Switching Power Supplies A - Z

Chapter 2

Quick-selection of Inductors Using “L × I” and “Load Scaling” Rules

Finally, having decided upon the value of r based on all the considerations outlined so far,

we first present a quick method of picking an inductor for a given application. After that we

will proceed to a more detailed analysis and worked example.

As mentioned previously, from the inductor equation V = LdI/dt, we can derive another

useful relationship that we are calling the “L × I” equation



L × I

L



=

Et

r

(any topology)

Symbolically

L × I =

voltseconds



current ripple ratio

(any topology)

So if we know the voltseconds (from our application conditions), and have a target value

for