LAMP FLASHING CIRCUIT

• US 3,772,564 A
• Filed: 05/25/1972
• Issued: 11/13/1973
• Est. Priority Date: 05/25/1972
• Status: Expired due to Term

• Current Assignee: Morton B. Leskin
• Original Assignee: Morton B. Leskin
• Inventors: Leskin, Morton B.
• Primary Examiner(s): Lake, Roy
• Assistant Examiner(s): Dahl, Lawrence J.
• Application Number:
  US05/256,838
• Time in Patent Office: 537 Days
• Field of Search: 315/223,2A,241S,242
• US Class Current: 315/200.00A
• CPC Class Codes: H05B 41/32 for single flash operation

Abstract

A circuit for flashing a xenon or other high power flash lamp employs a capacitor incrementally charged from a non-saturating inductor storing energy supplied at a low dc voltage. A transistor switches current to the inductor. The transistor is controlled by a transformer having a primary connected across the inductor. At the beginning of each capacitor charging cycle the transistor is turned on by regenerative action through the transformer. Current is supplied to the inductor until the transformer saturates, causing transistor turn-off. Energy stored in the inductor then is transferred to the capacitor via a diode. A reverse current coupled through the transformer maintains the transistor off until substantially all energy stored in the inductor has been transferred to the capacitor. The charging cycle repeats until the voltage across the capacitor is sufficient to fire the lamp.

Claims

1. A lamp flashing circuit powered by a dc supply and including a capacitor charged incrementally during successive charging cycles to a level sufficiently high to flash said lamp, comprising:

a semiconductor switching device, an inductor connected in series with said device across said supply, means for coupling energy stored in said inductor to said capacitor as the field of said inductor collapses, a control transformer having a primary connected in parallel with said inductor and a secondary operatively connected to control said switching device, circuit means including said transformer secondary for regeneratively turning on said switching device at the beginning of each charging cycle to permit current flow to said inductor for energy storage therein, said control transformer saturating before saturation of said inductor, saturation of said transformer causing turn-off of said switch device to terminate said current flow to said inductor, the resultant collapse of said inductive field inducing a reverse polarity signal in said transformer secondary which maintains said switching device off until substantially all energy stored in said inductor has been coupled to said capacitor.

2. A lamp flashing circuit according to claim 1 wherein said power switching device comprises a first transistor and where said circuit means comprises:

a circuit connecting one terminal of said transformer secondary to the base of said first transistor, a first diode connecting the other terminal of said transformer secondary to a terminal of said supply, and a resistor connected between said transformer secondary other terminal and the other terminal of said supply to provide, in conjunction with the output of said transformer, a signal regeneratively initiating turn-on of said first transistor.

3. A lamp flashing circuit according to claim 2 wherein said circuit connecting comprises:

a second transistor having a base connected to said transformer secondary one terminal and operatively connected to turn on said first transistor when said second transistor is on.

4. A lamp flashing circuit according to claim 3 wherein one non-control element of said second transistor is connected to a tap on said inductor and wherein the other non-control element is resistor connected to a terminal of said supply and to the base of said first transistor.

5. A lamp flashing circuit according to claim 1 wherein said means for coupling comprises:

a secondary winding inductively coupled to said inductor, and unidirectional current flow means connecting said secondary winding to said capacitor.

6. A lamp flashing circuit according to claim 5 further comprising:

voltage divider means for sensing when the voltage across said capacitor is sufficient to flash said lamp, and ignitor means cooperating with said voltage divider means for igniting said lamp when sufficient capacitor voltage is sensed.

7. A lamp flashing circuit according to claim 6 further cOmprising:

means for inhibiting the incremental charging of said capacitor should the voltage across said capacitor substantially exceed said sufficient voltage.

8. A circuit powered by a low voltage dc source for incrementally charging a capacitor during successive charging cycles to a high voltage, comprising:

an inductor, a transistor connected in series with said inductor across said source to provide current from said source to said inductor when said transistor is on, a transformer having a primary connected across said inductor and a secondary, said transformer saturating prior to said inductor, circuit means connecting one terminal of said transformer secondary to the control electrode of said transistor, bias supply means cooperating with current induced in said transistor secondary regeneratively to drive said transistor into conduction at the beginning of each charging cycle, conduction of said transistor causing current flow to said inductor with concomitant inductive energy storage therein, until saturation of said transformer causes said transistor to turn off, thereby terminating current flow to said inductor, energy transfer means for transferring the stored energy from said inductor to said capacitor as the magnetic field in said inductor collapses subsequent to turn-off of said transistor, reverse current induced in said transformer secondary as said inductor field collapses maintaining said transistor off while substantially all of the energy stored in said inductor is transferred to said capacitor.

9. A circuit according to claim 8 together with a winding inductively coupled to said inductor and a diode connecting said winding to said capacitor, collapse of the magnetic field in said inductor resulting in energy transfer via said winding and said diode to said capacitor.

10. A circuit according to claim 9 wherein the reverse current resultant as said inductor field collapses produces via said transformer a signal maintaining said transistor off, said circuit including a second diode operatively connected to permit flow of said signal.

11. A circuit according to claim 10 wherein said second diode and the secondary of said transformer are connected in series between one terminal of said source and a transistor base, and wherein said bias supply means comprises a resistor connected from the other terminal of said source to the junction of said second diode and said transformer secondary, and wherein said transformer produces prior to saturation a signal enhancing conduction of the transistor providing current to said inductor.

12. A circuit according to claim 11 wherein said transformer secondary is connected to the base of the transistor providing current to said inductor.

13. A circuit according to claim 11 together with a second transistor connected to control conduction of said transistor providing current to said inductor, and wherein said transformer secondary is connected to the base of said second transistor.

14. A circuit according to claim 8 together with a flash lamp connected to be powered by the energy stored in said capacitor, and means for igniting said lamp when the voltage across said capacitor reaches a value sufficient to flash said lamp.