Buck Converter Calculator
Calculate duty cycle, inductance, and switching parameters for step-down DC-DC converter circuits
Buck Converter Design
Typical: 100-500 kHz (low power), 1-3 MHz (compact)
Typically 10-40% of average output current
Calculation Results
Formulas used:
D = Vout / Vin = Ton / Tsw
L = (Vin - Vout) × D / (fs × Iripple)
Ton = D × Tsw, Toff = (1-D) × Tsw
Performance Analysis
Example Calculations
5V Output from 13.2V Input
Given: Vin = 13.2V, Vout = 5V, fs = 250kHz, Iripple = 220mA
Duty Cycle: D = 5V ÷ 13.2V = 0.3788 = 37.88%
Inductance: L = (13.2V - 5V) × 0.3788 ÷ (250kHz × 0.22A) = 56.47µH
Result: Buck converter steps down 13.2V to 5V efficiently
Timing Analysis
Switching Frequency: 250kHz
Switching Period: Tsw = 1/250kHz = 4µs
Switch ON Time: Ton = 37.88% × 4µs = 1.515µs
Switch OFF Time: Toff = 62.12% × 4µs = 2.485µs
Switching Frequency Guide
100-500 kHz
Low-power applications
Standard components, lower EMI
1-3 MHz
Compact designs
Smaller components, higher efficiency
Above 3 MHz
Lightweight applications
Very compact, requires careful design
Design Guidelines
Advantages
High efficiency (85-95%)
Good voltage regulation
Low output ripple
Simple control circuit
Applications
Understanding Buck Converter Circuits
What is a Buck Converter?
A buck converter is a DC-to-DC step-down converter that efficiently reduces a higher input voltage to a lower output voltage. It's a type of switched-mode power supply (SMPS) that uses energy storage elements and electronic switches to achieve high efficiency.
How Does It Work?
- •Switch ON: Current flows through inductor, charging it
- •Switch OFF: Inductor discharges through diode
- •Output: Capacitor smooths voltage ripples
- •Control: Duty cycle determines output voltage
Key Formulas
Duty Cycle
D = Vout / Vin
Also: D = Ton / Tsw
Inductance
L = (Vin - Vout) × D / (fs × Iripple)
Critical for continuous conduction mode
Switch Timing
Ton = D × Tsw
Where Tsw = 1 / fs
Buck Converter Components
Switch (Transistor)
Controls power transfer through duty cycle modulation. Usually MOSFET for high efficiency.
Inductor
Stores energy during switch-on period and releases it during switch-off period.
Diode (Freewheeling)
Provides current path when switch is off. Often replaced with synchronous rectifier.
Input Capacitor
Reduces input voltage ripple and provides instantaneous current during switch transitions.
Output Capacitor
Smooths output voltage ripple and provides stable DC output voltage.
Control Circuit
Regulates switching frequency and duty cycle to maintain desired output voltage.