KR102619910B1 - Apparatus and method for controlling a start of BLDC motor using detection of phase voltage - Google Patents

Abstract

The present invention forcibly aligns the position of the rotor during the initial operation of the BLDC motor, performs phase switching, detects the back electromotive force of the phase to which no voltage is applied, and detects the back electromotive force of the phase to which no voltage is applied, and when it stabilizes within the set value, the sensor A brushless direct current motor starting control method and device using phase-to-phase voltage detection that enable operation in a lease mode are disclosed.
The disclosed brushless direct current motor starting control device includes a rectifier that rectifies and smoothes AC power and supplies it as DC power; BLDC motor having a rotor; An inverter that converts the DC power supplied from the rectifier into pulse-shaped three-phase AC power (U, V, W) with an arbitrary variable frequency and supplies it to the BLDC motor; A terminal voltage detection unit that detects the terminal voltage of each phase (U, V, W) from the three-phase AC power supplied to the BLDC motor; and forcibly align the position of the rotor, and when the alignment of the rotor is completed, perform phase switching for acceleration, and generate back electromotive force of the phase to which no voltage is applied through the terminal voltage detector. Detects and performs phase switching a certain number of times until the detected back electromotive force value is within a preset value, and includes a control unit that controls the inverter in sensorless mode when the detected back electromotive force value is within a preset value. .

Description

Brushless DC motor starting control method and device using phase voltage detection {Apparatus and method for controlling a start of BLDC motor using detection of phase voltage}

The present invention relates to a method and device for controlling the starting of a brushless direct current motor using phase voltage detection, and more specifically, to forcibly align the position of the rotor during the initial operation of a BLDC (BrushLess Direct Current) motor. A brushless DC motor starting control method and device using phase voltage detection that performs (phase) switching, detects the back electromotive force of the phase to which no voltage is applied, and operates in sensorless mode when it stabilizes within the set value. It's about.

Typically, the stator of a BLDC (BrushLess Direct Current) motor uses an armature formed by flowing current through a coil, and the rotor uses a permanent magnet formed by repeating the N and S poles. . In order for a BLDC motor to rotate continuously, it is necessary to form a continuous rotating magnetic field of the BLDC motor. In order to form a continuous rotating magnetic field, the commutation of the current flowing in the coils of each phase of the armature must be done at an appropriate time. In order to switch, the position of the rotor must be accurately recognized. Here, switching means changing the direction of current in the motor stator coil so that the rotor can rotate.

In order to operate such a BLDC motor smoothly, the position of the rotor and the switching point of the phase current must be precisely matched, and for this purpose, a device for detecting the position of the rotor is required. In general, a device for detecting the position of the rotor is required. Position detection sensors such as Hall sensors, resolver elements, and encoders have been used, but these position detection sensors have problems such as increased manufacturing costs and complicated driving circuits, so they require electrical circuits. A method was sought to detect the position of the rotor using

As a result, electric circuits that detect the position of the rotor using the back electromotive force of the BLDC motor are widely used, and the operation mode that detects the position of the rotor using an electric circuit instead of a position detection sensor is called sensorless operation mode. do.

However, this conventional sensorless operation control method of a BLDC motor essentially requires rotor position information to drive the BLDC motor.

If voltage is applied to a random stator winding without knowing the rotor position information, overcurrent will flow, causing large torque pulsations, and there is also a risk of demagnetization of the rotor's permanent magnets due to overcurrent.

In addition, a rotor position detection device is required for smooth operation of a BLDC motor, and the provision of such a rotor position detection device has the problem of increasing manufacturing costs.

Korean Patent Publication No. 10-2016-0056622 (publication date: 2016.05.20)

The purpose of the present invention to solve the above-described problem is to forcibly align the position of the rotor during the initial operation of the BLDC motor, perform phase switching, and reduce the counter electromotive force of the phase to which no voltage is applied. The purpose of the present invention is to provide a brushless direct current motor starting control method and device using phase voltage detection, which allows operation in sensorless mode when the detection is detected and stabilized within a set value.

A brushless direct current motor starting control device using phase voltage detection according to the present invention to achieve the above-described object includes a rectifier that rectifies and smoothes AC power and supplies it as DC power; BLDC motor having a rotor; An inverter that converts the DC power supplied from the rectifier into pulse-shaped three-phase AC power (U, V, W) with an arbitrary variable frequency and supplies it to the BLDC motor; A terminal voltage detection unit that detects the terminal voltage of each phase (U, V, W) from the three-phase AC power supplied to the BLDC motor; and forcibly align the position of the rotor, and when the alignment of the rotor is completed, perform phase switching for acceleration, and generate back electromotive force of the phase to which no voltage is applied through the terminal voltage detector. Detects and performs phase switching a certain number of times until the detected back electromotive force value is within a preset value, and includes a control unit that controls the inverter in sensorless mode when the detected back electromotive force value is within a preset value. .

Additionally, the control unit may determine a phase change point by comparing the detected back electromotive force value with a preset value.

In addition, the control unit compares the detected back electromotive force value with a preset value and performs phase switching when the detected back electromotive force value deviates from the preset value, until the detected back electromotive force value is within the preset value. Phase transition can be performed.

Meanwhile, the brushless direct current motor starting control method using phase voltage detection according to the present invention to achieve the above-described object includes the steps of: (a) the control unit forcibly aligning the rotor position of the BLDC motor through an inverter; (b) the control unit performing phase switching of the BLDC motor through an inverter; (c) a terminal voltage detection unit detecting back electromotive force of a phase to which no voltage is applied; (d) the control unit performing phase switching a certain number of times until the detected back electromotive force value is within a preset value; and (e) the control unit controlling the inverter in sensorless mode when the detected back electromotive force value is within a preset value.

Additionally, in step (d), the control unit may determine a phase change point by comparing the detected back electromotive force value with a preset value.

And, in step (d), the control unit compares the detected back electromotive force value with a preset value and performs a phase change if the detected back electromotive force value deviates from the preset value. Phase conversion is performed until the value is within the range.

According to the present invention, there is an advantage that it is possible to detect the rotor position of a BLDC motor using back electromotive force without a rotor position detection device.

In addition, it is possible to detect the position of the motor rotor using only back electromotive force without additional circuit configuration for measuring phase current of the motor.

Additionally, the startup failure rate can be reduced by controlling the motor with a small current in the initial startup stage.

Additionally, the probability of startup failure can be reduced through accurate and quick alignment of the rotor.

1 is a configuration diagram showing the main configuration of a motor rotor control device according to an embodiment of the present invention.
Figure 2 is a diagram showing an example of the circuit configuration of a brushless direct current motor starting control device according to an embodiment of the present invention.
Figure 3 is a diagram showing a detailed configuration example of a terminal voltage detection unit applied to the present invention.
FIG. 4 is a flowchart illustrating a method of starting and controlling a brushless direct current motor using phase-to-phase voltage detection according to an embodiment of the present invention.
Figure 5 is a diagram showing the voltage and frequency that change during initial driving of a BLDC motor according to an embodiment of the present invention.
Figure 6 is a diagram showing a current waveform according to the rotor position and phase switching timing of the stator winding according to the present invention.
FIG. 7 is a rear-end unipolar PWM pattern diagram applied to the present invention, and FIG. 8 is a terminal voltage pattern diagram of a brushless DC motor when using the rear-end unipolar PWM pattern of FIG. 7.
Figure 9 is a diagram showing the process of obtaining a preset value in the brushless direct current motor starting control method using phase voltage detection according to an embodiment of the present invention.

Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. The present invention may be implemented in many different forms and is not limited to the embodiments described herein.

In order to clearly explain the present invention, parts that are not relevant to the description are omitted, and identical or similar components are assigned the same reference numerals throughout the specification.

Throughout the specification, when a part is said to be "connected" to another part, this includes not only cases where it is "directly connected," but also cases where it is "electrically connected" with another element in between. . Additionally, when a part "includes" a certain component, this means that it may further include other components rather than excluding other components, unless specifically stated to the contrary.

When a part is referred to as being “on” another part, it may be directly on top of the other part or it may be accompanied by another part in between. In contrast, when a part is said to be "directly above" another part, it does not entail any other parts in between.

Terms such as first, second, and third are used to describe, but are not limited to, various parts, components, regions, layers, and/or sections. These terms are used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, the first part, component, region, layer or section described below may be referred to as the second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is only intended to refer to specific embodiments and is not intended to limit the invention. As used herein, singular forms include plural forms unless phrases clearly indicate the contrary. As used in the specification, the meaning of "comprising" refers to specifying a particular characteristic, area, integer, step, operation, element and/or ingredient, and the presence or presence of another characteristic, area, integer, step, operation, element and/or ingredient. This does not exclude addition.

Terms indicating relative space, such as “below” and “above,” can be used to more easily describe the relationship of one part shown in the drawing to another part. These terms are intended to include other meanings or operations of the device in use along with the meaning intended in the drawings. For example, if the device in the drawing is turned over, some parts described as being “below” other parts will be described as being “above” other parts. Accordingly, the exemplary term “down” includes both upward and downward directions. The device can be rotated 90° or at other angles, and terms indicating relative space are interpreted accordingly.

Although not defined differently, all terms including technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted as having meanings consistent with related technical literature and currently disclosed content, and are not interpreted in ideal or very formal meanings unless defined.

Hereinafter, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein.

Figure 1 is a configuration diagram showing the main configuration of a brushless direct current motor starting control device according to an embodiment of the present invention.

Referring to Figure 1, the brushless direct current motor starting control device 100 according to the present invention includes a BLDC motor 110, an inverter 120, a control unit 130, a rectifier 140, and a terminal voltage detection unit 150. Includes.

The BLDC motor 110 has a rotor and receives power from the inverter 120 to rotate the rotor to provide rotational force.

Here, the BLDC motor 110 has a three-phase winding that generates an inductance component. In other words, a BLDC motor is a structure that does not have an insulating conductor such as a carbon brush to transmit power. There is a magnet on the motor shaft and a coil on the inner wall of the motor case, so the power supply for the motor to rotate is inside the non-rotating motor. There is no need for a brush as it is supplied to a coil attached to the wall.

The inverter 120 converts the DC power supplied from the rectifier 140 into pulsed three-phase AC power (U, V, W) with an arbitrary variable frequency and supplies it to the BLDC motor 110. That is, the inverter 120 converts direct current voltage into three-phase alternating current voltage and supplies it to the BLDC motor 110. At this time, in the inverter 120, each power switching element (Q1 to Q6) is connected to the three-phase (U, V, W) winding as shown in FIG. 2. That is, the inverter 120 may include a three-phase switching element, for example, an upper three-phase FET and a lower three-phase FET.

The control unit 130 forcibly aligns the position of the rotor, and when the alignment of the rotor is completed, performs phase switching for acceleration, but the phase to which no voltage is applied through the terminal voltage detection unit 150 ( phase) and perform phase switching a certain number of times until the detected back electromotive force value falls within the preset value. When the detected back electromotive force value falls within the preset value, the inverter 120 is controlled in sensorless mode. do.

Additionally, the control unit 130 may determine the phase change point by comparing the detected back electromotive force value with a preset value.

Then, the control unit 130 compares the detected back electromotive force value with the preset value, and performs a phase change if the detected back electromotive force value deviates from the preset value, until the detected back electromotive force value is within the preset value. For example, the phase change can be performed about 6 times.

The rectifier 140 rectifies and smoothes AC power and supplies it as DC power.

The terminal voltage detector 150 detects the terminal voltage of each phase (U, V, W) from the three-phase AC power supplied to the BLDC motor 110.

Meanwhile, when the motor 110 is initially driven, the control unit 130 applies an alignment vector that causes the rotor to rotate in the alignment direction and a zero (0) vector that reduces the rotation speed of the rotor to the BLDC motor 110. The inverter 120 can be controlled as much as possible.

In addition, when the motor 110 is in a stopped state, the control unit 130 performs an alignment process of moving the rotor to a predetermined specific position and a forced drive of generating a rotating magnetic field in the motor with the rotor aligned to force the motor to drive. process, and when back electromotive force is generated in a forcibly driven motor, the operation of the BLDC motor 110 can be controlled through a sensorless control process in which the position information of the rotor is obtained using the back electromotive force and the motor is controlled sensorless.

In addition, the control unit 130 turns on all three-phase switches at the top of the inverter 120, or turns on all three-phase switches at the bottom of the inverter 120 to set zero (0). The vector can be controlled to be applied to the BLDC motor 110.

Then, the control unit 130 applies an alignment vector to the BLDC motor 110 through the inverter 120 so that the rotor rotates in the alignment direction, and applies a zero vector to the BLDC motor 110 to rotate the rotor. After reducing the speed, the alignment vector is again applied to the BLDC motor 110 to generate rotational force of the rotor, and the zero vector is again applied to the BLDC motor 110 to control the rotation speed of the rotor to be reduced. It will stop at the self-aligning position.

Figure 2 is a diagram showing an example of the circuit configuration of a brushless direct current motor starting control device according to an embodiment of the present invention.

Referring to FIG. 2, in the brushless direct current motor starting control device 100 according to the present invention, the inverter 120 provides each power switching element FET (Q1 to Q6) in the three-phase (U, V, W) winding. ) is connected. That is, the inverter 120 can use a typical switching circuit consisting of six switching elements (Q1 to Q6) and a diode.

The terminal voltage detection unit 150 detects the terminal voltage of each phase (U, V, W) from the three-phase AC power supplied to the BLDC motor 110 and inputs it to the control unit 130.

The control unit 130 can obtain position information of the rotor by detecting the zero crossing point (ZCP) of the back electromotive force according to the terminal voltage of each phase (U, V, W) detected by the terminal voltage detection unit 150.

Additionally, the control unit 130 can be implemented as a microprocessor that controls the timing of voltage application and controls the pattern of the PWM signal supplied to the inverter 30 to prevent overcurrent from being supplied to the BLDC motor 110.

The PWM signal generator 132 generates a PWM signal pattern based on the output of the control unit 130 and supplies it to the inverter 120.

At this time, power factor correction capacitors (not shown) may be connected in parallel on the connection lines between the three-phase windings of the inverter 120 and the BLDC motor 110. That is, three power factor correction capacitors C may be connected in parallel among the three phases at the output terminal of the inverter 120: between the U phase and the V phase, between the V phase and the W phase, and between the W phase and the U phase. Additionally, the capacity size of the power factor correction capacitor C can be set to remain the same as the size of the inductance component of the BLDC motor 110.

The control unit 130 applies the switching drive signal of each power switching element (Q1 to Q6) to the inverter 120. That is, the control unit 130 controls the starting, operation, and speed of the BLDC motor 110 by controlling the switching operation of each switching element (Q1 to Q6) of the inverter 120 according to the user's operation, and each switching element A switching drive signal for switching (Q1 to Q6) is generated and applied to the inverter 120.

Figure 3 is a diagram showing a detailed configuration example of a terminal voltage detection unit applied to the present invention.

In Figure 3, the terminal voltage of each phase (U, V, W) of the BLDC motor 110 is divided by resistors (R1, R2) and input to the A/D input port 134 of the control unit 130. At this time, a separate Zener diode may be added to the A/D input port 134 so that the voltage value divided by each resistance distribution circuit (R1, R2) can be limited within the A/D input voltage range of each phase terminal voltage. .

In addition, in the sensorless operation section, the terminal voltage of each phase (U, V, W) and half (1/2) of the inverter DC terminal voltage (V) are used to detect the zero crossing point (ZCP) of the back electromotive force from the terminal voltage of each phase. ) The result of comparing the values through the comparator 52 is input to the digital input port 136 of the control unit 130.

FIG. 4 is a flowchart illustrating a method of starting and controlling a brushless direct current motor using phase-to-phase voltage detection according to an embodiment of the present invention.

Referring to FIG. 4, in the brushless direct current motor starting control device 100 according to the present invention, the control unit 130 forcibly aligns the rotor position of the BLDC motor 110 through the inverter 120 (S410). .

That is, the control unit 130 can apply an alignment vector to the BLDC motor 110 through the inverter 120 to align the rotor. Here, the alignment vector refers to an alignment current applied to the BLDC motor 110 so that the rotor rotates in a specific direction to align the rotor.

Next, the control unit 130 performs phase switching of the BLDC motor 110 through the inverter 120 (S420).

That is, the control unit 130 supplies current to any two phases of the BLDC motor 110 to forcibly align the rotor position, and when the alignment of the rotor is completed, the BLDC motor 110 as shown in FIG. Phase switching is performed while performing synchronous acceleration to accelerate the rotor of the BLDC motor 110 to a certain speed by varying the magnitude and frequency of the voltage applied to the BLDC motor 110. Figure 5 is a diagram showing the voltage and frequency that change during initial driving of a BLDC motor according to an embodiment of the present invention. For example, if current is supplied to the U-V phase winding when the rotor is forcibly aligned, the phase is switched to the U-W phase and current is supplied to the U-W phase winding. At this time, when the rotational speed of the rotor reaches a speed at which back electromotive force can be detected from the stator winding of the BLDC motor 110, the control unit 130 adjusts the magnitude of the voltage applied to the BLDC motor 110 as shown in FIG. 5. By adjusting it, the phases of the rotor magnetic field and the stator magnetic field are switched.

In the sensorless operation mode, when the BLDC motor 40 is initially started, a voltage greater than the voltage appropriate for the load applied to the BLDC motor 40 is applied to the BLDC motor 40 to reduce the startup failure rate. Therefore, in the section where the BLDC motor 40 is synchronously accelerated, the phase switching timing of the stator winding is delayed, as shown in (a) of FIG. 6. Figure 6 is a diagram showing a current waveform according to the rotor position and phase switching timing of the stator winding according to the present invention. Figure 6 (a) is a case in which the timing of voltage application to the stator winding relative to the rotor position is late, and not only does the phase of the back electromotive force and phase current not coincide with each other, but the size of the phase current becomes excessively large in the latter half of the phase current. You can see that

Figure 6(b) is a case where the timing of voltage application to the stator winding relative to the rotor position is fast, and not only does the phase of the back electromotive force and phase current not coincide with each other, but the size of the phase current becomes excessively large in the first half of the phase current. You can see that

Next, the terminal voltage detector 150 detects the back electromotive force of the phase to which no voltage is applied (S430).

At this time, the control unit 130 may determine the phase change point by comparing the detected back electromotive force value with a preset value. FIG. 7 is a rear-end unipolar PWM pattern diagram applied to the present invention, and FIG. 8 is a terminal voltage pattern diagram of a brushless DC motor when using the rear-end unipolar PWM pattern of FIG. 7. In Figure 8, when using the unipolar PWM pattern at the rear end, the terminal voltage of the OFF phase when the PWM is in the OFF state in the section where the back electromotive force (e) of the phase to which no voltage is applied (hereinafter referred to as the OFF phase) increases. V_off is as follows.

On the other hand, in the section where the back electromotive force (e) of the OFF phase falls, the ON/OFF status of V_off PWM is as follows.

Here, V is the voltage level of the DC terminal of the inverter 30.

In the section where the back electromotive force (e) rises, V_off has a smaller value than V_off in the section where the back electromotive force (e) falls.

As shown in Equation 1, it can be seen that it is proportional to 1.5 times the OFF-phase counter electromotive force (e) based on 0 voltage. On the other hand, in the section where the back electromotive force (e) falls, the back electromotive force information appears in the OFF-phase terminal voltage based on V/2 or V.

Therefore, in the section where the back electromotive force (e) increases, the values of the resistance distribution circuits (R1, R2) of FIG. 3 are adjusted so that the V_off value falls within the A/D input range of the control unit 130. Even so, the signal transmitted to the A/D input port 134 includes the back electromotive force signal included in V_off without significant attenuation.

On the other hand, in the section where the back electromotive force (e) decreases, the values of the resistance distribution circuits (R1, R2) of FIG. 3 are adjusted so that the V_off value falls within the A/D input range of the control unit 130. In this case, the signal transmitted to the A/D input port 134 has a greatly attenuated value of the back electromotive force signal included in V_off.

When the BLDC motor 110 rotates at low speed, the back electromotive force value has a small value.

Therefore, when using the rear-end unipolar PWM pattern, relatively accurate back electromotive force information can be detected from the OFF-phase terminal voltage in the section where the OFF-phase back electromotive force (e) increases. In systems with severe load fluctuations at low speeds, such as compressors, a relatively accurate phase change point can be obtained by integrating the back electromotive force detected from the terminal voltage in the OFF phase.

When performing a phase change, the control unit 130 determines whether it is a section in which the back electromotive force of the OFF phase increases (see FIG. 8), and if it is a section where the back electromotive force increases, as shown in FIG. 8, the control unit 130 integrates the back electromotive force to determine the exact phase change point. can be decided.

Next, the control unit 130 performs phase switching a certain number of times until the detected back electromotive force value falls within the preset value (S440).

That is, the control unit 130 compares the detected back electromotive force value with the preset value, and performs phase switching when the detected back electromotive force value deviates from the preset value, until the detected back electromotive force value is within the preset value. For example, the phase change is performed approximately 6 times. Here, in order to control the speed with Closeloop, a speed sufficient to find the Zero Crossing Point is required, so it is difficult to secure sufficient speed with only 3 times on the U-phase, V-phase, and W-phase, so about 6 times. This is to perform a phase change.

Then, the control unit 130 controls the inverter 120 in sensorless mode when the detected back electromotive force value is within a preset value (S450).

That is, when the phase switching time of the BLDC motor 110 is determined, the control unit 130 detects whether the back electromotive force detection is a stabilized section from the terminal voltage of each phase based on the frequency of the voltage currently applied to the rotor and performs sensorless operation. It determines whether it is a mode conversion stage, and if it is not a sensorless switching stage, it feeds back to the phase switching stage and performs phase switching.

Here, the preset values can be said to be the maximum and minimum voltage values of each phase (U, V, W) obtained through the process shown in FIG. 9. Figure 9 is a diagram showing the process of obtaining a preset value in the brushless direct current motor starting control method using phase voltage detection according to an embodiment of the present invention. As shown in FIG. 9, the highest and lowest values of each step for the U phase, V phase, and W phase are measured and determined as a standard preset value.

In the sensorless switching stage, the control unit 130 performs phase switching, detects the zero crossing point (ZCP) of the back electromotive force from the terminal voltage of each phase, and switches the phase and BLDC motor 110 based on the zero crossing point (ZCP) information. ) is to perform a sensorless operation mode that controls the rotation speed.

As described above, according to the present invention, during the initial operation of the BLDC motor, the position of the rotor is forcibly aligned, then the phase is switched, and the back electromotive force of the phase to which no voltage is applied is detected to set the set value. It is possible to realize a brushless direct current motor starting control method and device using phase voltage detection that allows operation in sensorless mode when stabilization is achieved.

Those skilled in the art to which the present invention pertains should understand that the present invention can be implemented in other specific forms without changing its technical idea or essential features, and that the embodiments described above are illustrative in all respects and not restrictive. Just do it. The scope of the present invention is indicated by the claims described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. .

100: Brushless direct current motor starting control device
110: BLDC motor
120: inverter
130: control unit
140: rectifier
150: terminal voltage detection unit

Claims (6)

A rectifier that rectifies and smoothes AC power and supplies it as DC power;
BLDC motor having a rotor;
An inverter that converts the DC power supplied from the rectifier into pulse-shaped three-phase AC power (U, V, W) with an arbitrary variable frequency and supplies it to the BLDC motor;
A terminal voltage detection unit that detects the terminal voltage of each phase (U, V, W) from the three-phase AC power supplied to the BLDC motor; and
The position of the rotor is forcibly aligned, and when the alignment of the rotor is completed, phase switching for acceleration is performed, and the counter electromotive force of the phase to which no voltage is applied is generated through the terminal voltage detector. Detects and compares with a preset value, performs phase switching if the detected back electromotive force value deviates from the preset value as a result of the comparison, and controls the inverter in sensorless mode when the detected back electromotive force value is within the preset value. control unit;
Brushless direct current motor starting control device using phase voltage detection including.
According to claim 1,
The control unit determines a phase change point by comparing the detected back electromotive force value with a preset value. A brushless direct current motor starting control device using phase voltage detection.
delete (a) the control unit forcibly aligns the rotor position of the BLDC motor through the inverter;
(b) the control unit performing phase switching of the BLDC motor through an inverter;
(c) a terminal voltage detection unit detecting back electromotive force of a phase to which no voltage is applied;
(d) a control unit comparing the detected back electromotive force value with a preset value, and performing phase switching if the detected back electromotive force value deviates from the preset value as a result of the comparison; and
(e) a control unit controlling the inverter in sensorless mode when the detected back electromotive force value is within the preset value;
Brushless direct current motor starting control method using phase voltage detection including.
According to claim 4,
In step (d), the control unit determines a phase change point by comparing the detected back electromotive force value with a preset value.
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