Motor driving device supporting direct current power supply

Abstract

The embodiment of the invention provides a motor driving device supporting direct current power supply, which comprises a first node, a second node, a third node and a fourth node, the first node, the second node and the third node are suitable for being connected with an external direct current power supply, and the fourth node is suitable for being connected to a first input end of an inverter unit. The second node is suitable for being connected to the second input end of the inversion unit; a first switching device connected between the first node and the third node; a second switching device connected between the third node and the second node; the first fly-wheel diode is connected with the first switching device in an anti-parallel manner, and allows current to flow unidirectionally in the direction from the third node to the first node under the condition that the first switching device is turned off; and a second freewheeling diode which is connected in anti-parallel with the second switching device and allows the current to flow unidirectionally in the direction from the second node to the third node when the second switching device is turned off.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to the field of motor drive technology, and more specifically, to a motor drive device supporting direct current power supply. Background Art

[0002] With the increasing popularity of solar panels, wind turbines, and other renewable energy sources, the use of DC power is becoming more and more popular. DC power is essential for the efficient integration and distribution of power from renewable energy sources. DC power can be directly stored in batteries or used to power DC loads without conversion, thus maximizing efficiency.

[0003] The rapid growth of electric vehicles (EV) and hybrid electric vehicles (HEV) has led to the development of a DC power infrastructure for charging stations, enabling faster and more convenient charging. Many electronic devices, such as computers, smartphones, and light-emitting diodes (LEDs), have internal DC circuits. Using a DC power source eliminates the need for additional AC / DC conversion, making it easier to connect and power such devices.

[0004] On the other hand, common DC links are widely used in motor drives and servo motion system drives. Common DC links refer to shared DC bus or power supplies that are connected to multiple motor drives in the system. In this configuration, the DC power supply provides a common source of DC voltage that is shared between different motor drives. Common DC links allow power exchange and energy sharing between motor drives, which can improve energy efficiency and reduce the cost of the entire system. Common DC links are commonly used in various motor control systems, regenerative systems, and network drive systems.

[0005] However, the conventional method of using a DC power supply to power a motor driver usually only supports a specific voltage level, but cannot support different DC bus voltage levels, nor can it support bidirectional energy flow, which limits the application of DC power supply in the field of motor drives. Summary of the invention

[0006] An object of the present disclosure is to provide a motor drive device supporting DC power supply to at least partially solve the above problems.

[0007] In one aspect of the present disclosure, a motor drive device supporting DC power supply is provided, including: a first node, a second node, a third node and a fourth node, wherein the first node, the second node and the third node are suitable for connecting to an external DC power supply, the fourth node is suitable for connecting to a first input terminal of an inverter unit, and the second node is suitable for connecting to a second input terminal of the inverter unit; a first switching device, connected between the first node and the third node; a second switching device, connected between the third node and the second node; a first freewheeling diode, connected in anti-parallel to the first switching device, and allowing current to flow unidirectionally in a direction from the third node to the first node when the first switching device is turned off; and a second freewheeling diode, connected in anti-parallel to the second switching device, and allowing current to flow unidirectionally in a direction from the second node to the third node when the second switching device is turned off.

[0008] In some embodiments, the first node is connected to the fourth node, and the motor drive device also includes a first inductor, one end of the first inductor is connected to the third node, the other end of the first inductor is connected to the positive side of the external DC power supply, and the negative side of the external DC power supply is connected to the second node.

[0009] In some embodiments, when the motor is in a braking state, the second switching device remains turned off, and the first switching device is alternately turned on and off.

[0010] In some embodiments, when the motor is in a normal working state, the first switching device remains turned off, and the second switching device is alternately turned on and off.

[0011] In some embodiments, the first node is connected to the positive side of the external DC power supply, the second node is connected to the negative side of the external DC power supply, and the motor drive device also includes a second inductor, which is connected between the third node and the fourth node.

[0012] In some embodiments, when the motor is in a braking state, the first switching device remains turned off, and the second switching device is alternately turned on and off.

[0013] In some embodiments, when the motor is in a normal working state, the second switching device remains turned off, and the first switching device is alternately turned on and off.

[0014] In some embodiments, the first node is connected to the fourth node, the fourth node is connected to the positive side of the external DC power source, and the second node is connected to the negative side of the external DC power source.

[0015] In some embodiments, the motor drive device further includes an internal DC energy storage circuit, and the internal DC energy storage circuit is connected between the second node and the fourth node.

[0016] In some embodiments, the internal DC energy tank circuit includes a capacitor.

[0017] The motor drive device supporting DC power supply according to the embodiment of the present disclosure can support different DC bus voltage levels and simultaneously support bidirectional flow of energy.

[0018] It should be understood that the content described in this content section is not intended to limit the key features or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements, wherein:

[0020] Figure 1 and Figure 2 shows the circuit topology of a conventional motor drive;

[0021] Figure 3 The circuit topology of the motor driving device supporting DC power supply according to the embodiment of the present disclosure is shown;

[0022] Figure 4 A circuit schematic diagram of a motor drive device supporting DC power supply according to a first embodiment of the present disclosure is shown;

[0023] Figure 5 and Figure 6 Shows Figure 4 The schematic diagram of the operation of the motor drive device during the motor braking phase is shown;

[0024] Figure 7 and Figure 8 Shows Figure 4 The operating principle diagram of the motor drive device shown in the normal working stage of the motor;

[0025] Fig. 9 A circuit schematic diagram of a motor drive device supporting DC power supply according to a second embodiment of the present disclosure is shown;

[0026] Fig.10 and Fig.11 Shows Fig. 9 The schematic diagram of the operation of the motor drive device during the motor braking phase is shown;

[0027] Fig.12 and Fig.13 Shows Fig. 9 The operating principle diagram of the motor drive device shown in the normal working stage of the motor; and

[0028] Fig.14 A circuit schematic diagram of a motor drive device supporting DC power supply according to a third embodiment of the present disclosure is shown.

[0029] Description of reference numerals:

[0030] 11. First Switching Device

[0031] 21 First freewheeling diode

[0032] 12. Second switching device

[0033] 22 Second freewheeling diode

[0034] 31 First Node

[0035] 32 Second Node

[0036] 33 Third Node

[0037] 34 Fourth Node

[0038] 4 Inverter unit

[0039] 41 First input

[0040] 42 Second input

[0041] 43 Output

[0042] 51 First Inductor

[0043] 52 Second inductor

[0044] 6 External DC power supply

[0045] 7 Internal DC Tank Circuit

[0046] 8 Rectification unit

[0047] 9 Braking energy dissipation circuit DETAILED DESCRIPTION

[0048] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0049] As used herein, the term "including" and its variations mean open inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "based at least in part on". The terms "an example embodiment" and "an embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc. may refer to different or the same objects.

[0050] Conventional motor drivers usually use an alternating current power source, such as 220V or 380V mains power, to power the motor. Figure 1 and Figure 2 A circuit topology of a conventional motor driver is shown.

[0051] Figure 1 The motor driver shown includes a rectifier unit 8, a braking energy dissipation circuit 9 and an inverter unit 4. The rectifier unit 8 includes a rectifier bridge composed of diodes for converting AC power into DC power. The braking energy dissipation circuit 9 includes an insulated gate field effect transistor (IGBT), a diode and a braking resistor connected in parallel with the diode to dissipate the energy generated by the motor during braking. The inverter unit 4 includes six IGBTs for converting DC power into three-phase AC power to drive the motor with variable frequency and voltage amplitude.

[0052] Figure 2 The motor drive shown includes a rectifier unit 8 and an inverter unit 4. The rectifier unit 8 is capable of converting AC power into DC power, adjusting the power factor and providing bidirectional energy flow capability. The inverter unit 4 is used to convert DC power into three-phase AC power with variable frequency. Through the rectifier unit 8 and the inverter unit 4, the energy flow between the AC power grid or power supply and the load can be controlled, thereby allowing bidirectional energy exchange.

[0053] Figure 1 and Figure 2 The motor driver shown can only be used in AC power supply scenarios and cannot support DC power supply.

[0054] Conventional motor drives that support DC power supply usually only support specific DC bus voltage levels, but cannot support different DC bus voltage levels. In addition, some solutions that use DC / DC (DC / DC) converters to support different DC bus voltage levels cannot support bidirectional energy flow, which limits the application of DC power supply in the field of motor drives.

[0055] DC power supplies are classified into different voltage levels based on application requirements. The following are some common voltage level levels of DC power supplies: low voltage DC power supplies, which typically range from 1V to 24V, are commonly used to power small electronic devices, sensors, and microcontrollers; medium voltage DC power supplies, which range from 24 volts to several hundred volts, are commonly used to power industrial automation systems, motor control systems, and some electronic devices; high voltage DC power supplies, which range from several hundred volts to several thousand volts, are commonly used in applications such as electrostatic precipitators, scientific research, high voltage testing, cathode ray tubes (CRTs), and particle accelerators; ultra-high voltage DC power supplies, which range from several thousand volts to megavolts, are commonly used in professional applications such as medical equipment (electrotherapy), high-energy physics experiments, and some industrial processes.

[0056] Depending on the application, the common DC bus voltage may be higher, lower or equal to the DC link voltage of the motor drive. The motor drive device of the embodiment of the present disclosure can support different DC bus voltage levels and support bidirectional flow of energy at the same time. Figures 3 to 14 The principles of the present disclosure are described in detail.

[0057] Figure 3 FIG. 2 shows a circuit topology of a motor drive device supporting DC power supply according to an embodiment of the present disclosure. Figure 3 As shown, the device described herein includes a first node 31, a second node 32, a third node 33, and a fourth node 34. For ease of understanding and description, the first node 31 may also be referred to as node A herein, the second node 32 may also be referred to as node B herein, the third node 33 may also be referred to as node C herein, and the fourth node 34 may also be referred to as node D herein.

[0058] Figure 3 The motor drive device shown also includes a first switching device 11 and a second switching device 12, which are connected in series between node A and node B. The node between the first switching device 11 and the second switching device 12 is node C. The first switching device 11 and the second switching device 12 can be turned on or off under the control of a control signal applied to their control terminals. When the first switching device 11 is turned on, current can flow through the first switching device 11 in a direction from node A to node C. When the second switching device 12 is turned on, current can flow through the second switching device 12 in a direction from node C to node B.

[0059] In some embodiments, the first switching device 11 and the second switching device 12 may include IGBTs. It should be understood that the first switching device 11 and the second switching device 12 may include any appropriate type of switching device whose on / off state can be controlled by a control signal, and the embodiments of the present disclosure are not limited thereto.

[0060] Figure 3 The motor drive device shown also includes a first freewheeling diode 21 and a second freewheeling diode 22. The first freewheeling diode 21 is connected in anti-parallel to the first switching device 11. When the first switching device 11 is turned off, the first freewheeling diode 21 allows current to flow therethrough unidirectionally in a direction from node C to node A. The second freewheeling diode 22 is connected in anti-parallel to the second switching device 12. When the second switching device 12 is turned off, the second freewheeling diode 22 allows current to flow therethrough unidirectionally in a direction from node B to node C.

[0061] Figure 3 The motor drive device shown also includes an inverter unit 4, which includes a first input terminal 41, a second input terminal 42 and an output terminal 43. The output terminal 43 is suitable for connecting to the motor. The inverter unit 4 can convert the direct current received via the first input terminal 41 and the second input terminal 42 into an alternating current with adjustable voltage amplitude and frequency, and provide it to the motor via the output terminal 43. The first input terminal 41 is connected to the node D, and the second input terminal 42 is connected to the node B.

[0062] In some embodiments, Figure 3 As shown, the inverter unit 4 includes six IGBTs and diodes connected in anti-parallel to each IGBT, and by controlling the on-off state of each IGBT, a voltage with a desired frequency and amplitude can be output at the output terminal 43. It should be understood that the inverter unit 4 can have any appropriate structure for converting direct current into alternating current, and the embodiments of the present disclosure are not limited to this.

[0063] Node A, node B, node C and node D can be connected to appropriate devices so that Figure 3 The motor drive device shown is suitable for DC power supplies of different voltage levels. Figures 4 to 14 Describe this.

[0064] Figure 4 FIG. 2 shows a circuit schematic diagram of a motor drive device supporting DC power supply according to a first embodiment of the present disclosure. Figure 4 As shown, the first node 31 is connected to the fourth node 34, and the motor drive device further includes a first inductor 51. One end of the first inductor 51 is connected to the third node 33, the other end of the first inductor 51 is connected to the positive side of the external DC power supply 6, and the negative side of the external DC power supply 6 is connected to the second node 32. The motor drive device further includes an internal DC energy storage circuit 7, which is connected between the second node 32 and the fourth node 34. As an example, the internal DC energy storage circuit 7 may include a capacitor or any suitable type of energy storage element.

[0065] Figure 4The motor drive device shown is suitable for the case where the voltage level of the external DC power supply 6 is low, that is, the voltage level of the external DC power supply 6 is lower than the voltage level of the internal DC energy storage circuit 7. The voltage level of the external DC power supply 6 can be much lower than the voltage level of the internal DC energy storage circuit 7.

[0066] when Figure 4 When the motor connected to the motor drive device shown is in a braking stage, the mechanical energy of the motor can be converted into electrical energy, and the generated electrical energy can flow back through the motor drive device to the external DC power supply 6 for discharge. Figure 5 and Figure 6 Shows Figure 4 The operating principle diagram of the motor drive device during the motor braking phase is shown.

[0067] like Figure 5 As shown, when the motor is in the braking stage, the mechanical energy of the motor is converted into electrical energy and flows in reverse to the internal DC energy storage circuit 7 via the inverter 4. At this time, the first switching device 11 is turned on (ON), and the second switching device 12 is turned off (OFF). The internal DC energy storage circuit 7 can discharge the electrical energy to the first inductor 51 via the first switching device 11, and the first inductor 51 can use the electrical energy to charge the external DC power supply 6. In this process, a current path is formed in the direction indicated by the dotted line with an arrow. That is, the current flows out from the positive side of the internal DC energy storage circuit 7, flows to the positive side of the external DC power supply 6 via the first switching device 11 and the first inductor 51, and returns from the negative side of the external DC power supply 6 to the negative side of the internal DC energy storage circuit 7. In this way, the electrical energy generated by the motor in the braking stage can be discharged to the external DC power supply 6.

[0068] like Figure 6 As shown, the first switch device 11 and the second switch device 12 are both turned off. At this time, the first inductor 51 can continue to charge the external DC power source 6. In this process, a current path is formed that flows through the first inductor 51, the external DC power source 6 and the second freewheeling diode 22 in the direction indicated by the dotted line with an arrow. By using this current path, the electric energy stored in the first inductor 51 can be discharged to the external DC power source 6.

[0069] When the motor is in the braking phase, the motor drive device can be alternately Figure 5 and Figure 6 The operating state shown. That is, when the motor is in the braking state, the second switch device 12 remains off, and the first switch device 11 is alternately turned on and off. In this way, the electric energy generated by the motor in the braking stage can be discharged to the external DC power supply 6. It should be understood that the duty cycle of the control signal of the first switch device 11 can be adjusted as needed.

[0070] when Figure 4 When the motor connected to the motor drive device shown is in a normal working state, the external DC power supply 6 can provide electrical energy to the motor via the motor drive device. Figure 7 and Figure 8 Shows Figure 4 The operating principle diagram of the motor drive device during the normal working stage of the motor is shown.

[0071] like Figure 7 As shown in FIG. 1 , the first switching device 11 is turned off and the second switching device 12 is turned on. At this time, a current path is formed that flows through the first inductor 51, the second switching device 12 and the external DC power source 6 in the direction indicated by the dotted line with an arrow. In this process, the external DC power source 6 can charge the first inductor 51.

[0072] like Figure 8 As shown, the first switch device 11 and the second switch device 12 are both turned off. At this time, a current path is formed that flows through the first inductor 51, the first freewheeling diode 21, the internal DC energy storage circuit 7 and the external DC power supply 6 in the direction indicated by the dotted line with an arrow. In this process, the first inductor 51 can charge the internal DC energy storage circuit 7 with the stored electric energy. The electric energy stored in the DC energy storage circuit 7 can be converted into AC power via the inverter 4, thereby driving the motor.

[0073] When the motor is in the normal working stage, the motor drive device can be alternately in Figure 7 and Figure 8 The operating state shown. That is, when the motor is in a normal working state, the first switch device 11 remains off, and the second switch device 12 is alternately turned on and off. In this way, the external DC power supply 6 can power the motor via the motor drive device when the motor is in a normal working state. It should be understood that the duty cycle of the control signal of the second switch device 12 can be adjusted as needed.

[0074] Fig. 9 FIG. 2 shows a circuit schematic diagram of a motor drive device supporting DC power supply according to a second embodiment of the present disclosure. Fig. 9 As shown, the first node 31 is connected to the positive side of the external DC power supply 6, and the second node 32 is connected to the negative side of the external DC power supply 6. The motor drive device also includes a second inductor 52, which is connected between the third node 33 and the fourth node 34. The motor drive device also includes an internal DC energy storage circuit 7, which is connected between the second node 32 and the fourth node 34. As an example, the internal DC energy storage circuit 7 may include a capacitor or any suitable type of energy storage element.

[0075] Fig. 9The motor drive device shown is suitable for the case where the voltage level of the external DC power supply 6 is relatively high, that is, the voltage level of the external DC power supply 6 is greater than the voltage level of the internal DC energy storage circuit 7. The voltage level of the external DC power supply 6 can be much greater than the voltage level of the internal DC energy storage circuit 7.

[0076] when Fig. 9 When the motor connected to the motor drive device shown is in a braking stage, the mechanical energy of the motor can be converted into electrical energy, and the generated electrical energy can flow back through the motor drive device to the external DC power supply 6 for discharge. Fig.10 and Fig.11 Shows Fig. 9 The operating principle diagram of the motor drive device during the motor braking phase is shown.

[0077] like Fig.10 As shown, when the motor is in the braking stage, the mechanical energy of the motor is converted into electrical energy and flows in reverse to the internal DC energy storage circuit 7 via the inverter 4. At this time, the first switching device 11 is turned off, and the second switching device 12 is turned on, thereby forming a current path flowing through the second inductor 52, the second switching device 12 and the internal DC energy storage circuit 7 in the direction indicated by the dotted line with an arrow. Using this current path, the internal DC energy storage circuit 7 can charge the second inductor 52 using the stored electrical energy.

[0078] like Fig.11 As shown, the first switch device 11 and the second switch device 12 are both turned off. At this time, a current path is formed that flows along the direction indicated by the dotted line with an arrow through the second inductor 52, the first freewheeling diode 21, the external DC power supply 6 and the internal DC energy storage circuit 7. By using this current path, the electric energy stored in the second inductor 52 can be discharged to the external DC power supply 6.

[0079] When the motor is in the braking phase, the motor drive device can be alternately Fig.10 and Fig.11 The operating state shown. That is, when the motor is in the braking state, the first switch device 11 remains off, and the second switch device 12 is alternately turned on and off. In this way, the electric energy generated by the motor in the braking stage can be discharged to the external DC power supply 6. It should be understood that the duty cycle of the control signal of the second switch device 12 can be adjusted as needed.

[0080] when Fig. 9 When the motor connected to the motor drive device shown is in a normal working state, the external DC power supply 6 can provide electrical energy to the motor via the motor drive device. Fig.12 and Fig.13 Shows Fig. 9 The operating principle diagram of the motor drive device during the normal working stage of the motor is shown.

[0081] like Fig.12 As shown in FIG. 1 , the first switching device 11 is turned on, and the second switching device 12 is turned off. At this time, a current path is formed that flows through the first switching device 11, the second inductor 52, the internal DC energy storage circuit 7, and the external DC power supply 6 in the direction indicated by the dotted line with an arrow. In this process, the external DC power supply 6 can charge the second inductor 52, and the second inductor 52 can charge the internal DC energy storage circuit 7.

[0082] like Fig.13 As shown, the first switch device 11 and the second switch device 12 are both turned off. At this time, a current path is formed that flows through the second inductor 52, the internal DC energy storage circuit 7 and the second freewheeling diode 22 in the direction indicated by the dotted line with an arrow. In this process, the second inductor 52 can continue to charge the internal DC energy storage circuit 7 using the stored electrical energy.

[0083] like Fig.12 and 13 As shown, the electric energy stored in the DC energy storage circuit 7 can be converted into AC power via the inverter 4 to drive the motor.

[0084] When the motor is in the normal working stage, the motor drive device can be alternately in Fig.12 and Fig.13 The operating state shown. That is, when the motor is in a normal working state, the second switch device 12 remains off, and the first switch device 11 is alternately turned on and off. In this way, the external DC power supply 6 can power the motor via the motor drive device when the motor is in a normal working state. It should be understood that the duty cycle of the control signal of the first switch device 11 can be adjusted as needed.

[0085] Fig.14 A circuit schematic diagram of a motor drive device supporting DC power supply according to a third embodiment of the present disclosure is shown. Fig.14 The motor drive device shown is suitable for the case where the voltage level of the external DC power supply 6 is substantially equal to the voltage level of the internal DC energy storage circuit 7. Fig.14 As shown, the first node 31 is connected to the fourth node 34, the fourth node 34 is connected to the positive side of the external DC power supply 6, and the second node 32 is connected to the negative side of the external DC power supply 6. The motor drive device also includes an internal DC energy storage circuit 7, which is connected between the second node 32 and the fourth node 34. As an example, the internal DC energy storage circuit 7 may include a capacitor or any suitable type of energy storage element.

[0086] when Fig.14When the motor connected to the motor drive device shown is in the braking stage, the mechanical energy of the motor can be converted into electrical energy. By controlling the on / off state of the first switch device 11 and the second switch device 12, the generated electrical energy can flow back through the motor drive device to the external DC power supply 6 for discharge. Fig.14 When the motor connected to the motor drive device shown is in a normal working state, by controlling the on and off states of the first switch device 11 and the second switch device 12, the external DC power supply 6 can provide electrical energy to the motor via the motor drive device.

[0087] The motor drive device according to the embodiment of the present disclosure can support different DC bus voltage levels and support bidirectional energy flow at the same time. In addition, the motor drive device according to the embodiment of the present disclosure has a simple structure and can be flexibly configured as needed.

[0088] The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A motor drive device supporting DC power supply, comprising: a first node (31), a second node (32), a third node (33) and a fourth node (34), wherein the first node (31), the second node (32) and the third node (33) are suitable for connecting to an external DC power source (6), the fourth node (34) is suitable for connecting to a first input terminal (41) of an inverter unit (4), and the second node (32) is suitable for connecting to a second input terminal (42) of the inverter unit (4); A first switching device (11) connected between the first node (31) and the third node (33); A second switching device (12) connected between the third node (33) and the second node (32); a first freewheeling diode (21) connected in anti-parallel to the first switch device (11) and allowing current to flow unidirectionally from the third node (33) to the first node (31) when the first switch device (11) is turned off; as well as A second freewheeling diode (22) is connected in anti-parallel with the second switching device (12) and allows current to flow unidirectionally from the second node (32) to the third node (33) when the second switching device (12) is turned off.

2. The motor drive device according to claim 1, wherein the first node (31) is connected to the fourth node (34), and the motor drive device further comprises a first inductor (51), one end of the first inductor (51) is connected to the third node (33), the other end of the first inductor (51) is connected to the positive side of the external DC power supply (6), and the negative side of the external DC power supply (6) is connected to the second node (32).

3. The motor drive device according to claim 2, wherein when the motor is in a braking state, the second switching device (12) remains turned off, and the first switching device (11) is alternately turned on and off.

4. The motor drive device according to claim 2, wherein when the motor is in a normal working state, the first switching device (11) remains turned off, and the second switching device (12) is alternately turned on and off.

5. The motor drive device according to claim 1, wherein the first node (31) is connected to the positive side of the external DC power supply (6), the second node (32) is connected to the negative side of the external DC power supply (6), and the motor drive device also includes a second inductor (52), and the second inductor (52) is connected between the third node (33) and the fourth node (34).

6. The motor drive device according to claim 5, wherein when the motor is in a braking state, the first switching device (11) remains turned off, and the second switching device (12) is alternately turned on and off.

7. The motor drive device according to claim 5, wherein when the motor is in a normal working state, the second switching device (12) remains turned off, and the first switching device (11) is alternately turned on and off.

8. The motor drive device according to claim 1, wherein the first node (31) is connected to the fourth node (34), the fourth node (34) is connected to the positive side of the external DC power supply (6), and the second node (32) is connected to the negative side of the external DC power supply (6).

9. The motor drive device according to any one of claims 1 to 8, further comprising an internal DC energy storage circuit (7), wherein the internal DC energy storage circuit (7) is connected between the second node (32) and the fourth node (34).

10. The motor drive device according to claim 9, wherein the internal DC energy storage circuit (7) comprises a capacitor.

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