Pulse-width modulation control strategy for high efficiency LLC resonant converter with light load applications

Haiyan Pan; Chao He; Farooq Ajmal; Henglin Chen; Guozhu Chen

Pulse-width modulation control strategy for high efficiency LLC resonant converter with light load applications

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Author(s): Haiyan Pan ^{1, 2} ; Chao He ¹ ; Farooq Ajmal ¹ ; Henglin Chen ¹ ; Guozhu Chen ¹
- Affiliations: 1: College of Electrical Engineering, Zhejiang University, Hangzhou 310027, People's Republic of China;
  2: Department of Electronic and Electrical Engineering, Taizhou Vocational & Technical College, Taizhou 318000, People's Republic of China
Source: Volume 7, Issue 11, November 2014, p. 2887 – 2894
DOI: 10.1049/iet-pel.2013.0846 , Print ISSN 1755-4535, Online ISSN 1755-4543

Received 12/11/2013, Accepted 07/06/2014, Revised 08/05/2014, Published 16/10/2014

LLC resonant converters, generally adopting frequency modulation control, can hardly achieve high efficiency under both heavy and light load conditions. Especially under light load conditions, the high-switching frequency seriously degrades converter's efficiency. This study propose a new pulse-width modulation (PWM) control strategy for LLC resonant converters under light load applications on the premise of no change in the main circuit structure. The voltage gain of the converter is regulated by varying duty ratio instead of increasing switching frequency and therefore zero-current switching for rectifier diodes can be realised under light load conditions. With the proposed PWM control strategy, the gain is not affected by the load variations and an optimal design of the magnetic components is possible, therefore the efficiency is further improved by reducing both the switching losses and the losses in magnetic components. Experimental results demonstrate the effectiveness of the proposed PWM strategy by increasing the efficiency of LCC resonant converter, especially under light load conditions.

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Pulse-width modulation control strategy for high efficiency LLC resonant converter with light load applications

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