Motor driver and motor driving system

Abstract

The invention relates to a motor driver and a motor driving system, the motor driver comprises a rectification circuit, a direct current chain circuit and an inversion circuit, the direct current chain circuit is connected between the rectification circuit and the inversion circuit, the direct current chain circuit comprises a capacitor, a seventh switch device, a fly-wheel diode and an inductor, the first end and the second end of the capacitor are connected with the positive electrode output end and the negative electrode output end of the rectifying circuit respectively, the collector electrode of the seventh switching device is connected with the first end of the capacitor, the emitter electrode of the seventh switching device is connected with the negative electrode of the fly-wheel diode, and the positive electrode of the fly-wheel diode is connected with the second end of the capacitor. The first end of the inductor is connected with the midpoint between the seventh switching device and the fly-wheel diode, and the second end of the inductor and the positive electrode of the fly-wheel diode serve as two terminals used for being connected with the energy storage element.

Description

Technical Field

[0001] The present disclosure generally relates to the field of circuit technology, and more particularly, to a motor driver and a motor driving system. Background Art

[0002] Frequency converters (VFCs) are widely used in the motor drive and servo industries. In most cases, capacitors are used as power decoupling devices in the DC link circuit. During motor braking, regenerative energy will be applied to the capacitors of the DC link circuit, causing the DC voltage to rise. If the voltage continues to rise above the allowable operating voltage, the capacitor may be damaged. Usually, a braking resistor is used to dissipate the regenerative energy to prevent overvoltage damage to the components, but this brings other problems, such as heat dissipation and large size.

[0003] Figure 1 It is a topology of a motor drive 10 in the prior art. Ua, Ub and Uc are the three phases of the grid. Two single-phase diode rectifier bridges are used at the input. One of the branches from each rectifier bridge shares a grid phase to support 1AC or 3AC power input. An intelligent power module (IPM) is used in the DC / AC converter to achieve a compact design. A large braking resistor R1 is connected to the DC link through the power switch T7. If the DC voltage rises to the limit value, the power switch T7 will be activated and R1 will absorb the overvoltage. A freewheeling diode D9 is added to eliminate the transient overvoltage caused by the stray inductance of the braking resistor R1.

[0004] Since the brake resistor R1 needs to dissipate the regenerative energy of the motor, it should have a high power capacity and a large volume. At the same time, it is usually customized, so the cost is quite expensive. Most importantly, the large dissipated power will generate high temperature inside the resistor, even up to several hundred degrees Celsius, which will bring severe challenges to the heat sink and structural design of the entire system. Summary of the invention

[0005] A brief overview of the present invention is given below in order to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is merely to give certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0006] In view of the above, the present disclosure provides a motor driver capable of eliminating overvoltage damage.

[0007] According to one aspect of the present disclosure, a motor driver is provided, wherein an input end of the motor driver is connected to a three-phase power grid, an output end of the motor driver is connected to a motor, and the motor driver comprises: a rectifier circuit, a DC link circuit and an inverter circuit, wherein the rectifier circuit comprises a first rectifier bridge and a second rectifier bridge, and the inverter circuit comprises first, second and third DC / AC conversion branch circuits arranged in parallel between positive and negative output ends of the DC link circuit, wherein each of the first, second and third DC / AC conversion branch circuits comprises first and second, third and fourth, fifth and sixth switching devices, respectively, wherein:

[0008] The DC link circuit is connected between the rectifier circuit and the inverter circuit, and includes a capacitor, a seventh switching device, a freewheeling diode, and an inductor, wherein the first end and the second end of the capacitor are respectively connected to the positive output end and the negative output end of the rectifier circuit, the collector of the seventh switching device is connected to the first end of the capacitor, the emitter of the seventh switching device is connected to the negative electrode of the freewheeling diode, the positive electrode of the freewheeling diode is connected to the second end of the capacitor, the first end of the inductor is connected to the midpoint between the seventh switching device and the freewheeling diode, and the second end of the inductor and the positive electrode of the freewheeling diode serve as two terminals for connecting an energy storage element.

[0009] In this way, overvoltage damage to the capacitor can be avoided.

[0010] Optionally, in an example of the above aspect, the energy storage element is any one of a rechargeable battery, a capacitor arranged inside the motor driver, or an external power supply connected to the outside of the motor driver.

[0011] In this way, suitable energy storage elements can be selected according to needs.

[0012] Optionally, in an example of the above aspect, the positive electrode of the rechargeable battery is connected to the second end of the inductor, and the negative electrode of the rechargeable battery is connected to the positive electrode of the freewheeling diode.

[0013] When the motor connected to the motor driver operates in a braking regeneration mode, the regenerative energy generated during braking is stored in the rechargeable battery.

[0014] In this way, the regenerative energy generated during the braking process can be stored in the rechargeable battery, thereby effectively utilizing the regenerative energy. In addition, the drive itself requires an external power supply as an auxiliary power supply and motor holding brake power supply, so the rechargeable battery can also be directly used as an auxiliary power supply and motor holding brake power supply.

[0015] Optionally, in an example of the above aspect, the first to seventh switching devices include a fully-controlled power transistor and a diode, and the anode and cathode of the diode are respectively connected to the emitter and collector of the fully-controlled power transistor.

[0016] Optionally, in an example of the above aspect, the fully-controlled power transistor includes an insulated gate bipolar transistor.

[0017] According to another aspect of the present disclosure, a motor drive system is provided, comprising the motor driver as described above and a motor, wherein the motor driver is used to drive the motor, wherein:

[0018] When the motor operates in a braking regeneration mode, the regenerative energy generated during the braking process of the motor is stored in a rechargeable battery of the motor driver.

[0019] In the circuit topology of the motor driver according to the present invention, an inductor is added to the DC link circuit, thereby removing the brake resistor commonly used in the prior art, which is usually large in size, generates a lot of heat and has a high cost. Therefore, the technical solution according to the present invention has at least one of the following technical advantages.

[0020] 1. It is beneficial to the heat dissipation design of the system and can eliminate the influence of the braking resistor on other temperature sensing components.

[0021] 2. Saving volume. In the circuit topology of the prior art, the braking resistor needs to dissipate the regenerated energy, so it is bulky. Removing the resistor in the circuit topology of the present invention helps to save space.

[0022] 3. Adding a rechargeable battery can store the regenerative energy during the motor braking process, which is beneficial to saving energy; and the rechargeable battery can also be directly used as an auxiliary power supply for the motor driver and a motor holding brake power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other purposes, features and advantages of the present invention will be more easily understood by referring to the following description of the embodiments of the present invention in combination with the accompanying drawings. The components in the accompanying drawings are only for illustrating the principles of the present invention. In the accompanying drawings, the same or similar technical features or components will be represented by the same or similar reference numerals. In the accompanying drawings:

[0024] Figure 1 It is a circuit topology diagram of a motor driver in the prior art.

[0025] Figure 2 4 is a circuit topology diagram of a motor driver according to an embodiment of the present disclosure.

[0026] The reference numerals are as follows:

[0027] 10, 20: Motor driver Ua, Ub and Uc: three-phase power grid

[0028] D1-D9: diodes R1: Resistor

[0029] T1-T7: No. one To the seventh switching device 210: Rectifier circuit

[0030] 220: DC link circuit 230: Inverter circuit

[0031] M: Motor 2101: The first rectifier bridge

[0032] 2102: second rectifier bridge 2301, 2302, 2303: first to third DC / AC conversion branch circuits

[0033] L1: Inductor E: Rechargeable battery

[0034] C1: Capacitor DETAILED DESCRIPTION

[0035] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that the discussion of these embodiments is only to enable those skilled in the art to better understand and implement the subject matter described herein, and is not a limitation of the scope of protection, applicability or examples set forth in the claims. The function and arrangement of the elements discussed can be changed without departing from the scope of protection of the present disclosure. Various examples can omit, replace or add various processes or components as needed. For example, the described method can be performed in an order different from the described order, and various steps can be added, omitted or combined. In addition, the features described relative to some examples can also be combined in other examples.

[0036] As used herein, the term "including" and its variations represent open terms, meaning "including but not limited to". The term "based on" means "based at least in part on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment". The term "another embodiment" means "at least one other embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other definitions may be included below, whether explicit or implicit. Unless the context clearly indicates otherwise, the definition of a term is consistent throughout the specification.

[0037] In view of this, the present invention provides a motor driver, which can solve the above problems existing in the prior art.

[0038] Figure 2 FIG. 2 shows an exemplary circuit topology diagram of a motor driver 20 according to an embodiment of the present disclosure. Figure 2 As shown, the input end of the motor driver 20 is connected to the three phases Ua, Ub and Uc of the three-phase power grid, and the output end of the motor driver is connected to a motor M.

[0039] The motor driver 20 includes a rectifier circuit 210 , a DC link circuit 220 , and an inverter circuit 230 .

[0040] The rectifier circuit 210 includes a first rectifier bridge 2101 and a second rectifier bridge 2102 .

[0041] Specifically, the first rectifier bridge 2101 includes a first bridge arm and a second bridge arm, the first bridge arm and the second bridge arm are connected in parallel, the first bridge arm includes a first diode D1 and a second diode D2 connected in series, and the second bridge arm includes a third diode D3 and a fourth diode D4 connected in series. The second rectifier bridge 2102 includes a third bridge arm and a fourth bridge arm, the third bridge arm and the fourth bridge arm are connected in parallel, the third bridge arm includes a fifth diode D5 and a sixth diode D6 connected in series, and the fourth bridge arm includes a seventh diode D7 and an eighth diode D8 connected in series.

[0042] The a-phase input end of the three-phase power grid is connected to the midpoint between the first diode D1 and the second diode D2 of the first bridge arm, the b-phase input end of the three-phase power grid is connected to the midpoint between the third diode D3 and the fourth diode D4 of the second bridge arm and the midpoint between the fifth diode D5 and the sixth diode D6 of the third bridge arm, the c-phase output end of the three-phase power grid is connected to the midpoint between the seventh diode D7 and the eighth diode D8 of the fourth bridge arm, and the positive output end and the negative output end of the first rectifier bridge 2101 are respectively connected to the positive output end and the negative output end of the second rectifier bridge 2102.

[0043] It is understood that the three-phase power grid and the rectifier circuit 210 may also be connected in other ways, not limited to Figure 2 shown.

[0044] Figure 2 The circuit topology of the rectifier circuit 210 is a common circuit in the prior art. The rectifier circuit part of the present disclosure may not be limited to Figure 2 As shown in , other topologies may also be used, which will not be described in detail here.

[0045] The inverter circuit 230 is connected to the DC link circuit 220 and includes three parallel first, second and third DC / AC (direct current / alternating current) conversion branch circuits for converting the DC voltage output by the DC link circuit into an AC voltage.

[0046] Specifically, the inverter circuit 230 includes first to third DC / AC conversion branch circuits 2301, 2302, 2303 arranged in parallel between the positive output terminal and the negative output terminal of the DC link circuit 220, and each of the first to third DC / AC conversion branch circuits 2301, 2302, 2303 includes two switching devices, namely, the first and second, the third and fourth, and the fifth and sixth switching devices T1, T2, T3, T4, T5, T6 respectively.

[0047] The main improvement of the circuit structure of the motor driver according to the present invention lies in the DC link circuit part, which will be described in detail below.

[0048] The DC link circuit 220 is connected between the rectifier circuit 210 and the inverter circuit 230 and is used to filter the output voltage of the rectifier circuit.

[0049] Specifically, Figure 2 As shown, the DC link circuit 220 includes a capacitor C1, a seventh switch device T7, a freewheeling diode D9, an inductor L1, and a rechargeable battery E, wherein the first end and the second end of the capacitor C1 are respectively connected to the positive output end and the negative output end of the rectifier circuit 210, the collector of the seventh switch device T7 is connected to the first end of the capacitor C1, the emitter of the seventh switch device T7 is connected to the negative electrode of the freewheeling diode D9, the positive electrode of the freewheeling diode D9 is connected to the second end of the capacitor, the first end of the inductor L1 is connected to the midpoint between the seventh switch device T7 and the freewheeling diode D9, the second end of the inductor L1 is connected to the positive electrode of the rechargeable battery E, and the negative electrode of the rechargeable battery E is connected to the positive electrode of the freewheeling diode D9.

[0050] exist Figure 2 In the embodiment, a rechargeable battery E is connected between the inductor L1 and the freewheeling diode D9 as an energy storage element. It can be understood that a capacitor can also be used as an energy storage element.

[0051] Alternatively, the motor driver itself does not include an energy storage element, and the second end of the inductor L1 and the positive electrode of the freewheeling diode D9 form two terminals that can be used to connect an external energy storage element. For example, when the motor driver is working, an external power supply is connected between the second end of the inductor L1 and the positive electrode of the freewheeling diode D9.

[0052] like Figure 2As shown, the first to seventh switching devices are all composed of a fully-controlled power transistor and a diode, and the positive and negative electrodes of the diode are respectively connected to the emitter and collector of the fully-controlled power transistor. In other examples of the present disclosure, the single fully-controlled power transistor can be composed of multiple fully-controlled power transistors in parallel, series or mixed. Similarly, the single diode can also be composed of multiple diodes in parallel, series or mixed. In the present disclosure, the fully-controlled power transistor is, for example, an insulated gate bipolar transistor (IGBT). Those skilled in the art will understand that other types of power transistors can also be used, which will not be described in detail here.

[0053] When the motor operates in a braking regeneration mode, the seventh switch device T7, the freewheeling diode D9 and the inductor L1 in the motor driver according to the present invention can be used as a buck converter. During the motor braking process, the regenerative energy is applied to the capacitor in the DC link circuit, causing the DC voltage to rise. If the voltage continues to rise to exceed the allowable operating voltage, the DC capacitor may be damaged. Utilizing the circuit topology of the buck converter in the motor driver according to the present invention, when the DC voltage is greater than the protection voltage, the switch device T7 will be activated, and the loop formed by the seventh switch device T7, the freewheeling diode D9 and the inductor L1 can reduce the DC voltage.

[0054] If a rechargeable battery E is connected between the inductor and the diode, the regenerative energy generated during the braking process can be stored in the rechargeable battery E, thereby effectively utilizing the regenerative energy. In addition, for the low-voltage servo drive, an external power supply is required as an auxiliary power supply and a motor holding brake power supply, so the rechargeable battery E can also be directly used as an auxiliary power supply and a motor holding brake power supply.

[0055] The rechargeable battery E can select a suitable voltage as required, for example, a 24V rechargeable battery can be used.

[0056] Figure 2 The whole also shows a motor drive system, including the motor driver 20 and the motor M as described above, the motor driver 20 is used to drive the motor M, wherein when the motor M operates in a braking regeneration mode, the regenerative energy generated during the braking process of the motor M is stored in the rechargeable battery E of the motor driver 20.

[0057] In the circuit topology of the motor driver according to the present invention, an inductor is added to the DC link circuit, thereby removing the brake resistor commonly used in the prior art, which is usually large in size, generates a lot of heat and has a high cost. Therefore, the circuit topology of the motor driver according to the present invention has at least one of the following technical advantages.

[0058] 1. It is beneficial to the heat dissipation design of the system and can eliminate the influence of the braking resistor on other temperature sensing components.

[0059] 2. Saving volume. In the circuit topology of the prior art, the braking resistor needs to dissipate the regenerated energy, so it is bulky. Removing the resistor in the circuit topology of the present invention helps to save space.

[0060] 3. Adding a rechargeable battery can store the regenerative energy during the motor braking process, which is beneficial to saving energy; and the rechargeable battery can also be directly used as an auxiliary power supply for the motor driver and a motor holding brake power supply.

[0061] The specific embodiments described above in conjunction with the accompanying drawings describe exemplary embodiments, but do not represent all embodiments that can be implemented or fall within the scope of protection of the claims. The term "exemplary" used throughout this specification means "used as an example, instance or illustration" and does not mean "preferred" or "having advantages" over other embodiments. For the purpose of providing an understanding of the described technology, the specific embodiments include specific details. However, these technologies can be implemented without these specific details. In some instances, in order to avoid making the concepts of the described embodiments difficult to understand, well-known structures and devices are shown in block diagram form.

[0062] The above description of the present disclosure is provided to enable any person of ordinary skill in the art to implement or use the present disclosure. Various modifications to the present disclosure will be apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other variations without departing from the scope of protection of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but is consistent with the widest range of principles and novel features disclosed herein.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A motor driver (20), wherein an input end of the motor driver (20) is connected to a three-phase power grid (Ua, Ub, Uc), an output end of the motor driver (20) is connected to a motor (M), and the motor driver (20) comprises: A rectifier circuit (210), a DC link circuit (220) and an inverter circuit (230), wherein the rectifier circuit (210) comprises a first rectifier bridge (2101) and a second rectifier bridge (2102), and the inverter circuit (230) comprises first, second and third DC / AC conversion branch circuits (2301, 2302, 2303) arranged in parallel between the positive and negative output terminals of the DC link circuit (220), and each of the first, second and third DC / AC conversion branch circuits (2301, 2302, 2303) comprises first and second, third and fourth, fifth and sixth switching devices (T1, T2, T3, T4, T5, T6), respectively, characterized in that: The DC link circuit (220) is connected between the rectifier circuit (210) and the inverter circuit (230), and comprises a capacitor (C1), a seventh switch device (T7), a freewheeling diode (D9), and an inductor (L1), wherein a first end and a second end of the capacitor (C1) are respectively connected to the positive output end and the negative output end of the rectifier circuit (210), a collector of the seventh switch device (T7) is connected to the first end of the capacitor (C1), an emitter of the seventh switch device (T7) is connected to the negative electrode of the freewheeling diode (D9), a positive electrode of the freewheeling diode (D9) is connected to the second end of the capacitor (C1), a first end of the inductor (L1) is connected to the midpoint between the seventh switch device (T7) and the freewheeling diode (D9), and a second end of the inductor (L1) and a positive electrode of the freewheeling diode (D9) serve as two terminals for connecting an energy storage element.

2. The motor driver (20) of claim 1, wherein: The energy storage element is any one of the following: a rechargeable battery (E) arranged inside the motor driver, a capacitor, or an external power supply connected to the outside of the motor driver.

3. The motor driver (20) of claim 2, wherein: The positive electrode of the rechargeable battery (E) is connected to the second end of the inductor (L1), and the negative electrode of the rechargeable battery (E) is connected to the positive electrode of the freewheeling diode (D9). When the motor connected to the motor driver (20) operates in a braking regeneration mode, the regenerative energy generated during braking is stored in the rechargeable battery (E).

4. The motor driver (20) according to any one of claims 1 to 3, wherein: The first to seventh switching devices (T1, T2, T3, T4, T5, T6, T7) include a fully-controlled power transistor and a diode, wherein the anode and cathode of the diode are respectively connected to the emitter and collector of the fully-controlled power transistor.

5. The motor driver (20) of claim 4, wherein: The fully controlled power transistor is an insulated gate bipolar transistor.

6. A motor drive system, comprising a motor driver according to any one of claims 1 to 5 and a motor, wherein the motor driver is used to drive the motor, wherein: When the motor operates in a braking regeneration mode, the regenerative energy generated during the braking process of the motor is stored in a rechargeable battery of the motor driver.

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