基于能量模型的优化PSM控制电路的设计与实现

【作者】 甄少伟；

【导师】 罗萍；

【作者基本信息】 电子科技大学 ， 微电子学与固体电子学， 2008， 硕士

【摘要】 目前,在功率集成电路(PIC:Power Inregrated Circuit)中广泛采用了脉冲跨周期调制模式(PSM,Pulse Skip Modulation),可以克服脉冲调宽调制模式(PWM:Pulse Width Modulation)轻负载情况下变换效率较低、脉冲调频调制模式(PFM:Pulse Frequency Modulation)频谱分布随机的缺点。大量研究和仿真表明,该调制模式具有轻载时效率高、响应速度快、鲁棒性强、电路易于实现等特点。但PSM也有其不足之处:输出纹波较大,且易引入音频噪声。本论文对Boost开关变换器建立了普适性的能量平衡模型(EBM:EnergyBalance Model)。基于此能量平衡模型分析了经典PWM变换器的分叉参数规律和PSM变换器的稳定性,并对优化PSM控制策略运行规律进行了分析。完成具有优化PSM控制策略的升压变换器控制芯片设计、版图、流片和测试。本文主要工作包括以下几个方面内容:1)对工作于DCM模式的PSM变换器变换效率及输出电压纹波进行研究,并与相同条件下的PWM和PFM变换器模式性能进行比较。2)基于Boost变换器的能量平衡模型,分析PWM变换器的分叉和混沌现象,提出了能量量纲下PWM变换器的稳定性判据,并将各个分叉参数在能量模型下达到统一的表达。3)基于Boost变换器的能量平衡模型,分析PSM模式和优化PSM模式的特点,并分析验证了PSM变换器的稳定性和优化PSM变换器的低输出电压纹波。4)根据纹波大小和输出负载范围选择了优化PSM控制模式的中间占空比。设计了实现优化PSM控制芯片部分关键子电路模块,包括电流检测和电流极限比较器。5)参与设计了采用优化PSM控制策略的控制芯片(PSM501),采用0.5μm2P3M Mixed-Signal CMOS工艺,在CSMC(无锡华润上华)流片。对芯片进行了封装和测试,输出电压3V,输出电压纹波小于30mV,变换效率在整个负载范围内达到80%以上,最高达84%。更多还原

【Abstract】 At present, pulse skip modulation (PSM), is widely used in power integrated circuits (PIC). It can overcome low conversion efficiency of pulse width modulation (PWM) and random spectrum distribution of pulse frequency modulation (PFM). PSM has many merits such as high efficiency at light load, high response speed, robustness and ease of implementation, which are proved by theory analysis and simulation. However, PSM also has some disadvantages: large output voltage ripple and audio noise at light load.This dissertation gives energy balance model (EBM) for boost converter. Based on EBM, the bifurcation parameters of conventional PWM converter and stability of PSM converter are analyzed. The operation of optimized PSM is also studied. A controller chip of boost converter is designed, taped out and tested after packaged.The detailed works are listed as follows:1) Efficiency and output voltage ripple analysis of PSM operating at discontinuous current mode (DCM), and compared with that of PWM and PFM;2) Based on EBM of boost converter, bifurcation and chaos phenomena of PWM converter are studied, a stability estimation rule with energy dimension is proposed, and all the bifurcation parameters can be described in consistent energy dimension;3) Based on EBM of boost converter, the characteristics of PSM and optimized PSM are given. And the stability of PSM converter and low output ripple are proven;4) The medial duty cycle of optimized PSM converter is given according to output ripple and load range, and the key sub circuits to implement the control scheme are designed, including current sensing and current limit comparator;5) A controller with optimized PSM is designed. The chip is taped out in CSMC by 2P3M mixed signal process. Test results after package show that the output voltage is 3V, the output ripple is less than 30mV, the efficiency is above 80% in the whole load range and its maximum value is 84%.更多还原