基于STM32的多功能数控直流电源.doc

题目：多功能数控直流电源队员：队员：队员：指导教师：完成时间： 2015/7/26 摘要：利用STM32单片机系统，对键盘或者触摸屏输入的数据进展读取根据模式的设定，可以利用部的DAC以及外部电路实现数控直流电源输出，分为稳压源、稳流源两种同时也可以实现模式可调的信号发生器，可以在方波、三角波、锯齿波以及正弦波之间进展切换关键词：STM32，数控，直流电源，信号发生器Abstract：Using STM32 MCU, read the input data from keyboard or touch screen. According to the mode set now, the DAC inside cooperates with outside circuits can output DC power supply, which can be set to two modes, name as voltage source and current source. The same time, it can also work as an signal generator, which can be changed between square wave, triangle wave, saw tooth wave and sine wave.Keyword：STM32, numerical control, DC power supply, signal generator目录1. 设计任务与要求····························································31.1 设计任务·····························································31.2 设计要求·····························································32. 方案论证··································································32.1 总体设计·····························································32.2 关键问题·····························································43. 单元电路设计······························································93.1 总体电路图···························································93.2 参数计算····························································104. 软件设计·································································124.1 主程序······························································124.2 关键子程序··························································135. 系统测试·································································195.1 测试条件····························································195.2 测试方法与步骤······················································195.3 测试数据····························································215.4 结果分析····························································236. 结论·····································································246.1 综合评价····························································246.2 可改良的方向························································24参考文献·····································································25附录·········································································26附录1 元器件清单······················································26附录2 电路图···························································271. 设计任务与要求1.1 设计任务设计一个有一定输出电压、电流围的多功能数控电源。

1.2 设计要求1.2.1 根本要求（1） 有稳压源模式，给定输出电压围0~9.9V，步进0.1V；输出电压静态误差≤0.1V，电压波动≤0.05V，纹波峰峰值不大于20mV；稳压时输出电流围0~100mA；（2） 有过流保护功能，当电流到达105mA±2mA围时产生保护动作；（3） 有稳流源模式，给定输出电流围0~99mA，步进1mA；输出电流静态误差≤2mA，电流波动≤1mA；稳流时输出电压围0~10V；（4） 用十进制数码显示负载电压、电流值；显示效果清晰、稳定、无闪烁；（5） 有十进制数字键盘，用于设定输出电压或电流的给定值另有“+〞、“-〞两键，可直接控制负载电压或电流的步进增减键盘或按键的操作要求尽可能简便6） 输出电压或电流可预置在给定的围任意一个值，在下一次上电时无需操作即可按设定模式和设定参数输出1.2.2 发挥要求（1） 可用电位器分别调节负载电压和电流值，调节围符合上述输出给定围，调节特性平滑、稳定、快速；（2） 负载改变时，输出电压、电流需要同时满足不超过设定值的要求，并能实现稳压源模式与稳流源模式的自动切换；（3） 有信号源输出功能，信号输出种类有方波、三角波、锯齿波、正弦波等，每周波不少于32点；频率围：10Hz~10kHz，步进10Hz，频率误差≤10Hz；幅度〔峰峰值〕可调围：0~9.9V，步进0.1V；（4） 有通讯功能，可用上位机〔触摸式串口液晶屏〕控制下位机〔数控直流电源〕的输出电压或电流值，并能从下位机获取负载电压或电流数据，在上位机显示屏上显示该数据；（5） 其他。

2. 方案论证2.1 总体设计2.1.1 组成框图总体组成框图如图1所示图1 组成框图2.1.2 工作原理STM32单片机系统从数字键盘或触摸屏读取数据，根据读取的数据选择输出模式为稳压输出、稳流输出以及波形输出中的一种当设定为稳压输出时，STM32单片机通过DAC输出模拟电压为设定值的25%，外部电路对输出放大4倍，且通过功率放大以及负反应，实现0~9.9V的稳压输出当设定为稳流输出时，STM32单片机通过DAC当设定为波形输出时，STM32单片机通过DAC输出存储在EEPROM中的数据表，外部电路对其进展功率放大2.2 关键问题2.2.1 稳压输出〔1〕方案一：用运放和功率器件组成功放电路原理图如图2所示图2 稳压输出方案一原理图在电压放大级采用集成运放，功率放大级采用分立元件进展功率扩展通过改变电阻比值，可以方便地改变输出电压的调整围通过改变功放级分立元件的输出功率，也可以方便的改变输出的电流驱动能力此方案比拟灵活实用〔2〕方案二：用集成功率放大器作为功放电路集成功率放大器将运算放大器的输出级改为复合管形式，以增大输出电流采用集成功率放大器可以简化外围电路、改善性能、提高可靠性，减少电路的设计工作量。

但是其价格比普通运放要高许多，且最大输出电流或功率为固定值，不易调整，缺乏灵活性〔3〕方案三：用集成稳压器件可以通过外接电路改变基准点的电压值，可以使其输出端电压也随之改变这种可调稳压输出具有良好的负载特性，输出最大负载电流达1.5A，且部具有过流保护与过热保护等电路，有较好的性价比需要注意的是，7805的基准点电压围应该控制在-5~+5V之间，要求DAC采用双极性输出或参加电压偏移电路将单极性输出转换为双极性输出原理图如图3所示图3 稳压输出方案三原理图2.2.2 稳流输出〔1〕方案一：电压/电流转换器原理图如图4所示图4 稳流输出方案一原理图这是一种适用于接地负载的转换器，要求输入的电压信号vi2有一定的电流驱动能力〔2〕方案二：原理图如图5所示图5 稳流输出方案二原理图假设RS = 0.1，IL = 0～2A，Vi = 0～-5 V则，R5：R6 = 1：25； U2输出需加功率驱动其缺点是需要三个运放，不光是用了更多的资源，而且很容易引起振荡〔3〕方案三：原理图如图6所示图6 稳流输出方案三原理图假设RS = 0.1，IL = 0～2A，Vi = 0～5 V，则R4：R3 = 1：25；U5输出需加功率驱动。

〔4〕方案四：差分电路原理图如图7所示图7 稳流输出方案四原理图运用差分电路，将采样电阻上的压降增大一定的倍数，与设定的输入电压进展比拟，从而获得固定的电流为了让采样电阻上的电流尽可能接近负载上的电流，要使差分电路的电路较大2.2.3 波形输出〔1〕方案一：不参加直流偏置电路图如图8所示图8 波形输出方案一电路图为一个放大倍数为5倍的同向比例放大器，单片机输出为0~2V，则信号发生器的输出为0~10V〔2〕方案二：参加直流偏置电路图如图9所示图9 波形输出方案二电路图主体同样为一个放大5倍的同向比例放大器，在其电压基准点接入可以通过电位器调节的电压值，从而可以使得单片机的输出信号在5倍放大的同时，调节直流偏置2.2.4 过流保护过流保护电路的功能是当输出电流因负载变化而超过设定值时产生保护作用，使输出电压降低或完全关闭输出，以保护输出电路不会因过流、过热而造成永久性损坏〔1〕方案一：利用三极管的导通特性原理图如图10所示图10 过流保护方案一原理图三极管发射结导通时vBE ≈ 0.7V，当采样电阻R上因负载电路增加而使压降大于0.7V时使三极管T1、T2导通，产生过流保护信号；可以直接输出至驱动管，限制输出电流的继续增加，也可以送入数控局部，处理后切断电压信号。

〔2〕方案二：用电压比拟器原理图如图11所示图11 过流保护方案二原理图利用电压比拟器，当采样电阻压降到达设定值时，比拟。