US 4,393,335 AGranted

Electronic flash device

AssigneeWest Electric Company, Ltd.

InventorsShinji Hirata, Hirohiko Ina

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Abstract

In an electronic flash device of the type in which depending upon the exposure conditions an electronic flash lamp converts into light the energy stored on a main flash capacitor or the energies stored not only on the main flash capacitor but also on an auxiliary flash capacitor, a switching element which is turned on or off so as to permit or interrupt the discharge of the auxiliary flash capacitor is controlled by a simplified control circuit comprising a switching element control circuit which delivers a low voltage supplied from a low-voltage power source to the switching element as a turn-on signal and a detection circuit which controls the switching element control circuit in response to the exposure conditions such as a distance to a subject or a selected aperture. Therefore, an inversion circuit which is used in the prior art electronic flash devices can be eliminated.

Claims3

Dependent claims

An electronic flash device comprising

(a) a DC-DC converter which includes an npn type oscillation transistor and an oscillation transformer and which steps up a voltage across a low-voltage power source,
(b) a main flash capacitor charged by said DC-DC converter,
(c) a flash lamp which is connected across said main flash capacitor and which establishes a discharge-flash loop with said main flash capacitor,
(d) a trigger circuit which includes a trigger capacitor connected in parallel with said main flash capacitor and which excites said flash lamp,
(e) a diode whose anode is connected to the high-voltage-side terminal of said main flash capacitor,
(f) an auxiliary flash capacitor which is adapted to be charged through said diode by said DC-DC converter,
(g) a silicon controlled rectifier means which is connected across said diode in the opposite direction and which establishes a discharge loop of said auxiliary flash capacitor,
(h) a control circuit which is connected across said low-voltage power source and which controls the application of the gate signal to said silicon controlled rectifier means, said control circuit comprising:
(1) a drive circuit for delivering the gate signal to said silicon controlled rectifier means,
(2) a switching element which is connected across said low-voltage power source through a resistor and which is adapted to short-circuit the gate of said silicon controlled rectifier means, and
(3) a switching element control circuit for controlling said switching element, and
(i) a detection circuit which is adapted to control said control circuit in response to the exposure conditions.

9 more elements

Dependencies are inferred from the claim text.