Refrigerator refrigeration compressor controller based on dsPIC30F4012 (part 2)

Refrigerator refrigeration compressor controller based on dsPIC30F4012 (part 2)




3 Control System Hardware Design

The system by detecting the terminal voltage of "off the mid-point" rotor position obtained from the dsPIC30F4012 output PWM pulse square wave, after driving circuit driving the corresponding power tubes off and realize the correct power the motor, the motor running.



About 3.1 dsPIC30F4012

dsPIC30F4012 for Microchip's DSP processing power with a high-performance 16-bit microcontroller, and its unique modular architecture and powerful performance makes the storage of its application to brushless motor control has certain advantages. dsPIC30F4012 motor with a dedicated on-chip PWM controller (MCPWM); through the program can produce independent, with the same frequency and methods of work of the three-phase 6-channel PWM waveform, each pin drive current up to 25 mA, by the mouth directly RE output to drive, and the three-phase non-overlapping complementary. To prevent the same bridge arm of the two power tube through causing a short circuit occurs, the structure greatly simplifies the resulting PWM waveform control software and external hardware, the system adjusted by a potentiometer BLDC speed; resistor voltage VDC of the completion of testing, VDC / namely, two terminal voltage "off the mid-point" of the voltage; voltage feedback through the three resistors right to achieve.



3.2 Drive Circuit

Drive circuit shown in Figure 2. IR2101 is the IR produced a cost-effective drive, drive better effect and easy to operate. IR2101 drivers can drive a group of power tube, the entire power circuit can be only three, so that will not only save manufacturing costs, but also to improve system stability.



3.3 The current feedback and fault detection circuit

Current feedback and fault detection circuit shown in Figure 3. The first one current feedback op-amp current through the sample on the bus, amplification of the AN2 input pin to the dsPIC30F4012 achieved: the first one op-amp's output connected to the first two inverse operation amplifier circuit, for motor fault detection, when the busbar current is too large to let the microprocessor into the fault handling. Reasonable and practicable system of programs and algorithms.



4 system debugging and testing

Figure 4 for the system's main program flow, the main program is mainly to set the various device control word, to initialize the value of each variable and signs, open the corresponding interrupt and regulate the motor speed. Three-phase power inverter drives, PWM duty cycle register (PDCX) and rewrite the control register (OVDCON) with the use of the duty cycle registers to control the current flowing through the load, you can rewrite the control registers control the commutation. dsPIC30F4012 built-in motor dedicated PWM controller structure, and can greatly simplify the resulting PWM waveform control software and external hardware design. After the success with the ICD2 to debug a program downloaded to the dsPIC30F4012, the assembly of the entire system, tested, the system has good stability and controllability, and to respond quickly, run smoothly, has good static and dynamic performance. Figure 5 is a 4-channel oscilloscope collected four power tubes driving waveforms. Waveforms show that the system control program and algorithms used in reasonable and feasible.



5 Conclusion

After testing, the system design has good stability and controllability, although in low-speed startup, the motor performance than a sensorless brushless DC motor, while the performance with the performance starts fairly. Throughout the system hardware, low cost, control performance, flexible, and has broad market prospects.



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