Patent ID: 8115404

Claim:
A high pressure discharge lamp lighting device, comprising: a DC/DC converter for converting a power source voltage of a DC power source into a desired DC voltage and stably lighting a high pressure discharge lamp; a DC/AC inverter for inverting the DC voltage into an AC voltage; a starting pulse generating circuit for generating a high voltage required for the start-up of the high pressure discharge lamp; a lighting state decision unit for deciding a lighted/unlighted state of the high pressure discharge lamp by detecting a lamp voltage and then comparing a detected value of the lamp voltage with a predetermined decision threshold; and an operating state switching control unit for switching the operating state of at least one of the DC/DC converter, the DC/AC inverter, and the starting pulse generating circuit to another operating state, depending on a predetermined operation phase out of the start-up, stable lighting and power interrupt phases of the high pressure discharge lamp, and controlling the operating state, wherein the decision threshold changes for each operation phase.