The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 26, 1989
Filed:
Jul. 27, 1987
Jeffrey A Jorgensen, Bothell, WA (US);
Avtech Corporation, Seattle, WA (US);
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.