Motor system and motor driving method

Abstract

The present disclosure relates to a motor system and a motor driving method for detecting back electromotive force (BEMF) without affecting the stability of a motor device. The motor driving method includes the following steps: detecting a detection voltage between a first switch and a second switch in a driving circuit, wherein the driving circuit is electrically connected to a power supply and a motor device and controls the first and second switches according to a switching frequency to provide a driving current to the motor device; determining the driving current based on the detection voltage; when the driving current is less than a predetermined value, turning off the first and second switches for a detection period, wherein the detection period has a fixed duration; detecting the BEMF of the motor device during the detection period to calculate a return-to-zero time for the BEMF; and adjusting the switching frequency based on the return-to-zero time.

Description

Technical Field

[0001] The present disclosure relates to a motor system and a motor driving method, and more particularly to a technology for calculating rotor position by determining back electromotive force. Background Art

[0002] With technological advancements, the operating frequencies of various electronic devices have increased. However, this increase in operating frequency also leads to a relatively higher internal temperature of the electronic devices during operation. In order to prevent the high temperature from affecting the operation of electronic devices or even damaging them, the presence of fans is indispensable for maintaining the operation of electronic devices.

[0003] When a fan system is in operation, its operating status must be determined based on the motor's rotor position. While a position sensor can be configured within the fan system to detect the motor's rotor position, this approach requires higher costs and larger installation space. Therefore, a drive method suitable for sensorless fan systems is needed. Summary of the Invention

[0004] The present disclosure relates to a motor driving method, comprising the following steps: detecting a detection voltage value between a first switch and a second switch in a driving circuit, wherein the driving circuit is electrically connected to a power supply and a motor device, and is used to control the first switch and the second switch according to a switching frequency to provide a driving current to the motor device; determining the driving current based on the detection voltage value; when the driving current is less than a predetermined value, turning off the first switch and the second switch for a detection period, wherein the length of the detection period is a fixed value; during the detection period, detecting the reverse electromotive force of the motor device to calculate the return-to-zero time of the reverse electromotive force; and adjusting the switching frequency based on the return-to-zero time.

[0005] In one embodiment, the motor driving method further includes: detecting the back electromotive force of the motor device during the detection period to obtain a plurality of detected electromotive force values; and calculating a return-to-zero time of the back electromotive force based on the detected electromotive force values.

[0006] In one embodiment, the driving current passes through zero during the detection period.

[0007] In one embodiment, a method for calculating the return-to-zero time of the back electromotive force includes: obtaining a change characteristic line according to the detected electromotive force values; and calculating the return-to-zero time of the back electromotive force according to a slope of the change characteristic line.

[0008] In one embodiment, the driving circuit includes a plurality of bridge arm units, and the first switch and the second switch are located in the same one of the bridge arm units.

[0009] In one embodiment, when a detection voltage value between the first switch and the second switch is detected, the first switch and the second switch are turned off.

[0010] In one embodiment, the switching frequency is the frequency of the pulse width modulation signal, and the duration of the detection period is an integer multiple of the period of the pulse width modulation signal.

[0011] In one embodiment, the duration of the detection period is a fixed number of cycles of the pulse width modulation signal.

[0012] In one embodiment, the current phase and the voltage phase of the motor device vary according to the switching frequency.

[0013] In one embodiment, the motor device is a three-phase motor having three input nodes, and the detection node between the first switch and the second switch is connected to one of the input nodes.

[0014] The present disclosure also relates to a motor system comprising a drive circuit, a motor device, and a control circuit. The drive circuit is electrically connected to a power supply and includes at least a first switch and a second switch. The drive circuit is configured to generate a drive current. The motor device is electrically connected to the drive circuit to receive the drive current. The control circuit is electrically connected to the drive circuit to detect a detection voltage between the first switch and the second switch. When the control circuit determines that the drive current is less than a predetermined value based on the detection voltage, the control circuit turns off the first switch and the second switch for a detection period to detect the back electromotive force of the motor device and calculate the time it takes for the back electromotive force to return to zero.

[0015] In one embodiment, the control circuit detects the back electromotive force of the motor device during the detection period to obtain a plurality of detected electromotive force values, and calculates the return-to-zero time of the back electromotive force according to the detected electromotive force values.

[0016] In one embodiment, the driving current passes through zero during the detection period.

[0017] In one embodiment, the control circuit is further configured to obtain a change characteristic line according to the detected electromotive force values, and calculate the return-to-zero time of the back electromotive force according to the slope of the change characteristic line.

[0018] In one embodiment, the driving circuit includes a plurality of bridge arm units, the first switch and the second switch are located in the same one of the bridge arm units, and the control circuit controls the first switch and the second switch according to a switching frequency.

[0019] In one embodiment, when a detection voltage value between the first switch and the second switch is detected, the control circuit maintains the first switch and the second switch in an off state.

[0020] In one embodiment, the switching frequency is the frequency of the pulse width modulation signal, and the duration of the detection period is an integer multiple of the period of the pulse width modulation signal.

[0021] In one embodiment, the duration of the detection period is a fixed number of cycles of the pulse width modulation signal.

[0022] In one embodiment, the control circuit adjusts the switching frequency according to the return time of the back electromotive force to zero.

[0023] In one embodiment, the current phase and the voltage phase of the motor device vary according to the switching frequency.

[0024] The present disclosure utilizes the period during which the drive current crosses zero to detect the back EMF for a fixed period (i.e., the detection period), thereby inferring the time when the back EMF returns to zero. This avoids the problem of excessive detection time leading to instability or abnormality of the motor system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of a motor system according to some embodiments of the present disclosure;

[0026] Figure 2A is a schematic diagram of various signal waveforms according to some embodiments of the present disclosure;

[0027] Figure 2B is a partial schematic diagram of signal waveforms according to some embodiments of the present disclosure;

[0028] Figure 3 is a flow chart of a motor driving method according to some embodiments of the present disclosure.

[0029]

Explanation of symbols

[0030] 100: Motor system

[0031] 110: driving circuit

[0032] 120: Motor device

[0033] 130: Control circuit

[0034] B1-B3: Bridge arm unit

[0035] N1-N3: detection nodes

[0036] NU: Input Node

[0037] NV: Input Node

[0038] NW: Input node

[0039] Vb: power supply

[0040] Q1: First switch

[0041] Q2: Second switch

[0042] Vp: driving voltage

[0043] Ip: driving current

[0044] Ve: Back electromotive force

[0045] Td: Detection period

[0046] d1: first distance

[0047] d2: second distance

[0048] A: Detect the electromotive force value

[0049] B: Detection of electromotive force value

[0050] S301-S307: Steps DETAILED DESCRIPTION

[0051] The following drawings illustrate various embodiments of the present invention. For clarity, many practical details are included in the following description. However, it should be understood that these practical details are not intended to limit the present invention. In other words, in some embodiments of the present invention, these practical details are not essential. Furthermore, to simplify the drawings, some well-known and conventional structures and components are depicted in simplified schematic form.

[0052] As used herein, when an element is referred to as being "connected" or "coupled," it may refer to being "electrically connected" or "electrically coupled." "Connected" or "coupled" may also refer to the coordinated operation or interaction between two or more elements. Furthermore, while terms such as "first," "second," and so on are used herein to describe different elements, these terms are intended solely to distinguish between elements or operations described using the same technical terms. Unless the context clearly indicates otherwise, these terms are not intended to specify or imply an order or sequence, nor are they intended to limit the present invention.

[0053] Figure 1 Figure 1 is a schematic diagram of a motor system 100 according to some embodiments of the present disclosure. The motor system 100 includes a drive circuit 110, a motor device 120, and a control circuit 130. The drive circuit 110 is electrically connected to a power supply Vb and the motor device 120 and includes a plurality of switching elements. In one embodiment, the drive circuit 110 controls the on and off states of the switching elements based on control signals UH, UL, WH, WL, VH, and VL, respectively, to output a drive current.

[0054] The motor device 120 is electrically connected to the output terminal of the driver circuit 110 to receive a driving current. In one embodiment, the motor device 120 is used to rotate the blades (not shown) of the fan 100. In some embodiments, the motor device 120 is a three-phase motor having three input nodes NU, NV, and NW. In some embodiments, the motor system 100 is implemented in a fan system. That is, the motor device 120 is used to rotate the blades of the fan, but the present disclosure is not limited thereto and may also be applied to other types of devices.

[0055] The driver circuit 110 includes three bridge arm units B1-B3. Each bridge arm unit B1-B3 includes a first switch Q1 and a second switch Q2, electrically connected to different input nodes NU, NV, and NW, respectively. The first switch Q1 and the second switch Q2 of each bridge arm unit B1-B3 are turned on or off based on control signals UH, UL, WH, WL, VH, and VL, providing three-phase drive current to the motor device 120. The operation of a three-phase motor is well understood by those skilled in the art and will not be further described here.

[0056] The control circuit 130 is electrically connected to any bridge arm unit B1-B3 in the driving circuit 110 to provide control signals UH, UL, WH, WL, VH, VL, and to detect the detection voltage value of the detection node between the first switch Q1 and the second switch Q2. Figure 1 As shown, the control circuit 130 can be connected to any of the detection nodes N1, N2, and N3. In one embodiment, the control circuit 130 generates control signals UH, UL, WH, WL, VH, and VL based on the speed signal. The speed signal is a pulse-width modulated signal with a frequency corresponding to the control signals UH, UL, WH, WL, VH, and VLM, which is used to control the switching frequency of the first switch Q1 and the second switch Q2.

[0057] The control circuit 130 can determine current information about the drive current, such as the current magnitude and direction, based on the detected voltage value. When the control circuit 130 determines that the drive current is less than a predetermined value, it ensures that the connected first switch Q1 and second switch Q2 remain in the off state for a fixed period of time. For ease of explanation, this period is referred to as the "detection period." During the detection period, the control circuit 130 detects the magnitude and trend of the back electromotive force (back EMF) of the motor device 120 and calculates the time it takes for the back EMF to return to zero.

[0058] In one embodiment, the aforementioned "predetermined value" is a value close to zero. In other words, the control circuit 130 detects the back electromotive force during the period when the drive current crosses zero. The control circuit 130 may begin timing the "detection period" when the drive current approaches zero. In other embodiments, the control circuit 130 may also begin timing the "detection period" when it determines that the drive current is zero (i.e., the time when the drive current reaches zero is the starting point of the detection period).

[0059] Specifically, during the detection period, the control circuit 130 detects the back EMF of the motor device 120 at different time points to obtain multiple detected EMF values. Based on these detected EMF values, the changing trend of the back EMF can be calculated to estimate the time when the back EMF returns to zero.

[0060] In other embodiments, the control circuit 130 stores a parameter model of the motor device 120, allowing the control circuit 130 to detect the back EMF only once during the detection period to calculate the back EMF return-to-zero time. Alternatively, the control circuit 130 may not utilize a parameter model, but instead adjust the speed or drive voltage of the motor device 120 based on the detected back EMF to calculate the back EMF return-to-zero time.

[0061] Figure 2A 1 is a signal waveform diagram according to some embodiments of the present disclosure, including a driving voltage Vp, a driving current Ip, and a back electromotive force Ve of a motor device. Figure 2A The horizontal axis represents time, while the vertical axis represents the changing trends of current, voltage, and electromotive force. As shown in the figure, during the period when the drive current Ip crosses zero (i.e., detection period Td), the control circuit 130 detects the back electromotive force Ve of the motor device 120 to obtain at least two detected electromotive force values. These detected electromotive force values ​​form a characteristic curve. The time when the characteristic curve intersects zero can be calculated based on the slope of the characteristic curve or by applying trigonometric functions to the coordinates of the detected electromotive force values ​​A and B.

[0062] Figure 2B for Figure 2A A partially enlarged view. As shown in the figure, the control circuit 130 detects the reverse electromotive force Ve of the motor device 120 to obtain two detection electromotive force values ​​A and B. Since the curve of the driving current Ip is close to the curve of the reverse electromotive force Ve, when the driving current Ip approaches zero (that is, during the detection period Td), the reverse electromotive force Ve will also be near zero. Accordingly, the change characteristic line L formed by connecting these detection electromotive force values ​​A and B can be regarded as equivalent to the curve of the reverse electromotive force Ve. The control circuit 130 can obtain the first distance d1 (at Figure 2BIn the example, the driving current Ip corresponding to the detected electromotive force value A is zero, so the first distance d1 is the coordinate value of the detected electromotive force value A. Next, the second distance d2 can be calculated based on the first distance d1 and the slope of the characteristic line. The second distance d2 is the time difference between the time when the back electromotive force Ve returns to zero and the time when the detected electromotive force value A is detected.

[0063] The control circuit 130 calculates the rotor position of the motor device 120 based on the return-to-zero time of the back electromotive force Ve and the speed signal. This information can be used by the control circuit 130 to confirm whether the operating status of the motor system 100 meets expectations. Since those skilled in the art are familiar with the method for calculating the rotor position based on the back electromotive force, it will not be further described here.

[0064] Specifically, in order for the motor device 120 to operate at ideal efficiency and avoid unnecessary energy loss, the phases of the drive voltage Vp and the drive current Ip of the motor device 120 should correspond to each other (e.g., the phases of the signal waveforms should overlap). Therefore, in one embodiment, after the control circuit 130 calculates the return-to-zero time of the back electromotive force and the rotor position, the control circuit 130 adjusts the frequency of the speed signal accordingly (i.e., changes the switching frequency of the control signals UH, UL, WH, WL, VH, VL) to change the voltage phase of the drive voltage Vp and the current phase of the drive current Ip so that the phases of the two are close to each other.

[0065] In some embodiments, when the control circuit 130 detects the detection voltage between the first switch Q1 and the second switch Q2, the control circuit 130 maintains the first switch Q1 and the second switch Q2 in an off state to prevent abnormalities in the bridge arm units B1-B3 due to a short circuit. In other words, the control circuit 130 detects the detection voltage when both the first switch Q1 and the second switch Q2 are off.

[0066] This disclosure utilizes the period during which the drive current crosses zero (or approaches zero) to detect the back EMF for a fixed period (i.e., the detection period). By using multiple detected back EMF values ​​during the detection period, the time at which the back EMF crosses zero and returns to zero can be estimated. This avoids the problem of excessive detection time leading to instability or abnormality in the motor system 100.

[0067] In some embodiments, the control signals UH, UL, WH, WL, VH, and VL are generated based on the speed signal and are also pulse-width modulated signals. The detection period is a fixed number of cycles of the pulse-width modulated signal (e.g., an integer multiple of the cycle). For example, the detection period may be 2 to 5 cycles of the pulse-width modulated signal. In one embodiment, the detection period may be 3 cycles of the pulse-width modulated signal. The detection period is a fixed value, but is not limited to the aforementioned 2 to 5 cycles. It can be adjusted according to actual needs.

[0068] Figure 3 This is a flow chart of a motor driving method according to some embodiments of the present disclosure. In step S301, the control circuit 130 outputs control signals UH, UL, WH, WL, VH, and VL to the drive circuit 110 based on the speed signal, causing the drive circuit 110 to output a driving current to the motor device 120. The motor device 120 operates in response to the driving current, driving the fan blades.

[0069] In step S302, while the motor device 120 is operating, the control circuit 130 detects the states of the first switch Q1 and the second switch Q2 of one of the bridge arm units B1-B3. When both the first switch Q1 and the second switch Q2 are off, the control circuit 130 detects the detection voltage value between the first switch Q1 and the second switch Q2. In one embodiment, the control circuit 130 periodically repeats step S302 to record multiple detection voltage values.

[0070] In step S303, the control circuit 130 determines the current information of the driving current (such as the current magnitude and the current direction) according to the detection voltage value. In one embodiment, the control circuit 130 detects the driving current output by the driving circuit 110 when both the first switch Q1 and the second switch Q2 are turned off, and records it as a current curve (such as Figure 2A The driving current Ip shown).

[0071] In step S304, the control circuit 130 continuously determines whether the driving current is less than a predetermined value (eg, zero). If the driving current is not less than the predetermined value, the process continues with step S303. In some embodiments, the driving current passes through zero during the detection period.

[0072] In step S305 , when the driving current is less than the predetermined value, the control circuit 130 controls / changes the control signals UH, UL, WH, WL, VH, and VL to maintain the first switch and the second switch in the off state during a fixed detection period.

[0073] In step S306, the control circuit 130 detects the back EMF of the motor device 120 during the detection period to obtain a plurality of detected EMF values ​​and calculates the return-to-zero time of the back EMF. In one embodiment, the control circuit 130 uses the characteristic curve formed by the plurality of detected EMF values ​​as the trend of the back EMF change and calculates the return-to-zero time based on the slope of the curve.

[0074] In step S307, the control circuit 130 determines the rotor position of the motor device 120 based on the calculated return-to-zero time. The speed signal or control signal is then adjusted based on the rotor position. The switching frequencies of the control signals UH, UL, WH, WL, VH, and VL are altered accordingly, aligning the current and voltage phases of the motor device 120 to improve operating efficiency.

[0075] In one embodiment, the motor system 100 executes the aforementioned motor driving method during each cycle to ensure optimal performance. The number of times the control circuit 130 detects the back EMF can be adjusted by the user, but the detection period Td is fixed. Because the present disclosure calculates the return-to-zero time based on the characteristic curves of multiple detected EMF values, the control circuit 130 does not need to actually detect the point in time when the back EMF returns to zero. This prevents operational anomalies caused by the first and second switches Q1 and Q2 being off for extended periods of time.

[0076] The various elements, method steps or technical features in the aforementioned embodiments may be combined with each other and are not limited to the order of description in the text or the order of presentation in the drawings in this disclosure.

[0077] Although the present disclosure has been disclosed above in the form of implementation methods, it is not intended to limit the present disclosure. Anyone skilled in the art may make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the scope defined in the appended claims.

Claims

1. A motor driving method, characterized in that: Include: detecting a detection voltage value between a first switch and a second switch in a driving circuit, wherein the driving circuit is electrically connected to a power supply and a motor device and is configured to control the first switch and the second switch according to a switching frequency to provide a driving current to the motor device; Determine the magnitude of the driving current according to the detection voltage value; When the driving current is less than a predetermined value, the first switch and the second switch are turned off for a detection period, wherein the length of the detection period is a fixed value and the driving current passes through zero during the detection period; During the detection period, detecting a back electromotive force of the motor device to obtain a plurality of detection electromotive force values; obtaining a change characteristic line according to the plurality of detected electromotive force values; Calculating a zero return time of the back electromotive force according to a slope of the change characteristic line; as well as The switching frequency is adjusted according to the return-to-zero time.

2. The motor driving method according to claim 1, wherein: The driving circuit includes a plurality of bridge arm units, and the first switch and the second switch are located in the same one of the plurality of bridge arm units.

3. The motor driving method according to claim 2, wherein: When the detection voltage value between the first switch and the second switch is detected, the first switch and the second switch are turned off.

4. The motor driving method according to claim 1, wherein: The switching frequency is a frequency of a pulse width modulation signal, and a time length of the detection period is an integer multiple of a period of the pulse width modulation signal.

5. The motor driving method according to claim 4, wherein: The time length of the detection period is a fixed number of cycle lengths of the pulse width modulation signal.

6. The motor driving method according to claim 1, wherein: A current phase and a voltage phase of the motor device vary according to the switching frequency.

7. The motor driving method according to claim 1, wherein: The motor device is a three-phase motor having three input nodes. A detection node between the first switch and the second switch is connected to one of the three input nodes.

8. A motor system, characterized in that: Include: a driving circuit electrically connected to a power supply and comprising at least a first switch and a second switch, wherein the driving circuit is configured to generate a driving current; a motor device electrically connected to the driving circuit for receiving the driving current; as well as a control circuit electrically connected to the drive circuit and configured to detect a detection voltage between the first switch and the second switch. When the control circuit determines that the drive current is less than a predetermined value based on the detection voltage, the control circuit turns off the first switch and the second switch for a detection period to detect a back electromotive force of the motor device and calculate a return-to-zero time of the back electromotive force; wherein the control circuit detects the back electromotive force of the motor device during the detection period to obtain a plurality of detection electromotive force values, and calculates the return-to-zero time of the back electromotive force according to the plurality of detection electromotive force values; wherein the driving current passes through a zero point during the detection period; The control circuit is further configured to obtain a change characteristic line according to the plurality of detected electromotive force values, and calculate the return-to-zero time of the back electromotive force according to a slope of the change characteristic line.

9. The motor system according to claim 8, wherein: The driving circuit includes a plurality of bridge arm units. The first switch and the second switch are located in the same one of the plurality of bridge arm units. The control circuit controls the first switch and the second switch according to a switching frequency.

10. The motor system according to claim 9, wherein: When the detection voltage value between the first switch and the second switch is detected, the control circuit maintains the first switch and the second switch in an off state.

11. The motor system according to claim 9, wherein: The switching frequency is a frequency of a pulse width modulation signal, and a time length of the detection period is an integer multiple of a period of the pulse width modulation signal.

12. The motor system according to claim 11, wherein: The time length of the detection period is a fixed number of cycle lengths of the pulse width modulation signal.

13. The motor system according to claim 9, wherein: The control circuit adjusts the switching frequency according to the return-to-zero time of the back electromotive force.

14. The motor system according to claim 13, wherein: A current phase and a voltage phase of the motor device vary according to the switching frequency.

Images