Researchers at the Fraunhofer Institute of Applied Solid State Physics (IAF) in Germany have made major breakthroughs in the field of gallium nitride power devices. Integrated on a gallium nitride semiconductor chip, the function of the voltage converter of the gallium nitride power integrated circuit has been greatly improved, and it has brought hope for the manufacture of a more compact and more efficient electric vehicle car charger.
Electric vehicles need more flexible charging methods to be more competitive in the market. In order to make charging as convenient as possible using AC charging stations, wall charging stations or traditional plugs and sockets, car chargers are an essential key equipment for electric vehicles. Because it needs to be carried in a car, the car charger must be as compact and lightweight as possible and cost-effective. Therefore, very compact and efficient power electronics systems are needed, such as voltage converters.
Integrate multiple devices on a single chip
The Fraunhofer Institute of Applied Solid State Physics (IAF) in Germany has been engaged in research on monolithic integration of power electronic devices for many years. This research work requires the use of third-generation semiconductor material gallium nitride (GaN) to integrate power devices, control circuits, sensors and other devices onto the same semiconductor chip. In 2014, researchers successfully integrated intrinsic flywheel diodes and gate drivers into a 600-volt power transistor. On this basis, the researchers successfully operated a gallium nitride half-bridge monolithic integrated circuit at 400 volts for the first time in 2017.
Recently, they have obtained the latest research results. For the first time, they have integrated a current and temperature sensor, a 600-volt power transistor, an intrinsic flywheel diode, and a gate driver into a monolithic gallium nitride power integration with a size of only 4 × 3mm2. Circuit chip. As part of the GaNIAL-based integrated high-efficiency power electronics technology (GaNIAL) research project, researchers have verified all the functional characteristics of gallium nitride power integrated circuits and successfully achieved a breakthrough in the integration density of power electronics systems. By integrating sensors on GaN chips, researchers have succeeded in significantly improving the functionality of GaN technology in the power electronics field.
Integrated sensors for direct control
Compared with the traditional voltage converter, the newly developed power integrated circuit not only has a higher switching frequency and higher power density; it also provides a fast and accurate monitoring of the chip status inside the chip. Although the increasing switching frequency of gallium nitride-based power electronics has helped increasingly compact designs, it has also placed higher requirements on monitoring and control. This means that integrating sensors in the same chip will bring huge advantages.
Previously, current and temperature sensors were external applications to GaN chips. After the internal integration of the chip is implemented, the transistor current can be measured without feedback, closed-loop control and short-circuit protection can be realized, and the system space is greatly saved compared with the application of traditional external current sensors. The temperature of the power transistor can be directly measured by the monolithic integrated temperature sensor, thus eliminating the temperature deviation caused by the distance between the sensor and the measurement point. The integrated temperature sensor measures thermal critical points faster and more accurately than previous external sensors.
The monolithic integration of GaN power electronic devices with sensors and control circuits saves chip surface space, reduces assembly costs, and improves system reliability. This is critical for applications that need to integrate a large number of small, efficient systems in a limited space to improve electrical characteristics such as electrical mobility. The new GaN monolithic power integrated circuit chip is expected to be the basis for further development of more compact car chargers.
Leverage the unique characteristics of GaN materials
In the process of making a new type of monolithic integrated circuit, researchers deposited gallium nitride semiconductor material on a silicon substrate to form a power electronic device structure of gallium nitride on silicon (GaN-on-Si). Material characteristics: Current flows parallel to the chip surface, so that all connections are located on the top of the chip and connected through a conductor path. This laterally structured gallium nitride device helps integrate multiple components such as transistors, drivers, diodes, and sensors on a single chip. In addition, compared with other wide band gap semiconductor materials such as silicon carbide, gallium nitride has a large market advantage. GaN can be deposited on a large-area silicon substrate at low cost and is more suitable for large-scale industrial production.