10 August 2023
Transphorm’s GaN first to hit short-circuit robustness milestone key for motor drives
Transphorm Inc of Goleta, near Santa Barbara, CA, USA — which designs and manufactures JEDEC- and AEC-Q101-qualified gallium nitride (GaN) field-effect transistors (FETs) for high-voltage power conversion — has demonstrated up to 5μm short-circuit withstand time (SCWT) on a GaN power transistor with a patented technology. The achievement is claimed to be the first of its kind on record. 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 insulated-gate bipolar transistors IGBTs or silicon carbide (SiC) MOSFETs — a total addressable market (TAM) for GaN of over $3bn over the next five years.
The demonstration was developed with support from Transphorm’s long-term strategic partner Yaskawa Electric Corp of Kitakyushu, Japan (a manufacturer of low- and medium-voltage variable-frequency drives, servo motors, machine controllers and industrial robots). It is reckoned that this makes GaN a highly attractive power conversion technology for servo systems, as it allows for higher efficiency and reduced size compared with 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,” says 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,” he adds. “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 15mΩ 650V GaN device. Notably, that device reaches a peak efficiency of 99.2% and a maximum power of 12kW in hard-switching conditions at 50kHz. 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 5μm with no additional external components, thus retaining low cost and high performance,” notes Transphorm’s chief technology officer & co-founder Umesh Mishra. “We understand the demands of high-power, high-performance inverter systems,” he adds. “We have a long history of strong innovation, and we’re proud to say that experience helped us bring GaN to the next level.”
The full description explaining the SCWT achievement, the demonstration analysis, and more is expected to be presented at a major power electronics conference next year.