基于sigma-delta调制的低噪声高效率buck DC-DC变换器的研究与实现

【作者】 蔡曙江；

【导师】 李文宏；

【作者基本信息】 复旦大学 ， 微电子学与固体电子学， 2010， 硕士

【摘要】 电子系统的结构创新和性能提升离不开高性能电源系统的支持。效率和噪声一直是设计开关电源系统时主要的性能指标。这在便携式电子设备和无线通信系统中尤其明显。本论文主要在提高开关电源效率和降低噪声方面做了一些工作。在效率方面,主要研究了高效率的功率管驱动技术和相应的电路实现。在功率管驱动电路中,包含了死区时间控制功能,DCM功能,功率管栅宽调整功能。这些功能可以从不同的角度提升电源效率。在死区时间控制功能中,提出了一种新型的基于电荷泵的死区时间自适应控制电路。在功率管栅宽调整功能中,改进了传统的电流采样电路。传统的电流采样电路采样功率管漏电流峰值,这要求功率管开关信号具有固定的周期。而由于本文采用的调制方式,功率管的开关信号不再具有固定的周期,因此无法采样电流峰值。本文通过采样电流平均值的方法解决了这一难题。在降低噪声部分,将目前流行的sigma-delta技术引入到开关电源中。分析比较了PWM调制和(?)sigma-delta调制的噪声特性。阐述了在开关电源中应用sigma-delta调制时可能遇到的一些理论问题。在具体电路实现上,设计了一个二阶结构连续时间sigma-delta调制电路,并改进了其中的电流反馈方式,降低了积分器中OTA的功耗需求,提高了调制电路性能。另外,本文在0.35um CMOS工艺下,完成了基于sigma-delta调制的低噪声高效率开关电源的流片验证工作。芯片测试结果验证了相关理论分析和电路实现的有效性。更多还原

【Abstract】 The architecture innovation and performance promotion of electrical system cannot do without the support of high-performance power supply. While designing SMPS (switching-mode power supply), efficiency and noise performance are always the greatest consideration, especially in the application of portable electronic products and wireless communication system.Some research effort on improving efficiency and noise performance of SMPS is explored in this thesis. As to improving efficiency, high-efficient power MOSFET driving technology and circuit implementation are presented. The proposed MOSFET driver includes dead time controller, DCM controller and gate width controller. These controllers can improve efficiency from different aspects. In dead time controller, a novel auto-adaptive circuit based on charge-pump is proposed. In width controller, current-sensing circuit is improved. Traditional current-sensing circuit samples the peak current of power MOSFET, it requires the switching signal of power MOSFET has fixed duty cycle. Because of the different modulation method, the duty cycle varies. It make impossible to sampling peak current. A novel current-sensing method, sampling averaging current, is proposed to resolve this problem. As to reducing noise, a current popular technology, sigma-delta modulation, is introduced into the design of SMPS. First, the noise characteristic of PWM modulation and sigma-delta modulation are compared. And some theoretical problems are analyzed when applying sigma-delta modulation. In the circuit implementation, a second-order, continuous time modulator is designed, and the current feedback method is improved. The improvement reduces the power consumption of OTA and improves the performance of modulator. In addition, a low noise, high efficiency synchronous buck converter with a fully integrated second order single-bit continuous time sigma delta modulator based controller is designed and fabricated on a 0.35um CMOS process. Measurement results conform to the theoretical analysis and circuit simulation results.更多还原