Analysis and Design of Three-Level Full-Bridge LLC Resonant Converter Based on Pulse Frequency Modulation

Abstract

Aiming at the problem of serious switching loss in high-power and high-voltage occasions, the traditional LLC resonant network is difficult to adapt, the DC gain is difficult to obtain intuitively, and the voltage stress on the switch is too high, resulting in large switching losses and difficult selection of the switch. This paper uses a three-level full-bridge LLC resonant converter topology, the First Harmonic Approximation (FHA) is used to analyze the LLC resonant converter gain characteristics, and the parameter design ideas are given. A simulation experiment of a three-level full-bridge LLC resonant converter based on frequency modulation control is presented. The simulation results show that each primary side switch transistor can achieve zero voltage switching (ZVS), the secondary side diode realizes zero current switching (ZCS), and can obtain higher working efficiency, which verifies the feasibility of the design.

Application-Oriented Review of the LLC-Based Resonant Converters

“…A three-level converter using diodes and multiple switches in its switching network has been presented in [ 89 ] ,while [ 88 ] , replaces the input source with a PV panel and includes a battery pack as a backup source. The converters in [105][106][107][108], employ two-leg switching networks for high voltage gain applications but suffer from high conduction losses and expensive components due to the use of multiple switches and gate-drives.…”

A cascaded three‐level buck‐LLC DC/DC converter with high power density for high‐frequency applications

“…Ref. [19,20] integrates the advantages of the Hybrid Full Bridge Three Level (TL-HFB) converter and the LLC resonant converters. Three-level (TL) converter minimizes the voltage stress of switches while LLC converter improves the isolation and ZVS capability of the system.…”