The achievement is the first of its kind on record, marking an important milestone for the industry, as it proves Transphorm GaN’s ability to meet the required short circuit capabilities of rugged power inverters such as servo motors, industrial motors, and automotive powertrains served traditionally by silicon IGBTs or silicon carbide (SiC) MOSFETs.
The demonstration, developed with support from Yaskawa Electric – a specialist in low and medium voltage drives, servo systems, machine controllers, and industrial robots – shows GaN as being a highly attractive power conversion technology for servo systems, as it allows for higher efficiency and reduced size compared to incumbent solutions.
To do that, GaN must pass stringent robustness tests, of which, short-circuit survivability is the most challenging. In case of short-circuit faults, the device must survive extreme conditions with both high current and high voltage. The system can take up to a few microseconds to detect the fault and shut down the operations. During this time, the device must withstand the fault on its own.
“If a power semiconductor device cannot survive short-circuit events, the system itself may fail. There was a strong perception that GaN power transistors could not meet the short circuit requirements needed for heavy-duty power applications such as ours,” said Motoshige Maeda, Department Manager of Fundamental R&D Management Department, Corporate Technology Division, Yaskawa. “Having worked with Transphorm for many years, we believed that perception to be unfounded and have been proven right today. We’re excited about what their team has accomplished and look forward to demonstrating how this new GaN feature can benefit our designs.”
The short-circuit technology has been demonstrated on a newly designed 15 mΩ 650 V GaN device. Notably, that device reaches a peak efficiency of 99.2% and a maximum power of 12 kW in hard-switching conditions at 50 kHz. The device demonstrated not only performance, but also reliability, passing high-temperature high-voltage stress requirements.
“Standard GaN devices can withstand short-circuit for only a few hundredths of nanoseconds, which is too short for fault detection and safe shut-down. However, with our cascode architecture and key patented technology, we were able to demonstrate short-circuit withstand time up to 5 microseconds with no additional external components, thus retaining low cost and high performance,” said Umesh Mishra, CTO and Co-Founder, Transphorm. “We understand the demands of high-power, high-performance inverter systems. We have a long history of strong innovation, and we’re proud to say that experience helped us bring GaN to the next level. This is yet another validation of Transphorm’s global leadership in high voltage GaN robustness and reliability and will be a gamechanger for GaN in motor drives and other high-power systems.”
