Buck-boost three-level semi-dual-bridge resonant isolated DC-DC converter

The semi-dual-bridge resonant isolated dc-dc converter (SDBRC), as a class of emerging topologies, is suitable for the application situation that requires only the unidirectional power transfer while a wide buck-boost voltage conversion range. In this article, a three-level SDBRC is proposed. Its operation principle is analyzed, and the transfer power and voltage conversion ratio as the functions of the two phase shifts are derived. Furthermore, a coordinated control rule of the two phase shifts is proposed, which ensures the monotonicity between the phase shifts and the average output power over the entire power/voltage range. The voltage stress of the power devices of the proposed topology is reduced to half of the power supply voltage; therefore, the cost and ON-state loss of the power switches are effectively reduced. The detailed simulation and experimental results validate the correctness and feasibility of the proposed topology and its modulation strategy.