What you’ll learn:
- In what ways are STMicro’s new GaN parts family well-suited for electric supercharger apps?
- The impact on dc fast-charging stations.
- The system-in-package approach for 100-V devices.
GaN technology provides high-frequency operation with increased efficiency and higher power density compared to silicon-based transistors. But to meet the size, performance, and cost goals required by the automotive industry as it shifts to electrified platforms, suppliers are increasingly combining the advantages of GaN technology with traditional semiconductor materials.
For example, STMicroelectronics recently announced a new family of GaN parts designated STi2GaN, which stands for ST Intelligent and Integrated GaN.
The STi2GaN family combines a monolithic power stage along with drivers and protection in GaN technology as well as additional processing and control circuitry in system-in-package (SiP) solutions. The parts use ST’s bond-wire-free packaging technology to provide robustness and reliability. The new product family aims to leverage the high-power density and efficiency of GaN to offer a range of 100- and 650-V high-electron-mobility transistor (HEMT) devices.
STMicro’s STi2N SiP is comprised of a power stage, driver and protection circuitry, and control logic.
ST’s initial offering of STi2GaN solutions are targeted at such applications as on-board chargers (OBCs), LiDAR for autonomous driving, bidirectional dc-dc converters, Class-D amplifiers, and power-conversion systems, according to Alfio Russo, Group VP and GM of Low Voltage and STI2GaN Solutions Macro Division, STMicroelectronics.
ST started working on wide-bandgap materials (WBG) in 1996 with silicon-carbide (SiC) MOSFETs and SiC diodes. GaN products in the automotive space will focus on OBCs for EVs and mild-hybrid dc-dc converters. The bidirectional 48/12-V dc-dc converter is a monolithic GaN half-bridge with a high side of 2 mΩ and low side of 1 mΩ with the driver and controller in silicon.
With the aim of reducing CO2 emissions, turbocharger systems are evolving from exhaust gas-driven to electric-driven forms for use in mild hybrid electric vehicles (MHEVs). The superchargers improve the response of the engines at low revolutions and enhance performance. An electric supercharger responds instantaneously, removes turbo lag, and improves the vehicle’s acceleration.
ST is enabling the electric supercharger application with a product portfolio that includes an integrated solution for electric motors using the 48-V three-phase driver L9907 and a 32-bit automotive MCU. The package is completed by LDO voltage regulators and low on-state resistance N-channel power MOSFETs.
The increasing number of electric vehicles (EVs) on the roads has brought about the need for more charging stations, including dc fast-charging stations and CHAdeMO-compliant fast-charging stations. The dc fast charging stations provide vehicles with level 3 charging, enabling a 100-km driving range in around 10 minutes. While level 2 chargers supply ac power to the battery (which is then converted to dc power by the on-board charger), level 3 fast chargers directly deliver dc power, significantly improving charging time.
Currently, dc charging stations target three main power levels: ≤50 kW for city use, 150 kW for highways, and 350 kW for performance cars as well as trucks and buses. The dc fast chargers usually include 20-kW subunits and then stack them up to create a higher-power dc charging system.
Because it is based on a p-GaN gate structure, the GaN device is normally off, which is important for automotive applications, according to ST Sr. Technical Marketing Mgr. for GaN products Rodrigo Marquina. “ST is providing a dedicated unique design with its own design rules. For the 100-V devices we go a step further, and in a system-in-package approach, we integrate logic with our latest silicon-based technology, the BCD9 technology. This provides a simpler GaN power gate voltage driver, while at the same time enabling high-speed logic control.”
Furthermore, the package is characterized by a reduction of parasitic elements, which contributes to lower electromagnetic emissions (EMI). It also improves thermal features thanks to the double-side cooling, further simplifying the choice of thermal-dissipation strategy.
In a presentation at the e-Mobility Forum at PCIM Europe, ST’s Marquina noted that STi²GaN helps to drastically increase operating frequencies (in the megahertz range) for a compact, easie,r and cheaper design at system level: “This integration allows a switching speed up to 1 MHz, and if we go for a more typical PWM or 500 kHz, our target efficiency is 98%; this approach is suitable to address centralized as well as distributed power architectures.”
ST noted at PCIM that it’s already engaged with key partners on STi2GaN.