Design Of A Full Bridge Switching Power Supply Based On UC3846

With the development of power electronics technology, the demand of all kinds of electronic equipment for the performance of the power like the weight, volume, efficiency and reliability become more and more stringent.Today the switching power supply usually take the voltage-controlled technology as the way of control. Voltage-controlled technology only sample the output voltage, there exists several drawbacks, as a slow response, poor stability, even when the large signal changes, it tendency towards oscillation, resulting in the damage of the power tube. Based on the disadvantage of the voltage control circuit, the current control technology began developed during the last ten years, it consists of an inner current loop and voltage loop, is a double loop control system, it’s load regulation and transient response characteristics are very high, and over flow voltage protection are strong, therefore, it’s study and design have become more and more significance.Firstly, this paper respectively introduces the voltage control mode and current control mode, then analyzes and compares their advantages and disadvantages, finally Introduces the slope compensation circuit and give the step of the calculation of the slope compensation circuit. Secondly, according to the requirements of circuit design, the designer selects full-bridge topology circuit structure, and design the full-bridge topology circuit, also give the design and calculation method of the main circuit parameters of each element, it mainly includes:input and output rectifier filter circuit, anti-surge circuit and high frequency transformer design. Then select the current control chip, analysis and design the current chip, the power switch tube driving circuit in detail. Finally, based on the theoretical analysis and calculation, build the full-bridge topology circuit of the experimental platform, and give the circuit installation and commissioning.The experimental results show that using current mode control can achieve a good over-current protection, can improve the ability of inhibit the flux imbalance, and the load regulation, dynamic response speed are also high, for all this reason the current mode control has a good practical value.