便携式设备同步升压转换器延长电池寿命

　　介绍

　　升压转换器在便携式设备中经常使用产生较低的输出电压电池输入电压。常见的电池配置包括两到三个碱性或镍氢电池或，越来越多，Li Ion电池，产生典型的输入1.8V电压4.8v之间。

　　The 12Voutput converter showninFigure 1 isdesigned torunfromanytypicalsmallbatterypowersource. This design centers around the LTC®3122 boost converter， which can efficiently generate a regulated output up to 15V from a 1.8V to 5.5V input. The LTC3122 includes a 2.5A internal switch current limit and a full complement of features to handle demanding boost applications， including switching frequency programming， undervoltage lockout， BurstMode® operation or continuousswitchingmode， andtrueoutputdisconnect. The integrated synchronous rectifieris turned offwhen theinductorcurrentapproacheszero， preventingreverse inductorcurrentandminimizingpowerlossatlightloads.

　　This unique output disconnect feature is especially important in applications that have long periods of idle time. While idling， the part can be shut down， leaving the output capacitor fully charged and standing by for quick turn-on. In shutdown， the part draws less than 1µA from the input source.

　　Because the batteries used in portable devices are usually as small as possible， they present high internal impedance under heavy loads， especially close to the end of their discharge cycle. Unlike other boost converters that struggle with high source impedance at startup， the LTC3122 prevents high surge currents at startup.