Switched-mode power supply

A switched-mode power supply (SMPS), also called switching-mode power supply, switch-mode power supply, switched power supply, or simply switcher, is an electronic <a href="/facts/Power_supply/4A8zBRHn">power supply</a> that incorporates a <a href="/facts/Switching_regulator/RWQATaje">switching regulator</a> to <a href="/facts/Electric_power_conversion/sKmxxvHx">convert electrical power</a> efficiently.
Like other power supplies, a SMPS transfers power from a DC or AC source (often <a href="/facts/Mains_electricity/rjE90Hg0">mains power</a>, see <a href="/facts/AC_adapter/zyGpmNcX">AC adapter</a>) to DC loads, such as a <a href="/facts/Personal_computer/koaYfNce">personal computer</a>, while converting <a href="/facts/Voltage/EN2po6N2">voltage</a> and <a href="/facts/Electric_current/Dc1xdnUX">current</a> characteristics. Unlike a <a href="/facts/Linear_power_supply/4A8zBRHn">linear power supply</a>, the pass <a href="/facts/Transistor/Bmr8zwL0">transistor</a> of a switching-mode supply continually switches between low-<a href="/facts/Dissipation/C134STy1">dissipation</a>, full-on and full-off states, and spends very little time in the high-dissipation transitions, which minimizes wasted energy. <a href="/facts/Voltage_regulator/RWQATaje">Voltage regulation</a> is achieved by varying the ratio of on-to-off time (also known as <a href="/facts/Duty_cycle/B2tbtXTh">duty cycle</a>). In contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. The switched-mode power supply's higher <a href="/facts/Electrical_efficiency/HBBMzuon">electrical efficiency</a> is an important advantage.
Switched-mode power supplies can also be substantially smaller and lighter than a linear supply because the transformer can be much smaller. This is because it operates at a high switching frequency which ranges from several hundred <a href="/facts/Hertz/6Wshj5qm">kHz</a> to several MHz in contrast to the 50 or 60 Hz <a href="/facts/Mains_frequency/hd4jVcSk">mains frequency</a> used by the transformer in a linear power supply. Despite the reduced transformer size, the power supply topology and <a href="/facts/Electromagnetic_compatibility/vRBTnls5">electromagnetic compatibility</a> requirements in commercial designs result in a usually much greater component count and corresponding circuit complexity.
Switching regulators are used as replacements for linear regulators when higher efficiency, smaller size or lighter weight is required. They are, however, more complicated; switching currents can cause electrical noise problems if not carefully suppressed, and simple designs may have a poor <a href="/facts/Power_factor/TLKPkptn">power factor</a>.
Talking about the SMPS used in <a href="/facts/Desktop_computer/edFPINdK">desktop computers</a>, they work the same. They first filter the AC voltage out or rectify it if it is needed and feed the voltage into a high-frequency oscillator circuit composed of <a href="/facts/MOSFET/eTDJT2Km">mosfets</a>. These switches turn on and off rapidly (10,000 to 50,000 times per second according to set voltage and current) creating an insulated DC voltage.

Switched-mode power supply open-in-new

Switched-mode power supply