Light-emitting Diode Driver Research Articles

Harmonic Testing Analysis of Light Emitting Diode (LED) Lamps based SNI IEC 61000-3-2 Standard

The use of LED lamps in Indonesia has increased since 2013 because of low power consumption and high efficiency. LED lamps are non-linear loads that cause harmonic distortion in the electric power system. Harmonic distortion can impact to overheating in magnetic core electrical equipment. Therefore, it is necessary to standardize the limits of the harmonic emission limits of LED lamps. In this study, the harmonics measurements of LED lamps of 22 samples from 10 brands, which include different types of EMI filters in the LED drivers, are carried out to analyze harmonic currents. Measurements in this study conducted using Teseq ProfLine 2105. The results of parameter testing of third and fifth-order harmonic currents, peak current phase angle, beginning current flow at 60 degrees, and end current at 90 degrees were analyze based on the criteria for class C SNI IEC 61000-3-2 standard. The results showed that the three samples used EMI filter inductor in the LED driver can minimize third-order harmonic currents and comply with all parameters.

A combined universal generating function and physics of failure Reliability Prediction Method for an LED driver

The accurate and effective reliability prediction of light emitting diode (LED) drivers has emerged as a key issue in LED applications. However, previous studies have mainly focused on the reliability of electrolytic capacitors or other single components while ignoring circuit topology. In this study, universal generating function (UGF) and physics of failure (PoF) are integrated to predict the reliability of LED drivers. Utilizing PoF, lifetime data for each component are obtained. A system reliability model with multi-phase is established, and system reliability can be predicted using UGF. Illustrated by a two-channel LED driver, the beneficial effects of capacitors and MOSFETs for the reliability of LED drivers is verified. This study (i) provides a universal numerical approach to predict the lifetime of LED drivers considering circuit topology, (ii) enhances the modelling and reliability evaluation of circuits, and (iii) bridges the gap between component and circuit system levels.

High-Efficient Electrolytic-Capacitor-less Off-Line LED Driver with Reduced Power Processing

In this article, an integrated parallel buck–boost and boost converter (IPB3C) is proposed as an electrolytic-capacitor-less light-emitting diode (LED) driver. The IPB3C provides a high power factor (PF) and low total harmonic distortion (THD). The driver is composed of two converters that are connected in parallel, using just one controlled switch. The buck–boost duty is to deliver constant power to the LED, while ensuring a good PF. The boost converter is employed to cancel the low-frequency ripple at the LED. In return, this decreases the flicker effect and only a relatively small capacitance is needed to fulfill the standard requirements. The buck–boost converter handles the full power of the LED, while the boost converter handles only a portion of the LED power. Thus, better efficiency is ensured by this parallel configuration compared to conventional cascaded integrated converters. Moreover, the voltage across the switch is low, as it is the higher, whether buck–boost or boost converter, but not the addition of both. In this article, the IPB3C is analyzed, and its design methodology is presented. A universal input voltage range prototype of the proposed converter supplying an LED lamp of 108-V/ 0.35-A is presented. The prototype shows high PF, nearly equal to one, very small THD, nearly zero, output voltage ripple of 4.5%, output current ripple of 19%, and high efficiency, equal to 92.4%. Moreover, the converter requires the use of a bulk capacitance of only 68 μF, while the required output capacitance is just 1 μF.

A High-Performance Isolated SEPIC Converter for Non-Electrolytic LED Lighting

This paper proposes a high-performance isolated single-ended primary inductor converter (SEPIC) that is integrated with a non-dissipative snubber for a light-emitting diode (LED) driver. The proposed LED driver employs the snubber circuit to minimize any switching overvoltage caused by parasitic leakage inductance of the high-frequency transformer in the isolated SEPIC converter. This paper also presents a detail theoretical analysis of the proposed LED driver including its operating modes and design calculation. The experimental results of the proposed LED driver at the rated power of 18 W shows that it has a high-power factor, low harmonics, employs non-electrolytic capacitors, low switching stress, high reliability and high efficiency.

An Improved Power Quality Evaluation for LED Lamp Based on G1-Entropy Method

Nowadays, light emitting diode (LED) lamps have been widely utilized for lighting system due to its low-energy consumption. The harmonic emission standard is ignored by most of the manufacturers, high harmonic current will increase harmonic injection and cause fire risk. Existing research focuses on investigating harmonic emissions from several specific LED drivers, but a systematic evaluation approach is not given. The contribution of this paper proposed a LED harmonic evaluation in the management view, which can evaluate the harmonics of the LED lamps, accelerate the elimination of inferior LED lamps, and improve the power quality of distribution network. The evaluation approach combines G1 method and entropy method, which can make the weighting more scientific and rational. An evaluation model is established by collecting data, then the G1-entropy method is used to calculate the weights of harmonic characteristics in this model. Finally, we analyze and discuss the results, a specific evaluation approach is proposed, which can thoroughly and accurately represent the harmonic characteristics of LED lamps.

A New Current Mirror Balancing Circuit for AC-LED Lighting

This paper proposes a new current balancing method for alternating current (AC) - light emitting diodes (LED). The proposed method uses the bi-directional current mirror circuit with negative feedback that consists of two reference currents, n+1 NPN transistors, n+1 PNP transistors, and 2(n+1) resistors for n pairs of anti-parallel LED strings. It can balance the LED currents in multiple AC-LED strings regardless of the polarity of the AC source while reducing the differences in LED currents caused by the early effect. In addition, the proposed circuit can achieve LED current balancing even in the variations of parameters among the transistors due to the negative feedback operation. Simulations and experiments were performed to verify the effectiveness of the proposed circuit. The balancing operation of the proposed circuit was simulated at low (50/60 Hz) and high (60 kHz) frequencies. In addition, open/short protection, power factor, and efficiency of an LED driver using the proposed circuit were analyzed and compared with a basic mirror circuit. For the experiments, a prototype was built and tested for 5W LED lighting consisting of three pairs of anti-parallel LED strings. The maximum LED current difference $\Delta i_{LED} $ was reduced from 45 mA to 4 mA by the balancing operation of the proposed circuit.

Designing a high-speed light emitting diode driver circuit for visible light communications

Designing a high-speed light emitting diode driver circuit for visible light communications

A High-Efficiency High Power Driver Circuit for Joint Illumination and Communication System With Phase Shift Pre-Emphasis Technology

This paper presents an improved white light-emitting-diode (LED) wireless transmitter for the Joint Illumination and Communication (JIC) System, which consists of two parts: the driver circuit and the pre-emphasis circuit. The main purpose of the driver circuit part is to solve the problem of dissipated power when sweeping the remaining carriers during the signal modulation of the high-efficiency, high-power and high-speed white LED driver. A push-pull structure driver with a current conduction angle less than 180 degrees is proposed, which is analogous to a Class C power amplification driver, thus avoiding the simultaneous existence of voltage and current on the driver circuit when the remaining carriers are swept out, and improves the efficiency of the LED driver. On this basis, the pre-emphasis circuit part adopts the phase shift technology to improve the data transmission rate, and the system efficiency has also been improved. Then, an improved class C push-pull structure white LED driver with phase shift pre-emphasis technology is formed. This novel driver and pre-emphasis technology achieve a system efficiency of 95.73% with a 10 W LED. The test results show that the system communication -3 dB bandwidth expanded from the original 8.3 MHz to 13.67 MHz, and the best-obtained transceiver baud rate is 25 Mbps at a distance of 1.3 m with BER of 1.63 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> . The test result verifies that the LED driver proposed in this paper is currently the highest figure of merit (FoM) for high power JIC systems.

LLC LED Driver with Current-Sharing Capacitor Having Low Voltage Stress

In this paper, an LLC light-emitting diode (LLC LED) driver based on the current-sharing capacitor is presented. In the proposed LED driver, the LLC resonant converter is used to step down the high input voltage, to provide galvanic isolation, to offer a constant current for LEDs. Moreover, the current-sharing capacitor connected to the central-tapped point of the secondary-side winding is used to balance the currents in two LED strings. By doing so, the voltage stress on this capacitor is quite low. Above all, the equivalent forward voltages of the two LED strings are generally influenced by the temperature and the LED current, and this does not affect the current-sharing performance, as will be demonstrated by experiment on the difference in number of LEDs between the two LED strings. In addition, only the current in one LED string is sensed and controlled by negative feedback control, while the current in the other LED string is determined by the current-sharing capacitor. Moreover, this makes the current control so easy. Afterwards, the basic operating principles and analyses are given, particularly for how to derive the effective resistive load from the LED string. Eventually, some experimental results are provided to validate the effectiveness of the proposed LED driver.

In Vivo Evaluation of a Subcutaneously Injectable Implant with a Low-Power Photoplethysmography ASIC for Animal Monitoring.

Photoplethysmography is an extensively-used, portable, and noninvasive technique for measuring vital parameters such as heart rate, respiration rate, and blood pressure. The deployment of this technology in veterinary medicine has been hindered by the challenges in effective transmission of light presented by the thick layer of skin and fur of the animal. We propose an injectable capsule system to circumvent these limitations by accessing the subcutaneous tissue to enable reliable signal acquisition even with lower light brightness. In addition to the reduction of power usage, the injection of the capsule offers a less invasive alternative to surgical implantation. Our current prototype combines two application-specific integrated circuits (ASICs) with a microcontroller and interfaces with a commercial light emitting diode (LED) and photodetector pair. These ASICs implement a signal-conditioning analog front end circuit and a frequency-shift keying (FSK) transmitter respectively. The small footprint of the ASICs is the key in the integration of the complete system inside a 40-mm long glass tube with an inner diameter of 4 mm, which enables its injection using a custom syringe similar to the ones used with microchip implants for animal identification. The recorded data is transferred wirelessly to a computer for post-processing by means of the integrated FSK transmitter and a software-defined radio. Our optimized LED duty cycle of 0.4% at a sampling rate of 200 Hz minimizes the contribution of the LED driver (only 0.8 mW including the front-end circuitry) to the total power consumption of the system. This will allow longer recording periods between the charging cycles of the batteries, which is critical given the very limited space inside the capsule. In this work, we demonstrate the wireless operation of the injectable system with a human subject holding the sensor between the fingers and the in vivo functionality of the subcutaneous sensing on a pilot study performed on anesthetized rat subjects.

A Soft-Switching Transformer-Less Step-Down Converter Based on Resonant Current Balance Module

In this article, a soft-switching transformer-less step-down converter based on a resonant current balance module is proposed. An LED driver is taken as an example of the analysis and design of the converter. The converter is made up of a stacked half-bridge, resonant current balance modules, and pairs of light-emitting diode (LED) strings. The resonant current balance modules allow the proposed converter to realize automatic current sharing, soft switching, and extending to a 1/N converter. The proposed converter can operate in discontinuous conduction mode (DCM) or continuous conduction mode (CCM) mode by choosing different operation frequencies, and achieve zero current switching or zero voltage switching (ZVS), respectively. Also, by using frequency doubling technique in the half-bridge, the switching losses are reduced by half under the same conditions. A 15.8-W experimental prototype with 100 V input voltage and 25 V output voltage has been implemented in the laboratory, verifying the feasibility of the soft-switching transformer-less step-down converter.

Capacitance Reduction in Flicker-Free Integrated Offline LED Drivers

This article presents a deep analysis of the low-frequency ripple transferred from the bus voltage to the light-emitting diode (LED) current in integrated two-stage power converters, operating as offline LED drivers. This analysis presents a design methodology to select the optimum power control stage converter to the LED load and to reduce the bulk capacitance. The main focus is to analyze the ripple transfer ratio of the three main nonisolated dc-dc converters, namely buck, boost, and buck-boost. Moreover, this article presents a step-by-step case study for an existing converter and the proposed converter supplying a 26.9-W Luxeon 3014 LED load. The experimental results show that the integrated buck and boost converter requires a bus capacitance of 1200 μF, whereas in the integrated buck and buck-boost converter, the capacitance is reduced to 680 μF by applying the method proposed. This represents that the replacement of a boost converter by a buck-boost converter on the second stage allows a 50% reduction of the bus capacitance while keeping the same current ripple.

Single-Phase LED Driver With Reduced Power Processing and Power Decoupling

Reduced power processing is a new trend to improve the conversion efficiency of light-emitting diode (LED) driver systems. Based on the concept, a new LED driver architecture is proposed in this article, which requires fewer power semiconductors compared with prior works, leading to the potential of lower cost and higher efficiency. A new ac/dc LED driver topology is derived accordingly based on the architecture to achieve the constant output current and unity power factor with significant energy storage reduction of the 100-/120-Hz energy buffer. Through a split and shared inductor, the required magnetic energy storage in the derived topology is the same as the conventional single-stage power factor correction converter, indicating high power density. Experimental evaluation verifies the performance in terms of improved power quality and conversion efficiency.

Input voltage controlled full‐bridge series resonant converter for LED driver application

In this study, a phase shift controlled full-bridge series resonant converter (SRC) integrated with buck converters for light-emitting diode (LED) driver application is proposed. This LED driver supplies four LED loads simultaneously. The current through LED loads is controlled by phase shift control of the SRC, and its output is added to the input voltage. Zero-voltage switching (ZVS) switching of all the switches is achieved by operating the SRC at lagging power factor for all input voltage variations. As the only part of the output power is processed through the SRC and all the switches operating with ZVS, the efficiency of the converter is 95.7%, which is high. A 142 W LED driver is designed, and its performance is tested with PSPICE simulations and experimental prototype.

A 280 μW, 108 dB DR PPG-Readout IC With Reconfigurable, 2nd-Order, Incremental ΔΣM Front-End for Direct Light-to-Digital Conversion.

This paper reports on a low-power readout IC (ROIC) for high-fidelity recording of the photoplethysmogram (PPG) signal. The system comprises a highly reconfigurable, continuous-time, second-order, incremental delta-sigma modulator (I-ΔΣM) as a light-to-digital converter (LDC), a 2-channel 10b light-emitting diode (LED) driver, and an integrated digital signal processing (DSP) unit. The LDC operation in intermittent conversion phases coupled with digital assistance by the DSP unit allow signal-aware, on-the-fly cancellation of the dc and ambient light-induced components of the photodiode current for more efficient use of the full-scale input range for recording of the small-amplitude, ac, PPG signal. Fabricated in TSMC 0.18μm 1P/6M CMOS, the PPG ROIC exhibits a high dynamic range of 108.2dB and dissipates on average 15.7μW from 1.5V in the LDC and 264μW from 2.5V in one LED (and its driver), while operating at a pulse repetition frequency of 250Hz and 3.2% duty cycling. The overall functionality of the ROIC is also demonstrated by high-fidelity recording of the PPG signal from a human subject fingertip in the presence of both natural light and indoor light sources of 60Hz.

External temperature sensor assisted a new low power photoplethysmography readout system for accurate measurement of the bio-signs.

This study presents an external temperature sensor assisted a new low power, time-interleave, wide dynamic range, and low DC drift photoplethysmography (PPG) signal acquisition system to obtain the accurate measurement of various bio signs in real-time. The designed chip incorporates a 2-bit control programmable transimpedance amplifier (TIA), a high order filter, a 3:8 programmable gain amplifier (PGA) and 2 × 2 organic light-emitting diode (OLED) driver. Temperature sensor is used herein to compensate the adverse effect of low-skin-temperature on the PPG signal quality. The analog front-end circuit is implemented in the integrated chip with chip area of 2008 μm × 1377 μm and fabricated via TSMC T18 process. With the standard 1.8 V, the experimental result shows that the measured current sensing range is 20 nA–100 uA. The measured dynamic range of the designed readout circuit is 80 dB. The estimated signal to noise ratio is 60 dB@1 uA, and the measured input referred noise is 60.2 pA/Hz½. The total power consumption of the designed chip is 31.32 µW (readout) + 1.62 mW (OLED driver@100% duty cycle). The non-invasive PPG sensor is applied to the wrist artery of the 40 healthy subjects for sensing the pulsation of the blood vessel. The experimental results show that for every 1 °C decrease in mean ambient temperature tends to 0.06 beats/min, 0.125 mmHg and 0.063 mmHg increase in hear rate (HR), systolic (SBP) and diastolic (DBP), respectively. Similarly, for every 1 °C increase in mean ambient temperature tends to 0.13 beats/min, 0.601 mmHg and 0.121 mmHg increase in HR, SBP and DBP, respectively. The measured accuracy and standard error for the HR estimation are 96%, and − 0.022 ± 2.589 beats/minute, respectively. The oxygen stauration (SpO2) measurement results shows that the mean absolute percentage error is less than 5%. The resultant errors for the SBP and DBP measurement are − 0.318 ± 5.19 mmHg and − 0.5 ± 1.91 mmHg, respectively.Electronic supplementary materialThe online version of this article (10.1007/s00542-020-05106-y) contains supplementary material, which is available to authorized users.

Designing a high-speed light emitting diode driver circuit for visible light communications

LEDs are an essential component in visible light communication systems and need to be modulated for data transmission at the same time of lighting. The modulation speed of LEDs is limited by the remaining carriers that remain in the depletion capacitance when the LEDs turn off. This paper designs a high-speed LED driver that can remove remaining carriers, which shortens the falling time of modulation pulse, and thus improves the modulation speed. The driver is fabricated using three discrete FETs and some resistors and capacitors on a board. One FET is used to control the lighting and extinguishing of a LED and the other two FETs are used to remove remaining carriers. The performance of the driver is demonstrated by driving a blue LED and a near ultraviolet LED respectively. In experiments, the FETs on the board are triggered by a square-wave signal with the frequency of 1 MHz and the optical signals emitted from the LEDs are detected by a photoelectric detector. The experimental results show that this design decreased the falling time from 66 down to 32 ns for the blue LED as well as from 40 down to 26 ns for the near ultraviolet LED, which demonstrates the improvement of the LED modulation speed.

Multichannel sequential display LED driver with optimal transient performance and efficiency via synchronous integral control

This study proposes a high performance multichannel sequential display light emitting diode (LED) driver with pulse width modulated dimming control. A synchronous integral control strategy is developed for achieving optimal transient performances for the channel voltages and ideal rectangular waveforms for the LED current, which will help to maintain high efficiency and extend the lifetime of the LEDs. By synchronous integral control, each channel has a corresponding integrator whose input and output are turned on and off synchronously with the LED string. The proposed driver topology and control strategy are supported by detailed analysis on stability and transient response during on-time interval of a channel by using the averaged state-space model. The effectiveness of the design method is demonstrated with simulation. A three-channel LED driver is constructed to experimentally validate the high efficiency and high performance of the proposed topology and control strategy with desired LED current waveform and nearly constant channel voltages.

LED driver based on novel ripple cancellation technique for flicker‐free operation and reduced power processing

Light-emitting-diode (LED) drivers are required to maintain the power quality of both the AC input and DC output side. The regulation prevents adverse impacts on the grid and maintains the nominal operating condition of LEDs. Without significant filtering, the input power from a single-phase AC source can result in low-frequency flickers that raise health issues. This study proposes a LED driver topology to achieve low harmonics at the AC side and maintain flicker-free operation to drive LEDs. A novel ripple-cancelling scheme is developed to minimise redundant power processing and reduce circuit complexity to achieve high-conversion efficiency. The new topology supports a simple control strategy to operate the driver effectively. Experimental evaluation demonstrates the system performance and verifies the novelty and contribution.

Novel distortionless dimming in high power LED lighting using isolated SEPIC converter

A new low-cost energy-saving concept in the modern light-emitting diode (LED) illumination system is developed and implemented using an isolated single-ended primary inductance converter (SEPIC). The dimming scheme presented in this study is a single-step with negligible distortion in the AC mains current as compared to the traditional low-cost triode for alternating current (TRIAC) dimming system, which distorts the AC mains current wave-shape beyond sinusoidal nature due to the phase-cut techniques. This dimming concept is completely retrofitted, no additional arrangement is required to initiate the dimming as compared to a TRIAC dimmer or other controllers. The isolated SEPIC converter is modelled and analysed in detail using the state-space average technique. The stability of the designed converter and overall closed-loop control are verified using Bode-plot analysis. The full load converter efficiency is found around 93%, which is much higher than the conventional flyback topology-based LED driver. The concept presented in this study is tested with the help of a laboratory prototype with an LED load of 60 W.