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AssigneeNSI Enterprises, Inc.
InventorJames C. Johnson
Estimating the term…
Circuitry for operating an array of light emitting diodes such as in an emergency exit sign in a non-emergency AC mode while concurrently charging and maintaining the charge of a low-voltage battery used to drive the array in an emergency mode, the circuitry also allows operation of the same LED array in the emergency mode from the low-voltage battery. The advantages of the invention are realized in part through provision within the circuitry of a boost converter wherein the LED array and the battery are connected across the output of the usual boost circuit output capacitor, thereby allowing connection of the array and the battery in series to simplify operation from line power and to allow the same current limited source to operate the array and simultaneously charge the battery through the same current path. The functions so provided can be embodied in a form which allows all circuitry components including the battery to be mounted on a single, compact substrate such as a printed circuit board.
In a circuit having an array of light emitting diodes operable on AC mains power and on DC power from a battery when mains power is unavailable, battery charging and charge maintenance circuitry, a current limited source, and a boost converter circuit having an output capacitor, the LED array and the battery being connected across the output of the output capacitor to connect the LED array and the battery in series, thereby allowing the current limited source to operate the LED array on AC mains power with simultaneous charging and maintenance of charge of the battery through the same current path without switching or repositioning circuit components during DC operation.
A method for operating a circuit including an LED array by means of AC mains power and by DC power from a battery when AC power is unavailable and charging and maintaining charge of the battery during operation by AC mains power, the circuit including a boost converter circuit having an output capacitor and a current limited source, comprising the steps of:
In a circuit having an array of light emitting diodes operable on AC mains power and on DC power from a battery when mains power is unavailable, battery charging and charge maintenance circuitry, a current limited source, and a boost converter circuit having an output capacitor and being driven by a transister having a base, the light emitting diode array and the battery being connected across the output of the output capacitor to connect the light emitting diode array and the battery in series, the circuit further comprising means for identifying the presence of AC power on the circuit, the identifying means comprising a diode and a smoothing capacitor located in the circuit between the source of mains power and the light emitting diode array, the diode and the smoothing capacitor holding the base of the transistor below emitter potential during AC current flow, thereby allowing the current limited source to operate the LED array on AC mains power with simultaneous charging and maintenance of charge of the battery through the same current path.
Dependencies are inferred from the claim text.