Conclusion

AN2502

6/9

3

Conclusion

The need to generate a forced start up stepping sequence and to tune its stepping rate is

completely avoided. The waveforms shown in Figure 2 reveal the excellent starting

performance obtained with a low voltage (24V) BLDC motor that generates a very weak

BEMF at start up. For higher voltage motors, such as 300V DC, this method will be even

more reliable. This was verified by running a blower motor and a washing machine motor

and the performance was found to be satisfactory. Most low cost sensorless control

methods requires initial forced rotation of the rotor. But ST7FMC, because of its direct BEMF

detection method, differentiates itself from the rest by this superior start up performance.