| 摘要 |
PURPOSE:To secure safety operation in the final period of the lifetime of a discharge lamp by uncoupling a coupling means in conformity to the control signal of an inverter control means in synchronization with sensing of the final lifetime period, and thereby stooping the inverter circuit oscillating. CONSTITUTION:In the final period of the lifetime of a discharge lamp 1, a light emitting diode 30 is extinguished while a photo-transistor 31 is put off, and VDD is fed to the base of a transistor 40 which is thus turned on. A voltage VCC appears at the connection point of the resistance 65 with the transistor 40 to cause turning-on with the Zenor diode 66 break potential Vth exceeded, and another transistor 50 is turned on. This causes stopping of a resonator circuit which consists of a tertiary winding 53. The impression voltage of the Zenor diode 66 becomes below Vth, and the Zenor diode 66 is turned off. An inverter means B is stopped after a certain time T. Therefore, fine discharge of the discharge lamp 1 goes in stall, and control is made thereafter to accomplish low output to the inverter means B by an inverter control means D, and thereby a standby condition free from discharging can be achieved certainly. |
