KR102270421B1 - Apparatus and method for amending current sensing of brushless dc motor - Google Patents

Abstract

The present invention relates to a current sensing correction apparatus and method of a BLDC motor capable of stably correcting current sensing for a section in which an actual ripple current occurs by detecting whether a ripple current is generated based on a switching switching time.
The current sensing compensating device for a brushless DC motor according to an embodiment of the present invention is a current sensing compensating device for a brushless DC motor that receives three-phase voltage through a switching unit controlled according to a PWM signal, the brushless DC motor a phase voltage detection unit detecting a phase voltage signal from the phase voltage supplied to the motor; a freewheeling section detector configured to detect a freewheeling section using sensing data received from a Hall sensor installed in the brushless DC motor and the phase voltage signal detected by the phase voltage detecting section; a current sensing unit for sensing a current value of the switching unit synchronized with the PWM signal at predetermined time intervals; and a sensing correction unit configured to correct the sensed current value according to the freewheeling period.

Description

Current sensing compensation device and method of brushless DC motor {APPARATUS AND METHOD FOR AMENDING CURRENT SENSING OF BRUSHLESS DC MOTOR}

The present invention relates to a current sensing correction apparatus and method, and more particularly, to a current sensing correction apparatus and method for correcting current sensing of a brushless DC motor.

In general, a 3-phase BLDC (Brushless DC, Brushless DC) motor was developed to maintain the characteristics of a 3-phase DC motor while removing the brushes that act as a commutator in a general 3-phase DC motor. A rotor made of permanent magnets and a stator in which three coils, that is, U-phase, V-phase and W-phase coils are wound.

This 3-phase BLDC motor supplies 3-phase current to the U-phase, V-phase, and W-phase coils wound on the stator, and the U-phase, V-phase, and W-phase coils generate magnetic fields according to the supplied 3-phase current. to rotate the rotor made of permanent magnets.

At this time, in order to accurately control the rotor rotation speed of the BLDC motor, the position of the rotor must be accurately grasped. Accordingly, the BLDC motor is driven by detecting the position of the rotor with three Hall sensors and controlling switches having six control sections.

Such BLDC motors have been generally applied to systems that do not respond quickly, and accordingly, only the magnitude of the voltage according to the speed is controlled using a speed controller.

However, when applied to a system requiring fast response, the BLDC motor is controlled by configuring not only the speed controller but also the current controller. The current controller is driven by PI control by sensing the U-phase, V-phase, and W-phase currents generated through switch control at regular intervals.

However, the phase current and DC current components of the BLDC motor have a large ripple current due to the on/off characteristics of the switches. The ripple current causes a transient state in the PI control of the current controller, thereby causing the current control itself to become unstable.

In order to reduce such a ripple current, a method of correcting current sensing by providing a period in which no current is sensed is applied at the time of phase change of switches, that is, at the time of switching switching when on/off of the switches is changed. In detail, a dead period is arbitrarily set for a predetermined time based on the switching switching time, and an arbitrary value is assigned as a sensed value instead of not sensing a current in the set dead period.

However, since this method unconditionally sets the dead section based on the switching transition time and assigns an arbitrary value regardless of whether a ripple current actually occurs, the correction for current sensing is not stable. . For example, an abnormal sensing value may be given even though the ripple current does not occur, and if the ripple current occurs outside the set dead section, it is impossible to correct the ripple current itself.

Therefore, there is a need for a method for correcting current sensing in a section in which an actual ripple current occurs based on the switching transition time.

The technical problem to be achieved by the present invention is to provide a current sensing correction apparatus and method for a BLDC motor capable of stably correcting current sensing for a section in which an actual ripple current occurs by detecting whether a ripple current is generated based on a switching transition time. is to provide

The current sensing compensating device for a brushless DC motor according to an embodiment of the present invention is a current sensing compensating device for a brushless DC motor that receives a three-phase voltage through a switching unit controlled according to a PWM signal, the brushless DC motor a phase voltage detection unit detecting a phase voltage signal from the phase voltage supplied to the motor; a freewheeling section detector configured to detect a freewheeling section using sensing data received from a Hall sensor installed in the brushless DC motor and the phase voltage signal detected by the phase voltage detecting section; a current sensing unit for sensing a current value of the switching unit synchronized with the PWM signal at predetermined time intervals; and a sensing correction unit configured to correct the sensed current value according to the freewheeling period.

When a counter electromotive voltage is detected in the phase voltage signal in a switching transition period, the freewheeling period detector may detect a point from a start point of the switching change period to a point at which the counter electromotive voltage is detected as the freewheeling period.

The sensing compensator may replace the current value sensed within the detected freewheeling section with a current value sensed at a time before the freewheeling section.

The phase voltage detection unit may include a comparator that compares the phase voltages of three phases with a reference voltage and outputs the phase voltage signal.

The reference voltage may be a virtual neutral voltage.

The virtual neutral voltage may be an intermediate value of the maximum set value of the phase voltage.

The current sensing method of a brushless DC motor according to an embodiment of the present invention is a current sensing correction method of a brushless DC motor that receives a three-phase voltage through a switching unit controlled according to a PWM signal, and is synchronized with the PWM signal sensing the current value of the switching unit at predetermined time intervals; receiving sensing data from a Hall sensor installed in the brushless DC motor; detecting a phase voltage signal from the phase voltage supplied to the brushless DC motor; detecting a freewheeling section using the sensed data from the Hall sensor and the phase voltage signal; and correcting the sensed current value according to the freewheeling period.

The step of correcting the current may include replacing the sensed value of the current sensed within the freewheeling section with a current value sensed at a time before the freewheeling section.

The detecting of the freewheeling section includes: when a counter electromotive voltage is detected in the phase voltage signal in a switching transition section, detecting a point from the start point of the switching transition section to a point at which the back electromotive voltage is detected as the freewheeling section; may include

The detecting of the phase voltage signal may include outputting the phase voltage signal by comparing the phase voltages of the three phases with a reference voltage, respectively.

According to the present invention, the freewheeling section in which the actual ripple current occurs is accurately detected, and the sensed current value in the corresponding section is replaced with the sensed current value at the point before the freewheeling section and corrected.

Accordingly, even when a ripple current occurs, the reliability of current sensing is improved, thereby enabling stable current control for the brushless DC motor.

1 is a block diagram illustrating a current sensing correction apparatus of a BLDC motor according to an embodiment of the present invention.
2 is a diagram illustrating a phase voltage detection unit of a current sensing correction apparatus according to an embodiment of the present invention.
3 is a flowchart illustrating a current sensing correction method of a BLDC motor according to an embodiment of the present invention.
4 is a signal waveform diagram for explaining a current sensing correction method according to an embodiment of the present invention.
5A to 5C are simulation waveform diagrams illustrating the effect of correcting current sensing according to the present invention.

Since the present invention can have various changes and can have various embodiments, specific embodiments will be illustrated and described in the drawings. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

Terms including an ordinal number, such as first, second, etc., may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the second component may be referred to as the first component, and similarly, the first component may also be referred to as the second component. The term “and/or” includes a combination of a plurality of related listed items or any of a plurality of related listed items.

When a component is referred to as being “connected” or “connected” to another component, it is understood that the other component may be directly connected or connected to the other component, but other components may exist in between. it should be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that no other element is present in the middle.

Similarly, when an element such as a layer, film, region, plate, or sub-component is “on” another element, it is not only “on” the other element, but also when there is another element in-between. include Conversely, when an element is said to be "on top" of another element, it means that there are no other elements in the middle.

The terms used in the present application are only used to describe a specific embodiment, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in a commonly used dictionary should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

Hereinafter, the embodiment will be described in detail with reference to the accompanying drawings, but the same or corresponding components are given the same reference numerals regardless of reference numerals, and redundant description thereof will be omitted.

1 is a block diagram illustrating a current sensing correction apparatus of a brushless DC (BLDC) motor according to an embodiment of the present invention.

The current sensing correction apparatus of the present invention may be applied to current sensing correction of a BLDC motor (hereinafter, "motor") (M) supplied with three-phase voltage through the switching unit 100 . The switching unit 100 may be configured as a switching element capable of outputting three-phase phase voltage, and on/off of the switching element may be controlled according to a PWM signal of the PWM control unit 110 .

Hall sensors 11, 12, and 13 for detecting the position of the rotor may be installed in the motor M, and in this case, the Hall sensors may be provided for each phase.

In the present invention, the configuration of the motor M, the switching unit 100, and the PWM control unit 110 is not limited to FIG. 1 , and the current sensing correction device of the present invention includes various types of motors M and switching units as needed. (100), and the PWM control unit 110 may be applied.

Referring to FIG. 1 , a current sensing correction apparatus of a BLDC motor according to an embodiment of the present invention includes a phase voltage detection unit 210 , a freewheeling section detection unit 220 , a current sensing unit 230 , and a sensing correction unit 240 . ) may be included.

The phase voltage detection unit 210 may detect a phase voltage signal from a phase voltage output from the switching unit 100 and supplied to the motor M.

2 is a diagram illustrating an embodiment of the phase voltage detection unit 210 .

Referring to FIG. 2 , the phase voltage detector 210 may include comparators 211 , 212 , and 213 that compare the phase voltages of three phases with a reference voltage, respectively, and output a phase voltage signal for each phase. In this case, the reference voltage may be a virtual neutral voltage, and the virtual neutral voltage may be an intermediate value (Vdc/2) of the maximum set value (Vdc) of the phase voltage. Here, the phase voltage maximum set value Vdc may mean a positive voltage value set as the phase voltage.

That is, in the present invention, by comparing the phase voltage with the virtual neutral voltage, it is possible to more clearly and stably detect whether a ripple current is generated.

The freewheeling section detecting unit 220 may detect the freewheeling section using sensing data received from the hall sensors 11, 12, and 13 of the motor M and the phase voltage signal detected by the phase voltage detecting unit 210 . have. In detail, the freewheeling section detecting unit 220 may determine the switching switching section using sensing data received from the hall sensors 11 , 12 , and 13 . In addition, the freewheeling section detector 220 may detect, as a freewheeling section, from the start point of the switching transition section to the point at which the back electromotive voltage is detected when a counter electromotive voltage is detected in the phase voltage signal in the switching transition section. have. That is, the freewheeling section may mean a section in which an actual ripple current occurs.

The current sensing unit 230 may be installed inside the switching unit 100 to sense the current value of the switching unit 100 synchronized with the PWM signal of the PWM control unit 110 at predetermined time intervals. The sensing interval may be determined according to a setting.

The sensing compensator 240 may correct the sensed current value according to the freewheeling period. Specifically, the sensing compensator may compensate by replacing a current value sensed in the detected freewheeling section with a current value sensed at a previous point in the freewheeling section.

In the case of the current value sensed in the freewheeling section, since the current value reflects the ripple current, it acts as a noise in the current control of the motor (M). Accordingly, the most stable and reliable recent current value, that is, the current value sensed immediately before the freewheeling period, may be applied instead of the actual sensed current value that is not substantially beneficial to current control.

In the case of a current value sensed in a section other than the freewheeling section, since it is a normal current value, a separate correction is unnecessary.

As described above, the corrected current value or the unnecessary current value according to the present invention may be supplied to the current controller 250 .

The current controller 250 performs PI control based on the input current value, and the PI-controlled current value is supplied to the PWM controller 110 to be applied to the generation of the PWM signal.

In the prior art, when performing PI control for current, in order to minimize interference of ripple current, a software method such as arbitrarily setting a dead section was applied. Accordingly, there is a problem that the sensing correction is not stable and the effect is not high.

However, in the present invention, the freewheeling section is accurately detected by using a comparator in hardware, and the sensed current value in the detected freewheeling section is replaced with the sensed current value at the point before the freewheeling section and corrected, thereby providing stable current control. make it possible

Meanwhile, in FIG. 1 , the configurations of the PWM control unit 110 , the phase voltage detection unit 210 , the freewheeling section detection unit 220 , the sensing correction unit 240 , and the current control unit 250 are each independently shown, but this This is only an embodiment, and at least a part or the whole may be integrally configured as needed.

3 is a flowchart illustrating a current sensing correction method of a BLDC motor according to an embodiment of the present invention, and FIG. 4 is a signal waveform diagram illustrating a current sensing correction method according to an embodiment of the present invention.

A current sensing correction method of FIG. 3 will be described with reference to FIGS. 1 and 4 .

First, the current value of the switching unit 100 is sensed at predetermined time intervals through the current sensing unit 230 (S1).

As described above, the sensing interval may be determined according to the setting, and in the embodiment of FIG. 4 , sensing may be performed four times in each of six sectors generated when the motor M rotates 360 degrees once. have. That is, a total of 24 current sensing may be performed while the motor M rotates once.

Meanwhile, the sensed data from the hall sensors 11 , 12 , and 13 is input to the freewheeling section detecting unit 220 ( S2 ). In the embodiment of FIG. 4 , the sensing data of the hall sensors 11 , 12 , and 13 may be switched every 180 degrees, and the sensing data for each phase may be shifted by 120 degrees.

Next, a phase voltage signal is detected from the phase voltage supplied from the switching unit 100 to the motor M ( S3 ). The phase voltage signal may be output as a digital signal by comparing the phase voltages of the three phases (U, V, W) with a virtual neutral voltage (Vdc/2) that is a reference voltage, respectively, through a comparator.

Meanwhile, in FIG. 3 , the current sensing (S1), the hall sensor sensing (S2), and the phase voltage signal detection (S3) are sequentially illustrated, but this is for convenience of explanation, and the sequence of these three steps is Either step may take precedence, and may be performed simultaneously.

Next, a freewheeling section is detected (S4). The freewheeling section may be detected using sensing data from the Hall sensors 11 , 12 , and 13 and the detected phase voltage signal. In detail, when the counter electromotive voltage is detected in the phase voltage signal in the switching transition period, the freewheeling period may be detected from the start point of the switching transition period to the point at which the counter electromotive voltage is detected.

Referring to FIG. 4 , in the case of U phase, 3 and 6 sectors correspond to the switching transition period, in the case of V phase, 2 and 5 sectors correspond to the switching transition period, and in the case of W phase, 1 and 4 sectors correspond to the switching transition period. It corresponds to the switching transition period. And, in each switching transition period, a rising edge at which the voltage momentarily rises or a falling edge at which the voltage momentarily falls appears. Such a rising edge or a falling edge means a counter electromotive voltage.

That is, the freewheeling section detection unit 220 may detect a point from the start point of the switching transition section to the detection point of the counter electromotive voltage as the freewheeling section.

Accordingly, in the embodiment of FIG. 4 , one freewheeling section is detected for each sector, and when the motor M rotates 360 degrees once, six freewheeling sections (the hatched area in FIG. 4 ) can be detected. have.

In the section detected as the freewheeling section (S5-Y), current sensing correction is performed, and in the non-freewheeling section (S5-N), the sensed current value can be applied to the current control.

The current sensing correction is performed by applying a current value in the freewheeling section to a current value sensed before the freewheeling section, specifically, just before the freewheeling section. That is, in the freewheeling section in which the current value is unstable due to the ripple current, it is a normal value and the sensing current value immediately before the freewheeling section, which is the value at the closest point in time, is applied.

Accordingly, as shown in FIG. 4, in the case of the actual PWM synchronized current sensed value, a temporary current drop phenomenon appears in the freewheeling section, but it can be seen that the final sensed waveform appears evenly through the correction of the current sensed value for the freewheeling section. can

5A to 5C are simulation waveform diagrams illustrating the effect of correcting current sensing according to the present invention.

5A is a U-phase phase current waveform, FIG. 5B is a DC current waveform, and FIG. 5C is a torque waveform, respectively, in which blue is before current sensing correction is applied, and red is after current sensing correction is applied.

5A to 5C, before applying the current sensing correction according to the present invention, the waveform shows an unstable shape depending on the ripple current, but it can be seen that a stable waveform appears after the current sensing correction is applied.

Although the above has been described with reference to the preferred embodiment of the present invention, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention described in the claims below. You will understand that it can be done.

M: BLDC motor 11, 12, 13: Hall sensor
100: switching unit 110: PWM control unit
210: phase voltage detection unit 220: freewheeling section detection unit
230: current sensing unit 240: sensing correction unit
250: current controller

Claims (12)

In the current sensing and correcting device of a brushless DC motor that is supplied with three-phase voltage through a switching unit controlled according to a PWM signal,
a phase voltage detection unit detecting a phase voltage signal from the phase voltage supplied to the brushless DC motor;
a freewheeling section detector configured to detect a freewheeling section using sensing data received from a Hall sensor installed in the brushless DC motor and the phase voltage signal detected by the phase voltage detecting section;
a current sensing unit for sensing a current value of the switching unit synchronized with the PWM signal at predetermined time intervals; and
a sensing correction unit for correcting the sensed current value according to the freewheeling section;
When a counter electromotive voltage is detected in the phase voltage signal in a switching transition period, the freewheeling section detection unit detects a point from the start point of the switching transition section to a point at which the counter electromotive voltage is detected as the freewheeling section of the brushless DC motor. Current sensing compensator.
delete According to claim 1,
The sensing compensator replaces the current value sensed within the detected freewheeling section with a current value sensed before the freewheeling section.
According to claim 1,
and a comparator for outputting the phase voltage signal by comparing the phase voltages of the three phases with a reference voltage, respectively, in the phase voltage detection unit.
5. The method of claim 4,
The reference voltage is a virtual neutral voltage current sensing correction device of a brushless DC motor.
6. The method of claim 5,
The virtual neutral voltage is a current sensing correction device of a brushless DC motor that is an intermediate value of the maximum set value of the phase voltage.
In the current sensing correction method of a brushless DC motor supplied with three-phase voltage through a switching unit controlled according to a PWM signal,
sensing the current value of the switching unit synchronized with the PWM signal at predetermined time intervals;
receiving sensing data from a Hall sensor installed in the brushless DC motor;
detecting a phase voltage signal from the phase voltage supplied to the brushless DC motor;
detecting a freewheeling section using the sensed data from the Hall sensor and the phase voltage signal; and
Comprising the step of correcting the sensed current value according to the freewheeling section,
In the detecting of the freewheeling section, when a counter electromotive voltage is detected in the phase voltage signal in a switching transition section, the freewheeling section is a brushless detecting period from the start point of the switching transition section to the point at which the counter electromotive voltage is detected. How to calibrate the current sensing of a DC motor. delete delete delete delete delete

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