Light Emitting Diode Driver Circuit Research Articles

Electromagnetic emission measurement prediction of buck-boost converter circuits using machine learning methods

ABSTRACT In this paper, a prediction system has been developed using machine learning techniques to obtain the conduction emission levels ensure they remain below the limit values specified in test standards. An LED (Light-emitting diode) driver circuit based on a buck-boost type DC-DC converter has been employed in the experiments. Standards-compliant conducted emission testing processes have been performed and measurement results have been used to generate datasets. These datasets have been organized and processed according to the targeted machine learning methods. GPR, has achieved the highest success rate of 99% among ANN and regression methods. In order to improve the performance in EMI harmonic prediction, training was conducted using deep learning, and the obtained model has a mean squared error of 0.78. The harmonics are well captured with the method and the results are in good agreement with measurements. Consequently, the number of required pre-compatibility tests for a similar topology can be significantly reduced.

Soft‐switched full‐bridge converter for LED lighting applications with reduced switch current

SummaryLighting systems using light‐emitting diode (LED) have drawn significant attention across the world. This is due to their promising features such as high energy efficiency, reduced greenhouse gas emission, and eco‐friendly nature. However, these systems require constant current regulators to provide constant illumination. This article proposes a soft‐switched full‐bridge LED driver circuit for dc‐grid applications with dimming control operation. The circuit consists of a soft‐switched full‐bridge converter to power different LED lamps with reduced device count from dc‐grid voltage. The semiconductor switches of the full‐bridge converter conduct a small current during on time due to interleaved inductor and equal current sharing of lamp‐2 and lamp‐3. This feature reduces the conduction losses. In addition, the proposed converter yields less component count per lamp, dimming operation through on–off control and zero voltage switching, which results in low switching losses. The detailed steady‐state analysis of the proposed converter for dc‐grid applications with dimming control operation is presented in this work. The performance of the proposed converter is compared with other similar topologies available in the recent literature. Numerical simulations and real‐time experimental validations are conducted to evaluate the steady‐state performance of the proposed converter topology for LED applications, driving multiple lamp loads from dc‐grid. It has been established that the efficiency of the proposed full‐bridge converter is 97.52% at the rated power.

A single‐stage bridgeless LLC resonant converter with constant frequency control based LED driver

In this article, a single-stage bridgeless LLC resonant converter with a constant frequency control method is proposed for a high-brightness light-emitting diode (LED) driver. LED strings require drivers with high power density and high efficiency. This article presents a novel LED driver circuit topology based on switch integration and the switching controlled capacitor (SCC) technique. By combining the merits of a totem-pole bridgeless boost PFC unit and a high frequency SCC-LLC half-bridge resonant converter, the proposed topology can achieve high efficiency. Due to the SCC-LLC circuit topology structure, constant frequency control of the LLC resonant converter is achieved by the regulation of the equivalent resonant capacitance. The proposed novel LED driver topology can automatically achieve soft-switching characteristics and a high power factor. The operating principle of different operation modes and the characteristics of the proposed LED driver are analysed in detail. Finally, to demonstrate the feature of the proposed topology, a 100 W/70 V laboratory prototype is built. The satisfactory experimental results correspond with the theoretical analysis and parameter design.

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

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.

A Study on the Multiple Control Techniques for LED Dimming of Single Stage LLC Resonant Converter

This paper proposes the multiple control techniques for light emitting diode (LED) dimming of a single stage LLC resonant converter. In recent years, LEDs have emerged as a new next-generation light source and replaced conventional lighting devices such as incandescent and fluorescent lamps. Further, the use LEDs is increasing in many fields owing to their versatility and other advantages. However, LEDs are not available in commercial power; therefore, a driver circuit is required. Accordingly, the interest in LED driving circuits has increased, and there is an increasing demand for higher efficiency and further maximizing light efficiency and lifetime. A typical LED driver circuit comprises of two stages, i.e., a power-factor correction (PFC) stage and a DC/DC converter stage. This configuration results in unnecessary losses, in addition to the drawback in terms of a large driving-circuit volume. Further, when the conventional PWM dimming method is applied to an LLC resonant converter, there is a limit on the usable frequency range. The frequency cannot be indefinitely increased because the switching frequency is inversely related to the output characteristic. Thus, dimming function over a wide range is impossible. Therefore, to improve the overall efficiency of a LED driver circuit, a single-stage configuration is used to reduce the number of devices that cause unnecessary loss, and an asymmetric converter is used to reduce the voltage stress across the switch. Additionally, this paper proposes a converter circuit with a wider dimming range and PFC function through frequency-control, switching ratio control, and upper switching ON/OFF control.

Design and Implementation of 150 W AC/DC LED Driver with Unity Power Factor, Low THD, and Dimming Capability

This paper presents the implementation of a two-stage light-emitting diode (LED) driver based on commercial integrated circuits (IC). The presented LED driver circuit topology, which is designed to drive a 150 W LED module, consists of two stages: AC-DC power factor correction (PFC) stage and DC/DC power converter stage. The implementation of the PFC stage uses IC NCP1608, which uses the critical conduction mode to guarantee a unity input power factor with a wide range of input voltages. The DC/DC power converter with soft-switching characteristics for the entire load range uses IC FLS2100XS. Furthermore, the design of an electromagnetic interference (EMI) filter for the LED driver and the dimming control circuit are discussed in detail. The hardware prototype, an LED lighting system, with a rated power of 150 W/32 V from a nominal 220 V/50 Hz AC voltage supply was tested to show the effectiveness of the design. The presented LED driver was tested for street lighting, and the experimental results show that the power factor (PF) was higher than 0.97, the total harmonics distortion (THD) was lower than 7%, and the efficiency was 91.7% at full load. The results prove that the performance of the presented LED driver complies with the standards: IEC61000-3-2 and CIRSP 15:2009.

Design of Programmable LED Based Phototherapy System

Light based systems are frequently used in the field of medicine for diagnostic and surgical procedures, medical photography, phototherapy, etc. Phototherapy involves the use of light energy for the treatment of physical or mental illnesses. Illumination parameters such as wavelength and dose of therapy can be varied to have distinct effects on cells and tissues. This has necessitated the need to design a system which is programmable for various parameters related to therapy and can also be used by people at large for biomedical applications. The paper presents the design and implementation of a portable, hand-held and programmable Light Emitting Diode (LED) based phototherapy system using embedded technology. The system is designed around the ARM based TM4C123GH6PM microcontroller processor. The microcontroller has been programmed to allow for selection of various parameters such as frequency, duty cycle, and time of exposure. The matrix keypad interface and liquid crystal display (LCD) offer the ease of human interface. An LED driver circuit has been efficiently designed to modulate the output power of LED. Further, Super Bright LED (SLED) of wavelength ~633 nm has been successfully tested and results of optical characterization including spectral and spatial response have been presented in the results section. The designed system successfully achieves the programmable parameters required for dose optimisation required for enhancing the therapeutic effects of a phototherapy system.

Soft switched full‐bridge light emitting diode driver configuration for street lighting application

This study presents a light emitting diode driver circuit topology based on a full-bridge configuration with dimming control. It is more suitable for high power lighting loads. The proposed configuration has advantages of zero-voltage switching, reduced component count and high efficiency. It can power multiple lighting loads. Operation of the proposed circuit configuration is explained in detail and it is validated through simulated and experimental results on the 145 W experimental prototype with dimming control.

RGB LED Driver Circuit Design for an Optical Fiber Sensor System

In this paper, the design of a programmable mixed-signal electronic circuit to control the light output of a red-green-blue (RGB) light emitting diode (LED) to be used in an optical fiber sensor system is presented and discussed. The LED is to be used as a light transmitter (light source) within the sensor system. The output of each LED color is to be independently controlled using either a d.c. current or a pulse width modulation (PWM) encoded current. The idea for, and architecture of, the mixed-signal electronic circuit design is considered as both a discrete implementation using off-the-shelf components and the concept for an application specific integrated circuit (ASIC) solution using a 0.35 µm complementary metal oxide semiconductor (CMOS) fabrication process. In this paper, the design operation principles, circuit architecture, simulation results and hardware requirements for this LED driver circuit are considered.

Pulse Density Modulation Flyback Converter for LED Automotive Lighting

<p><em> </em><em>Switched mode power supply (SMPS) converter is a dc-dc power electronic converter which is used to step up or step down the dc output voltage. A dimmable driver circuit for Light Emitting Diode (LED) lamp for automotive lighting with dimming feature is used in this paper. A flyback converter is used as a driver circuit operated in discontinuous conduction mode to perform dimming control of LEDs. High overall circuit efficiency is achieved by regulating the current through the LED lamps using pulse density modulation scheme.</em><em> The </em><em>LED driver circuit design and operating principle is discussed in detail. A gentle current control feature is achieved by pulse density modulation technique. The high performance driver circuit is designed for 25 W LED lamps.</em><em> </em></p>

Overview of Passive Light Emitting Diode Driver Circuits for Street Lighting

This paper describes the overview and comparison of various passive Light Emitting Diode (LED) driver circuits employed for street lighting applications. Passive LED driver circuits are constructed with diodes and capacitors without using any power electronic semiconductor switches which in turn eliminates the secondary supply unit for control circuits and controllers. Passive LED driver circuits are simple in construction, low cost, less maintenance and control free. 50 W LED driver circuit is identified for performance comparison and simulations are performed in matlab- simulink to get an overview of different passive LED driver circuits. The most predominant parameters such as efficiency and total harmonic distortion are compared to identify the suitiblity of the driver circuits for various applications.

Novel Scanning Technique for LED Dot-Matrix Display to Reduce Flicker

A Conventional progressive scanning method can be used for small and medium size LED (Light Emitting Diode) dot-matrix display board. However, this conventional scanning approach has some drawbacks such as flicker, lower luminous intensity, requirement of high speed LED driver, etc., specifically for large LED dot-matrix display. This paper brings forward the analysis of scanning method clarifying the limitations of conventional scanning approach with several critical design parameters. After that, a new scanning approach, congenial to both small and large has been proposed to get over these limitations. Eventually, simulation of the mathematical models of the two methods are expounded that points to the vital design parameters constraints along with the advantages of new method. The mathematical models and analyses give understanding of system design approach to the LED driver circuit designers to estimate various design parameters.

Capsule Design for Blue Light Therapy against Helicobacter pylori.

A photo-medical capsule that emits blue light for Helicobacter pylori treatment was described in this paper. The system consists of modules for pH sensing and measuring, light-emitting diode driver circuit, radio communication and microcontroller, and power management. The system can differentiate locations by monitoring the pH values of the gastrointestinal tract, and turn on and off the blue light according to the preset range of pH values. Our experimental tests show that the capsule can operate in the effective light therapy mode for more than 32 minutes and the wireless communication module can reliably transmit the measured pH value to a receiver located outside the body.

DC-Level Dimmable LED Driver With Primary Side On-Time Control for DC Distribution

This paper proposes a light-emitting diode (LED) lighting system using a dc-level dimming technique. This new dimming method realizes LED lamp control by having the LED drivers in the same zone recognize the level of their input voltage as a dimming signal with a dc-level dimmer and minimum communication interfaces. The proposed dc LED system also achieves improved system efficiency by matching the variable input voltage to the LED load conditions. Practical design guidelines for the LED driver circuit are presented for system implementation. The prototype circuit for a 24-W LED lamp is designed following the guidelines for verification. The proposed dc-level dimming system and the conventional dimming LED lighting system, which dispatches communication modules to individual drivers to obtain dimming signal, are implemented for a two-story parking lot and their performance is compared and evaluated. The experimental results of the prototype system show 6.8% energy saving compared with conventional lighting, which results from the improved driver efficiency and reduced standby power consumption.

조광기용 MR16 안정기 호환 Flicker Free LED 구동회로 연구

LED(Light Emitting Diode) is a semiconductor device utilizing electroluminescent effect is a phenomenon in which a type of P-N junction diode, the light of short wavelength which a voltage is applied in the forward direction is released. LED is advantageous in reducing the energy as environmentally materials that can greatly reduce the carbon emissions, recent it has attracted attention IT(Information Technology) and GT(Green Technology) industry. In addition, there are advantages long life, high efficiency, and excellent response speed, LED have come into the spotlight as the illumination means to replace the existing fluorescent light and incandescent light bulb. When connecting to MR16 electronic transformer for existing LED driver circuit, due to malfunction of the dimmer and the electronic transformer, flicker occurs and linear dimming is not possible. Therefore, in this paper, we suggest an LED drive circuit there is no flicker with the corresponding dimming MR16 electronic transformer. Further, we explain the principles of the LED current control technique and the principle of the drive circuit of the LED, in order to validate the proposed circuit through prototyping and simulation.

Photoionization of optically trapped ultracold atoms with a high-power light-emitting diode

Photoionization of laser-cooled atoms using short pulses of a high-power light-emitting diode (LED) is demonstrated. Light pulses as short as 30 ns have been realized with the simple LED driver circuit. We measure the ionization cross section of (85)Rb atoms in the first excited state, and show how this technique can be used for calibrating efficiencies of ion detector assemblies.

Specially Designed Driver Circuits to Stabilize LED Light Output Without a Photodetector

This study proposes a novel light-emitting diode (LED) driver circuit that stabilizes the lighting output without a photodiode. The LED driver circuit is composed of a self-alignment circuit to compensate for the photo-power deviation and a feedback control system instead of a conventional photodetector to maintain the electrical power of the LED. The LED characteristics, based on electrical and optical measurements that varied with temperature, were built to be a lookup reference of the generated LED photopower, which serves as a compensator. A commercial full color LED system, which comprises red, green, and blue (RGB) LED chips, was implemented according to the novel concept. The impact of a conventional current regulator, a proposed electrical-power stabilization circuit, and a self-aligned photo-power stabilization circuit was studied graphically, followed by experimental verification. The maximal and minimal rate of change of the radiant flux Φ driven by the proposed LED drivers are 3.467% in a red LED, and 2.848% in green LED, respectively, over the ambient temperature range of 0.5-85 °C. The experimental results verified the implementation of a lighting power stabilization control system without the use of a photodiode for RGB LEDs.

A Capacitor-Isolated LED Driver With Inherent Current Balance Capability

This paper presents a capacitor-isolated light-emitting diode (LED) driver with inherent current-balancing capability. Based on a series resonant converter, the resonant capacitor can be used both for safety isolation and the current balancing with the proposed two-output rectifier structure. Compared to the conventional current-sharing technique, the proposed LED driver circuit is simple and has low cost and high performance. Also, the capacitor-isolated structure is more efficient and compact compared to the conventional transformer isolation. The detailed theoretical analysis and design considerations of the proposed circuit are presented. The performance of the proposed circuit is validated by the experimental results from a 60-W prototype with two balanced outputs.

Offset-voltage compensation for accurate current-source circuit

The offset-voltage compensation technique is proposed for an accurate current-source circuit. This current source is made of a transistor, a resistor, and operational amplifier feedback in order to achieve a high output resistance as well as high accuracy of a generated current signal. Discrepancy from the ideal value mainly results from the offset voltage of the operational amplifier. The transconductance amplifier is utilised with a feedback loop that is controlled by the switched-capacitor integrator. The proposed technique is incorporated in the light-emitting diode driver circuit applications and successfully verified with hardware measurement.