Abstract
This paper addresses the power penalty in an illumination LED caused by visible light communication (VLC). This study models the extra power consumption of the LED by taking into account the convex relation between the dissipated electrical power versus the LED current on one hand and the concave relation between the output luminous flux versus the current on the other hand. The ratio of the output luminous flux to input electrical power, which is known the LED luminous efficacy, is analyzed considering various recombination mechanisms and their dependency on current and temperature. As examples, the rapid light fluctuations induced by Pulse Amplitude Modulation (PAM) and orthogonal frequency division multiplexing (OFDM) are analyzed for joint illumination and communication (JIC) systems. Due to the signal modulation, there is a decrease in the output light of LED. Nevertheless, the total power offered to LED is larger than without modulation and thus extra heating occurs. Moreover, particularly when burst transmission is used in communication networks, visible flicker may occur.
Highlights
Light Emitting Diodes (LEDs) are commonly used for both specialized and general illumination applications
Where ηIQE is the ratio of photons generated by electron-hole recombination to the total number of electrons injected into the LED, and ηExt is defined as the ratio of the photons extracted out into the free space to the photon generated in the Quantum Well (QW)
This work showed that extra power was inevitably consumed in an illumination LED when it was used for data transmission
Summary
Light Emitting Diodes (LEDs) are commonly used for both specialized and general illumination applications. The output luminous flux is proportional to the average current (DC-bias) through LED with modulation [1, 9, 12]. This paper quantifies the extra power consumption associated with the luminous flux compensation in the LED. The power dissipation in the LED will increase the temperature, which in return decreases the light output in terms of decreased efficacy. The fast data modulation with both up and down current introduces increased power consumption but with reduced light output. This paper quantifies the LED power consumption, including the extra power loss induced by data transmission. The perceived output of commercial lighting LEDs is usually described in photometric units, such as the luminous flux in lumen (lm). We express LED luminous flux in terms of the driving current and temperature
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