Photoflash capacitor

A photoflash capacitor is a capacitor used in flash cameras, professional flashes, and solid-state laser power supplies. Their typical purpose is to power a high voltage flash tube, which then illuminates a photographic target or optically pumps a laser rod. As flash tubes require very high current to operate, photoflash capacitors are designed to safely supply high discharge current pulses without excessive internal heating. Compared with electrolytic capacitors usually used for power supply filtering at power frequency, a photoflash capacitor is designed to have lower series inductance, similar or higher capacitance value, (often) a higher rated voltage, and a low series resistance.

Nominal voltage for a small camera's photoflash capacitor ranges from 300-330 volts. The nominal capacitance is around 80-160 µF (microfarads) in most disposable cameras, with larger values in larger flash units. [ Forrest M. Mims, III, "Forrest Mims' Circuit Scrapbook II", Howard W. Sams & Co., Indianapolis IN, ISBN 0-672-22552-2, page 149. Mims gives the rating of the Kodak Disc camera flash as 160 uF and 180 volts. ] Their maximum operating temperature ratings are often mediocre in comparison to other capacitors, typically 55°C (compared to 85°C or greater for regular capacitors). Professional photoflashes may have larger flash tubes, and contain larger capacitors to supply the appropriate power.

Due to their ability to deliver a pulse of high current, photoflash capacitors are sometimes used in railgun and coilgun designs.

References