Series resonant inverter and method of lamp starting

Claim 2

An efficient, high power factor series resonant inverter comprising: a source of rectified voltage coupled to a pair of output terminals, first and second power rails, each rail fed from one of said output terminals, a direct drive inverter with a series resonant circuit including first and second electronic switches, each with a main current conduction path terminating in first and second terminals and a control element including a control terminal, said main conduction paths of both said electronic switches coupled to said power rails, said direct drive inverter further including: saturable means to provide drive current to said first and second electronic switches for establishing a conduction condition for each of said first and second electronic switches, said drive current terminating on saturation of said saturable means, said saturable means including a four winding saturable inductor wound on a single core, all of said windings, wound on said single core, tightly coupled to each other, said four winding saturable inductor having a saturation period no greater than half a period corresponding to a resonant frequency of said series resonant circuit, first means connecting said first electronic switch to a first pair of windings on said single core to provide positive feedback between said main conduction path of said first electronic switch and said control element of said first electronic switch, second means connecting said second electronic switch to a second pair of windings on said single core to provide positive feedback between said main conduction path of said second electronic switch and said control element of said second electronic switch, control means responsive to variations in current flow through a conducting one of said electronic switches for inhibiting forward biasing of a non-conducting one of said electronic switches.

Claim 3

Apparatus as recited in claim 1 wherein said control means comprises: a first pair of unidirectionally conducting devices coupled to a control terminal of one of said switches, oppositely poled terminals of said first pair of unidirectionally conducting devices connected to said control terminal of said one of said switches, a second pair of unidirectionally conducting devices coupled to one of said power rails, oppositely poled terminals of said second pair of unidirectionally conducting devices connected to said one of said power rails, and a capacitor connected between said series resonant circuit and those terminals of said first and second pairs of unidirectionally conducting devices not connected to said control terminal of said one of said switches and said one of said power rails.

Claim 4

An efficient, high power factor resonant inverter comprising: a source of rectified voltage coupled to a pair of output terminals, first and second power rails, each rail fed from one of said output terminals, a direct drive inverter and a series resonant circuit, said direct drive inverter including first and second electronic switches, each with a main current conduction path terminating in first and second terminals and a control element including a control terminal, said main conduction paths of both said electronic switches coupled to said power rails, said direct drive inverter connected between said power rails and said series resonant circuit, said direct drive inverter further including: saturable means to provide drive current to said first and second electronic switches for establishing a conduction condition for each of said first and second electronic switches, said drive current terminating on saturation of said saturable means, said saturable means including a multi winding saturable inductor wound on a single core, a primary winding on said core connected in said series resonant circuit, first means connecting said first electronic switch to a first winding to provide positive feedback between current flowing in said series resonant circuit and said control element of said first electronic switch by inductive coupling between said primary and said first windings, second means connecting said second electronic switch to a second winding to provide positive feedback between current flowing in said series resonant circuit and said control element of said second electronic switch by inductive coupling between said primary and said second windings, said primary, first and second windings tightly coupled to each other, and control means responsive to variations in current flow through a conducting one of said electronic switches for inhibiting forward biasing of a non-conducting one of said electronic switches.

Claim 5

An efficient, high power factor resonant inverter comprising: a source of rectified voltage coupled to a pair of output terminals, first and second power rails, each rail fed from one of said output terminals, a direct drive inverter and a series resonant circuit, said direct drive inverter including first and second electronic switches, each with a main current conduction path terminating in first and second terminals and a control element including a control terminal, said main conduction paths of both said electronic switches coupled to said power rails, said direct drive inverter connected between said power rails and said series resonant circuit, said direct drive inverter further including: saturable means to provide drive current to said first and second electronic switches for establishing a conduction condition for each of said first and second electronic switches, said drive current terminating on saturation of said saturable means, said saturable means including a multi winding saturable inductor wound on a single core, a primary winding on said core connected in said series resonant circuit, first means connecting said first electronic switch to a first winding to provide positive feedback between current flowing in said series resonant circuit and said control element of said first electronic switch by inductive coupling between said primary and said first windings, second means connecting said second electronic switch to a second winding to provide positive feedback between current flowing in said series resonant circuit and said control element of said second electronic switch by inductive coupling between said primary and said second windings, said primary, first and second windings tightly coupled to each other, and control means responsive to variations in current flow through a conducting one of said electronic switches for inhibiting forward biasing of a non-conducting one of said electronic switches.

Claim 6

Apparatus as recited in claim 3 wherein said control means comprises: a first pair of unidirectionally conducting devices coupled to a control terminal of one of said switches, oppositely poled terminals of said first pair of unidirectionally conducting devices connected to said control terminal of said one of said switches, a second pair of unidirectionally conducting devices coupled to one of said power rails, oppositely poled terminals of said second pair of unidirectionally conducting devices connected to said one of said power rails, and a capacitor connected between said series resonant circuit and those terminals of said first and second pairs of unidirectionally conducting devices not connected to said control terminal of said one of said switches and said one of said power rails.

Claim 7

An efficient, high power factor resonant inverter comprising: a source of rectified voltage coupled to a pair of output terminals, first and second power rails, each rail fed from one of said output terminals, a direct drive inverter including first and second electronic switches, each with a main current conduction path terminating in first and second terminals and a control element including a control terminal, said first switch having a first terminal connected to a first power rail and said second switch having a second terminal connected to said second power rail, said direct drive inverter further including: saturable means to provide drive current to said first and second electronic switches for establishing a conduction condition for each of said first and second electronic switches, said drive current terminating on saturation of said saturable means, said saturable means including a multi winding saturable inductor wound on a single core, said multi winding saturable inductor including a first pair of windings tightly coupled to each other and to a second pair of windings, a first winding of said first pair connected between said control terminal and said second terminal of said first electronic switch, a second winding of said first pair connected between said second terminal of said first electronic switch and said first terminal of said second electronic switch, said first and second windings of said first pair polarized to provide positive feedback from said main current path of said first electronic switch to said control terminal of said first electronic switch, said multi winding saturable inductor including said second pair of windings tightly coupled to each other and to said first pair of windings, a first winding of said second pair connected between said control terminal and said second terminal of said second electronic switch, a second winding of said second pair connected between said second terminal of said second electronic switch and said second power rail, said first and second windings of said second pair polarized to provide positive feedback from said main current path of said second electronic switch to said control terminal of said second electronic switch, and control means responsive to variations in current flow through a conducting one of said electronic switches for inhibiting forward biasing of a non-conducting one of said electronic switches.

Claim 8

An efficient, high power factor resonant inverter comprising: a source of rectified voltage coupled to a pair of output terminals, first and second power rails, each rail fed from one of said output terminals, a direct drive inverter including first and second electronic switches, each with a main current conduction path terminating in first and second terminals and a control element including a control terminal, said first switch having a first terminal connected to a first power rail and said second switch having a second terminal connected to said second power rail, said direct drive inverter further including: saturable means to provide drive current to said first and second electronic switches for establishing a conduction condition for each of said first and second electronic switches, said drive current terminating on saturation of said saturable means, said saturable means including a multi winding saturable inductor wound on a single core, said multi winding saturable inductor including a first pair of windings tightly coupled to each other and to a second pair of windings, a first winding of said first pair connected between said control terminal and said second terminal of said first electronic switch, a second winding of said first pair connected between said second terminal of said first electronic switch and said first terminal of said second electronic switch, said first and second windings of said first pair polarized to provide positive feedback from said main current path of said first electronic switch to said control terminal of said first electronic switch, said multi winding saturable inductor including said second pair of windings tightly coupled to each other and to said first pair of windings, a first winding of said second pair connected between said control terminal and said second terminal of said second electronic switch, a second winding of said second pair connected between said second terminal of said second electronic switch and said second power rail, said first and second windings of said second pair polarized to provide positive feedback from said main current path of said second electronic switch to said control terminal of said second electronic switch, and control means responsive to variations in current flow through a conducting one of said electronic switches for inhibiting forward biasing of a non-conducting one of said electronic switches.

Claim 9

Apparatus as recited in claim 5 wherein said control means comprises: a first pair of unidirectionally conducting devices coupled to a control terminal of one of said switches, oppositely poled terminals of said first pair of unidirectionally conducting devices connected to said control terminal of said one of said switches, a second pair of unidirectionally conducting devices coupled to one of said power rails, oppositely poled terminals of said second pair of unidirectionally conducting devices connected to said one of said power rails, and a capacitor connected between said series resonant circuit and those terminals of said first and second pairs of unidirectionally conducting devices not connected to said control terminal of said one of said switches and said one of said power rails.

Claim 10

An efficient, high power factor resonant inverter comprising: a source of rectified voltage coupled to a pair of output terminals, first and second power rails, each rail fed from one of said output terminals, a first series circuit including first and second switches connected in series across said rails, a second series circuit comprising a pair of capacitors connected across said rails, a third series circuit comprising first and second circuits connected in series across said rails, each of said first and second circuits comprising a capacitor and a unidirectional conductor connected in series, a junction of said first and second circuits connected to a junction between said capacitors of the second series circuit, and a further unidirectional conductor associated with each of said first and second circuits, each further unidirectional conductor connected between an associated one of the first and second circuits and one of the power rails, a series resonant circuit including a first capacitor and a first inductor, said series resonant circuit having one terminal connected to a junction between said switches and another terminal coupled to a junction of the capacitors of the second series circuit, and a load circuit connected in parallel with at least a portion of said series resonant circuit.

Claim 11

An efficient, high power factor resonant inverter comprising: a source of rectified voltage coupled to a pair of output terminals, first and second power rails, each rail fed from one of said output terminals, a first series circuit including first and second switches connected in series across said rails, a second series circuit comprising a pair of capacitors connected across said rails, a third series circuit comprising first and second circuits connected in series across said rails, each of said first and second circuits comprising a capacitor and a unidirectional conductor connected in series, a junction of said first and second circuits connected to a junction between said capacitors of the second series circuit, and a further unidirectional conductor associated with each of said first and second circuits, each further unidirectional conductor connected between an associated one of the first and second circuits and one of the power rails, a series resonant circuit including a first capacitor and a first inductor, said series resonant circuit having one terminal connected to a junction between said switches and another terminal coupled to a junction of the capacitors of the second series circuit, and a load circuit connected in parallel with at least a portion of said series resonant circuit.

Claim 12

A protected resonant inverter comprising: (a) a source of AC power, (b) a full wave rectifier connected across said source of AC power, said full wave rectifier including controlled rectifier means for conducting in response to a drive signal, (c) a resonant inverter supplied by said full wave rectifier and a load coupled to said resonant inverter, said resonant inverter including means for generating a sense signal related to a voltage in said resonant inverter, (d) circuit means coupled to said source of AC power for generating said drive signal on application of power thereto, (e) switching means coupled to said circuit means and to said sense signal for inhibiting said drive signal when said sense signal has a distinctive characteristic, whereby when said sense signal achieves said distinctive characteristic said switching means inhibits operation of said circuit means to terminate rectification of AC power by said full wave rectifier.

Claim 13

A protected resonant inverter comprising: (a) a source of AC power, (b) a full wave rectifier connected across said source of AC power, said full wave rectifier including controlled rectifier means for conducting in response to a drive signal, (c) a resonant inverter supplied by said full wave rectifier and a load coupled to said resonant inverter, said resonant inverter including means for generating a sense signal related to a voltage in said resonant inverter, (d) circuit means coupled to said source of AC power for generating said drive signal on application of power thereto, (e) switching means coupled to said circuit means and to said sense signal for inhibiting said drive signal when said sense signal has a distinctive characteristic, whereby when said sense signal achieves said distinctive characteristic said switching means inhibits operation of said circuit means to terminate rectification of AC power by said full wave rectifier.

Claim 14

A protected resonant inverter as recited in claim 8 wherein said resonant inverter includes a resonant circuit including a first winding, said first winding inductively coupled to a second winding, said means for generating a sense signal includes said second winding and a conductor connecting said second winding to said switching means.

Claim 15

A protected resonant inverter as recited in claim 9 wherein said circuit means includes a transformer including a primary and a secondary, said secondary coupled to said controlled rectifier means, and wherein said switching means includes means for short circuiting said primary of said transformer.

Claim 16

A protected resonant inverter as recited in claim 9 wherein said controlled rectifier means comprises two controlled rectifiers, said circuit means includes a transformer including a primary and two secondary windings, each of said secondary windings coupled to a different one of said two controlled rectifiers, and wherein said switching means includes means for short circuiting said primary of said transformer.

Claim 17

A protected resonant inverter as recited in claim 9 wherein said means for generating a sense signal further includes an RC circuit for driving a gate of a controlled rectifier, said switching means comprising said controlled rectifier.

Claim 18

A protected resonant inverter as recited in claim 12 wherein said circuit means includes a transformer with a primary and a secondary winding, said controlled rectifier coupled to said primary to short circuit said primary when said controlled rectifier is in conduction, and said secondary winding is coupled to said controlled rectifier means.

Claim 23

A method as recited in claim 15 wherein said generating step comprises: (a1) providing an R-C charging circuit energized from said inverter, and (a2) providing an FET switch enabled from said R-C charging circuit in a conduction path from a terminal of said inverter to a filament circuit supply so that current flows through said FET switch to said filament circuit supply only after a delay from initiation of inverter operation determined by said R-C circuit and a characteristic of said FET switch.

Claim 24

A method as recited in claim 15 comprising the further step of: (c) terminating current flow to lamp filaments.