| 摘要 |
PROBLEM TO BE SOLVED: To provide a high pressure discharge lighting device capable of easily turning off the high-pressure discharge lamp in case of abnormality. SOLUTION: When the voltage of the high-pressure lamp 15 becomes high due to the final stage of a service life after starting, a zener diode ZD4 is turned on to supply a base current to a transistor Q7. Turning on the transistor Q7 changes inputs to 8th and 10th pins of IC 66 to increase the frequency of an inverter circuit 61 until it matches the non-load resonant frequency of an LC resonant circuit 63, allowing the acoustic ringing of the high-pressure discharge lamp 15 to be generated. The high-pressure discharge lamp 15 is turned off by the acoustic ringing. A chopper circuit 52 and the inverter circuit 61 are protected from the generation of stress. Although the inverter circuit 61 starts generating a starting voltage again, the zener diode ZD3 and a thyristor Q6 are turned on after the lapse certain period of time, to stop the operation of the IC 66 to protect the inverter circuit 61 and the high-pressure discharge lamp 15. COPYRIGHT: (C)2004,JPO |
