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Buck Converter Power Stage Calculator

Circuit diagram of a buck converter

This calculator provides assistance when designing a buck regulator. The equations here are derived from TI's "Basic Calculation of a Buck Converter's Power Stage", SLVA477B. You'll want to be following along in that document as you fill this worksheet out.

This calculator accepts arbitrary units and expressions. For example, 5e10 / (1 hour) will be interpreted as "27.77 MHz".

Duty Cycle

The duty cycle of the buck converter is the proportion of the time that the switch spends closed, in other words, the fraction of the time that current is flowing through Q.

Maximum input voltage
Desired output voltage
Estimated efficiency of the converter
0.306

Inductor Ripple Current

The inductor ripple current is the difference between the maximum and the minimum current flowing through the output inductor L. This value is used later on to calculate the peak current flowing through Q.

Minimum switching frequency
Value of the inductor. Typical inductor values are sometimes found in the datasheet, otherwise use the calculator below.
0.806 A

Maximum Switch Current

This is the peak current that the inductor L, the switch Q, and the diode D must be designed to survive.

2.4 A

Inductor Selection

You should fill out this area of the worksheet if your datasheet doesn't provide you with suggested inductor values.

Typical input voltage
An estimated factor for the ripple current. A reasonable guess is between 0.2 and 0.4.
33.4 uH
0.6 A
This is the estimated ripple current if the above inductor is used.

Rectifier Diode Selection

Schottky doides are recommended in order to reduce losses. The forward current rating should be the same as the expected output current. Peak current ratings for Schottky diodes is usually much higher than the average rating, so there is no need to worry about the peak current calculated above.

The forward voltage for your diode. This is usually between 150mV and 450mV.
1.39 A
0.4 W