US3777212A - Electronic flash device - Google Patents

Electronic flash device Download PDF

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Publication number
US3777212A
US3777212A US00262998A US3777212DA US3777212A US 3777212 A US3777212 A US 3777212A US 00262998 A US00262998 A US 00262998A US 3777212D A US3777212D A US 3777212DA US 3777212 A US3777212 A US 3777212A
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United States
Prior art keywords
transistor
capacitor
circuit
level
main capacitor
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US00262998A
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English (en)
Inventor
Y Mashimo
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Canon Inc
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Canon Inc
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Filing date
Publication date
Application filed by Canon Inc filed Critical Canon Inc
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Publication of US3777212A publication Critical patent/US3777212A/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/30—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp
    • H05B41/32—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp for single flash operation

Definitions

  • a main capacitor for storing energy for flash illumination
  • a detecting means for detecting the charging amount across the main capacitor
  • a switching means controlled by said detecting means and connected to the charging circuit which opens to change the mode of oscillation of the oscillating device
  • a flashing vtube connected to said main capacitor.
  • the present invention relates to an electronic flash device, and more particularly relates to an electronic flash device which comprises a main capacitor charged byan output of an oscillator and when the charging amount across the main capacitor reaches a certain value, the mode of the oscillation of the oscillator is changed.
  • a conventional flash device in which a main capacitor is charged by the output of an oscillator takes a considerably long time for the charging of the main capacitor, and it has been long desired to shortenthe charging time. And in the conventional flashing device, a large bias current is passed toa transistor for oscillating the oscillator in order to shorten the charging time. However, when a large current is passed through the oscillating transistor, a considerable large current passes even after the charge across the main capacitor has reached a certain value sothat current consumption is too much and increased temperature of various circuit elements is caused.
  • a flash device was proposed in which the bias current of the oscillating transistor is controlled by a controlling transistor when the charge across the main capacitor reaches a certain value so as to decrease the charging current to a small current only enough to make up the lowering of the charging voltage of the main capacitor.
  • the above flash device contains the controlling transistor in the circuit of the oscillator, it has such defects that the circuit structure is complicated and the initial rise-up of the oscillator is bad.
  • An object of the present invention is to provide a flash device which has eliminated the above defects.
  • Another object of the present invention is to a flash device in which when'the charge across a main capacitor reaches a certain value, the mode of oscillation is changed by a controlling circuit provided in a charging circuit.
  • Still another object of the present invention is to provide a flash device inwhich when the charge across the main capacitor reaches a certain value the mode of oscillation of an oscillator is changed and the charging voltage of the main capacitor is maintained so as to obtain a constant flash illumination.
  • a further object of the present invention is to provide a flash device in which when the charge across a main capacitor reaches a certain value, the mode of oscillation of an oscillator is changed so as to save consumption of a power source.
  • FIG. 1 is a schematic view of a concuit structure of one embodiment of the present flash device.
  • FIG. 2 shows the collector current of the oscillating transistor shown in FIG. 1.
  • 1 is a power source such as a dry element cell and Ni-Cd cell.
  • 2 is a power source switch and when this switch is closed an oscillator as mentioned later starts oscillation and its output ischarged across the main capacitor.
  • 3 is a transistor for oscillation
  • 4 is a capacitor in an oscillation circuit. This capacitor 4 is required only to obtain the collector current of the transistor 3 and may be eliminated in other cases.
  • 5 is a transformer both for oscillation and boosting, which has a primary coils, P, P and a secondary coil S.
  • 6 is 2 a resistor provided in a supply circuit for supplying current to an oscillation control circuit, 7 is a resistor for setting the bias value of the oscillating transistor.
  • 8 is a diode provided in a charging circuit of the main capacitor 9, which rectifles the alternating current boosted by the transformer 5 into the direct current.
  • 10 is a triggering circuit
  • 11 is a flash tube
  • 12 is a changeover switch of the charge detecting circuit of the main capacitor 9, which changes the flash amount of the flash device from large to small or from small to large.
  • 13, 14 and 15 are resistors constituting the detecting circuit.
  • 16 is a neon lamp provided at the output portion of the detecting circuit.
  • 17 and 18 are transistors constituting the oscillation control circuit, and to the base of the transistor 17 the neon lamp 16 is connected. The relation between the neon lamp and the oscillation control circuit is such that when the neon lamp 16 is illuminated the transistors 17 and 18 become conductive.
  • the transistor 18 is connected to the charging circuit of the main capacitor 9 and cuts or passes the charging current according to the illumination or turnoff of the neon lamp.
  • the charging current is cut or passed not directly by the transistor 18, but the resistor 19 is inserted in the charging circuit of the main capacitor 9 by the conductivity or nonconductivity of the transistor 18.
  • X and Y are synchronizing terminals.
  • the oscillation circuit 3, 4, P starts to oscillate and an alternating current of high voltage is generated in the secondary coil S of the boosting transformer.
  • This alternating current is rectified by the diode 8 and passes into the large capacity main capacitor 9 and charges it.
  • the load impedance of the oscillation circuit takes a low value and thus a large current passes.
  • the neon lamp 16 of the detecting circuit 13, 14, and 15 is turned off, the oscillating transistor 17 is off and the transistor 18 is on, and the resistor 19 of the charging circuit is short-circuited bythe transistor 18.
  • the oscillator makes oscillation of the oscillation transistor in saturation as shown in FIG. 2 and the duration angle of oscillation wave is broad, and the charging current obtained by rectifying the oscillation is also large.
  • the charge across the main capacitor progresses and the voltage at the bleeding point of the detecting circuit reaches a standard value the neon lamp is illuminated.
  • the transistor 17 of the control circuit comes on, the transistor 18 becomes off and the resisting element 19 is inserted in the charging circuit of the main capacitor.
  • the load of the oscillator is reduced and the oscillation transforms from the saturated oscillation'to the CR oscillation which is determined by the integrated value of the capacitor 4 and the resistor 7 (see FIG. 2).
  • the oscillator ismaking CR oscillation, the duration angle of oscillation wave is very narrow and thus the consumption of the power source is negligibly small.
  • the charging of the main capacitor by its output is very small so that the terminal voltage is almost constant at the standard value and desired illumination is obtained.
  • control of the oscilla tion made as above can be made by selecting the value of the resisting element 19 more than several kilo ohms. Therefore, by providing the control circuit as shown, the oscillation is automatically controlled when the charge across the main capacitor reaches the standard value and the neon lamp is illuminated so that the illumination of the flash device is maintained at an almost constant value and waste consumption of the power source is prevented. By changing over the switch 12 desired guide numbers can be selected.
  • the present invention when the charge across the main capacitor progresses and illumination of a prescribed guide number is obtained, the oscillation of the power source circuit is automatically controlled, and as the circuit structure is very simple, it can be set in a small device and can prevent waste consumption of the power source.
  • the present invention is very advantageous for minimize the size of the device and the cell.
  • 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 re sponse to the varying voltage in the primarywinding, rectifying means coupled to said secondary winding, 21 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 non-conductive when said detecting means indicates that the level of charge of said capacitor means
  • 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.
  • 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 connected to the battery to render it conductive when the capacitor is not charged to the predetermined level.
  • 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
  • said detecting means includes a bleeder resistor connected across said level.

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  • Stroboscope Apparatuses (AREA)
  • Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
US00262998A 1971-06-18 1972-06-15 Electronic flash device Expired - Lifetime US3777212A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP4384271A JPS5419778B1 (enrdf_load_stackoverflow) 1971-06-18 1971-06-18

Publications (1)

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US3777212A true US3777212A (en) 1973-12-04

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US00262998A Expired - Lifetime US3777212A (en) 1971-06-18 1972-06-15 Electronic flash device

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US (1) US3777212A (enrdf_load_stackoverflow)
JP (1) JPS5419778B1 (enrdf_load_stackoverflow)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3882358A (en) * 1973-06-26 1975-05-06 Ibm Anti-holdover charging circuit for flash lamp
US3919593A (en) * 1972-08-28 1975-11-11 Canon Kk Flash safety device in a flash apparatus
US4068151A (en) * 1976-11-19 1978-01-10 Polaroid Corporation Regulated strobe with hysteresis
US4082983A (en) * 1975-06-23 1978-04-04 Rollei Of America, Inc. Capacitor charging system for electronic flash apparatus
DE2916529A1 (de) * 1978-04-24 1979-10-25 Olympus Optical Co Spannungsanzeiger fuer ein stroboskop
US4623824A (en) 1984-06-07 1986-11-18 Life Light Systems Controlled high voltage generator
US4924149A (en) * 1986-12-23 1990-05-08 Asahi Kogaku Kogyo Kabushiki Kaisha Apparatus for controlling the charging of a main capacitor of a flash unit
US5343125A (en) * 1990-11-15 1994-08-30 Patent-Treuhand-Gesellschaft Feur Elektrische Gluehlampen Mbh High-pressure discharge lamp with pulsed inverter operating circuit, and method of operating a discharge lamp
US5780976A (en) * 1996-02-20 1998-07-14 Matsuo; Takumi Constant-voltage automatic charging strobe circuit

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2977524A (en) * 1959-04-20 1961-03-28 Honeywell Regulator Co Electrical power supply apparatus
US3162786A (en) * 1960-07-09 1964-12-22 Loewe Opta Ag Circuit arrangements of electronic flash units for photographic purposes
US3310723A (en) * 1963-10-18 1967-03-21 Honeywell Inc High voltage power supply for photographic flash apparatus
US3569779A (en) * 1968-12-23 1971-03-09 Philips Corp High voltage power supply for a flash discharge lamp

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2977524A (en) * 1959-04-20 1961-03-28 Honeywell Regulator Co Electrical power supply apparatus
US3162786A (en) * 1960-07-09 1964-12-22 Loewe Opta Ag Circuit arrangements of electronic flash units for photographic purposes
US3310723A (en) * 1963-10-18 1967-03-21 Honeywell Inc High voltage power supply for photographic flash apparatus
US3569779A (en) * 1968-12-23 1971-03-09 Philips Corp High voltage power supply for a flash discharge lamp

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3919593A (en) * 1972-08-28 1975-11-11 Canon Kk Flash safety device in a flash apparatus
US3882358A (en) * 1973-06-26 1975-05-06 Ibm Anti-holdover charging circuit for flash lamp
US4082983A (en) * 1975-06-23 1978-04-04 Rollei Of America, Inc. Capacitor charging system for electronic flash apparatus
US4068151A (en) * 1976-11-19 1978-01-10 Polaroid Corporation Regulated strobe with hysteresis
DE2916529A1 (de) * 1978-04-24 1979-10-25 Olympus Optical Co Spannungsanzeiger fuer ein stroboskop
US4258297A (en) * 1978-04-24 1981-03-24 Olympus Optical Co., Ltd. Voltage indicator for a stroboscope
US4623824A (en) 1984-06-07 1986-11-18 Life Light Systems Controlled high voltage generator
US4924149A (en) * 1986-12-23 1990-05-08 Asahi Kogaku Kogyo Kabushiki Kaisha Apparatus for controlling the charging of a main capacitor of a flash unit
US5034662A (en) * 1986-12-23 1991-07-23 Asahi Kogaku Kogyo Kabushiki Kaisha Apparatus for controlling the charging of a main capacitor of a flash unit
US5343125A (en) * 1990-11-15 1994-08-30 Patent-Treuhand-Gesellschaft Feur Elektrische Gluehlampen Mbh High-pressure discharge lamp with pulsed inverter operating circuit, and method of operating a discharge lamp
US5780976A (en) * 1996-02-20 1998-07-14 Matsuo; Takumi Constant-voltage automatic charging strobe circuit

Also Published As

Publication number Publication date
JPS5419778B1 (enrdf_load_stackoverflow) 1979-07-18

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