| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a dimming system which can assure constant illuminance by preventing flicker or brightness fluctuation of modulated light regardless of fluctuation in commercial frequency and difference in commercial frequency band. SOLUTION: This dimming system is dims an illumination load 8 driven by a power supply 9 by phase control where a phase control element 7 is used. In this case, the dimming system is provided with a zero cross circuit 1 for generating zero cross signals being synchronized with a commercial frequency, a charge/discharge circuit 2 charged at a constant rate and periodically charge/ discharged in synchronization with the zero cross signals, a peak hold circuit 3 for holding a peak value of output signals of the charge/discharge circuit 2, a reference voltage generation circuit 4 for generating a reference voltage to provide a prescribed ratio of the peak value of the output signals of the peak hold circuit 3 thereto, a comparison circuit 5 for comparing the reference voltage with the output voltage of the charge/discharge circuit 2, and a trigger signal control circuit 6 for generating trigger signals from an output of the comparison circuit 5 to control the phase control element 7 in response to the trigger signals.</p> |
