Pulse motor driving device of sewing machines

Claim 1

A pulse motor driving device for a pulse motor having a plurality of windings each connected to a driving power source comprising detecting means for detecting a value of electric current flowing through the windings; reference voltage generating means producing a triangular wave signal of a predetermined period; comparator means comparing the detected value of electric current of the windings and the triangular wave signal, said comparator means producing a chopping signal providing a period for applying the voltage of the driving power source to the windings each time the level of the triangular wave signal becomes higher than that of the electric current of the windings; bridge circuits each composed of four switching elements for each of the windings, said bridge circuits being each connected to the driving power source through said detecting means at a point thereof between the joints of the adjacent switching elements on one diagonal of the bridge circuit, and each having the winding connected between the joints of the adjacent switching elements on the other diagonal of the bridge circuit; switching element control means for controlling the switching operation of the opposite switching elements in each of the bridge circuits, said switching element control means selectively applying a driving pulse signal to one of the opposite switching elements in each bridge circuit, which is connected to the respective detecting means to continuously make the switching element on and off, and selectively controlling the switching operation of the other of the switching elements in each bridge circuit in accordance with the chopping signal of the comparator means so as to supply the voltage of the driving power source to the switching element while the switching element is on due to the chopping signal; and diodes connected between one pole of the driving power source and both ends of the windings respectively, said diodes forming a short-circuit in which the electromagnetic energy of the windings may flow through said detecting means and said ones switching elements connected to the detecting means while the current flow from the driving power source to said others switching elements is blocked by the chopping signal.