Search Results (27)

In this research, a series resonant LED driver circuit based on the differential-mode transformer for current equalization is proposed. In this circuit, the series resonant converter adopts controlled frequency modulation to change the energy transferred to the output while realizing zero voltage switching (ZVS) turn-on of the half-bridge switch. To deal with the problem of unequal LED currents caused by two different forward conduction voltages of the output LED strings, a differential-mode transformer is employed to balance the currents between the two LED strings, and the relationship between the magnetizing inductance and the percentage of current sharing error are derived to facilitate the design. Furthermore, only the current of one LED string needs to be sensed to achieve current equalization, while the current of the other LED string is automatically determined by the differential-mode transformer. Full article

This paper introduces a new two-stage multi-parallel-channel LED driver using a CLL-C resonant converter as the first stage and a Time Division Multiple Control circuit as the second stage. The first stage of the proposed converter topology has been developed from CLL-C topology with an additional inductor in the primary side and a capacitor in the secondary side. The converter provides a constant current at a resonant frequency with a Zero Phase Angle (ZPA), thus achieving Zero Voltage Switching (ZVS) turn-on, nearly Zero Current Switching (ZCS) turn-off for the switches, and ZCS for the diodes. The Time Division Multiple Control (TDMC) circuit was applied in the second stage to share the balanced current to each LED string. A 200 W prototype with five output channels was implemented to verify the superior advantages of the proposed topology with a maximum efficiency of 95.05%. Full article

As the integration of renewable energy sources into the grid increases, the insulation systems of grid components such as transformers and switchgear encounter significant challenges due to the transients and harmonics generated by power-electronic-based converters. A test generator capable of replicating these component stresses is essential to accurately evaluate these insulation systems under real-grid conditions. This paper proposes a modular cascaded H-bridge-based high-voltage arbitrary waveform generator, prototyped with three stages to generate customized waveforms (triangular, sawtooth, pulse, and complex) up to 8 kV. The H-bridge modules are designed using Si MOSFETs with a maximum blocking voltage of 4.5 kV. The input to the HV H-bridge module is provided by a 10 kV medium-frequency transformer, whose design is described with a focus on the insulation system and winding configuration. This transformer is driven by a zero-voltage switching driver. This arbitrary waveform generator excels in several aspects, including a straightforward design procedure, compact size, high voltage capability, ease of integration, and cost. Full article

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. Full article

Underwater wireless power transfer (UWPT) systems are appropriate for battery charging of compact, submerged devices without a complicated and expensive sealing structure or human contact because the power source and load are not physically connected. For the shore-based power supply situation, the underwater power conversion and junction technology should be required to drop down shore-based voltage to the target voltage for the underwater energy supply of the UWPT system. This paper proposes a lightweight, high efficiency and power density underwater power conversion connector system for the UWPT system, in which the LLC resonant converter is constructed with SiC transistors. The full load range zero-voltage switching (ZVS) and load adaptive characteristics have been achieved. The optimized RC level shift driver is adopted to highly reduce the switching loss of SiC transistors. Shore-based voltage of 1000 V was converted to the target voltage of 375 V for the UWPT system. The highest measured efficiency is over 98% at a load power level of 1500 W underwater conditions. Full article

The demand for highly efficient and dynamic electric vehicles (EVs) has increased dramatically. The traction inverter, a pivotal component in an EV powertrain, plays a crucial role. This study is dedicated to designing a traction inverter with focus on achieving high efficiency and elevated power density and mitigating electromagnetic interference (EMI) issues. To realize these objectives, autonomous gate drivers (AGDs) are proposed and designed using LTspice simulation software. The aim is to achieve zero voltage switching (ZVS) at both turn-on and turn-off through the utilization of triangular current mode (TCM) control on the gate driver. The AGDs implement a current modulation scheme by sensing the current and voltage and generating gate-source voltage signals with minimal delays. The implemented current modulation scheme by the AGDs results in an efficiency exceeding 99% for a 10 kW power rating. The sinusoidal output waveforms not only contribute to extending the motor lifespan by mitigating sharp-edge voltages but also bring advantages such as reduced switch stress, decreased EMI, and simplified thermal management. Full article

In this paper, a high-efficiency and low-cost active cell-to-cell balancing circuit for the reuse of electric vehicle (EV) batteries is proposed. In the proposed method, a battery string is divided into two legs to transfer the charge from each cell in one leg to that in the other and a bidirectional CLLC resonant converter is used to transfer energy between the selected cells. Thanks to the proposed structure, the number of bidirectional switches and gate drivers can be reduced by half compared to the conventional direct cell-to-cell topologies, thereby achieving lower cost for the system. The CLLC converter is used to transfer the charge, and it is designed to work at resonant frequencies to achieve zero-voltage zero-current switching (ZVZCS) for all the switches and diodes. Consequently, the system’s efficiency can be enhanced, and hence, the fuel economy of the system can also be improved significantly. To verify the performance of the proposed active cell-balancing system, a prototype is implemented for balancing the three EV battery modules that contain twelve lithium-ion batteries from xEV. The maximum efficiency achieved for the charge transfer is 89.4%, and the balancing efficiency is 96.3%. Full article

The use of light-emitting diodes (LEDs) in street lighting applications has been greatly welcomed with the current trends of energy saving, environmental protection, carbon reduction, and sustainable development. This paper presents a novel AC-DC LED integrated streetlight driver that combines an interleaved buck converter with a coupled inductor and a half-bridge series resonant converter with a full-bridge rectifier into a single-stage power conversion topology with power factor correction (PFC) and soft switching capabilities. The PFC is achieved by designing the coupling inductor in the interleaved buck converter sub-circuit in discontinuous conduction mode. In addition, the resonant tank in the half-bridge series resonant converter sub-circuit is designed to be similar to an inductive load, thus giving the power switch a zero-voltage switching (ZVS) function, decreasing switching losses and increasing the overall efficiency of the proposed circuit. A prototype circuit of the proposed LED integrated streetlight driver with a power rating of 165 W (235 V/0.7 A) and 110 V input utility voltage has been developed and tested. According to the measurement results, a power factor greater than 0.98, a total harmonic distortion coefficient of the input current less than 3%, and an efficiency greater than 89% were obtained in the AC-DC LED integrated streetlight driver. Therefore, the experimental results are satisfactory and demonstrate the functionality of the proposed AC-DC LED integrated streetlight driver. Full article

For low-power applications, this paper presents the development and design of a compact and ultra-highly efficient half-bridge LLC resonant converter. By using Galium Nitride (GaN) devices and high-efficient magnetics, the efficiency and power density of resonant converters can be improved. Compared to Silicon MOSFETs, GaN high-electron-mobility transistors (GaN HEMT) have a lower output capacitance and gate charge, resulting in lower driving loss and shorter dead times. Consequently, the proposed LLC converter based on GaN devices has excellent performance characteristics such as ultra-high efficiency, low switching losses, compact size, high voltage endurance, high operating temperature and high operating frequency. Furthermore, the proposed resonant converter features soft switching properties that ensure that the switches and diodes on the primary side are always switched at zero voltage and current. By doing so, LLC resonant converter switching losses are significantly reduced by up to 3.1%, and an overall efficiency of 98.5% is achieved. The LLC resonant converter design with GaN HEMT has great advantages over Si MOSFET solution regarding efficiency, overall losses, switching loose and power factor correction. A 240 W, 240 V to 60 V half-bridge GaN HEMT LLC resonant converter is simulated with a switching frequency of 75 KHz, along with the comparative analysis of the Si metal oxide semiconductor field effect transistor (MOSFET) solution. Moreover, the design and analysis of highly efficient magnetics with a power factor of 0.99 at full load is presented. A 240-Watt single stage LED driver with power factor correction is also designed to verify and compare the performance of proposed LLC resonant converter. Full article

This article presents the concept of switching and conduction loss reduction in a T-NPC inverter based on IGBT transistors. The method of limiting switching losses involves the connection of an LC circuit designed to cause transistors in vertical branches to shut down under zero voltage conditions. In order to reduce conduction losses, it was proposed to use two reverse blocking transistors connected anti-parallel in the horizontal branch of the inverter. To ensure safe operation of the transistors, a gate driver proposal for controlling the IGBT reverse blocking transistor is presented. The solution is characterized by a changed part of the driver, responsible for short-circuit protection. It eliminates excessive, destructive currents that can potentially flow through the driver circuit under the influence of the power supply voltage of the power circuit connected backwards to the controlled transistor. Examples of applications and benefits of the proposed solution are presented and verified with laboratory tests. Full article

Conventional switch-mode LED drivers have problems such as poor performance in harmonic distortion, flickering, power factor correction, stresses on the switches, high switching losses, large size, and high cost. To resolve these problems, we propose a long-life LED driver with the ability of power factor correction. The proposed system is based on the integration of a half-bridge LLC resonant converter and two boundary-conducted boost converters. Both boost converters share a common inductor designed in such a way that both boost converters work in boundary conduction mode to attain the natural power factor correction. Half-bridge LLC resonant converter has soft switching characteristics, which assure the zero-voltage switching (ZVS) of primary-side switches and zero-current switching (ZCS) of diodes on the secondary side. This significantly reduces switching losses and improves the overall efficiency of the system. Voltage divider capacitors are used on the input side, which minimizes the bus voltages. The proposed system has two identical secondary windings with a coupled inductor to eliminate the mismatch between them, which powers two independent LED strings. The simulation of a 100-watt 240 V AC converter yields the approximate sinusoidal shape of the input current. It shows that the switches on the primary side are operated in ZVS and the diodes in ZCS. At 240-volt AC input, the efficiency is 87.4%, the total harmonics distortion (THD) is 10.98%, and the power factor (PF) is 0.98. Full article

This paper presents the circuit and control method for piezo-ceramic drives. With the proposed method, a gap is imposed in the transformer core to increase the leakage inductance. This flattens the voltage gain curve of the piezo-ceramic driver over the resonant frequency range, so voltage gain changes are insensitive to frequency changes. In addition, resonant frequency tracking and power control methods are developed, while the circuit is capable of zero-voltage soft-switching such that the circuit operation efficiency can be improved. In order to solidify the practicality of the circuit design, mathematical analysis and experimental validations have been thoroughly performed. The test results help to confirm the effectiveness of the proposed method and demonstrate its practicality in industrial applications. Full article

Nowadays, electronic circuits’ time to market is essential, with engineers trying to reduce it as much as possible. Due to this, simulation has become the main testing concept used in the electronics domain. In order to perform the simulation of a circuit, a behavioral model must be created. Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) are semiconductor devices found in a multitude of electronic circuits, and they are also used as power switches in many applications, such as low-dropout linear voltage regulators, switching regulators, gate drivers, battery management systems, etc. A MOSFETs’ behavior is extremely complex to model, thus, creating high-performance models for these transistors is an imperative condition in order to emulate the exact real behavior of a circuit using them. An essential parameter of MOSFET power switches is the ON-state resistance (RDS_ON), because it determines the power losses during the ON state. Ideally, the power losses need to be zero. RDS_ON depends on multiple factors, such as temperature, load current, and gate-to-source voltage. Previous studies in this domain focus on the modeling of the MOSFET only in specific operating points, but do not cover the entire variation range of the parameters, which is critical for some applications. For this reason, in this paper, there was introduced for the first time a novel ON-state resistance modeling technique for MOSFET Power Switches, which solves the entire RDS_ON dependency on the transistor’s variables stated above. The novel RDS_ON modeling technique is based on modulating the transistor’s gate-to-source voltage such that the exact RDS_ON value is obtained in each possible operating point. The method was tested as a real-life example by creating a behavioral model for an N-channel MOSFET transistor and the chosen simulation environment was Oregon, USA, Computer-Aided Design (OrCAD) capture. The results show that the model is able to match the transistor’s RDS_ON characteristics with a maximum error of 0.8%. This is extremely important for applications in which the temperatures, voltages, and currents vary over a wide range. The new proposed modeling method covers a gap in the behavioral modeling domain, due to the fact that, until now, it was not possible to model the RDS_ON characteristics in all operating corners. Full article

A series connection of SiC MOSFETs for kV blocking capability can enable more design flexibility in modular multi-level converters as well as other topologies. In this paper, a novel gate driver circuit capable of driving series-connected SiC MOSFETs for high voltage applications is proposed. The primary advantage of the proposed design is that a single gate driver was used to switch all the series devices. The circuit used switching capacitors to sequentially charge and discharge device gate capacitances during switching and enable a negative turn-off voltage to avoid device coupling from Miller-capacitive feedback effects. With the proposed gate driver design and appropriate component values selection, avalanche breakdown due to voltage divergence during switching transients could be avoided with only a minor imbalance in the top device. Simulations and experimental measurements showed that the zero-current turn-off transition of all switches was achieved, and this approved the validity of the design. Full article

Single-ended resonant converters such as Class-E inverters have been widely considered as a potential topology for small- and medium-power wireless power transfer (WPT) applications, which feature compact circuits, low switching losses, and cost benefits, as they only use a low-side switch with a simple gate driver. However, there remains a practical challenge in the design of voltage stress, efficiency, and power density. In this paper, a single-ended resonant converter with a primary parallel resonant-matching network is investigated to absorb the bulky input-choke inductors of the Class-E inverters into the coil inductance. The analytical expressions for all the converter parameters are derived based on time-domain resonant waveforms, including: (1) analysis of critical zero-voltage switching (ZVS) conditions and (2) power transfer capabilities under the given maximum switch voltage stress. Furthermore, this paper elaborates on the design methodology of the proposed single-ended resonant converters, and an optimal operating point is chosen to ensure soft-switching operation and rated power. Finally, the accuracy of the proposed model is verified by simulation and experimental results. Full article