Control of a single-coil BLDC motor

Abstract

This application discloses the control of a single-coil BLDC motor. A motor driver 100 is provided for driving the rotor 211 of a single-coil motor 210 in a clockwise or counterclockwise rotational direction relative to the stator 212 of the single-coil motor 210. The motor driver 100 is adapted to generate a position signal representing the angular position of the rotor 211 relative to the stator 212 and includes a controller 120, which includes a direction input 150 to define the rotational direction of the rotor 211, and is adapted to generate a drive signal for rotating the rotor in the defined rotational direction, wherein the drive signal is based on the position signal and on a signal indicating an electrical lead angle, wherein the signal indicating the electrical lead angle is set such that the total lead angle is positive in both rotational directions of the rotor.

Description

Technical Field

[0001] This invention relates to single-coil motors. More specifically, this invention relates to single-coil motors designed to operate in clockwise and counterclockwise rotational directions. Background Technology

[0002] Single-coil motors and their drive electronics are typically designed to operate in an energy-efficient manner in a preferred direction (e.g., when used to drive a fan). This design enables reliable fan startup in the preferred direction.

[0003] Single-coil motors can have slightly asymmetrical stator poles. This asymmetry causes some reluctance offset compared to the zero-torque position.

[0004] In some motor applications, such as motors driving fans in air exchangers, it may be necessary to start and operate the motor in either a clockwise (CW) or counterclockwise (CCW) direction. Motors with the slightly asymmetrical construction already mentioned may be used for this purpose.

[0005] Single-coil motors may have this problem: when they stop at the zero torque position, it may be difficult to start the motor, or it may start randomly in either the clockwise or counterclockwise direction.

[0006] If a single-coil motor and its drive electronics are designed to operate in an energy-efficient manner in a preferred direction, it may result in lower energy efficiency operation in the opposite rotational direction, which may also be compromised by increased noise levels.

[0007] Therefore, a motor driver and method are needed to drive the rotor of a single-coil motor in both clockwise and counterclockwise rotational directions. Summary of the Invention

[0008] The purpose of embodiments of the present invention is to provide a good motor driver for driving a single-coil motor in both clockwise and counterclockwise rotational directions.

[0009] The above objectives are achieved by the method and apparatus according to the present invention.

[0010] In a first aspect, embodiments of the invention relate to a motor driver for driving the rotor of a single-coil motor in a clockwise or counterclockwise rotational direction relative to the stator of the single-coil motor. The motor driver is adapted to generate a position signal representing the angular position of the rotor relative to the stator.

[0011] The motor driver includes a controller for generating a drive signal having an electrical lead angle and being defined such that the electrical lead angle is generated such that the total lead angle is positive regardless of the orientation of the motor.

[0012] The position signal can be obtained using magnetic sensors (such as Hall effect sensors) to determine the change of magnetic poles on the rotor. The number of poles is a multiple of 2, typically 4 or 8.

[0013] Angular position information can be extended based on timing information associated with the electrical half-cycle (EHP), which is the time between subsequently detected polar transitions.

[0014] The motor driver includes a controller for generating drive signals. The controller can be adapted to derive rotor speed information from timing information.

[0015] The controller defines drive signals to control the voltage or current drive signal waveform applied to the motor coils by the motor driver, whereby the drive signal can be used to operate the rotor at the detected speed during transient or steady-state operation. The drive signal waveform defines the amplitude of the current or voltage at a certain angle within the EHP. Typically, such a single-coil waveform is defined by the start-up moment when the voltage or current is applied after the instant when it is zero.

[0016] The motor driver controller also includes a direction input to define the rotor's direction of rotation based on an angular position signal, enabling it to determine the direction in which the coil current must flow to rotate the rotor in the defined direction. The current direction can be from the motor driver's first output 1 to the motor driver's second output 2, or from output 2 to output 1, depending on how the coil windings are interconnected. In some motor drivers, the direction input signal can be reversed to adapt to a given motor winding, thereby producing the desired direction of rotation. In other motor drivers, the interconnection or winding direction of the motor coils must be adapted to conform to a fixed direction input setting within the motor driver.

[0017] In embodiments of the invention, the direction input signal can be reversed. This can be achieved, for example, via an input pin on the motor driver package or via an internally generated signal. However, the invention is not limited thereto. In the case of an internally generated signal, the change of direction can be based, for example, on time (per minute, per hour, etc.), or the rotation direction can be selected such that after each start-up, the motor rotates in one direction for a short, predefined time, and then in the other direction for a longer time, for example, to blow out dust that may have been collected at the fan motor input during previous suction operations.

[0018] In the prior art, the lead angle of a single-coil motor driver is determined by the position of a Hall sensor relative to the stator. In such prior art motors, the Hall sensor is preferably positioned such that it detects a pole transition slightly before the poles align with the stator shoe in the target rotation direction. This position is called a positive lead angle and typically results in higher motor efficiency and lower noise.

[0019] However, this type of Hall sensor position will result in a pole transition being detected slightly after the poles are aligned in the opposite direction of rotation to the stator shoe alignment. This position is known as a negative lead angle and typically leads to lower motor efficiency and higher noise.

[0020] In embodiments of the invention, the total lead angle is the sum of the lead angle of the position signal (e.g., the lead angle based on the Hall sensor position, defined by the position of the Hall sensor relative to the stator) and the electrical lead angle, which is added by the controller based on speed information obtained from the position signal. Optionally, such electrical lead angle adjustment can also be a function of other parameters (such as speed, motor current, motor driver temperature, motor coil inductance, motor coil resistance, etc.).

[0021] In embodiments of the invention, the Hall sensor may be located midway between the two stator shoes. In such cases, the Hall sensor-based lead angle is equal to 0. In such cases, the electrical lead angles in the two directions may be the same or different. If the electrical lead angle (and therefore the total lead angle) is positive in one direction, the same electrical lead angle will produce a positive electrical lead angle (and therefore the total lead angle) in the other direction. A preferred embodiment is to make the Hall sensor-based lead angle substantially zero, for example, less than 5 kWh, or even less than 1 kWh. Generating the electrical lead angle is very difficult, or at least not optimal, during the first few EHPs, because timing information can only be acquired after at least one rotation, and because timing information is unreliable during the initial EHP due to the rapid acceleration of the motor. A positive lead angle based on a significant Hall sensor in one rotational direction may still affect motor operation during the initial start-up in the opposite direction.

[0022] An advantage of embodiments of the present invention is that an electrical lead angle can be defined such that the total lead angle is positive regardless of the direction of rotation. Furthermore, if the Hall sensor lead angle is not zero, an electrical lead angle can be generated such that a positive lead angle is applied in any direction of rotation of the motor.

[0023] Another advantage of embodiments of the present invention is that different total lead angles can be applied depending on the direction of rotation of the motor. Therefore, compared with a motor driver that is not configured with an electrical lead angle based on the direction of rotation, the peak value of the drive current obtained through the coil after changing the direction of rotation can be reduced.

[0024] This allows for optimization of motor operation in both clockwise and counterclockwise directions. The electrical lead angle can be positive or negative (the latter causing hysteresis). In embodiments of the invention, the signal indicating the electrical lead angle can be the lead time.

[0025] In embodiments of the present invention, the electrical lead angle is programmable. In embodiments of the present invention, the controller may include a waveform generator for generating drive signals.

[0026] In an embodiment of the present invention, the controller includes a lead angle generator for controlling the electrical lead angle of the drive signal according to the rotation direction of the rotor.

[0027] In an embodiment of the invention, the lead angle generator is configured to adjust the position signal, and the waveform generator is adapted to generate a drive signal synchronized with the adjusted position signal.

[0028] In embodiments of the invention, the signal indicating the electrical lead angle is obtained by electrically adjusting a position signal (e.g., a lead angle based on a Hall sensor) according to the rotor's rotation direction, and the controller is adapted to generate a drive signal based on the adjusted position signal such that the total lead angle is positive in both rotation directions. Therefore, the electrical lead angle can be set according to the rotation direction. The electrical lead angle can be adjusted by adjusting the position signal. This can be done according to the rotation direction.

[0029] An advantage of this invention is that the total lead angle of the drive signal can be adjusted by electrically adjusting (delaying or advancing) the periodic position signal.

[0030] In embodiments of the present invention, at least one signal indicating an electrical lead angle is predefined for each rotation direction.

[0031] In an embodiment of the invention, the motor driver includes an interface for retrieving a predefined signal indicating an electrical lead angle from an external device.

[0032] For each direction of rotation, a signal indicating the electrical lead angle (e.g., the electrical lead angle itself) can be stored, for example, in an external E2PROM.

[0033] In an embodiment of the invention, the motor driver includes an internal memory for retrieving a predefined signal indicating at least one electrical lead angle.

[0034] In embodiments of the invention, one or more signals indicating an electrical lead angle are determined based on one or more parameters, which indicate the ratio of the rotor's resistance to its inductance.

[0035] The total resistance and inductance seen from the drive current can be considered. This includes the resistance and inductance of the coils. In embodiments of the invention, a predefined electrical lead angle is determined before starting the motor.

[0036] In an embodiment of the invention, at least one signal indicating the electrical lead angle is determined based on the rotor speed.

[0037] A lookup table based on rotational speed can be used to define at least one signal indicating the electrical lead angle. This lookup table may exist, for example, for both clockwise and counterclockwise directions. In an alternative embodiment, a mathematical relationship can be defined between the signal indicating the electrical lead angle in the clockwise direction and the signal indicating the electrical lead angle in the counterclockwise direction.

[0038] In an embodiment of the invention, at least a portion of at least one electrical lead angle can be scaled as an electrode rotation speed.

[0039] In embodiments of the present invention, one or more lead angles can be determined based on a combination of one or more parameters, which indicate the ratio of rotor resistance to inductance to rotational speed.

[0040] In embodiments of the invention, at least one electrical lead angle can be defined during operation by analyzing the current waveform, for example, by analyzing the height of the peaks in the waveform at the beginning and end of the EHP.

[0041] In embodiments of the present invention, the position sensor is a magnetic sensor. For example, this could be a Hall sensor.

[0042] In an embodiment of the invention, the Hall sensor is located at essentially zero magnetic lead angle.

[0043] An advantage of embodiments of the present invention is that, compared to motor drivers where the Hall sensor is not located at the zero magnetic lead angle, it reduces the electrical adjustment of the position signal between clockwise and counterclockwise directions.

[0044] In a preferred embodiment of the invention, the magnetic lead angle can be, for example, between + / -1 degree, or even between + / -5 degrees, or even between + / -10 degrees. In a first case, the electrical adjustment of the position signal can be, for example, 10 degrees. With a magnetic lead angle of +5°, the electrical adjustment of the position signal can be, for example, +5° in one rotational direction and -15° in the opposite rotational direction.

[0045] In embodiments of the invention, the Hall sensor is positioned such that a large amount of electrical lead angle adjustment is not required in a rotational direction (e.g., lead angle adjustment is less than 1°, or even less than 0.1°, or even no lead angle adjustment is required).

[0046] An advantage of this invention is that the electrical lead angle adjustment only needs to be performed in one direction. For example, the position signal only needs to be adjusted in one direction. For example, the magnetic lead angle can be 10° in one rotational direction, and a compensating electrical lead angle of 20° can be introduced in the opposite rotational direction. Therefore, by shifting the position signal by more than 20°, a signal indicating the electrical lead angle can be obtained.

[0047] In an embodiment of the invention, the controller includes a waveform generator for generating drive signals.

[0048] In a second aspect, embodiments of the present invention relate to an electric motor system. The electric motor system includes a single-coil motor, which includes a rotor and a stator. According to an embodiment of the present invention, the electric motor system further includes a motor driver for driving the rotor of the single-coil motor in a clockwise or counterclockwise direction relative to the stator.

[0049] In a third aspect, embodiments of the present invention relate to a method for driving the rotor of a single-coil motor in a clockwise or counterclockwise rotational direction relative to the stator. The method includes:

[0050] - Generate a position signal representing the angular position of the rotor relative to the stator.

[0051] - Define the desired rotation direction,

[0052] - Generate a drive signal for rotating the rotor in a defined rotational direction, wherein the drive signal is based on the position signal and on a signal indicating an electrical lead angle, wherein the signal indicating the electrical lead angle is set according to the rotational direction of the rotor.

[0053] In various embodiments of the present invention, the method includes:

[0054] - The position signal is electrically adjusted when the rotation direction of the rotor is changed.

[0055] - The drive signal is generated based on the adjusted position signal, so that the electrical lead angle changes due to the variation in the adjusted position signal.

[0056] Specific and preferred aspects of the invention are set forth in the appended independent and dependent claims. Features from the dependent claims may be suitably combined with features of the independent claims and other dependent claims, and not merely as expressly set forth in the claims.

[0057] These and other aspects of the invention will be apparent from the embodiments described herein, and are illustrated with reference to these embodiments. Attached Figure Description

[0058] Figure 1 A schematic diagram of a single-coil motor is shown.

[0059] Figure 2 A block diagram of a motor driver according to an embodiment of the present invention is shown.

[0060] Figure 3The position signal, drive signal, BEMF voltage, and coil current at different positions of the position sensor are shown.

[0061] Figure 4 The detailed current distribution at different locations of the position sensor is shown.

[0062] Figure 5 The diagram illustrates that the optimal magnetic lead angle in the CCW direction is not necessarily the optimal magnetic lead angle in the CW direction.

[0063] Figure 6 The current shapes in the CCW and CW directions are shown when the Hall sensor is in the zero magnetic lead angle position.

[0064] Figure 7 The diagram illustrates the current shapes in the CCW and CW directions obtained from a signal indicating a lead angle according to an embodiment of the invention, whereby the lead angle is obtained by advancing the position signal based on rotation.

[0065] Figure 8 The diagram illustrates the current shapes in the CCW and CW directions obtained from a signal indicating an electrical lead angle according to an embodiment of the invention. This lead angle is obtained by advancing the position signal based on rotation, wherein the hysteresis angle in the CW direction is compensated by applying an electrical lead angle.

[0066] Figure 9 A block diagram of a motor driver according to an embodiment of the present invention is shown.

[0067] Any reference numerals in the claims should not be construed as limiting the scope.

[0068] In different accompanying drawings, the same reference numerals refer to the same or similar elements. Detailed Implementation

[0069] The invention will be described with reference to specific embodiments and particular drawings, but the invention is not limited thereto but is defined only by the claims. The described drawings are merely illustrative and not restrictive. In the drawings, some elements may be enlarged and not drawn to scale for illustrative purposes. Scale and relative scale do not correspond to a true reduction in scale for the practice of the invention.

[0070] The terms "first," "second," etc., used in the specification and claims are used to distinguish between similar elements and are not necessarily used to describe a temporal, spatial, hierarchical, or any other order. It should be understood that such terms are interchangeable where appropriate, and the embodiments of the invention described herein can be operated in a different order than that described or illustrated herein.

[0071] It should be noted that the term "comprising" as used in the claims should not be construed as referring to the means listed thereafter; it does not exclude other elements or steps. Therefore, the term should be interpreted as specifying the presence of the features, integers, steps, or components stated as mentioned, but does not exclude the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the scope of the statement "an apparatus comprising means A and means B" should not be limited to an apparatus consisting solely of components A and B. It means that, for the purposes of this invention, the only relevant components of the apparatus are A and B.

[0072] Throughout this specification, the reference to "an embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrase "in one embodiment" or "in an embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, but may refer to the same embodiment. Furthermore, in one or more embodiments, as will be obvious to those skilled in the art from this disclosure, particular features, structures, or characteristics can be combined in any suitable manner.

[0073] Similarly, it should be understood that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, drawing, or description for the purpose of simplification and aiding in the understanding of one or more of the various inventive aspects. However, this method of disclosure should not be construed as reflecting an intention to claim more features than are expressly recited in each claim. Rather, as reflected in the appended claims, inventive aspects exist in fewer features than all the features of a single foregoing disclosed embodiment. Therefore, the claims appended following the detailed description are thus explicitly incorporated into this detailed description, wherein each claim itself represents a separate embodiment of the invention.

[0074] Furthermore, as will be understood by those skilled in the art, although some embodiments described herein include some features included in other embodiments but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the appended claims, any claimed embodiment may be used in any combination.

[0075] Numerous specific details are set forth in the description provided herein. However, it should be understood that embodiments of the invention can be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description.

[0076] In embodiments of the reference Hall effect sensor of the present invention, reference is made to any type of magnetic sensor, such as, but not limited to, a magnetoresistive sensor or an inductive sensor.

[0077] In an embodiment of the reference drive signal of the present invention, a signal that generates current through the motor coils of a single-coil BLDC motor is referenced. The current may be generated by the average voltage difference across the motor coils generated by an output driver (e.g., a full-bridge output driver). The drive signal may be a pulse-width modulation (PWM) signal or a linearly controlled signal.

[0078] In embodiments using VDD power supply, the average voltage difference across the motor coils can be anywhere between 0V and VDD. The current increases accordingly.

[0079] In the PWM drive method, voltage is provided via time interrupts, thereby generating an average voltage difference across the coils. When the bridge driver of a single-coil BLDC motor and the resistive losses in the motor coils are ignored, when using a power supply voltage VDD = 12V and DC... 出 When driving a motor with 100% PWM, the average voltage difference is 12V. For example, when DC... 出 With a 50% PWM drive signal, the average voltage difference across the coil is 6V. Furthermore, when applying the PWM drive method, the phase current increases accordingly and can be expressed as I at any given time. 线圈 (t)=(VDD*DC 出 (t)–BEMF(t)) / Z, where Z is the impedance of the bridge driver and the motor coil, and BEMF is the back electromotive force voltage induced in the coil by the rotating permanent magnet on the rotor.

[0080] In embodiments of the present invention, the reference lead angle or lead time is referenced to the angular or time relationship between the starting position and the corresponding polar position. In the remainder of this patent description, the term lead angle refers to either the lead angle or the lead time.

[0081] In an embodiment of the present invention, the reference signal indicating the electrical lead angle is referenced to a signal that allows the controller to generate a drive signal with a specific electrical lead angle. The drive signal can make the total lead angle positive for both rotational directions. The drive signal can be generated relative to a position signal such that it leads BEMF by a lead angle.

[0082] In an embodiment of the present invention with a reference zero magnetic lead angle, the reference angle is the angle at which no force is applied to the rotor when current is applied through the coil. This is also referred to as the N / S zero crossing point of the magnetic poles in the rotor. If the position sensor generates a position signal of zero when the rotor is at this position, then the position sensor is at the zero magnetic lead angle.

[0083] In an embodiment of the reference magnetic lead angle of the present invention, the zero-crossing point of the position signal leads the N / S zero-crossing point of the magnetic poles in the rotor by an angle.

[0084] In a first aspect, embodiments of the invention relate to a motor driver 100 for driving the rotor 211 of a single-coil motor 210 in a clockwise or counterclockwise rotational direction relative to the stator 212 of the single-coil motor 210.

[0085] The motor driver 100 is adapted to generate a position signal representing the angular position of the rotor 211 relative to the stator 212. Therefore, the motor driver 100 may include a position sensor 110 or components implementing a sensorless method in which the rotor position can be detected and the position signal can be generated.

[0086] The motor driver includes a controller 120. The controller 120 includes a direction input 150 to define the rotational direction of the rotor 211. The controller 120 is adapted to generate a drive signal for rotating the rotor in the defined rotational direction. The drive signal is generated based on a position signal and a signal indicating an electrical lead angle, wherein the signal indicating the electrical lead angle is set according to the rotational direction of the rotor 211.

[0087] As will be shown later, compared to a motor driver that is not set to an electrical lead angle according to the direction of rotation, generating a drive signal based on a signal indicating the electrical lead angle and set according to the direction of rotation of the rotor can reduce the peak value of the drive current generated through the coil.

[0088] In embodiments of the invention, a signal indicating the electrical lead angle is obtained by electrically adjusting a position signal according to the direction of rotor rotation. Therefore, the signal can be delayed or advanced based on the position signal. Variations in the electrical lead angle can range, for example, from 0 to 10 kWh, and for high-inductance motors, this can increase to 22 kWh, or even 35 kWh. Therefore, the controller is adapted to generate a drive signal based on the adjusted position signal, such that the lead angle changes due to the adjusted position signal.

[0089] Figure 1 A schematic diagram of a single-coil motor 210 is shown. The motor includes a rotor 211 and a stator 212. The rotor 211 has permanent magnets, and the stator 212 includes stator shoes 213. Motor coils 214 are present on the stator shoes. Straight lines connecting the coils are drawn schematically. In practice, the coils may have multiple layers, either upwards or downwards, on the stator poles and interconnected around bearings.

[0090] Figure 2A block diagram illustrating different components of a motor driver 100 according to an embodiment of the present invention is shown. The diagram shows a controller 120. The controller 120 includes a direction input 150 to define the rotational direction of the rotor 211. This input may be an input pin controlled by an external input source or an internal signal. The internal signal may be configured, for example, to cause the orientation direction to change at a specific timestamp, for example, changing at a certain period (e.g., every few minutes).

[0091] exist Figure 2 In the example, component 110 is a position sensor adapted to generate a position signal representing the angular position of rotor 211 relative to stator 212. For example, this could be a Hall sensor. Figure 2 The single-coil output drivers, outputs 1 and 2, are also shown, defining the direction of current flow through motor coil 214. The direction of rotation is defined by a combination of the Hall sensor position, the winding of motor coil 214 on stator 212, the asymmetry of stator shoe 213, and how current flows through motor coil 214 during the first EHP at startup. The direction of rotation for a given motor design is reversed by reversing the current direction during the first EHP at startup.

[0092] In embodiments of the invention, at least one signal indicating an electrical lead angle may be predefined for each direction of rotation. This may be done, for example, in component 130, an optical component. It is an internal memory in which predefined electrical lead angles (or signals indicating those electrical lead angles) may be stored. These electrical lead angles (or signals indicating them) may be retrieved by a controller. Alternatively or in combination, the controller may be adapted to retrieve predefined electrical lead angles (or indication signals of those electrical lead angles) from an external device via interface 140. In embodiments of the invention, one or more signals indicating the electrical lead angle are determined based on one or more parameters, such as the ratio of rotor resistance to inductance, the shape of the current waveform during EHP while the rotor is rotating, the motor speed, etc. For example, the rise time of a pulse may be such an indication. For example, such test pulses may be applied before starting the motor.

[0093] In embodiments of the invention, the signal indicating the electrical lead angle of the drive signal can be defined as a fixed angle, a fixed time, or a variable angle or time. This signal can be defined as a function of rotational speed, current, or current shape. The signal indicating the electrical lead angle can be set according to the rotational direction of the motor or the rotational direction in which the motor should be started. The advantage of defining the total lead angle by applying an electrical lead angle will be utilized. Figures 3 to 8 The diagram is used to illustrate this.

[0094] The controller itself is adapted to generate drive signals for motor 210. Figure 2A complete motor system 200 according to a second aspect of the invention is also shown, the complete motor system 200 including a motor 210 and a motor driver 100 according to an embodiment of the invention.

[0095] exist Figure 3 In the example, a drive signal is generated based on a position signal produced by a Hall sensor. By changing the position of the Hall sensor, a positive or negative lead (or lag) angle of the current waveform relative to the BEMF induced in the motor coil can be generated. Figure 3 The example shows the motor current shape at different Hall sensor locations compared to the stator shoe poles. As indicated by the arrows, in Figure 3 A, Figure 3 B and Figure 3 In C, the rotation direction is the CCW direction.

[0096] exist Figure 3 In diagram A, the Hall sensor is in a positive lead position (magnetic lead angle LA) compared to the zero magnetic lead angle. The zero magnetic lead angle is the angle at which the zero-crossing point of the current or voltage waveform aligns with the zero-crossing point of the BEMF when a current or voltage is applied through the coil. In this example, the Hall latch is in a positive lead position compared to the 45-degree (mechanical) point. Note that, as these diagrams show, for a 2-pole pair motor, the 45-degree mechanical point corresponds to 90 degrees electrical.

[0097] exist Figure 3 In A, the Hall sensor being located ahead of the zero magnetic lead angle means that the N / S zero crossing point of the magnetic poles in the rotor passes the Hall sensor before passing through the 45-degree mechanical point.

[0098] exist Figure 3 In B, the Hall sensor is located exactly at the zero magnetic lead angle LA (in this example, at a 45-degree mechanical position, i.e., in the middle between the two stator shoes).

[0099] exist Figure 3 In C, the Hall sensor is located at a hysteresis angle LA compared to the zero magnetic lead angle (45 mechanical degrees in this example).

[0100] Figure 3 The following figures are shown from top to bottom (all are time functions): the magnetic field MF at the Hall sensor location, the Hall latch output HL with a switching point of 0mT, the voltage drive waveform DS (applied to make the voltage drive waveform DS in phase with the magnetic field at the Hall sensor location), the back electromotive force voltage (BEMF) induced in the motor coil, and the final motor current I.

[0101] These figures show that the final motor current shape varies depending on the position of the Hall sensor and the zero magnetic lead angle. The motor current shape is affected by factors such as the voltage drive waveform, motor inductance, motor speed, and mechanical load.

[0102] When the rotor rotates in only one direction, the optimal position of the Hall sensor relative to zero magnetic permeability angle can be found by positioning the Hall sensor with a small magnetic lead angle and evaluating the current shape. Based on the current shape, it can be determined whether to further increase or decrease the magnetic lead angle. Figure 3 Typical current shapes for different magnetic lead angles are shown. Figure 4 These current distributions of the magnetic Hall sensor, which is positioned to have a large magnetic lead angle, an optimal magnetic lead angle, a small magnetic hysteresis angle, and a large magnetic hysteresis angle, are shown in more detail from left to right.

[0103] The current shape at the optimal magnetic lead angle position has several advantages compared to other shapes. This current shape can provide higher efficiency, lower noise, lower vibration, etc.

[0104] As from Figure 5 It is evident that the optimal magnetic lead angle in the CCW direction (left figure) is not necessarily the optimal magnetic lead angle in the CW direction (right figure). Figure 5 In this configuration, the drive signal is in phase with the position signal from the Hall sensor. Figure 5 On the left side, this generates a drive signal that leads the BEMF induced in the motor coils. This produces the optimal shape of the motor current in the CCW direction. However, when the rotation direction is reversed, the drive signal lags behind the BEMF induced in the motor coils. This results in a peak in the motor current when operating in the CW direction.

[0105] Figure 6 The figure shows the results when the Hall sensor is moved at the zero magnetic lead angle position. This produces a similar current shape in both directions. The current shape shows a hysteresis angle in both directions, which is caused by the delay in the current waveform compared to the applied voltage waveform caused by the inductance of the motor coil. Compared to the optimal design, the fan efficiency is reduced in both directions, and noise / vibration is increased.

[0106] In embodiments of the invention, a drive signal is generated based on the rotor's rotation direction such that the drive signal has an electrical lead angle relative to the position signal. The drive signal can be generated in phase with a signal indicating the electrical lead angle. The signal indicating the electrical lead angle can be obtained by delaying or advancing the position signal. Therefore, the lead angle can be changed by adjusting the lead or lag of the position signal in the same way as the lead or lag adjustment of the position signal. The position signal can be an analog or digital position signal.

[0107] Its preferred implementation is as follows: Figure 7 As shown. From top to bottom, the following signals are shown: the magnetic field MF at the Hall sensor position, the Hall latch output HL with a 0mT switching point, the shifted Hall latch output HLS, the BEMF voltage, and the resulting current I. In this example, the position sensor is located at a zero magnetic lead angle position. The desired electrical lead angle for the drive signal is obtained by periodically advancing the position signal HL to acquire the signal HLS indicating the electrical lead angle. In this example, the position signal is the Hall latch output with a 0mT switching point. In this example, an electrical lead angle is introduced in both the CW and CCW directions to obtain the total lead angle. By doing so, the hysteresis angle caused by the Hall sensor lead angle is compensated by introducing an electrical lead angle in both directions. This electrical lead angle can be adjusted according to the rotation direction. Therefore, an advantage of embodiments of the invention is that the controller according to embodiments of the invention is adapted to define the electrical lead angle of the drive signal according to the rotation direction of the rotor.

[0108] Figure 8 The trace generated by a motor driver according to an alternative embodiment of the invention is shown. In this example, the Hall sensor is positioned such that no electrical lead angle is required in the CCW direction to optimize the motor current. Therefore, the Hall sensor has a small lead angle in the CCW direction. For example, the magnetic lead angle could be 2 degrees, or even 5 degrees, or even 10 degrees.

[0109] When the rotor's rotation direction is changed along the CW direction in this example, a large hysteresis angle is generated, which is compensated for by applying an electrical lead angle according to an embodiment of the invention.

[0110] Figure 9 A schematic diagram of a motor driver and motor system 200 according to an embodiment of the present invention is shown. Figure 2 A more general schematic diagram is shown, while this diagram illustrates more detailed possible implementations. A single-coil motor 210 is schematically drawn. The drive transistors of output drivers output 1 and output 2 are controlled by drive signals generated by controller 120.

[0111] The controller 120 includes a lead angle generator 122 for controlling the electrical lead angle of the drive signal according to the rotation direction of the rotor. For example, the lead angle generator 122 may be configured to adjust the position signal. In this case, the waveform generator 121 may be adapted to generate a drive signal synchronized with the adjusted position signal.

[0112] The controller 120 includes an output for outputting an FG / RD signal.

[0113] In this example, the motor driver 100 includes a position sensor 110, which is a Hall sensor. The analog signal from the Hall sensor is digitized (DIG) before being submitted to the controller 120.

[0114] The controller 120 receives optional additional inputs from internal memory 130 (e.g., E2PROM) or via external interface 140 (e.g., using resistors or other discrete configurations) and defines waveforms, shifting or updating the waveform in terms of additional time or electrical quantity according to the configuration to reflect the electrical lead angle. This adjustment is made according to the selected direction of rotation and may change when the direction of rotation is changed. This direction can be communicated via PWM input, through some encoding, or through external (e.g., dedicated input pin 150) or internal inputs (e.g., reprogramming of internal registers or E2PROM).

[0115] In embodiments of the invention, the controller can be adapted to set the electrical lead angle as a function of rotational speed, current, or other parameters. In embodiments of the invention, the controller can calculate the electrical lead angle based on actual measurements (e.g., motor coil inductance or L / R). Because the motor coils contain inductance, any applied voltage shape will result in a delay in the current shape. Such delay can become significant when the commutation speed approaches the timing delay. Therefore, as the rotational speed increases, the applied voltage shape shifts forward relative to the rotor position.

[0116] To achieve optimal efficiency, the lead angle should increase as the mechanical commutation speed approaches the delay of the current relative to the speed. Alternatively, a fixed lead time can be used, where the time is automatically converted into a gradual angle as the speed increases.

[0117] In some cases, the expected increase in the lead angle is greater than the proportional increase, and the reduction in efficiency is exchanged for some additional peak power.

[0118] Different starting methods can be applied to start the motor. The controller can be adapted to apply a soft-start method in one direction to minimize inrush current (which causes audible noise and applies mechanical stress to the fan structure, thus limiting the fan's lifespan), and apply a more aggressive start in the opposite direction to skip the zero-torque position and then fall back to a smoother start.

[0119] The controller according to an embodiment of the present invention can be adapted to start the motor in the CW or CCW direction.

[0120] To start the fan in both directions, the modification can be implemented in the startup sequence of the controller according to an embodiment of the invention. When the rotor of a motor with asymmetrical shoe poles is stopped near the zero torque position, more current must be injected compared to the other direction of rotation in order to skip the zero torque point.

[0121] Such adjustments can be implemented in controller 120. Lead angle generator 122 can, for example, be adapted to increase or decrease the signal indicating the electrical lead angle. This can be achieved, for example, by delaying or advancing the position signal.

[0122] For example, a motor driver may have two output pins, output 1 and output 2, which can be connected to a single coil of the motor. Upon startup, the controller can be adapted to drive the motor according to the table below.

[0123]

[0124] This table is for illustrative purposes only and is based on the motor winding connections. In this example, the position sensor is a Hall sensor, and a threshold B is defined. op and B RP Used to determine how to start the motor. To start the motor, the controller can be configured such that when the Hall sensor detects a magnetic field B > B... op At this time, the controller generates a drive signal, causing output 1 to go low and output 2 to go high. This is illustrated in the first row of the table. For applications including variable speed control, DC... 出 The output duty cycle is used to control output 2. In this example, current flows through the coil in the first direction, causing the motor to rotate clockwise due to the electromagnetic interaction between the rotor magnets and the current flowing through the stator coils.

[0125] According to the second row of the table, the controller generates a drive signal such that when B... rp When output 2 becomes low and output 1 becomes high, the current flows in opposite directions. Since the rotor magnets are reversed, the rotor will rotate clockwise again.

[0126] If the rotor should rotate in the CCW direction, then the controller's response is adjusted to generate a drive signal such that for B>B op If 2 is drawn, the value decreases; if 1 is drawn, the value increases. For B... rp When the value is 1, the value decreases, while when the value is 2, the value increases.

[0127] The advantage of embodiments of the present invention is that improved start-up and operation can be achieved in both clockwise and counterclockwise rotation directions.

[0128] In a third aspect, embodiments of the present invention relate to a method for driving the rotor of a single-coil motor in a clockwise or counterclockwise rotational direction relative to the stator. The method includes:​​

[0129] - Generate a position signal representing the angular position of the rotor relative to the stator.

[0130] - Define the desired rotation direction,

[0131] - Generate a drive signal for rotating the rotor in the defined rotational direction, wherein the drive signal is based on the position signal and on a signal indicating an electrical lead angle, wherein the signal indicating the electrical lead angle is set such that the total lead angle is positive for both rotational directions of the rotor, the total lead angle being the sum of the lead angle of the position signal and the electrical lead angle. In an embodiment of the invention, the electrical lead angle is set according to the rotational direction of the rotor.

[0132] In various embodiments of the present invention, the method includes:

[0133] - The position signal is electrically adjusted according to the direction of rotation of the rotor.

[0134] - The drive signal is generated based on the adjusted position signal, so that the electrical lead angle changes due to the variation in the adjusted position signal.

[0135] In embodiments of the present invention, a signal indicating the electrical lead angle is obtained by delaying or advancing the position signal.

Claims

1. A motor driver for driving a rotor of a single-coil motor in a clockwise or counterclockwise rotational direction relative to a stator of the single-coil motor, the motor driver being adapted to generate a position signal representing the angular position of the rotor relative to the stator and including a controller, the controller including a direction input to define the rotational direction of the rotor, and the controller being adapted to generate a drive signal for rotating the rotor in the defined rotational direction, wherein the drive signal is determined based on the position signal and a signal indicating an electrical lead angle, wherein the signal indicating the electrical lead angle is set such that a total lead angle is positive with respect to both rotational directions of the rotor, the total lead angle being the sum of the lead angle of the position signal and the electrical lead angle, wherein... For each rotation direction, at least one signal is predefined to indicate the electrical lead angle.

2. The motor driver according to claim 1, characterized in that, The signal indicating the electrical lead angle is obtained by electrically setting the position signal according to the rotation direction of the rotor, and wherein the controller is adapted to generate the drive signal based on the position signal such that the electrical lead angle is set by the position signal.

3. The motor driver according to claim 1, characterized in that, The motor driver includes a position sensor for generating a position signal representing the angular position of the rotor relative to the stator.

4. The motor driver of claim 1, wherein the motor driver includes an interface for retrieving a predefined signal from an external device, the predefined signal indicating the electrical lead angle.

5. The motor driver of claim 1, wherein the motor driver includes an internal memory for retrieving a predefined signal, the predefined signal indicating the electrical lead angle.

6. The motor driver according to claim 1, characterized in that, One or more signals indicating the electrical lead angle are determined based on one or more parameters, the one or more parameters indicating the ratio of the rotor's resistance to its inductance.

7. The motor driver according to claim 1, characterized in that, The at least one signal indicating the electrical lead angle is determined based on the rotor's rotational speed.

8. The motor driver according to claim 3, characterized in that, The position sensor is a magnetic sensor.

9. The motor driver according to claim 8, characterized in that, The position sensor is a Hall sensor, and the Hall sensor is positioned at a substantially zero magnetic lead angle.

10. The motor driver according to claim 9, characterized in that, Positioning the Hall sensor eliminates the need for extensive electrical lead angle adjustments in a rotational direction.

11. The motor driver according to claim 1, characterized in that, The controller includes a waveform generator for generating the drive signal.

12. An electric motor system comprising a single-coil motor, the single-coil motor including a rotor and a stator, the electric motor system further comprising a motor driver according to claim 1, the motor driver being configured to drive the rotor of the single-coil motor in a clockwise or counterclockwise direction relative to the stator.

13. A method for driving the rotor of a single-coil motor in a clockwise or counterclockwise rotational direction relative to a stator, the method comprising: Generate a position signal representing the angular position of the rotor relative to the stator. Define the desired rotation direction. A drive signal for rotating the rotor in a defined rotational direction is generated, wherein the drive signal is determined based on the position signal and a signal indicating an electrical lead angle, wherein the signal indicating the electrical lead angle is set such that the total lead angle is positive for both rotational directions of the rotor, the total lead angle being the sum of the lead angle of the position signal and the electrical lead angle, wherein at least one signal indicating the electrical lead angle is predefined for each rotational direction.

14. The method according to claim 13, wherein the method comprises: The position signal is electrically adjusted when the rotation direction of the rotor is changed. The drive signal is generated based on the adjusted position signal, such that the electrical lead angle changes due to variations in the adjusted position signal.

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