LIGHT EMITTING DIODE DRIVERS AND CONTROL

2011 ◽  
Vol 20 (02) ◽  
pp. 267-286
Author(s):  
STEVE WINDER
Keyword(s):  
Light Emitting Diode ◽  
Current Source ◽  
Constant Current ◽  
Constant Current Source ◽  
Basic Principles ◽  
Light Emitting ◽  
Control Techniques ◽  
Switching Regulator ◽  
Step Down ◽  
And Control

This paper outlines the various driving and control techniques for Light Emitting Diodes (LEDs). LEDs should be driven from a constant current source. High power LEDs are usually driven from a switching regulator, for reasons of efficiency. The types of drivers described include Buck (step-down), Boost (step-up) and Buck-Boost (step-up or step-down). Isolated drivers and Power Factor Correction (PFC) circuits are also described. This brief paper can only describe the basic outline of these circuits, but this should be sufficient to allow the basic principles to be understood.

Wide-band suppression of photon-number fluctuations in a high-speed light-emitting diode driven by a constant-current source

1998 ◽  
Vol 72 (3) ◽  
pp. 284-286 ◽  
Author(s):  
M. Kobayashi ◽  
M. Kohno ◽  
Y. Kadoya ◽  
M. Yamanishi ◽  
J. Abe ◽  
...  
Keyword(s):  
High Speed ◽  
Light Emitting Diode ◽  
Photon Number ◽  
Current Source ◽  
Wide Band ◽  
Constant Current ◽  
Constant Current Source ◽  
Light Emitting

Temperature Measurement and Control of Fiber Drawing Furnace Based on Virtual Instrument

2012 ◽  
Vol 529 ◽  
pp. 507-511
Author(s):  
Lei Chen ◽  
Zhong Dong Wang
Keyword(s):  
Temperature Measurement ◽  
Virtual Instrument ◽  
Current Source ◽  
Constant Current ◽  
Instrumentation Amplifier ◽  
Fiber Drawing ◽  
Constant Current Source ◽  
And Control ◽  
Measurement And Control ◽  
Conditioning Circuit

The temperature in fiber drawing is one of the key factors influencing fiber’s performance. To the temperature measurement and control problem, the four-wire lead configuration of Pt100 with current excitation was adopted, the signal conditioning circuit includes constant current source, instrumentation amplifier and anti-aliasing filter. The computer collected signals from the conditioning circuit and output control signals by data acquisition card PCI-6221M. The software program was based on LabVIEW, the function relationship between resistance and temperature based on international thermometric scale and the digital filter were applied to calculate temperature. The improved PID control algorithm and the PWM technique were used to realize the temperature control. The experiment results show that the deviation is 0.71°C when the average temperature of the furnace center is 170.25 °C, which satisfies the design requirements.

scholarly journals Illumination Adaptation in a Multi-Wavelength Opto-Electronic Patch Sensor

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4734 ◽  
Author(s):  
Liangwen Yan ◽  
Yue Yu ◽  
Sijung Hu ◽  
David Mulvaney ◽  
Panagiotis Blanos ◽  
...  
Keyword(s):  
Rapid Determination ◽  
Current Source ◽  
Constant Current ◽  
Blood Oxygen Saturation ◽  
Led Driver ◽  
Constant Current Source ◽  
Light Emitting ◽  
Multi Wavelength ◽  
The Individual ◽  
Microcontroller Unit

In capturing high-quality photoplethysmographic signals, it is crucial to ensure that appropriate illumination intensities are used. The purpose of the study was to deliver controlled illumination intensities for a multi-wavelength opto-electronic patch sensor that has four separate arrays each consisting of four light-emitting diodes (LEDs), the wavelength of the light generated by each array being different. The study achieved the following: (1) a linear constant current source LED driver incorporating series negative feedback using an integrated operational amplifier circuit; (2) the fitting of a linear regression equation to provide rapid determination of the LEDs driver voltage; and (3) an algorithm for the automatic adjustment of the output voltage to ensure suitable LED illumination. The data from a single centrally-located photo detector, which is capable of capturing all four channels of back-light in a time-multiplexed manner, were used to monitor heart rate and blood oxygen saturation. This paper provides circuitry for driving the LEDs and describes an adaptive algorithm implemented on a microcontroller unit that monitors the quality of the photo detector signals received in order to control each of the individual currents being supplied to the LED arrays. The study demonstrated that the operation of the new circuitry in its ability to adapt LED illumination to the strength of the signal received and the performance of the adaptive system was compared with that of a non-adaptive approach.

scholarly journals Low noise constant current source for bias dependent noise measurements

2011 ◽  
Vol 82 (1) ◽  
pp. 013906 ◽  
Author(s):  
D. Talukdar ◽  
R. K. Chakraborty ◽  
Suvendu Bose ◽  
K. K. Bardhan
Keyword(s):  
Current Source ◽  
Low Noise ◽  
Constant Current ◽  
Constant Current Source ◽  
Noise Measurements
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