Patent ID: 8159142

Claim:
A ballast, comprising: a first input terminal; a second input terminal; a switch circuit comprising a first switch and a second switch, a first terminal of the first switch being connected to the first input terminal, a second terminal of the first switch being connected to a first terminal of the second switch, and a second terminal of the second switch being connected to the second input terminal; and a plurality of lamp sets being connected to each other in parallel and having an arrangement sequence, each of the lamp sets being coupled to the first switch and the second switch and comprising: a first lamp, including a first filament; wherein the first filaments are connected in series according to the arrangement sequence to form at least one junction at the series connection point, the first one of the first filaments is coupled to the first switch, the last one of the first filaments is coupled to the second switch so that the at least one junction is connected to the switch circuit indirectly via a part of the first filaments.