Flux cancelling transformer line circuit
AssigneeModern Systems Research, Inc.
InventorSamuel F. Wood
Life of this patent
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Abstract
A flux cancelling transformer line circuit includes an AC current source that blocks AC current and passes DC current. The current source is connected between the primary and secondary windings of a transformer. Direct current flowing through the primary winding generates a magnetic flux. The current source passes the direct current to the secondary winding self-cancelling the DC flux created in the primary winding. Since DC current is coupled from the primary windings directly into the secondary windings, the same DC current flows in both windings. Thus, DC flux is precisely cancelled in the transformer. The current source includes a transistor, which is biased in a low impedance linear region by the DC signal and a capacitor that operates the transistor in a high AC impedance condition.
Claims27
A transformer line circuit comprising:
- a transformer having a primary winding and a secondary winding, the primary winding receiving both a direct current from a single power supply and an alternating current signal and the secondary winding transferring the alternating current signal to an external secondary circuit;
- and
- a flux cancelling circuit connected to the transformer that forms only one single current path in the transformer that passes current from the primary winding directly through the secondary winding and then through the flux cancelling circuit back to the primary winding, the flux cancelling circuit allowing the same internal direct current in that same single current path to pass through the primary and secondary winding in a manner such that a magnetic flux created in the primary winding from the internal direct current in that same single current path is cancelled by an equal amount of flux produced by the same internal direct current flowing through that same single current path in the secondary winding without using a compensation current generated from any external compensation circuit,
- the same flux cancelling circuit filtering the alternating current while allowing the magnetic flux generated by the alternating current to pass through the transformer from the primary winding to the secondary winding through that same single current path.
A transformer line circuit comprising:
- a primary winding for receiving an AC signal and a DC signal;
- a secondary winding;
- and
- a flux cancelling circuit coupled in series between the primary winding and the secondary winding, the flux cancelling circuit using only the AC signal and the DC signal to establish a single transformer current path that passes current from the primary winding, through the secondary winding and through the flux cancelling circuit and then back to the primary winding, the flux cancelling circuit allowing a common internal direct current in the single transformer current path to pass through the primary and secondary winding in a manner such that a magnetic flux created in the primary winding from the internal direct current in the single transformer current path is cancelled by an equal amount of flux produced by the same internal direct current flowing in the same transformer current path passing through the secondary winding without using a compensation current generated from any external compensation circuit,
- the same flux cancelling circuit blocking the alternating current while allowing the magnetic flux generated by the alternating current to pass through the transformer from the primary winding to the secondary winding through the same transformer current path.
A method for cancelling magnetic flux effects in a telephone line transformer having a primary winding and a secondary winding, the method comprising:
- generating a signal having an AC portion and a DC portion, the AC portion comprising a telephone signal and the DC portion used for controlling telephone circuitry;
- coupling the signal to the primary winding;
- and
- coupling the primary winding directly to the secondary winding to establish only one single current loop in the entire telephone line transformer that passes current through the primary winding, the secondary winding and then back to the primary winding;
- providing a low impedance path through that one single current loop allowing an internal direct current to pass through the primary and secondary winding in a manner such that a magnetic flux created in the primary winding from the internal direct current in that same one single current loop is cancelled by an equal amount of flux produced by the same internal direct current flowing in that same single current loop in the secondary winding without using a compensation current generated from any external compensation circuit and without using any other AC or DC portion of any other signal,
- the low impedance path blocking the alternating current while allowing the magnetic flux generated by the alternating current to pass through the transformer from the primary winding to the secondary winding.
Dependencies are inferred from the claim text.