PWM控制器處理多個(gè)拓?fù)浣Y(jié)構(gòu)與負(fù)輸入電壓

　　傳統(tǒng)上，電信和數(shù)據(jù)通信設(shè)備提供負(fù)的直流輸出電壓，如48伏，為系統(tǒng)總線。原因很簡(jiǎn)單：直流電壓保持低噪音，可以容易地產(chǎn)生從普通鉛酸電池，通常約12伏特。此外，負(fù)電源使電纜和銅線遠(yuǎn)離腐蝕。通常情況下，在應(yīng)用服務(wù)器和計(jì)算機(jī)，這不受管制的負(fù)直流輸出電壓倒正母線電壓驅(qū)動(dòng)各種降壓轉(zhuǎn)換器，必須產(chǎn)生一個(gè)穩(wěn)壓直流低電壓高電流輸出驅(qū)動(dòng)一個(gè)范圍廣泛的系統(tǒng)主板上的電子負(fù)載。這種系統(tǒng)板還使用諸如放大器，運(yùn)算放大器和傳感器的運(yùn)作，調(diào)節(jié)，負(fù)電源或分裂的供應(yīng)，以保持交流信號(hào)清潔。

　　將這種不受管制的負(fù)電源轉(zhuǎn)換成一個(gè)受規(guī)管的負(fù)降壓電源或一個(gè)調(diào)節(jié)的負(fù)升壓電壓，以及一個(gè)積極的調(diào)節(jié)電壓，是不平凡的。每個(gè)拓?fù)浣Y(jié)構(gòu)是復(fù)雜和耗時(shí)的分立元件。更重要的是，它不保證性能，可以花費(fèi)更多，同時(shí)占用更多的電路板空間。

　　To make such a task easy for designers， Linear Technology has developed a novel synchronous multi-topology DC/DC controller， the LT8709， which can be easily configured in buck， boost， buck-boost， and inverting topologies with negative input， making it highly versatile for a wide range of power supply designs. In addition， its synchronous operation means that the output diode is replaced with a high efficiency P-channel MOSFET， thereby increasing efficiency and allowing for higher output currents up to 20 A. As a result， it eliminates the heatsink typically required in medium- to high-power applications， thus enabling a designer to generate a wide range of DC/DC conversion solutions with negative input voltage for a wide range of power supply designs.

　　This article investigates the architecture of this novel DC/DC controller to understand why it is so easy to generate buck， boost， and buck-boost， as well as inverting topologies with negative input voltages. Besides uncovering its unique features and functionalities， we will also present working examples of LT8709-based negative-to-negative and negative-to-positive DC/DC conversion solutions at a desired output load current. Measured performance results for a design example also will be discussed.