Electronic flash device

Claim 2

An electronic flash apparatus for photographic purposes, comprising a low voltage battery, first circuit means responsive to the battery and including an oscillating transistor for producing varying voltages, a voltage transformer having a low voltage primary winding and a high voltage secondary winding, said parimary winding being coupled to said first circuit means so as to induce a high voltage in the secondary winding in response to the varying voltage in the primary winding, rectifying means coupled to said secondary winding, a main capacitor coupled to said rectifying means and chargeable by said rectifying means, detecting means for detecting the level of charge across said main capacitor, impedance means connected in series with said main capacitor for limiting the current flow to said main capacitor and in said secondary winding as well as said primary winding to a given average level, and switching means connected in parallel with said impedance means and responsive to said detecting means for becoming conductive when said detecting means indicates that the level of charge of said capacitor means is less than a predetermined value and for becoming nonconductive when said detecting means indicates that the level of charge of said capacitor means exceeds the predetermined value.

Claim 3

An apparatus as in claim 1, wherein said impedance means includes a resistor and said first circuit means includes an RC time constant circuit having a time constant exceeding a predetermined value connected to said transistor, said transistor having a base, said time constant circuit being connected to said base.

Claim 4

An apparatus as in claim 1, wherein said switching means is a transistor having a low compression resistance characteristic.

Claim 5

An apparatus as in claim 1, wherein said detecting means includes a bleeder resistor connected in parallel with said capacitor and a neon tube coupled to said bleeder resistor, said switching means including an input transistor and an output transistor connected in cascade, said input transistor being connected to the neon tube and the input of the output transistor being connected to the battery to render it conductive when the capacitor is not charged to the predetermined level.

Claim 6

An electronic flash apparatus for photographic purposes, comprising a battery, a voltage transformer having a low voltage primary and a high voltage secondary winding, first circuit means responsive to said battery and including an oscillating transistor for producing a varying voltage, said first circuit means being connected to said low voltage primary winding to cause said primary winding to induce a high voltage in said secondary winding, rectifying means responsive to said secondary winding for producing a rectified voltage, said transistor having a base, an RC time constant circuit having a time constant greater than a predetermined value and connected to the base of said transistor, a main capacitor connected to said rectifying means and being charged by said rectifying means, detecting means for detecting the level of charge across said main capacitor, impedance means connected in series with said main capacitor for limiting the charging rate to a given level, switching means responsive to said detecting means and connected across said impedance means for becoming conductive and bypassing said impedance means when said detecting means detects that the level of charge across said capacitor is less than a predetermined value and for becoming non-conductive when said detecting means detects at the level charge across said capacitor means exceeds the predetermined value, and second circuit means for charging the capacitor of said RC circuit in response to said switching means to a polarity opposite to that which the charged capacitor is charged by said oscillating transistor when said oscillating transistor is conductive.

Claim 7

An electronic flash apparatus for photographic purposes, comprising a battery, a voltage transformer having a low voltage primary and a high voltage secondary winding, first circuit means responsive to said battery and including an oscillating transistor for producing a varying voltage, said first circuit means being connected to said low voltage primary winding to cause said primary winding to induce a high voltage in said secondary winding, rectifying means responsive to said secondary winding for producing a rectified voltage, said transistor having a base, an RC time constant circuit having a time constant greater than a predetermined value and connected to the base of said transistor, a main capacitor connected to said rectifying means and being charged by said rectifying means, detecting means for detecting the level of charge across said main capacitor, impedance means connected in series with said main capacitor for limiting the charging rate to a given level, switching means responsive to said detecting means and connected across said impedance means for becoming conductive and bypassing said impedance means when said detecting means detects that the level of charge across said capacitor is less than a predetermined value and for becoming non-conductive when said detecting means detects at the level charge across said capacitor means exceeds the predetermined value, and second circuit means for charging the capacitor of said RC circuit in response to said switching means to a polarity opposite to that which the charged capacitor is charged by said oscillating transistor when said oscillating transistor is conductive.

Claim 8

An apparatus as in claim 5, wherein the capacitor of said RC time constant circuit is connected between the battery and the primary winding and the resistor of the RC time constant circuit is connected between the base of the oscillating transistor and the battery.

Claim 9

An apparatus as in claim 5, wehrein said switching means includes a transistor having a low compression resistance characteristic.

Claim 10

An apparatus as in claim 5, wherein said detecting means includes a bleeder resistor connected across said capacitor and a neon tube coupled to said bleeder resistor, said switching means including an input transistor and an output transistor connected in cascade with said input transistor, said input transistor being connected to the neon tube and the input of said output transistor being connected with the battery to render said output transistor conductive when the level to which the main capacitor is charged is less than the predetermined level.