Stepped sinusoidal-like waveform generating inverter circuit

Claim 2

A stepped alternating voltage generating circuit comprising: a transformer having a center tapped primary winding and at least one secondary winding: a source of D.C. voltage having a pair of D.C. output terminals, said D.C. output terminals being connected between a center tap point on said primary winding and a reference point; first and second switch means respectively connected between the ends of said primary winding and said reference point; control means for alternately rendering said switch means conductive during spaced intervals to effect current flow sequentially in opposite directions through different halves of said primary winding to generate pulses alternating in polarity in said secondary winding spaced by intervals where the output is substantially zero; and means for ensuring the sudden and continued disappearance in the output across said secondary winding during said spaced intervals including third switch means connectable across a winding of said transformer, and control means for rendering the latter switch means conductive during said spaced intervals wherein said third switch means is a current control device having a pair of load terminals connected in series with the center top point of said primary winding, and there is associated with said third switch means a pair of rectifier means connected respectively in the same sense between the load terminal of said current control device remote from said primary winding and the opposite ends of said primary winding, to form respective paths shunting the respective halves of the primary winding to bypass the current flow therethrough.

Claim 3

A stepped alternating voltage generating circuit comprising: a major and a minor inverter circuit, each inverter circuit comprising a transformer having a primary winding and at least one secondary winding, a pair of D.C. voltage input terminals connected between a center tap point on said primary winding and a reference point, first and second switch means respectively connected between the ends of said primary windinG and said reference point, first control means for alternately rendering said first and second switch means conductive during spaced intervals to effect current flow sequentially in opposite directions through different halves of said primary winding to generate pulses alternating in polarity in said secondary winding spaced by intervals where the output is substantially zero, and means for ensuring the sudden and continued disappearance in the output across said secondary winding during said spaced intervals comprising third switch means connectable across a winding of said transformer and second control means for rendering the latter switch means conductive during said spaced intervals; the control means of said major and minor bridge circuits rendering the associated first, second and third switch means conductive in different but complementary conduction patterns so the summation of the outputs of the secondary windings of the associated transformers produces a stepped, sinusoidal-like waveform; and means connecting the secondary windings of the transformers of said major and minor bridge circuits in series voltage additive relation.

Claim 4

A stepped alternating voltage generating circuit comprising: a major and a minor inverter circuit, each inverter circuit comprising a transformer having a primary winding and at least one secondary winding, a pair of D.C. voltage input terminals connected between a center tap point on said primary winding and a reference point, first and second switch means respectively connected between the ends of said primary windinG and said reference point, first control means for alternately rendering said first and second switch means conductive during spaced intervals to effect current flow sequentially in opposite directions through different halves of said primary winding to generate pulses alternating in polarity in said secondary winding spaced by intervals where the output is substantially zero, and means for ensuring the sudden and continued disappearance in the output across said secondary winding during said spaced intervals comprising third switch means connectable across a winding of said transformer and second control means for rendering the latter switch means conductive during said spaced intervals; the control means of said major and minor bridge circuits rendering the associated first, second and third switch means conductive in different but complementary conduction patterns so the summation of the outputs of the secondary windings of the associated transformers produces a stepped, sinusoidal-like waveform; and means connecting the secondary windings of the transformers of said major and minor bridge circuits in series voltage additive relation.

Claim 5

The circuit of claim 2 wherein said third switch means of each inverter circuit is a current control device having a pair of load terminals connected in series with the center tap point of said primary winding and a control terminal which effects conduction of the switch means when a drive signal of a given polarity is fed thereto by said second control means, and there is associated with each third switch means a pair of rectifier devices respectively coupled in the same sense between the load terminal of said current control device remote from said primary winding and the opposite ends of said primary winding, to form respective paths shunting the respective halves of the primary winding to bypass the current flowing therethrough.

Claim 6

The circuit of claim 2 where the conduction pattern of the first, second and third switch means of said major inverter circuit is that said first and second switch means are identically alternately rendered conductive during successive half cycles, each such switch means having one conducting interval occupying a majority of and centered in the half cycle involved, leaving relatively narrow non-conducting intervals at the beginning and end of the half cycle, and the third switch means is conductive during the intervals when said first and second switch means are not conductive; the conduction pattern of the first, second and third switch means of said minor inverter circuit is that said first and second switch means are identically alternately rendered conductive during successive half cycles, each such switch means having during each half cycle when the same is conductive a half cycle centered conducting interval and conducting intervals corresponding to said narrow non-conducting intervals of the corresponding switch means of the major inverter circuit.

Claim 7

The circuit of claim 3 wherein the conduction pattern of the first, second and third switch means of said major inverter circuit is that said first and second switch means are identically alternately rendered conductive during successive half cycles, each such switch means having only one conducting interval occupying a majority of and centered in the half cycle involved, leaving relatively narrow non-conducting intervals at the beginning and end of the half cycle, and the third switch means is conductive during the intervals when said first and second switch means are not conductive; the conduction pattern of the first, second and third switch means of said minor inverter circuit is that said first and second switch means are identically alternately rendered conductive during successive half cycles, each such switch means having during each half cycle when the same is conductive only a half cycle centered conducting interval and conducting intervals corresponding to said narrow non-conducting intervals of the corresponding switch means of the major Inverter circuit; the sum of the non-conducting intervals of the first and second switch means of the major inverter circuit over each cycle thereof being substantially the same as the sum of the non-conducting intervals of the first and second switch means of the minor inverter circuit; and said second control means of the said major and minor inverter circuits being a common inverter drive circuit comprising a transformer having a center-tapped primary winding and at least one secondary winding, a source of D.C. voltage having a pair of D.C. output terminals, said D.C. output terminals being connected between a center tap point on said primary winding and a reference point, first and second switch means respectively connected between the ends of said primary winding and said reference point, the latter secondary winding having a center tap point coupled to said reference point of said major and minor inverter circuits and the opposite ends thereof being respectively connected to said control terminals of said third switch means of said major and minor inverter circuits, major inverter circuit turn-off drive means and minor inverter circuit turn-off drive means for respectively rendering said first and second switch means of the common drive inverter circuit conductive over intervals corresponding to the desired conducting intervals of said third switch means of said major and minor inverter circuits.

Claim 8

An inverter circuit for cyclically driving two separate current control devices conductive in a conduction sequence wherein one of the current control devices is to be rendered conductive at a different time and more frequently than the other of same over a given cycle, each of said current control devices having load terminals and a control terminal which effects the conduction through the load terminals when voltage of the same given polarity is applied thereto, said inverter circuit comprising: a transformer having a center tapped primary winding and at least one center tapped secondary winding, a pair of D.C. input terminals connected between the center tap point on said primary winding and a common reference point, first and second switch means respectively connected between the ends of said primary winding and said reference point, means connecting the opposite ends of said center tapped secondary winding respectively to the control terminals of said pair of current control devices, and first and second control means for respectively controlling the conduction of said first and second switch means in accordance with the desired conduction patterns of said first and second current control devices, said first and second control means effecting cyclic conduction patterns of said first and second switch means wherein a summation of the conducting intervals of each of said first and second switch over a given cycle of operation is identical to provide balanced operation of the transformer.

Claim 9

An inverter circuit for cyclically driving two separate current control devices conductive in a conduction sequence wherein one of the current control devices is to be rendered conductive at a different time and more frequently than the other of same over a given cycle, each of said current control devices having load terminals and a control terminal which effects the conduction through the load terminals when voltage of the same given polarity is applied thereto, said inverter circuit comprising: a transformer having a center tapped primary winding and at least one center tapped secondary winding, a pair of D.C. input terminals connected between the center tap point on said primary winding and a common reference point, first and second switch means respectively connected between the ends of said primary winding and said reference point, means connecting the opposite ends of said center tapped secondary winding respectively to the control terminals of said pair of current control devices, and first and second control means for respectively controlling the conduction of said first and second switch means in accordance with the desired conduction patterns of said first and second current control devices, said first and second control means effecting cyclic conduction patterns of said first and second switch means wherein a summation of the conducting intervals of each of said first and second switch over a given cycle of operation is identical to provide balanced operation of the transformer.

Claim 10

The inverter circuit of claim 6 wherein said first and second current control devices and said first and second switch means are to be rendered conductive during spaced conducting intervals requiring cesession of current flow in said center tapped primary winding of the inverter circuit over prolonged intervals of time, and there is provided a second center tapped secondary winding on said transformer whose center tap point is connected to said common reference point and whose opposite ends thereof are coupled to a pair of rectifier means connected in the same sense to a common point, third switch means connected between said common point and said common reference point, and control means for said third switch means for rendering the same conductive during those intervals when current flow is to cease in said center tapped primary winding, conduction of said third switch means and one of said rectifier means establishing a low impedance short-circuiting path across one of the halves of said center tapped secondary winding.

Claim 11

An inverter circuit comprising: a tRansformer having a center tapped primary winding and at least one secondary winding, a pair of D.C. input terminals connected between the center tapped primary winding and a reference point, first and second means respectively connected between the ends of said primary winding and said reference point, control means for rendering said first and second switch means conductive respectively over spaced intervals of time wherein only one or the other of said switch means is conductive over any given interval and that interval is spaced from an interval during which the other switch means is to be rendered conductive, the conduction of said first and second switch means respectively resulting in current flow in opposite direction in different halves of the center tapped primary winding, means for terminating current flow through said primary winding between the spaced intervals during which the first and second switch means are conductive comprising a center tapped secondary winding of said transformer having a center tap point connected to said reference point and a pair of rectifier means connected in the same sense to a common point, and third switch means connected between said common point and said reference point, and control means for rendering said third switch means conductive when termination in the current flow through both halves of said primary winding is desired, to establish a short circuit path through said third switch means and one of said rectifier means across one of the halves of said center tapped secondary winding.

Claim 12

An inverter circuit comprising: a tRansformer having a center tapped primary winding and at least one secondary winding, a pair of D.C. input terminals connected between the center tapped primary winding and a reference point, first and second means respectively connected between the ends of said primary winding and said reference point, control means for rendering said first and second switch means conductive respectively over spaced intervals of time wherein only one or the other of said switch means is conductive over any given interval and that interval is spaced from an interval during which the other switch means is to be rendered conductive, the conduction of said first and second switch means respectively resulting in current flow in opposite direction in different halves of the center tapped primary winding, means for terminating current flow through said primary winding between the spaced intervals during which the first and second switch means are conductive comprising a center tapped secondary winding of said transformer having a center tap point connected to said reference point and a pair of rectifier means connected in the same sense to a common point, and third switch means connected between said common point and said reference point, and control means for rendering said third switch means conductive when termination in the current flow through both halves of said primary winding is desired, to establish a short circuit path through said third switch means and one of said rectifier means across one of the halves of said center tapped secondary winding.

Claim 13

A stepped alternating voltage generating circuit comprising: a transformer having a center-tapped primary winding and at least one secondary winding, a pair of D.C. input terminals connected between a center tap point on said primary winding and a reference point, first and second switch means respectively connected between the ends of said primary winding and said reference point, control means for alternately rendering said first and second switch means conductive to effect current flow sequentially in opposite directions through different halves of said primary winding, to generate pulses alternating in polarity in said secondary winding and spaced by intervals where the output is substantially zero, and turn-off means for ensuring the sudden and continued disappearance in the output across said secondary winding during said spaced intervals including third switch means connectable across at least the half of said primary winding carrying current at any instant, control means for rendering the latter switch means conductive during said spaced intervals, the conduction of said latter switch means resulting in a voltage drop thereacross which when applied across the primary winding will effect an imperfect zero output across said secondary winding, and zero output aiding means including means for applying a voltage in series with said switch means and said primary winding which substantially cancels the voltage otherwise applied across said primary winding halves during the period a zero output is desired.

Claim 14

A stepped alternating voltage generating circuit comprising: a transformer having a center-tapped primary winding and at least one secondary winding, a pair of D.C. input terminals connected between a center tap point on said primary winding and a reference point, first and second switch means respectively connected between the ends of said primary winding and said reference point, control means for alternately rendering said first and second switch means conductive to effect current flow sequentially in opposite directions through different halves of said primary winding, to generate pulses alternating in polarity in said secondary winding and spaced by intervals where the output is substantially zero, and turn-off means for ensuring the sudden and continued disappearance in the output across said secondary winding during said spaced intervals including third switch means connectable across at least the half of said primary winding carrying current at any instant, control means for rendering the latter switch means conductive during said spaced intervals, the conduction of said latter switch means resulting in a voltage drop thereacross which when applied across the primary winding will effect an imperfect zero output across said secondary winding, and zero output aiding means including means for applying a voltage in series with said switch means and said primary winding which substantially cancels the voltage otherwise applied across said primary winding halves during the period a zero output is desired.

Claim 15

The circuit of claim 9 wherein said third switch means is a current control device having a pair of load terminals connected in series with a center tap point of said primary winding and there is associated with said third switch means a pair of rectifier means respectively coupled in the same sense to the load terminal of said current control device remote from said primary winding; and said zero output aiding means comprises second transformer means having a primary winding and a pair of secondary windings respectively connected in an opposite sense between the opposite ends of said center tapped primary winding of the first mentioned transformer and said pair of rectifier means, and a source of alternating voltage connected to said primary winding of said second transformer means to produce in said respective secondary windings thereat voltages of a polarity which respectively cancel out the voltage drop across the associated recTifier means and said third switch means during the half cycle when the associated rectifier means is operative to shunt the associated primary winding half.

Claim 16

A stepped alternating voltage generating circuit comprising: a transformer having a center-tapped primary winding and at least one secondary winding, a pair of D.C. input terminals connected between a center tap point on said primary winding and a reference point, first and second switch means respectively connected between the ends of said primary winding and said reference point, control means for alternately rendering said first and second switch means conductive to effect current flow sequentially in opposite directions through different halves of said primary winding to generate pulses alternating in polarity in said secondary winding and spaced by intervals where the output is substantially zero, and turn-off means for ensuring the sudden and continued disappearance in the output across said secondary winding during said spaced intervals including third switch means having a pair of load terminals connected in series with the center tap point of said primary winding, and a pair of rectifier means respectively coupled in the same sense to the load terminal of said third switch means remote from said primary winding, and means comprising second transformer means having a primary winding and a pair of secondary windings respectively connected in an opposite sense between the opposite ends of said center tapped primary winding of the first mentioned transformer and said pair of rectifier means, and a source of alternating voltage connected to said primary winding of said second transformer.

Claim 17

A stepped alternating voltage generating circuit comprising: a transformer having a center-tapped primary winding and at least one secondary winding, a pair of D.C. input terminals connected between a center tap point on said primary winding and a reference point, first and second switch means respectively connected between the ends of said primary winding and said reference point, control means for alternately rendering said first and second switch means conductive to effect current flow sequentially in opposite directions through different halves of said primary winding to generate pulses alternating in polarity in said secondary winding and spaced by intervals where the output is substantially zero, and turn-off means for ensuring the sudden and continued disappearance in the output across said secondary winding during said spaced intervals including third switch means having a pair of load terminals connected in series with the center tap point of said primary winding, and a pair of rectifier means respectively coupled in the same sense to the load terminal of said third switch means remote from said primary winding, and means comprising second transformer means having a primary winding and a pair of secondary windings respectively connected in an opposite sense between the opposite ends of said center tapped primary winding of the first mentioned transformer and said pair of rectifier means, and a source of alternating voltage connected to said primary winding of said second transformer.