US 4,427,931 AGranted

Speed control apparatus for direct current motor

AssigneesSanyo Electric Co., Ltd., Tokyo Sanyo Electric Co., Ltd.

InventorAkira Tsukihashi

Life of this patent

Estimating the term…

Loading patent…

Abstract

A speed control apparatus for a direct current motor comprises a bridge circuit having an armature in one side thereof, a direct current voltage source, and a series connection of a switching transistor and an inductor inserted between the direct current voltage source and the bridge circuit. A detecting transistor detects an unbalanced voltage of the bridge circuit and control transistors are responsive to the detection to control the switching transistor to be turned on or off. The inductor stores a magnetic energy when the switching transistor is turned on and supplies an electromotive force induced by the stored magnetic energy to the bridge circuit when the switching transistor is turned off. To that end, a diode or a transistor cooperates with the inductor and the bridge circuit to constitute a closed loop. A capacitor is connected in parallel with the armature, thereby to restrict the operation of the detecting transistor and thus the on/off-period of the switching transistor.

Claims9

Dependent claims

A speed control apparatus for a direct current motor, comprising:

first and second terminals adapted to receive a dc current;
bridge circuit means including four arms, three of said arms comprising resistive means and the remaining arm comprising an armature of said motor, said bridge circuit further including unbalanced voltage detecting points;
unbalanced voltage detecting means responsive to a voltage appearing at said unbalanced voltage detecting points for detecting the unbalanced voltage of said bridge circuit means;
switching means coupled between said direct current voltage source means and said bridge circuit means for conducting or interrupting a supply of said dc current received from said first and second terminals;
control means responsive to said unbalanced voltage detecting means for turning said switching means to an on-state or an off-state;
inductor means coupled between said switching means and said bridge circuit means;
and
induced electromotive force supply means coupled to said bridge circuit for supplying thereto and induced electromotive force developed in said inductor means when said switching means is brought to an off-state.

5 more elements

Dependencies are inferred from the claim text.