JPH03190588A - Brushless motor drive circuit - Google Patents

Abstract

PURPOSE:To perform arbitrary low speed operation by switching the duration of OFF time, to be set at the start of driving interval, of a drive circuit for switching power conduction to a stator coil based on a rotor position detection signal. CONSTITUTION:Position of a permanent magnet rotor magnetized with multiple poles is detected through a Hall IC 1 and inputted through the amplifier 7 of a coil driving circuit 4 to a phase switching circuit 8. Output from the circuit 8 is amplified 9, 10 in order to energize stator coils 2, 3 alternately. A speed control circuit 5 generates a short pulse 14 at the time of inversion of output from the amplifier 7 to turn a transistor Tr 15 ON for a short time so as to discharge a capacitor 17, and a comparator 18 outputs an H level for a short time which is then inputted to the switching circuit 8 thus setting an OFF interval T0 at the start of driving interval. Output VCTL from a speed switching means 6 is turned ON/OFF through a Tr 22 and inputted to the comparator 18 thus controlling the duration of the OFF interval T0. By such arrangement, arbitrary low speed operation can stably be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive circuit for a brushless motor that constitutes a cooling fan motor in, for example, a copying machine.

[Prior Art] This type of conventional brushless motor described above has a circuit ↑6 as shown in, for example, Japanese Unexamined Patent Publication No. 59-37895.
It has become one success. That is, as shown in FIG. 10, stator windings 51 .
Driving transistor 5 that selectively switches energization of 52/\
3.54, the open phase changeover switch 55, the open phase IJJ changeover circuit 56, and the start-up compensation circuit 57.

The open phase switching circuit 56 stops energization of at least one phase of the stator winding 51.52/\ in response to the operation of the open phase changeover switch 55. Further, the starting compensation circuit 57 is activated by a signal from the position detecting means 50, and stops the open phase operation by the open phase switching circuit 56 when the permanent magnet rotor is locked.

The operation of the drive circuit having the above configuration is as follows. That is,
When the position detection means 50 outputs HI or LO due to the magnetic field of the permanent magnet rotor, the amplifier 58 turns on or off the drive transistors 53 and 54, and the amplifier output turns on and off the drive transistors 53 and 54, which are connected via the inversion circuit 59. The transistor 53 becomes in the opposite state to the drive transistor 54, and the stator windings 51 and 52 are selectively energized, producing rotational torque in one direction and continuing the rotation of the permanent magnet rotor. . When the use changeover switch 55 is closed and the open phase changeover circuit 56 is activated, the transistor 60 is turned on and the drive transistor 53 is turned off. Skillful moving transistor 5
3, the stator winding 51 connected to this stator winding 51 is de-energized, and only the other stator winding 52 is energized for its drive period, resulting in an open-phase operation in which the rotational speed is reduced. If the permanent magnet rotor is restrained fm (motor lock) during this open-phase operation, starting torque is generated, and even if the restrained state is released, it will not restart, so the starting compensation circuit 5
7 to compensate for restart after release of restraint.

That is, unnecessary power consumption is suppressed by switching the rotational speed by the open-phase drive, and when the lock is due to the open-phase drive, the lock can be released and restarted without resetting the power supply.

[Problems to be Solved by the Invention] In the conventional brushless motor drive circuit described above, the rotation speed is lowered by the open-phase operation by the open-phase switching circuit 56, so the low speed cannot be set to an arbitrary speed. In addition, there are issues that need to be resolved, such as the need for start-up compensation to deal with constraints due to open-phase operation.

This invention was made to solve such conventional problems, and the low speed can be set to any speed, and the IJ
An object of the present invention is to provide a drive circuit for a brushless motor that can be reliably started even when rotating far.

[Means for Solving the Problems] A drive circuit for a brushless motor according to one system of the present invention has a coil drive circuit that switches energization to the stator coil based on a signal from a rotor position detection means to drive each phase of the stator coil. The device is equipped with a speed control circuit that outputs an output to create an off time at the beginning of a period, and is provided with speed switching means for changing the length of this off time by one inch by changing the resistance value of a resistor.

In addition, the drive circuit for a brushless motor according to the present invention is particularly designed to raise the potential at the command value input point of the speed switching circuit to a potential at which the motor stops.

[Function] In the brushless motor drive circuit of the present invention, the off time at the beginning of the drive period of each phase of the stator coil is changed by changing the resistance value of the speed switching means, and the off time at the beginning of the drive period of each phase of the stator coil can be set to any low speed rotation. is obtained, and the startup is reliable even at low speed rotation.

Further, in the driving cycle n of the brush 1/smotor of the present invention, a stop mode can be provided by particularly increasing the command value input point potential of the speed switching circuit to a potential at which the motor stops.

[Embodiment] Each figure from FIG. 1 to FIG. 9 shows an embodiment of the present invention. First, the drive circuit of the brushless motor shown in FIG. 1 will be explained. This drive circuit includes a Hall ICI as a rotor position detection means for detecting the position of a multi-pole magnetized permanent magnet rotor, and a coil drive circuit 4 that switches energization to stator coils 2 and 3 based on a signal from the Hall IC 1. And, for this coil drive circuit 4, the off time To is set at the beginning of the drive period of each phase of the stator coils 2 and 3.
A speed switching means 6 for changing the above-mentioned off time To is connected to this speed control circuit 5, which is equipped with a speed ll1IJ control [IF5] for outputting a speed ll1IJ to produce the above-mentioned off time To. Hall ICI
The output is input to the lfl switching circuit 8 via the amplifier 7 of the coil drive circuit 4. An output amplifier 9 is connected in parallel to the output side of the phase switching circuit 8. ] 0 to the stator coils 2.3, respectively. Vcc is a DC power supply voltage, which is energized through a current limiting resistor 11 to a Zener diode 12 to form a constant voltage VC, which serves as a power supply for other circuits. A constant voltage Vc1 is applied to the Hall ICI via a resistor 13. The speed control circuit 5 can also be called an off-time generating circuit, so it receives the signal from the amplifier 7,
It includes a rotating pulse generating circuit 14 that outputs a short pulse when the amplifier 7 is inverted, and a transistor 15 that becomes conductive for a short time in response to this pulse. Transistor, 15 has a constant voltage V
A charging/discharging circuit consisting of the resistor 16 to which C1 is applied and the capacitor 17 is connected, and the voltage of the capacitor 17 is applied to the comparator 18 together with the voltage divided by the resistor 19.20 of the constant voltage Vc1.

A speed switching means 6 is connected in parallel to the resistor 20 to switch a command input resistor 21 using a transistor 22 as a switching means, thereby making the voltage applied to the comparator 18 variable. The output of the comparator 18 is input to the phase switching circuit 8, and the phase switching circuit 8 is input to the comparator 1.
When the output of 8 is HI, no movement is possible.

Subsequently, the operation of the circuit having the above configuration will be explained based on FIGS. 2 to 4. The Hall ICI, which is energized from the constant voltage Vc1 through the resistor 13, changes its output between positive and negative due to the magnetic field of the permanent magnet rotor, and the amplifier 7 receives this and changes the output to H.
It outputs a binary value of I or LO. Phase switching circuit 8 is amplifier 7
In response to the output of the amplifier 7, the output amplifier 9.
10, and the corresponding one of the stator coils 2.3 connected thereto is driven. As a result, rotational torque in one direction is generated, causing the permanent magnet rotor to rotate, and the stator coils 2 and 3 are alternately energized to continue their rotation. The speed control circuit 5 and speed switching means 6 work as follows. That is, upon receiving the output of the amplifier 7 when it is inverted, the rotation pulse generating circuit 14 outputs a short pulse,
This causes the l transistor 15 to become conductive for a short time. Due to the conduction of transistor 15, capacitor 17 is rapidly discharged to a voltage close to OV. When the transistor 15 becomes non-conductive, the capacitor 17 is charged via the resistor 16, and its voltage increases. 20 and a resistor 21 for command input
voltage (command value input point potential or control voltage) VcτL
While the voltage is lower, the output of the comparator 18 is HI, and the phase switching circuit 8 cannot operate. During this time, stator coil 2.3
There is an off time TO in which no current is applied to the terminal (see Fig. 2). When the voltage of the capacitor 17 being charged via the resistor 16 exceeds the command value input point potential VCTL, the comparator 18
is inverted and becomes the LO output, operating the phase switching circuit 8,
The stator coils 2 and 3 to be energized are energized. The off time TO becomes longer by lengthening the time constant formed by the resistor 16 and capacitor 17 or by increasing the command direct input point potential VCTL, and becomes shorter by shortening the time constant formed by the resistor 16 and capacitor 17 or by lowering the command value input point potential VCTL. Become. The longer the off time TO, the lower the rotation speed of the permanent magnet rotor, and the shorter the off time TO, the higher the rotation speed of the permanent magnet rotor (see Figure 3).
1 and transistor 22, the voltage would be divided by resistor 19.20. The resistor 21 for command input is the command value input point potential VC.
When it enters between TL and OV, the command value input point potential Vc TL becomes lower than the divided voltage of the resistor 19.20, the off time TO becomes shorter and the rotation speed increases (see FIG. 4), and the transistor 22 When conductive, the off time To disappears and the motor rotates at full speed. Therefore, the low speed can be adjusted by the resistor 21 for command input, and the transistor 22
It is possible to switch between high and low speeds by turning on and off the engine, and since low-speed operation is not caused by open-phase drive, even if a restraint condition occurs during low-speed operation, it will restart once the restraint is released.

5, 6, 7, and 9 show other specific examples of the speed switching means 6, respectively. That is, the embodiment shown in FIG. 5 has a configuration in which resistors 23 and 24 are connected in series between the command value input point potential V CT L and OV, and a transistor 25 is connected in parallel to the resistor 24. transistor 25
When the transistor 25 is turned on, the resistor 24 is short-circuited, and the high speed is determined by the resistor 23 alone, and when the transistor 25 is turned off, the resistor 23 is short-circuited.
．． 24 series circuits are formed, and the resistance value becomes large, which determines the low speed.

In addition, the embodiment of FIG. 6 has a command value input point T, a position VcTL and 0.
A resistor 26 is inserted between the
This is a configuration in which a series circuit of transistors 1 to 29 is connected. When the transistor 29 is turned on, the resistor 2S and the resistor 26 form a parallel circuit, and the resistance value becomes smaller than that of the four resistors 26, thereby determining a high speed. When the transistor 29 is turned off, only the resistor 26 is present, which determines the low speed.

The embodiment shown in FIG. 7 is equipped with a stop mode, and the embodiment shown in FIG.
As shown in the figure, the present invention can be applied to a device in which the permanent magnet rotor stops rotating when the command value input point voltage l1vcTL is equal to or higher than a predetermined voltage. That is, between the command value input point potential VCYL and Ov (
, 2) A transistor 30, a resistor 31, and a Zener diode 32 are connected in parallel. However, the Zener diode 32 is connected in the opposite direction. Further, a transistor 33 and a resistor 34 are connected in series between the DC power supply voltage Vcc and the command value input point potential VCTL.
A resistor 35 is inserted between the emitter and base of the transistor 3, and a resistor 36 and a transistor 37 are connected in series from the base to oV.

It is. When the transistor 37 is off and the transistor 30 is on, the command value input point potential VCTL is approximately O.
v, and the permanent magnet rotor rotates at full speed. Next, when the transformer and resistor 30 are turned off, the low speed is determined by the resistor 31. Furthermore, when transistor 37 is turned on, ■・transistor 3
3 is turned on, the command value input point potential VC is raised through the resistor 34, and becomes the Zener voltage at which the Zener diode 32 is energized. If this Zener voltage is set to the voltage at which rotation stops as shown in FIG. 8, the stop mode will be established.

The embodiment of FIG. 9 also has a stop mode.
A series circuit of three resistors (6), a transistor (4), and a reverse connection of a Zener diode (4) are inserted in parallel.
A resistor 42 is inserted between the DC power supply voltage VcC and the command value input point potential VCTI-. When the l-run resistor 38 is turned on, the command value input point potential VCTL becomes almost OV, and the permanent magnet +7- motor rotates at full speed. 1- When the transistor 38 is off and the transistor 40 is on, the command value input point potential VcTL is connected to the point where the DC power supply voltage Vcc is divided by the resistor 42.39, and the low speed is determined.

In this case, when the DC power supply voltage Vcc decreases, the speed decreases, but the command value input point potential VCTL also decreases and the speed increases, so that fluctuations in the DC power supply voltage Vcc can be offset to some extent.

Next, when the transistors 38 and 40 are both turned on, the command value input point potential vc'r (is pulled up by the resistor 42 and becomes the Zener voltage of the Zener diode 41. If this is set to the voltage at which rotation stops, the command value input point potential vc'r (is pulled up by the resistor 42 and becomes the Zener voltage of the Zener diode 41. becomes.

That is, each of the above-mentioned embodiments is characterized in that the low speed can be set to any desired speed by changing the resistance value of an external resistor, and that startup is ensured even during low speed rotation.

[Effects of the Invention] As described above, according to the brushless motor drive circuit of the present invention, by changing the resistance value of the speed switching means, the length of the off time at the beginning of the drive period of each phase of the stator coil is changed, and the off time is changed. Any low speed rotation can be obtained depending on the timing, and the effect of ensuring startup even at low speed rotation can be obtained.

In addition, according to another brush l/smoke drive circuit of the present invention, in particular, the command value input point potential of the speed switching circuit can be changed from motor to -
By reducing the temperature to a potential where the light stops, it is possible to have the effect of having a stop mode.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of a brushless motor drive circuit according to the present invention, Fig. 2 is an explanatory diagram showing waveforms of each part of Fig. 1, and Fig. 3 shows the relationship between off time and rotation speed. FIG. 4 is an explanatory diagram showing the relationship between the resistance inserted between VCTL and 0 and the rotation speed, and FIGS. 5, 6, 7, and 9 each illustrate the implementation of the speed switching means. An explanatory diagram showing an example as a set of a circuit diagram and a functional diagram; Fig. 8 is an explanatory diagram showing the relationship between VCTL and rotational speed in Fig. 7; and Fig. 10 shows a drive circuit of a brushless motor as a conventional example. It is a circuit diagram. In the figure, 1 is a Hall IC 22, 3 is a stator coil, 4 is a coil drive port, 5 is a speed control circuit, 6 is a speed switching means, 8 is a phase switching circuit, 14 is a rotation pulse generation circuit 4, and 15 is a transistor , 16 is a resistor, 17 is a capacitor, 18 is a comparator, 19.20 is a resistor, 21 is a resistor, 22 is an l transistor, 23.24 is a resistor, 25 is an l transistor, 26.28 is a resistor, 29 is an l transistor - Transistor, 30 is a transistor, 31 is a resistor, 32 is a Zener diode, 33 is a transistor, 34.35.36
is a resistor, 37 is a transistor, and VCTL is a command value input point potential (control voltage). In addition, the same symbols in the figure are
Indicates the same or equivalent part.

Claims (2)

[Claims] (1) A rotor position detection means for detecting the position of a multi-pole magnetized permanent magnet rotor, a coil drive circuit that switches energization to a stator coil based on a signal from this rotor position detection means, and a coil drive circuit for this coil drive circuit. The speed control circuit is equipped with a speed control circuit that outputs an output in order to create an off time at the beginning of the drive period of each phase of the stator coil, and the speed control circuit has a command value that changes by switching a command input resistor with a switching means. A brushless motor drive circuit characterized in that a speed switching means for changing the length of time is connected. (2) The brushless motor drive circuit according to claim 1, wherein the potential at the command value input point of the speed switching circuit can be raised to a potential at which the motor stops by switching the command input resistor by switching means.