Improved Back-Emf Detection Technique for Position Sensorless Control of Permanent Magnet Brushless DC Drive

In this paper, an improved back-emf zero crossing point (ZCP) detection technique for position sensorless control of permanent magnet brushless DC (PMBLDC) drive is presented. Many methods of ZCP detection have been discussed in literature for both continuous and discontinuous phase currents. In these methods, terminal voltage is sampled either during PWM OFF period or ON period for ZCP detection. The proposed method does not need to sample terminal voltage specifically during PWM OFF or ON period. It is sampled after every PWM cycle and a signal is generated which helps in ZCP detection. This technique offers advantage of simple implementation. Simulation and experimental results are presented for both continuous and discontinuous phase currents to demonstrate the efficacy of the proposed technique.