數字控制環(huán)路提高效率

　　有一個不斷推動更高的效率，功率轉換器設計。此外，需要支持高水平的計算處理能源效率導致了負荷的創(chuàng)作具有高度動態(tài)的行為，隨著處理器和外設激活和去激活基于他們的工作量。這是推動電源轉換器架構的變化，從模擬到數字實現。

　　開關模式功率轉換器的操作本質上是數字的，因為它依賴于從一個轉換器的另一側的離散電荷分組轉移到另一個。該技術主要是基于采樣的狀態(tài)在離散點的時間，以確定多久的開關，提供電荷應保持在。然而，盡管這種明顯的數字結構，大多數實現是基于模擬控制電路。

　　Under the pulse-width modulation （PWM） scheme employed by most switched-mode power supplies， the converter supplies a packet of charge to the output rail by first turning on one of two parallel FETs. The high-side FET is activated for a certain amount of time determined by the PWM controller. During this on time， the output voltage swings up towards the input voltage. The current flows into an inductor that is used as temporary storage for the charge. The current in the inductor rises linearly with its slope given by the formula （Vin - Vout）/L.

　　Once the controller switches off the high-side FET， the low-side switch is kept off for a short period. This prevents an unwanted and wasteful shoot-through of power across the two FETs. Then the low-side FET is activated for a short period and then allowed to switch on. The inductor current then begins to fall with a slope of -Vout/L until the low-side FET is turned off and the cycle begins again. As a result， the current on the output side tends to oscillate above and below an average level. Filtering by the inductor and output capacitors helps smooth the current and voltage delivered to the load.