摘要
白光LED是节能、环保、高效、长寿命的国际公认的下一代照明光源。白光LED已成为小型彩色LCD背光照明的最佳选择。随着白光LED技术的成熟，它将被更广泛地应用到各个领域。与传统光源不同，白光LED需要专用的驱动芯片才能使其高效持续地工作。
本次课题研究紧密结合市场动态的发展，设计了一款应用于白光LED背光驱动的DCM-CPM型白光LED驱动芯片，该驱动芯片输出电流可调，工作在1.2MHz的固定频率下，最多可驱动4个串联的白光LED和提供可调的电流来控制亮度和色纯度，此芯片具有过流限制保护、电流检测和开负载保护等功能。本文首先完成了DCM-CPM型驱动电路的建模，然后对各个主要模块电路进行了设计与分析，例如振荡器、带隙基准源、电流检测放大器、误差放大器、PWM比较器、过流保护比较器等模块。
在完成原理分析和电路设计的基础上，用EDA软件Cadence Spectre对各个子电路模块和整体电路进行了功能仿真，仿真结果均达到预定指标，验证了设计理论，说明本文设计的DCM-CPM型白光LED驱动芯片具有良好的性能。另外，整个环路是单极点系统，因此不需要补偿电路就能够保证系统的稳定性。
White LED is now regarded as the next generation of light source because of its power saving, high efficiency, long life, low pollution and low radioactivity. White LED is become the best selection for small color LCD backlighting. With the maturating of White LED technology, it will be applied in many fields. Different from the traditional source, a special driver IC is needed for the White LED to maintain its normal working status.
With an eye to the rapid market development, we design in this paper a DCM-CPM-White LED driver which is applied to White LED backlight driving with adjustable output current. It works at a fixed frequency, drive up to four White LED series and provide adjustable current to control brightness and color purity. This driver is featured by over-current protection, current detection and open-load protection features. This paper first completes DCM-CPM driver modeling, then designs and analyses each of the major modules of the circuit. For example, oscillator, band-gap reference source, the current detection amplifier, the error amplifier, PWM comparator, over-current comparator module and so on.
Based on the analysis of circuit theory and the circuit topology, every module and the entire circuit are simulated by the Cadence Spectre tool. The simulation result not only meets with the target specification, but also verifies the design, which demonstrates the excellent performance of White LED driver IC realized by current-mode DC-DC converter technology. In addition, the loop is a single polar system and the whole circuit is so stable that no compensation circuit is needed.
引文
[1]Divadar Szabo，DeAnn Wright．面向便携设备的LED驱动器[J]．世界电子元器件2003，(11)：29-30．
[2]胡央维.3V-5V电荷泵升压型半导体LED照明光源驱动芯片[D]．杭州：浙江大学信息学院，2006．
[3]平立．白光LED驱动综述[J]．现代显示，2006,(64)：44-48．
[4]Catalys半导体公司．新型高效而紧凑的白光LED驱动方案[J]．电子产品世界，2006,(10)：42．
[5]方佩敏．白色LED驱动器的发展概况[J]．今日电子，2005，(9)：54-59．
[6]Tony Armstrong．用于多显示屏背光照明的多用途白光LED驱动器[J]．半导体技术，2004，(10)：87-88．
[7]Gabriel A．Rrincon-Mora．A Low-voltage,Low Quiescent current，Low Drop-Out Regulator[J]．IEEE Journal of solid-state circuits，1998，1(33)：36-44．
[8]周志敏，周纪海，纪爱华，等．LED驱动电路设计与应用[M]．北京：人民邮电出版社，2006．101-103．
[9]林敬新．一种升压电流模式控制PWM开关电源控制器的研究[D]．成都：电子科技大学微电子与固体电子学院，2006．
[10]毕查德．拉扎维．模拟CMOS集成电路设计[M]．西安：西安交通大学出版社，2003．314-315．
[11]王华斌，袁佑新．PWM开关技术的分类及比较[J].国外建材建设，2002，(3)：34-36．
[12]赵莉，周海生．PWM软开关DC-DC变换器的研究[J]．华东交通大学学报，2000，17(1)：40-44.
[13]Middlebrook，Cuk R D，S．A general unified approach to modeling switching-Convergter power Stages[C]．In IEEE Proc．PESC，1976，18-34．
[14]丘水生．分析开关功率变换器的一种新方法[J]．华南理工大学学报，1994，22 (3)：74-81．
[15]Meares L G.New Simulation Techniques Using SPICE[C]．In IEEE Proc.APEC，1986，198-205．
[16]何希才.新型开关电源设计与应用．北京：科学技术出版社，2001．
[17] Robert W.Erickson, Dragan Maksimovic. Fundamentals of Power Electronics(Second Edition). Kluwer Academic Publishers, 2001.
[18] Abraham I.Pressman. Switching Power Supply Design. 2nd Edition McGraw-Hill. 1998: 143-189.
[19]张占松．开关电源的原理与设计(修订版)[M]．北京：电子工业出版社．2005： 27-40．
[20] Alkayal M F, Crebier J C. Integrated monolithic over-voltage protection circuit with adjustable threshold voltage. Industry Applications Conference,2004.39th IAS Annual Meeting. Conference Record of the 2004 IEEE Volume 3 ,2004, vol.3:1903-1909.
[21]银海，一种以恒定电流驱动串联白光LED的升压型DC／DC变换器．硕士论文，成都电子科技大学，2006，14-15．
[22]刘帘曦，杨银堂，朱樟明，等．一种高精度RC振荡器电路设计．电路与系统学报，2005，10(1)：14715．
[23]胡二虎，汪东旭．一种频率稳定的集成CMOS环形振荡器．微电子学，2003，33(3)：259-261．
[24]张兆华，岳瑞峰，刘理天．以环形振荡器作为敏感单元的加速度传感器．清华大学学报(自然科学版)，2004,44(1)：81-84．
[25]PhilipE．Allen，Do uglasR．Holberg．CMOS模拟集成电路设计(冯军等译)．北京：电子工业出版社，2005．
[26]许辛，高效率同步整流型DC-DC开关电源的研究与设计．硕士论文，浙江大学，2005．5 29-30,42-43，67-73．
[27] D. Hilbiber, A New Semiconductor Voltage Standard. ISSCC Dig. of Tech.Papers, pp.32-33,Feb.1964.
[28] Gabriel A. Rincon-Mora and Phillip Allen. A 1.1V Current-Mode and Piecewise-Linear Curvature- Corrected Band-gap Reference. IEEE Journal of Solid-State Circuits. 1998-10. 33(10).
[29] Van Staveren, A. Verhoeven, C.J.M. Structured electronic design of bandgap references. The 2001 IEEE International Symposium, Circuits and Systems(ISCAS'2001), 2005,6(2): 1-8.
[30] Sengupta, S. , Carastro, L. , Allen, P.E. Design considerations in bandgap references over process variations. Circuits and Systems(ISCAS'2005) IEEE International Symposium on 2005: 3869-3872
[31] Forghani-zadeh.H.P, Rincon-Mora G.A. Current-sensing techniques for DC-DC converters. Circuits and Systems. MWSCAS-2002,2002,vol.2:577-580
[32] C.F.Lee, P.K.T.Mok. On-Chip current sensing technique for CMOS monolithic switch-mode power converter. IEEE Int. Circuits and Systems, 2002,vol. 5:265-268
[33]John P．Uyemura．超大规模集成电路与系统导论(周润德译)．北京：电子工业出版社，2005