ABSTRACT: Fly-back converters have been widely used because of the irrelative simplicity and their excellent performance for multi output applications. They can save cost and volume compared with the other converters, especially in moderate low power applications..In a fly-back converter, a transformer is adopted to achieve galvanic isolation and energy storage. Modelling is done without parasitic as well as with parasitic components. A detailed analysis, simulation and different control strategy are conferred for Fly-back converter. To verify the design and modelling at primary stage, study of the converter in for input AC voltage220V at 50Hz and output DC voltage of 440V and 150W output power rating. I.INTRODUCTION Fly-back converter is the most commonly used SMPS circuit for low output power applications where the output voltage needs to be isolated from the input main supply. The output power of fly-back type SMPS circuits may vary from few watts to less than 100 watts. The overall circuit topology of this converter is considerably simpler than other SMPS circuits. Input to the circuit is generally unregulated dc voltage obtained by rectifying the utility ac voltage followed by a simple capacitor filter. The circuit can offer single or multiple isolated output voltages and can operate over wide range of input voltage variation. In respect of energy-efficiency, fly-back power supplies are inferior to many other SMPS circuits but it's simple topology and low cost makes it popular in low output power range. The commonly used fly-back converter requires a single controllable switch like, MOSFET and the usual switching frequency is in the range of 100 kHz. A two-switch topology exists that offers better energy efficiency and less voltage stress across the switches but costs more and the circuit complexity also increases slightly. Parameters such as switching frequency, distortion, losses, harmonic generation and speed of response are typical of the issues which must be considered when developing modulation strategies for a particular family of converters .The DC converter is a device which transforms AC to DC i
