Control of brushless DC motor with C50x
Brushless DC motors are more and more widely used due to their easy control, no commutator, simple structure, high speed and high efficiency. The continuous introduction of various special chips further promotes its application and development. The C50x is a microcontroller control chip developed by Siemens for brushless DC motors. It has a hardware commutation circuit inside, which simplifies the hardware structure of the brushless DC motor controller and enhances reliability. The C504 can control one motor and the C508 can control two. This paper takes C504 as an example to introduce the design method of brushless DC motor control speed control system.
Brushless DC motor speed control system structure and function
The structure of the brushless DC motor speed control system is shown in Figure 1. The system is mainly composed of single-chip controller, 1GBT drive circuit, 1GBT bridge, three-phase brushless DC motor rotor position detection circuit, protection circuit, liquid crystal display and operation circuit. The three-phase brushless DC motor rotor position detecting circuit converts the rotor magnetic pole position into an electric signal for C504 processing. This signal causes a three-phase 1GBT bridge to be commutated, and the 1GBT driving circuit completes the conversion from weak current to strong power.
The working principle of brushless DC motor and the characteristics of C504
2 is a main circuit diagram of a brushless DC motor speed control system, and FIG. 3 is a rotor position and a commutation relationship diagram. Corresponding to different rotor positions, only 6 of the 6 tubes of the main bridge arm are open at a time.
The C504 chip has a hardware commutation circuit inside. When the position signal of the three-phase rotor is detected and sent to C504, C504 switches the commutation control signal of the main circuit without software processing. This greatly reduces the difficulty of development and increases the reliability of commutation.
The C504 has a unique internal hardware protection circuit. In order to effectively protect the 1GBT and motor of the main control loop, an overvoltage and overcurrent detection circuit is provided in the circuit. When an overvoltage or overcurrent occurs, the protection detection circuit sends the detected signal to the P504 pin of the C504 with capture and lock function. The pin immediately blocks the main loop trigger control signal, cuts off the main loop current, and protects the components. Then notify C504 to perform fault interrupt processing, which is very effective and reliable.
From the rotor position detection signal, the actual speed of the motor can be known by calculation. When it is necessary to reset the speed or be disturbed, the chip can change the duty ratio of the output signal by programming, and the motor speed can be conveniently adjusted to achieve the required speed value.
System software design
The system software adopts a modular structure, and the main program flow is shown in Figure 4.
Conclusion
The hardware commutation circuit and interrupt protection circuit of the C50x series dedicated MCU controller can be used to construct the brushless DC motor speed control system conveniently, reliably and economically.
