JPS6223280Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a drive circuit for a brushless motor, and in particular, to an improvement of a drive circuit for a brushless motor that can rotate in both directions using only one drive control integrated circuit. It is something.

The electronic rotation control method for brushless motors includes:
There are devices that detect rotation using a magnetic sensor such as a Hall element or an optical sensor that combines a light emitting diode and a phototransistor, and control the servo circuit and drive circuit. I try to keep it at a constant speed. Furthermore, in terms of drive methods, there are two main types, sine wave drive and pulse drive, depending on the type of current passed through the motor windings.

Commonly used motors include commutator and brush motors. This is suitable for rotating in only one direction, but from the viewpoint of characteristics, reliability, and life, it is not suitable for rotating in both directions.
This is currently not possible.

The brushless motor drive circuit according to the present invention relates to a pulse drive method for bidirectional rotation, which is an advantage of brushless motors, and uses an integrated circuit element for drive control, so that current can be applied to the drive coil in either direction. It is of the type that has electronic switching control means.

FIG. 1 shows an example of a drive circuit that uses a mechanical switch to switch the current direction of a drive coil, and only the main parts thereof are shown.

It is equipped with mechanical switches S ₁ to _{S 4} , a rotation control drive integrated circuit 10 and a back electromotive force detection circuit 20 for detecting the rotation speed, and further includes an optical sensor 30 in this case.
The energization of the drive coils L ₁ and L ₂ is switched by this. That is, when the motor is rotating, the rotational position of the rotor is detected by the optical sensor 30, and on/off pulses are applied to the position signal processing circuit 11 from the collector of the transistor within the optical sensor 30. This on/off pulse is processed by the position signal processing circuit 11 and then sent to the winding drive circuit 12.
is applied to the power supply + _VB , which turns transistors Q _A and Q _B on and off alternately depending on the rotational position of the rotor.
The drive current is alternately supplied from the drive coils L ₁ and L ₂ to the drive coils L 1 and L 2 . This drive current generates a magnetic field in the drive coils L ₁ and L 2 , and torque is generated between the drive coils L 1 and L ₂ and the permanent magnets fixed to the rotor, causing the rotor of the brushless motor to rotate.
Back electromotive voltage detection circuit 2 connected to drive coil L ₂
0 is for extracting the back electromotive force generated when the drive coil L ₂ is in a non-energized state.
After the voltage value of this back electromotive voltage is adjusted by the level shift circuit 18, it is compared with the reference voltage of the reference voltage source 14 in the comparator circuit 13. If the motor speed increases too much, the back electromotive force will increase, so the comparator circuit 13 is connected to the transistor Q.
An error signal is output to the winding drive circuit 12 to delay the timing when _A and _QB turn on and off. Conversely, if the rotation of the motor decreases too much, the comparator circuit 13 outputs an error signal to the winding drive circuit 12 that advances the on/off timing of the transistors Q _A and Q _B.

In this way, by negatively feeding back the error signal based on the back electromotive force generated in the drive coil L ₂ to the emitter circuits of the transistors Q _A and Q _B of the winding drive circuit 12, the rotation speed of the motor is always kept constant. It is made to be.

In the figure, 15 is an LED drive circuit for driving the light emitting element of the optical sensor 30, 16 is a pause circuit used when it is necessary to temporarily stop the motor, and 17 is a circuit setting circuit in the integrated circuit 10. This is a constant voltage circuit that serves as a voltage source.

Although the brushless motor rotates as described above, current is supplied to the drive coils _L1 to _L2 in the opposite direction by interlocking and switching the switches _S1 to _S4 . Thereby, the drive coil L ₁ ,
The polarity of the magnetic field created in L ₂ changes, creating a rotational torque in the opposite direction, allowing it to rotate in the opposite direction. Note that the operations of the drive coils L ₁ and L ₂ are the same except for the current direction.

The present invention relates to a brushless motor drive circuit that switches the rotational direction by electronic switching means instead of mechanical switching means as described above, and immediately after transistors Q _A and Q _B are turned on and off. The purpose of this is to prevent oscillation phenomena that occur during transient periods. This oscillation phenomenon occurs because there is a difference in the timing of the switch operation between the transistors Q _A and Q _B that distribute the drive current to the drive coils L ₁ and L ₂ and the transistor that controls the direction of the current. Occur. When fluctuations in power supply voltage, temperature, load, etc. are added to this, the circuit system becomes unstable, causing motor noise, and this oscillation phenomenon is a major factor in deteriorating motor characteristics.

An embodiment of the present invention will be described below with reference to FIG. Note that the same reference numerals are given to parts corresponding to those in the conventional example described above in FIG. 2, and redundant explanation will be omitted.

The switching control circuit 40 generates a rotational direction control signal at a terminal or terminals according to an input signal.

Transistors Q ₁ to _{Q 10} are used to switch the energization of the drive coils L ₁ and L ₂ . Transistor Q ₁
The base of is connected to the terminal, and the collector is connected to the bases of transistors Q ₂ and Q ₆ . The emitters of the transistors Q ₂ and Q ₆ are connected to the power supply +V _B , and the collectors are connected to the node 5 at one end of the drive coils L ₁ and L ₂ , respectively.
1,52. On the other hand, transistor Q ₄ ,
_Q8 has its emitter connected to the power supply + _VB , and its collector connected to the nodes 53 and 54 at the other ends of the drive coils _L1 and _L2 . Transistor Q ₃ has its base connected to a terminal, its collector connected to node 53, and its emitter connected to the collector of transistor Q _A of winding drive circuit 12 of integrated circuit 10. The base of the transistor _Q5 is connected to the terminal, the collector is connected to the node 51, and the emitter is connected to the collector of the transistor _QA .
Similarly, the collectors of transistors Q ₇ and Q ₉ are connected to nodes 54 and 52, and the emitters are connected to the collector of transistor Q _B.

The emitters of transistors Q ₃ and Q ₅ are connected in common, connected to the collector of transistor Q _A , and grounded via capacitor C ₁ . Similarly, the emitters of transistors Q ₇ and Q ₉ are connected in common to the collector of transistor Q _B and grounded via capacitor C ₂ .

The rotational speed is detected in the back electromotive voltage detection circuit 20 from the nodes 52 and 54 via the diodes D ₁ and D ₂ , respectively. An OR circuit is formed by the two diodes, and back electromotive voltages generated in either direction from nodes 52 and 54 can be detected.

Next, the operation of each transistor will be explained.
When an H (High) level signal is input to the terminal and an L (Low) level signal is input to the terminal, the transistor Q ₁ is turned on, and thereby the transistors Q ₂ and Q ₆ are also turned on. Further, since the transistors Q ₃ and Q ₇ are also turned on, current from the power supply +V _B flows in the drive coils L ₁ and L ₂ from the node 51 to the node 53 and from the node 52 to the node 54. Of course, at this time, the transistors Q _A and Q _B are alternately turned on and off by the optical sensor 30, so the drive coils L ₁ and L ₂ are also alternately energized in accordance with the on/off operation.
The power will be de-energized. The transistor Q ₄ at this time,
Q ₅ , Q ₈ , Q ₉ , and Q ₁₀ are all off.

On the other hand, when an L level signal is applied to the terminal and an H level signal is applied to the terminal, the operation is completely opposite to that described above.
Then, the current from the power supply +V _B is applied to the drive coils L ₁ and L ₂ from the node 53 to the node 51, and from the node 54 to the node 54.
The flow starts to flow in the opposite direction from node 52 to node 52.

In this way, by switching the signals between the terminals in the switching control circuit 40, the direction of the current flowing through the drive coil is also switched, and the rotation direction of the motor is changed.

As described above, the transistors Q _A and Q _B in the integrated circuit 10 are turned on and off by the signal from the optical sensor 30 . Transistors Q ₃ and Q ₅ and transistors Q ₇ and Q ₉ cannot be turned on completely until transistors Q _A and Q _B are turned on.

Considering the case without capacitors C ₁ and C ₂ , when transistor Q _A or transistor Q _B is off, the emitters of transistors Q ₃ , Q ₅ , Q ₇ , and Q ₉ are floating with respect to ground. There is. For this reason,
When the base of transistor _Q3 is at H level, during the transition period from when transistor _QA is turned on until transistor _Q3 is completely turned on,
Parasitic oscillations occur when transistor Q _A is turned off and transistor Q ₃ is lifted off the ground again. This parasitic vibration is caused by a switch timing shift between two transistors inserted in series in the same drive current path.

In other words, since the emitters of the transistors Q ₃ , Q ₅ , Q ₇ , and Q ₉ for controlling the direction of current are floating from the ground, the transistors distribute the drive current to the drive coils L ₁ and L ₂ . Q _A , Q _B
This is caused by a shift in switch timing between the transistors Q ₃ , Q ₅ , Q ₇ , and Q ₉ .

However, in the present invention, the transistors Q ₃ ,
Since the emitters of Q ₅ and the transistors Q ₇ and Q ₉ are AC-grounded via the capacitors C ₁ and C ₂ , respectively, parasitic vibrations that occur during transitions when these transistors turn on and off are eliminated. Therefore, these transistors Q ₃ , Q ₅ , Q ₇ , and Q ₉ do not float from the ground in terms of alternating current, and smooth and stable on/off pulse waveforms are output.

As described above, according to the present invention, it is possible not only to reduce electrical noise caused by transient oscillations, but also to obtain a brushless motor drive circuit that operates stably even when there are temperature changes or load fluctuations.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a brushless motor drive circuit using mechanical switching means, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. L ₁ , L ₂ ... Drive coil, Q _A , Q _B ... Transistor, Q ₂ to _{Q 9} ... Transistor, C ₁ , C ₂ ...
capacitor.

Claims (1)

[Scope of utility model registration request] Transistors Q ₂ and Q ₃ are respectively connected to both ends of the drive coil L ₁ so that the first drive coil L ₁ can be energized in the first direction, and the drive coil L is connected to each end of the drive coil L 1 so that the first drive coil L ₁ can be energized in the opposite direction. transistors _{Q 4 and} Q ₅ connected to both ends of the drive coil L 2 respectively, and transistors Q ₆ and Q ₇ connected to both ends of the drive coil L ₂ so as to be able to conduct current in the first direction of the second drive coil L ₂ ; Transistors Q ₈ and Q ₉ are respectively connected to both ends of the drive coil L ₂ so as to conduct current in the opposite direction of the drive coil L ₂ , and switching transistors are connected to the first and second drive coils L ₁ and L ₂ respectively. The driving coil is provided with transistors Q _A and Q _B , and turns on and off the transistors Q _A and Q _B alternately.
In a brushless motor drive circuit in which L ₁ and L ₂ are alternately energized, the first drive coil L ₁
The emitters of the transistors Q ₃ and Q 5 connected to both ends of the transistor Q 3 and Q ₅ are commonly connected to ground through a capacitor, and connected to the collector of the transistor Q _A , and connected to both ends of the second drive coil L ₂ . The emitters of transistors Q ₇ and Q ₉ are commonly connected and grounded via a capacitor, and
A brushless motor drive circuit characterized by being connected to the collector of _B.