Energy-efficient power supplies benefit from uprated superjunction devices from ST

March 14, 2013 // By Paul Buckley
STMicroelectronics has introduced special fast-acting variants of the company’s advanced superjunction power MOSFETs used in energy-efficient consumer products, computing and telecom systems, lighting controllers and solar energy equipment.

The latest devices step up efficiency in the type of power supplies often used in equipment such as mid-sized televisions in the 200-500 W power range. If fitted in each of the 200 million LCD TVs produced each year, the new MDmesh II Plus Low Qg (low gate charge) power transistors featuring reduced gate charge could reduce greenhouse gas emissions by more than 140,000 tons per year, which is equivalent to taking around 30,000 passenger vehicles off the road .

Perfected only by a small number of manufacturers, superjunction technology allows power transistors to combine small size, high voltage capacity, and outstanding energy efficiency when turned on. ST is a world leader in this type of technology with its MDmesh power MOSFETs, and now delivers even better performance with its latest MDmesh II Plus Low Qg family. These devices feature a reduced internal charge for high efficiency when switching as well as when conducting, saving even more energy in resonant-type power supplies that are widely used in LCD TVs.

The enhanced design of the new devices results in a low gate charge (Qg) as well as low input and output capacitance. Each of these factors contributes to faster and more efficient switching, which encourages designers to use superjunction transistors in the resonant type of power supplies typically seen in LCD TVs. Until now, superjunction transistors have been used most effectively in hard-switching topologies, where the device is made to switch even while the current and voltage remain high. In a resonant power supply two inductors and a capacitor (LLC converter) ensure the transistor is switched at zero voltage to smooth the flow of energy in the system and help increase efficiency. The new MDmesh II Plus Low Qg family is also highly resistant to the effects of large and sudden changes in applied voltage (high dv/dt ruggedness), which can damage transistors and cause spurious switching. This allows the latest devices