Patent ID: 7541752

Claim:
An illuminating device comprising: a plurality of light-emitting element groups each including a plurality of series-connected light-emitting elements, the plurality of light-emitting element groups connected in parallel to each other; a load which is connected in series with only one of the light-emitting element groups, and forms a reference element group together with the one light-emitting element group; and a driving circuit which includes a monitor unit which monitors an electrical characteristic value of the reference element group, and supplies an electric current set on the basis of the electrical characteristic value obtained by the monitor unit to the reference element group and the other light-emitting element groups, wherein power consumption of the reference element group is larger than power consumption of each of the other light-emitting element groups, and wherein the driving circuit comprises a constant-current controller which supplies a constant electric current set on the basis of the electrical characteristic value to the reference element group and the other light-emitting element groups.