Smaller package sizes and increased power density levels are the order of the day in circuit designs intended for power conversion. They are just one of a broad range of pressures being exerted onto electronics engineers, however. Energy efficiency and operational reliability are two equally significant demands, along with cost constraints.
Power MOSFETs find wide employment in the switching and amplifying of electronic signals. They are the most commonly used low voltage (sub 200V) switches, but have drawbacks when switching rapidly at higher voltages. Superjunction MOSFETs were developed to help alleviate such problems. They offer reductions in a variety of different areas - including die size, which has a direct influence on device cost. However, they still require close attention to be paid to the system design, particularly in terms of reducing PCB parasitics.
For MOSFETs rated at 600V, more than 95% of the device resistance comes directly from the epitaxial layer. The objective of developing superjunction MOSFETs was to overcome this, using techniques such as deep trench filling.
This is exemplified in the latest generation DTMOS V devices from Toshiba. These are based on a single epitaxial process, rather than the multi-epitaxial process of earlier devices. As a consequence, they offer significant reductions in RDS(ON) (a 17% improvement) and lower EMI noise over the previous fourth generation devices.
The combination of superjunction MOSFETs and Schottky barrier diodes with silicon carbide (SiC) construction is proving to be tremendously helpful to engineers implementing power conversion systems - allowing them to reduce circuit size at the same time as increasing current density. Other advantages of using superjunction MOSFETs over more conventional planar silicon devices are the lowering of conduction losses for a given die size, the curbing of switching losses and reduced heat generation (thus simplifying the thermal management requirements). A further benefit is in relation to improved noise performance - as low EMI noise is increasingly expected from the power sources of applications as diverse as consumer goods, LED lighting, medical power supplies, notebook/tablet adapters.
You can find out more about Toshiba’s DTMOS V MOSFET technology and operational advantages when used in conjunction with SiC diode devices by downloading Toshiba’s white paper: