Adaptation of solid tantalum chip capacitors for high frequency DC-DC power supplies

In the field of power supplies, switching frequencies were previously limited to 50 or 100 kHz, therefore requiring the almost exclusive use of solid or nonsolid aluminium electrolytic capacitors for input/output filtering. The increase of these frequencies up to 500 kHz, 1 MHz or even more now allows the use of capacitors with different technologies. In this context, surface mount tantalum power capacitors, specific for this kind of application were developed. After having indicated the main characteristics of capacitors used in switching power supplies and their real operation stresses, the authors describe the technological solutions they have chosen for the manufacture of tantalum capacitors with regard to required characteristics. They present the results obtained using these capacitors submitted to usual climatic stresses and capacitors fitted in power converters after 2000 hour endurance tests. The results obtained after ripple current tests are also presented. Finally, the authors discuss the lessons learned from these investigations and the conclusions they have drawn.