ELECTRONIC FLASHLAMP POWER SUPPLY

• US 3,644,818 A
• Filed: 03/10/1971
• Issued: 02/22/1972
• Est. Priority Date: 03/10/1971
• Status: Expired due to Term

• Current Assignee: Fredrick W. Paget
• Original Assignee: Fredrick W. Paget
• Inventors: Paget, Fredrick W.
• Primary Examiner(s): Shoop, Jr., William M.
• Application Number:
  US05/122,793
• Time in Patent Office: 349 Days
• Field of Search: 321/2,18 315/29CD,241S,241P,DIG.5
• US Class Current: 315/241.00P
• CPC Class Codes: H02M 3/3388 of the parallel type
• CPC Class Codes: H05B 41/32 for single flash operation

Abstract

A flash system power supply for charging a storage capacitor employed in operating a flashlamp. A battery-powered multivibrator-type converter is coupled to the storage capacitor through a transformer-rectifier circuit, with the multivibrator being triggered into oscillation by a start circuit comprising a relaxation oscillator. Multivibrator operation is squelched by a negative voltage pulse from a stop circuit controlled by a relaxation oscillator-type voltage detector which senses a predetermined charge on the storage capacitor. The stop circuit is also controlled by a current-sensing resistor which detects discharge of the storage capacitor. Operation of the start circuit is clamped to the stop circuit through a diode, with the stop circuit having a time constant sufficient to delay restarting of the multivibrator beyond the deionization period of the flashlamp.

Claims

1. For use in a flash system having ignition means for operating a flashlamp in response to discharge of a first capacitor, a power supply for charging said first capacitor comprising:

means for generating an AC voltage;

means including a rectifier for coupling said voltage-generating means across said first capacitor;

first discharge means including a second capacitor for starting said voltage-generating means;

voltage detection means for sensing the voltage charge on said first capacitor and generating a threshold signal when the charge on said first capacitor reaches a predetermined level;

second discharge means including a third capacitor for applying a stop signal to disable said voltage-generating means in response to a threshold signal from said voltage detection means; and

means including a diode for clamping said second capacitor to said third capacitor.

2. A power supply according to claim 1 further including means for sensing discharge of said first capacitor and triggering said second discharge means to disable said voltage-generating means in response thereto.

3. A power supply according to claim 1 wherein said first discharge means further includes means for generating a pulse in response to said second capacitor being charged to a predetermined voltage level, said pulse being applied to start said voltage-generating means.

4. A power supply according to claim 3 wherein said first discharge means comprises a relaxation oscillator.

5. A power supply according to claim 1 wherein said second discharge means further includes controlled switching means for discharging said third capacitor in response to a threshold signal from said voltage detection means, and means for coupling a pulse produced by discharge of said third capacitor to said voltage-generating means, said pulse comprising said stop signal and having a polarity operative to disable said voltage-generating means, and discharge of said third capacitor causing any charge on said second capacitor to be drained through said diode clamping means.

6. A power supply according to claim 1 wherein said voltage detection means comprises a relaxation oscillator.

7. A power supply according to claim 1 wherein said means for generating an AC voltage comprises a battery-powered converter circuit, said first discharge means is operative to start Oscillation of said converter circuit, and the stop signal from said second discharge means is operative to squelch oscillation of said converter circuit.

8. A power supply according to claim 7 wherein said converter circuit includes a transformer having primary and secondary windings and a multivibrator connected to said primary windings, said rectifier coupling means being connected between the secondary winding of said transformer and said first capacitor.

9. A power supply according to claim 8 further including means for charging said second and third capacitors, said diode clamping means preventing the charge on said second capacitor from exceeding the charge on said third capacitor, and wherein said second discharge means includes an RC charge circuit comprising a first resistor and said third capacitor, gate-controlled switch connected for discharging said third capacitor in response to a control signal, and means for coupling said third capacitor to said multivibrator whereby discharge of said third capacitor is operative to apply a reverse biasing pulse of sufficient magnitude and duration to stop oscillation of said multivibrator.

10. A power supply according to claim 9 wherein said first discharge means is a relaxation oscillator comprising an RC charge circuit including a second resistor and said second capacitor, threshold switching means for discharging said second capacitor in response to said second capacitor being charged to a predetermined voltage level, and means for coupling said threshold switching means to said multivibrator whereby discharge of said second capacitor is operative to apply a forward biasing pulse for triggering said multivibrator into oscillation.

11. A power supply according to claim 10 wherein said voltage detection means comprises a relaxation oscillator operative to generate threshold signal pulses for the duration of said predetermined level of charge on said first capacitor, and means for coupling said threshold signal pulses as a control signal to said gate-controlled switch for discharging said third capacitor, discharge of said third capacitor causing any charge on said second capacitor to be drained through said diode clamping means.

12. A power supply according to claim 11 further including a current-sensing resistor connected in circuit with said first capacitor and said gate-controlled switch for applying a control signal to trigger said gate-controlled switch in response to discharge of said first capacitor, said triggered switch discharging said third capacitor and thereby causing any charge on said second capacitor to be drained through said diode clamping means, and wherein the RC charge circuit of said second discharge means has a time constant sufficient to delay starting of said multivibrator beyond the deionization period of said flashlamp.