A Passive-Impedance-Matching Concept for Multi-phase Resonant Converter

A passive impedance matching (PIM) concept is proposed for multi-phase resonant converters application. The new concept can achieve load current sharing between every unit automatically. A passive element such as an inductor or a capacitor is connected in the common branch of the two units (or multi-units), such that several sets of equivalent positive resistors and negative resistors are distributed into these units accordingly. The equivalent virtual resistors are of variable value, which automatically adjust the DC gain in each unit to achieve load sharing. Three equivalents LLC resonant converters with virtual variable resistor are analyzed. The theoretical analysis result shows that the first and third types have good load current sharing performance. A 600W, 12V two-phase LLC converter prototype is built based on the first type. The prototype verified the feasibility and demonstrated advantages of PIM multiphase resonant converter.