A new variable-mode control strategy for LLC resonant converters operating in a wide input voltage range

This paper proposes a new variable-mode control strategy that is applicable for LLC resonant converters operating in a wide input voltage range. This control strategy incorporates advantages from full-bridge LLC resonant converters, half-bridge LLC resonant converters, variable-frequency control mod...

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Bibliographic Details
Published in:Frontiers of information technology & electronic engineering 2017-03, Vol.18 (3), p.410-422
Main Authors: Lin, Hui-pin, Jin, Xiao-guang, Xie, Liang, Hu, Jin, Lu, Zheng-yu
Format: Article
Language:English
Subjects:
Circuits
Communications Engineering
Computer Hardware
Computer Science
Computer Systems Organization and Communication Networks
Digital signal processing
Digital signal processors
Electric bridges
Electric potential
Electrical Engineering
Electronics and Microelectronics
Frequency control
Instrumentation
Microprocessors
Networks
Switching
Voltage
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Summary:This paper proposes a new variable-mode control strategy that is applicable for LLC resonant converters operating in a wide input voltage range. This control strategy incorporates advantages from full-bridge LLC resonant converters, half-bridge LLC resonant converters, variable-frequency control mode, and phase-shift control mode. Under this control strategy, different input voltages determine the different operating modes of the circuit. When the input voltage is very low, it works in a full-bridge circuit and variable frequency mode（FB_VF mode）. When the input voltage rises to a certain level, it shifts to a full-bridge circuit and phase-shifting control mode（FB_PS mode）. When the input voltage further increases, it shifts into a half-bridge circuit and variable frequency mode（HB_VF mode）. Such shifts are enabled by the digital signal processor（DSP）, which means that no auxiliary circuit is needed, just a modification of the software. From light load to heavy load, the primary MOSFET for the LLC resonant converter can realize zero-voltage switching（ZVS）, and the secondary rectifier diode can realize zero-current switching（ZCS）. With an LLC resonant converter prototype with a 300 W rated power and a 450 V output voltage, as well as a resonant converter with 20–120 V input voltage, the experiments verified the proposed control strategy. Experimental results showed that under this control strategy, the maximum converter efficiency reaches 95.7% and the range of the input voltage expands threefold.
ISSN:2095-9184
2095-9230
DOI:10.1631/FITEE.1600029