脉冲在XLamp LED电流驱动：信息及注意事项

　　脉冲在XLamp LED电流驱动：信息及注意事项

　　有可能在更高的水平上以连续脉冲模式操作LED，但也有可能对效率、色度和长期可靠性产生不利影响的权衡。

　　在这样的应用支持团队经常被问及是否是安全的操作我们的LED脉冲电流超过最大数据表评级。这个问题通常是在合理的产品需求范围内提出的，如紧急车辆应用、特殊频闪照明甚至脉冲调制等一般照明调光应用。

　　简短的答案是“它取决于”多个变量影响LED的初始和长期性能和可靠性。这些包括热电阻，脉冲持续时间，以及电流振幅，频率和占空比。

　　一般来说，™Cree公司的XLamp LED产品组合是宽广到足以容纳照明大多数和脉冲电流的照明要求在这些组件数据表规格。产品如XLamp XM-L多安培最大电流规格。

　　However， to explore the limits of the possible， but not necessarily reasonable， we’ll review three types of overcurrent conditions：

　　Single-pulse events， e.g.， electrical overstress or EOS，

　　Repetitive pulsing， e.g. pulse-width modulation， and

　　Ripple effects.

　　Electrical overstress （EOS） is often associated with catastrophic failures such as an electrostatic discharge （ESD）， in-rush current， or other types of transient electrical surge.¹ Designers of LED drivers should be sure to take all necessary precautions to protect the LEDs from EOS. The second type of over-current condition is often associated with applications in which the LEDs operate in a flashing mode such as emergency vehicle lights， strobe lights， or signaling beacons. High-frequency pulsing， i.e.， greater than 120 hertz， is often used to control the brightness of LEDs in dimming applications. Finally， ripple current is a repetitive， cyclical peak-to-peak variation in a direct-current waveform that may be derived from an insufficiently filtered alternating current source or switched-mode power supply.

　　Within specification boundaries， none of these conditions is cause for concern in regard to the long-term lumen maintenance or reliability of the LED. But any of these in an “over-current” situation， i.e.， beyond data-sheet specification， can decrease LED lifetime.