news digest ♦ Power Electronics


“This is possible because GaN power devices will be grown on a larger, lower cost Silicon substrate”, says Richard Eden, Senior Market Analyst and author of “The World Market for Silicon Carbide and Gallium Nitride Power Semiconductors - 2012 edition”. “The key market driver is the speed at which GaN-on-Silicon devices can achieve price parity with Silicon MOSFETs, IGBTs or rectifiers with equivalent performance.”


IMS Research says the speed of GaN transistor developments has accelerated in the last two years, possibly due to its huge growth potential.


The launch of International Rectifier’s “GaNpowIR” and EPC’s “eGaN FET” devices started the low voltage market in 2010. The emergence of Transphorm and its 600 V GaN transistors in 2011 created considerable interest in the prospects of GaN competing with high voltage MOSFETs and IGBTs. Six of the world’s top ten discrete power semiconductor suppliers are planning to launch GaN power devices in the near future, and some may already be making devices for in-house end equipment.


IMS Research’s report analyses applications ranging from consumer electronics to industrial equipment and renewable energy. The first applications to adopt will be power supplies where the total system cost savings outweigh the unit price penalty of the device.


These include PC & notebook adaptors and servers as well as domestic appliances like air-conditioners, where efficiency improvements are being driven by Government initiatives or regulations. Once reliability and other potential problems are resolved, PV micro-inverters, electric vehicle battery charging and other new applications are likely to adopt GaN power devices in the future.


However, IMS Research says that there are some barriers to main-stream market acceptance of GaN power devices.


The first is availability, as few GaN transistors are available in mass production. Competing manufacturers’ products are non- standard and there are no second-sources.


Secondly, the technology lacks maturity. Overall device performance and GaN material defect rates need improvement.


A third issue is design inertia; the need to educate customers about both the potential benefits of GaN and how to use the devices.


Having said that, GaN could be the power of the future. SiC inverters halve the size


of EV motor systems Mitsubishi Electric says its silicon carbide inverter-equipped EV motor system is the industry’s smallest


Mitsubishi Electric Corporation has developed a prototype electric vehicle (EV) motor system with a built-in SiC inverter.


162 www.compoundsemiconductor.net April/May 2012


The EV motor system is claimed to be the smallest of its kind; it measures just half the dimensions of Mitsubishi Electric’s existing Silicon-based motor system that uses an external inverter.


All power chips in the new inverter are SiC-based, resulting in over 50% reduction of loss compared to the company’s Silicon- based inverter system.


The firm’s existing Silicon-based system consists of separate motors and inverters driving the motors, which requires more space for these components and their wiring.


SiC inverter-equipped EV motor system


The new motor system is expected to enable manufacturers to develop EVs offering more passenger space and greater energy efficiency. The company plans to commercialise the motor system after finalising other technologies for motor/ inverter cooling, downsizing and efficiency.


The global demand for EVs and hybrid EVs (HEVs) has been growing in recent years, reflecting increasingly strict regulation of fuel efficiency and growing public interest in saving energy resources and reducing CO2 emissions.


As EVs and HEVs require relatively large spaces to accommodate their robust battery systems, there is a strong need to reduce the size and weight of motor systems and other equipment to ensure sufficient room in passenger compartments.


Mitsubishi’s newly developed cylinder-shaped inverter matches the diameter of the motor, enabling it to be connected coaxially within a chassis, resulting in a substantial downsizing of the motor system.


Silicon chips have been widely used in power devices for inverter switching. Silicon carbide, however, is now recognised as a more suitable material for chips owing to its electrical characteristics, including a breakdown electric field that is 10 times greater compared to silicon chips. This greater breakdown electric field enables thinner chips, which reduces electrical resistance and lowers loss.


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