Purpose of a Buck Converter

A buck converter is a switching regulator that efficiently steps a higher DC voltage down to a lower one. Instead of dissipating excess power as heat like a linear regulator, it rapidly switches the input on and off while storing energy in an inductor. By controlling the duty cycle—the fraction of each switching period the input is connected—you can regulate the average output voltage. Buck converters appear in everything from phone chargers to automotive electronics because they offer far greater efficiency than linear solutions when the voltage difference is large.

The basic topology consists of a transistor, diode, inductor, and output capacitor. During the "on" portion of the cycle, the transistor applies the input voltage across the inductor, causing current to ramp up. When the transistor turns off, the diode conducts and the inductor current flows into the load, ramping down while still supplying energy. The capacitor smooths the voltage so that the output remains nearly constant even though the switch toggles thousands or millions of times per second.

Key Equations

The ideal relationship between input and output is simple:

Here $D$ is the duty cycle, $\mathrm{V\_\{out\}}$ the desired output, and $\mathrm{V\_\{in\}}$ the supply voltage. In practice, slight adjustments may be required to account for losses in the switch and diode, but the ratio provides an excellent starting point.

The current ripple through the inductor can be approximated by

where $f$ is the switching frequency. Keeping this ripple small ensures the current never falls to zero, maintaining continuous conduction for better performance.

How to Use the Tool

Enter your design parameters in the form above: the input and desired output voltages, inductance, switching frequency, and expected load current. Press the Compute button to view the resulting duty cycle and inductor ripple current. The calculations happen instantly in your browser. If you need to keep a record, use the Copy Result button to place the values on your clipboard.

Example Component Values

The following table lists typical diode drops for common technologies, which can affect the exact duty cycle once efficiency considerations come into play:

Diode Type	Forward Voltage	Common Use
Silicon	0.7 V	General purpose rectification
Schottky	0.3 V	High-efficiency switching supplies
Fast Recovery	0.9 V	High-voltage converters

Benefits of Switching Regulation

Switch-mode power supplies like the buck converter waste less energy than linear regulators because the power transistor operates primarily in its fully on or fully off state, minimizing resistive losses. They also handle a wide range of input voltages and can provide large current outputs in compact packages. However, their high-frequency operation introduces electrical noise, so proper layout and filtering are crucial. Engineers often trade a small increase in complexity for significant efficiency gains.

This calculator keeps the math straightforward, enabling quick estimates during the design phase or when studying how converter parameters interact. Because it runs entirely client-side with no external libraries, you can experiment even without an internet connection.