Rotor position detecting method for brushless direct current motor

TLDR: In this article, a brushless direct current motor with a permanent magnet rotor by a transistor circuit was used to detect the position of a rotor via an integrating filter and differential filter utilizing voltage wave form induced in a stator coil.

Abstract: PURPOSE:To eliminate a position detector signal line and to stabilize operation regardless of the ambient temperature by detecting the position of a rotor via an integrating filter and differential filter utilizing voltage wave form induced in a stator coil CONSTITUTION:When driving a brushless direct current motor having a permanent magnet rotor by a transistor circuit, induced voltages in each stator coil of multi-phase connection are applied to terminals a3, b3, c3 and are inputted to one terminal of comparators a5-c5 via filter circuits a4-c4, each having a integrating filter and differential filter, while the voltage of each filter is synthesized by a neutral point voltage synthesizer circuit 7 and is inputted to the other terminal of the comparators a5-c5 This output is processed in a logic processing circuit 6 and drives transistors provided for each phase This construction largely stabilizes detection of the rotor position without providing Hall elements