news digest ♦ Power Electronics
minimize fossil fuel consumption, development efforts are underway to increase the efficiency of components in devices and the electrical grid. Opportunity The power electronics or power management market addresses electronic components used in the efficient delivery of electrical power to the end user.
Typical applications include DC-DC and AC-DC power conversion for consumer devices such as PCs, cellular handsets and power supplies. The increasing consumption of data by enterprises and cloud storage is driving the need for high performance servers and server arrays. Applications requiring much higher power handling include inverters used to convert DC power into AC for grid connectivity and electric motor drives used in electric and hybrid electric vehicles (HEVs), as well as a number of other applications. Any power management technology incurs loss when converting current. With the growing emphasis on energy efficiency and renewable energy sources, there is a strengthening demand for devices that optimize the efficiency of this conversion, even if by only a few percent.
The migration towards micro-generation of energy through a distributed grid, with production on a much smaller scale will require large numbers of inverter modules and systems to feed the electricity into the grid as efficiently as possible. In addition to the benefits of a future that is not so dependent on fossil fuels, the electric grid provides an enormous opportunity. The U.S. electric grid, alone is estimated to contain more than 200,000 miles of high-voltage transmission lines and 5.5 million miles of local distribution lines, connecting many thousands of generating power plants to factories, homes and businesses1. Various estimates place the size of the global semiconductor device market (discrete devices, ICs and modules) for power electronics applications at somewhere between $15 billion and $20 billion dollars in 2012! This value is expected to grow in the future as power generation sources increase, companies become more conscious of energy consumption and the usage of consumer devices continues to increase quickly.
Technology Currently, the power management device market is dominated by silicon MOSFETs and IGBTs, technologies that replaced the vacuum tubes of the 1940 and 1950s. There is still a lot of development activity aimed at improving the performance of devices using these technologies. There is also a growing concern that these legacy technologies will not support the anticipated evolution of the grid. In some applications, requirements for blocking voltages, switching frequencies and efficiency already exceed the capability of silicon- based devices. With this as the backdrop, wide bandgap materials, primarily GaN and SiC are generating significant interest. The hope is devices using these materials will increase the efficiency and the reliability of the electric grid as it evolves.
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The electrical properties of these materials should enable higher switching frequencies, higher blocking voltages, lower switching losses, better thermal conductivity and higher operating temperatures. At present, SiC is farther along than GaN for these high power electronics applications. In the near term, Strategy Analytics expects SiC to be the primary replacement technology for silicon power devices, while GaN seeks initial commercial traction in applications with breakdown voltages of less than < 600V and power requirements of less than 5kW. Generic advantages of wide bandgap materials over silicon in power electronics device applications include:
· ·
Lower on-resistances, which result in lower con- ductivity losses and higher overall efficiency
Higher breakdown voltages: available Si Schott- ky diodes have breakdown voltage up to 300V, the first commercial SiC Schottky diodes are rated at 600V
· ·
Higher thermal conductivity compared to Si: this leads to a lower junction-to-case thermal resis- tance, allowing more efficient heat transfer
Higher temperature operation: SiC devices can operate up to 600°C, while Si devices can oper- ate at a maximum junction temperature of only 150°C
· · · ·
Forward and reverse characteristics that vary only slightly with temperature and time
Lower reverse recovery current, reducing switching losses and electromagnetic interfer- ence (EMI)
Operation at frequencies >20 kHz, which is not possible with Si-based devices at power levels of more than a few tens of kilowatts
Higher voltage input/output ratios that allow a single stage for DC-DC conversion from 48V to 1V, compared with a silicon power MOSFET converter that would normally require two or more stages
Initially, GaN-based devices seemed a likely fit for applications where the high voltage and power handling capability, coupled with conversion efficiencies than were higher than the silicon equivalents, would create a high- value niche. The advantages of wide bandgap materials for power electronics applications have partly been borne out by the deployment of SiC devices in hybrid electric vehicles, but the penetration of GaN-based power devices may be more likely in lower-voltage applications, where SiC is proving to be too expensive. In the power management segment, power conversion applications
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