Hybrid Control Strategy for an Integrated DAB–LLC–DCX DC–DC Converter to Achieve Full-Power-Range Zero-Voltage Switching

In this article, a dual active bridge (DAB)-LLC-DCX dc-dc converter with integrated magnetics and shared rectifier is proposed for point of load applications, which is able to achieve tight voltage regulation, zero-voltage switching (ZVS) operation for all switches and zero-current switching operation for rectifier. The challenge of the proposed converter is the realization of ZVS operation for all the switches within full power range to achieve high efficiency and high reliability, which is beneficial for light load efficiency improvement of microprocessors. Therefore, with different input voltage range, a hybrid control strategy is proposed to realize ZVS operation for all switches of the proposed converter within full power range in this article. When at high input voltage, extended phase shift control is applied to extend the ZVS range. When at low input voltage, variable gain LLC converter is designed to regulate the voltage distribution among DAB converter and LLC converter for the ZVS operation of DAB converter. Besides, the charging/discharging of junction capacitors are added into consideration of ZVS analysis. The operating principle, design considerations, and control schemes are presented. Finally, the experimental results of an 80-W prototype verified the theoretical analysis.