Design of a sensorless commutation IC for BLDC motors

This paper presents the design and realization of a sensorless commutation integrated circuit (IC) for brushless DC motors (BLDCMs) by using mixed-mode IC design methodology. The developed IC can generate accurate commutation signals for BLDCMs by using a modified back-EMF sensing scheme instead of using Hall-effect sensors. This IC can be also easily interfaced with a microcontroller or a digital signal processor (DSP) to complete the closed-loop control of a BLDCM. The developed sensorless commutation IC consists of an analog back-EMF processing circuit and a programmable digital commutation control circuit. Since the commutation control is very critical for BLDCM control, the proposed sensorless commutation IC provides a phase compensation circuit to compensate phase error due to low-pass filtering, noise, and nonideal effects of back-EMFs. By using mixed-mode IC design methodology, this IC solution requires less analog compensation circuits compared to other commercially available motor control ICs. Therefore, high maintainability and flexibility can be both achieved. The proposed sensorless commutation IC is integrated in a standard 0.35-(mu)m singlepoly four-metal CMOS process, and the realization technique of this mixed-mode IC has been given. The proposed control scheme and developed realization techniques provide illustrative engineering procedures for the system-on-a-chip solution for advanced digital motor control. Simulation and experimental results have been carried out in verification of the proposed control scheme.