Control circuit for commutatorless DC motor - sensing stages detect induced voltages in stator windings to activate ring counter producing phase signals

摘要

A switching circuit is used to provide connection between the supply and three stator windings in a commutator less d.c. motor using induced voltage within the windings. The three stator windings are coupled to inputs (1, 2, 3) of three sensing stages (4, 5, 6) each with an output (T) that is '1' when the winding voltage is positive and 'o' when negative. A NAND gate (7) combines these sensing signals to generate an output when any 'T' output goes low. The sensing stage processes the winding voltage through filter and is compared with a stored peak value. A comparator generates an output at a predetermined level that is differentiated to generate the 'T' signal. The NAND gate (7) generates a grating signal over an OR gate (8) to change the state of a ring counter (10) to produce the phase signals (PH1, PH2, PH3) at specific intervals.