一种具有线性调光功能的LED驱动芯片的设计

发布时间：2018-03-05 21:33

本文选题：LED驱动电源　切入点：原边反馈　出处：《电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：LED应用于照明,具有寿命长、节能环保、安全可靠等优点,随着近年来人们对节能环保的不断重视,LED电源逐渐进入人们的视野,并得到了快速的发展。目前的LED产业已经趋于成熟,并且其发展方向逐渐趋于结构简单化、设计功能化。如功率因数校正(PFC)技术的引进,使得LED电源减少了对电网的谐波污染,提高了电能使用效率;调光技术的引进,使得人们根据不同场合调节光线明暗程度成为可能。模拟调光技术是一种结构简单,成本低下的调光实现方案,广泛应用于对光线色温要求不高的低成本的场合。传统的模拟调光采用光电耦合器来反馈输出电压或电流信号,本文设计了一款采用原边反馈控制的带模拟调光的LED驱动芯片,该芯片由外部控制产生一个占空比可调的振荡信号来线性改变恒流的基准电压,然后通过误差放大器与原边采样信号进行比较放大,以调节对功率管开关信号(PWM)的占空比,最终实现对LED电源输出电流的线性调节。原边反馈控制技术的采用省去了光耦反馈器件的使用,节省了芯片面积和成本。它采用单级PFC反激式拓扑结构,利用输入电流跟随输入电压波形的技术实现了芯片功率因数的校正。芯片内部采用了谷底检测技术,使得开关管在其压降为最低的情况下打开,减小了导通损耗。芯片还包含有过温、过压、过流保护结构的设计,保证了芯片的正常安全工作。此外,芯片最大关断时间的设置,也保证了芯片的正常工作。本文首先分析阐述了芯片的拓扑结构和内部结构框图,然后分析了芯片恒流功能和PFC功能的实现。在确定了芯片的整体结构的基础上,本文针对调光环路的每个主要环节,对包含基准电压产生、PWM控制、误差放大器实现和线性调光等电路模块进行了设计与分析,并通过仿真验证了模块的功能与性能。最后本文采用TSMC_0.5 um BCD工艺,并应用Hspice仿真工具,对芯片整体功能实现完成了仿真与验证。仿真结果显示,当输入交流电压为220 V时,芯片的恒流输出为175 mA,当调光占空比为80%、60%、40%和20%时,输出平均电流分别为141.1mA、107.3 mA、74.6 mA和43.5 mA,可以实现精度较高的线性调光。
[Abstract]:The application of LED in lighting has the advantages of long life, energy saving and environmental protection, safety and reliability, etc. With the increasing attention paid to energy saving and environmental protection in recent years, the power supply of LED has gradually entered people's field of vision. At present, the LED industry has become mature, and its developing direction tends to simplify the structure and design function. For example, the introduction of power factor correction (PFC) technology makes the LED power supply reduce the harmonic pollution to the power grid. The introduction of dimming technology makes it possible for people to adjust the light intensity according to different occasions. Analog dimming technology is a simple structure and low cost dimming scheme. It is widely used in low cost cases where the color temperature of light is not high. The traditional analog dimming uses photocoupler to feedback the output voltage or current signal. In this paper, a LED driver with analog dimming is designed, which adopts the original side feedback control. The chip generates an oscillatory signal with adjustable duty cycle to change the reference voltage of constant current linearly, and then amplifies the signal by comparing the error amplifier with the original sampling signal to adjust the duty cycle of the switch signal PWM. Finally, the linear regulation of output current of LED power supply is realized. The original edge feedback control technology saves the use of optocoupler feedback device, and saves the chip area and cost. It adopts a single-stage PFC flyback topology. Using input current to follow the input voltage waveform, the chip power factor correction is realized. The bottom detection technology is used inside the chip, which makes the switch tube open under the condition that the voltage drop is the lowest. The chip also includes the design of over-temperature, overvoltage and over-current protection structure, which ensures the normal and safe operation of the chip. In addition, the maximum turn-off time of the chip is set. It also ensures the normal operation of the chip. In this paper, the topology structure and internal structure block diagram of the chip are analyzed, then the realization of the constant current function and the PFC function of the chip is analyzed. On the basis of the overall structure of the chip, the whole structure of the chip is determined. In this paper, the circuit modules including reference voltage generation PWM control, error amplifier realization and linear dimming are designed and analyzed for each main link of the dimming loop. The function and performance of the module are verified by simulation. Finally, the whole function of the chip is simulated and verified by using TSMC_0.5 um BCD technology and Hspice simulation tool. The simulation results show that when the input voltage is 220V, The constant current output of the chip is 175 Ma. When the dimming duty cycle is 80% and 20%, the average output current is 141.1 mAn 107.3 Ma 74.6 Ma and 43.5 Ma, respectively, which can achieve high precision linear dimming.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN312.8

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