Abstract:
A safety flashing detector that suitably detects unintentional flashing of the LED light engine in a traffic lamp is provided. The LED light engine may flash unintentionally when there are failures (hardware or software) inside a traffic lamp. In certain embodiments, unintentional flashing may be detected using a current sensor. If unintentional flashing is detected, the flashing detector may activate and shut down the LED light engine to remove the hazardous failure and eventually triggers the fuse blowout circuit. Hardware circuitry is suitably employed for both reliability and safety purposes, but software may also be employed.

Description:
BACKGROUND 
     The present exemplary embodiments relate generally to signal lighting. They find particular application in conjunction with Light Emitting Diode (LED) traffic lamps, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiments are also amenable to other like applications. 
     Traffic signals are typically disposed along roads to control the flow of traffic and/or make intersections more visible. Traffic signals may also be employed to provide warning to motorists, such as at railroad crossings. Traffic signals may include one or more traffic lamps, each having one or more light sources, such as LEDs, disposed therein. Typical colors used in traffic lamps include red, yellow and green. 
     One problem with traditional LED traffic lamps is that it is generally difficult to diagnosis failures. Namely, some failures may occur due to faults in the operating parameters of traffic lamps. There are some failure modes within a traffic signal that can create unsafe situations for the traffic system. One such failure mode is when the signal is flashing, but it should be ON or OFF continuously. 
     The present disclosure contemplates new and improved systems and/or methods for remedying this and other problems. 
     BRIEF DESCRIPTION 
     Various details of the present disclosure are hereinafter summarized to provide a basic understanding. This summary is not an extensive overview of the disclosure and is intended neither to identify certain elements of the disclosure, nor to delineate the scope thereof. Rather, the primary purpose of the summary is to present certain concepts of the disclosure in a simplified form prior to the more detailed description that is presented hereinafter. 
     In one embodiment, an LED traffic lamp is provided. The LED traffic lamp generally includes at least one LED light engine that generates light for the traffic lamp and an LED current sense circuit. The LED current sense circuit may be configured to monitor the current through the LED light engine and feed one or more output signals to a safety flashing detector and/or a fuse blow out circuit. The safety flashing detector may be configured to detect one or more abnormal fluctuations in the LED light engine current and/or frequency when such current and/or frequency should be steady at a predetermined threshold and to shut down the LED light engine. 
     In another embodiment, an LED traffic lamp is provided. The LED traffic lamp generally includes at least one LED light engine that generates light for the traffic lamp and an LED voltage control circuit. The LED voltage control circuit may be configured to control the power to the LED light engine to ensure proper operation of the traffic lamp where the traffic lamp is ON when it should be ON, OFF when it should be OFF and/or steady when it should be steady and wherein when unintentional flashing and/or failures within the traffic lamp lead to a wrong signal state. The LED voltage control circuit may be further configured to turn OFF the LED light engine and place the traffic lamp in a safe state. 
     In yet another embodiment, an LED traffic lamp is provided. The LED traffic lamp generally includes at least one LED light engine that generates light for the traffic lamp and an LED current sense circuit. The LED current sense circuit may be configured to monitor the current through the LED light engine and feed one or more output signals to a safety flashing detector and/or a fuse blow out circuit. The safety flashing detector may be configured to detect one or more abnormal fluctuations in the LED light engine current and/or frequency when such current and/or frequency should be steady at a predetermined threshold and to shut down the LED light engine. The LED traffic lamp may also include at least one LED light engine that generates light for the traffic lamp and an LED voltage control circuit. The LED voltage control circuit may be configured to control the power to the LED light engine to ensure proper operation of the traffic lamp where the traffic lamp is ON when it should be ON, OFF when it should be OFF and/or steady when it should be steady and wherein when unintentional flashing and/or failures within the traffic lamp lead to a wrong signal state. The LED voltage control circuit may be further configured to turn OFF the LED light engine and place the traffic lamp in a safe state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following description and drawings set forth certain illustrative implementations of the disclosure in detail, which are indicative of several exemplary ways in which the various principles of the disclosure may be carried out. The illustrative examples, however, are not exhaustive of the many possible embodiments of the disclosure. Other objects, advantages and novel features of the disclosure will be set forth in the following detailed description of the disclosure when considered in conjunction with the drawings, in which: 
         FIG. 1  is a perspective view of a traffic lamp; 
         FIG. 2  is a block diagram of the electronics for the traffic lamp, incorporating a safety flashing detector according to aspects of the present disclosure; 
         FIG. 3  is a block diagram of the safety flashing detector according to aspects of the present disclosure; 
         FIG. 4  is a block diagram of the flashing detector clock source according to aspects of the present disclosure; and 
         FIG. 5  is a block diagram of the flashing detector clock enable according to aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     One or more embodiments or implementations are hereinafter described in conjunction with the drawings, where like reference numerals are used to refer to like elements throughout, and where the various features are not necessarily drawn to scale. 
     With reference to  FIG. 1 , an illustrative embodiment of a tramp lamp  100  according aspects of the present disclosure is provided. The illustrated traffic lamp  100  is typical of what one would find overhanging an intersection. Other embodiments of the traffic lamp  100  are, however, contemplated. The traffic lamp  100  includes a housing  101  and one or more connectors  102 . The connectors  102  are provisioned to receive electrical power and, in certain embodiments, control commands from an external source (not shown), such as a traffic controller. Disposed within the housing  101 , the traffic lamp  100  includes traffic lamp electronics (shown in  FIG. 2  as reference numeral  103 ) for monitoring operating parameters. 
     With reference to  FIG. 2 , the traffic lamp electronics  103  is shown. The traffic lamp electronics  103  generally consists of an input stage  104 , a power stage  106 , a control stage  108 , a number of onboard accessories such as one or more sensors  110 , memory  112 , and one or more options boards  114 , one or more LED drivers  116 , an LED light engine  118 , a number of hardware safety circuits such as a safety flashing detector  122 , an LED current sense circuit  124 , and fuse blowout (FBO) circuits  126 , and an LED voltage control circuit  128 . 
     The input stage  104  may receive power from an external power source and distribute the power to the constituent components of the traffic lamp electronics  103 . The input voltage to the input stage  104  is typically an alternating current (AC) voltage, but it is contemplated that the received input voltage may be a direct current (DC) voltage. Further, the input voltage typically ranges from 0V to 265V and/or the input frequency typically ranges from 0 Hz to 150 Hz, insofar as the received input voltage is AC. The input stage  104  may include one or more of high voltage surge protection, input fuse protection, electromagnetic interference (EMI) filters, a full wave bridge rectifier, and the like. In certain embodiments, the input stage  104  may include a power factor correcting power supply. 
     The power stage  106  takes the output from the full wave bridge rectifier (not shown) of the input stage  104  and converts it to a compatible DC level for the control stage  108 , the LED drivers  116 , and other constituent components of the traffic lamp electronics  103 . 
     The LED light engine  118  may generate light for the traffic lamp  100 . Suitably, the LED light engine  118  generally includes one or more LEDs. The LED light engine  118  may be selected to control Correlated Color Temperature (CCT), Color Rendering Index (CRI) and other like characteristics of light. In certain embodiments, the color of LED light engine  118  may be one or more of yellow, green and red. 
     The control stage  108  controls the LED drivers  116  with respect to turning the LED light engine  118  ON or OFF, as well as dimming the LED light engine  118  based on a set of parameters, such as input voltage amplitude, temperature, LED nominal current, dimming options, etc. Besides controlling the LED drivers  116  and the LED light engine  118 , the control stage  108  also has the capability of controlling auxiliary options boards. When necessary, the control stage  108  can disable the LED light engine  118  if it detects one or more failures in the traffic lamp electronics  103 , and the FBO circuits  126  will blow out the fuse. 
     The control stage  108  may further instruct the LED driver  116  as to the proper output current to provide to the LED light engine  118 , so as to account for degradation factors. Degradation factors relate to the light output of the LED light engine  118  and may include one or more of operating time of the LED light engine  118 , temperature inside the traffic lamp  100 , and the like. As to traffic controller dimming (when enabled), the light output of the LED light engine  118  may vary with the input voltage. The control stage  108  also monitors the traffic signal operating conditions (e.g., temperature, voltage, current, etc.), communicates with external devices (e.g., the memory  112 , the options boards  114 , and others), and performs any digital or analog functions within the traffic lamp electronics  103 . The control stage  108  may include a digital/electronic processor, such as a microprocessor, microcontroller, graphic processing unit (GPU), and the like. In such embodiments, the controller suitably executes instructions stored on a memory (not shown) in the traffic lamp electronics  103 . In other embodiments, the memory is local to the control stage  108  and one of ROM, EPROM, EEPROM, Flash memory, and the like. 
     The sensors  110  generally measure one or more operating parameters, such as input voltage, input frequency, and the like, of the traffic lamp  100 . However, suitably the sensors  110  measure at least the operating (i.e., internal) temperature of the traffic lamp  100 . Temperature is an important operating parameter of the traffic lamp  100 . That is, temperature may affect the light output of the light sources  118 . In certain embodiments, the sensors  110  include one or more of passive and/or active electronic circuits, thermistors, temperature sensors, and the like. 
     The memory  112  generally stores data relating to LED degradation compensation. The memory  112  also contains the operating parameters of the traffic lamp  100  such as nominal LED current, dimming options, operating voltage, options boards, etc. The memory  112  can also be responsible for logging the conditions of the traffic lamp electronics  103 . 
     The options boards  114  suitably expand the functionality of the traffic lamp  100 . The options boards  114  may include the appropriate hardware to heat the traffic lamp  100 , simulate a dummy load, interface current pulsers with traffic controllers, and the like. However, other options boards are equally amenable. 
     The traffic lamp electronics  103  also includes hardware safety circuits external to the control stage  108  that protect the system when hazardous failures occur within the traffic lamp electronics  103 , such as failure(s) from the power stage  106 , the control stage  108 , the LED drivers  116 , the LED light engine  118  and/or the LED voltage control circuit  128 . In particular, the LED current sense  124  monitors the light engine conditions and feeds an output signal to the safety flashing detector  122  and/or the FBO circuits  126 . In one embodiment, the LED voltage control circuit  128  may be configured to control the power to the LED light engine  118  to ensure proper operation of the traffic lamp  100  where the traffic lamp  100  is ON when it should be ON, OFF when it should be OFF and/or steady when it should be steady. Thus, when unintentional flashing and/or failures within the traffic lamp  100  lead to a wrong signal state, the LED voltage control circuit  128  may turn OFF the LED light engine  118  and place the traffic lamp  100  in a “safe” state. 
     In operation, the safety flashing detector  122  may detect one or more abnormal fluctuations in the LED current and/or frequency when such current and/or frequency should be steady. In that case, the safety flashing detector  122  may turn off the LED voltage control circuit  128  so as to disable the power path to the LEDs and thus shut down the LED light engine  118 . Such action will generally have the effect of stopping the current from flowing through the LEDs and thus preventing the traffic lamp  100  from flashing when it should be continuously ON or OFF. Thus, it is important to be sure the fluctuation in the current is real before the deactivation of the LED light engine  118  process starts. 
     The FBO circuits  126  typically blow out the input fuse and permanently disconnect the traffic lamp  100  from the traffic controller if there is no more current flow through the LED light engine  118 , when the input voltage is within its normal operating range. 
     The control stage  108  directly controls the current level in the LED light engine  118  through the LED drivers  116 . If there are failures in the software or internal hardware of the control stage  108  and/or the LED drivers  116  such that the LED current fluctuates at a low frequency, the traffic lamp  100  may become a flashing signal when it should be continuously ON. The flashing detector  122  may remove this condition if it ever occurs and place the traffic lamp  100  in a safe state. 
     With reference now to  FIG. 3 , the safety flashing detector  122  for a traffic lamp is shown in greater detail. The safety flashing detector  122  for a traffic lamp generally comprises a digital device such as a flashing monitor  302 , a reset circuit  304 , a clock source  306 , a clock enable circuit  308 , and an LED light engine power control circuit  310 . 
     The digital device  302  generally comprises a microcontroller, a counter, and/or a divider. The digital device  302  may be described as the heart of the flashing detector  122 . It generally monitors the amplitude and/or frequency of the light engine current  314  as received from the LED current sense circuit  124 , disables the power path to the LED light engine  118  to turn OFF the LED light engine when abnormal fluctuations in the LED current  314  are detected. 
     The reset circuit  304  is a power-on reset, which acts as an input to the digital device  302  to initialize and ensure proper operation at power up. That is, the supply voltage (e.g., 5V) is the input signal to the reset circuitry. 
     In one embodiment, the digital device  302  comprises a decade counter. A decade counter (or mod-counter) is one that counts in decimal digits, rather than binary. A decade counter may have each digit binary encoded (that is, it may count in binary-coded decimal) or other binary encodings. The reset signal ensures a high output level on Q 0  or the first count of the decade counter. 
     In another embodiment, the digital device  302  comprises a microcontroller  302 . In that case, the power-on reset signal ensures proper hardware and software initialization for the microcontroller at power up. 
     The clock source  306  typically converts the LED current  214  into a digital clock for the digital device  302 . As shown in  FIG. 4 , the clock source  306  typically includes an amplitude/frequency monitor circuit  402  and a level shifter circuit  404 . The amplitude/frequency monitor circuit helps to ensure that the correct LED current level and/or frequency is met before producing an output signal. The level shifter circuit  404  takes the output signal from the amplitude/frequency monitor circuit  402  and translates the higher amplitudes to a compatible voltage level that is safe for the digital device  302  (e.g., 5V). The frequency from the LED current sense circuit  124  is directly proportional to the clock signal that feeds the digital device  302 . When the LED light engine current amplitude and/or frequency fluctuates below a predetermined threshold (e.g., 50 mA in amplitude, 120 Hz in frequency), the digital device  302  initiates the flashing detection process based on the “flashing” frequency of the faulty traffic signal. 
     With reference to  FIG. 5 , when powered up, a clock enable conditioning circuit  408  may select the default clock enable circuit  308  to allow the digital device  302  to advance to the next output from Q 0  (Q 1 , Q 2  . . . etc) on the rising and/or falling edge of the clock signal. When the “flashing detection” output (e.g., Q 4 ) from the digital device  302  is active, a clock deactivation circuit  406  may take over and deactivate the clock enable signal through the clock conditioning circuit  408 . The digital device  302  may hold its last output level permanently regardless of the clock input. To avoid random noise pickup and to reduce the sensitivity of the system, a predetermined number of flashes (e.g., 2 flashes) may be allowed before the digital device  302  enable the clock deactivation circuit  406  to disable the clock enable signal input to the digital device  302  and “latch” the flashing detection output (i.e., output Q 4 ) of the digital device  302  permanently. A latch is an example of a bi-stable multi-vibrator, that is, a device with exactly two stable states. These states are high-output and low-output. A latch has a feedback path, so information can be retained by the device. Therefore, latches can be memory devices, and can store one bit of data for as long as the device is powered. As the name suggests, latches are used to “latch onto” information and hold in place. 
     Once the digital device output is latched, the flashing detection output (Q 4 ) signal from the digital device  302  deactivates the power path to the LED light engine  118  through the light engine power control  310 . When the power path of the LED light engine  118  is disabled, current will stop flowing into the LEDs, whereby the LED light engine  118  will turn OFF. Once the LED light engine is OFF, the FBO circuits  126  will activate and blow out the input fuse. 
     The disclosure has been made with reference to preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the preferred embodiments be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.