Managing heat in power LED systems for optimal performance

When designing a solid-state solution with power LEDs, one cannot underestimate the importance of the thermal system design, as encapsulated in the phrase "Think Thermal First". Rudi Hechfellner explains. To understand the role of thermal design in LEDs, it's important to review how system and electronic drive conditions influence light output performance and long term behavior of high-power LEDs. The parameters are all influenced by the junction temperature of the LEDs, demonstrating the importance Of this subject.
Temperature has a direct impact on optical and electrical performance as well as on the overall quality and reliability of an LED-based product., it is critical that engineering teams understand the system's thermal parameters, and focus on thermodynamic competencies.
The higher current increases the dissipated power, causing heating within the LED, which has a negative impact on light output. Also, conversely , a higher junction temperature (caused for example by a higher ambient temperature) causes a reduction in the LED's forward voltage, reducing the dissipated power for a constant-current source.
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This article was published in the April 2009 issue of LEDs Magazine.
To read the full version of this article, please visit our Magazine page, where you can download FREE electronic PDF versions of all issues of LEDs Magazine.
You can also request a print copy of LEDs Magazine (available by paid subscription) and sign up for our free weekly email newsletter . About the Author Rudi Hechfellner is technical marketing manager with Philips Lumileds Lighting Company ( ), San Jose , California, USA. April 2009 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2004 2005 2006 2007 2008 2009

Plug In Series​ Diode

In the rectifier circuit; the use of diodes in series can increase the back pressure withstand value (usually the sum of the back pressure of all diodes, but it is best to use diodes of the same specification).
In the voltage stabilization circuit; the series connection of the diode is equal to the sum of the voltage stabilization value of the diode. The use of diodes in parallel is theoretically the sum of rated currents, but considering that it is impossible to be absolutely symmetrical, they can only be used below 80% of the total.

TVS transient suppressor diodes work in the same way as regulator diodes, but there are structural differences.The biggest difference is that the PN junction area composed of the general regulator diode is very small, it can withstand the reverse current is small.

Transient Voltage Suppressor,Transient Voltage Suppressor Diode,Series diode

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