CN219499247U

CN219499247U - High-speed brushless direct current motor driver

Info

Publication number: CN219499247U
Application number: CN202320335812.6U
Authority: CN
Inventors: 王从宁
Original assignee: Eller Power Technology Suzhou Co ltd
Current assignee: Eller Power Technology Suzhou Co ltd
Priority date: 2023-02-28
Filing date: 2023-02-28
Publication date: 2023-08-08
Anticipated expiration: 2033-02-28

Abstract

The present utility model provides a high-speed brushless DC motor driver, comprising: the system comprises a first-stage voltage reduction circuit, a second-stage three-phase two-level inverter and a control unit; the first-stage voltage reducing circuit, the second-stage three-phase two-level inverter and the control unit are connected with each other in pairs. The first-stage voltage reduction circuit is composed of a switching tube S0, an inductor L, a diode D and a capacitor C, wherein one end of the switching tube S0 is connected with the anode of an external voltage input, the other end of the switching tube S0 is connected with one end of the inductor L and the cathode of the diode D, the other end of the inductor L is connected with one end of the capacitor C, and the other end of the capacitor C and the anode of the diode D are both connected with the cathode of the external voltage input. The utility model can ensure the accuracy, stability and reliability of position detection.

Description

High-speed brushless direct current motor driver

Technical Field

The utility model relates to the technical field of brushless direct current motor driving, in particular to a high-speed brushless direct current motor driver.

Background

The existing brushless direct current motor driving product has the following defects:

1. the use of a position sensor to provide rotor position information for brushless dc motor drive algorithms takes up additional volume for miniaturized products and the price cost of the sensor is high for low cost applications.

2. The driving scheme of the position-free sensor adopting the hardware zero-crossing detection circuit depends on a specific detection circuit, and in order to ensure the stability and the accuracy of detection signals, a signal conditioning circuit is designed for the detection signals, the hardware circuit is complex in design, and the failure risk of the detection circuit exists under special working conditions.

3. The conventional position-free sensor driving method taking software zero crossing detection as a core collects voltage signals of each phase in a sequential sampling mode, and distinguishes the required back electromotive force zero crossing signals according to phase sequences and operation states, and due to inaccurate sampling time, excessive noise signals are doped in the sampled signals, a filter circuit is required to be arranged or a software filter method is required, so that signal time delay is introduced, and the method is not suitable for application occasions with higher motor rotating speeds.

4. The conventional position-sensor-free driving method taking software zero crossing point detection as a core still has the problem that when a zero crossing point signal is detected in a low-speed section of motor operation, the motor is still in an external synchronous operation state, so that high-frequency noise caused by doping pulse switching signals with detected back electromotive force signals influences the time for switching the motor into the self-synchronous operation state and the stability of the motor in the initial self-synchronous operation state.

5. The conventional position-free sensor driving method taking software zero crossing point detection as a core is characterized in that when a motor operates in a high-speed section, the time length of a non-conduction phase is reduced, so that the number of zero crossing detection is reduced, the limitation of PWM frequency is overlapped, the zero crossing point cannot be effectively judged in a 60-degree sector, and the step-out is easy to occur.

Disclosure of Invention

The aim of the utility model is achieved by the following technical scheme.

The present utility model provides a high-speed brushless DC motor driver, comprising:

the system comprises a first-stage voltage reduction circuit, a second-stage three-phase two-level inverter and a control unit;

the first-stage voltage reducing circuit, the second-stage three-phase two-level inverter and the control unit are connected with each other in pairs.

Further, the first stage step-down circuit is composed of a switch tube S0, an inductor L, a diode D and a capacitor C, wherein one end of the switch tube S0 is connected with the anode of the external voltage input, the other end of the switch tube S0 is connected with one end of the inductor L and the cathode of the diode D, the other end of the inductor L is connected with one end of the capacitor C, and the other end of the capacitor C and the anode of the diode D are both connected with the cathode of the external voltage input.

Further, the second-stage three-phase two-level inverter is composed of switching tubes S1, S2, S3, S4, S5 and S6, the switching tubes S1 and S2 are connected in series and then connected between the other end of the inductor L and the negative electrode of the external voltage input, the switching tubes S3 and S4 are connected in series and then connected between the other end of the inductor L and the negative electrode of the external voltage input, and the switching tubes S5 and S6 are connected in series and then connected between the other end of the inductor L and the negative electrode of the external voltage input; the connection point between the switching tubes S1 and S2, the connection point between the switching tubes S3 and S4, and the connection point between the switching tubes S5 and S6 are respectively used as three output terminals of the second-stage three-phase two-level inverter.

Further, the control unit receives input voltage, bus current, intermediate bus voltage, temperature and phase voltage signals of the first-stage step-down circuit and the second-stage three-phase two-level inverter, and outputs driving signals of 7 switching tubes.

Further, the driver further comprises an operation mode switching module for generating an operation mode switching signal and inputting the control unit to control the start, stop and speed command of the motor.

The utility model has the advantages that:

the driver comprises a first stage of step-down circuit, which reduces the input voltage before the motor starts to increase the speed, and maintains a relatively small intermediate bus voltage. Then, the control unit controls the rear-stage three-phase two-level inverter to realize the processes of pre-positioning, strong dragging and switching, and the duty ratio is increased to 100% and then kept unchanged. And then, the previous stage of step-down circuit is controlled to increase the voltage of the intermediate bus, the rotating speed of the motor is further increased, and a sampling mechanism of the combination opportunity and a dynamic comparison method executed by the control unit operate in a 100% duty ratio state, so that the accuracy, stability and reliability of position detection can be ensured even if the effective detection window time is reduced.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the utility model. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:

FIG. 1 illustrates a high-speed brushless DC motor driver architecture diagram according to an embodiment of the utility model;

FIG. 2 shows a specific circuit diagram of a high-speed brushless DC motor driver according to an embodiment of the utility model;

fig. 3 shows certain phase voltage and current waveforms when operating at 100% duty cycle according to an embodiment of the present utility model.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

The utility model relates to a position-sensor-free driver of a high-speed brushless direct current motor and a control strategy thereof, wherein a system schematic diagram is shown in figure 1 and comprises a voltage input, a driver and a brushless direct current motor. The driver comprises a driving control module, an operation mode switching module and a system protection module. The operation mode switching module and the system protection module adopt hardware and software implementation manners in the prior art, and are not described herein repeatedly because the operation mode switching module and the system protection module are not the utility model points of the present utility model.

The part in the dashed line box in fig. 1 is the driver of the present utility model, and the internal driving control module includes a first stage step-down circuit composed of a switching tube S0, an inductor L, a diode D, and a capacitor C, with an external input dc voltage, as shown in fig. 2. The second-stage three-phase two-level inverter consists of switching tubes S1, S2, S3, S4, S5 and S6, and output terminals a, b and c are connected with the brushless direct current motor windings. The control unit comprises a microprocessor, and input voltage, bus current, intermediate bus voltage, temperature and phase voltage signals of the main circuit part are all sent into the control unit through the sensor. After the control unit is processed by a program, 7 driving signals of the switching tubes are output. The operation mode switching signal is also input into the control unit for controlling the start and stop of the motor and the speed command.

The driver designed by the utility model is input into direct-current voltage, the first-stage voltage reduction circuit can reduce the amplitude of the input voltage to a proper size, namely the middle bus voltage by controlling the switching tube S0 through pulse width modulation so as to adapt to the rated voltage of the motor, and the driver can adapt to a very wide voltage range, adapt to higher motor rotating speed and improve the control flexibility of the driver.

The second stage is a three-phase two-level inverter, three bridge arms are formed by 6 switching tubes, the switching tubes are power electronic devices, usually of MOSFET type, a control unit outputs driving signals, S1, S2, S3, S4, S5 and S6 are controlled to be conducted or cut off in turn by high-frequency pulses of tens of thousands of hertz, and alternating-current pulsating voltages with adjustable frequency and amplitude are output to drive a direct-current brushless direct-current motor to operate.

Further, the starting process of the motor needs to be subjected to three steps of pre-positioning, strong dragging and switching to sensorless operation. In order to drive the brushless dc motor having a higher rotation speed, first, the switching tube S0 is controlled so that the output intermediate bus voltage value of the first-stage step-down circuit is half of the voltage input, and this state is maintained.

Further, the rear-stage three-phase two-level inverter is subjected to preset positioning and strong dragging, is switched to operate without a sensor, and keeps the operation duty ratio of the motor to be 100% based on a later combined sampling mechanism, so that zero crossing signal minimization loss is realized. The waveforms of the voltage and current of one phase of the motor are shown in fig. 3 when the inverter is operated at 100% duty cycle.

At this time, if the rotation speed of the motor is to be reduced, the control unit can control through the first-stage voltage reduction circuit, and control the on and off of the switching tube S0 through pulse width modulation, so as to further reduce the voltage of the intermediate bus, keep the 100% duty ratio of the rear-stage inverter to operate, and enable the sensorless position detection to be more stable and reliable.

Further, if the motor rotation speed is further increased, the control unit can control through the first-stage voltage reduction circuit, and control the on and off of the switching tube S0 through pulse width modulation, so that the intermediate bus voltage is increased, and the motor speed is increased. The back-stage inverter still keeps 100% duty cycle operation, and the accuracy and stability of position detection are guaranteed.

Further, in the operation process, the overcurrent protection function is realized by detecting the current of the bus. When the current exceeds a certain threshold value, the S1-S6 switching tube is turned off firstly, and after 2S delay, the S0 switching tube is turned off, so that the driver is protected.

Further, in the operation process, the temperature sensor detects the temperature, so that the over-temperature protection function is realized. When the temperature exceeds a certain threshold value, the S1-S6 switching tube is turned off firstly, and after 2S delay, the S0 switching tube is turned off, so that the driver is protected.

Further, in the operation process, the low-voltage and high-voltage protection function is realized by detecting the voltage of the intermediate bus. When the voltage of the middle bus exceeds a certain threshold, the S1-S6 switching tube is turned off firstly, and after 2S delay, the S0 switching tube is turned off, so that the driver is protected.

When the voltage of the middle bus is smaller than a certain threshold value, the S1-S6 switching tube is turned off firstly, and after 2S delay, the S0 switching tube is turned off, so that the driver is protected.

According to an embodiment of the present utility model, there is provided a driving method of a high-speed brushless direct current motor driver, including the steps of:

1. when the system is electrified and the starting signal is triggered, the control unit drives the switching tube S0 according to a high-speed driving strategy, and after the input voltage is reduced to 50%, the relatively small intermediate bus voltage is maintained.

2. The control unit drives the S1-S6 switching tube to conduct pre-positioning operation, and the motor rotor rotates from a certain initial position to a preset position at the moment.

3. After the pre-positioning is finished, the brushless direct current motor enters an external synchronous running state, enters a switching state after short acceleration, and enters a self-synchronous running state after detecting a zero crossing signal.

4. The brushless DC motor enters a self-synchronous running state, drives S1-S6 in turn according to an input signal, accelerates to a certain rotating speed according to a duty ratio of 100%, and is in a position sensor-free control mode at the moment.

5. The control unit drives S0, the voltage of the middle direct current bus is increased, and the rotating speed of the brushless direct current motor is further increased, so that high-speed operation is realized.

In the utility model, the driver comprises a first stage of step-down circuit, and the input voltage is reduced before the motor starts to rise, so that a relatively small intermediate bus voltage is maintained. Then, the control unit controls the rear-stage three-phase two-level inverter to realize the processes of pre-positioning, strong dragging and switching, and the duty ratio is increased to 100% and then kept unchanged. And then, the previous stage of step-down circuit is controlled to increase the voltage of the intermediate bus, the rotating speed of the motor is further increased, and a sampling mechanism of the combination opportunity and a dynamic comparison method executed by the control unit operate in a 100% duty ratio state, so that the accuracy, stability and reliability of position detection can be ensured even if the effective detection window time is reduced.

The present utility model is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present utility model are intended to be included in the scope of the present utility model. Therefore, the protection scope of the present utility model shall be subject to the protection scope of the claims.

Claims

1. A high-speed brushless dc motor driver, comprising:

the first-stage voltage reduction circuit, the second-stage three-phase two-level inverter and the control unit are connected with each other in pairs;

the first-stage voltage reduction circuit is composed of a switching tube S0, an inductor L, a diode D and a capacitor C, wherein one end of the switching tube S0 is connected with the anode of the external voltage input, the other end of the switching tube S0 is connected with one end of the inductor L and the cathode of the diode D, the other end of the inductor L is connected with one end of the capacitor C, and the other end of the capacitor C and the anode of the diode D are both connected with the cathode of the external voltage input;

the second-stage three-phase two-level inverter consists of switching tubes S1, S2, S3, S4, S5 and S6, wherein the switching tubes S1 and S2 are connected in series and then connected between the other end of the inductor L and the negative electrode of the external voltage input, the switching tubes S3 and S4 are connected in series and then connected between the other end of the inductor L and the negative electrode of the external voltage input, and the switching tubes S5 and S6 are connected in series and then connected between the other end of the inductor L and the negative electrode of the external voltage input; the connection point between the switching tubes S1 and S2, the connection point between the switching tubes S3 and S4, and the connection point between the switching tubes S5 and S6 are respectively used as three output terminals of the second-stage three-phase two-level inverter.

2. A high-speed brushless DC motor driver according to claim 1, wherein,

the control unit receives signals of input voltage, bus current, intermediate bus voltage, temperature and phase voltage of the first-stage voltage reduction circuit and the second-stage three-phase two-level inverter, and outputs driving signals of 7 switching tubes.

3. A high-speed brushless DC motor driver according to claim 2, wherein,

the driver further comprises an operation mode switching module for generating an operation mode switching signal and inputting the control unit to control the start, stop and speed instructions of the motor.