高稳定性快速瞬态响应片上集成LDO的研究与设计

发布时间：2018-05-20 23:45

本文选题：电源管理 + 低压差线性稳压器　；参考：《西南交通大学》2017年硕士论文

【摘要】：线性稳压器(LDO)作为电源管理IC中的重要一员,以其低成本、低噪声、快速瞬态响应等优点广泛应用于电子设备中。LDO可分为有外接电容和无外接电容(片上集成)两类。随着SOC技术的发展,各种功能集成在一颗芯片上,LDO集成在芯片内部可提升芯片的供电性能,节约成本。所以片上集成LDO是目前的研究热点。而去除外接电容后的设计难点在于LDO在全负载范围内的稳定性和负载瞬态响应性能。本文以LDO的高稳定性和快速瞬态响应特性为研究重点,通过公式推导分析了三级结构的片上集成LDO频率特性以及嵌套米勒补偿(Nested Miller Compensation,NMC)原理及其稳定条件。设计了一种基于改进的增强型AB跟随器的LDO电路,将增强型AB跟随器改为动态偏置电流电路,加快瞬态响应,并利用嵌套米勒补偿保证负载电流大于10μA时有大于60°的相位裕度。设计了一种基于推挽电路的LDO,推挽电路具有正向增益的低输出电阻,将第二级和第三级的极点设计为共轭复极点,合理设计缓冲级的增益和输出电阻可将这两个次极点设计在单位增益带宽之外,从而保证环路具有足够的相位裕度。对片上集成LDO的瞬态增强的原理进行分析总结得出,PMOS调整管栅极电压的调整速度是影响LDO的瞬态性能的重要因素。因此本文提出了一种瞬态增强电路,其通过RC电路检测输出电压在负载跳变时的过冲或下冲,将其放大并转换为脉冲电流,对调整管栅极电容充电或放电,缩短调整过程,减小输出电压变化。使用HSPICE进行仿真验证,设计的基于增强型AB跟随器的LDO电路,在负载电容为0～100pF范围内,负载电流在10OμA～100mA内相位裕度大于60°。当负载电流以99mA/μs跳变,输出电压最大下冲70mV,最大过冲103mV,平均1.37μs恢复稳定,静态电流仅15μA。基于推挽电路的LDO仿真结果表明,在负载电容为0～100pF内,本LDO在全负载范围内都有大于60°的相位裕度。负载以99mA/μs跳变时,输出电压最大下冲51mV,最大过冲43mV,平均恢复时间1.28μs。静态电流30μA。从理论推导和仿真结果可以看出,本文基于嵌套型米勒补偿的LDO电路在稳定性和瞬态响应性能上具有一定的优势。
[Abstract]:As an important member of power management IC, LDO (linear voltage regulator) is widely used in electronic equipment with low cost, low noise and fast transient response. LDO can be divided into two types: external capacitance and no external capacitance (on-chip integration). With the development of SOC technology, the integration of various functions on a single chip can improve the power supply performance of the chip and save the cost. Therefore, the on-chip integration of LDO is the current research hotspot. The design difficulty after removing the external capacitance lies in the stability of LDO in the whole load range and the transient response performance of the load. In this paper, the characteristics of high stability and fast transient response of LDO are studied. The frequency characteristics of integrated LDO and the nested Miller compensation principle and its stability conditions are deduced and analyzed by formula. A LDO circuit based on the improved enhanced AB follower is designed. The enhanced AB follower is replaced by a dynamic bias current circuit to speed up the transient response, and the phase margin greater than 60 掳is ensured by nested Hans Muller compensation when the load current is greater than 10 渭 A. A kind of LDO based on push-pull circuit is designed. The push-pull circuit has low output resistance with positive gain. The poles of the second and third stages are designed as conjugate complex poles. The two sub-poles can be designed beyond the unit gain bandwidth by reasonably designing the gain and output resistance of the buffer stage so as to ensure that the loop has sufficient phase margin. The principle of transient enhancement of on-chip integrated LDO is analyzed and summarized. It is concluded that the adjusting speed of gate voltage is an important factor affecting the transient performance of LDO. In this paper, a transient enhancement circuit is proposed, which detects the overshoot or downrush of output voltage during load jump by RC circuit, amplifies and converts it into pulse current, charges or discharges the gate capacitance of the adjusting tube, and shortens the adjustment process. Reduce the output voltage change. The LDO circuit based on the enhanced AB follower is simulated by HSPICE. The phase margin of the load current in 10O 渭 A~100mA is more than 60 掳when the load capacitance is in the range of 0~100pF. When the load current changes with 99mA/ 渭 s, the maximum output voltage is 70 MV, the maximum overshoot is 103 MV, the average is 1.37 渭 s and the static current is only 15 渭 A. The LDO simulation results based on push-pull circuit show that the phase margin of this LDO is more than 60 掳in the full load range when the load capacitance is 0~100pF. When the load is changed by 99mA/ 渭 s, the maximum output voltage is 51mV, the maximum overshoot is 43mV, and the average recovery time is 1.28 渭 s. The static current is 30 渭 A. From the theoretical derivation and simulation results, it can be seen that the LDO circuit based on nested Hans Muller compensation has some advantages in stability and transient response performance.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM44

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