基于STM32的小纹波高精度恒流源系统设计

Design of small ripple high precision constant current source system based on STM32

针对传统恒流源输出稳态误差大的问题,提出一种STM32单片机控制的双路斩波电路恒流方式的数控恒流源设计方案。主控制器应用PID算法不断将采样值与预期值比较修正后经D/A转换输出调整电压,与采样电阻端电压共同驱动SG3525产生两路占空比相同、相位差180°的PWM波驱动双路斩波电路,两路反向变化的脉动电流叠加后输出平稳电流,以此来减小纹波电流,从而提高输出精度。实验结果表明:设定电流可在20~2 000 mA内变化,输出纹波不大于0.20 mA,相对误差最小可达0.011%。系统纹波小、输出精度高,且在不同大小的负载下稳定性良好。

In allusion to the problem of large steady⁃state error of the output of traditional constant current source,a design scheme for numerical control constant current source with dual chopper circuit constant current mode controlled by STM32 single⁃chip microcomputer is proposed.In the main controller,the PID algorithm is used to compare and correct the sampled values with the expected values,and then output the adjusted voltage through D/A conversion.Together with the sampling resistor terminal voltage,it can drive the SG3525 to generate two PWM waves with the same duty cycle and a phase difference of 180°to drive the dual chopper circuit.The two reverse changing pulsating currents are combined to output a stable current,thereby reducing the ripple current and improving output accuracy.The experimental results show that the set current can vary between 20~2000 mA,the output ripple is not greater than 0.20 mA,and the minimum relative error can reach 0.011%.The system has small ripple,high output accuracy,and good stability under different sizes of loads.