Energy-efficient main drive inverter solution is the key to solving range anxiety

“Global environmental protection regulations are driving automakers to design electric powertrain systems that are smaller in size and weight and have the highest power efficiency. One of the challenges in designing an electric powertrain is that the battery provides DC power, while the main drive motor requires AC power. The main drive inverter is a key part of the electric powertrain, responsible for converting the DC voltage of the high-voltage battery (350-800 VDC) to the AC voltage of the three-phase AC sinusoidal current, which in turn rotates the induction motor and drives the vehicle forward.

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Global environmental protection regulations are driving automakers to design electric powertrain systems that are smaller in size and weight and have the highest power efficiency. One of the challenges in designing an electric powertrain is that the battery provides DC power, while the main drive motor requires AC power. The main drive inverter is a key part of the electric powertrain, responsible for converting the DC voltage of the high-voltage battery (350-800 VDC) to the AC voltage of the three-phase AC sinusoidal current, which in turn rotates the induction motor and drives the vehicle forward. The performance of this module affects the overall energy efficiency of the vehicle, including acceleration and driving range. ON semiconductor provides energy-efficient, reliable and cost-competitive main drive inverter solutions and advanced packaging technologies, including discrete solutions, isolated gate drivers and innovative VE-Trac series modules and wide bandgap (WBG) program to help increase the range of electric vehicles, thereby increasing the adoption rate of electric vehicles.

Main drive inverter solution topology

As shown in Figure 1, the topology includes 4 main functional blocks: three-phase inverter stage, isolated power supply, signal processing and conditioning, and communication bus.

3-phase inverter stage

The main components of the 3-phase inverter stage are the high-side and low-side switches in the half-bridge switches in each phase in the inverter and the corresponding high-isolation voltage gate drivers. Turning those switches on and off produces 3-phase AC. The sinusoidal waveform makes the induction motor run. A microprocessor-configured variable frequency drive control algorithm manages the high-side and low-side switching control of each inverter phase.

Main drive inverters typically employ high voltage battery systems of 400 V (HVL1) or 800 V (HVL2), the latter being increasingly popular in the latest designs. These systems require power semiconductor devices with a maximum operating voltage in the range of 600 V to 750 V, or 900 V to 1200 V, corresponding to HVL1 or HVL2, respectively. Power inverters are required to handle large amounts of power at current levels ranging from 400 A to 1000 A per phase. To this end, some manufacturers parallel discrete packaged devices, while most use power integrated modules (PIMs). ON Semiconductor offers discrete IGBTs, silicon carbide (SiC) MOSFETs and the innovative VE-Trac family of PIMs, as well as bare die for IGBTs and fast recovery diodes to build the main drive inverter phase. All of these schemes can be interfaced with high voltage gate drivers.

In addition to providing galvanic isolation for isolating high-voltage systems from low-voltage systems, ON Semiconductor’s high-voltage gate driver technology also has a key feature, the Desaturation (DESAT) detection feature, which prevents IGBT short-circuit conditions. “Breakthrough” effect. In addition, there is a Miller clamp function to prevent accidental conduction of one of the switches. And in order to enhance the protection, it also has a fault indication function to notify the system fault and enable the input.

ON Semiconductor’s AECQ-101 qualified discrete IGBT devices with excellent thermal and electrical performance. Due to the extremely low VCE(sat) and gate charge of the IGBT, conduction and switching losses are minimized for energy efficient operation. ON Semiconductor’s IGBTs are co-packaged with fast reverse recovery diodes and constructed using a competitive field stop trench technology that employs a fine cell pitch design to create high power density devices with stable immunity to dynamic characteristics of the latch-up condition. Depending on the power requirements of the motor, multiple IGBTs can be connected in parallel on the corresponding high-side and low-side switches on each half-bridge of the inverter.

ON Semiconductor’s VE-Trac family of PIMs, offering best-in-class electrical and thermal performance, supports two main drive inverter design platforms: VE-Trac™ Dual and VE-Trac™ Direct.

The VE-Trac Dual incorporates Double Sided Cooling (DSC) half-bridge modules that stack and expand within a compact footprint, providing a small footprint platform solution for applications ranging from 80 kW to 300 kW. The platform’s first device is the NVG800A75L4DSC, a module rated at 750 V and 800 A, double the capacity of existing competing devices. Efficient double-sided cooling ensures market-leading thermal performance, and there are no bond wires in this module, doubling its rated life. The NVG800A75L4DSC is an AQG-324 certified module with embedded smart IGBTs that integrates overcurrent and overtemperature protection functions to provide faster protection response time, thus providing a more robust overall solution. ON Semiconductor will introduce additional devices within the VE-Trac Dual platform with higher voltage and various current level options in the coming months to address a variety of emerging applications.

The VE-Trac Direct platform offers best-in-class performance and benefits, including excellent thermal performance with direct cooling. The platform’s first device is the AQG-324 qualified NVH820S75L4SPB. The device is packaged in a six-pack architecture and has been widely recognized and adopted by automotive OEMs (OEMs) and system suppliers. This will support multi-source provisioning with minimal layout changes. With multiple power levels available, the VE-Trac Direct platform will provide easy and fast power tuning for different automotive platforms and applications.

Both the VE-Trac Dual and VE-Trac Direct platforms are capable of continuous operation at junction temperatures up to 175ºC, delivering higher power in compact packages in modular solutions.

For an 800V battery EV system, 1200V, 20mΩ, 80mΩ SiC MOSFETs in D2PAK-7L and TO-247 packages can be inserted into the high-side and low-side switches on each half-bridge of the 3 inverters. SiC MOSFETs offer superior switching performance and higher reliability than silicon, with low on-resistance and compact die size, ensuring low capacitance and gate charge. These features bring system advantages, including high energy efficiency, fast operating frequency, higher power density, lower electromagnetic interference (EMI), and the convenience of a smaller footprint.

ON Semiconductor offers diode and IGBT die optimized for main drive inverter applications, capable of continuous operation at 175°C, low VCE (sat) and forward voltage (VF), with enhanced reliability and robustness.

Signal Processing and Conditioning

The main function of the analog measurement and signal conditioning module is to process the current and temperature detection signals from the inverter and the current and motor position detection signals from the induction motor. Isolated power supplies constructed using resonant and flyback controllers can power microcontrollers, signal conditioning, and analog measurement circuits. ON Semiconductor provides AECQ compliant logic components, comparators, operational amplifiers, and current sense amplifiers to build signal processing circuits that interface with microcontroller analog-to-digital converter units to form closed-loop systems.

communication bus

ON Semiconductor offers CAN, CAN-FD, LIN, Flexray and System Basis Chip (SBC) based transceivers that ensure reliable in-vehicle communications at data rates in excess of 1 Mbps to meet the requirements of modern in-vehicle networks. In addition, ON Semiconductor offers AECQ-101 qualified communication bus protection devices with a junction temperature of 175°C maximum to protect vehicle communication lines from electrostatic discharge (ESD) and other harmful transient voltage events. These devices provide bidirectional protection for each data line, providing system designers with a cost-effective option to increase system reliability and meet stringent EMI requirements.

Evaluation Kit

To allow designers to evaluate the performance of the VE-Trac Dual module and VE-Trac Direct power module respectively in the early stages of developing the main drive inverter, ON Semiconductor offers the VE-Trac Dual evaluation kit NVG800A75L4DSC-EVK and VE-Trac Direct evaluation kits Kit NVH820S75L4SPB-EVK can be used as a double pulse test to measure critical switching parameters or as a 3-phase inverter for motor control up to 150 kW.

The VE-Trac Dual evaluation kit contains three VE-Trac Dual power modules mounted on a double-sided cooling heatsink with a 6-channel gate driver board, DC bus capacitors, and external Hall-effect current for motor control Detect feedback, without pulse width modulation (PWM) controller. Its characteristics are as follows:

Integrated 800A, 750V Generation 4 Field Stop (FS4) IGBT/Diode Chipset
Automotive-grade isolated high-current, high-efficiency IGBT gate driver with built-in electrical isolation NCV57000/1
On-chip current sensing in power modules for faster and simpler overcurrent protection (OCP)
On-chip temperature sensing is integrated into the power module for faster and closer to true Tvj over-temperature protection (OTP)
Custom-designed double-sided heat sink provides low pressure drop and excellent thermal performance
Custom Thin Film DC Bus Capacitors rated up to 500 VDC, 500 uF

The VE-Trac Direct evaluation kit includes a VE-Trac Direct power module mounted in a cooling jacket with a 6-channel gate driver board, DC bus capacitors, and no PWM controller or external current detector. Its characteristics are as follows:

Integrated 820 A, 750V FS4 IGBT/diode chipset and direct cooling
Automotive-grade isolated high-current, high-efficiency IGBT gate driver with built-in electrical isolation NCV57000/1
Film DC Bus Capacitors rated up to 500VDC, 500 uF

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Summarize

One of the challenges in designing an electric powertrain is that the battery provides DC power, while the main drive motor requires AC power. Therefore, the main drive inverter is a key part of the powertrain. Improper component selection or design can result in inefficient inverters or large size (or both), which will be detrimental to the vehicle’s ability to travel further, and conduction and switching losses must be carefully evaluated to achieve The target drivetrain performance of the vehicle. ON Semiconductor provides energy-efficient, robust and cost-competitive main drive inverter solutions and advanced packaging technologies, including discrete power devices, isolated gate drivers and extended module solutions, as well as wide bandgap solutions, and continues to innovate , to address design challenges, provide scalability and automotive reliability for the rapidly growing main drive inverter market, and drive rapid development and adoption of electric powertrains.