Frequency Response Measurements Techniques for Current Mode DC-DC Converters

Application notes for vector network analyzers (VNA) are filled with setups for measuring the closed loop transfer function of switched mode power supplies (SMPS) by injecting the perturbation in the voltage feedback. This is an important practical case when the SMPS must regulate the output voltage and as such includes an outer voltage loop. However, there are practical cases where only a current feedback loop is sufficient and similar setups for practical measuring with a VNA are not so obvious. This paper proposes a method for measuring the transfer function for such cases of practical significance.