How does VE-Trac SiC make the main drive inverter stronger?

[Introduction]The dual carbon goal is accelerating the development of automobiles towards electrification. The innovation of semiconductor technology helps automobiles transition from fuel vehicles to electric vehicles. The new generation of semiconductor material silicon carbide (SiC) will change the future of electric vehicles due to its unique advantages. The use of SiC in the key main drive inverter can meet the requirements of higher power and lower energy efficiency, longer battery life, lower losses and lower weight, and the trend of migrating to 800 V can give full play to its advantages, but Faced with many challenges such as cost, packaging and technology maturity.

ON Semiconductor provides leading smart power solutions and has a deep history in the SiC field. It is one of the few suppliers in the world that can provide end-to-end SiC solutions from substrates to modules. Its innovative VE Trac™ Direct SiC and VE-Trac™ B2 SiC solutions use stable and reliable planar SiC technology, combined with sintering technology and die-cast mold packaging, to help designers solve the above challenges, and cooperate with the company’s other advanced smart power semiconductors to accelerate market adoption of electric vehicles and help the future transportation towards sustainable development.

The development trend of electric vehicle main drive

Regardless of the configuration of the electric vehicle, whether it is fully battery-driven or a series plug-in or parallel hybrid drivetrain, vehicle electrification has several key elements: First, the power is stored in the battery, and then the direct current is converted by the inverter to The AC output is converted into mechanical energy for the motor to drive the car. Therefore, the energy efficiency and performance of the main drive inverter is the key, which will directly affect the performance of the electric vehicle and the achievable driving range per charging cycle.

The main driver of electric vehicles pursues higher power, higher energy efficiency, higher bus voltage, lighter weight and smaller size. More power means greater continuous torque output and better acceleration performance. Higher energy efficiency enables longer battery life and lower losses. 400 V batteries are the current mainstream and are about to develop to 800 V. The 800 V architecture reduces charging time and losses and reduces weight, resulting in longer range. Whether the motor is on the front or rear axle, the smaller motor size makes more trunk and passenger space available. These trends have driven the transition from IGBTs to SiC power devices in the main drive of electric vehicles.

SiC is the future of main drive inverters

One of the most important properties of SiC is that its band gap is wider than that of Si, and its electron mobility is three times that of Si, resulting in lower losses. The breakdown voltage of SiC is 8 times that of Si, the high breakdown voltage and thinner drift layer are more suitable for high voltage architectures such as 800 V. The Mohs hardness of SiC is 9.5, which is only slightly softer than diamond, the hardest material, and 3.5 harder than Si. It is more suitable for sintering. After sintering, the reliability of the device is improved and the thermal conductivity is enhanced. The thermal conductivity of SiC is 4 times that of silicon, making it easier to dissipate heat, thereby reducing heat dissipation costs.

At the inverter level or at the vehicle level, SiC MOSFETs can achieve lower overall system-level cost, better performance and quality than IGBTs. The key design advantages of SiC MOSFETs over IGBTs in main drive inverter applications are:

1. SiC enables higher power density per unit area, especially at higher voltages (such as 1200 volt breakdown)

2. The conduction loss is relatively low at low current, resulting in higher energy efficiency at low load

3. Unipolar behavior, can work at higher temperature, lower switching loss

VE-Trac™ SiC series: sintering process + die-casting SiC technology, specially designed for main drive inverter

The SiC products launched by ON Semiconductor for the specific package of the main drive inverter are: VE-Trac™ Direct SiC (1.7 mΩ Rdson, 900 V 6-pack) power module, VE-Trac™ Direct SiC (2.2 mΩ Rdson, 900 V 6-pack) -pack) power module, VE-Trac™ B2 SiC (2.6 mΩ Rdson, 1200 V half-bridge) power module, provides the industry’s most IGBT or SiC-compatible package pins, reducing structural design changes.

Figure 1: VE Trac™ Direct SiC (left) and VE Trac™ B2 SiC (right)

To improve power output, heat dissipation is critical. In order to achieve the best heat dissipation effect, ON Semiconductor VE-Trac™ Direct SiC adopts the latest silver sintering process to directly sinter the SiC bare core on the DBC, and the DBC is soldered to the Pin Fin base plate. The direct cooling path between the 1.7 mΩ Rdson’s VE-Trac™ Direct SiC and the coolant helps to greatly reduce the thermal resistance of indirect cooling, thus ensuring greater power output, such as 1.7 mΩ Rdson’s VE-Trac™ Direct SiC thermal resistance of 0.10°C/W, compared to VE- Trac™ Direct IGBTs have 20% lower thermal resistance.

Figure 2: VE-Trac™ Direct SiC Key Features

Differentiated die-casting mold packaging technology, higher reliability than traditional gel modules, higher power density, lower stray inductance, better heat dissipation performance, easy to expand power, more cost advantages, due to SiC can withstand The working temperature is as high as 200 °C and the continuous working time is up to 175 °C. Therefore, the SiC-containing plastic die-casting mold package further increases the working temperature than the die-casting mold IGBT module, making the output power higher.

ON Semiconductor simulated and compared VE-Trac™ Direct IGBT and VE-Trac™ Direct SiC under the same conditions. When they provide the same output power, the junction temperature of VE Trac™ Direct SiC is 21% lower than that of VE Trac™ Direct IGBT. , resulting in lower losses and improved energy efficiency.

Figure 3: Simulation results: SiC losses are lower

The improvement in energy efficiency equates to longer cruising range or lower battery costs. For example, using the same 100 kWh battery, the cruising range with the SiC solution is 5% longer than with Si. If cost savings is the goal, the battery size can be reduced to provide the same range. For example, switching from the Si solution of the 140 kWh battery to the SiC solution of the 100 kWh battery reduces the battery cost by 5%, but the cruising range remains unchanged.

Under the same 450 V DC bus and 150 ℃ junction temperature (Tvj) conditions, the 820 A IGBT can provide 590 Arms of current, the output power of 213 kW, equivalent to 285 horsepower (HP). The 2.2 mOhm SiC can deliver 605 Arms of current and output 220 kW, which equates to 295 HP. The 1.7 mOhm SiC delivers 760 Arms of current and delivers 274 kW, which equates to 367 HP.

Why choose ON Semiconductor’s VE-Trac™ SiC?

SiC has been used in MOSFETs for more than 10 years, but it has not been widely used in main drive solutions by auto manufacturers. Suitable for multiple challenges such as main drive solutions.

The history of ON Semiconductor in the SiC field can be traced back to 2004. In recent years, it has acquired GTAT, an upstream SiC supplier, to achieve vertical integration of the industry chain. It is one of the few suppliers in the world that provides end-to-end SiC solutions from substrates to modules, including SiC ingot growth, substrates, epitaxy, device manufacturing, best-in-class integrated modules and discrete packaging solutions ensure a stable and reliable supply chain and contribute to cost optimization.

In terms of systems, ON Semiconductor also has strong technical and system knowledge to provide customers with global application support. One of the main advantages of the GTAT process is that its SiC provides very precise resistivity values ​​and its resistivity distribution is very uniform throughout the crystal.

In addition, ON Semiconductor is advancing 6-inch and 8-inch SiC crystal growth technology, and will also invest in more SiC supply chain links, including fab capacity and packaging lines. At the same time, with years of technology accumulation and the technical supplement brought by the acquisition of Fairchild Semiconductor Gene a few years ago, ON Semiconductor has continued to iterate. Its SiC technology has entered the third generation, and its comprehensive performance is in a leading position in the industry.

Figure 4: ON Semiconductor’s SiC leadership

VE-Trac™ SiC is highly compatible with the package pins of VE-Trac™ IGBT, so switching from IGBT to SiC reduces structural changes and design work. Reliable, can work continuously at 175°C, conforms to vehicle regulations AECQ101 and AQG324, and the power stage can be flexibly expanded.

VE-Trac™ B2 SiC integrates all of ON Semiconductor’s SiC MOSFET technologies in a half-bridge architecture. The die connection adopts sintering technology, which improves heat dissipation, energy efficiency, power density and reliability. It can work continuously at 175°C and even work at 200°C for a short period of time, in line with the AQG 324 automotive power module standard. The B2 SiC modules combine sintering technology for die attach and copper clips, and a die-cast molding process for reliable packaging. Its SiC chipset uses ON Semiconductor’s M1 SiC technology, which provides high current density, strong short-circuit protection, high blocking voltage and high operating temperature, bringing class-leading performance in electric vehicle main drive applications.

Figure 5: VE-Trac™ B2 SiC Value Proposition

Future products and the advantages of 800 V batteries

The higher breakdown voltage of SiC will enable widespread adoption of 800 V battery architectures. Lower current produces less heat, while higher DC battery voltage increases the power density of the inverter. From the perspective of the whole vehicle, the higher the voltage, the lower the current, so the cables and connectors of the cross-section are also smaller and lighter, and the charging speed is faster under the charging conditions of high current such as more than 35 kW. The performance has also been improved better, so the 800 V architecture will be preferred in high-performance models.

Summarize

SiC will change the future of electric vehicles. ON Semiconductor is one of the few suppliers in the world that can provide end-to-end SiC solutions from substrate to module. Differentiated die-casting mold packaging and innovative sintering process, in line with vehicle regulations, provide better heat dissipation, lower losses, higher power, and higher energy efficiency, making new energy vehicles longer cruising range, smaller batteries, and higher energy efficiency. The application support provided by the above technical team helps to solve the challenges of using SiC for the main drive in terms of cost, supply, technology, packaging, etc., and promote the development of electric vehicles from 400 V to 800 V.

In the future, ON Semiconductor will continue to innovate and provide leading smart power solutions, including IGBT, SiC and VE-Trac™ modules, enabling more powerful and reliable automotive products, helping to accelerate the adoption of electric vehicles in the market, and enabling future transportation to move towards a more sustainable future. continuous development.