Improvement of a new soft switching passive snubber cell for PFC converters

The increase in the use of grid connected nonlinear loads have caused lots of harmonic currents and electromagnetic interference (EMI) which, in return, have caused distortion, dissipation and inefficient use of electrical grid. Furthermore, energy resources have been exhausting rapidly. Hence, it has become very important to use electrical energy effectively. In addition to decreasing efficiency and distortion of electrical grid, harmonic currents also cause error and breakdown in electrical devices connected to grid. Therefore, various national and international standards and restrictions have been being carried out and enforced to use energy more effectively. As a result, there have been many industrial and academic studies performed on PFC circuits to ensure desired power factor and harmonic current limits. Desired harmonic current level and power factor usely achieved with passive filters, active filters and PFC converters. Performance of pasif filters is too low whereas they are costly.Since active filters are too complex and expensive they are only acceptable for high power unique application. However, in addition to connection of electrical devices to grid through AC ? DC converters,easy control, low cost and high performance have made PFC converters attractive. Furthermore, operation PFC converters with high frequency decreases size of filter compenents which in return low cost. High power density and high input current quality can only be achievedby increasing switching frequency. However, switching lossesand EMI also increase by increasing switching frequency. Softswitching techniques are applied to suppress switching lossesand EMI caused by increasing switching frequency. In this thesis, a new improved lossless passive snubber circuit for continuous conduction mode PFC converters proposed in order to decrease switching losses and EMI. The detailed steady-state analysis andthe simulation of the proposed circuit are carried out, and thistheoretical analysis is verified by implementing a 1-kW and 50-kHz converter.