Motor drive circuit system of high-speed air duct

Abstract

The invention relates to the technical field of motor driving, and discloses a motor driving circuit system of a high-speed air duct, which comprises a motor driving circuit composed of three half-bridge driving chips, and each chip is integrated with two high-voltage MOSFETs and a high-voltage grid driver to form a three-phase full-bridge driving topology; the current detection circuit comprises a single sampling resistor and a differential amplification circuit and is used for acquiring a motor phase current signal; the overcurrent comparison circuit comprises a high-speed comparator; a master control circuit; a back electromotive force detection circuit; an EMC filtering and power supply circuit; and a voltage detection circuit. High integration of a driving circuit is realized through a built-in half-bridge chip packaged by double MOSFETs and a driver QFN77, each chip integrates a temperature detection function and forms a three-phase full-bridge topology, the area of a PCB is reduced, the complete driving protection function is reserved, meanwhile, the layout complexity is remarkably reduced, and the requirements of portable equipment for compact space and low cost are met.

Description

Technical Field

[0001] The present invention relates to the technical field of motor drive, and in particular to a motor drive circuit system for a high-speed air duct. Background Art

[0002] A hair dryer, also known as an electric hair dryer, uses a motor to drive a fan to generate airflow, which is then gathered through a hair dryer to quickly dry hair or the surface of an object. As personal care devices become increasingly intelligent and portable, they require precise control of ultra-high speeds in a compact space while also meeting the requirements of low electromagnetic interference, dynamic temperature compensation, and real-time protection of multiple parameters.

[0003] Motor drive solution for traditional high-speed air ducts: While using an intelligent power module (IPM) to drive the motor can achieve complete power drive and protection functions, its large size (e.g., 18×29mm) results in a high PCB layout space utilization, making it difficult to meet the design requirements for miniaturization and lightweighting of hair dryers. Furthermore, the high cost of IPM modules limits the product's market competitiveness. The discrete design using three half-bridge gate drivers and six MOSFETs can reduce the size by reducing modular packaging, but it requires the configuration of a large number of additional peripheral components (such as drive resistors, sampling resistors, filter capacitors, etc.), resulting in a significant increase in circuit complexity and difficulty in layout for hardware engineers. In addition, the parameter consistency differences of discrete components can easily lead to system stability issues. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a motor drive circuit system for a high-speed hair dryer, which solves the problem that the high-speed hair dryer cannot simultaneously meet the requirements of simplicity, miniaturization, high stability and low cost for the drive circuit.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: A motor drive circuit system for a high-speed air duct, comprising: The motor drive circuit consists of three half-bridge driver chips, each of which integrates two high-voltage MOSFETs and a high-voltage gate driver to form a three-phase full-bridge drive topology; The current detection circuit includes a single sampling resistor and a differential amplifier circuit, which is used to obtain the motor phase current signal; An overcurrent comparison circuit, including a high-speed comparator, is used to compare the current signal after differential amplification with a preset threshold value and trigger a protection signal; The main control circuit is connected to the drive circuit and the overcurrent comparison circuit, and is used to execute the sensorless FOC algorithm through the main control chip and control the motor commutation according to the back electromotive force detection signal; Back electromotive force detection circuit, which identifies the back electromotive force zero crossing point by detecting the motor winding voltage signal; EMC filtering and power supply circuit, connected to the input power supply, including common-mode inductor, X capacitor and LDO regulator, used to suppress electromagnetic interference and provide stable power supply for the system; The voltage detection circuit includes a voltage divider resistor network, which is used to detect the bus voltage and provide an overvoltage protection signal.

[0006] Preferably, the half-bridge driver chip adopts a QFN7×7 package, and a temperature detection circuit is integrated inside the chip, and the MOSFET junction temperature signal is fed back to the main control circuit through a thermistor.

[0007] Preferably, the temperature detection circuit further includes an NTC thermistor mounted on the surface of the PCB board to monitor the ambient temperature.

[0008] Preferably, the output end of the voltage-dividing resistor network of the voltage detection circuit is connected to the ADC pin of the main control chip. When the detection voltage exceeds a preset threshold, the main control chip immediately turns off the output of the motor drive circuit and the heating wire control circuit.

[0009] Preferably, the single sampling resistor is connected in series to the common end of the lower bridge arm of the three-phase full bridge, obtains the current signal through the differential amplifier circuit, and forms a current detection loop with the low-pass filter.

[0010] Preferably, the process of the main control circuit executing the sensorless FOC algorithm includes: The back electromotive force zero-crossing signal of the three-phase winding is collected in real time by the back electromotive force detection circuit; Calculating the electrical angle and speed of the motor rotor according to the zero-crossing signal; The three-phase current signal is converted into direct-axis current component and quadrature-axis current component in a rotating coordinate system based on Clarke transformation and Park transformation; The PI controller is used to adjust the direct-axis current component and the quadrature-axis current component to the target value to generate a voltage vector control signal; The voltage vector signal is subjected to inverse Park transformation and space vector pulse width modulation, and a three-phase PWM drive signal is output to the integrated motor drive circuit.

[0011] Preferably, the back electromotive force detection circuit includes three differential comparators, which are respectively connected to the output ends of the three-phase windings and are used to synchronously collect the back electromotive force signals of each phase winding.

[0012] Preferably, the main control circuit further includes a heating wire control circuit, a negative ion circuit, a display circuit and a key circuit; The heating wire control circuit is used to adjust the power of the heating wire and realize over-temperature protection, and adjusts the power of the heating wire through PWM or phase control; The negative ion circuit is used to generate negative ions to purify the air; The display circuit displays the wind speed, temperature and operating status parameters of the air duct in real time through the LED or LCD module; The key circuit receives user instructions based on mechanical keys or touch sensors, and the user instructions include power on / off, gear position and mode adjustment.

[0013] Preferably, the sampling signal in the overcurrent comparison circuit is input into the high-speed comparator after filtering, and compared with the preset threshold value, and the overcurrent protection signal is triggered and sent to the main control circuit in response to shut down the output of the motor drive circuit.

[0014] Preferably, the system also includes a mains input terminal, which is connected to the ballast circuit and the step-down circuit in sequence, and is used to convert the AC mains into an input power supply terminal of a low-voltage DC power supply, and power the circuit through EMC filtering and power supply circuit.

[0015] The present invention provides a motor drive circuit system for a high-speed air duct, which has the following beneficial effects: 1. The present invention achieves a high degree of integration of the drive circuit by using a half-bridge chip with built-in dual MOSFETs and a driver in a QFN77 package. Each chip integrates a temperature detection function and forms a three-phase full-bridge topology, reducing the PCB area. While retaining complete drive protection functions, it significantly reduces layout complexity and meets the compact space and low-cost requirements of portable devices.

[0016] 2. The present invention extracts three-phase current signals through a single resistor sampling at the common end of the lower bridge arm in conjunction with a differential amplifier circuit. While ensuring the accuracy of overcurrent protection, it reduces sampling components and effectively overcomes the stability defects of the discrete component solution.

[0017] 3. The driver chip of the present invention has a built-in thermistor to realize real-time monitoring of MOS junction temperature, which significantly reduces the occupied area and facilitates PCB layout optimization. When the temperature is too high, the main control chip dynamically reduces the load or triggers hardware shutdown to achieve dual protection. At the same time, the temperature signal is fed back to the main control circuit to achieve dynamic power limitation or shutdown protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a motor drive circuit system for a high-speed air duct according to the present invention; Figure 2 is a circuit diagram of a motor drive circuit of the present invention; Figure 3 is a circuit diagram of a current detection circuit of the present invention; Figure 4 is a circuit diagram of an overcurrent comparison circuit of the present invention; Figure 5Schematic diagram of the main control circuit of the present invention; Figure 6 Schematic diagram of a back electromotive force detection circuit of the present invention; Figure 7 Schematic diagram of the EMC filter and power supply circuit of the present invention; Figure 8 FIG. 4 is a circuit diagram of a temperature detection circuit of the present invention.

[0019] Figure 9 FIG. 4 is a circuit diagram of a voltage detection circuit of the present invention. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] Please see the attached Figure 1 -Attached Figure 9 The embodiment of the present invention provides a motor drive circuit system for a high-speed air duct, comprising: The motor drive circuit consists of three half-bridge driver chips, each of which integrates two high-voltage MOSFETs and a high-voltage gate driver to form a three-phase full-bridge drive topology; The current detection circuit includes a single sampling resistor and a differential amplifier circuit, which is used to obtain the motor phase current signal; An overcurrent comparison circuit, including a high-speed comparator, is used to compare the current signal after differential amplification with a preset threshold value and trigger a protection signal; The main control circuit is connected to the drive circuit and the overcurrent comparison circuit, and is used to execute the sensorless FOC algorithm through the main control chip and control the motor commutation according to the back electromotive force detection signal; Back electromotive force detection circuit, which identifies the back electromotive force zero crossing point by detecting the motor winding voltage signal; EMC filtering and power supply circuit, connected to the input power supply, including common-mode inductor, X capacitor and LDO regulator, used to suppress electromagnetic interference and provide stable power supply for the system; The voltage detection circuit includes a voltage divider resistor network, which is used to detect the bus voltage and provide an overvoltage protection signal.

[0022] Specifically, the motor drive circuit uses three CRM50T06E1 half-bridge driver chips to build a three-phase full-bridge topology. Each chip integrates high-side and low-side MOSFETs and drivers, receives PWM signals through the HIN / LIN pin to control the switching action, and inputs 15V power supply through 100Ω current limiting resistors (such as R25, R26) to connect to the driver chip to ensure signal stability. The bootstrap circuit is composed of FR107 diodes (D5-D7) and 100μF / 25V capacitors (C9, C16, C23), and the VB pin is used for high-side MOSFETs provide floating drive voltages, and the three-phase output terminals (UH / UL, VH / VL, and WH / WL) are connected to the motor windings. By alternately turning on the MOSFETs, a three-phase sinusoidal wave is generated to drive the motor. Protection components (such as a 100mΩ sampling resistor (RS1) and a 10nF / 1kV capacitor (CB3) implement overcurrent detection and high-frequency noise suppression, thereby achieving high efficiency, low electromagnetic interference, and precise sensorless FOC control. Meanwhile, built-in chip temperature monitoring (TEMP pin) and hardware overcurrent protection ensure system reliability. When the motor is running, the current sensing circuit generates a slight voltage difference when the phase current flows through I_SHUNT. This signal is input to the non-inverting (OP1P) and inverting (OP1N) terminals of operational amplifier OP1 via R27 and R31. The gain is set by R32 / R61 (Gain = R32 / R27), amplifying the microvolt-level voltage to a range of 0-3.3V. After filtering out high-frequency noise through C19 / C20, the output is sent to the main control chip's ADC (IBUS_AVR). The R29 / R60 voltage divider provides a reference voltage to offset common-mode interference. GND2 is the signal ground, separated from the power ground to improve accuracy, thereby enhancing current sensing precision and providing real-time feedback to the FOC algorithm. Hardware filtering also suppresses PWM switching noise, ensuring system safety and optimizing efficiency. The integrated driver chip and single-resistor sampling design reduce PCB area, supporting the miniaturization of hair dryer products. The overcurrent comparator circuit sets the threshold voltage through the R75 / R76 voltage divider network, which is then input into the high-speed comparator C1N and C40 to form an RC filter network. This filters out high-frequency noise (such as MOSFET switching noise) and ensures comparator trigger stability. When the motor current is abnormal, the current signal from the differential amplifier circuit exceeds the set threshold voltage, causing the comparator output to flip (logical low to high), triggering an interrupt signal from the main control chip and immediately shutting down the drive circuit output, thereby achieving hardware-level overcurrent protection and ensuring safe system operation. The main control circuit is based on the SH79F2201, which collects back-electromotive force zero-crossing signals in real time through the BEMF_A / B / C pins (pins 7 / 8 / 9). Combined with the internal ADC module, it receives the amplified signal from the current detection circuit and executes the sensorless FOC algorithm. The PWM4 / P35 pin (pin 25) outputs three-phase PWM drive signals to the half-bridge driver chip (such as U5-U7). Complementary waveforms are used to control the alternating conduction of the high-side and low-side MOSFETs, generating a drive waveform with a phase difference of 120°. The INT3 / TXD pin (pin 24) receives the hardware interrupt signal from the overcurrent comparator circuit. Once triggered, the PWM output is immediately blocked. The main control chip then communicates with the external storage module through the SCL / SDA pins (pins 2 / 3) to dynamically adjust the FOC parameters (such as PI gain and dead time) to control the motor speed. In the back-EMF detection circuit, the three-phase windings (U / V / W) attenuate the winding voltage through high-precision voltage-dividing resistors (R64-R73, 510kΩ±1%), reducing the back-EMF signal to hundreds of volts within a range that can be processed by the MCU. Each phase signal is filtered through an RC filter network (R63 / C2, R67 / C38, R68 / C39, 10kΩ+100pF) to remove high-frequency switching noise (such as MOSFET dV / dt interference), effectively preserving the back-EMF zero-crossing characteristic. The filtered BEMF_A / B / C signals are then fed into the main control chip's ADC. A software algorithm accurately locates the rotor position, thereby reducing motor torque ripple and noise. In the EMC filtering and power supply circuits, a common-mode inductor L (07D471K), X-capacitor CX1 (220nF / 275V), and Y-capacitor CY1 (22nF) form the input-stage filtering network. After the AC power passes through fuse FUSE1 and a rectifier bridge (MF72-5D11), the common-mode inductor suppresses common-mode interference through high-frequency impedance. The X-capacitor filters differential-mode noise. The Y-capacitor, connected in parallel between the live / neutral wires and ground, further eliminates high-frequency radiation. The subsequent LDO regulator stabilizes the rectified DC voltage to 5V / 3.3V with a ripple of ≤50mV. Energy storage capacitors C30 and C1 suppress transient fluctuations, meeting CISPR32 Class B standards. This ensures output power stability, ensuring reliable operation of the main control chip and driver circuits. In the voltage detection circuit, the bus voltage (VBUS) is attenuated in a 1:1 ratio through the R48 / R49 (510kΩ±1%) voltage divider network to obtain a median voltage signal. This signal is then filtered out through an RC low-pass filter formed by R51 and C18 to remove high-frequency switching noise and generate a smooth detection voltage (VB3). The main control chip reads the VB3 voltage in real time via the ADC. When the bus voltage exceeds the nominal value, the drive circuit output is immediately cut off, ensuring the accuracy and anti-interference performance of the overvoltage protection and avoiding system shutdowns caused by false triggering.

[0023] The half-bridge driver chip adopts QFN7×7 package. The temperature detection circuit is integrated inside the chip, and the MOSFET junction temperature signal is fed back to the main control circuit through the thermistor.

[0024] Specifically, the half-bridge driver chip integrates a temperature detection circuit, which directly monitors the MOSFET junction temperature through a built-in thermistor. The signal is output to the main control circuit through the chip pin, and the temperature change is converted into a voltage signal through a voltage divider network. After the high-frequency noise is eliminated by a filter capacitor (such as C11), the signal is input into the main control ADC. Combined with the efficient heat dissipation design of the QFN7×7 package, the real-time detection accuracy is improved, the occupied area is significantly reduced, and the PCB layout optimization is facilitated. When the temperature exceeds 110°C, the main control chip dynamically reduces the load or triggers a hardware shutdown to achieve dual protection. At the same time, the temperature signal is fed back to the main control circuit to achieve dynamic power limiting or shutdown protection.

[0025] The temperature detection circuit also includes an NTC thermistor, which is mounted on the surface of the PCB to monitor the ambient temperature.

[0026] Specifically, the NTC thermistor is mounted on the surface of the PCB board and is connected in series with the metal film resistor (R24) to form a voltage divider network. It is powered by a +5V power supply. Temperature changes cause nonlinear changes in the NTC resistance value. The voltage at the divider point is filtered out of high-frequency interference by the RC low-pass filter composed of R23 and C11, and then output to the ADC pin of the main control chip to ensure stable operation of the equipment in extreme environments.

[0027] The output end of the voltage detection circuit's voltage divider resistor network is connected to the ADC pin of the main control chip. When the detection voltage exceeds the preset threshold, the main control chip immediately turns off the output of the motor drive circuit and the heating wire control circuit.

[0028] Specifically, the voltage detection circuit's voltage divider resistor network attenuates the bus voltage proportionally, and outputs a low-voltage signal that is linearly related to the bus voltage to the ADC pin of the main control chip. When the detection voltage exceeds the preset threshold, the main control chip immediately cuts off the output signal of the motor drive and heating wire control circuit through the hardware interrupt mechanism to achieve overvoltage protection function, thereby monitoring the abnormal state of the power supply voltage in real time, and avoiding the risk of breakdown of power devices due to voltage spikes or continuous overvoltage through rapid hardware response. At the same time, combined with software protection strategies, it ensures that the system operates within a safe voltage range, achieves rapid shutdown while avoiding false triggering, and effectively improves the reliability and service life of the equipment under complex working conditions.

[0029] A single sampling resistor is connected in series to the common end of the lower arm of the three-phase full bridge, and the current signal is obtained through the differential amplifier circuit, and a current detection loop is formed with the low-pass filter.

[0030] Specifically, a single sampling resistor is connected in series at the common end of the lower arm of the three-phase full-bridge. By detecting the total current of the common loop and combining it with a differential amplifier circuit to extract the tiny voltage difference across the resistor, it is converted into a voltage signal proportional to the current. A low-pass filter filters out high-frequency switching noise, retaining effective current information for input into the main control circuit, thereby simplifying the circuit structure, reducing the number of components and the complexity of the PCB layout. At the same time, the differential amplifier suppresses common-mode noise, ensuring the stability and anti-interference capability of current detection, and monitoring the motor phase current in real time, providing key feedback for overcurrent protection, torque control in the FOC algorithm, and efficiency optimization, ensuring the stable operation of the system under dynamic loads, and reducing the cost and power consumption of the multi-resistor sampling solution.

[0031] The process of the main control circuit executing the sensorless FOC algorithm includes: The back electromotive force zero-crossing signal of the three-phase winding is collected in real time through the back electromotive force detection circuit; Calculate the electrical angle and speed of the motor rotor based on the zero-crossing signal; The three-phase current signal is converted into direct-axis current component and quadrature-axis current component in a rotating coordinate system based on Clarke transformation and Park transformation; The PI controller is used to adjust the direct-axis current component and the quadrature-axis current component to the target value to generate a voltage vector control signal; The voltage vector signal is subjected to inverse Park transformation and space vector pulse width modulation, and a three-phase PWM drive signal is output to the integrated motor drive circuit.

[0032] Specifically, the back-EMF zero-crossing signal is used to estimate rotor position and speed in real time. The three-phase current is then decoupled into direct-axis and quadrature-axis (Iq) components using the Clarke / Park transform, controlling the magnetic field strength and torque output, respectively. A PI controller dynamically adjusts Id and Iq to target values, generating a voltage vector signal. This is then subjected to an inverse Park transform and SVPWM modulation to output a three-phase PWM drive waveform. This closed-loop control eliminates sensor dependency, reducing hardware costs and failure rates.

[0033] The back electromotive force detection circuit includes three differential comparators, which are respectively connected to the output ends of the three-phase windings and are used to synchronously collect the back electromotive force signals of each phase winding.

[0034] Specifically, the back-EMF detection circuit is directly connected to the three-phase winding output terminals via three differential comparators. This circuit synchronously collects back-EMF signals from each phase in real time to detect the winding voltage zero-crossing point during motor operation. Hardware-level comparators rapidly identify the rotor pole position, replacing traditional Hall sensors for sensorless control. The differential structure simultaneously suppresses common-mode interference (such as switching noise and ground line fluctuations) to ensure accurate zero-crossing detection. The three independent comparisons support full-cycle commutation determination, avoiding the phase blind spots associated with single-channel sampling. Combined with the commutation logic of the main control chip, this significantly improves motor torque stability and dynamic response efficiency, while reducing system cost and failure rate.

[0035] The main control circuit also includes a heating wire control circuit, a negative ion circuit, a display circuit and a key circuit; The heating wire control circuit is used to adjust the heating wire power and realize over-temperature protection, and adjust the heating wire power through PWM or phase control; Negative ion circuit is used to generate negative ions to purify the air; The display circuit displays the wind speed, temperature and operating status parameters of the air duct in real time through LED or LCD module; The key circuit receives user commands based on mechanical keys or touch sensors. User commands include power on / off, gear position and mode adjustment.

[0036] Specifically, the main control circuit achieves multi-functional collaboration by integrating heating wire control, negative ion, display, and button function modules: the heating wire control circuit uses PWM or phase control to adjust the heating power, combined with closed-loop temperature feedback to achieve over-temperature protection, ensuring the stability and safety of hot air output; the negative ion circuit generates negative ions through a high-voltage generator, neutralizing the charge of particulate matter in the air to enhance the purification effect; the display circuit drives the LED / LCD module to provide real-time feedback on wind speed, temperature, and operating status, providing intuitive human-computer interaction; the button circuit receives user commands based on hardware anti-shake design, supporting power on and off, mode switching, and gear adjustment. Under the unified scheduling of the main control chip, each module achieves seamless collaboration between hot air output, air purification, status monitoring, and user operation, improving equipment energy efficiency and user experience, while ensuring safe and reliable system operation through hardware-level protection mechanisms.

[0037] The sampling signal in the overcurrent comparison circuit is filtered and input into the high-speed comparator, which compares it with the preset threshold value and triggers the overcurrent protection signal to be sent to the main control circuit to respond and shut down the output of the motor drive circuit.

[0038] Specifically, the overcurrent comparison circuit collects the motor circuit current signal in real time, filters it to eliminate high-frequency noise, and then inputs it into a high-speed comparator for rapid comparison with a preset threshold voltage. When the current abnormally exceeds the threshold, the hardware circuit directly triggers the protection signal and transmits it to the main control chip, immediately shutting down the drive circuit output. This allows for rapid hardware-level response to intercept faults such as short circuits and stalls, preventing damage to power devices due to overcurrent. At the same time, the filtering design suppresses switching noise interference, significantly reducing the risk of false triggering. This mechanism works in conjunction with the main control chip's software protection to form multiple redundant protections, ensuring the safety and stability of the system under complex operating conditions.

[0039] The system also includes a mains input terminal, which is connected to a ballast circuit and a step-down circuit in sequence, and is used to convert the AC mains into an input power supply terminal of a low-voltage DC power supply, and power the circuit through EMC filtering and a power supply circuit.

[0040] Specifically, AC power is introduced through the mains input terminal, and after the ballast circuit suppresses surge current and filters out high-frequency interference, it is converted into a low-voltage DC power supply by the step-down circuit. The EMC filtering and power supply circuit further eliminate the conducted noise, providing stable power supply for modules such as the drive circuit and the main control chip, realizing reliable conversion from AC mains to low-voltage DC. Through multi-level protection design (surge voltage suppression, electromagnetic interference filtering, and voltage fluctuation compensation), the subsequent circuits are protected from abnormal power grid shocks, and at the same time, it ensures that each functional module operates in a low-ripple, high-stability power supply environment, thereby improving the overall anti-interference ability and long-term operation reliability of the system.

[0041] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A motor drive circuit system for a high-speed air duct, characterized in that: include: The motor drive circuit consists of three half-bridge driver chips, each of which integrates two high-voltage MOSFETs and a high-voltage gate driver to form a three-phase full-bridge drive topology; The current detection circuit includes a single sampling resistor and a differential amplifier circuit, which is used to obtain the motor phase current signal; An overcurrent comparison circuit, including a high-speed comparator, is used to compare the current signal after differential amplification with a preset threshold value and trigger a protection signal; The main control circuit is connected to the drive circuit and the overcurrent comparison circuit, and is used to execute the sensorless FOC algorithm through the main control chip and control the motor commutation according to the back electromotive force detection signal; Back electromotive force detection circuit, which identifies the back electromotive force zero crossing point by detecting the motor winding voltage signal; EMC filtering and power supply circuit, connected to the input power supply, including common-mode inductor, X capacitor and LDO regulator, used to suppress electromagnetic interference and provide stable power supply for the system; The voltage detection circuit includes a voltage divider resistor network, which is used to detect the bus voltage and provide an overvoltage protection signal.

2. A motor drive circuit system for a high-speed air duct according to claim 1, characterized in that: The half-bridge driver chip adopts QFN7×7 package, and the temperature detection circuit is integrated inside the chip, which feeds back the MOSFET junction temperature signal to the main control circuit through the thermistor.

3. The motor drive circuit system for a high-speed air duct according to claim 2, characterized in that: The temperature detection circuit also includes an NTC thermistor mounted on the surface of the PCB to monitor the ambient temperature.

4. The motor drive circuit system for a high-speed air duct according to claim 1, characterized in that: The output end of the voltage-dividing resistor network of the voltage detection circuit is connected to the ADC pin of the main control chip. When the detection voltage exceeds a preset threshold, the main control chip immediately turns off the output of the motor drive circuit and the heating wire control circuit.

5. The motor drive circuit system for a high-speed air duct according to claim 1, characterized in that: The single sampling resistor is connected in series to the common end of the lower bridge arm of the three-phase full bridge, obtains the current signal through the differential amplifier circuit, and forms a current detection loop with the low-pass filter.

6. The motor drive circuit system for a high-speed air duct according to claim 1, characterized in that: The process of the main control circuit executing the sensorless FOC algorithm includes: The back electromotive force zero-crossing signal of the three-phase winding is collected in real time by the back electromotive force detection circuit; Calculating the electrical angle and speed of the motor rotor according to the zero-crossing signal; The three-phase current signal is converted into direct-axis current component and quadrature-axis current component in a rotating coordinate system based on Clarke transformation and Park transformation; The PI controller is used to adjust the direct-axis current component and the quadrature-axis current component to the target value to generate a voltage vector control signal; The voltage vector signal is subjected to inverse Park transformation and space vector pulse width modulation, and a three-phase PWM drive signal is output to the integrated motor drive circuit.

7. The motor drive circuit system for a high-speed air duct according to claim 1, characterized in that: The back electromotive force detection circuit includes three differential comparators, which are respectively connected to the output ends of the three-phase windings and are used to synchronously collect the back electromotive force signals of the respective phase windings.

8. The motor drive circuit system for a high-speed air duct according to claim 1, characterized in that: The main control circuit also includes a heating wire control circuit, a negative ion circuit, a display circuit and a key circuit; The heating wire control circuit is used to adjust the power of the heating wire and realize over-temperature protection, and adjusts the power of the heating wire through PWM or phase control; The negative ion circuit is used to generate negative ions to purify the air; The display circuit displays the wind speed, temperature and operating status parameters of the air duct in real time through the LED or LCD module; The key circuit receives user instructions based on mechanical keys or touch sensors, and the user instructions include power on / off, gear position and mode adjustment.

9. The motor drive circuit system for a high-speed air duct according to claim 1, characterized in that: The sampling signal in the overcurrent comparison circuit is filtered and input into the high-speed comparator, and compared with the preset threshold value, which triggers the overcurrent protection signal to be sent to the main control circuit in response to shut down the output of the motor drive circuit.

10. The motor drive circuit system for a high-speed air duct according to claim 1, characterized in that: The system also includes a mains input terminal, which is connected to a ballast circuit and a step-down circuit in sequence, and is used to convert the AC mains into an input power supply terminal of a low-voltage DC power supply, and power the circuit through EMC filtering and a power supply circuit.

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