Magnetic pole detection circuit and motor control method

Abstract

A magnetic pole detection circuit includes a multi-phase voltage divider unit, a filter unit, a DC level compensation unit, an amplifier unit and a hysteresis comparison unit. The multi-phase voltage divider unit is used to detect the back electromotive force signal of the multi-phase motor. The filter unit is used to filter the back electromotive force signal to generate a filter signal. The DC level compensation unit is used to compensate the DC level of the back filter signal to generate a compensation signal. The amplifier unit is used to amplify the compensation signal to generate an amplified signal. The hysteresis comparison unit is used to generate a zero crossing point signal according to the amplified signal and a reference signal. The zero crossing point signal is suitable for controlling the excitation mode of the multi-phase motor.

Description

Technical Field

[0001] This case is about magnetic pole detection of a brushless DC motor, and more particularly, a magnetic pole detection circuit and a motor control method. Background Art

[0002] Traditionally, DC motors can be divided into brushed DC motors and brushless DC motors. Among them, brushless DC motors are more popular among users because of their advantages such as no carbon brush wear, no operating sparks and high efficiency.

[0003] In order to make the brushless DC motor commutate correctly, Hall sensors or rotary encoders are generally used to detect the motor pole position. However, the installation of components such as Hall sensors or rotary encoders will increase the manufacturing cost and require additional wiring, making the system reliability vulnerable to factors such as disconnection or component failure.

[0004] In addition, there is also a method of detecting the motor pole position by sensing the back electromotive force. However, the back electromotive force is easily disturbed by the pulse modulation (switching switch) voltage. Moreover, when the motor runs at a low speed, the back electromotive force is too small to be easily detected. Summary of the invention

[0005] The present case provides a magnetic pole detection circuit. In one embodiment, the magnetic pole detection circuit includes a multi-phase voltage divider unit, a filter unit, a DC level compensation unit, an amplifier unit, and a hysteresis comparison unit. The multi-phase voltage divider unit is used to detect the back electromotive force signal of the multi-phase motor. The filter unit is used to filter the back electromotive force signal to generate a filter signal. The DC level compensation unit is used to compensate the DC level of the filter signal to generate a compensation signal. The amplifier unit is used to amplify the compensation signal to generate an amplified signal. The hysteresis comparison unit is used to generate a zero crossing point signal based on the amplified signal and a reference signal. Among them, the zero crossing point signal is suitable for controlling the excitation mode of the multi-phase motor.

[0006] In some embodiments, the magnetic pole detection circuit further comprises a motor controller for controlling an excitation mode of the multi-phase motor according to the zero crossing point signal.

[0007] In some embodiments, the motor controller switches the excitation mode of the multi-phase motor when the zero-crossing point signal is detected, and maintains the excitation mode of the multi-phase motor when the zero-crossing point signal is not detected.

[0008] In some embodiments, the DC level compensation unit is a digital-to-analog converter to dynamically compensate the DC level of the back-EMF signal.

[0009] The present invention further provides a motor control method. In one embodiment, the motor control method includes: detecting a back electromotive force signal of a multi-phase motor; filtering the back electromotive force signal to generate a filter signal; compensating a DC level of the filter signal to generate a compensation signal; amplifying the compensation signal to generate an amplified signal; and generating a zero crossing point signal according to the amplified signal and a reference signal, wherein the zero crossing point signal is suitable for controlling an excitation mode of the multi-phase motor.

[0010] In some embodiments, the motor control method further includes: controlling an excitation mode of the multi-phase motor according to the zero-crossing point signal.

[0011] In some embodiments, the step of controlling the excitation mode of the multi-phase motor according to the zero crossing point signal includes: detecting the zero crossing point signal; switching the excitation mode of the multi-phase motor when the zero crossing point signal is detected; and maintaining the excitation mode of the multi-phase motor when the zero crossing point signal is not detected.

[0012] In some embodiments, the step of compensating the DC level of the back-EMF signal to generate the compensation signal is to dynamically compensate the DC level of the back-EMF signal by a digital-to-analog converter.

[0013] The present invention further provides a magnetic pole detection circuit. In one embodiment, the magnetic pole detection circuit includes a back-EMF amplifier circuit and a hysteresis comparison circuit. The back-EMF amplifier circuit is used to receive the back-EMF signal of the multi-phase motor and amplify the amplitude of the back-EMF signal. The hysteresis comparison circuit is used to receive the reference signal and the amplified back-EMF signal. The hysteresis comparison circuit is used to perform a hysteresis comparison between the reference signal and the amplified back-EMF signal to avoid signal bounce due to switch switching noise, and to generate a zero crossing point signal according to the result of the hysteresis comparison, wherein the zero crossing point signal is suitable for controlling the excitation mode of the multi-phase motor.

[0014] In some embodiments, the magnetic pole detection circuit further includes a digital-to-analog conversion circuit. The digital-to-analog conversion circuit is used to receive the back-electromotive force signal and dynamically compensate the DC level of the back-electromotive force signal to avoid phase lag. The back-electromotive force signal received by the back-electromotive force amplifier circuit is the back-electromotive force signal output after dynamic compensation by the digital-to-analog conversion circuit.

[0015] In some embodiments, the magnetic pole detection circuit further includes a low-pass filter circuit. The low-pass filter circuit is used to receive the back-electromotive force signal and perform low-pass filtering on the switch switching noise on the back-electromotive force signal. The back-electromotive force signal received by the digital-to-analog conversion circuit is the back-electromotive force signal output after low-pass filtering by the low-pass filter circuit.

[0016] In some embodiments, the magnetic pole detection circuit further includes a multi-phase voltage divider circuit. The multi-phase voltage divider circuit is coupled to the multi-phase motor. The multi-phase voltage divider circuit is used to detect the multi-phase motor to generate a back electromotive force signal and perform voltage division filtering on the switch switching noise on the back electromotive force signal. The back electromotive force signal received by the low-pass filter circuit is the back electromotive force signal output after voltage division filtering by the multi-phase voltage divider circuit.

[0017] The detailed features and advantages of the present invention are described in detail in the following implementation mode, and the content is sufficient to enable any technical personnel in this field to understand the technical content of the present invention and implement it accordingly. Moreover, according to the content disclosed in this specification, the scope of the patent application and the drawings, any technical personnel in this field can easily understand the relevant purposes and advantages of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. 1 is a block diagram of a first embodiment of a magnetic pole detection circuit and a multi-phase motor.

[0019] Figure 2 The diagram is a schematic circuit diagram of an embodiment of a magnetic pole detection circuit for detecting a back electromotive force signal of a phase of a multi-phase motor.

[0020] Figure 3 A schematic circuit diagram of a motor controller and a multi-phase motor according to an embodiment of the present invention.

[0021] Figure 4 FIG. 4 is a block diagram of a second embodiment of a magnetic pole detection circuit and a multi-phase motor.

[0022] Figure 5 Schematic diagram of the waveforms of the original back-electromotive force signal, the filtered signal, and the DC level compensation signal.

[0023] Figure 6 It is a schematic diagram of the waveform of the actual back-EMF voltage and the back-EMF after voltage division to simulate the neutral point voltage.

[0024] Figure 7 It is a waveform diagram of the back-EMF voltage to ground after voltage division, the voltage after back-EMF filtering and the zero-crossing point signal.

[0025] Figure 8 FIG. 4 is a flow chart of an embodiment of a motor control method.

[0026] Fig. 9 FIG. 4 is a flow chart of an embodiment of step S06 .

[0027] Explanation of symbols:

[0028] 100: Magnetic pole detection circuit

[0029] 101: Back EMF Amplifier Circuit

[0030] 102: Hysteresis comparison circuit

[0031] 103: Digital to analog conversion circuit

[0032] 104: Low-pass filter circuit

[0033] 105:Multi-phase voltage divider circuit

[0034] 110:Multi-phase voltage division unit

[0035] 120: Filter unit

[0036] 130: DC level compensation unit

[0037] 140: Amplification unit

[0038] 150: Hysteresis comparison unit

[0039] 160: Motor controller

[0040] 200:Multi-phase motor

[0041] B1-B4: Block

[0042] TA-TC: control signal

[0043] TA'-TC': control signal

[0044] V1: Back EMF signal

[0045] V2: Filtered signal

[0046] V3: Compensation signal

[0047] V4: Amplify the signal

[0048] V5: Zero crossing point signal

[0049] V6: Actual back EMF voltage

[0050] V7: Back EMF after voltage division to simulate neutral point voltage

[0051] V8: Back EMF voltage to ground after voltage division

[0052] V9: voltage after back EMF filtering

[0053] V10: Zero crossing point signal

[0054] VU: Back EMF signal

[0055] VV: Back EMF signal

[0056] VW: Back EMF signal

[0057] Z1: Zero crossing point

[0058] S01-S06: Steps

[0059] S061-S063: Steps DETAILED DESCRIPTION

[0060] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, the following is a detailed description with reference to the accompanying drawings.

[0061] Figure 1 is a block diagram schematically showing an embodiment of a magnetic pole detection circuit and a multi-phase motor. Figure 2 is a schematic circuit diagram of an embodiment of a magnetic pole detection circuit for detecting a back electromotive force signal of a phase of a multi-phase motor, and Figure 5 The figure is a waveform diagram of the original back-EMF signal, the filtered signal, and the DC level compensation signal. Figure 1 , Figure 2 and Figure 5 The magnetic pole detection circuit 100 is applicable to a multi-phase motor 200. The multi-phase motor 200 is a brushless DC motor (BLDC motor), and the magnetic pole detection circuit 100 can be used to detect the magnetic pole position of the rotor in the multi-phase motor 200 to accurately control the rotation speed of the multi-phase motor 200.

[0062] In some embodiments, the multi-phase motor 200 may be, but is not limited to, a two-phase or three-phase motor. The following description will be made by taking the multi-phase motor 200 as a three-phase motor composed of three-phase coils as an example. The three-phase coils of the multi-phase motor 200 may be connected in a Y manner, such as Figure 2 However, the present invention is not limited thereto, and the three-phase coils of the multi-phase motor 200 may also be connected in a Δ manner.

[0063] In the first embodiment of the magnetic pole detection circuit 100, the magnetic pole detection circuit 100 includes a multi-phase voltage division unit 110, a filter unit 120, a DC level compensation unit 130, an amplifier unit 140, and a hysteresis comparison unit 150. The multi-phase voltage division unit 110 is coupled to the multi-phase motor 200, the filter unit 120 is coupled to the multi-phase voltage division unit 110, the amplifier unit 140 is coupled to the filter unit 120 and the DC level compensation unit 130, and the hysteresis comparison unit 150 is coupled to the amplifier unit 140 and the multi-phase motor 200.

[0064] The multi-phase voltage dividing unit 110 is used to detect the back electromotive force signal V1 of the multi-phase motor 200. The waveform of the back electromotive force signal V1 can be as follows: Figure 5 As shown. Figure 5In the figure, the horizontal axis is time, and its unit is milliseconds (ms); the vertical axis is voltage, and its unit is millivolts (mV). In some embodiments, the multi-phase voltage divider unit 110 may include the same number of voltage dividers as the number of phase coils of the multi-phase motor 200. For example, when the multi-phase motor 200 is a three-phase motor composed of three-phase coils, the multi-phase voltage divider unit 110 may include three groups of voltage dividers, such as Figure 2 Here, the three groups of dividers of the multi-phase voltage divider unit 110 correspond to one of the three-phase coils of the multi-phase motor 200, and the three groups of dividers can be respectively coupled to one end of the corresponding phase coil to obtain the back electromotive force signals VU, VV, and VW of the two adjacent phase coils in the three-phase coil after voltage division.

[0065] In some implementations, each group of dividers of the multi-phase voltage divider unit 110 may include two resistors connected in series, such as Figure 2 However, the present invention is not limited thereto, and the multi-phase voltage dividing unit 110 can also be implemented by a buck converter.

[0066] The filter unit 120 is used to filter the back electromotive force signal V1 obtained by the multi-phase voltage divider unit 110 to generate a filter signal V2. The filter signal V2 is the back electromotive force signal V1 after the switch switching noise is filtered out by the filter unit 120. For example, when the back electromotive force signal V1 currently detected by the multi-phase voltage divider unit 110 is the back electromotive force signal VU, the filter unit 120 can filter the switch switching noise on the back electromotive force signal VU to generate the filter signal V2. The waveform of the filter signal V2 can be as follows: Figure 5 As shown, it can be seen that compared with the back electromotive force signal V1, the phase of the filtered signal V2 is delayed.

[0067] In some embodiments, the filter unit 120 may be a low-pass filter. In addition, in practice, the filter unit 120 may be further provided together with the multi-phase voltage divider unit 110. For example, a filter capacitor is further provided in each group of dividers of the multi-phase voltage divider unit 110 to form an RC filter. Figure 2 As shown in block B2 in the figure, but the present invention is not limited thereto.

[0068] In some embodiments, the transfer function of the filtered signal V2 may be as shown in Equation 1 below.

[0069]

[0070] The DC level compensation unit 130 is used to compensate the DC level of the filtered signal V2 to generate a compensation signal V3. The compensation signal V3 is the back electromotive force signal V1 after filtering and DC level compensation. The waveform of the compensation signal V3 can be as follows: Figure 5As shown. It can be seen that the phase of the compensation signal V3 is substantially the same as the phase of the back electromotive force signal V1. Here, the DC level compensation unit 130 is mainly used to compensate for the signal phase delay caused by the filter unit 120 and the hysteresis comparison unit 150. In some embodiments, the DC level compensation unit 130 can change the DC level of the filter signal V2 in a dynamic compensation manner to solve the problem of phase lag. In some implementations, the DC level compensation unit 130 can be implemented using a digital-to-analog converter, but the present invention is not limited thereto.

[0071] In some embodiments, taking the phase t=0 as an example, the relationship between the compensation value of the DC level compensation unit 130 and the negative lower limit value of the hysteresis comparison width of the hysteresis comparison unit 150 can be as shown in the following formula 2. Wherein, DAC refers to the compensation value of the DC level compensation unit 130, and -VZONE refers to the negative lower limit value of the hysteresis comparison width.

[0072]

[0073] The amplifier unit 140 is used to amplify the amplitude of the compensation signal V3 to generate an amplified signal V4. The amplified signal V4 is the back electromotive force signal V1 after filtering, DC level compensation and amplitude amplification, and the recognition of its zero crossing point has been relatively improved. Here, the amplifier unit 140 is mainly used to compensate for the signal amplitude reduction caused by the filter unit 120 and improve the signal detectability at low speed.

[0074] In some embodiments, the amplifier unit 140 may have a positive input terminal, a negative input terminal, and an output terminal. The positive input terminal of the amplifier unit 140 is coupled to the filter unit 120 and the DC level compensation unit 130 to receive the compensation signal V3 generated after filtering and DC level compensation. The negative input terminal of the amplifier unit 140 may be coupled to its output terminal through a resistor. In addition, the amplifier unit 140 outputs the amplified signal V4 through its output terminal.

[0075] In some implementations, the amplifier unit 140 may be implemented using an operational amplifier, but the present invention is not limited thereto. Figure 2 As shown in block B3, but the present case is not limited to this.

[0076] The hysteresis comparison unit 150 is used to generate a zero-crossing point signal V5 according to the amplified signal V4 and the reference signal VREF. The zero-crossing point signal V5 generated by the hysteresis comparison can avoid signal bounce due to small switching noise. The waveform of the zero-crossing point signal V5 can be as follows: Figure 5As shown. It can be seen that when the compensation signal V3 reaches its hysteresis upper limit (e.g., +0.25mV) or its hysteresis lower limit (e.g., -0.25mV), the hysteresis comparison unit 150 will cause the output zero-crossing point signal V5 to transition. In addition, it can be seen that if the hysteresis comparison unit 150 generates a zero-crossing point signal based on the back electromotive force signal (i.e., the filtered signal V2) without DC compensation and the reference signal VREF, the zero-crossing point signal generated at this time will have a phase delay problem.

[0077] In some embodiments, Figure 2 As shown in block B4, the hysteresis comparison unit 150 may have a positive input terminal, a negative input terminal, and an output terminal. The positive input terminal of the hysteresis comparison unit 150 is coupled to the output terminal of the amplifier unit 140 to receive the amplified signal V4, and the positive input terminal of the hysteresis comparison unit 150 may be further coupled to its output terminal through a resistor. The negative input terminal of the hysteresis comparison unit 150 is used to receive the reference signal VREF. In addition, the hysteresis comparison unit 150 may perform hysteresis comparison based on the amplified signal V4 and the reference signal VREF and output a zero crossing point signal V5 at its output terminal.

[0078] In some implementations, the hysteresis comparison unit 150 may be implemented using an operational amplifier, but the present invention is not limited thereto. In addition, the reference signal VREF may be a fixed voltage, and its voltage value may be, for example but not limited to, 1 volt, 1.65 volt, etc.

[0079] In some embodiments, the magnetic pole detection circuit 100 further includes a motor controller 160. The motor controller 160 is coupled to the output terminal of the hysteresis comparison unit 150 and the multi-phase motor 200. The motor controller 160 is used to obtain the magnetic pole position of the rotor in the multi-phase motor 200 according to the zero-crossing point signal V5, and can control the excitation mode of the multi-phase motor 200 according to the zero-crossing point signal V5.

[0080] Figure 3 FIG. 1 is a schematic diagram of a circuit diagram of an embodiment of a motor controller and a multi-phase motor. Figures 1 to 3 In some implementations, a circuit implementation of the motor controller 160 and the multi-phase motor 200 may be as follows: Figure 3 As shown, the present invention is not limited thereto. Here, the motor controller 160 can be a three-phase inverter mainly composed of six transistors, and each transistor is controlled by a corresponding control signal TA, TA', TB, TB', TC, TC'. The levels of the control signals TA, TA', TB, TB', TC, TC can be changed accordingly according to the zero crossing point signal V5.

[0081] When the motor controller 160 detects the zero-crossing point signal V5, the motor controller 160 switches the excitation mode of the multi-phase motor 200 (i.e., excites the next phase coil). When the motor controller 160 does not detect the zero-crossing point signal V5, the motor controller 160 maintains the current excitation mode of the multi-phase motor 200. For example, assuming that the current levels of the control signals TA, TA', TB, TB', TC, and TC are logic "1", logic "0", logic "0", logic "1", logic "0", and logic "0", respectively, the motor controller 160 can switch the levels of the control signals TA, TA', TB, TB', TC, and TC to logic "1", logic "0", logic "0", logic "0", logic "0", and logic "1" respectively when the zero-crossing point signal V5 is detected to switch the excitation mode of the multi-phase motor 200. On the contrary, when the motor controller 160 does not detect the zero-crossing point signal V5 , the levels of the control signals TA, TA′, TB, TB′, TC, and TC maintain their original values.

[0082] Figure 4 FIG. 1 is a block diagram schematically showing a second embodiment of a magnetic pole detection circuit and a multi-phase motor. Figure 4 In the second embodiment of the magnetic pole detection circuit 100, the magnetic pole detection circuit 100 includes a back-EMF amplifier circuit 101 and a hysteresis comparison circuit 102, and the back-EMF amplifier circuit 101 is coupled to the hysteresis comparison circuit 102. In addition, the magnetic pole detection circuit 100 may further include a digital-to-analog conversion circuit 103, a low-pass filter circuit 104, a multi-phase voltage divider circuit 105, and a motor controller 160. The multi-phase voltage divider circuit 105 is coupled to the multi-phase motor 200, the low-pass filter circuit 104 is coupled to the multi-phase voltage divider circuit 105, the digital-to-analog conversion circuit 103 is coupled to the back-EMF amplifier circuit 101, and the hysteresis comparison circuit 102 is coupled to the motor controller 160.

[0083] The multi-phase voltage divider circuit 105 is used to detect the multi-phase motor 200 to generate a back EMF signal V1, and to perform voltage division filtering on the back EMF signal V1 caused by the PWM voltage driving the multi-phase motor 200. Here, the back EMF signal V1 still contains high-frequency switching noise after voltage division filtering.

[0084] The low-pass filter circuit 104 is used to receive the back electromotive force signal V1 output after voltage division filtering by the multi-phase voltage division circuit 105, and to perform low-pass filtering on the switch switching noise on the back electromotive force signal V1. Here, in order to avoid excessive phase delay, the low-pass filter circuit 104 does not completely filter out the switch switching noise on the back electromotive force signal V1. In addition, the back electromotive force signal V1 (i.e., the aforementioned filtered signal V2) after low-pass filtering by the low-pass filter circuit 104 will have the problem of amplitude reduction and phase lag. Moreover, because the filtered back electromotive force signal V1 still contains high-frequency switch switching noise, it is easy to cause the zero crossing point signal V5 to have a transition bounce problem. However, these problems can be solved by the components described later to generate a zero crossing point signal V5 that can be used to accurately control the speed of the multi-phase motor 200.

[0085] The digital-to-analog conversion circuit 103 is used to receive the back electromotive force signal V1 (i.e., the aforementioned filtered signal V2) outputted after low-pass filtering by the low-pass filtering circuit 104, and dynamically compensate the DC level of the back electromotive force signal V12 to compensate for the phase lag caused by the low-pass filtering circuit 104 and the hysteresis comparator circuit 102 described later.

[0086] The back-EMF amplifier circuit 101 is used to receive the back-EMF signal V1 (i.e., the aforementioned compensation signal V3) output after dynamic compensation by the digital-to-analog conversion circuit 103, and amplify the amplitude of the back-EMF signal V1 to compensate for the signal amplitude reduction caused by the low-pass filter circuit 104 and improve the signal detectability at low speed.

[0087] The hysteresis comparison circuit 102 is used to receive the reference signal VREF and the back electromotive force signal V1 after the back electromotive force amplifier circuit 101 has amplified its amplitude (i.e., the aforementioned amplified signal V4). The hysteresis comparison circuit 102 can perform hysteresis comparison on the reference signal VREF and the back electromotive force signal V1 after the amplification of its amplitude, and generate a zero crossing point signal V5 to the motor controller 160 according to the result of the hysteresis comparison. In this way, the zero crossing point signal V5 can be prevented from bouncing due to the small switching noise on the back electromotive force signal V1. Among them, although the hysteresis comparison circuit 102 will make the signal delay phenomenon more serious, this has been compensated by the aforementioned digital-to-analog conversion circuit 103.

[0088] In some embodiments, the circuit architecture of the back-electromotive force amplifier circuit 101 may be substantially the same as the preceding amplifier unit 130, the circuit architecture of the hysteresis comparison circuit 102 may be substantially the same as the preceding hysteresis comparison unit 140, the circuit architecture of the digital-to-analog conversion circuit 103 may be substantially the same as the preceding DC level compensation unit 130, the circuit architecture of the low-pass filter circuit 104 may be substantially the same as the preceding filter unit 120, and the circuit architecture of the multi-phase voltage divider circuit 105 may be substantially the same as the preceding multi-phase voltage divider unit 110, so the detailed implementation thereof will not be repeated here.

[0089] Figure 6 is a waveform diagram of the actual back-EMF voltage and the back-EMF after voltage division to simulate the neutral point voltage, and Figure 7 Schematic diagram of the waveform of the back-EMF voltage to ground after voltage division, the voltage after back-EMF filtering and the zero crossing point signal. In some embodiments, the waveform of the actual back-EMF voltage V6 and the back-EMF voltage to simulated neutral point voltage V7 after voltage division obtained by the magnetic pole detection circuit 100 according to one embodiment can be as follows: Figure 6 As shown, the waveforms of the back-EMF ground voltage V8 obtained after voltage division, the back-EMF filtered voltage V9 and the zero crossing point signal V10 can be shown as follows: Figure 7 As shown. The horizontal axis is time, the unit is milliseconds; the vertical axis is voltage, the unit is millivolts; and the dotted box is the zero crossing point Z1. Figure 6 As shown in the figure, between 16ms and 17ms, the actual back-EMF voltage V6 gradually decreases from -31mV to 0 as time increases. After voltage division, the back-EMF voltage V7 of the simulated neutral point voltage fluctuates between approximately 15mV and -30mV. Figure 7 As shown, between 16ms and 17ms, the back-EMF voltage V8 after voltage division jumps between about 0.3mV and 1.3mV. The back-EMF voltage V9 after filtering is about 1mV. The zero-crossing point signal V10 changes state at the zero-crossing point Z1.

[0090] In summary, the magnetic pole detection circuit 100 of the present invention can accurately control the speed of the multi-phase motor 200 through the zero crossing point signal V5 with the correct phase switching timing. In addition, since the magnetic pole detection circuit 100 of the present invention can correctly feedback the magnetic pole position at both high and low speeds, the multi-phase motor 200 can have a large torque output at both high and low speeds, thereby expanding the speed control range of the multi-phase motor 200. Furthermore, with the expansion of the speed control range of the multi-phase motor 200, the application range of the multi-phase motor 200 is also wider. For example, the multi-phase motor 200 controlled by the magnetic pole detection circuit 100 of the present invention can be applied to a continuous positive pressure breathing apparatus that needs to output high torque at low speed or an electric trimmer with a wide speed control range to provide different speeds in response to various cutting and sawing conditions.

[0091] The magnetic pole detection circuit 100 of any embodiment can execute the motor control method of any embodiment to accurately control the rotation speed of the multi-phase motor 200. The magnetic pole detection circuit 100 of the first embodiment is taken as an example for description. Figure 8 FIG. 1 is a flow chart of an embodiment of a motor control method. Figures 1 to 8 In one embodiment of the motor control method, the magnetic pole detection circuit 100 can use the multi-phase voltage divider unit 110 to detect the back electromotive force signal V1 of the multi-phase motor 200 (step S01). Afterwards, the magnetic pole detection circuit 100 uses the filter unit 120 to filter the back electromotive force signal V1 to generate a filter signal V2 (step S02). Next, the magnetic pole detection circuit 100 can use the DC level compensation unit 130 to compensate the DC level of the filter signal V2 to generate a compensation signal V3 (step S03), and use the amplifier unit 140 to amplify the amplitude of the compensation signal V3 to generate an amplified signal V4 (step S04). Afterwards, the magnetic pole detection circuit 100 can use the hysteresis comparison unit 150 to generate a zero crossing point signal V5 suitable for controlling the excitation mode of the multi-phase motor 200 according to the amplified signal V4 and the reference signal VREF (step S05).

[0092] In one embodiment of the motor control method, the magnetic pole detection circuit 100 can further utilize the motor controller 160 to control the excitation mode of the multi-phase motor 200 according to the zero crossing point signal V5 (step S06). Afterwards, the magnetic pole detection circuit 100 can return to step S01 to re-execute the motor control method.

[0093] Fig. 9 FIG. 5 is a flow chart of an embodiment of step S06. Figures 1 to 9 In one embodiment of step S06, the magnetic pole detection circuit 100 may use the motor controller 160 to detect the zero crossing signal V5 at the output end of the hysteresis comparison unit 150 (step S061). When the zero crossing signal V5 is detected, the magnetic pole detection circuit 100 may use the motor controller 160 to switch the excitation mode of the multi-phase motor 200 according to the level of the zero crossing signal V5 (step S062). When the zero crossing signal V5 is not detected, the magnetic pole detection circuit 100 uses the motor controller 160 to maintain the current excitation mode of the multi-phase motor 200 (step S063).

[0094] In summary, the magnetic pole detection circuit and motor control method of the embodiment of the present invention amplifies the amplitude of the back electromotive force signal through an amplification unit or a back electromotive force amplification circuit to improve the signal detectability at low speed and make it applicable to the low-speed operation of the motor, and uses a hysteresis comparison unit or a hysteresis comparison circuit to generate a zero crossing point signal according to the back electromotive force signal and a reference signal to avoid the transition bounce of the zero crossing point signal caused by tiny switch switching noise. In addition, the magnetic pole detection circuit and motor control method of the embodiment of the present invention changes the DC level of the back electromotive force signal through a DC level compensation unit or a digital analog converter to compensate for the signal phase delay. In this way, the magnetic pole detection circuit and motor control method of the embodiment of the present invention can accurately control the speed of the multi-phase motor through the zero crossing point signal with the correct phase switching timing. In addition, the magnetic pole detection circuit and motor control method of the embodiment of the present invention can correctly feedback the magnetic pole position at high and low speeds, so that the multi-phase motor can have a large torque output at high and low speeds, thereby expanding the speed control range of the multi-phase motor and its applicable range. Furthermore, the magnetic pole detection circuit and the motor control method of the present embodiment do not need to use a Hall sensor or a rotary encoder to detect the rotor magnetic pole position, thereby reducing the driver cost.

[0095] Although the technical contents of this case have been disclosed as above in the preferred embodiments, they are not used to limit this case. Any slight changes and modifications made by any technical personnel in this field without departing from the spirit of this case should be included in the scope of this case. Therefore, the protection scope of this case shall be determined by the definition of the attached claims.

Claims

1. A magnetic pole detection circuit, comprising: A multi-phase voltage dividing unit for detecting a back electromotive force signal of a multi-phase motor; a filtering unit, used for filtering the back electromotive force signal to generate a filtering signal; A DC level compensation unit, used for compensating the DC level of the filtered signal to generate a compensation signal; an amplifying unit, configured to amplify the compensation signal to generate an amplified signal; and a hysteresis comparison unit, for generating a zero-crossing point signal according to the amplified signal and a reference signal, wherein the zero-crossing point signal is suitable for controlling an excitation mode of the multi-phase motor; in, The DC level compensation unit is a digital-to-analog converter for dynamically compensating the DC level of the back electromotive force signal.

2. The magnetic pole detection circuit according to claim 1, It is characterized in that Also includes: A motor controller is used to control the excitation mode of the multi-phase motor according to the zero-crossing point signal.

3. The magnetic pole detection circuit according to claim 2, It is characterized in that The motor controller switches the excitation mode of the multi-phase motor when the zero-crossing point signal is detected, and maintains the excitation mode of the multi-phase motor when the zero-crossing point signal is not detected.

4. A motor control method, comprising: Detecting a back electromotive force signal of a multi-phase motor; filtering the back electromotive force signal to generate a filtered signal; compensating a DC level of the filtered signal to generate a compensation signal; amplifying the compensation signal to generate an amplified signal; and Generating a zero-crossing point signal according to the amplified signal and a reference signal, wherein the zero-crossing point signal is suitable for controlling an excitation mode of a multi-phase motor; in, The step of compensating the DC level of the back-EMF signal to generate the compensation signal is to dynamically compensate the DC level of the back-EMF signal by a digital-to-analog converter.

5. The motor control method according to claim 4, It is characterized in that Also includes: The excitation mode of the multi-phase motor is controlled according to the zero-crossing point signal.

6. The motor control method according to claim 5, It is characterized in that The step of controlling the excitation mode of the multi-phase motor according to the zero-crossing point signal comprises: detecting the zero crossing point signal; When the zero-crossing point signal is detected, switching the excitation mode of the multi-phase motor; and When the zero-crossing point signal is not detected, the excitation mode of the multi-phase motor is maintained.

7. A magnetic pole detection circuit, comprising: a back-EMF amplifier circuit for receiving a back-EMF signal of a multi-phase motor and amplifying the amplitude of the back-EMF signal; and a hysteresis comparison circuit for receiving a reference signal and the amplified back-electromotive force signal, the hysteresis comparison circuit for performing a hysteresis comparison between the reference signal and the amplified back-electromotive force signal to avoid signal bounce due to switching noise, and generating a zero-crossing point signal according to the result of the hysteresis comparison, wherein the zero-crossing point signal is suitable for controlling an excitation mode of the multi-phase motor; in, The digital-to-analog conversion circuit is used to receive the back-electromotive force signal and dynamically compensate the DC level of the back-electromotive force signal to avoid phase lag, wherein the back-electromotive force signal received by the back-electromotive force amplifier circuit is the back-electromotive force signal output after dynamic compensation by the digital-to-analog conversion circuit.

8. The magnetic pole detection circuit according to claim 7, It is characterized in that Also includes: A low-pass filter circuit is used to receive the back-electromotive force signal and perform low-pass filtering on the switch switching noise on the back-electromotive force signal, wherein the back-electromotive force signal received by the digital-to-analog conversion circuit is the back-electromotive force signal output after low-pass filtering by the low-pass filter circuit.

9. The magnetic pole detection circuit according to claim 8, It is characterized in that Also includes: A multi-phase voltage divider circuit is coupled to the multi-phase motor, and is used to detect the multi-phase motor to generate the back-electromotive force signal and perform voltage divider filtering on the switch switching noise on the back-electromotive force signal, wherein the back-electromotive force signal received by the low-pass filter circuit is the back-electromotive force signal output after voltage divider filtering by the multi-phase voltage divider circuit.

10. The magnetic pole detection circuit according to claim 7, It is characterized in that Also includes: A motor controller is used for receiving the zero-crossing point signal and controlling the excitation mode of the multi-phase motor according to the zero-crossing point signal.

11. The magnetic pole detection circuit according to claim 10, It is characterized in that The motor controller switches the excitation mode of the multi-phase motor when the zero-crossing point signal is detected, and maintains the excitation mode of the multi-phase motor when the zero-crossing point signal is not detected.

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