The electric energy is not normally used in the form in which it was produced or distributed. Practically all electronic systems require some form of energy conversion. A device that transfers electric energy from a given source to a given load using electronic circuits is referred to as Power Supply.
A typical application of a power supply unit (PSU) is convert utility AC voltage into regulated DC voltage required for electronic equipment. Nowadays in PSU the energy flow is controlled with semiconductors that are continuously switching on an off with high frequency. Such devices are referred to as switch mode power supplies or SMPS. They offer greater efficiency compared with linear supplies because a switch can control energy flow with low losses: when a switch is off, it blocks the flow of voltage and current, can be relatively low in both states. SMPS are also smaller in size and lighter in weight due to the reduced size of passive components and lower heat generation. The industry tended toward miniaturization, advancements in semiconductor technology, as well as various energy efficiency regulations have made "switch" the dominant type of PSR across practically the full spectrum of applications. Most of the switchers manufactured today for AC input applications include a PFC front end.


電能通常不會用在其生產(chǎn)或分布的形式。幾乎所有的電子系統(tǒng)需要某種形式的能量轉換。通過電路把電能從一個特定源轉移到一個特定負載所用的設備稱作為電源。
電源裝置(PSU)的典型應用是將交流電轉換成電子設備所需直流電。如今在電源裝置，能量流通過不間斷高頻半導體開關來控制。這種裝置被稱為開關電源。與線性電源相比，他們能提供更大的效率，因為開關可以低損耗地控制能量：當開關關閉時，它會阻止電壓和電流的流動，在兩種狀態(tài)中均比較低。同時，開關電源的尺寸較小，重量較輕，從而減少了無源元件的尺寸，降低了熱量的產(chǎn)生。小型化傾向的行業(yè)，隨著半導體技術的發(fā)展進步，同時各種能量效率的控制使得“開關” 得到了全方位的應用，在壓力-狀態(tài)-響應中占主導地位。大部分的切換開關早就了今天包括PFC前端末端在內(nèi)的交流輸入的應用。