A IGBT parallel current sharing circuit

Abstract

The present application relates to an IGBT parallel current-sharing circuit, which includes a first IGBT branch circuit and at least one second IGBT branch circuit, wherein the first IGBT branch circuit is connected in parallel with the second IGBT branch circuit, the first IGBT branch circuit is a branch circuit through which current passes first, and an annular inductive element is commonly provided on the outer side of one end wire of each second IGBT branch circuit and the outer side of one end wire of the first IGBT branch circuit, and the current flow direction of the first IGBT branch circuit in each of the inductive elements is opposite to the current flow direction of the second IGBT branch circuit. The present application has the effect of facilitating current balancing in the branch circuit.

Description

Technical Field

[0001] The present application relates to the field of current balancing circuits, and in particular to an IGBT parallel current balancing circuit. Background Art

[0002] IGBT is the abbreviation of insulated gate bipolar transistor. IGBT is a device composed of MOSFET and bipolar transistor. Its input is MOSFET and its output is PNP transistor. It combines the advantages of these two devices: it has the advantages of low driving power and fast switching speed of MOSFET devices, and the advantages of low saturation voltage and large capacity of bipolar devices. Its frequency characteristics are between MOSFET and power transistors, and it can work normally in the frequency range of tens of kHz. IGBT has been more and more widely used in modern power electronics technology, and has a dominant position in high-frequency and medium-power applications.

[0003] Due to industrial requirements, IGBT modules are often connected in parallel. In an IGBT parallel circuit, if the resistance values ​​of each branch are equal, the current value of each branch is theoretically equal at the same voltage. However, due to the resistance of the wires in actual use, the current will preferentially choose the branch with the smallest resistance value. Therefore, the current in the branch closest to the power supply is the largest, and the IGBT modules in the branch are prone to damage. A common solution is to start from the physical characteristics: since the increase in current in a certain IGBT module will cause the temperature of the module to rise, according to the characteristics of the resistance in the module itself, the resistance will increase with the increase in temperature. Under the premise of unchanged voltage, the current in the module can be naturally reduced.

[0004] Regarding the above-mentioned related technologies, the inventors believe that since the current has a strong ability to take shortcuts, especially under high frequency conditions, the increase in resistance value when the temperature rises alone is not enough to make the currents in each parallel branch equal, and the current balancing effect is poor. Summary of the invention

[0005] In order to help make the currents in each parallel branch equal, the present application provides an IGBT parallel current sharing circuit.

[0006] The IGBT parallel current sharing circuit provided in this application adopts the following technical solution:

[0007] An IGBT parallel current sharing circuit comprises a first IGBT branch circuit and at least one second IGBT branch circuit, wherein the first IGBT branch circuit is connected in parallel with the second IGBT branch circuit, the first IGBT branch circuit is a branch circuit through which current passes preferentially, an annular inductive element is commonly sleeved on the outer side of one end wire of each of the second IGBT branch circuits and the outer side of one end wire of the first IGBT branch circuit, and the current flow direction of the first IGBT branch circuit in each of the inductive elements is opposite to the current flow direction of the second IGBT branch circuit.

[0008] By adopting the above technical solution, the role of the inductive element is to enhance the magnetic coupling between the two wires. The inductive element is sheathed on the outside of the wire, which is convenient to install and replace. In the case of current sharing, the magnetic flux in the inductive element is zero; when the current in the first IGBT branch circuit increases, according to the principle of mutual induction, the current in the second IGBT branch circuit will tend to increase, and since the total current remains unchanged, the current in the first IGBT branch circuit will tend to decrease and eventually tend to balance; when the current in a second IGBT branch circuit increases, since the second IGBT branch circuit and the first IGBT branch circuit are sheathed with an inductive element, the current in the first IGBT branch circuit will tend to increase from small to large, and at the same time, the current in the second IGBT branch circuit will tend to decrease from large to small, so that the currents of the first IGBT branch circuit and the second IGBT branch circuit tend to be equal, which helps to achieve the effect of current sharing. The circuit structure is simple and the working stability is high.

[0009] Optionally, the inductive element is sleeved on the outside of the wires at the output ends of the first IGBT branch circuit and each second IGBT branch circuit.

[0010] By adopting the above technical solution, it is easy to install the circuit, and it is also easy to isolate the inductive element, so as to prevent the leakage flux of the inductive element from affecting other circuits.

[0011] Optionally, the cross-sections of the output end wire of the first IGBT branch circuit and the output end wire of the second IGBT branch circuit in the inductive element are both semicircular with the same diameter, and the two wires are fitted together to form a complete circle, and the arc-shaped outer walls of the two wires are tightly attached to the corresponding inner wall of the inductive element.

[0012] By adopting the above technical solution, the cross-sections of the first IGBT branch circuit and the second IGBT branch circuit are equal. When the currents are equal, the magnetic fluxes they generate in the inductive element are equal, which helps to cancel each other out and become equal. At the same time, the radius of the two wires in the inductive element is as large as possible, so that the mutual inductance phenomenon generated is more obvious and the current sharing effect is better.

[0013] Optionally, the first IGBT branch circuit includes a first IGBT module, and the second IGBT branch circuit includes a second IGBT module; outputs of the first IGBT module and the second IGBT module are both connected to corresponding current acquisition circuits.

[0014] By adopting the above technical solution, it is convenient to detect the current of the first IGBT branch circuit and each second IGBT branch circuit.

[0015] Optionally, the input ends of the first IGBT module and the second IGBT module are connected to independent drive circuits, which are used to control the pulse input of the corresponding first IGBT module or the corresponding second IGBT module. The drive circuit and the current collection circuit located on the same branch circuit are connected through a feedback circuit.

[0016] By adopting the above technical solution, the first IGBT branch circuit and the second IGBT branch circuit are driven by independent driving circuits, and the power requirement for each independent driving circuit is relatively small. At the same time, the driving circuit can adjust the driving input to the IGBT module in a targeted manner according to the signal of the current acquisition circuit, thereby helping to achieve the current equalization effect.

[0017] Optionally, a common driving circuit is connected to the input ends of the first IGBT module and the second IGBT module, and the driving circuit is used to control the common pulse input of the first IGBT module and the second IGBT module. The driving circuit is connected to the current collection circuit of the first IGBT branch through a feedback circuit.

[0018] By adopting the above technical solution, the driving circuit helps to amplify the control signal, thereby realizing reliable driving of the IGBT module. At the same time, one driving circuit is used to drive all the IGBT modules, saving components.

[0019] Optionally, the rated power of the first IGBT module is greater than the rated power of the second IGBT module.

[0020] By adopting the above technical solution, due to the strong shortcut capability of the current itself, when the circuit is just turned on, the current of the first IGBT module is often larger. The larger rated power of the first IGBT module can avoid it from being damaged due to excessive current, which helps to improve safety.

[0021] Optionally, it also includes an alarm circuit and a temperature sensing circuit for detecting the ambient temperature, the input end of the temperature sensing circuit is connected to the input end of the entire circuit, and the output end of the temperature sensing circuit is connected to the input end of the alarm circuit.

[0022] By adopting the above technical solution, the temperature of the resistor will rise when the circuit works for a long time. Excessive temperature will damage the circuit and affect the performance of the inductive element. When the temperature in the circuit is too high, the temperature sensing circuit can capture this signal and warn the staff through the alarm circuit, which helps to ensure the safety of the circuit.

[0023] In summary, the present application includes at least one of the following beneficial technical effects:

[0024] 1. By arranging the inductive element outside the conductors of the first IGBT branch circuit and each second IGBT branch circuit, it helps to balance the current in each parallel IGBT branch circuit;

[0025] 2. The temperature sensing circuit can sense the temperature around the circuit in real time. When the temperature is too high, the alarm circuit will alert the staff to improve the safety of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of an existing IGBT parallel circuit;

[0027] Figure 2 is a schematic diagram of the circuit structure of Example 1 of the present application;

[0028] Figure 3 It is a structural schematic diagram used to reflect the positional relationship between the magnetic ring and the internal wires in Example 1 of the present application;

[0029] Figure 4 1 is a circuit connection diagram of the temperature sensing circuit and the alarm circuit of Example 1 of the present application;

[0030] Figure 5 This is a schematic diagram of the circuit structure of Example 2 of the present application.

[0031] Explanation of the accompanying drawings: 1. First IGBT branch circuit; 2. Second IGBT branch circuit; 3. Inductive element; 4. Driving circuit; 5. Current acquisition circuit; 6. Temperature sensing circuit; 7. Alarm circuit; 8. Feedback circuit. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of this application more clear, the following Figure 1-5 It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0033] Reference Figure 1, a common IGBT parallel circuit includes a first IGBT branch circuit 1 and multiple second IGBT branch circuits 2, wherein the first IGBT branch circuit 1 includes a first IGBT module, and the second IGBT branch circuit 2 includes a second IGBT module. The first IGBT branch circuit 1 and the second IGBT branch circuit 2 are connected in parallel, and each second IGBT branch circuit 2 is also connected in parallel, and the first IGBT branch circuit 1 is closest to the voltage input terminal in of the entire circuit. Since the current has a strong ability to take shortcuts, even if the resistance of the first IGBT module and the second IGBT module is the same, the current in the first IGBT branch circuit 1 is still greater than the current in the second IGBT branch circuit 2.

[0034] In addition, according to the characteristics of the resistors in the module: when a large current passes through the resistor, the power consumption is large, so the temperature rises significantly, causing the resistance value of the resistor itself to increase. Under the premise that the voltage across the resistor remains unchanged, the current in the resistor can naturally decrease. However, due to the large ability of the current to take shortcuts, the current that decreases with the increase in temperature is small, and the current imbalance still exists, that is, the current in the first IGBT branch circuit 1 is still greater than the current in the second IGBT branch circuit 2. The first IGBT module is prone to damage due to the long-term passage of large current.

[0035] In order to solve the above problems, an embodiment of the present application discloses an IGBT parallel current sharing circuit.

[0036] Example 1

[0037] Reference Figure 2 , an IGBT parallel current balancing circuit includes a first IGBT branch circuit 1 and multiple second IGBT branch circuits 2, the first IGBT branch circuit 1 and each second IGBT branch circuit 2 are connected in parallel, and an inductive element 3 is sleeved on the outside of the conductor of the first IGBT branch circuit 1 and each second IGBT branch circuit 2, and the inductive element 3 is a magnetic ring made of ferrite. In the inductive element 3, the current flow direction in the conductor of the first IGBT branch circuit 1 is opposite to the current flow direction in the conductor of the second IGBT branch circuit 2. According to the mutual induction principle, when the current of the first IGBT branch circuit 1 increases, the current of the second IGBT branch circuit 2 can tend to increase. Under the condition of equal total circuit current, the current of the second IGBT branch circuit 2 tends to decrease, so that the current in each branch circuit tends to be balanced, which helps to achieve the effect of current balancing.

[0038] Reference Figure 2, the output end of the first IGBT module is connected to an independent current acquisition circuit 5, and the output end of each second IGBT module is also connected to an independent current acquisition circuit 5, the current acquisition circuit 5 is a sampling resistor circuit, the first IGBT module is connected in series with the sampling resistor of the corresponding branch, and the second IGBT module is also connected in series with the sampling resistor of the corresponding branch. By converting the current of the corresponding first IGBT branch circuit or the corresponding second IGBT branch circuit into a voltage on the sampling resistor, it is helpful to achieve the effect of real-time detection of branch current. Furthermore, the rated power of the first IGBT module is greater than the rated power of the second IGBT module, which helps to avoid the first IGBT module from being damaged due to the large current passing through when the circuit is turned on and the inductive element 3 has not yet been adjusted.

[0039] Reference Figure 2 The first IGBT branch circuit 1 and the second IGBT branch circuit 2 each include an independent drive circuit 4, which is an IGBT drive circuit. The drive circuit 4 helps to amplify the control signal, thereby realizing reliable control of the first IGBT module and the second IGBT module. The input end of the drive circuit 4 is connected to the voltage input end in of the entire circuit, the input end of the first IGBT module is connected to the output end of the drive circuit 4 in the first IGBT branch circuit 1, and the input end of each second IGBT module is connected to the output end of the drive circuit 4 in the corresponding branch.

[0040] Reference Figure 2 , the first IGBT branch circuit 1 and the second IGBT branch circuit 2 each include an independent feedback circuit 8, the feedback circuit 8 is a current series negative feedback circuit, one input end of the feedback circuit 8 is connected to the output end of the current acquisition circuit 5, the other input end of the feedback circuit 8 is connected to the comparison voltage, and the output end of the feedback circuit 8 is connected to the PWM input end of the drive circuit 4 of the branch where the feedback circuit 8 itself is located. When the current of the first IGBT branch circuit 1 or a second IGBT branch circuit 2 fluctuates so that the current between the branches is unbalanced, and the inductive element 3 fails to completely equalize the current in each branch, the corresponding current acquisition circuit 5 can capture this signal and feed it back to the corresponding drive circuit 4 through the corresponding feedback circuit 8, which helps the drive circuit 4 to turn off the IGBT module by soft closing, thereby shortening the pulse input time of the branch with larger current, which helps to achieve the effect of equalizing current.

[0041] Reference Figure 3In the annular inductive element 3, the cross section of the wire of the first IGBT branch circuit 1 and the cross section of the wire of the second IGBT branch circuit 2 are of the same shape and size, both of which are semicircular, and the two semicircular cross sections can be spliced ​​into a complete circle. The arc-shaped outer wall of the wire of the first IGBT branch circuit 1 and the wire of the second IGBT branch circuit 2 are closely attached to the inner wall of the inductive element 3, so as to increase the magnetic flux intensity in the wire as much as possible, and make the mutual inductance between the two wires more obvious under the premise of ensuring easy installation and disassembly.

[0042] Reference Figure 4 The first IGBT branch circuit 1 is connected in parallel with a temperature sensing circuit 6, and the input end of the temperature sensing circuit 6 is connected to the voltage input end in. The temperature sensing circuit 6 includes a thermistor RT and a grounded voltage divider resistor R1, the voltage divider resistor R1 is connected in series with the thermistor RT, and one end of the thermistor RT is connected to the output end of the control circuit 9. The thermistor RT can decrease as the ambient temperature increases, so that the voltage on R1 decreases as the temperature increases.

[0043] Reference Figure 4 , one end of the temperature sensing circuit 6 is connected to an alarm circuit 7, and the alarm circuit 7 includes a voltage comparator module U1, a transistor Q and a buzzer L. One input end of the voltage comparator module U1 is connected to a comparison voltage VA, the other input end of the voltage comparator module U1 is connected to the connection end of the thermistor RT and the voltage divider resistor R1, and the output end of the voltage comparator module U1 is connected to the base of the transistor Q. The transistor Q is an NPN transistor, the collector of the transistor Q is connected to the working voltage VCC, the emitter of the transistor Q is connected to the positive electrode of the buzzer L, and the negative electrode of the buzzer L is grounded. When the temperature sensing circuit 6 detects that the ambient temperature is too high, it will alarm through the alarm circuit 7 to warn the staff, which helps to improve the safety of the circuit.

[0044] The implementation principle of an IGBT parallel current balancing circuit in an embodiment of the present application is as follows: when the current in the first IGBT branch circuit 1 or the second IGBT branch circuit 2 fluctuates, such as when the current in the first IGBT branch circuit 1 increases, since the inductive element 3 enhances the mutual induction between the wires, it can drive the current in all the second IGBT branch circuits 2 to increase, and the second IGBT branch circuit 2 plays a shunt role, the current of the first IGBT branch circuit 1 decreases, and the currents between the first IGBT branch circuit 1 and the second IGBT branch circuit 2 tend to be equal; at the same time, the current acquisition circuit 5 detects the current situation and feeds back the current situation to the independent drive circuit 4 on each branch, and the drive circuit 4 adjusts the pulse time delivered to the IGBT module according to the situation on the corresponding branch, which helps to achieve the effect of current balancing.

[0045] Example 2

[0046] The difference between this embodiment and embodiment 1 is that: Figure 5 , the drive circuit 4 is not independent for each IGBT branch circuit, but is shared by all branches. The input end of the drive circuit 4 is connected to the voltage input end in of the entire circuit, and the output end of the drive circuit 4 is connected to the input ends of the first IGBT module and each second IGBT module. The drive circuit 4 is connected to the current collection circuit 5 in the first IGBT branch circuit 1 through the feedback circuit 8, which helps to reduce the drive input of the entire circuit when the current of the first IGBT branch circuit 1 is too large.

[0047] The above are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Any feature disclosed in this specification (including the abstract and drawings), unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

Claims

1. An IGBT parallel current sharing circuit, comprising a first IGBT branch circuit (1) and at least one second IGBT branch circuit (2), wherein the first IGBT branch circuit (1) and the second IGBT branch circuit (2) are connected in parallel, and the first IGBT branch circuit (1) is a branch circuit through which current flows preferentially, and is characterized in that: An annular inductive element (3) is sleeved on the outer side of one end of the conductor of each second IGBT branch circuit (2) and the outer side of one end of the conductor of the first IGBT branch circuit (1); the current flow direction of the first IGBT branch circuit (1) in each of the inductive elements (3) is opposite to the current flow direction of the second IGBT branch circuit (2); the inductive element (3) is sleeved on the outer side of the conductor at the output end of the first IGBT branch circuit (1) and each of the second IGBT branch circuits (2); the cross-sections of the output end conductor of the first IGBT branch circuit (1) and the output end conductor of the second IGBT branch circuit (2) in the inductive element (3) are both semicircular with the same diameter, and the two conductors are attached to form a complete circle, and the arc-shaped outer walls of the two conductors are both in close contact with the inner wall of the corresponding inductive element (3); the first IGBT branch circuit ( 1) comprises a first IGBT module, and the second IGBT branch circuit (2) comprises a second IGBT module; the outputs of the first IGBT module and the second IGBT module are both connected to corresponding current acquisition circuits (5); the input ends of the first IGBT module and the second IGBT module are connected to a common drive circuit (4), the drive circuit (4) is used to control the common pulse input of the first IGBT module and the second IGBT module, and the drive circuit (4) is connected to the current acquisition circuit (5) of the first IGBT branch (1) through a feedback circuit (8); the IGBT parallel current sharing circuit also includes an alarm circuit (7) and a temperature sensing circuit (6) for detecting the ambient temperature, the input end of the temperature sensing circuit (6) is connected to the input end of the entire circuit, and the output end of the temperature sensing circuit (6) is connected to the input end of the alarm circuit (7).

2. The IGBT parallel current sharing circuit according to claim 1, characterized in that: The input ends of the first IGBT module and the second IGBT module are both connected to independent drive circuits (4), the drive circuits (4) being used to control the pulse input of the corresponding first IGBT module or the corresponding second IGBT module, and the drive circuits (4) and the current collection circuit (5) located on the same branch circuit are connected via a feedback circuit (8).

3. The IGBT parallel current sharing circuit according to claim 1, characterized in that: The rated power of the first IGBT module is greater than the rated power of the second IGBT module.

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