Buck Converter Calculator | Step-Down SMPS Design
Power Electronics

Buck Converter Designer

Professional design tool for Step-Down (Buck) Converters. Calculates Inductor Sizing, critical Input Capacitor RMS Current, and Component Stress for reliable high-efficiency power supplies.

Specs & Margins

Input
Operating Point
V
V
A
kHz
Derating (Safety)
%
%
Targets
%
%
A
mΩ
Inverting Buck-Boost Converter Schematic Diagram with MOSFET and Diode

Design Analysis

CCM Mode
Required Inductance (L)
— µH
—Peak Ipk
—Duty Cycle
—Power Loss
Component Sizing Guide
Minimum rated values (with margins)
MOSFET VDS — V
Diode VR — V
Input Cap IRMS — A
MOSFET ID — A
Diode IF — A
Inductor Isat — A
—Min Cout
—Total Ripple
—LC Res (fLC)
Inductor Current (IL) Buck Converter Inductor Current Waveform I_pk I_out 0A Time

Buck Converter vs LDO

Why choose a Switching Regulator (Buck) over a Linear Regulator (LDO)?

FeatureBuck ConverterLDO (Linear)
EfficiencyHigh (80-95%)Low (Vout/Vin)
Heat GenerationLow (Cold)High (Hot)
ComplexityMedium (L, C, Diode)Simple (Cap only)
Use CaseHigh Power / Big Step-DownLow Noise / Small Step-Down

Physics Explained

Input Capacitor Stress

In a Buck converter, the input current is pulsed. The input capacitor must handle significant RMS Ripple Current, roughly 50% of Iout at 50% duty cycle.

Component Stress

Unlike Boost converters, the MOSFET and Diode in a Buck converter must withstand Vin (plus ringing spikes), not just Vout.

LC Resonance

Buck converters have a double pole at fLC. The control loop bandwidth is usually set between fLC and fsw/10.

How to Use

1

Set Operating Point

Define Input (High) and Output (Low) voltages. Ensure Vin > Vout.

2

Check Input Cap

Pay close attention to the Input Cap IRMS result. Use low-ESR ceramic capacitors (X7R/X5R) to handle this heating.

3

Verify Stability

Note the fLC (Resonant Frequency). Your compensation network needs to handle the phase drop occurring at this frequency.