Isolated dual active bridge (DAB) converter circuits include first and second bridge circuits connected to primary and secondary sides of a transformer for DC to DC conversion. DAB converters can be used in unidirectional or bidirectional power conversion applications. The direction of power transfer is controlled by the leading or lagging phase relationship between switches of the first and second bridge circuits, where the bridge that is driven with a leading phase transmits power to the bridge operated with a lagging phase. Controlling the phase shift between the primary and secondary side bridge circuits allows control of the power flux and the amount of energy transferred through the isolation transformer. Isolated DAB converters provide low noise operation through linear control capabilities, along with the ability to implement zero voltage switching (ZVS) over a large phase shift range. These converters can also achieve lower RMS current levels for the same average output current compared to other types of DC to DC converters. However, the phase shift control mechanism requires operation of the primary and secondary bridge circuits according to shared clock information. Conventional isolated DAB converters use an isolated communication channel to share a clock between the primary and secondary sides, such as optical, capacitive or inductive circuits to transfer a clock signal from one side to the other. The shared clock can be used to implement closed-loop output voltage regulation by controlling the phase shift between the primary and secondary bridge switching signals. However, the additional isolated communication channel adds cost and complexity to the circuit designed and increases circuit area.
USPTO Backgrounds
USPTO Backgrounds