A remote speed regulation circuit, speed regulation chip and speed regulation method for a single-phase brushless DC motor

Abstract

The application discloses a remote speed regulation circuit, a speed regulation chip and a speed regulation method for a single-phase brushless direct-current motor, and relates to the technical field of brushless direct-current motors. The remote speed regulation circuit comprises a rectification and filtering unit, which is used for converting alternating current into high-voltage direct current; an adjustable constant-voltage and constant-current circuit, an input end of which is connected with an output end of the rectification and filtering unit, and an output end of which is used for connecting the single-phase brushless direct-current motor and converting the high-voltage direct current into direct current with controllable output voltage or output current to drive the motor; and a low-voltage stabilizing unit, an input end of which is connected with an output end of the adjustable constant-voltage and constant-current circuit; the remote control circuit and a single-chip computer (MCU) are both powered by the low-voltage stabilizing unit, the MCU generates a speed regulation signal according to a remote control instruction, and the adjustable constant-voltage and constant-current circuit adjusts output electrical parameters according to the speed regulation signal to change the rotating speed of the motor. The application avoids the periodic acceleration and deceleration problem of chopper speed regulation, realizes smooth operation of the motor, and reduces vibration and noise.

Description

Technical Field

[0001] This application relates to the field of brushless DC motor technology, and in particular to a remote control speed regulation circuit, speed regulation chip and speed regulation method for a single-phase brushless DC motor. Background Technology

[0002] With intelligentization, miniaturization, and high efficiency becoming the development trend of modern fan products (including electric fans, exhaust fans, and fan lights), brushless DC motors are gradually replacing traditional AC motors as the core power component. Compared to three-phase brushless DC motors, single-phase brushless DC motors have only one winding, making winding simple. The Hall electronic commutator is highly integrated with the motor body, resulting in low cost and an efficiency of up to 80%. Moreover, its drive circuit only needs to provide a stable output voltage or output current to operate, making it very suitable for fan applications where high speed accuracy is not required.

[0003] Currently, the speed control scheme for single-phase brushless DC motors mainly adopts PWM chopper speed control. Specifically, when the PWM pulse signal is high, the switching transistor is turned on, and the motor draws electrical energy from the AC / DC constant voltage circuit to accelerate; when the PWM pulse signal is low, the switching transistor is turned off, the motor loses power supply, and the rotor and blades decelerate due to inertia. The motor alternates between acceleration and deceleration during the speed control process, and does not operate at a constant speed.

[0004] However, in existing PWM chopper speed control solutions, the motor is constantly in a periodic, non-uniform speed operation state, alternating between acceleration and deceleration. This results in significant motor vibration, poor operational stability, and high noise, severely impacting user experience, and the motor's operating efficiency is not optimal. Furthermore, these defects become more pronounced as the motor power increases. In low-power applications (e.g., below 5W), the performance of this speed control solution is acceptable; however, in medium-to-high-power applications (e.g., above 8W), the higher the power, the greater the vibration, the less stable the operation, and the more prominent the noise, making it unacceptable to the market. Therefore, in fields such as high-power electric fans and fan lights, this solution cannot practically meet product requirements, leading to the replacement of single-phase brushless DC motors with three-phase brushless DC motors in these areas. Summary of the Invention

[0005] The purpose of this application is to provide a remote control speed regulation circuit, speed regulation chip and speed regulation method for a single-phase brushless DC motor, which can realize stable, low noise and high efficiency remote control speed regulation of single-phase brushless DC motor in medium and high power application scenarios.

[0006] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a remote speed control circuit for a single-phase brushless DC motor, comprising: AC input port, used for connecting to the AC power grid; A rectifier and filter unit, connected to the AC input port, is used to convert AC power into high-voltage DC power; An adjustable constant voltage and constant current circuit is provided, with its input terminal connected to the output terminal of the rectifier and filter unit. The output terminal of the adjustable constant voltage and constant current circuit is used to connect to a single-phase brushless DC motor. The adjustable constant voltage and constant current circuit is used to convert the high-voltage DC power into DC power with a controllable and adjustable output voltage or output current to drive the single-phase brushless DC motor. The low-voltage regulator unit has its input terminal connected to the output terminal of the adjustable constant voltage and constant current circuit, and is used to output a stable low-voltage operating voltage. The remote control circuit, powered by the low-voltage regulator unit, is used to receive external remote control commands and output the remote control commands. The single-chip microcomputer (MCU) is powered by the low-voltage regulator unit and connected to the remote control circuit. It is used to receive the remote control command and generate a speed control signal according to the remote control command. A motor start / stop switch transistor is connected in series between the output terminal of the adjustable constant voltage and constant current circuit and the single-phase brushless DC motor; the control terminal of the motor start / stop switch transistor is connected to the single-chip microcomputer MCU, and is used to control the start and stop of the single-phase brushless DC motor according to the control signal output by the single-chip microcomputer MCU. The adjustable constant voltage and constant current circuit has a speed regulation signal input terminal, which is connected to the speed regulation signal output terminal of the single-chip microcomputer MCU. The adjustable constant voltage and constant current circuit adjusts the output voltage or output current according to the speed regulation signal to change the speed of the single-phase brushless DC motor.

[0007] Secondly, this application provides a remote speed control chip for a single-phase brushless DC motor, wherein the remote speed control chip is a flyback control chip, a first buck control chip, or a second buck control chip. When the remote control speed regulation chip is a flyback control chip, it includes: a speed regulation signal input port for receiving a speed regulation signal with a variable duty cycle from a single-chip microcomputer MCU; a reference ground port for connecting to the reference ground of the single-chip microcomputer MCU; a pulse drive signal output port for outputting a pulse switching signal with a variable duty cycle to control the conduction and cutoff of an external power switch; a current sampling input port for receiving a current feedback signal; a voltage sampling input port for receiving an output voltage feedback signal; and a duty cycle decoding unit for multiplying the duty cycle information D of the speed regulation signal with an internal reference voltage and then filtering to obtain a speed regulation DC voltage. The remote control speed regulation chip sends the speed regulation DC voltage to a constant voltage error amplifier or a constant current error amplifier inside the chip to adjust the output voltage or output current of the chip, thereby achieving stepless speed regulation. The chip also includes a current error amplifier and a constant voltage error amplifier. When constant voltage speed regulation is used, the current error amplifier only performs peak current limiting protection; when constant current speed regulation is used, the constant voltage error amplifier only performs peak voltage limiting protection. When the remote control speed regulation chip is a first buck control chip, the first buck control chip is used in a first buck-type adjustable constant voltage and constant current circuit, including: a power supply terminal for receiving an external power supply voltage, the power supply terminal being coupled to the speed regulation signal output terminal of a single-chip microcomputer MCU through a level conversion circuit; a first decoder for detecting voltage changes at the power supply terminal to obtain the encoding information of the speed regulation signal and decoding the encoding information; a gear register connected to the first decoder for storing current gear information; a digital-to-analog converter module for converting the gear digital signal stored in the gear register into a corresponding DC reference voltage and sending it to an error amplifier; a power logic drive circuit for generating a variable duty cycle drive signal to control the conduction and cutoff of an external buck power switch; and an undervoltage reset unit for resetting all digital circuits within the chip when the power supply voltage is lower than a threshold. The first decoder outputs a reset signal or a shift signal to the gear register according to the encoding information of the speed regulation signal to switch the gear in the gear register, thereby changing the output voltage or output current of the chip to achieve limited gear speed regulation. When the remote control speed regulation chip is a second buck control chip, the second buck control chip is used in a second buck-type adjustable constant voltage and constant current circuit, including: a power supply terminal for receiving external power supply voltage; a speed regulation signal input terminal for directly receiving speed regulation signals from a single-chip microcomputer MCU; a second decoder for directly detecting level changes of the speed regulation signal to obtain the encoding information of the speed regulation signal and decoding the encoding information; a gear register connected to the second decoder for storing current gear information; a digital-to-analog conversion module for converting the gear digital signal stored in the gear register into a corresponding DC reference voltage and sending it to an error amplifier; a power logic drive circuit for generating a variable duty cycle drive signal to control the conduction and cutoff of an external buck power switch; and an undervoltage reset unit for resetting all digital circuits in the chip when the power supply voltage is lower than a threshold. The decoder outputs a reset signal or a shift signal to the gear register according to the encoding information of the speed regulation signal to switch the gear in the gear register, thereby changing the output voltage or output current of the chip to achieve limited gear speed regulation.

[0008] Thirdly, this application provides a remote speed control method for a single-phase brushless DC motor, applied to the remote speed control circuit for a single-phase brushless DC motor described above, comprising: The remote control circuit receives external remote control commands and transmits the remote control commands to a single-chip microcomputer (MCU). The single-chip microcomputer (MCU) generates a speed control signal according to the remote control command. The adjustable constant voltage and constant current circuit adjusts the output voltage or output current according to the speed control signal to change the electrical parameters output to the single-phase brushless DC motor. The single-phase brushless DC motor operates at a speed corresponding to the magnitude of the output voltage or output current. When the adjustable constant voltage and constant current circuit is a flyback adjustable constant voltage and constant current circuit, the single-chip microcomputer MCU generates a pulse signal with a variable duty cycle as the speed regulation signal. The flyback control chip multiplies the duty cycle information D of the speed regulation signal with the internal reference voltage and then filters it to obtain the speed regulation DC voltage, which is then sent to the internal constant voltage error amplifier or constant current error amplifier to control the output voltage or output current. When the adjustable constant voltage and constant current circuit is a first step-down adjustable constant voltage and constant current circuit, the single-chip microcomputer (MCU) generates an encoded pulse signal as the speed control signal. The speed control signal is coupled to the power supply terminal of the first step-down control chip through a level conversion circuit. The first step-down control chip detects the encoded information of the speed control signal according to the voltage change at the power supply terminal. When the high-level duration of the speed control signal is detected to be greater than a first preset time, the internal gear register is reset to the default gear. When the high-level duration of the speed control signal is detected to be less than the first preset time, the gear of the internal gear register is switched according to the cyclic shifting rule, and the gear digital signal stored in the gear register is converted into a corresponding DC reference voltage to control the output voltage or output current. When the adjustable constant voltage and constant current circuit is the second step-down adjustable constant voltage and constant current circuit, the single-chip microcomputer MCU generates an encoded pulse signal as the speed control signal. The motor start / stop switch and the second step-down control chip both directly receive the speed control signal. When the speed control signal is detected to be low for a duration greater than the second preset time, the internal gear register is reset to the default gear. When the speed control signal is detected to be low for a duration less than the second preset time, the gear in the internal gear register is switched according to the cyclic shifting rule, and the gear digital signal stored in the gear register is converted into a corresponding DC reference voltage to control the output voltage or output current.

[0009] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a remote control speed regulation circuit, speed regulation chip, and speed regulation method for a single-phase brushless DC motor. This application receives a speed regulation signal from a single-chip microcomputer (MCU) through an adjustable constant voltage and constant current circuit, and adjusts the output voltage or current according to the speed regulation signal, enabling the single-phase brushless DC motor to obtain a continuous and stable power supply. Compared to existing technologies that use PWM chopping speed regulation, which causes periodic acceleration and deceleration of the motor and generates vibration and noise, this application avoids periodic fluctuations in motor speed by directly adjusting the voltage or current supplied to the motor. This ensures that the motor operates at a constant speed during speed regulation, significantly reducing vibration and operating noise, making it particularly suitable for fan-related applications (such as electric fans, exhaust fans, and fan lights) where noise and stability requirements are high. This application includes a low-voltage regulator unit, whose input is connected to the output of the adjustable constant voltage and constant current circuit, providing a stable low-voltage operating voltage to power both the remote control circuit and the MCU. Because the low-voltage regulator unit draws power from the output of the adjustable constant voltage and constant current circuit, the circuit does not need to be shut down in standby mode. The low-voltage regulator unit continuously provides operating voltage to the remote control circuit and the MCU, ensuring the remote control circuit remains in standby mode and can respond to external remote control commands at any time, providing a user experience of instant power-on and instant speed adjustment. Simultaneously, this low-voltage regulator unit independently powers the control section, allowing the output of the adjustable constant voltage and constant current circuit to be flexibly adjusted to different voltages or currents to adapt to different speed requirements, without being limited by the power supply requirements of the control chip. This application includes a motor start / stop switch transistor connected in series between the output of the adjustable constant voltage and constant current circuit and the single-phase brushless DC motor. Its control terminal is connected to a single-chip microcomputer (MCU), and the control signal output by the MCU independently controls the start and stop of the motor. The switching transistor allows the motor's start and stop to be independent of the output state of the adjustable constant voltage and constant current circuit. Even if the adjustable constant voltage and constant current circuit is always in operation (to maintain the standby power supply for the remote control circuit and MCU), the motor power supply circuit can be reliably cut off through this switching transistor, achieving a balance between low standby power consumption and high response speed, while also improving system safety and control flexibility. The circuit architecture defined in this application consists of an AC input port, a rectifier and filter unit, an adjustable constant voltage and constant current circuit, a low-voltage regulator unit, a remote control circuit, an MCU, and a motor start / stop switching transistor. Each functional module has a clear division of labor and a clear connection relationship. Compared to three-phase brushless DC motor drive solutions that require three-phase windings and a 32-bit high-performance MCU, this application only requires a single-phase winding and a low-cost MCU to achieve remote speed control, significantly reducing system costs while ensuring speed control performance. This makes it suitable for large-scale application in cost-sensitive household appliances such as electric fans, exhaust fans, and fan lights. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 A schematic diagram of the principle of a single-phase brushless DC motor drive circuit using PWM chopper speed regulation in the prior art, provided as an embodiment of this application; Figure 2 A schematic diagram of a system architecture for a remote control speed regulation circuit for a single-phase brushless DC motor, provided as an embodiment of this application; Figure 3 A schematic diagram of the principle of a flyback adjustable constant voltage and constant current circuit provided in an embodiment of this application; Figure 4 A schematic diagram of the principle of a first step-down adjustable constant voltage and constant current circuit (ADJ and ON / OFF separate mode) provided in an embodiment of this application; Figure 5 Provided for an embodiment of this application Figure 4 The diagram shows the encoding and decoding timing sequence of the step-down adjustable constant voltage and constant current circuit. Figure 6 The embodiment provided in this application corresponds to Figure 4 The diagram shows the internal module of the step-down control chip in the circuit shown. Figure 7 A schematic diagram of the principle of a second step-down adjustable constant voltage and constant current circuit (ADJ and ON / OFF combined into one) provided in an embodiment of this application; Figure 8 Provided for an embodiment of this application Figure 7 The diagram shows the encoding and decoding timing sequence of the step-down adjustable constant voltage and constant current circuit. Figure 9 The embodiment provided in this application corresponds to Figure 7 The diagram shows the internal functional module block diagram of the step-down control chip in the circuit shown. Figure 10 This is a schematic diagram of a closed-loop speed control system provided in an embodiment of this application.

[0012] Figure reference numerals: AC / DC constant voltage circuit -100, control switch -101, rectifier bridge -102, low voltage regulator unit -103, remote control circuit -104, single-phase brushless DC motor -105, motor start / stop switch transistor -106, high voltage filter capacitor -107, output filter capacitor -108, single-chip microcomputer MCU -120, adjustable constant voltage and constant current circuit -200, primary-side power switch transistor -211, flyback transformer -212, rectifier diode -213, first sampling resistor -214, second sampling resistor -215, first current feedback resistor -216, buck power switch transistor -221, output filter inductor -222, freewheeling diode -223, third sampling resistor -224, fourth sampling resistor -225, second current feedback resistor -226, power supply resistor -227, power supply capacitor -228, high voltage... NPN transistor-229, current limiting resistor-231, flyback control chip-310, internal multiplier module-311, error amplifier-312, logic circuit-313, first buck control chip-320, gear register-322, first decoder-321, digital-to-analog converter module-323, error amplifier-324, power logic drive circuit-325, undervoltage reset module-326, second buck control chip-330, second decoder-331, speed control signal-ADJ, adjustable constant voltage and constant current circuit output node-CVCI, pulse switch signal-DRV, system reference ground-GND, buck control chip reference ground-GNDIC, high voltage DC node-HV, current sampling signal-IFB, power on / off signal-ON / OFF, power supply voltage-VDD, output voltage feedback signal-VFB. Detailed Implementation

[0013] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0014] Powered by the AC grid, the most advanced modern electric fans, exhaust fans, and fan lights are characterized by their intelligence (remote control, voice control), miniaturization, and high efficiency, with brushless DC motors as their core power source. Compared to traditional AC motors, brushless DC motors are significantly smaller, more efficient, and easier to adjust in speed.

[0015] The key component of a brushless DC motor is the electronic commutator. The advent of an electronic commutator with Hall effect sensors in 1962 marked the birth of the modern brushless DC motor. However, brushless DC motors didn't truly enter the practical application stage until the 1980s. With advancements in modern semiconductor technology, the cost of brushless DC motors has continuously decreased, while their performance has become increasingly powerful, leading to their wider and more extensive applications. For example, brushless DC motors drive new energy electric vehicles, power drones, and are the core power components within the various moving joints of humanoid robots. Brushless DC motors are mainly divided into two categories: three-phase brushless DC motors and single-phase brushless DC motors.

[0016] The electric vehicles, drones, and humanoid robots mentioned earlier all use three-phase brushless DC motors. These applications place high demands on motor speed and motion control. Like three-phase AC motors, three-phase brushless DC motors have three-phase windings. The difference lies in their wiring: AC three-phase motors are directly connected to a three-phase AC power grid, while the three-phase windings of a three-phase brushless DC motor are connected to a three-phase electronic commutator controlled by an MCU. Three-phase brushless DC motors are not inexpensive, both in terms of the motor itself and the three-phase electronic commutator composed of a 32-bit MCU.

[0017] The 105 single-phase brushless DC motor has only one winding, making winding simple. The Hall effect electronic commutator is highly integrated with the motor body, resulting in low cost. It does not require precise speed control and can achieve an efficiency of up to 80%. Its drive circuit only needs to provide a stable output voltage or current, making it inexpensive and compatible with global AC power grids. It is suitable for applications where high speed accuracy is not required.

[0018] Electric fans, exhaust fans, and fan lights do not require high speed precision, so theoretically, using a low-cost single-phase brushless DC motor 105 to replace an AC motor would be very suitable. However, the reality is different. In low-power applications below 5W, the single-phase brushless DC motor 105 does dominate. Specifically, traditional exhaust fans are single-speed and do not require speed adjustment, so regardless of power, there is no dispute that the single-phase brushless DC motor 105 can replace an AC motor. However, in the electric fan and fan light sector, applications above 8W are currently dominated by three-phase brushless DC motors, with the single-phase brushless DC motor 105's market share being negligible. The main reason for this is that three-phase brushless DC motors inherently have extremely easy speed adjustment capabilities. Because they use a 32-bit MCU with powerful computing support and highly intelligent drive algorithms, remote speed control is effortless, and functions such as reversal and braking can be easily implemented. In contrast, the single-phase brushless DC motor 105's remote speed control methods are much less sophisticated. In low-power applications below 5W, a simple and direct chopper speed control method can be used, such as... Figure 1 As shown, its performance is acceptable. The so-called chopper speed control works as follows: when the PWM pulse signal is high, the NMOS switch 106 is turned on, and the motor draws power from the AC / DC constant voltage circuit 100 to accelerate; when the PWM pulse signal is low, the NMOS switch 106 is turned off, the motor has no power supply, and the rotor, carrying the blades, decelerates due to inertia; the motor is in a state of alternating acceleration and deceleration, not uniform speed operation, and its reliability and efficiency are not optimal. Therefore, in applications above 8W, the shortcomings of the simple and crude chopper speed control become apparent: the higher the power, the greater the motor speed control vibration, the more unstable the operation, and the greater the noise, making it unacceptable to the market. This is the main reason why the single-phase brushless DC motor 105 is inferior to the three-phase brushless DC motor. This application aims to solve the problem of difficult remote control speed regulation of the single-phase brushless DC motor 105.

[0019] In the field of modern fans, exhaust fans, and fan lights powered by AC mains electricity, the speed regulation of existing single-phase brushless DC motors 105 is mainly based on chopper speed regulation, suitable for micro fans with a power consumption of less than 5W. As mentioned earlier: Figure 1 This type of chopper-controlled motor operates cyclically, accelerating and decelerating intermittently, rather than at a constant speed. Consequently, its reliability and efficiency are not optimal. The industry needs a high-performance, high-efficiency, and low-cost remote speed control circuit system for single-phase brushless DC motors (105) suitable for medium to high-power applications.

[0020] In theory, the optimal speed control method for a single-phase brushless DC motor 105 is to adjust its operating voltage or current, thus achieving smooth speed control. In other words, as long as the remote control circuit 104 can control the output voltage or current of the AC / DC constant voltage and constant current circuit, smooth speed control of the single-phase brushless DC motor 105 can be achieved. This application proposes... Figure 2In the process, after receiving the speed control command, the remote control circuit 104 sends a single data stream to the MCU 120. The MCU 120 then decodes the data into a speed control signal ADJ that can be recognized by the AC / DC adjustable constant voltage and constant current circuit. The speed control signal ADJ can directly control the output voltage or output current of the AC / DC adjustable constant voltage and constant current circuit, thus achieving speed control of the motor 105. During the speed control process, the NMOS switch 106 remains in the ON state. The most basic function of the NMOS switch 106 is to turn the motor on / off; that is, when the NMOS switch 106 is turned off, the motor is turned off. The motor can also be turned off by shutting down the AC / DC adjustable constant voltage and constant current circuit. However, since the remote control circuit 104 and the MCU 120 are both powered by the AC / DC adjustable constant voltage and constant current circuit, the 5V power supply 103 must maintain a 5V output voltage during standby. Therefore, the AC / DC adjustable constant voltage and constant current circuit must never be turned off, which is why the NMOS switch 106 must be retained.

[0021] Existing technology uses PWM chopper speed control, which is not the optimal speed control method for a single-phase brushless DC motor 105. This application proposes a new remote control speed control system suitable for remote speed control of medium-to-high power single-phase brushless DC motor 105.

[0022] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] In one exemplary embodiment, such as Figure 2 As shown, a remote control speed regulation circuit for a single-phase brushless DC motor 105 is provided, including: an AC input port, a rectifier and filter unit, an adjustable constant voltage and constant current circuit 200, a low voltage regulator unit 103, a remote control circuit 104, a single-chip microcomputer MCU 120, and a motor start / stop switch transistor 106.

[0024] The AC input port is used to connect to the AC power grid.

[0025] A rectifier and filter unit, connected to the AC input port, is used to convert AC power into high-voltage DC power.

[0026] An adjustable constant voltage and constant current circuit 200 is provided, with its input terminal connected to the output terminal of the rectifier and filter unit. The output terminal of the adjustable constant voltage and constant current circuit 200 is used to connect to a single-phase brushless DC motor 105. The adjustable constant voltage and constant current circuit 200 is used to convert the high-voltage DC power into DC power with a controllable and adjustable output voltage or output current to drive the single-phase brushless DC motor 105.

[0027] The low-voltage regulator unit 103 has its input terminal connected to the output terminal of the adjustable constant voltage and constant current circuit 200, and is used to output a stable low-voltage operating voltage.

[0028] The remote control circuit 104, powered by the low-voltage regulator unit 103, is used to receive external remote control commands and output the remote control commands.

[0029] The single-chip computer MCU120 is powered by the low-voltage regulator unit 103 and connected to the remote control circuit 104. It is used to receive the remote control command and generate a speed adjustment signal according to the remote control command.

[0030] The motor start / stop switch 106 is connected in series between the output terminal of the adjustable constant voltage and constant current circuit 200 and the single-phase brushless DC motor 105; the control terminal of the motor start / stop switch 106 is connected to the single-chip microcomputer MCU 120 and is used to control the start and stop of the single-phase brushless DC motor 105 according to the control signal output by the single-chip microcomputer MCU 120.

[0031] The adjustable constant voltage and constant current circuit 200 has a speed regulation signal input terminal, which is connected to the speed regulation signal output terminal of the single-chip computer MCU 120. The adjustable constant voltage and constant current circuit 200 adjusts the output voltage or output current according to the speed regulation signal to change the speed of the single-phase brushless DC motor 105.

[0032] This embodiment receives speed control signals from the single-chip microcomputer MCU 120 through an adjustable constant voltage and constant current circuit 200, and adjusts its output voltage or current according to the speed control signal, so that the single-phase brushless DC motor 105 obtains a continuous and stable power supply. Compared with the existing technology that uses PWM chopping speed control, which causes the motor to periodically accelerate and decelerate, resulting in vibration and noise, this embodiment avoids the periodic fluctuation of the motor speed by directly adjusting the voltage or current supplied to the motor, so that the motor always runs at a constant speed during the speed regulation process, significantly reducing vibration and operating noise. It is especially suitable for fan-type applications (such as electric fans, exhaust fans, and fan lights) with high requirements for noise and stability. This embodiment sets up a low-voltage regulator unit 103, whose input terminal is connected to the output terminal of the adjustable constant voltage and constant current circuit 200, and outputs a stable low-voltage operating voltage to power the remote control circuit 104 and the single-chip microcomputer MCU 120. Since the low-voltage regulator unit 103 draws power from the output of the adjustable constant voltage and constant current circuit 200, the adjustable constant voltage and constant current circuit 200 does not need to be turned off in standby mode. The low-voltage regulator unit 103 continuously provides operating voltage to the remote control circuit 104 and the MCU, ensuring that the remote control circuit 104 remains in standby mode and can respond to external remote control commands at any time, providing a user experience of instant power-on and instant speed adjustment. Simultaneously, the low-voltage regulator unit 103 independently supplies power to the control section, allowing the output of the adjustable constant voltage and constant current circuit 200 to be flexibly adjusted to different voltages or currents to adapt to different speed requirements without being limited by the power supply requirements of the control chip. This embodiment includes a motor start / stop switch 106, connected in series between the output of the adjustable constant voltage and constant current circuit 200 and the single-phase brushless DC motor 105. Its control terminal is connected to the single-chip microcomputer MCU 120, and the control signal output by the MCU independently controls the start and stop of the motor. The switching transistor allows the motor's start and stop to be independent of the output state of the adjustable constant voltage and constant current circuit 200. Even if the adjustable constant voltage and constant current circuit 200 is always in operation (to maintain the standby power supply of the remote control circuit 104 and the MCU), the motor power supply circuit can be reliably cut off through this switching transistor, achieving a balance between low standby power consumption and high response speed, while also improving system safety and control flexibility. The circuit architecture defined in this embodiment consists of an AC input port, a rectifier and filter unit, an adjustable constant voltage and constant current circuit 200, a low-voltage regulator unit 103, a remote control circuit 104, an MCU, and a motor start / stop switching transistor 106. Each functional module has a clear division of labor and a clear connection relationship. Compared to a three-phase brushless DC motor drive scheme that requires three-phase windings and a 32-bit high-performance MCU, this embodiment only requires a single-phase winding and a low-cost MCU to achieve remote speed control. While ensuring speed control performance, it significantly reduces system costs and is suitable for large-scale application in cost-sensitive household appliances such as electric fans, exhaust fans, and fan lights.

[0033] In another exemplary embodiment of this application, the adjustable constant voltage and constant current circuit 200 is a flyback adjustable constant voltage and constant current circuit 200.

[0034] The flyback adjustable constant voltage and constant current circuit 200 includes: a flyback transformer 212, a flyback control chip 310, and a primary-side power switch 211; there is no electrical isolation between the primary-side coil and the secondary-side coil of the flyback transformer 212, and the reference ground of the flyback control chip 310 is connected to the reference ground of the single-chip computer MCU 120.

[0035] The speed control signal is directly input to the speed control signal input terminal of the flyback control chip 310. The flyback control chip 310 adjusts the output voltage or output current of the flyback adjustable constant voltage and constant current circuit 200 according to the duty cycle information of the speed control signal, so as to realize the stepless speed regulation of the single-phase brushless DC motor 105.

[0036] One end of the primary winding of the flyback transformer 212 is connected to the high-voltage DC node, and the other end is connected to the drain of the primary power switch 211. The source of the primary power switch 211 is connected to the system reference ground through a first current feedback resistor 216. The voltage across the first current feedback resistor 216 is sent to the flyback control chip 310 as a current sampling signal. The flyback control chip 310 outputs a pulse switching signal with a variable duty cycle to the gate of the primary power switch 211 to control the charging and discharging of the flyback transformer 212.

[0037] One end of the secondary coil of the flyback transformer 212 is connected to the positive terminal of the rectifier diode 213, and the negative terminal of the rectifier diode 213 is connected to the output node. The output node is connected to the other end of the secondary coil through the output filter capacitor 108, and the other end of the secondary coil is connected to the system reference ground. The first current feedback resistor 216 has both primary coil charging current detection and secondary coil discharging current feedback functions: when the primary power switch 211 is turned on, the first current feedback resistor 216 collects the primary coil charging current; when the primary power switch 211 is turned off, the first current feedback resistor 216 collects the secondary coil discharging current and uses it as a feedback signal for constant current control.

[0038] In another exemplary embodiment of this application, the flyback adjustable constant voltage and constant current circuit 200 further includes an output voltage sampling circuit.

[0039] The output voltage sampling circuit is composed of a first sampling resistor 214 and a second sampling resistor 215 connected in series. One end of the first sampling resistor 214 is connected to the connection node between the secondary coil and the positive terminal of the rectifier diode 213. The other end of the first sampling resistor 214 is connected to one end of the second sampling resistor 215, and this connection node provides an output voltage feedback signal to the flyback control chip 310. The other end of the second sampling resistor 215 is connected to the system reference ground.

[0040] The flyback control chip 310 sends the speed regulation signal to its internal multiplication module 311 to obtain a speed regulation DC voltage, the product of the duty cycle information D of the speed regulation signal and the internal reference voltage. This speed regulation DC voltage is then sent to the constant voltage error amplifier VEA or constant current error amplifier IEA 312 within the flyback control chip 310. When constant voltage speed regulation is used, the current loop within the flyback control chip 310 only performs peak current limiting protection; when constant current speed regulation is used, the voltage loop within the flyback control chip 310 only performs peak voltage limiting protection. The result from the error amplifier 312 is then sent to the logic circuit 313 within the chip 310, which outputs a pulse switching signal with a variable duty cycle to the gate of the primary-side power switch 211 to control the charging and discharging of the flyback transformer 212.

[0041] In another exemplary embodiment of this application, the adjustable constant voltage and constant current circuit 200 is a first buck adjustable constant voltage and constant current circuit 200.

[0042] The first step-down adjustable constant voltage and constant current circuit 200 includes: a first step-down control chip 320, a step-down power switch 221, and an output filter inductor 222; the reference ground of the first step-down control chip 320 is independent of the reference ground of the single-chip computer MCU 120.

[0043] The speed control signal is connected to the power supply terminal of the first buck control chip 320 through a level conversion circuit. The first buck control chip 320 detects the encoding information of the speed control signal according to the voltage change of the power supply terminal, and switches the gear of the internal gear register 322 according to the encoding information to change the output voltage or output current of the buck adjustable constant voltage and constant current circuit 200, thereby realizing the limited gear speed regulation of the single-phase brushless DC motor 105.

[0044] The drain of the buck power switch 221 is connected to the high-voltage DC node, and the source of the buck power switch 221 is connected to one end of the second current feedback resistor 226 and the negative terminal of the freewheeling diode 223. The positive terminal of the freewheeling diode 223 is connected to the system reference ground GND of the single-chip computer MCU120, and the other end of the second current feedback resistor 226 is connected to the reference ground node of the first buck control chip 320. One end of the output filter inductor 222 is connected to the reference ground node of the first buck control chip 320, and the other end is connected to the output node. The output filter inductor 222 operates in current critical mode, that is, when the inductor discharge current drops to zero, a new charging cycle is immediately started.

[0045] In another exemplary embodiment of this application, the level shifting circuit includes a high-voltage NPN transistor 229 and a current-limiting resistor 231.

[0046] The collector of the high-voltage NPN transistor 229 is connected to the power supply terminal of the first buck control chip 320, the base of the high-voltage NPN transistor 229 is connected to the speed control signal, and the emitter of the high-voltage NPN transistor 229 is connected to the system reference ground GND through the current limiting resistor 231. The power supply terminal of the first buck control chip 320 is also connected to the high-voltage DC node through a start-up resistor, and a power supply capacitor 228 is connected between the power supply terminal and the reference ground of the first buck control chip 320.

[0047] When the speed control signal is high, the high-voltage NPN transistor 229 is turned on, the power supply capacitor 228 is discharged, the voltage at the power supply terminal is pulled down to below the first threshold, and the first buck control chip 320 stops working; when the speed control signal is low, the high-voltage NPN transistor 229 is turned off, the power supply capacitor 228 is charged through the power supply resistor 227, and when the voltage at the power supply terminal rises to above the second threshold, the first buck control chip 320 resumes working.

[0048] In another exemplary embodiment of this application, the first buck control chip 320 internally includes a first decoder 321, a gear register 322, and a digital-to-analog converter module 323.

[0049] The first decoder 321 is used to convert the gear position digital signal stored in the gear position register 322 into a corresponding DC reference voltage through the digital-to-analog converter module 323 and send it to the error amplifier 324. The error amplifier 324 amplifies the difference between the DC reference voltage and the output current feedback signal or the output voltage feedback signal and outputs it to the power logic drive circuit 325. The power logic drive circuit 325 generates a drive signal with a variable duty cycle to control the conduction and cutoff of the buck power switch 221.

[0050] When the duration of the high level of the speed control signal is greater than the first preset time, the first decoder 321 outputs a reset signal to the gear register 322, causing the gear register 322 to return to the default gear. When the duration of the high level of the speed control signal is less than the first preset time, after the speed control signal changes from high level to low level and the voltage at the power supply terminal rises above the second threshold, the first decoder 321 outputs a shift signal to the gear register 322, causing the gear register 322 to switch gears according to the cyclic shifting rule.

[0051] In another exemplary embodiment of this application, the first buck adjustable constant voltage and constant current circuit 200 further includes an output voltage sampling circuit.

[0052] The output voltage sampling circuit is composed of a third sampling resistor 224 and a fourth sampling resistor 225 connected in series. One end of the third sampling resistor 224 is connected to the output node, and the other end of the third sampling resistor 224 is connected to one end of the fourth sampling resistor 225. This connection node provides an output voltage feedback signal to the first buck control chip 320. The other end of the fourth sampling resistor 225 is connected to the reference ground node of the first buck control chip 320.

[0053] The first buck control chip 320 also includes an undervoltage reset module 326; the undervoltage reset module 326 is connected to the power supply terminal, and when the voltage of the power supply terminal is lower than the third threshold, the undervoltage reset module 326 resets all digital circuits inside the first buck control chip 320, including the gear register 322.

[0054] In another exemplary embodiment of this application, the adjustable constant voltage and constant current circuit 200 is a second step-down adjustable constant voltage and constant current circuit 200, including a second step-down control chip 330, a step-down power switch 221, and an output filter inductor 222; the control terminal of the motor start-stop switch 106 is not connected to the single-chip microcomputer MCU 120 by a separate power on / off signal; the control terminal of the motor start-stop switch 106 is directly connected to the speed control signal, and the conduction and cutoff of the motor start-stop switch 106 are controlled by the speed control signal. The power on / off function and the speed control function share the same signal line. When the speed control signal is low, the motor start-stop switch 106 is cut off, and the single-phase brushless DC motor 105 stops working. If a constant voltage and current limiting control strategy is adopted, the second step-down control chip 330 enters a light load hiccup mode; if a constant current and voltage limiting control strategy is adopted, the second step-down control chip 330 enters a voltage limiting protection mode. When the duration of the low level of the speed control signal is greater than the second preset time, the second buck control chip 330 resets the internal gear register 322 to the default gear; when the duration of the low level of the speed control signal is less than the second preset time, the second buck control chip 330 switches the gear of the internal gear register 322 according to the rule of cyclically changing the speed gear.

[0055] In another exemplary embodiment of this application, a remote control speed control chip for a single-phase brushless DC motor 105 is provided, wherein the remote control speed control chip is a flyback control chip 310, a first buck control chip 320, or a second buck control chip 330.

[0056] When the remote control speed regulation chip is a flyback control chip 310, it includes: a speed regulation signal input port for receiving a speed regulation signal with a variable duty cycle from a single-chip microcomputer MCU120; a reference ground port for connecting to the reference ground of the single-chip microcomputer MCU120; a pulse drive signal output port for outputting a pulse switching signal with a variable duty cycle to control the conduction and cutoff of an external power switch; a current sampling input port for receiving a current feedback signal; a voltage sampling input port for receiving an output voltage feedback signal; and a duty cycle decoding unit for multiplying the duty cycle information D of the speed regulation signal with an internal reference voltage and then filtering to obtain a speed regulation DC voltage. The remote control speed regulation chip sends the speed regulation DC voltage to a constant voltage error amplifier or a constant current error amplifier inside the chip to adjust the output voltage or output current of the chip, thereby achieving stepless speed regulation. The chip also includes a current error amplifier VEA and a constant voltage error amplifier IEA 312. When constant voltage speed regulation is used, the current error amplifier IEA only performs peak current limiting protection; when constant current speed regulation is used, the constant voltage error amplifier VEA... It only provides peak voltage limiting protection. The result of the error amplifier 312 is then sent to the logic circuit 313 inside the chip 310, which outputs a pulse switching signal with a variable duty cycle to the gate of the primary-side power switch 211 to control the charging and discharging of the flyback transformer 212.

[0057] When the remote control speed regulation chip is a first step-down control chip 320, the first step-down control chip 320 is used in a first step-down adjustable constant voltage and constant current circuit 200, including: a power supply terminal for receiving an external power supply voltage, the power supply terminal being coupled to the speed regulation signal output terminal of a single-chip computer MCU120 through a level conversion circuit; a first decoder 321 for detecting voltage changes at the power supply terminal to obtain the encoded information of the speed regulation signal and decoding the encoded information; a gear register 322 connected to the first decoder 321 for storing the current gear information; and a digital-to-analog conversion module 323 for converting the gear register... The gear position digital signal stored in register 322 is converted into a corresponding DC reference voltage and sent to error amplifier 324; power logic drive circuit 325 is used to generate a drive signal with a variable duty cycle to control the conduction and cutoff of external step-down power switch 221; undervoltage reset unit is used to reset all digital circuits in the chip when the supply voltage is lower than the threshold; the first decoder 321 outputs a reset signal or shift signal to the gear position register 322 according to the encoding information of the speed regulation signal to switch the gear position of the gear position register 322, thereby changing the output voltage or output current of the chip to realize limited gear speed regulation.

[0058] When the remote control speed adjustment chip is the second buck control chip 330, the second buck control chip 330 is used in the second buck-type adjustable constant voltage and constant current circuit 200, including: a power supply terminal for receiving external power supply voltage; a speed adjustment signal input terminal for directly receiving speed adjustment signals from the single-chip computer MCU120; a second decoder 331 for directly detecting the level change of the speed adjustment signal to obtain the encoded information of the speed adjustment signal and decoding the encoded information; a gear register 322 connected to the second decoder 331 for storing the current gear information; and a digital-to-analog conversion module 323 for converting the gear register... The gear position digital signal stored in register 322 is converted into a corresponding DC reference voltage and sent to error amplifier 324; power logic drive circuit 325 is used to generate a drive signal with a variable duty cycle to control the conduction and cutoff of external step-down power switch 221; undervoltage reset unit is used to reset all digital circuits in the chip when the supply voltage is lower than the threshold; the second decoder 331 outputs a reset signal or shift signal to the gear position register 322 according to the encoding information of the speed regulation signal, so as to switch the gear position of the gear position register 322, thereby changing the output voltage or output current of the chip to realize limited gear speed regulation.

[0059] In another exemplary embodiment of this application, a remote speed control method for a single-phase brushless DC motor 105 is provided, applied to the remote speed control circuit for the single-phase brushless DC motor 105 described above, comprising: S1. The remote control circuit 104 receives external remote control commands and transmits the remote control commands to the single-chip computer MCU 120.

[0060] S2. The single-chip computer MCU120 generates a speed adjustment signal according to the remote control command.

[0061] S3. The adjustable constant voltage and constant current circuit 200 adjusts the output voltage or output current according to the speed regulation signal to change the electrical parameters output to the single-phase brushless DC motor 105.

[0062] S4. The single-phase brushless DC motor 105 operates at a speed corresponding to the magnitude of the output voltage or output current.

[0063] S5. When the adjustable constant voltage and constant current circuit 200 is a flyback adjustable constant voltage and constant current circuit 200, the single-chip computer MCU120 generates a pulse signal with a variable duty cycle as the speed regulation signal. The flyback control chip 310 multiplies the duty cycle information D of the speed regulation signal with the internal reference voltage and then filters it to obtain the speed regulation DC voltage, and sends it to the internal constant voltage error amplifier or constant current error amplifier 312 to control the output voltage or output current. The result of the error amplifier 312 is then sent to the logic circuit 313 inside the chip 310, and outputs a pulse switching signal with a variable duty cycle to the gate of the primary side power switch 211 to control the charging and discharging of the flyback transformer 212.

[0064] When the adjustable constant voltage and constant current circuit 200 is a first step-down adjustable constant voltage and constant current circuit 200, the single-chip computer MCU 120 generates an encoded pulse signal as the speed control signal. The speed control signal is coupled to the power supply terminal of the first step-down control chip 320 through a level conversion circuit. The first step-down control chip 320 detects the encoded information of the speed control signal according to the voltage change of the power supply terminal. When the high-level duration of the speed control signal is detected to be greater than a first preset time, the internal gear register 322 is reset to the default gear. When the high-level duration of the speed control signal is detected to be less than the first preset time, the gear of the internal gear register 322 is switched according to the cyclic shifting rule, and the gear digital signal stored in the gear register 322 is converted into a corresponding DC reference voltage to control the output voltage or output current. When the adjustable constant voltage and constant current circuit 200 is the second step-down adjustable constant voltage and constant current circuit 200, the single-chip computer MCU 120 generates an encoded pulse signal as the speed control signal. The motor start / stop switch 106 and the second step-down control chip 330 both directly receive the speed control signal. When the speed control signal is detected to be low for a duration greater than the second preset time, the internal gear register 322 is reset to the default gear. When the speed control signal is detected to be low for a duration less than the second preset time, the gear of the internal gear register 322 is switched according to the cyclic shifting rule, and the gear digital signal stored in the gear register 322 is converted into a corresponding DC reference voltage to control the output voltage or output current.

[0065] In this embodiment, the rule for cyclically changing the speed gear is to take the default first gear as the initial gear, and take three speed gears as an example, to cycle through the gears in the order of first gear, second gear, third gear, and first gear.

[0066] In this application, the "adjustable constant voltage and constant current circuit" is the core functional module connecting the rectifier and filter unit and the single-phase brushless DC motor. It is used to convert high-voltage DC power into DC power with a controllable and adjustable output voltage or current to drive the motor. In this application, the adjustable constant voltage and constant current circuit provides three parallel implementation methods: the first is a flyback adjustable constant voltage and constant current circuit (e.g., Figure 3 As shown), it uses a flyback transformer as the energy conversion element. There is no electrical isolation between the primary and secondary coils. The reference ground of the flyback control chip is connected to the reference ground of the single-chip microcomputer MCU. The speed control signal is directly input to the flyback control chip. The flyback control chip adjusts the output voltage or output current according to the duty cycle information of the speed control signal, which can realize stepless speed regulation of a single-phase brushless DC motor. It is suitable for application scenarios with high speed regulation accuracy requirements. The second type is the first step-down adjustable constant voltage and constant current circuit (such as...). Figure 4 As shown), it adopts a non-isolated buck circuit architecture. The reference ground of the first buck control chip is independent of the reference ground of the MCU. The speed control signal is coupled to the power supply terminal of the first buck control chip through a level conversion circuit composed of a high-voltage NPN transistor and a current-limiting resistor. The first buck control chip obtains the encoded information of the speed control signal by detecting the voltage change at the power supply terminal, and switches the gear of the internal gear register accordingly to achieve limited gear speed regulation. This method adopts a two-wire communication strategy with ADJ and ON / OFF separated, making the control more flexible; the third type is a second buck adjustable constant voltage and constant current circuit (such as Figure 6 As shown in the diagram, it also adopts a non-isolated buck circuit architecture. The reference ground of the second buck control chip is independent of the reference ground of the MCU. However, unlike the first buck type, this method eliminates the level conversion circuit. The control terminal of the motor start / stop switch is directly connected to the speed control signal. ADJ and ON / OFF are combined into one, and the power-on and speed control functions share the same signal line. The second buck control chip directly detects the level change of the speed control signal and switches the gear accordingly. The circuit structure is simpler and suitable for applications with extremely high space requirements. All three methods are based on the same core inventive concept—receiving the speed control signal from the single-chip microcomputer MCU through an adjustable constant voltage and constant current circuit and adjusting the output voltage or output current accordingly to achieve smooth remote speed control of a single-phase brushless DC motor. Each of the three methods is suitable for different application needs and can be implemented individually.

[0067] Specifically, in this application Figure 1 It is an existing technology that uses PWM chopper speed control, which results in large vibrations and noise, and is only used in low-power scenarios, such as less than 5W.

[0068] For the application of single-phase brushless DC motor 105 in medium and high power scenarios, this application proposes a new remote control speed regulation system, namely... Figure 2This system features high performance (low vibration, low noise) and low cost. Alternating current passes through control switch 101 and enters rectifier bridge 102 for rectification. High-voltage filter capacitor 107 then filters the current, generating high-voltage direct current (HV) with an amplitude of several hundred volts. The constant voltage / constant current circuit 200 is a high-efficiency switching power supply circuit. Its input is the high-voltage HV, and its output is a stable voltage CVCI (CV stands for constant voltage, CI for constant current) filtered by a large-capacity output capacitor 108. To match medium-to-high power single-phase DC motor applications, the CVCI voltage operates within a range of 5V to 30V. Figure 2 The control brain is a single-chip microcomputer MCU120. A low-cost 5V linear power supply 103 (with its input connected to the CVCI node) provides a stable 5V operating voltage with a small current to the MCU120 and the remote control circuit 104. After the system is powered on normally, the MCU120 receives remote control commands from the remote control circuit 104. The MCU120 then generates two output signals according to its internal software algorithm: one is an ON / OFF signal, which is sent to the gate of the NMOS switch 106 to control the motor 105 to turn on or off; the other is a speed control signal ADJ sent to the constant voltage and constant current circuit 200. The speed control signal ADJ can directly control the output voltage or output current of the constant voltage and constant current circuit 200. The remote control circuit 104 can take several forms: 1. Infrared remote control, which has the lowest cost but requires no obstacles in the middle and has structural requirements; 2. 433MHz radio frequency remote control, which has a slightly higher cost but can bypass obstacles; 3. 2.4GHz remote control, which can be networked and can also bypass obstacles; 4. Voice control, which may become a standard configuration in the future; 5. Network control, including artificial intelligence control, etc.

[0069] The focus of this application is how to construct Figure 2 The present invention pertains to an AC / DC adjustable constant voltage and constant current circuit. In fact, high-performance adjustable constant voltage and constant current power supplies have long existed in industry, characterized by several features: 1. High power (from over 100 watts to several kilowatts); 2. High cost, employing an isolation structure, with primary and secondary sides optocoupler isolation or magnetic isolation, using high-precision external voltage and current references, and high-precision external operational amplifier circuits. Currently, the industry lacks a professional, low-cost, remote-controlled adjustable constant voltage and constant current circuit 200 suitable for ordinary fans using single-phase brushless DC motors 105. The fan field covered in this application (including ordinary electric fans, exhaust fans, and fan lights) has relatively low power, with the vast majority (e.g., 95%) below 50 watts, making them sensitive to cost and space constraints, especially exhaust fans. Therefore, this application aims to propose a new high-performance, but much lower-cost, constant voltage and constant current circuit.

[0070] In the power range below 50 watts, the constant voltage and constant current circuit 200 has two basic switching power supply circuit structure implementations: one is a flyback structure; the other is a non-isolated buck structure. In terms of space, the former is significantly smaller than the latter, which can use surface-mount I-type inductors, due to the size limitation of the flyback transformer 212. Similarly, the latter has a greater cost advantage. However, the former is not without its merits; its biggest advantage is that its core control chip and MCU 120 use the same reference ground, namely the negative output terminal GND of the rectifier 102, allowing the speed control signal ADJ to be directly interconnected. In contrast, the latter's core control chip uses a completely different reference ground than the MCU 120, making the interconnection of the speed control signal ADJ very difficult. Since both structures have their advantages and disadvantages, this application will describe them separately.

[0071] Let's first discuss the implementation method of constant voltage and constant current 200: flyback structure, such as... Figure 3As shown. One of its significant features is the flyback transformer 212. Another significant feature is that the primary and secondary coils are directly electrically connected without electrical isolation. There are two main reasons for this lack of electrical isolation between the primary and secondary sides: 1. In fan applications, the load is a motor, which is not exposed and poses no risk of electric shock, so electrical isolation between the primary and secondary sides is unnecessary; 2. Cost. Without electrical isolation, the secondary circuit does not require any optical or magnetic isolation components, nor does it need a high-precision external voltage reference, high-precision current reference, or high-precision external operational amplifier circuit, greatly simplifying the secondary circuit. Simultaneously, the control logic of the primary-side flyback adjustable constant voltage and constant current chip 310 is also simplified, improving system reliability. The primary-side circuit adopts a conventional structure: one end of the primary-side coil is connected to the high-voltage HV node, and the other end is connected to the drain of the power switch 211. The source of the switch 211 is connected to GND through resistor 216. The voltage IFB at the end of resistor 216 is used as a sampling signal for the primary-side coil current and sent to chip 310. Chip 310 outputs a pulse switching signal DRV with a variable duty cycle and sends it to the gate of the switch 211. When DRV is high, the switch 211 is turned on and the flyback transformer 212 is charged. When DRV is low, the switch 211 is turned off and the flyback transformer 212 is discharged. When the output signal DRV of chip 310 is high, NMOS power transistor 211 is turned on, charging the primary winding of flyback transformer 212. At this time, no current flows through the secondary winding. When the output signal DRV of chip 310 is low, power transistor 211 is turned off, and the magnetic field energy stored in the primary winding is discharged through the secondary winding to the load. Rectifier diode 213 only allows unidirectional current flow in the secondary winding. Capacitor 108 is a large-capacity, low-voltage (typically, the operating voltage of a DC motor is below 30V) filter capacitor. It is important to emphasize that the discharge current of the secondary winding first flows through rectifier diode 213, then through filter capacitor 108, motor 105, and switch 106, before converging at node IFB. Finally, it returns to the system reference ground, which is the other end of the secondary winding, via current sampling feedback resistor 216. The current sampling feedback signal IFB directly reflects the discharge current information of the secondary winding, with completely consistent phase information. This greatly simplifies the design of the constant current control system of chip 310. It should be noted that the current sampling signal IFB consists of two parts: When the power switch 211 changes from the on state to the off state, the IFB signal reflects the discharge current of the secondary winding coil. At this time, the IFB signal should be sent to the current error amplifier 324IEA for integration. When the power switch 211 changes from the off state to the on state, the IFB signal reflects the charging current of the primary winding coil. At this time, the IFB signal cannot be sent to the current error amplifier 324IEA for integration; it can only be used for primary winding charging current detection. In other words, the current feedback resistor performs two functions, which helps to simplify the system.Resistors 214 and 215 form the sampling feedback circuit for the output voltage, with the VFB signal, which is the sampling feedback signal for the output voltage CVCI, connected at the middle point. The other end of resistor 214 is connected to the connection node between the secondary coil and the positive terminal of rectifier diode 213; the other end of resistor 215 is connected to the other end of the secondary coil, which is GND. The peripheral components of the system are extremely simple, and the design concept of chip 310 is also very clear: it receives the speed control pulse signal ADJ from MCU 120 (its duty cycle D is the speed control information; the larger D is, the higher the speed, and D=1 corresponds to the maximum speed). Chip 310 then multiplies the duty cycle D information of the speed control pulse signal ADJ with the reference voltage REF of error amplifier 324 and then filters it to obtain a speed control DC voltage (the magnitude of which is equal to D). The speed control signal (REF) is then sent to the error amplifier 324EA to ultimately achieve motor speed regulation. As mentioned earlier, the speed regulation of a single-phase brushless DC motor 105 can be achieved using either constant voltage or constant current. If constant voltage speed regulation is used, the speed regulation DC reference voltage D... REF is sent to the constant voltage error amplifier 324VEA; if constant current speed regulation is used, the speed regulation DC reference voltage D is sent to the constant current speed regulation DC reference voltage D. REF is sent to the constant current error amplifier 324IEA. To minimize design complexity and increase system reliability, it's generally not advisable to perform both constant voltage and constant current control simultaneously: if constant voltage speed regulation is used, the current loop only performs peak current limiting protection, not closed-loop constant current control; similarly, if constant current speed regulation is used, the voltage loop only performs peak voltage limiting protection, not closed-loop constant voltage control. Furthermore, constant current design is generally easier to implement, has better loop stability, and offers higher system safety. Therefore, this application argues that a constant current speed regulation + voltage limiting protection strategy is more competitive than a constant voltage speed regulation + current limiting protection strategy. Figure 3 The biggest advantage is that the motor speed is only related to the duty cycle information D of the speed control signal ADJ, so stepless speed regulation can be achieved very easily. This is the biggest advantage of the flyback speed control circuit. Of course, analog voltage speed regulation can also be used, that is, the MCU 120 directly generates a variable analog voltage REF through the internal DAC circuit (digital-to-analog converter) and sends it to the chip 310. The principle is the same. However, the cheapest 8-bit MCU will definitely not have a DAC circuit, so the PWM speed control MCU here has the lowest cost.

[0072] The second implementation method of constant voltage and constant current circuit 200 is discussed below: step-down adjustable constant voltage and constant current circuit 200, which is divided into two subtypes: the first subtype is that the ADJ speed control signal and the motor on / off signal are separated; the second type is that the ADJ speed control signal and the motor on / off signal are combined into one.

[0073] Let's first discuss the first seed type, such as Figure 4 As shown: The ON / OFF signal from MCU 120 only controls switch 106 to turn the motor on or off; the speed control signal from MCU 120 is not directly connected to the step-down adjustable constant voltage and constant current control chip 320, but is connected to the chip's VDD power supply pin through a high-voltage NPN 229 (with a withstand voltage greater than 400V, the most economical model is the SOT23-3 packaged 13001 NPN small power transistor, with a market price of 2 to 3 cents RMB) and a resistor 231: the high-voltage collector of NPN 229 is connected to the VDD node; the base of NPN 229 is connected to the speed control signal ADJ; the emitter of NPN 229 is connected to one end of resistor 231, and the other end of resistor 213 is connected to GND. Figure 4 This type of step-down constant voltage and constant current power supply and Figure 3 The biggest difference between the flyback constant voltage and constant current power supplies is that the reference ground GNDIC of the former's constant voltage and constant current control chip 320 is completely different from the reference ground GND of the MCU 120, while the reference ground of the flyback structure chip 310 is directly connected to the MCU's reference ground. During normal system operation, Figure 4 The chip reference ground GNDIC differs drastically from the MCU's reference ground GND: because the drain of power transistor 221 is fixedly connected to the high-voltage HV node, when power transistor 221 is turned on (corresponding to a high gate voltage DRV for switching transistor 221), the chip reference ground GNDIC node voltage equals the HV node voltage (the voltage difference between the HV node and the GND node is as high as several hundred volts); when power transistor 221 is turned off (corresponding to a low gate voltage DRV for switching transistor 221), the chip reference ground GNDIC node voltage equals the GND node voltage. Therefore, communication between MCU 120 and the buck-type adjustable constant voltage / constant current control chip 320 is relatively difficult. MCU 120 needs to generate a customized speed control signal ADJ according to agreed-upon encoding rules, and chip 320 then decodes it into speed control information that the chip can execute according to agreed-upon decoding rules. Figure 5 It's just right Figure 4A practical encoding / decoding rule: When ADJ is high, i.e., 5V, the maximum pull-down current of NPN 229 after it is turned on is equal to (5-0.7) / R231. As long as this pull-down current is greater than the average external charging current of the power supply capacitor 228 of chip 320, the voltage across capacitor 228 (i.e., the chip's power supply voltage VDD) will be pulled down. When it drops to a certain threshold, such as below 6V, chip 320 will stop working, and the adjustable constant voltage and constant current circuit will stop outputting. When ADJ=0, NPN 229 is in the off state and will not have any effect on the VDD node voltage. The charging current provided by resistor 227 charges the power supply capacitor 228 of chip 320, and the power supply voltage of chip 320 continues to rise. When it rises to a threshold, such as above 7V, chip 320 resumes operation, and the system outputs normally. When MCU 120 If the ADJ signal is high for a duration greater than 0.1 seconds (it can be 0.2 seconds or longer, but not so long as to be noticeable to the user), chip 320 will actively reset gear register 322 (gear register 322 is actually a shift counter; for three gears, register 322 is a ternary shift counter). Once ADJ changes from high to low and VDD voltage rises above 7V, chip 320 will output at the default first gear speed. If the MCU 120 outputs an ADJ signal high for a duration less than 0.1 seconds, after ADJ changes from high to low and VDD voltage rises above 7V, chip 320 will change the system's output voltage or current according to the cyclic speed gear switching rule. The cyclic speed gear switching rule is as follows, taking three speed gears as an example: the default is the first gear, and the gears cycle through first gear -> second gear -> third gear -> first gear. Figure 5 This is just one type of speed-adjusting encoding and decoding rule; there can be other different encoding and decoding rules, which will not be discussed here. Figure 5 This specific encoding and decoding rule requires matching with the custom circuitry inside the 320 chip; in other words, the software and hardware must be compatible. Figure 6 As shown. The decoder's function is to translate the gear position digital signal stored in the gear position register 322 into a DC reference voltage REF usable by the error amplifier 324. Different gear positions correspond to different magnitudes of the DC reference voltage REF. The error amplifier 324 calculates the difference between REF and the feedback signal IFB or VFB, amplifies it, and sends it to the subsequent power logic drive circuit 325 to generate a variable duty cycle drive signal DRV to control the on and off of the external power switch 221.

[0074] The second type of adjustable step-down constant voltage and constant current circuit 200 structure subtype: such as... Figure 6 As shown, the significant feature is the absence of Figure 5The NPN transistor 229 and resistor 231 in the motor, and the gate signal of the NMOS switch 106 below the motor is the speed control signal ADJ, not... Figure 5 In the ON / OFF configuration, the MCU 120 only outputs the ADJ signal and does not need to output the ON / OFF signal. That is, the ADJ and ON / OFF signals are combined into one. Figure 7 This is a block diagram of the internal module of the second type of step-down adjustable constant voltage and constant current circuit 200. The decoder translates the gear position digital signal stored in the gear position register 322 into a DC reference voltage REF usable by the error amplifier 324. The error amplifier 324 subtracts REF from the feedback signal IFB or VFB and amplifies it before sending it to the subsequent power logic drive circuit 325, generating a variable duty cycle drive signal DRV to control the on / off state of the external step-down power switch 221. This requires a new speed control encoding and decoding rule, such as... Figure 8 As shown: When ADJ is low, the motor stops working, and chip 330 enters a light-load hiccup mode (corresponding to chip 330 using a constant voltage and current limiting strategy) or a voltage limiting protection mode (corresponding to chip 330 using a constant current and voltage limiting strategy). If this state lasts for more than 0.1 seconds, chip 330 will reset its internal gear register 322; if ADJ is low for less than 0.1 seconds, the chip will change gears according to the rule of cyclically changing speed gears. The rule of cyclically changing speed gears mentioned above is the same here, taking three speed gears as an example: the default is the first gear as the initial gear, and the gears are cycled according to first gear -> second gear -> third gear -> first gear. The new rule also requires changes to the internal circuitry of chip 330 to match it, such as... Figure 9 As shown. From the circuit structure perspective, the second type of adjustable step-down constant voltage and constant current circuit 200 structure ( Figure 6 ) is better than the first one ( Figure 4 The first method is simpler, but it uses two-wire communication (ADJ signal and ON / OFF signal), which is more flexible and can match more complex encoding and decoding rules. We will not discuss it further here.

[0075] The most significant difference between the flyback adjustable constant voltage and constant current circuit 200 and the two types of buck adjustable constant voltage and constant current circuits 200 is that the former has a direct connection to the speed control signal ADJ, supporting stepless speed regulation; the latter does not support stepless speed regulation and only supports a limited number of speed levels, such as 2, 3, 5, 6, 7, and 8 speeds. The former is suitable for applications with high speed regulation requirements, while the latter is suitable for low-cost applications and applications with high space requirements but lower speed regulation requirements. For example, in the exhaust fan field, where power supply space requirements are very high and the motor and drive circuit must be integrated, only the buck adjustable constant voltage and constant current circuit 200 using an I-type inductor can meet these requirements.

[0076] To add to this, the core of both types of buck-type adjustable constant voltage and constant current circuit subtype embodiments adopts the most widely used circuit architecture in the industry: 1. The third sampling resistor 224 and the fourth sampling resistor 225 constitute the output voltage feedback sampling circuit, with the VFB signal, which is the sampling feedback signal of the output voltage CVCI, connected at the middle point and sent to the first buck control chip 320. The other end of the third sampling resistor 224 is connected to the output node CVCI, and the other end of the fourth sampling resistor 225 is connected to the reference ground node GNDIC of the first buck control chip 320; 2. The output current feedback sampling is completed by the second current feedback resistor 226: the second current feedback resistor 226... One end (IFB node) is connected to the source of the buck power switch 221 and the negative terminal of the freewheeling diode 223. The positive terminal of the freewheeling diode 223 is connected to the system reference ground GND. The other end of the second current feedback resistor 226 is connected to the reference ground node GNDIC of the first buck control chip 320 and one end of the output filter inductor 222. The other end of the output filter inductor 222 is connected to the output node CVCI. The output filter inductor 222 operates in current critical mode (i.e., when the inductor discharge current drops to zero, a new charging cycle is immediately started). 3. The output voltage can be as low as below 1V, which is a low-cost non-isolated buck drive circuit architecture for single-phase brushless DC motors.

[0077] In addition, Figure 6 and Figure 8 In each chip, there is a function module 326 that checks whether VDD is less than 2.5V. VDD voltage is the power supply voltage for chips 320 and 330. Once the power supply voltage is lower than 2.5V, the chip will actively reset all digital circuits, including the gear register 322.

[0078] There are two types of motor speed control: open-loop and closed-loop. Generally speaking, open-loop speed control has lower accuracy, while closed-loop speed control has higher accuracy. The above discussion pertains to open-loop speed control: it doesn't perform any speed monitoring, relying entirely on the stability of the materials (such as permanent magnets) and manufacturing process to ensure the stability of the motor speed. For example, if the parameters of the motor's permanent magnet material have a large error, using an open-loop speed control strategy will result in a large error in the motor's speed. Generally, open-loop speed control can meet the needs of most application scenarios; for example, traditional AC motor fans (floor fans, table fans, ceiling fans) all use open-loop speed control. In a few demanding applications, a small motor speed error is required. This necessitates closed-loop speed control, which involves continuously monitoring the motor speed and comparing it to a target speed defined within the MCU 400. If the motor speed is lower than the target speed, the MCU 400 uses software to modify the speed control signal ADJ to increase the output voltage or current of the adjustable constant voltage / constant current circuit 200, thereby increasing the motor speed. Conversely, if the motor speed is higher than the target speed, the MCU 400 uses software to modify the speed control signal ADJ to decrease the output voltage or current of the adjustable constant voltage / constant current circuit 200, thereby decreasing the motor speed. Ultimately, the system automatically adjusts the motor speed to near the target speed. Figure 10 This is one method of closed-loop speed control: Resistor 401 is used to detect the operating current of the single-phase brushless DC motor 105. One end of resistor 401 is connected to the source of switch 106 and pin MTC (motor current) of MCU 400, and the other end is connected to GND. That is, resistor 401, motor 105, and switch 106 are connected in series, and the current flowing through the three is the same, that is, V(MTC) = R401. I105. For a single-phase brushless DC motor, the current flowing through the motor is the current in its single-phase coil. The coil current waveform is approximately trapezoidal, and the frequency is twice the motor's rotational speed frequency. Therefore, the MCU 4000 can obtain the motor speed by detecting the frequency of the MTC node signal. Combined with the closed-loop speed control algorithm inside the MCU 400, the motor speed can be gradually adjusted to near the target speed.

[0079] Compare the single-phase DC open-loop speed control system proposed in this application. Figure 2 and closed-loop speed control system Figure 10 It can be observed that the only difference between the two systems in terms of hardware is a 401 resistor. The biggest difference lies in the software, specifically the closed-loop speed control system. Figure 10 The MCU 400 has a closed-loop speed control algorithm, while the open-loop speed control system... Figure 2 The MCU 200 uses an open-loop speed control algorithm. The MCU400 and MCU 200 have the same hardware cost, and their internal software marginal cost is zero. Therefore, the open-loop speed control system for a single-phase brushless DC motor... Figure 2 and closed-loop speed control system Figure 10 The only difference in cost is a 401 resistor, making the cost almost the same. This further confirms the easy speed adjustment feature of brushless DC motors.

[0080] To achieve remote speed control of a single-phase DC motor, this application proposes a complete solution from multiple levels: 1) At the system level, a flyback structure or a common buck converter structure is selected; 2) At the hardware level, various chips are customized; 3) At the software level, various different speed control encoding and decoding rules are adopted, which require MCU software implementation.

[0081] This application can facilitate the widespread adoption of single-phase DC motors in the fan industry (electric fans, exhaust fans, and fan lights). This application proposes that, in the future, the single-phase brushless DC motor 105 will become the main power source in the fan industry, rather than the three-phase brushless DC motor.

[0082] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A remote control speed regulation circuit for a single-phase brushless DC motor, characterized in that, include: AC input port, used for connecting to the AC power grid; A rectifier and filter unit, connected to the AC input port, is used to convert AC power into high-voltage DC power; An adjustable constant voltage and constant current circuit is provided, with its input terminal connected to the output terminal of the rectifier and filter unit. The output terminal of the adjustable constant voltage and constant current circuit is used to connect to a single-phase brushless DC motor. The adjustable constant voltage and constant current circuit is used to convert the high-voltage DC power into DC power with a controllable and adjustable output voltage or output current to drive the single-phase brushless DC motor. The low-voltage regulator unit has its input terminal connected to the output terminal of the adjustable constant voltage and constant current circuit, and is used to output a stable low-voltage operating voltage. The remote control circuit, powered by the low-voltage regulator unit, is used to receive external remote control commands and output the remote control commands. The single-chip microcomputer (MCU) is powered by the low-voltage regulator unit and connected to the remote control circuit. It is used to receive the remote control command and generate a speed control signal according to the remote control command. A motor start / stop switch transistor is connected in series between the output terminal of the adjustable constant voltage and constant current circuit and the single-phase brushless DC motor; the control terminal of the motor start / stop switch transistor is connected to the single-chip microcomputer MCU, and is used to control the start and stop of the single-phase brushless DC motor according to the control signal output by the single-chip microcomputer MCU. The adjustable constant voltage and constant current circuit has a speed regulation signal input terminal, which is connected to the speed regulation signal output terminal of the single-chip microcomputer MCU. The adjustable constant voltage and constant current circuit adjusts the output voltage or output current according to the speed regulation signal to change the speed of the single-phase brushless DC motor.

2. The remote control speed regulation circuit for a single-phase brushless DC motor according to claim 1, characterized in that, The adjustable constant voltage and constant current circuit is a flyback adjustable constant voltage and constant current circuit. The flyback adjustable constant voltage and constant current circuit includes: a flyback transformer, a flyback control chip, and a primary-side power switch; there is no electrical isolation between the primary and secondary coils of the flyback transformer, and the reference ground of the flyback control chip is connected to the reference ground of the single-chip computer MCU. The speed control signal is directly input to the speed control signal input terminal of the flyback control chip. The flyback control chip adjusts the output voltage or output current of the flyback adjustable constant voltage and constant current circuit according to the duty cycle information of the speed control signal to realize stepless speed regulation of the single-phase brushless DC motor. One end of the primary winding of the flyback transformer is connected to the high voltage DC node, and the other end is connected to the drain of the primary power switch. The source of the primary power switch is connected to the system reference ground through a first current feedback resistor. The voltage across the first current feedback resistor is sent to the flyback control chip as a current sampling signal. The flyback control chip outputs a pulse switching signal with a variable duty cycle to the gate of the primary power switch to control the charging and discharging of the flyback transformer. One end of the secondary coil of the flyback transformer is connected to the positive terminal of the rectifier diode, and the negative terminal of the rectifier diode is connected to the output node. The output node is connected to the other end of the secondary coil through an output filter capacitor, and the other end of the secondary coil is connected to the system reference ground. The first current feedback resistor has both primary coil charging current detection and secondary coil discharging current feedback functions: when the primary power switch is turned on, the first current feedback resistor collects the primary coil charging current; when the primary power switch is turned off, the first current feedback resistor collects the secondary coil discharging current and uses it as a feedback signal for constant current control.

3. The remote control speed regulation circuit for a single-phase brushless DC motor according to claim 2, characterized in that, The flyback adjustable constant voltage and constant current circuit also includes an output voltage sampling circuit; The output voltage sampling circuit is composed of a first sampling resistor and a second sampling resistor connected in series; one end of the first sampling resistor is connected to the connection node between the secondary coil and the positive terminal of the rectifier diode, the other end of the first sampling resistor is connected to one end of the second sampling resistor and the connection node provides an output voltage feedback signal to the flyback control chip, and the other end of the second sampling resistor is connected to the system reference ground. The flyback control chip multiplies the duty cycle information D of the speed regulation signal with the internal reference voltage and then filters the result to obtain a speed regulation DC voltage equal to the product of the duty cycle information D and the internal reference voltage. This speed regulation DC voltage is then sent to the constant voltage error amplifier or constant current error amplifier inside the flyback control chip. When constant voltage speed regulation is used, the current loop inside the flyback control chip only performs peak current limiting protection. When constant current speed regulation is used, the voltage loop inside the flyback control chip only performs peak voltage limiting protection.

4. The remote control speed regulation circuit for a single-phase brushless DC motor according to claim 1, characterized in that, The adjustable constant voltage and constant current circuit is a first step-down adjustable constant voltage and constant current circuit. The first step-down adjustable constant voltage and constant current circuit includes: a first step-down control chip, a step-down power switch, and an output filter inductor; the reference ground of the first step-down control chip is independent of the reference ground of the single-chip microcomputer MCU. The speed control signal is connected to the power supply terminal of the first buck control chip through a level conversion circuit. The first buck control chip detects the encoding information of the speed control signal according to the voltage change of the power supply terminal, and switches the gear of the internal gear register according to the encoding information to change the output voltage or output current of the buck adjustable constant voltage and constant current circuit, thereby realizing the limited gear speed regulation of the single-phase brushless DC motor. The drain of the buck power switch is connected to the high-voltage DC node, the source of the buck power switch is connected to one end of the second current feedback resistor and the negative terminal of the freewheeling diode, the positive terminal of the freewheeling diode is connected to the system reference ground (GND) of the MCU, and the other end of the second current feedback resistor is connected to the reference ground node of the first buck control chip; one end of the output filter inductor is connected to the reference ground node of the first buck control chip, and the other end is connected to the output node; the output filter inductor operates in current critical mode, that is, a new charging cycle is started immediately when the inductor discharge current drops to zero.

5. The remote control speed regulation circuit for a single-phase brushless DC motor according to claim 4, characterized in that, The level conversion circuit includes a high-voltage NPN transistor and a current-limiting resistor; The collector of the high-voltage NPN transistor is connected to the power supply terminal of the first buck control chip, the base of the high-voltage NPN transistor is connected to the speed control signal, and the emitter of the high-voltage NPN transistor is connected to the system reference ground GND through the current limiting resistor; the power supply terminal of the first buck control chip is also connected to the high-voltage DC node through a start-up resistor, and a power supply capacitor is connected between the power supply terminal and the reference ground of the first buck control chip. When the speed control signal is high, the high-voltage NPN transistor is turned on, the power supply capacitor discharges, and the voltage at the power supply terminal is pulled down to below the first threshold, and the first buck control chip stops working; when the speed control signal is low, the high-voltage NPN transistor is turned off, the power supply capacitor is charged through the power supply resistor, and when the voltage at the power supply terminal rises to above the second threshold, the first buck control chip resumes working.

6. The remote control speed regulation circuit for a single-phase brushless DC motor according to claim 5, characterized in that, The first buck control chip includes a first decoder, a gear register, and a digital-to-analog converter module. The first decoder is used to detect the voltage change at the power supply terminal to obtain the encoding information of the speed control signal and decode the encoding information. The gear position digital signal stored in the gear position register is converted into a corresponding DC reference voltage by the digital-to-analog converter module and sent to the error amplifier. The error amplifier calculates the difference between the DC reference voltage and the output current feedback signal or the output voltage feedback signal and amplifies it, and outputs it to the power logic drive circuit. The power logic drive circuit generates a drive signal with a variable duty cycle to control the conduction and cutoff of the buck power switch. When the duration of the high level of the speed control signal is greater than the first preset time, the first decoder outputs a reset signal to the gear register, causing the gear register to return to the default gear; when the duration of the high level of the speed control signal is less than the first preset time, after the speed control signal changes from high level to low level and the voltage at the power supply terminal rises above the second threshold, the first decoder outputs a shift signal to the gear register, causing the gear register to switch gears according to the cyclic shifting rule.

7. The remote control speed regulation circuit for a single-phase brushless DC motor according to claim 4, characterized in that, The first step-down adjustable constant voltage and constant current circuit also includes an output voltage sampling circuit; The output voltage sampling circuit is composed of a third sampling resistor and a fourth sampling resistor connected in series. One end of the third sampling resistor is connected to the output node, and the other end of the third sampling resistor is connected to one end of the fourth sampling resistor. This connection node provides an output voltage feedback signal to the first buck control chip. The other end of the fourth sampling resistor is connected to the reference ground node of the first buck control chip. The first buck control chip also includes an undervoltage reset module; the undervoltage reset module is connected to the power supply terminal, and when the voltage of the power supply terminal is lower than the third threshold, the undervoltage reset module resets all digital circuits inside the first buck control chip, including the gear register.

8. The remote control speed regulation circuit for a single-phase brushless DC motor according to claim 1, characterized in that, The adjustable constant voltage and constant current circuit is a second step-down adjustable constant voltage and constant current circuit, including a second step-down control chip, a step-down power switch, and an output filter inductor. The control terminal of the motor start-stop switch is not connected to the MCU (Microcontroller Unit) via a separate power on / off signal; instead, it is directly connected to the speed control signal. The on / off state of the motor start-stop switch is controlled by the speed control signal, and the power on / off function and speed control function share the same signal line. When the speed control signal is low, the motor start-stop switch is off, and the single-phase brushless DC motor stops working. If a constant voltage and current limiting control strategy is adopted, the second step-down control chip enters a light-load hiccup mode; if a constant current and voltage limiting control strategy is adopted, the second step-down control chip enters a voltage limiting protection mode. When the duration of the low level of the speed control signal is greater than a second preset time, the second step-down control chip resets its internal gear register to the default gear. When the duration of the low level of the speed control signal is less than the second preset time, the second step-down control chip switches the gear in its internal gear register according to the rule of cyclically changing the speed gear.

9. A remote control speed control chip for a single-phase brushless DC motor, characterized in that, The remote control speed regulation chip is a flyback control chip, a first buck control chip, or a second buck control chip. When the remote control speed regulation chip is a flyback control chip, it includes: a speed regulation signal input port for receiving a speed regulation signal with a variable duty cycle from a single-chip microcomputer MCU; a reference ground port for connecting to the reference ground of the single-chip microcomputer MCU; a pulse drive signal output port for outputting a pulse switching signal with a variable duty cycle to control the conduction and cutoff of an external power switch; a current sampling input port for receiving a current feedback signal; a voltage sampling input port for receiving an output voltage feedback signal; and a duty cycle decoding unit for multiplying the duty cycle information D of the speed regulation signal with an internal reference voltage and then filtering to obtain a speed regulation DC voltage. The remote control speed regulation chip sends the speed regulation DC voltage to a constant voltage error amplifier or a constant current error amplifier inside the chip to adjust the output voltage or output current of the chip, thereby achieving stepless speed regulation. The chip also includes a current error amplifier and a constant voltage error amplifier. When constant voltage speed regulation is used, the current error amplifier only performs peak current limiting protection; when constant current speed regulation is used, the constant voltage error amplifier only performs peak voltage limiting protection. When the remote control speed regulation chip is a first buck control chip, the first buck control chip is used in a first buck-type adjustable constant voltage and constant current circuit, including: a power supply terminal for receiving an external power supply voltage, the power supply terminal being coupled to the speed regulation signal output terminal of a single-chip microcomputer MCU through a level conversion circuit; a first decoder for detecting voltage changes at the power supply terminal to obtain the encoding information of the speed regulation signal and decoding the encoding information; a gear register connected to the first decoder for storing current gear information; a digital-to-analog converter module for converting the gear digital signal stored in the gear register into a corresponding DC reference voltage and sending it to an error amplifier; a power logic drive circuit for generating a variable duty cycle drive signal to control the conduction and cutoff of an external buck power switch; and an undervoltage reset unit for resetting all digital circuits within the chip when the power supply voltage is lower than a threshold. The first decoder outputs a reset signal or a shift signal to the gear register according to the encoding information of the speed regulation signal to switch the gear in the gear register, thereby changing the output voltage or output current of the chip to achieve limited gear speed regulation. When the remote control speed regulation chip is a second buck control chip, the second buck control chip is used in a second buck-type adjustable constant voltage and constant current circuit, including: a power supply terminal for receiving external power supply voltage; a speed regulation signal input terminal for directly receiving speed regulation signals from a single-chip microcomputer MCU; a second decoder for directly detecting level changes of the speed regulation signal to obtain the encoding information of the speed regulation signal and decoding the encoding information; a gear register connected to the second decoder for storing current gear information; a digital-to-analog conversion module for converting the gear digital signal stored in the gear register into a corresponding DC reference voltage and sending it to an error amplifier; a power logic drive circuit for generating a variable duty cycle drive signal to control the conduction and cutoff of an external buck power switch; and an undervoltage reset unit for resetting all digital circuits in the chip when the power supply voltage is lower than a threshold. The decoder outputs a reset signal or a shift signal to the gear register according to the encoding information of the speed regulation signal to switch the gear in the gear register, thereby changing the output voltage or output current of the chip to achieve limited gear speed regulation.

10. A remote control speed regulation method for a single-phase brushless DC motor, applied to the remote control speed regulation circuit for a single-phase brushless DC motor as described in any one of claims 1-8, characterized in that, include: The remote control circuit receives external remote control commands and transmits the remote control commands to a single-chip microcomputer (MCU). The single-chip microcomputer (MCU) generates a speed control signal according to the remote control command. The adjustable constant voltage and constant current circuit adjusts the output voltage or output current according to the speed control signal to change the electrical parameters output to the single-phase brushless DC motor. The single-phase brushless DC motor operates at a speed corresponding to the magnitude of the output voltage or output current. When the adjustable constant voltage and constant current circuit is a flyback adjustable constant voltage and constant current circuit, the single-chip microcomputer MCU generates a pulse signal with a variable duty cycle as the speed regulation signal. The flyback control chip multiplies the duty cycle information D of the speed regulation signal with the internal reference voltage and then filters it to obtain the speed regulation DC voltage, which is then sent to the internal constant voltage error amplifier or constant current error amplifier to control the output voltage or output current. When the adjustable constant voltage and constant current circuit is a first step-down adjustable constant voltage and constant current circuit, the single-chip microcomputer (MCU) generates an encoded pulse signal as the speed control signal. The speed control signal is coupled to the power supply terminal of the first step-down control chip through a level conversion circuit. The first step-down control chip detects the encoded information of the speed control signal according to the voltage change at the power supply terminal. When the high-level duration of the speed control signal is detected to be greater than a first preset time, the internal gear register is reset to the default gear. When the high-level duration of the speed control signal is detected to be less than the first preset time, the gear of the internal gear register is switched according to the cyclic shifting rule, and the gear digital signal stored in the gear register is converted into a corresponding DC reference voltage to control the output voltage or output current. When the adjustable constant voltage and constant current circuit is the second step-down adjustable constant voltage and constant current circuit, the single-chip microcomputer MCU generates an encoded pulse signal as the speed control signal. The motor start / stop switch and the second step-down control chip both directly receive the speed control signal. When the speed control signal is detected to be low for a duration greater than the second preset time, the internal gear register is reset to the default gear. When the speed control signal is detected to be low for a duration less than the second preset time, the gear in the internal gear register is switched according to the cyclic shifting rule, and the gear digital signal stored in the gear register is converted into a corresponding DC reference voltage to control the output voltage or output current.

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