Research On Parallel-Parallel And Serial-Parallel Combined Two-Transistor Forward Converter

This paper presents and does research on two topologies: parallel-parallel combined two-transistor forward converter and serial-parallel combined two-transistor forward converter.Two types of steady operation principle of two-transistor forward converter are introduced in this paper. Then the operation principle of parallel-parallel combined two-transistor forward converter with LCD non-dissipative snubber is analyzed. The switches are turned off with zero voltage transaction. And the characteristics of this topology are introduced. The combined converter is simulated and analyzed with PSpice software. The design of parameters for LCD snubber is introduced. Finally, a 2.3kW prototype is researched and developed successfully.Serial-parallel combined two-transistor forward converter is presented for high input voltage and high power application, and the operation principle of the topology is analyzed in this paper. All switches are turned off with zero voltage switching, and the two switches of them are turned on with zero current and zero voltage switching. The difference of input capacitances, conducting voltage drop of switches, duty cycle and windings of the transformer of the combined converter influences the voltage balance of the input capacitors. The results are simulated and analyzed with Saber software. The design of RCD snubber and voltage feedback loop is introduced. Finally, a 1kW prototype is researched and developed successfully to verify the operation principle of the combined converter.