A series connection of a reverse direction diode 10 and a main capacitor 2 is connected across both terminals of a DC power source 1. Another series connection of a strobe tube 3 and forward semiconductor switching device 9 is connected across both terminals of the DC power source 1. A forward diode 11 is coupled between the series connections. Charging the main capacitor 2 is accomplished by a circuit form the DC power source 1, the main capacitor 2, the forward direciton diode 11 and the semiconductor switching device 9: whereas, discharging the strobe tube 3 is made through the strobe tube 3, the semiconductor device 9 and the reverse direction diode 10. The semiconductor switching device 9 is controlled both by a charge control circuit 14 and a light adjusting circuit 8.