Brushless DC motor, ceiling fan

Abstract

We provide technology that enables operation without causing discomfort to the user. [Solution] A magnet is attached to the rotor 122. A three-phase winding is attached to the stator 120. The inverter circuit 108 has a plurality of upper switching elements connected to the positive side of the DC voltage and a plurality of lower switching elements connected to the negative side of the DC voltage, and applies a drive voltage to the three-phase winding by switching the upper and lower switching elements. The drive circuit 112 estimates the position of the rotor 122 based on the phase current generated in the three-phase winding as the rotor 122 rotates, and controls the operation of the inverter circuit 108 by three-phase vector control according to the estimated position of the rotor 122. The drive circuit 112 turns on all of the plurality of lower switching elements, and then determines that the rotor has stopped if the amplitude of the phase current is included in the stop range for a certain period of time.

Description

Technical Field

[0001] The present disclosure relates to a brushless DC motor without a sensor and a ceiling fan.

Background Art

[0002] A brushless DC motor includes a rotor, a stator, and an inverter circuit. The rotor is a permanent magnet with N and S poles alternately applied and is configured to be rotatable. The stator has three-phase windings wound around a core formed by laminating electromagnetic steel sheets. The inverter circuit applies a voltage to the windings to cause a current to flow through the windings, rotating the rotor in a predetermined rotational direction (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a brushless DC motor, it is necessary to detect the position of the rotor. When a hall sensor for detecting the position of the rotor is not used, the position of the rotor is detected by using the induced voltage generated during the rotation of the rotor. On the other hand, when the rotor is stopped, the rotor must be rotated by energizing the windings to detect the position of the rotor. When a brushless DC motor is mounted on a ceiling fan, it is difficult to smoothly start the brushless DC motor because the blades move unnecessarily due to the rotation of the rotor. In the case of a ceiling fan, since the user can visually see the blades, a delicate movement that does not give the user a sense of discomfort is required not only during startup but also during stopping and restarting from the stopping operation.

[0005] Therefore, this disclosure aims to solve the above-mentioned problems and provide technology that enables operation without causing discomfort to the user. [Means for solving the problem]

[0006] To solve the above problems, a brushless DC motor in one aspect of the present disclosure includes a rotor with magnets, a stator with three-phase windings, a plurality of upper switching elements connected to the positive side of a DC voltage, and a plurality of lower switching elements connected to the negative side of a DC voltage, and comprises an inverter circuit that supplies a drive voltage to the three-phase windings by switching the upper and lower switching elements, and a drive device that estimates the position of the rotor based on the phase current generated in the three-phase windings as the rotor rotates, and controls the operation of the inverter circuit according to the estimated rotor position. The drive device turns on all of the plurality of lower switching elements, and then determines that the rotor has stopped if the amplitude of the phase current is included in the stop range for a certain period of time, and the stop range has a constant width centered on zero in the region of the amplitude of the phase current.

[0007] Furthermore, any combination of the above components, as well as any conversion of the expressions of this disclosure between methods, apparatus, systems, recording media, computer programs, etc., are also valid forms of this disclosure. [Effects of the Invention]

[0008] According to this disclosure, it is possible to achieve operation that does not cause any discomfort to the user. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram shows the configuration of the ceiling fan according to this embodiment. [Figure 2] This diagram shows the configuration of a brushless DC motor. [Figure 3] This figure shows the time variation of the total voltage, U-phase current, and motor voltage when starting the rotation of the brushless DC motor shown in Figure 2. [Figure 4]Figures 4(a)-(b) show the time changes of the total voltage, U-phase current, and motor voltage when brake control is performed on the brushless DC motor shown in Figure 2. [Figure 5] This figure shows the time changes in the total voltage, U-phase current, and motor voltage when a stop command is received for the brushless DC motor shown in Figure 2. [Figure 6] Figures 6(a)-(b) show the time changes in the total voltage, U-phase current, and motor voltage when a stop command is received and then a restart command is received for the brushless DC motor shown in Figure 2. [Figure 7] Figure 2 is a flowchart showing the procedure for brake control in a brushless DC motor. [Figure 8] Figure 2 is a flowchart showing the stopping procedure for a brushless DC motor. [Modes for carrying out the invention]

[0010] Before specifically describing the embodiments of this disclosure, an overview of the embodiments will be given. This embodiment relates to a brushless DC motor mounted on a ceiling fan. As mentioned above, in a brushless DC motor, the position of the rotor must be detected. The brushless DC motor according to this embodiment does not use a Hall sensor to detect the rotor position, but detects the rotor position by using the induced voltage generated during the rotation of the rotor. In such a situation, in a ceiling fan where the blades can be seen by the user, fine movements are required that do not cause discomfort to the user during startup, stopping, and restarting from a stopped state. The brushless DC motor according to this embodiment aims to achieve operation that does not cause discomfort to the user in a ceiling fan.

[0011] The embodiments described below all represent preferred specific examples of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement and connection configurations of components, as well as the steps (processes) and their order shown in the following embodiments are examples and are not intended to limit the present disclosure. Accordingly, among the components in the following embodiments, those components that are not described in the independent claims representing the highest-level concepts of the present disclosure will be described as optional components. In addition, substantially identical components are denoted by the same reference numerals in each figure, and redundant explanations are omitted or simplified.

[0012] Figure 1 shows the configuration of the ceiling fan 1000. The ceiling fan 1000 comprises a brushless DC motor 100, a control circuit 200, and blades 300. The ceiling fan 1000 is installed on the ceiling. The ceiling fan 1000 has a brushless DC motor 100 and a control circuit 200 built into it. The blades 300 are attached to the drive shaft of the brushless DC motor 100, and the brushless DC motor 100 rotates the blades 300.

[0013] The brushless DC motor 100 will be described below in the following order: (1) basic configuration and operation, (2) initial position estimation and rotation start, (3) brake control, and (4) deceleration control and re-rotation control.

[0014] (1) Basic configuration and basic operation Figure 2 shows the configuration of the brushless DC motor 100. The brushless DC motor 100 includes a power supply 102, a smoothing circuit 104, a capacitor 106, an inverter circuit 108, a motor 110, and a drive circuit 112 (drive device). The inverter circuit 108 includes upper switching elements Q1, Q2, Q3, Q4, Q5, Q6, a recirculating diode D1, D2, D3, D4, D5, and D6. The motor 110 includes a stator 120 and a rotor 122.

[0015] The power supply 102 supplies an AC voltage, and the smoothing circuit 104 smooths the AC voltage from the power supply 102 and outputs a DC voltage. Instead of the power supply 102 and the smoothing circuit 104, a power supply that supplies a DC voltage may be used. The DC voltage from the smoothing circuit 104 is supplied to the inverter circuit 108 via the capacitor 106. The DC voltage is also denoted as the total voltage Vm.

[0016] The inverter circuit 108 has a configuration of a three-phase inverter bridge. The three-phase inverter bridge includes six switching elements from the upper switching element Q1 to the lower switching element Q6. Among them, the upper switching element Q1, the upper switching element Q2, and the upper switching element Q3 are connected to the positive electrode 130 side of the DC voltage, and the lower switching element Q4, the lower switching element Q5, and the lower switching element Q6 are connected to the negative electrode 132 side of the DC voltage. The upper switching element Q1 and the lower switching element Q4 perform switching for the U phase. The upper switching element Q2 and the lower switching element Q5 perform switching for the V phase. The upper switching element Q3 and the lower switching element Q6 perform switching for the W phase. By performing the switching of these switching elements, the inverter circuit 108 applies a driving voltage to the three-phase windings of the stator 120 described later.

[0017] A freewheeling diode D1 is connected in parallel to the upper switching element Q1, a freewheeling diode D2 is connected in parallel to the upper switching element Q2, and a freewheeling diode D3 is connected in parallel to the upper switching element Q3. A freewheeling diode D4 is connected in parallel to the lower switching element Q4, a freewheeling diode D5 is connected in parallel to the lower switching element Q5, and a freewheeling diode D6 is connected in parallel to the lower switching element Q6. These freewheeling diodes in the inverter circuit 108 form a circulation route for the current flowing through the three-phase windings of the stator 120 described later.

[0018] The stator 120 connected to the inverter circuit 108 is provided with a three-phase winding having a phase difference of 120 degrees in electrical angle. The three-phase winding includes a U-phase winding LU, a V-phase winding LV, and a W-phase winding LW. The U-phase winding LU is connected to the U-phase of the inverter circuit 108, the V-phase winding LV is connected to the V-phase of the inverter circuit 108, and the W-phase winding LW is connected to the W-phase of the inverter circuit 108. The rotor 122 is provided with a permanent magnet formed by mixing ferrite-based magnet powder and resin and having N and S poles alternately applied to its surface.

[0019] The inverter circuit 108 outputs a U-phase current IU, which is the current of the U-phase, a V-phase current IV, which is the current of the V-phase, and a W-phase current IW, which is the current of the W-phase, to the drive circuit 112. Based on the U-phase current IU, V-phase current IV, and W-phase current IW generated in the three-phase winding due to the rotation of the rotor 122, the drive circuit 112 calculates the induced voltage of the three-phase winding by the rotor 122 and estimates the position of the rotor 122. Here, the induced voltage is the voltage generated in the coil (such as the U-phase winding LU) to prevent the change when the magnetic flux penetrating through the coil changes. A known technique may be used for estimating the position of the rotor 122 in the drive circuit 112.

[0020] Based on the estimated position of the rotor 122, the drive circuit 112 generates motor voltages U+, V+, W+, U-, V-, and W- so as to follow the target position of the rotor 122. Here, three-phase vector control is used for generating the motor voltages U+, V+, W+, U-, V-, and W-.

[0021] Three-phase vector control is a known technique, and the following steps are performed in order: (A) conversion from three-phase current values ​​to two-phase current values, (B) coordinate transformation from fixed coordinates to rotating coordinates for the two-phase current values, (C) PI control to bring the coordinate-transformed two-phase current values ​​closer to the target value, (D) inverse coordinate transformation from rotating coordinates to fixed coordinates for the two-phase voltage values ​​obtained by PI control, and (E) spatial vector transformation from the two-phase voltage values ​​obtained by the inverse coordinate transformation to the three-phase motor voltage. In this process, the estimated position of the rotor 122 is used in coordinate transformation (B) and inverse coordinate transformation (D).

[0022] The drive circuit 112 outputs the motor voltage U+ to the upper switching element Q1, the motor voltage V+ to the upper switching element Q2, and the motor voltage W+ to the upper switching element Q3. The drive circuit 112 also outputs the motor voltage U- to the lower switching element Q4, the motor voltage V- to the lower switching element Q5, and the motor voltage W- to the lower switching element Q6. The inverter circuit 108 rotates the rotor 122 by switching the switching elements based on the motor current and supplying motor current to the U-phase winding LU, the V-phase winding LV, and the W-phase winding LW. In other words, the drive circuit 112 controls the operation of the inverter circuit 108 by three-phase vector control according to the estimated position of the rotor 122.

[0023] In the aforementioned drive circuit 112, while the rotor 122 is rotating, the induced voltage is calculated based on the energization status to each phase and the phase current of each phase at that time.

[0024] (2) Initial position estimation and rotation start As described above, the drive circuit 112 estimates the position of the rotor 122 by calculating the induced voltage from the phase current when the rotor 122 is rotating. Therefore, before the rotor 122 starts rotating, that is, when the rotor 122 is stopped, the drive circuit 112 cannot calculate the induced voltage and thus cannot estimate the position of the rotor 122. Consequently, the drive circuit 112 estimates the position of the rotor 122 by forcibly turning a specific switching element on and off to calculate the induced voltage.

[0025] If the period for outputting the motor voltage to turn on the switching element is short, or if the motor voltage is low, a sufficient phase current for estimating the position of the rotor 122 cannot be obtained, and the accuracy of estimating the position of the rotor 122 will decrease. On the other hand, if the period for outputting the motor voltage is long, or if the motor voltage is high, in order to improve the accuracy of estimating the position of the rotor 122, the time from when the user starts operation until the blades 300 start to operate will be longer, which may cause discomfort to the user. In addition, abnormal noise may be generated due to resonance of the brushless DC motor 100.

[0026] In this embodiment, the drive circuit 112 outputs the motor voltage to the inverter circuit 108 so that current flows while switching between the directions of current flow from the U-phase winding LU to the V-phase winding LV, from the V-phase winding LV to the W-phase winding LW, from the W-phase winding LW to the U-phase winding LU, from the V-phase winding LV to the U-phase winding LU, from the W-phase winding LW to the V-phase winding LV, and from the U-phase winding LU to the W-phase winding LW. For example, the drive circuit 112 performs, for example, three sets of multiple repetitions of current flowing in these six directions.

[0027] Figure 3 shows the time evolution of the total voltage Vm, U-phase current IU, and motor voltage U- when starting the rotation of the brushless DC motor 100. The U-phase current IU and motor voltage U- are examples, and may be phase currents and motor voltages of other phases. A high level is output three times discretely during the initial position estimation 400 of the motor voltage U-. This corresponds to the three sets mentioned above. Based on this, the drive circuit 112 estimates the initial position of the rotor 122.

[0028] From the start of rotation 402 after the initial position estimation 400, the drive circuit 112 outputs a motor voltage to the inverter circuit 108 to forcibly rotate the rotor 122 with low-frequency synchronous startup for acceleration. Subsequently, the aforementioned control is performed.

[0029] (3) Brake control When the brushless DC motor 100 receives a command to start rotating, if the rotor 122 is stopped, the drive circuit 112 only needs to estimate the initial position of the rotor 122 and then rotate the rotor 122. On the other hand, if the rotor 122 is rotating by inertia when the brushless DC motor 100 receives a command to start rotating, and the drive circuit 112 performs the above process, the actual rotation of the rotor 122 and the timing of the motor voltage will not synchronize, resulting in a loss of step. Rotor 122 rotating by inertia corresponds to a situation where the state of the rotor 122 is unknown. Therefore, in such a case, when the brushless DC motor 100 receives a command to start rotating, the drive circuit 112 needs to stop the rotor 122 once. If this stopping process results in a long delay between the user operating the ceiling fan 1000 and the blades 300 starting to operate, it may cause discomfort to the user.

[0030] The brushless DC motor 100 in this embodiment performs brake control to shorten the time between stopping the rotor 122 and estimating the initial position of the rotor 122. Here, brake control is performed when the brushless DC motor 100 receives an instruction to start rotation, regardless of whether the rotor 122 is rotating by inertia or stopped.

[0031] When the control circuit 200 receives an external command to start the rotation of the brushless DC motor 100, it outputs a command to start the rotation of the brushless DC motor 100 to the brushless DC motor 100. When the drive circuit 112 of the brushless DC motor 100 receives the command to start the rotation of the brushless DC motor 100, it sets the motor voltages U+, V+, and W+ to low levels and sets the motor voltages U-, V-, and W- to high levels. This is equivalent to turning off all upper switching elements Q1 through Q3 and turning on all lower switching elements Q4 through Q6. As a result, the current flowing through the stator 120 is regenerated, and the rotor 122 is braked. This type of control is called "brake control".

[0032] After starting brake control, the drive circuit 112 monitors at least one of the U-phase current IU, V-phase current IV, and W-phase current IW. The drive circuit 112 defines a stop range as a range with a constant width centered on zero within the amplitude range of the phase currents. The stop range is defined as the range that the amplitude of the phase currents may exceed when the rotor 122 is rotating, and the range that the amplitude of the phase currents does not exceed when the rotor 122 is stopped. The drive circuit 112 also defines a certain period of time. The certain period is defined as the period during which the amplitude of the phase currents does not exceed the stop range when the rotor 122 is rotating. For example, the certain period is set to "500ms".

[0033] The drive circuit 112 determines that the rotor 122 is rotating if the amplitude of the phase current does not fall within the stopping range for a certain period of time. If the drive circuit 112 determines that the rotor 122 is rotating, it continues the brake control.

[0034] On the other hand, the drive circuit 112 determines that the rotor 122 is stopped if the amplitude of the phase current is included in the stopping range for a certain period of time. Normally, the stopping of the rotor 122 was determined by monitoring the pattern of fluctuations in the amplitude of the phase current, but in that case, it is necessary to monitor for a period several times the period of the fluctuation, so the period until the stopping of the rotor 122 is determined becomes long. In contrast, in this embodiment, the condition is that the amplitude of the phase current is included in the stopping range for a certain period of time, so it is not necessary to monitor for a period several times the period of the fluctuation, and the period until the stopping of the rotor 122 is determined is shortened.

[0035] The drive circuit 112 stops brake control when it determines that the rotor 122 is stopped. In other words, the drive circuit 112 sets the motor voltage U-, motor voltage V-, and motor voltage W- to low levels and turns off all lower switching elements Q4 through Q6.

[0036] The drive circuit 112 estimates the initial position of the rotor 122 by performing the aforementioned process after stopping the brake control. In other words, the drive circuit 112 estimates the initial position of the rotor 122 based on the phase current when the switching element is forcibly switched.

[0037] Figures 4(a)-(b) show the time variation of the total voltage Vm, U-phase current IU, and motor voltage U- when brake control is performed on the brushless DC motor 100. Figure 4(a) shows the case where the rotor 122 is stopped in the initial state. At brake start 410, the drive circuit 112 starts brake control. When the period during which the U-phase current IU is included in the stopping range 420 reaches a certain period 422, the drive circuit 112 stops brake control at brake release 412. At the initial position estimation 400 of the motor voltage U-, a high level is output three times discretely. This allows the drive circuit 112 to estimate the initial position of the rotor 122. From the rotation start 402 after the initial position estimation 400, the drive circuit 112 outputs a motor voltage to the inverter circuit 108 to forcibly rotate the rotor 122 with low-frequency synchronous start and accelerate it.

[0038] Figure 4(b) shows the initial state in which the rotor 122 is rotating by inertia. At brake start 410, the drive circuit 112 starts brake control. Since the rotor 122 is rotating by inertia, the U-phase current IU is not initially included in the stopping range 420, but decreases due to brake control. When the period in which the U-phase current IU is included in the stopping range 420 reaches a certain period 422, the drive circuit 112 stops brake control at brake release 412. At the initial position estimation 400 of the motor voltage U-, a high level is output three times discretely. This allows the drive circuit 112 to estimate the initial position of the rotor 122. From the rotation start 402 after the initial position estimation 400, the drive circuit 112 outputs a motor voltage to the inverter circuit 108 to forcibly rotate the rotor 122 with low-frequency synchronous start and accelerate it.

[0039] (4) Deceleration control and re-rotation control When the blades 300 of the ceiling fan 1000 are rotating, if the user instructs the blades 300 to stop, the brushless DC motor 100 stops controlling the rotation. As a result, it no longer recognizes the position of the rotor 122. If the user instructs the blades 300 to start rotating again before they stop, the brushless DC motor 100, having not recognized the position of the rotor 122, must estimate the position of the rotor 122 after it has stopped before restarting its rotation. Consequently, the time it takes for the blades 300 of the ceiling fan 1000 to start rotating again becomes longer, which can cause discomfort to the user.

[0040] When the rotor 122 of the brushless DC motor 100 rotates, causing the blades 300 of the ceiling fan 100 to rotate, the control circuit 200 receives a command from the user to stop the blades 300. In response, the control circuit 200 outputs a command to the drive circuit 112 to stop the rotor 122. When the drive circuit 112 receives a command to stop the rotor 122 while the rotor 122 is rotating, it controls the operation of the inverter circuit 108 using three-phase vector control to reduce the rotational speed of the rotor 122. This control reduces the rotational speed of the rotor 122.

[0041] The drive circuit 112 estimates the position of the rotor 122 based on the phase current, and measures the rotational speed of the rotor 122 based on the estimated position of the rotor 122. The drive circuit 112 compares the estimated rotational speed of the rotor 122 with a lower limit rotational speed. The lower limit rotational speed is predetermined and is set to, for example, "50 rpm". When the rotational speed of the rotor 122 reaches the lower limit rotational speed, the drive circuit 112 stops controlling the operation of the inverter circuit 108 using three-phase vector control.

[0042] Figure 5 shows the time variation of the total voltage Vm, U-phase current IU, and motor voltage U- when a stop command is received in the brushless DC motor 100. When the rotor 122 is rotating, the drive circuit 112 receives a stop command 430. The drive circuit 112 reduces the rotational speed of the rotor 122 by 3-phase vector control. The timing when the rotational speed of the rotor 122 reaches the lower limit rotational speed is 432. At the lower limit rotational speed reach 432, the drive circuit 112 stops the 3-phase vector control.

[0043] In the following, we will explain the case where the blades 300 of the ceiling fan 1000 are rotating, and the user instructs the blades 300 to stop, and then instructs the user to restart the blades 300, in the order of (4-1) restarting during 3-phase vector control and (4-2) restarting after the completion of 3-phase vector control.

[0044] (4-1) Restart during 3-phase vector control As described above, when the drive circuit 112 receives a command to stop the rotor 122 while the rotor 122 is rotating, it controls the operation of the inverter circuit 108 by three-phase vector control to reduce the rotational speed of the rotor 122. This control reduces the rotational speed of the rotor 122. In this situation, the control circuit 200 receives a command from the user to restart the blades 300. In response, the control circuit 200 outputs a command to the drive circuit 112 to restart the rotor 122.

[0045] The drive circuit 112, after receiving a command to stop the rotor 122 and reducing the rotational speed of the rotor 122 using three-phase vector control, receives a command from the control circuit 200 to restart the rotor 122. The drive circuit 112 controls the operation of the inverter circuit 108 using three-phase vector control to increase the rotational speed of the rotor 122. This control increases the rotational speed of the rotor 122.

[0046] (4-2) Restarting after 3-phase vector control is complete As described above, when the drive circuit 112 receives a command to stop the rotor 122 while the rotor 122 is rotating, it controls the operation of the inverter circuit 108 by three-phase vector control to reduce the rotational speed of the rotor 122. This control reduces the rotational speed of the rotor 122. When the rotational speed of the rotor 122 reaches the lower limit, the drive circuit 112 stops controlling the operation of the inverter circuit 108 by three-phase vector control. In this situation, the control circuit 200 receives a command from the user to restart the blades 300. In response, the control circuit 200 outputs a command to the drive circuit 112 to restart the rotor 122.

[0047] The drive circuit 112 receives an instruction from the control circuit 200 to restart the rotor 122 after stopping control of the inverter circuit 108 by three-phase vector control. The drive circuit 112 starts brake control by turning off all upper switching elements Q1 to Q3 and turning on all lower switching elements Q4 to Q6. During the execution of brake control, the drive circuit 112 determines that the rotor 122 is stopped if the amplitude of the phase current is included in the stopping range 420 for a certain period 422.

[0048] The drive circuit 112 stops brake control when it determines that the rotor 122 is stopped. That is, the drive circuit 112 sets the motor voltage U-, motor voltage V-, and motor voltage W- to low levels and turns off all lower switching elements Q4 through Q6. After stopping brake control, the drive circuit 112 estimates the initial position of the rotor 122 by performing the aforementioned process. That is, the drive circuit 112 estimates the initial position of the rotor 122 based on the phase current when the switching elements are forcibly switched.

[0049] Figures 6(a)-(b) show the time changes of the total voltage Vm, U-phase current IU, and motor voltage U- in the brushless DC motor 100 when a stop command is received and then a restart command is received. Figure 6(a) shows the case of restart during (4-1) 3-phase vector control. With the rotor 122 rotating, the drive circuit 112 receives a stop command 430. The drive circuit 112 reduces the rotational speed of the rotor 122 by 3-phase vector control. Before the rotational speed of the rotor 122 reaches the lower limit, the drive circuit 112 receives a restart command 434. The drive circuit 112 increases the rotational speed of the rotor 122 by 3-phase vector control.

[0050] Figure 6(b) shows the case of restarting after the completion of (4-2) 3-phase vector control. While the rotor 122 is rotating, the drive circuit 112 receives a stop instruction 430. The drive circuit 112 reduces the rotational speed of the rotor 122 by 3-phase vector control. The timing when the rotational speed of the rotor 122 reaches the lower limit rotational speed is the lower limit rotational speed arrival 432. At the lower limit rotational speed arrival 432, the drive circuit 112 stops the 3-phase vector control. After that, the drive circuit 112 receives a restart instruction 434. At brake start 410, the drive circuit 112 starts brake control. When the period during which the U-phase current IU is included in the stop range 420 (not shown) reaches a certain period 422 (not shown), the drive circuit 112 stops brake control at brake release 412. At initial position estimation 400, the drive circuit 112 estimates the initial position of the rotor 122. From the start of rotation 402 after the initial position estimation 400, the drive circuit 112 outputs a motor voltage to the inverter circuit 108 to forcibly rotate the rotor 122 with low-frequency synchronous startup and accelerate it.

[0051] The subject of the apparatus, system, or method in this disclosure comprises a computer. The functions of the subject of the apparatus, system, or method in this disclosure are realized by the computer executing a program. The computer comprises a processor as its main hardware component, which operates according to the program. The processor is of any type as long as it can realize its functions by executing the program. The processor consists of one or more electronic circuits, including semiconductor integrated circuits (ICs) or LSIs (Large Scale Integrations). Multiple electronic circuits may be integrated on one chip or provided on multiple chips. Multiple chips may be aggregated in one device or provided on multiple devices. The program is recorded on a non-temporary recording medium such as a ROM, optical disc, or hard disk drive that is readable by the computer. The program may be pre-stored on the recording medium or supplied to the recording medium via a wide-area communication network, including the Internet.

[0052] The operation of the brushless DC motor 100 with the above configuration will now be explained. Figure 7 is a flowchart showing the procedure for brake control in the brushless DC motor 100. The drive circuit 112 performs brake control (S10). When the phase current is included in the stop range 420 (Y in S12) and this state persists for a certain period of 422 (Y in S14), the drive circuit 112 determines that the stator 120 has stopped (S16). After that, the drive circuit 112 releases the brake control (S18). If the phase current is not included in the stop range 420 (N in S12), or if the state in which the phase current is included in the stop range 420 has not persisted for a certain period of 422 (N in S14), the drive circuit 112 determines that the stator 120 is rotating (S20) and returns to step 10.

[0053] Figure 8 is a flowchart showing the stopping procedure for the brushless DC motor 100. The rotor 122 rotates (S50). The drive circuit 112 receives a command to stop the rotor 122 (S52). The drive circuit 112 reduces the rotational speed of the rotor 122 using three-phase vector control (S54). When the rotational speed reaches the lower limit (Y in S56), the drive circuit 112 stops the three-phase vector control (S58). On the other hand, if the rotational speed does not reach the lower limit (N in S56) and the drive circuit 112 does not receive a command to restart the rotor 122 (N in S60), the process returns to step 54. If the drive circuit 112 receives a command to restart the rotor 122 (Y in S60), the drive circuit 112 increases the rotational speed of the rotor 122 using three-phase vector control (S62).

[0054] In this embodiment, since the rotor 122 is stopped only when the amplitude of the phase current is within the stopping range for a certain period of time after all of the lower-stage switching elements have been turned on, the time until the rotor 122 is stopped can be shortened. Also, since the time until the rotor 122 is stopped is shortened, the user's waiting time can be shortened. Also, since the user's waiting time is shortened, operation that does not cause discomfort to the user can be achieved. Furthermore, since the rotation of the rotor 122 is determined only when the amplitude of the phase current is not within the stopping range for a certain period of time after all of the lower-stage switching elements have been turned on, the rotation of the rotor 122 can be determined earlier.

[0055] Furthermore, when it is determined that the rotor 122 has stopped, the state in which all of the lower switching elements are turned on is released, allowing the next process to be executed earlier. Also, when it is determined that the rotor 122 is rotating, the state in which all of the lower switching elements are turned on is maintained, allowing the rotor 122 to be stopped. After releasing the state in which all of the lower switching elements are turned on, the initial position of the rotor 122 is estimated based on the phase current when the upper and lower switching elements are switched, allowing the rotor 122 to rotate earlier.

[0056] Furthermore, when a command to stop the rotor 122 is received, the rotational speed of the rotor 122 is reduced by three-phase vector control, so the rotational speed can be reduced while recognizing the position of the rotor 122. Also, because the rotational speed is reduced while recognizing the position of the rotor 122, other processing for the rotor 122 can be executed earlier. Also, because other processing for the rotor 122 is executed earlier, operation that does not cause discomfort to the user can be achieved. In addition, when the rotational speed of the rotor 122 reaches the lower limit rotational speed, the control of the inverter circuit 108 by three-phase vector control is stopped, so three-phase vector control becomes unnecessary when the rotor 122 is close to stopping.

[0057] Furthermore, if a command to restart the rotor 122 is received while the rotor speed of the rotor 122 is being reduced by three-phase vector control, the rotation speed of the rotor 122 is increased by three-phase vector control, allowing for early restart. Because the restart is performed early, operation that does not cause discomfort to the user is achieved. Also, if a command to restart the rotor 122 is received after the control of the inverter circuit 108 by three-phase vector control has been stopped, brake control is performed before estimating the initial position of the rotor 122, thus shortening the time until restart. Because the time until restart is shortened, operation that does not cause discomfort to the user is achieved.

[0058] An overview of one aspect of this disclosure is as follows: (Item 1-1) A rotor with magnets attached, A stator with three-phase windings, An inverter circuit having a plurality of upper switching elements connected to the positive side of a DC voltage and a plurality of lower switching elements connected to the negative side of the DC voltage, which provides a drive voltage to the three-phase winding by performing switching of the upper and lower switching elements, The system includes a drive device that estimates the position of the rotor based on the phase current generated in the three-phase winding as the rotor rotates, and controls the operation of the inverter circuit by three-phase vector control corresponding to the estimated rotor position. When the drive device receives an instruction to stop the rotor while the rotor is rotating, it reduces the rotational speed of the rotor using the three-phase vector control. The drive device measures the rotational speed of the rotor based on the estimated position of the rotor, and when the rotational speed of the rotor reaches a lower limit, it stops controlling the operation of the inverter circuit by the three-phase vector control, which is a brushless DC motor.

[0059] (Item 1-2) The brushless DC motor described in item 1-1, wherein the drive device, after receiving an instruction to stop the rotor and while reducing the rotational speed of the rotor by the three-phase vector control, receives an instruction to restart the rotor, increases the rotational speed of the rotor by the three-phase vector control.

[0060] (Item 1-3) If the drive device receives an instruction to restart the rotor after stopping the control of the inverter circuit by the three-phase vector control, it turns on all of the plurality of lower switching elements, and then determines that the rotor has stopped if the amplitude of the phase current is included in the stopping range for a certain period of time. The brushless DC motor according to item 1-1, wherein the drive device, when it determines that the rotor has stopped, releases the state in which all of the plurality of lower switching elements are turned on, and estimates the initial position of the rotor based on the phase current when the upper switching element and the lower switching element are switched.

[0061] (Items 1-4) A ceiling fan equipped with a brushless DC motor as described in any one of items 1-1 to 1-3.

[0062] (Item 2-1) A rotor with magnets attached, A stator with three-phase windings, An inverter circuit having a plurality of upper switching elements connected to the positive side of a DC voltage and a plurality of lower switching elements connected to the negative side of the DC voltage, which provides a drive voltage to the three-phase winding by performing switching of the upper and lower switching elements, The system includes a drive device that estimates the position of the rotor based on the phase current generated in the three-phase winding as the rotor rotates, and controls the operation of the inverter circuit according to the estimated position of the rotor. The drive device turns on all of the plurality of lower switching elements, and then determines that the rotor has stopped if the amplitude of the phase current is included in the stopping range for a certain period of time. The stop range is a brushless DC motor having a constant width centered on zero in the amplitude range of the phase current.

[0063] (Item 2-2) The drive device is a brushless DC motor according to item 2-1, in which the rotation of the rotor is determined when all of the plurality of lower switching elements are turned on and the amplitude of the phase current does not fall within the stop range for a certain period of time.

[0064] (Item 2-3) The brushless DC motor according to item 2-2, wherein the drive device, when it determines that the rotor has stopped, releases the state in which all of the plurality of lower switching elements are turned on, and when it determines that the rotor is rotating, continues the state in which all of the plurality of lower switching elements are turned on.

[0065] (Item 2-4) The brushless DC motor according to item 2-3, wherein the drive device estimates the initial position of the rotor based on the phase current when the upper and lower switching elements are switched after releasing the state in which all of the plurality of lower switching elements are turned on.

[0066] (Item 2-5) A ceiling fan equipped with a brushless DC motor as described in any one of items 2-1 to 2-4.

[0067] Although the present disclosure has been explained above based on the examples, it can be easily inferred that the present disclosure is not limited in any way to the above examples, and that various improvements and modifications are possible without departing from the spirit of the present disclosure. [Explanation of Symbols]

[0068] Q1 Upper switching element, D1 Recirculating diode, Q2 Upper switching element, D2 Recirculating diode, Q3 Upper switching element, D3 Recirculating diode, Q4 Lower switching element, D4 Recirculating diode, Q5 Lower switching element, D5 Recirculating diode, Q6 Lower switching element, D6 Recirculating diode, 100 Brushless DC motor, 102 Power supply, 104 Smoothing circuit, 106 Capacitor, 108 Inverter circuit, 110 Motor, 112 Drive circuit, 120 Stator, 122 Rotor, 130 Positive pole, 132 Negative pole, 200 Control circuit, 300 Blades, 400 Initial position estimation, 402 Rotation start, 410 Brake start, 412 Brake release, 420 Stop range, 422 Fixed period, 430 Stop command, 432 Lower limit rotation speed reached, 434 Restart command, 1000 Ceiling fan, U,V,W Motor voltage, IU U-phase current, IV V-phase current, IW W-phase current, LU U-phase winding, LV V-phase winding, LW W-phase winding, Vm Total voltage.

Claims

1. A rotor with magnets attached, A stator with three-phase windings, An inverter circuit having a plurality of upper switching elements connected to the positive side of a DC voltage and a plurality of lower switching elements connected to the negative side of the DC voltage, which provides a drive voltage to the three-phase winding by performing switching of the upper and lower switching elements, The system includes a drive device that estimates the position of the rotor based on the phase current generated in the three-phase winding as the rotor rotates, and controls the operation of the inverter circuit according to the estimated position of the rotor. The drive device turns on all of the plurality of lower switching elements, and then determines that the rotor has stopped if the amplitude of the phase current is included in the stopping range for a certain period of time. The stop range is a brushless DC motor having a constant width centered on zero in the amplitude range of the phase current.

2. The brushless DC motor according to claim 1, wherein the drive device turns on all of the plurality of lower switching elements and then determines the rotation of the rotor if the amplitude of the phase current does not fall within the stop range for a certain period of time.

3. The brushless DC motor according to claim 2, wherein the drive device, when it determines that the rotor has stopped, releases the state in which all of the plurality of lower switching elements are turned on, and when it determines that the rotor is rotating, continues the state in which all of the plurality of lower switching elements are turned on.

4. The brushless DC motor according to claim 3, wherein the drive device estimates the initial position of the rotor based on the phase current when the upper switching element and the lower switching element are switched after releasing the state in which all of the plurality of lower switching elements are turned on.

5. A ceiling fan equipped with a brushless DC motor according to any one of claims 1 to 4.

Images