基于LM3S8962的简易恒流电子负载

Electronic Load of a Simple Constant-Current Mode Based on LM3S8962

为测试开关电源的性能指标,设计了一种基于LM3S8962的简易恒流电子负载.该系统以LM3S8962单片机作为核心控制器,产生D/A输出信号加至功率MOS管IRF540的栅极,通过PI调节改变功率管的栅压从而控制其导通电阻,同时通过采样反馈电路检测端口电压及电流,经A/D转换后送给单片机,形成对电源端口电流的闭环控制,使负载上的电流保持相对恒定.该装置可通过键盘设定输出电流值,可调范围在100～1 000 mA之间设置,分辨率为10 mA,可检测被测电源电流值、电压值等参数,并通过LCD显示,系统具备过压保护功能.该装置结构简单,操作方便,显示界面直观明了.测试结果表明,该电子负载恒流效果良好,系统误差在±1%范围之内.

To detect the reliability and properties of switching power supply system, an electronic load working in constant current mode is designed and realized. In the system, a microprocessor of LM3S8962 is used as the core mi- crocontroller, the output signal from D/A is inputted to the gate of the power MOS transistor （IRF540） through a PI regulator and the on-resistance of IRF540 can be controlled by adjusting the gate voltage. In addition, the terminal current can be kept in a constant value by using a close-loop control, in which the terminal current and voltage are measured through a sample-hold circuit and then fed back to LM3S8962 through an A/D converter. The output current of the system can be set ranging from 100 to 1 000 mA with precision of 10 mA, and can be inputted from the key- board. The actual voltage and current can be also measured under an overvoltage protection and then displayed in LCD. Moreover, the designed equipment is characterized by simple structure, friendly interface and convenient opera- tion. The measurement results indicate the equipment enjoys high precision and the error between the set and actual value is less than ±1%.