Asymmetrical Phase-Shifted Full-Bridge Converters in Input-Parallel Output-Parallel Configuration

This paper presents an analysis of asymmetrical modular phase-shifted full-bridge (PSFB) converters in input-parallel output-parallel (IPOP) configuration for high-current and high-power applications and proposes a new control method that enhances system efficiency. The performance of the asymmetric IPOP-PSFB system under nonideal parametric mismatches in transformer turns-ratio, filter and leakage inductances is studied under various control methods. The widely employed common duty ratio scheme (CDR) and its implications on power sharing among the modules are compared with an independent duty ratio control (IDC) scheme. Contrary to the equal power-sharing scheme among symmetrical modules, a Lagrangian loss optimal load-sharing (L <tex-math notation="LaTeX">²</tex-math> OL) technique leveraging the parametric asymmetry among the modules is proposed. This technique improves the overall system efficiency by appropriately loading individual PSFB modules. The proposed control method improves light load efficiency by 5.7%, mid load efficiency by 0.5% while preserving the full load efficiency compared to that obtained from equally loaded symmetrical modules. The effect of parametric asymmetry on power sharing using CDR and IDC schemes and power loss in symmetrical and L <tex-math notation="LaTeX">²</tex-math> OL strategies are compared based on analysis and simulations. This is validated on a laboratory hardware prototype comprising two PSFB modules, for a 2 <tex-math notation="LaTeX">$kW$</tex-math> , 400 <tex-math notation="LaTeX">V</tex-math> to 48 <tex-math notation="LaTeX">V</tex-math> system.