A partial bootstrap gate drive circuit and control method for reducing switching loss

Abstract

The application belongs to the technical field of gate drive circuit, and discloses a partial self-boosting gate drive circuit and control method for reducing switching loss, which comprises a switching device, a PWM, a power supply, signal isolation, a non-isolated driving chip, a self-boosting structure, a driving resistor, a Mon and a Moff. Compared with a voltage source type drive, the application can significantly improve switching speed and reduce switching loss; compared with a current source type drive, the application has the characteristic of self-adaptation, does not need additional timing control, and does not have the risk of overcharging loss of switching devices; compared with a complex active drive, the application has the advantages of simple structure and high reliability. In the application, the self-boosting structure is used to realize double voltage output without increasing the power supply, overcome the limitation of the large gate internal parasitic resistance of the wide band gap device, and significantly reduce the switching loss.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gate drive circuit, and particularly relates to a partial bootstrap gate drive circuit and control method for reducing switching loss. BACKGROUND

[0002] At present, with the development of traffic electrification and new energy, more and more power electronic converters are applied. The efficiency improvement of the power electronic converter plays a crucial role in reducing energy consumption and carbon emissions, and reducing switching loss is a main method to improve the efficiency of the converter. The switching loss of the converter is directly related to the gate drive circuit used, and reducing the switching loss by improving the gate drive circuit can achieve the purpose of saving energy and reducing carbon emissions. Therefore, it is of great significance to develop a gate drive technology that can reduce switching loss.

[0003] At present, the gate drive circuits at home and abroad mainly have the following schemes, one is a voltage source-based drive circuit, that is, a positive voltage is output when the device is turned on, and a negative voltage is output when the device is turned off, and a resistor is connected after the voltage source to adjust the switching speed and switching loss. Although this method can reduce switching loss by reducing resistance, the effect of reducing loss is limited due to the large internal parasitic resistance of the wide bandgap device; two is a current source-based drive circuit, that is, through an energy storage element such as an inductor, a positive current is injected into the gate when the device is turned on, and a negative current is injected into the gate when the device is turned off, and the switching loss can be adjusted by adjusting the size of the current. This method greatly increases the size of the drive circuit if an additional inductor and control circuit are required, and if the current source cannot be accurately controlled, the gate will be overcharged, which will damage the power device; three is an active drive circuit with complex control logic, which can reduce loss while suppressing parasitic oscillation by monitoring the voltage and current parameters of the device and adjusting the drive speed in real time. Although this method has good performance, it requires a large number of peripheral circuits to implement, which not only increases the cost but also reduces the reliability of the entire system. On the other hand, the existing drive circuit is limited by the large internal parasitic resistance of the wide bandgap device when applied to the wide bandgap device, and an additional power supply is required to increase the switching speed, which also results in additional cost.

[0004] Taking Cree Company as an example, the gate driver products launched are basically voltage source type drive circuits. Except for the non-core part, the core part of a general commercial gate driver, such as Figure 9As shown in the diagram. Here, g and s are the outputs of the gate driver, connected to the gate of the switching device; PWM is the control signal, connected to the control circuit and interface circuit. When the PWM control signal wants to turn on the switching device, Mon is on, Moff is off, and gs output voltage is 15V; when the PWM signal wants to turn off the device, Moff is on, Mon is off, and gs output voltage is -5V; Ron and Roff are used to adjust the switching speed. Besides the widely used commercial gate driver structure, there are also designs using multiple power supplies and multiple control signals for state switching, but all of these have many drawbacks.

[0005] Therefore, a drive circuit scheme that does not require an additional power supply or complex control signals, is simple and reliable, and can effectively reduce switching losses still needs further research.

[0006] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0007] (1) Wide bandgap devices have a large internal parasitic resistance at the gate. When driven by a voltage source, the current injected into the gate is limited by this resistance, requiring an additional high-voltage power supply to further improve the switching speed. However, the additional power supply greatly increases the cost of the driver, and due to the stability of the gate oxide of the switching device, the voltage increase range for the drive is very small.

[0008] (2) Current source-based drive circuits require additional inductors to generate constant current. The additional inductors increase costs and require additional control circuits. More importantly, if the charging time is not well controlled during the charging process of the gate using an inductor, overcharging of the gate will occur. Due to the stability of the gate oxide of the switching device, the excessively high gate voltage will damage the reliability of the device and may even directly damage the device.

[0009] (3) Existing active drive circuits with complex control logic require real-time switching of output voltage or output current based on the operating state of the switching devices. While this method can theoretically provide the best drive performance, its normal operation is highly dependent on monitoring the operating state of the switching devices. Additional monitoring hardware will increase costs on the one hand, and on the other hand, the measured information needs to be calculated in the microcontroller, which will lead to the occupation of computing resources.

[0010] (4) Traditional drive circuits only require one control signal, while existing current source drive circuits or active drive circuits often require a large number of auxiliary control signals to ensure normal operation of the circuit. Too many control signals will not only occupy more microcontroller port resources, but also reduce the anti-interference capability of the drive circuit. Summary of the Invention

[0011] To address the problems existing in the prior art, this invention provides a partially bootstrap gate drive circuit and control method for reducing switching losses.

[0012] The present invention is implemented as follows: a partial bootstrap gate drive circuit control method for reducing switching losses includes: in the drive circuit, a bootstrap structure is used as the output part, so that the drive circuit outputs a higher drive voltage during the switching process without using an additional power supply; by controlling the capacitance value of the capacitor, the output voltage of the drive circuit automatically drops to the power supply voltage at the end of the switching process.

[0013] Furthermore, the bootstrap structure consists of at least one capacitor and at least one diode, used to double the voltage of the power supply during output transients to increase the switching speed.

[0014] Furthermore, the partial bootstrap gate drive circuit control method that reduces switching losses specifically includes the following steps:

[0015] Step 1: In the off steady state, the PWM is at a low level, the outputs of the driver chip Bon and Boff are low level, the switch Mon is turned off and Moff is turned on.

[0016] Step 2: When the dynamic is activated, the PWM switches from low level to high level, the outputs of the driver chip Bon and Boff are high level, the switch Mon is turned on and Moff is turned off.

[0017] Step 3: When the steady state is turned on, the PWM is at a high level, the outputs of the driver chip Bon and Boff are high level, the switch Mon is turned on and Moff is turned off.

[0018] Step 4: When the dynamic is turned off, the PWM switches from high level to low level, the outputs of the driver chip Bon and Boff are low level, Mon is turned off and Moff is turned on.

[0019] Furthermore, in step one, the turn-on portion is in a pre-charge state, Con is charged to 15V to prepare for the next turn-on dynamic; the charge on Coff is completely released in the previous stage, diode Doff is turned on, the gate voltage of the switching device is -5V, and the switching device is in a reliable turn-off state.

[0020] Furthermore, in step two, the turn-off section is disconnected from the switching device and enters a pre-charge state, where Coff is charged to 5V to prepare for subsequent turn-off dynamics. Since the voltage across the capacitor cannot change abruptly, the turn-on section is bootstrapped to 30V, and the voltage gradually decreases as the drive provides current to the switching device. If the capacitor value is designed appropriately so that the stored voltage is equal to the total gate charge of the device, the charge on Con will be automatically and completely released at the end of the turn-on process, preventing gate overcharging.

[0021] Furthermore, in step three, the turn-off section is in a pre-charge state, and Coff is charged to 5V to prepare for the next turn-off. Since the charge on Con is completely released in the previous stage, diode Don is turned on, the gate voltage of the switching device is 15V, and the switching device is in a reliable turn-on state.

[0022] Furthermore, in step four, the turn-on portion is disconnected from the switching device and enters a pre-charging state, where Con is charged to 15V in preparation for subsequent turn-on. Since the voltage across the capacitor cannot change abruptly, the turn-off voltage is bootstrapping to -10V, and the voltage gradually decreases as the turn-off process proceeds. If the capacitor value is designed appropriately so that the stored voltage is equal to the total gate charge of the device, then at the end of the turn-off, the charge on Coff is automatically and completely released, preventing gate overcharging.

[0023] Another object of the present invention is to provide a partially bootstrap gate drive circuit for reducing switching losses, comprising: a switching device, which is equivalent to a resistor and capacitor connected in series;

[0024] The control signal input unit of the PWM microcontroller: a high level indicates that the device is turned on, and a low level indicates that the device is turned off.

[0025] The power supply is a DC power module with 15V and 5V outputs, which is responsible for providing power to other parts of the circuit.

[0026] Signal isolation unit is used to isolate the microcontroller from the main power devices;

[0027] A non-isolated driver chip used to switch the operating state of the circuit according to the PWM control signal;

[0028] The bootstrap structure, including capacitors and diodes, is responsible for providing faster drive speeds and reducing drive losses when the drive circuit is operating.

[0029] Gate resistors are used to adjust switching speed and balance switching losses and transient overvoltages;

[0030] Metal-oxide-semiconductor field-effect transistors are used to control the operating state of circuits and switch them.

[0031] Another object of the present invention is to provide a power electronic converter for transportation equipment, the power electronic converter for transportation equipment being equipped with the aforementioned partially bootstrap gate drive circuit that reduces switching losses.

[0032] Based on the above technical solutions and the technical problems solved, please analyze the advantages and positive effects of the technical solution to be protected by this invention from the following aspects:

[0033] First, addressing the technical problems existing in the prior art and the difficulty in solving them, this paper closely analyzes, in conjunction with the technical solution to be protected by this invention and the results and data obtained during the research and development process, how the technical solution of this invention solves the technical problems, and the inventive technical effects brought about by solving these problems. The specific description is as follows:

[0034] In the drive circuit, the output section is a bootstrap structure, enabling the drive circuit of this invention to output twice the drive voltage during switching without using an external power supply, thereby greatly improving the switching speed. By controlling the capacitance values ​​of Con and Coff, this invention ensures that the output voltage of the drive circuit automatically drops to the power supply voltage at the end of the switching process, avoiding overcharging and eliminating the need for additional control signals.

[0035] Second, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by this invention are specifically described as follows:

[0036] Compared to voltage-source drives, this invention significantly improves switching speed and reduces switching losses. Compared to current-source drives, this invention is adaptive, requires no additional timing control, eliminates the risk of overcharging losses in the switching devices, and eliminates the need for additional inductors. Compared to complex active drives, this invention offers advantages in simple structure and high reliability. Furthermore, this invention uses a bootstrap structure, achieving voltage multiplication without increasing the power supply, overcoming the limitation of switching speed imposed by the large gate parasitic resistance of wide-bandgap devices, and significantly reducing switching losses.

[0037] Commercial gate drivers are mainly voltage source drive circuits. Compared with commercial drivers, this invention can greatly reduce switching losses, does not require additional control signals or additional power supply, has a simple structure, and good stability.

[0038] Third, as supplementary evidence of the inventive step of the claims of this invention, it is also reflected in the following important aspects:

[0039] (1) The expected benefits and commercial value of the technical solution of this invention after transformation are as follows:

[0040] Commercially available drive circuits are mostly voltage source type. These circuits cannot provide a sufficiently large drive current when the gate resistance of the switching device is high, resulting in slow switching speed and high switching losses. Currently, the academic community has proposed many methods to increase the drive current, such as using an inductor to generate a constant current or using a higher voltage power supply to generate a larger drive current. However, these methods require additional control signals, additional inductors, and additional isolation power supplies. The cost of these additional hardware components often exceeds the cost of the commercial drive circuit itself, making commercialization difficult. Furthermore, most of these circuits lack adaptability and can even damage the switching device when control malfunctions. This invention uses an output structure similar to a bootstrap circuit, combined with reasonable control, enabling the invented gate driver to temporarily output twice the power supply voltage. This output voltage gradually decreases as the switching process progresses, eventually automatically decaying to the power supply output voltage at the end of the switching process, preventing gate overcharging and device damage. The greatest advantage of this invention is that the proposed drive circuit does not require an additional power supply or additional control signals, only a few low-cost, low-voltage components, and possesses adaptive characteristics that prevent device damage when operating conditions change. Therefore, this solution has enormous commercial potential.

[0041] Based on the experimental results of the prototype, using the drive circuit structure of this invention to replace the traditional commercial drive can reduce the turn-on loss by 50%-75% and the turn-off loss by about 10%. Therefore, this invention can greatly reduce the switching loss of the converter, improve efficiency, and save energy.

[0042] (2) The technical solution of this invention fills a technical gap in the industry both domestically and internationally:

[0043] Compared with existing drive circuit solutions at home and abroad, this invention is the first gate drive circuit that does not use additional power supply and control signals, can automatically adapt to different load conditions, and can significantly reduce switching losses. The symmetrical bootstrap structure of the turn-on and turn-off sections is also proposed for the first time, filling a research gap in this field.

[0044] (3) Whether the technical solution of the present invention solves the technical problem that people have long wanted to solve but have never been able to solve successfully:

[0045] The academic community has proposed many methods to improve drive performance, such as using an inductor to generate a constant current or using a higher voltage power supply to generate a larger drive current. However, these methods all require additional control signals, additional inductors, and additional isolation power supplies. The cost of this additional hardware often exceeds the cost of the commercial drive circuit itself, making it difficult to commercialize. On the other hand, most of these circuits lack adaptability and may even damage the switching devices when control malfunctions. This invention solves the problem of a new drive circuit structure that significantly reduces switching losses without significantly increasing hardware costs and control complexity. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a flowchart of a partial bootstrap gate drive circuit control method that can reduce switching losses, provided by an embodiment of the present invention.

[0048] Figure 2 This is a schematic diagram of a partial bootstrap gate drive circuit structure that can reduce switching losses, provided in an embodiment of the present invention.

[0049] Figure 3 This is a schematic diagram of the equivalent circuit in the turn-off steady state provided in an embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of the equivalent circuit during dynamic activation provided in an embodiment of the present invention;

[0051] Figure 5 This is a schematic diagram of the equivalent circuit in steady state during turn-on provided in an embodiment of the present invention;

[0052] Figure 6 This is a schematic diagram of the equivalent circuit during the shutdown dynamic provided in the embodiment of the present invention;

[0053] Figure 7 These are experimental comparison diagrams provided in the embodiments of the present invention;

[0054] Figure 8 This is a diagram illustrating the loss reduction effect provided in an embodiment of the present invention;

[0055] Figure 9 This is a schematic diagram of the core structure of a commercially available gate driver provided in this embodiment of the invention. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0057] To address the problems existing in the prior art, the present invention provides a partially bootstrap gate drive circuit and control method for reducing switching losses. The present invention will be described in detail below with reference to the accompanying drawings.

[0058] I. Explanatory and Illustrative Embodiments. To enable those skilled in the art to fully understand how the present invention is specifically implemented, this section provides an explanatory and illustrative description of the embodiments described in the claims.

[0059] like Figure 1 As shown, the partial bootstrap gate drive circuit control method for reducing switching losses provided in this embodiment of the invention includes the following steps:

[0060] S101, when in the off steady state, the PWM is at a low level, the outputs of the driver chip Bon and Boff are low level, the switch Mon is turned off and Moff is turned on;

[0061] S102, when the dynamic is activated, the PWM switches from low level to high level, the outputs of the driver chip Bon and Boff are high level, the switch Mon is turned on and Moff is turned off;

[0062] S103, when in steady state, PWM is at high level, the outputs of driver chip Bon and Boff are high level, switch Mon is turned on and Moff is turned off;

[0063] S104, when the dynamic is turned off, the PWM switches from high level to low level, the outputs of the driver chip Bon and Boff are low level, Mon is turned off and Moff is turned on.

[0064] The novel partial bootstrap driving circuit structure provided in this embodiment of the invention is as follows: Figure 2 As shown, it can be divided into on and off sections.

[0065] The switching device is equivalent to a resistor and capacitor connected in series. The resistor is the parasitic resistance inside the gate of the switching device, and the capacitor is the input capacitance of the switching device.

[0066] The control signal input unit of the PWM microcontroller: a high level indicates that the device is turned on, and a low level indicates that the device is turned off.

[0067] The power supply is a DC power module with 15V and 5V output, which is responsible for providing power to other parts of the circuit;

[0068] Signal isolation unit, used to electrically isolate the microcontroller from the main power devices;

[0069] Bon and Boff are non-isolated driver chips used to switch the operating state of the circuit according to the PWM control signal;

[0070] Don and Doff are diodes, and Con and Coff are capacitors. Don, Con, Doff, and Coff form a bootstrap structure, which is responsible for providing faster drive speed and reducing drive losses when the drive circuit is working.

[0071] Ron and Roff are driving resistors used to adjust the driving speed and balance switching losses and transient overvoltages;

[0072] Metal-oxide-semiconductor field-effect transistors (Mon is an N-type MOSFET, Moff is a P-type MOSFET) are used to control the operating state of a circuit and switch it.

[0073] In a preferred embodiment of the present invention, such as Figure 2 As shown, it specifically includes:

[0074] (1) The PWM signal is the output control signal of the microcontroller. A high level means that the switching device needs to be turned on, and a low level means that the switching device needs to be turned off. The switching device frame represents the actual switching device, which is generally a silicon carbide field-effect transistor or a silicon IGBT. It can be simply equivalent through a capacitor-resistor series structure.

[0075] (2) The main function of signal isolation is to electrically isolate the control signal from the main circuit in order to protect the control circuit.

[0076] (3) The isolation power supply is responsible for providing power to the entire circuit. It generally requires a 15V and a 5V power supply module. The specific voltage can be finely adjusted according to the application requirements.

[0077] (4) Bon and Boff are driving chips. When the PWM signal is high, the output of the driving chip will be connected to the high potential of its power supply. When the PWM signal is low, the output of the driving chip will be connected to the ground potential of its power supply. The load of these two components switches the circuit working state according to the control signal.

[0078] (5) Mon is an NMOS and Moff is a PMOS. These two components are related to the switching of the circuit's operating state.

[0079] (6) Con and Coff are capacitors, and Don and Doff are diodes. Together they form a bootstrap structure, which is used to double the voltage of the power supply during output transients to improve the switching speed.

[0080] (7) Ron and Roff are gate resistors used to adjust the switching speed.

[0081] The specific operation mode of the circuit provided in this embodiment of the invention is as follows:

[0082] 1. In the off-state steady state, the equivalent circuit is as follows: Figure 3As shown. In the off steady state, the PWM signal is low, and both driver chips, Bon and Boff, output low levels. Therefore, Mon is off and Moff is on. The on-state is disconnected from the switching device, and Con is charged by the 15V power supply in preparation for subsequent actions. The charge on Coff is completely released in the previous stage, so Doff conducts, and the gate voltage of the switching device is -5V, maintaining a stable off state.

[0083] Furthermore, when the steady state is turned off, since the PWM is at a low level, the outputs of the driver chip Bon and Boff are also at a low level. Therefore, the switch Mon is turned off and Moff is turned on.

[0084] At this point, the turn-on section is in a pre-charge state, with Con charged to 15V in preparation for the next turn-on dynamic. The charge on Coff was completely released in the previous stage, so diode Doff conducts. At this time, the gate voltage of the switching device (the voltage across gs) is -5V, and the switching device is in a reliable turn-off state.

[0085] 2. When the dynamic state is activated, the equivalent circuit is as follows: Figure 4 As shown, the PWM signal switches from low to high, and the outputs of the driver chips Bon and Boff are also high. Therefore, switch Mon is turned on and Moff is turned off. Specifically, during the turn-on process, the PWM signal changes from low to high, and both driver chips Bon and Boff output high levels, so Mon is on and Moff is off. The turn-off section disconnects from the switching device, and Coff is charged to 5V by the power supply to prepare for subsequent switching. Since the voltage across the capacitor cannot change abruptly, at the instant the PWM signal changes from low to high, the output voltage of the driver circuit is twice the steady-state turn-on voltage, i.e., 30V. As the turn-on process progresses, the charge on Con gradually decreases. By controlling the value of Con, it can be ensured that the output of the driver circuit automatically decreases to 15V at the end of the turn-on process. This accelerates the turn-on process during the turn-on period without causing gate overcharging in the steady state.

[0086] At this point, the turn-off section disconnects from the switching device and enters a pre-charge state. Coff is charged to 5V to prepare for subsequent turn-off dynamics. Since the voltage across the capacitor cannot change abruptly, the turn-on section will be bootspinned to 30V, and this voltage will gradually decrease as the drive provides current to the switching device. If the capacitor value is properly designed so that the stored voltage is equal to the total gate charge of the device, then at the end of turn-on, the charge on Con will be automatically and completely released, preventing gate overcharging.

[0087] 3. In steady state after turn-on, the equivalent circuit is as follows: Figure 5 As shown.

[0088] When the steady state is turned on, since the PWM is at a high level, the outputs of the driver chip Bon and Boff are also at a high level. Therefore, the switch Mon is turned on and Moff is turned off.

[0089] At this time, the turn-off section is in the pre-charge state. Coff is charged to 5V to prepare for the next turn-off. Since the charge on Con is completely released in the previous stage, the diode Don is turned on. At this time, the gate voltage of the switching device is 15V, and the switching device is in a reliable turn-on state.

[0090] Specifically, during steady-state turn-on, the PWM signal is high, and both driver chips, Bon and Boff, output high levels. Therefore, Mon is in the on state while Moff is in the off state. The off section disconnects from the switching device, and Coff is charged to 5V by the power supply in preparation for subsequent switching. The charge on Con is completely released in the previous stage, thus Don conducts, and the gate voltage of the switching device is 15V, maintaining a stable on-state.

[0091] 4. When the dynamic is turned off, the equivalent circuit is as follows: Figure 6 As shown.

[0092] At this point, the PWM switches from high to low, and the outputs of the driver chip Bon and Boff are also low. Therefore, Mon is turned off while Moff is turned on. At this time, the turn-on section disconnects from the switching device and enters a pre-charge state, with Con charged to 15V in preparation for subsequent turn-on. Since the voltage across the capacitor cannot change abruptly, the turn-off voltage will be bootstrapped to -10V, and this voltage will gradually decrease as the turn-off process progresses. If the capacitor value is properly designed so that the stored voltage is equal to the total gate charge of the device, then at the end of the turn-off, the charge on Coff will be automatically and completely released, preventing gate overcharging.

[0093] Specifically, during the shutdown dynamic, the PWM signal changes from high to low, and both driver chips, Bon and Boff, output low levels. Therefore, Mon is in the off state while Moff is in the on state. The on section disconnects from the switching device, and Con is charged to 15V by the power supply in preparation for subsequent switching. Since the voltage across the capacitor cannot change abruptly, at the instant the PWM changes from high to low, the output voltage of the driver circuit is twice the steady-state shutdown voltage, i.e., -10V. As the shutdown dynamic progresses, the charge on Coff gradually decreases. By controlling the value of Coff, it can be ensured that the output of the driver circuit automatically decreases to -5V at the end of the shutdown dynamic. This accelerates the shutdown process during the shutdown dynamic without causing gate overcharging in steady state.

[0094] Due to the use of a bootstrap structure, the drive circuit of this invention can output twice the drive voltage during switching without using an external power supply, thereby greatly improving the switching speed. By controlling the capacitance values ​​of Con and Coff, this invention ensures that the drive circuit output voltage automatically drops to the power supply voltage at the end of the switching process, avoiding overcharging and eliminating the need for additional control signals.

[0095] II. Application Examples. To demonstrate the inventiveness and technical value of the technical solution of this invention, this section provides application examples of the technical solution of the claims on specific products or related technologies.

[0096] A Buck converter prototype was built and tested using electrolytic capacitors, silicon carbide MOSFETs, Schottky diodes, and load inductors. The test results showed that, compared with traditional commercial voltage source drives, the proposed drive circuit can reduce turn-on losses by up to 75% and turn-off losses by 10%. Furthermore, no gate overvoltage phenomenon was observed during the operation of the Buck prototype. The proposed drive can automatically adapt well to different operating conditions as junction temperature and load current change.

[0097] III. Evidence of the Relevant Effects of the Embodiments. The embodiments of the present invention have achieved some positive effects during research and development or use, and indeed possess significant advantages compared to existing technologies. The following description, in conjunction with data, charts, and other materials from the experimental process, illustrates these advantages.

[0098] The double-pulse test is a commonly used method for verifying switching performance. It can verify not only the switching performance of the switching device but also the performance of the drive circuit and short-circuit protection circuit. Its hardware is almost identical to that of a Buck converter, the difference being that the double-pulse test platform generally uses a pulse operation mode. This invention constructs a double-pulse test platform based on silicon carbide field-effect transistors (MOSFETs). The test platform bus voltage is 400 volts, and the maximum load current can reach 30 amps. A gate driver prototype was also constructed. Figure 7 These are experimental comparison diagrams provided in the embodiments of the present invention; and tests were conducted on a dual-pulse test platform. Experimental results show that the proposed gate drive circuit can reduce turn-on losses by 50%-75% and turn-off losses by 10%, such as... Figure 8 As shown, it operates stably without gate overcharging or other issues. Figure 9 This is a schematic diagram of the core structure of a commercially available gate driver provided in this embodiment of the invention.

[0099] The detailed experimental data comparison under different operating conditions at a 400V bus voltage is shown in the table below:

[0100]

[0101]

[0102] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for controlling a partially bootstrap gate drive circuit to reduce switching losses, characterized in that, The partial bootstrap gate drive circuit control method for reducing switching losses includes: In the drive circuit, a bootstrap structure is used as the output section, enabling the drive circuit to output twice the supply voltage during the switching process without using an external power supply; by controlling the capacitance value, the output voltage of the drive circuit automatically drops to the power supply voltage at the end of the switching process. The bootstrap structure consists of at least one capacitor and at least one diode, used to double the voltage of the power supply during output transients to increase the switching speed. The driving circuit is an equivalent switching device composed of Rgint and Ciss connected in series. A 15V isolation power supply is connected to the half-bridge driving chip Bon to power it. The control terminal of Bon is connected to the signal isolation module. The output terminal is connected to the bootstrap circuit composed of bootstrap diode Don and bootstrap capacitor Con, and the gate of N-type MOSFET switch Mon. The bootstrap circuit is also connected to one end of the turn-on resistor Ron. The other end of Ron is connected to the g node of the switching device. Mon is connected to the s node of the switching device. The anode of the bootstrap diode Don is connected to the positive potential of the 15V isolation power supply. The cathode of the bootstrap diode Don is connected to one end of the turn-on resistor Ron and one end of the bootstrap capacitor Con. The other end of the turn-on resistor Ron is connected to one end of Rgint. The other end of Rgint is connected to one end of Ciss. The other end of the bootstrap capacitor Con is connected to the gate of N-type MOSFET switch Mon and the output terminal of half-bridge driving chip Bon. The drain of N-type MOSFET switch Mon is connected to the other end of Ciss and the drain of P-type MOSFET switch Moff. The source of N-type MOSFET switch Mon is connected to the negative potential of the 15V isolation power supply. The -5V isolated power supply is connected to the half-bridge driver chip Boff to power it. The control terminal of Boff is connected to the signal isolation module. The output terminal is connected to the bootstrap circuit composed of bootstrap diode Doff and bootstrap capacitor Coff, and the gate of P-type MOSFET switch Moff. The bootstrap circuit is also connected to one end of the turn-off resistor Roff. The other end of Roff is connected to the g node of the switching device. Moff is connected to the s node of the switching device. The PWM signal is connected to the signal isolation module. The method for controlling the partially bootstrap gate drive circuit to reduce switching losses specifically includes the following steps: Step 1: In the off steady state, the PWM is at a low level, the outputs of the driver chip Bon and Boff are low level, the switch Mon is turned off and Moff is turned on. Step 2: When the dynamic is activated, the PWM switches from low level to high level, the outputs of the driver chip Bon and Boff are high level, the switch Mon is turned on and Moff is turned off. Step 3: When the steady state is turned on, the PWM is at a high level, the outputs of the driver chip Bon and Boff are high level, the switch Mon is turned on and Moff is turned off. Step 4: When the dynamic is turned off, the PWM switches from high level to low level, the outputs of the driver chip Bon and Boff are low level, Mon is turned off and Moff is turned on.

2. The partial bootstrap gate drive circuit control method for reducing switching losses as described in claim 1, characterized in that, In step one, the turn-on part is in a pre-charge state, and Con is charged to 15V to prepare for the next turn-on dynamic; the charge on Coff is completely released in the previous stage, the diode Doff is turned on, the gate voltage of the switching device is -5V, and the switching device is in a reliable turn-off state.

3. The partial bootstrap gate drive circuit control method for reducing switching losses as described in claim 1, characterized in that, In step two, the turn-off section is disconnected from the switching device and enters a pre-charge state. Coff is charged to 5V to prepare for subsequent turn-off dynamics. Since the voltage across the capacitor cannot change abruptly, the turn-on section is bootstrapping to 30V, and the voltage gradually decreases as the drive provides current to the switching device. If the capacitor value is designed reasonably so that the stored voltage is equal to the total gate charge of the device, the charge on Con will be automatically and completely released when the turn-on ends, without causing gate overcharging.

4. The partial bootstrap gate drive circuit control method for reducing switching losses as described in claim 1, characterized in that, In step three, the turn-off section is in a pre-charge state, and Coff is charged to 5V to prepare for the next turn-off. Since the charge on Con is completely released in the previous stage, diode Don is turned on, the gate voltage of the switching device is 15V, and the switching device is in a reliable turn-on state.

5. The partial bootstrap gate drive circuit control method for reducing switching losses as described in claim 1, characterized in that, In step four, the turn-on portion is disconnected from the switching device and enters a pre-charging state. Con is charged to 15V to prepare for subsequent turn-on. Since the voltage across the capacitor cannot change abruptly, the turn-off voltage is bootstrapping to -10V, and the voltage gradually decreases as the turn-off process proceeds. If the capacitor value is designed reasonably so that the stored voltage is equal to the total gate charge of the device, the charge on Coff will be automatically and completely released at the end of the turn-off, preventing gate overcharging.

6. A partially bootstrap gate drive circuit for reducing switching losses using the partially bootstrap gate drive circuit control method for reducing switching losses according to any one of claims 1-5, characterized in that, The bootstrap gate drive circuit for reducing switching losses includes: a switching device, which is equivalent to a resistor and capacitor connected in series. The control signal input unit of the PWM microcontroller: a high level indicates that the device is turned on, and a low level indicates that the device is turned off. The power supply is a DC power module with 15V and 5V outputs, which is responsible for providing power to other parts of the circuit. Signal isolation unit is used to isolate the microcontroller from the main power devices; A non-isolated driver chip used to switch the operating state of the circuit according to the PWM control signal; The bootstrap structure, including capacitors and diodes, is responsible for providing faster drive speeds and reducing drive losses when the drive circuit is operating. Gate resistors are used to adjust switching speed and balance switching losses and transient overvoltages.

7. The partially bootstrap gate drive circuit for reducing switching losses as described in claim 6, characterized in that, The bootstrap gate drive circuit for reducing switching losses also includes a metal-oxide-semiconductor field-effect transistor (MOSFET) for controlling the circuit's operating state and switching it.

8. A power electronic converter for transportation equipment, characterized in that, The power electronic converter for transportation equipment is equipped with a partially bootstrap gate drive circuit for reducing switching losses as described in any one of claims 6 to 7.

Images