Dynamic switching speed control to reduce loss, bearing current and electromagnetic interference

Abstract

The invention relates to dynamic switching speed control to reduce loss, bearing current, and electromagnetic interference. A vehicle includes a system for controlling the vehicle. The vehicle includes an electric motor. The system includes an inverter and a gate controller. The inverter has a switch for controlling current to the motor. The gate controller is configured to apply a gate current to the switch at a first turn-on current control level during a first turn-on phase of a turn-on operation of the switch, the gate current is reduced to a second turn-on current control level less than the first turn-on current control level during a second turn-on phase of the turn-on operation, and the gate current is raised to a third turn-on current control level during a third turn-on phase of the turn-on operation, wherein the third turn-on current control level is greater than the second turn-on current control level.

Description

Technical Field

[0001] The present disclosure relates to the operation of an inverter, and in particular, to systems and methods for controlling the operation of switches of the inverter to prevent the occurrence of voltage overshoot and / or current overshoot. Background Art

[0002] An inverter in a vehicle may be used to convert between a direct current (DC) voltage and an alternating current (AC) voltage. The inverter includes a switch that may be turned on and off to coordinate the conversion. The switch may be a transistor. A gate driver may provide a signal to the gate of the transistor to turn the transistor on and off, thereby allowing or preventing current from flowing through the transistor. Faster switching times increase the amount of voltage overshoot and / or current overshoot through the transistor, which may result in bearing currents through the motor, electromotive ringing, and higher stress on the transistor. Therefore, it is desirable to provide a method of turning the switch on and off that optimizes the occurrence of voltage and current overshoots while also keeping losses to a minimum at certain operating points. Summary of the invention

[0003] In one exemplary embodiment, a method of operating a vehicle is disclosed. During a first conduction phase of a turn-on operation of a switch of an inverter of the vehicle, a gate current is applied to the switch at a first turn-on current control level. During a second conduction phase of the turn-on operation, the gate current is reduced to a second turn-on current control level that is less than the first turn-on current control level. During a third conduction phase of the turn-on operation, the gate current is increased to a third turn-on current control level, wherein the third turn-on current control level is greater than the second turn-on current control level.

[0004] In addition to one or more features described herein, the method also includes reducing the gate current to a second on-current control level when the drain-source current of the switch reaches a nominal maximum value to reduce overshoot of the drain-source current at the end of the first on-stage.

[0005] In addition to one or more features described herein, the method also includes increasing the gate current to a third on-current control level when the drain-source voltage is equal to or close to zero.

[0006] In addition to one or more features described herein, the method also includes turning off the switch by applying a gate current to the switch at a first off current control level during a first off phase until a gate-source voltage drops to an intermediate voltage level.

[0007] In addition to one or more features described herein, the method also includes applying a gate current to the switch at a second off current control level during a second switch off phase until the drain-source current begins to decrease from a maximum value.

[0008] In addition to one or more features described herein, the method also includes applying a gate current to the switch at a third off current control level during a third switch off phase until a gate-to-source voltage is equal to or close to zero.

[0009] In addition to one or more features described herein, the method includes selecting a switching speed of the switch based on at least one of a temperature of the switch, a magnitude of an inverter current when the switching occurs, and an operating region of the vehicle.

[0010] In another exemplary embodiment, a system for controlling a vehicle is disclosed. The system includes an inverter and a gate controller. The inverter has a switch for controlling current to a motor of the vehicle. The gate controller is configured to apply a gate current to the switch at a first on-current control level during a first on-phase of an on-operation of the switch, reduce the gate current to a second on-current control level less than the first on-current control level during a second on-phase of the on-operation, and increase the gate current to a third on-current control level during a third on-phase of the on-operation, wherein the third on-current control level is greater than the second on-current control level.

[0011] In addition to one or more features described herein, the gate controller is further configured to reduce the gate current to a second conduction current control level when the drain-source current of the switch reaches a nominal maximum value to reduce overshoot of the drain-source current at the end of the first conduction phase.

[0012] In addition to one or more features described herein, the gate controller is further configured to increase the gate current to a third conduction current control level when the drain-source voltage is equal to or close to zero.

[0013] In addition to one or more features described herein, the gate controller is configured to turn off the switch by applying a gate current to the switch at a first off current control level until a gate-source voltage drops to an intermediate voltage level during a first off phase.

[0014] In addition to one or more features described herein, the gate controller is further configured to apply a gate current to the switch at a second off current control level during a second off phase until the drain-source current begins to decrease from the maximum value.

[0015] In addition to one or more features described herein, the gate controller is further configured to apply a gate current to the switch at a third off current control level during a third off phase until the gate-source voltage is equal to or close to zero.

[0016] In addition to one or more features described herein, the gate controller is further configured to select a switching speed of the switch based on at least one of a temperature of the switch, a magnitude of an inverter current when the switching occurs, and an operating region of the vehicle.

[0017] In another exemplary embodiment, a vehicle is disclosed. The vehicle includes a motor, an inverter, and a gate controller. The inverter has a switch for controlling current to the motor. The gate controller is configured to apply a gate current to the switch at a first on-current control level during a first on-phase of an on-operation of the switch, reduce the gate current to a second on-current control level less than the first on-current control level during a second on-phase of the on-operation, and increase the gate current to a third on-current control level during a third on-phase of the on-operation, wherein the third on-current control level is greater than the second on-current control level.

[0018] In addition to one or more features described herein, the gate controller is further configured to reduce the gate current to a second conduction current control level when the drain-source current of the switch reaches a nominal maximum value to reduce overshoot of the drain-source current at the end of the first conduction phase.

[0019] In addition to one or more features described herein, the gate controller is further configured to increase the gate current to a third conduction current control level when the drain-source voltage is equal to or close to zero.

[0020] In addition to one or more features described herein, the gate controller is configured to turn off the switch by applying a gate current to the switch at a first off current control level until a gate-source voltage drops to an intermediate voltage level during a first off phase.

[0021] In addition to one or more features described herein, the gate controller is further configured to apply a gate current to the switch at a second off current control level during a second off phase until the drain-source current begins to decrease from a maximum value, and to apply a gate current to the switch at a third off current control level during a third off phase until the gate-source voltage is equal to or close to zero.

[0022] In addition to one or more features described herein, the gate controller is further configured to select a switching speed of the switch based on at least one of a temperature of the switch, a magnitude of an inverter current when the switching occurs, and an operating region of the vehicle.

[0023] The above features and advantages and other features and advantages of the present disclosure are apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, advantages and details appear, by way of example only, from the following detailed description, which refers to the accompanying drawings, in which:

[0025] Figure 1 An embodiment of a vehicle according to an exemplary embodiment is shown;

[0026] Figure 2 A circuit diagram of an electrical system for an electric vehicle is shown;

[0027] Figure 3 A circuit diagram showing a variable current gate controller for controlling the operation of switches / transistors of an inverter of an electrical system;

[0028] Figure 4 A circuit diagram of a variable voltage gate controller for controlling the operation of switches / transistors of an inverter is shown;

[0029] Figure 5 showing first and second graphs depicting coordination of various electrical parameters of switches of an inverter during an "on" operation in accordance with an illustrative embodiment;

[0030] Figure 6 A graph showing switching power losses at different switching rates during an "on" operation;

[0031] Figure 7 showing first and second graphs depicting coordination of various electrical parameters of switches of an inverter during an "off" operation in accordance with an illustrative embodiment;

[0032] Figure 8 A graph showing switching power losses at different switching rates during an "off" operation;

[0033] Fig. 9 showing a graph indicating a sinusoidal curve of the inverter current at the switch;

[0034] Fig.10 shows a graph depicting various operating regions of the vehicle; and

[0035] Fig.11 A diagram of an inverter cooling system in an illustrative embodiment is shown. DETAILED DESCRIPTION

[0036] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate the same or corresponding parts and features.

[0037] According to an exemplary embodiment, Figure 1An embodiment of a vehicle 10 is shown that includes a body 12 that at least partially defines an occupant compartment 14. The body 12 also supports various vehicle subsystems, including a propulsion system 16, and other subsystems for supporting the functions of the propulsion system 16 and other vehicle components, such as a braking subsystem, a suspension system, a steering subsystem, etc.

[0038] The vehicle 10 may be an electric vehicle (EV), a hybrid vehicle, or any other vehicle. In an embodiment, the vehicle 10 is an electric vehicle including a plurality of motors and / or a drive system. Any number of drive units may be included, such as one or more drive units for applying torque to the front wheels (not shown) and / or the rear wheels (not shown). The drive units are controllable to operate the vehicle 10 in various operating modes, such as a normal mode, a high-performance mode (in which additional torque is applied), all-wheel drive ("AWD"), front-wheel drive ("FWD"), rear-wheel drive ("RWD"), etc.

[0039] For example, the propulsion system 16 is a multi-drive system, which includes a front drive unit 20 for driving the front wheels and a rear drive unit for driving the rear wheels. The front drive unit 20 includes a front motor 22 and a front inverter 24 (e.g., a front power inverter module or FPIM), as well as other components such as a cooling system. The left rear drive unit 30L includes a left rear motor 32L and a left rear inverter 34L. The right rear drive unit 30R includes a right rear motor 32R and a right rear inverter 34R. The front inverter 24, the left rear inverter 34L, and the right rear inverter 34R (e.g., a power inverter unit or PIM) each convert the direct current (DC) power from the high voltage (HV) battery system 40 into a multi-phase (e.g., two-phase, three-phase, six-phase, etc.) alternating current (AC) power to drive the front motor 22, the left rear motor 32L, and the right rear motor 32R.

[0040] like Figure 1 As shown, the drive system features a single motor. However, the embodiments are not limited thereto. For example, instead of a single motor, multiple drives may be provided by a single machine having multiple sets of windings that are physically independent.

[0041] Also like Figure 1 As shown, the drive system is configured so that the front motor 22 drives the front wheels (not shown), and the left rear motor 32L and the right rear motor 32R drive the rear wheels (not shown). However, the embodiments are not limited to this, as there can be any number of drive systems and / or motors at various locations (e.g., a motor driving each wheel, dual motors for each axle, etc.). In addition, the embodiments are not limited to dual drive systems, as the embodiments can be used with vehicles having any number of motors and / or power inverters.

[0042] In the propulsion system 16, the front drive unit 20, the left rear drive unit 30L, and the right rear drive unit 30R are electrically connected to a battery system 40. The battery system 40 may also be electrically connected to other electrical components (also referred to as "electrical loads"), such as vehicle electronics (e.g., via an auxiliary power module or APM 42), heaters, cooling systems, etc. The battery system 40 may be configured as a rechargeable energy storage system (RESS).

[0043] In one embodiment, the battery system 40 includes a plurality of individual battery assemblies, each of which can be charged independently and can be used to independently power one or more drive systems. For example, the battery system 40 includes a first battery assembly, such as a first battery pack 44 and a second battery pack 46 connected to the front inverter 24. The first battery pack 44 includes a plurality of battery modules 48, and the second battery pack 46 includes a plurality of battery modules 50. Each battery module 48, 50 includes a plurality of individual battery cells (not shown). In various embodiments, one or more of the battery packs may include MODACS (Multi-Output Dynamically Adjustable Capacity) batteries.

[0044] Each of the front motor 22 and the left rear motor 32L and the right rear motor 32R is a three-phase motor having a three-phase motor winding. However, the embodiments described herein are not limited thereto. For example, the motor may be any multi-phase machine supplied by a multi-phase inverter, and the drive unit may be implemented using a single machine having several sets of independent windings.

[0045] The battery system 40 and / or the propulsion system 16 includes a switching system having various switching devices for controlling the operation of the first battery pack 44 and the second battery pack 46 and selectively connecting the first battery pack 44 and the second battery pack 46 to the front drive unit 20, the left rear drive unit 30L, and the right rear drive unit 30R. The switching device can also be operated to selectively connect the first battery pack 44 and the second battery pack 46 to the charging system. The charging system can be used to charge the first battery pack 44 and the second battery pack 46, and / or supply power from the first battery pack 44 and / or the second battery pack 46 to charge another energy storage system (e.g., vehicle-to-vehicle (V2V) and / or vehicle-to-everything (V2X) charging). The charging system includes one or more charging modules. For example, a first onboard charging module (OBCM) 52 is electrically connected to a charging port 54 for charging and charging from an AC system or device (such as a public AC power supply). A second OBCM 53 may be included for DC charging (e.g., DC fast charging or DCFC). As Figure 1 As shown, the utility AC power source is a charging station 110 connected to the charging port 54 via an electrical line 112 .

[0046] In one embodiment, the switching system includes a first switching device 60 and a second switching device 62, wherein the first switching device 60 selectively connects the first battery pack 44 to the front inverter 24, the left rear inverter 34L, and the right rear inverter 34R, and the second switching device 62 selectively connects the second battery pack 46 to the front inverter 24, the left rear inverter 34L, and the right rear inverter 34R. The switching system also includes a third switching device 64 (also referred to as a "battery switching device") for selectively connecting the first battery pack 44 in series to the second battery pack 46.

[0047] Any of a variety of controllers may be used to control the functions of the battery system 40, the switching system, and the drive unit. The controller includes any suitable processing device or unit, and an existing controller such as a drive system controller, a RESS controller, and / or a controller in a drive system may be used. For example, a controller 65 may be included to control the switching and drive control operations as discussed herein.

[0048] The controller 65 may include processing circuitry that may include an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) executing one or more software or firmware programs and memory, combinatorial logic circuits, and / or other suitable components that provide the described functionality. The controller 65 may include a non-transitory computer readable medium storing instructions that, when processed by one or more processors of the controller 65, implement a method of determining an anode voltage and a cathode voltage during charging and adjusting a charging rate of a vehicle based on the anode voltage and the cathode voltage according to one or more embodiments detailed herein.

[0049] The vehicle 10 also includes a computer system 55 including one or more processing devices 56 and a user interface 58. The computer system 55 can communicate with the charging system controller, for example, to provide commands thereto in response to user input. The various processing devices, modules, and units can communicate with each other via a communication device or system, such as a controller area network (CAN) or a transmission control protocol (TCP) bus.

[0050] As shown herein, the vehicle 10 is an electric vehicle. In alternative embodiments, the vehicle 10 may be an internal combustion engine vehicle, a hybrid vehicle, or the like.

[0051] Figure 2A circuit diagram 200 of an electrical system for an electric vehicle is shown. The electrical system includes a battery 202, an electric motor 204, and an inverter 206 coupling the battery to the electric motor. For purposes of illustration, the electric motor 204 is a three-phase electric motor. The inverter 206 includes three branches connected to corresponding phase windings of the electric motor 204. A first branch 208 extends between a positive DC bus 220 and a negative DC bus 222 of the battery 202 and includes two switches S1 and S2. A first phase winding 214 of the electric motor 204 is connected to the first branch 208 at a first AC terminal 215 between the switch S1 and the switch S2. A second branch 210 extends between the positive DC bus 220 and the negative DC bus 222 and includes two switches S3 and S4. A second phase winding 216 of the electric motor 204 is connected to the second branch 210 at a second AC terminal 217 between the switch S3 and the switch S4. The third branch 212 extends between the positive DC bus 220 and the negative DC bus 222 and includes two switches S5 and S6. A third phase winding 218 of the motor 204 is connected to the third branch 212 at a third AC terminal 219 between the switches S5 and S6.

[0052] Each switch can be a transistor, such as a field effect transistor (FET) having a drain, a source, and a gate. Each switch has a gate controller that controls a gate voltage or a gate current at the FET, thereby controlling the state of the FET (i.e., on or off). For example, the first gate controller 224 controls the voltage or current at the gate of the switch S1, and the second gate controller 226 controls the voltage or current at the gate of the switch S2.

[0053] Figure 3 A circuit diagram 300 of a variable current gate controller 302 for controlling the operation of the switches / transistors of the inverter 206 is shown. The variable current gate controller 302 includes a first variable current source 304 and a second variable current source 306. The first variable current source 304 is connected to the positive bus and the second variable current source 306 is connected to the negative bus or ground. The first variable current source 304 provides a gate current I for controlling the “ON” operation at the switch. g The second variable current source 306 provides a gate current I for controlling the “off” operation of the switch. g The first variable current source 304 and the second variable current source 306 can be used independently of each other.

[0054] Figure 4A circuit diagram 400 of a variable voltage gate controller 402 for controlling the operation of switches / transistors of the inverter 206 is shown. The variable voltage gate controller 402 includes a first variable voltage source 404 and a second variable voltage source 406. The first variable voltage source 404 is connected to a positive voltage and the second variable voltage source 406 is connected to a negative voltage. The first variable voltage source 404 may include two or more voltage controlled transistors S a , S b , which can be independently turned on and off to provide a selected gate voltage suitable for turning on the switch. Similarly, the second variable voltage source 406 may include two or more voltage-controlled transistors S c , S d , which can be turned on and off independently to provide a selected gate voltage for turning off the switch.

[0055] Figure 5 A first graph 500 and a second graph 501 depicting coordination of various electrical parameters of switches of inverter 206 during an "on" operation are shown in accordance with an illustrative embodiment. Time is shown along the abscissa. Electrical parameters of the switches are shown along the ordinate axis.

[0056] The phases of the “on” operation are marked along the abscissa. The first on phase 502 starts at a first time t A Extend to the second time t B The second conduction phase 504 starts from the second time t B Extend to the third time t C The third conduction phase 506 occurs at a third time t C After that, the electrical parameters include the drain-source voltage 508 (V DS ), gate-source voltage 516 (V GS ), drain-source current 512 (I DS ) (shown on the first graph 500) and the gate current I g (514) (shown on the second graph 501). In the initial off state, the drain-source current I DS is zero, the gate-source voltage V GS is at the off voltage (which can be zero or a negative voltage), and the drain-source voltage V DS At the nominal maximum value. Gate current I g is set to zero. The gate controller provides control over other electrical parameters (i.e., V DS 、V GS ,I DS ) of the gate current I g For illustrative purposes, the gate controller is discussed herein as a variable current gate controller 302. However, a variable voltage gate controller 402 may be used in alternative embodiments.

[0057] When the variable current gate controller 302 sets the gate current I g Set to the first gate conduction current level (I g0 ), the first conduction phase 502 begins (at time t A ). At this time, the gate-source voltage V GS When the gate-source voltage V GS rises above the voltage threshold V TH When (at time t A' ), drain-source current I DS starts to rise from zero. When the drain-source current I DS Reach the set maximum value I DS_max , the first conduction phase 502 ends.

[0058] At the beginning of the second conduction phase 504, the variable current gate controller 302 sets the gate current I g From the first on-current control level I g0 Reduced to the second on-current control level I g1 The switching speed is proportional to the gate current. Therefore, during the first conduction phase 502, there is a high first gate conduction current level I g0 This results in increased switching speed, thereby reducing switching losses without increasing the voltage slew rate (dV DS / dt). During the second conduction phase 504, the second gate conduction current level I g1 This results in a reduced switching speed, which reduces the voltage slew rate to reduce the occurrence of common-mode currents, electromagnetic interference, and bearing currents. DS remains at the set maximum level, and the gate-source voltage V GS Maintained at mid-voltage level. Drain-source voltage V DS begins to decrease from its nominal maximum value.

[0059] At the beginning of the third conduction phase 506, the variable current gate controller 302 sets the gate current I g Increases to a level greater than the second gate voltage level I g1 The third conduction current control level I g2 . Drain-source voltage V DS decreases to zero, and the drain-source current I DS Maintained at the set maximum value. Gate-source voltage V GS During the third on-phase 506, the controller increases the gate current to a third on-level I g2 To accelerate V gsThis decreases the transistor channel resistance and thus reduces switching losses.

[0060] During operation of the switch, a shunt resistor or current sensor can be used to measure and sense the gate current I g , a voltage sensor can be used to measure the gate-source voltage V GS , and the drain-source voltage V can be measured by measuring the resistor voltage across the transistor DS When the variable current gate controller 302 receives an "on" command (circle 520), the start of the first conduction phase 502 can be detected. The gate-source voltage V GS , drain-source voltage V DS and the drain-source current I DS The start of the second conduction phase 504 is detected by the change of the gate-source voltage V GS From having a positive slope to having a zero slope (circle 526). Alternatively, the gate-source voltage V GS is close to the Miller voltage of the transistor. In addition, the drain-source voltage V DS From having a zero slope to having a negative slope (circle 524). In addition, the drain-source current I DS From having a positive slope to having a slope close to zero (circle 522). Alternatively, the drain-source current I DS Equal to or close to the phase current of the switch.

[0061] The gate-source voltage V GS and the drain-source voltage V DS The end of the second conduction phase 504 is detected by the change of the gate-source voltage V GS From having a zero slope to having a positive slope (circle 528), the gate-source voltage V GS rises above the Miller voltage of the transistor. In addition, the drain-source voltage V DS From having a negative slope to having a zero slope, where the drain-source voltage V DS is equal to or close to zero volts (circle 530). When the gate-source voltage V GS When approximately the maximum gate voltage is reached, the end of the "ON" operation is detected (circle 532).

[0062] Figure 6 Graph 600 showing switching power losses at different switching rates during an "on" operation. Time is shown along the abscissa. A first time marker t B1 Indicates the time of transition from the first conduction phase 502 to the second conduction phase 504 when the switch is operated at the first switching rate. The second time marker tB2 5 shows the transition time from the first conduction phase 502 to the second conduction phase 504 when the switch is operated at a second switching rate. Due to the difference in switching rates, the second time marker t B2 Mark the first time t B1 The first switching rate is marked by the first time t B1 The slope of the first drain-source current 602 is indicated by the second switching rate indicated by the second time mark t B2 The slope of the second drain-source current 604 before is indicated. Figure 6 As shown, as a result of the switching method disclosed herein, the second switching rate is faster than the first switching rate (ie, dI DS2 / dt>dI DS1 / dt). The second drain-source voltage 608 is at the second time mark t B2 The slope after (dV DS2 / dt) is greater than the first drain-source voltage 606 at the first time mark t B1 The slope after (dV DS1 In other words, the drain-source voltage changes more slowly for the second switching rate than for the first switching rate, thereby reducing common-mode voltage and current, bearing current, and electromagnetic interference.

[0063] By alternating the "on" operation so that the change in drain-source voltage is reduced, the switching power loss can be reduced. The first power loss of the first switching rate is indicated by the first region 610, and the second power loss of the second switching rate is indicated by the second region 612. The second region 612 is smaller than the first region 610, so that the second switching rate has less power loss than the first switching rate.

[0064] Figure 7 A first graph 700 and a second graph 701 depicting coordination of various electrical parameters of switches of inverter 206 during an "off" operation are shown in accordance with an illustrative embodiment. Time is shown along the abscissa. Electrical parameters of the switches are shown along the ordinate axis.

[0065] The stages of the "off" operation are marked along the abscissa. The first off stage 702 starts at a first time t D Extend to the second time t E The second off phase 704 starts from the second time t E Extend to the third time t F The third off phase 706 occurs at a third time t F After that. In the initial off state, the drain-source current I DS At the nominal maximum level, the drain-source voltage V DS is at zero, and the gate-source voltage VGS At nominal maximum.

[0066] When the variable current gate controller 302 sets the gate current I g Set to the first off current control level (I g0 ), the first off phase 702 begins (at time t E During the first off phase 702, the drain-source current I DS and the drain-source voltage remains at its nominal on-state value. The gate-source voltage V GS begins to decrease from its nominal maximum level. When the gate-source voltage V GS When the intermediate voltage value is reached, the first switch-off phase 702 ends.

[0067] At the beginning of the second off phase 704, the variable current gate controller 302 sets the gate current I g From the first off current control level I g0 Increase to the second off current control level I g1 . Drain-source voltage V DS starts to rise, and the gate-source voltage V GS is held at the mid-voltage value, and the drain-source current remains at its nominal on-value.

[0068] At the beginning of the third off stage 706, the variable current gate controller 302 sets the gate current I g Reduced to the third off current control level I g2 , the third off current control level I g2 Less than the second off current control level I g1 During this off phase, the drain-source current I DS drops from its on-state value, and the drain-source voltage V DS The drain-source voltage V DS An overshoot of this level may be experienced during the third turn-off phase 706. The gate-source voltage V GS starts to drop from the intermediate voltage level. When the gate-source voltage V GS When the shutdown voltage (eg, 0V, ~4V) is reached, the end of the "shutdown" operation occurs.

[0069] The start and end of the shutdown phase are indicated by various measurable parameters. The start of the first shutdown phase (i.e., time t E ). Through the gate-source voltage V GS and the drain-source voltage V DS The start of the second turn-off phase 704 is detected by the change of the gate-source voltage VGS From having a negative slope to having a zero slope (circle 722). Alternatively, the gate-source voltage V GS is equal to or close to the Miller voltage of the transistor. In addition, the drain-source voltage V DS From having a zero slope to having a positive slope (circle 724), or increasing from its nominal minimum value.

[0070] Through the gate-source voltage V GS , drain-source voltage V DS and the drain-source current I DS The beginning of the third turn-off phase 706 is detected by the change of the drain-source current I DS From having a zero slope to a negative slope. Alternatively, the drain-source current I DS drops to less than the phase current of the switch, or drops from its nominal maximum value. In addition, the gate-source voltage V GS From having a zero slope to having a negative slope (circle 730), where the gate-source voltage V GS decreases to below the Miller voltage of the transistor. In addition, the drain-source voltage V DS From having a positive slope to having a zero slope, and the drain-source voltage V DS is equal to or close to the DC voltage of the inverter (circle 728). GS When φ is equal to or close to zero, the end of the off phase is detected (circle 732).

[0071] Figure 8 Graph 800 shows switching power losses at different switching rates during an "off" operation. A first time mark t F1 Indicates the time of transition from the second off phase 704 to the third off phase 706 when the switch is operated at the first switching rate. The second time marker t F2 706 when the switch is operated at a second switching rate. Due to the difference in switching rates, the first time mark t F1 At the second time mark t F2 Before. The first switching rate (dI DS1 / dt) is marked by the first time t F1 The slope of the first gate-source current 804 after that indicates the second switching rate (dI DS2 / dt) is marked by the second time t F2 The slope of the second gate-source current 802 after dI is indicated. As a result of the switching method disclosed herein, the second switching rate is faster than the first switching rate (ie, dI DS2 / dt>dI DS1 / dt), such as Figure 8 As shown, this results in less switching power loss. The first time mark t F2 The slope of the second drain-source voltage 806 (dV DS2 / dt) is less than (smaller positive) the first time mark t F1 The slope of the first drain-source voltage 808 (dV DS1 / dt). In other words, the drain-source voltage changes more slowly for the second switching rate than for the first switching rate. The slower change in drain-source voltage results in less common-mode voltage and current, bearing current, and electromagnetic interference. The first power loss of the first switching rate is indicated by the first region 810, and the second power loss of the second switching rate is indicated by the second region 812. The second region 812 is smaller than the first region 810. Therefore, the second switching rate has a smaller switching power loss than the first switching rate. During the third off phase 706, the controller reduces I g2 (increase its current amplitude) to accelerate the gate-source voltage V GS of the transistor, thereby reducing the leakage current through the transistor and reducing switching losses.

[0072] The switching speed can be changed by changing the parameters provided by the gate controller (i.e., the gate current). When the temperature of the inverter increases, the turn-off speed can be increased and the turn-on speed can be reduced, and vice versa. In addition, the switching speed can also be changed to be consistent with the phase current at the corresponding branch of the inverter.

[0073] Fig. 9 A graph 900 of a sinusoidal curve 902 indicating the inverter current (i.e., drain-source current) at the switch is shown. Most switching events occur when the inverter current is below its peak amplitude. The switching speed can be selected based on the amplitude of the inverter current at which switching occurs. In particular, when the inverter current is at its extreme value (i.e., at high 904 and low 906), the conduction speed can be the fastest, and when the current is at a value close to zero (i.e., point 908), the conduction speed can be the slowest. The switching speed can be selected to match any specific amplitude of the inverter current.

[0074] Fig.10 A graph 1000 depicting various operating regions of a vehicle is shown. Motor speed is shown in revolutions per minute (RPM) along the abscissa, and motor torque is shown in Newton-meters (Nm) along the ordinate axis. Each operating region has a corresponding switching speed suitable for that region. The graph includes a maximum torque region 1002, a normal drive region 1004, a bearing current damage region 1006, a regenerative drive region 1008, a high speed drive region 1010, and a heating region 1012, where the inverter is controlled to generate heat at the electric vehicle.

[0075] Table 1 shows a list of actions to be taken and corresponding changes that can be made to the switching speed to achieve the actions. The first column includes changes in operating conditions; the second column includes switch on speed; and the third column includes switch off speed.

[0076]

[0077]

[0078] For example, if the phase current is to be increased, the controller increases the turn-on speed and decreases the turn-off speed.

[0079] Fig.11 A diagram 1110 of an inverter cooling system in an illustrative embodiment is shown. The inverter cooling system includes a plurality of power modules 1102a-1102c disposed within a coolant 1104. The coolant 1104 enters the system via an inlet 1106 and exits the system via an outlet 1108, thereby absorbing heat from the plurality of power modules 1102a-1102c as it passes through the cooling system. Thus, the power module closest to the inlet 1106 (i.e., power module 1102a) is the coldest, while the power module farthest from the inlet (i.e., power module 1102c) is the hottest, wherein the temperature of each power module is related to its distance from the inlet.

[0080] The controller controls the switching speed of the switch based on the temperature of the switch. Therefore, the switching speed of the cooler power module can be slower than the switching speed of the hotter power module. In other words, the switching speed of power module 1102a is slower than the switching speed of power module 1102c. It can also be said that the switching speed is related to the distance from the switch to the inlet. Controlling the switching speed of each power module or switch can balance their temperature differences, thereby improving reliability.

[0081] The terms "one" and "an" do not indicate a limitation of quantity, but rather indicate the presence of at least one of the referenced item. Unless the context clearly indicates otherwise, the term "or" means "and / or". References to "aspects" throughout the specification mean that a particular element (e.g., a feature, structure, step, or characteristic) described in conjunction with that aspect is included in at least one aspect described herein, and may or may not be present in other aspects. In addition, it should be understood that the described elements may be combined in any suitable manner in the various aspects.

[0082] When an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present.

[0083] Unless otherwise indicated herein, all test standards are the most current standards in effect as of the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the test standards appear.

[0084] Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0085] Although the above disclosure has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from its scope. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the disclosure without departing from the basic scope of the disclosure. Therefore, it is intended that the disclosure is not limited to the specific embodiments disclosed, but will include all embodiments falling within its scope.

Claims

1. A method of operating a vehicle, comprising: applying a gate current to a switch at a first on-current control level during a first on-phase of a turn-on operation of a switch of an inverter of the vehicle; During a second on-phase of the on-operation, reducing the gate current to a second on-current control level that is less than the first on-current control level; as well as During a third on-phase of the turn-on operation, the gate current is increased to a third on-current control level, wherein the third on-current control level is greater than the second on-current control level.

2. The method according to claim 1, further comprising: When the drain-source current of the switch reaches a nominal maximum value, the gate current is reduced to the second on-current control level to reduce an overshoot of the drain-source current at the end of the first on-stage.

3. The method according to claim 1, further comprising: When the drain-source voltage is equal to or close to zero, the gate current is increased to the third on-current control level.

4. The method according to claim 1, further comprising: The switch is turned off by applying the gate current to the switch at a first off current control level during a first off phase until a gate-source voltage drops to an intermediate voltage level.

5. The method of claim 1 further comprising selecting a switching speed of the switch based on at least one of: (i) a temperature of the switch; (ii) a magnitude of inverter current when switching occurs; and (iii) an operating region of the vehicle.

6. A system for controlling a vehicle, comprising: an inverter having switches for controlling current to an electric motor of the vehicle; as well as a gate controller configured to apply a gate current to the switch at a first on-current control level during a first on-phase of a turn-on operation of the switch, reduce the gate current to a second on-current control level less than the first on-current control level during a second on-phase of the turn-on operation, and increase the gate current to a third on-current control level during a third on-phase of the turn-on operation, wherein the third on-current control level is greater than the second on-current control level.

7. The system according to claim 6, wherein: The gate controller is further configured to reduce the gate current to the second on-current control level when the drain-source current of the switch reaches a nominal maximum value to reduce an overshoot of the drain-source current at the end of the first on-stage. 8 . The system of claim 6 , wherein the gate controller is further configured to increase the gate current to the third on-current control level when the drain-source voltage is equal to or close to zero.

9. The system according to claim 6, wherein: The gate controller is further configured to turn off the switch by applying a gate current to the switch at a first off current control level during a first turn-off phase until a gate-source voltage drops to an intermediate voltage level.

10. The system of claim 6, wherein the gate controller is further configured to select a switching speed of the switch based on at least one of: (i) a temperature of the switch; (ii) a magnitude of inverter current when switching occurs; and (iii) an operating region of the vehicle.

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