Current-sharing circuit for switch devices, and power conversion circuit

Abstract

Provided in the present application are a current-sharing circuit for switch devices, and a power conversion circuit. A collector of each switch device is connected to a collector interface, and an emitter thereof is connected to an emitter interface; a first end of a first resistor is connected to a gate interface, and a second end thereof is connected to a gate of a first switch device; a first end of a second resistor is connected to a second end of the first resistor and the emitter interface, and a second end thereof is connected to a Kelvin emitter interface; a first end of a third resistor is connected to the gate interface, and a second end thereof is connected to a gate of a second switch device; a first end of a fourth resistor is connected to the second end of the third resistor and the emitter interface, and a second end thereof is connected to the Kelvin emitter interface, wherein each resistor connected to a gate serves as a driving resistor for receiving a driving signal, and each resistor connected to the Kelvin emitter is used for suppressing an emitter circulating current and realizing current sharing. In this way, the magnitudes of two resistors can be separately designed with respect to a driving signal and a power signal, so as to better implement the current sharing of switch devices.

Description

A switching device current sharing circuit and power conversion circuit

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on December 14, 2023, with application number 202323413823.0 and invention name "A switching device current equalizing circuit and power conversion circuit", the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of switching devices, and in particular to a current sharing circuit and a power conversion circuit for switching devices. Background Art

[0004] With the growing market demand for high-power converters, the parallel connection of switching devices has become a trend. This is primarily due to the advantages of parallel switching devices, such as higher current, flexible layout, and high cost-performance. By combining switching devices in parallel, equivalent circuits with different rated currents can be obtained. Furthermore, the parallel connection methods are very flexible and diverse. Therefore, the parallel connection of switching devices is one of the best solutions for high-power design applications. However, when switching devices are connected in parallel, static or dynamic current imbalance may occur, which affects the reliability and lifespan of the switching devices. Therefore, it is necessary to design a current sharing circuit to ensure static and dynamic current sharing when the switching devices are connected in parallel. Summary of the Invention

[0005] In the first aspect, the present application provides a switching device current sharing circuit, the circuit including a collector interface, a gate interface, an emitter interface, a Kelvin emitter interface, a first switching device, a second switching device, a first resistor, a second resistor, a third resistor and a fourth resistor. The first switching device and the second switching device both include a gate, a collector and an emitter. The collectors of the first switching device and the second switching device are both connected to the collector interface, and the emitters of the first switching device and the second switching device are both connected to the emitter interface. The first end of the first resistor is connected to the gate interface, the second end of the first resistor is connected to the gate of the first switching device, the first end of the second resistor is connected to the second end of the first resistor and the emitter interface, the second end of the second resistor is connected to the Kelvin emitter interface, the first end of the third resistor is connected to the gate interface, the second end of the third resistor is connected to the gate of the second switching device, the first end of the fourth resistor is connected to the second end of the third resistor and the emitter interface, and the second end of the fourth resistor is connected to the Kelvin emitter interface.

[0006] In this application, the first resistor serves as a driving resistor corresponding to the first switching device to limit the driving current of the first switching device. The third resistor serves as a driving resistor corresponding to the second switching device to limit the driving current of the second switching device, thereby preventing the current of the instantaneous driving signal from being too large, resulting in insufficient driving capability or damage. The second resistor is used to suppress the emitter circulating current of the first switching device, and the fourth resistor is used to suppress the emitter circulating current of the second switching device. In this way, the size of each resistor can be independently designed according to the drive signal and power signal to better achieve current sharing among each switching device.

[0007] As a possible implementation, the circuit further includes: a fifth resistor, a sixth resistor, a first capacitor, and a second capacitor, the fifth resistor and the first capacitor being connected in series, and the sixth resistor and the second capacitor being connected in series, wherein the first end of the second resistor is connected to the second end of the first resistor through the fifth resistor and the first capacitor being connected in series; and the first end of the fourth resistor is connected to the second end of the third resistor through the sixth resistor and the second capacitor being connected in series.

[0008] By adopting the above structure, it is possible to ensure that the voltage between the gate and the Kelvin emitter remains stable, prevent the influence of high-frequency interference on the circuit, and improve the reliability and performance of the circuit.

[0009] As a possible implementation, the circuit further includes a plurality of wires, the plurality of wires including a first wire and a second wire, the collector of the first switching device is connected to the collector interface via the first wire, the collector of the second switching device is connected to the collector interface via the second wire, and the length difference between the first wire and the second wire is less than a first set threshold.

[0010] Using this structure, the present embodiment decouples the original emitter resistor into two resistors, one coupled to the Kelvin emitter and the other to the collector, thereby preventing the drive signal and the power signal from sharing the same resistor. The equivalent DC impedance of the first and second wires enables static current sharing between the two switching devices, while the equivalent AC impedance of the first and second wires enables dynamic current sharing between the two switching devices.

[0011] As a possible implementation, the equivalent DC impedance of the first wire and the second wire is at the mΩ level, and the second resistance is at the Ω level.

[0012] As a possible implementation manner, the lengths of the first wire and the second wire are greater than 0.5 mm.

[0013] As a possible implementation, the length of the first wire and the length of the second wire conform to the following formula:

[0014] or Wherein, L1 is the length of the first wire, and L2 is the length of the second wire.

[0015] As a possible implementation, the circuit further includes multiple wires, including a third wire and a fourth wire, the emitter of the first switching device is connected to the emitter interface via the third wire, the collector of the second switching device is connected to the emitter interface via the fourth wire, and the length difference between the third wire and the fourth wire is less than a second set threshold.

[0016] Using this structure, the present embodiment decouples the original emitter resistor into two resistors, one coupled to the Kelvin emitter and the other to the emitter, thereby preventing the drive signal and the power signal from sharing the same resistor. The equivalent DC impedance of the first and second wires enables static current sharing between the two switching devices, while the equivalent AC impedance of the first and second wires enables dynamic current sharing between the two switching devices.

[0017] As a possible implementation, the equivalent DC impedance of the third wire and the fourth wire is at the mΩ level, and the fourth resistor is at the Ω level.

[0018] As a possible implementation manner, the lengths of the third wire and the fourth wire are greater than 0.5 mm.

[0019] As a possible implementation, the length of the third wire and the length of the fourth wire conform to the following formula:

[0020] or Wherein, L3 is the length of the third wire, and L4 is the length of the fourth wire.

[0021] As a possible implementation, the first switching device and the second switching device are insulated gate bipolar transistors IGBTs or metal oxide semiconductor field effect transistors MOSs.

[0022] In a second aspect, the present application provides a power conversion circuit, which includes a controller and a current-sharing circuit for switching devices as in the first aspect, wherein the controller is used to control the first switching device or the second switching device to turn on, or to control the first switching device or the second switching device to turn off. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic structural diagram of a current sharing circuit;

[0024] FIG2 is a structural schematic diagram 1 of a current sharing circuit for a switching device provided by the present application;

[0025] FIG3 is a second structural diagram of a current sharing circuit for a switching device provided by the present application;

[0026] FIG4 is a third structural diagram of a current sharing circuit for a switching device provided in the present application;

[0027] Figure 5 is a schematic diagram of collector connection;

[0028] FIG6A is a schematic diagram of collectors of two switching devices connected in parallel;

[0029] FIG6B is a schematic diagram of three switching devices connected in parallel;

[0030] FIG6C is a second schematic diagram of three switching devices connected in parallel;

[0031] FIG6D is a third schematic diagram of three switching devices connected in parallel;

[0032] Figure 7 is a schematic diagram of emitter connection. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be understood as being limited to the embodiments set forth herein; on the contrary, these embodiments are provided to make the present application more comprehensive and complete, and to fully convey the concepts of the example embodiments to those skilled in the art. The same figure marks in the figures represent the same or similar structures, and thus their repeated descriptions will be omitted. The words expressing position and direction described in this application are all explained using the accompanying drawings as examples, but changes can be made as needed, and all changes are included in the scope of protection of this application. The drawings in this application are only used to illustrate relative position relationships and do not represent true proportions.

[0034] It should be noted that, in the description of this application, "at least one" refers to one or more, wherein, "a plurality" refers to two or more. In view of this, in the embodiments of this application, "a plurality" may also be understood as "at least two". "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / ", unless otherwise specified, generally indicates that the previous and next associated objects are in an "or" relationship. In addition, it should be understood that, in the description of this application, words such as "first" and "second" are only used to distinguish the purpose of description, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order.

[0035] Below, some of the terms involved in the embodiments of the present application are explained to facilitate understanding by those skilled in the art.

[0036] (1) Static current sharing refers to the even distribution of current across multiple parallel devices when the switching devices are in the on state, i.e., when the switching devices are in steady-state operation without any switching action. Causes of static current imbalance include, but are not limited to, structural differences in the switching devices, aging of the switching devices, and differences in the switching device parameters.

[0037] (2) Dynamic current sharing refers to the process in which the current is evenly distributed among multiple parallel devices when the switching device is in a transitional state, that is, when the switching device switches from on to off, or vice versa. This is considered dynamic current sharing. Causes of dynamic current imbalance include, but are not limited to, differences in the switching speeds of the switching devices, the response times of the switching devices, and the drive circuits corresponding to the switching devices.

[0038] (3) Kelvin emitter: In switching devices, to enhance switching performance, reduce conduction losses, and improve reliability, a Kelvin emitter is introduced. It is a low-inductance path for the gate drive signal, separated from the main power current path. Switching devices with the addition of a Kelvin emitter can reduce switching delay and increase switching frequency.

[0039] (4) Emitter circulating current: Due to the asymmetry or asynchrony of one or more factors, a potential difference is generated at the moment the switching device is turned on or off. The emitters of the switching devices are connected together through emitter resistors. In this way, emitter circulating current will be generated between the emitter resistors.

[0040] (5) Insulated gate bipolar transistor (IGBT) is a composite fully controlled voltage-driven power semiconductor device composed of a bipolar junction transistor (BJT) and an insulated gate field effect transistor (MOS). It combines the advantages of MOSFET's high input impedance and GTR's low on-state voltage drop. GTR has a low saturation voltage drop and a high current density, but a large drive current. MOSFET has a very low drive power and a fast switching speed, but a large on-state voltage drop and a low current density. IGBT combines the advantages of the above two devices, with low drive power and low saturation voltage drop. It has been increasingly widely used in modern power electronics technology and has occupied a dominant position in high-frequency, high- and medium-power applications.

[0041] (6) Printed circuit board (PCB) is the carrier for the electrical connection of electronic components. Because it is made using electronic printing technology, it is called a printed circuit board.

[0042] (7) Oscillation: When a switching device is switched on or off, it may oscillate due to the inductance of the switching device and the wires connected to it. Oscillation may not only damage the device but also affect the stability and performance of the circuit.

[0043] (8) Negative feedback of driving voltage occurs when the switch is turned on and the current flowing through the emitter resistor generates a voltage drop. The voltage across the resistor then creates a negative feedback effect on the gate-emitter voltage. Due to the voltage drop, the driving voltage between the gate and emitter is actually reduced. When the current increases, the feedback causes the gate voltage to decrease, thereby controlling the current to increase further.

[0044] In high-power power electronic converter applications, paralleling switching devices is a common option due to the limited current capabilities of individual switching devices. However, due to differences in switching device parameters, circuit parasitic parameters, and inconsistent switching device driving, static and dynamic current imbalances can occur between paralleled switching devices, impacting module reliability and lifespan. Therefore, when designing parallel switching circuits, it is important to consider both static and dynamic current sharing.

[0045] As a possible implementation, FIG1 shows a current-sharing circuit structure. The current-sharing circuit includes two switching devices connected in parallel, with the gates of the two switching devices connected in series with a first gate resistor Rg1 and a second gate resistor Rg2, respectively. The emitters of the two switching devices are connected in series with a first auxiliary resistor Re1 and a second auxiliary resistor Re2, respectively, to form a negative feedback circuit. The first auxiliary resistor Re1 and the second auxiliary resistor Re2 can reduce dynamic current imbalance caused by asymmetric loop stray inductance, thereby achieving the purpose of current balancing.

[0046] Among them, the first auxiliary resistor Re1 serves as both the driving resistor for the first switching device Q1 to conduct the driving signal and the emission resistor for conducting the emission signal, and the second auxiliary resistor Re1 serves as both the driving resistor for the second switching device Q2 to conduct the driving signal and the emission resistor for conducting the emission signal. Therefore, since the driving signal is applied to the gate and the emitter, and the power signal is applied to the collector and the emitter, the auxiliary resistors (the first auxiliary resistor Re1 and the second auxiliary resistor Re2) connected in series with the emitter of each switching device are shared by the driving signal and the power signal. This makes it difficult to determine the values ​​of the driving resistor and the emission resistor. If the value of the auxiliary resistor is small, the purpose of dynamic current sharing cannot be achieved. If the value of the auxiliary resistor is large, the heating temperature of the auxiliary resistor is high, and the resulting loss is also large. Therefore, it is difficult to find an auxiliary resistor that meets the above requirements.

[0047] In view of this, the present application provides a current-sharing circuit for switching devices. A resistor connected to the gate acts as a drive resistor to receive a drive signal, and a resistor connected to the Kelvin emitter suppresses emitter circulating current and achieves current sharing. In this way, the size of each resistor can be independently designed based on the drive signal and power signal to better achieve current sharing among the switching devices.

[0048] 2 , the switching device current sharing circuit 200 includes a collector interface 201 , a gate interface 202 , an emitter interface 203 , a Kelvin emitter interface 204 , a first switching device 205 , a second switching device 206 , a first resistor 207 , a second resistor 208 , a third resistor 209 and a fourth resistor 210 .

[0049] Among them, the first switching device 205 and the second switching device 206 both include a gate, a collector and an emitter. The collectors of the first switching device 205 and the second switching device 206 are both connected to the collector interface 201, and the emitters of the first switching device 205 and the second switching device 206 are both connected to the emitter interface 203.

[0050] The first switching device 205 and the second switching device 206 may be insulated gate bipolar transistors (IGBTs) or metal oxide semiconductor field effect transistors (MOSFETs). The present application does not impose any restrictions on the specific internal structures of the first switching device 205 and the second switching device 206.

[0051] Continuing to refer to Figure 2, the first end of the first resistor 207 is connected to the gate interface 202, the second end of the first resistor 207 is connected to the gate of the first switching device 205, the first end of the second resistor 208 is connected to the second end of the first resistor 207 and the emitter interface 203, the second end of the second resistor 208 is connected to the Kelvin emitter interface 204, the first end of the third resistor 209 is connected to the gate interface 202, the second end of the third resistor 209 is connected to the gate of the second switching device 206, the first end of the fourth resistor 210 is connected to the second end of the third resistor 209 and the emitter interface 203, and the second end of the fourth resistor 210 is connected to the Kelvin emitter interface 204.

[0052] With this structure, the drive signal is input through the gate interface 202 and the Kelvin emitter interface 204. Therefore, the first resistor 207 serves as the drive resistor corresponding to the first switching device 205, and the first resistor 207 can limit the drive current of the first switching device 205. The third resistor 209 serves as the drive resistor corresponding to the second switching device 206, and the third resistor 209 can limit the drive current of the second switching device 206, thereby preventing the current of the instantaneous drive signal from being too high, resulting in insufficient drive capability or damage. In addition, the damping effect provided by the first resistor 207 and the third resistor 209 is used to eliminate the oscillation signal generated by the first switching device 205 and the second switching device 206.

[0053] The second resistor 208 is used to suppress the emitter circulating current of the first switching device 205 and is connected in series between the Kelvin emitter of the first switching device 205 and the Kelvin emitter interface 204. The fourth resistor 210 is used to suppress the emitter circulating current of the second switching device 206 and is connected in series between the Kelvin emitter of the second switching device 206 and the Kelvin emitter interface 204. When the first switching device 205 and the second switching device 206 reach the switching transient state, negative feedback of the driving voltage is achieved, thereby suppressing the emitter circulating current oscillation. In addition, the second resistor 208 and the fourth resistor 210 connected in series with the emitter can also, to a certain extent, offset the dynamic uneven current problem caused by the asynchronous switching of the first switching device 205 and the second switching device 206 due to inconsistent threshold voltages and asynchronous driving signals.

[0054] If the threshold voltages of first switching device 205 and second switching device 206 are inconsistent, the switching device with the lower gate voltage will reach the Miller plateau time first, and the driving current of the switching device that is turned on later will be cut off. The Miller plateau is an extremely short plateau that occurs during the turn-on and turn-off of a switching device. This situation will cause an imbalance in the turn-on time of the switching devices, thereby causing dynamic current imbalance in the entire parallel circuit.

[0055] Furthermore, asynchrony in the drive signals can also lead to uneven transient current distribution when the first and second switching devices 205 and 206 are turned on and off. The drive signal must pass through a series of electronic components and wires before reaching the gates of the respective switching devices. This process results in a certain time difference in the drive signals, causing the parallel switching devices to turn on and off at different times. The switching device that turns on or off first will bear a larger overcurrent.

[0056] As a possible embodiment, referring to FIG3 , the switching device current sharing circuit 200 further includes: a fifth resistor 301, a sixth resistor 302, a first capacitor 303 and a second capacitor 304, wherein the fifth resistor 301 and the first capacitor 303 are connected in series, the sixth resistor 302 and the second capacitor 304 are connected in series, the first end of the second resistor 208 is connected to the second end of the first resistor 207 via the fifth resistor 301 and the first capacitor 303 connected in series, and the first end of the fourth resistor 210 is connected to the second end of the third resistor 209 via the sixth resistor 302 and the second capacitor 304 connected in series. Wherein, the fifth resistor 301, the first capacitor 303 and the sixth resistor 302 and the second capacitor 304 respectively constitute a resistor-capacitor (RC) buffer circuit, which is used to provide a stable bias voltage and filter out high-frequency interference. This circuit forms a low-pass filter. By selecting appropriate resistance and capacitance data, high-frequency signals can be attenuated while low-frequency signals can pass through. This ensures that the voltage between the gate and the Kelvin emitter remains stable, prevents the influence of high-frequency interference on the circuit, and improves the reliability and performance of the circuit.

[0057] It should be noted that the switching device current sharing circuit provided in this application can not only achieve current sharing when two switching devices are connected in parallel, but also achieve current sharing when multiple switching devices are connected in parallel. For example, taking three switching devices connected in parallel as an example, as shown in Figure 4, the switching device current sharing circuit 200 can also include a third switching device 211, a seventh resistor 212, and an eighth resistor 213. The collector of the third switching device 211 is also connected to the collector interface 201, and the emitter of the third switching device 211 is also connected to the emitter interface 203.

[0058] The first end of the seventh resistor 212 is connected to the gate interface 202, the second end of the seventh resistor 212 is connected to the gate of the third switching device 211, the first end of the eighth resistor 213 is connected to the second end of the seventh resistor 212 and the emitter interface 203, and the second end of the eighth resistor 213 is connected to the Kelvin emitter interface 204.

[0059] The seventh resistor 212 serves as a driving resistor corresponding to the third switching device 211 and can limit the driving current of the third switching device 211. The eighth resistor 213 serves as a power resistor corresponding to the third switching device 211 and is connected in series with the emitter. The eighth resistor 213 provides negative feedback of the driving voltage when the third switching device 211 reaches a switching transient state, thereby suppressing emitter oscillation.

[0060] We understand that the current sharing performance of multiple switching devices connected in parallel is mainly affected by the following factors, including but not limited to the following factors:

[0061] 1. The turn-on threshold voltage of the switching device. The higher the turn-on threshold voltage, the later the switching device turns on. 2. The collector-emitter saturation voltage and diode forward voltage of the switching device. These factors are determined by the manufacturing process and inherent parameters of the switching device. 3. The junction temperature of the switching device. 4. The magnetic field in which the switching device is located.

[0062] Among the above factors, when multiple switching devices are connected in parallel, parameters such as the junction temperature of each switching device and the magnetic field in which the switching devices are located can be basically considered to be the same. However, the influence of the differences between the switching devices themselves caused by reasons such as the manufacturing process on the current sharing is difficult to eliminate. Therefore, in order to further achieve current sharing, as a possible implementation method, referring to Figure 5, the switching device current sharing circuit 200 includes multiple wires, which include a first wire 501 and a second wire 502. The collector of the first switching device 205 is connected to the collector interface 201 through the first wire 501, and the collector of the second switching device 206 is connected to the collector interface 201 through the second wire 502. The length difference between the first wire 501 and the second wire 502 is less than a first set threshold.

[0063] The equivalent DC impedance of the first wire 501 and the second wire 502 is in the milli-ohm range, while the second resistor 208 and the fourth resistor 210 are in the ohm range. Therefore, the equivalent DC impedance of the first wire 501 is smaller than that of the second resistor 208, and the equivalent DC impedance of the second wire 502 is smaller than that of the fourth resistor 210. Because the wire lengths can be flexibly adjusted, current sharing between the first switching device 205 and the second switching device 206 is facilitated. Optionally, the switching device current sharing circuit 200 includes a PCB, and the first wire 501 and the second wire 502 can be PCB traces on the PCB. Current sharing between the first switching device 205 and the second switching device 206 can be achieved by adjusting the PCB trace lengths.

[0064] Furthermore, the first wire 501 and the second wire 502 also have equivalent AC impedance, which facilitates dynamic current sharing between the first switching device 205 and the second switching device 206. When current flows through a wire, the current path forms a closed loop. According to Faraday's law of electromagnetic induction, the current changes in the closed loop generate a magnetic field. This magnetic field interacts with the current, causing the current to form a loop in the wire. The inductance formed by this loop is the AC impedance.

[0065] The DC impedance and AC impedance of the wires (first wire 501 and second wire 502) are related to factors such as the wire's geometry, material, and length. Generally speaking, the larger the wire's cross-sectional area, the smaller its equivalent DC impedance and AC impedance. Conversely, the smaller the wire's cross-sectional area, the larger its equivalent DC impedance and AC impedance. The longer the wire, the larger its equivalent DC impedance and AC impedance. Conversely, the shorter the wire, the smaller its equivalent DC impedance and AC impedance.

[0066] By adopting this structure, the embodiment of the present application decouples the original emitter resistor into two resistors, and the two resistors are respectively coupled to the Kelvin emitter (the second resistor 208 and the fourth resistor 210) and the collector (the equivalent resistance of the first wire 501 and the second wire 502). This design can avoid the drive signal and the power signal sharing the same resistor for current sharing. Moreover, under the design of this structure, the size of the two resistors can be independently designed, thereby avoiding the problem that the value of a single emitter resistor is too small to play a role in current sharing, and the value is too large to cause high loss. In addition, the equivalent DC impedance of the first wire 501 and the second wire 502 can achieve static current sharing of the two switching devices, and the equivalent AC impedance of the first wire 501 and the second wire 502 can achieve dynamic current sharing of the two switching devices.

[0067] As a possible implementation, the lengths of the first and second wires 501, 502 need to be greater than 0.5 mm. Since the equivalent DC impedance and AC impedance of the first and second wires 501, 502 are also very small when their lengths are too small, the first and second wires 501, 502 cannot achieve static and dynamic current sharing. Therefore, the lengths of the first and second wires 501, 502 need to be greater than 0.5 mm to achieve better static and dynamic current sharing.

[0068] To further improve the static and dynamic current sharing when the switching devices are connected in parallel, as shown in FIG6A , if the first switching device 205 and the second switching device 206 are connected in parallel, the length of the first wire 501 from the collector of the first switching device 205 to the collector interface 201 is L1, and the length of the second wire 502 from the collector of the second switching device 206 to the collector interface 201 is L2. In this case, the collector interface 201 can serve as a common node for the first switching device 205 and the second switching device 206.

[0069] In order to improve the effect of static current sharing and dynamic current sharing, the length of the first wire 501 and the length of the second wire 502 meet the following formula:

[0070] or

[0071] Wherein, L1 is the length of the first wire, and L2 is the length of the second wire.

[0072] In this way, the length error between the first wire 501 and the second wire 502 can be reduced, making the lengths of the first wire 501 and the second wire 502 as close as possible, thereby further improving the static current sharing and dynamic current sharing effects when the switching devices are connected in parallel.

[0073] As a possible implementation, in a scenario where three or more switching devices are connected in parallel, refer to Figure 6B, taking three devices in parallel as an example, if the first switching device 205, the second switching device 206 and the third switching device 211 are connected in parallel, then the length of the first wire 501 from the collector of the first switching device 205 to the collector interface 201 is L1, the length of the second wire 502 from the collector of the second switching device 206 to the collector interface 201 is L2, and the length of the third wire from the collector of the third switching device 211 to the collector interface 201 is L3.

[0074] In order to improve the effect of static current sharing and dynamic current sharing, the length of the first wire 501, the length of the second wire 502, and the length of the third wire meet the following formula:

[0075] or L2 or

[0076] In this way, the effects of static current sharing and dynamic current sharing when the switching devices are connected in parallel can be further improved.

[0077] 6C , when the first switching device 205 , the second switching device 206 and the third switching device 211 are connected in parallel, if the length of the collector-to-collector interface 201 of each switching device is not adjusted, the current sharing effect of each switching device will be worse.

[0078] 6D , if the relative positions of the collector interface 201 , the first switching device 205 , the second switching device 206 , and the third switching device 211 are fixed, the length differences among L1 , L2 , and L3 can be reduced by adjusting the layout of the wires from each collector interface 201 to each switching device.

[0079] As a possible implementation, referring to FIG7 , the switching device current sharing circuit 200 includes multiple wires, including a third wire 701 and a fourth wire 702. The emitter of the first switching device 205 is connected to the emitter interface 203 via the third wire 701, and the emitter of the second switching device 206 is connected to the emitter interface 203 via the fourth wire 702. The length difference between the third wire 701 and the fourth wire 702 is less than a first set threshold.

[0080] The equivalent DC impedance of the third wire 701 and the fourth wire 702 is in the milli-ohm range, while the second resistor 208 and the fourth resistor 210 are in the ohm range. The equivalent DC impedance of the third wire 701 is smaller than that of the second resistor 208. The equivalent DC impedance of the fourth wire 702 is smaller than that of the fourth resistor 210. Because the wire lengths can be flexibly adjusted, current sharing between the first switching device 205 and the second switching device 206 is facilitated. Optionally, the switching device current sharing circuit 200 includes a PCB, and the third wire 701 and the fourth wire 702 can actually be PCB traces on the PCB. By adjusting the PCB trace lengths, current sharing between the first switching device 205 and the second switching device 206 can be achieved.

[0081] Furthermore, the third wire 701 and the fourth wire 702 also have equivalent AC impedance, which facilitates dynamic current sharing between the first switching device 205 and the second switching device 206. When current flows through a wire, the current path forms a closed loop. According to Faraday's law of electromagnetic induction, the current changes in the closed loop generate a magnetic field. This magnetic field interacts with the current, causing the current to form a loop in the wire. The inductance formed by this loop is the AC impedance.

[0082] The DC impedance and AC impedance of the wires (third wire 701 and fourth wire 702) are related to factors such as the wire's geometry, material, and length. Generally speaking, the larger the wire's cross-sectional area, the smaller its equivalent DC impedance and AC impedance. Conversely, the smaller the wire's cross-sectional area, the larger its equivalent DC impedance and AC impedance. The longer the wire, the larger its equivalent DC impedance and AC impedance. Conversely, the shorter the wire, the smaller its equivalent DC impedance and AC impedance.

[0083] By adopting this structure, the embodiment of the present application decouples the original emitter resistor into two resistors, which are respectively coupled to the Kelvin emitter (the second resistor 208 and the fourth resistor 210) and the emitter (the equivalent resistance of the third wire 701 and the fourth wire 702). This design can prevent the drive signal and the power signal from sharing the same resistor. In addition, under the design of this structure, the sizes of the two resistors can be independently designed, thereby avoiding the problem that a single emitter resistor is too small to play a role in current sharing, and too large a value causes high loss. In addition, the equivalent DC impedance of the third wire 701 and the fourth wire 702 can achieve static current sharing of the two switching devices, and the equivalent AC impedance of the third wire 701 and the fourth wire 702 can achieve dynamic current sharing of the two switching devices.

[0084] As a possible implementation, the lengths of the third wire 701 and the fourth wire 702 need to be greater than 0.5 mm. Since the equivalent DC impedance and AC impedance of the third wire 701 and the fourth wire 702 are also very small when their lengths are too small, the third wire 701 and the fourth wire 702 cannot achieve static current sharing and dynamic current sharing. Therefore, the lengths of the third wire 701 and the fourth wire 702 need to be greater than 0.5 mm to achieve better static current sharing and dynamic current sharing.

[0085] To further improve the static and dynamic current sharing when the switching devices are connected in parallel, if the first switching device 205 and the second switching device 206 are connected in parallel, the length of the third wire 701 from the emitter of the first switching device 205 to the emitter interface 203 is L3, and the length of the fourth wire 702 from the emitter of the second switching device 206 to the emitter interface 203 is L4. In this case, the emitter interface 203 can serve as a common node for the first switching device 205 and the second switching device 206.

[0086] In order to improve the effect of static current sharing and dynamic current sharing, the length of the third wire 701 and the length of the fourth wire 702 meet the following formula:

[0087] or Wherein, L3 is the length of the third wire, and L4 is the length of the fourth wire.

[0088] Based on the same concept, the present application also provides a power conversion circuit, which includes: multiple switching devices, a controller, and a switching device current sharing circuit 200 as in the above embodiment, wherein the controller is used to control the first switching device or the second switching device to turn on, or to control the first switching device or the second switching device to turn off.

[0089] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A switching device current sharing circuit, characterized in that: The circuit includes a collector interface, a gate interface, an emitter interface, a Kelvin emitter interface, a first switch device, a second switch device, a first resistor, a second resistor, a third resistor and a fourth resistor; The first switch device and the second switch device each include a gate, a collector and an emitter, the collectors of the first switch device and the second switch device are both connected to the collector interface, and the emitters of the first switch device and the second switch device are both connected to the emitter interface; The first end of the first resistor is connected to the gate interface, the second end of the first resistor is connected to the gate of the first switching device, the first end of the second resistor is connected to the second end of the first resistor and the emitter interface, and the second end of the second resistor is connected to the Kelvin emitter interface; the first end of the third resistor is connected to the gate interface, the second end of the third resistor is connected to the gate of the second switching device, the first end of the fourth resistor is connected to the second end of the third resistor and the emitter interface, and the second end of the fourth resistor is connected to the Kelvin emitter interface.

2. The circuit according to claim 1, characterized in that The circuit further includes: a fifth resistor, a sixth resistor, a first capacitor and a second capacitor, the fifth resistor and the first capacitor are connected in series, and the sixth resistor and the second capacitor are connected in series; Among them, the first end of the second resistor is connected to the second end of the first resistor through the fifth resistor and the first capacitor connected in series; the first end of the fourth resistor is connected to the second end of the third resistor through the sixth resistor and the second capacitor connected in series.

3. The circuit according to claim 1 or 2, characterized in that The circuit also includes multiple wires, including a first wire and a second wire, the collector of the first switching device is connected to the collector interface through the first wire, the collector of the second switching device is connected to the collector interface through the second wire, and the length difference between the first wire and the second wire is less than a first set threshold.

4. The circuit according to claim 3, characterized in that The equivalent DC impedance of the first wire and the second wire is at the mΩ level, and the second resistance is at the Ω level.

5. The circuit according to claim 3, characterized in that The lengths of the first electric wire and the second electric wire are greater than 0.5 mm.

6. The circuit according to claim 3, characterized in that The length of the first wire and the length of the second wire meet the following formula: or Wherein, L1 is the length of the first wire, and L2 is the length of the second wire.

7. The circuit according to any one of claims 1 to 6, characterized in that: The circuit also includes multiple wires, including a third wire and a fourth wire, the emitter of the first switching device is connected to the emitter interface through the third wire, the collector of the second switching device is connected to the emitter interface through the fourth wire, and the length difference between the third wire and the fourth wire is less than a second set threshold.

8. The circuit according to claim 7, characterized in that The equivalent DC impedance of the third electric wire and the fourth electric wire is at the mΩ level, and the fourth resistor is at the Ω level.

9. The circuit according to claim 7, characterized in that The lengths of the third electric wire and the fourth electric wire are greater than 0.5 mm.

10. The circuit according to claim 7, characterized in that The length of the third wire and the length of the fourth wire meet the following formula: or Wherein, L3 is the length of the third electric wire, and L4 is the length of the fourth electric wire.

11. The circuit according to any one of claims 1 to 10, characterized in that: The first switching device and the second switching device are insulated gate bipolar transistors IGBT or metal oxide semiconductor field effect transistors MOS.

12. A power conversion circuit, characterized in that: The circuit includes: a controller and a switching device current sharing circuit as described in any one of claims 1 to 11, wherein the controller is used to control the first switching device or the second switching device to turn on, or to control the first switching device or the second switching device to turn off.

Images