Burn-out preventive circuit for commutatorless motor

摘要

A burn-out preventive circuit for a commutatorless motor comprises drive windings of two phases, driving power transistors connected in series with the drive windings respectively, a position detecting element detecting the angular position of rotation of a permanent magnet rotor for alternately turning on the driving power transistors, and a protective circuit detecting a counter-electromotive force induced in the drive windings during rotation of the permanent magnet rotor for interrupting energization of the drive windings when the detected counter-electromotive force is lower than a predetermined level or zero.