Electronic flash apparatus

Claim 1

An electronic flash apparatus using a flash tube, comprising: a flash tube having a triggering electrode; a direct current source, a main capacitor connected to the direct-current source and charged thereby; a coil; a first series circuit connected in parallel with said main capacitor through said coil and comprising the flash tube and a normally nonconducting main switching element; a control switch; a trigger circuit connected to the triggering electrode of the flash tube for triggering the flash tube in response to the conduction of the main switching element; a firing circuit connected to said control switch and responsive to the state thereof for rendering the main switching element conductive; a second series circuit connected in parallel with said first series circuit and comprising a first auxiliary switching element, a commutating capacitor and a second auxiliary switching element connected in the order named and wherein the first and second auxiliary switching elements have the same polarity as the main switching element; charging means electrically coupled through the commutating capacitor to said direct-current source for charging the commutating capacitor to a voltage having a polarity which is the reverse of that of the charged voltage of the main capacitor with respect to the forward current in the first and second auxiliary switching elements; light sensitive means for generating a detection signal responsive to reflected light which is reflected from a flashed object resulting from a light flash from the flash tube; an integrator receptive of said detection signal for integrating same and developing a corresponding output signal; and control means receptive of the output signal of said integrator and connected to the first and second auxiliary switching elements for triggering same when the output signal of the integrator exceeds a predetermined value.