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Algorithms for selecting LEDs to imitate a group of daylight spectra, instead of fixed-spectrum lighting, are based on minimizing two indices. The first index related to the LEDs only is minimized for determining LED candidates. Minimizing the second index obtained by applying the daylight spectra to the candidates achieves a minimax solution. The sum of the second indices of the daylight spectra can be well approximated by that of the average spectrum of the daylight spectra and is treated as a target spectrum for the LED selection. A pruning process is followed to delete redundant LEDs. OCIS codes: 230.0230, 230.3670, 070.4790, 300.6170.

A compact-size and high-conversion-efficiency regulator used to stabilize the luminous flux of alternating-current-operated light-emitting diodes (ACOLEDs) is proposed. The presented regulator is composed of a full-bridge rectifier and a power switch to supply directly from ac power source for the ACOLEDs without any ac/dc converter. Commonly adopted pulsewidth modulation techniques are utilized to regulate the input power fed into ACOLEDs. Design guidelines and experimental results of the prototyping regulator for an 8-W ACOLED operating under different input ac voltages (110 \pm 10\ \Vrms, 60 Hz) are provided. According to the experimental results, the advantages of the proposed regulator include simplified design, compact size, high conversion efficiency, and low cost. Since no magnetic component is required in the presented system, therefore, it can easily be fabricated into the same ACOLED chip in the future. [ABSTRACT FROM AUTHOR]

In this paper, a new dimmable electronic ballast for metal-halide (MH) lamps based on a three-stage structure is proposed. The presented dimmable electronic ballast can dim smoothly without acoustic resonance from 50% to 100% brightness. A novel current-control method with constant-power capability is also presented to solve the power-drifting problem resulting from the V– I characteristic variations between lamps or caused by the aging of lamp. The dimming capability allows the ballast to adjust its working condition according to the environments or the dimming command; this further improves the energy efficiency. Finally, a 150-W MH lamp ballast prototype is built to verify the feasibility of the proposed methods. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents a solar-powered lighting system, using cold-cathode fluorescent-lamps (CCFLs), with its battery-charging circuit and lamp-ignition circuit being separated so that its solar panels can be installed at any distance deemed necessary away from the lighting site in order to receive the maximum solar energy available. This system adopts the maximum-power point tracking (MPPT) method to control the power output of the solar panels and uses the zero-voltage switching (ZVS) DC–DC converter, as the charging circuit, to increase the panels’ power generation efficiency and the charging circuit’s conversion efficiency. The electronic ballast circuit for the CCFL is constructed with a half-bridge inverter, a resonant inductor, and a Rosen-type piezoelectric transformer, which forms a piezoelectric resonant-type inverter: to simplify the circuitry and to improve the power conversion efficiency, the ballast circuit is designed to directly step up the battery voltage in igniting the lamp. We also establish the transmission-parameter model for the piezoelectric resonant-type inverter to provide the base for the electric-power circuit design. Our experimental results indicate that the proposed system possesses some advantages, such as greater energy efficiency, circuitry simplicity, and so on, and is suitable for night lighting in house yards, parks and advertising panels. [Copyright &y& Elsevier]