线性恒流LED驱动电路设计

发布时间：2018-10-21 08:40

【摘要】：LED是新一代绿色光源,它的优势在于发光效率极高、耗电量极少并且安全可靠、寿命长。现在已经普遍应用在显示屏、汽车、背光源、家用照明等领域。LED的大量应用必将刺激与之相关的LED驱动电路的迅速发展。随着研究的深入,LED驱动方式越来越多样化,LED驱动电路的性能越来越优良,功能越来越齐全。本文所叙述的线性恒流LED驱动电路,集成了功率LDMOS、控制电路和保护电路,具备PWM调光,线性调光和完善的保护措施。在220V交流条件下,芯片的输出电流高达80mA并且可调。在全温度范围内,电流精度为6%。本文首先基于对各种LED驱动方式优缺点的比较,确定了线性恒流驱动方式。然后介绍了芯片的整体结构和工作原理,并详细叙述了芯片的部分电路模块:括带隙基准电路、电压调整电路、误差放大器和线性调光电路。带隙基准电路用来产生一个稳定可靠的带隙基准电压,提供给电压调整电路。电压调整电路的功能是基于低压差线性稳压器的设计思想,将带隙基准电压通过电阻分压网络得到所需的基准电压供芯片其他电路模块使用。误差放大器是整个芯片的关键模块,它通过比较采样电阻上电压和基准电压调节功率管的栅极,从而维持LED电流恒定。线性调光电路向LED电流回路注入或抽取电流。此电流随线性调光电路的输入电压线性变化,流经反馈电阻会造成采样电阻上电压也随之线性变化,从而使得LED电流也发生线性变化。本文对以上四个电路模块进行了详细的阐述:从分析电路参数对电路性能的影响入手,制定了能满足电路性能的指标要求;基于设定的指标,设计电路并叙述了设计思路;之后再对电路模块进行仿真、验证是否满足指标要求。最后搭建整体电路,仿真、验证整体电路的功能,并优化整体电路的性能指标。
[Abstract]:LED is a new generation of green light source, which has the advantages of high luminous efficiency, low power consumption, safety and reliability, long life. Now it has been widely used in display, automobile, backlight, home lighting and so on. A large number of applications of LED will certainly stimulate the rapid development of related LED drive circuits. With the development of the research, the LED driver is becoming more and more diversified, and the performance of LED driver circuit is becoming more and more excellent and the function is more and more complete. The linear constant-current LED drive circuit described in this paper integrates the power LDMOS, control circuit and the protection circuit. It has PWM dimming, linear dimming and perfect protection measures. At 220 V AC, the output current of the chip is up to 80mA and adjustable. In the full temperature range, the current accuracy is 6. Firstly, based on the comparison of the advantages and disadvantages of various LED drivers, the linear constant-current drive mode is determined. Then the whole structure and working principle of the chip are introduced, and some circuit modules of the chip are described in detail, including bandgap reference circuit, voltage adjustment circuit, error amplifier and linear dimming circuit. The bandgap reference circuit is used to generate a stable and reliable bandgap reference voltage, which is provided to the voltage adjusting circuit. The function of the voltage adjusting circuit is based on the design idea of the low voltage difference linear regulator. The bandgap reference voltage is obtained through the resistive voltage divider network to be used by other circuit modules of the chip. The error amplifier is the key module of the whole chip. It adjusts the grid of the power transistor by comparing the voltage on the sample resistor with the reference voltage so as to maintain the LED current constant. The linear dimming circuit injects or extracts current into the LED current loop. The current changes linearly with the input voltage of the linear dimming circuit, and the voltage on the sample resistor changes linearly through the feedback resistor, which makes the LED current change linearly. In this paper, the above four circuit modules are described in detail: starting with the analysis of the influence of circuit parameters on the circuit performance, the paper formulates the index requirements that can meet the circuit performance, designs the circuit based on the set index, and describes the design ideas. Then the circuit module is simulated to verify whether it meets the requirements. Finally, the whole circuit is built, simulated, the function of the whole circuit is verified, and the performance index of the whole circuit is optimized.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM923.34

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