Calculator Inputs
Use the responsive grid below. It shows three columns on large screens, two on medium screens, and one on mobile.
Example Data Table
Use these sample cases to test the calculator and compare typical ripple levels across common converter topologies.
| Topology | Vin | Vout | fs | L | Iout | Ripple current |
|---|---|---|---|---|---|---|
| Buck | 24 V | 12 V | 200 kHz | 68 µH | 4 A | 0.441 A p-p |
| Boost | 12 V | 24 V | 100 kHz | 100 µH | 2 A | 0.600 A p-p |
| Buck-Boost | 18 V | -36 V | 150 kHz | 120 µH | 1.5 A | 0.667 A p-p |
Formula Used
Buck converter
Duty relation: D = Vout / Vin
Ripple current: ΔIL = (Vin - Vout) × D / (L × fs)
In a buck stage, the inductor sees Vin - Vout during on-time and -Vout during off-time.
Boost converter
Duty relation: D = 1 - (Vin / Vout)
Ripple current: ΔIL = Vin × D / (L × fs)
In a boost stage, the inductor charges from the source during on-time and discharges toward the output during off-time.
Buck-Boost converter
Duty relation: D = |Vout| / (Vin + |Vout|)
Ripple current: ΔIL = Vin × D / (L × fs)
The ideal output polarity is negative. The calculator accepts a positive magnitude, then applies the sign internally.
Useful supporting expressions
T = 1 / fs, ton = D × T, toff = (1 - D) × T
IL,min = IL,avg - ΔIL/2, IL,max = IL,avg + ΔIL/2
Ripple ratio = (ΔIL / IL,avg) × 100%
How to Use This Calculator
- Select the converter topology: Buck, Boost, or Buck-Boost.
- Enter the input voltage and the desired output voltage magnitude.
- Enter switching frequency, inductance, and output current.
- Choose auto duty mode to derive duty from voltages, or manual mode to test a fixed duty cycle.
- Set a target ripple percentage if you want a recommended inductance value.
- Press Calculate Ripple Current to show the result block above the form.
- Review ripple current, inductor current limits, operating mode, and waveform graph.
- Use the CSV and PDF buttons to export the result summary.
FAQs
1. What is inductor ripple current?
Inductor ripple current is the peak-to-peak change in inductor current during one switching cycle. It reflects how much current rises and falls as the switch turns on and off in a power converter.
2. Why does ripple current matter?
Ripple current affects core loss, copper loss, output voltage ripple, thermal stress, and converter stability. Too much ripple can push the converter toward discontinuous conduction and reduce design margin.
3. How does inductance affect ripple?
Higher inductance lowers ripple current because current changes more slowly for the same applied voltage and switching interval. Lower inductance makes the current waveform steeper and increases ripple.
4. What happens when switching frequency increases?
Higher switching frequency shortens the switching period. That reduces the current change during each cycle, so ripple current usually decreases when all other values stay unchanged.
5. When should I use auto duty mode?
Use auto duty mode when you want an ideal duty cycle from the entered voltages. It is useful for quick design estimates and for checking whether a chosen inductor is suitable.
6. When is manual duty mode better?
Use manual duty mode when you want to test a known controller setting, compare several duty conditions, or inspect how ripple changes when duty departs from the ideal voltage ratio.
7. What does continuous conduction likely mean?
It means the estimated minimum inductor current stays above zero. In that case, the inductor current never fully collapses during the cycle, so the converter is likely operating in continuous conduction mode.
8. Does this calculator replace full converter simulation?
No. It is an engineering estimate tool. Real converters also include resistance, diode drop, MOSFET loss, control behavior, tolerances, saturation limits, and transient effects that need deeper analysis.