Patent ID: 10879818

Abstract:
A linear actuator comprises a brushless DC motor (31), a driver circuit (51) for providing a multiphase voltage signal to the motor (31) and a controller (58) for detecting a rotor position and providing control signals to the driver circuit (51) in dependence thereof. Detector circuitry (61) detects a signal indicative of rotor speed. The controller (58) is configured to control the driver circuit (51) to drive the motor with a first waveform of the multiphase voltage signal, when the indicative signal indicates that the rotor speed does not exceed a predetermined speed; and control the driver circuit (51) to drive the motor with a second waveform of the multiphase voltage signal, when the indicative signal indicates that the rotor speed exceeds the predetermined speed, wherein the second waveform is selected to drive the motor (31) with an efficiency less than the efficiency when driven by the first waveform.