【作者】 张兢；

【导师】 沈绪榜；

【作者基本信息】 华中科技大学 ， 模式识别与智能系统， 2007， 硕士

【摘要】 作为小尺寸液晶显示屏首选背光源的白光发光二极管,在手机、数码相机等便携电子设备上得到日益广泛的应用。而白光LED(Light Emitting Diode,发光二极管)驱动芯片,作为白光LED背光照明系统中的关键组成部分,其电路设计面临严峻挑战。这是因为目前便携电子设备小型化的趋势要求白光LED驱动芯片具备高效率、高可靠性和高功率密度等特点。本文首先系统地研究了现有的白光LED驱动芯片设计技术,从中总结出三种不同的LED驱动设计方案。然后根据课题的设计要求选择了基于Boost DC/DC开关电源原理的驱动方案,并结合方案所涉及到的关键技术对芯片整体架构进行了设计。接下来,对芯片中的三个主要子模块——带隙基准源电路、斜坡补偿电路和数字接口电路的设计进行了详细讨论,并利用HSPICE仿真工具结合UMC 0.6μm BCD工艺库对所设计电路进行了仿真验证。在带隙基准电路的设计中,成功实现了一种新颖的带隙核结构,从而简化了电路架构,并同时达到了较高的电气性能;在斜坡补偿电路的设计中,创造性地提出了一种动态斜坡补偿电路,利用该电路可以简单有效地解决Boost DC/DC中容易出现的过补偿问题;数字接口电路的引入,使得所设计的白光LED驱动芯片具有数字调光功能,和传统PWM调光相比,该功能的实现能有效降低处理器的功耗。最后,建立了典型应用电路,在选取合适的外部器件模型的基础上,用HSPICE对芯片进行了全局仿真。结果表明:在典型应用条件下,芯片启动时间在300μs以内,在10～40mA驱动电流范围内电源转换效率可达80%以上,能实现数字亮度调光和PWM调光功能,芯片的主要电气性能基本达到预期指标要求。更多还原

【Abstract】 As the best choice of small-size LCD’s backlights, white LEDs have been used more and more in portable applications such as mobile phones and digital cameras. Meanwhile, white LED driver IC, which is the key component of LCD backlighting system, is facing critical challenge in its design. Because of the demand on small size for handheld devices, white LED driver IC should have the figures of high efficiency, high reliability and high power density.In this thesis, with the in-deep study of current technique for white LED drivers, three main driving methods are proposed firstly. According to the application demands for this research, one of these methods is chosen for the design, which is based on Boost DC/DC switching power supply. And then, the key interrelated technique for Boost DC/DC is studied and the whole chip structure is constructed. The main subcircuits such as bandgap reference(BGR), ramp compensation and digital interface are designed and implemented with UMC 0.6μm BCD process, and the simulation results are also presented. A novel bandgap core structure is used in the BGR. Compared with conventional bandgap reference circuit, this bandgap structure is more immune to errors caused by current offset; a dynamic ramp compensation technology is used so that the over compensation problem in Boost DC/DC can be solved; the unique digital brightness control function can save processor power and battery life.Finally, the whole chip simulation results by HSPICE are given: in typical application condition, the start-up time of the chip is only 300μs; the efficiency is above 80% when the LED current ranges from 10mA to 40mA; the digital brightness control and PWM dimming functions can be operated properly. In a whole, the results show that the main electrical characteristics of this chip matched the specification.更多还原