CN214900698U

CN214900698U - Direct current brushless motor reversing system

Info

Publication number: CN214900698U
Application number: CN202120089640.XU
Authority: CN
Inventors: 肖观音
Original assignee: Shenzhen Barley Zhichuang Technology Co ltd
Current assignee: Shenzhen Barley Zhichuang Technology Co ltd
Priority date: 2021-01-13
Filing date: 2021-01-13
Publication date: 2021-11-26
Anticipated expiration: 2031-01-13

Abstract

The utility model relates to a DC brushless motor reversing system, which comprises a controller, a driver, a motor and a rotor position detector; the controller is used for sending a driving signal to the driver; the driver is used for driving the motor to run according to the driving signal; the rotor position detector is used for detecting the position of the motor rotor and sending a rotor position signal to the controller; the controller obtains the phase change position of the rotor according to the rotor position signal, and sends a PWM modulation command to the driver before the rotor reaches the phase change position, so that the input current of the motor is reduced to zero in advance.

Description

Direct current brushless motor reversing system

Technical Field

The utility model relates to a brushless DC motor switching-over system.

Background

A control schematic diagram of a single-phase dc brushless motor in the prior art is shown in fig. 1, and a basic control model is as follows: the controller obtains Hall signals of the motor, and controls the bridge switch (SW1/SW2/SW3/SW4) according to the Hall signals so as to control the current flow direction of the motor coil and generate corresponding magnetic fields to enable the motor to operate.

In a single-phase brushless dc motor, a back electromotive force 2 times or even several times of a driving voltage is generated at the time of phase change and thrown onto a dc bus, as shown in fig. 2, which may cause great damage to electronic components of the motor. The lower waveform of fig. 2 is a bus current waveform, the upper waveform of fig. 2 is a motor bus voltage waveform, the measurement range reason of the test probe is that the numerical value displayed by the voltage is reduced by 10 times, the sharp pulse in the bus voltage waveform is caused by the counter electromotive force of the motor during phase change, the voltage of the bus 12V and the counter electromotive force are already rushed to 40V, and thus, the electronic components of the motor can be greatly damaged. In addition, because the current sudden change is large during the reversing, relatively large jitter exists during the rotating reversing of the motor, and large motor noise is generated.

In summary, the existing commutation methods have at least the following three disadvantages:

1. the large reverse electromotive force can cause the damage of components.

2. The abrupt change of the commutation current is large, and large motor noise is generated.

3. The energy consumed by commutation is large, so that the efficiency of the motor is reduced

SUMMERY OF THE UTILITY MODEL

For solving the technical defect, the utility model discloses a following technical scheme:

the utility model provides a DC brushless motor reversing system, which comprises a controller, a driver, a motor and a rotor position detector;

the controller is used for sending a driving signal to the driver;

the driver is used for driving the motor to run according to the driving signal;

the rotor position detector is used for detecting the position of the motor rotor and sending a rotor position signal to the controller;

the controller obtains the phase change position of the rotor according to the rotor position signal, and sends a PWM modulation command to the driver before the rotor reaches the phase change position, so that the input current of the motor is reduced to zero in advance.

Preferably, the rotor position detector is a hall sensor.

The utility model has the advantages that: the utility model discloses the structure uses the PWM that lower or reduce the duty cycle gradually to go the modulation MOS pipe before single-phase DC brushless motor commutation, lets the motor before the commutation, descends the electric current of motor to zero earlier. Therefore, the process of follow current and current mutation can be omitted when the motor is in phase change, the back electromotive force of the motor is obviously reduced, and the stability of the direct current bus voltage cannot be influenced.

Drawings

FIG. 1 is a schematic diagram of a control scheme of a prior art single-phase DC brushless motor

FIG. 2 Prior Art Current and counter-EMF waveforms

FIG. 3 is a schematic view of the structure of the present invention

FIG. 4 is a comparison of prior art and utility model switching control waveforms and bus current waveforms

FIG. 5 shows the bus voltage and current waveforms of the present invention

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Referring to fig. 3, a dc brushless motor commutation system includes a controller, a driver, a motor, a rotor position detector;

the controller is used for sending a driving signal to the driver;

In a preferred embodiment, the rotor position detector is a hall sensor.

In this embodiment, before the phase change of the single-phase dc brushless motor, the MOS transistor is modulated by using the PWM with a lower or gradually decreasing duty ratio, so that the current of the motor is reduced to zero before the phase change of the motor. Therefore, the process of follow current and current mutation can be omitted when the motor is in phase change, the back electromotive force of the motor is obviously reduced, and the stability of the direct current bus voltage cannot be influenced. The principle is as follows:

1. and detecting the magnet signal change of the rotor by using a Hall sensor.

2. The magnet signal of the controller rotor changes, and the angle change of the rotor rotation is calculated, so that the angle position of the motor commutation is known, and the position to which the PWM modulation aims is further known.

3. And the controller sends a PWM modulation command to the driver before the rotor reaches a phase change position, and the PWM modulation processing is carried out to reduce the input current of the motor to zero in advance.

The reason that the motor current cannot change suddenly at the phase change moment is reduced: when the phase is changed, the current is small, so that high reverse electromotive force cannot be generated and can follow current through a body diode of the MOS tube and be thrown onto a direct current bus. Compared with the prior art, the utility model discloses can save the circuit that absorbs the busbar voltage surge part, reduce the withstand voltage specification of device, reduce the cost of circuit. But also facilitates the simplification of the circuit. Additionally, the utility model discloses a structure lets the excessive more smooth-going of drive current constantly of commutation, reduces because of the energy loss that the commutation caused, improves the efficiency of motor to improve the overall efficiency of fan. The current of the phase change is more smooth through processing, so that the problem of motor noise of the single-phase motor can be well improved.

As shown in fig. 4, comparing SW3 switch control waveforms: the left wave form diagram of fig. 4 is prior art's commutation means, and the right side does the utility model discloses the commutation means that adopts, wherein the rectangular waveform of top is SW3 on-off control waveform, and the curve waveform of below is the bus current waveform, the utility model discloses to SW3 on-off control increased the PWM modulation before the commutation, effectively reduced the electric current sudden change, make the electric current level and smooth reduction to zero before the switching-over, it snatchs the back electromotive force and observes, as shown in fig. 5, its back electromotive force obviously reduces, and the biggest only 16V of the same motor back electromotive force, wherein, the waveform of fig. 5 top is the bus voltage waveform, and the waveform of below is the bus current waveform.

Compared with the prior art, the utility model, can eliminate when the switching-over because of huge back electromotive force throw give the busbar voltage surge part, make optional electronic component's withstand voltage specification reduce to reduce the cost of circuit. But also facilitates the simplification of the circuit. Additionally the utility model discloses a structure lets more smooth-going of the drive current transition constantly of commutation, reduces because of the energy loss that the commutation caused, improves the efficiency of motor to improve the overall efficiency of fan. The current of the phase change is more smooth through processing, so that the problem of motor noise of the single-phase motor can be well improved.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A DC brushless motor commutation system comprises a controller, a driver, a motor and a rotor position detector; the method is characterized in that:

the controller is used for sending a driving signal to the driver;

the controller obtains the phase change position of the rotor according to the rotor position signal, sends a PWM (pulse width modulation) modulation command to the driver before the rotor reaches the phase change position, and reduces the input current of the motor to zero before the rotor changes the phase.

2. The dc brushless motor commutation system of claim 1, wherein the rotor position detector is a hall sensor.