27 August 2012

Rohm develops first SiC power MOSFET with internal Schottky barrier diode

Last month, Rohm Co Ltd of Kyoto, Japan  launched the SCH2080KE, a second-generation high-voltage (1200V) silicon carbide (SiC) power MOSFET designed for inverters and converters in power conditioners for industrial devices and photovoltaic power generation. Features include low power loss and high reliability, reducing power consumption and enabling support for smaller peripheral components.

Existing silicon insulated-gate bipolar transistors (IGBTs) commonly used in 1200V-class inverters and converters cause power switching loss due to tail current or recovery of the external FRD, creating a need for SiC power MOSFETs capable of operating with low switching loss at high frequencies. However, conventional SiC power MOSFETs have been plagued with reliability problems, including characteristic degradation due to body diode conduction (e.g. increased ON resistance, forward voltage, and resistance degradation) and failures of the gate oxide film, making full-scale integration impossible.

Also, due to the characteristics of silicon carbide, SiC power MOSFET body diodes typically feature a higher rise voltage (2.5V or more), possibly resulting in increased switching loss during inverter operation.

Rohm says that it has overcome these problems by improving processes related to crystal defects and device structure and reducing ON-resistance per unit area by about 30% compared to conventional, first-generation products, leading to increased miniaturization. The new SiC power MOSFETs do not feature the voltage rise common with Si IGBTs, ensuring low switching loss even during low-load operation.

By using proprietary mounting technology, the SCH2080KE is claimed to be the first SiC power MOSFET to integrate a SiC Schottky barrier diode (SBD) - which conventionally was externally mounted - into the same package. This reduces forward voltage (VF) by at least 70% compared with silicon-based insulated-gate bipolar transistors (IGBTs) used in general inverters, so operating power loss is reduced by 70% or more, says the firm. This not only minimizes switching loss, but enables compatibility with smaller, lightweight peripheral components by supporting frequencies above 50kHz. Also, fewer external components are required, saving space.

Rohm also offers the SCT2080KE, an SiC power MOSFET with no internal SiC SBD. Both the SCH20801KE and SCT2080KE can be configured according to customer requirements. Rohm showcased the SiC power MOSFETs at the TECHNO-FRONTIER 2012 exhibition at Tokyo Big Sight (11-13 July).

Tags: Rohm SiC power MOSFET

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