基于TMS320C240的SPWM调制信号的设计

Design of Modulation Signals in a SPWM Mode Based on TMS320C240

研究使用 TMS32 0 C2 4 0在线生成用于闭环变频调速的 SPWM波形。利用分段同步调制法、压频比算法以及对正弦函数值的拟和 ,实时计算不同频率下的采样周期、电压幅值及输出脉宽 ,并将这些时间计数值送入 TMS32 0 C2 4 0事件管理器 EV中的定时器 ,利用定时中断向接口电路送出相应的高低电平 ,实时产生 SPWM波形。产生可实现变化压频比、实时频率变换的 SPWM波形。与单片机产生的 SPWM波形相比 ,该 SPWM的输出速度快、谐波小、对称性好。频率范围为 0～ 4 0 0 Hz时 ,精度可达约 0 .0 15Hz。

The paper investigates the application of TMS320C240 in generating a series of SPWM waveform signals online for variable frequency loop systems. Using the algorithm of subsection modulation, voltage frequency ratio as well as numeration of sine function, real time sampling cycle, voltage amplitude, and pulse width at different frequencies are achieved and the time values are put into the timers of the special event manager EV in TMS320C240. Then through timing interrupt the high low voltages are sent to the interface circuits to generate real time SPWM waves. A series of SPWM waveform signals where the voltage frequency ratio and frequency can be changed real time is then achieved. The harmonic of SPWM generated by TMS320C240 is decreased. The output is fast and of good symmetry compared with that of a singlechip. The precision attainable is at the order of 0 015 Hz in the range 0～400 Hz.