JPH09149681A - Driver of brushless dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drive a rotor smoothly without using a pole position detector such as a Hall sensor by a method wherein stator winding current waveform patterns corresponding to various types of loads are stored beforehand and a detected current waveform pattern is compared with the stored waveform patterns and, in accordance with the comparison result, a pulse voltage supplied to the winding is adjusted. SOLUTION: A three-phase power supply 1 is rectified and smoothed to obtain a DC voltage which is chopped by power semiconductor devices 4a 4f and supplied to the stator windings 6 of a DC motor 5 and a rotor 7 is synchronized with rotary magnetic fields of the stator side to rotate. In a driver like this, a load current is detected by a current detecting resistor 11 and inputted to a microprocessor 8 and stored temporarily in a memory device 12. The load current waveform pattern is compared with current waveform patterns which correspond to various types of loads and are stored in a ROM 9 and the power semiconductor devices 4a-4f are operated in accordance with the comparison result. With this constitution, the step out caused by the load fluctuation can be avoided and the brushless DC motor 5 can be driven stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for a brushless DC motor, and in particular, a commutation signal is generated without using a magnetic pole detection device such as a Hall sensor, and a rotor is set at an optimum voltage according to a load. The present invention relates to a drive device for rotating.

[0002]

2. Description of the Related Art A brushless DC motor comprises a stator having windings of plural phases and a rotor having plural magnetic poles of N and S poles, and supplies a switching current to the windings of plural phases. Thus, a rotating magnetic field is formed in the stator, and the rotor is rotated in synchronization with the rotating magnetic field. Then, a magnetic pole detection device such as a Hall element is provided to detect the magnetic pole position of the rotor, and a commutation signal of an energization pulse voltage for energizing the winding is obtained from the signal. The generation of the commutation signal of the energizing pulse voltage that energizes this winding has been performed by a semiconductor control circuit that has a power semiconductor switching element on the output line of its driving device and controls the opening and closing of the switching element.

However, when a pump or the like is driven by a brushless DC motor, in a use environment where the temperature and pressure in the motor rise, the magnetic pole detection device using a semiconductor malfunctions and a smooth commutation operation is performed. There was a problem that it hindered the. Therefore, avoid the use of Hall effect elements that are easily affected by temperature rise, etc., and replace the magnetic pole position detection signal with the counter electromotive voltage generated in an empty coil that is not energized in the stator winding during motor rotation. The method of detecting the following signal has been used in a drive device of a brushless DC motor.

Generally, in a brushless DC motor driving device, the magnitude of the DC voltage applied to the motor winding is determined by forming an energizing pulse of the DC power supply voltage and modulating the energizing pulse by pulse width to change the duty. , Any effective energizing pulse voltage is changed. However,
When the counter electromotive voltage generated in the empty coil of the motor is detected to generate the energizing pulse switching timing signal, an oscillating voltage is superimposed on the detected counter electromotive voltage by the chopping of the pulse width modulation described above, and the timing signal is generated. There is a problem that it is easy to erroneously detect.

As a method of detecting a commutation timing signal other than the above-mentioned counter electromotive voltage, generating a commutation timing signal from the shape of the motor current waveform is described in "Permanent magnet synchronization" by Nakamura, Kudo, and Hanai. Power Factor ≈ 1 Control Method for Electric Motors "
Has been published in a paper entitled.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and supplies an energizing pulse to a motor stator winding without using a magnetic pole position detecting device such as a Hall element. It is an object of the present invention to provide a brushless DC motor drive device capable of smoothly rotating a rotor having magnetic poles.

[0007]

A drive device for a brushless DC motor according to the present invention comprises a plurality of switching circuits for sequentially applying energizing pulses to windings of a plurality of phases included in the motor, and the switching circuits having an arbitrary frequency and energizing. A pulse width modulation circuit that performs pulse width modulation to supply a pulse voltage to the winding, a motor current detection circuit that detects a motor current flowing in the motor winding, and a memory that stores a waveform pattern of the detected motor current. A device and a storage device that stores a current waveform pattern corresponding to various loads in advance,
It is provided with means for comparing the detected current waveform pattern with the previously stored current waveform pattern, and control means for adjusting the energizing pulse voltage supplied to the motor winding based on the result of the comparison. And

The comparison of the current waveform patterns is 1
It is characterized in that the current waveform pattern is performed at two points of the first half and the second half.

According to the above-described configuration of the present invention, current waveform patterns corresponding to various loads are stored in advance and compared with the detected current waveform pattern. And
Based on the comparison result, the magnitude of the energizing pulse supplied to the winding is adjusted by changing the duty in the pulse width modulation circuit. By repeating such adjustments, it is possible to obtain an optimum energizing pulse in which the rotor is completely synchronized with the rotating magnetic field on the stator side.

[0010]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an example of an overall connection diagram of the brushless DC motor of the present invention. Reference numeral 1 is a three-phase commercial AC power supply. This power supply 1 is rectified by the full-wave rectification diode bridge circuit 2, its voltage is smoothed by the electrolytic capacitor 3, and becomes a DC voltage source. The DC voltage generated here is used for the semiconductor power device 4 such as a power transistor.
By chopping with a, 4b, 4c, 4d, 4e, 4f, it is supplied to the winding coil 6 of the DC motor 5 as an energizing pulse. The energizing pulse is generated by the power elements 4a, 4b, 4
The gates of c, 4d, 4e and 4f are formed by applying the drive pulse shown in FIG. A rotating magnetic field is generated in the motor stator by the energizing pulse. When the motor is rotating normally, the voltage waveforms shown in FIG. 3 are generated in the windings U, V and W. In the present embodiment, the rotor 7 is N, S,
Since it has a disk of permanent magnets having four magnetic poles of N and S, it rotates in synchronization with the rotating magnetic field on the stator side.

Here, one of the energizing pulses in FIGS.
The section T is composed of 6 sections (6T), which constitutes one cycle. That is, the section T has a relationship proportional to the reciprocal of the rotation speed of the motor. The section T is large when the motor is started, and the section T becomes smaller as the speed increases. The height (+ V ₀ , −V ₀ ) of the energizing pulse is obtained by chopping the DC power supply voltage, but the energizing pulse in one section is composed of a large number of pulse-width modulated pulses. By changing the degree of pulse width modulation (duty), the effective height of the energizing pulse, that is, the voltage value can be changed.

FIG. 4 shows various current waveforms flowing through the current detection resistor 11. In the first section, the U-phase voltage is + V ₀ and the V-phase voltage is −V _0, so current flows from the U-phase to the V-phase. Similarly, in the next section, the current flows from the U phase to the W phase,
Further, in the next section, the current flows from the V phase to the W phase. In this way, the voltage waveform corresponding to the current waveform flowing in each phase winding appears in the current detection resistor 11 for each section.

This current waveform becomes a lag phase waveform or a lead phase waveform depending on the size of the load with respect to the voltage which is effectively constant of the energizing pulse. That is, when the load is heavy with respect to a constant energizing pulse voltage, the rotation of the rotor is delayed and synchronized with the rotating magnetic field on the side of the stator, and the pattern has a current waveform A. In addition, when the load is appropriate for a constant energizing pulse voltage, the rotation of the rotor is vertically synchronized with respect to the rotating magnetic field on the stator side, and the pattern shown in the current waveform B is obtained. . Further, when the load is light with respect to the constant energizing pulse voltage, the rotation of the rotor advances and synchronizes with the rotationally-moving magnetic field on the side of the stator, and the pattern has a current waveform C.

The load current flowing through the motor winding is detected by the current detection resistor 11, is input to the microprocessor 8 and is temporarily stored in the storage device 12. Further, a memory device (ROM) 9 in the microprocessor 8 has a current waveform pattern of a delayed phase as shown in FIG.
Current waveform pattern with no delay or advance like (C)
The current waveform pattern of the leading phase as described above is stored in advance corresponding to various energizing pulse voltages. In addition, data for controlling the increase of the energization pulse voltage and the decrease of the energization pulse voltage are also stored.

In the apparatus having such a configuration, by switching the energization of the switching circuit in a predetermined drive pattern as shown in FIG. 2, the phase voltage of each phase shown in FIG. Rotate. When the motor is started, it is driven by a conduction pulse having a certain low constant frequency. At this time, the time T of one section is measured by using the timer in the microprocessor 8. That is, when the rotation speed at startup is set, the time T of one section is calculated. This time T is measured by a timer to perform commutation. For example, in the embodiment of FIG. 2, the switching element 4e is turned off after the time T has elapsed.
As the FF, the switching element 4f is turned on. This starts the next time T.

When the timer is set at the same time as such a commutation operation and the value of the timer next elapses ¼ of T (T ₁ ).
The current value of the first half of one section is detected. This current value is A
After the D / D conversion, the data is stored in the storage device. Next, T 3
When / 4 has elapsed (T ₂ ), the current value of the latter half of one section is similarly measured and stored in the storage device. These two-point pattern and the pattern stored in advance are processed by the microprocessor 8
Compare with the internal comparison device. That is, with respect to the current waveform (B) which is stored in advance and which is in synchronization with the apex, whether the phase is a delay phase, a lead phase, or a degree of delay and advance is compared with a stored current waveform. And judge.

In the case of the delay phase, the load is considered to be heavier than the energizing pulse voltage, so the energizing pulse voltage is increased. If the lead phase,
Since it is considered that the load is light with respect to the energizing pulse voltage,
The energizing pulse voltage is lowered. The energization pulse voltage can be increased or decreased easily by changing the degree (duty) of pulse width modulation because the energization pulse itself is a set of a large number of pulse width modulated pulses. Then, the process of detecting the load current waveform pattern flowing through this winding, making a comparison determination with each reference current waveform, and adjusting the energizing pulse voltage according to the magnitude of the load based on this determination result is performed in each section T. Repeat every time.
By performing such control, it is possible to adjust to an optimum energization pulse voltage corresponding to the current command rotation speed so that the commutation timing is synchronized with the rotor.

By performing the above-mentioned control, the phase of the commutation timing is synchronized with the rotor, and the motor can be rotationally driven without step out due to the load. The motor rotation speed can be increased or decreased by gradually increasing or decreasing the section timer T while performing the above control. Further, when it is desired to increase the rotation speed at a constant rate, it can be realized by reducing T at a constant rate while performing the above-described control. Further, when it is desired to decrease the rotation speed at a constant rate, it can be realized by increasing T at a constant rate while performing the control described above.

This embodiment is one embodiment in which a pulse width modulation circuit, a current detection circuit, a comparison circuit, etc. are realized by using a microprocessor, and each necessary function is realized by using other hardware. It goes without saying that the same effect can be obtained in the system as well.

[0021]

According to the present invention, by the above-mentioned control, there is no step out due to load fluctuations, and there is no need to use a member such as a Hall element which is easily affected by temperature.
The brushless DC motor can be driven stably.
Further, in order to compare the load current waveform with the reference current waveform, it is possible to measure and compare the current values of only two points in one section. This reduces the burden on the microprocessor,
The present invention can be implemented by an inexpensive processor having a slow processing speed. Overall, according to the present invention, it is possible to provide a drive device capable of stably operating a brushless DC motor at a relatively low cost. Of course, the operation is not limited to two points, and the operation for several points is also possible.

[Brief description of the drawings]

FIG. 1 is an overall circuit diagram of a brushless DC motor according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of a gate drive pattern of a power element in a switching circuit.

FIG. 3 is a waveform diagram of energization pulses supplied to each phase winding.

FIG. 4 is a waveform diagram of a current flowing through each phase winding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Diode bridge 3 Smoothing capacitors 4a-4f Power element 5 Brushless DC motor 6 Stator winding 7 Rotor 8 Microprocessor 9 ROM 10 Gate drive circuit 11 Current detection resistor 12 Storage device

Claims (2)

[Claims] 1. A plurality of switching circuits for sequentially applying energizing pulses to windings of a plurality of phases included in a motor, and pulse width modulation so that the switching circuits supply arbitrary frequencies and energizing pulse voltages to the windings. A pulse width modulation circuit, a motor current detection circuit that detects a motor current flowing in the motor winding, a storage device that stores the waveform pattern of the detected motor current, and a current waveform pattern that corresponds to various loads in advance. And a means for comparing the detected current waveform pattern with the previously stored current waveform pattern, and a control means for adjusting the energizing pulse voltage supplied to the motor winding based on the comparison result. A drive device for a brushless DC motor, characterized by being provided. 2. The brushless DC motor drive device according to claim 1, wherein the comparison of the current waveform patterns is performed at two points of the first half and the second half for one current waveform pattern.