| 摘要 |
When a control unit is operated by a lighting control signal, when a reference voltage source unit outputs the reference voltage, voltage inputted into an error amplifier from a time constant circuit increases gradually with passage of time so as to reach the reference voltage. The error amplifier compares the voltage, which gradually increases with a power to be impressed to a lamp. An inverter circuit controls power to be supplied to the lamp according to the error signal. Thereby, the lamp power is controlled at time immediately after the lamp lighting signal is inputted. In addition, by providing a thermo-sensitive element for detecting circumference environmental temperature, it is possible to reduce influence to the light intensity due to the circumference environmental temperature. Further, the time constant circuit and the thermo-sensitive element may be provided in the detecting circuit.
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