數(shù)字控制環(huán)路提高效率

　　有一個(gè)不斷推動(dòng)更高的效率，功率轉(zhuǎn)換器設(shè)計(jì)。此外，需要支持高水平的計(jì)算處理能源效率導(dǎo)致了負(fù)荷的創(chuàng)作具有高度動(dòng)態(tài)的行為，隨著處理器和外設(shè)激活和去激活基于他們的工作量。這是推動(dòng)電源轉(zhuǎn)換器架構(gòu)的變化，從模擬到數(shù)字實(shí)現(xiàn)。

　　開(kāi)關(guān)模式功率轉(zhuǎn)換器的操作本質(zhì)上是數(shù)字的，因?yàn)樗蕾?lài)于從一個(gè)轉(zhuǎn)換器的另一側(cè)的離散電荷分組轉(zhuǎn)移到另一個(gè)。該技術(shù)主要是基于采樣的狀態(tài)在離散點(diǎn)的時(shí)間，以確定多久的開(kāi)關(guān)，提供電荷應(yīng)保持在。然而，盡管這種明顯的數(shù)字結(jié)構(gòu)，大多數(shù)實(shí)現(xiàn)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.