A Comprehensive Overview in Control Algorithms for High Switching-Frequency LLC Resonant Converter

Abstract

An LLC resonant converter has been widely used in various industrial applications because of its high cost-effectiveness, high power conversion efficiency, simple design methodology, and simple control algorithms using a pulse frequency modulation (PFM). In addition, the soft switching capability of the LLC resonant converter is good to obtain high switching frequency operations, which can get the high-power density of the power converter. Over the past years, several studies have been conducted to improve the performance of a high switching frequency LLC resonant converter with resonant tank design, optimal power stage design, and enhanced control algorithms. This paper is the review paper in terms of the control algorithms for the LLC resonant converter. It focuses on the overview of the high switching-frequency LLC resonant converter in terms of the control algorithms. The advanced control algorithm can improve power conversion efficiency, dynamic performance, tight output voltage regulation, and small electro-magnetic interference. The operational principles of the control algorithms are briefly explained to show their own characteristics and advantages. Thereafter, the research issues for the future works will be discussed in the conclusion.

Simulation optimal and design of 3-kW DC-DC converter for pure electric vehicles

“…(1) The operating waveform of the resonant converter when f k > f r is shown in Figure 4. 27 The light blue waveform is the driving waveform of switches Q 1 and Q 4 . The yellow waveform is the driving waveform of switches Q 2 and Q 3 .…”

An Adaptive Synchronous Rectification Driving Strategy for Bidirectional Full-Bridge LLC Resonant Converter

“…However, in order to output a large current, a current doubler circuit is often utilized, but the current doubler circuit has too many magnetic elements, which are not in favor of enhancing power density. LLC resonant converters can achieve zero voltage switching (ZVS) with primary-/secondary-side switches, affording good performances in terms of efficiency [6][7][8]. In addition, LLC resonant converters can reduce the size of magnetic components by operating at high frequencies to achieve high power densities.…”