JPH0739187A - Starting method for brushless motor - Google Patents

Abstract

PURPOSE:To obtain safety and certainty of starting a driving circuit by executing a conducting pattern to a switching circuit to become a frequency of a revolving magnetic field which is varied in a synchronization pull-in frequency band of a brushless motor by a synchronizing signal. CONSTITUTION:A starting circuit 5 outputs a synchronizing signal which is varied in a synchronization pull-in frequency band 14 to be decided by a rating of a brushless motor, and controls transistors 9, 10, 11, 12 through a logic processor 8 to execute a conducting pattern. In the case of the pattern to cross the band in a predetermined time by varying a frequency of a revolving magnetic field from below to above in one direction, the heavier weights of a magnetron of the motor and a blade, etc., mounted at the magnetron are, the larger an inertial moment becomes. Accordingly, it is slowly synchronized from a low frequency to be rotated while avoiding a step-out, and the frequency is gradually increased to a counterelectromotive force which can be detected by a position detector 6. As a result, it can be effectively started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a starting method in a drive circuit of a brushless motor for detecting a relative position between a stator coil and a magnet rotor from a counter electromotive voltage of the stator coil to drive the brushless motor.

[0002]

2. Description of the Related Art As a conventional drive circuit for a brushless motor, there is, for example, the one shown in Japanese Patent Laid-Open No. 62-281791. This is a three-phase full-wave drive system, in which the Hall element detects the magnetic flux of the magnet rotor, the position detection circuit inputs a three-phase position detection signal to the logic processing circuit, and the switching element is controlled to control the brushless motor. Is to drive.

Further, as disclosed in Japanese Patent Application Laid-Open No. 4-161092, the relative position between the stator coil and the magnet rotor is detected by the induced voltage of the stator coil without using a position sensor such as a Hall element. There is also a sensorless drive circuit that controls a switching element based on this to drive a brushless motor.

[0004]

In the conventional drive circuit for a brushless motor as described above, it is difficult to reduce the size and the cost of the former due to the Hall element and the wirings associated therewith. It is moving to a sensorless system. However, in the sensorless method, the start-up tends to be unstable, and for example, the above-mentioned Japanese Patent Laid-Open No.
In Japanese Patent Laid-Open No. 161092, the capacitor is charged and discharged to alternately energize and shake it to start. And, to prevent malfunctions caused by noise when the switch is turned on, the power is cut off during that time.
There are still challenges to the stability and reliability of startup.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to obtain stability and certainty of starting in a sensorless drive circuit.

[0006]

According to a first aspect of the present invention, there is provided a starting method for a sensorless brushless motor drive circuit,
A starter circuit that generates a synchronizing signal for forcibly starting the brushless motor is provided, and the energizing pattern to the switching circuit becomes the frequency of the rotating magnetic field that changes at least in the synchronous pull-in frequency band of the brushless motor by the synchronizing signal. It was made to be performed by.

According to a second aspect of the present invention, in the starting method according to the first aspect, the counter signal generates a counter electromotive voltage which can be detected by the position detection circuit across the sync pull-in frequency band from the sync pull-in frequency band of the brushless motor. The drive circuit causes the drive circuit to carry out an energization pattern to the switching circuit at which the frequency of the rotating magnetic field gradually increases to the level.

According to a third aspect of the present invention, in the starting method according to the first aspect, the sync signal is lowered from a frequency higher than the sync pull-in frequency band to below the sync pull-in frequency band and then the sync pull-in frequency band is set. The drive circuit causes the drive circuit to perform an energization pattern across the switching circuit that has a frequency of the rotating magnetic field that gradually increases to the level of the counter electromotive voltage that can be detected by the position detection circuit.

According to a fourth aspect of the present invention, in the means of the first aspect, the position detection circuit detects the position of the synchronous pull-in frequency band after crossing the synchronous pull-in frequency band of the brushless motor a predetermined number of times by the synchronizing signal. The drive circuit causes the switching circuit to have an energization pattern in which the frequency of the rotating magnetic field gradually increases to a possible back electromotive force level.

[0010]

According to the first aspect of the invention, the frequency of the rotating magnetic field changes in the synchronous pull-in frequency band of the brushless motor, and the synchronous pull-in is performed somewhere.

According to the second aspect of the present invention, the frequency of the rotating magnetic field gradually increases from the bottom in the synchronous pull-in frequency band of the brushless motor, so that the synchronous pull-in is slowly performed even in the rotor having a large moment of inertia, and the start-up time is increased. Step out will be avoided.

According to the third aspect of the invention, the frequency of the rotating magnetic field in the synchronous pull-in frequency band of the brushless motor is gradually lowered from the high frequency at which the synchronous pull-in does not occur at first so that the synchronous pull-in frequency band is lowered. Since it gradually increases from the vicinity of the band, it becomes possible to prevent the reverse rotation that may occur due to the mutual positional relationship between the magnet rotor and the stator coil.

In the invention of claim 4, since the frequency of the rotating magnetic field changes up and down a predetermined number of times in the vicinity of the synchronous pull-in frequency band of the brushless motor, the frequency gradually increases to a high frequency, so that the chance of starting increases and the starting starts. The probability of will be improved.

[0014]

1 is a circuit diagram of a drive circuit for a two-phase sensorless brushless motor showing an embodiment of the present invention.
In the figure, reference numerals 1 and 2 denote an S-phase stator coil and an M-phase stator coil of a brushless motor, which together with a magnet rotor (not shown) constitute a motor body of the brushless motor. Reference numeral 3 denotes a voltage doubler rectifier circuit that converts the AC power supply 4 into a voltage doubler and rectifies it to create a DC power supply of 280 V and 140 V, for example, and an S phase stator coil 1 and an M phase stator coil 2
Supply to. A start-up circuit 5 outputs a synchronization signal for forcibly starting. A position detection circuit 6 detects the relative position of the magnet rotor from the counter electromotive voltages of the S-phase stator coil 1 and the M-phase stator coil 2. 7 is a signal switching circuit, which inputs the outputs from the starting circuit 5 and the position detecting circuit 6,
Either of them is determined and output. 8 is a logic processing circuit,
Receives the output of the signal switching circuit 7 and forms a phase arm 4
Transistors 9, 10, 11, 12 are connected to form an H bridge, and transistors 9, 10, 11, 12 are connected.
The control output of conduction interruption is output to. 13 is a synchronization determination circuit,
It is determined from the output of the position detection circuit 6 and the output of the signal switching circuit 7 whether or not the magnet rotor and the rotating magnetic field are synchronized, and when they are synchronized, the output frequency of the starting circuit 5 is increased.

In the drive circuit having the above configuration, the logic from the logic processing circuit 8 sequentially turns on the transistors 9, 10, 11, 12 of each phase arm, so that S
The brushless motor is rotated by energizing the phase stator coil 1 and the M phase stator coil 2. That is, the transistor 9 is turned on by the base signal, a current flows through the S-phase stator coil 1 from the high potential side to the medium potential side, and the phase 9
The transistor 9 is turned off after energization for 0 degree. Next, the transistor 10 is turned on by the base signal, a current flows through the M-phase stator coil 2 from the high potential side to the medium potential side, and the transistor 10 is turned off after 90 degrees of energization in phase. Subsequently, the transistor 11 is turned on by the base signal, a current flows through the S-phase stator coil 1 from the medium potential side to the low potential side, and the transistor 11 is turned off after 90 degrees of phase energization. Further, the transistor 12 is turned on by the base signal, a current flows in the M-phase stator coil 2 from the medium potential side to the low potential side, and the transistor 12 is turned off after 90 degrees of energization in phase. Thereafter, by repeating this series of operations, a rotating magnetic field is generated in a fixed direction, and the brushless motor rotates.

The position detection circuit 6 detects the position of the magnet rotor by the counter electromotive voltage generated in the M-phase stator coil 2 and the S-phase stator coil 1 when the motor is driven, and the signal processing circuit 8 outputs the position to the logic processing circuit 8. Send a signal. The logic processing circuit 8 processes this signal and processes the transistors 9, 10,
The energization switching timing is determined by the base signals 11 and 12. Since the counter electromotive voltage is not generated in the S-phase stator coil 1 and the M-phase stator coil 2 at the start of activation, the position detection circuit 6 cannot detect the proper position of the magnet rotor. Therefore, the signal switching circuit 7 is not the position detection circuit 6,
The signal from the starting circuit 5 is sent to the logic processing circuit 8. The start-up circuit 5 forcibly switches the energization and outputs a synchronization signal for starting the motor, and the logic processing circuit 8 which receives the synchronization signal through the signal switching circuit 7 processes the signals to form the transistors 9, 10, 11 and 12 are driven to forcibly start the magnet rotor. After the start-up, the signal switching circuit 7 switches the input to the logic processing circuit 8 to the signal of the position detection circuit 6.

The starting circuit 5 outputs a synchronizing signal which changes at least in the synchronous pull-in frequency band 14 determined by the rating of the brushless motor, controls the transistors 9, 10, 11, 12 through the logic processing circuit 8 to execute the energization pattern. Let Hereinafter, some energization patterns by the starting circuit 5 will be described.

<Embodiment 1 of energization pattern> The frequency 15 of the rotating magnetic field is changed in one direction from the bottom to the top so that the sync pull-in frequency band 14 is crossed over a predetermined time as shown in FIG. It is a pattern. The larger the weight of the magnet rotor of the brushless motor and the blades attached to it, the larger the moment of inertia and the more difficult it is to rotate.Therefore, slowly synchronize from a low frequency and rotate while avoiding step-out, and gradually The frequency is gradually increased to the back electromotive force level that can be detected by the position detection circuit 6.
As a result, even in the case of a magnet rotor having a large moment of inertia, it can be surely started without causing a step out.

<Embodiment 2 of energization pattern> The frequency 15 of the rotating magnetic field is once lowered from a frequency higher than the sync pull-in frequency band 14 to a frequency lower than the sync pull-in frequency band 14, and then the sync pull-in frequency band 14 is crossed over a predetermined time. 4 is a parabolic linear energization pattern as shown in FIG. 3 in which the back electromotive force level that can be gradually increased and detected by the position detection circuit 6 is raised. That is, the frequency 15 of the rotating magnetic field is first lowered from a high frequency that does not cause the synchronous pull-in to gradually fall below the lower limit of the synchronous pull-in frequency band 14, and then the synchronous pull-in frequency band 14 is crossed again, and the position detection circuit is detected. In step 6, the back electromotive force level is detected. As a result, since the synchronous pull-in frequency band 14 is covered twice, the certainty of starting is increased. Also, depending on the mutual positional relationship between the magnet rotor and the S-phase and M-phase stator coils 1 and 2, reverse rotation may occur when the frequency 15 of the rotating magnetic field is simply increased from bottom to top. This reversal is avoided in this energization pattern, which changes from top to bottom and bottom to top.

<Embodiment 3 of energization pattern> The frequency 15 of the rotating magnetic field is vertically changed a predetermined number of times so as to traverse it in the vicinity of the sync pull-in frequency band 14, and after shaking, the sync pull-in frequency band 14 is set. The energization pattern is as shown in FIG. 4, which is gradually increased from the bottom to the top over a predetermined time so as to cross the counter electromotive voltage level that can be detected by the position detection circuit 6. In this energization pattern, it may not start with a single increase in the frequency 15 of the rotating magnetic field,
Since the frequency 15 of the rotating magnetic field is fluctuated several times, the probability of activation is improved and the activation becomes more reliable.

[0021]

As is apparent from the above description of the embodiments, according to the invention of claim 1, the frequency of the rotating magnetic field changes and changes in the synchronous pull-in frequency band of the brushless motor. Then, the synchronization pull-in is performed, and the startup is stabilized.

According to the second aspect of the present invention, the frequency of the rotating magnetic field gradually increases from the bottom in the synchronous pull-in frequency band of the brushless motor, so that the synchronous pull-in is slowly performed even in the rotor having a large moment of inertia, and at the time of start-up. The out-of-step is avoided, and the certainty of starting increases.

According to the third aspect of the present invention, the synchronous pull-in frequency band of the brushless motor is gradually lowered from the high frequency of the rotating magnetic field so that the synchronous pull-in does not occur at first, and the synchronous pull-in frequency band is gradually lowered. Since the frequency gradually increases from the vicinity of the frequency band, it is possible to prevent the reversal that may occur due to the mutual positional relationship between the magnet rotor and the stator coil, and the starting stability is increased.

According to the invention of claim 4, since the frequency of the rotating magnetic field changes up and down a predetermined number of times in the vicinity of the synchronous pull-in frequency band of the brushless motor, the frequency gradually increases to a high frequency, so there is a lot of chance of starting, and the starting The probability of increases and the certainty increases.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a drive circuit of a sensorless brushless motor showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a frequency change of a rotating magnetic field according to an energization pattern of the present invention.

FIG. 3 is an explanatory diagram showing a frequency change of a rotating magnetic field according to another energization pattern of the present invention.

FIG. 4 is an explanatory diagram showing a frequency change of a rotating magnetic field according to another energization pattern of the present invention.

[Explanation of symbols]

 1 S-phase stator coil 2 M-phase stator coil 5 Starter circuit 6 Position detection circuit 9 Transistor 10 Transistor 11 Transistor 12 Transistor 14 Synchronous pull-in frequency band 15 Rotating magnetic field frequency

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kamo Shigeki 2-3-3 Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd. (72) Inoue Shiro Tanaka 2-3-2, Marunouchi, Chiyoda-ku, Tokyo No. Sanryo Electric Co., Ltd. (72) Inventor Takahiro Hayakawa 3-40 Tegano Shimobane, Nakatsugawa City, Gifu Prefecture Mitsubishi Electric Engineering Co., Ltd. Nagoya Office Nakatsugawa Branch Office

Claims (4)

[Claims] 1. A relative position between a stator coil and a magnet rotor is detected by a position detection circuit from a back electromotive voltage of a stator coil connected in multiple phases, and a switching circuit determines an energization timing to the stator coil based on the detected position. The drive circuit that drives the brushless motor is provided with a starter circuit that generates a synchronization signal for forcibly starting the brushless motor, and the rotation magnetic field that changes at least in the synchronous pull-in frequency band of the brushless motor is provided by the synchronization signal of this starter circuit. A method for starting a brushless motor, characterized in that a drive circuit performs an energization pattern of a switching circuit having a frequency. 2. A switching circuit having a frequency of a rotating magnetic field that gradually increases from a frequency equal to or lower than the synchronous pull-in frequency band of the brushless motor to a counter electromotive voltage level that can be detected by the position detection circuit by a synchronous signal from the starter circuit. The method for starting a brushless motor according to claim 1, wherein the energization pattern to the drive circuit is performed by a drive circuit. 3. A counter electromotive voltage that can be detected by the position detection circuit across the sync pull-in frequency band after lowering from a frequency higher than the sync pull-in frequency band to below the sync pull-in frequency band by the sync signal of the starter circuit. 2. The method of starting a brushless motor according to claim 1, wherein the drive circuit performs an energization pattern to the switching circuit having a frequency of the rotating magnetic field that gradually increases to a level. 4. After crossing the synchronous pull-in frequency band of the brushless motor a predetermined number of times by the synchronous signal of the starting circuit,
2. The drive circuit causes the drive circuit to carry out an energization pattern to the switching circuit having a frequency of the rotating magnetic field that gradually increases to the level of the counter electromotive voltage that can be detected by the position detection circuit across the synchronous pull-in frequency band. How to start a brushless motor.