低成本DC-LED驱动器电路设计
来源：中国LED网
作者：---
时间：2012-01-31 00:00
led
http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ DC-LED驱动技术路线分析：http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ LED驱动电路控制LED（发光二极管）点亮所需电力的电源电路时。LEDhttp://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 的正向压降（VF）随制造时的误差和环境温度发生改变，无法采用恒压驱动。因此，一般需要使用恒流驱动，使供应给LEDhttp://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 的电流保持恒定。LED驱动的电路构造与普通的开关稳压器（DC-DC转换器）基本相同，没有太大的差异。但LED驱动有特殊的要求，大致有两个差别。
http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 第一个差别是反馈电压低（图）。反馈电压是指检测输出电压，反馈给开关稳压器IC的电压。LED驱动IC采用恒流控制，是把输出电流转换成电压后作为反馈电压的。
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图1http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 技术路线原理图http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/
http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 通常，开关稳压器IC设定的反馈电压约为1.2V。但对于LED驱动IC，1.2V过大。因为把输出电流转换成电压的数百mΩhttp://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 的电阻（电流检测用电阻）需要与LED串联。对于照明器具等使用的高亮度LED，流经的是1.5A和2A等大电流。如果500mΩ的电流检测用电阻中通过1.5A的电流，仅此一项就会产生0.75W的电力损耗。因此，LED驱动IC把反馈电压设定在了非常低的0.2V左右。这样一来，不仅可以使用较小的电流检测用电阻，而且在大电流通过时，也可以把电力损耗控制在较低的水平。
http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 第二个差别是为实现更精确的恒流控制进行了改进。因为单纯依靠检测输出电流进行反馈，很难补偿输入电压的变化、LEDhttp://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 正向压降的变化、电感器和电容器的特性变化等。
http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 各LED驱动IC厂商为了实现更正确的恒流控制进行的代表性改进是“恒定脉动方式”。发生上述变化后，与供应给LED的电流相重叠的脉动成分的振幅也会改变，导致LED亮度发生变化。一般来说，脉动成分的振幅由输入电压、输出电压、电感、开关控制的导通时间决定。为此，恒定脉动方式是检测输入电压和输出电压，按照电压来调整导通时间。也就是通过精密控制开关的频率，实现更精确的恒流控制。
http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 长运通光电DC-LED设计路线：
http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 长运通光电多年来一直经营CYT34063，市占率位居前列。在此理论基础上并结合在LED驱动技术的理解，设计出高恒流精准度的DC驱动器，正式批量推出DC-LED驱动器-CYT34065。
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http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ CYT34065是在CYT34063基础上，改进设计而派生的LED驱动器。CYT34065继续保留CYT34063优秀的特点外，并且还能高效率的驱动LED。CYT34065是专门为LED大功率而设计的一款直流驱动器，可选择升压、或降压应用，最大输出典型值1A，效率高达85%以上。http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ 蓄电池直流应用设计场所中CYT34065有着较高的性价比，高可靠性、稳定性高，恒流效果极佳。
http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ CYT34065特别适合设计3-12V升压设计，输出12-24V以上。也可以设计36V-24V甚至低于12V降压驱动线路，CV或CC模式，降压低至1.25V以上的输出电压。CYT34065仍然满足输出DC恒压模式设计，完全兼容CYT34063应用。输出采样基准需要重新计算外，不需要修改原设计PCB线路。并且还能设计低于1.25V或更低的电压范围。
http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ CYT34065推出28V和40V两款规格，设计升、降压型恒流LED驱动电路，内置1A功率达林顿管，开关型高效转换器，轻巧型SOP8或DIP8封装，频率工作在100KHz，低至300mV采样效率可达85%，达到DC驱动恒流设计高性价比。
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http://www.hqew.com/file/CMSImages/2012/01/http://www.hqew.com/file/CMSImages/2012/01/ CYT34065设计开辟了，CV和CC模式兼容应用先河，找到了CV与CC直流输出应用兼容设计的新方式。长运通光电技术有限公司一直致力于LED驱动IC设计研究，在公司多年DC电源IC设计基础上，找到了新的设计方向，接下来长运通光电技术公司会陆续推出全系列DC应用电路，并且CV与CC模式兼容。
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