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Supertex公司的HV9957是帶故障保護六路LED驅動器,包括一個開關模式升壓轉換器和六個低壓降線性穩流器,提供了高效率和精密的電流控制,電流精度達±1.5%,占空比精度達0.5%.每路電流高達30mA,采用相位PWM調光,輸出電壓額定值56V.保護功能包括欠壓,過壓,開路/短路,過流和超溫等.主要用在多串固態照明和手持LED背光照明.本文介紹了HV9957主要特性, 簡化框圖,故障保護框圖, 典型應用電路以及六路LED驅動器演示板主要特性和指標,電路圖, 布局圖和連接圖. Six-Channel LED Driver with Integrated Fault Protection The HV9957 LED driver combines a switch-mode boost converter and six low-dropout linear current regulators to provide the advantages of high efficiency with precise current control. It may be configured for many applications, and is especially suited for one to three cell lithium-ion powered devices. An internal boost controller with an integrated switch eliminates the need for an external MOSFET. Phased PWM dimming eliminates audible noise, reduces transient load on the boost converter, and minimizes supply current ripple. PWM dimming may be synchronized to an external signal such as the display refresh rate or, internally generated by a resistor or crystal oscillator. Fault protection is provided against open/shorted LEDs, over voltage, under voltage, over current, and over temperature conditions. When a string fails, either shorted or open, the affected channel is removed from feedback and the rest continue operating normally. HV9957主要特性: Drives six strings of LEDs, up to 30mA each Phased PWM dimming Pin-programmable dimming frequency or synchronizable to an external signal PWM dimming to very low duty cycles ±1.5% typical current and 0.5% duty cycle matching Optional crystal oscillator for precision dimming frequency Outputs rated to 56V Robust protection against under voltage, over voltage, open/shorted strings, over current, and over temperature. Good strings remain lit. Programmable boost converter frequency 10μA maximum input current in shutdown state Resistor-programmable full-scale LED current 24-Lead 4×4 QFN package HV9957應用: Multi-string solid-state lighting applications Portable LED backlighting applications 
圖1.HV9957簡化框圖
圖2.HV9957故障保護框圖
圖3.HV9957典型應用電路 六路LED驅動器演示板 The HV9957 LED driver combines a switch-mode boost converter and six low-dropout linear current regulators to provide the advantages of high efficiency with precise current control. 六路LED驅動器演示板主要特性: ►► Phased dimming ►► Temperature-triggered faulty LED protection ►► Smart ‘outlier’ faulty string discrimination ►► Overcurrent protection ►► Precise dimming frequency ►► Accurate channel matching 六路LED驅動器演示板指標:
圖4.六路LED驅動器演示板電路圖 六路LED驅動器演示板材料清單:
圖5.六路LED驅動器演示板布局圖和連接圖 詳情請見: http://www.supertex.com/pdf/datasheets/HV9957.pdf 和 http://www.supertex.com/pdf/misc/HV9957DB1.pdf |
