High-intensity discharge lamp

摘要

A high-intensity discharge lamp 1 includes an arc tube 2 having a pair of main electrodes 3, 4, a starting circuit 13 having a thermally-actuated switch 19 for disconnecting the starting circuit 13, and an outer tube 14 for containing the arc tube and the starting circuit, and the lamp 1 is lighted by means of a reactance ballast 21. The thermally-actuated switch 19 includes an envelope bulb 27 that covers contacts 23, 24 of the thermally-actuated switch 19. Thereby, occurrence of sustained arc discharge in the outer tube 14 is prevented in the case of a starting failure or a break-off of the arc tube 2 at the end of the lamp's life.