Ballast having starting current restraint circuitry for preventi

Details Ballast having starting current restraint circuitry for preventi Ballast having starting current restraint circuitry for preventi

1992-11-12

1994-06-14

Pascal, Robert J.

Electric lamp and discharge devices: systems

Periodic switch in the supply circuit

Periodic switch in the primary circuit of the supply...

315244, 315291, 315DIG7, 315DIG5, H05B 3702

Patent

active

053213378

ABSTRACT:
An improved electronic ballast for a florescent lamp includes rectifying/filtering circuity coupled to an A.C. power source, high frequency switching circuitry, starting circuitry connected to the output terminal of the high frequency switching circuitry, and both starting current restraint circuitry connected to the output terminal of the rectifying/filtering circuitry and protection circuitry coupled to the starting circuitry. The starting current restraint circuitry includes a thermistor with a negative temperature coefficient which causes current flows through the filaments of the lamp to gradually increase during activation of the lamp tube so as to modify the heating of the filaments, lengthening the opertional life of the lamp. If a lamp starting failure occurs, a coupling winding in the protection circuitry couples excess voltage to charge a capacitor, which in turn triggers a diac that activates a silicon controlled rectifier to forward bias a diode which brings the transistor gate voltage to ground to stop oscillation of the transistor and prevent continuous high voltage from appearing at both ends of the lamp tube so as to protect the circuit thereof.

REFERENCES:
patent: 4104715 (1978-08-01), Lawson, Jr.
patent: 4165475 (1979-08-01), Pegg et al.
patent: 4392087 (1983-07-01), Zansky
patent: 5055742 (1991-10-01), Jurell et al.

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