Switched-mode power supplies can also be substantially smaller and lighter than a linear supply because the transformer can be much smaller. The switched-mode power supply's higher electrical efficiency is an important advantage.

In contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. Voltage regulation is achieved by varying the ratio of on-to-off time (also known as duty cycles). A hypothetical ideal switched-mode power supply dissipates no power. 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. Like other power supplies, an SMPS transfers power from a DC or AC source (often mains power, see AC adapter) to DC loads, such as a personal computer, while converting voltage and current characteristics. An adjustable switched-mode power supply for laboratory useĪ 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.

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