Dimming Techniques Focusing on the Improvement in Luminous Efficiency for High-Brightness LEDs

Abstract

The pulse width modulation (PWM) dimming mode features good dimming linearity and has been widely used for driving high-brightness light-emitting diodes (HBLEDs), in which the brightness change is reached by modulating the duty cycle of the dimming signal to regulate the average current flowing through LEDs. However, the current-illuminance characteristic curve of most LEDs is nonlinear in nature. Namely, under the same lighting power fed, the conventional PWM dimming cannot make the LED exert its best luminous efficiency (LE) specified in datasheets. This paper focuses on the study of further improving LED luminous efficacy via dimming manipulation. Thereby, two multilevel current dimming techniques with varied dimming signal voltage and varied current sensing resistance are presented. With limited dimming capability, the proposed dimming strategies can efficiently raise the luminous flux ratio without increasing the power consumption. A prototype constructed for a 115 W HBLED driver is developed and the devised dimming schemes are realized by a digital signal controller (DSC). Experimental results exhibited with illuminance-power curves and CIE1931 and CIE1976 chromaticity diagrams are given to validate the theoretical derivation and effectiveness. Compared with conventional PWM dimming, under the same illuminance, the driver average output power is respectively reduced by 17.08% and 13.17%; the improvement in average illuminance under the same output power is 13.66% and 11.17%, respectively. In addition, the entire average LE boost has respectively increased by 21.36% and 16.37%.

An Approach to Improve Energy Efficiency during Antimicrobial Blue Light Inactivation: Application of Pulse-Width Modulation Dimming to Balance Irradiance and Irradiation Time

“…The irradiance of LEDs can be changed by adjusting the drive current or the duty cycle of the pulse-width modulation (PWM). The former method will result in a limited dimming range, decreased luminous efficiency, and color shift in LEDs [ 33 ], while PWM dimming has been widely used for driving LEDs due to its fast response and linear dimming [ 34 , 35 ]. Adjusting the duty cycle of PWM, the peak irradiance in every single cycle remains constant, whereas the output average irradiance is regulated in accordance with varying duty cycles.…”

Investigation of an LED Strip Controller Based on a PWM Driver and a PIC Series Microcontroller

“…Over the past decades, LED lighting technologies have not only rapidly developed and improved, but at the same time, their use in various fields has increased significantly. The main reasons for the investment in LED technologies and the increase in their consumption are that using LEDs can save huge amounts of electricity (compared to old incandescent bulbs, use of LEDs can save 10 times more electricity) [1][2][3]. Another important reason for the popularity of LEDs is that the entire spectrum of visible light can be easily obtained.…”

“…and the LED characteristics is often a linear expression. When using PWM controllers for LED control, it is very important to apply various programming strategies that would allow lighting control at the highest LED energy consumption efficiency [2,3,[12][13][14][15].…”

“…The DMX transmission rate is limited, so there may be limitations if you need to control fast and high-resolution light effects (based on LED technology). RDM (remote device management) is a technology that allows remote control and configuration of various devices, including LED lights, using the DMX (Digital Multiplex) communication protocol [3,4,[16][17][18][19][20]. This technology enriches traditional DMX control by providing more functions and possibilities.…”

An Influence of Parameters of the Control Signal of Power LEDs on Their Junction Temperature and Emitted Light

“…Papers [23][24][25][26] present a review of the techniques of controlling power LEDs using the rectangular PWM signal controlling the gate of the power transistor, full-bridge and half-bridge systems. The operating characteristics of the current and voltage stabilizer systems with the use of a series resistor to limit the current flowing through the power LED and a classical voltage divider are also mentioned and shown.…”