Two phase motor drive circuit

Claim 2

In a circuit for driving each winding of an alternating current motor of the type having each winding center tapped, the center tap driven by a direct current source, first and second output transistors, said winding driven via the collector-emitter paths of said first and second transistors, and the bases of said first and second transistors driven by a square wave, the improvement comprising: first and second current transformers; the primaries of said first and second current transformers connected in series with the collector-emitter paths of said first and second transistors respectively and said motor winding; and the secondaries of said first and second current transformers driving the bases of said first and second transistors.

Claim 3

A circuit as claimed in claim 1 wherein said first and second current transformers are wound on the same core to provide for direct current cancellation.

Claim 4

The circuit as claimed by claim 1 and further including: third and fourth transistor switches; the collector-emitter path of said third transistor connected in series with the secondary of said first current transformer; the base of said third transistor driven by the square wave drive to the base of said second transistor; the collector-emitter path of said fourth transistor connected in series with the secondary of said second current transformer; and the base of said fourth transistor driven by the square wave drive to the base of said first transistor.

Claim 5

The circuit as claimed by claim 1 and further including a transient suppressor shunted across the winding of said motor driven by the circuit.

Claim 6

A circuit for driving a two phase alternating current motor, wherein each winding of said motor is center tapped, from a source of direct current power comprising: means coupling the source of direct current power to the center tap of each winding; a square wave generator driven by said source of direct current power; a first circuit driven by said square wave generator driving the first phase windings of said motor; a 90* phase shifter driven by said square wave generator; a second circuit identical to said first circuit driven by said phase shifter driving the second phase windings of said motor.

Claim 7

A circuit for driving a two phase alternating current motor, wherein each winding of said motor is center tapped, from a source of direct current power comprising: means coupling the source of direct current power to the center tap of each winding; a square wave generator driven by said source of direct current power; a first circuit driven by said square wave generator driving the first phase windings of said motor; a 90* phase shifter driven by said square wave generator; a second circuit identical to said first circuit driven by said phase shifter driving the second phase windings of said motor.

Claim 8

The circuit as claimed in claim 5 wherein said first and second circuits are identical and comprise: first and second transistor switches; means connecting the bases of said first and second transistors to said square wave generator; means grounding the emitters of said first and second transistors; first and second current transformers; means connecting one end of said winding in series with the primary of said first transformer and the collector of said first transistor; means connecting the other end of said winding in series with the primary of said second transformer and the collector of said second transistor; means connecting the secondary of said first current transformer to the base of said first transistor; and means connecting the secondary of said second current transformer to the base of said second transistor.

Claim 9

The circuit as claimed in claim 6 and further including: third and fourth transistor switches; means grounding the emitters of said third and fourth transistors; means coupling the secondaries of said first and second transformers in series with said third and fourth transistors respectively; means coupling the base of said third transistor with the square wave drive to the base of the second transistor; and means coupling the base of said fourth transistor with the square wave drive to the base of the first transistor.

Claim 10

The circuit as claimed in claim 7 and further including: a transformer interposed between the square wave generator and the base drive of said first and second transistors; the secondary of said transformer being center tapped and grounded; and the primary of said transformer being center tapped and receiving a low voltage via a resistor; so that if said square wave generator fails, the transformer will saturate and block further current flow in the secondary of said transformer.

Claim 11

The circuit as claimed by claim 3 and further including a transient suppressor shunted across the winding of said motor driven by the circuit.