FLASHER CIRCUIT

• US 3,710,185 A
• Filed: 06/07/1971
• Issued: 01/09/1973
• Est. Priority Date: 06/07/1971
• Status: Expired due to Term

• Current Assignee: Henry N. Switsen
• Original Assignee: Henry N. Switsen
• Inventors: Switsen, Henry N.
• Primary Examiner(s): Lake, Roy
• Assistant Examiner(s): Dahl, Lawrence J.
• Application Number:
  US05/146,568
• Time in Patent Office: 582 Days
• Field of Search: 307/252.90,305 315/72,74,75,209,240,1F,2A 340/331
• US Class Current: 315/240
• CPC Class Codes: H05B 41/34 to provide a sequence of flashes
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps

Abstract

A circuit which can be connected in a fluorescent lamp fixture in place of the starter, to create a bright, psychedelic flashing effect. The circuit includes a silicon controlled rectifier (SCR) that is turned on by a timing circuit once in every several cycles of the A.C. source to clamp the voltage across the fluorescent lamp to a low level so that the lamp cannot light. The timing circuit preferably operates the SCR a minority of the time so that the lamp is on most of the time to provide a high average illumination level, and the timing circuit preferably operates the SCR to turn off the lamp at rate of at least 5 times per second so that the sensed effect is similar to that of a bright light flashed on for a brief time rather than a moderate intensity light that is turned off for a brief time. The timing circuit includes a diode, resistor, and timing capacitor connected in series across the lamp terminals, and a diac or neon tube connected across the capacitor and to the gate of the SCR to discharge the capacitor and turn on the SCR once in every several cycles of the A.C. source.

Claims

1. In combination with a fluorescent-type lamp that is energized from an A.C. source and that has a pair of lamp terminals, a flasher apparatus for repetitively turning off the lamp comprising:

means defining first and second flasher terminals for coupling to said lamp terminals;

controlled switch means having an anode connected to said first flasher terminal, a cathode connected to said second flasher terminal, and a gate said switch means being of a type which is turned on by a voltage supplied to the gate and which thereafter remains on so long as current continues to flow in the same direction between the anode and cathode; and

a timing circuit connected to said gate and generating a pulse that turns on said switch means so it thereafter remains on during positive half cycles of said A.C. source, when said first terminal is positive with respect to said second terminal, said timing circuit generating only one pulse during a plurality of cycles of said A.C. source, but generating said pulse during the first half of a positive half cycle, whereby to keep said lamp substantially off for an entire cycle using a simple switch that can clamp the voltage across said lamp only during the positive half of the cycle.

2. Apparatus for use with an ordinary fluorescent lighting fixture, of a type which normally employs a repleaceable starter for starting a lamp that is energized from an A.C. source to provide continuous illumination, to permit rapid conversion of the fixture to a psychedelic flashing device and to permit rapid reconversion back to a condition for providing continuous illumination, comprising:

a case with a pair of terminals for installation in said fluorescent lighting fixture in place of said starter;

controlled rectifier means disposed within said case, with an anode coupled to a first of said terminals on said case, a cathode coupled to a second of said terminals on said case, and a gate for turning on said controlled rectifier means, said rectifier means being of a type which remains on until the anode-to-cathode voltage drops to nearly zero;

a timing capacitor having first and second terminals;

capacitor discharging means including diac means, discharge coupling means coupling said diac means between said first and second terminals of said capacitor through said gate and cathode of said controlled rectifier means, so that when said capacitor reaches the breakdown voltage of said diac means said capacitor discharges to provide gate current that turns on said rectifier means; and

a capacitor-charging circuit including a diode and resistance coupling said capacitor across said case terminals to charge the capacitor to the diac breakdown voltage after a plurality of cycles of the A.C. source, said diode oriented to conduct only during the half cycle Of the A.C. source when said anode is positive with respect to said cathode, whereby the timing capacitor reaches a diac firing voltage only during said predetermined half cycle of the A.C. source when the controlled rectifier means can clamp the lamp so the lamp is positively held off during the remainder of the half cycle and remains substantially off during the succeeding negative half cycle.

3. The apparatus described in claim 2 wherein:

said resistance includes a first portion connected between said first capacitor terminal and first case terminal and a second portion connected between said second capacitor terminal and second case terminal; and

including an auxiliary capacitor connected across the series combination of one of said resistance portions and said timing capacitor, whereby to provide a rapidly rising timing capacitor voltage at the beginning of each positive half cycle to assure firing of the diac and silicon controlled rectifier means at the beginning of the positive half cycle.

4. A flasher circuit for use with a fluorescent lamp that is energized from an A.C. source comprising:

first and second flasher terminals for connection across the terminals of said lamp;

controlled rectifier means having an anode connected to said first flasher terminal, a cathode connected to said second flasher terminal, and a gate, said rectifier being of a type which can be turned on by a current supplied to the gate and which thereafter will remain on so long as current flows from the anode to the cathode;

a timing capacitor;

capacitor charging means including a first and second resistors and a diode connecting said timing capacitor across said flasher terminals, said diode oriented to pass capacitor charging current only during the positive half cycles of the A.C. source when the anode of the rectifier means is positive with respect to the cathode thereof; and

capacitor discharging means coupled to said gate, including diac means and means coupling said diac means through said capacitor, so that when said capacitor reaches the breakdown voltage of said diac means said capacitor discharges to provide gate current that turns on said rectifier means;

said capacitor charging means including a resistance between said timing capacitor and second flasher terminal and an auxiliary capacitor connected in parallel with the series connection of the second resistor and said timing capacitor whereby to assure that the controlled rectifier means begins clamping the lamp near the beginning of a positive half cycle.

5. The flasher circuit described in claim 4 wherein:

said capacitor discharging means includes a second diode connected in parallel with said resistance and oriented to conduct current in a direction from said second flasher terminal towards said timing capacitor, whereby to bypass said resistance in discharging the diac means.