Direct-current circuit breaker

Abstract

A switch branch comprises a silicon carbide field effect transistor SiC MOSFET and an insulated gate bipolar transistor IGBT, the silicon carbide field effect transistor SiC MOSFET and the insulated gate bipolar transistor IGBT are connected in parallel, in a normal conduction state, the silicon carbide field effect transistor SiC MOSFET is conducted, and current flows through the silicon carbide field effect transistor SiC MOSFET with low conduction voltage drop; when a surge current or a short-circuit fault occurs, the silicon carbide field effect transistor SiC MOSFET enters a desaturation state, the drain-source voltage of the SiC MOSFET rises, the insulated gate bipolar transistor IGBT is triggered to be conducted at the moment, the subsequently rising fault current is borne by the insulated gate bipolar transistor IGBT, and then the surge current or the short-circuit fault occurs. And the conduction voltage drop of the insulated gate bipolar transistor IGBT clamps the voltage at the two ends of the silicon carbide field effect transistor SiC MOSFET.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a DC solid-state circuit breaker and its processing method. Background Technology

[0002] Mechanical circuit breakers are commonly used in traditional DC power distribution systems. However, since there is no current zero-crossing point in the DC circuit, arc extinguishing is difficult, and the operating speed of mechanical circuit breakers is relatively slow (usually measured in milliseconds). They cannot quickly and reliably cut off the current during high-current faults. With the increasing demand for all-DC power supply in fields such as ships and new energy, higher requirements are placed on the breaking speed and current waveform control of DC circuit breakers.

[0003] Currently, DC system short-circuit faults exhibit extremely high current rise rates in some applications, necessitating stringent requirements for breaking speed. For example, shipboard DC power distribution systems require circuit breakers to respond in microseconds and rapidly limit fault current to ensure bus selectivity and the safety of downstream equipment. Solid-state DC circuit breakers reported by manufacturers such as ABB can break short-circuit fault current to zero within <0.5ms and achieve current clamping within <10μs. Phoenix Contact's products also demonstrate that DC circuit breakers employing hybrid technology can complete short-circuit shutdown within <10μs, highlighting the importance of extremely short response times. Furthermore, applications such as DC data centers and energy storage power stations require extremely high tolerance for sudden surges in fault current (high di / dt) and extremely fast response times to prevent equipment damage and power outages.

[0004] While current all-IGBT solid-state circuit breakers can withstand high currents, their low on-state voltage leads to significant conduction losses. All-SiC MOSFET solutions, due to their junction capacitance and fast switching characteristics, are prone to high-amplitude voltage spikes and oscillations during turn-off, posing a challenge to system reliability. Furthermore, high-voltage circuit breakers typically require multiple devices connected in series to meet voltage requirements, increasing drive complexity and cost. Existing research has proposed improving high-voltage DC breaking capacity by mixing fully controlled and semi-controlled devices in series, achieving high-voltage, high-current breaking at low cost. Other technical solutions introduce a hybrid breaking topology of mechanical switches and multi-stage IGBT modules in series into DC circuit breakers to reduce device costs, balancing low losses and fast breaking speed. However, existing solutions are either prohibitively expensive (e.g., parallel IGCT solutions) or require complex semiconductor devices, failing to reconcile the trade-off between low conduction losses and strong overcurrent turn-off capability.

[0005] The information disclosed in the background section is only for enhancing the understanding of the background of this invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] In view of the above problems, the purpose of this invention is to overcome the existing defects by providing a DC solid-state circuit breaker and processing method that takes into account both low conduction voltage drop and high surge interruption capability.

[0007] The objective of this invention is achieved through the following technical solutions.

[0008] A DC circuit breaker includes a front port and a rear port, and a switching branch connecting the front port and the rear port. The switching branch includes a silicon carbide field-effect transistor (SiC MOSFET) and an insulated-gate bipolar transistor (IGBT) connected in parallel. Under normal conduction conditions, the SiC MOSFET conducts current. When a surge current or short-circuit fault occurs, the SiC MOSFET enters a desaturation state, and its drain-source voltage rises, triggering the IGBT to turn on. The subsequent rise in fault current is borne by the IGBT, and the on-state voltage drop of the IGBT clamps the voltage across the SiC MOSFET. During the turn-off operation, the SiC MOSFET is turned off first, and then the IGBT is turned off with a delay, thus interrupting the current.

[0009] The DC circuit breaker also includes a desaturation detection circuit for real-time monitoring of the drain-source voltage or current of the silicon carbide field-effect transistor (SiC MOSFET). When the voltage exceeds a preset threshold or the current exceeds a set value, the IGBT is triggered to conduct within 3μs to achieve rapid shunting of the fault current.

[0010] In the DC circuit breaker, the silicon carbide field-effect transistor (SiC MOSFET) and the insulated-gate bipolar transistor (IGBT) are driven by independent gate drive circuits, and the control logic coordinates their switching timing to ensure that the SiC MOSFET turns off before the IGBT during the turn-off process, with a delay time of 1μs to 10μs.

[0011] The DC circuit breaker also includes a buffer circuit, which is connected in parallel across the parallel branch of the silicon carbide field-effect transistor (SiC MOSFET) and the insulated gate bipolar transistor (IGBT) to suppress the voltage rise rate dV / dt during the turn-off process and prevent dynamic avalanche breakdown.

[0012] In the DC circuit breaker, the buffer circuit is an RC buffer circuit, an RCD buffer circuit, or a single capacitor snubber circuit.

[0013] The DC circuit breaker also includes an energy-absorbing branch for absorbing the energy generated during the turn-off process and limiting the voltage peak to within 90% of the rated voltage of the silicon carbide field-effect transistor (SiC MOSFET) and the insulated gate bipolar transistor (IGBT). The energy-absorbing branch is connected in parallel across the switching branch and is composed of a varistor (MOV) or a surge arrester.

[0014] In the DC circuit breaker, the circuit breaker is a bidirectional solid-state circuit breaker, including a forward branch and a reverse branch. Each branch is composed of a silicon carbide field-effect transistor (SiC MOSFET) and an insulated gate bipolar transistor (IGBT) connected in parallel, and the two branches are connected in reverse parallel to realize bidirectional conduction and cutoff of forward and reverse current.

[0015] In the DC circuit breaker described above, each branch has a silicon carbide field-effect transistor (SiC MOSFET) and an insulated gate bipolar transistor (IGBT) connected in reverse parallel with a diode to realize the reverse freewheeling function of the unidirectional branch.

[0016] The DC circuit breaker also includes a sensor module, which includes a voltage sensor, a current sensor, and a temperature sensor to monitor the system status in real time and to perform overcurrent, overvoltage, undervoltage, and overheat protection by controlling the turn-off of silicon carbide field-effect transistors.

[0017] The handling method for DC circuit breakers includes the following steps:

[0018] During normal operation, the silicon carbide field-effect transistor (SiC MOSFET) is turned on, and the insulated-gate bipolar transistor (IGBT) is turned off. Current flows through the SiC MOSFET, achieving low conduction loss. When a surge or short-circuit fault is detected, the SiC MOSFET enters a desaturation state, and its voltage rises, triggering the IGBT to turn on. The fault current is transferred to the IGBT.

[0019] The controller initiates the shutdown process by first turning off the silicon carbide field-effect transistor (SiC MOSFET) to completely transfer the current to the insulated gate bipolar transistor (IGBT). After a delay of 1–10 μs, the IGBT is turned off, and the current is safely shut off with the cooperation of the buffer circuit and the energy absorption branch.

[0020] The system enters a protection lockout state, and can be manually or automatically reset after the fault is cleared.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] This invention achieves a fusion of low conduction loss and high turn-off capability by connecting SiC MOSFETs and IGBTs in parallel. During normal conduction, only the SiC MOSFET receives the drive signal, and the overall on-state voltage drop of the solid-state circuit breaker is only the on-state voltage drop of the SiC MOSFET. When a short circuit or surge current occurs, the SiC MOSFET enters the desaturation stage, and the IGBT is controlled to turn on by detecting the terminal voltage, allowing the IGBT to bear the surge current and clamp the terminal voltage. During disconnection, the controller first turns off the SiC MOSFET and then the IGBT, effectively suppressing voltage spikes and achieving safe disconnection. This solution is suitable for DC protection applications requiring extremely high fast turn-off capability, such as marine power systems, data centers, and energy storage stations. It has a simple structure, precise control, and broad industrial application prospects.

[0023] The above description is merely an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer and more understandable, so that those skilled in the art can implement it according to the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0024] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0025] In the attached diagram:

[0026] Figure 1 This is a topology diagram of the unidirectional DC circuit breaker of the present invention;

[0027] Figure 2 This is a topology diagram of the bidirectional DC circuit breaker of the present invention;

[0028] Figure 3 This is a schematic diagram of the drive control in the simulation verification of the present invention;

[0029] Figure 4 This is a schematic diagram of the module current in the simulation verification of the present invention;

[0030] Figure 5 This is a schematic diagram of the module voltage in the simulation verification of this invention;

[0031] Explanation of reference numerals in the attached diagram: 1-Positive input terminal; 2-Negative input terminal; 3-Positive output terminal; 4-Negative output terminal; Q1-IGBT; Q2-SiC MOSFET; Q3-IGBT; Q4-SiC MOSFET; D1-Diode; D2-Diode; R1-Resistor; R2-Varistor or surge arrester; C1-Capacitor.

[0032] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0033] The following will refer to the appendix. Figures 1 to 5 Specific embodiments of the invention will be described in more detail below. While specific embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0034] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0035] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0036] Figure 1 This describes the topology of a single-pole unidirectional DC circuit breaker that applies this scheme. Figure 1In this configuration, an IGBT (Q1) and a SiC MOSFET (Q2) are connected in parallel with each other in the same direction, and a diode (D1) is connected in parallel with both in the opposite direction. The collector (C) of Q1, the drain (D) of Q2, and the cathode of Q3 are connected to the positive input terminal 1, while the emitter (E) of Q1, the source (S) of Q2, and the anode of Q3 are connected to the positive output terminal 3. The negative input terminal 2 and the negative output terminal 4 are arranged parallel to the positive input terminal 1 and the positive output terminal 3. A series-connected buffer resistor (R1) and a buffer capacitor (C1) are connected in parallel across the two ends of the above components as a buffer branch, respectively connected to the positive input terminal 1 and the positive output terminal 3. Similarly, a varistor (R2) is connected in parallel across the two ends of the above components as a power dissipation branch, connected to the positive input terminal 1 and the positive output terminal 3. Under normal conduction conditions, current flows through the silicon carbide MOSFET (SiC MOSFET), which has a low on-state voltage drop. When a severe short-circuit fault occurs, the gate voltage changes of the SiC MOSFET (Q2) and the IGBT (Q1) are as follows: Figure 3 As shown, the current waveforms of the drain-source current I_DS of a silicon carbide field-effect transistor (SiCMOSFET) and the collector-emitter current I_CE of an insulated-gate bipolar transistor (IGBT) are as follows: Figure 4 As shown, the voltage between the positive input terminal 1 and the positive output terminal 3 after parallel connection is as follows: Figure 5 As shown, when the silicon carbide field-effect transistor (SiC MOSFET) enters desaturation, its drain-source voltage rises, triggering the insulated-gate bipolar transistor (IGBT) to turn on. The subsequent rise in fault current is borne by the IGBT, and the on-state voltage drop of the IGBT clamps the voltage across the SiC MOSFET. During the turn-off operation, the SiC MOSFET is turned off first, and then the IGBT is turned off with a delay, thus completing the current interruption.

[0037] Figure 2This is the topology of a unipolar bidirectional DC circuit breaker using this scheme. An insulated-gate bipolar transistor (IGBT) (Q1) and a silicon carbide field-effect transistor (SiC MOSFET) (Q2) are connected in parallel, and a diode (Q3) is then connected in reverse parallel with them. The collector (C) of Q1, the drain (D) of Q2, and the cathode of Q3 are connected to the positive input terminal 1, while the emitter (E) of Q1, the source (S) of Q2, and the anode of Q3 are connected to node 5. Similarly, the emitter (E) of Q3 (IGBT), the source (S) of Q4 (SiC MOSFET), and the anode of D2 (diode) are electrically connected to node 5, while the collector (C) of Q3, the drain (D) of Q4, and the anode of D2 are connected to the positive output terminal 3. A buffer resistor (R1) and a buffer capacitor (C1) are connected in series to the positive input terminal 1 and the positive output terminal 3, respectively. A varistor (R2) serves as the energy dissipation branch and is connected to both the positive input terminal 1 and the positive output terminal 3. This topology enables bidirectional DC circuit breaker functionality, with a turn-off process identical to that of a unidirectional DC circuit breaker.

[0038] In a preferred embodiment of the DC circuit breaker, a desaturation detection circuit is further included for real-time monitoring of the drain-source voltage or current of the silicon carbide field-effect transistor (SiC MOSFET). When the voltage exceeds a preset threshold or the current exceeds a set value, the IGBT is triggered to conduct within 3μs to achieve rapid shunting of the fault current.

[0039] In a preferred embodiment of the DC circuit breaker, the silicon carbide field-effect transistor (SiC MOSFET) and the insulated-gate bipolar transistor (IGBT) are driven by independent gate drive circuits, and the control logic coordinates their switching timing to ensure that the SiC MOSFET turns off before the IGBT during the turn-off process, with a delay time of 1μs to 10μs.

[0040] In a preferred embodiment of the DC circuit breaker, a buffer circuit is further included. The buffer circuit is connected in parallel across the parallel branch of the silicon carbide field-effect transistor (SiC MOSFET) and the insulated-gate bipolar transistor (IGBT) to suppress the voltage rise rate dV / dt during the turn-off process and prevent dynamic avalanche breakdown.

[0041] In a preferred embodiment of the DC circuit breaker, the buffer circuit is an RC buffer circuit, an RCD buffer circuit, or a single capacitor snubber circuit.

[0042] In a preferred embodiment of the DC circuit breaker, an energy-absorbing branch is further included to absorb the energy generated during the turn-off process and limit the voltage peak to within 90% of the rated voltage of the silicon carbide field-effect transistor (SiC MOSFET) and the insulated-gate bipolar transistor (IGBT). The energy-absorbing branch is connected in parallel across the switching branch and is composed of a varistor (MOV) or a surge arrester.

[0043] In a preferred embodiment of the DC circuit breaker, the circuit breaker is a bidirectional solid-state circuit breaker, including a forward branch and a reverse branch. Each branch is composed of a silicon carbide field-effect transistor (SiC MOSFET) and an insulated gate bipolar transistor (IGBT) connected in parallel, and the two branches are connected in reverse parallel to realize bidirectional conduction and cutoff of forward and reverse current.

[0044] In a preferred embodiment of the DC circuit breaker, each branch has a silicon carbide field-effect transistor (SiCMOSFET) and an insulated gate bipolar transistor (IGBT) connected in reverse parallel with a diode to realize the reverse freewheeling function of the unidirectional branch.

[0045] In a preferred embodiment of the DC circuit breaker, a sensor module is further included, which includes a voltage sensor, a current sensor, and a temperature sensor to monitor the system status in real time and to perform overcurrent, overvoltage, undervoltage, and overheat protection by controlling the turn-off of silicon carbide field-effect transistors.

[0046] The handling method for DC solid-state circuit breakers includes the following steps:

[0047] During normal operation, the silicon carbide field-effect transistor (SiC MOSFET) is turned on, the insulated gate bipolar transistor (IGBT) is turned off, and the current flows through the silicon carbide field-effect transistor, achieving low conduction loss.

[0048] When a surge or short-circuit fault is detected, the silicon carbide field-effect transistor (SiC MOSFET) enters a desaturation state, and its voltage rises to trigger the insulated-gate bipolar transistor (IGBT) to turn on, and the fault current is transferred to the IGBT.

[0049] The controller initiates the shutdown process by first turning off the silicon carbide field-effect transistor (SiC MOSFET) to completely transfer the current to the insulated gate bipolar transistor (IGBT). After a delay of 1–10 μs, the IGBT is turned off, and the current is safely shut off with the cooperation of the buffer circuit and the energy absorption branch.

[0050] The system enters a protection lockout state, and can be manually or automatically reset after the fault is cleared.

[0051] In one embodiment, the DC circuit breaker includes a front port, a rear port, and a switching branch connecting the front port and the rear port, such as... Figure 1 As shown, the switching branch includes a silicon carbide field-effect transistor (SiC MOSFET) and an insulated-gate bipolar transistor (IGBT) connected in parallel; in the normal conduction state,

[0052] The current primarily flows through the silicon carbide (SiC) MOSFET. When a surge current or short-circuit fault occurs, the current rises until the SiC MOSFET enters desaturation. At this point, the insulated-gate bipolar transistor (IGBT) is turned on, and the IGBT handles the further surge current, limiting the voltage rise. During disconnection, the SiC MOSFET is first turned off, followed by the IGBT, to interrupt the current flow, thus balancing the low conduction loss and high breaking capacity characteristics of a solid-state circuit breaker. Furthermore, this invention provides a bidirectional solution, such as... Figure 2 The diagram shows a bidirectional solid-state circuit breaker. A silicon carbide field-effect transistor (SiC MOSFET) and an insulated-gate bipolar transistor (IGBT) are connected in parallel with a reverse diode to achieve bidirectional conduction capability of the circuit breaker. The forward and reverse branches are arranged according to the parallel structure. Furthermore, in this bipolar circuit breaker, each single pole is connected to... Figure 1 or Figure 2The topology of one pole containing the components is the same. Further, a buffer circuit is connected in parallel on the parallel branch of the silicon carbide field-effect transistor (SiC MOSFET) and the insulated-gate bipolar transistor (IGBT) to buffer the overvoltage rise rate during turn-off. An energy-absorbing branch, composed of a varistor or surge arrester, is connected in parallel at both ends of the parallel branch to limit the peak value of the overvoltage, ensuring that the voltage spike generated during turn-off does not exceed 90% of the rated voltage of the SiC MOSFET and the IGBT, and to absorb energy during turn-off. Further, a circuit for detecting the desaturation of the SiC MOSFET is included. This circuit is characterized by a very fast detection speed, with a detection time of less than 3µs, and does not require adjustment or other anti-disturbance processing. When the drain-source voltage of the SiC MOSFET exceeds a preset threshold or the current flowing through it exceeds a preset threshold, the IGBT is triggered to conduct, thereby shunting the fault current. If the desaturation circuit detection is a false alarm, the insulated-gate bipolar transistor (IGBT) is turned off, returning to a state where only the silicon carbide MOSFET (SiC MOSFET) is on. Furthermore, the SiC MOSFET and IGBT are driven by independent gate drive circuits, coordinated by a control board to achieve all functions of the solid-state circuit breaker. Furthermore, the controller of the DC circuit breaker also includes other protection strategies, such as overcurrent protection, overvoltage protection, undervoltage protection, and overheat protection. Activation of these protection strategies only requires controlling the SiC MOSFET to turn off. Furthermore, the solid-state circuit breaker is equipped with voltage, current, and temperature sensors, which are used to implement the aforementioned protection strategies. Furthermore, the control strategy utilizes the faster turn-off speed of the SiC MOSFET when interrupting short-circuit current, ensuring that the SiC MOSFET turns off before the IGBT during the turn-off process. Furthermore, this circuit breaker is suitable for DC systems, including marine DC power distribution, data center power systems, and energy storage conversion devices. It can be configured with solid-state circuit breakers of different voltage and current levels, including single-pole, double-pole, unidirectional, and bidirectional types, as needed. Further, the circuit breaker is characterized by its ability to be expanded by paralleling more silicon carbide field-effect transistors (SiCMOSFETs), insulated-gate bipolar transistors (IGBTs), and other components to meet larger capacity DC breaking requirements.

[0053] In one embodiment, in a unidirectional switching topology, a switching branch consisting of a silicon carbide MOSFET (SiC MOSFET) and an insulated-gate bipolar transistor (IGBT) connected in parallel can be connected in series between the input (front port) and the load (rear port). The primary function of the SiC MOSFET is to continuously carry the rated current, and its selection follows these criteria:

[0054] Rated voltage: at least twice the maximum operating voltage of the DC system to prevent overvoltage during shutdown;

[0055] Rated current: It should be able to continuously carry the maximum normal load current of the system, and with the matching heat dissipation system, its temperature rise should be kept within a safe range.

[0056] On-resistance: the lower the better. This is a key parameter that determines the conduction loss during normal system operation. Low conduction loss can significantly improve the efficiency of solid-state circuit breakers.

[0057] Short-circuit withstand capability: Although the insulated gate bipolar transistor (IGBT) ultimately bears the fault current, the silicon carbide field-effect transistor (SiC MOSFET) needs to withstand a certain amount of large current when the terminal voltage rises to the set threshold and during the short-circuit setting time of the controller. Therefore, the selection still needs to have a certain short-circuit withstand capability.

[0058] The function of an Insulated Gate Bipolar Transistor (IGBT) is to carry surge current in environments with high di / dt. Its selection follows these criteria:

[0059] Rated voltage: Must match the rated voltage of the silicon carbide field-effect transistor (SiC MOSFET) and be at least twice the maximum operating voltage of the DC system to prevent damage from line overvoltage when the inductive load is turned off;

[0060] Rated current: No requirements are made for its ability to carry the rated current for a long time, but the surge current withstand capability and short-circuit current interruption capability are related to this parameter;

[0061] Surge current withstand capability: The selected insulated gate bipolar transistor (IGBT) should be able to withstand high surge currents and ensure that no failures such as desaturation, latch-up, or other overcurrent-induced failures occur during the surge current process;

[0062] Short-circuit current turn-off capability: Insulated gate bipolar transistors (IGBTs) should have the ability to turn off high surge currents to ensure that they do not fail due to dynamic avalanche breakdown, thermal breakdown, or other factors during the turn-off process with the help of a buffer circuit.

[0063] On-saturation voltage drop: A lower on-saturation voltage drop can reduce the power consumption of an insulated gate bipolar transistor (IGBT) under surge current.

[0064] The diode selection must possess sufficient surge withstand capability and ensure its ability to continuously conduct rated current. The buffer circuit must ensure that the turn-off voltage rise rate during the turn-off process does not trigger dynamic avalanche breakdown. The clamping circuit must ensure that the peak turn-off voltage does not exceed the rated voltage of the silicon carbide MOSFET (SiC MOSFET) and the insulated-gate bipolar transistor (IGBT). Under normal operating current conditions, the gate drive signal controls the SiC MOSFET to turn on, and the IGBT to turn off. At this time, the current is borne by the SiC MOSFET, which has a low on-state voltage drop. When a surge current or short-circuit fault occurs, the MOSFET enters the desaturation region. The principle is that during normal conduction, the drain-source voltage V_DS of the SiC MOSFET is typically very low (tens of millivolts to hundreds of millivolts). When a short circuit or severe overload occurs, although the gate still has a drive signal, the conduction capability of the silicon carbide MOSFET (SiCMOSFET) is insufficient to handle the rapidly increasing current, causing it to enter a desaturation state. At this time, V_DS will rapidly rise to a value far higher than the normal on-state voltage drop (e.g., it may rise to several volts or even higher, but far below the bus voltage). When V_DS exceeds a set threshold, the insulated-gate bipolar transistor (IGBT) is triggered to conduct. The IGBT quickly absorbs part of the fault current, and the voltage drop generated by its V_CE clamps the terminal voltage of the SiCMOSFET, preventing the MOSFET's on-state voltage from becoming too high. Once the IGBT absorbs the current, the MOSFET automatically carries a smaller current due to entering a desaturation state, thus keeping its temperature controllable. When performing surge current interruption, the controller first turns off the MOSFET gate to disconnect the current path, and then delays turning off the IGBT gate (e.g., 1-10 microseconds, optimized according to actual conditions) to complete the current interruption. This delay ensures that the current from the silicon carbide (SiC) MOSFET is completely transferred to the insulated-gate bipolar transistor (IGBT), preventing the IGBT from turning off earlier than the SiC MOSFET and causing the SiC MOSFET to carry inrush current. This control strategy fully utilizes the low loss and high-speed turn-off of the MOSFET during turn-on, as well as the steady-state capability of the IGBT when carrying large currents, thus achieving high-speed, arc-free interruption while ensuring low loss. In the bidirectional interruption topology, two of the above parallel structures are connected in reverse parallel to achieve bipolar interruption for both forward and reverse currents.Specifically, a set of parallel silicon carbide field-effect transistors (SiCMOSFETs) and insulated-gate bipolar transistors (IGBTs) can be set in the positive and negative branches respectively (each parallel branch can be connected in parallel with a reverse-conducting diode D to achieve unidirectional current shunting). Both branches are then connected in series with a current-limiting element. The same control strategy can be used for both the positive and negative branches: under normal conditions, the MOSFETs in both branches are turned on; under fault conditions, the MOSFETs desaturate, and the IGBTs carry the current, eventually turning off sequentially to achieve full current interruption. For bidirectional topologies, energy-absorbing devices such as metal-oxide rheostats (MOVs) can be connected in parallel across each parallel branch to absorb residual energy during the interruption process and prevent device overvoltage.

[0065] For other protection strategies, including overcurrent protection, overvoltage protection, overtemperature protection, and undervoltage lockout, since these faults develop slowly, calculations and judgments can be performed through a sensor-control unit to ensure the reliability of the functions. For overcurrent protection, a fast-response current sensor is used to monitor the total circuit breaker current in real time. Upon determining a slight overload, the SiC MOSFET is controlled to directly interrupt the current based on a preset time delay. For overvoltage protection or undervoltage lockout, voltage sensors connected to the positive and negative buses are used for judgment. When the voltage exceeds the rated allowable safety threshold, the SiC MOSFET is controlled to interrupt the current. For overtemperature protection, a temperature sensor (such as an NTC thermistor) inside the power module is used for real-time monitoring. An overheat alarm is issued and the circuit breaker is forcibly shut down to protect the device when a certain temperature is exceeded.

[0066] In terms of control strategy design, the rise in drain-source voltage can be monitored by setting a desaturation detection point (e.g., using a DESAT detection circuit) in the drive circuit of the silicon carbide field-effect transistor (SiC MOSFET). When MOSFET desaturation is detected (V_DS exceeds the threshold) or the voltage drop across the current sensing resistor exceeds a set value, the circuit triggers the parallel conduction of the insulated-gate bipolar transistor (IGBT), thereby allowing the IGBT to share the fault current. The IGBT's shutdown can be delayed after the MOSFET is turned off to control the rate of change of current during the turn-off process. In a typical embodiment, a SiC MOSFET (e.g., 1.2kV, tens of milliohms on-resistance) and an IGBT (e.g., 1.2kV, hundreds of amperes rated current) with a rated voltage matched to the system bus can be selected, with fast recovery diodes (or anti-parallel diodes) connected in series to meet the bidirectional blocking requirements. The control unit can use a high-speed DSP or FPGA to sample the current and current-limiting inductor voltage monitored through the shunt or differential amplifier. Once a fault current or di / dt exceeding the threshold is detected, the drive system immediately activates MOSFET desaturation detection and simultaneously triggers the insulated-gate bipolar transistor (IGBT) to enter steady-state conduction, clamping the fault current for a short time. Then, the MOSFET is turned off first, followed by the IGBT, completing fault clearance. Simulation results show that the solid-state circuit breaker using this invention can suppress sudden current surges and achieve rapid breaking without zero-crossing current within microseconds.

[0067] The feasibility of this circuit was verified using simulation software. The circuit started operating at 0µs and a short circuit occurred at 30µs. At this point, the current was carried by the silicon carbide MOSFET. After 2µs, the insulated-gate bipolar transistor (IGBT) turned on, and the further increase in short-circuit current was carried by the IGBT. At this time, the SiC MOSFET was operating in the linear region, and the current no longer increased further, while the voltage was clamped by the on-state voltage drop of the IGBT. After 40µs, the control module determined that a short-circuit fault had occurred, and the SiC MOSFET and IGBT were turned off. The circuit was then shut down through a buffer circuit and an energy absorption circuit.

[0068] It should be noted that the buffer circuits (such as RC buffers, RCD buffers, or single-capacitor energy absorption circuits) in this invention are merely auxiliary circuits used to improve voltage spikes and energy absorption during device turn-off. Their specific implementation does not affect the core concept of this invention, namely the collaborative strategy of parallel connection of silicon carbide MOSFETs (SiC MOSFETs) and insulated-gate bipolar transistors (IGBTs). Therefore, the aforementioned buffer circuits can be equivalently replaced or optimized according to different application scenarios, without constituting a substantial change to the technical solution of this invention. The circuit breaker structure and control scheme shown in this embodiment balance low conduction losses and strong turn-off capability, making it suitable for scenarios such as shipborne DC power distribution, DC data centers, and energy storage power stations. It can significantly improve system efficiency and ensure high-speed and reliable fault protection.

[0069] Furthermore, this invention connects SiC MOSFETs and IGBTs in parallel in the switching branch, utilizing their different electrical characteristics to achieve functional division: SiC MOSFETs have low on-resistance, suitable for long-term conduction to reduce losses; IGBTs have strong current carrying capacity and good short-circuit tolerance, suitable for stable operation under high surge currents. During normal operation, the current mainly flows through the SiC MOSFET; in case of a fault, the SiC MOSFET desaturates, and the IGBT automatically takes over the current. This breaks through the performance bottleneck of a single device, achieving a unified "efficient turn-on + robust turn-off". The low RDS(on) of the SiC MOSFET significantly reduces steady-state conduction losses (by 30%~50%). The IGBT bears the surge current, preventing the SiC MOSFET from thermally failing due to overcurrent desaturation. By detecting changes in the drain-source voltage (V_DS) or current of the SiC MOSFET, when it exceeds a preset threshold (indicating entry into the desaturation region), the IGBT is triggered to turn on within ≤3μs. This detection can be implemented by a dedicated DESAT circuit, without relying on the main controller for judgment, resulting in a fast response speed. Much faster than traditional software protection (typically >10μs), it preemptively controls the initial current rise window, preventing thermal breakdown or avalanche damage caused by prolonged operation at high V_DS. Hardware-level detection is independent of the main control chip, providing strong anti-interference capabilities. During shutdown, the controller first turns off the SiC MOSFET gate, and only turns off the IGBT after the current has fully transferred to it (delay 1–10μs). This timing ensures that the SiC MOSFET is not forcibly turned off after the IGBT is turned off, preventing breakdown caused by high V_DS shutdown. It fully utilizes the IGBT's stronger turn-off capability to complete the final current cutoff. The SiC MOSFET and IGBT are configured with independent gate drive circuits, coordinated by a unified control board (such as FPGA / DSP) to achieve precise timing control and fault response. Independent drives prevent malfunctions caused by shared drive paths. Parameters such as drive voltage and turn-on / turn-off resistance can be optimized separately, facilitating the implementation of complex protection logic and status monitoring. An RC or RCD snubber circuit is connected in parallel across the SiC MOSFET and IGBT parallel branch to absorb inductive energy during turn-off, suppress the voltage rise rate (dV / dt), and prevent voltage oscillations and dynamic avalanche. This reduces the risk of overvoltage during turn-off, protecting the SiC MOSFET and IGBT from breakdown. It also slows down dV / dt, reducing high-frequency noise radiation and minimizing cumulative damage from repetitive voltage stress. An energy-absorbing branch, consisting of an MOV or surge arrester, is connected in parallel across the switching branch to absorb energy released by stray inductance during turn-off, limiting the voltage peak to within 90% of the device's rated voltage. This prevents excessive bus voltage from damaging the SiC MOSFET and IGBT and absorbs fault energy, preventing energy feedback to the power supply side.Each SiC MOSFET and IGBT on each branch is connected in reverse parallel with a diode. A fast recovery diode is then connected in reverse parallel across the parallel SiC MOSFET and IGBT, forming a bidirectional conduction path. In a bidirectional DC circuit breaker, the forward and reverse branches are connected in reverse parallel, and the diode in each branch allows reverse current to pass through, achieving bidirectional conduction and shutdown capabilities. This allows the circuit breaker to be used in bipolar DC systems (such as ±380V data center buses). When one branch is turned off, the diode in the other branch provides a path for reverse current, preventing voltage backflow. No additional anti-parallel module is needed, reducing size and cost. It supports various configurations such as unidirectional / bidirectional and unipolar / bipolar, making it widely applicable. Voltage, current, and temperature sensors are configured to monitor system status in real time, supporting overcurrent, overvoltage, undervoltage, and overheat protection functions. Minor faults can be quickly responded to by simply turning off the SiC MOSFET. This provides a data foundation for intelligent control and predictive maintenance. Minor overloads are quickly interrupted by the SiC MOSFET, while severe faults are handled collaboratively by the IGBT. To prevent long-term overheating or overvoltage operation from causing device aging or failure.

[0070] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0071] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A DC circuit breaker, characterized in that, It includes a front port and a rear port, and a switching branch connecting the front port and the rear port. The switching branch includes a silicon carbide field-effect transistor (SiC MOSFET) and an insulated-gate bipolar transistor (IGBT) connected in parallel. Under normal conduction conditions, the SiC MOSFET is turned on, while the IGBT is turned off, and current flows through the SiC MOSFET, which has a lower on-state voltage drop. When a surge current or short-circuit fault occurs, the SiC MOSFET enters a desaturation state, and its drain-source voltage rises. At this time, the IGBT is turned on, and the subsequent rising fault current is borne by the IGBT. The on-state voltage drop of the IGBT clamps the voltage across the SiC MOSFET. When performing a turn-off operation, the SiC MOSFET is turned off first, and then the IGBT is turned off with a delay, thus completing the current interruption.

2. The DC circuit breaker as described in claim 1, characterized in that, Preferably, it also includes a desaturation detection circuit for real-time monitoring of the drain-source voltage or current of the silicon carbide field-effect transistor (SiC MOSFET). When the voltage exceeds a preset threshold or the current exceeds a set value, the IGBT is triggered to turn on, thereby achieving rapid shunting of fault current.

3. The DC circuit breaker as described in claim 1, characterized in that, The silicon carbide field-effect transistor (SiC MOSFET) and the insulated-gate bipolar transistor (IGBT) are driven by independent gate drive circuits, and the control logic coordinates their switching timing to ensure that the SiC MOSFET turns off before the IGBT during the turn-off process, with a delay time of 1μs to 10μs.

4. The DC circuit breaker as described in claim 1, characterized in that, It also includes a buffer circuit, which is connected in parallel across the parallel branch of the silicon carbide field-effect transistor (SiC MOSFET) and the insulated gate bipolar transistor (IGBT) to suppress the voltage rise rate dV / dt during the turn-off process and prevent dynamic avalanche breakdown.

5. The DC circuit breaker as described in claim 4, characterized in that, The buffer circuit is an RC buffer circuit, an RCD buffer circuit, or a single capacitor absorption circuit.

6. The DC circuit breaker as described in claim 1, characterized in that, It also includes an energy-absorbing branch for absorbing the energy generated during the turn-off process and limiting the voltage peak to within 90% of the rated voltage of the silicon carbide field-effect transistor (SiC MOSFET) and the insulated gate bipolar transistor (IGBT). The energy-absorbing branch is connected in parallel across the switching branch and is composed of a varistor (MOV) or a surge arrester.

7. The DC circuit breaker as described in claim 1, characterized in that, The circuit breaker is a bidirectional solid-state circuit breaker, including a forward branch and a reverse branch. Each branch is composed of a silicon carbide field-effect transistor (SiC MOSFET) and an insulated gate bipolar transistor (IGBT) connected in parallel, and the two branches are connected in reverse parallel to realize bidirectional conduction and cutoff of forward and reverse current.

8. The DC circuit breaker as described in claim 7, characterized in that, Each branch has a silicon carbide MOSFET and an insulated gate bipolar transistor (IGBT) connected in reverse parallel with a diode to enable reverse freewheeling for the unidirectional branch.

9. The DC circuit breaker as described in claim 1, characterized in that, It may also include a sensor module, which includes a voltage sensor, a current sensor, and a temperature sensor to monitor the system status in real time and perform overcurrent, overvoltage, undervoltage, and overheat protection by controlling the turn-off of silicon carbide field-effect transistors.

10. A method for processing a DC circuit breaker according to any one of claims 1-9, characterized in that, It includes the following steps, During normal operation, the silicon carbide field-effect transistor (SiC MOSFET) is turned on, the insulated gate bipolar transistor (IGBT) is turned off, and the current flows through the silicon carbide field-effect transistor, achieving low conduction loss. When a surge or short-circuit fault is detected, the silicon carbide field-effect transistor (SiC MOSFET) enters a desaturation state, and its voltage rises to trigger the insulated-gate bipolar transistor (IGBT) to turn on, and the fault current is transferred to the IGBT. The controller initiates the shutdown process by first turning off the silicon carbide field-effect transistor (SiC MOSFET) to completely transfer the current to the insulated gate bipolar transistor (IGBT). After a delay of 1–10 μs, the IGBT is turned off, and the current is safely shut off with the cooperation of the buffer circuit and the energy absorption branch. The system enters a protection lockout state, and can be manually or automatically reset after the fault is cleared.

Images