Patent ID: 7084585

Claim:
A discharge lamp lighting apparatus comprising: a high-voltage generating coil connected in a discharge lamp for applying a high voltage to said discharge lamp to turn on said lamp; an inverter for inverting a dc voltage into an ac voltage in order to supply a lamp current to said discharge lamp on an alternating basis through said high voltage generating coil; a lamp voltage detecting circuit for detecting a voltage across said discharge lamp as a lamp voltage on the basis of a voltage across a current path on which said high-voltage generating coil and said inverter lie, said lamp current passing in said current path to flow in said discharge lamp; and a lamp power control circuit for controlling an ac power supplied to said discharge lamp from said inverter on the basis of said lamp voltage detected by said lamp voltage detecting circuit; wherein said lamp voltage detecting circuit detects said lamp voltage by subtracting a voltage in proportion to a sum of voltage drops across devices other than said discharge lamp lying on a current path over which said lamp current flows from a voltage in proportion to said dc voltage.