Patent Application
20140097761
The present invention relates to lighting, and more specifically, to solid state light sources.
A typical solid state light engine includes one or more solid state light sources (such as but not limited to light emitting diodes (LEDs), organic light emitting diodes (OLEDs), polymer light emitting diodes (PLEDs), and/or any other semiconductor device that emits light (whether in the visible spectrum or not), and/or combinations thereof, whether connected in series, parallel, and/or combinations thereof, whether formed of one or more individual semiconductor dies, one or more chips, one or more packages, and/or combinations thereof.) driven by a driver circuit. Some driver circuits output a constant current drive signal. The solid state light sources may be configured in any number of ways, such as but not limited to parallel strings of series-connected solid state light sources. The driver circuit then generates an output voltage Vout across each of the parallel strings. The value of the output voltage may depend on the current level and the number of solid state light sources in each string.
Any individual solid state light source may fail at some point and that failure may result in an open circuit condition or a short circuit condition at that location in the circuit. Such failures may cause excess current to be diverted to the other solid state light sources and/or cause voltage surges in the light engine, which may in turn shorten the life of the remaining solid state light sources and/or the entire light engine, or result in premature failure of the light engine or damage to the driver circuit.
Embodiments disclosed herein provide a driver circuit that is configured to provide a drive current to a light engine including one or more parallel strings of series-connected solid state light sources. The driver circuit and light engine may be included in a lamp assembly. A light engine controller circuit may be configured to monitor the output voltage generated by the driver circuit, which is applied across each of the strings, to detect voltage changes that may result from failure of one or more of the solid state light sources. In response to a detected voltage change, the light engine controller circuit may provide a feedback control signal to the driver circuit to reduce the drive current so that the output voltage returns to a nominal operating value.
In some embodiments, the light engine controller may signal a detected failure to a system controller that may be associated with multiple lamp assemblies, for example lamp assemblies located throughout a building or other facility. The light engine controller may also provide an identifier, or ID code, to the system controller so that the system controller can identify a lamp assembly (or light engine or string of solid state light sources) that needs to be replaced. The light engine controller (or driver circuit) may also monitor the ID code to determine when a replacement or repair has been performed so that the drive current may be restored to its original level.
In an embodiment, there is provided a system. The system includes: a light engine configured to emit light in response to a drive current, the light engine comprising a light engine controller circuit and one or more parallel strings of series-connected solid state light sources; and a driver circuit configured to provide the drive current; wherein the light engine controller circuit is configured to: monitor an output voltage of the driver circuit; detect a failure of one of the solid state light sources, the failure associated with a change in the output voltage of the driver circuit; and transmit a first signal to the driver circuit in response to detecting a failure, wherein the driver circuit is configured to decrease the drive current in response to the first signal.
In a related embodiment, the light engine controller circuit may be further configured to verify the detected failure by detecting a decrease in the output voltage to a pre-determined voltage range in response to the decrease in the drive current. In another related embodiment, the system may further include a system controller, and the system may be configured to report an error condition to the system controller, the error condition may be associated with the failure detection, and the system controller may be configured to monitor the system. In a further related embodiment, the light engine may further include a light engine identification circuit configured to identify the light engine via a light engine ID, wherein the reported error condition may include the light engine ID. In a further related embodiment, the light engine controller circuit may be further configured to detect a change in the light engine ID and to transmit a second signal to the driver circuit in response to the detected change in the light engine ID, wherein the driver circuit may be configured to increase the drive current in response to the second signal.
In another further related embodiment, the system may be further configured to communicate with the system controller over a communication path selected from the group consisting of a universal asynchronous receive transmit (UART) port, an inter-integrated circuit (I2C) bus, and a serial peripheral interface (SPI) bus.
In yet another related embodiment, the light engine controller circuit may be further configured to detect a rate of change of the output voltage, and in response to the rate of change exceeding a threshold, report an error condition to a system controller. In a further related embodiment, the light engine controller circuit may be further configured to, in response to the rate of change exceeding the threshold, transmit the first signal to the driver circuit. In another further related embodiment, the light engine controller circuit may be further configured to, in response to the rate of change exceeding the threshold, latch the system. In yet another further related embodiment, the driver circuit may be a switched mode power supply circuit.
In another embodiment, there is provided a method for failure detection and recovery of a lighting system. The method includes: monitoring an output voltage of a driver circuit configured to provide a drive current to a light engine, the light engine comprising one or more parallel strings of series-connected solid state light sources; detecting a failure of one of the solid state light sources, the failure associated with a change in the output voltage of the driver circuit; transmitting a first control signal to the driver circuit in response to the failure detection; and decreasing the drive current in response to the first control signal.
In a related embodiment, the method may further include verifying the detected failure by detecting a decrease in the output voltage to a pre-determined voltage range in response to the decrease in the drive current. In another related embodiment, the method may further include reporting an error condition to a system controller, the error condition associated with the failure detection, wherein the system controller may be configured to monitor the system. In a further related embodiment, the method may further include determining a light engine ID associated with the light engine and including the light engine ID in the error report. In a further related embodiment, the method may further include detecting a change in the light engine ID and transmitting a second control signal to the driver circuit in response to the detected light engine ID change, wherein the drive current may be increased in response to the second control signal.
In still another related embodiment, the method may further include detecting a rate of change of the output voltage, and in response to the rate of change exceeding a threshold, reporting an error condition to a system controller. In a further related embodiment, the method may further include transmitting the first control signal to the driver circuit in response to the rate of change exceeding the threshold. In another further related embodiment, the method may further include latching the system in response to the rate of change exceeding the threshold.
The foregoing and other objects, features and advantages disclosed herein will be apparent from the following description of particular embodiments disclosed herein, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles disclosed herein.
The driver circuit 102 and the light engine 104 may be, and in some embodiments are, positioned remotely from each other, e.g. in separate housings, or may be provided within the same lamp housing 106 of a lamp assembly 108. The lamp assembly 108 is configured to fit existing lighting fixtures configured to energize lamps including non-solid state light sources, e.g. fluorescent or gas-discharge sources. A lamp assembly 108 may be inserted directly into such a lighting fixture to operate on the AC input thereto.
The driver circuit 102 and the light engine 104 may be, and in some embodiments are, directly coupled by a communication path 114 for carrying communication signals according to a communication protocol. The communication path 114 may be, and in some embodiments is, a circuit configured to carry a feedback signal, such as, for example but not limited to, a pulse width modulation (PWM) signal to control a DC-DC converter in the driver circuit 102. In some embodiments, the communication path 114 and the communication protocol facilitate any suitable communication including bi-directional and full duplex communication between the driver circuit 102 and the light engine 104. The communication protocol may, and in some embodiments does, include message acknowledgements and/or error correction. Direct communication between the driver circuit 102 and the light engine 104 allows for the light engine 104 to request a change in the drive current Idrive to compensate for variations in the monitored output voltage Vout, which may result from failure of one or more solid state light sources in any of the strings of solid state light sources. The driver circuit 102 thus dynamically adjusts the drive current Idrive during operation of the light engine 104 to ensure that the light engine 104 continues to operate and provide light output 112. Such communication also allows the driver circuit 102 to request and receive information from the light engine 104, such as but not limited to light engine identification information.
An extension of the communication path 116 may be, and in some embodiments is, established between the driver circuit 102 and/or the light engine 104 and a system controller 110. The system controller 110 is configured to communicate directly with the driver circuit 102 and/or the light engine 104 to, for example, monitor the operational status or failure conditions of the lamp assembly 108. The system controller 110 may, and in some embodiments does, communicate with and monitor multiple lamp assemblies 108, for example, throughout a facility or building.
The input voltage Vin is coupled to the switching converter circuit 204, either directly or through the rectifier circuit 202 if the input voltage is an AC voltage. A variety of rectifier circuit configurations are well-known in the art. In some embodiments, for example, the rectifier circuit 202 includes a known diode bridge rectifier or H-bridge rectifier. The switching converter circuit 204 provides drive current Idrive to the light engine 104a. The switching converter circuit 204 may include any known switching regulator configuration, such as but not limited to a buck, boost, buck-boost, or flyback regulator, along with a known controller for controlling the switch within the regulator. A variety of controllers for controlling a switching regulator are well-known. In embodiments wherein the switching regulator configuration is a buck converter, for example, the controller may be a model number TPS40050 controller presently available from Texas Instruments Corporation of Dallas, Tex., USA. The switching converter circuit 204 may also include a known power factor correction (PFC) circuit configured to provide an output to the controller portion of the switching regulator, e.g. in response to a signal representative of the output of the rectifier circuit 202 and a feedback signal representative of the current through the light engine 104a.
The light engine 104a includes one or more parallel strings of series-connected solid state light sources 206a, 206b, . . . 206n and the light engine controller 208. The drive current Idrive provided by the switching converter circuit 204 is directed to the solid state light source strings 206a, 206b, . . . 206n, such that output voltage Vout is applied across each of the solid state light source strings 206a, 206b, . . . 206n causing the solid state light sources to emit light 112 (see
Table 1 below shows how the output voltage Vout measured across a string of solid state light sources may depend on the drive current through the string:
One or more solid state light sources in a string may eventually fail. For example,
The light engine controller 208 is configured to monitor the voltage across the strings Vout. In response to a detected voltage increase in the voltage across the strings Vout, the light engine controller 208 causes the switching converter circuit 204 to decrease the drive current Idrive, for example by transmitting a control signal over the communication path 114, or by any other suitable mechanism. In some embodiments, the light engine controller 208 causes the drive current Idrive to be reduced, for example in a continuous or a step-wise fashion, until the voltage across the strings Vout returns to a nominal operational value, for example the value prior to the failure. This approach may be particularly advantageous in situations where the arrangement and number of strings of solid state light sources is not known.
In some embodiments, the light engine controller 208 determines a drive current value that is predicted to return the voltage across the strings Vout to a nominal value based on an assumed failure of one of the strings (or of any given number of the strings) out of a known number of strings of solid state light sources. For example, if one of the three strings fails, as explained previously, the drive current in the remaining two strings may increase from one-third of the total drive current to one-half of the total drive current. Consequently, a 33% reduction in the drive current generated by the switching converter circuit 204 would be expected to restore the current in each string to the original (pre-failure) value and thus restore the voltage across the strings Vout to the corresponding pre-failure value. The light engine controller 208 transmits a control signal to the switching converter circuit 204 to cause the generated drive current to be reduced by the determined amount associated with the presumed failure of a given number of the strings. The light engine controller 208 then verifies the failure of that given number of strings by detecting that the output voltage has returned to a nominal operational (pre-failure) value.
In some embodiments, the light engine controller 208 determines a solid state light source failure associated with a failure mode that creates an open circuit condition at the failed solid state light source, by detecting a voltage drop in the output voltage Vout. In response to detection of a failure of one or more solid state light sources, the light engine controller 208 communicates a failure report, for example to the system controller 110a, which may be a local controller for one or more local lamp assemblies 108 or a global controller for lighting systems throughout a building or other facility. The system controller 110a may be, and in some embodiments is, configured to log failures, notify personnel, and schedule repair or replacement of failed components including the strings 206, the light engines 104 and/or the lamp assemblies 108. The light engine controller 208 is further configured to control the switching converter circuit 204 to maintain the adjusted drive current at an appropriate value, as explained above, until the detected failure condition is remedied, after which the nominal driver current may be restored.
The light engine identification (ID) circuit 210 is configured to identify the light engine 104, for example with a unique value or code (i.e., a light engine ID). The light engine ID is provided to, or read by, the system controller 110, for example to identify the status and location of the lamp assemblies and to guide maintenance in response to failure reports. The light engine ID may also be, and in some embodiments is, provided to, or read by, the light engine controller 208 to determine that a light engine or string has been replaced so that the drive current may be restored to a nominal value.
In some embodiments, the light engine ID circuit 210 is implemented as a microcontroller and/or EEPROM configured to store and report an ID value. In some embodiments, the light engine ID circuit 210 is a resistor, the value of which may be read, to represent one or more bits of information. The resistance value may also be changed, for example by the light engine controller 208, the system controller 110/110a, and/or the driver circuit 102, by the application of a current of sufficiently high value to cause the resistor to fail to an open circuit. This may be done to indicate a failure in the light engine 104. The resistor may be coupled to the system through a separate wire or may be coupled in parallel with one or more of the strings, in which case reading or writing the value of the resistor may be accomplished through the application of a voltage of opposite polarity across the string.
In some embodiments, the light engine controller 208 is configured to monitor the rate of change of the output voltage, d(Vout)/dt, and report a failure of a string, or other error condition, as previously described, in response to the rate of change of Vout exceeding a threshold. The threshold may be associated with or correspond to a failure in a given number of the strings. For example, a failure in a single string may not be a concern while a failure of five strings may be of sufficient concern to trigger an error condition. The light engine controller 208 may also be, and in some embodiments is, configured to initiate a safe-mode in response to the rate of change of Vout exceeding the threshold. The safe-mode may be associated with any or all of the following actions. The drive current may be reduced to a lower value. The drive current may be reduced until a nominal output voltage is reached. The lamp assembly may be shut down or latched.
Communication between elements of the system, including the light engine controller 208, the switching converter circuit 204, the system controller 110 and/or the light engine ID circuit 210 is achieved in any known way, such as but not limited to use of a universal asynchronous receive transmit (UART) port, an inter-integrated circuit (I2C) bus, and/or a serial peripheral interface (SPI) bus, among others. In some embodiments, for example, one or more communication controller circuits are employed, where each communication controller circuit is a known microcontroller having internal memory and a universal asynchronous receive transmit (UART) port. One example of a microcontroller useful as a communication controller circuit is a model number C20000 microcontroller presently available from Texas Instruments Corporation of Dallas, Tex., USA. The communication paths 114 and 116 of
Advantageously, therefore, real time communication between the light engine 104a and the driver circuit 102a allows the light engine 104a to request a modification of the drive current Idrive from the driver circuit 102a at any time during operation of the system 100a to thereby offset adverse effects arising from solid state light source failures and avoid premature failure of the remaining functional solid state light sources.
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Embodiments are not limited to power supplies that include a single output channel, but may be extended to multichannel power supplies. Embodiments may function with any number of strings connected in parallel, with each string having any number of solid state light sources. Further, in some embodiments, a string itself may include two or more sub-strings connected in parallel. Of course, the verification method described above would need to be adjusted for sub-strings, such that the current through each sub-string would need to be regulated appropriately to determine if a sub-string included the failed solid state light source(s).
The methods and systems described herein are not limited to a particular hardware or software configuration, and may find applicability in many computing or processing environments. The methods and systems may be implemented in hardware or software, or a combination of hardware and software. The methods and systems may be implemented in one or more computer programs, where a computer program may be understood to include one or more processor executable instructions. The computer program(s) may execute on one or more programmable processors, and may be stored on one or more storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), one or more input devices, and/or one or more output devices. The processor thus may access one or more input devices to obtain input data, and may access one or more output devices to communicate output data. The input and/or output devices may include one or more of the following: Random Access Memory (RAM), Redundant Array of Independent Disks (RAID), floppy drive, CD, DVD, magnetic disk, internal hard drive, external hard drive, memory stick, or other storage device capable of being accessed by a processor as provided herein, where such aforementioned examples are not exhaustive, and are for illustration and not limitation.
The computer program(s) may be implemented using one or more high level procedural or object-oriented programming languages to communicate with a computer system; however, the program(s) may be implemented in assembly or machine language, if desired. The language may be compiled or interpreted.
As provided herein, the processor(s) may thus be embedded in one or more devices that may be operated independently or together in a networked environment, where the network may include, for example, a Local Area Network (LAN), wide area network (WAN), and/or may include an intranet and/or the internet and/or another network. The network(s) may be wired or wireless or a combination thereof and may use one or more communications protocols to facilitate communications between the different processors. The processors may be configured for distributed processing and may utilize, in some embodiments, a client-server model as needed. Accordingly, the methods and systems may utilize multiple processors and/or processor devices, and the processor instructions may be divided amongst such single- or multiple-processor/ devices.
The device(s) or computer systems that integrate with the processor(s) may include, for example, a personal computer(s), workstation(s) (e.g., Sun, HP), personal digital assistant(s) (PDA(s)), handheld device(s) such as cellular telephone(s) or smart cellphone(s), laptop(s), handheld computer(s), or another device(s) capable of being integrated with a processor(s) that may operate as provided herein. Accordingly, the devices provided herein are not exhaustive and are provided for illustration and not limitation.
References to “a microprocessor” and “a processor”, or “the microprocessor” and “the processor,” may be understood to include one or more microprocessors that may communicate in a stand-alone and/or a distributed environment(s), and may thus be configured to communicate via wired or wireless communications with other processors, where such one or more processor may be configured to operate on one or more processor-controlled devices that may be similar or different devices. Use of such “microprocessor” or “processor” terminology may thus also be understood to include a central processing unit, an arithmetic logic unit, an application-specific integrated circuit (IC), and/or a task engine, with such examples provided for illustration and not limitation.
Furthermore, references to memory, unless otherwise specified, may include one or more processor-readable and accessible memory elements and/or components that may be internal to the processor-controlled device, external to the processor-controlled device, and/or may be accessed via a wired or wireless network using a variety of communications protocols, and unless otherwise specified, may be arranged to include a combination of external and internal memory devices, where such memory may be contiguous and/or partitioned based on the application. Accordingly, references to a database may be understood to include one or more memory associations, where such references may include commercially available database products (e.g., SQL, Informix, Oracle) and also proprietary databases, and may also include other structures for associating memory such as links, queues, graphs, trees, with such structures provided for illustration and not limitation.
References to a network, unless provided otherwise, may include one or more intranets and/or the internet. References herein to microprocessor instructions or microprocessor-executable instructions, in accordance with the above, may be understood to include programmable hardware.
Unless otherwise stated, use of the word “substantially” may be construed to include a precise relationship, condition, arrangement, orientation, and/or other characteristic, and deviations thereof as understood by one of ordinary skill in the art, to the extent that such deviations do not materially affect the disclosed methods and systems.
Throughout the entirety of the present disclosure, use of the articles “a” and/or “an” and/or “the” to modify a noun may be understood to be used for convenience and to include one, or more than one, of the modified noun, unless otherwise specifically stated. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
Elements, components, modules, and/or parts thereof that are described and/or otherwise portrayed through the figures to communicate with, be associated with, and/or be based on, something else, may be understood to so communicate, be associated with, and or be based on in a direct and/or indirect manner, unless otherwise stipulated herein.
Although the methods and systems have been described relative to a specific embodiment thereof, they are not so limited. Obviously many modifications and variations may become apparent in light of the above teachings. Many additional changes in the details, materials, and arrangement of parts, herein described and illustrated, may be made by those skilled in the art.
The present application claims priority of U.S. Provisional Application Ser. No. 61/709,869, filed Oct. 4, 2012 and entitled “SOLID STATE LIGHT SOURCE MODULE FAILURE DETECTION”, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61709869 | Oct 2012 | US |
