5 Nov 2012

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As the trend towards greener energy applications continues, more electrical power is obtained from energy storages devices for use in electric vehicles, solar micro-inverters, photovoltaic string inverters, etc.

Along with this, there are stricter regulations and standards for power and efficiency that need to be complied with in system design. One of the main components in a green energy application is the power switching device, and its current and voltage handling capability always seems to increase as the load requirements keep on increasing.

STMicroelectronics is now positioned to assist technology companies in satisfying these power and efficiency targets set by eco-design standards with their new family of reliable high-efficiency power products.

As a major supplier of super-junction MOSFETs, STMicroelectronics now offers the highest voltage rating in the market with their new SuperMESH 5 Power MOSFETs. These new N-channel enhancement mode MOSFETs are the first in ST’s SuperMESH 5 fifth-generation super-junction family.

The super-junction technology is based on an innovative proprietary vertical structure, which results in a drastic reduction in on-resistance and ultra low gate charge. This family includes what is claimed to be the first super-junction transistors (MOSFETs) capable of withstanding peak voltages up to 950 V. With a little lower voltage rating (900-V), some devices are said to have the highest energy efficiency available, and with yet a little lower voltage rating, an 850-V device (the STL23N85K5) has the most compact size available with an ultra thin PowerFLAT 8x8 HV package.

This surface-mount package has a footprint of 64mm2 and a mounted height of 1mm, which is well below industry standards, such as the D2PAK package.

The 950V STx20N95K5 and the 900V STx21N90K5 come in various package options. MOSFETs that use the super-junction technology are able to achieve higher operating voltages and very low electrical on-resistances relative to the package size. With given dimensions for overall size, these MOSFETs enable power supplies to operate with greater reliability and energy efficiency. Energy efficiency can be measured by the Figure of Merit (FOM), which indicates the device’s overall energy efficiency when switching on or off.

The 900V STP21N90K5 claims to have the world’s best FOM, which is 62.5% better than any comparable alternative. This is the result of a very low RDS(on) and an ultra low gate charge.

Each MOSFET device has three integrated Zener diodes for protection against ESD and transients. There are two Zener diodes built in between the gate and the source and one between the drain and source. There would be no need to use external components for protection as transients are safely absorbed through the Zeners.

Other important design parameters include a gate-Source Breakdown Voltage of 30 V, a continuous drain current of 18.5 A, a resistance drain-source RDS (on) of 0.299 Ohms, a power dissipation of 250 W, and a temperature range of - 55 C to +150 C. These devices are 100% avalanche tested, and have an extremely high dv/dt capability.

The latest fifth generation SuperMESH 5 technology provide a good combination of energy efficiency and safety margin in a compact and cost-effective form factor, which enables designers to use these MOSFETs as the main power switch for LED lamps, panels, and displays.

- James Reinholm