<P> A switched - mode power supply (switching - mode power supply, switch - mode power supply, switched power supply, SMPS, or switcher) is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently . Like other power supplies, an SMPS transfers power from a DC or AC source (often mains power) 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 . Ideally, a switched - mode power supply dissipates no power . 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 . </P> <P> Switching regulators are used as replacements for linear regulators when higher efficiency, smaller size or lighter weight are required . They are, however, more complicated; their switching currents can cause electrical noise problems if not carefully suppressed, and simple designs may have a poor power factor . </P>

Smps are superior to linear power supplies in respect of