Automatic power control unit for multiple lighting arrays

Abstract

A system for operating one or more light-emitting devices, comprising: an illumination array (20, 20A, 20B, 20C) consisting of at least one light-emitting device (110); at least two negative temperature coefficient devices (314, 316, 318) in thermal communication with the illumination array (20, 20A, 20B, 20C); and an operational amplifier (222, 302) having a negative feedback loop (350), wherein the at least two negative temperature coefficient type devices (314, 316, 318) are electrically coupled in parallel and are included in the negative feedback loop (350), the system further comprising two fixed value resistors (310, 312) in the negative feedback loop (350), and wherein a first of the two fixed value resistors (310, 312) is in direct electrical connection with an inverting input (303) of the amplifier (222, 302) and an output (305) of the amplifier (222, 302), and wherein a second of the two fixed value resistors (310, 312) is connected to the first of the two fixed value resistors (310, 312), the inverting input of the amplifier (222, 302), and the at least two negative temperature coefficient type devices (314, 316, 318) are in direct electrical connection.

Description

BACKGROUND / SUMMARY

[0001] A photoreactive system may include a solid-state illumination array for curing photosensitive media such as coatings, including inks, adhesives, preservatives, etc. The curing time of these photosensitive media may respond to the irradiance of the solid-state illumination array. Furthermore, the irradiance of a solid-state illumination array may be affected by temperatures of solid-state illumination devices that comprise the solid-state illumination array. Therefore, if the solid-state illumination devices operate at temperatures outside their rated operating temperature, photosensitive media may not cure sufficiently, or electrical power consumption may increase due to changes in the irradiance levels of the solid-state illumination devices.Additionally, the solid-state lighting devices may be thermally coupled to a heat sink to control the temperature of the solid-state lighting devices. However, the heat sink may have multiple temperature zones whose temperatures vary relative to other temperature zones of the heat sink. Consequently, some solid-state lighting devices in the solid-state lighting array may operate at different temperatures than other solid-state lighting devices in the solid-state lighting array. As a result, the irradiance of one region of the lighting array may vary more than desired relative to the irradiance of another region of the lighting array, particularly when the lighting arrays are operated independently.

[0002] DE 10 2013 221 033 A1 and US 2012 / 0306 370 A1 both disclose systems for operating one or more light-emitting devices comprising independently controlled illumination arrays. Temperature-dependent control of the light sources is achieved using so-called NTCs.

[0003] The present inventor has recognized the aforementioned disadvantages and developed a system for operating one or more light-emitting devices, characterized by the features of claim 1. The system comprises: at least two independently controlled illumination arrays consisting of at least one light-emitting device; and an amplifier with a negative feedback loop, wherein at least two negative temperature coefficient devices are electrically coupled in parallel and included in the negative feedback loop, wherein each of the at least two negative temperature coefficient devices is in thermal communication with one of the at least two independently controlled illumination arrays.

[0004] By electrically coupling two or more negative temperature coefficient type devices in parallel in a negative feedback loop of an amplifier that controls current flow through one or more light-emitting devices, it may be possible to control the irradiance of two or more illumination arrays in a photoreactive system with a single amplifier.The inventor has recognized that a negative temperature coefficient device in a parallel electrical circuit with other negative temperature coefficient devices may dominate in determining the gain, such that when one illumination array monitored by the one negative temperature coefficient device is active while other illumination arrays monitored by other negative temperature coefficient devices are inactive, the gain may be more influenced by the one negative temperature coefficient device than by the other negative temperature coefficient devices in the parallel electrical circuit. Consequently, the gain may be appropriate for the activated illumination array monitored by the one negative temperature coefficient device.In one example, two or more negative temperature coefficient devices are thermally coupled to two or more illumination arrays via a heat sink. The temperatures sensed at the heat sink by the two or more negative temperature coefficient devices provide temperature feedback to the amplifier for each illumination array, allowing the radiation from each illumination array to be controlled to provide a desired irradiance level for the photoreactive system.

[0005] The present description can offer several advantages. Specifically, the approach can improve the light intensity control of an illumination system. Additionally, the approach can provide control for more than two independently controlled illumination arrays using a single amplifier. Furthermore, the approach can provide more uniform curing of photosensitive media.

[0006] The foregoing advantages and other advantages and features of the present description will be readily apparent from the following detailed description taken alone or in conjunction with the accompanying drawings.

[0007] It should be understood that the foregoing summary is provided to introduce, in a simplified form, a selection of concepts further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is determined solely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that resolve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE CHARACTERS Fig. 1 shows a schematic representation of a lighting system; Fig. 2 and Fig. 3 shows circuit diagrams of an exemplary system for controlling radiation from lighting devices; Fig. Figure 4 shows a graphical representation of the gain for systems where one of three illumination arrays is activated and where three of three illumination arrays are activated; and Fig. Figure 5 shows an exemplary method for controlling radiation in a lighting system. DETAILED DESCRIPTION

[0008] The present description relates to a lighting system which emits a substantially constant irradiance value (e.g. + 5%). Fig. Figure 1 shows an exemplary illumination system that includes a single amplifier for controlling the irradiance of two or more independently controlled illumination arrays. The control of the illumination array's radiation can be achieved using the Fig. 2 and Fig. 3 shown exemplary circuits. The lighting system can be designed according to the graphical representations of Fig. 4 work. In Fig. Figure 5 shows a method of operating a lighting system to provide substantially constant radiation. Electrical connections provided between components in the various electrical circuit diagrams represent current paths between the illustrated devices.

[0009] With reference now to Fig. Figure 1 shows a block diagram of a photoreactive system 10 according to the system and method described herein. In this example, the photoreactive system 10 includes an illumination subsystem 100, a controller 108, a power source 102, and a cooling subsystem 18.

[0010] The illumination subsystem 100 may include a plurality of light-emitting devices 110. The light-emitting devices 110 may be, for example, LED devices. Selected ones of the plurality of light-emitting devices 110 are implemented to provide a radiant output 24. The radiant output 24 is directed toward a workpiece 26. Returned radiation 28 may be directed from the workpiece 26 (e.g., by reflecting the radiant output 24) back to the illumination subsystem 100.

[0011] The radiant power 24 may be directed to the workpiece 26 using coupling optics 30. The coupling optics 30 may be implemented in various ways when used. For example, the coupling optics may comprise one or more layers, materials, or other structures placed between the light-emitting devices 110 providing radiant power 24 and the workpiece 26. For example, the coupling optics 30 may comprise a microlens array to collect, focus, collimate, or otherwise improve the quality or effective size of the radiant power 24. As another example, the coupling optics 30 may comprise a microreflector array. Using such a microreflector array, each semiconductor device providing radiant power 24 may be arranged in a respective microreflector on a one-to-one basis.

[0012] Each of the layers, materials, or other structures may have a selected refractive index. By properly selecting each refractive index, reflection at interfaces between layers, materials, and other structures in the path of the radiant power 24 (and / or the returned radiation 28) can be selectively controlled. By controlling, for example, differences in such refractive indices at a selected interface disposed between the semiconductor devices and the workpiece 26, reflection at that interface can be reduced, eliminated, or minimized to enhance the transmission of radiant power at that interface for ultimate delivery to the workpiece 26.

[0013] The coupling optics 30 can be used for various purposes. Example purposes include, alone or in combination, protecting the light-emitting devices 110, retaining cooling fluid associated with the cooling subsystem 18, collecting, condensing, and / or collimating the radiant power 24, collecting, directing, or rejecting returning radiation 28, or for other purposes. As another example, the photoreactive system 10 can utilize the coupling optics 30 to improve the effective quality or magnitude of the radiant power 24, particularly when delivered to the workpiece 26.

[0014] Selected ones of the plurality of light-emitting devices 110 can be coupled to the controller 108 via coupling electronics 22 to provide data to the controller 108. As further described below, the controller 108 can also be implemented to control these data-providing semiconductor devices, e.g., via the coupling electronics 22.

[0015] The control unit 108 is preferably also connected to the power source 102 and the cooling subsystem 18 and implemented to control them. Furthermore, the control unit 108 can receive data from the power source 102 and the cooling subsystem 18.

[0016] The data received by controller 108 from one or more of power source 102, cooling subsystem 18, and illumination subsystem 100 may be of different types. For example, the data may be representative of one or more properties associated with respective coupled semiconductor devices 110. As another example, the data may be representative of one or more properties associated with the respective component 12, 102, 18 providing the data. As yet another example, the data may be representative of one or more properties associated with workpiece 26 (e.g., representative of the energy or spectral component(s) of the radiant power directed at the workpiece). Furthermore, the data may be representative of a combination of these properties.

[0017] The controller 108, upon receiving such data, may be implemented to respond to this data. For example, in response to such data from such a component, the controller 108 may be implemented to control one or more of the power source 102, the cooling subsystem 18, and the lighting subsystem 100 (including one or more such coupled semiconductor devices). For example, in response to data from the lighting subsystem indicating that the light energy is insufficient at one or more points associated with the workpiece, the controller 108 may be implemented to either (a) increase the current and / or voltage supply from the power source to one or more of the semiconductor devices 110, (b) increase cooling of the lighting subsystem by means of the cooling subsystem 18 (i.e.certain light-emitting devices deliver greater radiant power when cooled), (c) increasing the time during which power is supplied to those devices, or (d) a combination of the foregoing.

[0018] Individual semiconductor devices 110 (e.g., light-emitting diode (LED) devices) of the lighting subsystem 100 may be independently controlled by the controller 108. For example, the controller 108 may control a first group of one or more individual LED devices to emit light of a first intensity, wavelength, and the like, while controlling a second group of one or more individual LED devices to emit light of a different intensity, wavelength, and the like. The first group of one or more individual LED devices may be within the same array of semiconductor devices 110 or may come from more than one array of semiconductor devices 110. Arrays of semiconductor devices 110 may also be controlled by the controller 108 independently of other arrays of semiconductor devices 110 in the lighting subsystem 100.For example, the semiconductor devices of a first array may be controlled to emit light of a first intensity, wavelength, and the like, while those of a second array may be controlled to emit light of a second intensity, wavelength, and the like.

[0019] As another example, under a first set of conditions (e.g., for a particular workpiece, photoreaction, and / or operating conditions), the controller 108 may operate the photoreactive system 10 to implement a first control strategy, whereas under a second set of conditions (e.g., for a particular workpiece, photoreaction, and / or operating conditions), the controller 108 may operate the photoreactive system 10 to implement a second control strategy. As described above, the first control strategy may involve operating a first group of one or more individual semiconductor devices (e.g.,LED devices) to emit light of a first intensity, wavelength, and the like, while the second control strategy may include operating a second group of one or more individual LED devices to emit light of a second intensity, wavelength, and the like. The first group of LED devices may be the same group of LED devices as the second group and may span one or more arrays of LED devices, or may be a different group of LED devices than the second group, and the different group of LED devices may include a subset of one or more LED devices from the second group.

[0020] The cooling subsystem 18 is implemented to control the thermal behavior of the illumination subsystem 100. For example, the cooling subsystem 18 generally provides for cooling this subsystem 12 and, more specifically, the semiconductor devices 110. The cooling subsystem 18 may also be implemented to cool the workpiece 26 and / or the space between the workpiece 26 and the photoreactive system 10 (e.g., specifically, the illumination subsystem 100). For example, the cooling subsystem 18 may be an air or other fluid cooling system (e.g., a water cooling system).

[0021] The photoreactive system 10 can be used for various applications. Examples include, without limitation, curing applications ranging from color printing to DVD manufacturing and lithography. In general, the applications utilizing the photoreactive system 10 have associated parameters. That is, an application may include associated operating parameters such as providing one or more radiant power levels at one or more wavelengths applied for one or more time periods. To properly achieve the photoreaction associated with the application, optical power may need to be applied to or near the workpiece at or above one or more predetermined values ​​of one or more of these parameters (and / or for a specific time, times, or time ranges).

[0022] To comply with the parameters of a planned application, the semiconductor devices 110 that provide radiant power 24 can be operated according to various characteristics associated with the application parameters, e.g., temperature, spectral distribution, and irradiance. At the same time, the semiconductor devices 110 can have certain operating specifications that may be associated with the manufacture of the semiconductor devices and may be followed, among other things, to prevent destruction and / or degradation of the devices. Other components of the photoreactive system 10 can also have associated operating specifications. These specifications can include, among other parameter specifications, ranges (e.g., maximum and minimum ranges) for operating temperatures and applied electrical power.

[0023] Accordingly, the photoreactive system 10 supports monitoring the application parameters. Furthermore, the photoreactive system 10 may provide for monitoring semiconductor devices 110, including their respective properties and specifications. Furthermore, the photoreactive system 10 may also provide for monitoring selected other components of the photoreactive system 10, including their properties and specifications.

[0024] Providing such monitoring may enable verification of proper system operation so that the operation of the photoreactive system 10 may be reliably assessed. For example, the photoreactive system 10 may be operating in an undesirable manner with respect to one or more of the application parameters (e.g., temperature, radiant power, etc.), component properties associated with those parameters, and / or the component's respective operating specifications. Providing monitoring may be responsive and executed according to data received by the controller 108 from one or more of the system components.

[0025] Monitoring may also support the control of system operation. For example, a control strategy may be implemented by controller 108 receiving and responding to data from one or more system components. This control, as described above, may be implemented directly (i.e., by controlling a component through control signals sent to the component based on data that considers the operation of that component) or indirectly (i.e., by controlling the operation of a component through control signals designed to adjust the operation of other components).For example, a radiant power of a semiconductor device may be adjusted indirectly by control signals sent to the power source 102 that adjust the power delivered to the lighting subsystem 100 and / or by control signals sent to the cooling subsystem 18 that adjust the cooling applied to the lighting subsystem 100.

[0026] Control strategies can be used to enable and / or enhance proper system operation and / or application performance. In a more specific example, control can also be used to enable and / or enhance a balance between the array's radiant power and its operating temperature, e.g., to prevent heating of the semiconductor devices 110 or the array of semiconductor devices 110 beyond their specifications, while also directing sufficient radiant energy to the workpiece 26 to properly complete the application's photoreaction(s).

[0027] In some applications, a high irradiance may be delivered to the workpiece 26. Accordingly, the subsystem 12 may be implemented using an array of semiconductor light-emitting devices 110. For example, the subsystem 12 may be implemented using a high-density light-emitting diode (LED) array. Although LED arrays may be used and are described in more detail herein, it should be understood that the semiconductor devices 110 and array(s) thereof may be implemented using other light-emitting technologies without departing from the principles of the description. Examples of other light-emitting technologies include, without limitation, organic LEDs, laser diodes, and other semiconductor lasers.

[0028] The plurality of semiconductor devices 110 may be provided in the form of an array 20, or an array 20 may consist of a plurality of arrays (e.g., 20A, 20B, and 20C), as shown in Fig. 2. The array 20 may be implemented such that one or more or most of the semiconductor devices 110 are configured to provide radiant power. At the same time, however, one or more of the semiconductor devices 110 of the array are implemented to provide monitoring of selected characteristics of the array. The monitoring devices 36 may be selected from among the devices in the array 20 and may, for example, have the same structure as the other emitting devices. The distinction between emitting and monitoring may be determined, for example, by the coupling electronics 22 associated with the particular semiconductor device (in a basic form, an LED array may, for example, comprise monitoring LEDs, where the coupling electronics provide reverse current, and emitting LEDs, where the coupling electronics provide forward current).

[0029] Further, based on the coupling electronics, selected ones of the semiconductor devices in the array 20 may be either / or both / and multi-function devices and / or multi-mode devices, where (a) multi-function devices may detect more than one property (e.g., radiant power, temperature, magnetic fields, vibration, pressure, acceleration, and other mechanical forces or deformations) and may be switched between these detection functions according to the application parameters or other governing factors, and (b) multi-mode devices may be capable of emission, detection, and another mode (e.g., off) and may be switched between these modes according to the application parameters or other governing factors.

[0030] With reference to Fig. 2 shows a circuit diagram of a first lighting system circuit that can supply different amounts of current to a lighting array. The lighting system 100 includes one or more light-emitting devices 110. In this example, the light-emitting devices 110 are light-emitting diodes (LEDs). Each LED 110 includes an anode 201 and a cathode 202. A Fig. The switching power source shown in Figure 1 supplies 48V DC to a voltage regulator 204 via a path or conductor 264. The voltage regulator 204 supplies DC to the anodes 201 of the LEDs 110 via conductor or path 242. The voltage regulator 204 is also electrically connected to cathodes 202 of the LEDs 110 via a conductor or path 240. The voltage regulator 204 is shown with reference to electrical ground 260 and, in one example, may be a buck regulator. The voltage regulator 204 selectively supplies electrical power to the lighting array 20, which consists of independently controlled lighting arrays 20A, 20B, and 20C, via switches 270, 271, and 272. The controller 108 is shown in electrical communication with the voltage regulator 204 and switches 270, 271, and 272. The switches 270-272 provide independent control of the illumination arrays 20A, 20B and 20C. In other examples, discrete input generating devices (e.g.Switch) replaces the control unit 108. The control unit 108 includes a central computer 290 for executing instructions stored in a non-volatile memory 292. The control unit 108 also includes inputs and outputs (I / O) 288 for operating the voltage regulator 204 and other devices. A read-only memory 292 can store non-volatile executable instructions, while a random access memory 294 can store variables. The voltage regulator 204 supplies the LEDs 110 with an adjustable voltage.

[0031] The variable resistor 220 in the form of a field-effect transistor (FET) receives an intensity or radiation control signal voltage from the controller 108 or via another input device from an amplifier 222. The amplifier 222 provides a control signal or output to an FET gate 298 via a conductor 231. The amplifier 222 receives an intensity or radiation command from the controller 108 at a non-inverting input, as shown in Fig. 3. As shown in Fig. As shown in Figure 3, negative temperature coefficient devices 225, 226, and 227 (e.g., thermistors) are included in a negative feedback loop or circuit of amplifier 222. Furthermore, negative temperature coefficient devices 225, 226, and 227 are in thermal communication with LEDs 110 via a heat sink 221. FET source 297 is electrically coupled to a current sensing resistor 255. While the present example describes the variable resistor as an FET, it should be noted that the circuit may utilize other forms of variable resistors.

[0032] In this example, at least one element of the array comprises 20 solid-state light-emitting elements, such as light-emitting diodes (LEDs) or laser diodes, that generate light. The elements can be configured as a single array on a carrier, as multiple arrays on a carrier, as multiple arrays either individually or multiple on multiple interconnected carriers, etc. In one example, the array of light-emitting elements can be made of Silicon Light Matrix™ (SLM) manufactured by Phoseon Technology, Inc.

[0033] The Fig. The circuit shown in Figure 2 is a closed current control loop 208. In the closed current control loop 208, the variable resistor 220 receives an intensity voltage control signal via conductor or path 231 by means of amplifier 222. The voltage between the variable resistor 220 and the array 20 is controlled to a desired voltage determined by the voltage regulator 204. The desired voltage value can be supplied by the controller 108 or another device, and the voltage regulator 204 controls the voltage on the conductor or path 242 to a value that provides the desired voltage in a current path between the array 20 and the variable resistor 220. The variable resistor 220 controls the current flow from the array 20 to the current sensing resistor 255 in the direction of arrow 245.The target voltage may also be adjusted in response to the type of lighting fixture, the type of workpiece, curing parameters, and various other operating parameters. An electrical current signal may be passed back along conductor or path 236 to the controller 108 or other device that adjusts the intended intensity voltage control signal. Specifically, if the electrical current signal differs from a desired electrical current, the intensity voltage control signal passed via conductor 230 is increased or decreased to adjust the electrical current through the array 20. A current feedback signal, indicating electrical current flow through the array 20, is passed via conductor 236 as a voltage value that changes as the electrical current flowing through the current sensing resistor 255 changes.

[0034] In an example where the voltage between variable resistor 220 and array 20 is set to a constant voltage, the current flow through array 20 and variable resistor 220 is adjusted by adjusting the resistance of variable resistor 220. Thus, a voltage signal carried along conductor 240 from variable resistor 220 does not reach array 20 in this example. Instead, the voltage feedback between array 20 and variable resistor 220 follows conductor 240 and reaches a voltage regulator 204. Voltage regulator 204 then outputs a voltage signal 242 to array 20. Consequently, voltage regulator 204 adjusts its output voltage in response to a voltage downstream of array 20, and the current flow through array 20 is adjusted by means of variable resistor 220.Controller 108 may include commands for adjusting a resistance value of variable resistor 220 in response to an array current fed back as a voltage via conductor 236. Conductor 240 provides electrical connection between the cathodes 202 of LEDs 110, an input 299 (e.g., a drain of an N-channel MOSFET) of variable resistor 220, and the voltage feedback input 293 of voltage regulator 204. Thus, the cathodes 202 of LEDs 110, an input side 299 of variable resistor 220, and the voltage feedback input 293 are at the same voltage potential.

[0035] The variable resistor can take the form of a FET, a bipolar transistor, a digital potentiometer, or any electrically controllable current-limiting device. The drive circuit can take different forms depending on the variable resistor used.

[0036] The closed system operates such that an output voltage regulator 204 remains approximately 0.5 V above a voltage for operating the array 20. The regulator output voltage adjusts the voltage applied to the array 20, and the variable resistor controls an electrical current flow through the array 20 to a setpoint. The present circuit can improve the generation of a constant irradiance of the array 20. In the example of Fig. 2, the variable resistor 220 typically produces a voltage drop in the range of 0.6 V. However, the voltage drop across the variable resistor 220 may be less than or greater than 0.6 V depending on the design of the variable resistor.

[0037] With reference now to Fig. 3, an exemplary amplifier 222 for supplying a radiation or intensity control voltage to a variable resistor that controls the flow of electrical current through independently controlled illumination arrays is shown. The amplifier 222 includes an operational amplifier 302. A control voltage for outputting a desired radiation or light intensity is input to the amplifier 222 at the non-inverting input 304. The amplifier 222 includes an output 305 for supplying the Fig. 2. The negative feedback loop 350 includes only two fixed-value resistors (e.g., resistors having resistance values ​​that change by less than a predetermined percentage, such as 2%) depending on a fixed temperature range, comprising a first resistor (R1) 310 and a second resistor (R2) 312. The negative feedback loop 350 also includes three negative temperature coefficient devices 314, 316, and 318 electrically coupled in parallel. In some examples, the devices 314, 316, and 318 may be referred to as temperature-dependent resistors, such that the negative feedback loop includes only five resistors. In this example, the negative temperature coefficient devices 314, 316, and 318 each include one side that is directly electrically coupled to the electrical ground 260.The first resistor (R1) determines the gain change from the minimum to the maximum temperature of the illumination array. The second resistor (R2) sets a maximum slope for a predetermined equilibrium temperature of the illumination array. The values ​​of R1 and R2 are adjusted to provide equivalent gain for a feedback loop using only a negative temperature coefficient device and resistors R1 and R2 with values ​​other than those shown in . Fig. 3. In this way, a gain of the amplifier 222 can be adjusted so that the Fig. 3, which includes three negative temperature coefficients, may be similar to a circuit including only one negative temperature coefficient type device.

[0038] Thus, amplifier 222 is a non-inverting amplifier that includes negative feedback in a negative feedback loop 350. The inverting input 303 and the non-inverting input 304 have a very high impedance. Consequently, essentially no electrical current flows into the inverting input 303 or the non-inverting input 304, respectively. The amplifier gain can be expressed as: VoVin=1+R1R2+RT where Vo is the output voltage of amplifier 222 at 305, Vin is the voltage at the inverting input 303, R1 is the value of resistor 310, R2 is the value of resistor 312 and R T equal to 1 / (1 / R T1 +1 / R T2 +1 / R T3 ) is (e.g. R T1 -R T3 Values ​​of the Fig. 3 shown negative temperature coefficient type devices). If the temperature of the illumination array is cold and the value of 1 / R Tis higher, the gain is thus closer to 1. When the temperature of the illumination array is warm and the value of 1 / RT is lower, the gain is closer to 1+R1 / R2. When only one illumination array is active, the resistance of the negative temperature coefficient device associated with the active illumination array decreases as the temperature of the active illumination array increases, so the gain moves closer to 1+R1 / R2 than 1. The lower resistance of the negative temperature coefficient device associated with the active illumination array further dominates the parallel resistance value, so the gain is appropriate for the one active illumination array and is less affected by the inactive illumination arrays and their corresponding negative temperature coefficient devices.In particular, a gain to drive a single illumination array is within 2% of the gain once all in . Fig. 3 were active and their respective negative temperature coefficient devices were at the same temperature. Thus, a gain for driving only one lighting array may be substantially equal (e.g., within 2%) to the gain for driving more than one lighting array. In some examples, the output of amplifier 222 may be referred to as an automatic power control (APC) command or signal.

[0039] It is understood that the values ​​of R1, R2 and R T may vary between different lighting systems. Furthermore, the gain may be different in some embodiments without departing from the scope and intent of the present description.

[0040] The system of Fig. 1-3 thus provides a system for operating one or more light-emitting devices, comprising: at least two independently controlled illumination arrays consisting of at least one light-emitting device; and an amplifier having a negative feedback loop, wherein at least two negative temperature coefficient devices are electrically coupled in parallel and included in the negative feedback loop, each of the at least two negative temperature coefficient devices being in thermal communication with one of the at least two independently controlled illumination arrays. The system includes the amplifier being an operational amplifier, further comprising a variable resistance device and a controller, wherein the variable resistance device is in electrical communication with a cathode side of the at least two independently controlled illumination arrays.

[0041] In some examples, the system includes the at least two independently controlled lighting arrays being controlled by at least two switches. The system includes at least one side of each of the at least two negative temperature coefficient devices being directly electrically coupled to an electrical ground. The system further includes only two fixed value resistors in the negative feedback loop. The system includes only one of the two fixed value resistors being directly coupled to the at least two negative temperature coefficient devices. The system includes the at least two negative temperature coefficient devices being in thermal communication with a heat sink, and the at least two independently controlled lighting arrays being in thermal communication with the heat sink.

[0042] The system of Fig. 1-3 also provides a system for operating one or more light-emitting devices, comprising: an illumination array consisting of at least one light-emitting device; at least two negative temperature coefficient devices in thermal communication with the illumination array; and an amplifier having a negative feedback loop, wherein the at least two negative temperature coefficient devices are electrically coupled in parallel and included in the negative feedback loop. The system includes one side of each of the at least two negative temperature coefficient devices being directly electrically coupled to an electrical ground. The system includes the negative feedback loop providing an electrical connection between an inverting input of the amplifier and an output of the amplifier.The system comprises that the illumination array consists of at least two independently controlled illumination arrays, and that the at least two independently controlled illumination arrays are controlled by means of at least two switches. The system further comprises only two fixed-value resistors in the negative feedback loop. The system comprises that a first of the only two fixed-value resistors is in direct electrical connection with an inverting input of the amplifier and an output of the amplifier, and that a second of the only two fixed-value resistors is in direct electrical connection with the first of the only two fixed-value resistors, the inverting input of the amplifier, and the at least two negative temperature coefficient devices.

[0043] Based on Fig. 4 is now a graphical representation of the gain for the amplifier 222 of Fig. 3. The vertical axis represents the gain, and the gain increases in the direction of the vertical axis arrow. The horizontal axis represents the temperature of a heat sink that is in thermal communication with one or more illumination arrays and one or more negative temperature coefficient devices. The temperature increases from the left side of Fig. 4 to the right of Fig. 4.

[0044] Curve 402 represents the gain when activating three independently controlled illumination arrays of a photoreactive system and providing feedback from three negative temperature coefficient type devices to the Fig. 3. Curve 404 represents the gain when activating an independently controlled illumination array of the photoreactive system and providing feedback from three negative temperature coefficient type devices to the amplifier 222 shown in Fig. 3. The heat sink may have a temperature difference of 20°K from one end of the heat sink to the other end of the heat sink when only one illumination array is activated. The gains of curves 402 and 404 are within 2%. The amplifier 222 can thus control the irradiance of a single illumination array in a manner nearly equivalent to the way the amplifier 222 controls the irradiance of the three illumination arrays. Consequently, a single amplifier can be used to control two or more illumination arrays where two or more amplifiers would have been used in the past. The amplifier 222 also provides substantially the same gain (e.g., within 2%) when driving a single illumination array as when driving more than one illumination array.

[0045] With reference now to Fig. 5 shows an exemplary method for controlling the electrical power and radiation of an illumination array. The method of Fig. 5 may be included as instructions stored in a non-volatile memory of a control unit, as in Fig. 1 and Fig. 2 is shown.

[0046] At 502, the desired intensity or irradiance of the illumination array is determined. The desired intensity may vary from illumination system to illumination system and from workpiece to workpiece. In one example, the desired intensity may be determined from a control parameter file, or an operator may manually select the desired intensity or irradiance value. The control parameter file may include empirically determined irradiance values ​​for the illumination array. After determining the irradiance or intensity of the illumination array, method 500 proceeds to 504.

[0047] At 504, method 500 determines the current and / or power to operate the lighting array at the irradiance level determined at 502. In one example, the power of the lighting array may be determined by indexing a function or table that includes empirically determined current or power values ​​that can be indexed by the desired irradiance. The table or function outputs the desired current and / or power of the lighting array and proceeds to 506.

[0048] At 506, method 500 converts the desired current or power into a control voltage or current for driving the variable resistor that controls current flow through the illumination array. In one example, method 500 passes the desired current or power value through a transfer function to determine an irradiation command for the illumination array. The irradiation command may be in the form of a voltage or a value of a parameter. After determining the irradiation command, method 500 proceeds to 508.

[0049] At 508, method 500 activates one or more SLMs or illumination arrays to provide the desired irradiation. In one example, one or more illumination arrays may be activated by closing a switch for each illumination array to be activated. A switch controls current flow to an illumination array such that five switches are closed if five illumination arrays are to be activated. The number of illumination arrays to be activated may depend on the required irradiance level and / or the test specimen configuration. After activating one or more illumination arrays, method 500 proceeds to 510.

[0050] At 510, the method 500 utilizes one or more negative temperature coefficient or transfer function type devices in a negative feedback loop of an amplifier (e.g., amplifier 222 of Fig. 2), which supplies a control voltage or current to a variable resistor.

[0051] In one example, the one or more negative temperature coefficient devices may be included in a negative feedback loop of an amplifier, as in Fig. 2 and Fig. 3. The negative temperature coefficient type devices adjust a gain when a temperature of the illumination arrays changes, which is reflected in a temperature change of a heat sink that is in thermal communication with the illumination arrays. In one example, the gain of the amplifier is as shown in Fig. 4. The control voltage determined at 506 is applied to a non-inverting input of the amplifier.

[0052] In another example, voltages or resistances representing temperatures of the lighting arrays are input to a controller, and the voltages or resistances are passed through a transfer function that converts the voltages or resistances into negative temperature coefficient output parameters. For example, if a voltage representing a lighting array temperature is input to the controller, the voltage is converted to a resistance value such that the resistance value decreases in response to an increasing lighting array temperature. The resistance values ​​can then be applied to a transfer function representing an amplifier with one or more negative temperature coefficient devices in its feedback path. The controller can, for example, Fig. 3 and its transfer function in the form of a digital filter stored in memory. The control voltage determined at 506 is applied to the digital filter. After applying the negative temperature coefficient to a feedback path of an amplifier that adjusts a current and / or power of an illumination array, method 500 proceeds to 512.

[0053] At 512, method 500 adjusts the current and / or power of the illumination array by applying a current or voltage to a variable resistor. In one example, the current or power may be adjusted using an amplifier, as shown in Fig. 3. In another example, the current or power may be adjusted by a controller supplying a current or voltage from an analog output, where the current or voltage is determined from the output of the digital filter described at 510.

[0054] Thus, the procedure of Fig. 5 can be implemented using a digital controller or an analog circuit. The method applies negative temperature coefficients to a negative feedback path of an amplifier to maintain illumination array radiation at a constant value in the presence of changing illumination array temperatures of one or more independently controllable illumination arrays.

[0055] The procedure of Fig.5 provides a method of operating one or more light-emitting devices, comprising: sensing temperatures at two or more locations on a thermal conductor, the thermal conductor being in thermal communication with an illumination array, the temperatures at the two or more locations being sensed by two or more negative temperature coefficient devices electrically coupled in parallel, and adjusting current flow through the illumination array in response to output from a controller including the two or more negative temperature coefficient devices in a negative feedback loop. The method includes each of the two or more negative temperature coefficient devices including one side electrically coupled directly to an electrical ground.

[0056] In some examples, the method includes adjusting the current flow through the illumination array using an operational amplifier. The method includes adjusting the current flow through the illumination array using commands in the controller. The method includes the illumination array consisting of at least two independently controlled illumination arrays. The method includes controlling the at least two independently controlled illumination arrays using at least two switches. The method includes adjusting the current flow to provide a substantially constant irradiance output by the illumination array.

[0057] It should be noted that the exemplary control and estimation routines contained herein may be utilized in various lighting system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-volatile memory and executed by the control system, including the controller combined with the various sensors, actuators, and other lighting system hardware. The particular routines described herein may represent one or more of a number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Thus, various steps, operations, and / or functions shown may be performed in the sequence shown, in parallel, or in some cases, skipped.Similarly, the order of processing is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. Depending on the particular strategy used, one or more of the illustrated steps, operations, and / or functions may be performed repeatedly. Further, the described steps, operations, and / or functions may graphically represent code to be programmed into non-volatile memory of the machine-readable storage medium in the lighting control system, wherein the described steps are performed by executing the instructions in a system including the various lighting system hardware components combined with the electronic control unit.

[0058] This concludes the description. A reading of the description by those skilled in the art may suggest many modifications and variations without departing from the spirit and scope of the description. For example, illumination sources that produce different wavelengths of light may benefit from the present description.

Claims

[1] A system for operating one or more light-emitting devices, comprising: an illumination array (20, 20A, 20B, 20C) consisting of at least one light-emitting device (110); at least two negative temperature coefficient devices (314, 316, 318) in thermal communication with the illumination array (20, 20A, 20B, 20C); and an operational amplifier (222, 302) having a negative feedback loop (350), wherein the at least two negative temperature coefficient type devices (314, 316, 318) are electrically coupled in parallel and are included in the negative feedback loop (350), the system further comprising two fixed value resistors (310, 312) in the negative feedback loop (350), and wherein a first of the two fixed value resistors (310, 312) is in direct electrical connection with an inverting input (303) of the amplifier (222, 302) and an output (305) of the amplifier (222, 302), and wherein a second of the two fixed value resistors (310, 312) is connected to the first of the two fixed value resistors (310, 312), the inverting input of the amplifier (222, 302), and the at least two negative temperature coefficient type devices (314, 316, 318) are in direct electrical connection. [2] The system of claim 1, wherein one side of each of the at least two negative temperature coefficient devices (314, 316, 318) is electrically coupled directly to an electrical ground (260). [3] The system of claim 1, wherein the illumination array (20, 20A, 20B, 20C) consists of at least two independently controlled illumination arrays, and wherein the at least two independently controlled illumination arrays are controlled by means of at least two switches. [4] A method of operating one or more light-emitting devices (110) using a system according to any one of claims 1 to 3, comprising: Detecting temperatures at two or more locations on a heat conductor, the heat conductor being in thermal communication with an illumination array (20, 20A, 20B, 20C), the temperatures at the two or more locations being detected by means of two or more negative temperature coefficient devices (314, 316, 318) electrically coupled in parallel; and Adjusting current flow through the illumination array (20, 20A, 20B, 20C) in response to output of a controller (108) comprising the two or more negative temperature coefficient type devices (314, 316, 318) in a negative feedback loop (350). [5] The method of claim 4, wherein each of the two or more negative temperature coefficient devices (314, 316, 318) includes a side directly electrically coupled to an electrical ground (260). [6] The method of claim 4, wherein the current flow through the illumination array is adjusted by means of the operational amplifier (222). [7] The method of claim 4, wherein the current flow through the illumination array (20, 20A, 20B, 20C) is adjusted by means of commands in the controller (108). [8] The method of claim 4, wherein the illumination array (20, 20A, 20B, 20C) consists of at least two independently controlled illumination arrays. [9] The method of claim 8, wherein the at least two independently controlled illumination arrays (20, 20A, 20B, 20C) are controlled by means of at least two switches. [10] The method of claim 4, wherein the current flow is adjusted to provide a substantially constant irradiance output from the illumination array (20, 20A, 20B, 20C).

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