Abstract:
The inventive signal incorporates an intelligent diagnosis module inside a light emitting diode (LED) signal, such as an LED traffic signal. The inventive signal can self-extinguish or send a signal through its communication port at the end of its useful life when the LEDs are no longer providing the required light output. Additionally, the inventive signal sends a signal to increase the current as the LEDs degrade to ensure the light output is above a threshold minimum.

Description:
This application is a CIP of U.S. application Ser. No. 10/762,743 filed 22 Jan. 2004 now abandoned entitled Intelligent LED Traffic Signal Modules that claimed the benefit of U.S. Provisional Application No. 60/442,082 filed 23 Jan. 2003. 

   BACKGROUND OF THE INVENTION 
   The present invention related to LED traffic signals. More particularly, it relates to an intelligent self-diagnosing traffic signal that identifies the end of the useful life of the signal. 
   1. Field of the Invention 
   2. Description of Related Art 
   Light Emitting Diodes (LEDs) traffic signals usage is wide spread. LEDs offer interesting advantages over incandescent lights. Those advantages include, for example, low power consumption and long life. 
   While LEDs last for a very long time (typical meantime between failure or MTBF is in the millions of hours), their light output intensity degrades over time. Manufacturers generally warranty their LED products for a certain period of time (typically 5 years). Depending on the operating conditions, including ambient temperature and signal duty cycle, the signal light output might be satisfactory for a period exceeding the warranty period. Users would like to use the LED signal until it reaches the end of its useful life; however because faulty traffic signals can result in an unsafe road condition, signals are required to have sufficient light output. One approach is to replace all signals upon warranty expiration. However, this results in signals being replaced while there is still significant useful life left in them. Another approach is to have the lamp measured in a lab at and/or after warranty expiration to assess the signal&#39;s condition. This only provides information at a particular moment in time and does not provide on-going data about the condition of the lamp. There is a need for an intellig3ent self-diagnosing traffic signal that allows users to make use of the long life of the LEDs without compromising safety. 
   U.S. application Ser. No. 10/762,743 is herein incorporated in its entirety. The LED signal has a communication link with a traffic controller. It receives commands and provides feedback information to the traffic controller. In the present invention, the signal is a stand-alone system. The traffic controller feeds voltage, but the signal does not have any additional interface with it. 
   U.S. Pat. No. 6,667,623 is also incorporated in its entirety. A system to monitor light output degradation is disclosed. The invention in U.S. Pat. No. 6,667,623 uses a light sensor to detect end of life. The proposed invention compiles a database of the various parameters (temperature, hours of operation, light output etc) in order to more accurately assess the signal&#39;s end of life and adjust the LED current to extend the signal&#39;s life. 
   A prior art method to change the LED current in response to a sensor&#39;s output uses a variable load in parallel with the LEDs. In the present invention, there is no variable load; current is directly adjusted by the power supply. One prior art signal utilizes a compensation circuit based on light output feedback from a photosensor. The present invention uses the photosensor feedback primarily in order to detect end of life of the signal and to compensate light output by increasing LED current as long as it is in the permissible range in order to extend the signal&#39;s life. The present invention also has communication capabilities. 
   An alternative prior art method senses the light output of an extra LED and adjusting the power supply according to the light output generated by the extra LED. The present invention measures the light output for the complete array, calculates the number of hours of operation and determine end of life. 
   A prior art system predicts when light output will fall under predetermined threshold. The present invention does not predict but actually shuts down the signals or send an EOL signal when the signal has reached the end of its useful life. 
   SUMMARY OF THE INVENTION 
   The inventive signal addresses the problem of users being unable to fully take advantage of the longer LED life. The inventive signal comprises an intelligent diagnosis system inside the LED signal. The signal can self-extinguish or send a signal through its communication port at the end of its useful life when the LEDs are no longer providing the required light output. The inventive signal also utilizes the fact that LEDs put out more light and need less current at the beginning of their life than they do as they degrade over time. Over time, the LEDs need more current to maintain a given light output as they age. The control module in the LED signal provides a signal that increases the current so that the LED signal can continue to provide sufficient light output. 
   In the present invention, the LED signal is a stand-alone system. Voltage is still fed by the traffic controller, but the signal does not have any further interface with it. The inventive signal compiles a database of various parameters, such as temperature, hours of operation, light output etc. in order to accurately assess the signal&#39;s end of life and adjust the LED current to extend the signal&#39;s life. 
   The inventive signal uses a photosensor feedback primarily in order to detect end of life of the signal and to compensate for light output degradation by increasing LED current in order to extend the signal&#39;s life. The present invention preferably also has communication capabilities. The inventive signal measures the light output for the complete array, calculates the number of hours of operation and uses the measured data to determine end of life for the signal. The present invention does not predict the end of life, but actually shuts down the signals or send an EOL signal when the signal has reached the end of its useful life. 
   The inventive signal addresses the need to utilize the LED signal for its full useful life without sacrificing safety by incorporating intelligent diagnosis system inside the LED signal. The signal can self-extinguish or send a signal through its communication port at the end of its useful life when the LEDs are no longer providing the required light output. This invention will also take advantage of the fact that LEDs put out more light at the beginning of their lifer and need less current. They will need more current to maintain a given light output as they age. 
   In one aspect, an intelligent LED signal is illustrated. The intelligent LED signal includes a power supply, an LED array powered by the power supply, and a control module for controlling the signal wherein the control module is adapted to receive LED data and to generate control signals. The intelligent LED signal includes at least one LED data sensor that measures LED data. The at least one LED data sensor is a voltage sensor, a current sensor, a thermal sensor, a photosensor and/or a timer, and the LED data includes an input voltage, a temperature, an output current, a light output, an average input voltage, an average temperature, hours of operation of the LED array, and/or a lamp (or LED array) ID. In addition, the signal has a signal ID. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
       FIG. 1  is a block diagram of the inventive signal. 
       FIG. 2  is a schematic of the inventive control module. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The inventive signal is an LED signal, preferably an LED traffic signal, with a control module to measure traffic signal data and using that data determine the useful life of the Led signal. 
     FIG. 1  is a block diagram of the LED traffic signal module  10 . LED traffic signal module  10  comprises a power supply  12  regulating current through an LED array  14 . The module further comprises a control module  20  inside the LED signal  10 . Control module  20  performs all the checks, diagnosis and communication functions. An optional portable receiver  16  is to be used by authorized personnel in order to check the lamp status. Control module  20  has a communication link  18  allowing it to communicate with receiver  16 . Receiver  16  preferably has a display. Optionally, receiver  16  can have a speaker or other broadcast capabilities. Receiver  16  can be provided with memory allowing data to be stored and later downloaded in a central location. Display can display one or more pieces of data. Preferably, the display shows Lamp ID  42 , light output status  52  and number of hours of operation  48 . 
   Control module  20  is shown in  FIG. 2 . Microcontroller  30  samples at a first predetermined rate input voltage  32  and ambient temperature  34  and will compile average input voltage  44 , average ambient temperature  46  and number of hours of operation  48 . Microcontroller  30  also samples at a second predetermined rate output current  36  and light output  38 . Light output  38  is measured by photo sensor or photo diode receiving light from the LED array  14  either directly or indirectly through some other light-collecting device. 
   Lamp data  32 ,  34 ,  36 ,  38  will be compiled in a table. Light output status  52  is determined using the lamp data  32 ,  34 ,  36  and  38 . If light output cannot be maintained any more, the LED signal  10  either self-terminates  66  or sends an end-of-life signal  62 . An example is given in Table 1. 
   Lamp ID  42  is an identification given to the lamp  14  for communication purposes. Average input voltage  44  is the average line voltage  32  supplied to the lamp. The input voltage  32  is sampled and average input voltage  44  is calculated and stored in the database or flash memory  40 . Average ambient temperature  46  is the temperature seen by the LEDs  14  inside the signal module  10 . A thermal sensor is fitted on the power supply PCB or on the LEDs PCB and an average temperature  46  is calculated throughout the signal&#39;s life. The number of hours of operation  48  is the number of hours of service for the LED array  14 . A counter is incremented to keep track of the signal&#39;s life. Output current  36  and light output  38  are compiled over time. Output current  36  is obtained by sampling the LED current and storing the data at a fixed interval. Light output  38  is obtained by sampling the light output with a photo sensor receiving light from the LEDs either directly or indirectly through some other light-collecting device. 
   The end of life (EOL) signal  62  is derived by comparing the measured light output  38  sensor with a reference level. The reference level may be set by government regulation, the signals environment or be based on other factors. If light output  36  is lower than the reference level and if output current  36  cannot be adjusted anymore to and if number of hours of operation  48  at the average temperature  46  is higher than the minimum number of hours for a given average temperature, then EOL  62  is enabled. The EOL signal  62  activates an EOL circuit that shuts the signal or sends an EOL signal to receiver  16 , traffic controller or other location or device. 
   If the light output  38  has fallen below the reference level and output current  36  is below a maximum current, output current adjust  64  provides a signal that increases output current  36  to maintain a sufficient light output. The turn off signal  66  turns the signal off if input voltage is under 35V. 
   Table 1 lists exemplary sampling and refresh rates and operational parameters for the inventive self-diagnosing signal. The sampling rates, refresh rates, and other operational parameters may be selected based on lamp color and/or application. The measured and calculated data is stored in the memory  40  of control module  20 . Lamp ID  42  is preferably assigned at the factory. Input voltage  32  is measured more frequently than every 1 ms and average input voltage  44  is calculated. Ambient temperature  34  is measured more frequently than every 100 ms. Average ambient temperature  46  is calculated. An incremental timer keeps track of the number of hours of operation of the signal, the hours of operation is refreshed more frequently than every 1 ms. Output current  36  and light output  38  are measured after every 168 hours of operation. This LED signal data is used to determine whether to send and EOL signal  62 , output current adjust 64, and/or to send turn-off signal  66 . If the input voltage  32  is less than 35 V turn-off signal  66  is generated. If light output  38  is less than a minimum light output and output current  36  is less than a maximum current, an output current adjust signal  64  is generated. If the hours of operation  48  is greater than a calculated maximum number of hours and/or light output  38  is less than a minimum light output and current exceeds the maximum current, end of life signal  62  is generated. LED signal data including average temperature  46  are used to calculate the maximum number of hours. 
   
     
       
             
             
             
           
             
             
             
             
           
             
             
             
           
         
             
               TABLE 1 
             
             
                 
             
           
           
             
                 
               Sampling 
                 
             
             
               Variable 
               Rate 
               Method of Determination 
             
             
                 
             
             
               Lamp ID 
               n/a 
               Factory assigned 
             
           
        
         
             
               Average Input 
               &lt;1 
               ms 
               Average of samples of Input 
             
             
               Voltage 
                 
                 
               Voltage 
             
             
               Average Ambient 
               &lt;100 
               ms 
               Average of samples of Ambient 
             
             
               Temperature 
                 
                 
               Temperature 
             
             
               Number of hours of 
               &lt;1 
               ms 
               Increment timer 
             
             
               operation 
             
             
               Output Current 
               168 
               hours 
               Each sample of output current 
             
             
                 
                 
                 
               stored in a Table 
             
             
               Light Output 
               168 
               hours 
               Each sample of light sensor 
             
             
                 
                 
                 
               stored in a Table 
             
             
                 
             
           
        
         
             
                 
               Refresh 
                 
             
             
               Control variables 
               Rate 
               Method of Determination 
             
             
                 
             
             
               End of Life signal 
               168 hours 
               If (nb of h &gt; (Max h = 
             
             
               (EOL) 
                 
               f(Avg T))) AND 
             
             
                 
                 
               (Light Output &lt; Min) 
             
             
                 
                 
               THEN EOL 
             
             
               Output Current 
               168 hours 
               If (Light Output &lt; Min) AND 
             
             
               Adjust 
                 
               (I &lt; Imax) THEN (Increment I) 
             
             
               Turn-off 
               n/a 
               If Vin &lt; 35 V 
             
             
                 
             
           
        
       
     
   
   As the LEDs degrade, the control module in the LED signal provides an output current adjust signal  64  to increase the current so that the LED signal can continue to provide sufficient light output. Once the current no longer be increased, the inventive signal self-extinguishes or sends a EOL signal  62  through its communication port at the end of its useful life when the LEDs are no longer providing the required light output. 
   In the present invention, the LED signal is preferably a stand-alone system. Voltage is fed by the traffic controller, but the signal does not have any further interface with it. The inventive signal stores the various measured and calculated parameters preferably in a database to accurately assess the signal&#39;s end of life and adjust the LED current to extend the signal&#39;s life.