| 摘要 |
<p>PURPOSE:To keep the tube wall temperature constant even under a high temperature environment at idling by detecting the tube wall temperature of a fluorescent tube and controlling the pre-heat voltage of a filament accordingly. CONSTITUTION:A photosensor 2 sensing the light quantity is provided in the vicinity of a fluorescent tube 1 and a thermister 3 sensing the tube wall temperature is provided in the vicinity of a filament 1a. The output of the sensor 2 is converted into a DC level by an amplifier 4, led to the input terminal 5a of a control section 5 and the output of the thermister 3 is led to an input terminal 5b. A control section 5 is switched by using a control signal S1 to switch lighting/pre-heat, and outputs a control voltage V1 controlling the light quantity constant in response to the output of the sensor 2 at lighting and a control voltage V2 controlling the tube wall temperature constant at pre- heating. The control voltages V1, V2 and the control signal S1 are inputted to a balast 6, from which the voltage V1 is converted into a high frequency AC voltage to prevent flicker at lighting to be supplied to a filament 1a and the voltage V2 is converted into an AC voltage at pre-heating to be supplied to the filament 1a.</p> |
