【作者】 王辉；

【导师】 郭宝龙；

【作者基本信息】 西安电子科技大学 ， 电路与系统， 2011， 博士

【摘要】 随着微电子技术以及半导体工艺的迅猛发展,电源管理类芯片已广泛应用于通信网络、计算机以及汽车电子等诸多产品领域。近年来,集成DC-DC变换器的高电压、高效率、快速响应、小体积使得其应用前景非常广阔。本文主要以电感型DC-DC为主线,系统研究了DC-DC关键技术及其理论分析,并针对DC-DC的几个关键技术：高电压技术、高效率技术、快速响应技术和自适应技术,进行了深入的分析与研究；根据应用环境的不同,分类设计了两种高压IC芯片的内部基准电路,实现了两种高电压条件下的应用和内部电路的调节；同时,根据影响DC-DC效率的三种主要因素：静态损耗、开关损耗以及导通损耗,文中有针对性分别提出了相应的解决方案,提高DC-DC的效率；其次针对DC-DC两种不同控制环路,分类设计了提高两种环路响应速度的电路,实现负载快速瞬态响应的要求；然后为了有效的减小上电时的过充现象,提出一种自适应软启动电路,用以保护整个系统。最后将以上研究成果根据不同场景,分别应用到不同条件下的DC-DC变换器,以提高DC-DC的各种性能指标,并最终适应市场需求。本文的主要研究工作以及贡献如下：1、针对电源输入范围较宽的IC芯片,提出一款不需Trimming调节,可快速启动的高精度电压基准电路。该设计的思想是利用齐纳二极管的稳压特性,在电压基准电路前设计一款TTL_BUFFER缓冲电路和一快速启动电路,TTL_BUFFER电路,不仅展宽输入电压的范围,而且提高了电压基准的精度；快速启动电路的引入大大提高了基准启动速度。2、针对高压芯片的功耗问题,提出一种新颖的片内高压转低压电源转换方案。与传统的片内电源转换方案不同,该方案直接利用带隙原理产生一个输出可调的基准电压,并利用推挽输出增大基准输出的带载能力,使其可以作为高压IC中的内部电源,完成电源高低压的转换；同时设计了高阶温度补偿电路,保证了输出电压的精度。3、为了减小静态损耗,提出了一种基于滤波器的无损耗电感电流采样电路。通过设计超宽带宽的跨导运放使DC-DC可以工作在较高的开关频率下,从而抵消采样电路中电感与电容的时常数对采样精度的影响。所设计的跨导放大器同时完成采样电流信号的I/V变换,将其通过交流耦合输入到PWM求和比较器。与传统的电感电流采样电路相比,该电路无直流损耗,可以应用在大功率输出的IC中。4、针对Buck型开关稳压器的不连续工作模式(DCM),提出了一种新颖的负载电流检测电路。该结构直接应用与负载电流变化几乎同步的同步管栅极驱动信号作为“电流采样”信号,实现了负载平均电流的检测。有效的提高了开关电源整个负载范围内的效率。5、Buck型DC-DC工作在不连续电感电流模式(DCM)下会出现电感电流倒灌现象,这种情况会使得系统的效率大幅度的下降。针对这一问题,设计实现了一款电感电流过零检测电路。该电路利用失调电阻抵消同步管关断延迟,达到了快速关断同步管的目的,有效的减小了电流倒灌现象的发生。6、针对非线性控制环路中输出电压纹波大和频率不固定的问题,提出了一种新颖的非线性控制环路方案。该方案将DC-DC变换器中的主比较器、驱动、功率管和电感电容滤波网络等效看作一个环形振荡器,在主比较器处设计两对起辅助输入作用的RC网络来拓宽环路的稳定频率范围,消除环路由寄生谐振引起的不稳定和输出电压纹波大的问题；在驱动和主比较器处增加一频率锁存环(FLL)将其频率锁定在某一固定的基准频率处以消除其频率不稳定的现象,有效的实现了负载的快速瞬态响应。更多还原

【Abstract】 With the rapid development of the microelectronics and semiconductor technology, the power management chips have been widely used in the field of communication networks, computers, automotive electronics and so on. In recent years, the characteristics such as the high-voltage, high-efficiency, quick response and small volume of the integrated DC-DC converters have made the application of the power management chips become a new trend. This paper is mainly focused on the study of the inductive DC-DC. The key technology of DC-DC and its theoretic analysis are presented and certain technologies have been deeply researched such as the high-voltage, high-efficiency, rapid response and self adaptive technology. By connecting with different high-voltage converters under different application environments, two kinds of internal reference circuits in IC chips under different high-voltage application environments are designed, thus realizing the applications and the internal regulation under two different high voltage conditions. Meanwhile, considering the three main factors:static losses, switching losses and conduction losses which affects the DC-DC efficiency, corresponding solutions are proposed to promote the DC-DC efficiency systematically. Secondly, aiming at the two different DC-DC control loops, two fast transient response circuits are designed to realize the requirements of the fast transient response under different application scenarios. Thirdly, in order to reduce the overcharge phenomenon during the charging process, a kind of soft-start circuit is proposed to protect the whole system. Finally, results of the above research are applied to DC-DC converters of different application conditions according to different scenarios in order to promote the performance of the chips and eventually adapt the market requirements.The main research work and contributions are as follows:1. A kind of fast start-up and high precision voltage reference circuit without trimming adjustment is proposed, aiming at the wide range of input voltage. By using the characteristics of the Zener diode, a kind of TTLBUFFER with simple topology and fast start-up is designed in front of the voltage reference. The TTLBUFFER not only widens the range of the input voltage but also increases the precision of the voltage reference. The adoption of fast start-up circuit greatly accelerates the start-up speed of the reference circuit.2. A novel on-chip high to low voltage power conversion circuit solution is achieved against power dissipation of high-voltage IC.This solution makes use of the gap principle and generates an adjustable output voltage reference, other than the traditional on-chip power convert solution. The Push-Pull output method is also used for increasing the load capacity of the reference power, therefore it can be used as the internal power of high voltage IC and then realizes the high to low voltage conversion. The high order temperature compensation circuit is also designed to ensure the precision of the output voltage.3. A filter-based lossless inductor current sensing circuit is proposed in this paper to reduce static power dissipation. By using the design of an ultra-wide bandwidth trans-conductance amplifier, the DC-DC can work under higher switching frequencies, thus eliminating the effect to the precision of the sampling current from the time constant of the inductors and capacitors. Meanwhile, the trans-conductance amplifier designed can realize the I/V conversion of sampling current, and then input it into the PWM comparator through AC-coupling. Compared with the traditional current sampling circuit, this circuit has no DC loss and can be used in high power output IC.4. Targeted on the discontinuous current mode (DCM) of the Buck switching regulator, a kind of novel load current detection circuit is proposed. The synchronous gate driving signal which almost changes synchronously with load current as the current sampling signal is designed to realize the average load current detection, which can effectively increase the efficiency of the switching power supply within the range of the load.5. The inductor current backflow phenomenon occurs when the Buck-type DC-DC works under the discontinuous current mode (DCM). This condition will greatly lower the efficiency of the system. In consideration of this problem, a kind of zero-cross detection circuit is designed. By using the disordered resistance to counteract the turn-off delay, the fast shutdown of the Synchronous Transistor will be realized and the probability of the current back flow will be reduced.6. A kind of novel non-linear loop control solution is proposed, aiming at the problem of high output voltage ripple and unfixed frequency in nonlinear control loops. The solution views the main comparator, driving transistor, power transistor and the inductor-capacitor filter network in the DC-DC converter as a ring oscillator. The RC network is designed near the main comparator to widen the stable frequency range, and to eliminate the instability caused by the parasitic resonance in the loop ring. By adding the FLL to the driving and the main comparators, the frequency can be locked to a fixed reference frequency to eliminate the phenomenon of frequency instability; therefore the fast load transient response will be realized.更多还原