The Design Of BLDC Speed Controlling System Basing On DSP

The brushless DC motor replaces the mechanical electrical brushes and phase changing devices with electrical phase changing devices, which makes it have both merits of DC motor and AC motor. All of these make it develop fast after it appeared.The BLDC motor must implements two kind of controlling processes: speed controlling and phase changing. For this cause, BLDC motor needs to use position feedback devices, such as Hall element, photoelectrical coder. The speed controlling also use the position detecting device to calculate real speed value, and then use the PI control theory to change the ratio of PWM which is used to change speed. Therefore, the controlling IC should do a lot of calculations. Although there are some special ICs to control BLDC motors, for most applications, it is necessary to do some other control or transmission work. According to this, we have to select an IC which has PWM function and strong calculation ability. The IC of TMS320LF2407A which is made by TI has strong calculating ability and plentiful periphery functions, all of these make it adapt to take step in the BLDC controlling system.For costumer’s certain application, because its special technology and cost target, universal BLCD controlling system can’t meet this need. We need to design a new one with special functions for each costumer, which greatly cut down the cost. These individual demands have a considerable quantity and require high reliability. All of these points make designing a product of intellectual property rights meaningful and practical.This paper brings forward the scheme of BLDC control system basing on DSP technology. This system includes two parts: the control circuit and main circuit. The control theory takes double closed loop control theory. The outer loop is speed loop and its output is the current input; the inner loop is current loop and its output is the changed ratio of PWM.In this paper, firstly, I raised the overall scheme of BLDC control system basing on DSP; secondly, I introduced the control method of BLDC and the two loop control theory; in the third place, I expounded the hardware and software design in the system; in the last, I gave forth the conclusion of this system, including the real devices and its running wave figures.