Bidirectional desaturation detection circuit for solid state circuit breaker overcurrent fault protection

Abstract

The application belongs to the field of new energy vehicle electronic control, and particularly relates to a bidirectional desaturation detection circuit for over-current fault protection of a solid-state circuit breaker, which comprises: symmetrically and parallelly arranged first and second voltage detection circuits, the first voltage detection circuit comprising a first high-voltage blocking diode D s1 , a first current-limiting resistor R s1 and a constant current source, the second voltage detection circuit comprising a second high-voltage blocking diode D s2 , a second current-limiting resistor R s2 and a constant current source, and the first and second voltage detection circuits are respectively provided with first and second low-voltage blocking diodes D blo1 and D blo2 second low-voltage blocking diodes for avoiding mutual interference between the outputs of the voltage detection circuits and realizing a shared fault determination circuit, the structure of the above symmetrically parallel design and shared fault determination circuit can ensure the consistency of over-current detection in two directions and reduce the difficulty of circuit debugging on the basis of reducing the hardware size and cost of the protection circuit.

Description

Technical Field

[0001] This invention belongs to the field of electronic control for new energy vehicles, specifically relating to a bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers. Background Technology

[0002] In modern military equipment, armored vehicles serve as crucial combat platforms, and their combat performance and reliability directly impact the success or failure of a war. With technological advancements and the increasing complexity of battlefield environments, the demands on the electrical systems of armored vehicles are constantly rising. They are typically equipped with high-power electrical equipment and sophisticated electronic systems, requiring robust power distribution protection mechanisms to ensure their stable operation.

[0003] Solid-state circuit breakers (SSDs) offer advantages such as fast switching speed and long switching life, playing a crucial role in ensuring the safety of armored vehicle power distribution systems. Overcurrent detection technology, a key technology for SSDs, is required to quickly and accurately identify overcurrent faults in the power distribution system and promptly control the SSD to trip, preventing system overcurrent failure. This not only ensures the safe operation of the SSDs but also provides crucial support for the stability of the entire power distribution system and the combat capability of the armored vehicles.

[0004] Commonly used overcurrent detection techniques include four methods: sampling resistor detection, current sensor detection, current mirror detection, and desaturation detection. The sampling resistor method requires a sampling resistor to be connected in series with the power distribution system, increasing system losses and making it unsuitable for high-power power distribution systems. The current mirror method is a further extension of the sampling resistor method, where an auxiliary power device is connected in parallel inside the chip being tested. After the solid-state circuit breaker is turned on, a portion of the current flows through this auxiliary device at a certain ratio (e.g., 1 / 1000). The required current information can be obtained by measuring the on-state voltage of the sampling resistor connected in series with this auxiliary device. This method avoids the additional losses associated with the traditional sampling resistor method, but its reliance on special manufacturing processes for power devices leads to higher costs and greater implementation difficulty. The current sensor method requires the use of current sensors such as Hall effect sensors and giant magnetoresistive sensors to collect system current and process it through processing circuits for fault detection and protection. This method is both bulky and costly, and similarly unsuitable for collecting large currents.

[0005] Traditional desaturation detection technology originated from overcurrent detection in IGBTs of power converters and has gradually been extended to other power devices (such as SiC MOSFETs). This technology reflects the on-state current of a power device by detecting its on-state voltage. When the on-state voltage exceeds a certain set threshold, it indicates an overcurrent fault, and the power device is then turned off via gate drive to ensure the system is not damaged by the overcurrent fault. Since solid-state circuit breakers use power semiconductor devices as the main switches, overcurrent fault detection in solid-state circuit breakers can also be achieved using this technology.Figure 1 This describes the application principle of traditional desaturation detection technology in solid-state circuit breakers. The core switch of this solid-state circuit breaker is a single IGBT, therefore it can only interrupt unidirectional current, and the desaturation detection circuit can only detect unidirectional fault current.

[0006] In battery power distribution and DC microgrid systems, solid-state circuit breakers (SSDs) are typically required to enable bidirectional current flow and interruption; these are generally referred to as bidirectional SSDs. Taking IGBT-based SSDs as an example, to achieve this, their main switches often employ a reverse-connected IGBT configuration. Simultaneously, their overcurrent detection technology also needs to enable bidirectional overcurrent fault detection.

[0007] To achieve bidirectional overcurrent fault detection, this invention proposes a bidirectional desaturation detection technology for bidirectional solid-state circuit breakers. This technology, by sharing key components such as comparators and high-voltage diodes, effectively reduces the size and cost of the detection system while meeting the aforementioned overcurrent detection requirements. Summary of the Invention

[0008] (a) Technical problems to be solved The technical problem to be solved by the present invention is: how to provide a bidirectional desaturation detection method and its implementation circuit to overcome the defects of traditional desaturation detection such as unidirectional and inflexible protection strategy, so as to achieve: (1) overcurrent detection and fault disconnection of current in both positive and negative directions; (2) reducing system hardware cost and volume, improving integration, and adapting to the needs of various protection strategies in complex environments.

[0009] (II) Technical Solution To solve the above technical problems, the present invention provides a bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers. The front end of the bidirectional desaturation detection circuit is connected to the bidirectional solid-state circuit breaker body. The bidirectional solid-state circuit breaker body includes a gate driver, a first solid-state circuit breaker IGBT1, and a second solid-state circuit breaker IGBT2, which are used to send an enable signal and an on-state voltage characterizing the original fault information to the bidirectional desaturation detection circuit. The bidirectional desaturation detection circuit includes two symmetrically parallel voltage detection circuits, namely a first voltage detection circuit and a second voltage detection circuit. The first voltage detection circuit includes a first high-voltage blocking diode. D s1 First current-limiting resistor R s1 The constant current source and the second voltage detection circuit include a second high-voltage blocking diode. D s2 Second current-limiting resistor R s2With a constant current source, this structure is used to detect the on-state voltage of power devices connected in reverse series and to avoid high voltage damage to the bidirectional desaturation detection circuit; Based on this, a first low-voltage blocking diode is also provided in both the first voltage detection circuit and the second voltage detection circuit. D blo1 Second low-voltage blocking diode D blo2 This is used to avoid mutual interference between the outputs of voltage detection circuits, thereby enabling a shared back-end fault determination circuit. The fault determination circuit includes a blanking capacitor. C blk Clamping diodes D blk The symmetrical parallel design and shared fault determination circuit structure described above can ensure the consistency of overcurrent detection in both directions and reduce the difficulty of circuit debugging while reducing the hardware size and cost of the protection circuit.

[0010] The working principle of the bidirectional desaturation detection circuit is as follows: When the output voltage of the gate drive is positive, the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2 will be turned on at the same time. At this time, the bus voltage forms a path through the first solid-state circuit breaker IGBT1, the second solid-state circuit breaker IGBT2 and the load, and the power distribution system starts to work normally. Then, the output voltage of the gate drive V GS Send an enable signal to cause the constant current source to output a constant current. I s constant current I s The potential circulation routes include: branch road ①, branch road ②, branch road ③ and branch road ④; The branch circuit ① includes: a constant current source and a first current-limiting resistor. R s1 First high-voltage blocking diode D s1 First solid-state circuit breaker IGBT1; The branch ② includes: a constant current source and a first low-voltage blocking diode. D blo1 Blanking capacitor C blk ; The branch circuit ③ includes: a constant current source and a second current-limiting resistor. R s2 Second high-voltage blocking diode D s2 Second solid-state circuit breaker IGBT2; The branch ④ includes: a constant current source and a second low-voltage blocking diode. D blo2Blanking capacitor C blk ; Through branches ② and ④, the constant current source will supply power to the blanking capacitor. C blk Charge until the blanking capacitor voltage is reached. V Cblk Satisfy one of the following two equations: (1) (2) in, V Ds1 , V Ds2 These are the first high-voltage blocking diodes. D s1 Second high-voltage blocking diode D s2 The on-state pressure drop is a constant. V Rs1 , V Rs2 The first current-limiting resistor is respectively R s1 Second current-limiting resistor R s2 The voltage across the two ends is a constant. V CE1 , V CE2 These are the on-state voltages of the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2, respectively. V Dblo1 , V Dblo2 These are the first low-voltage blocking diodes. D blo1 Second low-voltage blocking diode D blo2 The on-state pressure drop is a constant. , These represent the objects to be assigned values ​​for the blanking capacitor voltage under different conduction directions, where... This corresponds to the case where the power current flows in the forward direction. This corresponds to the situation where the power current flows in the opposite direction.

[0011] Among them, if the current of the power distribution system I L The direction is from the first solid-state circuit breaker IGBT1 to the second solid-state circuit breaker IGBT2. This is defined as the first operating condition, i.e., when the power current flows in the forward direction. V CE1 The voltage is a positive voltage. V CE2The voltage is negative; according to the above formulas (1) and (2), it can be seen that... V ' Cblk Greater than V " Cblk Therefore, diode D blo2 In the blocking state, only branches ① and ② are in the active state; under the above conditions, the blanking capacitor voltage... V Cblk When formula (1) is satisfied, then V Cblk Values This formula shows that the blanking capacitor voltage... V Cblk On-state voltage of forward-conducting IGBT1 V CE1 The phase difference is a constant, therefore the blanking capacitor voltage V Cblk This can reflect the on-state voltage of IGBT1. V CE1 Size.

[0012] Among them, if the current of the power distribution system I L The direction is from the second solid-state circuit breaker IGBT2 to the first solid-state circuit breaker IGBT2. This is defined as the second operating condition, i.e., when the power current flows in reverse. V CE2 The voltage is a positive voltage. V CE1 The voltage is negative; according to the above formulas (1) and (2), it can be seen that... V ' Cblk Less than V " Cblk Therefore, diode D blo1 In the blocking state, only branches ③ and ④ are in the active state; under the above conditions, the blanking capacitor voltage... V Cblk When formula (2) is satisfied, then V Cblk Values This formula shows that the blanking capacitor voltage... V Cblk On-state voltage of forward-conducting IGBT2 V CE2 The phase difference is a constant, therefore the blanking capacitor voltage V Cblk This can reflect the on-state voltage of IGBT2. V CE2 Size.

[0013] Wherein, the blanking capacitor C blk The negative input of the comparator is connected to the positive input, and a constant threshold voltage is connected to the positive input. V th ; When an overcurrent fault occurs in the first operating condition, as the current flowing through IGBT1 increases, its V CE1 and V Cblk Simultaneously increase; when V Cblk equal V th When the comparator outputs a turn-off signal, it turns off both IGBT1 and IGBT2 simultaneously; at this time, the on-state voltage of IGBT1... V CE1 With threshold voltage V th The relationship is represented as: (3) When an overcurrent fault occurs in the second operating condition, as the current flowing through IGBT2 increases, its V CE2 and V Cblk Simultaneously increase; when V Cblk equal V th When the comparator outputs a turn-off signal, it turns off both IGBT1 and IGBT2 simultaneously; at this time, the on-state voltage of IGBT2... V CE2 With threshold voltage V th The relationship is adjusted by referring to formula (3).

[0014] In practical applications, the threshold voltage V th Able to use adjustable resistors R ad Adjustment allows for the adjustment of the overcurrent protection operating current value according to actual needs.

[0015] Among them, the first high-voltage blocking diode D s1 Second high voltage blocking diode D s2 It is a high-voltage diode, and its function is to prevent the high voltage at the emitter from damaging the detection circuit after the IGBT is turned off. Wherein, the first current-limiting resistor R s1 Second current-limiting resistor R s2Its function is to prevent high interference from IGBT switching transients (through high voltage change rate d). v / d t (Characteristics) The parasitic capacitance of the detection circuit generates a large instantaneous current, which in turn damages the detection circuit.

[0016] Wherein, the blanking capacitor C blk Its function is to reduce the voltage rise rate at the negative terminal of the comparator, thereby preventing false protection from occurring when the voltage across the IGBT fails to immediately drop to the on-state voltage upon turn-on; simultaneously, this capacitor is also used to set the delay time of the overcurrent detection circuit, i.e., the blanking time. t blk The calculation formula is as follows: (4) Where, Δ V This represents the change in blanking capacitor voltage. It's important to note that for desaturation detection of power devices in traditional converters, to ensure the detection speed of the detection circuit and the reliability of the converter system, the blanking time should be ensured. t blk The smaller the time, the better, provided it is greater than the turn-on time of the power device. However, unlike converters, solid-state circuit breakers, as devices for power system protection, should have a certain delay overcurrent protection function to avoid malfunctions when transient overloads occur in the power supply system. Therefore, for desaturation detection of power devices in solid-state circuit breakers, under the premise of ensuring that the power devices are in the safe operating area, it is necessary to adjust the overcurrent fault action delay time, i.e., the blanking time, by adjusting the size of the blanking capacitor.

[0017] Among them, the clamping diode D blk It is a Zener diode, whose function is to limit the maximum voltage of the blanking capacitor and ensure that the comparator is not damaged by overvoltage; D blk The regulated voltage should be greater than the threshold voltage. V th It is less than the withstand voltage of the comparator input.

[0018] (III) Beneficial Effects Compared with the prior art, the present invention has the following beneficial effects: Traditional bidirectional overcurrent protection technologies for bidirectional solid-state circuit breakers often directly incorporate symmetrical designs of unidirectional overcurrent protection circuits, resulting in high system redundancy and consequently, higher circuit size and cost. This invention, a bidirectional desaturation detection circuit for overcurrent fault protection in solid-state circuit breakers, achieves the required bidirectional overcurrent protection for bidirectional solid-state circuit breakers by adding only three low-voltage diodes and one resistor. This effectively reduces system size and cost and provides a superior overcurrent protection solution for solid-state circuit breaker applications. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the traditional unidirectional desaturation detection principle.

[0020] Figure 2 This is a schematic diagram illustrating the principle of bidirectional desaturation detection. Detailed Implementation

[0021] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0022] To address the problems of existing technologies, this invention provides a bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers. The front end of the bidirectional desaturation detection circuit is connected to the bidirectional solid-state circuit breaker body. The bidirectional solid-state circuit breaker body includes a gate driver, a first solid-state circuit breaker IGBT1, and a second solid-state circuit breaker IGBT2, which are used to send an enable signal and an on-state voltage characterizing the original fault information to the bidirectional desaturation detection circuit. like Figure 2 As shown, the bidirectional desaturation detection circuit includes two symmetrically parallel voltage detection circuits, namely a first voltage detection circuit and a second voltage detection circuit. The first voltage detection circuit includes a first high-voltage blocking diode. D s1 First current-limiting resistor R s1 The constant current source and the second voltage detection circuit include a second high-voltage blocking diode. D s2 Second current-limiting resistor R s2 With a constant current source, this structure is used to detect the on-state voltage of power devices connected in reverse series and to avoid high voltage damage to the bidirectional desaturation detection circuit; Based on this, a first low-voltage blocking diode is also provided in both the first voltage detection circuit and the second voltage detection circuit. D blo1 Second low-voltage blocking diode D blo2 This is used to avoid mutual interference between the outputs of voltage detection circuits, thereby enabling a shared back-end fault determination circuit. The fault determination circuit includes a blanking capacitor. C blk Clamping diodes D blk The symmetrical parallel design and shared fault determination circuit structure described above can ensure the consistency of overcurrent detection in both directions and reduce the difficulty of circuit debugging while reducing the hardware size and cost of the protection circuit.

[0023] The working principle of the bidirectional desaturation detection circuit is as follows: When the output voltage of the gate drive is positive, the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2 will be turned on at the same time. At this time, the bus voltage forms a path through the first solid-state circuit breaker IGBT1, the second solid-state circuit breaker IGBT2 and the load, and the power distribution system starts to work normally. Then, the output voltage of the gate drive V GS Send an enable signal to cause the constant current source to output a constant current. I s constant current I s Potential distribution channels include: Figure 2 Branch road ①, branch road ②, branch road ③, and branch road ④; The branch circuit ① includes: a constant current source and a first current-limiting resistor. R s1 First high-voltage blocking diode D s1 First solid-state circuit breaker IGBT1; The branch ② includes: a constant current source and a first low-voltage blocking diode. D blo1 Blanking capacitor C blk ; The branch circuit ③ includes: a constant current source and a second current-limiting resistor. R s2 Second high-voltage blocking diode D s2 Second solid-state circuit breaker IGBT2; The branch ④ includes: a constant current source and a second low-voltage blocking diode. D blo2 Blanking capacitor C blk ; Through branches ② and ④, the constant current source will supply power to the blanking capacitor. C blk Charge until the blanking capacitor voltage is reached. V Cblk Satisfy one of the following two equations: (1) (2) in, V Ds1 , V Ds2 These are the first high-voltage blocking diodes. D s1 Second high-voltage blocking diode D s2 The on-state pressure drop is a constant.V Rs1 , V Rs2 The first current-limiting resistor is respectively R s1 Second current-limiting resistor R s2 The voltage across the two ends is a constant. V CE1 , V CE2 These are the on-state voltages of the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2, respectively. V Dblo1 , V Dblo2 These are the first low-voltage blocking diodes. D blo1 Second low-voltage blocking diode D blo2 The on-state pressure drop is a constant. , These represent the objects to be assigned values ​​for the blanking capacitor voltage under different conduction directions, where... This corresponds to the case where the power current flows in the forward direction. This corresponds to the situation where the power current flows in the opposite direction.

[0024] Among them, if the current of the power distribution system I L The direction is from the first solid-state circuit breaker IGBT1 to the second solid-state circuit breaker IGBT2, that is... Figure 2 The diagram, arranged from top to bottom, defines this as the first operating condition, i.e., when the power current flows in the forward direction. V CE1 The voltage is a positive voltage. V CE2 The voltage is negative; according to the above formulas (1) and (2), it can be seen that... V ' Cblk Greater than V " Cblk Therefore, diode D blo2 In the blocking state, only branches ① and ② are in the active state; under the above conditions, the blanking capacitor voltage... V Cblk When formula (1) is satisfied, then V Cblk Values This formula shows that the blanking capacitor voltage... V Cblk On-state voltage of forward-conducting IGBT1 V CE1 The phase difference is a constant, therefore the blanking capacitor voltage VCblk This can reflect the on-state voltage of IGBT1. V CE1 Size.

[0025] Among them, if the current of the power distribution system I L The direction is from the second solid-state circuit breaker IGBT2 to the first solid-state circuit breaker IGBT2, that is... Figure 2 The diagram, arranged from bottom to top, defines this as the second operating condition, i.e., when the power current flows in reverse. V CE2 The voltage is a positive voltage. V CE1 The voltage is negative; according to the above formulas (1) and (2), it can be seen that... V ' Cblk Less than V " Cblk Therefore, diode D blo1 In the blocking state, only branches ③ and ④ are in the active state; under the above conditions, the blanking capacitor voltage... V Cblk When formula (2) is satisfied, then V Cblk Values This formula shows that the blanking capacitor voltage... V Cblk On-state voltage of forward-conducting IGBT2 V CE2 The phase difference is a constant, therefore the blanking capacitor voltage V Cblk This can reflect the on-state voltage of IGBT2. V CE2 Size.

[0026] Wherein, the blanking capacitor C blk The negative input of the comparator is connected to the positive input, and a constant threshold voltage is connected to the positive input. V th ; When an overcurrent fault occurs in the first operating condition, as the current flowing through IGBT1 increases, its V CE1 and V Cblk Simultaneously increase; when V Cblk equal V th When the comparator outputs a turn-off signal, it turns off both IGBT1 and IGBT2 simultaneously; at this time, the on-state voltage of IGBT1... V CE1 With threshold voltageV th The relationship is represented as: (3) When an overcurrent fault occurs in the second operating condition, as the current flowing through IGBT2 increases, its V CE2 and V Cblk Simultaneously increase; when V Cblk equal V th When the comparator outputs a turn-off signal, it turns off both IGBT1 and IGBT2 simultaneously; at this time, the on-state voltage of IGBT2... V CE2 With threshold voltage V th The relationship is adjusted by referring to formula (3).

[0027] In practical applications, the threshold voltage V th Able to use adjustable resistors R ad Adjustment allows for the adjustment of the overcurrent protection operating current value according to actual needs.

[0028] Among them, the first high-voltage blocking diode D s1 Second high voltage blocking diode D s2 It is a high-voltage diode, and its function is to prevent the high voltage at the emitter from damaging the detection circuit after the IGBT is turned off. Wherein, the first current-limiting resistor R s1 Second current-limiting resistor R s2 Its function is to prevent high interference from IGBT switching transients (through high voltage change rate d). v / d t (Characteristics) The parasitic capacitance of the detection circuit generates a large instantaneous current, which in turn damages the detection circuit.

[0029] Wherein, the blanking capacitor C blk Its function is to reduce the voltage rise rate at the negative terminal of the comparator, thereby preventing false protection from occurring when the voltage across the IGBT fails to immediately drop to the on-state voltage upon turn-on; simultaneously, this capacitor is also used to set the delay time of the overcurrent detection circuit, i.e., the blanking time. t blk The calculation formula is as follows: (4) Where, Δ VThis represents the change in blanking capacitor voltage. It's important to note that for desaturation detection of power devices in traditional converters, to ensure the detection speed of the detection circuit and the reliability of the converter system, the blanking time should be ensured. t blk The smaller the time, the better, provided it is greater than the turn-on time of the power device. However, unlike converters, solid-state circuit breakers, as devices for power system protection, should have a certain delay overcurrent protection function to avoid malfunctions when transient overloads occur in the power supply system. Therefore, for desaturation detection of power devices in solid-state circuit breakers, under the premise of ensuring that the power devices are in the safe operating area, it is necessary to adjust the overcurrent fault action delay time, i.e., the blanking time, by adjusting the size of the blanking capacitor.

[0030] Among them, the clamping diode D blk It is a Zener diode, whose function is to limit the maximum voltage of the blanking capacitor and ensure that the comparator is not damaged by overvoltage; D blk The regulated voltage should be greater than the threshold voltage. V th It is less than the withstand voltage of the comparator input.

[0031] In summary, the above scheme, in addition to the forward conduction condition of the first operating condition, also considers the operation of the overcurrent detection circuit when the current flows in reverse under the second operating condition, thus realizing overcurrent detection under the reverse conduction condition; in conclusion, the overcurrent fault detection scheme realizes bidirectional overcurrent fault detection of solid-state circuit breakers.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers, characterized in that, The bidirectional desaturation detection circuit is connected to the bidirectional solid-state circuit breaker body at its front end; the bidirectional solid-state circuit breaker body includes a gate driver, a first solid-state circuit breaker IGBT1, and a second solid-state circuit breaker IGBT2, which are used to send an enable signal and an on-state voltage characterizing the original fault information to the bidirectional desaturation detection circuit. The bidirectional desaturation detection circuit includes two symmetrically parallel voltage detection circuits, namely a first voltage detection circuit and a second voltage detection circuit. The first voltage detection circuit includes a first high-voltage blocking diode. D s1 First current-limiting resistor R s1 The constant current source and the second voltage detection circuit include a second high-voltage blocking diode. D s2 Second current-limiting resistor R s2 With a constant current source, this structure is used to detect the on-state voltage of power devices connected in reverse series and to avoid high voltage damage to the bidirectional desaturation detection circuit; Based on this, a first low-voltage blocking diode is also provided in both the first voltage detection circuit and the second voltage detection circuit. D blo1 Second low-voltage blocking diode D blo2 This is used to avoid mutual interference between the outputs of voltage detection circuits, thereby enabling a shared back-end fault determination circuit. The fault determination circuit includes a blanking capacitor. C blk Clamping diodes D blk The symmetrical parallel design and shared fault determination circuit structure described above can ensure the consistency of overcurrent detection in both directions and reduce the difficulty of circuit debugging while reducing the hardware size and cost of the protection circuit.

2. The bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers as described in claim 1, characterized in that, The working principle of the bidirectional desaturation detection circuit is as follows: When the output voltage of the gate drive is positive, the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2 will be turned on at the same time. At this time, the bus voltage forms a path through the first solid-state circuit breaker IGBT1, the second solid-state circuit breaker IGBT2 and the load, and the power distribution system starts to work normally. Then, the output voltage of the gate drive V GS Send an enable signal to cause the constant current source to output a constant current. I s constant current I s The potential circulation routes include: branch road ①, branch road ②, branch road ③ and branch road ④; The branch circuit ① includes: a constant current source and a first current-limiting resistor. R s1 First high-voltage blocking diode D s1 First solid-state circuit breaker IGBT1; The branch ② includes: a constant current source and a first low-voltage blocking diode. D blo1 Blanking capacitor C blk ; The branch circuit ③ includes: a constant current source and a second current-limiting resistor. R s2 Second high-voltage blocking diode D s2 Second solid-state circuit breaker IGBT2; The branch ④ includes: a constant current source and a second low-voltage blocking diode. D blo2 Blanking capacitor C blk ; Through branches ② and ④, the constant current source will supply power to the blanking capacitor. C blk Charge until the blanking capacitor voltage is reached. V Cblk Satisfy one of the following two equations: （1） （2） in, V Ds1 , V Ds2 These are the first high-voltage blocking diodes. D s1 Second high-voltage blocking diode D s2 The on-state pressure drop is a constant. V Rs1 , V Rs2 The first current-limiting resistor is respectively R s1 Second current-limiting resistor R s2 The voltage across the two ends is a constant. V CE1 , V CE2 These are the on-state voltages of the first solid-state circuit breaker IGBT1 and the second solid-state circuit breaker IGBT2, respectively. V Dblo1 , V Dblo2 These are the first low-voltage blocking diodes. D blo1 Second low-voltage blocking diode D blo2 The on-state pressure drop is a constant. , These represent the objects to be assigned values ​​for the blanking capacitor voltage under different conduction directions, where... This corresponds to the case where the power current flows in the forward direction. This corresponds to the situation where the power current flows in the opposite direction.

3. The bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers as described in claim 2, characterized in that, If the power distribution system current I L The direction is from the first solid-state circuit breaker IGBT1 to the second solid-state circuit breaker IGBT2. This is defined as the first operating condition, i.e., when the power current flows in the forward direction. V CE1 The voltage is a positive voltage. V CE2 The voltage is negative; according to the above formulas (1) and (2), it can be seen that... V ' Cblk Greater than V " Cblk Therefore, diode D blo2 In the blocking state, only branches ① and ② are in the active state; under the above conditions, the blanking capacitor voltage... V Cblk When formula (1) is satisfied, then V Cblk Values This formula shows that the blanking capacitor voltage... V Cblk On-state voltage of forward-conducting IGBT1 V CE1 The phase difference is a constant, therefore the blanking capacitor voltage V Cblk This can reflect the on-state voltage of IGBT1. V CE1 Size.

4. The bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers as described in claim 3, characterized in that, If the power distribution system current I L The direction is from the second solid-state circuit breaker IGBT2 to the first solid-state circuit breaker IGBT2. This is defined as the second operating condition, i.e., when the power current flows in reverse. V CE2 The voltage is a positive voltage. V CE1 The voltage is negative; according to the above formulas (1) and (2), it can be seen that... V ' Cblk Less than V " Cblk Therefore, diode D blo1 In the blocking state, only branches ③ and ④ are in the active state; under the above conditions, the blanking capacitor voltage... V Cblk When formula (2) is satisfied, then V Cblk Values This formula shows that the blanking capacitor voltage... V Cblk On-state voltage of forward-conducting IGBT2 V CE2 The phase difference is a constant, therefore the blanking capacitor voltage V Cblk This can reflect the on-state voltage of IGBT2. V CE2 Size.

5. The bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers as described in claim 4, characterized in that, The blanking capacitor C blk The negative input of the comparator is connected to the positive input, and a constant threshold voltage is connected to the positive input. V th ; When an overcurrent fault occurs in the first operating condition, as the current flowing through IGBT1 increases, its V CE1 and V Cblk Simultaneously increase; when V Cblk equal V th When the comparator outputs a turn-off signal, it turns off both IGBT1 and IGBT2 simultaneously; at this time, the on-state voltage of IGBT1... V CE1 With threshold voltage V th The relationship is represented as: （3） When an overcurrent fault occurs in the second operating condition, as the current flowing through IGBT2 increases, its V CE2 and V Cblk Simultaneously increase; when V Cblk equal V th When the comparator outputs a turn-off signal, it turns off both IGBT1 and IGBT2 simultaneously; at this time, the on-state voltage of IGBT2... V CE2 With threshold voltage V th The relationship is adjusted by referring to formula (3).

6. The bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers as described in claim 5, characterized in that, In practical applications, threshold voltage V th Able to use adjustable resistors R ad Adjustment allows for the adjustment of the overcurrent protection operating current value according to actual needs.

7. The bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers as described in claim 5, characterized in that, The first high voltage blocking diode D s1 Second high voltage blocking diode D s2 It is a high-voltage diode, and its function is to prevent the high voltage at the emitter from damaging the detection circuit after the IGBT is turned off.

8. The bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers as described in claim 5, characterized in that, First current limiting resistor R s1 Second current-limiting resistor R s2 Its function is to prevent high transient interference from IGBT switching from generating a large instantaneous current through the parasitic capacitance of the detection circuit, thereby damaging the detection circuit.

9. The bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers as described in claim 5, characterized in that, The blanking capacitor C blk Its function is to reduce the voltage rise rate at the negative terminal of the comparator, thereby preventing false protection from occurring when the voltage across the IGBT fails to immediately drop to the on-state voltage upon turn-on; simultaneously, this capacitor is also used to set the delay time of the overcurrent detection circuit, i.e., the blanking time. t blk The calculation formula is as follows: （4） Where, Δ V This represents the change in blanking capacitor voltage. It's important to note that for desaturation detection of power devices in traditional converters, to ensure the detection speed of the detection circuit and the reliability of the converter system, the blanking time should be ensured. t blk The smaller the time, the better, provided it is greater than the turn-on time of the power device. However, unlike converters, solid-state circuit breakers, as devices for power system protection, should have a certain delay overcurrent protection function to avoid maloperation when transient overload occurs in the power supply system. Therefore, for desaturation detection of power devices in solid-state circuit breakers, under the premise of ensuring that the power devices are in the safe operating area, it is necessary to adjust the overcurrent fault action delay time, i.e., the blanking time, by adjusting the size of the blanking capacitor.

10. The bidirectional desaturation detection circuit for overcurrent fault protection of solid-state circuit breakers as described in claim 5, characterized in that, The clamping diode D blk It is a Zener diode, whose function is to limit the maximum voltage of the blanking capacitor and ensure that the comparator is not damaged by overvoltage; D blk The regulated voltage should be greater than the threshold voltage. V th It is less than the withstand voltage of the comparator input.

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