Energy Reports (Sep 2023)
A novel digital sensor-less synchronous rectification method for CLLLC resonant converters
Abstract
With the rapid development of the renewable energy vehicles, pursuing the power converters with high efficiency and high reliability has caught more attention recently. In order to solve those problem with low cost, this paper proposes a sensor-less synchronous rectification method for the CLLLC resonant converters. The precise conduction time of the synchronous switches is obtained based on the analysis of the working principle of CLLLC resonant converter, and the relationship between the SRs switching time and the inverter switching time can be derived as well. To achieve the wide output voltage range, the converter requires wide working frequency. And the correct turn-on and turn-off time for the synchronous switches can be obtained respectively by calculation and piecewise linear function fitting methods within full working frequency range. Compared with traditional synchronous rectification control for CLLLC, which require additional high bandwidth voltage sensors or current sensors, the method proposed in this paper is realized by only one low-cost output voltage sensor. And the proposed method is suitable for high-power applications with a wide voltage and load variation. Moreover, because of the symmetrical topology, this method is valid in bidirectional power transfer. Additionally, the exist analog synchronous rectification control chips suffer from losing accuracy with wide bus voltage variation, however, this method can overcome this shortcoming. Thus, the proposed synchronous rectification method is a low-cost and suitable for high-power, high power density, high efficiency application which benefit from its simple algorithm. Finally, the proposed sensor-less synchronous rectification method is validated by the simulation results and experimental results. The results of simulation and experimental have shown the proposed method offers significant benefits which increases the efficiency of the whole CLLLC system by about 3%, and the reliability of the converter are greatly increased, due to the cooler SRs.
