【作者】 李勇；

【导师】 潘永雄； 李云鹤；

【作者基本信息】 广东工业大学 ， 电子科学与技术， 2019， 硕士

【摘要】 LED照明具有效率高、寿命长、绿色环保的优点,正逐步取代白炽灯、荧光灯等传统照明灯具。近年来为了提高LED照明驱动电源的通用性,让同一驱动电源支持不同工作电压的LED光源,要求驱动电源输出电压范围尽可能宽。传统的PWM控制的硬开关拓扑在效率、体积、输出功率以及通用性等方面已经无法满足现有LED照明设备需求。线路简单、效率高、寿命长、负载变化范围大的软开关拓扑将是未来LED照明驱动电源的发展方向。现如今在中大功率的LED驱动电源中比较常见的软开关拓扑是LLC,但是LLC在恒流输出模式下,输出电压下限一般不能低于满载时的50%,否则在满载条件下设计的谐振腔参数不再满足输出要求;另外LLC拓扑在输出电压变化时,开关频率变化范围很大,输出滤波器难以设计。通过对LCC拓扑在恒流模式下的特性进行详细分析,发现其可以有效地克服LLC拓扑的这些缺点,但是LCC拓扑在应用于中大功率LED驱动电源领域时,国内外并没有一种有效的谐振腔参数设计算法,工程师仅凭经验反复更换谐振腔元件参数,甚至变压器匝数,以期达到较理想的效果。本课题在前人的基础上,提出了一种简单有效的设计方法,以减少工程师的工作量,缩短产品开发周期,降低研发成本。本课题完成的主要工作包括以下几点:(1)对应用于恒流输出模式下的传统PWM控制硬开关拓扑进行了简要的分析,总结出其在LED驱动电源应用中的优缺点。(2)对串联、并联以及LLC谐振拓扑的特性进行分析总结,画出它们的电压、电流增益特性曲线。发现其无法满足现有LED驱动电源的应用要求。(3)从谐振变换器的整体结构出发,简要分析半桥、全桥方波发生器的区别以及全波、全桥和倍流整流电路的特点。(4)详细分析LCC谐振拓扑的整个工作过程,发现LCC谐振变换器在并联谐振电容C_P容量远小于串联谐振电容C_r时,可忽略等效电容对谐振腔的影响,变压器初级绕组N_P端电压u_P仍可近似为方波。基于此特点采用一次谐波分析法(FHA)获取电压和电流增益特性曲线,根据电流增益曲线的特征提出了最佳工作区域选择策略,并详细给出了LCC谐振腔、变压器参数计算公式的推导过程。(5)根据给定的输入输出条件计算出LCC谐振变换器谐振腔参数,应用MATLAB对相关波形进行仿真,然后完成整个电路图以及图中参数的设计。以此制作了一台96W的实验样机,并对其相关电气参数进行测试,验证了设计方法的合理性。更多还原

【Abstract】 LED lighting is replacing traditional lighting equipment such as incandescent lamps and fluorescent lamps with the advantages of high efficiency,long life and energy saving.In recent years,in order to improve the versatility of LED drivers,a LED driver is required to support different working voltage LED light sources,meaning that the LED driver need to support an as far as possible wide output voltage range.The traditional PWM-controlled hard-switching topology power supply has been unable to meet the requirement of current LED lighting equipment in terms of efficiency,volume,output power,and versatility.The soft-switching power supply with the advantages of simple circuit,high efficiency,long life and wide load variation range will be the future development trend of LED lighting driver.Nowadays,LLC topology is the most common soft-switching topology in medium and high power LED driver.However,the lower limit value of output voltage should not be lower than 50%at full load in constant current output mode.Otherwise,the resonator parameters designed under full load condition no longer meet the output requirements;In addition,the switching frequency varies widely when the LLC topology output voltage changes,so it is difficult to design the output filter.Through detailed analyzing the characteristics of LCC topology in constant current mode,it’s found that it can effectively overcome these shortcomings of LLC topology.But,there is no effective design algorithm for resonator parameters at home and abroad when LCC topology is applied in the field of medium and high power LED driver power supply.In order to achieve better results,engineers only depend on experience to repeatedly change the parameters of resonant cavity components,or even the number of transformer turns.On the basis of predecessors,this paper proposed a simple and effective design method to reduce the workload of engineers,shorten the product development cycle and reduce the cost of research and development.The main work of this topic includes the following points:(1)A brief analysis is made for traditional PWM control hard switching topology used in constant current output mode which shows the advantages and disadvantages of the topology in the application of LED driver.(2)Analyze and summarize the characteristics of series,parallel and LLC resonant topologies with their voltage and current gain characteristics.It was found that it could not meet the application requirements of current LED driver power supplies.(3)Based on the overall structure of the resonant converter,the differences between the half-bridge and full-bridge square wave generators and the characteristics of full-wave,full-bridge and double-current rectifier circuits are briefly analyzed.(4)Analyze the whole working process of LCC resonant topology in detail.It is found that the LCC resonant converter can ignore the influence of equivalent capacitance on the resonant cavity when the parallel resonant capacitor C_P capacity is much smaller than the series resonant capacitor C_r and the transformer primary winding N_P terminal voltage u_P can still be approximate as a square wave.Based on this feature,the first harmonic analysis method(FHA)is used to obtain the voltage and current gain characteristic curves.According to the characteristics of current gain curve,the optimal working area selection strategy is proposed,and the derivation process of the calculation formula of LCC resonant cavity and transformer parameters is given in detail.(5)According to the given input and output conditions,the resonant cavity parameters of the LCC resonant was calculated,the relevant waveforms were simulated by MATLAB,and then the whole circuit diagram with parameters was completed to design.At last,a 96W experimental prototype was produced and its relevant electrical parameters were tested to verify the rationality of the design method.更多还原