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%.
Highlights
In recent years, solid-state lighting (SSL) components have become the mainstream light source in many lighting applications
V 1 + R ⋅ gm this paper is aimed at further rbetteringS the luminous efficiency of light-emitting diodes (LEDs), and thusTherefore, two multilevel current dimming with varied the closed loop gain Afmechanisms of the linear current control (LCC) circuit can becurrent figuredsensing out as resistance (VCSR) and varied dimming signal voltage (VDSV) are studied
A square hole was cut on the side to facilitate wiring, which was sealed with A
Summary
Solid-state lighting (SSL) components have become the mainstream light source in many lighting applications. It includes high/low PWM current levels and duty cycles to provide a 2-D luminosity control capability and to reduce the energy consumption This proposed method can be derived to an n-level driving way for bettering the electricalto-light conversion efficiency of LEDs. A general n-level driving approach based on the PWM driving mode is proposed in Ref. Due to the nonlinearity of dimming cannot emit the brightness should have.fed In other words, it cannot current versus illuminance behavior,that theitsame power to light the LED withachieve the best luminous efficiency conversion specified in its specifications. It cannot current versus illuminance behavior,that theitsame power to light the LED withachieve the best luminous efficiency conversion specified in its specifications In this dimming cannot emit the brightness that it should have.
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