Photoflash power supply

Claim 2

A photoflash power supply system comprising a photoflash lamp, a capacitor, means for selectively discharging said capacitor through said flash lamp, a source of unregulated voltage, and circuit means for charging said capacitor from said source of unregulated voltage to a predetermined value, said circuit means including an electronic valve connected in series with said capacitor across said source of unregulated voltage, and means responsive to the voltage across said capacitor permitting the voltage across said capacitor to charge through said electronic valve to said predetermined value and then cutting off said electronic valve when said voltage reaches said predetermined value.

Claim 3

A photoflash power supply system as recited in claim 1 wherein said electronic valve has a gate electrode, the conductivity of said electronic valve being controlled in accordance with a signal applied to said gate electrode, said means responsive to the voltage across said capacitor comprising an amplifier having a signal corresponding to the voltage across said capacitor applied to the input thereof and driving said gate electrode with the output thereof, said circuit means delaying the turning off of said electronic valve as the voltage across said capacitor approaches said predetermined value whereby said predetermined value to which said capacitor is charged causes said amplifier to drive said electronic valve completely to cut off.

Claim 4

A photoflash power supply system as recited in claim 2 wherein said electronic valve comprises a transistor, said amplifier driving said transistor to saturation when said voltage is below said predetermined value, the turning off of said transistor bEing delayed as the voltage across said capacitor approaches said predetermined value as the result of minority carrier depletion.

Claim 5

A photoflash power supply system as recited in claim 3 wherein said amplifier includes a second transistor of the opposite conductivity type from that of said first-mentioned transistor, said second transistor having its collector connected to the base of said first-mentioned transistor and having its emitter connected to the collector of said first-mentioned transistor.

Claim 6

A photoflash power supply system as recited in claim 1 wherein said circuit means further comprises a resistance connected in series with said capacitor and said electronic valve whereby the voltage drop across said resistance is transferred to be across said electronic valve when said electronic valve is cut off.

Claim 7

A photoflash power supply system as recited in claim 1 wherein said electronic valve comprises a transistor, wherein said means responsive to the voltage across said capacitor saturates said transistor when the voltage across said capacitor is below said predetermined value, the turning off of said transistor being delayed as the voltage across said capacitor approaches said predetermined value due to the minority carrier depletion whereby said predetermined value to which said capacitor is charged is sufficiently high to cause said means responsive to the voltage across said capacitor to drive said transistor completely to cut off.

Claim 8

A photoflash power supply system as recited in claims 6 wherein said means responsive to the voltage across said capacitor includes a second transistor of the opposite conductivity type from that of said first-mentioned transistor having its collector connected to the base of said first transistor and having its emitter connected to the collector of said first transistor.

Claim 9

A photoflash power supply system as recited in claim 6 wherein said circuit means includes a resistance connected in series with said capacitor and said transistor across said source of unregulated voltage, the voltage drop across said resistance being transferred to be across said transistor when said transistor is cut off.