Research On A High Reliability Active Clamp Forward DC-DC Converter

After years of development, switching power supply has replaced the linearregulated power supply with its superior performance. And it is more and more widelyapplied in almost all fields. The excitation converter due to its high reliability andefficiency are widely used in aerospace system, communication power supply, computerpower supply and so on. In recent years, along with the technology innovation ofcomputer and microelectronics industry, switching power supply with low voltage andhigh current output has became the hot topics in the study by scientific researchpersonnel. In this paper, the high reliability DC-DC power supply with low voltage andhigh current output is made in-depth research.Firstly, this paper compared with the advantages and disadvantages of severalkinds of magnetic reset, and the active clamp magnetic reset method was adopted torealize zero voltage opening. It can use the clamping capacitance, output capacitance ofthe switch tube and the inductance of excitation transformer winding in resonance tocreate the condition of soft switch, reduce the switching loss, so as to improve thepower efficiency. And during the period of the main switch off, clamping switch canlimit the voltage value of main switch, to overcome the leakage inductance of thetransformer in a conventional hard switching circuit and the voltage spike of theparasitic capacitanceControl technology is used to ensure the stability of switch power supply outputvoltage and current. At first, on the basis of analyzing and studying the differentfeedback control methods, and then designs the amplitude modulation magneticfeedback circuit with the voltage control mode, introduces its working principle, andcarries on the simulation. The simulation results show that the method can effectivelyguarantee that the power supply has a stable output voltage and a good dynamiccharacteristic. The transformer isolation method has a simple structure, can effectivelyrealize the signal isolation between the input and output. It also has a long life and agood irradiation resistance. In order to analysis of the power supply loop effectively intheory, this paper builds the model of the active clamp forward, and then makes a smallsignal analysis of the amplitude modulation magnetic feedback. On this basis, thecompensation circuit has been designed. The simulation results show that the loop hasgood amplitude and frequency characteristics.Finally, this paper designs a DC-DC power supply prototype with5V/20Aoutput. Through analysis the experimental waveforms including output voltage andcurrent when load switching, voltage ripple, and tests the efficiency curve, the prototype can meet the requirements of the indicators. A good stability and dynamiccharacteristics can be achieved using the design of this paper, at the same time,achieving a high efficiency.