Author:
Heath Ogurisu, Technical Product Marketing Manager, Rohm
Date
06/12/2024
PDF
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Figure 1: Reverse recovery time & power loss: PrestoMOS vs. Standard SJ-MOS
This trend extends beyond consumer electronics into industrial and commercial applications such as lighting power supplies, pumps, and motors. However, miniaturization isn’t merely a function of reducing the physical size; it also demands improved power efficiency and reliability. A major challenge is designing power supplies that fit into increasingly smaller spaces without compromising on their ability to deliver sufficient power, maintain efficiency, and function durably in various operational environments.
Traditionally, achieving higher voltage ratings and low on-resistance in MOSFETs involved trade offs in terms of size. Super-Junction MOSFETs (SJ-MOS) leverage a specialized multi-epitaxial growth process that enables a denser doping of the semiconductor, which results in a distinctive structural formation. The result is a reduction in the ON-resistance while retaining high-voltage blocking capabilities. Consequently, SJ-MOS are able to effectively manage higher power levels within a compact size — critical in modern electronic devices demanding compact power solutions. The objective of this paper is to provide an understanding of SJ-MOS, outlining its role in achieving a balance between miniaturization and high performance. It will also discuss SJ-MOS design and operational functionality, and introduce ROHM’s SJ-MOS for industrial applications.
The terms “Super Junction MOSFETs,” “SJ-MOS,” and “SJ MOSFET” are used interchangeably throughout the paper.
The superior performance of SJ-MOS in terms of high breakdown voltage and low on-resistance is attributed to a unique structure and fabrication process. Traditional MOSFETs are built using a planar structure, where the breakdown voltage is a function of the doping concentration as well as the thickness of the N-epitaxial layer, forcing a trade-off between higher breakdown voltage and increased ON-resistance due to higher resistivity in the heavily doped drift region. SJ-MOS overcome this limitation by introducing a vertical structure of alternating P and N layers along the drift region, called the “Super-Junction.” Advanced techniques like Deep Trench Technology and Multi-Epitaxial Layer Growth allow for precise control over the doping levels and thickness of each layer, achieving a balance that maximizes the breakdown voltage. This ensures that the electric field is evenly distributed across the semiconductor. A low ON-resistance is achieved by increasing the doping concentration of the N-region to reduce the width of the depletion region.
ROHM has introduced a line of compact SOT-223-3 package 600V SJ-MOS for commercial and industrial applications. This product line includes the R6004END4, R6003KND4, R6006KND4, R6002JND4, and R6003JND4 SJ-MOS. Offering distinctive features, three of the models have been optimized for power supplies. The R6004END4, characterized by its low noise operation, is ideal for applications where noise is a concern and can seamlessly replace traditional planar MOSFETs, while the R6003KND4 and R6006KND4, are ideal for systems requiring high-speed switching and high efficiency. The R6002JND4 and R6003JND4 series use ROHM’s PrestoMOS technology which achieves shorter reverse recovery times (trr).
“Presto” is an Italian musical term meaning “very fast.” PrestoMOS technology is engineered to minimize the reverse recovery time of the MOSFET’s internal diode, which is highly beneficial in applications involving high-speed switching, e.g., pulse width modulation (PWM) in motor drives, where even microsecond delays can result in efficiency losses. In motor control systems, shorter reverse recovery times allow for precise control over motor speeds and torque, leading to finer adjustments and enhanced performance. Moreover, lower switching losses enhance the power efficiency and lower thermal stress on components, extending their lifespan and reliability.
ROHM’s SOT-223-3 600V MOSFETs offer several improvements over standard SJ MOSFETs in terms of size and compactness, switching speeds, while the R60xxENx/R60xxKNx models offer low losses, and low noise operation. Below is a look at these features in closer detail.
ROHM SOT-223-3 600V MOSFETs balance small design and robust performance in a package that is smaller in area and thinner than TO-252 packages, addressing the critical need for space savings without compromising the performance. Their SOT-223-3 packages are also compatible with TO-252 land patterns for easy integration into existing circuit boards. This feature could be useful for designers looking to upgrade their systems with more advanced components without undergoing a redesign of their circuit boards. This compatibility not only simplifies the integration but also reduces the time and cost of implementing new technology into existing designs.
The R600xEND4, R600xKND4, and R600xJND4 SJ-MOS offer a considerable reduction in area and thickness at 31% and 27% respectively, compared to standard TO-252 products. In lighting power supplies, this miniaturization translates into efficient use of space within LED drivers and lighting control circuits, allowing for slimmer, more attractive lighting solutions without sacrificing electrical performance. For pumps and motors, particularly in appliances or HVAC systems, their reduced size allows designers to create smaller, more energy-efficient devices. Their SOT-223-3 package measures 6.5×7.0×1.66mm which improves the overall compactness, and allows these MOSFETs to be integrated into smaller circuit boards and/or space-constrained applications.
Figure 2 shows the outline drawings of DPAK and the SOT-223-3 package. In comparison with DPAK, SOT-223-3 is 31.1% smaller in area and 48.3% smaller in area:
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Figure 2: Outline drawings of DPAK and the SOT-223-3 package size comparison
In power supplies, especially those used in lighting and home appliances, minimizing electrical noise is vital for ensuring consistent performance and avoiding interference that can disrupt the functionality of nearby electronics. The R600xEND4 SJ-MOS ensures low noise operation in the power supplies, contributing to the development of more accurate and dependable devices.
The high-speed switching capability of the R600xKND4 series is crucial for efficient operation in power conversion and regulation circuits. In LED lighting systems, faster switching enables more precise control over the light intensity and color, contributing to energy savings and extending a LED’s lifespan. Similarly, rapid switching is beneficial in dimming systems to ensure smooth and flicker-free illumination The fast switching operation of SJ-MOS are also suitable for applications requiring rapid adjustments, such as variable-speed pumps or fan controllers.
PrestoMOS technology enhances the reverse recovery time of these MOSFETs, which is vital in applications involving motor drives and other inductive loads where rapid switching is frequent. The reduced switching losses directly translate to lower power consumption and diminished heat generation within the device. This reduction in thermal stress not only extends the lifespan of the SJ-MOS but also contributes to the overall reliability and performance of the system.
ROHM SJ MOSFETs allow designers and engineers to design more compact power supplies for industrial and commercial lighting systems such as LED drivers and fluorescent lighting ballasts. For example, they deliver high-speed switching capability with reduced switching losses in PWM controllers in LED drivers — by switching rapidly, these products help to minimize energy wastage during the transition phases and enhance the overall efficiency of the power supply. The low ON resistance of ROHM’s SJ-MOS also translates to less heat generation during operation, allowing for simpler and more cost-effective thermal management solutions.
In industrial pumps, ROHM solutions deliver substantial benefits over typical SJ-MOS in terms of efficiency, reliability, and compactness. Their shorter reverse recovery times minimize switching losses in AC-DC converters for industrial pumps, which leads to increased efficiency. A high voltage withstand capability also ensures stable operation under fluctuating voltages. Moreover, the small footprint of the SJ-MOS allows engineers to design compact and lightweight systems for industrial and consumer applications where space is at a premium.
ROHM SJ MOS also achieves enhanced performance and energy savings in motor applications, industrial machines, and consumer appliances. These MOSFETs offer low ON-resistance which lowers conduction losses in motor control systems as well as ultra-fast switching in motor drive inverters, contributing to overall system efficiency. The robustness of these SJ MOS ensures stable operation over a wide operating temperature range and under various load conditions.
ROHM’s Super-Junction 600V MOSFETs play a crucial role in creating energy-efficient designs. The combination of low ON-resistance and high-speed switching significantly cuts power losses, leading to energy-efficient devices and systems. However, the environmental impact of ROHM's MOSFETs extends beyond just energy efficiency. By enabling devices and systems to operate more efficiently, ROHM’s SJ-MOS contribute to reduced energy consumption and lower carbon emissions, aligning with global environmental sustainability goals. Their compact sizes also lead to smaller products, reducing the use of materials and contributing to less waste and a smaller environmental footprint.
The unique construction of Super-junction MOSFETs enables a high breakdown voltage and low ON-resistance. This structure is a departure from traditional planar MOSFETs, utilizing a vertical arrangement of alternating P-N layers. The outcome of this technology is a component that is compact, yet does not sacrifice performance or reliability. ROHM’s SOT-223-3 SJ MOSFETs not only meet stringent demands of miniaturization in electronic applications, but also address the need for energy efficiency and environmental sustainability. Their compact sizes, fast switching capabilities, and low noise operation make them suitable for a variety of applications, including lighting power supplies, industrial pumps, and motor control systems.
