Fast Loop Gain Measurement of a Switched-Mode Converter Using a Binary Signal With a Specified Fourier Amplitude Spectrum

Switched-mode power converters are extensively used to power various electronic loads and processes. The use of low-cost components with high parameter variation together with the requirement of short time to market has set new challenges for the designers such as the necessity to characterize a large number of converters before production ramp-up. It has been shown that the frequency-domain characterization yields most useful information on the quality of a converter. The conventional frequency response analyzers can be used for measuring the responses, but the time required for one measurement is too long for characterizing hundreds or thousands of converters. Recent studies show that the time for single measurement can be drastically reduced by using broadband excitation signals such as the maximum length pseudorandom binary sequence (MLBS). The MLBS excitation signal is not well suited for measuring the voltage or current loop gains because of their sensitivity to the disturbance signals. This paper proposes a new method based on the use of MLBS but with a specified Fourier amplitude spectrum in order to avoid the said problem. The method is verified both with simulation and practical measurements, and the results are compared to the conventional MLBS technique.