Buck电路设计与MATLAB仿真

Buck电路设计与仿真计算机仿真技术作业题目：Buck电路的设计与仿真1、Buck电路设计：设计一降压变换器，输入电压为20V，输出电压5V，要求纹波电压为输出电压的0.5％，负载电阻10欧姆，求工作频率分别为10kHz和50kHz时所需的电感、电容。比较说明不同开关频率下，无源器件的选择。2、Buck电路理论计算:由以下公式计算:20.252.0.5A(1)3.5%8()4.2odooososdoLBOBVDVVIRVTDVLCDTVVIIL1.占空比:负载电流:纹波电压:电流连续条件：得到下列计算结果fs(KHz)L(mH)C(μF)100.375500500.0751003、Buck电路仿真:利用simpowersystems中的模块建立所设计降压变换器的仿真电路。输入电压为20V的直流电压源，开关管选MOSFET模块(参数默认)，用PulseGenerator模块产生脉冲驱动开关管。分别做两种开关频率下的仿真。(1)使用理论计算的占空比(D=0.25)，记录直流电压波形，计算稳态直流电压值，计算稳态直流纹波电压，并与理论公式比较，验证设计指标。4、仿真过程::A．建立模型:建立仿真模型如下如所示:B.记录数据:仿真算法选择ode23tb,最大步长为0.1s，占空比D=0.25进行仿真，记录数据如下表所示：开关频率fs(KHz)电感L(mH)电容C(μF)输出电压稳态值Vo(V)输出电压纹波值ΔVo(V)电感电流波动值ΔIo(A)100.3755004.7360.026710.454174.3390.02750.8750.18755006.4350.05101.8500.0751004.7450.01971.0140.0983.34.3960.02240.875与理论值对比开关频率fs(KHz)电感L(mH)电容C(μF)输出电压稳态值Vo(V)输出电压纹波值ΔVo(V)电感电流波动值ΔIo(A)100.37550050.02510.4541750.0250.8330.187550050.0252500.07510050.02510.0983.350.0250.833C．仿真过程:当fs=10KHz,L=0.375mHC=500μF,占空比D=0.25,电流连续的临界状态时，记录稳态直流电压值Vo=4.736V，稳态直流电压理论值5V计算稳态直流纹波电压的理论值2(1D)0.025V8sooTVVCL,通过图中得到直流纹波电压为0.0267V当fs=10KHz,L=0.375mH,C=500μF,占空比D=0.25,电流连续的临界状态时,由(1)oSLVDTIL，得电感电流波动理论值是1A，由图像得到电感电流波动值是1A，与理论计算相符合0.10870.10880.10890.1090.10910.10920.10930.10940.1095-1-0.500.511.52Time/sPulse/VSwitch(fs=10KHz,L=0.375mH,C=500uF)0.10870.10880.10890.1090.10910.10920.10930.10940.1095-1-0.500.511.52Time/sIL/VInductorCurrent(fs=10KHz,L=0.375mH,C=500uF)0.04360.04380.0440.04420.04440.04460.04480.0450.04520.04544.724.7254.734.7354.744.7454.75Time/sUo/VUo(fs=10KHz,L=0.375mH,C=500uF)Figure-1fs=10KHz,L=0.375mH,C=500μF,占空比D=0.25,电流连续的临界状态取1.2倍临界电感值时，输出电压稳态值是4.399V，理论值是5V，纹波电压理论值0.025V记录波形测得纹波电压为0.0275V电感电流波动理论值为0.833A，由图像得到电感电流波动值是0.875A0.02450.0250.02550.026-1-0.500.511.52Time/sPulse/VPulse(fs=10KHz,L=0.45mH,C=417uF)0.02450.0250.02550.026-1-0.500.511.52Time/sIL/AInductorCurrent(fs=10KHz,L=0.45mH,C=417uF)0.1970.19750.1980.19850.1990.19950.20.20050.2010.20154.384.3854.394.3954.44.4054.41Time/sUo/VUo(fs=10KHz,L=0.45mH,C=417uF)取1.2倍电感值时Figure-2取1.2倍电感值时fs=50KHz,L=0.075mH,C=100μF,占空比D=0.25,电流连续的临界状态时，记录稳态直流电压值Vo=4.745V，理论值是5V，稳态直流纹波电压理论值0.025V,由输出电压波形得到实际值为0.0197V电感电流波动理论值为1A，测量值为1.014A0.02470.02480.02490.025-1-0.500.511.52Time/sPulse/VPulse(fs=50KHz,L=0.075mH,C=100uF)0.02470.02480.02490.025-1-0.500.511.52Time/sIL/AInductorCurrent(fs=50KHz,L=0.075mH,C=100uF)66.026.046.066.086.1x10-34.7354.744.7454.754.7554.76Time/sUo/VUo(fs=50KHz,L=0.075mH,C=100uF)Figure-3fs=50KHz,L=0.075mH,C=100μF,占空比D=0.25,电流连续的临界状态取1.2倍临界电感时，输出电压平均值为4.396V，理论值是5V，纹波电压理论值为0.025V，实际为0.0224V电感电流波动理论值为0.833A，实际值为0.875A0.02470.02480.02490.025-1-0.500.511.52Time/sPulse/VPulse(fs=50KHz,L=0.09mH,C=83.3uF)0.02470.02480.02490.025-1-0.500.511.52Time/sIL/AIductorCurrent(fs=50KHz,L=0.09mH,C=83.3uF)4.524.544.564.584.64.624.64x10-34.384.3854.394.3954.44.4054.41Time/sUo/VUo(fs=50KHz,L=0.09mH,C=83.3uF)Figure-4取1.2倍电感时(2)画出电感电流波形，计算电流波动值并与理论公式对比记录数据如下表开关频率fs(KHz)电感L(mH)电容C(μF)电感电流波动值ΔIo(A)电感电流波动实际值ΔIo(A)100.375500110.454170.8330.8750.187550021.8500.07510011.0140.0983.30.8330.8750.10870.10880.10890.1090.10910.10920.10930.10940.1095-1-0.500.511.52Time/sPulse/VSwitch(fs=10KHz,L=0.375mH,C=500uF)0.10870.10880.10890.1090.10910.10920.10930.10940.1095-1-0.500.511.52Time/sIL/VInductorCurrent(fs=10KHz,L=0.375mH,C=500uF)Figure-5fs=10KHz,L=0.375mH,C=500μF,占空比D=0.25,电流连续的临界状态0.02450.0250.02550.026-1-0.500.511.52Time/sPulse/VPulse(fs=10KHz,L=0.45mH,C=417uF)0.02450.0250.02550.026-1-0.500.511.52Time/sIL/AInductorCurrent(fs=10KHz,L=0.45mH,C=417uF)Figure-6fs=10KHz,L=0.45mH,C=417μF,占空比D=0.250.02470.02480.02490.025-1-0.500.511.52Time/sPulse/VPulse(fs=50KHz,L=0.075mH,C=100uF)0.02470.02480.02490.025-1-0.500.511.52Time/sIL/AInductorCurrent(fs=50KHz,L=0.075mH,C=100uF)Figure-7fs=50KHz,L=0.075mH,C=100μF,占空比D=0.25,电流连续的临界状态0.02470.02480.02490.025-1-0.500.511.52Time/sPulse/VPulse(fs=50KHz,L=0.09mH,C=83.3uF)0.02470.02480.02490.025-1-0.500.511.52Time/sIL/AIductorCurrent(fs=50KHz,L=0.09mH,C=83.3uF)Figure-8fs=50KHz,L=0.09mH,C=83.3μF,占空比D=0.25(3)修改占空比，观察直流电压值的变化。fs=10KHz,L=3.75e-4,C=500μF,临界连续占空比D(%)12.525507590Vo(V)2.234.7369.57214.7117.9400.10.20.30.40.50.60.70.80.9102468101214161820DVo/VVo-D(Vd=20V)Figure-9输出电压与占空比关系曲线(4)将电感改为临界电感值的一半，运行仿真模型(只仿真开关频率10k时的情况，使用理论计算的占空比)：记录电感电流波形，电感电流波动值为1.8A观察不连续电流的波形；记录直流电压波形，计算稳态直流电压值，与理论公式6.67V对比，，实际值6.435V并与同一占空比下电流连续时的直流电压值4.736V进行比较；计算稳态直流纹波电压，由图中得到纹波电压为0.0510V并与理论公式比较（需根据电流波形计算D2的大小）。理论值计算：1875.0101010875.144SRTL5.0281212CCCDDD则：VUDDDUSCCC67.6205.025.025.012102,max22,max=0.00003s1.8A,0.645A1()4LBooodLBIIVDIVDI，[()][()()(())]2()0.0373VsdoosdoooodosdoooodooDTVVLIDTVVVLIVVVDTVVLIVLCVVVV实际仿真值：6.435VV可见理论公式算出来的值比实际仿真出来的值要大一些，是由于反并联二极管作用导致。但是，在同一占空比情况下，电流不连续情况下比连续情况的输出电压大，比较稳态直流纹波电压：由图像得到输出电压的纹波为0.0510V在同一占空比的情况下，电流不连续情况下的纹波电压比连续情况明显增大。0.1290.12910.12920.12930.12940.12950.1296-1-0.500.511.52Time/sPulse/VPulse(fs=10KHz,L=0.1875mH,C=500uF,D=0.25)0.1290.12910.12920.12930.12940.12950.1296-1-0.500.511.52Time/sIL/AIductorCurrent(fs=10KHz,L=0.1875mH,C=500uF,D=0.25)0.0170.01710.01720.01730.01740.01750.01760.01776.4