Small Signal Phasor Modeling of Phase-shift Modulated Series Resonant Converters with Constant Input Current

Series resonant converters (SRCs) being deployed in dc current distribution systems have constant input current, leading to variable input voltage. This results in significantly different steady state and dynamic behavior in comparison with traditional constant input voltage scenarios, and these differences and associated system design and stability challenges have not been well studied in the literature. This paper develops and validates small signal models using dynamic phasor modeling techniques for phase-shift modulated SRCs with constant input current and derives explicit analytical expressions for all key transfer functions, including input impedance and control-to-output. The small signal models and transfer functions are suitable for feedback loop design, system stability evaluation and related design oriented analysis. Results are provided for a 250 kHz SRC with 500 V input voltage and a 250 kHz SRC with 1 A input current, 0.33 A output current to validate the analytical models.