US 8,274,234 B1 · Dimming ballast with parallel lamp operation

Abstract

An electronic ballast is provided for powering one or more discharge lamps independently connected in parallel. An inverter having a pair of switching elements converts a DC supply signal into AC power. A transformer has a primary winding coupled to an output terminal of the inverter. A load circuit includes independently operable discharge lamp circuits coupled in parallel with each other and across a secondary winding of the transformer. An inductance control circuit includes an inductive element coupled in series with the primary winding of the transformer and a bi-directional switch coupled in parallel across the inductive element. A switch state of the bi-directional switch is controllably adjustable between first and second switch states and in accordance with a desired duty ratio. A magnitude of a voltage across the secondary winding of the transformer and thereby across each lamp circuit is dependent on the switch state of the bi-directional switch.

Claims20

Dependent claims

An electronic ballast comprising:

an inverter circuit comprising a pair of switching elements and configured to convert a DC supply signal into an AC signal;
a first transformer having a primary winding coupled to an output terminal between the pair of switching elements of the inverter circuit and a secondary winding;
a load circuit comprising one or more discharge lamps each having lamp filaments, the load circuit coupled in parallel with the secondary winding of the first transformer;
a second transformer having a primary winding coupled in series with the primary winding of the first transformer, and further having one or more secondary windings coupled across the filaments of the one or more discharge lamps in the load circuit;
and
a switching circuit coupled across the primary winding of the second transformer, wherein a magnitude of a voltage across said secondary winding of the first transformer is dependent on a switch state of the switching circuit.

3 more elements

An electronic ballast comprising:

an inverter circuit comprising a pair of switching elements and configured to convert a DC supply signal into an AC signal;
a transformer having a primary winding coupled to an output terminal between the pair of switching elements of the inverter circuit;
a load circuit comprising one or more discharge lamps, the load circuit coupled in parallel with a secondary winding of the transformer;
and
an inductance control circuit comprising an inductive element coupled in series with the primary winding of the transformer and a bi-directional switch coupled in parallel across the inductive element;
and
wherein a switch state of the bi-directional switch is controllably adjustable in accordance with a desired duty ratio, a magnitude of a voltage across said secondary winding of the transformer being dependent on a switch state of the bi-directional switch.

4 more elements

An electronic ballast comprising:

an inverter circuit comprising a pair of switching elements and configured to convert a DC supply signal into an AC signal;
a transformer having a primary winding coupled to an output terminal between the pair of switching elements of the inverter circuit and a secondary winding;
a load circuit comprising one or more independently operable discharge lamp circuits coupled in parallel with each other and across the secondary winding of the transformer, each discharge lamp circuit further comprising a discharge lamp and a capacitor coupled in series;
an inductance control circuit comprising an inductive element coupled in series with the primary winding of the transformer and a bi-directional switch coupled in parallel across the inductive element;
and
wherein a switch state of the bi-directional switch is controllably adjustable in accordance with a desired duty ratio, a magnitude of a voltage across said secondary winding of the transformer being dependent on a switch state of the bi-directional switch, wherein a magnitude of a voltage across each lamp circuit is further dependent on a switch state of the bi-directional switch.

3 more elements

Dependencies are inferred from the claim text.

Dimming ballast with parallel lamp operation

Life of this patent

Dimming ballast with parallel lamp operation

Life of this patent

Abstract

Claims20