Hold-up Capacitance



Suggests a capacitance value for power-supply interruption based on several inputs like downstream circuit power dissipation, maximum holdup time, and voltage requirements.

High reliability electronics frequently require some sort of short-term power interruption tolerance, specified in milliseconds.  This worksheet will allow the user to find the amount of capacitance required to hold up a piece of electronics equipment.  The internal power supply (that regulates power from outside) often has a hold-up circuit that charges a capacitor whose voltage is bled off when power is interrupted.  A boost converter is used to store additional energy and gain a greater holdup margin.  When bled, the voltage off the capacitor is buck/boost regulated to normal operational range for the held-up equipment.  Large-value capacitors are greatly affected by temperature and have fairly large tolerances in addition.

Calculation Reference
Pasahow, Edward. Electronics Pocket Reference, 2nd Edition. New York: McGraw-Hill, 1994.


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Submitted On:
22 Dec 2009
File Size:
68.50 Kb
File Version:
File Author:
Jason B Mansfield Sr

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Comments: 2
samholgen 1 year ago
very interesting and nice. good job!
AB9BI 12 years ago
Thanks AB9BI I have extended your existing XLC pro subscription by 6 months and added the usual graphics and links to your download page. I have learned a little about capacitors too. Well done.