Research On Asymmetrical Half Bridge Converter

With the development of power electronics technology, Pulse Width Modulation DC-DC converters get more and more application. Nowadays, high performance, high efficiency and light weight are the most important performance figure of all kinds of PWM DC-DC converters. In order to increase the power density and output efficiency, the soft switching techniques is the key. However it makes the circuit complex, which means the increase of cost, and affects the competitiveness of commercial product.This thesis presents an improved asymmetric zero-voltage half-bridge topology. It can realize soft-switch technology without increase the cost of converter. The improved Asymmetrical Half-Bridge can also remove the resonant peak voltage. The topology of asymmetrical half bridge is introduced in Chapter 2, including the principle of the circuit,the relationship between the duty cycle ,input voltage and output voltage ,and the deflection of magnetism. The voltage of block capacitor and the current of the original turns of transformer of each state have been discussed, then deduce the condition of Zero voltage switch(ZVS),which give the theory guidance for setting the reasonable dead time. Finally, the possibility of zero voltage switching is proved by the simulation of pspice software. In part 3. ,a small average circuit half bridge converter power stage is established by method of state space averaging. In term of the method referred, a system model of total converter is founded. The characteristic of stabilization and dynamic is analysed and the compensator is designed basing on it. At last,the simulation performed by Matlab software confirm the stabilization of system. Based on the analysis above, a two-class AC/DC converter ,consist of power factor circuit and asymmetrical half bridge circuit is designed to prove that the asymmetrical half bridge can achieved zero voltage switching .In conclusion, the correctness and feasibility of the new converter are proved by theory analysis, simulation research and experimental validation.