| In some certain cases, such as in the new energy field, the input voltage may exceed the normal range and change over a wide range. In order to fit for such situation, an ISOP full bridge Boost converter is adopted. The full bridge part in the normal full bridge Boost converter is replaced by an ISOP structure, which can reduce the output voltage ripple as well as voltage and current stress of components.First, the work principle of the converter is explained. Conclusion is made that the boost ratio is not affected by the series connection structure. In order to improve the reliability of the ISOP FB-boost converter, a three-interval control scheme is used, in which the converter operates in boost, FB-boost and FB modes in low, medium and high input voltage regions, respectively. The transition interval width selection principle is given.A novel passive auxiliary circuit for zero-voltage-switching(ZVS) operation is then analyzed. For a similar peak current in the auxiliary branch, needed for ZVS, a reduction in rms current is achieved to decrease the conduction losses in the power switches and in the auxiliary circuit.According to the former results, a two-module ISOP full bridge Boost circuit is designed, using multi-channel analog switch selector switch to choose working state. Complete designing and testing of the main circuit and control circuit.Finally, small-signal model is built for different working mode to make preparations for the closed-loop control. Common duty ratio control is adopted for its simple and effectiveness. Large signal feed forward is added for its outstanding performance on regulating output voltage when there is an input fluctuation. |
