A PWM constant average current driving technique for solar LED lighting systems
Journal
Journal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao
Journal Volume
30
Journal Issue
6
Pages
455-465
Date Issued
2009
Author(s)
Abstract
A stand-alone solar LED lighting system usually consists of a DC/DC converter to convert the floating battery voltage into a constant current to drive the LED. A 15% energy loss of the DC/DC converter will be introduced. The DC/DC converter may also increase system costs and reduce system reliability due to its additional components. The present study develops a PWM technique to drive the LED luminaire directly from the battery output using the PWM's constant average current. However, the instantaneous current stress may decrease the overall light efficiency of an LED luminaire when it is driven by a PWM current. The result shows that the overall lighting efficiency loss is between 10.7% to 13.1% for a junction temperature at 70°C when using a 24V battery system. This study shows that the direct PWM driving technique is feasible and able to drive an LED directly from battery output in a stand-alone solar system. Removing the traditional DC/DC converter increases system reliability and reduces system costs.
Subjects
Constant average driving technique; LED direct PWM driving technique; Pulse-driven LED; Stand-alone solar LED lighting system
Other Subjects
Average currents; Battery systems; Battery voltages; Constant current; Energy loss; Instantaneous current; Junction temperatures; LED lighting system; Light efficiency; Lighting efficiency; PWM techniques; Stand -alone; System costs; System reliability; Cost reduction; DC-DC converters; Energy dissipation; Lighting; Lighting fixtures; Solar system; Light emitting diodes
Type
journal article