Battery float charge technique using parallel-loaded resonant converter for discontinuous conduction operation

This work presents a battery float charge technique based on a parallel-loaded resonant converter. The main purpose of the float charge is to ensure that the battery remains fully charged indefinitely. With a simple circuit configuration and few components, low switching loss and high efficiency are achieved. The proposed parallel-loaded resonant converter is operated in discontinuous current mode to achieve high efficiency at a fixed switching frequency. With carefully designed circuit parameters, the power switches can support zero voltage switching and zero current switching. The operating principles and equivalent circuit are analyzed in detail. Experimental results are obtained using a 12V-150Ah rechargeable battery to confirm the feasibility of the proposed scheme. The maximum charging efficiency of the proposed topology during the overall float charge period is 97.6%. The measurements yield satisfactory performance.