Power transistor driving circuit and driving method based on filter

Abstract

The invention relates to a power transistor driving circuit and method based on a filter, and the circuit comprises a power supply; the input side of the driving branch is connected with the power supply, the output side of the driving branch is connected with the power transistor, and the output side of the driving branch outputs a driving signal for driving the power transistor; the filter is arranged between the power supply and the driving branch; whether the control filter is connected or not is adjusted, or a magnetic element in the control filter is adjusted, and the relative voltage between the control electrode and the signal electrode of the power transistor is adjusted. That is to say, the relative voltage between the signal electrode and the control electrode in the turn-on or turn-off process of the power transistor is adjusted by controlling the access of the filter or controlling the filtering effect of the filter, and the influence of the induced voltage of the signal electrode of the power transistor on the control electrode is adjusted. Therefore, the driving rate of the power transistor can be adjusted, the cost is low, and the adaptability is high.

Description

Technical Field

[0001] The present invention relates to the technical field of power transistor drive control, and in particular to a filter-based power transistor drive circuit and a drive method. Background Art

[0002] Power transistors are an important part of power conversion circuits. The purpose of power conversion can be achieved by controlling and driving power transistors. When controlling and driving power transistors, the drive circuit is a key component connecting the control circuit and the power circuit. It drives the power transistor to turn on or off by amplifying the control signal. However, under some working conditions, the voltage stress of the power transistor may exceed its maximum tolerance. For example, the national standard GB / T 19964 "Technical Regulations for Photovoltaic Power Station Access to Power System" points out: "When a fault in the power system causes the voltage at the grid connection point of the photovoltaic power station to increase, the photovoltaic power station should have a high voltage ride-through capability of up to 1.3 times." High AC voltage will raise the DC bus voltage through the photovoltaic inverter, thereby increasing the voltage stress of the power transistor. The traditional fixed drive circuit solution is simple to implement and does not require an additional adjustment mechanism, but it is difficult to achieve a balance between reducing voltage stress and reducing the loss of power transistors and drive circuits. In addition, in order to ensure the reliability of the system, it may be necessary to design a large safety margin for the power transistor and the drive circuit, which will increase the overall cost of the power converter. Therefore, it is necessary to: In the working condition where the voltage stress of the power transistor may reach the maximum tolerance, the driving circuit should be able to reduce its own driving rate to suppress the voltage rise of the power transistor too fast, so that the voltage stress of the power transistor is below the limit; When the voltage stress of the power transistor is significantly lower than the maximum tolerance, the drive circuit should be able to increase its own drive rate to reduce the voltage-current overlap time in the power transistor and the voltage-current overlap time of the drive circuit, thereby reducing the loss of the power transistor and the drive circuit.

[0003] There are currently three main solutions to this problem: 1. Adjusting the driving impedance network solution Advantage: Allows direct adjustment of the drive impedance network.

[0004] Limitations: Since the current on the driving impedance network is between the signal level and the power level, this requires the control circuit to have a strong load capacity. At the same time, directly adjusting the driving impedance may cause the gate of the power transistor to oscillate, affecting its stable operation.

[0005] 2. Adjust the driving voltage solution Advantage: The drive circuits of all power transistors can be adjusted uniformly.

[0006] Limitations: The drive voltage is usually filtered by a large-capacity capacitor, which results in a slow voltage change rate and makes it difficult to quickly respond to the need to adjust the drive rate.

[0007] 3. Add multiple drive voltage solutions Advantages: It can provide more flexible drive rate adjustment capability.

[0008] Limitations: The introduction of multiple driving voltage branches may cause some branches to be idle, which not only increases the cost of the power converter but also reduces its power density.

[0009] Therefore, how to improve the driving circuit and driving method to solve at least one of the above technical limitations is the technical problem that this application aims to solve. Summary of the invention

[0010] A main purpose of the present invention is to overcome at least one of the above-mentioned defects, and to provide a filter-based power transistor driving circuit and driving method, which can realize the driving rate adjustment of the power transistor, has low cost and strong adaptability.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is: The present invention provides a filter-based power transistor driving circuit, which includes: Power supply; A driving branch, the input side of which is connected to the power supply, the output side of which is connected to the power transistor, and the output side of the driving branch outputs a driving signal for driving the power transistor; A filter is arranged between the power supply and the driving branch; Wherein, either the connection of the filter is regulated and controlled, or the magnetic element in the filter is regulated and controlled to adjust the relative voltage between the control electrode and the signal electrode of the power transistor.

[0012] According to one embodiment of the present invention, the filter has two positive and negative connecting lines, at least one of which is provided with a control switch, and both ends of the control switch are connected in parallel to the connecting line; The filter is connected when the control switch is turned off, and the filter is removed when the control switch is turned on.

[0013] According to one embodiment of the present invention, the filter includes a magnetic element, and the magnetic element is a device with adjustable parameters.

[0014] According to one embodiment of the present invention, the magnetic element is at least one of an inductor, a magnetic bead, a common-mode inductor, and a differential-mode inductor. The magnetic element may also be other components with inductance characteristics.

[0015] According to one embodiment of the present invention, the filter includes a plurality of magnetic elements, and a control switch is connected in parallel at both ends of at least one of the plurality of magnetic elements; The magnetic element is connected when the control switch is turned off, and the magnetic element is removed when the control switch is turned on.

[0016] According to one embodiment of the present invention, a power transistor driving circuit includes at least two driving branches, each driving branch drives a power transistor respectively, and emitters or sources of the power transistors are connected.

[0017] In particular, the present application also provides a filter-based power transistor driving method, wherein a power supply is used to power at least two power transistors, and the power supply is divided into at least two output power supplies, each output power supply is connected to a driving branch of each power transistor via a filter, wherein the relative voltage between the signal electrode and the control electrode of the power transistor during the opening or closing process is adjusted by controlling whether the filter is connected or the filtering effect of the filter is controlled.

[0018] According to one embodiment of the present invention, when the filter is controlled to be connected to adjust the relative voltage between the signal electrode and the control electrode of the power transistor during the on or off process, If the filter is connected to a power transistor driving circuit, the filter divides the voltage during the process of turning the power transistor on or off to adjust the relative voltage between the control electrode and the signal electrode of the power transistor, so that the control electrode voltage of the power transistor is less affected by the signal electrode, thereby improving the driving rate of the power transistor.

[0019] According to one embodiment of the present invention, when the filtering effect of the filter is controlled to adjust the relative voltage between the signal electrode and the control electrode of the power transistor during the on or off process, If the magnetic properties of the filter are enhanced, the voltage division of the filter increases during the process of turning on or off the power transistor, which is used to adjust the relative voltage between the control electrode and the signal electrode of the power transistor, so that the control electrode voltage of the power transistor can be less affected by the signal electrode.

[0020] According to one embodiment of the present invention, the signal electrode of the power transistor is the emitter or source of the power transistor.

[0021] Compared with the prior art, the advantages and beneficial effects of the filter-based power transistor driving circuit and driving method of the patent application of the present invention are: The present application sets a filter between the power supply and the driving path of the power transistor, controls the addition or removal of the filter, or enhances or weakens the filtering effect of the filter, thereby adjusting the relative voltage between the control electrode and the signal electrode of the power transistor, and further adjusting the driving rate of the power transistor. The present application can use the original circuit to achieve the driving rate of the power transistor, with low investment cost and strong adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings: Figure 1 is a schematic structural diagram of a filter-free power transistor driving circuit according to an embodiment of the present invention; Figure 2 is a schematic structural diagram of a power transistor driving circuit with a filter according to an embodiment of the present invention; Figure 3 is a schematic diagram of the framework structure of a filter according to an embodiment of the present invention; Figure 4 is a schematic diagram of a framework structure of two filters in a cascaded state according to an embodiment of the present invention; Figure 5 is a schematic diagram of a circuit structure in which a filter is added or removed by controlling a switch according to an embodiment of the present invention; Figure 6 is a schematic diagram of a circuit structure for adjusting the filtering effect strength of a magnetic element in a filter according to an embodiment of the present invention; Figure 7 is a schematic diagram of a circuit structure in which a magnetic element in a filter is added or removed by controlling a switch according to an embodiment of the present invention; Figure 8 1 is a schematic diagram of a circuit structure of a power transistor slow shutdown process performed by a filter-free power transistor driving circuit according to an embodiment of the present invention; Fig. 9 1 is a schematic diagram of a circuit structure of a power transistor fast-turning process performed by a power transistor driving circuit with a filter according to an embodiment of the present invention; Fig.10 1 is a schematic diagram of a circuit structure of a power transistor slow turn-on process performed by a filter-free power transistor driving circuit according to an embodiment of the present invention; Fig.11The present invention is a schematic diagram of a circuit structure of a power transistor driving circuit with a filter performing a power transistor fast turn-on process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Embodiment 1: like Figure 1 As shown, multiple power transistors share a set of power supply, and the rear end of the power supply is divided into multiple power output branches, each power output branch is connected to the input side of a driving branch to supply power to the driving branch, and the output side of each driving branch is respectively connected to a power transistor for outputting a driving signal for driving the power transistor.

[0026] The driving branch generally includes a protection capacitor, a driving switch, a driving impedance network, a driving positive voltage unit as a positive voltage stabilizing unit, and a driving negative voltage unit as a negative voltage stabilizing unit. Figure 1 As shown, the drive switch adopts a single-pole double-throw style switch, the drive switch includes a moving end and a static end, the static end includes an upper contact and a lower contact, wherein the upper contact is connected to the positive electrode of the power output branch of the power supply, the lower contact is connected to the negative electrode of the power output branch of the power supply, and the moving end is connected to the drive impedance network, the other side of the drive impedance network is connected to the control electrode of the power transistor (in this embodiment, MOSFET is taken as an example, and the control electrode is the gate of the MOSFET); the protection capacitor is connected in parallel between the positive and negative output lines of the power supply; the drive positive voltage unit and the drive negative voltage unit are connected in series and then in parallel between the positive and negative output lines of the power supply, and the connection midpoint of the drive positive voltage unit and the drive negative voltage unit is connected to the source of the power transistor. By controlling the action of the drive switch through an external input signal, the output side of the drive branch can output a drive signal for driving the power transistor.

[0027] For scenarios where the driving rate needs to be changed, the current commonly used solution is to adjust the above driving impedance network, change the driving impedance to achieve the adjustment of the driving rate, or change the output of the driving voltage to achieve the adjustment of the driving rate. However, as mentioned in the previous background technology, there are defects to varying degrees.

[0028] In view of the shortcomings of the prior art, the present application sets a filter between the power supply and the drive branch. By adjusting the filter, the presence or absence of the filter or the strength of the filtering effect can change the influence of the signal pole induced voltage on the control pole during the opening or closing process of the power transistor, thereby changing the opening or closing rate of the power transistor. In other words, either adjusting and controlling the access of the filter or adjusting and controlling the magnetic element in the filter, it is used to adjust the relative voltage between the control pole and the signal pole of the power transistor.

[0029] After the filter is connected between the power supply and the driving branch, the power transistor driving circuit is as follows Figure 2 As shown, the filter divides the voltage during the process of turning on or off the power transistor, and absorbs the signal electrode (such as the induced voltage of the source electrode of the MOSFET in this embodiment) to adjust the relative voltage between the control electrode and the signal electrode of the power transistor, so that the control electrode voltage of the power transistor is less affected by the signal electrode, thereby improving the driving rate of the power transistor.

[0030] The filter can generally be a magnetic element, a resistive element, a capacitive element, or a combination of the above elements. Figure 3 As shown, the magnetic element in the filter can be set on the positive connection line connected to the positive pole of the power supply, or on the positive connection line connected to the negative pole of the power supply, and the capacitive element is connected across the positive connection line and the negative connection line, and the resistive element can be connected in series with the magnetic element or the capacitive element. It can be understood that as long as the normal function of the filter is not affected, or at least one magnetic element that can play a voltage divider role is retained, the protection of this application should be included.

[0031] Among them, the magnetic element can be any component with inductive characteristics, including but not limited to inductors, magnetic beads, common-mode inductors, differential-mode inductors, etc. The resistive element includes but is not limited to resistors and elements that show resistive characteristics to the outside, and the capacitive element includes but is not limited to capacitors and elements that show capacitive characteristics to the outside.

[0032] In addition, Figure 3 The filters shown are cascaded to form Figure 4The structure of more than two filter cascades shown should also be protected in this application.

[0033] In one embodiment, the filter has two positive and negative connecting lines corresponding to the lines connected to the positive and negative poles of the power supply, and a control switch is provided on at least one of the positive and negative connecting lines, and the two ends of the control switch are connected to the connecting lines in parallel. When the control switch is disconnected, the filter is connected, and when the control switch is turned on, the filter is removed. Figure 5 As shown, a first control switch K1 is provided on the positive connection line, and the two ends of the first control switch K1 are connected in parallel to the positive connection line, and the connection points of the first control switch K1 and the positive connection line are respectively located at the input side and the output side of the filter; a second control switch K2 is provided on the negative connection line, and the two ends of the second control switch K2 are connected in parallel to the negative connection line, and the connection points of the second control switch K2 and the negative connection line are respectively located at the input side and the output side of the filter. In short, when the first control switch K1 and the second control switch K2 are turned on, the input side and the output side of the filter can be short-circuited, thereby removing the filter.

[0034] In another embodiment, the magnetic element in the filter is adjusted. Generally, there are two adjustment methods. One adjustment method is to use a device with adjustable parameters as the magnetic element of the filter, such as Figure 6 As shown in the figure, when the filter function needs to be strengthened, the filtering effect or inductance value of the magnetic element of the filter is increased. Conversely, when the filter function needs to be weakened, the filtering effect or inductance value of the magnetic element of the filter is reduced. Another adjustment method is to add or remove some magnetic elements through circuit design, such as Figure 7 As shown, the filter includes four magnetic elements, and control switches are connected in parallel at both ends of two of the four magnetic elements; the magnetic elements are connected when the control switch is disconnected, and the magnetic elements are removed when the control switch is turned on. The number of control switches can be set as needed to determine the number of magnetic elements that can be added or removed, which should all be protected by the present application.

[0035] Embodiment 2: This embodiment describes a power transistor driving method based on a filter, wherein a power supply is used to power at least two power transistors, and the power supply is divided into at least two output power supplies, each output power supply is connected to a driving branch of each power transistor via a filter, and the overall circuit can be implemented as in Embodiment 1. Figure 2As shown. Among them, by controlling whether the filter is connected or not or controlling the filtering effect or the strength of the inductance value of the filter, the relative voltage between the signal electrode and the control electrode of the power transistor during the on or off process is adjusted. The signal electrode here generally refers to the emitter or source of the power transistor (such as the emitter of an IGBT or the source of a MOSFET).

[0036] When controlling whether the filter is connected to adjust the relative voltage between the signal electrode and the control electrode of the power transistor during the on-or-off process, if the filter is connected to the power transistor driving circuit, the filter divides the voltage during the on-or-off process of the power transistor to adjust the relative voltage between the control electrode and the signal electrode of the power transistor, so that the control electrode voltage of the power transistor is less affected by the signal electrode, thereby improving the driving rate of the power transistor.

[0037] When controlling the filtering effect of the filter to adjust the relative voltage between the signal electrode and the control electrode of the power transistor during the on-or-off process, if the filtering effect of the filter is enhanced, the voltage division of the filter increases during the on-or-off process of the power transistor, which is used to adjust the relative voltage between the control electrode and the signal electrode of the power transistor, so that the control electrode voltage of the power transistor can be less affected by the signal electrode.

[0038] Generally speaking, the voltage divider adjustment of the filter is achieved by determining whether the filter is working or the strength of the filtering effect.

[0039] The following takes the driving of two power transistors as an example to illustrate the role of the filter in the process of turning on or off the power transistors. The case is based on the addition or removal of the filter between the power supply and the driving branch. As for strengthening or weakening the role of the filter, it is similar to this, so it is not repeated here. Please be advised.

[0040] First of all, it is clear that in power circuit scenarios such as power converters, leakage inductance is usually inevitable in the commutation circuit of power transistors, so leakage inductance is introduced at the power transistor. Due to the existence of leakage inductance, the drain current will change rapidly during the process of turning on or off the power transistor, which will cause the source to generate voltage due to the leakage inductance.

[0041] The slow turn-off process of the power transistor 1 without filter is as follows Figure 8As shown. When the power transistor 1 is turned off, the current iD on the drain of the power transistor 1 suddenly decreases, and its rate of change diD / dt is relatively high, and a relatively high voltage Ls1*diD / dt is induced at the leakage inductance Ls1 of the source of the power transistor 1. The voltage Ls1*diD / dt is divided by the driving branch and the inductances of various parts of the power circuit, such as Lg1, Lg2, and Ls2, and a voltage vLg1 is obtained on Lg1. The voltage vLg1 increases the voltage vGS1 between the gate G1 and the source S1 of the power transistor 1, thereby preventing the voltage vGS1 between the gate G1 and the source S1 from decreasing, thereby slowing down the turn-off speed of the power transistor 1, and finally reducing the voltage stress of the power transistor 1.

[0042] The fast turn-off process of power transistor 1 after adding the filter is as follows: Fig. 9 As shown. When the power transistor 1 is turned off, the current iD on the drain of the power transistor 1 suddenly decreases, and its rate of change diD / dt is relatively high, and a relatively high voltage Ls1*diD / dt is induced at the leakage inductance Ls1 of the source of the power transistor 1. The voltage Ls1*diD / dt is divided by the driving branch and the inductances of various parts of the power circuit, such as Lg1, Lg2, Ls2, etc., and the filter. Most of the voltage will be divided by the filter, and the voltage vLg1 divided on Lg1 can be ignored. The voltage vLg1 has almost no effect on the falling speed of the voltage vGS1 between the gate G1 and the source S1 of the power transistor 1, thereby increasing the turn-off speed of the power transistor 1 and ultimately reducing the turn-off loss of the power transistor 1.

[0043] The slow turn-on process of the power transistor 1 without filter is as follows Figure 8 As shown. When the power transistor 1 is turned on, the current iD on the drain of the power transistor 1 suddenly increases, and its rate of change diD / dt is relatively high, and a relatively high voltage Ls1*diD / dt is induced at the leakage inductance Ls1 of the source of the power transistor 1. The voltage Ls1*diD / dt is divided by the driving branch and the inductances of various parts of the power circuit, such as Lg1, Lg2, and Ls2, and a voltage vLg1 is obtained on Lg1. The voltage vLg1 will reduce the voltage vGS1 between the gate G1 and the source S1 of the power transistor 1, thereby hindering the voltage vGS1 between the gate G1 and the source S1 from rising, thereby slowing down the turn-on speed of the power transistor 1, and finally reducing the voltage stress of the power transistor 1.

[0044] The fast turn-on process of power transistor 1 after adding the filter is as follows: Fig. 9As shown. When the power transistor 1 is turned on, the current iD on the drain of the power transistor 1 suddenly increases, and its rate of change diD / dt is relatively high, and a relatively high voltage Ls1*diD / dt is induced at the leakage inductance Ls1 of the source of the power transistor 1. The voltage Ls1*diD / dt is divided by the driving branch and the inductances of various parts of the power circuit, such as Lg1, Lg2, Ls2, etc., and the filter. Most of the voltage will be divided by the filter, and the voltage vLg1 divided on Lg1 can be ignored. The voltage vLg1 has almost no effect on the rising speed of the voltage vGS1 between the gate G1 and the source S1 of the power transistor 1, thereby increasing the turn-on speed of the power transistor 1 and ultimately reducing the turn-on loss of the power transistor 1.

[0045] In summary, the present application sets a filter between the power supply and the driving path of the power transistor, controls the addition or removal of the filter, or enhances or weakens the filtering effect of the filter, thereby adjusting the relative voltage between the control electrode and the signal electrode of the power transistor, and thus adjusting the driving rate of the power transistor. The present application can use the original circuit to achieve the driving rate of the power transistor, with low investment cost and strong adaptability.

[0046] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A filter-based power transistor driving circuit, characterized in that: include: Power supply; A driving branch, the input side of which is connected to the power supply, the output side of which is connected to the power transistor, and the output side of the driving branch outputs a driving signal for driving the power transistor; A filter is arranged between the power supply and the driving branch; Wherein, either the connection of the filter is regulated and controlled, or the magnetic element in the filter is regulated and controlled to adjust the relative voltage between the control electrode and the signal electrode of the power transistor.

2. The filter-based power transistor driving circuit according to claim 1, characterized in that: The filter has two positive and negative connecting lines, at least one of which is provided with a control switch, and both ends of the control switch are connected in parallel to the connecting line; The filter is connected when the control switch is turned off, and the filter is removed when the control switch is turned on.

3. The filter-based power transistor driving circuit according to claim 1, characterized in that: The filter includes a magnetic element, and the magnetic element is a device with adjustable parameters.

4. The filter-based power transistor driving circuit according to claim 3, characterized in that: The magnetic element is at least one of an inductor, a magnetic bead, a common mode inductor, and a differential mode inductor.

5. The filter-based power transistor driving circuit according to any one of claims 1 to 4, characterized in that: The filter comprises a plurality of magnetic elements, and a control switch is connected in parallel at both ends of at least one of the plurality of magnetic elements; The magnetic element is connected when the control switch is turned off, and the magnetic element is removed when the control switch is turned on.

6. The filter-based power transistor driving circuit according to claim 1, characterized in that: The power transistor driving circuit comprises at least two driving branches, each driving branch drives a power transistor respectively, and the emitters or sources of the power transistors are connected.

7. A power transistor driving method based on a filter, characterized in that: The power supply is used to supply power to at least two power transistors. The power supply is divided into at least two output power supplies. Each output power supply is connected to a driving branch of each power transistor via a filter. The relative voltage between the signal electrode and the control electrode of the power transistor during the on-off or off-off process is adjusted by controlling whether the filter is connected or the filtering effect of the filter.

8. The filter-based power transistor driving method according to claim 7, characterized in that: When the filter is connected or not to adjust the relative voltage between the signal electrode and the control electrode of the power transistor during the on or off process, If the filter is connected to a power transistor driving circuit, the filter divides the voltage during the process of turning on or off the power transistor to adjust the relative voltage between the control electrode and the signal electrode of the power transistor.

9. The filter-based power transistor driving method according to claim 7, characterized in that: When the filtering effect of the filter is controlled to adjust the relative voltage between the signal electrode and the control electrode of the power transistor during the on or off process, If the magnetic properties of the filter are enhanced, the voltage division of the filter increases during the process of turning on or off the power transistor, so as to adjust the relative voltage between the control electrode and the signal electrode of the power transistor.

10. The filter-based power transistor driving method according to any one of claims 7 to 9, characterized in that: The signal electrode of the power transistor is the emitter or the source of the power transistor.

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