A brushless DC motor driver, motor and servo system

Abstract

This invention belongs to the field of motor technology, specifically disclosing a brushless DC motor driver, a motor, and a servo system. The brushless DC motor driver includes: a positive bus and a negative bus; an inverter circuit connected to both the positive and negative buses; and an RCD snubber circuit, comprising a snubber resistor, a capacitor, and a diode. The first end of the snubber resistor is connected to the positive bus, the second end of the snubber resistor is connected to the first end of the capacitor, the second end of the capacitor is connected to the negative bus, the anode of the diode is connected to the positive bus, and the cathode of the diode is connected between the second end of the snubber resistor and the first end of the capacitor. This invention solves the problem of poor reliability in brushless DC motor drivers in related technologies.

Description

Technical Field

[0001] This invention belongs to the field of motor technology, specifically relating to a brushless DC motor driver, a motor, and a servo system. Background Technology

[0002] In actual use, servo systems involve frequent motor starts, braking, and reversing. These processes are primarily achieved by controlling power devices to frequently switch on and off according to control logic. The switching on and off of these power devices, in turn, causes surge voltages and currents on the motor driver's power bus. These surge voltages and currents can easily lead to excessive electrical stress on the DC bus capacitors, causing capacitor damage. Furthermore, these surge voltage and current signals can be conducted and radiated into the low-voltage control circuit, threatening its reliability and making it difficult to meet the electromagnetic compatibility requirements of the servo system.

[0003] The use of multi-core ceramic capacitors and tantalum capacitors in related technologies is not effective in suppressing surge voltage and surge current, especially when used in high-power applications, where the defects are particularly obvious, resulting in poor reliability of brushless DC motor drivers. Summary of the Invention

[0004] The purpose of this invention is to provide a brushless DC motor driver, motor, and servo system to solve the problem of poor reliability of brushless DC motor drivers in related technologies.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] According to a first aspect of the present invention, a brushless DC motor driver is provided, comprising: a positive bus and a negative bus; an inverter circuit connected to the positive bus and the negative bus; and an RCD snubber circuit, comprising a snubber resistor, a capacitor, and a diode, wherein a first end of the snubber resistor is connected to the positive bus, a second end of the snubber resistor is connected to a first end of the capacitor, a second end of the capacitor is connected to the negative bus, the anode of the diode is connected to the positive bus, and the cathode of the diode is connected between the second end of the snubber resistor and the first end of the capacitor.

[0007] Furthermore, the absorption resistor is a non-inductive resistor, the capacitor is a film capacitor, and the diode is a fast recovery diode.

[0008] Furthermore, the inverter circuit is a three-phase inverter bridge circuit, and there are three RCD snubber circuits, which are set up one-to-one with the three arms of the three-phase inverter bridge circuit.

[0009] Furthermore, the capacitance value Among them, C s L is the capacitance value of the capacitor. sL1 is the equivalent parasitic inductance of the driver power bus in the brushless DC motor driver, L2 is the equivalent parasitic inductance of the RCD snubber circuit, I0 is the turn-off current of the driver power bus, and V... pek U is the surge voltage of the driver power bus. d The supply voltage for the driver power bus.

[0010] Furthermore, the resistance value of the absorption resistor Among them, R s L is the resistance value of the absorption resistor. s L1 is the equivalent parasitic inductance of the driver power bus of the brushless DC motor driver, L2 is the equivalent parasitic inductance of the RCD snubber circuit, and C is the equivalent parasitic inductance of the RCD snubber circuit. s is the capacitance value, and f is the PWM modulation frequency.

[0011] Furthermore, the reverse withstand voltage rating of the diode is the same as that of the IGBT in the three-phase inverter bridge circuit, and the reverse recovery time trr of the diode is less than the time t of the IGBT to reach the Miller plateau when it is turned on. f The rated DC current of the diode Among them, I d I0 is the rated DC current of the diode, I0 is the turn-off current of the driver power bus of the brushless DC motor driver, and t0 is the rated DC current of the diode. f f is the time it takes for the IGBT to reach the Miller plateau when it is turned on, and f is the PWM modulation frequency.

[0012] Furthermore, the brushless DC motor driver also includes a tantalum capacitor, with the positive terminal of the tantalum capacitor connected to the positive bus and the negative terminal of the tantalum capacitor connected to the negative bus.

[0013] Furthermore, the brushless DC motor driver also includes a power bus absorption capacitor, the two ends of which are connected to the positive bus and the negative bus respectively.

[0014] According to a second aspect of the present invention, an electric motor is provided, the electric motor including a brushless DC motor body and a driver connected to the brushless DC motor body, wherein the driver is the brushless DC motor driver described above.

[0015] According to a third aspect of the present invention, a servo system is provided, the servo system including a brushless DC motor, a driver connected to the brushless DC motor, a controller, a reducer, and an angle sensor, the controller being connected to the driver to control the driver to supply power to the brushless DC motor, the input shaft of the reducer being connected to the output shaft of the brushless DC motor, the angle sensor being used to detect the rotation angle of the output shaft of the reducer, and the angle sensor being communicatively connected to the controller, wherein the driver is the aforementioned brushless DC motor driver.

[0016] The brushless DC motor driver using the technical solution of this invention includes: a positive bus and a negative bus; an inverter circuit connected to the positive and negative buses; and an RCD snubber circuit, which includes a snubber resistor, a capacitor, and a diode. The first end of the snubber resistor is connected to the positive bus, the second end of the snubber resistor is connected to the first end of the capacitor, the second end of the capacitor is connected to the negative bus, the anode of the diode is connected to the positive bus, and the cathode of the diode is connected between the second end of the snubber resistor and the first end of the capacitor. This brushless DC motor driver design, with its RCD snubber circuit including a snubber resistor, a capacitor, and a diode, where the snubber resistor and capacitor are connected in series between the positive and negative buses, and the diode is connected in parallel with the snubber resistor, achieves rapid clamping and absorption of pulse voltage and pulse current on the power bus of the brushless DC motor driver, slows down the surge power discharge rate, suppresses voltage fluctuations on the driver's power bus, reduces the electrical stress on the power devices in the driver, improves the reliability of the driver, and solves the problem of poor reliability in brushless DC motor drivers in related technologies. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a brushless DC motor driver according to an embodiment of the present invention.

[0018] The above figures include the following reference numerals:

[0019] 1. Positive busbar; 2. Negative busbar; 3. Inverter circuit; 4. RCD snubber circuit; 41. Snubber resistor; 42. Capacitor; 43. Diode; 5. Tantalum capacitor; 6. Power bus snubber capacitor. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and are not to a precise scale, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0021] It should be noted that, in order to clearly illustrate the content of this invention, several embodiments are provided to further explain different implementations of the invention. These embodiments are enumerated rather than exhaustive. Furthermore, for the sake of brevity, content mentioned in the preceding embodiments is often omitted in the following embodiments. Therefore, content not mentioned in the later embodiments can be referred to in the preceding embodiments.

[0022] like Figure 1As shown, an embodiment of the present invention provides a brushless DC motor driver, which includes: a positive bus 1 and a negative bus 2; an inverter circuit 3 connected to the positive bus 1 and the negative bus 2; and an RCD snubber circuit 4, which includes a snubber resistor 41, a capacitor 42, and a diode 43. The first end of the snubber resistor 41 is connected to the positive bus 1, the second end of the snubber resistor 41 is connected to the first end of the capacitor 42, the second end of the capacitor 42 is connected to the negative bus 2, the anode of the diode 43 is connected to the positive bus 1, and the cathode of the diode 43 is connected between the second end of the snubber resistor 41 and the first end of the capacitor 42. The brushless DC motor driver with this structural design incorporates an RCD snubber circuit including a snubber resistor 41, a capacitor 42, and a diode 43. The snubber resistor 41 and the capacitor 42 are connected in series between the positive bus 1 and the negative bus 2, and the diode 43 is connected in parallel with the snubber resistor. This enables rapid clamping and absorption of pulse voltage and pulse current on the power bus of the brushless DC motor driver, reduces the discharge rate of surge power, suppresses voltage fluctuations on the driver's power bus, reduces electrical stress on the power devices in the driver, improves the reliability of the driver, and solves the problem of poor reliability of brushless DC motor drivers in related technologies.

[0023] Preferably, the absorption resistor 41 is a non-inductive resistor, the capacitor 42 is a thin-film capacitor, and the diode 43 is a fast recovery diode.

[0024] In this way, the advantages of fast recovery diodes, such as fast clamping rate of pulse voltage, short blocking recovery time, and low blocking recovery power, as well as the advantages of film capacitors, such as fast charging and discharging rate compared to ordinary capacitors, and the advantages of non-inductive power resistors, such as limiting capacitor charging current and quickly consuming capacitor discharge power, can be utilized to better control the surge voltage in the driver power bus, resulting in better control effect, especially suitable for medium and high power motor drivers.

[0025] Specifically, inverter circuit 3 is a three-phase inverter bridge circuit, and there are three RCD snubber circuits 4, with each of the three RCD snubber circuits corresponding to one of the three arms of the three-phase inverter bridge circuit.

[0026] Specifically, the capacitance value of capacitor 42 Among them, C s The capacitance value is 42, L s L1 is the equivalent parasitic inductance of the driver power bus of the brushless DC motor driver, L2 is the equivalent parasitic inductance of RCD snubber circuit 4, I0 is the turn-off current of the driver power bus, and V... pek U is the surge voltage of the driver power bus. d The supply voltage for the driver power bus.

[0027] To more reasonably determine the capacitance value of capacitor 42, the theoretical value of the energy stored in capacitor 42 when the power device IGBT (Insulated Gate Bipolar Transistor) in the driver is in steady-state conduction is:

[0028]

[0029] The energy stored in the stray inductance Ls of the main power supply circuit of the driver and the parasitic inductance L2 of the RCD absorption circuit 4 is:

[0030]

[0031] The energy consumed by the absorption resistor 41 in the RCD absorption circuit 4 is:

[0032]

[0033] For capacitor 42, a low-impedance, fast-charging-discharging-rate film capacitor is selected. Based on the principle of energy conservation, the capacitance value of capacitor 42 is calculated as follows: Among them, C s L is the capacitance value of the capacitor 42. s L1 is the equivalent parasitic inductance of the driver power bus of the brushless DC motor driver, L2 is the equivalent parasitic inductance of the RCD snubber circuit 4, I0 is the turn-off current of the driver power bus, and V pek U is the surge voltage of the driver power bus. d The supply voltage for the power bus of the driver.

[0034] The resistance value of absorption resistor 41 Among them, R s The resistance value of the absorption resistor 41, L s L1 is the equivalent parasitic inductance of the driver power bus of the brushless DC motor driver, L2 is the equivalent parasitic inductance of RCD snubber circuit 4, and C is the equivalent parasitic inductance of the RCD snubber circuit 4. s Here, f is the capacitance of capacitor 42, and f is the PWM modulation frequency.

[0035] If the resistance value of the absorption resistor 41 is too large, the capacitor 42 will charge and discharge too slowly, affecting the absorption effect. If it is too small, the discharge current will be too fast, causing a large pulse voltage and pulse current to be generated on the driver power bus. In addition, the absorption resistor 41 with a suitable resistance value can suppress the oscillation of the discharge current of the absorption capacitor. Preferably, the charging and discharging time constant of the absorption resistor 41 and the capacitor 42 in the RCD absorption circuit 4 is selected as (1 / 3 to 1 / 6) of the PWM modulation frequency of the driver, for example, 1 / 4. Therefore, in order to ensure the suppression effect on pulse voltage and pulse current, the resistance value of the absorption resistor 41 is selected as follows: Among them, R s L is the resistance value of the absorption resistor 41. sL1 is the equivalent parasitic inductance of the driver power bus of the brushless DC motor driver, L2 is the equivalent parasitic inductance of the RCD snubber circuit 4, and C is the equivalent parasitic inductance of the RCD snubber circuit 4. s f is the capacitance value of the capacitor 42, and f is the PWM modulation frequency.

[0036] Specifically, the reverse withstand voltage rating of diode 43 is the same as that of the IGBT in the three-phase inverter bridge circuit, and the reverse recovery time trr of diode 43 is less than the time t_r of the IGBT reaching the Miller plateau when it is turned on. f The rated DC current of diode 43 Among them, I d I0 is the rated DC current of diode 43, I0 is the turn-off current of the driver power bus of the brushless DC motor driver, and t0 is the rated DC current of diode 43. f f is the time it takes for the IGBT to reach the Miller plateau when it is turned on, and f is the PWM modulation frequency.

[0037] For a three-phase inverter bridge circuit, the fast recovery diode selection in the centralized RCD snubber circuit 4 should be: the reverse withstand voltage should be consistent with the voltage rating of the IGBT power devices in the three-phase inverter bridge, and the reverse recovery time (trr) should be less than the time trecovery for the IGBT to reach the Miller turn-on plateau when it is turned on. f To ensure effective suppression of pulse voltage and pulse current in the driver power bus, the rated DC current of the fast recovery diode is calculated as follows: Among them, I d I0 is the rated DC current of the diode 43, I0 is the turn-off current of the driver power bus of the brushless DC motor driver, and t0 is the rated DC current of the diode 43. f The time it takes for the IGBT to reach the Miller plateau when it is turned on is f, where f is the PWM modulation frequency.

[0038] Specifically, the brushless DC motor driver also includes a tantalum capacitor 5, the positive terminal of which is connected to the positive bus 1, and the negative terminal of which is connected to the negative bus 2.

[0039] By setting tantalum capacitor 5, the driver power bus can be filtered and stored, which helps to improve the stability of voltage and current in the driver power bus.

[0040] The brushless DC motor driver also includes a power bus absorption capacitor 6, the two ends of which are connected to the positive bus 1 and the negative bus 2 respectively.

[0041] Setting up a power bus absorption capacitor 6 can further improve the absorption effect of pulse voltage and pulse current in the power bus. Preferably, the power bus absorption capacitor 6 is a multi-core ceramic capacitor.

[0042] For the rapid start-up, acceleration, commutation, and braking conditions of the motor in the steering system, the solutions in related technologies cannot achieve rapid suppression of surge voltage and surge current. The solutions can only improve the reliability of the power devices in the motor driver by increasing the derating of power devices and filter capacitors and sacrificing the size of the motor driver. However, the brushless DC motor driver with the above-mentioned structural design of the present invention has the following advantages compared with the drivers in related technologies:

[0043] The circuit design is simple, which can reduce the capacitance and loss of the power bus filter capacitor in related technologies. It is suitable for filter circuits of medium and high power electric servo motors ranging from 2kW to 4kW.

[0044] It can quickly clamp the surge voltage and surge current generated during the rapid switching of power devices in the driver, reduce the electrical stress of the power devices, and enhance the reliability of the driver.

[0045] Utilizing the fast recovery diode's fast pulse voltage clamping rate, short blocking recovery time, and low blocking recovery power, the film capacitor's faster charging and discharging rate compared to ordinary capacitors, and the non-inductive power resistor's ability to limit capacitor charging current and rapidly dissipate capacitor discharging power, this technology is low in cost, highly feasible, and applicable to medium and high power motor drivers.

[0046] It can suppress the back electromotive force overshoot generated by the motor during the braking process of the rudder system, reduce the voltage fluctuation of the driver power bus, and improve the working stability of the rudder system;

[0047] By combining RCD circuits, the size of the driver can be reduced, which is beneficial to improving the power-to-volume ratio of the driver.

[0048] In addition, embodiments of the present invention also provide a motor, the motor including a brushless DC motor body and a driver connected to the brushless DC motor body, wherein the driver is the brushless DC motor driver described above.

[0049] Finally, embodiments of the present invention also provide a servo system, which includes a brushless DC motor, a driver connected to the brushless DC motor, a controller, a reducer, and an angle sensor. The controller is connected to the driver to control the driver to supply power to the brushless DC motor. The input shaft of the reducer is connected to the output shaft of the brushless DC motor. The angle sensor is used to detect the rotation angle of the output shaft of the reducer. The angle sensor is communicatively connected to the controller. The driver is the aforementioned brushless DC motor driver.

[0050] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise.

[0051] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A brushless DC motor driver, characterized in that, The brushless DC motor driver includes: Positive busbar (1) and negative busbar (2); Inverter circuit (3), the inverter circuit (3) is connected to the positive bus (1) and the negative bus (2); The RCD absorption circuit (4) includes an absorption resistor (41), a capacitor (42), and a diode (43). The first end of the absorption resistor (41) is connected to the positive bus (1), the second end of the absorption resistor (41) is connected to the first end of the capacitor (42), the second end of the capacitor (42) is connected to the negative bus (2), the positive terminal of the diode (43) is connected to the positive bus (1), and the negative terminal of the diode (43) is connected between the second end of the absorption resistor (41) and the first end of the capacitor (42). The absorption resistor (41) is a non-inductive resistor, the capacitor (42) is a thin film capacitor, and the diode (43) is a fast recovery diode; The inverter circuit (3) is a three-phase inverter bridge circuit, and there are three RCD absorption circuits (4). The three RCD absorption circuits are arranged one-to-one with the three bridge arms of the three-phase inverter bridge circuit. The capacitance value of the capacitor (42) Among them, C s L is the capacitance value of the capacitor (42). s L1 is the equivalent parasitic inductance of the driver power bus of the brushless DC motor driver, L2 is the equivalent parasitic inductance of the RCD snubber circuit (4), I0 is the turn-off current of the driver power bus, and V pek U is the surge voltage of the driver power bus. d The power supply voltage for the driver power bus; The resistance value of the absorption resistor (41) Among them, R s L is the resistance value of the absorption resistor (41). s L1 is the equivalent parasitic inductance of the driver power bus of the brushless DC motor driver, L2 is the equivalent parasitic inductance of the RCD absorption circuit (4), and C is the equivalent parasitic inductance of the RCD absorption circuit (4). s f is the capacitance value of the capacitor (42), and f is the PWM modulation frequency; The reverse withstand voltage rating of the diode (43) is the same as that of the IGBT in the three-phase inverter bridge circuit, and the reverse recovery time trr of the diode (43) is less than the time t of the IGBT to reach the Miller plateau when it is turned on. f The rated DC current of the diode (43) Among them, I d I0 is the rated DC current of the diode (43), I0 is the turn-off current of the driver power bus of the brushless DC motor driver, and t0 is the rated DC current of the diode (43). f f is the time it takes for the IGBT to reach the Miller plateau when it is turned on, and f is the PWM modulation frequency.

2. The brushless DC motor driver as described in claim 1, characterized in that, The brushless DC motor driver also includes a tantalum capacitor (5), the positive terminal of which is connected to the positive bus (1), and the negative terminal of which is connected to the negative bus (2).

3. The brushless DC motor driver as described in claim 2, characterized in that, The brushless DC motor driver also includes a power bus absorption capacitor (6), the two ends of which are connected to the positive bus (1) and the negative bus (2) respectively.

4. An electric motor, characterized in that, The motor includes a brushless DC motor body and a driver connected to the brushless DC motor body, wherein the driver is a brushless DC motor driver as described in any one of claims 1 to 3.

5. A servo motor system, characterized in that, The servo system includes a brushless DC motor, a driver, a controller, a reducer, and an angle sensor connected to the brushless DC motor. The controller is connected to the driver to control the driver to supply power to the brushless DC motor. The input shaft of the reducer is connected to the output shaft of the brushless DC motor. The angle sensor is used to detect the rotation angle of the output shaft of the reducer. The angle sensor is communicatively connected to the controller. The driver is a brushless DC motor driver as described in any one of claims 1 to 3.

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