Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/10—Controlling the intensity of the light
  • H05B45/18—Controlling the intensity of the light using temperature feedback
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
  • G01K11/12—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in colour, translucency or reflectance
  • G01K11/16—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in colour, translucency or reflectance of organic materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/85—Packages
  • H10H20/858—Means for heat extraction or cooling
  • H10H20/8584—Means for heat extraction or cooling electrically controlled, e.g. Peltier elements
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
  • H05B47/10—Controlling the light source
  • H05B47/105—Controlling the light source in response to determined parameters

Definitions

• Online wet chemistry analyzers are used in a variety of industries to provide a continuous indication of an analyte in a process sample. This continuous indication can be provided locally by the analyzer and/or remotely to one or more suitable devices in order to provide control and/or monitoring of a chemical process.
• online wet chemistry analyzer is an online silica analyzer.
• These devices are configured to generate a reaction in the process sample that allows an indication of silica in the sample to be determined.
• Such analyzers are useful in determining silica content in boiler water, boiler feedwater, demineralized water, and steam condensate. While such analyzers are useful in a variety of industries, they are of particular use in power plant boilers. In such systems, silica can form silicate deposits that can damage turbines and other generation equipment that is used in the water-steam turbine cycle. Accordingly, power plants with high pressure turbines generally monitor silica carefully in order to ensure effective detection and removal/remediation.
• An online silica analyzer is sold under the trade designation Model CFA3030 Silica Analyzer from Rosemount Analytical, an Emerson Automation Solutions company.
• An online silica analyzer will generally employ a known reaction to render the silica in the process sample readily detectable.
• a reaction is known as the molybdenum blue method.
• molybdate usually in the form of potassium molybdate
• the silica content in water is measured based on the color of the silicomolybdic acid formed through the wet chemistry process.
• a temperature-stabilized LED irradiance system includes an LED.
• a temperature sensor is disposed to sense a temperature proximate the LED.
• Circuitry coupled to the temperature sensor and the LED, is configured to adjust power to the LED based on the sensed temperature.
• FIG. 1 illustrates a portion of a colorimetric analyzer in accordance with an embodiment of the present invention.
• FIG. 2A is a chart illustrating irradiance versus temperature in accordance with an embodiment of the present invention.
• FIG. 2B is a chart illustrating irradiance versus current in accordance with an embodiment of the present invention.
• FIGS. 3A-B illustrate a LED circuits in accordance with an embodiment of the present invention.
• FIG. 4 illustrates a flow diagram of a method for LED control in accordance with an embodiment of the present invention.
• the present disclosure relates to a light emitting diode (LED) that maintains a constant irradiance during temperature variations.
• LED light emitting diode
• a variety of colorimetric wet chemistry analyzers employ LEDs in order to generate the light required for colorimetric measurements. LED's utilize electron flow across a p-n junction to generate light. When driven at a constant current, the irradiance of an LED is a function of the temperature of the environment of the LED, i.e., the temperature of the LED substrate (die). This is especially so as the LED emits light closer to the infra-red light (IR) spectrum. In many situations, these temperature-based variations in the irradiance may be acceptable to a user of the LED. However, in some applications, such as colorimetric analyzers, such variations can cause measurement errors.
• I is the measured light intensity when color has been developed after reactions
• 1° is the measured light intensity before the color is developed.
• these two measurements of light intensity occur at different times. If the ambient temperature changes during the process and if the LED is driven at a constant electric current, the calculation of the measured (1/1°) will include an error caused by the irradiance dependency on temperature.
• FIG. 1 illustrates a portion of a colorimetric analyzer in accordance with an embodiment of the present invention.
• Colorimeter analyzer 100 may be useful to analyze a liquid 108 located in photometric cell 106 by passing an illumination 104 through liquid 108.
• LED 102 generates illumination 104 which passes through liquid 108 and is detected by a photo sensor 110.
• Photo sensor 110 may be any sensor that detects a characteristic of light, including, but not limited to, a colorimeter, spectroradiometer, spectrophotometer, or densitometer.
• Chart 200 has an X-axis 202 representing temperature and Y-axis 204 representing irradiance.
• Trend line 206 illustrates how as temperature of an LED increases, the irradiance of the LED decreases.
• FIG. 2B is a chart illustrating irradiance versus current in accordance with an embodiment of the present invention.
• Chart 250 has an X-axis 252 representing current and a Y-axis 254 representing irradiance.
• Trend line 256 illustrates how as current supplied to an LED increase, the irradiance of the LED increases.
• current supplied to the LED For example, as temperature increases, current will also have to increase to maintain a constant irradiance.
• FIG. 3A illustrates an LED circuit in accordance with an embodiment of the present invention.
• LED circuit 300 comprises an LED 302, LED driver circuitry 304, feedback circuitry 308 and temperature sensor 306.
• Temperature sensor 306 is disposed to sense the temperature proximate LED 302.
• Temperature sensor 306 can be any suitable structure that has an electrical characteristic that varies with temperature. Examples, include a resistance temperature detector (RTD), a thermocouple, a thermistor, etc.
• Temperature sensor 306, in one embodiment, may be coupled to the LED 302 die/substrate utilizing a heatsink.
• Temperature sensor 306 is coupled to feedback circuitry 308, which provides a signal to LED driver circuitry 304.
• Feedback circuitry 308 and/or driver circuitry 304 can be embodied in any combination of digital or analog circuitry.
• feedback circuitry 308 could be embodied using a microcontroller having an analog to digital converter that receives a signal from temperature sensor 306 and provides a digital indication of temperature. This digital indication can then be used by LED driver circuitry 304 to compute and adjust the power provided to LED 302, thereby controlling irradiance based on the measured temperature.
• LED driver circuitry 304 and feedback circuitry 308 are components of a single circuitry.
• FIG. 3A illustrates temperature sensor 306 separate from LED 302, it is expressly contemplated that embodiments can be practiced where the temperature sensor is a part of LED 302 or disposed within the LED package.
• FIG. 3B illustrates an embodiment, wherein LED driver circuitry 304, feedback circuitry 308 and temperature sensor 306 are disposed within LED 302. However, any of these components may be separate from LED 302.
• FIG. 4 illustrates a flow diagram of a method for LED control in accordance with an embodiment of the present invention.
• Irradiance stabilization 400 comprises three steps. At block 402, a temperature is measured proximate the LED. In one embodiment, the temperature measurement is taken within the LED.
• a power adjustment is calculated.
• the calculation of power adjustment uses the temperature measured in block 402 as an input.
• the calculation in one embodiment, includes temperature vs irradiance data from the manufacturer. In another embodiment, the calculation comprises a temp-radiance constant multiplied by the measured temperature.
• the power to the LED is adjusted utilizing the calculation from block 404.
• the adjustment may be made can be by circuitry, embodied in any combination of digital and/or analog circuitry. After the power supplied to the LED is adjusted, the cycle may repeat and the power supplied constantly adjusted to compensate for any change in temperature.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Spectrometry And Color Measurement (AREA)
• Arrangement Of Elements, Cooling, Sealing, Or The Like Of Lighting Devices (AREA)
• Circuit Arrangement For Electric Light Sources In General (AREA)

Priority Applications (2)

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Publications (1)

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Family Applications (1)

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Citations (5)

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• 2016
  • 2016-09-27 US US15/277,710 patent/US10080271B2/en active Active
• 2017
  • 2017-01-23 WO PCT/US2017/014500 patent/WO2017142680A1/en not_active Ceased
  • 2017-01-23 EP EP17753619.0A patent/EP3417676A4/en not_active Ceased
  • 2017-01-23 JP JP2018540428A patent/JP6903065B2/ja active Active

Patent Citations (5)

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