by Steven Keeping:
High-efficiency LEDs are impressive devices. Many leading semiconductors companies sell proven, commercial devices with efficacies in excess of 100 lm/W and lifetimes exceeding 50,000 hours.
However, while contemporary products perform well, indium gallium nitride (InGaN)-based white LEDs (the most common type produced today) have a theoretical efficacy limit of around 250 lm/W, so there is still plenty of room for improvement. Factors such as carrier injection-, internal quantum-, and light extraction-efficiency are under intense scrutiny by academics and researchers working for the leading LED companies alike.
This article reviews the progress that these scientists and engineers have made so far, and casts an eye forward as to what improvements we might see next.
What’s Next for High-Power LEDs? - [Link]
Literally endless long bands of a linear light can be produced with LEDs of the Duris E3 and E5 series. A wide-angle beam and a very uniform light distribution make these LEDs very easily applicable.
This is exactly the case of Duris E3 and Duris E5 LEDs. Thanks to their compact SMT packages, they can be freely used on PCBs of virtually any shapes. Small dimensions of both LEDs enable tight placing of LEDs next to each other. OSRAM Duris E3 and Duris E5 LEDs feature a very homogenous radiation pattern in a wide angle (120°) and a high efficiency of up to 110lm/W. The result is a perfectly homogenous light without visible dots. That´s why they´re perfectly suitable for a construction of replacements of classic fluorescent lamps (CCFL) (T5 a T8) and bulbs. Duris E3 and E5 have very similar optical specification, the main difference is in the maximum current of 30mA/E3 versus 180mA/E5.
It is good to realize, that a maximum current of LED has nothing in common with efficiency, i.e. even low-power LEDs feature a high efficiency (lm/W). That´s why approximately the same-efficient light source can be created by 1 OSRAM OSLON Square LED, but even by for example 50 pcs Duris E3 or 8 pcs Duris E5. An advantage of high-power LEDs is an easy achievement of a high luminous flux from a small area (spot lights) and an easy application of optics. On the other hand, less powerful LEDs are usually more easily applicable, no secondary optics is necessary and often even no additional heatsink is necessary because the power is dispersed on a bigger area and already the PCB itself is often able to lead away and dissipate a generated heat. That´s why the usage of Duris E3 and E5 is very simple and virtually immediately after soldering LED to a PCB we gain a working source of a homogenous light. .
A light without an end with OSRAM Duris E3 and E5 LEDs - [Link]
The TPS92510 by Texas Instruments is a 1.5-A constant current DC/DC buck converter with a combo of frequency synchronization, pulse-width modulation (PWM) dimming and thermal foldback firsts. Used with the WEBENCH LED Architect, users rapidly design a power management circuit to drive a string of up to 17 high-brightness LEDs at up to 97% power efficiency in automotive, industrial, and general lighting applications.
The TPS92510 operates with fixed frequency by using its internally generated clock or via synchronization to an external PWM clock source. Thermal foldback ensures light output remains even in an LED over-temperature condition, adding safety. [via]
- 3.5-V to 60-V input voltage operating range supports a wide variety of DC LED lighting applications, including area and street lighting.
- Fixed switching frequency range from 100 kHz to 2.5 MHz can be synchronized to optimize for efficiency or solution size.
- LED thermal foldback with external negative temperature coefficient (NTC) protects LED array from over-temperature while maintaining reduced light output.
- Dedicated PWM dimming input from 100 Hz to 1 kHz adjusts LED brightness without color shift or perceivable flicker.
Buck converter drives high-brightness LEDs - [Link]
This article shows you the process involved for building an 8x8x8 LED cube (that’s 512 LEDs!). It explains both how to build the LED cube and how to make the electronics that control it. Don’t miss the demo videos!
Building An 8x8x8 LED Cube - [Link]
Carolyn Mathas writes:
The LT3763 by Linear Technology is a synchronous buck LED driver controller that delivers more than 300W of LED power. With an input voltage range of 6V to 60V, it targets such applications as automotive, industrial and architectural lighting. Output voltage from 0V to 55V enables it to driver LEDs in a single string. The driver features input and output current monitors and limiting and accurate input and output voltage regulation.
Buck LED driver delivers 300W of power - [Link]
Ray reports he’s just finished working on a new open source wearable electronics controller board called SquareWear. It’s small (1.6″x1.6″) and has built-in USB port (used for programming the microcontroller, USB serial communication, and charging battery). It also has 4 on-board MOSFETs for switching high-current load (up to 500mA). The board is based on Microchip’s PIC18F14k50, and includes a SquareWear library to make it as easy to use as Arduino. Check out RaysHobby website for the source code and programming guide.
SquareWear open source controller board - [Link]
Unit is based on Arduino Atmega328P MCU, with over 430 UV LEDs. The PCB board is made using Toner transfer method and isn’t perfect. It was just too big and I was too lazy to do it again. However, marker here, scratch it there and it it good enough.
The unit itself is on single sided copper clad board, no additional cables, no narrow paths (except for one for power on the MCU). Design is straight forward. It’s designed to be powered from 12V source (computer) and take around 2,7Amps @ full power which means around 30Watts.
DIY UV Exposure Unit with LED and Arduino - [Link]
An Arduino-based clock with 180 RGB LEDs. The LEDs are driven via 12 TLC5925 1- channel constant-current addressable drivers – [via]
Its built on doublesided copper clad board using Toner transfer method. The routes aren’t smaller than 0.44mm and all vias are made for 0.8mm drilling (truly DIY). Just around 5 vias are under a component and 7 segment displays have singnals only from bottom side (for easy soldering)
- 180 RGB LEDs driven by TLC5925 constant current LED drivers
- each LED addressed separately (12x TLC5925 with 16 outputs each)
- each colour adressed individually
- 4x 7 segment LED display
- Atmega328P as MCU
- DS1307 real time clock
- Photoresistor (for adjusting brightness)
- And DHT11 for temperature and humidity
- Backup battery for clock
- 5V DC (eg USB)
Clock with 180 RGB LEDs on home-etched circuit board - [Link]
1962: Nick Holonyak, Jr. demonstrates the world’s first visible light-emitting diode (LED) to General Electric suits, changing the world of lighting forever. Holonyak later said that the LED would replace incandescent lights. It’s just taking a little bit longer than expected.
Scientists at the GE Advanced Semiconductor Laboratory were researching a way to create energy-efficient visible light from LEDs. The incandescent lights that we still use today rely on igniting a filament housed in a vacuum to create light. The process is inefficient and only uses 10 percent of available energy to produce light. The rest is lost as heat.
In the early 1960s, the only light emitted from LEDs was infrared. The race to produce a visible LED had GE researchers scrambling to be first.
50th Anniversary of the Visible Light LED - [Link]