| 摘要 |
A first circuit arrangement including a zener diode coupled to the base of a transistor for keeping the transistor turned ON in response to the magnitude of voltage developed across a storage capacitor. The capacitor provides power to a photographic flash tube connected in series with a silicon controlled rectifier (SCR). After the flash tube is ignited, energy is drained from the charged capacitor until its voltage level reaches a predetermined magnitude at which time the zener diode becomes non-conducting, turning OFF the transistor, which causes a commutation of the SCR, terminating the flash of the flash tube. The capacitor is then recharged for preparation of the next flash operation. A second circuit arrangement utilizes a programmable unijunction transistor in which the voltage magnitude of the flash storage capacitor is followed by the gate of the unijunction transistor until the gate voltage reaches a corresponding voltage level preset at the anode of the unijunction transistor. The preset voltage level is a stored voltage which is proportional to the capacitor voltage immediately prior to flash actuation.
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