The impact of the driving frequency on the output flux of high-power InGaAlP-LEDs during high-current pulsed operation

Benjamin Schulz; Stefan Morgott

doi:10.1117/12.2272438

6 September 2017 The impact of the driving frequency on the output flux of high-power InGaAlP-LEDs during high-current pulsed operation

Benjamin Schulz, Stefan Morgott

Author Affiliations +

Proceedings Volume 10378, Sixteenth International Conference on Solid State Lighting and LED-based Illumination Systems; 103780O (2017) https://doi.org/10.1117/12.2272438
Event: SPIE Optical Engineering + Applications, 2017, San Diego, California, United States

Abstract

Direct red light-emitting diodes based on InGaAlP comprise a strong temperature sensitivity regarding their output flux. In étendue-limited applications, like digital projectors, these LEDs are usually driven at current densities exceeding 3 A/mm² in pulsed mode. The losses inside the semiconductor lead to a large amount of heat, which has to be removed most efficiently by a heatsink to keep the junction temperature as low as possible and therefore to obtain the maximum output flux. One important performance parameter is the thermal resistance R_th of the LED, which has been improved during the last few years, e.g. by the development of new high-power chips and packages. In our present approach, we investigated the influence of the driving frequency – which is closely related to the thermal impedance Z_th – on the luminous and the radiant flux of red LEDs. A simulation model based on the electro-thermal analogies was implemented in SPICE and the optical and electrical characteristics of one LED type (OSRAM OSTAR Projection Power LE A P1W) were measured under application-related driving conditions while varying the parameters frequency, duty cycle, forward current, and heatsink temperature. The experimental results show clearly that the luminous and the radiant flux go up when the driving frequency is increased while the other parameters are maintained. Moreover, it can be noticed that the degree of this effect depends on the other parameters. The largest impact can be observed at the lowest tested duty cycle (30 %) and the highest tested current density (4 A/mm²) and heatsink temperature (80 °C). At this operating point, the luminous and the radiant flux increase by 20 % and 14 % respectively when raising the frequency from 240 Hz to 1920 Hz.

Conference Presentation

Citation Download Citation

Benjamin Schulz and Stefan Morgott "The impact of the driving frequency on the output flux of high-power InGaAlP-LEDs during high-current pulsed operation", Proc. SPIE 10378, Sixteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 103780O (6 September 2017); https://doi.org/10.1117/12.2272438

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available