Craig and Antonelli
Transformer coupling circuit providing for cancellation of D.C. fluxes
 In a coupling circuit for A.C. coupling a switching network to a trunk circuit through a coupling transformer, a magnetic flux cancel circuit is provided for canceling non-varying magnetic fluxes produced by direct current components of a switch-hold current and a control signal which are applied, respectively, to the primary and the secondary windings of the transformer at its core to each other. The flux cancel circuit comprises a rectifier circuit such as a diode bridge circuit. The rectifier circuit is connected at least between the trunk circuit and the secondary winding of the transformer coupled therewith such that the direction of an output current of the rectifier is predetermined with respect to that of a direct current supplied to the primary winding to cancel the non-varying magnetic fluxes by the direct currents in the transformer. 
Hitachi, Ltd.
H
H04Q
inventional
Hidetaka
Yamashita