Digital Implementation of Optimal Phase Calculation for Buck-Boost LLC Converters

Buck-Boost LLC (BBLLC) converters based on a PWM + phase control strategy are good candidates for high efficiency, high power density and wide input range applications. Nevertheless, they suffer from large computational complexity when it comes to calculating the optimal phase for ZVS of all the switches. In this paper, a method is proposed for a microcontroller unit (MCU) to calculate the optimal phase quickly and accurately. Firstly, a 2-D lookup table of the phase is established with an index of the input voltage and output current. Then, a bilinear interpolation method is applied to improve the accuracy. Meanwhile, simplification of the phase equation is presented to reduce the computational complexity. When compared with conventional curve-fitting and LUT methods, the proposed method makes the best tradeoff among the accuracy of the optimal phase, the computation time and the memory consumption of the MCU. Finally, A 350V-420V input, 24V/30A output experimental prototype is built to verify the proposed method. The efficiency can be improved by 1% when compared with the LUT method, and the computation time can be reduced by 13.5% when compared with the curve-fitting method.

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Cite this article

[IEEE Style]

Q. Qian, B. Ren, Q. Liu, C. Zhan, W. Sun, "Digital Implementation of Optimal Phase Calculation for Buck-Boost LLC Converters," Journal of Power Electronics, vol. 19, no. 6, pp. 1429-1439, 2019. DOI: 10.6113/JPE.2019.19.6.1429.

[ACM Style]

Qinsong Qian, Bowen Ren, Qi Liu, Chengwang Zhan, and Weifeng Sun. 2019. Digital Implementation of Optimal Phase Calculation for Buck-Boost LLC Converters. Journal of Power Electronics, 19, 6, (2019), 1429-1439. DOI: 10.6113/JPE.2019.19.6.1429.