Fifth-Generation Planar Schottky Barrier Diodes Enable Lower Power Consumption of Electronic Equipment

Increasing Demand for Lower Power Consumption to Achieve Carbon Neutrality

In recent years, large-scale weather disasters have become more frequent around the world. Although the link between weather disasters and global warming has not been clearly established, the risk of heavy rainfall and heat waves may increase in the future as a result of the increasing severity of climate change, with ever greater impacts on agriculture, forestry, fisheries, ecosystems, health, industry, and economic activities.

A sustainable future cannot be achieved with industrial and social systems optimized for immediate wealth and growth alone. To address this critical situation, more than 120 countries and regions around the world are taking various steps toward decarbonization, with the goal of achieving carbon neutrality by 2050. The Japanese Government formulated the “Green Growth Strategy Through Achieving Carbon Neutrality in 2050” program in 2021. Japan will promote not only the use of renewable energy sources such as solar power and offshore wind power, but also the use of low-power-consumption vehicles, factory equipment, office equipment and facilities, and home equipment and appliances.

Electronic equipment, which is indispensable to modern society, is likewise required to consume less power. To reduce the power consumption of electronic equipment, we tend to think only of measures for components with particularly high power consumption, such as the processors, displays, and communication circuits in personal computers and smartphones. Although it is important to reduce the power consumption of these components, to contribute to decarbonization, it is also necessary to incorporate measures to reduce power consumption in circuits that are essential for ensuring the stable operation and reliability of devices, such as power supply and protection circuits (Figure 1). In response to such demand, smaller, more power-efficient switching power supplies are increasingly being used even in applications where linear power supplies have been traditionally used to reduce cost.

Figure 1 For decarbonization, lower power consumption is required for power supply circuits in electronic equipment

How to Select Diodes for High-Efficiency Compact Switching Power Supplies

Schottky barrier diodes (SBDs) are used in automotive, industrial, and consumer equipment as rectifiers in switching power supplies and to protect electronic circuits from overvoltage and other problems, due to their high efficiency and small size. They have a lower forward voltage (\( V_F \)), a lower power loss, and better switching characteristics than those of p-n junction diodes. Because of the suitability of SBDs for power-efficient switching power supplies, their application scope is expanding, driven by the development of applications that contribute to decarbonization.

It is essential to select an SBD with the optimal characteristics for the given application. SBDs have a higher leakage current (\( I_R \)) in the reverse direction and generate more heat than p-n junction diodes, resulting in thermal runaway without appropriate thermal design. In general, there is a trade-off between \( V_F \) and \( I_R \), so it is necessary to determine whether low \( V_F \) or low \( I_R \) is required for the given application and select the appropriate SBD.

In addition, it is important to select an SBD with the necessary breakdown voltage and current tolerance for the given application, while providing the optimal balance between \( V_F \) and \( I_R \).

Fifth-Generation Planar Schottky Barrier Diodes Introduced for Further Efficiency

Although there is a trade-off between \( V_F \) and \( I_R \), improvements in the element structure and manufacturing process for SBDs can balance both parameters at higher levels.

ROHM offers a diverse range of products with suitability for different applications, including the ultra-low- \( V_F \) RBS series, the low- \( V_F \) RBR series, the low- \( I_R \) RBQ series, and the ultra-low- \( I_R \) RBxx8 series (Figure 2). These products are used in a wide range of applications, including the automotive market, where particularly high quality is required.

Figure 2 SBDs are available to suit various application needs

At the same time, ROHM is promoting continuous characteristic improvements. In June 2021, ROHM introduced additional fifth-generation products to the RBR series and RBQ series, which employ a new proprietary planar element process. These products achieve a 25% increase in efficiency compared to the previous generation. Both the RBR and RBQ series include products with high reliability in accordance with the AEC-Q101 automotive reliability standard.

Fifth-Generation RBR/RBQ Series Contribute to Lower Power Consumption and Miniaturization

The new additions to the RBR series have approximately 25% better \( V_F \) characteristics than those of conventional products of the same size and achieve lower losses while maintaining the \( I_R \) characteristics required for the intended application (Figure 2, left). With fifth-generation products, it is thus possible to achieve performance equivalent to that of conventional products in a smaller package.

Figure 3 Fifth-generation SBDs with significantly improved basic characteristics
Left: Comparison of forward voltage (\( V_F \)) between RBR series and conventional products.
Right: Comparison of reverse power losses due to reverse current (\( I_R \)) between RBQ series and
conventional products.

The 12 fifth-generation products added to the RBR series (six products each for consumer and automotive applications) have elements encapsulated in 2.5 mm × 1.6 mm PMDE packages. The same characteristics as those of elements previously encapsulated in 3.5 mm × 1.6 mm PMDU packages can be achieved with chips in PMDE packages, reducing the mounting area by approximately 42% compared with that of conventional products. Applications include on-board chargers for electric vehicles (EVs) that are driven at relatively low voltages, LED headlamps, car accessories, and laptop computers.

The new additions to the RBQ series have 60% lower reverse power losses than those of conventional products (Figure 3, right). This further reduces the risk of thermal runaway during high-temperature operation and leads to excellent temperature characteristics. The 12 fifth-generation additions to the RBQ series (six each for consumer and automotive applications) are all 100-V models. They are used in power supplies for high-voltage-drive and high-temperature applications such as industrial equipment, audio equipment, laptop computers, electric vehicles, engine control units, AC-DC converters, and DC-DC converters with secondary-side rectification.

ROHM’s RBR/RBQ series SBDs are essential devices for the decarbonization of electronic equipment.

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