凌力爾特公司（Linear）推出80V高壓側(cè)電流檢測DC/DC轉(zhuǎn)換器LT3956,該器件為作為恒定電流和恒定電壓穩(wěn)壓器工作而設(shè)計。它非常適用于驅(qū)動大電流LED以及給電池和超級電容器充電。其4.5V至80V輸入電壓范圍使其非常適用于多種應(yīng)用，包括汽車、工業(yè)和建筑照明。LT3956使用一個內(nèi)部N溝道MOSFET,可以從標(biāo)稱值為12V的輸入驅(qū)動多達(dá)18個350mA的白光LED,從而提供超過25W的功率。它采用高壓側(cè)電流檢測，允許使用升壓、降壓、降壓-升壓或SEPIC和反激式拓?fù)?。LT3956在升壓模式時提供超過94%的效率，從而無需外部散熱措施。一個頻率調(diào)節(jié)引腳允許用戶在100kHz至1MHz范圍設(shè)定頻率，從而優(yōu)化了效率，同時限度地減小外部組件的尺寸和成本。結(jié)合5×6mmQFN封裝，LT3956提供一個高度緊湊的25WLED驅(qū)動器解決方案。

    The LT?3956 is a DC/DC converter designed to operate as a constant-current source and constant-voltage regulator. It is ideally suited for driving high current LEDs. It features an internal low side N-channel power MOSFET rated for 84V at 3.3A and driven from an internal regulated 7.15V supply. The fixed frequency, current-mode architecture results in stable operation over a wide range of supply and output voltages. A ground referenced voltage FB pin serves as the input for several LED protection features, and also makes it possible for the converter to operate as a constant-voltage source. A frequency adjust pin allows the user to program the frequency from 100kHz to 1MHz to optimize efficiency, performance or external component size.

    The LT3956 senses output current at the high side of the LED string. High side current sensing is the most flexible scheme for driving LEDs, allowing boost, buck mode or buck-boost mode configuration. The PWM input provides LED dimming ratios of up to 3000:1, and the CTRL input provides additional analog dimming capability.

    LT3956主要特性：

    3000:1TrueColorPWM調(diào)光

    寬輸入電壓范圍：4.5V至80V

    輸出電壓高達(dá)80V

    內(nèi)部3.3A/84V開關(guān)

    恒定電流和恒定電壓調(diào)節(jié)

    250mV高壓側(cè)電流檢測

    以升壓、降壓、降壓-升壓、SEPIC或反激式拓?fù)潋?qū)動LED

    可調(diào)頻率：100kHz至1MHz

    LED開路保護(hù)

    具遲滯的可編程欠壓閉鎖

    恒定電壓環(huán)路狀態(tài)引腳

    PWM斷接開關(guān)驅(qū)動器

    CTRL引腳調(diào)節(jié)高壓側(cè)電流檢測門限

    低停機(jī)電流：<1μA

    可編程軟啟動

    采用36引線（5×6mm）QFN封裝

    LT3956應(yīng)用：

　　高功率LED
　　蓄電池充電器
　　準(zhǔn)確的電流限制電壓調(diào)節(jié)器

圖1. LT3956方框圖

圖2. LT3956效率95%25W WLED汽車頭燈驅(qū)動電路圖

圖3. LT3956升-降壓模式LED驅(qū)動電路圖

圖4. LT3956超大電容充電電路圖

圖5. LT3956效率90% 20W SPEIC LED驅(qū)動電路圖

圖6. LT3956降壓模式90W LED驅(qū)動電路圖