Power semiconductor circuits for motor drives

Abstract

A multi-phase full-bridge drive system for driving a motor includes: a multi-phase full-bridge circuit, which includes at least three identical half-bridge circuits, wherein each half-bridge circuit includes a first transistor and a second transistor, and the short-circuit resistance of the first transistor is stronger than the short-circuit resistance of the second transistor, and the short-circuit saturation current of the first transistor is lower than the short-circuit saturation current of the second transistor, and each half-bridge circuit also includes a first transistor drive circuit and a second transistor drive circuit, which are respectively connected to the control terminal of the first transistor and the control terminal of the second transistor to control the first transistor and the second transistor.

Description

Technical Field

[0001] The present disclosure relates to the fields of power semiconductors and motor drives, and in particular to a power semiconductor circuit for motor drives. Background Art

[0002] In the motor drive field, a three-phase full-bridge circuit composed of power semiconductors is required to convert DC power to AC power and vice versa. A three-phase full-bridge circuit is composed of three half-bridge circuits, each typically implemented using switching elements composed of power semiconductors. Current flow and conversion are achieved by controlling the on and off of these switching elements.

[0003] The main power semiconductor transistors currently used in motor drives include IGBTs, MOSFETs, silicon carbide MOSFETs, silicon carbide JFETs, and gallium nitride HEMTs. Silicon carbide MOSFETs are becoming more widely used in motor drives due to their high efficiency. However, due to their inherent characteristics, silicon carbide MOSFETs have weak short-circuit resistance, resulting in poor reliability in drive systems using them. Similarly, gallium nitride HEMTs have even weaker short-circuit resistance and are highly susceptible to explosion in the event of a short circuit, causing damage to the drive system and presenting a significant bottleneck in their application in motor drives. Summary of the Invention

[0004] In response to the above-mentioned problems, the present application discloses a power semiconductor circuit for motor driving. This power semiconductor circuit can be embodied in the form of a half-bridge circuit, a multi-phase full-bridge circuit including multiple half-bridge circuits, and the like. These power semiconductor circuits disclosed in the present disclosure use a half-bridge circuit of a hybrid device formed by combining a power semiconductor transistor with weak short-circuit resistance and a power semiconductor transistor with strong short-circuit resistance. In the face of a phase-to-phase short circuit or a bridge arm short circuit, the device with strong short-circuit resistance in each half-bridge circuit can reliably shut off the short-circuit current, avoiding damage to the switching device / semiconductor transistor with weak short-circuit resistance, thereby improving the reliability of the entire drive system.

[0005] In one aspect, the present application discloses a half-bridge circuit comprising: a first switching element located in an upper bridge arm and a second switching element located in a lower bridge arm. The half-bridge circuit is composed of two switching elements, an upper bridge arm and a lower bridge arm, implemented by power semiconductors. The first switching element is composed of a power semiconductor transistor and its transistor driver component, and the first switching element can optionally be connected in reverse parallel to a power semiconductor diode. The second switching element is composed of a power semiconductor transistor and its transistor driver component, has a stronger short-circuit resistance than the first switching element, and its saturation current at the time of short circuit is less than that of the first switching element. The second switching element can optionally be connected in reverse parallel to a power semiconductor diode.

[0006] The upper arm of the half-bridge circuit may be formed by the first switching element, and the lower arm by the second switching element; alternatively, the upper arm may be formed by the second switching element, and the lower arm by the first switching element. The upper arm is connected to both the motor terminal and the positive power bus; the lower arm is connected to both the motor terminal and the negative power bus.

[0007] In another aspect, the present application discloses a multi-phase full-bridge drive system for motor drive, which includes a multi-phase full-bridge circuit composed of at least three half-bridge circuits as described above, and a controller connected to it to control it and output the target multi-phase drive voltage.

[0008] In yet another aspect, the present application discloses a three-phase full-bridge drive system for motor driving, which includes a three-phase full-bridge circuit composed of three half-bridge circuits as described above.

[0009] Generally, in the field of motor drives, a motor can be either a synchronous motor or an asynchronous motor. Such a motor is typically a three-phase motor having at least three lead terminals. Each lead terminal is connected to one of the aforementioned half-bridge circuits. Thus, the three half-bridge circuits together form a three-phase full-bridge circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Specific exemplary embodiments of the present disclosure will now be described with reference to the accompanying drawings. The features, aspects, and advantages of the present disclosure will become apparent by reading the following detailed description in conjunction with the accompanying drawings. In the accompanying drawings:

[0011] Figure 1 A schematic diagram showing a three-phase full-bridge drive system for motor driving according to an embodiment of the present application; and

[0012] Figure 2 A schematic diagram of a three-phase full-bridge drive system for driving a motor according to another embodiment of the present application is shown. DETAILED DESCRIPTION

[0013] Some implementations of the present disclosure will now be described more fully below with reference to the accompanying drawings, in which some, but not all, implementations of the present application are shown. Indeed, various implementations of the present application may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided to better convey the scope of the present disclosure to those skilled in the art.

[0014] Figure 1 Schematic diagram of a three-phase full-bridge drive system for motor driving according to an embodiment of the present application is shown. Figure 1In the embodiment, a DC power supply 1 supplies DC power to a three-phase full-bridge drive system 2. In one embodiment, the DC power supply 1 is a rechargeable battery. The three-phase full-bridge drive system 2 outputs a target three-phase drive voltage for driving a synchronous motor or an asynchronous motor 3. The three-phase full-bridge drive system 2 includes a three-phase full-bridge circuit 5 and a controller 6. In another embodiment, the three-phase full-bridge drive system 2 also includes a smoothing capacitor 4.

[0015] The three-phase full-bridge circuit 5 is a DC-AC converter circuit that converts the DC voltage applied by the DC power supply 1 into three-phase AC power to control the motor 3, and also converts the three-phase AC power generated by the motor into DC power. The three-phase full-bridge circuit is composed of three half-bridge circuits 51, 52, and 53. Each half-bridge circuit is connected to the three terminals 31, 32, and 33 of the motor 3.

[0016] The controller 6 is used to transmit control signals to the transistor driving components 511a, 521a, 531a, 513a, 523a, 533a in the three-phase full-bridge drive system 2 through signal terminals 611, 612, 621, 622, 631, 632 for controlling the three-phase full-bridge drive system 2. The controller 6 can be implemented in the form of a programmable logic device, a processor, a microprocessor, etc. The transistor driving components 511a, 521a, 531a, 513a, 523a, 533a are respectively connected to the control terminals of the transistors of the upper bridge arm and the lower bridge arm of each half-bridge circuit to drive the corresponding transistors to turn on or off. In one embodiment, each transistor driving component can also configure the performance of the connected transistor, such as its switching loss, short-circuit resistance, and short-circuit saturation current.

[0017] The three half-bridge circuits 51, 52, and 53 are identical. For clarity, only half-bridge circuit 51 will be described in detail. Half-bridge circuit 51 consists of an upper arm and a lower arm. The upper arm is connected to the positive electrode of DC power supply 1 and motor terminal 31. The lower arm is connected to the negative electrode of DC power supply 1 and motor terminal 31. Figure 1The upper bridge arm shown in the figure includes a switching element 511 and a power semiconductor diode 512 connected in reverse parallel thereto. The switching element 511 includes a power semiconductor transistor 511b and a transistor driving component 511a connected to the control terminal of the power semiconductor transistor 511b (e.g., the gate of the transistor) for driving or otherwise configuring it. The transistor driving component 511a receives a control signal 611 from the controller 6, thereby enabling the controller 6 to control the upper bridge arm. The lower bridge arm includes a switching element 513 and a power semiconductor diode 514 connected in reverse parallel thereto. The switching element 513 includes a power semiconductor transistor 513b and a transistor driving component 513a connected to the control terminal of the power semiconductor transistor 513b for driving or otherwise configuring it. The transistor driving component 513a receives a control signal 612 from the controller 6, thereby enabling the controller 6 to control the lower bridge arm. The short-circuit resistance of the switch element 513 of the lower bridge arm is weaker than that of the switch element 511 of the upper bridge arm, and the short-circuit saturation current of the switch element 513 of the lower bridge arm is greater than that of the switch element 511 of the upper bridge arm. Figure 1 The switching element shown in FIG6 is illustrated as including a transistor and a corresponding transistor driving component. The two can be integrated together. Alternatively, the two can be discrete devices. In another embodiment, the transistor driving component can be integrated into the controller 6. Regardless of the form in which it is embodied, the transistor driving component is used to drive the transistor connected thereto to turn on or off, or to configure the characteristics of the transistor connected thereto, such as adjusting its switching loss, short-circuit resistance, and short-circuit saturation current.

[0018] exist Figure 1In the illustrated embodiment, the power semiconductor transistor 511b is composed of a silicon carbide JFET, and the power semiconductor diode 514 forming a commutation loop therewith comprises a silicon carbide diode with a Schottky structure or a fast recovery diode. The power semiconductor transistor 513b is composed of a silicon carbide MOSFET, and the power semiconductor diode 512 forming a commutation loop therewith comprises a silicon carbide diode with a Schottky structure. Silicon carbide diodes include silicon carbide Schottky barrier diodes (SBDs), junction barrier Schottky diodes (JBSs), and hybrid pin Schottky diodes (MPSs). Fast recovery diodes are generally silicon-based, have good forward conduction performance, and are less expensive than silicon carbide Schottky diodes. Therefore, in the case where anti-parallel diodes are optionally provided, setting the diodes in the three-phase full-bridge drive system 2 as fast recovery diodes can facilitate the use of their good forward conduction performance. Because power semiconductor transistor 511b (i.e., silicon carbide MOSFET) has reverse recovery capability, power semiconductor diode 512 can be omitted from the circuit. If diode 512 is omitted, reverse recovery will occur in power semiconductor transistor 511b. When power semiconductor transistor 513b is turned on, the reverse recovery loss in power semiconductor transistor 511b will be higher. However, since one diode is eliminated, the cost of the entire three-phase full-bridge drive system can be reduced. Because power semiconductor transistor 513b (i.e., silicon carbide MOSFET) has reverse recovery capability, power semiconductor diode 514 can be omitted from the circuit. If diode 514 is omitted, reverse recovery will occur in power semiconductor transistor 513b. When power semiconductor transistor 511b is turned on, the reverse recovery loss in power semiconductor transistor 513b will be higher. However, since one diode is eliminated, the cost of the entire three-phase full-bridge drive system can be reduced. The short-circuit resistance of the lower arm switch element 513 is weaker than that of the upper arm switch element 511. That is, the short-circuit resistance of the switching element including the silicon carbide MOSFET is weaker than that of the switching element including the silicon carbide JFET. At the same time, the short-circuit saturation current of the switching element including the silicon carbide MOSFET is higher than that of the switching element including the silicon carbide JFET.

[0019] The gate control circuit 511a can control the power semiconductor transistor 511b to enter the on state and connect the corresponding motor terminal 31 to the positive pole of the DC power supply. The transistor control circuit 513a can control the power semiconductor transistor 513b to enter the on state and connect the corresponding motor terminal 31 to the negative pole of the DC power supply. When the transistor control circuit 511a of the upper bridge arm controls the power semiconductor transistor 511b to be in the on state, the corresponding transistor control circuit 513a of the lower bridge arm controls the power semiconductor transistor 513b to be in the off state; when the transistor control circuit 513a of the lower bridge arm controls the power semiconductor transistor 513b to be in the on state, the corresponding transistor control circuit 511a of the upper bridge arm controls the corresponding power semiconductor transistor 511b to be in the off state. When the upper and lower bridge arm switching elements switch between switching states, a certain dead time is generally set. During this dead time, the switching elements of the upper and lower bridge arms are simultaneously in the off state. This ensures that current does not flow directly from the upper bridge arm to the lower bridge arm.

[0020] In this embodiment, a half-bridge circuit is formed by combining a silicon carbide JFET and a silicon carbide MOSFET, and a full-bridge circuit is correspondingly formed by multiple such half-bridge circuits. Among them, the silicon carbide JFET has good switching performance, strong short-circuit resistance, lower cost than silicon carbide MOSFET, and due to the lack of a gate oxide layer, better reliability. However, the short-circuit resistance of the silicon carbide MOSFET is weaker. When a phase-to-phase short circuit or a bridge arm short circuit occurs in the drive system, the silicon carbide JFET can bear most of the bus voltage. At this time, the silicon carbide JFET can be selected to shut off the short-circuit current. Since the silicon carbide JFET itself has strong short-circuit resistance, it can reliably and stably shut off the short-circuit current. Since the silicon carbide JFET has already borne most of the bus voltage, and the bus voltage borne by the silicon carbide MOSFET is very small, the silicon carbide MOSFET can also be used to shut off the short-circuit current. Since the voltage across the silicon carbide MOSFET is very low, the actual short-circuit energy is also very small, so the short-circuit current can also be reliably shut off.

[0021] Since silicon carbide JFET is a normally-on device, when the system drive loses the control voltage, the power semiconductor transistors 511b, 521b, and 531b composed of silicon carbide JFET are all in the on state. At this time, the motor will enter the ASC (active short circuit) state. In the ASC state, all the upper bridge arms or all the lower bridge arms in the three-phase bridge arm are turned on at the same time. Implementing the active short circuit state has many advantages for motor drive, especially for motor drive in new energy vehicles, including: when the whole vehicle is out of control, the implementation of ASC can generate reverse torque to achieve safe parking; when the power battery fails, the implementation of ASC can isolate the motor and motor controller from the power battery to ensure the high voltage safety of the whole vehicle; when a switch tube fails in the inverter circuit of the motor controller, the implementation of ASC can avoid damage to other devices or the power battery by the uncontrolled rectifier current. The existing control methods for making the drive system using IGBT or other normally-off transistors on both the upper and lower bridges enter ASC in the event of a fault are relatively complex and difficult to implement reliably. As for Figure 1 The three-phase full-bridge drive system shown uses a combination of normally-on transistors (silicon carbide JFETs) and normally-off transistors (silicon carbide MOSFETs). This allows the normally-on transistors in the three-phase full-bridge circuit to automatically turn on simultaneously in the event of a drive system failure or other faults, thereby short-circuiting all three phase terminals of the motor through the upper bridge arm and allowing the motor to enter the ASC state without the need for additional complex control methods. Figure 1 The described embodiments have great practicality and benefits when applied in the field of electric vehicles.

[0022] Figure 2A schematic diagram of a three-phase full-bridge drive system for motor drive according to another embodiment of the present application is shown. Based on the first embodiment. The JFET is replaced with a silicon carbide MOSFET, that is, both the upper and lower bridges use MOSFETs. The short-circuit resistance of one of the silicon carbide MOSFETs is stronger than that of the other silicon carbide MOSFET, and its short-circuit saturation current is smaller than that of the other silicon carbide MOSFET. In one embodiment, the upper and lower bridge arms can also use exactly the same MOSFET. In the case where the upper and lower bridges use exactly the same MOSFET, the short-circuit resistance of one of the silicon carbide MOSFETs is improved and its short-circuit saturation current is reduced by controlling the driving component connected to the control terminal (i.e., its gate) of the MOSFET of the upper and lower bridge arms, i.e., the transistor driving component. In one embodiment, the improvement of its short-circuit resistance is achieved by reducing the driving voltage of the silicon carbide MOSFET. At this time, the short-circuit saturation current will be reduced synchronously by reducing the driving voltage. In another embodiment, different types of silicon carbide MOSFETs are selected as transistors for the upper and lower bridge arms respectively. One type of MOSFET is selected as a silicon carbide MOSFET with stronger short-circuit resistance and lower short-circuit saturation current.

[0023] The above describes a combination of two transistors. The first is a combination of a silicon carbide JFET with stronger short-circuit resistance and a MOSFET with weaker short-circuit resistance to form a half-bridge circuit, and ultimately form a three-phase full-bridge drive system. The second is to form a half-bridge circuit using a combination of a MOSFET and a MOSFET. The MOSFETs of the upper and lower bridge arms can be the same transistor, and the MOSFETs of the upper and lower bridge arms have different short-circuit resistances through the control of their driving components, and the MOSFETs with stronger short-circuit resistance have lower short-circuit saturation current at the same time. In addition, the MOSFETs of the upper and lower bridge arms can be different types of MOSFETs, which are themselves designed to have different performances, and one type of MOSFET has stronger short-circuit resistance and lower short-circuit saturation current. The drive circuit or system described in this application can overcome the shortcomings of the weak short-circuit resistance of MOSFET to a certain extent.

[0024] It should be noted that a transistor with stronger short-circuit resistance can be located in the lower bridge arm, while a transistor with weaker short-circuit resistance can be located in the upper bridge arm, and vice versa. In addition, although the above is developed in the context of the above-mentioned combinations of transistors, this is not intended to be limiting. In fact, the present disclosure may also include various other transistor combinations, such as a combination of a gallium nitride HEMT and a silicon carbide HEMT, a combination of a gallium nitride HEMT with stronger short-circuit resistance and another gallium nitride HEMT with weaker short-circuit resistance, and so on.

Claims

1. A multi-phase full-bridge drive system for driving a motor, comprising: A multi-phase full-bridge circuit comprising at least three identical half-bridge circuits, wherein each half-bridge circuit comprises a first transistor and a second transistor, wherein the short-circuit resistance of the first transistor is stronger than that of the second transistor, and the short-circuit saturation current of the first transistor is lower than that of the second transistor, and wherein each half-bridge circuit further comprises a first transistor driving component and a second transistor driving component, which are respectively connected to a control terminal of the first transistor and a control terminal of the second transistor to control the first transistor and the second transistor; a controller connected to the first transistor driving component and the second transistor driving component of each half-bridge circuit, respectively, for controlling the multi-phase full-bridge circuit to generate a target multi-phase driving voltage for driving the motor; In response to an interphase short circuit or a bridge arm short circuit occurring in the multi-phase full-bridge drive system, the first transistor bears most of the bus voltage so that the short-circuit current of the interphase short circuit or the bridge arm short circuit is cut off.

2. The multi-phase full-bridge drive system according to claim 1, wherein the first transistor and the second transistor are respectively a silicon carbide (SiC) JFET and a silicon carbide MOSFET; or the first transistor and the second transistor are respectively the same SiC MOSFET; or the first transistor and the second transistor are respectively a first type of SiC MOSFET and a second type of SiC MOSFET; or the first transistor and the second transistor are respectively a SiC JFET and a gallium nitride (GaN) HEMT.

3. The multi-phase full-bridge drive system according to claim 2, wherein when the first transistor and the second transistor are respectively the same silicon carbide MOSFET, the first transistor and the second transistor of each half-bridge circuit are respectively configured by adjusting the first transistor driving component and the second transistor driving component of each half-bridge circuit so that the short-circuit resistance of the first transistor is stronger than the short-circuit resistance of the second transistor, and the short-circuit saturation current of the first transistor is lower than the short-circuit saturation current of the second transistor. 4 . The multi-phase full-bridge drive system according to claim 1 , wherein each half-bridge circuit further comprises a first diode connected in anti-parallel with the first transistor and a second diode connected in anti-parallel with the second transistor. 5 . The multi-phase full-bridge drive system according to claim 4 , wherein the first diode and the second diode are both selected from the group consisting of a diode having a Schottky structure and a fast recovery diode made of silicon carbide.

6. The multi-phase full-bridge drive system according to any one of claims 1 to 3, wherein the first transistor and the second transistor are respectively a normally-on device and a normally-off device, and in response to the multi-phase full-bridge drive system losing control, the first transistor of each half-bridge circuit is turned on simultaneously to put the motor into an active short-circuit state. 7 . The multi-phase full-bridge drive system according to claim 6 , wherein the first transistor and the second transistor are a silicon carbide JFET and a silicon carbide MOSFET, respectively.

8. A half-bridge circuit for driving a motor, comprising: a first transistor and a second transistor, wherein the short-circuit resistance of the first transistor is stronger than that of the second transistor, and the short-circuit saturation current of the first transistor is lower than that of the second transistor; as well as A first transistor driving component and a second transistor driving component are respectively connected to the control terminal of the first transistor and the control terminal of the second transistor to control the first transistor and the second transistor, wherein, in response to a bridge arm short circuit in the half-bridge circuit, the first transistor bears most of the bus voltage so that the short-circuit current of the bridge arm short circuit is turned off.

9. The half-bridge circuit according to claim 8, wherein the first transistor and the second transistor are respectively a silicon carbide JFET and a silicon carbide MOSFET; or the first transistor and the second transistor are respectively the same silicon carbide MOSFET; or the first transistor and the second transistor are respectively a first type of silicon carbide MOSFET and a second type of silicon carbide MOSFET; or the first transistor and the second transistor are respectively a silicon carbide JFET and a gallium nitride HEMT.

10. The half-bridge circuit according to claim 9, wherein when the first transistor and the second transistor are respectively the same silicon carbide MOSFET, the first transistor and the second transistor of each half-bridge circuit are configured respectively by adjusting the first transistor driving component and the second transistor driving component of each half-bridge circuit so that the short-circuit resistance of the first transistor is stronger than the short-circuit resistance of the second transistor, and the short-circuit saturation current of the first transistor is lower than the short-circuit saturation current of the second transistor. 11 . The half-bridge circuit according to claim 8 , further comprising a first diode connected in anti-parallel to the first transistor and a second diode connected in anti-parallel to the second transistor. 12 . The half-bridge circuit according to claim 11 , wherein the first diode and the second diode are both selected from the group consisting of a diode having a Schottky structure and a fast recovery diode including silicon carbide.

13. A three-phase full-bridge drive system for driving a motor, comprising a three-phase full-bridge circuit consisting of three half-bridge circuits according to any one of claims 8 to 12, wherein: In response to an inter-phase short circuit or a bridge arm short circuit occurring in the three-phase full-bridge drive system, the first transistor bears most of the bus voltage so that the short-circuit current of the inter-phase short circuit or the bridge arm short circuit is cut off.

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