Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
1999-07-12
2002-12-31
Hilten, John S. (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C363S101000
Reexamination Certificate
active
06502044
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to emergency lighting systems normally operable from a mains power supply and configured to operate from an emergency power source on failure of mains power, the invention particularly relating to programmable self-test and/or self-diagnostic systems for emergency lighting fixtures and which are capable of manual or automatic performance of testing and diagnostic functions on the circuitry, power supply, charging system and lamping thereof.
2. Description of the Prior Art
Emergency lighting systems have become ubiquitous due to code requirements, power typically being provided to emergency lighting systems under normal operating conditions by mains power supplied both to a normal AC ballast for light generation and to an emergency ballast for maintaining a charge on a power supply typically carried by the emergency lighting system, the power supply usually taking the form of an internal battery. Loss of line voltage results in the switching of the emergency ballast to power the lamping of the emergency lighting system through the emergency power supply, power being typically provided to the lamping for operation of the emergency lighting system for a relatively short period of time. Since the emergency lighting system is effectively in stand-by mode during normal operation thereof, periodic testing of the system is desirable in order to ensure proper functioning during emergency conditions, that is, loss of mains power. Conventionally, emergency lighting systems are tested by the active intervention of building maintenance personnel by manual operation of a test switch to simulate a power outage and to monitor the operation of the emergency lighting system. Neglect of testing procedures often occurs and results in detection of the failure of the emergency lighting system only when an emergency situation arises. In relatively recent years, automatic self-test and/or diagnostic circuitry for emergency lighting systems has become available. In such circuitry, an internal control system such as a microprocessor automatically causes a number of different tests to be conducted in sequence, such tests including detection of lamp current flow, power transfer from charger to battery and battery voltage. Failure conditions are typically indicated in such circuitry through illumination of a visual indicator such as a light emitting diode to indicate that maintenance is required. Systems monitored at central locations would also produce an indication of test failure on a computer display terminal at a central monitoring location. Systems capable of automatic testing include the supervisory emergency lighting system disclosed by Balcom et al in U.S. Pat. No. 4,799,039, this patent also describing other emergency lighting systems having periodic testing and self-diagnostic capabilities. The supervisory system of Balcom et al continuously monitors selected parameters of an emergency lighting system and periodically tests the system under simulated full-load emergency conditions automatically. The Balcom et al system also includes a closed loop three-mode battery charging control circuit. Vosika et al, in U.S. Pat. No. 5,574,423, disclose a self-diagnostic circuit for an emergency lamp which includes a high-impedance circuit path connected in series with the lamp and including a visual indicator energized by battery current passing through the circuit path and lamp during standby mode operation. A second high impedance circuit path is connected in parallel with the lamp to energize a second visual indicator whenever proper electrical continuity does not exist through the lamp. In U.S. Pat. No. 5,666,029, McDonald automatically tests the emergency ballast of an emergency lighting system, testing functions being facilitated by providing the emergency ballast with a transistorized inverter cutoff unit.
While circuitry of the prior art provides improved testing and diagnosis of emergency lighting systems when compared to manual testing as has been standard in the art for many years, the art is improved by the present invention which provides a low power, low cost circuit board combining all functions of a self-test/self-diagnostic system with control of all diagnostic, charging and transfer functions through the use of software, a microprocessor so controlled not only monitoring operation of charger/transfer circuitry but also controlling the charger/transfer circuitry to enable alternate strategies for alleviation of a given failure. The present self-test and self-diagnostic circuitry is thus capable of optimal function at extraordinarily low cost, the present system thereby producing a valuable advance in the art.
SUMMARY OF THE INVENTION
The invention provides an emergency lighting fixture having both manual and automatic self-test/self-diagnostic capabilities and wherein all diagnostic, charging and transfer functions are controlled by a microprocessor operating with software instructions. Microprocessor control is accomplished without modification of standard charger, inverter and lamp topology such as are conventionally employed in emergency lighting systems now available in the marketplace. The present electronic self-test and/or self-diagnostic circuitry combines with an emergency lighting system to perform under manual or automatic control testing and diagnostic functions on the circuitry, power supply, charger and lamping of a fixture. The diagnostic circuitry of the invention not only monitors operation of charger/transfer circuitry but also controls such circuitry to enable implementation of alternate strategies for alleviation of a given failure. In an LED exit sign, for example, a two-stage inverter powers the light emitting diodes and is controlled by the microprocessor, the microprocessor being efficiently powered in inverter mode. Further, battery power supply to the microprocessor is controlled by the microprocessor and is discontinued after appropriate operation until primary power is restored. Configuration of the test and diagnostic system in an exit signage embodiment can occur through use of a two-wire serial link between modular elements of the system, allowing the system to be flexibly configured in a low power low cost circuit board, flexibility further being provided by separate treatment of lamping from charger and diagnostic electronics.
In the LED exit signage mode, the present diagnostic circuitry employs the two-stage inverter indicated herein as being controlled by a microprocessor to convert voltage from one or more cells to a higher voltage for driving a string of light emitting diodes such as form the lamping of the exit sign or the like, driving of the light emitting diodes being accomplished in a manner similar to that described in U.S. Pat. No. 5,739,639, the disclosure of which is incorporated hereinto by reference. An EEPROM memory is used in this embodiment of the present system to set factory determined configuration parameters, thereby allowing accurate calibration without the need to use unreliable and costly potentiometers and further providing a field diagnostic log containing information relating to testing and diagnostic history. The LED exit signage embodiment of the present system further utilizes all solid state transfer switches for switching between emergency charging and diagnostic modes, this embodiment of the invention not utilizing relays and therefore using less power with more reliability than prior systems so configured. Since the microprocessor used according to the invention controls its own power supply and turns itself off once battery voltage has reached a low voltage disconnect threshold, very low power is consumed once the required emergency discharge is complete, a further benefit which allows the system to be shipped in this first embodiment without disconnecting the battery. Emergency lighting fixtures configured according to this first embodiment of the invention therefore do not require connection of the battery on site during installation
Farthing Richard C.
Lane John Evan
Acuity Brands Inc.
Darnell Kenneth E.
Hilten John S.
Pretlow Demetrius
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