Ripple current calculator
Estimate capacitor ripple voltage and ripple (AC) current for rectifiers and switching converters. Enter load, frequency, C, and topology to get ΔVₚₚ and Iᵣ(rms).
buck converter ripple current
The speed with which the capacitor empties between pulses of recharging determines the capacitor ripple ( 1/C). In the case of rectifiers, 1/f (half-wave), 1/2 f (full-wave) is the time between peaks in conduction. Heating is defined by ripple current (the AC part of the current flowing through the capacitor). So topology-specific approximations (e.g., I_c,rms = 0.483 I_load for full-wave) should apply, compared to ratings of the capacitor (RMS current or ESR value)
Formula & Table Summary:
Rectifier:
ΔVpp = I_load · Δt / C
(half-wave Δt=1/f ; full-wave Δt=1/(2f))
C = I_load · Δt / ΔVpp
I_c,rms ≈ 0.483·I_load (full-wave), ≈0.707·I_load (half-wave)
Buck converter:
ΔI_L = (Vin - Vout)/L · D / f_s
I_c,rms ≈ ΔI_L / (2√3)
ΔVpp ≈ ΔI_L / (8 f_s C) + (ΔI_L/2)·ESR
capacitor ripple voltage formula
Calculate the capacitor ripple voltage 1vpp and capacitor RMS ripple current (estimate) of rectifiers (half/full wave) and switching converters (buck). To verify the ripple and thermal limits, enter load/current, line/switching frequency, C, L (for converters), VIN/VOUT and ESR.
capacitor ripple calculator
| Topology | Inputs | Computed | Result |
|---|---|---|---|
| Full-wave rectifier | I=1.0 A, f=50 Hz, C=1000 μF | ΔVpp = I/(2fC); I_c,rms≈0.483·I | ΔVpp=1/(2·50·1000e-6)=0.01 V; I_c,rms≈0.483 A |
| Half-wave rectifier | I=0.5 A, f=60 Hz, C=470 μF | ΔVpp = I/(fC); I_c,rms≈0.707·I | ΔVpp=0.5/(60·470e-6)=17.7 mV; I_c,rms≈0.3535 A |
| Buck converter | Vin=12 V, Vout=5 V, L=10 μH, fs=500 kHz, C=47 μF | D=5/12, ΔI_L=(Vin-Vout)/L·D/fs | ΔI_L≈(7/10e-6)*(0.4167/5e5)=0.583 A; I_c,rms≈0.583/(2√3)=0.168 A; ΔVpp≈0.583/(8·5e5·47e-6)=0.0031 V + ESR term |
| Large smoothing cap | I=10 A, f=50 Hz, C=10000 μF | ΔVpp=I/(2fC) | ΔVpp=10/(2·50·1e-2)=0.10 V; I_c,rms≈4.83 A |
| Small converter cap | ΔI_L=0.2 A, fs=200 kHz, C=10 μF | I_c,rms≈ΔI_L/(2√3) | I_c,rms≈0.2/(2·1.732)=0.0577 A; ΔVpp≈0.2/(8·2e5·10e-6)=0.0156 V |
