Design And Study Of Miniaturized, High Efficiency And Reliability Switching Power Supply

With the electronic devices developing towards high integrated, high efficiency and low power loss, the performance requirement of the power system is higher and higher. Module power supply has been widely used in computer, communication and aerospace field, due to the small size, light weight and flexibility, etc. Meanwhile, for module power supply, it brings about higher requirements on efficiency, power density and reliability.The rapid growth of semiconductor devices brings about higher integration level and efficiency for power module. In contrast, the development of power magnetic components, which occupy large space in power module, is slower. This paper focuses on the transformer which is high loss and high heat, then improve the efficiency and reliability of the transformer. Afterwards, adopt the active clamp forward converter and optimize the circuit and PCB layout. Then we complete the design of the switching power supply which possesses miniaturized, high efficiency and high reliability.Firstly, the theoretical analysis of transformer is introduced. Compared with traditional transformer, planar transformer has a series of virtues such as smaller size, lower leakage inductance and high produce consistency, which is ideal choice for isolated DC/DC power module. Because of the special structure, the design process of planar transformer is different from the traditional transformer, then, a thermal design process of planar transformer is presented.Secondly, optimization analysis on the winding structure of the planar transformer is presented. The windings of the planar transformer can be affected by skin effect and proximity effect on high operating frequency, which cause the change of winding loss and other parasitic parameters. By using the finite element analysis software of Maxwell, the wingding structure can be simulated analyzed with related theory. The result shows that interleaving techniques can obviously reduce the leakage inductance and wingding loss. By using the software platform ANSYS Workbench, we carry on the electromagnetism-thermal coupling simulation for the planar transformer, which meets the design requirements.Next, the active clamped forward converter has been analyzed. This isolated topology has lower voltage stress, broader input voltage and higher efficiency, which are suitable for low and medium power supply application. Compared with single ended forward converter, this converter needs no magnetic flux reset coil and has high utilization of magnetic core. The secondary of isolated transformer adopt self-driven synchronous rectifier technique. It can effectively reduce the transmission loss caused by Schottky rectifier. By using the LM5025 D solution of TI company, we complete the circuit design of power stage and control stage. And we also do some works on parts selection and optimizing of PCB layout.Finally, combined with the result of planar transformer and circuit design, an experimental prototype has been made. This switching power supply is tested under the condition of room temperature, standard input voltage 28 V, output voltage 5 V and output current 12 A, the efficiency is about 92%, the power density is 2.0 W/cm3, the ripple voltage is 64 mV; under the condition of input voltage 16-36 V, output voltage 5 V and output current 12 A, the efficiency is more than 90%, the ripple voltage is less than 80 mV. The module power supply is placed into heat oven and work steadily for 48 hours under the temperature of 100℃. In conclusion, this experimental prototype has small size(quarter brick), high efficiency(more than 90%), high temperature reliability(working steadily for 48 hours under 100℃), etc. And these results also verify the validity of the theoretical analysis above and design of module power supply.