SiC driving circuit and auxiliary inverter for urban rail transit

Abstract

The application provides a SiC driving circuit and an auxiliary inverter for urban rail transit, and the SiC driving circuit comprises an isolated power supply module, an isolated driving module and an isolated feedback module; wherein the isolated power supply module provides an electrically isolated and stable gate driving voltage for each phase of the three-phase auxiliary inverter and two SiC MOSFETs above and below; the isolated driving module is used for isolating and power amplifying the output signal of the controller and driving the SiC MOSFET of the auxiliary inverter; and the isolated feedback module is used for feeding back the working state of the SiC MOSFET to the controller. The application reduces the connection between the main control board and the power module, improves the system integration, the electrical isolation and the fault protection response speed.

Description

Technical Field

[0001] This invention relates to the field of rail transit technology, specifically to a SiC drive circuit and auxiliary inverter for urban rail transit. Background Technology

[0002] Currently, silicon-based insulated-gate bipolar transistors (IGBTs) are commonly used as the core power switching devices in auxiliary inverters for urban rail transit. With the increasing maturity of silicon carbide (SiC) semiconductor technology, SiC MOSFETs have demonstrated superior performance compared to traditional IGBTs. Therefore, introducing SiC MOSFETs into subway train auxiliary inverters to replace traditional IGBTs has become an important technological path to improve the performance of auxiliary power supply systems.

[0003] However, when SiC MOSFETs are applied to auxiliary power supply systems for subway trains, the required drive circuits differ significantly from those for traditional IGBTs. Existing drive circuits designed for auxiliary inverter IGBTs lack adaptability and struggle to meet the reliability and performance requirements of SiC MOSFETs in high-frequency, high-speed switching. Therefore, there is an urgent need in the industry to develop a high-performance, high-reliability SiC drive circuit specifically for urban rail transit train auxiliary inverter applications. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a SiC drive circuit and auxiliary inverter for urban rail transit.

[0005] According to the present invention, a SiC drive circuit for urban rail transit includes: An isolated power supply module is used to provide electrically isolated gate drive voltages for SiC MOSFETs; An isolation drive module is used to isolate and amplify the controller output signal and drive the SiC MOSFET. An isolation feedback module is used to monitor the operating status of the SiC MOSFET and feed it back to the controller.

[0006] Preferably, the input terminal of the isolated power supply module accepts external power, and its output terminal provides four mutually isolated secondary power supplies; The four secondary power supplies include a first isolated positive power supply for providing drive power to the upper SiC MOSFET, a first isolated negative power supply for providing turn-off power to the upper SiC MOSFET, a second isolated positive power supply for providing drive power to the lower SiC MOSFET, and a second isolated negative power supply for providing turn-off power to the lower SiC MOSFET.

[0007] Preferably, the isolated power supply module includes a power management PWM chip control circuit, a push-pull drive circuit, and a linear voltage regulation unit.

[0008] Preferably, the power management PWM chip control circuit uses a UC1524A chip to output complementary PWM signals; The push-pull drive circuit includes two N-type MOSFETs and an isolation transformer. The gates of the two N-type MOSFETs receive the PWM signal, and their drains are connected to the first and third pins of the isolation transformer, respectively.

[0009] Preferably, the secondary windings of the isolation transformer are each connected to a full-bridge rectifier circuit and an RC filter circuit, and then connected to a linear regulator. The linear regulator outputs the mutually isolated secondary power supplies.

[0010] Preferably, the isolation driving module is divided into an upper SiC driving unit and a lower SiC driving unit; The input terminals of the upper SiC drive unit and the lower SiC drive unit respectively receive the PWM signal from the controller, and output it to the gate driver after optocoupler isolation, so as to obtain signals suitable for the upper and lower SiC MOSFETs to turn on and off respectively.

[0011] Preferably, the isolation driving module includes an optocoupler, an inverting driver, and a gate driver; The optocoupler receives the signal from the controller and outputs the signal to the input terminal of the inverting driver. The output terminal of the inverting driver is connected to the input terminal of the gate driver, and the output terminal of the gate driver is connected to the SiC MOSFET.

[0012] Preferably, the inverter driver includes a first inverter, a second inverter, and a third inverter connected in series; The gate driver has a fault status pin and a ready pin for connecting to the input of the isolation feedback module.

[0013] Preferably, the isolation feedback module is divided into an upper SiC feedback unit and a lower SiC feedback unit; The input terminals of the upper and lower SiC feedback units are used to collect the fault status of the upper and lower SiC MOSFET gate drivers, respectively. The fault status signal is output to the controller after being isolated by the feedback optocoupler. The isolation feedback module includes a driver chip, a timing chip, and an optocoupler; The driving chip receives the status signal of the gate driver and connects to the timing chip. When the SiC is working normally, the timing counting module composed of the timing chip outputs its output signal to the controller through an optocoupler.

[0014] According to the present invention, an auxiliary inverter for urban rail transit includes the aforementioned SiC drive circuit for urban rail transit.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention integrates the drive circuits of the upper and lower two SiC MOSFETs in each phase of a three-phase inverter into a single module, significantly reducing the number of physical connections between the inverter main control board and the power module, thereby effectively improving the integration of the entire drive system.

[0016] 2. In this invention, each SiC MOSFET has a completely independent isolated power supply, optocoupler isolation circuit, gate driver, and feedback optocoupler, achieving complete electrical isolation. This meets the special requirements of high-frequency, high-speed switching of SiC MOSFETs and provides them with a stable gate drive voltage.

[0017] 3. The optocoupler feedback circuit integrated in this invention can monitor fault signals such as overcurrent and undervoltage generated by the gate driver in real time. The monitored SiC MOSFET operating status and fault signals can be quickly transmitted to the controller through opto-isolation, so that the controller can perform protection actions. The feedback loop design is simple and the response is fast. Attached Figure Description

[0018] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is an internal functional block diagram of a single-phase drive circuit according to an embodiment of the present invention; Figure 2 This is a circuit diagram of the isolated power supply module according to an embodiment of the present invention; Figure 3 This is a circuit diagram of the isolation drive module according to an embodiment of the present invention; Figure 4 This is a circuit diagram of the isolation feedback module according to an embodiment of the present invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0020] I. Overall System Architecture Please see Figure 1This embodiment provides a SiC drive circuit for urban rail transit, specifically a SiC power device drive circuit applied to a subway train auxiliary inverter. This circuit drives the upper and lower SiC MOSFETs of any phase in a three-phase auxiliary inverter for rail transit. Each SiC MOSFET requires an independent isolated power supply module. The controller outputs two PWM signals with adjustable duty cycles to the isolated drive module. The isolated drive module amplifies the PWM signal power to drive the SiC MOSFET. The isolated drive module collects the drain and source voltages of the SiC MOSFET and outputs a feedback signal. This feedback signal is isolated by the isolated feedback module and then output to the controller. The controller then judges the feedback signal and outputs the corresponding drive signal. The system as a whole includes three core modules: an isolated power supply module, an isolated drive module, and an isolated feedback module.

[0021] By integrating the drive circuits of the two SiC MOSFETs on each phase into a single module, the number of connections between the inverter main control board and the power module is reduced, improving system integration. Each SiC MOSFET has a completely independent isolated power supply, optocoupler isolation circuit, gate driver, and feedback optocoupler, achieving complete electrical isolation.

[0022] II. Isolated Power Supply Module The isolated power supply module provides electrically isolated and stable gate drive voltages for SiC MOSFETs to meet the special requirements of high-frequency, high-speed switching of SiC MOSFETs. Its input accepts an external DC power supply, and its output provides four mutually isolated secondary power supplies required by the SiC MOSFETs. These four power supplies include: a first isolated positive power supply providing drive power to the upper SiC MOSFET, a first isolated negative power supply providing turn-off power to the upper SiC MOSFET, a second isolated positive power supply providing drive power to the lower SiC MOSFET, and a second isolated negative power supply providing turn-off power to the lower SiC MOSFET.

[0023] Reference Figure 2 As shown, this module specifically includes a power management PWM chip control circuit, an optocoupler isolation circuit, a push-pull drive circuit, and a linear voltage regulation unit: 1. Power Management PWM Chip Control Circuit: The PWM control unit uses the UC1524A power management chip. Pins 6 (RT) and 7 (CT) of the UC1524A's internal oscillator are connected to the second terminals of resistor RT and capacitor CT, respectively, while the first terminals of resistor RT and capacitor CT are grounded. Pins 11 and 14 of the UC1524A output two complementary PWM square wave signals.

[0024] The first PWM signal is output from pin 11 of the UC1524A, passes through resistor R3 to pin 2 of optocoupler OP1, then through pin 6 of optocoupler OP1, and finally through resistor R6 to drive N-type MOSFET Q1. Diode D3 and resistor R5 are connected in series and then in parallel with resistor R3 to accelerate the turn-off speed of the N-type MOSFET.

[0025] The second PWM signal is output from pin 14 of the UC1524A, passes through resistor R13 to pin 2 of optocoupler OP2, then through pin 6 of optocoupler OP2, and finally through resistor R16 to drive the N-type MOSFET Q2. Diode D15 and resistor R15 are connected in series and then in parallel with resistor R16, also to accelerate the turn-off speed of the N-type MOSFET.

[0026] 2. Push-Pull Drive Unit: Includes N-type MOSFETs Q1 and Q2 and an isolation transformer. The gates of N-type MOSFETs Q1 and Q2 receive the PWM signal output from the aforementioned PWM control unit. In specific connections, the drain of Q1 is connected to pin 3 (or pin 1) of the isolation transformer, and the drain of Q2 is connected to pin 1 (or pin 3) of the transformer. Pin 3 of the isolation transformer is connected to a 24V power supply, and the sources of Q1 and Q2 are grounded.

[0027] 3. Linear Voltage Regulation Unit: The secondary structure of the isolation transformer is a four-winding structure NS1, NS2, NS3, and NS4. Each of these four secondary windings is connected to a full-bridge rectifier circuit, an RC filter, and a linear voltage regulator unit, corresponding to four linear voltage regulation power supplies: The first linear voltage regulation power supply provides the first isolated positive power supply to the upper SiC MOSFET to drive it; the second linear voltage regulation power supply provides the first isolated negative power supply to the upper SiC MOSFET to turn it off; the third linear voltage regulation power supply provides the first isolated positive power supply to the lower SiC MOSFET to drive it; and the fourth linear voltage regulation power supply provides the first isolated negative power supply to the lower SiC MOSFET to turn it off.

[0028] Taking the first secondary winding NS1 as an example: the fifth pin of the transformer is connected to the second pin of the rectifier bridge VD1, and the sixth pin of the transformer is connected to the third pin of the rectifier bridge VD1. The first pin of the rectifier bridge is connected to the first terminal of resistor R8, and the fourth pin is connected to the first terminal of resistor R9. The other ends of R8 and R9 are connected to the two ends of an RC filter circuit. The first terminal of the RC filter circuit is connected to the third pin of the linear regulator LT1086, and the other terminal is connected to the ground of the first isolation power supply. The first pin of LT1086 is connected to the first terminal of resistor R12, the second terminal of resistor R11, and the first terminal of capacitor C2; the second terminal of resistor R12 is connected to the second terminal of capacitor C2 and then to the ground of the first isolation power supply. The second pin of LT1086 is connected to the second terminal of resistor R11, the positive terminal of capacitor C3, and the negative terminal of diode D5; the positive terminal of diode D5 and the negative terminal of capacitor C3 are connected to the ground of the first isolation power supply.

[0029] III. Isolation Driver Module The isolation drive module is divided into an upper SiC drive unit and a lower SiC drive unit, which are used to isolate and amplify the PWM signal output by the controller, and finally drive the SiC MOSFET of the auxiliary inverter. The input terminals of the upper and lower drive units receive the PWM signal from the controller, which is then output to the gate driver after optocoupler isolation, thereby obtaining the appropriate signals for turning on and off the upper and lower SiC MOSFETs, respectively.

[0030] Please see Figure 3 This module specifically includes an optocoupler, an inverting driver, and a gate driver: 1. Optocoupler Isolation Circuit: An HFBR-2522 optocoupler is used. The optocoupler receives signals from the controller. Pins 2, 5, and 8 are connected to ground, and pin 3 is connected to the second terminal of resistor R33. The first terminal of resistor R33 is connected to the 5V power supply. The first terminal of capacitor C13 is connected to the second terminal of resistor R33. Pin 1 of the optocoupler converts the optical signal into an electrical signal and outputs it to the input of the inverting driver to enhance the drive signal.

[0031] 2. Inverter and Gate Driver Circuit: The output of the inverter driver is connected to the input of the gate driver, and the output of the gate driver is connected to SiC. Specifically, driver 1ED020I12FTA is used, and the external components include resistors R34-R37, capacitor C14, Zener diodes D9-D10, and first, second, and third inverters.

[0032] Inverter connection: The first terminal of the first inverter is connected to the output terminal of the optocoupler, and the second terminal is connected to the first terminal of the second inverter; the second terminal of the second inverter is connected to the first terminal of the third inverter; the second terminal of the third inverter is connected to pin 13 of the driver 1ED020I12FTA.

[0033] The driver 1ED020I12FTA pin configuration is as follows: pins 4, 11, 12, 14, 19, and 20 are grounded. Pins 1, 2, 9, and 10 are connected to the first isolation negative power supply. Pin 17 is connected to a 5V power supply, pin 18 is connected to a 5V power supply after resistor R34, and pin 6 is connected to a 15V power supply.

[0034] Output and control connections: Pin 7 is connected to the control terminal of the SiC transistor to provide the drive signal for the SiC. Pin 3 is connected to the first end of resistor R37, the second end of R37 is connected to the positive terminal of Zener diode D9, and the negative terminal of D9 is connected to the input terminal of the SiC transistor.

[0035] Feedback signal interface: Pin 15 is connected to both the input of the isolation feedback module and the second terminal of resistor R35, with the first terminal of R35 connected to a 5V power supply. Pin 16 is connected to both the input of the isolation feedback module and the second terminal of resistor R36, with the first terminal of R36 connected to a 5V power supply.

[0036] IV. Isolation Feedback Module The isolation feedback module is divided into an upper SiC feedback unit and a lower SiC feedback unit. It is used to monitor the operating status of the SiC MOSFET (such as acquiring the fault status of the gate driver) and transmit the reports to the controller through opto-isolation, so that the controller can execute protection actions. The integrated optocoupler feedback circuit can monitor fault signals such as overcurrent and undervoltage generated by the gate driver in real time, and the feedback loop is simple and fast.

[0037] Please see Figure 4 The isolation feedback module includes a driver chip MAX4427, a timer / counter module (timer chip 7555), and an optocoupler HFBR-1527. When the SiC is operating normally, the output signal of the timer / counter module is output to the controller through the optocoupler.

[0038] The specific circuit connection is as follows: 1. 7555 timer chip and peripheral circuit: The peripheral circuit includes resistors R38-R43 and capacitors C15-C19. Pin 1 of the 7555 chip is grounded. Pin 4 is connected to the first terminal of resistor R41, the first terminal of capacitor C17, and the first terminal of resistor R42; the second terminals of resistor R41 and capacitor C17 are connected to power ground. Pin 8 is connected to the second terminal of resistor R38, the first terminal of capacitor C16, and the first terminal of resistor R39; the first terminal of resistor R38 is connected to a 15V power supply, and the second terminal of capacitor C16 is grounded. Pin 2 is connected to pin 6 of the 7555 chip, the second terminal of resistor R40, and the first terminal of capacitor C15; the other terminal of capacitor C15 is grounded. Pin 7 is connected to the anode of diode D11, the first terminal of resistor R40, and the second terminal of resistor R39 to form a timing oscillation circuit. Pin 3 is connected to the first terminal of resistor R43 and then to pin 2 of the optocoupler (HFBR-1527). Pin 1 of the optocoupler is connected to a 15V power supply.

[0039] 2. Connection of driver chip MAX4427: Pin 2 of driver chip MAX4427 is connected to pin 16 of gate driver 1ED020I12FTA, pin 4 is connected to pin 15 of gate driver 1ED020I12FTA, and pin 7 is connected to the first end of resistor R42. Pin 5 of MAX4427 is connected to the cathode of diode D11 and the first end of capacitor C19, and the second end of capacitor C19 is connected to power ground.

[0040] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0041] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A SiC driving circuit for urban rail transit, characterized in that, include: An isolated power supply module is used to provide electrically isolated gate drive voltages for SiC MOSFETs; An isolation drive module is used to isolate and amplify the controller output signal and drive the SiC MOSFET. An isolation feedback module is used to monitor the operating status of the SiC MOSFET and feed it back to the controller.

2. The SiC driving circuit for urban rail transit according to claim 1, characterized in that: The input of the isolated power supply module accepts external power, and its output provides four mutually isolated secondary power supplies. The four secondary power supplies include a first isolated positive power supply for providing drive power to the upper SiC MOSFET, a first isolated negative power supply for providing turn-off power to the upper SiC MOSFET, a second isolated positive power supply for providing drive power to the lower SiC MOSFET, and a second isolated negative power supply for providing turn-off power to the lower SiC MOSFET.

3. The SiC driving circuit for urban rail transit according to claim 2, characterized in that: The isolated power supply module includes a power management PWM chip control circuit, a push-pull drive circuit, and a linear voltage regulation unit.

4. The SiC drive circuit for urban rail transit according to claim 3, characterized in that: The power management PWM chip control circuit uses the UC1524A chip to output complementary PWM signals; The push-pull drive circuit includes two N-type MOSFETs and an isolation transformer. The gates of the two N-type MOSFETs receive the PWM signal, and their drains are connected to the first and third pins of the isolation transformer, respectively.

5. The SiC drive circuit for urban rail transit according to claim 4, characterized in that: The secondary windings of the isolation transformer are each connected to a full-bridge rectifier circuit and an RC filter circuit, and then connected to a linear regulator. The linear regulator outputs the mutually isolated secondary power supplies.

6. The SiC driving circuit for urban rail transit according to claim 1, characterized in that: The isolation driving module is divided into an upper SiC driving unit and a lower SiC driving unit; The input terminals of the upper SiC drive unit and the lower SiC drive unit respectively receive the PWM signal from the controller, and output it to the gate driver after optocoupler isolation, so as to obtain signals suitable for the upper and lower SiC MOSFETs to turn on and off respectively.

7. The SiC drive circuit for urban rail transit according to claim 6, characterized in that: The isolation drive module includes an optocoupler, an inverting driver, and a gate driver; The optocoupler receives the signal from the controller and outputs the signal to the input terminal of the inverting driver. The output terminal of the inverting driver is connected to the input terminal of the gate driver, and the output terminal of the gate driver is connected to the SiC MOSFET.

8. The SiC drive circuit for urban rail transit according to claim 7, characterized in that: The inverter driver includes a first inverter, a second inverter, and a third inverter connected in series; The gate driver has a fault status pin and a ready pin for connecting to the input of the isolation feedback module.

9. The SiC drive circuit for urban rail transit according to claim 1, characterized in that: The isolation feedback module is divided into an upper SiC feedback unit and a lower SiC feedback unit; The input terminals of the upper and lower SiC feedback units are used to collect the fault status of the upper and lower SiC MOSFET gate drivers, respectively. The fault status signal is output to the controller after being isolated by the feedback optocoupler. The isolation feedback module includes a driver chip, a timing chip, and an optocoupler; The driving chip receives the status signal of the gate driver and connects to the timing chip. When the SiC is working normally, the timing counting module composed of the timing chip outputs its output signal to the controller through an optocoupler.

10. An auxiliary inverter for urban rail transit, characterized in that, Includes the SiC drive circuit for urban rail transit as described in any one of claims 1 to 9.

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