US3882358A - Anti-holdover charging circuit for flash lamp - Google Patents

Anti-holdover charging circuit for flash lamp Download PDF

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Publication number
US3882358A
US3882358A US373848A US37384873A US3882358A US 3882358 A US3882358 A US 3882358A US 373848 A US373848 A US 373848A US 37384873 A US37384873 A US 37384873A US 3882358 A US3882358 A US 3882358A
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US
United States
Prior art keywords
lamp
circuit
flash
path
charging
Prior art date
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
Application number
US373848A
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English (en)
Inventor
Stephen Deskevich
James C Peacock
Richard F Tynan
Alan D Wilson
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International Business Machines Corp
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International Business Machines Corp
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Publication date
Application filed by International Business Machines Corp filed Critical International Business Machines Corp
Priority to US373848A priority Critical patent/US3882358A/en
Priority to FR7416716A priority patent/FR2235569B1/fr
Priority to DE2422201A priority patent/DE2422201A1/de
Priority to GB2118474A priority patent/GB1434463A/en
Application granted granted Critical
Publication of US3882358A publication Critical patent/US3882358A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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

Definitions

  • ABSTRACT Charging circuit for a flash lamp in which flash holdover is prevented by establishing a high impedance charging circuit for a predetermined time after flash initiation to allow deionization of the lamp plasma and, after a predetermined time, establishing a low im- [52] U S Cl 315/241 315/240 320/1 pedance charging circuit to provide a fast charging [51] H05; 37/00 rate for the energy storage device.
  • SCR silicon con- 320/1 trolled rectifier
  • FIG. 2 A CURRENT DRIVER DELAY (a )FLASH TRIGGER TL (b )LAMP CURRENT c )PRIOR ART CHARGE CURRENT (d) PRIOR ART CHARGE VOLTAGE 5T (e)CHARGE CURRERTM (f)CHARGE VOLTAGE W (9 )CURRENT DRIVER 3W FIG. 2
  • Yet another important object of this invention is to provide a charging circuit for a flash lamp which has variable charging rates and which is simple. reliable and inexpensive.
  • the low impedance gate control device is switched on so that charging can occur to replenish the energy storage capacitor. After charging has been completed. the low impedance path is again switched offin preparation for the subsequent flash initiating signal. Means are provided between the initiating signal and switchable low impedance gate to maintain a fixed time relation to insure that charging will not occur for the lamp circuit until lamp conduction has terminated.
  • the flash lamp circuit can be operated at either polarity merely by appropriately poling the few polarity sensitive devices for proper current flow.
  • the use of the gate-controlled impedance device enables attainment of higher repetition frequencies for the flash lamp by permitting the use of a high impedance device in parallel with the controlled impedance. This. in effect. terminates current flow to the energy storage capacitor or flash lamp until dissipation of the previously stored charge.
  • the circuit has the advantage of permitting the controlled impedance in the charging circuit to be optionally connected to the initiating trigger pulse or to some extraneous signal known to occur at a predetermined time after the trigger pulse. Also. with the controllable charging impedance. the usual R-C charging circuit can have a much shorter time constant to thus achieve a higher repetition rate.
  • FIG. 1 is a schematic diagram of a flash lamp circuit constructed according to the principles of the invention.
  • FIG. 2 is a diagram of electrical waveforms illustrating timing relations among various components in the circuit of FIG. 1 and prior art circuits.
  • FIG. 3 is a schematic diagram of an alternative embodiment of the circuit shown in FIG. 1.
  • a flash lamp 10. with anode l1 and cathode 12. is connected in parallel with an energy storage capacitor I3 across a source 14 of potential. indicated as a battery.
  • resistor 15 Connected between the positive terminal of the battery and the capacitor is resistor 15 which forms with capacitor I3 and R-C charging circuit for lamp 10.
  • a diode 16 is placed between anode 11 and the junction of resistor I5 and the capacitor 13 to block reverse current flow during triggering of the lamp. as will be evident later.
  • Lamp cathode 12 is directly connected to the opposite side of storage capacitor 13 and to the anode of a silicon controlled rectifier (SCR) 17.
  • SCR silicon controlled rectifier
  • the cathode is connected to the negative terminal of battery 14.
  • the SCR has a control electrode 18 which can be pulsed for gating the SCR into conduction at selected times.
  • the SCR also has a resistor 19 connected in parallel therewith. This resistor is preferably many times the impedance of resistor 15.
  • the flashing of lamp 10 is initiated through the amplification of a high voltage pulse supplied through a trigger circuit indicated generally as 20 to the right of lamp 10 in FIG. 1.
  • Terminal 21 of the trigger circuit is connected to a source 32 of positive potential such as 100 volts and to current limiting resistor 22 which. in turn. is connected to a blocking capacitor 23 and the anode of an SCR 24 which has a control electrode 25 connected to an imput signal terminal 26.
  • Capacitor 23 is connected in series with one terminal of the primary winding ofa transformer 27. The other terminal of the primary winding is connected in common at line 28 with the cathode of SCR 24 and thr trigger power source 32 at terminal 29.
  • transformer 27 The secondary winding of transformer 27 is connected at one end to lamp cathode 12 and at the other end through a resistor 30 and capacitor 31 to anode ll of flash lamp 10.
  • Input control terminal 26. in addition to being connected to control electrode 25 of SCR 24 also serves as an input to single shot circuit 33 which produces a narrow output pulse upon each activation which is supplied to a current driver 34.
  • the current driver provides an output signal of predetermined duration which is supplied to control electrode 18 of SCR 17 to thereby switch the SCR to a conductive state for the duration of the driver output.
  • an input flash control signal is applied at terminal 26 and electrode which gates SCR 24 into conduction allowing discharge of capacitor 23 thus producing a pulse in the primary winding of transformer 27.
  • a triggering pulse is thereby induced in the secondary winding and appears across resistor and across capacitor 31 as a high voltage spike superimposed on the potential existing at anode ll.
  • Diode 16 isolates the pulse from the charging circuit. It may be assumed storage capacitor 13 is fully charged from source 14 in the R-C network of resistor 15 and capacitor 13. When the high voltage spike appears at anode 11, it is sufficient to produce ionization of the gas in lamp 10 and initiate discharge of capacitor 13 through diode 16 and flash lamp 10 back to capacitor 13. Lamp current resulting from the trigger pulse is shown in waveforms a and b of HO. 2. The dotted line in waveform b indicates the current level necessary to sustain conduction in flash tube 10.
  • waveforms c and d. respectively. illustrate the current'flow and charging voltage during the recharging of storage capacitor 13. It will be seen that recharging occurs as soon as conduction is initiated within flash tube 10, and that potential source 14 will provide sufficient current to. sustain lamp conduction beyond the period desired resulting in'flash holdover.
  • SCR l7 and resistor 19 have been placed as shown in FIG. 1.
  • the trigger control signal occurs at terminal 26 to turn on SCR 24, it also starts single shot circuit 33.
  • the single shot produces an output signal for a predetermined time after being turned on. This time period is selected to be of sufficient length to allow the flash tube to deionize and. thus, stop conduction.
  • the end of the delay produced by the single shot output turns on current driver circuit 34 which turns on SCR 17 at gate electrode 18.
  • the effect of the delay in turning on SCR 17 is shown by waveforms e and fof FIG. 2, respectively, showing current flow and voltage change at storage capacitor 13.
  • the amount of delay after the occurrence of an input flash control signal at terminal 26 depends upon the characteristics of the particular flash lamp being used. Such delay is usually in the order of a few milliseconds, at which time the lamp has deionized and charging can occur for storage capacitor 13.
  • the gating signal for SCR 17 has been shown as coupled with the input flash initiation control signal. it can alternatively be supplied from various other sources which bear a known time relationship to the signals supplied at terminal 26. Such other signal sources may be a clock pulse generator or counter output, for example.
  • the circuit shown in FIG. 1 can be connected with the negative terminal of source 14 at ground potential.
  • the flash lamp cathode and capacitor terminals would be floated above ground when the SCR 17 turns off. They are substantially at ground when the SCR is on and the capacitor is charging.
  • An alternative to this construction is shown in H0. 3.
  • the cathode of SCR 17 and the flash lamp can be connected to ground.
  • the positive terminal of source 14 will then be substantially at ground when SCR 17 is conducting.
  • the positive terminal of the source is floating.
  • the lamp is inserted in the circuit reversed from FIG. 1.
  • One terminal of the storage capacitor and lamp would always be at ground potential as in theconventional case when no SCR is present in the circuit.
  • the alternative embodiment may be preferred because the lamp is not floated above ground during part of the flash cycle.
  • An advantage of the circuits disclosed in FIGS. 1 and 3 is that the impedance of resistor 15 can be decreased with the corresponding decrease in the charging circuit time constant for a given storage capacitor 13 so that the flash lamp may be operated at high flash frequency at the same energy pulse. This can occur without danger of flash lamp holdover since the charging voltage does not appear across the lamp until such time as the lamp is able to withstand that voltage.
  • a voltage comparable to the holdover condition across the lamp but limited by a large resistor could be used to control the SCR gate current and insure that the lamp is in a nonconductive state when the SCR is turned on.
  • a circuit for permitting high frequency repetition of a flash lamp comprising:
  • said charging means including a first constant impedance path and a second path with switch means having an on-state and an off-state in parallel with said first path to vary the rate of energy supplied to said storage circuit.
  • said second path switch states being selectable in response to a control signal;
  • trigger pulse means for initiating flashing of said lamp and discharge of said storage circuit
  • Apparatus as described in claim 1 further including means for terminating said control signal a predetermined time after said switch means has been selected to said on-state.

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  • Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
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US373848A 1973-06-26 1973-06-26 Anti-holdover charging circuit for flash lamp Expired - Lifetime US3882358A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US373848A US3882358A (en) 1973-06-26 1973-06-26 Anti-holdover charging circuit for flash lamp
FR7416716A FR2235569B1 (enrdf_load_stackoverflow) 1973-06-26 1974-05-07
DE2422201A DE2422201A1 (de) 1973-06-26 1974-05-08 Zuendschaltung fuer blitzlampen
GB2118474A GB1434463A (en) 1973-06-26 1974-05-14 Flash lamp circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US373848A US3882358A (en) 1973-06-26 1973-06-26 Anti-holdover charging circuit for flash lamp

Publications (1)

Publication Number Publication Date
US3882358A true US3882358A (en) 1975-05-06

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Family Applications (1)

Application Number Title Priority Date Filing Date
US373848A Expired - Lifetime US3882358A (en) 1973-06-26 1973-06-26 Anti-holdover charging circuit for flash lamp

Country Status (4)

Country Link
US (1) US3882358A (enrdf_load_stackoverflow)
DE (1) DE2422201A1 (enrdf_load_stackoverflow)
FR (1) FR2235569B1 (enrdf_load_stackoverflow)
GB (1) GB1434463A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4054815A (en) * 1975-04-15 1977-10-18 Siemens Aktiengesellschaft Circuit arrangement for igniting a gas discharge flash tube
US4082983A (en) * 1975-06-23 1978-04-04 Rollei Of America, Inc. Capacitor charging system for electronic flash apparatus
US5574337A (en) * 1994-06-30 1996-11-12 Eastman Kodak Company Single touch flash charger control
US5634153A (en) * 1995-12-21 1997-05-27 Eastman Kodak Company Static immunity for single touch flash charger control

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2608652C2 (de) * 1976-03-03 1983-08-25 Robert Bosch Gmbh, 7000 Stuttgart Schaltungsanordnung für lichtmengengesteuerte Elektronenblitzgeräte
NO145320C (no) * 1980-01-11 1982-02-24 Julius Hartai Blinklysanordning.

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3098947A (en) * 1960-05-02 1963-07-23 American Speedlight Corp Electrical systems including capacitors
US3375403A (en) * 1965-10-04 1968-03-26 Berkey Photo Inc Electrical system for discharge device
US3764849A (en) * 1972-03-24 1973-10-09 Minolta Camera Kk Electronic flash charging and triggering circuitry
US3777212A (en) * 1971-06-18 1973-12-04 Canon Kk Electronic flash device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3098947A (en) * 1960-05-02 1963-07-23 American Speedlight Corp Electrical systems including capacitors
US3375403A (en) * 1965-10-04 1968-03-26 Berkey Photo Inc Electrical system for discharge device
US3777212A (en) * 1971-06-18 1973-12-04 Canon Kk Electronic flash device
US3764849A (en) * 1972-03-24 1973-10-09 Minolta Camera Kk Electronic flash charging and triggering circuitry

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4054815A (en) * 1975-04-15 1977-10-18 Siemens Aktiengesellschaft Circuit arrangement for igniting a gas discharge flash tube
US4082983A (en) * 1975-06-23 1978-04-04 Rollei Of America, Inc. Capacitor charging system for electronic flash apparatus
US5574337A (en) * 1994-06-30 1996-11-12 Eastman Kodak Company Single touch flash charger control
US5634153A (en) * 1995-12-21 1997-05-27 Eastman Kodak Company Static immunity for single touch flash charger control

Also Published As

Publication number Publication date
DE2422201A1 (de) 1975-01-16
FR2235569B1 (enrdf_load_stackoverflow) 1977-10-28
GB1434463A (en) 1976-05-05
FR2235569A1 (enrdf_load_stackoverflow) 1975-01-24

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