Thus to find comparable design of DAB1 and DAB3, the operating point of DAB1 can be first determined, with a selection of L, d and Ф that makes the whole DAB1 system of relatively high efficiency. Transformer current IL1 can be determined from calculation or simulation, and the corresponding DAB3 will 2/3 of the DAB1 current. With d3=d1, the other two variables of L3 and Ф3 can be determined by IL3 and Po.