Design of loop gain for load converters in a Distributed System

In a distributed power system, stability criterion requires source impedance smaller than load input impedance when their phase differ by 180°. In this paper, the input impedance of four common DC-DC converter types (Buck and Boost, voltage-mode and current-mode) are analyzed, their relationship with voltage loop crossover frequency and phase margin are established. It reveals that lower crossover and higher phase margin will increase impedance, thus a guideline on design of load DC-DC converter loop gain is provided to get preferred input impedance and meet stability criterion. This method generally applies to all DC-DC converters like Boost, Buck, Buck-Boost, and converters derived from them.

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