load resistor 21, and the rotor 11 is rotated at a low speed.

In FIG. 5(B), the oscillation of the oscillation circuit 25 is stopped, and the rotor 11 is rotated at high speed with the oscillation circuit 25 in a high impedance state. In addition, the oscillation circuit 2
5 to cause oscillation at a frequency sufficiently higher than that of the output pulse of the Hall element 10, and by making the diodes 26 and 27 conductive during the low level period of the oscillation pulse, the transistor ``
The conduction period of each of rl and 'r2 is shortened, and the rotor 11 is rotated at a low speed.

[Problem to be solved by the invention]

Among the conventional examples described above, in the method of inserting the load resistor 21 shown in FIG. 5 (A>), the load resistor 21 generates heat during low speed rotation.
This results in a decrease in efficiency and also affects other load circuits.

Furthermore, in the method of thinning out the pulse width using oscillation pulses as shown in FIG. There is a problem in that noise increases in the drive voltage line due to the influence of the first induction.

The present invention has been made in view of the above points, and an object of the present invention is to provide a rotation control system for a pulse motor that does not generate heat in the load resistance during low-speed rotation and generates less noise in the drive voltage line.

[Means to solve the problem]

FIG. 1 shows a diagram of the principle of the present invention.

In the same figure, the Hall element 10 detects the magnetic poles of the magnet 12 of the rotor and generates first and second detection pulses having mutually different polarities. Two sets of coils L+ and L3 whose magnetic fluxes are orthogonal
．． The current flowing through L2 and L4 is switched and controlled. This causes the rotor to rotate.

The pulse width conversion circuit 20 converts the first,
The high level period of one of the second detection pulses is extended by a predetermined period.

[Effect]

In the present invention, when the high level period of one detection pulse is extended in the pulse width conversion circuit 2o, the two sets of coils L
1 and L3. The energization times of L12 and L4 overlap, creating drive resistance and reducing the rotation of the rotor.

In this way, since no load resistance is required on the drive voltage line, there is no heat generation due to the load resistance, and there is no need to thin out the coil current with oscillation pulses, so noise generation on the drive voltage line is reduced.

〔Example〕

FIG. 2 shows a circuit diagram of an embodiment of the rotation control circuit according to the present invention. In the figure, the same parts as in FIG. 5 are designated by the same reference numerals, and the explanation thereof will be omitted.

In FIG. 2, the Hall element 10 detects the rotation of the rotor 11, and the pancreas 10a. 3(A) from each of 10b. (B)
1st as shown in each. A second detection pulse is output.

A resistor R constituting the pulse width conversion circuit 20 is connected to the terminal 10a.
One end of the transistor Tr3 is connected to the transistor Tr3, and the other end is connected to the base of the transistor Tr3. A driving voltage is applied to the collector of the transistor Tr3, and the emitter is grounded via a resistor R2 and a capacitor C1, and is connected to the terminal 10a via a discharge diode D1.

The voltage at the connection point ◎ between the resistor R2 and the capacitor C+ is integrated by the resistor R2 and the capacitor C1 to form a substantially triangular wave as shown in FIG. ．． It is compared with the voltage at point ◎ divided by R4.

By the way, the control signal from the terminal 22 is at the mouth level when the ambient temperature is high and the cooling fan is rotating at high speed, and is at the L level when the surrounding temperature is low and the cooling fan is rotating at low speed with low noise.

During high-speed rotation, the transistors 4, which are supplied with the daily level control signal, are cut off, so the comparator 21 stops operating, and the output terminal of the comparator 21 connected to the transistor ``r2'' enters a high impedance state. As a result, the base voltages of the transistors "r2" and "r1" become as shown in Fig. 3 (D) and (E), and the transistors "r2 and Trl perform the switching operations shown in Fig. 3 (F) and (G), respectively. The rotor 11 having the magnet 12 rotates at high speed.

During low speed rotation, the transistor Tr4 supplied with the H-level υjilt signal becomes conductive, and the resistor R5. An operating current is supplied through the transistor Tr4, and the comparator 21 outputs an L level during a period when the voltage at point O is lower than the voltage at point ◎.

As a result, the base voltage of the transistor "r2" becomes as shown in FIG. is the same at high speed rotation as shown in FIG.

Therefore, each of the transistors "r2 and "r1 is as shown in Fig. 3 (J).
．． Perform the switching operation shown in (K) and coil 2.
．． The excitation period of L4 becomes longer and overlaps with the excitation period of coils L+ and L3, and this becomes a driving resistance, causing the rotor 11 to rotate at a low speed.

In this way, since there is no load resistance on the line that coils the drive voltage and supplies it to 1 to L4, there is no heat generation due to the load resistance during low speed rotation. Further, since there is no thinning of the currents in the coils 1 to L4 due to oscillation pulses, noise generation in the drive voltage line is reduced.

〔Effect of the invention〕

As described above, according to the pulse motor rotation υ1lIl method of the present invention, there is no heat generation in the load resistor, and less noise is generated in the drive voltage line, which is extremely useful in practice.

[Brief explanation of drawings]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a circuit diagram of an embodiment of the circuit according to the present invention, Fig. 3 is a waveform diagram for explaining the operation of the circuit of Fig. 2, and Fig. 4 is a diagram of the pulse motor. Structural Diagram FIG. 5 is a circuit diagram of each example of a conventional circuit. In the figure, 10 is a Hall element, 11 is a rotor, 12 is a magnet, 13 is a stator, 20 is a pulse width conversion circuit, and 21 is a comparator.

Claims (1)

[Claims] The magnetic poles of the magnets (12) of the rotor (11) are detected by the Hall element (10) to generate first and second detection pulses having mutually different polarities, and the first and second detection pulses have different polarities. Two sets of coils (L) whose magnetic fluxes are perpendicular to each other in the stator (13)
In a pulse motor rotation control method that rotates the rotor (11) by switching and controlling the current flowing through the currents (1 and L_3, L_2 and L_4), one of the first and second detection pulses is It has a pulse width conversion circuit (20) that extends the high level period by a predetermined period, and by extending the high level period of one of the detection pulses with the pulse width conversion circuit (20), the two sets of coils (L_1 and L_3, L_2 and L_4) overlap each energizing time,
A rotation control method for a pulse motor, characterized in that the rotation speed of the rotor (11) is reduced.