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开关变换器的数字控制研究

The Study of Digital Control for Switching Converter

【作者】 陈亚爱

【导师】 张卫平; 刘伟力;

【作者基本信息】 北方工业大学 , 控制工程, 2009, 硕士

【摘要】 开关变换器的控制技术是建立在模型之上的,由于开关调节系统是一个高阶-离散-非线性-时变的病态控制系统,要建立精确的解析模型很困难。传统的控制方法是建立在低频小信号分析上的、所采用的控制技术应用于大信号条件下的系统可能是不稳定的。目前,开关调节系统的非线性控制技术或先进的控制策略已成为研究热点之一,但这些优越的控制策略一般用模拟电路很难实现或根本无法实现。研究开关变换器的数字控制,无论在技术上还是在实际应用上都有十分重要的意义。论文以Buck变换器为例对开关调节系统的模拟控制和数字控制进行了深入分析和研究。模拟控制是传统控制方式,论文以能量守恒为基本思想,用三端开关器件模型法,研究连续导电模式下非理想变换器的模型,建立了Buck变换器的小信号精确模型,用实验和仿真的方法验证了模型的正确性。在此基础上对电压控制和峰值电流控制型开关调节系统进行了仿真与实验研究,取得了有意义的研究成果。开关变换器发展趋势是高频化、模块化、数字化、绿色化。因此,数字控制是高频功率开关变换器控制技术的发展方向,许多学者和研究者正致力于开关变换器的全数字控制的研究,其中开关变换器的控制策略是数字控制技术的核心。论文针对传统控制技术存在过冲和调节时间不能相互协调的问题,运用电容平衡原则推导了突增或突降负载时的控制算法,仿真和实验结果表明该控制算法能明显改善DC-DC变换器动态性能。主电路和控制电路的硬件设计直接影响到开关变换器的运行性能。论文介绍了开关变换器数字控制系统的主电路、控制电路、采样调理电路、数字驱动电路、辅助电源等的硬件设计。研制了输出功率为60W的基于TMS320F2000系列DSP的开关调节数字控制实验样机,为以后研究先进的开关变换器数字控制策略提供了实验平台。基于该实验平台,介绍了用C语言对开关变换器的软启动、数字PI控制和电容电荷平衡控制进行软件设计的流程图以及完成的数字控制实验研究,并对各种实验数据进行了比较与分析,给出了相应的结论。

【Abstract】 The control technique of switching converter is based on its model. As the switching regulation system is a high order, discrete, nonlinear, time-varying, ill-conditioned control system and difficult to build exact resolution model. The traditional control technique is for low frequency small-signal, so it’s maybe unstable for big-signal systems. The nonlinear and other advanced control strategies for the switching converter have gotten more and more attentions, but it’s too hard to realize those strategies on analog circuits. So it’s meaningful to study the digital control of switching converter both in technique and practice. Taking the Buck converter for example, this paper deeply analyzes and studies on analog and digital control of the switching regulation system.Analog control is the traditional control method. Based on conversation of energy, this paper studies the non-ideal converter model at the continuous conducting mode, builds the small signal precise model of the Buck converter and validates the veracity of the model in experiment and simulation by the three-terminal switching device model. On this foundation, the paper simulates and experimentally studies the voltage control and peak current control switching modulation system and gets useful research results.Switching converter is developing to high frequency, modularization, digital and green, so the digital control is the developing direction of high frequency power switching converter. Now a lot of scholars and investigators are studying on the whole digital control of the switching converter, and the core is the control strategy. According to the traditional control’s problem that overshoot and regulating time are not mutual coordination, this paper deduces the control arithmetic when the load increases or decreases suddenly based on the capacitance balance principle. The simulation and experiment results indicate that this control arithmetic improves the dynamic performance of DC-DC converter effectively.The hardware design of main circuit and control circuit will affect the running performances of the switching converter directly. This paper introduces the hardware design of the main circuit, control circuit, sample adjusting circuit, digital driving circuit and assistant power supply of switching converter’s digital control system. An experimental prototype of switching regulation digital control based on the DSP of TMS320F2000 is developed and its output power is 60W. This prototype can be used as an experimental platform for the new advanced digital control strategy. Base on this prototype, the paper introduces the flowchart of the software design by C including soft-starting, digital PI control and capacitance charge balance control for the switching converter, the finished research of the digital control experiments, analyzes and compares the experiment data and gives the corresponding conclusion.

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