JPS5550229A - Power source circuit of dimming circuit in electronic flash device - Google Patents

Abstract

PURPOSE:To make the constitution of the power source circuit simple by connecting impedances to the discharge line of the auxiliary capacitor for the discharge tube and supplying drive voltage to the dimming circuit. CONSTITUTION:When a trigger switch 31 is closed, an SCR 35 is conducted by the trigger voltage from a capacitor 9, causing a discharge tube 17 to be triggered by discharging of a trigger capacitor 39. On the other hand, an auxiliary capacitor 47 discharges through a diode 43, conducting SCR 35, impedance circuits 51, 53, 55, 57 and resistance 50. The discharge tube 17 is then let to flash and emit light even during continuous triggering by the sum of the discharge voltages of the capacitor 47 and main capacitor 13. Further, when current flows to the circuits 51, 53, 55, 57 owing to discharging of the capacitor 47, a Zener voltage is generated across the Zener diode 57 and is then applied to a dimming circuit 49. Hence, the auxiliary capacitor is used also as the capacitor for light souce of the dimming circuit without providing any intrinsic capacitor, thus the constitution of the power source of the dimming circuit becomes simple.