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Buck Converter Calculator

A buck converter is a type of switching regulator which we use to step down a high DC voltage to a lower DC voltage. The inductor is a very important part of the circuit because it stores and releases energy to keep output power almost same as input power. This is biggest advantage of a buck converter.

Meaning while a buck converter steps down a high voltage to a desired lower output voltage, it proportionately increases the current, depending on how much voltage has been reduced at the output.

This results in retention of input power and minimized heat dissipation and overall high working efficiency.

Buck Converter Inductor Calculator

Buck Converter Inductor Calculator

Enter the values below to calculate the optimal inductor value based on your desired ripple current.

Results:

Duty Cycle: 0 %

Optimal Inductor Value: 0 µH

What Does the Inductor Do in a Buck Converter?

The inductor helps in many ways:

How the Inductor Works in a Buck Converter

When the MOSFET switch is ON:

When the MOSFET switch is OFF:

This happens again and again at the switching frequency. In the end the output becomes a steady DC voltage.

How to Calculate the Inductor for a Buck Converter

Now, to calculate the inductor value (L), we use the following formula:

L = (V_in - V_out) * D / (Δ I_L * f)

Where:

What is Ripple Current?

Now the ripple current is a small variation in the current which is usually set as 30% of the output current. So, if the output current is 2A, then the ripple current (Δ I_L) will be:

Δ I_L = 0.3 * I_out

So for a 2A output current, the ripple current would be 0.6A. The ripple current affects how big the inductor needs to be. Larger ripple current means we can use a smaller inductor but it causes more noise and losses. On the other hand, smaller ripple current needs a larger inductor but the converter is more stable. The 30% rule is a good balance between size and performance.

Duty Cycle

The duty cycle is how long the MOSFET switch stays ON during each cycle, and it depends on the ratio of Vout to Vin. We calculate it like this:

D = V_out / V_in

If the duty cycle is too high, the switch will be ON for a longer time, giving more energy to the load. If it’s low, the switch will be ON for less time.

Example Calculation

Now let us say we have:

Now we calculate the duty cycle first:

D = 5 / 12 = 0.416

Now we can calculate the inductor:

L = (12 - 5) * 0.416 / (0.6 * 100000)

L = 7 * 0.416 / 60000

L = 2.91 / 60000 = 48.5µH

So for this setup the inductor value is 48.5 µH.

Summary:

Example of a high Voltage Buck Converter

High voltage buck converter
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