High-Efficiency Flicker-Free LED Driver with Soft-Switching Feature

Cheng, Hung‐Liang; Hwang, Lain-Chyr; Chang, Heidi H.; Wang, Qiyou; Cheng, Chun-An

doi:10.3390/mi13050797

Cited by 3 publications

(1 citation statement)

References 20 publications

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“…Papers [17][18][19][20] describe techniques and systems using full-bridge power converters with soft switching techniques as control systems for single power LEDs or LED modules in order to improve the power quality characterized by the total harmonic distortion (THD) of the supply current. These systems are prepared to be supplied from the power grid or from photovoltaic systems with the use of the dedicated DC energy accumulators, for off-grid operation when supplying highways lighting lamps.…”

Section: Introductionmentioning

confidence: 99%

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

Górecki,

Ptak,

Gensikowski

2023

Energies

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This article presents the method of implementation and the results of experimental investigations illustrating an influence of parameters of the signal controlling the current flowing through power LEDs on their junction temperature and on parameters characterizing the light emitted by them. The measurement system used and the tested power LEDs are described. The results of measurements of the junction temperature of the tested devices, the values of the average value of the power dissipated in the tested devices and the photometric and radiometric parameters of these devices obtained for different values of frequency and the duty cycle of the signal controlling the current flowing through the tested diodes are presented and discussed. It is shown that the operation of the considered semiconductor devices is more effective at low frequency values. The possibility of adjusting the optical parameters of the power LEDs in the considered range of frequency and the duty cycle adjustment is assessed. Additionally, the measured waveforms of the current supplying the tested LEDs is shown. The influence of the parasitic capacitances of the tested devices is discussed. On the basis of the obtained investigation results, some recommendations for the designers of lighting systems can be formulated. In order to obtain an almost linear dependence of the illuminance on the duty cycle, the values of frequency not exceeding 10 kHz should be used.

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Section: Introductionmentioning

confidence: 99%

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

Górecki,

Ptak,

Gensikowski

2023

Energies

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LED light can falsify pulse oximetry readings via the stroboscopic effect

Wald,

Erwin,

Annon-Eberharter

et al. 2023

Phys Eng Sci Med

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Because of its simplicity, pulse oximetry plays a ubiquitous role in neonatology. Its measurements are based on the absorption of light by hemoglobin. Ambient light can affect these values, therefore algorithms are designed to compensate for constant ambient light. Modern light-emitting diodes often flicker at a very high frequency. Such flickering ambient light can lead to significant measurement errors in saturation. To present a novel way in which light-emitting diodes influence the function of pulse oximeters and to demonstrate mathematically that a stroboscopic effect may well be responsible for this disturbance. Using publicly available data, a mathematical model of a pulse oximeter with a calibration curve and a proprietary measurement algorithm was created. This was used to simulate saturation measurements in flickering ambient light. To do this, photopletysmograms for red and infrared light at 98% oxygen saturation were mathematically superimposed on the light emission from an examination lamp used in the intensive care unit. From these results, presumable saturation measurements from a pulse oximeter were extrapolated. The light-emitting diodes in the examination lamp flicker at 207 Hz. The pulsating light from the light-emitting diodes causes superimposition of the photoplethysmogram due to the stroboscopic effect. With increasing brightness, the saturation dropped to 85% and the pulse rate to 108 bpm. The pulsed light of light-emitting diodes can distort pulse oximetry measurements. The stroboscopic effect leads to low saturation values, which can lead to the risk of blindness in premature infants due to excessive oxygenation.

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Interleaved Modified SEPIC Converters with Soft Switching and High Power Factor for LED Lighting Appliance

Cheng,

Chang

et al. 2024

Applied Sciences

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A novel ac/dc LED driver with power factor correction and soft-switching functions is proposed. The circuit topology mainly consists of two modified single-ended primary inductance converters (SEPIC) with interleaved operation. The first half stage of SEPIC operates like a boost converter and the second half stage operates like a buck–boost converter. Each boost converter is designed to operate in discontinuous current mode (DCM) to function as a power factor corrector (PFC). The two buck–boost converters that share a commonly coupled inductor are designed to operate at near boundary conduction mode (BCM). Without using any active clamping circuit, auxiliary switch or snubber circuit, the active switches can achieve zero-voltage switching on, and all diodes achieve zero-current switching off. First, operation modes in steady state are analyzed, and the mathematical equations for design component parameters are derived. Finally, a prototype circuit of 180 W rated power was built and tested. Experimental results show satisfactory performance of the proposed circuit.

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High-Efficiency Flicker-Free LED Driver with Soft-Switching Feature

Cited by 3 publications

References 20 publications

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

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

LED light can falsify pulse oximetry readings via the stroboscopic effect

Interleaved Modified SEPIC Converters with Soft Switching and High Power Factor for LED Lighting Appliance

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