Small-Signal Modeling of the LLC Half-Bridge Resonant Converter

Abstract

This paper proposes a small-signal modeling method for building an LLC half-bridge resonant converter. In recent years, the LLC half-bridge resonant converter has attracted the attention of many researchers because of its high-power conversion efficiency and high-power density. Generally, the LLC half-bridge resonant converter consists of many passive components, including stray and parasitic elements, resulting in a high-order system. Because the fundamental harmonic approximation (FHA) method for an LLC resonant converter only considers the fundamental harmonic and neglects higher harmonics, it is not accurate and introduces large errors in a higher-order system. In this paper, according to the operation principle of the LLC half-bridge resonant converter, a small-signal model is established. Based on the small-signal model, the input-to-output and control-to-output transfer function is derived. The experimental result verified that the proposed model yields a high accuracy, thereby highlighting the usefulness and versatility of the proposed model over other existing models.