Electronic photographic flash apparatus

Claim 2

An electronic photographic flash apparatus comprising: a DC power source; a transformer having primary, secondary and feedback windings, the secondary winding being adapted to produce a high-frequency voltage; an oscillator transistor, wherein the primary winding of said transformer and said DC power source are connected serially between the collector and emitter electrodes of said transistor, and the feedback winding coupled electromagnetically with the primary winding of said transformer is connected through a first capacitor between the base and emitter electrodes of said transistor; a main discharge capacitor; oscillator control means for stopping and starting oscillation of said oscillator transistor to maintain a substantially constant voltage across said discharge capacitor, said oscillator control means including switching means having a control terminal and connected between the base and emitter electrodes of said transistor, and voltage applying means for applying a voltage to said control terminal corresponding to the voltage across the first capacitor which is proportional to the voltage across the main discharge capacitor to control the starting and stopping of oscillation of said oscillatOr transistor in relation to the voltage of said discharge capacitor; a discharge tube having a trigger circuit associated therewith connected to the output of said discharge capacitor; and rectifier means interconnecting said main discharge capacitor and the secondary winding of said transformer.

Claim 3

An apparatus according to claim 1, wherein said voltage applying means comprises said first capacitor and a variable resistance means connected in parallel with each other between the feedback winding of said transformer and the emitter electrode of said transistor, the control terminal of said switching means being connected to said variable resistance means.

Claim 4

An apparatus according to claim 2, further including indicating means comprising a luminescent diode connected in series with said switching means.

Claim 5

An apparatus according to claim 2, further including indicating means for indicating the starting and stopping of oscillation of the transistor oscillator, said indicating means comprising a luminescent diode connected in parallel with said switching means, thereby to discharge an energy stored in said second capacitor through said luminescent diode.

Claim 6

An apparatus according to claim 1, wherein said voltage applying means comprises a diode and a smoothing circuit, including a variable resistor and a further capacitor connected in parallel, serially connected across the primary winding of said transformer, the control terminal of said switching means being connected to said variable resistor.

Claim 7

An apparatus according to claim 1, further including indicating means for indicating the starting and stopping of oscillation of the transistor oscillator, said indicating means comprising a series circuit of a further capacitor and a luminescent element connected on the secondary winding side of said transformer, said further capacitor being operable to pass only an AC signal component from the secondary winding.

Claim 8

An apparatus according to claim 1, further including indicating means for indicating the starting and stopping of oscillation of the transistor oscillator, said indicating means comprising a luminescent diode connected across the primary winding of said transformer, in such a polarity that the cathode of the diode is connected to one end of the primary winding which is connected to the collector of the oscillation transistor.

Claim 9

An apparatus according to claim 6, wherein said indicating means comprises a luminescent diode and a diode connected in series with said luminescent diode.

Claim 10

An apparatus according to claim 1, wherein said switching means comprises a composite transistor composed of first and second transistors, and said apparatus further comprises a diode connected in parallel with one transistor of said composite transistor, said diode having a forward voltage lower than the threshold voltage of said one transistor, thereby to stabilize the oscillation control voltage.

Claim 11

An electronic photographic flash apparatus comprising: a DC power source; a transformer having primary, secondary and feedback windings, the secondary winding being adapted to produce a highfrequency voltage; an oscillator transistor, wherein the primary winding of said transformer and said DC power source are connected serially between the collector and emitter electrodes of said transistor, and the feedback winding coupled electromagnetically with the primary winding of said transformer is connected between the base and emitter electrodes of said transistor; variable resistance means connected in parallel with said DC power source; a main discharge capacitor; oscillator control means for stopping and starting oscillation of said oscillator transistor in relation to the discharging of said discharge capacitor to maintain a substantially constant voltage across said discharge capacitor, said oscillator control means including switching means having a control terminal and connected between the base and emitter electroDes of said transistor, and voltage applying means for applying a voltage to said control terminal according to the voltage across said DC power source through a tap of said variable resistance means to control the starting and stopping of oscillation of said oscillator transistor in relation to the discharging of said discharge capacitor; a discharge tube having trigger circuit associated therewith and connected to said discharge capacitor; and rectifier means interconnecting said main discharge capacitor and the secondary winding of said transformer.

Claim 12

An electronic photographic flash apparatus comprising: a DC power source; a transformer having primary, secondary and feedback windings, the secondary winding being adapted to produce a highfrequency voltage; an oscillator transistor, wherein the primary winding of said transformer and said DC power source are connected serially between the collector and emitter electrodes of said transistor, and the feedback winding coupled electromagnetically with the primary winding of said transformer is connected between the base and emitter electrodes of said transistor; variable resistance means connected in parallel with said DC power source; a main discharge capacitor; oscillator control means for stopping and starting oscillation of said oscillator transistor in relation to the discharging of said discharge capacitor to maintain a substantially constant voltage across said discharge capacitor, said oscillator control means including switching means having a control terminal and connected between the base and emitter electroDes of said transistor, and voltage applying means for applying a voltage to said control terminal according to the voltage across said DC power source through a tap of said variable resistance means to control the starting and stopping of oscillation of said oscillator transistor in relation to the discharging of said discharge capacitor; a discharge tube having trigger circuit associated therewith and connected to said discharge capacitor; and rectifier means interconnecting said main discharge capacitor and the secondary winding of said transformer.

Claim 13

An apparatus according to claim 10, further including indicating means comprising a variable resistor connected in parallel with said DC power source and a luminescent diode connected between a given point of said variable resistor and one terminal of said power source.