Electromagnetic disturbance of an electrical system affecting itself or another system is called electromagnetic interference (EMI). In modern design of electrical systems, the system must be compatible with its surrounding environment and its performance degradation due to the existing disturbances should be minimized. Environmental noises bring some considerations into primary design of an electrical circuit to prevent performance degradation in dealing with some acceptable levels of noise. Switching converters generate high frequency electromagntic interference noise because of fast current and voltage switchings. These generated noises are called conducted EMI noise. Due to extensive use of power electronic converters and communication systems, EMI minimization is an important problem. Minimizing conducted EMI noise is often done by trial and error to be adapted to standards. It is possible to predict EMI before production with software simulations and then attempting to reduce it. Although this is a widespread method, there exists some developed systematic EMI reduction techniques and design methods. These extensive techniques fall into two categories: 1) post generation noise reduction and 2) noise reduction in generation phase. In this research, some essential problems in EMI are studied and conducted EMI reduction is considered in switching converters. A pulsewidth modulation soft single switched (PWM ) converter is studied from EMI viewpoint. The capacitive coupling of the MOSFET to the heat sink and resonance between the leakage inductance of coupled inductors and the switch junction capacitor are major participants in common-mode (CM) electromagnetic interference noise in this converter. To reduce the conducted EMI, two methodes of parasitic cancellation techniques are proposed. In these methodes, with the help of generatated negative capacitance and negative inductance, the parasitic capacitance and the leakage inductance can be canceled. Thereupon the conducted EMI will be reduced. These methods are applied to a PWM boost converter, then the conducted EMI of the converters are modeled and predicted. After modelling the components of the converters and obtaining the results of computer simulation, a prototype of the converter is implemented in the laboratory. Simulation results and experimental measurements are compared, and precision of the simulation results are confirmed. Key Words 1- Electromagnetic interference (EMI), 2- Switching converters, 3- Conducted EMI, 4- Pulsewidth modulation soft single switched (PWM ) converter