Switching device current sharing circuit and power conversion circuit

Abstract

The utility model provides a switching device current sharing circuit and a power conversion circuit. A collector of each switching device is connected with a collector interface, and an emitter is connected with an emitter interface. The first end of the first resistor is connected with the gate interface, the second end is connected with the gate of the first switching device, the first end of the second resistor is connected with the second end of the first resistor and the emitter interface, and the second end is connected with the Kelvin emitter interface. The first end of the third resistor is connected with the gate interface, the second end of the third resistor is connected with the gate of the second switching device, the first end of the fourth resistor is connected with the second end of the third resistor and the emitter interface, and the second end of the fourth resistor is connected with the Kelvin emitter interface. Wherein the resistor connected to the grid electrode is used as a driving resistor and is used for receiving a driving signal, and the resistor connected to the Kelvin emitting electrode is used for inhibiting the circulating current of the emitting electrode and realizing current sharing, so that the sizes of the two resistors can be independently designed according to the driving signal and a power signal, and the current sharing of each switching device can be better realized.

Description

Technical Field

[0001] The present application relates to the field of switch devices, and in particular to a switch device current sharing circuit and a power conversion circuit. Background Art

[0002] As the market demand for high-power converters increases day by day, the parallel connection of switching devices has become a trend. This is mainly due to the advantages of higher current, flexible layout and high cost performance of the parallel connection switching devices. By combining the switching devices in parallel, equivalent circuits with different rated currents can be obtained. In addition, the parallel connection method is also very flexible and diverse. Therefore, the parallel connection of switching devices is one of the best solutions for high-power design applications. However, when the switching devices are connected in parallel, static or dynamic current imbalance will occur, which will affect the reliability and life of the switching devices. In view of this, it is necessary to design a current sharing circuit to ensure that the switching devices can achieve static current sharing and dynamic current sharing when connected in parallel. Utility Model Content

[0003] In a first aspect, the present application provides a switching device current sharing circuit, the circuit comprising 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 comprising 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, 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.

[0004] In the present application, the first resistor is used as a driving resistor corresponding to the first switching device to limit the driving current of the first switching device. The third resistor is used 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 capacity 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 driving signal and the power signal to better achieve current sharing of each switching device.

[0005] As a possible implementation, the circuit also 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, the sixth resistor and the second capacitor are 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 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.

[0006] 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.

[0007] As a possible implementation, 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.

[0008] 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 and the collector, thereby preventing the drive signal and the power signal from sharing the same resistor. The equivalent DC impedance of the first wire and the second wire can realize static current sharing of the two switching devices, and the equivalent AC impedance of the first wire and the second wire can realize dynamic current sharing of the two switching devices.

[0009] 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.

[0010] As a possible implementation manner, the lengths of the first electric wire and the second electric wire are greater than 0.5 mm.

[0011] As a possible implementation, the length of the first wire and the length of the second wire meet the following formula:

[0012] or Wherein, L1 is the length of the first wire, and L2 is the length of the second wire.

[0013] As a possible implementation, 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.

[0014] 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 and the emitter, thereby preventing the drive signal and the power signal from sharing the same resistor. The equivalent DC impedance of the first wire and the second wire can realize static current sharing of the two switching devices, and the equivalent AC impedance of the first wire and the second wire can realize dynamic current sharing of the two switching devices.

[0015] 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.

[0016] As a possible implementation manner, the lengths of the third wire and the fourth wire are greater than 0.5 mm.

[0017] As a possible implementation, the length of the third wire and the length of the fourth wire meet the following formula:

[0018] or Wherein, L3 is the length of the third electric wire, and L4 is the length of the fourth electric wire.

[0019] As a possible implementation, the first switch device and the second switch device are insulated gate bipolar transistors IGBT or metal oxide semiconductor field effect transistors MOS.

[0020] In a second aspect, the present application provides a power conversion circuit, which includes a controller and a current-sharing circuit of a switching device 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

[0021] Figure 1 It is a structural schematic diagram of a current balancing circuit;

[0022] Figure 2 A schematic diagram of a switch device current sharing circuit provided in this application Figure 1 ;

[0023] Figure 3 A schematic diagram of a switch device current sharing circuit provided in this application Figure 2 ;

[0024] Figure 4 A schematic diagram of a switch device current sharing circuit provided in this application Figure 3 ;

[0025] Figure 5 This is a schematic diagram of the collector connection;

[0026] Fig. 6AIt is a schematic diagram of the collectors of two switching devices connected in parallel;

[0027] Figure 6B Schematic diagram of three switching devices connected in parallel Figure 1 ;

[0028] Figure 6C Schematic diagram of three switching devices connected in parallel Figure 2 ;

[0029] Fig.6D Schematic diagram of three switching devices connected in parallel Figure 3 ;

[0030] Figure 7 This is the emitter connection diagram. DETAILED DESCRIPTION

[0031] 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 in conjunction with the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as being limited to the embodiments described 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 may be made as needed, and all changes are included in the scope of protection of this application. The drawings of this application are only used to illustrate the relative position relationship and do not represent the true proportions.

[0032] It should be noted that in the description of the present 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 the present 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 associated objects before and after are in an "or" relationship. In addition, it should be understood that in the description of the present application, words such as "first" and "second" are only used for the purpose of distinguishing descriptions, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order.

[0033] Below, some of the terms involved in the embodiments of the present application are explained to facilitate easy understanding by those skilled in the art.

[0034] (1) Static current sharing refers to when the switch device is in the on state, that is, when the switch device is in a steady-state working condition without switching action, if the current can be evenly distributed among multiple parallel devices, it is static current sharing. The reasons for static current imbalance include but are not limited to: structural differences of switch devices, aging of switch devices, differences in switch device parameters, etc.

[0035] (2) Dynamic current sharing refers to when the switch device is in the transition process, that is, when the switch device is switched from on to off, or when the switch device is switched from off to on, if the current can be evenly distributed among multiple parallel devices, it is dynamic current sharing. The reasons for dynamic current imbalance include but are not limited to: different switching speeds of the switch devices, different response times of the switch devices, different drive circuits corresponding to the switch devices, etc.

[0036] (3) Kelvin emitter: In order to enhance switching performance, reduce conduction loss and improve reliability, a Kelvin emitter is introduced in a switching device. It is a low-inductance path for the gate drive signal and is separated from the main power current path. Switching devices with an added Kelvin emitter can reduce switching delay and increase switching frequency.

[0037] (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.

[0038] (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 has the advantages of both the high input impedance of MOSFET and the low on-state voltage drop of GTR. GTR has a low saturation voltage drop and a large current density, but a large driving current. MOSFET has a very low driving 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 driving power and low saturation voltage drop. It has been increasingly widely used in modern power electronics technology and has a dominant position in high-frequency, medium-power applications.

[0039] (6) Printed circuit board (PCB) is the carrier for the electrical connection of electronic components. Because it is made by electronic printing technology, it is called a printed circuit board.

[0040] (7) Oscillation: When a switching device is switched, it may oscillate due to the inductance effect 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.

[0041] (8) Negative feedback of driving voltage means that when the switch device is turned on, the current passes through the emitter resistor to generate a voltage drop. At this time, the voltage across the resistor creates a negative feedback effect on the voltage between the gate and the emitter. Due to the existence of the voltage drop, the driving voltage between the gate and the emitter is actually reduced. When the current increases, the feedback causes the gate voltage to decrease, thereby controlling the current to further increase.

[0042] In the application of high-power power electronic converters, due to the limitation of single-cell current capacity, parallel connection of switching devices has become a common choice. However, due to the differences in the parameters of the switching devices themselves, the differences in the parasitic parameters of the lines, the inconsistent driving of the switching devices, etc., static and dynamic current imbalance occurs between the parallel switching devices, thus affecting the reliability and life of the module. Therefore, when designing a parallel circuit of switching devices, it is necessary to consider the static and dynamic current sharing of the switching devices.

[0043] As a possible implementation, see Figure 1 As shown, it is a structure of a current balancing circuit, which includes two switching devices connected in parallel, and the gates of the two switching devices are respectively connected in series with a first gate resistor Rg1 and a second gate resistor Rg2. The emitters of the two switching devices are respectively connected in series with a first auxiliary resistor Re1 and a second auxiliary resistor Re2, thereby forming a negative feedback circuit. The first auxiliary resistor Re1 and the second auxiliary resistor Re2 can reduce the dynamic current imbalance caused by the asymmetry of the loop stray inductance, thereby achieving the purpose of current balancing.

[0044] Among them, the first auxiliary resistor Re1 is used as the driving resistor of the first switch device Q1 for conducting the driving signal and the emission resistor for conducting the emission signal, and the second auxiliary resistor Re1 is used as the driving resistor of the second switch device Q2 for conducting 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 resistor (the first auxiliary resistor Re1 and the second auxiliary resistor Re2) connected in series with the emitter of each switching device is shared by the driving signal and the power signal. This makes it difficult to determine the value 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 loss caused is also large. Therefore, it is difficult to find an auxiliary resistor that meets the above requirements.

[0045] In view of this, the present application provides a current sharing circuit for a switching device, which uses a resistor connected to the gate as a driving resistor to receive a driving signal, and uses a resistor connected to the Kelvin emitter to suppress the emitter circulating current and achieve current sharing. In this way, the size of each resistor can be independently designed according to the driving signal and the power signal to better achieve current sharing of each switching device.

[0046] See also Figure 2 As shown, the switch 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 switch device 205, a second switch device 206, a first resistor 207, a second resistor 208, a third resistor 209 and a fourth resistor 210.

[0047] 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.

[0048] The first switch device 205 and the second switch device 206 may be insulated gate bipolar transistors (IGBT) or metal oxide semiconductor field effect transistors (MOSFET), etc. The present application does not impose too many restrictions on the specific internal structures of the first switch device 205 and the second switch device 206.

[0049] Continue reading Figure 2 As shown, 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.

[0050] With this structure, the drive signal is used to be input through the gate interface 202 and the Kelvin emitter interface 204. Therefore, the first resistor 207 serves as a drive resistor corresponding to the first switch device 205, and the first resistor 207 can limit the drive current of the first switch device 205. The third resistor 209 serves as a drive resistor corresponding to the second switch device 206, and the third resistor 209 can limit the drive current of the second switch device 206, thereby preventing the current of the instantaneous drive signal from being too large, resulting in insufficient driving 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 switch device 205 and the second switch device 206.

[0051] The second resistor 208 is used to suppress the emitter circulating current of the first switch device 205, and is connected in series between the Kelvin emitter of the first switch device 205 and the Kelvin emitter interface 204. The fourth resistor 210 is used to suppress the emitter circulating current of the second switch device 206, and is connected in series between the Kelvin emitter of the second switch device 206 and the Kelvin emitter interface 204. When the first switch device 205 and the second switch device 206 reach the switching transient state, negative feedback of the driving voltage is realized, thereby suppressing the emitter circulating current oscillation. In addition, the second resistor 208 and the fourth resistor 210 in series on the emitter can also offset the dynamic uneven current problem caused by the asynchronous switching of the first switch device 205 and the second switch device 206 due to inconsistent threshold voltages and asynchronous driving signals to a certain extent.

[0052] If the threshold voltages of the first switch device 205 and the second switch device 206 are inconsistent, the switch device with the lower gate voltage among the two switch devices will reach the Miller platform time first, and then the driving current of the switch device turned on will be cut off. The Miller platform is an extremely short platform that appears during the turning on and off of the switch device. Once this happens, it will cause an imbalance in the turn-on time of the switch device, thereby causing the entire parallel circuit to have a dynamic current imbalance.

[0053] In addition, the asynchrony of the driving signal will also lead to uneven transient current distribution when the first switch device 205 and the second switch device 206 are turned on and off. The driving signal needs to be transmitted through a series of electronic components and wires before reaching the gates of the switch devices. This process will cause a certain time difference in the driving signal, causing the parallel switch devices to turn on and off at different time nodes. The switch device that is turned on or off first will bear a larger overcurrent.

[0054] As a possible implementation, see Figure 3As shown, the switch device current balancing circuit 200 also includes: a fifth resistor 301, a sixth resistor 302, a first capacitor 303 and a second capacitor 304, 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 through 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 through 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, the second capacitor 304 respectively constitute a resistor-capacitor (RC) buffer circuit, and the resistor-capacitor buffer circuit is used to provide a stable bias voltage and filter out high-frequency interference. This circuit will form a low-pass filter, and by selecting appropriate resistance and capacitance data, the high-frequency signal can be attenuated, while the low-frequency signal can pass. This can ensure that the voltage between the gate and the Kelvin emitter remains stable, and prevent the influence of high-frequency interference on the circuit, thereby improving the reliability and performance of the circuit.

[0055] It should be noted that the switch device current sharing circuit provided in the present application can not only achieve current sharing when two switch devices are connected in parallel, but also achieve current sharing when multiple switch devices are connected in parallel. Figure 4 As shown, the switch device current sharing circuit 200 may further include a third switch device 211 , a seventh resistor 212 and an eighth resistor 213 . The collector of the third switch device 211 is also connected to the collector interface 201 , and the emitter of the third switch device 211 is also connected to the emitter interface 203 .

[0056] 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.

[0057] The seventh resistor 212 serves as a driving resistor corresponding to the third switching device 211, and the seventh resistor 212 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 to the emitter. The eighth resistor 213 realizes negative feedback of the driving voltage when the third switching device 211 reaches the switching transient state, thereby suppressing emitter oscillation.

[0058] 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:

[0059] 1. The difference in the turn-on threshold voltage of the switch device. The higher the turn-on threshold voltage, the later the switch device turns on. 2. The collector-emitter saturation voltage and diode forward voltage of the switch device. This factor is determined by the manufacturing process and inherent parameters of the switch device. 3. The junction temperature of the switch device is different. 4. The magnetic field in which the switch device is located is different.

[0060] Among the above factors, when multiple switch devices are connected in parallel, the parameters such as the junction temperature of each switch device and the magnetic field in which the switch device is located can be basically regarded as the same. However, the influence of the differences of each switch device itself caused by the manufacturing process and other reasons on the current sharing is difficult to eliminate. Therefore, in order to further achieve current sharing, as a possible implementation method, refer to Figure 5 As shown, the switching device current equalizing circuit 200 includes multiple wires, including 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.

[0061] The equivalent DC impedance of the first wire 501 and the second wire 502 is at the mΩ level, and the second resistor 208 and the fourth resistor 210 are at the Ω level. Therefore, the equivalent DC impedance of the first wire 501 is smaller than the second resistor 208, and the equivalent DC impedance of the second wire 502 is smaller than the fourth resistor 210. Since the length of the wire can be flexibly adjusted, it is convenient to share the current of the first switch device 205 and the second switch device 206. Optionally, the switch 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. By adjusting the length of the PCB traces, the current sharing of the first switch device 205 and the second switch device 206 is achieved.

[0062] In addition, the first wire 501 and the second wire 502 are equivalent to AC impedance, which also facilitates the dynamic current sharing of the first switch device 205 and the second switch device 206. When the current flows in the wire, the current path forms a closed loop. According to Faraday's law of electromagnetic induction, the current change in the closed loop will generate a magnetic field. This magnetic field will interact with the current, causing the current to generate a loop in the wire. The inductance formed by this loop is the AC impedance.

[0063] The magnitude of the DC impedance and AC impedance on the wires (the first wire 501 and the second wire 502) is related to factors such as the geometric shape, material and length of the wires. Generally speaking, the larger the cross-sectional area of ​​the wire, the smaller its equivalent DC impedance and AC impedance, and conversely, the smaller the cross-sectional area of ​​the wire, the larger its equivalent DC impedance and AC impedance. The longer the length of the wire, the larger its equivalent DC impedance and AC impedance, and conversely, the shorter the length of the wire, the smaller its equivalent DC impedance and AC impedance.

[0064] 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). The use of this design can avoid the drive signal and the power signal sharing the same resistor for current sharing. In addition, under the design of this structure, the size of the two resistors can be independently designed, thereby avoiding the problem that the single emitter resistor is too small to play a role in current sharing, and the value is too large to cause high loss, and 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.

[0065] As a possible implementation, the length of the first wire 501 and the second wire 502 needs to be greater than 0.5 mm. Since the equivalent DC impedance and AC impedance of the first wire 501 and the second wire 502 are also small when the length is too small, the first wire 501 and the second wire 502 cannot play the role of static current sharing and dynamic current sharing. Therefore, the length of the first wire 501 and the second wire 502 needs to be greater than 0.5 mm, so as to achieve better static current sharing and dynamic current sharing effects.

[0066] In order to further improve the static and dynamic current sharing effects when the switch devices are connected in parallel, refer to Fig. 6A As shown, if the first switch device 205 and the second switch device 206 are connected in parallel, the length of the first wire 501 from the collector of the first switch device 205 to the collector interface 201 is L1, and the length of the second wire 502 from the collector of the second switch device 206 to the collector interface 201 is L2. At this time, the collector interface 201 can serve as a common node of the first switch device 205 and the second switch device 206.

[0067] 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:

[0068] or

[0069] Wherein, L1 is the length of the first wire, and L2 is the length of the second wire.

[0070] In this way, the length error between the first wire 501 and the second wire 502 can be reduced, and the lengths of the first wire 501 and the second wire 502 can be made as close as possible, thereby further improving the static current sharing and dynamic current sharing effects when the switch devices are connected in parallel.

[0071] As a possible implementation, in a scenario where three or more switch devices are connected in parallel, refer to Figure 6B As shown, taking three devices in parallel as an example, if the first switch device 205, the second switch device 206 and the third switch device 211 are connected in parallel, the length of the first wire 501 from the collector of the first switch device 205 to the collector interface 201 is L1, the length of the second wire 502 from the collector of the second switch device 206 to the collector interface 201 is L2, and the length of the third wire from the collector of the third switch device 211 to the collector interface 201 is L3.

[0072] 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:

[0073] or L2 or

[0074] In this way, the effects of static current sharing and dynamic current sharing when the switch devices are connected in parallel can be further improved.

[0075] For example, see Figure 6C As shown, when the first switch device 205, the second switch device 206 and the third switch device 211 are connected in parallel, if the length of the collector-to-collector interface 201 of each switch device is not adjusted, the current sharing effect of each switch device will be worse.

[0076] See also Fig.6D As shown, if the relative positions of the collector interface 201, the first switch device 205, the second switch device 206 and the third switch device 211 are fixed, the length difference between L1, L2 and L3 can be reduced by adjusting the layout of the wires from each collector interface 201 to each switch device.

[0077] As a possible implementation, see Figure 7As shown, the switching device current equalizing 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 through the third wire 701, and the emitter of the second switching device 206 is connected to the emitter interface 203 through the fourth wire 702. The length difference between the third wire 701 and the fourth wire 702 is less than the first set threshold.

[0078] The equivalent DC impedance of the third wire 701 and the fourth wire 702 is at the mΩ level, and the second resistor 208 and the fourth resistor 210 are at the Ω level. The equivalent DC impedance of the third wire 701 is less than the second resistor 208. The equivalent DC impedance of the fourth wire 702 is less than the fourth resistor 210. Since the length of the wire can be flexibly adjusted, it is convenient to share the current of the first switch device 205 and the second switch device 206. Optionally, the switch 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 length of the PCB traces, the current sharing of the first switch device 205 and the second switch device 206 is achieved.

[0079] In addition, the third wire 701 and the fourth wire 702 are equivalent to AC impedance, which also facilitates the dynamic current sharing of the first switch device 205 and the second switch device 206. When the current flows in the wire, the current path forms a closed loop. According to Faraday's law of electromagnetic induction, the current change in the closed loop will generate a magnetic field. This magnetic field will interact with the current, causing the current to generate a loop in the wire. The inductance formed by this loop is the AC impedance.

[0080] The magnitude of the DC impedance and AC impedance of the wires (the third wire 701 and the fourth wire 702) is related to factors such as the geometric shape, material and length of the wires. Generally speaking, the larger the cross-sectional area of ​​the wire, the smaller its equivalent DC impedance and AC impedance, and conversely, the smaller the cross-sectional area of ​​the wire, the larger its equivalent DC impedance and AC impedance. The longer the length of the wire, the larger its equivalent DC impedance and AC impedance, and conversely, the shorter the length of the wire, the smaller its equivalent DC impedance and AC impedance.

[0081] 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 emitter (the equivalent resistance of the third wire 701 and the fourth wire 702). The use of this design can avoid the drive signal and the power signal sharing the same resistor. In addition, under the design of this structure, the size of the two resistors can be independently designed, thereby avoiding the problem that the single emitter resistor is too small to play a current balancing role, and the value is too large to cause high loss, and the equivalent DC impedance of the third wire 701 and the fourth wire 702 can achieve static current balancing of the two switching devices, and the equivalent AC impedance of the third wire 701 and the fourth wire 702 can achieve dynamic current balancing of the two switching devices.

[0082] As a possible implementation, the length of the third wire 701 and the fourth wire 702 needs 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 small when the length is too small, the third wire 701 and the fourth wire 702 cannot play the role of static current sharing and dynamic current sharing. Therefore, the length of the third wire 701 and the fourth wire 702 needs to be greater than 0.5 mm, so as to achieve a better static current sharing and dynamic current sharing effect.

[0083] In order to further improve the effect of static current sharing and dynamic current sharing when each switch device is connected in parallel, if the first switch device 205 and the second switch device 206 are connected in parallel, the length of the third wire 701 from the emitter of the first switch device 205 to the emitter interface 203 is L3, and the length of the fourth wire 702 from the emitter of the second switch device 206 to the emitter interface 203 is L4. At this time, the emitter interface 203 can serve as a common node for the first switch device 205 and the second switch device 206.

[0084] 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:

[0085] or Wherein, L3 is the length of the third electric wire, and L4 is the length of the fourth electric wire.

[0086] 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 equalization 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.

[0087] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also 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.

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