Buck Converter
Vout = Vin × D
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Formula
Description
A buck converter is a switching regulator that steps voltage down efficiently by rapidly switching the input on and off and filtering the result with an inductor and capacitor. The duty cycle D (the fraction of each switching period during which the input is connected) directly determines the output voltage in continuous conduction mode. Unlike a linear regulator which wastes excess voltage as heat, the buck converter transfers energy magnetically through the inductor, achieving typical efficiencies of 85-95%. The output voltage is always less than or equal to the input voltage.
Variables
- Vout — Output voltage (V)
- Vin — Input voltage (V)
- D — Duty cycle (0 to 1)
Practical Notes
This ideal formula assumes continuous conduction mode and 100% efficiency. Real converters have slightly different transfer functions due to diode drops, MOSFET on-resistance, and inductor DCR. At very light loads, the converter may enter discontinuous conduction mode where the relationship changes. Switching frequencies typically range from 100kHz to several MHz.
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