Increasing efficiency with power MOSFETs

The electronics manufacturing segment is being constantly pushed to pursue increasing the power efficiency. The power MOSFET has been successful in supporting such moves.

High-voltage end >200V power MOSFETs were said to be driven by the power supply, lighting and motor drive markets. The mid-voltage range from >30 to 200V focused on the automotive and telecom markets, and the low-voltage products were driven by portable and computer markets.

According to Zetex Semiconductors, trends driving the demand for MOSFETs included portable applications that focus on smaller size, increased power density, increased functionality and longer battery life; more generally, the increasing demand for efficient DC-DC conversion to support the numerous voltage rails required in today’s systems; growth in LCD panel market requiring MOSFETs for driving CCFL backlight; the need for higher performance and efficient cooling systems cooling (DC Fans); and the move toward switching amplifiers for audio.

As the electronics market was being pushed to increase power efficiency, driven by governments’ legislation for energy conservation, the MOSFET developments to support this initiative were following two main tracks.

One was the shrinking of geometries to enable smaller packaging and higher power densities, and the other was the process and geometry optimization to improve the switching performance. A move to leadless packaging was a parallel activity to support higher power densities.

The need to drive MOSFETs at higher frequency to improve efficiency in power conversion applications and reduce system size was setting challenges for driving MOSFETs. Despite being voltage driven, in order to switch a power MOSFET at high speed requires high current to charge and discharge the gate capacitance.

This is currently an area of focus for Zetex. As a provider of leading-edge bipolar transistors, the supplier offers products that offer high drive current capability in very compact packages.

Keke Ke of Mainland based Guangdong Kexin added that electronic manufacturers were making efforts on decreasing the power dissipation and increasing efficiency, which calls for MOSFET to provide lower RDS (on) to decrease power dissipation. Meanwhile, gate charge and ratio of gate charge should be lowered to reduce conduction loss and switching loss to further increase efficiency.

Demand mostly emanted from portable products for smaller packaging of components. Kexin rolled out a variety of MOSFETs packaged by horizontal pin SOT-723 having the packaging size of 1.2x0.8x0.5mm. Such new packaging made use of PCB’s 1.44mm2 area and can increase the ratio of silicon/packaging area to decrease the power dissipation.

Kexin’s TSSOP-8 production line has been put into use. Compared with SOP-8, it can perform smaller packaging size. E.g., one TSSOP-8 component is up to SOP-8 in terms of performance, but its packaging size is only 25 percent of the SOP-8’s.

(Picture with the report is of Fuyong, Shenzhen, where I'd the pleasure of having lunch with my friends Simon Wang and Edmund. Don't have Kexin's image!)