【作者】 沈丽君；

【导师】 冯全源；

【作者基本信息】 西南交通大学 ， 微电子学与固体电子学， 2008， 硕士

【摘要】 随着电子产品的普及和对节能要求的不断提高,电源管理芯片的应用日益广泛。高性能、高效率、小体积、低功耗、低成本的开关电源成为其发展趋势,而振荡器作为PWM控制系统中一个不可或缺的模块,其输出时钟信号的频率决定着开关电源的开关频率。本文在分析和比较现有开关电源调制模式和控制方式的基础上,设计了一种应用于混合调制电流控制模式开关电源的振荡器。该振荡器结构简单,频率稳定,在典型条件下能够提供中心频率为750kHz的低脉冲信号,同时通过对振荡电路中斜坡源的引用,能够产生消除电流控制模式开关电源中占空比大于50%时出现开环不稳定等缺点所需要的斜坡补偿信号,通过整形电路和使能信号的控制能够得到振荡器可同步的频率范围。论文研究了振荡器的基本组成单元和工作原理,在总结两种片内常用振荡器的优缺点和分析传统弛张振荡器工作过程的基础上,结合论文的设计要求,提出了本文所设计的振荡器结构。由恒流源充放电环路和RC充放电环路组成结构简单的双环路振荡产生电路。为了得到稳定的时钟输出信号,通过自偏置结构产生受电源电压影响较小的充电电流,同时在恒流源产生电路中采用电阻补偿技术以减小充电电流的相对温度系数。通过对电流模式中的系统不稳定问题的分析,得出补偿信号的斜率大小,斜坡补偿信号产生电路通过对振荡产生电路中斜坡源的引用以及斜率的调整得到系统所需要的斜坡补偿信号。结合本文所设计的振荡产生电路,通过使能信号和整形电路参数的设定,控制振荡器的可同步范围在500kHz到1000kHz之间。设计基于UMC 0.6μm BiCMOS工艺,利用HSPICE仿真软件对振荡器电路在电源电压、温度变化以及工艺漂移的条件下进行了仿真验证,结果表明:该振荡器能够实现设计所要求的功能,同时输出时钟信号频率在以上三种条件变化组合下,其变化范围为-12.2%～9.88%,能够满足设计要求。更多还原

【Abstract】 With the popularization of electronic products and the requirement of energy saving, power management IC is more and more widely applied. SMPS (switched-mode power supply) with high performance, high efficiency, small volume, low power and low cost becomes the research hotspot of power management IC. The switching frequency is decided by the output frequency of oscillator which is an indispensable module for the control system of SMPS. Based on the analysis and comparison of modulation and control modes of SMPS, an oscillator applied in the hybrid control current mode SMPS is presented. This novel oscillator with simple structure and stable frequency can generate low pulse signal whose central frequency is 750kHz under the typical condition. At the same time, slope compensation signal which is needed when the duty cycle is more than 50% in current mode SMPS is obtained by citing the slope source generated in the oscillating circuit. Also, through enable signal and the setting of the parameters of shaping circuit, the range of external synchronization can be controlled precisely.The basic units and working principle of the oscillator are studied. Meanwhile, based on the analysis of merits and demerits about common structure of oscillator on chip and the working process of conventional relaxation oscillator, and combined with the design requirements, the structure of the oscillator is presented in this thesis. The two-circles oscillating generation circuit is composed of constant current source charging/discharging circuit and RC charging/discharging circuit. In order to obtain the stable clock signal, the charging current, which is less sensitive to the supply voltage, is got by means of the self-biased structure. Simultaneous in the constant current generation circuit resistor compensation is used to reduce the relative temperature coefficient. The magnitude of the slope of compensation signal is got by studying the instability problem of system in current mode. By citing the slope source in the oscillating generation circuit and adjusting the magnitude of the slope, the essential slope compensation signal in the system is obtained. Combining the oscillating generation circuit presented in this thesis and through enable signal and the setting of the parameters of shaping circuit, the range of external synchronization is set between 500kHz and 1000kHz.The circuit is realized in UMC 0.6μm BiCMOS process. HSPICE simulation results show that the required functions of oscillator have be realized. And under the fluctuation of supply voltage, temperature and process corner, the error is acceptable between -12.2% and 9.88% . The design meets the requirements.更多还原