A CREE MCE4-LED mounted on a STAR PCB. Available in cold white, warm white and RGBW versions, can be powered by a constant current of up to 700 mA – 430 lm
A CREE XP-G LED mounted on a STAR PCB. Available in three shades of white and powered by a constant current up to 1050 mA. Matching lenses of 7°, 15.5° or 25° beam angle are available as accessories.
Giorgos Lazaridis writes:
Some time ago i published a theory page regarding the LED driving and controlling methods. These methods were all linear regulators, very simple to make but very inefficient -in terms of power consumption- for high current applications. The idea was to use this theory page as an entrance level for the SMPS LED drivers.
The first SMPS (Switching Mode Power Supply) LED driver that i made is a Buck-Regulating LED Driver using a chip from Allegro Microsystems, the A6210. I was provided some samples from Farnell for testing and prototyping, along with some other cool staff. Do not forget to pay a visit to Farnell on-line store and Element14 website.
The A6210 can drive up to 3A load with constant current, with switching frequencies up to 2 MHz and supply voltage from 9 to 46 volts. It has additionally an optional PWM input to control the brightness of the LED. The sense voltage is limited to 0.18 volts for higher efficiency, since the power dissipation on this sense resistor is minimal. I will be using a 10-12V 1A 10 Watt LED, powered from 24 VDC supply.
High Efficiency High Current LED Buck Driver using the A6210 - [Link]
Giorgos Lazaridis writes:
The idea for this project came from Viktor’s site, a guy that has some interesting projects in his DIY subdirectory. He cloned a HDD spindicator with 10 LEDs driven from a 4017 chip. I liked the idea but the implementation was kinda… sterilized. So, i decided to make one for my PC, but spice it up with PWM control…
HDD LED Spindicator - [Link]
Isolated offline-flyback controller LT3799 enables to create a powerful LED driver with a minimum of external components, which is moreover compatible with common triac dimmers.
At the design of a new LED driver, we usually have to consider more factors like for example an output current stability, shortcut or open LED protection, efficiency, safety (isolated secondary circuit form the primary one), power factor correction, EMI, number of external components and other.
LT3799 meets all these requirements and offers another benefits, like for example a possibility to use a smaller transformer thanks to the use of critical conductivity mode, powerful external MOSFET driver, internal LDO regulator and also a very good output current regulation – typically +-5%, moreover with no opto-isolator. A big bonus is the active power factor correction, thanks to which it reaches typical values of 0,96 (at 230V AC), thus meeting the most stringent requirements in this field, as well as IEC 61000-3-2 class C about harmonic currents emission. When we look closer at the recommended application circuit, we´ll find out that behind a diode bridge we won´t find any (otherwise common) input electrolytic capacitor with value of tens or hundreds of uF. That´s why the input voltage of the controller and a of the power transformer “copies” input sinusoid. Excellent power factor is reached just thanks to it, that LT3799 knows immediate input voltage value and based on this value, it sets the input current limit (in a given cycle of the SMPS), proportionally to the immediate value of the input AC voltage. Further LT3799 gains information about the immediate current from the primary side, that´s why it doesn´t require an opto-coupler. Thanks to this, LT3799 works like a current source in every period of input voltage, that´s why it is even possible to use classic triac regulators, which are often already a part of the buildings installation. In other words – LT3799 doesn´t try to compensate “dropouts” in power supply caused by a phase control of a triac, what causes decreasing of an output LED current and their fluent dimming. Neither this control method doesn´t cause LED blinking, because there is an electrolytic capacitor on the transformer output.
LT3799 – create a LED driver with an active PFC - [Link]
Tenty LED Brake Lights. Pete writes – [via]
I Purchased a motorcycle about two weeks ago. Interestingly, whenever I tell someone this news, they immediately proceed to tell me the most gruesome injuries and stomach turning plights that they or someone they know, has fallen victim to while motorcycling. In some cases, these raconteur’s briefly pause to look over their shoulder, presumably scanning for small children or otherwise offendable ears, before delivering the goriest details.
One commonality in these stories, aside from the macabre and arguably poor timing involved in telling them to me is that many accidents come down to a lack of visibility of motorcycles and their riders. Less than Argus-eyed motorists often pull out into the path of a motorcycle and with insufficient time for evasive action, that quickly an accident has occurred. Other times, drivers may focus on the car ahead of the motorcycle and in the event of stopping at a red light or similar, fail to leave enough room.
Tenty LED Brake Lights - [Link]
Richard Comerford writes:
More than ever, cameras are becoming a part of the personal and business devices we carry in our pockets. While the light levels at which today’s photographic image sensors can work is extremely low, having flash lighting means users can capture greater detail at faster speeds. And to be sure that flash systems do not consume a lot of the power budget of these battery-run portable electronics, designers have turned to using LEDs as the light source, rather than the traditional xenon tube.
A broad array of devices is available today for driving LEDs as flash devices. Many can deliver high current so that LEDs can be driven to maximum output. However, the increased efficacy of today’s LEDs – meaning they can deliver more light from less current – means that drivers can also focus on reducing current drain on batteries.
Five Solutions for Driving LED Flash in Mobile Devices - [Link]
The LT3791 is the latest in Linear Technology’s growing family of high power, high performance LED drivers designed to simplify power delivery to high brightness LEDs. The 4-switch buck-boost controller topology operates from input voltages above, below or equal to the output voltage while delivering constant currents from 1A up to tens of amps. The LT3791 also provides ±4% LED current accuracy and ±1.5% output voltage accuracy to ensure the highest performance LED solutions.
- 4-Switch Single Inductor Architecture Allows VIN Above, Below or Equal to VOUT
- Wide VIN Range: 4.7V to 60V
- Wide VOUT Range: 0V to 60V (55V LED)
- ±2% Output Voltage Accuracy
- Synchronous Switching: Up to 98.5% Efficiency
- ±6% LED Current Accuracy: 0V ≤ VOUT < 60V
LT3791 – 60V 4-Switch Synchronous Buck-Boost LED Driver Controller - [Link]
Simple and interesting circuit to fade LEDs. Watch effect on the link. It’s cool.
LED Fade – Pulsing Effect - [Link]
This is the successor to my old (and lame) RGB LED Ring project. Now you get 6-bit color depth (per color!) and a lot more bang.
Version ’2.0 alpha’ – an intermediate step to true enlightenment – uses one LED driver IC and 3 P-channel MOSFETs cycling through the primary colors. This requires special attention in the code to attempt color balancing (forced dot correction at all times).
As of ’2.0 beta’ (likely to become the final version) it comes with 3 dedicated constant current LED driver chips (MBI5168), which completely avoids multiplexing the LEDs and boosts brightness again. Color balancing is done entirely in hardware using 3 potentiometers. The hardware differences should be taken care of in the core part of the demo code, ‘User-land’ code is mostly the same.
RGB LED Ring V2 - [Link]