| 摘要 |
PROBLEM TO BE SOLVED: To provide a high pressure discharge lamp having high safety by constituting a parallel circuit of a series circuit and a heating resistor, and connecting this parallel circuit and a series circuit equipped with second switch in parallel with a light-emitting tube. SOLUTION: In a high pressure discharge lamp, a heating resister 4 is connected to a series circuit composed of a starting apparatus composed of a glow starter 3 and a thermally-actuated switch 2 in parallel. To this parallel circuit, a current limiting resistor 5 and second actuated switch 6 are connected in series. This series circuit is connected to a light-emitting tube 1 in series. When a power source voltage is applied via a ballast 7, the glow starter 3 starts a switching action so that a pulse voltage is generated between the terminals of the ballast 7. When the discharge of the light-emitting tube 1 starts, a light-emitting tube voltage is reduced. Therefore, the operation of the glow starter 3 stops, and a current flowing into the glow starter 3 stops. At a stable lighting time, the thermally-actuated switch 6 is opened by radiation heat from the light-emitting tube 1 so that current supply to the heating resistor 4 stops. |
