Analysis and Research of Dynamic Optimal Algorithms for High Frequency LLC Resonant Conversion Control System

With the rapid and iterative development of computer technology and electronic technology, the key switching power supply system tends to develop in the direction of high frequency, high efficiency and high power density. LLC resonant converter, as an excellent converter to meet the development trend of modular power supply system, has excellent performance at high frequency. However, with the switching power supply frequency entering the MHz era, the dynamic performance of LLC resonant converter control system is deteriorating day by day. In view of the deterioration of the dynamic performance of LLC resonant converter at high frequency, a novel control algorithm of LLC resonant converter based on state trajectory method is proposed, and the dynamic processing part of the control system is optimized. The innovation of the proposed algorithm is that the dynamic switching time is estimated based on the charge and discharge of the resonant capacitor in the resonant slot of LLC resonant converter, which improves the speed of dynamic switching. At the same time, aiming at the problem of voltage overshoot in the dynamic switching process, the new sampling strategy proposed in this paper effectively realizes the voltage overshoot control. At last, the whole power level circuit and control system are simulated by using MATLAB and SABER. At the same time, a LLC resonant conversion system with DC400 V input and 24 V/6A output is built. Finally, the core control algorithm proposed in this paper is implemented by STM32F407. The test results show that the proposed algorithm has obvious advantages over the traditional PID control algorithm in dynamic performance.