PSM控制器主体模块的研究

【作者】 刘永根；

【导师】 李肇基；

【作者基本信息】 电子科技大学 ， 微电子学与固体电子学， 2007， 硕士

【摘要】 脉冲跨周期调制模式(PSM)因其轻负载效率高、响应速度快、抗干扰能力强等众多优点,已广泛应用于开关电源DC-DC变换器中。首先本文基于本课题组提出的一种优化的PSM控制器及5μm BiCMOS工艺库,绘制了控制器的全部版图,其包括电流极限比较器、电流极限状态机、基准源、数字控制、序列检测和主控门六个模块。然后着重研究PSM控制器中常用模拟电路模块,包括电流极限比较器、电压基准源和误差运放三个部分。本文主要完成以下工作:1)PSM控制器最核心的电路模块—电流极限比较器包括电感电流检测电路、电感电流比较电路和斜坡补偿电路。本文首先研究该三个组成部分的工作原理及传统的电路结构,然后分别提出了一种改进的电路结构。其中所设计的电流检测电路具有电路结构简单、精度较高和可省去脉冲前沿消隐电路的优点;所设计的电流比较电路不需要开关管和电阻网络就可以产生系统所需的多个离散的占空比,并且该电路还具有低功耗和低电源电压的优点;所设计的斜坡补偿电路对于升压转换器具有自调节斜坡补偿功能,可以防止斜坡过补偿或欠补偿。最后基于0.5μm CMOS工艺用Hspice软件对子电路和整体电路进行仿真,仿真结果表明所提出的电路结构与理论分析相符合,成本较低,并能保证较高的成品率,适合于工程应用。2)对于电压基准源模块,本文仅研究带隙电压基准源的高阶温度曲率补偿技术。首先基于传统的指数曲率补偿技术提出了一种新的抛物线曲率补偿技术,其利用晶体管电流增益的温度特性和禁带宽度变窄因子来补偿一阶电压基准源。然后针对该新的曲率补偿方法,提出了二个改进的电路结构,并基于BiCMOS工艺进行了电路仿真。仿真结果表明:所提出的曲率补偿技术和基准源电路能产生具有三阶曲率补偿的基准电压,在-400C到+1250C的温度范围内温度系数仅为0.52ppm/0C,在10KHz频率处的电源抑制比(PSRR)大于60dB。3)对于误差运放模块,本文仅研究用于线性调整管(LDO)的单密勒电容补偿的低压三级误差运放。首先详细介绍了已提出的二种单密勒电容补偿的低压三级误差运放结构及其频率补偿技术,并分析其各自的优缺点。然后提出一种改进的低压三级误差运放电路结构,其能产生二个左半平面的零点对运放进行频率补偿。针对该电路结构,本文详细分析了零极点分布对运放频率特性的影响,最后经过比较分析,提出了一种新的频率补偿技术。该补偿技术能非常方便地利用一个左半平面零点对运放主极点进行补偿,从而打破了主极点及电压增益对带宽的限制,大大扩展了误差运放的带宽,同时第二个左半平面的零点能保证运放具有较好的相位裕度。最后基于0.5μm CMOS工艺用Hspice软件对运放进行仿真,仿真结果与理论分析完全一致,所设计的运放在1.5V的电源电压和120pF的负载电容下,具有100dB的电压增益、22MHz的带宽和620的相位裕度,并且还具有较好的成品率。更多还原

【Abstract】 Pulse skipping modulation, due to its high efficiency at light loads, is very popular in DC to DC converter of power switching supply.This thesis, firstly, introduces a boost converter with improved PSM control proposed by other members in our team. The control circuit contain current-limited comparator, current-limtied state machine, voltage reference, digital control, sequence detect and main control gate. The layout of these control circuits with 5μm technology is presented. Then, this thesis rearches on some important and often used analog circuit blocks in DC-DC converter with PSM control. It include current-limited comparator, voltage reference and error amplifier.Current-limited comparator consists of three components including inductor current detector, inductor comparator and slope compensator. Firstly, an improved inductor current detector with low cost and high accuracy is proposed. Then, a novel inductor comparator with low cost and low power consumption is presented. Finally, a self-regulated and high accuracy slope compensator for boost converter is proposed. For voltage reference, first of all, this thesis introduces the principle of first-order and high-order temperature compensation. Next, an improved curvature compensation technique and its corresponding circuit structure are proposed. The simulation results show that the proposed voltage reference has three-order temperature compensation and its temperature coefficiency is about 0.52ppm/0C.For error amplifier, this thesis only concentrates on the amplifier with large load capacitor using sigle miller compensation technique. An improved low voltage three-stage amplifier with new frequency compensation technique is proposed. Compared with other structures and compensation techniques, the presented error amplifier has better frequency charateristics, and it could break the limit of voltage gain and -3dB bandwidth to the bandwidth, which is very useful for LDO applications. The simulation results show that the bandwidth of the proposed error amplifier is about 22MHz, the DC voltage gain is about 100dB, the phase margin is about 62o and the miller capacitor is only 2pF.更多还原