白光LED的恒流驱动电路的设计

论文编号:JD1000   论文字数:18286,页数:59

摘要

 小型化和多功能是便携式电子产品的发展趋势，因此要求DC/DC转换器具有高效率、低静态电流、小的板级面积、小体积和低成本等特性。传统的电源管理方法是使用电感模式的DC/DC转换器，但是随着业微米技术的发展和多层陶瓷大电容的使用，电荷泵的效率得到提高，所以电荷泵不仅在低功耗而且在较大输出电流应用中仍然得到广泛的应用。
    在对电荷泵原理研究的基础上，论文采用0.6um标准Bi-CMOS工艺设训一了一种具有宽输入电压范围和多电流输出规格的恒流型电荷泵DC/DC转换器。输入电压范围为2. 7V-5. 5V，输出电压恒定为5. 1V，输出电流为1. 2A, 400mA, 240mA二种规格。在空载情况下，静态电流为5mA;在关断情况下，静态电流小十luA。
    本文所设计的线性电荷泵稳压芯片主要应用于5. 1V的低压供电电源。其主体架构是由2倍的电荷泵电路与LDO线性降压稳压电路组成。当电池的供电能力不足的时候，即低于所需的额定电压输出值时，电荷泵将泵浦输入电压，最大输出值将为输入电压的两倍.这个输出电压经过分压电阻的分压后，反馈到误差放大器(AMP)的负极输入端。将此电压与基准点压源(REF)进行比较，得到了被放大的误差电压。这个误差电压被用作是控制电荷泵导通电阻(又称之为压控电阻)，进而得到了一个稳定的输出电压。
    该电荷泵的优点是无论输入电源电压高于或者低于输出电压，输出电压都能通过自动选择降压或者升压模式保持恒定。升压和降压模式都不需要电感元件，可提供低EMI的DC/DC转换。高的开关频率允许选用小的表面陶瓷电容，可节省板级面积、降低成本和减小输出电压纹波。具有热保护和电流限制功能，保护工作在不正常条件下的负载元件和芯片。输出端通过过载比较器组成的反馈回路调节输出电流使其稳定.通过24mV比较器来确定电压调节和电流调节模式。
    本文对电荷泵DC/DC转换器的基本原理和系统功能作了详细分析，首先介绍了整体结构，然后重点介绍了部分子模块电路。在电荷泵基本理论中，详细分析了线性(Linear)模式、跳周期(SkipCycles)模式;同时也介绍了电荷泵的升压/降压工作原理以及主要性能参数及其意义。在子电路中，重点介绍了带隙基准电压源、运算放大器、欠压保护、热保护。每一个子电路分别介绍了基本工作原理、主要参数的计算方法和仿真结果。
    在电荷泵原理分析和子电路设计基础上，运用HSPICE仿真软件对整体电路的关键指标进行了仿真并给出了详细的仿真结果。整体仿真结果表明电荷泵的功能和重要性能指标均达到设计要求。
关键词：电荷泵，带隙基准源，运算放大器，热保护，欠压保护，软启动

Abstract
 The miniaturization and multi-purpose is the portable electronic products trend of development, therefore requests the DC/DC switch to have high characteristics and so on efficiency, low quiescent current, small board level area, small volume and low cost. The traditional power source management is uses the inductance pattern the DC/DC switch, but along with industry the micron technology's development and the multi-layered ceramics big electric capacity's use, the electric charge pump's efficiency has the enhancement, therefore the electric charge pump not only moreover still obtained the widespread application in the low power loss in the big output current application. To the electric charge pump principle research's foundation, the paper used 0.6um the standard Bi-CMOS craft to suppose teaches one kind to have the wide input voltage scope and the multi-electric current output specification constant flow electric charge pump DC/DC switch.
 The input voltage scope is 2. 7V-5. 5V, the output voltage constant is 5. 1V, the output current is 1. 2A, 400mA, 240mA two kind of specifications. In the idling situation, the quiescent current is 5mA; In shuts off in the situation, quiescent current small ten luA. This article designs the linear electric charge pump constant voltage chip mainly applies in 5. 1V low pressure electric power supply. Its main body construction is composed of 2 time of electric charge pump electric circuit and the LDO linear voltage dropping voltage-stabilizer circuit. When battery's power supply ability is insufficient, when namely is lower than the rated voltage value of exports which needs, electric charge pump pump input voltage, maximum output value for input voltage two times. This output voltage after voltage-division resistance differential pressure, feeds back to the erroneous amplifier (AMP) cathode input end. Press source (REF) this voltage and the reference point to carry on the comparison, obtained the error voltage which enlarges. This error voltage serves as is controls the electric charge pump breakover resistance (to call that it controls resistance pressure), then obtained a stable output voltage.
   This electric charge pump's merit is regardless of the input supply voltage is higher than or is lower than the output voltage, the output voltage can maintain constant through the automatic selection voltage dropping or the pressure-rise pattern. Pressure-rise and the voltage dropping pattern does not need the inductance part, may provide low EMI the DC/DC transformation. The high turn-on frequency permission selects the small superficial ceramics electric capacity, may save the board level area, reduce the cost and to reduce the output voltage ripple. Has the hot protection and the current limitation function, protects the work under the normal condition load part and the chip. Out-port the feedback loop adjustment output current which composes through the overload comparator causes its stable. Determines the voltage regulation and the electric current adjustment pattern through the 24mV comparator. This article has made the multianalysis to the electric charge pump DC/DC switch's basic principle and the system function, first introduced the overall construction, then introduced the partial submodule electric circuit with emphasis. In electric charge pump elementary theory, multianalysis linear (Linear) pattern, jumping cycle (SkipCycles) pattern; Simultaneously also introduced the electric charge pump's pressure-rise/voltage dropping principle of work as well as the main performance parameter and the significance. In the sub-electric circuit, introduced the band gap datum potential source, the operational amplifier, the undervoltage protection, the hot protection with emphasis. Each sub-electric circuit introduced the key job principle, the main parameter computational method and the simulation result separately. In the electric charge pump principle analysis and the sub-circuit design foundation, has carried on the simulation using the HSPICE simulation software to integrated circuit's key indicator and has given the detailed simulation result. The overall simulation result indicated that the electric charge pump's function and the important performance index achieves the design requirements.

key word: Electric charge pump, band gap datum source, operational amplifier, hot protection, undervoltage protection, soft start

目     录
第一章 引言 1
1.1电源管理芯片的发展现状及其分类 1
1.2本课题的研究内容 3
第二章 电荷泵原理及总体结构设计 5
2.1总体电路功能 5
2.2系统功能分析 5
2.2.1系统工作过程 5
2.2.2主要模块功能分析 5
2.3电荷泵的设计 6
2.3.1电荷泵的介绍 6
2.3.2电荷泵升压工作原理 7
2.3.3电荷泵降压工作原理 9
2.4功率开关管，电源及衬底的选择 10
第三章 子电路模块设计与仿真 13
3.1带隙基准电压源 13
3.1.1基本原理 13
3.1.2电路工作原理分析 14
3.1.3仿真结果 16
3.2软启动模块 17
3.2.1电路功能描述 17
3.2.2功能特性分析 18
3.2.3简要仿真结果 20
3.3过温保护模块 22
3.3.1电路功能描述 23
3.3.2简要仿真结果 24
3.4欠压锁定（UVLO）模块 25
3.4.1电路功能描述 25
3.4.2简要仿真结果 26
3.5过压保护（OVP）模块 28
3.5.1电路功能描述 28
3.5.2简要仿真结果 31
3.6误差放大器（EA）模块 31
3.6.1电路原理分析 32
3.6.2特性分析 34
3.6.3仿真结果 34
3.6.4讨论与分析 40
3.7振荡器（OSC模块） 40
3.7.1电路原理分析 40
3.7.2仿真结果 42
3.8基准电压选择(V REF60_100_300)模块 43
3.8.1电路原理分析 44
3.8.2简要仿真结果 45
第四章 整体仿真 47
4.1瞬态仿真 47
4.2效率仿真 48
4.3电源电流与输入电压关系仿真 50
第五章 结论 51
参考文献 52

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