Determining Ripple Current Capability In Tantalum Hybrid Capacitors

By David Evans

Introduction

Tantalum Hybrid® capacitors are finding use in applications ranging from radar phased array antennas and laser power supplies to computer and avionics power hold-up. Many of these capacitors suit military and high reliability needs. Hybrid capacitors have very high specific power compared to electrochemical supercapacitors and high specific energy compared to electrolytic capacitors.

A capacitor has internal resistance and its temperature rises when current is present at its terminals. The temperature rise is proportional to the square of the current and is directly related to the power dissipation. The degree of temperature rise is an important design consideration especially where large currents are necessary, such as in power supply filtering and dc pulse forming applications. This is true not only because a certain maximum temperature must not be exceeded but also because the life of a capacitor is strongly related to its operating temperature.

Because of its high specific power, the tantalum Hybrid capacitor fits where other capacitors do not, but its small size is sometimes a disadvantage with respect to heat dissipation. Electrolytic capacitors with similar electrical characteristics compared to Hybrid capacitors have several times the physical size and therefore have much larger surface areas from which to radiate heat. This paper evaluates the relationship between ripple current and temperature rise in tantalum Hybrid capacitors.