Full-bridge resonant converter with hybrid control for wide input voltage range applications
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ORIGINAL ARTICLE
Full‑bridge resonant converter with hybrid control for wide input voltage range applications Yufei Zhou1 · Xin’an He1 · Lunhui Sheng2 Received: 6 April 2020 / Revised: 17 September 2020 / Accepted: 22 September 2020 © The Korean Institute of Power Electronics 2020
Abstract This paper proposes a hybrid control strategy for a full-bridge resonant converter. In the applications with a wide input voltage, a resonant converter with variable frequency control (VFC) has to modulate the converter operating in a wide switching frequency range to satisfy gain requirements, which results in some problems such as difficulty in optimizing the design of magnetic components, increased power loss and deteriorated electromagnetic interference. By use of VFC, primary-side phase shift control and secondary-side phase shift control, the frequency variable range can be greatly reduced and the conversion efficiency can be increased, which make the converter appropriate for a wide input voltage range. With this hybrid control strategy, the converter can automatically convert to the corresponding control mode according to variations of the input voltage and load, which has a good transient performance. The working principle, gain characteristics and design considerations of a hybrid controlled CLL resonant converter are introduced in detail. Experimental results are shown to demonstrate its validity and feasibility. Keywords Full-bridge resonant converter · Variable frequency · Phase shift · High efficiency
1 Introduction In recent decades, renewable energy has attracted a great deal of interest due to its environmental and economic benefits. Unpredictable factors such as solar radiation level and ambient temperature cause renewable energy generation units to have a wide output voltage range [1–3]. Therefore, for the purpose of providing a stable output voltage for appliances, a DC–DC converter suitable for a wide input voltage variation range is required. The LLC resonant converter is widely adopted in the power electronics industry due to its high efficiency when compared to traditional PWM converters like the phaseshifted full-bridge (PSFB) converter [4–6], active clamp forward (ACF) converter [7, 8] and asymmetric half bridge (AHB) converter [9, 10]. However, one of the problems with the LLC resonant converter is the wide range of
* Yufei Zhou [email protected] 1
College of Electronic and Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, China
Huawei Technologies Co., Ltd., Shanghai, China
2
switching frequency, especially for applications with wide gain requirement. The improved LLC resonant converters in [11–14] are utilized for wide input ranges. They can achieve voltage gain requirements and have simple structures to implement soft-switching, whereas when the input voltage is low, it is necessary to reduce the switching frequency with a small magnetizing inductance to obtain a high gain, which increases the conduction loss and makes it difficult to design magne
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