Supertex公司的HV9957是带故障保护六路LED驱动器,包括一个开关模式升压转换器和六个低压降线性稳流器,提供了高效率和精密的电流控制,电流精度达±1.5%,占空比精度达0.5%.每路电流高达30mA,采用相位PWM调光,输出电压额定值56V.保护功能包括欠压,过压,开路/短路,过流和超温等.主要用在多串固态照明和手持LED背光照明.本文介绍了HV9957主要特性, 简化框图,故障保护框图, 典型应用电路以及六路LED驱动器演示板主要特性和指标,电路图, 布局图和连接图.

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应用:

Multi-string solid-state lighting applications

Portable LED backlighting applications

图1.HV9957简化框图

图2.HV9957故障保护框图

图3.HV9957典型应用电路

六路LED驱动器演示板

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驱动器演示板主要特性:

►► Phased dimming

►► Temperature-triggered faulty LED protection

►► Smart ‘outlier’ faulty string discrimination

►► Overcurrent protection

►► Precise dimming frequency

►► Accurate channel matching

六路LED驱动器演示板指标:


图4.六路LED驱动器演示板电路图
六路LED驱动器演示板材料清单:


图5.六路LED驱动器演示板布局图和连接图
详情请见:
http://www.supertex.com/pdf/datasheets/HV9957.pdf
和
http://www.supertex.com/pdf/misc/HV9957DB1.pdf