【正文】 絕對值 ≤ 輸出電流值的 1％ +10 mA； （ 5）紋波電流 ≤ 2mA； （ 6）自制電源。 目前在電力電子器件方面，幾乎都為旋紐開關調節(jié)電壓，調節(jié)精度不高，而且經常跳變，使用麻煩。但其產品存在數(shù)控程度達不到要求、分辨率不高 、功率密度比較低、可靠性較差的缺點。隨著數(shù)控電源在電子裝置中的普遍使用，普通電源在工作時產生的誤差，會影響整個系統(tǒng)的精確度。單片機系統(tǒng)還兼顧對恒流源進行實時監(jiān)控，輸出電流經過電流 /電壓轉換后，通過 A/D 轉換芯片 MAX1241，實時把模擬量轉化為數(shù) 字 量，再經單片機分析處理，通過數(shù)字量形式的反饋環(huán)節(jié)，使電流更加穩(wěn)定，這樣構成穩(wěn)定的壓控電流源。 關鍵詞 ： 壓控恒流源 ； AT89S52； 數(shù)控電源； II Abstract In the system, the digitally programmable signal from SCM is converted to analog value by DAC AD5320, is sent to the base electrode of power transistor, so an adjustable output current can be available with the base electrode voltage of power transistor. On the other hand, The constant current source can be monitored by the SCM system realtimely, its work process is that output current is converted voltage, then its analog value is converted to digital value by ADC MAX1241, finally the digital value as a feedback loop is processed by SCM so that output current is more stable, so a stable voltagecontrolled constant current power is designed. KeyWords： voltagecontrolled constant current source； AT89S52； Numerical controlled source； III 目 錄 摘 要 ............................................................................................................................ I Abstract ............................................................................................................................. II 引 言 ........................................................................................................................... 1 第一章 概述 ................................................................................................................... 2 設計要求 ..................................................................................................... 2 理論分析 ..................................................................................................... 2 系統(tǒng)介紹 ..................................................................................................... 3 第二章 硬件設計 ........................................................................................................... 4 電源模塊 ..................................................................................................... 4 電源設計 ......................................................................................... 4 恒流源模塊 ................................................................................................. 5 單片機 模塊 ................................................................................................. 6 AT89S52 芯片介紹 ........................................................................ 6 AT89S52 硬件電路設計 ............................................................... 9 鍵盤模塊 ................................................................................................... 10 MM74C922 ................................................................................... 10 鍵盤電路 ....................................................................................... 10 顯示模塊 ................................................................................................... 11 1602LCD 顯示 .............................................................................. 11 LCD 顯示硬件電路 ...................................................................... 12 A/D 模塊 ................................................................................................. 13 芯片 MAX1241 ............................................................................ 13 A/D 模塊電路 ............................................................................... 14 D/A 模塊 ................................................................................................. 14 存儲模塊 ................................................................................................... 15 2? C 總線 ....................................................................................... 15 芯片 24C02C ................................................................................ 15 存儲模塊電路 ............................................................................... 16 第三章 軟件設計 ......................................................................................................... 17 編程語言描述 ........................................................................................... 17 系統(tǒng)軟件的功能模塊 ............................................................................... 17 主程序設計 ................................................................................... 17 中斷程序設計 ............................................................................... 18 第四章 軟件仿 真及硬件調試 ..................................................................................... 21 Proteus..................................................................................................... 21 軟件仿真 ................................................................................................... 21 硬件調試 ................................................................................................... 22 IV 單片機最小系統(tǒng)調試 ................................................................... 22 鍵盤及液晶顯示調試 ................................................................... 22 數(shù)模轉換與功放電路調試 ........................................................... 22 模數(shù)轉換電路調試 ....................................................................... 23 存儲器電路調試 ........................................................................... 23 第五章 設計總結 ......................................................................................................... 24 致謝 ................................................................................................................................. 25 參考文獻 .......................................................................................................