Electric power steering system driving module and method
By using a current-driven pre-drive module and segmented control of the MOSFET switching process, the problems of EMI degradation and increased external components in electric power steering systems have been solved, resulting in cost reduction and performance improvement, and adaptability to different motor loads.
Patent Information
- Application Number
- CN202610339427.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-19
- Publication Date
- 2026-05-12
AI Technical Summary
In existing electric power steering systems, EMI characteristics deteriorate during the switching process of MOSFETs, and the addition of external components leads to increased layout area, higher production costs, and reduced circuit integration.
A current-driven pre-drive module is adopted, which communicates with the gate drive chip module GDU through the SPI interface of the microcontroller unit (MCU). Combined with the high-speed comparator module, the drain-source voltage of the MOSFET is detected in real time, and the MOSFET's turn-on and turn-off processes are controlled in segments, eliminating the need for external resistors and diodes, and realizing digital drive.
It eliminates the need for additional electrical components, reduces production costs, minimizes PCB layout area, improves MOSFET switching performance and system EMC performance, adapts to different torque motor loads, and shortens production cycles.
Smart Images
Figure CN122026700A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the automotive field, and in particular to a drive module based on current-driven pre-drive for an electric power steering system. Background Technology
[0002] In the field of electric power steering systems, in synchronous motor MOSFET power drive modules that reach ASILD level, the gate drive chip is mostly voltage driven. The turn-on and turn-off speed of the MOSFET is adjusted by externally driving the gate resistor to optimize switching losses, waveform quality, and improve motor control efficiency and EMI characteristics.
[0003] Because MOSFETs have parasitic inductance and stray capacitance in their traces and loops on the PCB, the rapid changes in voltage and current during MOSFET switching generate voltage and current spikes due to the interaction of capacitance and inductance, which degrade EMI characteristics. To reduce dv / dt and di / dt, the MOSFET turn-on speed needs to be reduced. At the same time, to reduce EMI, the turn-off speed needs to be increased. Therefore, the turn-on drive circuit and the turn-off discharge circuit need to be separated. Typically, a gate drive resistor Ron is set in the turn-on circuit, and a smaller turn-off resistor Roff is set in the turn-off circuit and connected in series with a diode Doff. These three devices need to be configured on each MOSFET.
[0004] The three-phase bridge circuit requires an additional 18 of the aforementioned components, and the number of components for the six-phase motor increases exponentially, significantly increasing the layout area. Furthermore, when changing motor loads with different torques, the resistance values of Ron and Roff need to be adjusted individually, making it impossible to quickly lock in the hardware circuit design. The procurement and board manufacturing cycles for resistors with different resistance values are long, increasing production costs and cycles. At the same time, the increase in peripheral components also reduces the production cycle and circuit integration. Summary of the Invention
[0005] The summary of this invention introduces a series of simplified concepts, all of which are simplifications of existing technologies in the field, and will be further explained in detail in the detailed description section. This summary is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.
[0006] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide an electric power steering system drive module and method that can flexibly adjust the switch according to the MOSFET operating state without increasing electrical components and production costs.
[0007] To solve the above-mentioned technical problems, the electric power steering system drive module provided by the present invention includes: The microcontroller unit MCU 10, the gate drive chip module GDU 20, and the three-phase bridge load half-bridge 30 are provided. The three-phase bridge load half-bridge 30 is provided in three and forms a three-phase bridge structure. Each three-phase bridge load half-bridge 30 includes a high-side MOSFET Q1 and a low-side MOSFET Q2. The microcontroller unit MCU 10 is the control core of the drive circuit. It configures the internal registers of the gate drive chip module GDU 20 through the SPI interface, obtains the status feedback signal, and after processing, issues MOSFET switching control commands through the IHx_N and ILx signals. The gate driver chip module GDU 20 is the core of drive execution and signal acquisition, and integrates an SPI unit, a state machine and a diagnostic unit 40 and three control units 50. The SPI unit, state machine, and diagnostic unit 40 are the communication and control core of the gate driver chip module GDU 20, used to realize SPI data interaction with MCU 10, distribute drive instructions to each control unit 50, and diagnose the module's working status. The three control units 50 correspond one-to-one with the three three-phase bridge load half-bridges 30. Each control unit 50 is a phase-level drive core, which integrates a high-side gate drive module 60, a high-speed comparator module 80 and a low-side gate drive module 70. The high-side gate drive module 60 is used to receive instructions from the control unit 50 and output drive signals to control the high-side MOSFET Q1 of the corresponding three-phase bridge load half-bridge 30 to be turned on and off. The low-side gate drive module 70 is used to receive instructions from the control unit 50 and output drive signals to control the low-side MOSFET Q2 of the corresponding three-phase bridge load half-bridge 30 to turn on and off. The high-speed comparator module 80 is used to collect the drain-source voltage signals of the high-side MOSFET Q1 and low-side MOSFET Q2 in the corresponding three-phase bridge load half-bridge 30, compare them with the preset threshold, and then feed them back to the MCU 10 to provide a basis for the determination of active / freewheeling MOSFETs.
[0008] Furthermore, the MCU 10 and the SPI unit, state machine and diagnostic unit 40 of the gate driver chip module GDU 20 are connected bidirectionally through the SPI interface, IHx_N signal and ILx signal. The SPI unit, state machine and diagnostic unit 40 are connected bidirectionally to the three control units 50. The high-side gate driver module 60 of each control unit 50 is connected to the gate of the corresponding high-side MOSFET Q1 through the high-side drive port GHx, the low-side gate driver module 70 is connected to the gate of the corresponding low-side MOSFET Q2 through the low-side drive port GLx, and the high-speed comparator module 80 is connected to the drain and source of the corresponding high and low-side MOSFETs through VDH, SHx and low-side sampling port SLx to acquire voltage signals. The high-side MOSFET Q1 is connected to the VBAT1 power supply after the vehicle filter, and the low-side MOSFET Q2 and the high-speed comparator module 80 are both grounded. The GDU 20 is also provided with CP1 and CP2 power supply ports, which provide drive power to the low-side gate drive module 70 and the high-side gate drive module 60, respectively.
[0009] Preferably, the electric power steering system drive module is further improved in that the high-speed comparator module 80 acquires the drain-source voltage VDHVShx of the high-side MOSFET Q1 through comparator 1 CF1, acquires the drain-source voltage VShxGND of the low-side MOSFET Q2 through comparator 2 CF2, and then compares the acquired voltage values with the high voltage threshold VSHH and the low voltage threshold VSHL, respectively.
[0010] Preferably, the electric power steering system drive module is further improved, wherein the high-side gate drive module 60 includes a first surface mount resistor R1, MOS1Q01, a second surface mount resistor R2, and MOS2Q02. One end of the first resistor R1 is connected to the SPI unit, state machine, and diagnostic unit 40, and the other end is connected to the first terminal of MOS1Q01. The second terminal of MOS1Q01 is connected to the CP2 port of the gate drive chip module GDU20, and the third terminal of MOS1Q01 is connected to the high-side drive port GHx of the gate drive chip module GDU20. One end of the second resistor R2 is connected to the SPI unit, state machine, and diagnostic unit 40, and the other end is connected to the first terminal of MOS2Q02. The second terminal of MOS2Q02 is connected to the third terminal of MOS1Q01, and the third terminal of MOS2Q02 is connected to the high-side sampling port SHx of the gate drive chip module GDU20.
[0011] Preferably, the electric power steering system drive module is further improved, wherein the low-side gate drive module 70 includes a third surface mount resistor R3, a MOS3 Q03, a fourth surface mount resistor R4, and a MOS4 Q04. One end of the third surface mount resistor R3 is connected to the SPI unit, the state machine, and the diagnostic unit 40, and the other end is connected to the first terminal of the MOS3 Q03. The second terminal of the MOS3 Q03 is connected to the CP1 port of the GDU 20, and the third terminal of the MOS3 Q03 is connected to the low-side drive port GLx of the GDU 20. One end of the fourth surface mount resistor R4 is connected to the SPI unit, the state machine, and the diagnostic unit 40, and the other end is connected to the first terminal of the MOS4 Q04. The second terminal of the MOS4 Q04 is connected to the third terminal of the MOS3 Q03, and the third terminal of the MOS4 Q04 is connected to the low-side sampling port SLx of the GDU 20.
[0012] Preferably, the electric power steering system drive module is further improved in that the MCU 10 interacts with the gate drive chip module GDU 20 through the SCK clock line, SDI master-slave input line, SDO master-slave output line, and CS chip select line of the SPI interface, and sends the switching status commands of the three-phase bridge high and low side MOSFETs to the gate drive chip module GDU 20 through the IHx_N and ILx signals.
[0013] Preferably, the electric power steering system drive module is further improved by replacing the three-phase bridge load half-bridge 30 with a six-phase bridge load half-bridge, and the number of control units 50 of the gate drive chip module GDU 20 is increased accordingly. The structure and driving method of each control unit are the same as those of the three-phase bridge, and the adaptation is achieved by matching the internal register parameters of the gate drive chip module GDU 20 through the SPI interface of the MCU 10.
[0014] This invention provides a driving method for an electric power steering system, which is implemented based on the electric power steering system driving module described in any one of the above-mentioned methods, and includes the following steps: S1, MCU 10 sends a switching status command to the gate driver chip module GDU 20 through the SPI interface. After receiving the command, the gate driver chip module GDU 20 uses the high-speed comparator module 80 to collect the drain-source voltage of the high-side MOSFET Q1 and the low-side MOSFET Q2. S2, the high-speed comparator module 80 compares the collected drain-source voltage with the high voltage threshold VSHH and the low voltage threshold VSHL respectively, and feeds back the comparison result to the MCU 10 via SPI. The MCU 10 determines the active MOSFET and the freewheeling MOSFET, wherein the active MOSFET is a MOSFET that controls the phase voltage slope, and the freewheeling MOSFET is a MOSFET that only participates in freewheeling and does not control the phase voltage slope. S3, the gate drive chip module GDU 20 adjusts the drive current parameters according to the judgment result of MCU 10, and controls the turn-on and turn-off processes of the active MOSFET and the freewheeling MOSFET in segments, so as to achieve precise control of the di / dt slope and dv / dt slope during the MOSFET switching process.
[0015] Preferably, in a further improved electric power steering system driving method, the determination rule for the active MOSFET and freewheeling MOSFET in step S2 is as follows: 1. If the phase voltage VShx > the high voltage threshold VSHH and the high-side MOSFET Q1 is about to turn on, then the low-side MOSFET Q2 is an active MOSFET and the high-side MOSFET Q1 is a freewheeling MOSFET. 2. If the phase voltage VShx < the low voltage threshold VSHL and the low-side MOSFET Q2 is about to turn on, then the high-side MOSFET Q1 is an active MOSFET and the low-side MOSFET Q2 is a freewheeling MOSFET. 3. If the high voltage threshold VSHHVSHL < phase voltage VShx < low voltage threshold VSHL, then the next MOSFET to be turned on is an active MOSFET.
[0016] Preferably, in a further improved electric power steering system driving method, the conduction process of the active MOSFET in step S3 is divided into four stages: a. Pre-charge stage: The gate drive chip module GDU 20 outputs current I1 for a duration of T1 to pre-charge the gate and source of the active MOSFET, so that the gate and source voltage reaches the turn-on threshold Vth. b. Miller plateau rising stage: The gate driver chip module GDU 20 outputs current I2 for a duration of T2, continuing to charge until the gate-source voltage reaches the Miller plateau voltage Vplat, until the phase voltage VShx reaches the low voltage threshold VSHL; if the phase voltage VShx reaches the high voltage threshold VSHH during this stage, then skip step c and proceed directly to step d. c. Miller charging stage: The gate driver chip module GDU 20 outputs current I3 for a duration of T3 to maintain the Miller platform voltage Vplat until the phase voltage VShx reaches the high voltage threshold VSHH. During this stage, the dv / dt slope is controlled. d. Holding charging phase: The gate driver chip module GDU 20 first outputs current I4 to charge until the blanking time and filtering time set by the software end, and then switches to holding current I5 to continuously supply power.
[0017] Preferably, in a further improved electric power steering system driving method, the cutoff process of the freewheeling MOSFET in step S3 is divided into three stages: e. Pre-discharge stage: The gate drive chip module GDU 20 outputs a discharge current I6 for a duration of T7 to pre-discharge the gate and source of the freewheeling MOSFET, causing the gate and source voltage to drop to VGS_PDT; f. Continuous discharge phase: During the timeout period T8T7 set in the software, the gate drive chip module GDU 20 continuously discharges by outputting the discharge current I5. g Current switching phase: When the rising edge of the PWM signal of the active MOSFET is triggered, the gate drive chip module GDU 20 outputs current I8; after the T4 time period of the active MOSFET ends and continues for T16 time, it switches to the discharge current I5 and maintains it.
[0018] Preferably, in a further improved electric power steering system driving method, the cutoff process of the active MOSFET in step S3 is divided into four stages: h Pre-discharge stage: The gate drive chip module GDU 20 outputs a discharge current I6 for a duration of T7, which is used for pre-discharge of the gate and source of the active MOSFET, so that the gate and source voltage drops to VGS_PDT; Miller platform maintenance phase: The gate driver chip module GDU 20 outputs a discharge current I9 to maintain the gate-source voltage at the Miller platform voltage Vplat until the phase voltage VShx reaches the high voltage threshold VSHH and continues for a period of T10, until the phase voltage VShx reaches the low voltage threshold VSHL. During this phase, the di / dt slope is controlled. j. Miller voltage discharge stage: The gate driver chip module GDU 20 outputs a discharge current I11, which reduces the gate-source voltage to 0V until the Miller voltage discharge stage ends. This stage controls the dv / dt slope. k Subsequent discharge phase: The gate drive chip module GDU 20 outputs a discharge current I12 until the rising edge of the PWM signal of the freewheeling MOSFET is triggered, then switches to discharge current I8, and after the T16 time ends, switches to discharge current I5 and maintains it.
[0019] Preferably, in a further improved electric power steering system driving method, step S3 involves the conduction process of the freewheeling MOSFET divided into two stages: l Pre-charge stage: The gate driver chip module GDU 20 outputs current I1 for a duration of T1 to pre-charge the gate and source of the freewheeling MOSFET, so that the gate and source voltage reaches the turn-on threshold Vth. During the holding charging phase: the gate driver chip module GDU 20 outputs current I11 to continue charging until the blanking and filtering times set by the software are completed, at which point it switches to holding current I5 to continuously supply power.
[0020] The working principle of this invention is as follows; This invention consists of three parts: a microcontroller unit (MCU), a gate driver chip module (GDU), and a three-phase bridge load. The MCU communicates with the GDU via an SPI bus, configures its internal registers, and acquires status information, while simultaneously sending switching commands via a PWM signal line. The GDU integrates an SPI unit, a state machine, a diagnostic unit, and three control units, each containing a high-side gate driver module, a low-side gate driver module, and a high-speed comparator module. The three-phase bridge load consists of three half-bridges, each containing one high-side MOSFET and one low-side MOSFET.
[0021] Traditional solutions employ voltage-driven control, adjusting the MOSFET switching speed via an external gate resistor. This requires numerous external components and suffers from inflexible parameter adjustments. This invention utilizes a current-driven pre-drive module, directly controlling gate charging and discharging through an internal programmable current source, completely eliminating external resistors and diodes and achieving digital, segmented drive control.
[0022] This invention uses a high-speed comparator to detect the phase voltage VShx in real time and compares it with preset thresholds, a high-voltage threshold VSHH and a low-voltage threshold VSHL, to determine the current state of the active MOSFET and the freewheeling MOSFET. When the phase voltage VShx is higher than the high-voltage threshold VSHH and the high-side MOSFET is about to be turned on, the high-side MOSFET is determined to be the freewheeling MOSFET and the low-side MOSFET to be turned on. When the phase voltage VShx is lower than the low-voltage threshold VSHL and the low-side MOSFET is about to be turned on, the low-side MOSFET is determined to be the freewheeling MOSFET and the high-side MOSFET to be turned on. When the phase voltage VShx is between the two thresholds, the next MOSFET to be turned on is the active MOSFET. The active MOSFET is responsible for controlling the phase voltage slope, while the freewheeling MOSFET only provides a freewheeling path and does not participate in control.
[0023] The active MOSFET conducts in four stages: In the pre-charge stage, a large current I1 is output for a duration of T1, causing the gate-source voltage to quickly reach the turn-on threshold Vth; in the first charging stage, a medium current I2 is output for a duration of T2, causing the voltage to rise to the Miller plateau voltage Vplat, while controlling the current change rate dI / dt. If the phase voltage VShx reaches the high voltage threshold VSHH ahead of schedule in this stage, the next stage is skipped; in the Miller charging stage, a small current I3 is output for a duration of T3, maintaining the Miller plateau voltage, and controlling the voltage change rate dV / dt to achieve precise adjustment of the phase switching rate; in the second charging stage, a small current I4 is output for a duration of T4 until the blanking time ends, finally switching to a holding current I5 to maintain the conduction state.
[0024] The active MOSFET is also turned off in four stages: the pre-discharge stage outputs a large negative current I6 for a duration of T7, which rapidly reduces the gate-source voltage to the pre-discharge threshold voltage VGS_PDT; the Miller discharge stage outputs a medium negative current I9 for a duration of T10 to maintain the Miller plateau voltage and control the dI / dt slope; the full discharge stage outputs a small negative current I11 to reduce the voltage to zero and control the dV / dt slope; the hold stage first outputs a negative current I12, then switches to I8 for a duration of T16 depending on the freewheeling MOSFET state, and finally holds at I5.
[0025] The driving process of the freewheeling MOSFET is relatively simple. When turned on, it only goes through two stages: pre-charging and charge holding, outputting currents I1 and I11 respectively, and then holding at I5. When turned off, it goes through three stages: pre-discharging, discharge holding, and active MOSFET turn-on triggering, outputting negative currents I6 and I5 and positive current I8 respectively, and then holding at I5.
[0026] During MOSFET switching, rapidly changing voltage and stray capacitance generate current spikes, while rapidly changing current and parasitic inductance generate voltage spikes, affecting the system's EMI characteristics. This solution uses segmented current control to adjust the dI / dt slope during the first charging and Miller discharging phases, and the dV / dt slope during the Miller charging and full discharging phases. This effectively suppresses voltage and current spikes and optimizes EMC performance without requiring external buffer circuitry.
[0027] After the system powers on, the MCU first configures the internal registers of the GDU via the SPI bus, setting parameters such as the drive current value, time period, and voltage threshold for each stage. Upon entering the working cycle, the high-speed comparator samples the phase voltage VShx in real time. Based on the comparison result, the MCU determines the current state of the active MOSFET and freewheeling MOSFET and sends a PWM switching command to the GDU. After parsing the command, the GDU outputs the corresponding drive current according to the switching stage of the MOSFET, while continuously feeding back drain-source voltage information to achieve closed-loop dynamic adjustment of the drive parameters.
[0028] Based on the above working principle, the present invention can achieve at least the following technical effects; 1. This invention uses a current-driven pre-drive module to replace the traditional voltage-driven method, eliminating the need for external gate drive resistors, turn-off resistors, diodes, and other devices. The three-phase bridge circuit can reduce external components, thereby reducing the PCB layout area and lowering production costs.
[0029] 2. This invention uses VDS voltage feedback to determine the active / freewheeling MOSFET and flexibly adjusts the drive current parameters according to the working state. There is no need to manually adjust the parameters of external devices. It can adapt to motor loads with different torques, quickly lock in the hardware circuit design, and shorten the product development and production cycle.
[0030] 3. This invention precisely controls the di / dt slope and dv / dt slope during the switching process by segmenting the drive current of the MOSFET to turn on and off. This effectively suppresses voltage and current spikes caused by parasitic inductance and stray capacitance, reduces EMI interference during the switching process, and improves the switching performance of the MOSFET and the EMC performance of the system.
[0031] 4. This invention integrates the core functions of drive control into the gate drive chip module. Parameter adjustment can be achieved by configuring the register through the MCU's SPI interface. This optimizes the design of the chip's peripheral circuits, improves the integration and reliability of the electric power steering system controller, and meets the functional safety requirements of ASILD level. Attached Figure Description
[0032] The accompanying drawings are intended to illustrate the general characteristics of the methods, structures, and / or materials used in specific exemplary embodiments of the invention, supplementing the description in the specification. However, the drawings are schematic diagrams not drawn to scale and may not accurately reflect the precise structural or performance characteristics of any of the given embodiments. The drawings should not be construed as limiting or restricting the range of numerical values or properties covered by exemplary embodiments of the invention. The invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0033] Figure 1 This is a block diagram of the pre-drive module of the present invention.
[0034] Figure 2 This is a timing diagram for the measurement of the high-speed comparator module of the present invention.
[0035] Figure 3 This is a timing diagram of the conduction process of the active MOS of the present invention.
[0036] Figure 4 This is a timing diagram of the cutoff process of the active MOS of the present invention.
[0037] Explanation of reference numerals in the attached figures: 10 Microcontroller Unit (MCU), 20 Gate Driver Module (GDU), 30 Three-Phase Bridge Load Half-Bridge, 40 SPI Unit, State Machine, and Diagnostic Unit, 50 Control Unit, 60 High-Side Gate Driver Module, 70 Low-Side Gate Driver Module, 80 High-Speed Comparator Module, Q01MOS1, Q02MOS2, Q03MOS3, Q04MOS4, Q1 High-Side MOSFET, Q2 Low-Side MOSFET, CF1 Comparator 1, CF2 Comparator 2, R1 First SMD Resistor, R2 Second SMD Resistor, R3 Third SMD Resistor, R4 Fourth SMD Resistor, CP1 and CP2 are different power supply ports, GHx High-Side Driver Port, GLx Low-Side Driver Port, SHx High-Side Sampling Port, SLx Low-Side Sampling Port, VDH High-Voltage Sampling Port. Detailed Implementation
[0038] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can fully understand other advantages and technical effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments, and various details in this specification can also be applied based on different viewpoints, with various modifications or changes made without departing from the overall design concept of the invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. The following exemplary embodiments of the present invention can be implemented in many different forms and should not be construed as being limited to the specific embodiments set forth herein. It should be understood that these embodiments are provided to make the disclosure of the present invention thorough and complete, and to fully convey the technical solutions of these exemplary embodiments to those skilled in the art. It should be understood that when an element is referred to as "connected" or "combined" to another element, the element can be directly connected or combined to the other element, or there may be intermediate elements. The difference is that when an element is referred to as "directly connected" or "directly combined" to another element, there are no intermediate elements. Throughout the drawings, the same reference numerals always denote the same elements.
[0039] First embodiment; like Figure 1 As shown, this embodiment provides an electric power steering system drive module based on current-driven pre-drive, including: a microcontroller unit (MCU) 10, a gate drive chip module (GDU) 20, and a three-phase bridge power conversion circuit composed of three load half-bridges 30. Each load half-bridge 30 includes a high-side MOSFET Q1 and a low-side MOSFET Q2.
[0040] The gate driver chip module GDU 20 includes a serial peripheral interface (SPI) unit, a state machine and diagnostic unit 40, and three control units 50. Each control unit 50 contains a high-side gate driver module 60, a high-speed comparator module 80, and a low-side gate driver module 70.
[0041] The high-side gate drive module 60 includes a first surface-mount resistor R1 (first gate resistor), MOS1 Q01, a second surface-mount resistor R2 (second gate resistor), and MOS2 Q02. One end of the first surface-mount resistor R1 is connected to the Serial Peripheral Interface (SPI) unit, state machine, and diagnostic unit 40, and the other end is connected to the gate of MOS1 Q01. The source of MOS1 Q01 is connected to the CP2 port boost power supply port of the gate drive chip module GDU 20, and the drain is connected to the GHx port high-side gate drive port of the gate drive chip module GDU 20. One end of the second surface-mount resistor R2 is connected to the SPI unit, state machine, and diagnostic unit 40, and the other end is connected to the gate of MOS2 Q02. The source of MOS2 Q02 is connected to the drain of MOS1 Q01, and the drain is connected to the SHx half-bridge midpoint detection port of the gate drive chip module GDU 20.
[0042] The high-speed comparator module 80 includes comparator 1 CF1 and comparator 2 CF2. The positive input of comparator 1 CF1 is connected to the high-voltage sampling port VDH (high-side drain voltage detection port) of the gate driver chip module GDU 20, the negative input is connected to the high-side sampling port SHx, and the output is connected to the serial peripheral interface (SPI) unit, state machine, and diagnostic unit 40. The positive input of comparator 2 CF2 is connected to the high-side sampling port SHx, the negative input is grounded, and the output is connected to the serial peripheral interface (SPI) unit, state machine, and diagnostic unit 40.
[0043] The low-side gate driver module 70 includes a third surface-mount resistor R3 (third gate resistor), a MOS3 Q03, a fourth surface-mount resistor R4 (fourth gate resistor), and a MOS4 Q04. One end of the third surface-mount resistor R3 is connected to the Serial Peripheral Interface (SPI) unit, state machine, and diagnostic unit 40, and the other end is connected to the gate of the MOS3 Q03. The source of the MOS3 Q03 is connected to the first power supply port CP1 of the gate driver chip module GDU 20, and the drain is connected to the low-side drive port GLx of the gate driver chip module GDU 20. One end of the fourth surface-mount resistor R4 is connected to the Serial Peripheral Interface (SPI) unit, state machine, and diagnostic unit 40, and the other end is connected to the gate of the MOS4 Q04. The source of the MOS4 Q04 is connected to the drain of the MOS3 Q03, and the drain is connected to the low-side sampling port SLx of the gate driver chip module GDU 20 and grounded.
[0044] In the load half-bridge 30, the gate of the high-side MOSFET Q1 is connected to the GHx port, the drain is connected to the high-voltage sampling port VDH and the VBAT1 after filtering by the vehicle battery on the ECU, and the source is connected to the high-side sampling port SHx. The gate of the low-side MOSFET Q2 is connected to the low-side drive port GLx, the drain is connected to the source of the high-side MOSFET Q1, and the source is connected to the low-side sampling port SLx and grounded.
[0045] The microcontroller unit MCU 10 is connected to the gate driver chip module GDU 20 via an SPI interface. The SPI interface uses four signal lines: SCK clock signal line, SDI master output / slave input, SDO master input / slave output, and CS slave select signal line. Simultaneously, the microcontroller unit MCU 10 is connected to the gate driver chip module GDU 20 via the IHx_N and ILx signal lines. IHx_N contains the input signals IH1_N, IH2_N, and IH3_N of the U-phase, V-phase, and W-phase high-side MOSFETs, respectively, while ILx contains the input signals IL1, IL2, and IL3 of the U-phase, V-phase, and W-phase low-side MOSFETs.
[0046] Second embodiment; This embodiment provides a driving method for an electric power steering system, which is implemented based on the electric power steering system driving module described in the first embodiment, and specifically includes the following steps: The microcontroller unit MCU 10 configures the internal registers of the gate driver chip module GDU 20 via the SPI interface to obtain current status information. In the high-speed comparator module 80, comparator 1 CF1 compares the voltage at the high-voltage sampling port VDH with the voltage at the SHx port, i.e., the drain-source voltage VDS of the high-side MOSFET Q1. Comparator 2 CF2 compares the voltage at the SHx port with the ground voltage, i.e., the drain-source voltage VDS of the low-side MOSFET Q2. The comparison results are fed back to the microcontroller unit MCU 10 via the SPI interface.
[0047] The microcontroller unit MCU 10 determines the active MOSFET and freewheeling MOSFET according to the following logic based on the comparator output and the current PWM instruction: If the phase voltage VSHx > the high voltage threshold VSHH corresponds to the forward voltage drop of the body diode of the high-side MOSFET and the high-side MOSFET is about to be turned on: at this time, the low-side MOSFET is in the on state, the high-side MOSFET is off, and the current freewheels through the parasitic body diode of the high-side MOSFET. Therefore, the high-side MOSFET is determined to be a freewheeling MOSFET and the low-side MOSFET is an active MOSFET.
[0048] If the phase voltage VShx < the low voltage threshold VSHL, corresponding to the forward voltage drop of the low-side MOSFET's body diode and the low-side MOSFET is about to be turned on: at this time, the high-side MOSFET is in the on state, the low-side MOSFET is off, and the current freewheels through the parasitic body diode of the low-side MOSFET. Therefore, the low-side MOSFET is determined to be a freewheeling MOSFET, and the high-side MOSFET is an active MOSFET.
[0049] If the low voltage threshold VSHL < phase voltage VShx < high voltage threshold VSHH: then there is no obvious difference between the freewheeling MOSFET and the active MOSFET, and the next MOSFET to be turned on is determined to be the active MOSFET.
[0050] The temporal relationship of the above judgment process is as follows: Figure 2 As shown.
[0051] Based on the judgment result, the microcontroller unit MCU 10 configures the current and time parameters of the internal register of the gate driver chip module GDU through the SPI interface, and controls the high-side gate driver module 60 or the low-side gate driver module 70 to output segmented drive current.
[0052] The conduction process of an active MOSFET is as follows, refer to... Figure 3 As shown: Pre-charge phase T1: Starting from the rising edge of the PWM signal of the active MOSFET, the gate drive chip module GDU outputs the first charging current I1 to the active MOSFET and continues for a first preset time T1 to pre-charge the gate-source capacitor of the external MOSFET so that the gate-source voltage VGS reaches the turn-on threshold voltage Vth of the MOSFET.
[0053] In the first charging stage, T2: the gate driver chip module GDU outputs a second charging current I2 and continues for a second preset time T2, charging the gate and source to the Miller plateau voltage Vplat, until the midpoint voltage VShx of the half-bridge reaches the third threshold voltage VSHL. This stage is the time period during which the MOSFET's VGS voltage reaches the Miller plateau from Vth, mainly controlling the current change rate di / dt. If VShx reaches the first threshold voltage VSHH in this stage, step c) is skipped and the process proceeds directly to step d).
[0054] The second charging stage, T3, is the Miller charging stage: the gate driver chip module GDU outputs a third charging current I3 and continues for a third preset time T3 to continue charging the gate and source, maintaining the Miller plateau voltage Vplat until the half-bridge midpoint voltage VShx reaches the first threshold voltage VSHH. This stage is the phase switching conversion rate stage T6, which mainly controls the voltage change rate dv / dt.
[0055] The third charging stage, T4: After the Miller charging stage ends, the gate driver chip module GDU outputs the fourth charging current I4 to charge the gate and source until the blanking time and filter time set by the software end. At this time, it switches to the fifth charging current I5 to hold the current and maintain the MOSFET in a fully on state.
[0056] The cutoff process of the freewheeling MOSFET is as follows: Freewheeling pre-discharge stage T7: Starting from the falling edge of the PWM signal of the freewheeling MOSFET, the gate drive chip module GDU outputs the first discharge current -I6 and continues for a fourth preset time T7 to discharge the gate and source of the freewheeling MOSFET until the VGS voltage drops to the preset discharge threshold VGS_PDT.
[0057] Freewheeling discharge phase T8-T7: During the timeout period T8 set in the software, the current is set to the sixth discharge current - I5, continuously discharging the gate and source of the freewheeling MOSFET.
[0058] Freewheeling cutoff completion phase: When the rising edge of the PWM signal of the active MOSFET begins, the output current of the freewheeling MOSFET is set to the ninth discharge current - I8. When the T4 phase of the active MOSFET ends, i.e., after a sixth preset time T16, the output current of the freewheeling MOSFET is switched to the tenth discharge current - I5 holding current to maintain the MOSFET in a fully off state.
[0059] For the cutoff process of an active MOSFET, refer to [reference needed]. Figure 4 As shown: Pre-discharge stage T7: Starting from the falling edge of the PWM signal of the active MOSFET, the gate drive chip module GDU outputs the first discharge current -I6 and continues for a fourth preset time T7 to pre-discharge the gate and source of the external MOSFET so that the VGS voltage reaches the preset discharge threshold VGS_PDT.
[0060] In the first discharge stage (T10), the gate driver chip module (GDU) outputs a second discharge current, -I9, causing the VGS voltage to reach the Miller plateau voltage Vplat. After the half-bridge midpoint voltage VShx reaches the first threshold voltage VSHH, this process continues for a fifth preset time (T10) to maintain the Miller plateau voltage Vplat until the half-bridge midpoint voltage VShx reaches the third threshold voltage VSHL. This stage primarily controls the current change rate di / dt.
[0061] The second discharge stage, T11: The gate driver chip module (GDU) outputs a third discharge current, -I11, causing the VGS voltage to drop to 0V until the Miller voltage discharge stage ends. This stage primarily controls the voltage change rate dv / dt.
[0062] In the third discharge stage T12, the gate drive chip module GDU outputs the fourth discharge current -I12 until the PWM signal of the freewheeling MOSFET changes from low to high. At this time, the current switches to the fifth discharge current -I8 until the sixth preset time T16 ends, and the current switches to the sixth discharge current -I5 to maintain the MOSFET in a completely off state.
[0063] The conduction process of the freewheeling MOSFET is as follows: Freewheeling pre-charge stage T1: Starting from the rising edge of the PWM signal of the freewheeling MOSFET, the gate drive chip module GDU outputs the eleventh charging current I1 and continues for the first preset time T1 to pre-charge the gate and source of the external MOSFET so that the VGS voltage reaches the turn-on threshold voltage Vth.
[0064] Freewheeling conduction completion stage: The gate driver chip module GDU outputs the twelfth charging current I11 to charge the gate and source of the freewheeling MOSFET until the blanking time and filtering time set by the software end. At this time, it switches to the thirteenth charging current I5 to hold the current and maintain the MOSFET in a fully conducting state.
[0065] According to the electromagnetic interference generation mechanism, the rapidly changing voltage and current during MOSFET switching generate current and voltage spikes under the influence of parasitic capacitance and inductance. Their relationship can be described by the following formula: I = C × dV / dt (Formula 1) U = L × di / dt (Formula 2) Where I is the current spike, C is the stray capacitance, dV / dt is the voltage change rate, U is the voltage spike, L is the parasitic inductance, and di / dt is the current change rate.
[0066] This invention achieves independent adjustment of dV / dt and di / dt at each stage through segmented current control; Controlling di / dt: During the first charging phase T2 when the active MOSFET is turned on and the first discharging phase T10 when it is turned off, the rate of change of the gate-source voltage before the Miller plateau is controlled by adjusting the magnitude of the second charging current I2 and the second discharging current -I9, thereby controlling the rate of change of the drain current di / dt and reducing the voltage spikes caused by parasitic inductance.
[0067] Controlling dv / dt: During the second charging phase T3 when the active MOSFET is turned on, the Miller phase, and the second discharging phase T11 when it is turned off, the duration of the Miller plateau is controlled by adjusting the magnitude of the third charging current I3 and the third discharging current -I11, thereby controlling the rate of change of the drain-source voltage dv / dt and reducing the current spikes caused by stray capacitance.
[0068] Through the above-mentioned segmented control, the present invention can achieve fine control of the slope of each stage of the switching process without the need for external resistors and capacitors, taking into account both switching losses and EMI suppression, and significantly improving the switching performance of MOSFETs and the EMC performance of the system.
[0069] Further explanation: This embodiment provides parameter configuration: All current parameters I1, I2, I3, I4, I5, I8, I9, I11, I12, etc., and time parameters T1, T2, T3, T4, T7, T8, T10, T16, etc., are configured by writing to the internal registers of the gate driver chip module (GDU) via the SPI interface. The microcontroller unit (MCU) can dynamically adjust these parameters according to different motor load characteristics and operating conditions. Software configurability allows the same hardware platform to adapt to multiple motor specifications without replacing external components, significantly improving the system's platformization capabilities and market responsiveness.
[0070] Unless otherwise defined, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will also be understood that, unless explicitly defined herein, terms such as those defined in a general dictionary shall be interpreted as having the meaning consistent with their meaning in the relevant field context, and not as having an idealized or overly formal meaning.
[0071] The present invention has been described in detail above through specific embodiments and examples, but these are not intended to limit the invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the invention, and these should also be considered within the scope of protection of the present invention.
Claims
1. A drive module for an electric power steering system, characterized in that, include: The microcontroller unit (MCU) (10), the gate drive chip module (GDU) (20) and the three-phase bridge load half-bridge (30) are provided. The three-phase bridge load half-bridge (30) is provided in three and forms a three-phase bridge structure. Each three-phase bridge load half-bridge (30) includes a high-side MOSFET (Q1) and a low-side MOSFET (Q2). The microcontroller unit (MCU) (10) configures the internal registers of the gate drive chip module (GDU) (20) through the SPI interface, obtains the status feedback signal, and after processing, issues MOSFET switching control commands through the IHx_N and ILx signals; The gate driver chip module GDU (20) integrates an SPI unit, a state machine and a diagnostic unit (40), and three control units (50). The SPI unit, state machine, and diagnostic unit (40) are used to realize SPI data interaction with the MCU (10), distribute drive instructions to each control unit (50), and diagnose the working status of the module; The three control units (50) correspond one-to-one with the three three-phase bridge load half-bridges (30). Each control unit (50) integrates a high-side gate drive module (60), a high-speed comparator module (80), and a low-side gate drive module (70). The high-side gate drive module (60) is used to receive instructions from the control unit (50) and output drive signals to control the high-side MOSFET (Q1) of the corresponding three-phase bridge load half-bridge (30) to turn on and off. The low-side gate drive module (70) is used to receive instructions from the control unit (50) and output drive signals to control the low-side MOSFET (Q2) of the corresponding three-phase bridge load half-bridge (30) to turn on and off. The high-speed comparator module (80) is used to collect the drain-source voltage signals of the high-side MOSFET (Q1) and low-side MOSFET (Q2) in the corresponding three-phase bridge load half-bridge (30), compare them with the preset threshold, and then feed them back to the MCU (10) to provide a basis for judging whether the MOSFET is active or freewheeling.
2. The electric power steering system drive module according to claim 1, characterized in that: The high-speed comparator module (80) acquires the drain-source voltage (VDHVShx) of the high-side MOSFET (Q1) through comparator 1 (CF1), and acquires the drain-source voltage (VShxGND) of the low-side MOSFET (Q2) through comparator 2 (CF2). The acquired voltage values are then compared with the high voltage threshold (VSHH) and the low voltage threshold (VSHL) respectively.
3. The electric power steering system drive module according to claim 1, characterized in that: The high-side gate drive module (60) includes a first surface mount resistor (R1), MOS1 (Q01), a second surface mount resistor (R2), and MOS2 (Q02). One end of the first resistor (R1) is connected to the SPI unit, state machine, and diagnostic unit (40), and the other end is connected to the first terminal of MOS1 (Q01). The second terminal of MOS1 (Q01) is connected to the CP2 port of the gate drive chip module GDU (20), and the third terminal of MOS1 (Q01) is connected to the high-side drive port (GHx) of the gate drive chip module GDU (20). One end of the second resistor (R2) is connected to the SPI unit, state machine, and diagnostic unit (40), and the other end is connected to the first terminal of MOS2 (Q02). The second terminal of MOS2 (Q02) is connected to the third terminal of MOS1 (Q01), and the third terminal of MOS2 (Q02) is connected to the high-side sampling port (SHx) of the gate drive chip module GDU (20).
4. The electric power steering system drive module according to claim 1, characterized in that: The low-side gate drive module (70) includes a third surface mount resistor (R3), a MOS3 (Q03), a fourth surface mount resistor (R4), and a MOS4 (Q04). One end of the third surface mount resistor (R3) is connected to the SPI unit, the state machine, and the diagnostic unit (40), and the other end is connected to the first terminal of the MOS3 (Q03). The second terminal of the MOS3 (Q03) is connected to the CP1 port of the GDU (20), and the third terminal of the MOS3 (Q03) is connected to the low-side drive port (GLx) of the GDU (20). One end of the fourth surface mount resistor (R4) is connected to the SPI unit, the state machine, and the diagnostic unit (40), and the other end is connected to the first terminal of the MOS4 (Q04). The second terminal of the MOS4 (Q04) is connected to the third terminal of the MOS3 (Q03), and the third terminal of the MOS4 (Q04) is connected to the low-side sampling port (SLx) of the GDU (20).
5. The electric power steering system drive module according to claim 1, characterized in that: The MCU (10) interacts with the gate drive chip module GDU (20) through the SCK clock line, SDI master output slave input line, SDO master input slave output line, and CS chip select line of the SPI interface. It sends the switching status instructions of the three-phase bridge high and low side MOSFETs to the gate drive chip module GDU (20) through the IHx_N and ILx signals.
6. The electric power steering system drive module according to any one of claims 1, characterized in that: The three-phase bridge load half-bridge (30) can be replaced with a six-phase bridge load half-bridge. The number of control units (50) of the gate drive chip module GDU (20) is increased accordingly. The structure and driving method of each control unit are the same as those of the three-phase bridge. Adaptation is achieved by matching the internal register parameters of the gate drive chip module GDU (20) with the SPI interface of the MCU (10).
7. A driving method for an electric power steering system, implemented based on the electric power steering system driving module according to any one of claims 1, comprising the following steps: S1, MCU (10) sends a switch status command to gate driver chip module GDU (20) through SPI interface. After receiving the command, gate driver chip module GDU (20) collects the drain-source voltage of high-side MOSFET (Q1) and low-side MOSFET (Q2) by high-speed comparator module (80). S2, the high-speed comparator module (80) compares the collected drain-source voltage with the high voltage threshold (VSHH) and low voltage threshold (VSHL) respectively, and feeds back the comparison result to the MCU (10) via SPI. The MCU (10) determines the active MOSFET and the freewheeling MOSFET, wherein the active MOSFET is a MOSFET that controls the phase voltage slope, and the freewheeling MOSFET is a MOSFET that only participates in freewheeling and does not control the phase voltage slope. S3, the gate drive chip module GDU (20) adjusts the drive current parameters according to the judgment result of MCU (10).
8. The electric power steering system driving method according to claim 7, characterized in that: In step S2, the rules for determining the active MOSFET and the freewheeling MOSFET are as follows: 1) If the phase voltage VShx > high voltage threshold (VSHH) and the high-side MOSFET (Q1) is about to turn on, then the low-side MOSFET (Q2) is an active MOSFET and the high-side MOSFET (Q1) is a freewheeling MOSFET; 2) If the phase voltage VShx < the low voltage threshold (VSHL) and the low-side MOSFET (Q2) is about to turn on, then the high-side MOSFET (Q1) is an active MOSFET and the low-side MOSFET (Q2) is a freewheeling MOSFET; 3) If the high voltage threshold (VSHH) VSHL < phase voltage VShx < low voltage threshold (VSHL), then the next MOSFET to be turned on is an active MOSFET.
9. The electric power steering system driving method according to claim 7, characterized in that: In step S3, the conduction process of the active MOSFET is divided into four stages: a) Pre-charge stage: The gate drive chip module GDU (20) outputs current I1 for a duration of T1 to pre-charge the gate and source of the active MOSFET, so that the gate and source voltage reaches the turn-on threshold (Vth). b) Miller plateau rise phase: The gate driver chip module GDU (20) outputs current I2 for a duration of T2, continuing to charge until the gate-source voltage reaches the Miller plateau voltage Vplat, until the phase voltage (VShx) reaches the low voltage threshold (VSHL); if the phase voltage (VShx) reaches the high voltage threshold (VSHH) during this phase, skip step c) and proceed directly to step d). c) Miller charging stage: The gate driver chip module GDU (20) outputs current I3 for a duration of T3 to maintain the Miller platform voltage Vplat until the phase voltage (VShx) reaches the high voltage threshold (VSHH). During this stage, the dv / dt slope is controlled. d) Holding charging phase: The gate driver chip module GDU (20) first outputs current I4 to charge until the blanking time and filtering time set by the software end, and then switches to holding current I5 to continuously supply power.
10. The electric power steering system driving method according to claim 7, characterized in that: In step S3, the cutoff process of the freewheeling MOSFET is divided into three stages: e) Pre-discharge stage: The gate drive chip module GDU (20) outputs a discharge current I6 for a duration of T7, which is used to pre-discharge the gate and source of the freewheeling MOSFET, so that the gate and source voltage drops to VGS_PDT; f) Continuous discharge phase: The gate drive chip module GDU (20) continuously discharges by outputting the discharge current I5 within the timeout period T8T7 set by the software. g) Current switching stage: When the rising edge of the PWM signal of the active MOSFET is triggered, the gate drive chip module GDU (20) outputs current I8; after the T4 time period of the active MOSFET ends and continues for T16 time, it switches to the discharge current I5 and maintains it.
11. The electric power steering system driving method according to claim 7, characterized in that: In step S3, the turn-off process of the active MOSFET is divided into four stages: h) Pre-discharge stage: The gate drive chip module GDU (20) outputs a discharge current I6 for a duration of T7, which is a pre-discharge of the gate and source of the active MOSFET, causing the gate and source voltage to drop to VGS_PDT; i) Miller plateau maintenance phase: The gate drive chip module GDU (20) outputs a discharge current I9 to keep the gate-source voltage at the Miller plateau voltage Vplat until the phase voltage (VShx) reaches the high voltage threshold (VSHH) and continues for a time T10, until the phase voltage (VShx) reaches the low voltage threshold (VSHL). During this phase, the di / dt slope is controlled. j) Miller voltage discharge stage: The gate drive chip module GDU (20) outputs a discharge current I11 to reduce the gate-source voltage to 0V until the Miller voltage discharge stage ends. This stage controls the dv / dt slope. k) Subsequent discharge stage: The gate drive chip module GDU (20) outputs a discharge current I12 until the rising edge of the PWM signal of the freewheeling MOSFET is triggered, and then switches to discharge current I8. After the T16 time ends, it switches to discharge current I5 and maintains it.
12. The electric power steering system driving method according to claim 7, characterized in that: In step S3, the conduction process of the freewheeling MOSFET is divided into two stages: l) Pre-charge stage: The gate drive chip module GDU (20) outputs current I1 for a duration of T1 to pre-charge the gate and source of the freewheeling MOSFET, so that the gate and source voltage reaches the turn-on threshold (Vth). m) Holding charging phase: The gate driver chip module GDU (20) outputs current I11 to continue charging until the blanking time and filtering time set by the software are completed, then switches to holding current I5 to continuously supply power.