Variable slew rate gate driver for hybrid switching power module

Abstract

A variable slew rate gate drive system for powering an electric machine. The system may include a gate driver operable to control each of the plurality of hybrid switching power modules between open and closed states to facilitate powering the electric machine. The gate driver may be operable to select a slew rate and control on and off states of first and second semiconductor switches included as part of each power module to optimize power supply of the electric machine by varying the slew rate as a function of performance characteristics of the first and second semiconductor switches.

Description

[0001] introduction Technical Field

[0002] The present disclosure relates to systems configured for powering an electric machine, such as, but not necessarily limited to, a slew rate variable system configured for managing transitions of a hybrid switching power module when operating to provide electric power to a traction motor of an electric vehicle. Background Art

[0003] During power inversion, pulse width modulation, pulse density modulation, delta-sigma modulation, pulse frequency modulation, or other binary (on / off) switching control signals suitable for the application can be used to facilitate transitioning the switch between different states for the purpose of powering the motor. For example, a control signal can alternate the conduction state of the switch to convert direct current (DC) electrical power into alternating current (AC) electrical power suitable for powering the motor. Some of the more common switches used in higher power applications (such as those used to electrically power the traction motor of an electric vehicle) can be voltage and / or current controlled between on and off states. Wide bandgap (WBG), gallium nitride (GaN), silicon carbide (SiC), and other semiconductor switches (such as metal oxide field effect transistors (MOSFETs) and insulated gate bipolar transistors (IGBTs) semiconductor switches) can form a class of switches capable of supporting a wide variety of switching events. The rate, speed, timing, etc. of a switching event—or more specifically, the transition of a switch between on and off, or between open and closed states—can be characterized as a slew rate. Depending on the type of motor being powered, such as, for example, when powering a traction motor used to propel an electric vehicle, the ability to carefully select and control the slew rate can be beneficial in minimizing second order effects such as overvoltage spikes, electromagnetic interference (EMI) carrying current, voltage overshoot, etc. Summary of the Invention

[0004] One aspect of the present disclosure relates to a variable slew rate gate drive system for powering a motor. The system may include: a plurality of hybrid switching power modules operable to convert a direct current (DC) input into an alternating current (AC) output suitable for powering the motor. Each hybrid switching power module may include two or more semiconductor switches, wherein at least two of the semiconductor switches have different performance characteristics. A controller may be configured to vary the slew rate of the semiconductor switches based on the different performance characteristics of the semiconductor switches to optimize DC to AC conversion. The slew rate may be varied to maximize the use of the semiconductor switches based on the characteristics that best suit the current operating conditions of the motor.

[0005] One aspect of the present disclosure relates to a variable slew rate gate drive system for powering a motor. The system may include a plurality of hybrid switching power modules operable to convert a direct current (DC) input into an alternating current (AC) output suitable for powering the motor. The hybrid switching power modules may each include a first semiconductor switch connected in parallel with a second semiconductor switch, optionally wherein the first semiconductor switch has a first set of performance characteristics and the second semiconductor switch has a second set of performance characteristics that is at least partially different from the first set of performance characteristics. The system may include a gate drive system operable to control each hybrid switching power module between an open and closed state to facilitate converting the DC input into an AC output. The gate drive system may be configured to: provide corresponding first and second control signals to each power module for controlling its first and second semiconductor switches, respectively, between an on and an off state; provide corresponding first and second slew rate signals to each power module for controlling first and second slew rates of its first and second semiconductor switches, respectively; and independently select the first and second control signals and the first and second slew rate signals for each power module based on operating conditions of the motor and the first and second sets of performance characteristics to optimize transitions between the open and closed states.

[0006] The gate drive system may include a controller configured to determine the first and second slew rates based on a plurality of slew rate regions defined relative to operating conditions of the motor and the first and second sets of performance characteristics.

[0007] The slew rate regions may include at least a first region, a second region, and a third region, the first region defining a slower slew rate than the second region, and the second region defining a slower slew rate than the third region.

[0008] The boundaries between the first, second and third regions may be defined relative to voltage, current and / or temperature values ​​selected to demarcate operating conditions of the electric machine.

[0009] The controller may be configured to generate the first and second control signals according to a plurality of operating modes defined relative to operating conditions of the electric machine and the first and second sets of performance characteristics.

[0010] The operating modes may include a dual mode for simultaneously controlling both the first and second semiconductor switches to an on state, a single mode for controlling one of the first and second switches to an on state and the other of the first and second semiconductor switches to an off state, and an off mode for simultaneously controlling both the first and second semiconductor switches to an off state.

[0011] The gate drive system may include first and second variable resistance circuits for each power module, optionally wherein the first variable resistance circuit is connected to a first gate of a first semiconductor switch associated therewith and the second variable resistance circuit is connected to a second gate of a second semiconductor switch associated therewith.

[0012] The first and second variable resistance circuits may each include a plurality of snubber switches and a plurality of resistors, optionally wherein each snubber switch is operable between on and off states to connect and disconnect associated one or more resistors from the positive and / or negative power rails, respectively.

[0013] The first and second slew rate signals may be operable to selectively control the first and second slew rates by individually controlling the snubber switches between on and off states and thereby connecting or disconnecting the resistors from the positive and / or negative power rails.

[0014] The hybrid switching power module includes a first module, a second module, a third module, a fourth module, a fifth module, and a sixth module configured to connect a motor to a rechargeable energy storage system (RESS) via a first phase leg, a second phase leg, and a third phase leg. The first and second modules can be connected in series to form a first phase leg, the third and fourth modules can be connected in series to form a second phase leg, and the fifth and sixth modules can be connected in series to form a third phase leg.

[0015] The first semiconductor switch may be configured as a metal oxide semiconductor field effect transistor (MOSFET), and the second semiconductor switch may be configured as an insulated gate bipolar transistor (IGBT).

[0016] The first semiconductor switch may be configured as a silicon carbide (SiC) metal oxide semiconductor field effect transistor (MOSFET), and the second semiconductor switch may be configured as a Si insulated gate bipolar transistor (IGBT).

[0017] The first semiconductor switch may be configured as a silicon type device, and the second semiconductor switch may be configured as a wide bandgap (WBG) type device.

[0018] One aspect of the present disclosure relates to a variable slew rate gate drive system for powering an electric motor. The system may include a first hybrid switching power module, a second hybrid switching power module, a third hybrid switching power module, a fourth hybrid switching power module, a fifth hybrid switching power module, and a sixth hybrid switching power module configured to connect the electric motor to a rechargeable energy storage system (RESS) via a first phase leg, a second phase leg, and a third phase leg. The first and second hybrid switching power modules may be connected in series to form a first phase leg, the third and fourth hybrid switching power modules may be connected in series to form a second phase leg, and the fifth and sixth hybrid switching power modules may be connected in series to form a third phase leg. Each of the first, second, third, fourth, fifth, and sixth hybrid switching power modules may each include a first semiconductor switch connected in parallel with a second semiconductor switch, optionally wherein the first semiconductor switch has a first set of performance characteristics and the second semiconductor switch has a second set of performance characteristics that are different from the first set of performance characteristics. The system may include a gate drive system operable to control each of the first, second, third, fourth, fifth, and sixth hybrid switching power modules between an open and closed state to convert a direct current (DC) output of the RESS into an alternating current (AC) input suitable for powering the motor via the first, second, and third phase legs. The gate drive system may be configured to: provide corresponding first and second control signals to each of the first, second, third, fourth, fifth, and sixth hybrid switching power modules for controlling its first and second semiconductor switches, respectively, between an on and off state; provide corresponding first and second slew rate signals to each of the first, second, third, fourth, fifth, and sixth hybrid switching power modules for controlling first and second slew rates of its first and second semiconductor switches, respectively; and independently select the first and second control signals and the first and second slew rate signals for each power module based on operating conditions of the motor and first and second sets of performance characteristics to optimize conversion of the DC input to an AC output.

[0019] The first set of performance characteristics may correspond to a first switching speed rating, a first voltage rating, a first current rating, and a first efficiency rating, and the second set of performance characteristics may correspond to a second switching speed rating, a second voltage rating, a second current rating, and a second efficiency rating. The first switching speed rating may be faster than the second switching speed rating, the first voltage rating may be less than the second voltage rating, the first current rating may be less than the second current rating, and the first efficiency rating may be greater than the second efficiency rating.

[0020] The first semiconductor switch may be configured as a silicon carbide (SiC) metal oxide semiconductor field effect transistor (MOSFET), and the second semiconductor switch may be configured as a Si insulated gate bipolar transistor (IGBT).

[0021] The gate drive system may include first and second variable resistance circuits for each of the first, second, third, fourth, fifth, and sixth hybrid switching power modules, optionally wherein the first variable resistance circuit is connected to a first gate of a first semiconductor switch associated therewith, and the second variable resistance circuit is connected to a second gate of a second semiconductor switch associated therewith. The first and second variable resistance circuits may each include a plurality of snubber switches and a plurality of resistors, optionally wherein each snubber switch is operable between on and off states to connect and disconnect the associated one or more resistors from the positive and / or negative power rails, respectively.

[0022] The gate drive system includes a controller configured to: generate first and second slew rate signals based on a plurality of slew rate regions defined relative to operating conditions of the motor and first and second sets of performance characteristics; and generate first and second control signals for switching the snubber switch between on and off states based on a plurality of operating modes defined relative to the operating conditions of the motor and the first and second sets of performance characteristics.

[0023] One aspect of the present disclosure relates to a vehicle. The vehicle may include: an electric motor configured to convert an alternating current (AC) input into a mechanical output suitable for propelling the vehicle; a rechargeable energy storage system (RESS) connected to the electric motor via a first phase leg, a second phase leg, and a third phase leg, the RESS configured to provide a direct current (DC) output; and a first hybrid switching power module connected in series with a second hybrid switching power module to form a first phase leg, a third hybrid switching power module connected in series with a fourth hybrid switching power module to form a second phase leg, and a fifth hybrid switching power module connected in series with a sixth hybrid switching power module to form a third phase leg. Each of the first, second, third, fourth, fifth, and sixth hybrid switching power modules may each include a first semiconductor switch connected in parallel with a second semiconductor switch, optionally wherein the first semiconductor switch has a first set of performance characteristics and the second semiconductor switch has a second set of performance characteristics. The vehicle may include a gate drive system operable to control each of the first, second, third, fourth, fifth, and sixth hybrid switching power modules between an open and closed state to convert the DC output into the AC input. The gate drive system can be configured to: provide corresponding first and second control signals to each of the first, second, third, fourth, fifth and sixth hybrid switching power modules for controlling its first and second semiconductor switches between on and off states, respectively; provide corresponding first and second slew rate signals to each of the first, second, third, fourth, fifth and sixth hybrid switching power modules for controlling the first and second slew rates of its first and second semiconductor switches, respectively; and independently select the first and second control signals and the first and second slew rate signals for each power module based on the first and second groups of performance characteristics to optimize the power supply to the motor.

[0024] The first set of performance characteristics may correspond to a first switching speed rating, a first voltage rating, a first current rating, and a first efficiency rating, and the second set of performance characteristics may correspond to a second switching speed rating, a second voltage rating, a second current rating, and a second efficiency rating. The first switching speed rating may be faster than the second switching speed rating, the first voltage rating may be less than the second voltage rating, the first current rating may be less than the second current rating, and / or the first efficiency rating may be greater than the second efficiency rating.

[0025] These features and advantages of the present teachings, together with other features and advantages, will be readily apparent from the following detailed description of the modes for carrying out the present teachings when considered in conjunction with the accompanying drawings. It should be understood that although the following figures and embodiments may be described separately, their individual features may be combined into additional embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate implementations of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0027] Figure 1 A schematic diagram of a variable slew rate system according to one aspect of the present disclosure is illustrated.

[0028] Figure 2 A partially schematic view of a system according to one aspect of the present disclosure is illustrated.

[0029] Figure 3 A flow chart illustrating a method for variable slew rate powering of an electric machine according to one aspect of the present disclosure is shown.

[0030] Figure 4 Illustrated is a slew rate graph according to one aspect of the present disclosure. DETAILED DESCRIPTION

[0031] As needed, detailed embodiments of the present disclosure may be disclosed herein; however, it is understood that the disclosed embodiments may be merely illustrative of the present disclosure, which may be embodied in various and alternative forms. The figures may not necessarily be to scale; some features may be exaggerated or minimized to illustrate details of particular components. Therefore, the specific structural and functional details disclosed herein may not be construed as limiting, but merely as a representative basis for teaching those skilled in the art to employ the present disclosure in different ways.

[0032] Figure 1A schematic diagram of a variable slew rate system 10 according to one aspect of the present disclosure is illustrated. The system 10 may include a gate drive system 12 operable to power an electric machine 14, which, for exemplary purposes, is primarily described as an electric motor 14, often referred to as a traction motor 14. The electric motor 14 may be of the type employed in a vehicle, such as an electric vehicle, to provide mechanical traction operable to propel the vehicle or otherwise perform work. As described in greater detail below, the gate drive system 12 may be operable to finely select and vary the slew rates of a plurality of hybrid switching power modules M1, M2, ..., M6, which function as part of a power inverter module (PIM) 16, to facilitate powering the electric machine 14. The plurality of hybrid switching power modules M1, M2, ..., M6 may include a first module M1, a second module M2, a third module M3, a fourth module M4, a fifth module M5, and a sixth module M6, which are configured to connect the electric machine 14 to a rechargeable energy storage system (RESS) 20 via a first phase leg 24, a second phase leg 26, and a third phase leg 28. The first and second modules M1, M2 can be connected in series to form a first phase leg 24, the third and fourth modules M3, M4 can be connected in series to form a second phase leg 26, and the fifth and sixth modules M5, M6 can be connected in series to form a third phase leg 28. The gate drive system 12 can be operable to individually control the power modules M1, M2, ..., M6 between open and closed states to facilitate converting a direct current (DC) output 30 of the RESS 20 into an alternating current (AC) input 32 to the motor 14.

[0033] The RESS 20 may be a battery or other energy storage device capable of selectively supplying and receiving electrical power to and from the motor 14 via the PIM 16. A DC link capacitor 36 may be included to smooth, filter, and otherwise process the DC output 30 for use by the PIM 16. The gate drive system 12 may include a gate controller 38 operable to individually and specifically control a plurality of gate drive circuits 40 to control the rate, speed, timing, etc. of switching events of the power modules M1, M2, ..., M6, including those for controlling the transitions of the power modules M1, M2, ..., M6 between on and off or between open and closed states. The transitions of the power modules M1, M2, ..., M6 between states may be performed according to corresponding control signals 44 provided from the gate controller 38. The controller 38 may be configured to provide control signals 44 to each gate drive circuit 40 individually. The controller 38 may include a non-transitory computer-readable storage medium having stored thereon a plurality of non-transitory instructions that, when executed by an associated processor or processors, may be operable in accordance with the present disclosure to generate control signals 44 in a manner that provides a desired slew rate while also managing the AC input 32 as needed for proper powering of the motor 14. The controller 38 may be used in this manner to facilitate switching events of the power modules M1, M2, ..., M6, whereby the DC output 30 may be converted to the AC input 32. The AC input 32 may be generated in the illustrated manner to provide a multi-phase output having a plurality of AC signals 46, 48, 50 suitable for use in powering the motor 14, the plurality of AC signals 46, 48, 50 being illustrated for non-limiting purposes to correspond to a three-phase implementation in which the three-phase AC input 32 is provided to an AC bus or winding of the motor 14, such as via corresponding input terminals of the associated AC input 32.

[0034] Figure 2A partially schematic diagram of a system according to one aspect of the present disclosure is illustrated. This diagram illustrates one of the gate drive circuits 40 interacting with a first power module M1, representing how each gate drive circuit 40 will interact with the remaining power modules M2, ..., M6. This diagram additionally illustrates an aspect of the present disclosure, whereby each of the power modules M1, M2, ..., M6 can include two or more semiconductor switches 54, 56, wherein the two or more switches 54, 56 have different performance characteristics. The illustrated example includes power module M1 having a first semiconductor switch 54 connected in parallel with a second semiconductor switch 56. The first and second semiconductor switches 54, 56 are shown connected in parallel for illustrative purposes, as the present disclosure fully contemplates the switches 54, 56 being connected in series and / or employing additional switches 54, 56 in situations where the additional switches 54, 56 are connected in series and / or in parallel with each other. The first and second semiconductor switches 54, 56 can be of different technologies, such that the first semiconductor switch 54 can have a first set of performance characteristics, and the second semiconductor switch 56 can have a second set of performance characteristics that differ from the first set of performance characteristics. One aspect of the present disclosure contemplates varying the slew rates of the semiconductor switches 54 , 56 to optimize DC to AC conversion, optionally by utilizing different performance characteristics of the semiconductor switches 54 , 56 according to those performance characteristics that best suit the current operating conditions of the motor.

[0035] The semiconductor switches 54, 56 can be composed of a variety of semiconductors or other types of switches 54, 56 with different technologies to facilitate the operation contemplated herein. Such switches 54, 56 can include, for example, a first semiconductor switch 54, 56 configured as a metal oxide semiconductor field effect transistor (MOSFET) or a silicon carbide (SiC) MOSFET and a second semiconductor switch 54, 56 configured as an insulated gate bipolar transistor (IGBT) or a Si IGBT, and / or other variations, such as the first semiconductor switch 54 being configured as a silicon type device and the second semiconductor switch 56 being configured as a wide bandgap (WBG) type device. In this variable technology configuration, the first set of performance characteristics can correspond to a first switching speed rating, a first voltage rating, a first current rating, and / or a first efficiency rating, and the second set of performance characteristics can correspond to a second switching speed rating, a second voltage rating, a second current rating, and / or a second efficiency rating. The first switching speed rating can be faster than the second switching speed rating, the first voltage rating can be less than the second voltage rating, the first current rating can be less than the second current rating, and / or the first efficiency rating can be greater than the second efficiency rating. The controller 38 can utilize these performance differences to control the transition of the semiconductor switches 54, 56 between the on and off states according to the variable slew rate.

[0036] The power modules M1, M2 ... M6 can be individually constructed as discrete or separate integrated circuits (ICs) that can be packaged in corresponding housings. The power modules M1, M2 ... M6 can each use separate chips for the first and second semiconductor switches 54, 56 and / or the additional switches included thereon. The power modules M1, M2 ... M6 can include pins, traces, or other physical structures to facilitate the electrical interconnection contemplated herein. Although other arrangements are contemplated, the power modules M1, M2 ... M6 are shown as including an input 60 and an output 62 to the associated phase branch 24, a drain 64 of the first semiconductor switch 54 connected to the collector 66 of the second semiconductor switch 56, a source 68 of the first semiconductor switch 54 connected to the emitter 70 of the second semiconductor switch 56, and a plurality of interfaces that can operate together with the gate drive circuit 40 to bias the gate 74 of the first semiconductor switch 54 and the gate 76 of the second semiconductor switch 56. The gate drive circuit 40 may include first and second variable resistance circuits 82, 84 for each of the power modules M1, M2, ..., M6. The variable resistance circuits 82, 84 may each include a plurality of snubber switches 88, 90, 92, 94 and a plurality of resistors. The snubber switches 88, 90, 92, 94 may be operable between on and off states to connect and disconnect the associated one or more resistors from the positive and / or negative power rails 98, 100, 102, 104, respectively. The illustrated configuration includes each of the first and second variable resistance circuits 82, 84 including two on snubber switches 88, 90, 92, 94 and two off snubber switches 88, 90, 92, 94 for connecting and disconnecting the two on resistors Rg1_on, Rg2_on and the two off resistors Rg1_off, Rg2_off to the positive and / or negative power rails 98, 100, 102, 104 and the gates 76, 78 of the corresponding first and second semiconductor switches 54, 56, respectively.

[0037] The controller 38 can be configured to generate control signals 44 to provide corresponding first and second control signals 108, 110 to each gate drive circuit 40 for controlling the first and second semiconductor switches 54, 56 between on and off states, respectively, and corresponding first and second slew rate signals 112, 114 for controlling the first and second slew rates of the first and second semiconductor switches 54, 56, respectively. The gate drive circuit 40 can include a gate driver 118 operable to process the control signals and slew rate signals 108, 110, 112, 114 to achieve desired control via the variable resistance circuits 82, 84. The gate driver 118 can process the slew rate signals 112, 114 to determine a desired combination of on and off resistors, and process the control signals 108, 110 to determine a desired timing of the snubber switches 88, 90, 92, 94 between on and off states. While the present disclosure fully contemplates the use of additional on and off resistors and / or on and off snubber switches 88, 90, 92, 94 to facilitate additional resistor combinations, the illustrated configuration provides three different resistor combinations for each on and off resistor, namely, R1 on / off, R2 on / off, or R1 on / off plus R2 on / off. The duty cycle of the control signals 108, 110 (which are shown as pulse width modulated (PWM) signals) can be varied to finely adjust the gate voltage and / or current at a precise level depending on the desired slew rate, for example, to facilitate real-time adjustment of the slew rate based on the desired operation of the motor 14. Although not separately shown in detail, a plurality of sensors or other features may be employed to facilitate measuring or otherwise determining the DC voltage of the DC source 20, the temperature of the DC link capacitor 36, the current of one or more of the AC inputs 32, and the junction temperature, maximum discharge time, drain-source voltage (Vds), and voltage threshold (Vth) of the power modules M1, M2, ..., M6. The gate controller 38 may process the sensor measurements, metrics, and the like to determine a desired slew rate for each of the power modules M1, M2, ..., M6, which may include selecting a control signal 44 to optimize transitions between open and closed states based on the operating conditions of the motor and the first and second sets of performance characteristics.

[0038] One aspect of the present disclosure contemplates that the controller 38 uses temperature (simulated, calculated, or measured) as an input per semiconductor switch technology (i.e., for each of the semiconductor switches 54, 56 having different performance characteristics), which allows for configurable over-temperature warnings, shutdown limits, or protections for slew rate usage. The controller 38 may include a slew rate selection process based on individual or combined operating conditions: inverter terminal voltage, RESS open circuit voltage, RESS terminals, transistor temperature (measured or estimated), inverter output current, motor torque, motor speed, PWM frequency, PWM modulation type, transistor dV / dt or dI / dt, transistor threshold voltage, and / or voltage at the semiconductor switches 54, 56. The slew rate may be controlled by the current / future operating conditions of the motor and / or the current or future operating conditions of the electric propulsion system and / or other systems cooperating with the motor 14. For example, the inverter may be controlled to set the torque and speed of the motor 14. The controller 38 can use one set of resistors to increase efficiency in the enhanced current output performance (ECOP) region, another set of resistors for peak current, and a final set of resistors to increase losses in the inverter for use with the hybrid switches 54, 56, either individually or in parallel. This can be used to optimize losses in different operating regions by using specific transistors and slew rates in specific regions. Furthermore, optimization can be accomplished using a combination of (one or more) specific transistors and additional specific slew rates. The controller 38 can use variable slew rates to reduce losses, increase peak performance, and reduce chip / die temperature during operation of the power electronics system with parallel or individual transistor operation, and / or to protect the semiconductor switches 54, 56 from overvoltage.

[0039] Figure 3A flowchart 124 is shown of a method for variable slew rate powering of an electric motor according to one aspect of the present disclosure. For non-limiting purposes, the method is primarily described with respect to powering an electric motor configured to convert an AC input into a mechanical output suitable for propelling a vehicle, as the present disclosure fully contemplates that the method is useful for powering other types of electric motors. Block 126 relates to a performance characterization process whereby the controller 38 or other functional element determines performance characteristics of a plurality of semiconductor switches 54, 56 included within each of a plurality of power modules M1, M2, ..., M6 configured to convert a DC output 30 into an AC input 32 suitable for powering the electric motor 14. The performance characteristics may relate to a variety of parameters, constraints, capabilities, and other aspects of the semiconductor switches 54, 56, including those aspects that may differentiate the capabilities of the semiconductor switches 54, 56 relative to each other. Depending on the technology of the semiconductor switches 54, 56, one of the semiconductor switches 54, 56 included in one of the power modules M1, M2 ... M6 may be more efficient, less expensive, more reliable, or have higher operating margins than another of the semiconductor switches 54, 56 included in the same power module M1, M2 ... M6. These performance characteristics can be analyzed to determine when one of the semiconductor switches 54, 56 may be more advantageous than the other semiconductor switch 54, 56 and / or when conditions may warrant the simultaneous use of both semiconductor switches 54, 56.

[0040] Block 128 relates to an operating condition process, whereby the controller 38 or other functional element can determine the operating conditions of the motor 14. The operating conditions can relate to a variety of parameters, constraints, capabilities, values, and other aspects of the motor 14, including those associated with current or ongoing operating conditions and / or operating conditions expected to occur in the near future. For example, the operating conditions can relate to carrying current, motor peak voltage, motor torque, motor speed, temperature, etc. Block 130 relates to a slew rate preference process, whereby the controller 38 or other functional element can determine a preference for varying the on / off slew rate of the semiconductor switches 54, 56, and thereby determine the transitions of the power modules M1, M2, ..., M6 between open and closed states. The slew rate preference process can include analyzing performance characteristics associated with the semiconductor switches 54, 56 and the operating conditions of the motor 14 to determine whether a faster slew rate, a slower slew rate, or a customized slew rate is desirable or optimal. A faster slew rate may result in less losses, but with the consequence of less electromagnetic compatibility (EMC), ie more electromagnetic interference (EMI), whereas a slower slew rate may have the opposite result, ie more losses, but with greater or improved EMC.

[0041] Figure 4A slew rate chart 136 according to one aspect of the present disclosure is illustrated. The chart includes a vertical axis 138 and a horizontal axis 140 to represent values ​​useful in selecting or distinguishing between preferred or desired slew rates at a particular time. The values ​​included in axes 138, 140 can be contoured based on various performance characteristics of semiconductor switches 54, 56 and / or operating conditions of motor 14. For non-limiting purposes, vertical axis 138 is described as corresponding to motor torque, and horizontal axis 140 is described as corresponding to motor speed. Chart 136 indicates a plurality of slew rate regions 142, 144, 146 defined relative to boundaries set based on motor torque and speed; however, similar demarcations can be defined and / or motor torque and speed can be correlated or extrapolated based on voltage, current, temperature, etc. Slew rate regions 142, 144, 146 can correspond to desired slew rates for different combinations of motor torque and speed, and in the illustrated configuration include a first region 142, a second region 144, and a third region 146. The first region 142 can be associated with a slower slew rate than the second region 144, and the second region 144 can be associated with a slower slew rate than the third region 146. Based on the above-described variable resistance circuits 82, 84 including three different resistor combinations, the use of three slew rates is presented for non-limiting purposes, i.e., each resistor combination is associated with a difference in rate. As can be appreciated by those skilled in the art, additional granularity in slew rate can be achieved by including additional resistor combinations in the variable resistance circuits 82, 84 or other capabilities for adjusting the bias of the semiconductor switches 54, 56.

[0042] Return to Figure 3 , block 150 involves generating control signals and slew rate signals for turning on / off semiconductor switches 54, 56 and their associated slew rates, respectively. Depending on the slew rate regions 142, 144, 146, the corresponding signals may cause one or both of the switches 54, 56 to be controlled between the on and off states. Return to Figure 4, a first region 142 may include two switches 54, 56 in an on state, which may be referred to as dual mode, wherein the resistor is configured to provide a first slew rate, a second region 144 may include two switches 54, 56 in an on state, wherein the resistor is configured to provide a second slew rate, and a third region 146 may include the first switch in an on state and the second semiconductor switch 56 in an off state, wherein the resistor is configured to provide a third slew rate. The first, second, and third regions 142, 144, 146 are shown as being repeated or used at multiple locations because their use may be desirable for more than one range of operating conditions. Additional slew rate charts, diagrams, lookup tables, algorithms, formulas, etc. may be used to similarly define different slew rate regions, particularly depending on desired preferences. For example, this may include defining different slew rate regions based on efficiency, optimal losses, non-optimal losses, high losses, EMC, EMI, etc.

[0043] As supported above, a variable slew rate gate drive system can be beneficial in mitigating the effects of different turn-on / off characteristics of semiconductor switches of two device types to ensure synchronous switching, controlling two or more different device types for use independently or in parallel, keeping those switches / transistors within rated operation, while achieving higher efficiency by having discrete slew rates for each device's extreme case operation and / or having optimized slew rates for operating regions important for minimum losses, providing gate driver flexibility and configurability that avoids limiting the types of semiconductors that can be used in mixed-switch power modules, and / or reducing switching losses. Variable slew rates can be created by having at least two sets of gate resistors for both turn-on and turn-off for each transistor technology (a total of four sets per technology), such as four sets of Rg for SiC MOSFETs and four sets for Si IGBTs. The two sets of gate resistors for turn-on and turn-off can be used independently or in parallel, thereby creating at least three sets of slew rates for turn-on per transistor technology and three sets of slew rates for turn-off per transistor technology. Variable slew rates can be used to keep transistors within their rated operating boundaries at maximum output current and maximum input voltage, while reducing losses in areas where power electronic switches are used most. In addition to ensuring that switches operate within their rated voltages and are as efficient as possible, multi-slew rate designs can also benefit current sharing and balancing between transistor technologies by independently controlling turn-on and turn-off delays between technologies to accommodate potential inherent or necessary operating delays. Additionally, gate drive details can be used to select the gate voltage required for the switch, ensuring that the switch remains off, protected from overcurrent and overvoltage, and optionally simplifying PWM control.

[0044] Although various embodiments have been described, this description is intended to be illustrative rather than restrictive, and it will be apparent to those skilled in the art that many more embodiments and implementations are possible within the scope of the embodiments. Unless otherwise specified, any feature of any embodiment may be used in combination with or in place of any other feature or element in any other embodiment. Therefore, the embodiments are not limited except in light of the appended claims and their equivalents. Furthermore, various modifications and variations may be made within the scope of the appended claims. Although several modes for practicing many aspects of the present teachings have been described in detail, those skilled in the art to which these teachings relate will recognize various alternative aspects for practicing the present teachings within the scope of the appended claims. It is intended that all content contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and exemplary of the entire range of alternative embodiments that a person skilled in the art would recognize, and not limited to those explicitly depicted and / or described embodiments, such alternative embodiments being implied by the included content, structurally and / or functionally equivalent to the included content, or otherwise apparent based on the included content.

Claims

1. A variable slew rate gate drive system for powering a motor, comprising: a plurality of hybrid switching power modules operable to convert a direct current (DC) input into an alternating current (AC) output suitable for powering a motor, the hybrid switching power modules each comprising a first semiconductor switch connected in parallel with a second semiconductor switch, the first semiconductor switch having a first set of performance characteristics, and the second semiconductor switch having a second set of performance characteristics that is at least partially different from the first set of performance characteristics; as well as a gate drive system operable to control each hybrid switching power module between open and closed states to facilitate converting a DC input into an AC output, the gate drive system being configured to: providing corresponding first and second control signals to each hybrid switching power module for controlling its first and second semiconductor switches between on and off states, respectively; providing corresponding first and second slew rate signals to each hybrid switching power module for controlling first and second slew rates of its first and second semiconductor switches, respectively; as well as The first and second control signals and the first and second slew rate signals are independently selected for each hybrid switching power module based on operating conditions of the motor and the first and second sets of performance characteristics to optimize transitions between open and closed states.

2. The system of claim 1, wherein: The gate drive system includes a controller configured to determine first and second slew rates based on a plurality of slew rate regions defined relative to operating conditions of the motor and first and second sets of performance characteristics.

3. The system of claim 2, wherein: The slew rate regions include at least a first region, a second region, and a third region, the first region defining a slower slew rate than the second region, and the second region defining a slower slew rate than the third region.

4. The system of claim 3, wherein: The boundaries between the first, second and third regions are defined relative to voltage, current and / or temperature values ​​selected to delimit the operating conditions of the electric machine.

5. The system of claim 2, wherein: The controller is configured to generate first and second control signals according to a plurality of operating modes defined relative to operating conditions of the electric machine and first and second sets of performance characteristics.

6. The system of claim 5, wherein: The operating modes include a dual mode for simultaneously controlling both the first and second semiconductor switches to an on state, a single mode for controlling one of the first and second switches to an on state and the other of the first and second semiconductor switches to an off state, and an off mode for simultaneously controlling both the first and second semiconductor switches to an off state.

7. The system of claim 6, wherein: The gate drive system includes first and second variable resistance circuits for each hybrid switching power module, wherein the first variable resistance circuit is connected to a first gate of a first semiconductor switch associated therewith, and the second variable resistance circuit is connected to a second gate of a second semiconductor switch associated therewith.

8. The system of claim 7, wherein: The first and second variable resistance circuits each include a plurality of snubber switches and a plurality of resistors, wherein each snubber switch is operable between on and off states to connect and disconnect associated one or more resistors from the positive and / or negative power rails, respectively.

9. The system of claim 8, wherein: The first and second slew rate signals are operable to selectively control the first and second slew rates by individually controlling the snubber switches between on and off states and thereby connecting or disconnecting the resistors from the positive and / or negative power rails.

10. The system of claim 9, wherein: The hybrid switching power module includes a first module, a second module, a third module, a fourth module, a fifth module, and a sixth module, which are configured to connect an electric machine to a rechargeable energy storage system (RESS) via a first phase leg, a second phase leg, and a third phase leg, wherein the first and second modules are connected in series to form the first phase leg, the third and fourth modules are connected in series to form the second phase leg, and the fifth and sixth modules are connected in series to form the third phase leg.

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