Constant Current Driver Research Articles

Development and testing of a discrete coil magnetostrictive actuator

Active combustion control (ACC) technology is an effective measure for suppressing the combustion oscillation of aero-engines. The magnetostrictive actuator is the most suitable choice for the ACC actuator due to its excellent high-frequency characteristics and high-temperature resistance. In order for the magnetostrictive actuator to produce high-frequency displacement, the constant current driver must have sufficient power, which results in a larger mass of the driver. A solution is to use multi-channel and low-power constant current driver. Therefore, the coil of the magnetostrictive actuator is axially dispersed and driven by two four-channel servo amplifiers. The driver’s mass is significantly reduced while maintaining the same electromagnetic conversion effect. In addition, an analytical model of a discrete coil magnetostrictive actuator is established, and a series of experiments are conducted. The maximum hysteresis error of output displacement at 200 Hz is reduced by 15.2%. Furthermore, under PID closed-loop control, the root mean square (RMS) error is less than 2% when tracking a 10 Hz sinusoidal displacement with coil switching drive.

A new LED constant current driver

A new LED constant current driver

A Current Sharing Using Switched-Capacitor ZVS Driver for Power LEDs

This paper proposes a switched-capacitor converter to source power light emitting diodes (LEDs). In contrast to conventional constant DC current drivers, the current pulse is provided by switched-capacitor LED driver. In the present driver it is possible to obtain several output circuits, where the capacitor is charged and discharged through the output circuit and the transfer of power from the grid for the LED is controlled by the switch. The effects of switching devices on the proposed converter are presented and evaluated. The experimental results demonstrated the technical feasibility of using the proposed circuit for the parallel association of LEDs, as well as to improve current sharing among LED strings. The proposed circuit driver with two output circuits presented an efficiency of 91%

A High-Efficiency Single-Stage Isolated Sepic-Flyback AC–DC Led Driver

Regulating LED current and voltage is critical to maintaining a constant luminous flux in AC- or DC-powered LED lighting circuits. Today, users require constant current drivers that can provide a wide range of output voltages to drive different numbers of series-connected LED arrays. This work proposes an LED driver by combining an isolated SEPIC converter operating in the continuous conduction mode (CCM) and a modified Vienna rectifier. The proposed LED driver offers a single-switch control structure by adding a Vienna rectifier to the integrated SEPIC-FLYBACK converter. This driver structure provides many advantages over traditional bridge rectifier structures. The prototype circuit was tested in an 18 W continuous current mode (CCM) to verify its feasibility. As a result of the values obtained from both simulation and prototype circuit models, it has been shown to provide many of the following advantages: 95% high efficiency, high reliability, 4% low total harmonic distortion, 97% high power factor, and 70 V low switching voltage. This work meets class C 3-2 and IEC 61000 standards.

Portable Protein and Fat Detector in Milk Based on Multi-Spectral Sensor and Machine Learning

To address the challenges of a long measurement period, high testing cost, and environmental pollution of traditional milk composition detection methods, a portable detection instrument was developed by combining multi-spectral sensors, machine learning algorithms, and an embedded system to rapidly detect the main components of milk. A broadband near-infrared (NIR) LED constant-current driver circuit and multi-spectral sensor module were designed to obtain six NIR features of milk samples. Based on a comparison of several machine learning algorithms, the XGBoost model was selected for training, and the trained model was ported to a Raspberry Pi unit for sample detection. The validation results showed that the coefficients of determination (R2) for the investigated protein and fat models were 0.9816 and 0.9978, respectively, and the corresponding mean absolute errors (MAE) were 0.0086 and 0.0079. Accurate measurement of protein and fat contents of milk can be facilitated in a short time interval by using the proposed low-cost portable instrument.

Monitoring chip-branches failure of multichip IGBT module using change rate of gate voltage

In order to increase system reliability, it is an economical and efficient method to monitor the defective multichip insulated gate bipolar transistor (IGBT) modules, which are widely used in various high-power electronic systems. A method is presented to monitor chip-branches failure caused by bond-wires defects inside the multichip IGBT modules when the modules are in the off-state. It is based on that the gate input capacitance of the multichip IGBT module will be changed by the failure of chip branches caused by bond-wires defects. The change rate of gate voltage under the constant gate current can be used to characterize the failure. Firstly, according to the gate charge characteristics, the relationship between the change rate of gate voltage and the chip-branches failure under the constant gate current is given. The process of monitoring chip-branches failure is described. Then, a gate driver is presented, which contains a constant current source, and the feasibility of the monitoring method is verified. The study results show that under the constant current source driver and within the specific range of gate voltage, the change rate of gate voltage is independent of temperature and collector–emitter voltage, only related to the failure of chip branches due to bond-wires defects in the multichip IGBT module and increases significantly with the chip-branches failure. Finally, the characteristics of this method are analyzed by comparison with other similar condition monitoring methods. This method is easy to measure and can be applied to the case of real-time and online monitoring.

Design of multi-channel LED constant current driver in radiometric calibration light source

Design of multi-channel LED constant current driver in radiometric calibration light source

Digital Predictive Current-Mode Control for Asymmetrical Half-Bridge LED Constant-Current Driver

In this paper, we propose three advanced digital predictive current-mode control (DPCC) algorithms based on a simplified estimation method of duty cycle lost time for asymmetric half-bridge (AHB) LED constant-current driver. They are the digital predictive peak current mode control(DPPCC) algorithm based on leading-edge modulation, the digital predictive quasi-valley current mode control(DPqVCC) algorithm based on trailing-edge modulation, and the digital predictive quasi-average current mode control(DPqACC) algorithm based on double-edge modulation. Simulation and experimental results demonstrate that the three DPCC algorithms can effectively offset the effect of delay on digital control performance, which confirms the superiority of DPqACC. When the DPqACC is applied, the series-load-jump transition times are below 4.5 ms, the maximum load adjustment rate is 0.5%/ V, and the output current can be tuned continuously between 0.3 A and 4.5 A with the longest transition time of 1 ms. Moreover, the three DPCC algorithms are capable of compensating for low-frequency ripples due to the rapid regulation speed of the inner loop. With the electrolytic capacitance removed without additional ripple compensation, the maximum peak-to-peak value of the low-frequency secondary ripple is 0.1163 A (2.91%) when the input is 400 53sin(2ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>lin</i></sub> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> ) V and the output is 4 A. This approach provides an excellent solution for the digital design of low-ripple AC-DC LED constant-current drivers without electrolytic capacitance.

Design of a high performance AC-DC LED driver based on SEPIC topology

Light emitting diodes (LEDs) are current driven devices. So, it is essential to maintain the stability of LED voltage and current. Variation of temperature may cause of instabilities and bifurcations in the LED driver. Driving LEDs from an offline power source faces design challenges like it have to maintain low harmonics in input current, to achieve high power factor, high efficiency and to maintain constant LED current and to ensure long lifetime. This paper proposes the technique of harmonics reduction by using parametric optimization of Single ended primary inductor converter (SEPIC) based LED driver. Without optimization of SEPIC parameters input energy will not be properly transferred to the load and this un-transferred energy will be transmitted to the source. Consequently, the quality of input current will be hampered i.e. harmonics will contaminate the input current. Focussing this, the paper has presented the design of a non-isolated integrated-stage single-switch constant current LED driver operating in discontinuous conduction mode (DCM) in SEPIC incorporating the design of control circuit with soft start mechanism. This LED driver has achieved a good efficiency (90.6%) and high-power factor (0.98) with reduced harmonics (3.35%). System stability has been determined and simulation studies are performed to confirm the validity of the LED driver circuit. A laboratory prototype is built.

A Universal Block of Series-Connected SiC MOSFETs Using Current-Source Gate Driver

SiC MOSFET has superior switching performance over Si IGBT in terms of power loss and temperature characteristics. In order to significantly improve the efficiency and power density of medium-voltage drive and high-power converters, this article proposes a current-source gate driver (CS-GD) for series-connected SiC MOSFETs, forming a universal block of series-connected SiC devices with the higher voltage rating. The proposed CS-GD has better gate voltage synchronization performance because of its constant gate current and novel gate driver structure. By implementing synchronized gate voltages, the snubber circuit is designed only for power loop difference and gate displacement current difference, and the snubber can be minimized or even be eliminated. The proposed block has been verified by LTSPICE simulations and multipulse test experiments under 200-kHz, 2-kV, 0~60-A condition using three 1.2-kV/60-A C2M0040120D SiC MOSFETs connected in series.

Discrete-Time Modeling of High Power Asymmetric Half-Bridge LED Constant-Current Driver Controlled by Digital Current Mode

The high-power Asymmetric half-bridge Converter (AHBC) LED constant current driver controlled by digital current mode is a fourth-order system. Static operating point, parasitic resistance, load characteristics, sampling effect, modulation mode and loop delay will have great influence on its dynamic performance. In this paper, the small-signal pulse transfer function of the driver is established by the discrete-time modeling method for two operating points with three modulation modes of trailing-edge, leading-edge and double-edge. And, the effects of parasitic parameters, delay, sampling and load etc. are fully considered in modeling. For a large number of complex exponential matrix operations, the first order Taylor formula is used for approximate calculation after the coefficient matrix is obtained by substituting the data. Then, the designed average current mode compensators based on state-space averaging small-signal model(SSA) are used for analog and digital control, and the loop characteristics and control performance are analyzed. Simulation and experimental comparison results show that the proposed discrete-time model(DTM) can more accurately describe the characteristics of resonant peak, high-frequency dynamic and loop delay, and is very suitable for the design of high frequency digital controller.

Fuzzy controlled Modified Switched-Capacitor converter Based LED Driver

This article discusses a switched capacitor-based converter to drive high power light emitting diodes (LEDs). The current pulse is provided by a switched capacitor, which is differing from that of conventional constant current dc drivers. The proposed approach differs from the traditional switched-capacitor-based one, because it uses a small inductor to improve the switching behaviour of the converter. The effects of switching devices on the proposed converter are evidenced and evaluated, based on the charge control analysis.Experimental results are presented and discussed to demonstrate the technical feasibility of the proposed MSC converter applied as LED driver through Matlab simulation and hardware result.

Analysis and design of a multi‐channel constant current LED driver based on DC current bus distributed power system structure

The colourful light emitting diode (LED) strings require the corresponding driver to achieve independent control of each output current in the applications of RGB mixed colour LED lighting, LED projection etc. For this purpose, a multi-channel constant current LED driver based on DC current bus distributed power system structure is proposed and analysed here, which is composed of a source converter and several load converters as needed. The source converter adopts the flyback converter to realise power factor correction, electrical isolation, and the load converter adopts the current-type buck converter to realise independent control of the corresponding output current. A 60 W experimental prototype for 42.8 V/0.35 A, 40 V/0.5 A, 35.7 V/0.7 A three outputs with the universal input voltages 90–264 V is designed and implemented, and the experimental results are presented to verify the correctness of the theory analysis.

Enhanced Visible Light Communication Modulator With Dual-Feedback Control

This article presents a modulator for optical wireless communication (OWC) via LEDs, controlled by a dual closed loop. While the potential communication speed and performance of OWC have received a lot of research attention, the design of appropriate modulator circuits has not been studied so widely. This article addresses the control aspects to minimize power losses and to ensure automatic adaptation to component spreads or aging, for “high-power” LED emitters. We initially address a “low-bandwidth– system, particularly suited for indoor camera-based detection, and then a “higher bandwidth” one for Li-Fi data communication. In contrast to maximizing data throughput as it applies to high-speed modulators, low-speed modulators aim at high power and high efficiency in general lighting applications. Specifically, for the high-power modulator, we propose a control strategy that allows a wide range of combinations of LED types and LED power supplies. The power consumption of the modulator is minimized by voltage margin setting that is automatically adapt to the modulation and the LED type using the nonlinear detector. The common industry practice is to use constant-current LED drivers for powering LEDs. After creating a theoretical framework of some generality to evaluate designs and control loops with rationals and verified models, we realize modulator designs that are supplied by constant current LED drivers and verify their performance by simulation and measurements.

Accelerated Degradation Test Investigation for Life-Time Performance Analysis of LED Luminaires

LED luminaires are a common lighting source used in general lighting application as they are energy-efficient and long-lasting. However, the reliability of an LED luminaire is not well established, and no standard method for estimating the performance of an LED luminaire is developed. This article presents an investigation to understand the performance of LED luminaires at the accelerated degradation test (ADT) condition and analyzes the reliability of LED luminaires. An LED luminaire has two subsystems, an LED light engine and the LED constant current driver that are subjected to ADT, and the light engine factors, lumen output, and Duv changes are analyzed. Similarly, the driver output stage electrolytic capacitor capacitance and equivalent series resistance (ESR) are estimated. The study of continuous operation in time and study when subjected to switching cycles to quantify reliability in terms of operating cycles is performed. All four key parameters-lumen maintenance, Duv, capacitance, and ESR-are estimated up to their specified threshold and reliability is analyzed. The LED light engine lumen output is found to degrade very quickly compared with other factors. LED luminaire failure at ADT is mainly due to lumen depreciation followed by color shift and, after significant intervals of time and cycles, the driver capacitor ESR follows as reason for the failure of the LED luminaire. A scanning electron microscope (SEM) energy dispersive spectroscopy (EDS) analysis is performed on the LED package, and results show that LED silver (Ag) mirror tarnish is the main reason for a significant reduction in light output.

Analysis and Design of a Single-Stage Bridgeless High-Frequency Resonant AC/AC Converter

A single-stage high-frequency resonant ac/ac converter converts the ac-line input voltage into the high-frequency sinusoidal output voltage, which consists of two power conversion units, i.e., a power factor correction (PFC) unit and a high-frequency resonant dc/ac unit, and it can be used to derive a modular multichannel constant current LED driver. By adopting a totem-pole bridgeless PFC boost rectifier to reduce conduction losses, a single-stage bridgeless high-frequency resonant ac/ac converter is proposed in this paper. The operating principle is described, and the performance analysis is presented in detail. Moreover, the quantitative parameter design method of the main circuit is presented, which is suitable for other single-stage ac input converters, such as a single-stage PFC rectifier. Finally, a 130-W prototype has been built and tested to verify the correction of related theoretical analysis and parameter design.

Synchronous High Step-Down Ratio Non-Isolated LED Constant Current Driver Based on Improved Watkins-Johnson Topology

In the field of non-isolated light-emitting diode (LED) driver, the omnipresent buck-based LED constant current driver shows poor efficiency in occasions of high step-down ratio due to the marginal operating duty cycle. In order to overcome such drawback and to provide an alternative topological scheme for an LED driver, a Watkins-Johnson topology-based solution is proposed in this paper, by improving the original circuit structure into a dual low-side power switch version and introducing a feedback network for regulating the output current to a constant level. Theoretical analysis, including accurate model construction, steady-state analysis, dynamic analysis, and design consideration, is conducted. Also, an experimental prototype is realized to drive all kinds of LED arrays for acquiring electrical parameters and evaluating performance. The innovative points include invoking the low-side-ize approach to realize the power circuit transformation, and furthermore, theWatkins-Johnson topology is first applied to the constant current power supply. The proposed LED driver holds salient features of low-terminal current ripple, ease of driving, high-voltage conversion ratio tolerance, and inherent energy recovery functionality. The application scope covers low-voltage dc input or automotive lighting use.

New design of the LED current controller

In the work traditional and innovative methods for constant current LED drivers have been studied. The low-cost solutions for energy effective low lighting flicker current regulation have been proposed. The advantage is due to fact that auxiliary switch-mode regulator converts only small part of output power. The proposed solution can be used in LED drivers to reduce pulsations of the light flux, as well as in driverless AC LED modules to monitor LED currents and/for power correction.

大功率半导体激光器驱动电源及温控系统设计

In order to solve the output wavelength and power stability of high power semiconductor laser, high power semiconductor laser constant current driver and temperature control system were designed. Deep negative feedback circuit was used to control the laser drive current, the analog Proportional-Integral (PI) circuit and constant current driver were adopted to control the working current of Thermoelectric Cooler (TEC), the laser working temperature can be kept accurately. The design can realize the linear adjustment of output current from 0-12.5 A, and has the function of current detection, over-current protection and Transistor-Transistor Logic (TTL) modulation. The control precision of the temperature control system can achieve 0.05℃. Temperature can be adjusted continuously and can be monitored in real time. Experiment results show that the design can guarantee the output current and temperature control stably, which satisfies the requirement of high power semiconductor laser.

A Review of LED Drivers and Related Technologies

Light-emitting diode (LEDs) have a promising prospect because of its outstanding advantages: 1) long lifetime, 2) environmentally friendly, 3) flexibility of color mixing, 4) high illumination efficiency, etc. Based on the electrical characteristics of LEDs, a constant current driver is needed to support the LED working performance. With the wide applications of LEDs, many new technologies are presented. In this paper, advantages and disadvantages of different LED drivers are discussed. A detailed technology review is presented which is good for researchers and engineers to make right choices in design and selection of LED drivers.