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TOOL IDB-ELE-003
Capacitor energy

Desktop only

Engineering tools are available only on desktop screens.

Capacitor energy & hold-up

Stored energy and how long the cap keeps a load running between V0 and Vmin. Sizes bulk caps for brown-out ride-through.

Hold-up window — V drop
0 V V0 Vmin Usable energy
Engineering notes

Formulas

  • Stored: E = ½ · C · V²
  • Usable: ΔE = ½ · C · (V0² − Vmin²)
  • Hold-up at const I: Δt = C · (V0 − Vmin) / I

Caveats

  • Caps lose capacitance with ageing and bias — derate ceramics 20–50%.
  • Electrolytics have ESR; high-current discharge adds IR drop.

Result

Live