Multimode Topology Morphing Control of Impedance Control Network Resonant DC-DC Converters

This paper introduces a multimode control approach for output voltage regulation in impedance control network (ICN) resonant dc-dc converters, in which the rectifier of the ICN converter dynamically alternates between full-bridge and half-bridge topologies. The proposed control approach allows the ICN converter to maintain soft-switching across power levels, while substantially reducing input and output capacitance requirements and improving partial-power efficiencies compared to the conventional burst mode (on/off) control. These performance enhancements are analytically evaluated and quantified for an example ICN converter design. A closed-loop control architecture for the proposed multimode topology morphing is also introduced, which ensures smooth mode transitions while regulating output voltage across input voltage and load transients. A prototype 1-MHz, 120-W step-down ICN resonant converter designed for an input voltage range of 18 V to 36 V, an output voltage of 12 V, and a 10:1 output power range is built and tested. Compared to burst mode control, the topology morphing control reduces the output capacitance requirement in the prototype ICN converter by 57% and reduces converter losses at partial power levels by up to 46.5%, validating the analytical predictions. The prototype converter is also tested under closed-loop control, and is shown to successfully regulate its output voltage with smooth mode transitions in the face of input voltage and load variations.