Electric lamp and discharge devices: systems – Current and/or voltage regulation – Automatic regulation
Patent
1987-07-27
1989-09-26
Griffin, Robert L.
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Automatic regulation
315308, H05B 4136
Patent
active
048703273
ABSTRACT:
A ballast for controlling the light emitted by fluorescent lamps (25) is disclosed. DC power derived from either a DC source or a rectified AC source is switched on and off at a high frequency rate by a switch (15) to control the flow of current through the primary winding of the transformer of a flyback converter (27). The switched output is rectified and applied by the flyback converter to the filaments of the fluorescent lamps (25) to be controlled. The rectified, switched output is also applied by a .pi. filter (17) to a commutator circuit (21) that controls the starting of the fluorescent lamps (25). The commutator circuit (21) is switched at a lower frequency rate. The bridge input voltage and current are sensed and fed back to a control circuit (23), which includes a regulating pulse width modulator and a bridge switching circuit. The control circuit (23) also receives a pulse current feedback signal from the switch (15) and an external dimming control signal. The control circuit (23) controls the application of high frequency switching signals to the switch (15) that controls the application of power by the flyback converter based on the voltage, current and pulse current feedback signals. Which one of these three signals actually controls is determined by which signal first reaches a reference level. If the magnitude of the feedback voltage first reaches the magnitude set by an open circuit voltage reference, the feedback voltage signal controls. If the magnitude of the feedback pulse current signal first exceeds a predetermined magnitude, the feedback pulse current signal controls. If the feedback current first exceeds a reference magnitude controlled by the external dimming control, the feedback current signal controls.
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"A dimmable (1000:1 range) fluorescent ballast for instrument panel lighting", by P. O. Lauritzen et al., Journal of IES, Jan. 1983, pp. 86-90.
Avtech Corporation
Becker Stephen A.
Griffin Robert L.
Salindong T.
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