Measurement of incidental power losses in switching power devices

A special technique for measuring incidental dissipation in power devices during switching is developed which readily allows evaluation of the separate losses. It is based on high frequency sampling of the voltage and current waveforms. The data is sampled through a digital oscilloscope and then transferred to a PC via a general purpose interface bus. The PC is then used for calculating the on, off and saturation losses. It is found that the switch-on and switch-off losses of a typical semiconductor switch are very different from the values predicted by the use of linear ramp representation of the switching characteristics