# Class D inductor current calculation

How do I calculate the required inductor current (RMS, saturation) for a class D amplifier?

Assuming the following configuration:

• Speaker impedance (Z) = 4 ohms
• Power output (P) = 400W

(calculations are rounded and assume no switching losses at the output)

• $V_{pp} = 113V$
• $V_{rms} = 113V \times 0.3535 = 40V$
• $P = \dfrac{V_{rms}^2}{Z} = \dfrac{1600V}{4R} = 400W$

Is the current calculated as follows?

• $I_{pp} = \dfrac{V_{pp}}{Z} = \dfrac{113V}{4R} = 28A$
• $I_{rms} = \dfrac{V_{rms}}{Z} = \dfrac{40V}{4R} = 10A$

Does this mean that I need an inductor that is rated for at least 10A RMS and exceeds 28A saturation current?

The Class-D amplifier I'm using is a "H-bridge" output configuration, meaning it generates the required 40Vpp from a single 20V supply. So I need two inductors per speaker output. Does this mean that my required inductor should be rated for 14A saturation/5A current?

Are my calculations correct? I know the ones I posted are valid for a linear amplifier (Class-AB for example) but I don't know if they are the same for class-D, considering a Class-D amp is always switching max V, and thus, I is always at the max during a short period all the time.

In other posts I've seen mention of "core loss" and "V/us". What does this mean?

(The amplifier in question is a TI TAS5630B. The datasheet doesn't specify a suggested inductor, and the EVM was made with custom ones).