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A switched-mode power supply (switching-mode power supply, switch-mode 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 source, like mains power, to a load, 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. 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. ==History== ; 1910: An inductive discharge ignition system invented by Charles F. Kettering and his company (Delco) goes into production for Cadillac. This is a mechanically-switched version of a flyback boost converter with an autotransformer (the ignition coil). Variations of this ignition system are in all non-diesel internal combustion engines. ; 1926: "Electrical Condensors" by Coursey〔(【引用サイトリンク】title=When was the SMPS power supply invented? )〕 mentions high frequency welding〔(【引用サイトリンク】title=Electrical condensers (Open Library) )〕 and furnaces.〔 ; ca 1936: Car radios used electromechanical vibrators to transform the 6 V battery supply to a suitable B+ voltage for the vacuum tubes.〔Cadillac model 5-X, a 5 tube supherheterodyne radio, used a synchronous vibrator to generate its B+ supply. RadioMuseum.org, http://www.radiomuseum.org/r/cadillacge_5x.html#a〕 ; 1959: Transistor oscillation and rectifying converter power supply system is filed.〔(google.com/patents - Transistor converter power supply system )〕 ; 1970: High-Efficiency Power Supply produced from about 1970 to 1995.〔(slack.com - Test Equipment and Electronics Information )〕〔(kahrs.us - The Tektronix 7000 Oscilloscope series )〕〔(tek.com - 7000 Series oscilloscopes FAQ )〕〔(docmesure.free.fr - TEKSCOPE March 1971 ) 7704 High-Efficiency Power Supply (service manual march-1971 .pdf)〕 ; 1972: HP-35, Hewlett-Packard's first pocket calculator, is introduced with transistor switching power supply for light-emitting diodes, clocks, timing, ROM, and registers.〔(jacques-laporte.org - The HP-35's Power unit and other vintage HP calculators. )〕 ; 1977: Apple II is designed with a switching mode power supply. "''Rod Holt was brought in as product engineer and there were several flaws in Apple II that were never publicized. One thing Holt has to his credit is that he created the switching power supply that allowed us to do a very lightweight computer''".〔(businessinsider.com - EXCLUSIVE: Interview With Apple's First CEO Michael Scott ) 2011-05-24〕 ; 1980: The HP8662A synthesized signal generator went with a switched power supply.〔(【引用サイトリンク】title=HP 3048A )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Switched-mode power supply」の詳細全文を読む スポンサード リンク
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