WOBBLbuck

What is the ripple on this 12 V to 5 V buck at 2 A?

Circuit report
2026-10-15 19:18
OK

Output ripple 8.56 mV peak to peak on 5.07 V (within the 50 mV limit); inductor ripple 0.604 A, peak 2.33 A.

ripple
8.56 mV
output
5.07 V
inductor ripple
0.604 A
duty
43.7%

Confidence high

  • passed hand calculation, steady state, time step convergence

Simulation

Bench setup drawn from this run. A 12 V supply feeds a buck converter switching at 500 kHz into a 2.5 ohm load, and the scope shows 8.56 mV of ripple on 5.07 V. DC POWER SUPPLY 12.00 V CV OSCILLOSCOPE ELECTRONIC LOAD 5.07 V 2.03 A CR VIN VOUT S1 D1 L1 C1 OUTPUT RIPPLE 8.56 mV OK 50 mV limit
Bench setup, drawn from this run
Schematic of Buck converter power stage, open loop at the steady state duty cycle, drawn from the netlist. SCHEMATIC Buck converter power stage, open loop at the steady state V1 12 V S1 on 50 mΩ L1 10 µH D1 SCHOTTKY C1 22 µF R2 10 mΩ RLOAD 2.5 Ω VG pulse 0 to 5 V 500 kHz, 44% on vin 12 V sw out 5.07 V
Schematic, drawn from the netlist
Simulated waveform
Simulated waveform

Checks

statuscheckresult
passhand calculationideal waveform math (triangular inductor ripple dI = 0.583 A through C and ESR) gives 7.95 mV; ngspice 8.56 mV and 0.604 A (8% apart; the math ignores switch and diode drops)
passsteady stateaverage output moved 0.0069% between the last two 20 cycle windows
passtime step convergenceoutput ripple 0.00856 with the normal step, 0.00856 with half the step (0.0022% apart)

Assumptions

  1. Open loop at the steady state duty cycle 43.7%; real controllers add their own ripple and transients.
  2. Switch on resistance 0.05 ohm, Schottky catch diode.
  3. Capacitor ESR 10 mohm, no ESL.