Patent ID: 8053999

Claim:
Power control apparatus for providing current to a lamp, comprising: a full/half bridge switching circuit including two first switching elements connected in series between high and low power supplies, each one of the two first switching elements for supplying power to the lamp when a respective first switching element is switched on; means for switching a state of each said first switching element only at a time when a substantially zero voltage is applied across said first switching element; first and second inductive elements, a node between the two first switching elements being connected to a first lamp terminal via the first and second inductive elements; and a capacitor connected in parallel with said lamp between the first lamp terminal and a second lamp terminal and arranged to provide a resonant circuit together with the first inductive element connected to the first lamp terminal to strike the lamp during a start-up mode of operation; wherein said apparatus comprises a lamp ballast and said full/half bridge switching circuit comprises a full bridge switching circuit; and wherein said full bridge switching circuit comprises two diagonal pairs of switching elements each pair comprising one of said first switching elements arranged to repeatedly switch on and off when a remaining switching element in the pair is on and to remain off when said remaining switching element is off.