AN ULTRA-COMPACT THREE-PORT DC/DC CONVERTER

Abstract

The need for compact size DC power sources is increasingly rising. Several industrial and information technology (IT) sectors demand power supply designers to reduce the overall power supply size while increasing its efficiency. All power supply subsystems are subject to intensive research where their size and efficiency are optimized. The inductive components represent a significant percentage of the total power supply volume. The most common technique to reduce their size is by increasing the switching frequency either directly or through interleaving. In the current work, a different approach is followed. In this work, the core permeability is increased instead. Improving relative permeability of the ferrite cores used in switch-mode power supplies (SMPS) is a challenging task to reduce the requirements of the core size in the circuit. Two methods are introduced in this work. The first method is magnetic shaking that is widely used in shielding applications. An AC component is added to the core of the winding used in SMPS. The relative permeability is improved, causing the inductance of the coil to increase. However, the method is facing some technical difficulties to be integrated in the power circuit. Another method is also introduced by adding a DC magnetic field component equivalent to the DC flux component of the main winding in SMPS. This brings the operating point from the non-linear near saturation region to the more linear region. This not only keeps the inductance constant, but also causes a significant increase in its value. As a result, the core size is dramatically reduced. The principle is explained and the method is verified to reduce the inductor ripple and size requirement. Another approach is taken to reduce the overall power supply size. Optimizing the number of components is another desired issue in power supply topologies. Reducing the component count results in board size reduction and power density improvement. In the current work, a low component count three-port buck-boost converter is proposed. This converter has only two active components and three passive components. The converter is optimized for renewable energy utilization where energy is stored in batteries for some period and discharged into the load in another period. Solar street lighting is a typical application. The proposed circuit was analyzed, simulated, and proved well suited for the application.