Digital oscilloscope measurements in high-frequency switching power electronics

The requirements for measuring instantaneous power of a switching power circuit using a digital storage oscilloscope are discussed. The measurements are difficult to perform and involve the use of high-speed, high-resolution measurement instrumentation. Careful consideration needs to be given to overload conditions. Averaging and advanced sampling techniques are necessary to obtain a satisfactory result. Performance enhancements of instruments that will allow improvement of the quality of the measurements remain desirable. An indication of measurement accuracy is obtained by comparing the mean dissipated power to the same quantity obtained by a calorimetric test (water flow heating). The mean dissipated power is the integral of the instantaneous power divided by the switching period. The two results agree within 5%. >