TWI876349B - Motor start-up method - Google Patents

Abstract

The present invention discloses a motor start-up method, including: sensing a Hall signal which indicates a position range of a motor rotor, wherein the Hall signal has two states and the position of the motor rotor is expressible by a phase angle; and when the Hall signal is at one state, starting providing a current to start-up the motor by a current driving mode which corresponds to a position of the motor rotor that is close to a state switching point of the Hall signal.

Description

Motor starting method

The present invention relates to a motor starting method, which can effectively prevent the motor from reversing during starting, especially in a multi-phase motor such as a three-phase motor.

Depending on the driving method used, there are different types of motors, such as single-phase and multi-phase. The motor uses a Hall sensor to sense the state of the motor rotor magnetic pole, generate a Hall signal, and execute the drive current supply process according to the Hall signal to control the motor rotation. However, when the motor starts running, since only the polarity displayed by the Hall signal is known, that is, only the position range of the motor rotor is known, but the relative position of the rotor and stator cannot be determined. Therefore, if current is applied to generate a magnetic field to drive the motor, it may cause the motor to reverse when it starts.

Please refer to Figure 1, which shows a typical three-phase motor architecture driven by a pulse width modulation (PWM) signal, in which a Hall sensor (not shown) senses the magnetic pole state of the motor M to generate a Hall signal, which is transmitted to the controller IC. The controller IC generates a PWM type control signal to control three sets of upper and lower bridge circuits (including upper bridge transistors Q1, Q3, Q5, and lower bridge transistors Q0, Q2, Q4), thereby generating an output signal to control the three-phase (U, V, W) current path to conduct current to drive the motor. Please refer to the table below. In the prior art motor system using a single Hall sensor, the learned start-up drive method of the three-phase motor is as follows:

As shown in the table above, if the Hall signal sensed is 1 when the motor is about to start, the table is looked up and the output is started from number 1, that is, transistors Q1 and Q4 are turned on. At this time, the U phase current is positive, the V phase current is 0, and the W phase current is negative; after the estimated start-up time, the actions of the following numbers are performed in sequence. If the Hall signal sensed is 0 when the motor is about to start, the table is looked up and the output is started from number 4, that is, transistors Q5 and Q0 are turned on. At this time, the U phase current is negative, the V phase current is 0, and the W phase current is positive; after the estimated start-up time, the actions of the following numbers are performed in sequence. After executing the action of number 6, it returns to number 1 and repeats the cycle.

However, please refer to Figure 2. In the above-mentioned prior art starting drive method, there will be a problem of reverse motor starting. As shown in the figure, the large arrow indicates that the motor is intended to start counterclockwise, but the applied current will cause a pulling force in the opposite direction, and as shown by the small arrow, the motor will rotate clockwise, resulting in uneven starting and unnecessary energy consumption.

Please refer to Figure 3. In principle, the upper half of the circle in the figure represents a Hall signal of 1. Assuming that the motor is to be started counterclockwise and the rotor position is at the position of the black circle in the figure, since the sensed Hall signal is 1, the table is checked to get the serial number 1, so the positive U-phase current and the negative W-phase current will be supplied, as shown by the thick arrow in the figure. (Since the Hall signal has a delay, when the Hall signal is sensed, the phase angle will be advanced by 60 degrees. When the Hall signal is 1, the U-phase is positive and the W-phase is negative. When the Hall signal is 0, the W-phase is positive and the U-phase is negative.) However, as shown by the dotted arrow in the figure, this will cause a pulling force to rotate the rotor clockwise, causing the motor to start in reverse.

This invention proposes a solution to the above problem.

From one perspective, the present invention provides a motor starting method, comprising: sensing a Hall signal representing the position range of a rotor of the motor, wherein the Hall signal has two states, and the position of the rotor can be represented by an angle phase; and when the Hall signal is sensed to be in one of the states, starting to supply current to start the motor in a current driving manner corresponding to a critical point of the Hall signal switching to another state.

In one preferred embodiment, the critical point close to the Hall signal switching to another state is 30 degrees or closer to the critical point.

In one preferred embodiment, the critical point close to the Hall signal switching to another state is 1/6 or lower when the phase occupied by one state of the Hall signal is used as the denominator and the angular phase from the critical point is used as the numerator.

In one of the preferred implementation forms, the motor is a three-phase motor, and the method further includes: after starting to supply current to start the motor, supplying positive, negative, and zero current to each phase in turn, and the three phases are different to form six combinations, and executing in a cycle.

In one preferred embodiment, the current driving method corresponding to the critical point of the Hall signal switching to another state is: two of the three phases supply positive current and the other phase supplies negative current, or two of the three phases supply negative current and the other phase supplies positive current; none of the phases has zero current.

The following detailed description is based on specific embodiments, which will make it easier to understand the purpose, technical content, features and effects of the present invention.

M: Motor

IC: Controller

Q0~Q5: Transistor

S1~S5: Steps

U, V, W: current phase

Figure 1 shows a typical three-phase motor architecture.

Figure 2 shows the problem of motor starting reverse in the prior art.

Figure 3 explains in principle why the start-up reversal occurs.

Figures 4 and 5 show that the present invention solves the problems of the prior art by adding a startup step (or startup phase).

Figure 6 shows a method implementation example of the present invention in the form of a flow chart.

The diagrams in this invention are schematic, and are mainly intended to show the relationship between the components of the circuit. The shapes and sizes are not drawn to scale.

Please refer to Figure 4 and compare it with the following table, which shows an embodiment of the present invention. In the present invention, an initial startup step is added during startup, as shown in the sequence numbers 3a and 6a in the following table:

Assuming that when the motor is about to start rotating counterclockwise, the sensed Hall signal is 1, the table is looked up and the output starts from sequence number 3a, that is, transistors Q1, Q2 and Q5 are turned on to provide positive U-phase current, negative V-phase current and positive W-phase current; after starting from this step, after the estimated start-up operation time, the cycle of 3→4→5→6→1→2 is entered. If the sensed Hall signal is 0 when the motor is about to be started, the table is looked up and the output starts from sequence number 6a, that is, transistors Q3, Q0 and Q4 are turned on to provide positive V-phase current, negative U-phase current and negative W-phase current; after starting from this step, after the estimated start-up operation time, the cycle of 6→1→2→3→4→5 is entered.

Please refer to Figure 4. Taking the upper half of the circle as an example, when the rotor is in the position shown in the figure, it will not be subjected to the tension as in the previous technology, and can smoothly start to rotate counterclockwise.

Please refer to Figure 5. Taking the upper half of the circle as an example, when the rotor is in the position shown in the figure, firstly, the probability of this happening is already low. Secondly, although the rotor will be pulled clockwise, it will not generate a huge rotational force like the previous technology. Instead, it will quickly overcome this pulling force and start to rotate counterclockwise smoothly.

Please refer to Figure 6. From the perspective of the process, in one embodiment, the present invention includes the following steps: in step S1, start the motor startup procedure; in step S2, sense the Hall signal, when the Hall signal is 1, enter step S3, and when the Hall signal is 0, enter step S4; in step S3, execute sequence number 3a, or in step S4, execute sequence number 6a; then proceed to step S5, and enter a six-step loop.

It should be noted that the above embodiments are described using a single Hall sensor and a three-phase motor driven by a PWM signal as an example, but the present invention is not limited to using only a single Hall sensor, nor is it limited to being applied to a three-phase motor driven by a PWM signal. The core concept of the present invention is that when the Hall signal is sensed to be in a first state (e.g., 1), current is supplied to start the motor from a phase as close as possible to the second state (e.g., 0) of the Hall signal, that is, as close as possible to the Hall signal switching critical point. When driven by PWM signal, the phase that can be controlled as close as possible to the second state of the Hall signal is U+V-W+ and V+U-W- as shown in Figures 4 and 5 by using the existing circuit without adding other components. However, if driven by sine wave instead of PWM signal, or other components are added, the phase can be closer to the second state of the Hall signal. If it is a single-phase motor, the same can be said. The so-called "as close as possible" mentioned above, in the embodiments shown in Figures 4 and 5, U+V-W+ is 30 degrees away from W+V-, and V+U-W- is 30 degrees away from V+W-, that is, when the two states of the Hall signal each occupy 180 degrees of phase, the so-called "as close as possible" means 30 degrees or closer to the Hall signal switching critical point (when driven by a sine wave or with other components, it can be lower than 30 degrees), or 1/6 or lower of the phase occupied by one state of the Hall signal (that is, the phase occupied by one state of the Hall signal is the denominator, and the angular phase from the critical point is the numerator).

The present invention has been described above with respect to the preferred embodiment, but the above is only for those familiar with the art to easily understand the content of the present invention, and is not used to limit the maximum scope of the rights of the present invention. Under the same spirit of the present invention, those familiar with the art can think of various equivalent changes. As mentioned above, the present invention can be applied not only to a three-phase motor driven by a single Hall sensor and a PWM signal, but also to a situation using multiple Hall sensors, or a situation not driven by a PWM signal, or a situation of a non-three-phase motor (such as a single-phase motor); in addition, in addition to the method steps shown, other steps can be added, such as the judgment and execution steps of turning on the motor rotor control switch in advance or in delay, etc. The scope of the present invention should cover the above and all other equivalent changes.

S1~S5: Steps

Claims (5)

A motor starting method includes: sensing a Hall signal representing the position range of a rotor of the motor, wherein the Hall signal has two states and the position of the rotor can be represented by an angle phase; and when the Hall signal is sensed to be in one of the states, starting to supply current to start the motor in a current driving manner corresponding to a critical point of the Hall signal switching to another state. The motor starting method as described in claim 1, wherein the critical point close to the Hall signal switching to another state is 30 degrees or closer to the critical point. The motor starting method as described in claim 1, wherein the critical point close to the Hall signal switching to another state is 1/6 or lower when the phase occupied by one state of the Hall signal is used as the denominator and the angular phase from the critical point is used as the numerator. A motor starting method as described in claim 1, wherein the motor is a three-phase motor, and the method further comprises: after starting to supply current to start the motor, supplying positive, negative, and zero current to each phase in turn, and the three phases are different to form six combinations, and executing in a cycle. As described in claim 4, the motor starting method, wherein the current driving method corresponding to the critical point of the Hall signal switching to another state is: two of the three phases supply positive current and the other phase supplies negative current, or two of the three phases supply negative current and the other phase supplies positive current; none of the phases is zero current.

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