The Design Of Wide Input Voltage Range Isolated Converter

Wide input voltage converter are widely used in renewable energy systems, such as photovoltaic systems, fuel cells and super capacitor hybrid systems, and other Chemical batteries systems. The paper intends to design a new type of wide input isolation converter to broade the range of input voltage to 8:1.A new kind of bridge circuit with variable structures was designed by the thesis, which foucs the advantages of variable structure type converter and double transforms type converter. According to the changes of input voltage,the system could work in three different modes to keep the system in high efficient at different input voltage levels. We found that the loop gain was also changed according to the change of input voltage through the small signal modeling.To improve the dynamic response of the converter and simplify the control loop, the thesis introduced the input voltage to triangular wave generating circuit with different proportion under each modes, so the system had voltage feedforward PWM control features. In addition, through the designed triangular wave generating circuit, the transfer function of entire loop are same to the two order buck circuit. Thus the design of compensation was very simple and had good dynamic response.Through magnetic integration technology which integrated the input filter capacitor, output filter capacitor, and isolation transformers into a magnetic core, the power density of system were greatly improved. The interaction between the transform and inductor was small for wounding with a appropriate decoupled manner. Compared to using separate components parts, the performance of the system will remain basically unchanged. The input and output inductors were coupled with reverse manner for the purpose that DC flux of public magnetic circuit could be offset each other to prevent the core saturation.Though simulation and experiment test, the feasibility of the variable structure of the bridge circuit in wide-range voltage input applications was verified in the thesis. When the input voltage changed and load mutated, the system could still be stable and operated well.