Research On High Efficiency Two Transistor Forward Converter

High power density as well as high reliability has always been the goal to pursue in the field of modern electric power converters. As one kind of the modern electric power converters, two transistor forward converter has many attractive characteristics, such as low switch voltage stress, inherent anti-break-through capability, and high reliability. It becomes one of the most widely used topology in the industrial application, especially in the telecommunication energy systems, welding machines and computer power supply.Based on driven approach of main power switch in the primary side of the transformer and rectifier circuit, this paper aims at not increasing the complexity of the main circuit and control circuit of origin, to improve the traditional two transistor forward converter and enhance the efficiency of circuit. The paper made analysis of the process of improved circuit and the specific problems encountered by the application and gave the solutions of the problems. Compared with the traditional circuit, the control circuit of the improved converter has been modified to streamline, one of the two main switches can work in a ZCS state, synchronous rectifier circuit can overcome the dead zone and light load loop current, and the circuit's overall performance has been enhanced.Using the current mode PWM controller, a 15V/300W power system was developed during the experiment by the author. The experiment proved stable jobs of the system and simplifying control circuit (similar with the Forward circuit).The circuit improved 3-4 percentage points more efficient than traditional circuit, with the maximum efficiency of 88% of full load.