TEChNOLOgy REviEW
Developments in passive components provide solutions for PSU design
this review Focuses on some oF the new products From a number oF leading manuFacturers and highlights a Few key attributes that will prove useFul to engineers working on power supply design.
Designers of power supplies (PSUs) face a number of challenges: they need to deliver high quality solutions that address a range of criteria and standards. Designs not only need to meet basic input/output requirements for their target applications, but frequently need to do so in harsh and demanding environmental conditions. Efficient and reliable operation is increasingly taken for granted but should never be overlooked – superior performance can provide differentiation in a fiercely competitive market. Safety is another facet of power supply design, and achieving compliance with international standards is a prerequisite in the component selection process for many equipment buyers. These requirements do not just impact the design of the power
supply itself; they extend to components used within the PSU, even commonplace passive devices such as capacitors, inductors and resistors. Fortunately component vendors are well aware of this and offer products specifically tailored for use in various power supply applications.
capacitors (electrolytic and ceramic) The cylindrical can aluminium electrolytic capacitor has been the mainstay of most switched-mode powers supplies (SMPS) and uninterruptable powers supplies (UPS) for many years, where it provides the higher values of storage capacitance essential for these designs. Recent developments from manufacturers such as
Kemet include new screw terminal capacitors that are designed for high-voltage and high- ripple-current applications. The ALS30/31 series is ideally suited for industrial and commercial applications that demand high reliability and long-life expectancy such as frequency converters and UPS and SMPS systems. The low-inductance ALS30/31 series screw terminal
Kemet ALS30/31
www.avnet-abacus.eu 16
capacitors address internal voltage peaks in frequency converters that are used in inverter and motor drive applications. Ideally suited for industrial and commercial applications that demand high reliability and long-life expectancy, the electrolytic capacitors reduce the inherent inductance by as much as 40%, lowering voltage and allowing the use of lower-rated and lower-cost associated circuitry. Exhibiting excellent surge voltage characteristics (withstanding up to 600V for
Panasonic V-FT Series
500ms), the capacitors offer a life expectancy of up to 20,000 hours at +85°
C and the range is rated for operation from 25 to 500V DC and
capacitance values from 100μF to 680,000μF. Another new electrolytic capacitor, which targets use in switching
power supplies and DC/DC converters among other applications, is the V-FT series of surface-mount low-ESR (Equivalent Series Resistance) aluminium electrolytic capacitors from Panasonic Industrial. Responding to market demands for high performance within small- size formats, the series disposes of high capacitance and low resistance values combined with small-sized cases with diameters from 4 to 10mm. The device’s excellent performance is achieved with the use if high-capacity electrode foil and sophisticated low-resistance technology. ESR has been reduced down to 50% of that offered by previous Panasonic capacitor families such as the V-FK and V-FP and also to comparable competitive products. Offering high stability operation, ripple current handling capability has also increased by up to 1.4 times. Electrical characteristics include a voltage range of 6.3 to 50V DC and a capacitance range from 10μF to 2200μF. The operating temperature range is –55 to +105°
C with an endurance figure of 2000 hours at +105° C focus magazine - issue 17
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