Dual-edge phase-shift-modulation for circulating current control in full-bridge resonant converters

Paralleling multiple resonant converters can be used to expand power capacity, increase system reliability, accommodate more power sources, and improve high efficiency curves. However, because of the difference of the power and control circuits of individual modules, and the coupling between modules, current circulates between the paralleled modules. Current sharing control with voltage feedback control can be used to minimize the circulating current. Unfortunately the conventional phase shift modulation introduces different phase angle shift of the bridge voltage for different modulation levels. We investigated a dual- edged phase-shift modulation for these applications, with which the phase angle of the bridge voltage of the resonant converter is independent of the modulation signals. This modulation can be used for circulating current minimization control and voltage feedforward control in a multiple module system. For different input voltages, or different power capacities of individual module, the modulation level will be different for each module. But the phase angles of the output voltages are independent of the modulation level. Simulation and experiment results verified the concept.