Switched Mode Power Supply (SMPS) is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently. An SMPS transfers power from a DC or AC source to DC loads, such as a personal computer, while converting voltage and current characteristics. Unlike a linear power supply, the pass transistor of a switching-mode supply continually switches between low-dissipation, full-on and full-off states, and spends very little time in the high dissipation transitions, which minimizes wasted energy. Voltage regulation is achieved by varying the ratio of on to off time. In contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. This higher power conversion efficiency is an important advantage of a switched mode power supply. Switched mode power supplies may also be substantially smaller and lighter than a linear supply due to the smaller transformer size and weight. Recently SMPSs are categorized by their power efficiency like 80 Plus White, 80 Plus Bronze, 80 Plus Silver, 80 Plus Gold, 80 Plus Platinum and 80 Plus Titanium.