A brushless dc motor controller

Abstract

This invention discloses a brushless DC motor controller, comprising: a power supply module, a main control module, a drive circuit module, a back EMF zero-crossing detection circuit module, a current detection module, a voltage detection module, and a speed control module. The power supply module provides power to the main control module, drive circuit module, current detection module, voltage detection module, and speed control module. The main control module outputs a PWM signal, which is amplified by the drive circuit module to drive the brushless motor. The back EMF zero-crossing detection circuit module outputs the motor's back EMF zero-crossing signal to the main control module, calculates the motor's commutation control signal, and sends it to the drive circuit module, which then controls the brushless DC motor's commutation. The current detection module collects the DC bus current signal for overcurrent protection. The voltage detection module detects the DC bus voltage for overvoltage or undervoltage protection. The speed control module inputs a speed setting signal via a potentiometer and outputs it to the main control module to control the motor's speed adjustment. This brushless DC motor controller does not require a position sensor and has advantages such as small size, light weight, and high reliability.

Description

Technical Field

[0001] This invention relates to the field of motor controller technology, and specifically to a brushless DC motor controller. Background Technology

[0002] Brushless DC motors use electronic commutators instead of traditional carbon brushes, featuring low loss, high reliability, and precise control. They have significant advantages in efficiency, lifespan, noise, control precision, and safety, and are therefore widely used in various fields of production and daily life, such as household appliances like air conditioners, washing machines, and vacuum cleaners; electric vehicles like air conditioner compressors and electric power steering; as well as various power tools, medical equipment, and industrial automation.

[0003] The core of brushless DC motor control is commutation control, and the key to commutation control lies in the detection of rotor position. This can typically be achieved using position sensors, but these sensors require additional space and can reduce motor reliability and increase costs. Therefore, developing a small, lightweight, and highly reliable sensorless brushless DC motor controller is an urgent problem to be solved. Summary of the Invention

[0004] To address the problems mentioned above, this invention provides a brushless DC motor controller that fully utilizes the internal resources of the main control module's microcontroller and, in conjunction with simple peripheral circuitry, improves motor control performance while achieving sensorless control of the brushless DC motor and reducing costs.

[0005] This invention provides the following technical solution:

[0006] A brushless DC motor controller includes: a power supply module, a main control module, a drive circuit module, a back EMF zero-crossing detection circuit module, a current detection module, a voltage detection module, and a speed control module;

[0007] The power supply module is electrically connected to the main control module, drive circuit module, current detection module, voltage detection module and speed control module to provide power to them;

[0008] The main control module is connected to the drive circuit module, and the drive circuit module is connected to the three-phase winding of the brushless DC motor. The main control module outputs a PWM signal, which is amplified by the drive circuit module to drive the brushless motor to work.

[0009] The input terminal of the back EMF zero-crossing detection circuit module is connected to the output terminal of the three-phase winding of the brushless motor, and the output terminal is connected to the main control module. It outputs the back EMF zero-crossing signal of the motor and sends it to the main control module to calculate the commutation control signal of the motor and then sends it to the drive circuit module. The drive circuit module controls the brushless DC motor to perform commutation.

[0010] The input terminal of the current detection module is connected to the drive circuit module, and the output terminal is connected to the main control module. It is used to collect the DC bus current signal of the drive circuit and realize overcurrent protection.

[0011] The input terminal of the voltage detection module is connected to the power supply module, and the output terminal is connected to the main control module. It is used to detect the DC bus voltage and perform overvoltage or undervoltage protection.

[0012] The speed control module receives a speed setting signal via a potentiometer, and its output is connected to the main control module. The speed control signal is then sent to the main control module, which controls the motor to operate at a controlled speed.

[0013] The power module includes a 24V / 15V conversion submodule and a 15V / 5V conversion submodule.

[0014] The main control module uses an STC32G12K128 microcontroller.

[0015] The drive module includes a half-bridge drive chip and a MOSFET power transistor, and the half-bridge drive chip is connected to the motor through the MOSFET power transistor.

[0016] The back EMF zero-crossing detection circuit module includes a three-phase voltage divider circuit composed of resistors R35 to R40, a virtual neutral point reconstruction circuit composed of resistors R41 to R43, and a filter circuit composed of capacitors C16 to C18.

[0017] The first terminals of resistors R35 to R37 are connected to the output terminals a, b, and c of the three-phase windings of the motor, respectively. The second terminals of resistors R35 to R37 are connected to the first terminals of resistors R38 to R40, respectively. The second terminals of resistors R38 to R40 are all grounded. The second terminals of resistors R35 to R37 are connected to pins 24 (P5.0), 25 (P5.1), and 28 (P3.7) of the microcontroller, respectively. The first terminals of resistors R41 to R43 are connected to the first terminals of resistors R38 to R40, respectively. The second terminals of resistors R41 to R43 are connected together and then connected to pin 27 (P3.6) of the microcontroller. The first terminals of capacitors C16 to C18 are connected to the first terminals of resistors R38 to R40, respectively. The second terminals of capacitors C16 to C18 are all grounded.

[0018] The current detection module includes a two-stage operational amplifier.

[0019] The voltage detection module is a voltage divider filter circuit.

[0020] The speed control circuit is a potentiometer voltage regulation circuit.

[0021] The beneficial effects of this invention are as follows: This invention provides a brushless DC motor controller, comprising a power supply module, a main control module, a drive circuit module, a back EMF zero-crossing detection circuit module, a current detection module, a voltage detection module, and a speed control module. The main control module controls the motor rotation through the drive circuit module. The back EMF zero-crossing detection circuit module detects the three-phase winding back EMF zero-crossing signal by reconstructing a virtual neutral point detection circuit, sends it to the main control circuit, calculates the motor's commutation time and sequence, and controls the motor to commutate in an orderly manner. This eliminates the need for a position sensor, giving the controller advantages such as low cost, small size, and high reliability. During motor operation, overcurrent protection is achieved through the current detection module, and overvoltage or undervoltage protection is achieved through the voltage detection module, improving the motor's operational reliability. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0023] Figure 1 This is a block diagram of a brushless DC motor controller;

[0024] Figure 2 This is a diagram of the power module components;

[0025] Figure 3 This is the pin diagram of the STC32G12K128 microcontroller;

[0026] Figure 4 This is a diagram of the internal modules of the STC32G12K128 microcontroller.

[0027] Figure 5 This is the circuit diagram of the driver module;

[0028] Figure 6 This is a schematic diagram of the three-phase winding connection of the motor;

[0029] Figure 7 These are the three back electromotive forces and current waveforms of a brushless motor;

[0030] Figure 8 It is a back EMF zero-crossing detection circuit module;

[0031] Figure 9 This is a structural diagram of the selectable input comparator inside the microcontroller;

[0032] Figure 10 It is a current detection module;

[0033] Figure 11 It is a voltage detection module;

[0034] Figure 12 It is a speed control module circuit.

[0035] Figure 1 1 is the power supply module, 2 is the main control module, 3 is the drive circuit module, 4 is the back EMF zero-crossing detection circuit module, 5 is the current detection module, 6 is the voltage detection module, and 7 is the speed control module. Detailed Implementation

[0036] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0037] Brushless DC motor controllers with position sensors control the current commutation of the motor windings based on rotor position information provided by the sensor. While simple and accurate, the position sensor increases the controller's size, weight, and cost, and its susceptibility to damage affects the motor's reliable operation. Sensorless brushless DC motor controllers eliminate the position sensor, obtaining rotor position information from detectable electrical signals. These controllers offer advantages such as small size, light weight, low cost, and high reliability, making them a hot research topic for promoting brushless DC motor applications. This invention provides a sensorless brushless DC motor controller solution.

[0038] Figure 1 This is a block diagram of a sensorless brushless DC motor controller according to an embodiment of the present invention. The brushless DC motor controller includes: a power supply module, a main control module, a drive circuit module, a back EMF zero-crossing detection circuit module, a current detection module, a voltage detection module, and a speed control module.

[0039] The power supply module is electrically connected to the main control module, drive circuit module, current detection module, voltage detection module and speed control module to provide power to them;

[0040] The main control module is connected to the drive circuit module, and the drive circuit module is connected to the three-phase winding of the brushless DC motor. The main control module outputs a PWM signal, which is amplified by the drive circuit module to drive the brushless DC motor to work.

[0041] The input terminal of the back EMF zero-crossing detection circuit module is connected to the output terminal of the three-phase winding of the brushless motor, and the output terminal is connected to the main control module. It outputs the back EMF zero-crossing signal of the motor and sends it to the main control module. The main control module calculates the commutation control signal of the motor and sends it to the drive circuit module. The drive circuit module controls the commutation of the brushless DC motor.

[0042] The power supply circuit includes a 24V / 15V conversion submodule and a 15V / 5V conversion submodule, as shown in the power module diagram. Figure 2 As shown.

[0043] The main control module uses an STC32G12K128 microcontroller. The pinout of the STC32G12K128 microcontroller is as follows: Figure 3 As shown, it includes 48 pins and internally comprises a CPU, PWM generator, ADC analog-to-digital converter, and CMP comparator module. The internal module diagram of the STC32G12K128 microcontroller is shown below. Figure 4 As shown.

[0044] The drive module circuit is as follows Figure 5 As shown, it includes a half-bridge driver chip U2 and MOSFET power transistors Q1 and Q2. The input of the half-bridge driver chip is connected to the PWM generator of the microcontroller, and the output of the half-bridge driver chip is connected to the motor through the MOSFET power transistors.

[0045] Specifically, in this invention, the drive module uses three half-bridge drive chips U2 with output interlock dead zones, and three sets of MOSFET power transistors Q1 and Q2 to form three half-bridge circuits. The three half-bridge circuits actually form a three-phase full-bridge circuit, which drives the motor to perform commutation.

[0046] The brushless DC motor includes a three-phase winding, which is Y-connected with the neutral point connected inside the motor. A schematic diagram of the three-phase winding wiring is shown below. Figure 6 As shown, a, b, and c are the output terminals of the three-phase winding.

[0047] The key to commutation in a brushless motor lies in the detection of the rotor position, which can be determined by analyzing the back EMF waveforms of the three windings. The three-way back EMF and current waveforms of a brushless motor are shown below. Figure 7 As shown in the figure, e a e b e c These are three back electromotive forces, i a i b i c The brushless DC motor is driven by a three-phase full-bridge circuit, using a two-phase conduction method. At any given time, only two phase windings are conducting, while the third phase winding is not. During normal operation, a back electromotive force (EMF) directly related to the rotor position is generated at the ends of the non-conducting phase windings. Specifically, when the rotor poles pass the neutral point of that phase winding, the back EMF crosses zero. After detecting the zero-crossing point of the non-conducting back EMF, and delaying by 30° electrical angle, that phase can be commutated and become conductive. Therefore, by detecting the zero-crossing point of the back EMF of the non-conducting phase, the conduction sequence of each phase winding can be determined. The conduction angle of each phase winding is 120° electrical angle. Furthermore, with... Figure 7 Taking the zero-crossing point of the back electromotive force of phase b as an example, at this time, phase b is not conducting, while phases a and c are conducting. a =-i c ib =0, after the opposite electromotive force of b crosses zero and is delayed by 30° electrical angle, commutation is performed, so that phase a is disconnected and phase b is connected. In this way, the commutation of the three-phase winding can be performed, so that the motor rotates smoothly.

[0048] Because the stator windings of a brushless DC motor are Y-connected, and the neutral point of the three-phase windings is connected inside the motor, it is inconvenient to measure the voltage of individual phases. Only the terminal voltages of each phase (i.e., the phase-to-ground voltages) can be measured and then compared with the neutral point-to-ground voltage. A zero-crossing point is identified when the terminal voltage changes from being greater than the neutral point voltage to being less than the neutral point voltage, or vice versa. However, since there are no external leads for the neutral point, its voltage is also inconvenient to measure. To solve the problem of back EMF measurement, a back EMF zero-crossing detection circuit can be designed, using a method of reconstructing a virtual neutral point to detect the back EMF zero-crossing point of each phase winding.

[0049] The back EMF zero-crossing detection circuit module is as follows: Figure 8 As shown, the circuit includes a three-phase voltage divider circuit composed of resistors R35 to R40, a virtual neutral point reconstruction circuit composed of resistors R41 to R43, and a filter circuit composed of capacitors C16 to C18. The first terminals of R35 to R37 are connected to the output terminals a, b, and c of the three-phase windings of the motor, respectively. The second terminals of R35 to R37 are connected to the first terminals of R38 to R40, respectively. The second terminals of R38 to R40 are all grounded. The divided voltage value of the three-phase voltage can be obtained from the second terminals of R35 to R37. This divided voltage value is reduced to a level that the microcontroller can withstand and can be directly sent to the microcontroller's pin input terminals. The second terminals of R35 to R37 are marked as EMFA. Points EMFB and EMFC are connected to pins 24 (P5.0), 25 (P5.1), and 28 (P3.7) of the microcontroller, respectively. The first terminals of resistors R41 to R43 are connected to the first terminals of resistors R38 to R40, respectively. The second terminals of resistors R41 to R43 are connected together to form a virtual neutral point, i.e., the zero-crossing point of the back EMF, marked as CMP-point. CMP-point is connected to pin 27 (P3.6) of the microcontroller. The first terminals of capacitors C16 to C18 are connected to the first terminals of resistors R38 to R40, respectively. The second terminals of capacitors C16 to C18 are all grounded to form a filter circuit.

[0050] The STC32G12K128 microcontroller contains an optional input comparator, the structure of which is as follows: Figure 9 As shown, the comparator has three selectable input pins at its positive input terminal: P5.0, P5.1, and P3.7, and one input pin at its inverting input terminal: P3.6. The microcontroller's internal selectable input comparator is used to... Figure 8By comparing the voltages at EMFA, EMFB, and EMFC points with the voltage at CMP- point in turn, the zero-crossing point of the back EMF of each phase can be detected, thereby calculating the commutation position of each phase and realizing position detection technology without position sensors.

[0051] The input terminal of the current detection module is connected to the motor, and the output terminal is connected to the ADC module of the microcontroller, specifically to pins P0.0 and P3.5 of the microcontroller. This allows it to receive the bus current signal collected by the current detection module, thus achieving overcurrent protection. The current detection module is described as follows: Figure 10 As shown, a two-stage operational amplifier configuration of U6A and U6B is used. U6A adjusts the bus current to a voltage that can be measured by the microcontroller, while U6B is used for fast PWM protection against abnormal current values.

[0052] The input terminal of the voltage detection module is connected to the power supply, and the output terminal is connected to the ADC module of the main control module and then to the P0.1 pin of the microcontroller for detecting the DC bus voltage. The voltage detection module is as follows: Figure 11 As shown, a voltage divider filter circuit is used to adjust the bus voltage to a voltage that can be measured by a microcontroller, and to provide overvoltage or undervoltage protection.

[0053] The speed control module receives a speed setting signal via a potentiometer and sends this signal to the main control module, which then controls the motor to adjust its speed. The speed control module circuit is as follows: Figure 12 As shown, this is a potentiometer voltage adjustment circuit. The input terminal is connected to a 5V power supply, and the output terminal is connected to the ADC module of the main control module and then to the P0.3 pin of the microcontroller. The main control module adjusts the duty cycle of the PWM module output according to the signal sent by the speed control circuit, thereby controlling the motor speed.

[0054] The beneficial effects of this invention are as follows: This invention provides a brushless DC motor controller, comprising a power supply module, a main control module, a drive circuit module, a back EMF zero-crossing detection circuit module, a current detection module, a voltage detection module, and a speed control module. The main control module controls the motor rotation through the drive module. The back EMF zero-crossing detection circuit module detects the back EMF zero-crossing signal of the three-phase windings by reconstructing a virtual neutral point. The microcontroller calculates the commutation time and sequence of the motor, controlling the motor to commutate in an orderly manner. This eliminates the need for a position sensor and offers advantages such as low cost and small size. During motor operation, the current detection module collects current and provides overcurrent protection, while the voltage detection module collects voltage and provides overvoltage and undervoltage protection, improving the reliability of the motor.

Claims

1. A brushless DC motor controller, characterized by include: Power supply module, main control module, drive circuit module, back EMF zero-crossing detection circuit module, current detection module, voltage detection module, and speed control module; The power supply module is electrically connected to the main control module, drive circuit module, current detection module, voltage detection module and speed control module to provide power to them; The main control module is connected to the drive circuit module, and the drive circuit module is connected to the three-phase winding of the brushless DC motor. The main control module outputs a PWM signal, which is amplified by the drive circuit module to drive the brushless motor to work. The input terminal of the back EMF zero-crossing detection circuit module is connected to the output terminal of the three-phase winding of the brushless motor, and the output terminal is connected to the main control module. It outputs the back EMF zero-crossing signal of the motor and sends it to the main control module to calculate the commutation control signal of the motor and then sends it to the drive circuit module. The drive circuit module controls the brushless DC motor to perform commutation. The input terminal of the current detection module is connected to the drive circuit module, and the output terminal is connected to the main control module. It is used to collect the DC bus current signal of the drive circuit and realize overcurrent protection. The input terminal of the voltage detection module is connected to the power supply module, and the output terminal is connected to the main control module. It is used to detect the DC bus voltage and perform overvoltage or undervoltage protection. The speed control module receives a speed setting signal via a potentiometer, and its output is connected to the main control module. The speed control signal is then sent to the main control module, which controls the motor to operate at a controlled speed.

2. The brushless DC motor controller of claim 1, wherein: The power module includes a 24V / 15V conversion submodule and a 15V / 5V conversion submodule.

3. The brushless DC motor controller of claim 1, wherein: The main control module uses an STC32G12K128 microcontroller.

4. The brushless DC motor controller of claim 1, wherein: The drive module includes a half-bridge drive chip and a MOSFET power transistor, and the half-bridge drive chip is connected to the motor through the MOSFET power transistor.

5. The brushless DC motor controller according to claim 1, characterized in that: The back EMF zero-crossing detection circuit module includes a three-phase voltage divider circuit composed of resistors R35 to R40, a virtual neutral point reconstruction circuit composed of resistors R41 to R43, and a filter circuit composed of capacitors C16 to C18. The first terminals of resistors R35 to R37 are connected to the output terminals a, b, and c of the three-phase windings of the motor, respectively. The second terminals of resistors R35 to R37 are connected to the first terminals of resistors R38 to R40, respectively. The second terminals of resistors R38 to R40 are all grounded. The second terminals of resistors R35 to R37 are connected to pins 24 (P5.0), 25 (P5.1), and 28 (P3.7) of the microcontroller, respectively. The first terminals of resistors R41 to R43 are connected to the first terminals of resistors R38 to R40, respectively. The second terminals of resistors R41 to R43 are connected together and then connected to pin 27 (P3.6) of the microcontroller. The first terminals of capacitors C16 to C18 are connected to the first terminals of resistors R38 to R40, respectively. The second terminals of capacitors C16 to C18 are all grounded.

6. The brushless DC motor controller according to claim 1, characterized in that: The current detection module includes a two-stage operational amplifier.

7. The brushless DC motor controller according to claim 1, characterized in that: The voltage detection module is a voltage divider filter circuit.

8. The brushless DC motor controller according to claim 1, characterized in that: The speed control circuit is a potentiometer voltage regulation circuit.

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