Better snubber circuits with low-loss capacitors
10 September 2002
Passive Components
Snubber circuits are now able to perform better at high frequencies with new low-loss capacitors from Murata.
The trends in switching power supplies and DC-DC converters are to smaller and lighter designs, higher switching frequencies and lower costs. These need good noise suppression and guaranteed high temperature operation, preferably at no extra cost.
To date, the conventional MLCC transistor snubber used across the collector-emitter of the transistor has had palladium electrodes and a ±15% temperature characteristic dielectric. At higher frequencies, this starts to become lossy and a lower loss capacitor, usually requiring more space, is needed. However, this would take up more space.
To meet this need, Murata has introduced a new 630 V low-loss COG (0 ±30 ppm/°C) dielectric in the original EIA1206 chip size, putting more performance in the same space. This improvement contributes to the size and weight reduction of equipment and makes Murata's GRM31A5C series ideal for resonant circuits in inverters and fluorescent lamps.
It also eliminates the problems of uncertain Pd availability with its attendant price swings. Base metal inner electrodes improve dielectric loss, heat generation at high frequencies, power handling capacity and equipment reliability. The most popular values from 100 to 1000 pF are on offer in COG dielectric.
Rated to 630 V d.c. with a guaranteed withstand voltage of 945 V d.c., the low-loss guarantees operation up to 125°C and both wave and reflow-soldering can be applied. They can replace the ceramic disk or film capacitors that have been used for this task until now.
For more information contact Avnet Kopp, 011 809 6100, [email protected], www.avnet.co.za
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