Self-diagnostic circuitry for emergency lighting fixtures

• US 6,502,044 B1
• Filed: 07/12/1999
• Issued: 12/31/2002
• Est. Priority Date: 07/12/1999
• Status: Expired due to Term

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: Acuity Brands, Inc.
• Inventors: Lane, John Evan, Farthing, Richard C.
• Primary Examiner(s): Hilten, John S.
• Assistant Examiner(s): PRETLOW, DEMETRIUS R
• Application Number:
  US09/352,184
• Time in Patent Office: 1,268 Days
• Field of Search: 702/60, 702/63, 702/82, 702/108, 702/183, 340/333, 340/693.1, 340/693.2, 340/3.1, 340/693--69, 315/86, 363/101
• US Class Current: 702/63
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/0029 with safety or protection devices or circuits
• CPC Class Codes: H02J 9/005 using a power saving mode for copiers G03G15/5004
• CPC Class Codes: H02J 9/02 in which an auxiliary distribution system and its associated lamps are brought into service
• CPC Class Codes: H02M 7/05 Capacitor coupled rectifiers
• CPC Class Codes: H05B 39/044 continuously H05B39/042 takes precedence
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output
• CPC Class Codes: H05B 45/58 involving end of life detection of LEDs
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 70/30 Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
• CPC Class Codes: Y04S 20/20 End-user application control systems

Abstract

Electronic self-test and/or self-diagnostic systems particularly useful with emergency lighting fixtures, including exit signage having light emitting diodes as light sources and unit emergency fixtures powered with lead-acid batteries, the systems perform testing and diagnostic functions on the circuitry, power supply, charger and lamping of such fixtures either by manual or automatic initiation. Testing functions are provided through use of a programmable microprocessor, the diagnostic circuitry 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. In emergency mode of a light emitting diode exit sign, a microprocessor-controlled two-stage inverter is employed not only to power the LED light source, but also to efficiently power the microprocessor. Power to the microprocessor is controlled by the microprocessor itself and can therefore be discontinued after appropriate operation until mains power is restored, thereby effectively reducing power consumption to zero. System operation can be flexibly configured through use of a two-wire serial link between modular elements of the system. Incandescent emergency unit fixtures due to high drain rates and output loads require emergency mode operation through use of lead-acid batteries, thereby requiring voltage controlled charging and relay transfer, the self-test and/or self-diagnostic circuitry of the invention used with emergency unit fixtures thus differing in various respects from the circuitry employed for the LED exit signage fixtures and primarily in the need to measure both charge and discharge currents, the circuitry having a larger dynamic range in addition to a capability of measuring both positive and negative currents.

Claims

1. In an emergency lighting system operable in an emergency mode to energize at least one emergency lamp from emergency power provided by a battery on sensing of an emergency condition such as utility power failure, the lighting system having a boost converter circuit, the lighting system further having a diagnostic system capable of performing self-diagnostic and/or self-test functions indicative of the operational state of the emergency lighting system, the diagnostic system including at least one microprocessor, the improvement comprising:

means for monitoring current in the boost converter circuit; and

,

means for controlling the rate of battery drain current in response to current values in the boost converter circuit received from the boost converter current monitoring means, the battery drain current controlling means comprising,

a boost switch in the boost converter circuit and,

means for generating a reference voltage in response to boost converter current to provide a feedback signal to the microprocessor when current sensed by the boost converter current monitoring means reaches a predetermined level of a voltage greater than the reference voltage, the microprocessor acting to change the status of the boost switch to cause energy in the boost converter circuit to be delivered to the lamp to complete a switching cycle of the boost switch.

2. In the emergency lighting system of claim 1 wherein the boost switch comprises a transistor having a base, the microprocessor turning the base to an off condition to cause energy in the boost converter circuit to be delivered to the lamp.

3. In the emergency lighting system of claim 2 wherein the boost converter circuit further comprises a pair of inductors and a diode.

4. In the emergency lighting system of claim 2 wherein the boost converter circuit comprises at least one inductor that holds the energy which is to be delivered to the lamp.

5. In the emergency lighting system of claim 1 wherein the boost converter current monitoring means comprises a resistor.

6. In the emergency lighting system of claim 1 wherein the reference voltage generating means comprises an operational amplifier.

7. In the emergency lighting system of claim 1 wherein the microprocessor has an interrupt pin, the feedback signal being provided to the interrupt pin.

8. In the emergency lighting system of claim 1 wherein the improvement further comprises:

means for adjusting the switching cycle of the boost switch to control the time of operation of the boost switch in order to permit operation of the switching cycle of the switch.

9. In the emergency lighting system of claim 8 wherein the boost switch comprises a transistor and the reference voltage generating means comprises an operational amplifier.

10. In the emergency lighting system of claim 1 wherein the improvement further comprises:

means for changing battery drain rate by controlling the time of operation of the boost switch in order to adjust the switching cycle of the switch and thus permit alteration of the switching cycle of the switch.

11. In the emergency lighting system of claim 1 wherein the battery drain current rate controlling means comprises:

means for providing a current path between the battery and the boost switch through the boost converter circuit on placement of a high feedback signal on the boost switch to turn the switch to an on condition, said high signal indicating the existence of a voltage across the boost converter current monitoring means that is greater than or equal to a reference voltage generated by the reference voltage generating means, the microprocessor thus initiating a switching sequence on the boost converter circuit through placement of the high feedback signal on the boost switch.

12. In the emergency lighting system of claim 1 wherein the improvement further comprises:

means for self-calibration of the diagnostic system on initial operation of the diagnostic system causing exposure of the diagnostic system to an unknown load characteristic of the lighting system, a loading value particular to the lighting system being provided to the microprocessor.

13. In the emergency lighting system of claim 1 wherein the lighting system includes an inverter and the boost converter circuit comprises a first inductor and a second inductor, the inverter providing power to the microprocessor when the lighting system is operating in emergency mode, the first inductor providing a relatively higher voltage to the lamp and the second inductor providing a relatively lower voltage to the microprocessor.

14. In the emergency lighting system of claim 13 wherein the diagnostic system further comprises:

regulator means receiving a lower voltage input from the second inductor for generating a precise voltage that is provided to the microprocessor.

15. In the emergency lighting system of claim 1 wherein the boost converter circuit comprises two inductors, the diagnostic system further comprising:

regulator means for generating a precise voltage to the microprocessor; and

,

means for supplying a predetermined voltage to the regulator means, the regulator means supplying through the inductors a peak current of a fixed value regardless of inductor value or load, thereby regulating current to the lamp to provide a more consistent light output.

16. In the emergency lighting system of claim 1 wherein the lighting system includes an inverter, the improvement further comprising:

a regulator located in the diagnostic system between the battery and the microprocessor for supplying voltage of a predetermined level to the microprocessor during emergency mode operation; and

,

means disposed in a current path between the battery and the regulator for blocking the current path to prevent current flow to the regulator in the event of the existence of voltage across said blocking means of less than a predetermined value, current flow through the blocking means being prevented except during operation of the inverter, thus causing a minimum amount of power to be consumed by the lighting system on discontinuation of inverter operation.

17. In the emergency lighting system of claim 16 wherein the blocking means comprises a Zener diode.

18. In the emergency lighting system of claim 16 wherein the current path between the battery and the regulator includes an inductance.

19. In the emergency lighting system of claim 1 wherein the lighting system includes an inverter and the improvement further comprises:

means for storing parameters characteristic of differing lighting systems and for providing the stored parameters to the microprocessor for varying off time of the inverter, the microprocessor determining a desired off time based on the lighting system with which the diagnostic system is operated.

20. In the emergency lighting system of claim 13 wherein the parameter storage means comprises an EEPROM.

21. In the emergency lighting system of claim 20 wherein the EEPROM records an activity log for field return diagnosis to allow a precise evaluation of field returns necessary to quantify operating conditions and to facilitate failure analysis.

22. In the emergency lighting system of claim 20 wherein the EEPROM stores configuration parameters for control of lighting system operation and system configuration.

23. In the emergency lighting system of claim 1 wherein the lighting system includes a current controller operable to control current to the battery during charging of the battery and a circuit for sensing utility power, the microprocessor comprising means for monitoring and controlling operation of the battery charger;

means for monitoring and controlling operation of the controller circuit and means for monitoring and controlling operation of the utility power sensing circuit.

24. In the emergency lighting system of claim 1 wherein the lamp comprises an array of light emitting diodes.

25. In the emergency lighting system of claim 1 wherein the battery comprises at least one nickel/cadmium cell.

26. In the emergency lighting system of claim 1 wherein the improvement further comprises an EEPROM and a two-wire serial data interface between the microprocessor and the EEPROM.

27. In the emergency lighting system of claim 1 wherein the lamp comprises a DC incandescent lamp.

28. In an emergency lighting system operable in an emergency mode to energize at least one lamp from emergency power provided by a battery on sensing of discontinuation of utility power to the lighting system and having a diagnostic system capable of performing self-diagnostic and/or self-test functions indicative of the operational state of the emergency lighting system, the diagnostic system including at least one microprocessor and a boost converter having a boost switch, a method for controlling battery drain rate comprising the steps of:

monitoring boost converter current;

generating a reference voltage proportional to boost converter currant;

generating a feedback signal on sensing of a boost converter current sufficient to produce a voltage of a predetermined level greater than the reference voltage;

feeding the feedback signal to the microprocessor; and

,

altering the status of the boost switch through control by the microprocessor to cause energy in the boost converter circuit to be delivered to the lamp to complete a switching cycle of the boost switch.