Increasing the voltage and the switching frequency in a dual active bridge using a normally-on SiC JFET in a cascode configuration

Silicon Carbide (SiC) transistors are becoming increasingly available in the market due to the fact that its manufacturing process is more mature. These new semiconductors have several advantages compared with traditional Silicon (Si) devices, such as, for example, higher voltage blocking capability, lower conduction voltage drop and faster transitions, which make them more suitable for high-power and high-frequency converters. The introduction of these new devices in switching power supply systems provides better performance enabling higher frequencies and consequently smaller, lighter and cheaper systems. Moreover, the increasing demand of an intermediate storage of electrical energy in battery systems has resulted in the need of bidirectional DC/DC power converters with galvanic isolation, for example due to the use of renewable energy or the incoming traction applications. A Dual Active Bridge (DAB) is a bidirectional DC/DC converter often used in these applications. This topology presents the advantages of soft-switching commutations, low cost, and high efficiency. Therefore, the use of this topology is proposed for applications where power density, cost, weight, and reliability are critical factors. This paper is focused in the inclusion of commercially available SiC transistors in a DAB converter taking advantage of the characteristic of these devices, as their good switching performance and their high voltage blocking capability. The main goal is to increase the voltage of the input or output voltage in a DAB and also to increase the switching frequency at the same time.