<p><strong><span style="font-size: 9.0pt; font-family: 'Times New Roman',serif; mso-fareast-font-family: 等线; mso-fareast-theme-font: minor-fareast; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="EN-US">When the random pulse width modulation (RPWM) technique is applied to insulated gate bipolar transistor (IGBT) modules, the switching losses are decreased to different degrees. In order to study the principle of this control method, this paper starts from the perspective of Joule heating principle.