JPH06253584A - Driver for sensorless brushless motor - Google Patents

Abstract

PURPOSE:To allow commutation at an appropriate timing without requiring any delay pulse by correcting the exciting time such that phase shift is eliminated between the rotary position of rotor and conduction of coil. CONSTITUTION:Conduction is started forcibly for each phase of a three-phase motor. Excitation is performed by dividing one period of 360 deg. into 12 patterns of 30 deg.. A microprocessor 1 observes the waveform of voltage induced during nonconducting period and corrects the exciting time such that the phase shift of rotor is eliminated. A comparator 4 compares the induced voltage with an applying voltage of motor while dividing into tri-levels at a specific timing and phase lock control is performed based on the comparison results. Consequently, stabilized operation of rotor equivalent to a brushless motor equipped with a rotary position sensor can be achieved. Furthermore, rotation synchronized with a command speed 14 can be achieved by comparing the speed command with an averaged exciting time and varying the duty of PWM signal.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is used in home appliances and the like.
The present invention relates to a drive device that drives a brushless motor that does not have a position detection sensor such as a fan or a pump.

[0002]

2. Description of the Related Art In the field of home electric appliances and the like, brush life motors have come to be used along with the long life and high reliability of products. As for the driving method, many sensorless driving methods have been proposed.

A method of sensorless driving will be described below. FIG. 7 shows a schematic block diagram of a drive circuit of a conventional sensorless brushless motor. The motor used in the figure is a two-phase full-wave drive.

When the motor is rotating, each coil La,
At both ends of Lb, sinusoidal induced voltages Ea and Eb having a 90-degree phase difference are generated as shown in the waveform diagram of FIG. The waveforms of the induced voltages Ea and Eb are shaped at the neutral voltage of the motor by the comparators 24 and 25 having two inputs connected to both ends of the coils La and Lb. Therefore, as shown in FIG. 8B, the pulse signals S1 and S2 having the same period and phase as the induced voltages Ea and Eb and a phase difference of 90 degrees are obtained from the comparators 24 and 25, respectively.

The pulse signals S1 and S2 are supplied to the delay circuit 23, and as shown in FIG. 8C, a delayed clock DCK whose rising edge is delayed by the time T is formed from both rising edges of S1 and S2. The time T corresponds to an electrical angle of 45 degrees, so that a 90-degree width electrical angle can be set with the front edge at a position of 45 degrees from the magnetic pole boundary that is the reference position of the rotor magnet without a rotational position sensor. The switching circuit 21 is switched at the timing shown in (e) to drive the brushless motor sensorlessly.

[0006]

However, in the above-mentioned conventional configuration, since energization switching of the motor is performed with reference to the delay pulse DCK, an additional delay circuit must be provided, and the delay pulse includes a time error. If so, it will not be possible to commutate at an appropriate timing.

The present invention provides a drive device for a brushless motor capable of sensorless driving, which can perform commutation at an appropriate timing without providing a delay pulse.

[0008]

A sensorless brushless motor drive apparatus according to the present invention comprises a starting means for starting the energization state, a means for outputting the excitation switching time of each coil, and a voltage applied to the motor in three levels. And a means for correcting the excitation time so as to eliminate the phase deviation by detecting the phase difference between the rotational position of the rotor and the coil energization by comparing the induced voltage appearing in the non-energization period with the three-valued level. There is.

Further, there are provided a pulse width modulation signal output means and a means for observing the induced voltage waveform in synchronization with the pulse width modulation signal.

[0010]

According to the present invention, with the above-described configuration, it is possible to create an excitation time according to the rotation speed of the motor without using the rotation position sensor of the rotor, and to switch the energization optimally. It is possible to provide a brushless motor having high performance that synchronously rotates at a rotation speed according to the rotation speed of the

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a drive device for a sensorless brushless motor according to the present invention. In FIG. 1, reference numeral 1 is a microprocessor for determining the excitation switching time of each coil, outputting the excitation switching signals P1 to P6 of each coil, and taking in the rotor phase information P10 and P11 from the induced voltage to determine the rotor rotation position and coil energization. Correct the excitation time to eliminate the phase difference of.

Reference numeral 2 is a driver for switching the excitation of each coil, and reference numeral 3 is a brushless motor in which three phases are connected, and performs three-phase full-wave drive. Reference numeral 4 is a comparator for comparing the induced voltage level of a specific one of the three exciting coils of the motor with a ternary level obtained by dividing the applied voltage of the motor into three stages, and 5 is an output level of the comparator 4. Is a level conversion circuit for converting the. When performing speed control, a pulse width modulation signal P12 is output from the microprocessor. Based on the output, the permitting circuit 6 for observing the induced voltage only at a specific timing, the gate circuit 8 for determining whether to perform PWM control, and the gate circuit 7 for controlling the exciting voltage based on the pulse width modulation signal. Need.

FIG. 2 is an example of an internal configuration diagram of a microprocessor that can be used in the present invention. The outputs P10 and P11 of the level conversion circuit, and the speed instruction command P
14 is a central processing unit of 9 (hereinafter C
(Abbreviated as PU). CPU 9 has 12 timers 1 and 14
Connected to each memory. When speed control is performed, 13 timers 2 must be connected. Reference numeral 11 denotes an output circuit, which supplies a driver whose CPU output is 2 and PWM control signals P12 and P13.

The operation of the embodiment of the present invention will be described. First, energization of each of the three phases is forcibly started from the stopped state of the motor. This energization method is called a so-called full-wave drive method for a three-phase motor.
If V and W, then U → V, W → V, W for each phase of U, V, W
→ U, V → U, V → W, U → W are sequentially energized. At this time, the rotor rotates synchronously in a so-called open loop in response to this excitation.

At the time of startup, the so-called slow-up drive is performed in which the excitation time of each excitation pattern is long enough to start the motor, and the excitation time is gradually increased to increase the rotation speed of the rotor. When the rotation speed of the rotor reaches a sufficient speed, the induced voltage reaches a level that can be processed.

FIG. 3 is a timing diagram of phase detection. When the induced voltage reaches a processable level, the induced voltage waveform in the non-energized period is observed at the timing shown in FIG. 3, and the excitation time is corrected so as to eliminate the phase shift of the rotor.

The energization is carried out in one cycle of 360 degrees for 12 times every 30 degrees.
Excitation is performed by breaking it down into patterns. The excitation time is set by the timer 1 of 12, an interrupt is generated every time, and an excitation pattern is output. Then, the non-energization period is set at the time of the first interrupt and the seventh interrupt.

Therefore, when the first interrupt occurs,
The induced voltage is compared with the next voltage level before outputting the excitation pattern. If the voltage applied to the motor is Vm, Vm is divided into three stages. That is, 0-VTL, VTL-VT
It is divided into three levels of H and VTH to Vm.

The phase shift of the rotor can be detected by comparing the three-valued level with the induced voltage and combining the results. This state is shown in FIG. When the result of the comparison is level-converted, the phase information signals P10 and P11 can be detected as a combination of 0 and 1. The phase shift detection capability is
Determined by VTH and VTL to be set.

When it is judged to be delayed or advanced, the excitation time output by the microprocessor is corrected. The correction value corrects the excitation time at a certain ratio to the current excitation time. After that, the motor rotates with the corrected excitation time.

Then, the first interrupt occurs. When the first interruption occurs, the induced voltage is compared with the three-valued level before the excitation pattern is output. Based on the result, the excitation time is corrected and the phase shift is reduced.

Further, in order to improve the load followability, not only the first interruption but also the non-conduction period at the seventh interruption, the induced voltage is observed at the seventh interruption and the phase shift is observed. Is detected and the excitation time is corrected.

By repeating the above flow, it is possible to rotate the brushless motor synchronously.

Next, when the pulse width modulation signal is output for speed control, the induced voltage appearing during the non-conduction period is affected by the pulse width modulation signal, and the phase information of the rotor position cannot be accurately determined.

This state is shown in FIG. FIG. 5A is an induced voltage during a non-energization period when speed control is not performed, FIG. 5B is a pulse width modulation signal for performing speed control, and FIG. 5C is a non-energization time when speed control is performed. The induced voltage that appears during the period is shown. It can be seen from FIG. 5C that the induced voltage during the non-energization period is affected by the pulse width modulation signal. Therefore, it can be seen that the phase information is not accurate in this waveform.

Here, attention is paid to the waveforms (b) and (c) of FIG. When the induced voltage waveform is observed in synchronization with the fall of the pulse width modulated signal, it can be seen that the induced voltage waveform can be observed without being affected by the pulse width modulated signal.

Therefore, by observing the induced voltage using the permitting circuit 6 of FIG. 1 in synchronism with the fall of the pulse width modulated signal, phase information that is not affected by the pulse width modulated signal can be fetched. it can.

Thus, by observing the induced voltage in synchronization with the fall of the pulse width modulation signal, stable rotation can be obtained without the position sensor of the rotor. At that time, as the excitation voltage of the motor, a voltage determined by the duty of the pulse width modulation signal is applied.

Next, a method of synchronously rotating at the commanded rotation speed will be described. The speed instruction signal P14 indicating the number of revolutions is input to the microprocessor. The rotation speed of the motor at that time is proportional to the excitation time output from the microprocessor. This is because the excitation switching of the motor is all determined by the microprocessor, and the excitation time is corrected based on the phase information in order to maintain stable rotation.

Therefore, in order to know the number of rotations of the motor,
The excitation time output by the microprocessor may be observed. Therefore, the speed instruction value is converted into a time corresponding to an electrical angle of 30 degrees, and the converted value is compared with the actual speed, that is, the excitation time output by the microprocessor. Based on the comparison result, the duty of the pulse width modulation signal is varied, and the motor rotates at the number of rotations synchronized with the command speed.

Here, when comparing the command speed and the actual rotation speed, the average value of the excitation times of a specific number of times among the excitation times set at the first interruption is compared as the actual rotation speed.

Further, the following processing is performed as a fail safe. Due to the characteristics of the motor, when the output excitation time is set to the time when the motor does not rotate, processing such as restarting starting from the open loop drive or shutting off the motor power is performed.

Further, since the excitation time and the excitation pattern are output from the microprocessor, even if the motor is locked, the microprocessor continues to output the excitation pattern according to the excitation time at that time, and the phase information signal P10 is output. , P11 are used to correct the excitation time.

That is, the excitation is not fixed and the microprocessor always outputs an excitation pattern according to a certain excitation time, so that no lock current flows and the switching element can be protected without a special protection element. .

The excitation time is continuously corrected, and finally the excitation time in which the motor does not rotate is detected due to the characteristics of the motor as described above.
The switching element can be protected by performing processing such as restarting from open loop driving or shutting off the motor power supply.

FIG. 6 shows a flowchart of an embodiment in which the microprocessor having the structure shown in FIG. 2 is used.

When the motor is driven by forced commutation and the induced voltage becomes observable, an interrupt is generated at each excitation time output by the microprocessor. When the first interruption occurs, the phase information of the rotor is read and the excitation time is corrected based on the result. Judge whether the corrected time is appropriate, and if it is abnormal, return to the start. If normal, the excitation pattern is output according to the interrupt, and after the 12th output, the first interrupt is awaited.

Although the embodiment in which the present invention is applied to the three-phase full-wave drive type brushless motor has been described above, the present invention can be applied to a half-wave or full-wave drive type sensorless brushless motor of two or more phases. It is possible.

Further, when measuring the induced voltage, the induced voltage of one exciting coil was measured, but the same effect can be obtained by using two or three exciting coils.

Further, an embodiment has been shown in which the excitation switching is performed on the basis of the position where the induced voltage waveform of the W phase crosses from the positive potential to the negative potential at the reference position of the commutation timing of the motor. If it is a brushless motor,
It goes without saying that the same effect can be obtained by switching the excitation with reference to any one of the positions where the induced voltage of any of the U, V, and W coils crosses the neutral point potential.

[0042]

As described above, according to the present invention, rotation is performed for an excitation time corresponding to an electrical angle of 30 degrees output from the microprocessor, and the induced voltage and the motor applied voltage are divided into three stages at specific timings. By performing comparison with the three-valued level and performing phase lock control based on the result, stable operation equivalent to that of a brushless motor with a rotor rotation position sensor can be obtained.

Furthermore, by comparing the commanded speed with the averaged excitation time and varying the duty of the pulse width modulation signal based on the result, rotation in synchronism with the commanded speed can be obtained, and the rotation speed detection device. It is possible to obtain stable rotation equivalent to speed control of a brushless motor using.

[Brief description of drawings]

FIG. 1 is a block diagram of a drive circuit according to an embodiment of the present invention.

FIG. 2 is an internal configuration diagram of a microprocessor according to an embodiment of the present invention.

FIG. 3 is a timing diagram of phase detection according to an embodiment of the present invention.

FIG. 4 is a conceptual diagram of phase detection in one embodiment of the present invention.

FIG. 5 is a diagram illustrating a method of processing an induced voltage during speed control according to an embodiment of the present invention.

FIG. 6 is a flowchart.

FIG. 7 is a block diagram of a drive circuit of a conventional sensorless brushless motor.

FIG. 8 is a waveform diagram of a main part of a drive circuit of a conventional sensorless brushless motor.

[Explanation of symbols]

 1 Microprocessor 2 Driver 3 3-phase brushless motor 4 3-value level comparator 5 Level conversion circuit 6 Permitting circuit used during speed control 7 AND gate for excitation voltage control 8 OR gate for pulse width modulation control 9 Central processing unit (CPU) 10 Input circuit 11 Output circuit 12 Timer 1 13 Timer 2 14 Memory 21 Switching circuit 22 Drive pulse generation logic 23 Delay circuit 24 Comparator 25 Comparator 26 Microprocessor

Claims (5)

[Claims] 1. A means for rotating a motor by an excitation signal output from a microprocessor to a driver of the motor, and a means for observing a phase of a rotor by an induced voltage of a coil appearing during a non-energization period of the coil of the motor. Sensorless brushless motor drive device. 2. The sensorless brushless according to claim 1, wherein the motor applied voltage has a plurality of levels, and the excitation time is corrected by comparing the induced voltage appearing in the non-energized period with the plurality of levels. Motor drive device. 3. A drive device for a sensorless brushless motor according to claim 1, wherein the excitation pattern for energizing the motor coil is decomposed into 12 patterns for every 30 electrical degrees to perform excitation. 4. When the motor is started, the drive device is started in an open loop, the rotation speed is gradually increased, and after the induced voltage of the exciting coil becomes detectable, the phase difference between the coil energization and the rotor position is eliminated. The drive device for a sensorless brushless motor according to claim 1, wherein the excitation time of the motor coil is controlled. 5. The sensorless brushless motor driving device according to claim 1, wherein the exciting voltage of the motor coil is pulse width modulated to control the rotation speed.