Frequency-Response Measurement of Switched-Mode Power Supplies in the Presence of Nonlinear Distortions

Switched-mode converters have become extensively used in powering different consumer products. The increased mass production using low-cost components with high parameter variation has set new challenges to designers. Recent studies have shown that frequency-domain characterization yields most useful information about the dynamics and quality of a converter. This has been widely recognized and fast correlation-based techniques have been developed enabling the use of frequency-response measurements both in design and production phases. These techniques are based on a broad-band excitation signal that is injected into a converter and its response is analyzed. Most of the previous papers have used the pseudorandom binary sequence (PRBS) as the excitation. The conventional binary sequence do not, however, suit well for the processes suffering from strong nonlinear distortions. This paper proposes an excitation signal that can be used similarly to the conventional PRBS but provides much more accurate frequency-response estimates. Inverse-repeat binary sequence (IRS) is applied to cancel the effect of even-order nonlinearities and the frequency response is measured by means of spectrum method. The proposed technique is verified with practical measurements.