Lecturers at recent EV events presented a view that SiC devices will be widely designed into electric vehicles from 2014 and GaN from 2018. With manufacturers currently designing vehicles to be launched onto the market in 2018, it is predicted that by this date GaN semiconductors will attain price parity with silicon devices. This will make the technology attractive as a replacement for silicon for use in the power electronics in both pure electric and hybrid vehicles.
"Pure electric & hybrid electric vehicles are full of power electronics, from battery management, auxiliary power, braking, valve timing, cruise control, security systems, instrument clusters - all of which are currently suffering the limitations imposed by silicon, as it doesn't switch quickly or cope with elevated temperatures," said Girvan Patterson, CEO of GaN Systems in the UK.
"New generation GaN and SiC semiconductors overcome these difficulties and are lighter, smaller and easier to package. These new devices will lead to dramatic improvements in automotive power electronics and present a major opportunity for the industry," said Patterson.
Julian Styles, director business development at GaN Systems, explained the technological advances in semiconductor materials which he believes will lead to the replacement of traditional silicon in power converters for new generation electric and hybrid vehicles. Styles explained what he sees as the benefits of WBG power semiconductors based on GaN, such as greater efficiency, weight reduction and lower cost to power electronics for EHVs.
Automotive qualification can take up to five years, Roussel pointed out. So even if qualification for use in electric and hybrid electric vehicles is on-going, it will not be clear if SiC has been successful until 2015. Qualification for EV/HEV Charger inverters would be quicker but SiC faces a greater challenge there from silicon superjunction MOSFETs, IGBTs, and also wide-bandgap GaN devices in EVs.
Market analysts Yole Développement describes two scenarios for SiC industry evolution. Its more optimistic scenario will see SiC devices used commercially in EV/HEV from 2015 onwards, taking 11% of the market from silicon IGBT devices by 2020. In the pessimistic scenario EV/HEV implementation doesn't start until 2017/2018, making PV inverters the number one SiC application in 2020.
Today there remains much room for increasing SiC device usage in PV inverter applications, Yole's Philippe Roussel, Business Unit Manager Compound Semiconductors, Power Electronics, LED & Photovoltaics underlined, "Each inverter manufacturer's product line-up has just one or two models with SiC in them, among dozens," he said. "But it's a very positive starting point." That helped SiC power device industry revenues to $76 million in 2012, including R&D but excluding military use. PV inverter producers are the second industry to broadly adopt SiC devices, after manufacturers using SiC for power factor correction in high-end server power supplies.
Some PV inverter manufacturers use a SiC diode and silicon IGBT or MOSFET, and some offer full SiC inverters. "They're just the first attempt, as inverter makers have limited their SiC development investment," Roussel said. "They're doing a simple replacement for silicon devices, taking the minimum extra work." But that means that inverter producers are selling more expensive SiC products on their efficiency, without fully exploiting the material's benefits. "The next step will definitely be a full redesign within the inverter that should fit with SiC's high frequency and temperature capabilities, reducing the number of capacitors and inductors needed," Roussel said.
Forecast of SiC market by application
Working with reverse costing specialist System Plus Consulting, Yole has modelled the benefits of increasing the standard PV inverter switching frequency from 12 to 32 kHz. That shortens the payback time on the SiC investment, and would make large 50 kW SiC inverters cheaper than their silicon equivalents by 2020. Such benefits will help increase annual revenues for SiC devices sold into PV inverters to $200 million by 2020, Yole predicts.
Even though PV inverters are currently better established, EV/HEV inverter producers could still be more advanced in making full use of SiC. "Efficiency drives adoption, but putting SiC in any system could also make it smaller and lighter," Roussel stressed. "For EV/HEV, that is just fantastic. Of course, further adoption outside EVs will help with that necessary cost reduction. As the cost of clean energy technologies continues to come down, seamless and efficient grid integration will help make these resources and products even more affordable, while giving Americans more control over how they use energy in their homes and businesses. WBG semiconductors will help overcome a range of generation, transmission, distribution and end-use challenges to support a cleaner, affordable and more secure U.S. energy mix."