In a previous article, MasteringElectronicsDesign.com:How to Derive the RMS Value of A Trapezoidal Waveform – Part 1, I showed how to derive the RMS value of a trapezoidal signal with a flat plateau and different rise/fall time values. In some applications, the trapezoidal signal plateau is not flat, but rather a ramp, as shown in Figure 1. A typical example is a DC-DC converter, where the transformer winding current might look like the signal in Figure 1. Of course, in the DC-DC converter example, the amplitude is current and not voltage. No matter, the calculations are the same.
This waveform is still considered a trapezoidal waveform. Let’s calculate its RMS value.