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10 February 2009


STMicroelectronics launches SiC Schottky diodes

Power semiconductor manufacturer STMicroelectronics of Geneva, Switzerland has launched silicon carbide (SiC) Schottky diodes, targeting the saving of the energy normally lost during switching (since ordinary silicon diodes used in switched-mode power supplies lose up to 1% efficiency by not turning off immediately).

The firm says that the STPSC806D and STPSC1006D SiC Schottky diodes are especially useful in converters for solar power systems, where every fractional efficiency percentage is valuable. Power supplies for servers and telecom systems, which are operational around the clock, can also benefit from the cumulative savings of the apparently small improvement in efficiency. The diodes can also be used in motor controllers, which are deployed in large numbers, saving the environmental impact of many thousands of Watts of generated energy.

Moreover, by saving the energy normally dissipated as heat by the silicon diode, SiC technology allows a lower maximum current rating for the diode, enabling smaller components to be used without sacrificing usable power. In high-power applications where heat-sinks are normally used, these can also be made smaller, leading to more compact power supplies delivering higher power density.

A further benefit for switched-mode power supply (SMPS) designers is that SiC diodes allow higher switching frequencies, which enable other components such as filtering capacitors and inductors to become smaller and less expensive, as well as consuming less power.

SiC technology can deliver these benefits because no reverse recovery charge accumulates during the diode’s normal conduction period. When a conventional bipolar silicon diode is turned off, this charge must be dispelled by recombination between groups of charge carriers close to the diode junction. The current flowing during this recombination period is called the reverse recovery current. This undesired current, when combined with the voltage across associated semiconductor power switches, generates heat that is dissipated by the switches. By eliminating this reverse recovery charge, SiC Schottky diodes have much lower switching losses across the board, leading to higher efficiency and lower heat dissipation.

The 8A-rated STPSC806D and 10A STPSC1006D, for 600V applications, are in full production in the industry-standard TO-220AC package, and available at $3.9 and $4.9, respectively, in quantities of 10,000.

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