Buck Converter: Design Guide & Calculator

Buck Converters: Step-Down Voltage Regulation

What is a Buck Converter?

A buck converter is a DC-DC switching regulator that efficiently steps down higher input voltage to a lower output voltage. Key features:

  • High efficiency (typically 85-95%)
  • Wide input voltage range
  • PWM-based voltage regulation
  • Compact size compared to linear regulators

Basic Operation

Working Principle

  1. Switch (MOSFET) turns ON: Current flows through inductor to load
  2. Switch turns OFF: Inductor current continues through diode
  3. Output capacitor filters the pulsating voltage
  4. Control circuit maintains output through PWM

Key Design Formulas

Duty Cycle

D = Vout / Vin

Inductor Selection

L = (Vin - Vout) × D / (ΔIL × f)

Output Capacitance

Cout = ΔIL / (8 × f × ΔVout)

Component Selection Guide

Component Selection Criteria
Inductor Low DCR, saturation current > peak current
Capacitor Low ESR, voltage rating 1.5×Vout
Diode Fast recovery, current rating > Iout
MOSFET Low RDS(on), fast switching

Common Applications

  • Voltage regulation for microcontrollers
  • Battery-powered devices
  • LED drivers
  • Automotive electronics
  • Solar power systems