App note: Comparison of LED circuits


Another application note from OSRAM on different LED circuit design failure mode. Link here (PDF)

In recent years, Light Emitting Diodes (LEDs) have become a viable alternative to conventional light sources. The overriding advantages long life, high efficiency, small size and short reaction time have lead to the displacement, in ever increasing numbers, of incandescent bulbs. One of the markets where this change has become most evident is Automotive, where LEDs are used now not only for backlighting dashboards and switches, but also for exterior illumination in Center High Mounted Stop Lights (CHMSL), Rear Combination Lamps (RCL), turn signals and puddle lighting.

Despite the long life and low failure rates of LEDs, cars can be found, on occasion, with failed LEDs in their CHMSL. Most often this is due to a flawed circuit design wherein the LEDs were allowed to be overdriven. It is with that supposition in mind that this application note is written: to identify, characterize and comment on LED behavior and failure modes in serial and matrix circuits.

App note: Dimming LEDs with respect to grouping current


App note from OSRAM describing the behaviour of LEDs in respect to brightness by varying the current and to suggest solutions for avoiding negative influence for the application. Link here (PDF)

In the design of a driving circuit for LEDs, the dimming behaviour is an important topic to fulfill the end customer requirements. The behaviour of the LEDs in respect to brightness is investigated by varying the current and solutions for avoiding negative influence for the application are suggested.

App note: Light quality – White light parameters


App note from OSRAM on consistency of colors specifically white lights. Link here (PDF)

White light is not the same as white light. When different light sources are used, color differences may become visible. To understand why this can happen, it is necessary to understand how people perceive color and light. Nevertheless, it is possible to reduce the color shifts by choosing suitable white LEDs combined with an appropriate system setup. This application note provides basic information on optical quantities, color spaces and CIE chromaticity diagrams. Furthermore, it describes how color consistency for white light applications can be achieved.

App note: Ambient lighting design utilizing RGB LEDs


App note from OSRAM on using RGB LEDs or their MULTILED® for automotive interior lighting. Link here (PDF)

This application note describes the advantages and challenges of utilizing RGB LEDs for ambient lighting control. Besides pointing out practical challenges, preferred solutions for RGB LEDs are outlined and discussed to assist customers with engineering design solutions.

App note: Thermal consideration of flash LEDs


Pulsed LED application like flash LEDs requires adequate thermal management to counter the heavy heat caused by larger current, here’s an app note from OSRAM discussing on thermal management of LEDs. Link here (PDF)

This application note focuses on how to develop an adequate thermal management for LEDs in camera flash applications. It provides information on critical factors and the thermal properties of LEDs during a range of operation modes as well as information on how to develop an adequate thermal management in flashlight applications.

App note: Dimming InGaN LEDs


App note from OSRAM on InGaN LEDs dimming method without penalty on its wavelength. Link here (PDF)

While the InGaN technology produces the brightest light output across Blue, Deep blue, Verde, True green and White, it is important to understand that the wavelength of the light emitted depends on the forward current. In order to avoid shifts in the color, the dimming strategy must be considered carefully.

App note: Driving LEDs with a PIC Microcontroller

An App note from OSRAM on an Intelligent control circuitry example using a PIC Microcontroller. Link here (PDF)

Nowadays, applications increasingly make use of LEDs as a replacement for traditional light bulbs. For example, LEDs are frequently used in the design of automobile tail lights, signal lights, traffic signals, and variable message signs.

LEDs provide several advantages over traditional light bulbs, such as smaller size and longer life. In many applications, the LEDs must be driven with intelligent control circuitry. According to the task at hand, this control circuitry must be able to fulfill various functions and tasks.

App note: Package-related thermal resistance of LEDs


App note from OSRAM on thermal resistance for LEDs and IREDs (IR emitting diodes). Link here (PDF)

In order to achieve the expected reliability, lifetime and optimal performance of LEDs, especially for high-power LEDs, appropriate thermal management is of the utmost importance. One of the key parameters for good thermal management is the temperature of the active semiconductor layer designated as the junction temperature. The manufacturer’s recommended maximum junction temperature should therefore not be exceeded during operation, in order to prevent damage to the component. Ideally, the junction temperature should be kept as low as possible for the given application.

Due to the design principle of the LEDs, the junction temperature of the LED can not be measured directly.

App note: Ambient light sensor SFH5701


App note from OSRAM on their ALS device SFH5701, its operation and application method. Link here (PDF)

The SFH5701 is a small, two-wire, linear output current ambient light sensor (ALS) with current amplifier and dark current compensation. The ALS is capable of resolving a wide range of ambient light levels (10 mlx – 10 klx) tailored to the spectral response of the human eye and operational from -40 °C to 100 °C.