Buck converters efficiently step down voltages – the 12 V to 1 V regulators that feed processors, or the USB chargers in cars. Unlike linear regulators, they waste little power as heat.
How to use the Buck Converter Calculator
- Input voltage V_in
- Output voltage V_out
- Switching frequency f_sw
- Inductor ripple current ΔI_L
- Efficiency (%)
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the input and output voltages, the switching frequency, the ripple current and the efficiency.
Inputs explained
| Field | What to enter |
|---|---|
| Input voltage V_in | Units: V, mV, kV, µV, MV |
| Output voltage V_out | Units: V, mV, kV, µV, MV |
| Switching frequency f_sw | Units: kHz, MHz, Hz |
| Inductor ripple current ΔI_L | Units: A, mA, µA, kA |
| Efficiency (%) | A number |
What each result means
- Duty cycle D = [Output voltage V_out]÷([Input voltage V_in]×[Efficiency (%)]÷100)×100
- Inductance L = ([Input voltage V_in] – [Output voltage V_out])×[Output voltage V_out]÷([Input voltage V_in]×[Efficiency (%)]÷100)÷([Switching frequency f_sw]×[Inductor ripple current ΔI_L])
Example values
How the main result changes when Input voltage V_in changes and everything else stays at the example values above:
| Input voltage V_in (V) | Duty cycle D (%) |
|---|---|
| 6 | 90.5797 |
| 9 | 60.3865 |
| 12 | 45.2899 |
| 15 | 36.2319 |
| 18 | 30.1932 |
| 24 | 22.6449 |
Formula
D = V_out / (V_in·η), L = (V_in − V_out)·D / (f_sw·ΔI_L)
Worked example
Inputs — Input voltage V_in: 12 V; Output voltage V_out: 5 V; Switching frequency f_sw: 500 kHz; Inductor ripple current ΔI_L: 0.6 A; Efficiency (%): 92.
Results — Duty cycle D = 45.2899 %; Inductance L = 10.56763 µH.
Key terms
- Step-down converter
- Another name for a buck converter.
Frequently asked questions
Why are buck converters efficient?
The switch is either fully on or off, so it dissipates little power.
What does ripple current affect?
Output voltage ripple and core losses.
Can D exceed 100%?
No – the output can't exceed the input.
How do I choose the frequency?
Higher frequencies allow smaller inductors but increase switching losses.