Controlled electronic ballast

Details Controlled electronic ballast Controlled electronic ballast

1989-02-21

1991-09-17

LaRoche, Eugene R.

Electric lamp and discharge devices: systems

Periodic switch in the supply circuit

Silicon controlled rectifier ignition

315224, 315291, 315307, 315DIG5, 315DIG7, H05B 3702, H05B 3904, H05B 3702, G05F 100

Patent

active

050497871

ABSTRACT:
A self-oscillating half-bridge inverter is powered from a power-line-operated DC voltage source. The inverter is loaded by way of a series-tuned high-Q LC circuit connected across its output. A pair of fluorescent lamps is series-connected across the tank-capacitor of the LC circuit. The inverter has two bipolar transistors, each driven by an associated saturable current transformer that provides for a transistor ON-time dependent upon the magnitude of an associated bias voltage. One of the transistors has a control arrangement connected in circuit with its associated saturable transformer and operative to control the magnitude of its associated bias voltage. As the magnitude of this bias voltage is controlled, the magnitude of the voltage across the tank-capacitor, as well as of the current available therefrom, is correspondingly controlled. The magnitude of the bias voltage is automatically controlled such that: (a) with the lamps not-yet-ignited, the magnitude of the voltage across the tank-capacitor is maintained at a level somewhat higher than normal lamp operating voltage, except that for 10 milli-seconds once each second the magnitude is increased to a level high enough to cause lamp ignition; (b) after the lamps have ignited, the magnitude of the lamp current is limited to an adjustably preset level; and (c) the magnitude of any ground-fault current is limited to a level considered safe from shock hazard.

REFERENCES:
patent: 4079292 (1978-03-01), Kaneda
patent: 4245177 (1981-01-01), Schmitz

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