Buck Designer
DC-DC Step-Down Filter
Duty Cycle
41.7%
Min Inductor
9.72 µH
Min Cap
22.5 µF
Assumes 90% efficiency and 30% inductor ripple current ($\Delta I_L$).
Always choose an inductor with a saturation current ($I_{sat}$) > $I_{peak}$.
Always choose an inductor with a saturation current ($I_{sat}$) > $I_{peak}$.
A Buck converter uses a high-speed switch (MOSFET), a diode (or synchronous FET), and an LC filter to convert energy.
Key Formulas:
- Continuous Conduction Mode (CCM): This calculator assumes the converter stays in CCM, where the inductor current never hits zero. If your load is very light, the converter may enter Discontinuous mode (DCM), changing its behavior.
- Saturation Current: When picking an inductor, the most important spec is Isat. If the peak current exceeds this, the inductance collapses, potentially destroying the switch.
- ESR (Equivalent Series Resistance): The output ripple is often dominated by the capacitor’s ESR rather than its bulk capacitance. For high frequencies, use X7R Ceramic or Polymer capacitors.