Research On Wide Input Voltage Range Multi-Output Low Power Switching Power Supply

Multi-output low power switching power supply calls for not only the different low voltage low power outputs, but also the quality of the voltage and the high reliability of the entire switching power supply.We can choose single-stage converter as the topology of the multi-output low power switching power supply, for example, single-ended Forward converter, single-ended Flyback converter and Push-Pull converter. However, Due to the limitations of the single-stage converter, when the bus voltage is high and wide input voltage range, the single-stage converter is not suitable for multi-output low power switching power supply. Then the two-stage cascaded power architecture is proposed in the thesis. The cascaded Buck converter and Push-Pull converter is selected. Then the voltage-fed topology and current-fed topology of cascaded topology is researched and compared.The excitation style of Push-Pull converter transformer is bilateral excitation, due to the impact of the transformer leakage inductance, the power switches withstand large drain voltage stresses and shock when they switch off, So the method should be researched to reduces the transformer leakage inductance and eliminate shock.The interaction between individually designed power converters may cause the instability of the whole power system in the cascaded topology. In a small-signal sense, system level stability is determined by the impedance ratio between source converter output impedance and load converter input impedance. So the impedance characteristics of Buck converter and push-pull converter should be analyzed.The controller of switching power supply is designed with the average current mode control. First, the current loop controller is researched based on the characteristic of the current loop. Then, the voltage loop controller is researched based on the current loop which can be seen as a whole. In the end, the simulation result is presented with the tool of MATLAB.